GB2053262A

GB2053262A - Process and Apparatus for Producing Gaseous Mixtures including H2 and CO

Info

Publication number: GB2053262A
Application number: GB8018649A
Authority: GB
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1979-07-13
Filing date: 1980-06-06
Publication date: 1981-02-04
Also published as: NO155696B; NO801879L; AU540270B2; AU5944680A; NO155696C; BR8004344A; IN151458B; DE3024469A1; GB2053262B

Abstract

A hot raw gas stream, as produced by the partial oxidation of a solid carbonaceous fuel such as coal, is partially cooled and cleaned to remove entrained solid matter and slag in an apparatus comprising a closed cylindrical insulated vertical pressure vessel (46) containing a lower quench chamber (48) in communication with an upper solids separation chamber (49) separated by a choke-ring (50). The hot raw gas stream introduced through inlet (45) is cooled in the lower chamber by impingement and direct heat exchange with an oppositely directed coaxial stream of cooled, cleaned, and compressed recycle quench gas introduced through inlet (55). The cooled gas leaving the turbulent lower chamber passes up through a choke- ring (50) into the comparatively calmer upper chamber counter- currently with solid slag droplets which separate out by gravity. Residual solid particles are removed from the gas stream by at least one cyclone separator (56) located in the upper chamber. A portion of the gas stream leaving the vessel, with further cooling and with or without further cleaning downstream is recycled back to the vessel through inlet (55) for use as said quench gas. Slag particles and other solid matter that are separated within the pressure vessel are removed at the bottom outlet (52) of the lower chamber. <IMAGE>

Description

SPECIFICATION Process and Apparatus for Producing Gaseous Mixtures Including H2 and CO This invention relates to the manufacture of clean gaseous mixtures comprising H2 and CO. More particularly, it pertains to the apparatus and related process for cooling and cleaning the hot raw gas stream produced by the partial oxidation of solid carbonaceous fuels and principally comprising H2, CO, CO2, H20 and containing entrained solid matter and slag.

In the partial oxidation of liquid and solid hydrocarbonaceous fuels with steam and free oxygen to produce gaseous mixtures comprising carbon monoxide and hydrogen, the gases leave the gas generator at a temperature in the range of about 17000 to 30000 F. Depending on the feed and operating conditions, entrained in the gas stream leaving the gas generator are various amounts of molten slag and solid matter such as soot and ash. It is often desirable to reduce the concentration of these entrained materials. For example, by removing solids from the gas stream, one may increase the life of downstream apparatus that is contacted by the gas stream, such as the life of gas coolers and turbines. Solids removal from the synthesis gas will also prevent plugging of catalyst beds. Further, environmentally acceptable gas may be produced.

In coassigned U.S. Patent 2,871,11 4-Du Bois Eastman, the product gas and slag from the gasification of coal are passed into a slag pot placed directly below the generator. Water is supplied to the slag pot to collect and solidify the slag which drops out of the gas stream. The gas stream leaves the slag pot and is passed into a quench accumulator vessel where the gas is intimately contacted with water and cooled to a temperature in the range of about 300--6000F. The gas stream leaving the quench tank is saturated with H20. Furthermore, all the sensible heat in the gas stream is thereby dissipated in the quench water at a comparatively low temperature level.When the raw gas stream leaving a coal fired generator at a temperature above about 1 7000F is introduced directly into a gas cooler, the slag entrained in the gas stream will deposit out on the inside surfaces of the gas cooler and foul the heat exchange surfaces. In U.S. Patent 4,054,424 no means is provided for removal of the slag from the system.

In contrast with the prior art, by the subject invention the raw synthesis gas is cleaned without quenching in water and is therefore not saturated. It is also cooled to a temperature in the range of about 12000 to 1 8000F, and below the initial deformation temperature of the slag. The thermal energy in the gas stream may be recovered at a high temperature level. Further, the solidified slag particles are removed from the system. Fouling of equipment located downstream for recovering energy from the hot gas stream is thereby avoided.

This invention pertains to a process for producing hot raw gas stream principally comprising H2, CO, CO2, H20 and containing entrained solid matter and molten slag, by the partial oxidation of a solid carbonaceous fuel such as coal and cooling and cleaning the raw gas stream to remove the entrained solid matter and slag.The invention provides a process for the partial oxidation of an ash-containing solid carbonaceous fuel for producing a cleaned stream of synthesis gas, fuel gas or reducing gas comprising: (1) reacting particles of said solid fuel with a free-oxygen containing gas and with or without a temperature moderator in a down-flow refractory lined gas generator at a temperature in the range of about 17000 to 31000F and a pressure in the range of about 10 to 200 atmospheres to produce a raw gas stream comprising H2, CO, CO2 and at least one material selected from the group consisting of H20, H2S, COS, CH4, NH3, N2, and A, and containing molten slag and/or particulate matter;; (2) passing the raw gas stream through a thermally insulated transfer line and first gas inlet into the lower chamber of a gas-solids separation zone comprising a closed vertical cylindrical thermally insulated pressure vessel containing said lower chamber which is coaxial with the central vertical axis of said pressure vessel and in communication with a coaxial upper chamber, said lower and upper chambers being connected by a coaxial choke-ring passage, and wherein a portion of said slag and/or particulate matter settles out by gravity, and falls to the bottom of said lower chamber; (3) passing the mixture of gases from the lower chamber upwardly through said choke-ring into said upper chamber in counter-flow with slag droplets, and then into a gas-solids separation means, if any, located in said upper chamber;; (4) separating slag and/or particulate matter from said gas mixture in said upper chamber and removing same from said vessel by way of an outlet in the bottom of said lower chamber, and (5) removing cleaned gas from said upper chamber and discharging said gas through an outlet at the top of said vertical vessel.

The invention also provides a novel gas-gas quench cooling and solids separation apparatus suitable for use in a method according to the invention. The apparatus comprises a closed cylindrical insulated vertical pressure vessel containing a lower quench chamber in communication with an upper solids separation chamber. Hot raw gas stream can be introduced into the lower chamber where the gas temperature is reduced to a temperature in the range of about 12000 to 1 8000F and below the initial deformation temperature of the slag by impingement and direct heat exchange with an oppositely directed coaxial stream of cooled, cleaned and compressed recycled quench gas. Solid particles are separated from the raw gas stream and are discharged through an outlet at the bottom of the lower chamber. A choke-ring passage separates the lower chamber from the upper chamber.The stream of cooled gas leaving the turbulent lower chamber passes up through the choke-ring countercurrently with solid slag droplets which separate out from above by gravity. Optionally, a solids separation means from the group single-stage and multi-stage cyclones, impingement separator, filter, and combinations thereof may be located in the upper chamber to remove residual carbon containing fines and solid slag droplets that remain in the cooled gas stream. In a preferable embodiment, a solids separation means from the group single-stage cyclone, multi-stage cyclones, and combinations thereof are mounted in said upper chamber. A cooled and cleaned gas stream is discharged from the upper chamber, and subjected to further cooling, and if necessary additional cleaning.A portion of this gas stream is then compressed and returned to the lower chamber as said cooled and cleaned recycled quench gas stream.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of the gas-gas quench cooling and solids separation apparatus according to the invention in vertical cross section, Figure 2 is a schematic drawing of a plant utilizing the apparatus of Figure 1 for performing a process according to the invention, Figure 3 is a schematic drawing of a second plant utilizing the apparatus of Figure 1 for performing a second process according to the invention.

The present invention pertains to an improved continuous process and related apparatus for cooling and cleaning a hot raw gas stream principally comprising H2, CO, CO2, and H 20 and containing entrained solid matter and molten slag. The apparatus is particularly useful for cooling and cleaning the hot raw stream of gas that is produced by the partial oxidation of a solid carbonaceous fuel.

The recovery of energy from the hot raw gas stream from the partial oxidation gas generator will increase the thermal efficiency of the gasification process. Thus, by-product steam for use in the process or for export may be produced by heat exchange of the hot gas stream with water in a gas cooler. Energy recovery, however, is made difficult by the presence in the generator exhaust gases of droplets of molten slag resulting from the fusion of the ash content of the coal fed to the generator. The instant invention is a means and method for solidifying the molten slag droplets and removing the resulting particulates from the gases thereby simplifying energy recovery. Common problems with build-up of slag are avoided in the subject invention by solidifying the slag particles before they impinge on solid surfaces.Further, solid surfaces are removed from the point of inception of slag cooling.

Depending on the amount of unconverted solids and ash in the raw gas stream leaving the gas generator, the subject means and method may stand alone or may follow a preliminary separation of solids and liquid slag from the gases. While apparatus according to the invention may be used to process the hot raw effluent gas stream from almost any type of gas generator, it is particularly suitable for use down stream of a partial oxidation gas generator. An example of such a gas generator is shown and described in coassigned U.S. Patent 2,829,957, which is-incorporated herewith by reference. In one embodiment, our novel gas-gas quench cooling and solids separation apparatus may be connected before a gas cooler in 2 system which includes a gas generator for producing synthesis gas and a gas cooler.For example, a partial oxidation gas generator and a waste heat boiler may be interconnected by a plenum, with or without a separable catch pot as shown in coassigned U.S. Patent 3,565,588, which is incorporated herewith by reference. In such case, the subject apparatus may be connected in the line immediately upstream of a gas cooler or waste heat boiler in which boiler feed water is converted into steam. By the subject invention, combustion residue in the gas stream is removed, fouling of boiler tubes is prevented, and the life of convection-type heat exchangers is increased.

The subject apparatus comprises a closed cylindrical vertical pressure vessel whose inside walls are thermally insulated. For example, the vessel may be internally lined with high temperature resistant refractory. Within the vessel are two cylindrical vertical refractory lined chambers that are coaxial with the central axis of the vessel and which are in communication with each other. These chambers are a lower quench chamber and an upper solids separation chamber. A coaxial choke-ring passage connects the two chambers. The longitudinal axis of at least one pair of opposed coaxial internally insulated inlet nozzles passes through the walls of the lower chamber. The inlet nozzles are spaced 1 80O apart and are located on opposite sides of the lower chamber.The hot raw gas stream is passed through one inlet nozzle and a comparatively cooler and cleaner recycle stream of quench gas is passed through the opposite inlet nozzle. The two streams impinge each other within the lower chamber and the head-on collision produces a turbulent mixture of gases. The high turbulence results in rapid mixing of the opposed gas streams and direct heat exchange.

While the following discussion pertains to a single pair of inlet nozzles, which is the usual design, a plurality of pairs of inlet nozzles, say 2 to 10, of similar description, may be employed. The pairs of nozzles may be evenly spaced around the vessel. The longitudinal axis of the inlet nozzles may be inclined to direct raw gas flow upward as shown in the drawing, or enter horizontally. Alternatively, the longitudinal axis may be inclined to direct raw gas flow downward if better suited to the overall configuration of the gas generator and the subject quench-separator apparatus.Thus, the longitudinal axis common to each pair of inlet nozzles is in the same plane with the central vertical axis of the vessel and may be at any angle in the range of about 300 to 1 500 with dnd measured clockwise from the central vertical axis of the vessel. Suitably, this angle may be in the range of about 400 to 1 350, say about 450 as shown in the drawing. The actual angle is a function of such factors as temperature and velocity of the gas streams, and the composition, concentration and characteristics of the entrained matter to be removed. For example, when the raw gas stream contains liquid slag of high fluidity, the longitudinal axis of the raw gas inlet nozzle may be pointed upward at an angle of about 450 measured clockwise from the central vertical axis of the vessel.Much of the slag would then run down the transfer line and be collected in a slag pot upstream of the subject apparatus. On the other hand when the liquid slag is viscous, the flow of the slag may be helped by pointing the raw gas inlet nozzle downward, say at of about 1350 measured clockwise from the central vertical axis of the vessel. The high velocity of the hot raw gas stream through the inlet nozzle and the force of the gravity would then help to move the viscous liquid slag into the lower chamber, where it solidifies and is separated from the gas stream by gravity.

The hot raw gas stream enters through one inlet nozzle at a temperature in the range of about 17000 to 31000F. such as 20000 to 30000F., say about 23000 to 28000F., for example 25000F. The pressure is in the range of about 10 to 200 atmospheres, say about 25 to 85 atmospheres and typically about 40 atmospheres. The velocity is in the range of about 10 to 100 feet per second say about 20 to 50 feet per second, and typically about 30 feet per second. The concentration of the solids in the entering hot raw gas stream may be in the range of about 0.1 to 4.0 grams per standard cubic foot (SCF), say about 0.25 to 2.0 grams per SCF.The particle size may be in the range of about 40 to 1000 micrometers or roughly equivalent to Stairmand's coarse dust-Filtration and Separation Vol. 7, No. 1 page 53, 1 970 Uplands Press Ltd., Croydon, England.

The cooled cleaned recycle stream of quench gas which enters through the opposite inlet nozzle is obtained from at least a portion i.e. about 20 to 80 mol % say about 30 to 65 mol %, and typically about 60 mol % of the overhead stream from the subject apparatus, with or without further cleaning and/or cooling. The temperature of the quench gas is in the range of about 2000 to 8000F., say about 3000 to 6000F., and typically about 3500F. The mass flow rate and/or the velocity of the hot raw gas stream and the cooled cleaned recycled stream of quench gas are adjusted so that the momentum of the two opposed inlet gas streams is about the same.

In Table I below, there are shown in columns 3 and 4 temperature and composition of typical gas mixtures that are produced when streams of raw synthesis gas and cooled cleaned recycle quench gas, at the temperatures shown in columns 1 and 2, collide in the lower quench chamber.

Table I Gas Mixture Leaving Lower Quench Chamber Amount of Synthesis Recycle Recycle Quench Raw Gas Quench Gas Temperature Gas in OF OF OF Mixture-mol % 3100 800 1200 85 1700 300 1300 30 2800 600 1500 62 2500 400 1700 41 2650 500 1600 52 2650 500 1800 43 2650 500 1400 61 The ends of each pair of opposed inlet nozzles preferably do not extend significantly into the chamber. Preferably, the opposed inlet nozzles terminate in planes normal to their centerline. By this means, deviation of these streams from concentricity is minimized. The jets of gas which leave from the opposed nozzles travel about 5 to 10 feet, say about 8 feet, before they directly impinge with each other. The high turbulence that results in the lower chamber promotes rapid mixing of the gas streams.

This promotes gas to particle heat transfer. Thus through turbulent mixing of the cooled and cooling streams of gas, solidification of the outer layer of the slag particles takes place before the slag can impinge on solid surfaces. A gas mixture is produced having a temperature below the initial deformation temperature of the slag entering with the raw gas stream i.e. about 1200 to 18000 F.

typically about 1 4000F. The entrained slag is cooled and a solidified shell is formed on the slag particles which prevent them from sticking to the inside walls of the apparatus, or to any solid structural member contained therein. In one embodiment, from about 1 to 50 volume % of the recycle quench gas stream is introduced into the subject quench separation apparatus by way of a plurality of tangential nozzles located at the top of the lower chamber and/or the bottom of the upper chamber. By this means, a swirl is imparted to the upward flowing gases. Additionally, this will provide a protective belt of cooler gas along the inside wall of the choke ring and above.

Solid matter i.e. unconverted coal, carbon particles, carbon containing particulate solids, slag particles, ash, and bits of refractory, separate from the raw gas stream and fall to the bottom of the lower chamber where they are removed through an outlet of the bottom of the pressure vessel. A lockhopper system for maintaining the pressure in the vessel is connected to the bottom outlet. Preferably, the bottom of the pressure vessel has a low point that is connected to the bottom outlet. For example, the bottom of the pressure vessel may be a truncated cone, or spherically, or elliptically shaped.

The choke ring provides a corridor joining the lower and upper chambers. It is used to dampen out the turbulence of the gas stream from the lower chamber. By this means the upward flow of the gas stream is made orderly. In comparison with the turbulence in the bottom chamber, the gas rising through the upper chamber is relatively calm. This promotes gravity settling of solid particles which fall down through the choke ring and into the bottom of the lower chamber. The choke ring is preferably made from a thermally resistant refractory. Its diameter is smaller than either the diameter of the upper or the lower chamber. The diameters of the upper and lower chambers depend on such factors as the velocity of the gas stream flowing therein and the size of the entrained particles.The ratio of the diameter of the upper chamber (du) to the diameter of the lower chamber (dl) is in the range of about 1.0 to 1.5, and typically about 1.0. The ratio of the diameter of the choke ring (dc) to diameter of the lower chamber (d,) is in the range of about 0.5 to 0.9, such as about 0.6 to 0.8, say 0.75.

While the upper chamber may be vacant to provide additional space for gravity settling of entrained solids, preferably, mounted within the upper chamber are at least 1, such as 2-12, say 2 gas-solids separation means for removing at least a portion of the solid particles remaining in the gas stream. Typical gas-solids means that may be used in the upper chamber may be selected from the group: single-stage cyclone separator, multi-stage cyclone separator, impingement separator, filter, and combinations thereof. In a preferable embodiment, single-stage or multi-stage cyclone separators, or combinations thereof are employed in the upper chamber as said gas-solid separation means.The actual number of gas-solids separation means employed will depend on such factors as the dimensions of the upper chamber and the actual volumetric rate of the gas stream approaching the entrance to the gas-solids separation means at the top of the upper chamber. At this point, the concentration of solids is in the range of about 0.05 to 2 grams per SCF. The particle size is in the range of about 40 to 200 micrometers or approximately equivalent to Stairmand's fine dust. Any conventional continuous gassolids separation means may be employed that will remove over about 65 wt. % of the solid particles in the gas stream and which will withstand the operating conditions in the upper chamber. The pressure drop through the gas solid separation means is preferably less than 20 inlet velocity heads.Further, the separation means should withstand hot abrasive gas streams at a temperature up to about 20000F or up to about 30000F.

Typical gas solids separation means that may be used in the upper chamber may be selected from the group: single-stage cyclone separator, impingement gas solid separator, filter and combinations thereof.

Preferred gas solids separators are of the cyclone-type. A cyclone is essentially a settling chamber in which the force of gravity is replaced by centrifugal acceleration. In the dry-type cyclone separator, the stream of raw gas laden with particulate solids enter a cylindrical conical chamber tangentially at one or more entrances at the upper end. The gas path involves a double vortex with the raw gas stream spiralling downward at the outside and the clean gas stream spiralling upward on the inside to a central, or concentric gas outlet tube at the top. The clean gas stream leaves the cyclone and then passes out of the vessel through an outlet at the top. The solid particles, by virtue of their inertia, will tend to move in the cyclone toward the separator wall from which they are led into a discharge pipe by way of a central outlet at the bottom.Small sized particles will form clusters that may be easily removed by the cyclone. The discharge pipe or dipleg extends downward within the pressure vessel from the bottom of the cyclone to preferably below the longitudinal axes of the inlet nozzles in the bottom chamber, and below the highly turbulent area. Particulate solids that are separated in the cyclone may be thereby passed through the dipleg and discharged through a check valve into the bottom of the lower chamber below the zone of vigorous mixing. The dipleg may be removed from the path of the slag droplets by one or more of the following ways: keeping the dipleg close to the walls of the vessel, straddling the axis of the hot gas and quench gas inlet nozzles, or by putting ceramic diplegs in the refractory wall. Alternately, the diplegs may be shortened to terminate any place above the top of the lower chamber.

For example, at least one single stage cyclone may be mounted within the upper chamber with its inlet facing the horizontal circular component of a rising spiral flow pattern, which will be existent in the embodiment wherein a portion of the quench gas enters the vessel tangentially or will otherwise be induced by the cyclone inlet flow. With a plurality of single-stage cyclones connected in parallel, the gas outlet tube for each cyclone may discharge into a common internal plenum chamber that is supported within the upper chamber. The cleaned gas stream exits from the plenum chamber through the gas outlet at the top of the upper chamber. In another embodiment, at least one multiple-stage cyclone unit is supported within the upper chamber. In such case, the partially cleaned gas stream that is discharged from a first-stage internal cyclone is passed into a second-stage cyclone that is supported within the upper chamber. The clean gas stream from each second-stage cyclone is discharged into a common internal plenum chamber that is supported at the top of the upper chamber. From there, the may be partially solidified and reduced to acceptable levels of concentration and particle size. This gas may be used as synthesis gas, fuel gas, or reducing gas.

In processes according to the invention the thermal efficiency of the partial oxidation gasification process may be increased by recovering energy from the hot raw gas stream by producing by product steam for use in the process or for export by heat exchange of the hot gas stream in some embodiments with water in a gas cooler, and, in other embodiments with boiler feed water and steam in a main gas cooling zone. Energy recovery is as stated above made difficult by the presence in the generator exhaust gases of droplets of molten slag and/or particulate solids. In the instant invention, the molten slag droplets are partially solidified and removed before they encounter heat exchange surfaces.By partially solidifying the slag particles before they impinge on solid surfaces, and/or by removing particulate solids entrained in the gas stream common problems with fouling of gas coolers are avoided. Solid surfaces are removed from the point of inception of slag cooling. Comparatively, simple low cost gas coolers are employed for heat exchange. By means of the subject invention, the recovery of thermal energy from the hot gases is facilitated.

While these specific gas cooler systems for energy recovery could be used to process the hot raw effluent gas stream from almost any type of gas generator, they are particularly suitable for use downstream of a partial oxidation gas generator. An example of such a gas generator is shown and described in coassigned U.S. Patent No. 2,871,114, which is incorporated herewith by reference. A burner is located in the upper portion of the gas generator for introducing the feedstreams. A typical annulus type burner is shown in coassigned U.S. Patent No. 2,928,460.

The free-flow unobstructed reaction zone of the gas generator is contained in a vertical cylindrical steel pressure vessel line on the inside with a thermal refractory material. Preferably, the pressure vessel may comprise the following three communicating sections: (1) reaction zone, (2) gas diversion chamber, and (3) quench chamber. The central vertical axes of the three sections are preferably coaxial.

Alternately, said three sections may be contained in two or three separate pressure vessels connected in series. In the main embodiment, the reaction zone is located in the upper portion of a pressure vessel; the gas diversion chamber is located about in the centre portion of the same vessel; and, the quench chamber is located in the bottom portion of the same vessel below the gas diversion chamber.

In the gas diversion chamber, a portion of the molten slag and/or particulate matter, separate out by gravity from the hot gas stream and pass through a bottom outlet into the quench chamber. The main gas stream is diverted away from the inlet to the quench chamber which is located below the gas diversion chamber and into a side exit passage. The quench chamber contains water for quench cooling the slag and/or particulate matter i.e., unconverted carbon, ash. Slag, particulate matter, and water are removed from the bottom of the quench chamber by way of an outlet in the bottom of the vessel.

In operation, the hot raw gas stream produced in the reaction zone, leaves the reaction zone by way of a centrally located outlet in the bottom of the reaction zone which is coaxial with the central longitudinal axis of the gas generator. The hot gas stream passes through said bottom outlet and expands directly into the diversion chamber which is preferably located directly below the reaction zone. The velocity of the hot gas stream is reduced and molten slag and/or particulate matter drop out of the gas stream. This solid matter and/or molten slag move by gravity through an outlet located in the bottom of the diversion chamber into the pool of water contained in the quench chamber located below.From about 0 to 20 vol. %, such as 0.5 to 1 5 vol. %, of the raw gas stream may be drawn through the bottom outlet in the diversion chamber as a stream of bleed gas, thereby carrying said separated portion of molten slag and/or particulate matter with it. The partially cooled bleed gas stream is removed from the quench chamber by way of a side outlet and a cooled control valve. The hot bleed gas stream passing through the bottom outlet in the gas diversion chamber prevents solids from building up and thereby bridging and plugging the bottom outlet. Preferably, said bottom outlet in the diversion chamber is centrally located and coaxial with the vertical axis of the diversion chamber.

Preferably, the quench chamber is located directly below the bottom outlet in the diversion chamber.

The shape of the diversion chamber may be cylindrical, or it may be outwardly diverging or expanding conically from the entrance to an enlarged central portion followed by an inwardly converging or converging conically portion to the bottom and side outlets.

At least a portion i.e. about 80.0 to 100 vol. % of the hot gas stream entering the diversion chamber is directed by the internal configuration of the diversion chamber, which may optionally include baffles, into a refractory lined side exit passage that is connected to an antechamber. The angle between this side exit passage and the longitudinal axis of the antechamber is in the range of about 300 to 1350, such as about 450 to 1050, say about 600, measured clockwise from the central vertical axis of said antechamber starting in the third quadrant. There is substantially no drop in temperature or pressure of the gas stream as it passes through the gas diversion chamber.

The hot raw gas stream leaving the diversion chamber by way of the refractory lined passage enters directly into the inlet to the above described apparatus for cooling and cleaning the hot raw stream of gas (hereinafter termed "the antechamber") where additional entrained slag and/or particulate matter are removed, and, optionally the gas stream is partially cooled. Fouling of the boiler clean gas is discharged through an outlet at eho top of the upper chamber. In still other embodiments, one and two stage cyclones are arranged external to the upper chamber, with or without the inclusion of cyclones inside the upper chamber. For a more detailed discussion of cyclone and impingement separators, reference is made to Chemical Engineers Wandbook--Pzrry and Chilton, Fifth Edition 1973 McGraw-Hill Book Co.Pages 20-80 to 20-87 which is incorporated herewith by reference.

A discharge pipe or dip leg extends downward within the pressure vessel from the bottom of the cyclone to preferably below the axes of the inlet nozzles in the bottom chamber, and below the highly turbulent area. Particulate solids that are separated in the cyclone may be thereby passed through the dip leg and discharged through a check valve in the dip leg into the bottom of the lower chamber below the zone of vigorous mixing. The dip leg may be removed from the path or the slag droplets by one or more of the following ways: keeping the dig leg close to the walls of the vessel, straddling the axis of the hot gas and quench gas inlet nozzles, or by putting ceramic dip legs in the refractory wall.

Alternately, the dip legs may be shortened to terminate any place above the top of the lower chamber.

The upward superficial velocity of the gas stream in the upper chamber and the diameter and height of the upper chamber, preferably shall be such that the inlet to the cyclone separator (or separators) is above the choke ring by a distance at least equal to the Transport Disengaging Height (TDH), also referred to as the equilibrium disengaging height. Above the TDH, the rate of decrease in entrainment of the solid particles in the gas stream approaches zero. Particle entrainment varies with such factors as viscosity, density and velocity of the gas stream; specific gravity and size distribution of the solid particles; and height above the choke ring. The velocityof the gas stream through the choke ring may vary in the range of about 2 to 5 ft. per sec.The velocity or the gas stream through the upper chamber basis net cross section may vary in the range of about 1 to 3 ft. per sec. The transport Disengaging Height may vary in the range of about 10 to 25 feet. Thus for example, if the velocity of the gas stream is about 3.5 ft./sec through the hoke ring and about 2 ft./sec basis total cross section of the upper chamber or 2.5 ft./sec. basis net cross section of the upper chamber, then, the Transport Disengaging Height may be about 1 5 to 20 feet in an upper chamber having an inside diameter of about 10 to feet.

The gas stream leaving from the plenum chamber at the top of the cyclone separators passes through an outlet in the upper portion of the upper chamber at a temperature in the range of about 1200 to 1 8000F. The pressure drop of the stream of synthesis gas passing through the subject gassolids separation system is less than about 5 psi. The concentration of solids in the exit gas stream from the separation vessel is in the range of about 30 to 700 Mgm per SCF. A portion of this gas stream is subjected to additional cooling and with or without further cleaning downstream by conventional means in order to produce the previously discussed recycle stream of quench gas. For example, a conventional gas-solids separation means may be inserted in the line downstream from the gas-gas quench cooling and solids separation apparatus.This gas-solids separation means may be selected from the group single and multi-stage cyclones, impingement separator, filter, electrostatic separator, and combinations thereof.

Advantageously, by the subject apparatus from about 85 to 95 wt. , of the entrained solid matter and slag may be removed from the hot raw gas stream leaving the partial oxidation gas generator while reducing the temperature of the gas stream to a temperature that the downstream apparatus for recovering energy from the hot gas stream will tolerate. Preferably, no liquid scrubbing fluid is employed. By this means the sensible heat in the hot gas stream is not wasted by vaporizing scrubbing fluid, which may then contaminate the gas stream. Rather, the sensible heat remaining in the cleaned gas stream leaving the subject apparatus and with or without additional cooling, cleaning or both downstream may be recovered in a convection type waste heat boiler located downstream.Thus, H20 or boiler feed water may be thereby converted into steam by indirect heat exchange. The steam may be used elsewhere in the process i.e., for heating purposes, for producing power, or in the gas generator. Alternatively, or additionally, energy recovery may be effected by other means. For example, a portion of the cooled and cleaned gas stream is passed through an expansion turbine for the production of mechanical energy, electrical energy, or both.

It should be noted that in some embodiments of processes according to the invention the amount of slag entrained in the hot raw gas stream entering the lower chamber of the above described apparatus for cleaning a raw gas stream is minimized or eliminated by control of the composition of the solid carbonaceous fuel and the temperature in the gasifier. In such case, the element of gas-gas impingement and quench cooling of the entering hot raw gas stream with a cooled and cleaned recycle gas stream may be advantageously minimized or completely eliminated. In such case the gas stream leaves the gas cleaning apparatus at substantially the same temperatures as that of the entering hot raw gas stream, less ordinary thermal losses. All other aspects of the antechamber are the same as that for the mode employing gas-gas quenching.

The present invention includes an improved continuous process for cooling and cleaning a hot raw gas stream principally comprising H2, CO, CO2 and one or more materials from the group H20, H2S, COS, CH4, NH3, N2, A and containing molten slag and/or entrained solid matter. The hot raw gas stream is made by the partial oxidation of an ash containing solid carbonaceous fuel, such as coal. By means of the subject invention the combustion residues entrained in the raw gas stream from the gas generator tubes in the main gas cooling section is thereby reduced, minimizing maintenance problems. The antechamber precedes the main gas cooling section.

In some embodiments in place of or in addition to the gas solids separation means located inside of the upper chamber of the antechamber, outside gas solids separation means may be located downstream from the antechamber and prior to the main gas cooling zone. The gas solids separation means located outside of the antechamber means may be selected from the group: single or multiple cyclone separators, gas solids impingement separators, filters, electrostatic precipitators, and combinations thereof.

In preferred embodiments of the invention, a main gas cooling zone, is located directly downstream from the antechamber or any solids separation means located after the antechamber. The temperature of the gas stream entering the main gas cooling zone is in the range of about 12000 to 30000 F, such as about 12000 to 1 8000 F, say about 1 6000 F. The concentration of solids in this gas stream is in the range of about 10 to 700 Mgr. per SCF. Next, most of the sensible heat in the gas stream is removed in the main gas cooling zone comprising one or more interconnected shell-andstraight fire tube gas coolers i.e. heat exchangers. Each gas cooler has one or more passes on the shell and tube sides, and preferably has fixed tube sheets.In comparison, with the gas coolers employed in the subject process, the conventional synthesis gas coolers for producing high pressure steam are of a spiral-tube, helical-tube, or serpentine-coil design. Gas coolers with such coils of tubes are difficult to clean and maintain; they are relatively expensive; and they tend to plug if the solids loading in the gas is significant. Costly down-time results when boilers with such coils require servicing. Advantageously, these problems are avoided in the subject process which employs one or more gas coolers each comprising a shell-and-a plurality of parallel straight fire tubes.

The gas coolers are preferably arranged in the subject process to provide two stages of cooling a first or high temperature stage, and a second or low temperature stage. In the first or high temperature stage a preferred embodiment comprises one shell-and-straight fire tube heat exchanger with fixed tube sheets, and with one pass on the tube and shell sides. The raw gas is on the tube-side and the coolant is on the shell-side. Inlet and outlet ends of the plurality of straight parallel tubes in the tube bundle contained in the pressure shell are supported on each end by a tube sheet. The tube ends are in communication with respective inlet and outlet i.e. front end and rear end, stationary heads. The inlet and outlet sections and inlet tube sheet are refractory lined.Metal or ceramic ferrels may also be used in the inlet tube sheet to provide additional thermal protection for the tubes. The first heat exchanger is sized as short as possible to facilitate cleaning the tubes and to minimize the thermal expansion stress imposed on the fixed tube sheets. The tube sheets themselves are designed to flex slightly to eliminate excessive thermal stress. The tube O.D. is in the range of 1.5 to 2.0 times the tube O.D. of the second stage cooler. This is done to minimize the possibility of plugging the exchanger. The gas velocity is set high enough to keep the fouling problems within an acceptable range.For further details of tube-side and shell-side construction of fixed-tube-sheet heat exchangers, see pages 11-5 to 11-6, Figure 11-2 (b), and pages 11-10 to 11-18 of Chemical Engineers' Handbook-Perry and Chilton-fifth Edition, McGraw-Hill Book Co., New York.

In some embodiments, the second or low temperature stage of the gas cooler may have two tube-side passes and one shell-side pass. This exchanger is designed similarly to the first stage gas cooler. However, in this exchanger smaller tubes may be used due to fewer plugging problems at lower temperatures. By this means, the surface area available for a given shell diameter may be increased.

For example, the tube diameters in the first stage gas cooler may be 3 inch O.D. while the second stage gas cooler may be 2 inch O.D.

The direction of the longitudinal axes of the straight fire tube heat exchangers may be horizontal, vertical, or a combination of both directions. However, preferably as shown in the drawing, the longitudinal axes of the shell-and-straight tube heat exchangers are vertical. This permits separating by gravity of entrained particulate solids from the gas stream, and easy removal of particulate matter from an outlet in the lower end of the gas cooler. Further, the inlet to the first stage gas cooler is preferably located directly above the antechamber, or any additional entrained solids removal means following the antechamber.

The prefered combination of shell-and-straight vertical fire tube heat exchangers with one and two tube-side passes and fixed tube sheets is shown in the drawing and will be described later in greater detail. In said embodiment, the hot gas stream is cooled in the first stage gas cooler to a temperature in the range of about 8000 to 1 2000F, such as 9000 to 11 000F, say about 10000 F, by indirect heat exchange with a coolant i.e. boiler feed water or steam. The hot gas stream passes through a bundle of parallel straight tubes. The single pass of straight tubes will distribute the thermal stresses equally over the fixed tube sheets. Next, the second stage cooler, the temperature of the gas stream is reduced to within about 150 to 900F, say to about 200F of the chosen steam temperature.

For example, the temperature of the gas stream leaving the second stage gas cooler is in the range of about 4500 to 5900F say about 5500 F. In the second stage gas cooler, by employing two passes on the tube-side, the length of the tubes is effectively increased for a given shell size. Savings in construction are thereby achieved. Multiple passes on the tube side are used to reduce thermal stresses on the fixed tube sheets due to expansion. Also, multiple tube passes will reduce plot area or elevations depending on the orientation of the exchanger.

In other embodiments the second or low temperature stage of the gas cooler may comprise one or more shell-and-straight fire tube heat exchangers with fixed tube sheets, and with one or more passes on the shell and tube sides. While the design of the second stage gas cooler(s) are similar in most respects to the design of the first stage gas cooler, smaller tubes may be used in a second stage gas cooler due to fewer plugging problems at lower temperatures. By this means, the surface area available for a given shell diameter may be increased. For example, the tube diameters in the first stage gas cooler may be 3 inch O.D. while those in a second stage gas cooler may be 2 inch O.D. In one preferred embodiment, two gas coolers are in the second stage. One of the gas coolers superheats saturated steam that is produced in the other gas coolers.In another embodiment, the superheater is located in the first stage.

The direction of the longitudinal axes of the shell-and-straight fire tube heat exchangers in the main gas cooling zone may be horizontal, vertical or a combination of both directions. However, preferably as shown in the drawling, the longitudinal axes of all the shell-and-straight tube heat exchangers are vertical. An upright position permits separation of entrained particulate solids from the gas stream by gravity, and easy removal of particulate matter from an outlet in the lower end of the gas cooler. Further, the inlet to the first stage gas cooler is preferably located directly above the antechamber, or any additional entrained solids removal means following the antechamber.

For producing superheated steam in the main gas cooling zone, the preferred combination of gas coolers comprises three interconnected shell-and-straight vertical fire tube heat exchangers with one or two tube-side passes, one shell-side pass, and with fixed tube sheets as shown in the drawing. The construction of these gas coolers will be described later in greater detail.In operation of the preferred embodiment, the hot gas stream at a temperaturn in the range of about 12000 to 30000 F, say about 12000 to 13000 F, say about 1 6000F and at a pressure in the range of about 10 to 200 atmospheres is passed in indirect heat exchange with boiler feed water up through the plurality of parallel straight tubes on the tube-side of the first upright gas cooler having one pass on the tube-side and shell-side.

The partially cooled gas stream leaves the first gas cooler at a temperature in the range of about 11 000F, to 20080F, such as about 11000 to 1 6000F, say about 1 2000F. The coolant i.e. boiler feed water (BFW) from a steam drum is introduced into the first gas cooler on the shell-side at a temperature in the range of about 500 to 6000F, say about 4900 to 6000F, say about 5700F and leaves as saturated steam at a temperature in the range of about 4300 to 6000 F, say about 4900 to 6000F, say 5700F. The saturated steam is stored in the steam drum.

At least a portion i.e. 50 to 100 vol. %, say about 80 to 100 vol. %, say 90 vol. % of the gas stream leaving the first gas cooler is introduced into the second upright gas cooler as the hot stream.

Preferably, the bulk of the hot gas stream from the first cooler is introduced into the straight tubes of the second gas cooler. The portion of the gas which by-passes the second cooler is set by the desired steam temperature leaving the second gas cooler. The hot gas stream is passed down through the plurality of parallel straight tubes of the one pass on the tube-side and shell-side second gas cooler in indirect heat exchange with saturated steam and leaves at a temperature in the range of about 8500 to 17500 F, say about 8500 to 13500 F, say about 9500 F. At least a portion, i.e. about 80 to 100 vol. %, say about 90 vol. % of the saturated steam produced by the process and stored in the steam drum is introduced into the second gas cooler on the shell-side as the coolant.Superheated steam is removed from the second gas cooler with about 1000 to 4700 F, say about 1000 to 41 00 F, say about 2800F of superheat. This by-product superheated steam may be used elsewhere in the subject process as a heating medium, or as the working fluid in a turbine for producing mechanical and/or electrical energy.

Excess superheated steam may be exported.

The partially cooled gas stream leaving the second gas cooler is mixed with the remainder of the partially cooled gas stream from the first gas cooler that by-passes the second gas cooler. This gas stream at a temperature in the range of about 8000 to 12000F, say about 1 0000 F is passed through the plurality of parallel straight tubes of the two pass on the tube-side one pass on the shell-side upright third gas cooler in indirect heat exchange with boiler feed water. The gas stream passes up through the tubes in the first tube-side pass and then down through the tubes in the second tube-side pass.The partially cooled gas stream leaves the third gas cooler at a temperature in the range of about 4500 to 7000F, say about 5100 to 7000 F, say about 5900 F. The pressure drop through the main gas cooling zone is about 1 to 10 psig. The coolant i.e. boiler feed water from the steam drum is introduced into the third gas cooler on the shell-side at a temperature in the range of about 500 to 6000F, and leaves as saturated steam at a temperature in the range of about 4300 to 6000F, say about 4900 to 6000F, say 5700 F. The saturated steam is stored in the steam drum. In the third gas cooler, by employing two passes on the tube-side, the length of the tubes is effectively increased for a given shell size. Savings in construction are thereby achieved. Multiple passes on the tube-side are used to reduce thermal stresses on the fixed tube sheets due to expansion. Also, multiple tube passes will reduce plot area or elevations depending on the orientation of the exchanger.

Ordinarily, superheated steam is made by heating saturated steam in a conventional externally fired heater. In one variation of the subject process, superheated steam leaving the second gas cooler, as previously described is passed through an externally fired heater where it receives additional heat.

By means of this combination of steam heaters, superheated steam may be produced at a higher temperature levels i.e. having from about 3000 to 570"F, say about 3000 to 5100F, say 4300F of superheat. Further, by this means the duty of the fired heater is minimized.

Optionally, as a temperature control on the superheated steam water may be injected into the superheated steam leaving the fired heater in order to lower the degree of superheat, while the fuel rate to the fired heater is adjusted.

The second and third gas coolers in the low temperature stage are designed to withstand a maximum inlet gas temperature. If for example, the tubes of the first gas cooler in the high temperature stage are fouled so that the temperature of the gas stream exiting from the first gas cooler goes up, than an optional emergency steam injection circuit has been provided to protect the second and third gas coolers from being damaged. Thus, when the inlet gas temperature exceeds a safe maximum temperature, a temperature transmitter in the gas inlet line to either or both gas cooler signals a temperature controller to open a valve in the auxiliary high pressure steam line. The control valve opens and steam is injected into the hot gas stream, thereby lowering its temperature.

In the subject process, the term "fire tube" means that the hot gas always passes through the bank of parallel straight tubes of the gas cooler. The coolant passes on the shell-side. The internal flow of the coolant within the gas cooler is controlled by such elements as: one or more inlet and exit nozzles and their location; and the number, locations, and design of transverse baffles, partitions and weirs. Besides directing the shell-side coolant through a prescribed path, baffles are commonly used to support the straight tubes within the tube bundle.

Small diameter tubes (1 to 4 inch O.D.) may be used in the construction of the subject gas coolers. The tube diameter is chosen basis ecrlnornic analysis of its effect on heat transfer, pressure drop, fouling and plugging tendencies. Long tubes afford potential savings in construction at higher pressures as the investment per unit area of he3 transfer service is less for longer heat exchangers.

The gas and coolant flow velocities within the heat exchanger are limited so as to avoid destructive mechanical damage by vibration or erosion, to maintain an allowable pressure drop, and to control the buildup of deposits. For example, the velocity of the hot gas through the straight tubes may be in the range of about 40 to 55 ft./sec. for a 2 inch O.D. tube depending on the temperature and pressure at any given point in the exchanger. Larger diameter tubes are used when heavy fouling is expected, and to facilitate the mechanical cleaning of the inside of the tubes. Tube-to-tube sheet attachment may be accomplished by the combination of tube end welding and rolled expansion. The tubes may be arranged on a triangular, square, or rotated-square pitch.Center-to-center spacings tube pitch, baffle type and spacing are chosen to provide good coolant circulation avoiding hot spots on the inlet tube sheet. The heat exchanger's shell size is directly related to the number of tubes and to the tube pitch.

Generally, the shell of the heat exchanger used in the subject process is constructed from high grade carbon-steel. When high pressure steam is being generated or superheated, alloy steels may be employed to reduce the required shell thickness and to lower the equipment cost.

The inlet and outlet sections of the gas coolers will normally be made of alloy steels due to the temperature and hydrogen partial pressure in the raw gas. Tube materials will generally be alloy steel by similar reasoning; however, the last pass(es) of the second stage gas cooler may be carbon steel in some cases. Flow patterns between the shell and tube-side fluids include counter-current flow, cocurrent flow and combinations thereof.

Relevant factors affecting the size of the heat exchanger, and therefore the cost, include: pressure drop, gas composition, gas and coolant flow rates, log-mean-temperature difference, and fouling factors. An optimum heat-exchanger design is the function of many of the previously discussed interacting parameters.

While any suitable liquid or gaseous coolant may be passed on the shell-side of the gas coolers, boiler feed water (BFW) or steam are the preferred coolants. By this means, by-product saturated or superheated steam at a temperature in the range of about 5200 to 9000F, at pressures approaching 100 atm may be produced for use elsewhere in the system or for export.

The following advantages are achieved by passing the hot solids containing gas stream through the straight tubes of the subject gas cooler vs. conventional coiled tube synthesis gas coolers: (1) Heat Transfer-higher heat-transfer rates are obtained due to less fouling, (2) Fouling-velocities of the hot gases through the tubes tend to reduce fouling; straight tubes allow mechanical cleaning, (3) Pressure drop-lower pressure drop due to fewer bends and reduced possibility for plugging, and (4) Cost-lower fabrication cost due to a less complex design.

The stream of gas leaving the main cooling zone may be used as synthesis gas, reducing gas, or fuel gas. Alternately, the sensible heat remaining in the gas stream may be extracted in one or more economizers i.e. heat exchangers by preheating boiler feed water. Additional entrained particulate matter may be then removed from the gas stream by scrubbing the gas stream with water in a carbon scrubber. By this means the concentration of entrained solids may be further reduced to less than 2 Mgs per normal cubic meter. The clean gas stream leaving the carbon scrubber saturated with water may be then dewatered. Thus, the gas stream is cooled below the dew point by indirect heat exchange with boiler feed water or clean fuel gas. Condensed water is separated from the gas stream in a knockout drum.The condensate, optionally in admixture with makeup water, is returned to the carbon scrubber for use as the final stage scrubbing agent. The clean gas stream leaving from the top of the knockout drum is at a temperature in the range of about 2000 to 6000F, such as about 2750 to 4000 F, say about 3400 F. A portion of this clean gas stream in the range of about 0 to 80 vol. %, such as about 30 to 60 vol. %, say about 50 vol. % may be compressed to a pressure greater than that in the antechamber. The compressed gas stream may be recycled to the antechamber where it is introduced into the lower quench chamber as said recycle gas. The remainder of the cooled clean gas stream is removed from the top of the knockout drum as the product gas.

When a bleed gas stream is employed in the gas diversion chamber, it is also cooled and cleaned in the gas scrubbing zone along with the main gas stream. The bleed gas stream, which is split from the main gas stream in the gas diversion chamber, is passed through the bottom outlet of the gas diversion chamber, and then through a communicating dip tube which discharges under water. By this means the bleed gas stream and separated molten slag and/or particulate solids are quenched in a pool of water contained in the bottom of the quench chamber. The quench water may be at a temperature in the range of about 50 to 600"F. Optionally, the hot quench water on the way to a carbon recovery facility may be used to preheat one or more of the feed streams to the gas generator by indirect heat exchange.The bleed gas stream, after being quenched, is at a temperature in the range of about 200 to 6000F.

A wide range of ash containing combustible carbonaceous solid fuels may be used in the subject process. The term solid carbonaceous fuel as used herein to describe various suitable feed stocks is intended to include (1) pumpable slurries of solid carbonaceous fuels; (2) gas-solid suspensions, such as finely ground solid carbonaceous fuels dispersed in either a temperature moderating gas, a gaseous hydrocarbon, or a free-oxygen containing gas; and (3) gas-liquid-solid dispersions, such as atomized liquid hydrocarbon fuel or water and solid carbonaceous fuel dispersed in a temperature-moderating gas, or a free-oxygen containing gas. The solid carbonaceous fuel may be subjected to partial oxidation either alone or in the presence of a thermally liquefiable or vaporizable hydrocarbon or carbonaceous materials and/or water.Alternately, the solid carbonaceous fuel free from the surface moisture may be introduced into the gas generator entrained in a gaseous medium from the group stream, CO2, N2, synthesis gas, and a free-oxygen containing gas. The term solid carbonaceous fuels includes coal, such as anthracite, bituminous, sub-bituminous, coke, from coal and lignite; oil shale; tar sands; petroleum coke; asphalt; pitch; particulate carbon (soot); concentrated sewer sludge; and mixtures thereof.The solid carbonaceous fuel may be ground to a particle size in the range of ASTM El 1-70 Sieve Designation Standard (SDS) 1 2.5 mm (Alternative 1/2 in.) to 75 um (Alternative No. 200). Pumpable slurries of solid carbonaceous fuels may have a solids content in the range of about 25-65 weight percent (wt. %), such as 45-60 wt. %, depending on the characteristics of the fuel and the slurrying medium. The slurrying medium may be water, liquid hydrocarbon, or both.

The term liquid hydrocarbon, as used herein, is intended to include various materials, such as liquified petroleum gas, petroleum distillates and residues, gasoline, naphtha, kerosene, crude petroleum, asphalt, gas oil, residual oil, tar-sand and shale oil, oil derived from coal, aromatic hydrocarbons (such as benzene, toluene, and xylene fractions), coal tar, cycle gas oil from fluidcatalytic-cracking operation, furfural extract of coker gas oil, and mixtures thereof. Also included within the definition of liquid hydrocarbons are oxygenated hydrocarbonaceous organic materials including carbohydrates, cellulosic materials, aldehydes, organic acids, alcohols, ketones, oxygenated fuel oil, waste liquids and by-products from chemical processes containing oxygenated hydrocarbonaceous organic materials, and mixtures thereof.

The use of a temperature moderator to moderate the temperature in the reaction zone of the gas generator is optional and depends in general on the carbon to hydrogen ratio of the feed stock and the oxygen content of the oxidant stream. Suitable temperature moderators include H2O, CO2-rich gas, liquid CO2, a portion of the cooled clean exhaust gas from a gas turbine employed downstream in the process with or without admixture with air, by-product nitrogen from the air separation unit used to produce substantially pure oxygen, and mixtures of the aforesaid temperature moderators. A temperature moderator may not be required with feed slurries of water and solid carbonaceous fuel.

However, steam may be the temperature moderator with slurries of liquid hydrocarbon fuels and solid carbonaceous fuel. Generally, a temperature moderator is used with liquid hydrocarbon fuels and with substantially pure oxygen. The temperature moderator may be introduced into the gas generator in admixture with either the solid carbonaceous fuel, feed, the free-oxygen containing stream, or both.

Alternatively, the temperature moderator may be introduced into the reaction zone of the gas generator by way of a separate conduit in the fuel burner. When supplemental H20 is introduced into the gas generator either as a temperature moderator, a slurrying medium, or both, the weight ratio of supplemental water to the solid carbonaceous fuel plus liquid hydrocarbon fuel if any, is preferably in the range of about 0.2 to 0.50.

The term free-oxygen containing gas, as used herein is intended to include air, oxygen-enriched air, i.e., greater than 21 mol. % oxygen, and substantially pure oxygen, i.e., greater than 95 mol. % oxygen, (the remainder comprising N2 and rare gases). Free-oxygen containing gas may be introduced into the burner at a temperature in the range of about ambient to 12000 F. The atomic ratio of free oxygen in the oxidant to carbon in the feed stock (O/C, atom/atom) is preferably in the range of about 0.7 to 1.5, such as about 0.85 to 1.2.

The relative proportions of solid carbonaceous fuel, liquid hydrocarbon fuel if any, water or other temperature moderator, and oxygen in the feed streams to the gas generator are carefully regulated to convert a substantial portion of the carbon, e.g. at least 80 wt. % to carbon oxides e.g. CO and CO2 and to maintain an autogenous reaction zone temperature in the range of about 17000 to 31000F. For example, in one embodiment employing a coal-water slurry feed, a slagging-mode gasifier may be operated at a temperature in the range of about 23000 to 28000F. For the same fuel, a fly-ash mode coal gasifier may be operated at a lower temperature in the range of about 1700 to 2100 F. The pressure in the reaction zone is in the range of about 10 to 200 atmospheres.The time in the reaction zone in seconds is in the range of about 0.5 to 50, such as about 1.0 to 10.

The effluent gas stream leaving the partial oxidation gas generator has the following composition in mol. %: H2 8.0 to 60.0, CO 8.0 to 70.0, CO2 1.0 to 50.0, H20 2.0 to 50.0, CH4 0 to 30.0, H2S 0.0 to 2.0, COS 0.0 to 1.0, N2 0.0 to 85.0, and A 0.0 to 2.0. Entrained in the effluent gas stream is about 0.5 to 20 wt. % of particulate carbon (basis weight of carbon in the feed to the gas generator). Molten slag resulting from the fusion of the ash content of the coal, and/or fly-ash, bits of refractory from the walls of the gas generator, and other bits of solids may also be entrained in the gas stream leaving the generator.

By means of the subject process the following advantages are achieved: (1) About 90-99.9 wt.

% of the entrained molten slag and/or particulate matter in the hot raw gas stream leaving the partial oxidation gas generator may be removed. (2) Substantially all of the sensible heat in the hot raw gas stream leaving the partial oxidation gas generator is utilized thereby increasing the thermal efficiency of the process. (3) By-product steam is produced at a high temperature level. The steam may be used elsewhere in the process i.e., for heating purposes, for producing power, or in the gas generator.

Alternately, a portion of the by-product steam may be exported. (4) Molten slag and/or particulate matter from the solid carbonaceous fuel may be readily removed upstream from the gas cooler. Fouling of heat exchange surfaces is thereby prevented. (5) One or more comparatively low cost shell-andstraight fire-tube gas coolers are employed. The design of such gas coolers allows thermal stresses to be equally distributed over the tube sheets, simplifies tube cleaning and maintenance operations, and minimizes plot area and elevation.

Reference will now be made specifically to the drawings. Figure 1 shows an apparatus according to the invention for quenching cooling and cleaning a hot raw gas stream containing solid matter and slag and Figures 2 and 3 show respectively two plants utilizing such an apparatus. Similar components in the plants of Figures 2 and 3 have been given like reference numerals.

With reference to Figures 2 and 3, in line 1 a slurry comprising 1/4 inch diameter bituminous coal in water having a solids content of 40 wt. % is pumped by means of pump 2 through line 3 into heat exchanger 4. The temperature of the coal slurry is increased in heat exchanger 4 from room temperature to 2000F, by indirect heat exchange with quench water. The quench water enters heat exchanger 4 by way of line 5 and leaves by way of line 6 after giving up heat to the coal slurry. The heated coal slurry is then passed through line 7 and into the annulus passage 8 of burner 9. Burner 9 is mounted in upper inlet 10 of synthesis gas generator 11.Simultaneously, a stream of free-oxygen containing gas, such as substantially pure oxygen from line 1 2 is heated by indirect heat exchange with steam in heat exchanger 13, and passed into gas generator 11 by way of line 1 4 and the central conduit 1 5 of burner 9.

Synthesis gas generator 11 is a free-flow steel pressure vessel comprising the following principle sections; reaction zone 1 6, gas diversion chamber 1 7 and quench chamber 1 8. Reaction zone 1 6 and gas diversion chamber 17 are lined on the inside with a thermally resistant refractory material.

Alternately, these three sections may comprise two or more distinct and interconnected communicating units.

The vertical central axis of upper inlet 10 is aligned with the central vertical axis of the gas generator 11. The reactant streams impinge on each other and partial oxidation takes place in reaction zone 1 6. A hot raw gas stream containing entrained molten slag and/or particulate matter including unconverted carbon and bits of refractory passes through the axially aligned opening 1 9 located in the bottom of reaction zone 1 6 and enters into an enlarged gas diversion chamber 1 7. The velocity and direction of the hot gas stream are suddenly changed in diversion chamber 17. A small portion i.e.

bleedstream of the raw gas is, optionally, drawn through the bottom throat 20 of the gas diversion chamber 17, dip leg 21, and into water 22 contained in the bottom of quench chamber 18. By this means outlet 20 is kept open, a portion of the molten slag and/or particulate matter is quench cooled, and the slag may be solidified. Periodically, solid particles and ash are removed from quench chamber 1 8 by way of lower axially aligned outlet 23, line 24, valve 25, line 26, lock hopper 27, line 28, valve 29, and line 30. Ash and other solids are separated from the quench water by means of ash conveyor 31 and sump 32. The ash is removed through line 33 for use as fill. Quench water is removed from the sump by way of line 34, pump 35 and line 36 and may be recycled to the quench chamber. A portion of the quench water is removed from the bottom of the quench chamber through outlet 37 and is introduced by way of line 5 into heat exchanger 4, as previously described. The cooled quench water containing carbon in line 6 is introduced into a conventional carbon removal facility (not shown) for reclaiming the quench water by way of line 38. The recovered carbon is then added to the coal slurry as a portion of the feed to the gas generator. Any bleed gas is removed from quench chamber 18 through side outlet 39, line 40, valve 41 and line 42.

The hot raw gas stream leaving diversion chamber 1 7 with a portion of the molten slag and/or particulate matter removed is diverted through refractory lined side exit passage 43 and is then upwardly directed through refractory lined transfer line 44, and inlet 45 of antechamber 46 as shown in more detail in Figure 1. Alternatively, in some embodiments such hot raw gas stream may be passed through a preliminary solids and slag removal means 1 lA, e.g. a conventional catch pot, before entering inlet 45 as illustrated diagrammatically in Figure 1. Antechamber 46 is a closed cylindrical vertical steel pressure vessel lined on the inside throughout with refractory 47 and includes coaxial lower solids separating chamber 48, coaxial upper solids separating chamber 49, and coaxial refractory choke ring 50.Choke ring 50 forms a cylindrically shaped passage of reduced diameter between lower chamber 48 and upper chamber 49. Antechamber 46 has a conical shaped bottom 51 that converges into refractory lined coaxial bottom outlet 52. Hemispherical dome 53 at the top of vessel 46 is equipped with refractory lined top outlet 54. Outlet 54 is coaxial with the vertical axis of vessel 46. A pair of refractory lined opposed coaxial inlet nozzles 45 and 55 extend through the vessel wall and are directed into lower chamber 46. The longitudinal axis of inlet nozzles 45 and 55 makes an angle in the range of about 300 and 1500 with and measured clockwise from the vertical central axis of vessel 46 and lies in the same plane. Preferred examples of said angle are about 450 and about 600. Inlet nozzle 45, for introducing a hot raw gas stream, is pointed upward.Inlet nozzle 55, for introducing a stream of clean and comparatively cooler recycle quench gas, is pointed downward. While only one pair of inlet nozzles is shown in the drawing, additional pairs may be included in the apparatus.

In the preferred embodiment, at least one cyclone 56, with its longitudinal vertical axis parallel or coaxial with the vertical axis of vessel 46, is supported within upper chamber 49. Each cyclone is resistant to heat and abrasion and has a gas inlet 57 near the upper portion of the upper chamber.

When multiple cyclones are employed, they may be uniformly spaced within the chamber. The face of rectangular inlet 57 of cyclone 56 is preferably parallel to the vertical axis of vessel 46. The inlet is oriented to face the direction of the incoming gas stream. Thus, the cyclone inlet or inlets may be oriented to continue the direction of swirl.

Cyclone 56 is of conventional design including a cylindrical body, a converging conical shaped bottom portion, reverse chamber, outlet plenum which connects into upper outlet 54, dipleg 58, and a check valve near the bottom end of the dipleg. Dipleg 58 may be off-set to pass close to the walls of vessel 46 and thereby avoid intersecting the common longitudinal axis of inlets 45 and 55. By this means contact and build-up on the dipleg of uncooled slag particles are avoided. Cooled clean synthesis gas is discharged through top outlet 54. Particulate solids are discharged through bottom outlet 52 by way of line 59, valve 60, and line 61 and pass into a lock-hopper, not shown.

Optionally, from about 1 to 4 tangential quench gas inlets 62 are evenly spaced around the circumference of vessel 46, for example, near the top of the lower chamber 48 and/or the bottom of the upper chamber 49. By this means, a supplemental amount of cooled clean recycle quench gas may be introduced into vessel 46. The spiraling clockwise direction of the stream of recycled gas helps to direct all of the gases in the vessel upwardly. It also maintains a cool gas stream along the wall of vessel 46 which protects the refractory lining. The cooled clean recycled gas stream that may be introduced into inlet 55 and optionally into said tangential inlets 62 comprises at least a portion of the cooled clean gas stream from line 63.

If it is desired to further reduce the solids concentration or the size of the particulate solids in the gas stream leaving antechamber 46 by way of top outlet 54, then the gas stream in line 64 may be optionally introduced into a conventional solids separation zone 64A which may be located outside of antechamber 46. Cyclones, impingement separators, bag filter, electrostatic precipitators, or combinations thereof may be used for this purpose. These are located downstream from the antechamber and prior to the main gas cooling zone.

In the embodiment of Figure 2, most of the sensible heat in the gas stream leaving the antechamber is removed in the main gas cooling zone which in the preferred embodiment comprises two vertically disposed shell-and-straight fire tube heat exchangers 65 and 66 which are connected in series. Both gas coolers 65 and 66 have fixed tube sheets i.e. lower tube sheet 67 and upper tube sheet 68. While both gas coolers 65 and 66 have one-pass on the shell side, gas cooler 65 has onepass on the tube-side and gas cooler 66 has two-passes on the tube-side.

The hot gas stream from antechamber 46, or optionally from a supplemental solids removal facility (not shown) located downstream from antechamber 46, is cooled by being passed upwardly through lower inlet nozzle 69 into refractory lined lower stationary-head bonnet 70, past lower fixed tube sheet 67, through tube bundle 71 comprising a plurality of parallel straight vertical tubes located within shell 72, past upper fixed tube sheet 68, into upper stationary-head bonnet 73, through connecting passage 74 and into the left side 75 of upper stationary-head bonnet 76 of the second gas cooler 66. Central baffle 77 separates upper bonnet 76 into left side 75 and right side 78.The gas stream on the left side 75 is passed by upper fixed tube sheet 68, down through the left bank of parallel straight tubes 79, through lower fixed tube sheet 67, into the bottom stationary-head bonnet 80, up through the right bank of parallel straight vertical tubes 51, into the right section 78 of upper stationary-head bonnet 76, and out through upper stationary-head exit nozzle 82 and line 83.

Particulate solids that fall into the bottom heads 70 and 80 respectively of gas coolers 65 and 66, are removed by way of bottom outlets, such as flanged nozzle 84 for gas cooler 66. A suitable arrangement for introducing a coolant, in this case boiler feed water, into each of the two gas coolers 65 and 66 is shown in the drawing. By-product steam is produced in gas coolers 65 and 66 and is collected in steam drum 90. Boiler feed water from drum 90 is passed through line 91 and inlet nozzle 92 into the shell-side of gas cooler 65. Steam is removed from gas cooler 65 through outlet nozzle 93, and passed into steam drum 90 by way of line 94. Similarly, boiler feed water from steam drum 90 is passed through line 95 and inlet nozzle 96 into the shell-side of gas cooler 66. Steam is removed from gas cooler 66 through outlet nozzle 97 and is passed into steam drum 90 by way of line 98.Preheated boiler feed water is introduced into steam drum 90 through line 99. Saturated steam is removed from steam drum 90 by way of line 100. This steam may be used elsewhere in the process, for example, as the heating medium in heat exchanger 13, or as the temperature-moderator in gas generator 11, or as the working fluid in a steam turbine (not shown) for the production of mechanical and/or electrical power. Alternately, the saturated steam may be superheated.

Additional entrained solids and sensible heat are removed from the gas stream leaving the second gas cooler by way of outlet 82 and line 83, by passing the gas stream through economizer 101, line 102, and into carbon scrubber 103.

In the embodiment of Figure 3, most of the sensible heat in the gas stream leaving the antechamber is removed in the main gas cooling zone which in the preferred embodiment comprises three vertically disposed shell-and-straight fire tube heat exchangers 65, 66 and 67. These three gas coolers have fixed tube sheets i.e. upper tube sheets 68 and lower tube sheets 69. While gas coolers 65 and 66 have one-pass on the tube side End shell-side, gas cooler 67 has two passes on the tubeside and one pass on the shell-side.

The hot gas stream from antechamber 46, or optionally from a supplemental solids removal facility (not shown) located downstream from antechamber 46, is cooled by being passed upwardly through line 64 and lower inlet nozzle 70 of gas cooler 65 into refractory lined lower stationary-head bonnet 71, past lower fixed tube sheet 69, through tube bundle 72 comprising a plurality of parallel straight vertical tubes located within shell 73, past upper fixed tube sheet 68, into upper stationaryhead bonnet 74, through upper outlet 75, and line 76. The coolant in gas cooler 65 is boiler feed water and saturated steam. Boiler feed water in steam drum 77 is pumped by means of pump 78 through lines 79 to 81, and lower inlet 82 into the shell-side of gas cooler 65. Saturated steam leaves the shellside of gas cooler 65 through upper outlet 83 and passes into steam drum 77 by way of line 84.At least a portion of the saturated steam leaves steam drum 77 through line 85 and is passed into gas cooler 66 as the coolant by way of line 86 and inlet 87. The remainder of the saturated steam, if any, is passed through line 88, valve 89 and line 90. Advantageously, this steam may be used in the process or exported. For example, a portion of this steam may be used as the heating fluid in heat exchanger 13.

Most of the partially cooled stream in line 76 is passed into upright gas cooler 66 as the heating medium to superheat saturated steam by indirect heat exchange. The gas enters by way of line 91, valve 92, line 93 and upper inlet 94 into upper bonnet 95. The gas is then passed on the tube-side through upper tube sheet 68, down through the bundle of straight parallel tubes 96 within shell 97, past lower tube sheet 69, through lower bonnet 98, and out through lower outlet 99 and line 100.

Saturated steam in line 86 is passed through inlet 87 of gas cooler 66, and then upwardly on the shellside. By-product superheated steam is removed through upper outlet 461, lines 462, 463, valve 464, and line 465. The by-product superheated steam may be used within the subject process, for example, as the working fluid in an expansion turbine for the production of mechanical power or electrical energy.

In another embodiment, at least a portion of the superheated steam in line 462 is passed through line 166, valve 167, and line 1 68 into externally fired heater 1 69 where the temperature of the superheated steam feed is increased. By-product superheated steam, at a higher temperature level, leaves heater 1 69 through lines 1 70 and 1 71. The superheat temperature of the steam may be controlled by water injection through line 172, valve 1 73, and line 174.

In one embodiment, the gas stream leaving gas cooler 65 is used as a trim control in order to increase the temperature of the gas stream leaving gas cooler 66 through line 103. This may be accomplished by passing a small portion of the gas stream in line 76 through line 175, valve 1 76, line 177, and mixing the two gas streams in line 1 78.

Additional saturated steam may be made in gas cooler 67 by passing the gas stream in line 1 78 through line 179, lower inlet 180 into the left side 181 of lower bonnet 182, up past lower fixed tube sheet 69, up through the left pass on the tube-side 1 83, into upper bonnet 184, down through the right pass on the tube-side 185, into the right side 1 86 of lower bonnet 1 82, and out through lower outlet 1 87 and line 1 88. The gas stream passes in indirect heat exchange with a portion of the boiler feed water in line 80 from steam drum 77. The boiler feed water is passed through line 200, valve 201, line 202 and lower inlet 203 into the one-pass shell side of gas cooler 67.Saturated steam leaves gas cooler 67 through upper outlet 204 and is passed through line 205 into steam drum 77.

Particulate solids that fall into lower bonnets 71, 98, and 182 respectively of gas coolers 65, 66 and 67 may be removed by way of bottom outlets, such as flanged outlet 206 for gas cooler 67.

An emergency steam injection system is provided to control the temperature of the gas stream entering gas coolers 66 and 67. Thus, the temperature of the gas stream entering gas cooler 66 through line 93 is measured and a temperature transmitter signals temperature controller 1 90 to open valve 191 which controls the quantity of steam from lines 192 and 1 93 that is required to cool the gas stream from line 76.

Similarly, the temperature of the gas stream entering gas cooler 67 through line 179 is measured and a temperature transmitter signals temperature controller 194 to open valve 195 which controls the quantity of steam from lines 1 96 and 197, that is required to cool the gas stream from line 1 78.

Advantageously, the steam for operating the emergency steam injection system may be produced internally.

Additional entrained solids and sensible heat are removed from the gas stream leaving gas cooler 67 by way of outlet 1 87 and line 188, by passing the gas stream through economizer 101, line 102, and into carbon scrubber 1 03.

In either embodiment, carbon scrubber 103 comprises a two section vertical vessel including upper chamber 104, and lower chamber 105. The gas stream in line 102 is passed through inlet 106 in lower chamber 105, and then through diptube 107 into water-bath 108 contained in the bottom of lower chamber 1 05. The once-washed gas stream leaves the lower chamber 105 by way of outlet 109, and is passed through lines 110 and 111 into venturi scrubber 112. There the gas stream is scrubbed with water from line 11 6. The scrubbed gas stream from venturi scrubber 112 is passed into upper chamber 104 by way of line 11 7 and inlet 11 8. By way of diptube 11 9, the gas stream is next introduced into and washed in waterbath 120.Before leaving upper chamber 104 by way of upper outlet 121 in the top of chamber 78, the gas stream may be given a final rinse by means of water spray 122 or by a wash tray (not shown). For example, condensate 123 from the bottom of knock-out drum 124 may be passed through line 125 and introduced through inlet 126 into spray 122. Water from pool 120 is passed through pipe 127, outlet 128, line 129, pump 130, lines 131 and 132, inlet 133, and pipe 134 into quench chamber 18. A portion of the water in line 131 may be recycled to lower chamber 105 of gas scrubber 103 by way of line 135, valve 136, lines 137 and 138, and inlet 139.

Another portion of water in line 137 is passed through line 140 and mixed in line 11 6 with make-up water from line 141, valve 142, and line 143. The water in line 116 is introduced into venturi 112 as previously described. Water containing dispersed solids 108 from the bottom of chamber 105 is passed through outlet 144, line 145, valve 146, line 147, and mixed in line 38 with the water dispersion from line 6. The water dispersion in line 38 is sent to a conventional carbon recovery facility (not shown) where water is separated from the entrained solids. The recovered water is returned to the system as make-up. The make-up water may be introduced at various locations, for example through line 141 as previously described.

The cleaned gas stream leaving upper chamber 104 of carbon scrubber 103 by way of upper outlet 121 and line 155 is passed through economizer 1 56 where it is cooled below the dew point. The wet gas stream passes through line 1 57 into knockout drum 1 24 where separation of the condensed water from the gas stream takes place. A cooled and cleaned stream of product gas leaves the top of knockout drum 124 by way of lines 1 58 and 1 59.Optionally but preferably when gasifier 11 is operated in the slagging mode, a portion of this cooled and cleaned product gas stream is passed through line 1 60, valve 1 61, line 162, gas compressor 1 63, and recycled as the stream of quench gas to lower chamber 48 of antechamber 46 by way of line 63 and inlet passage 55, and optionally through tangential gas inlets 62.

Make-up boiler feed water (BFW) for cooling shell-and-straight tube heat exchangers 65 and 66 is preheated by being passed through line 164, economizer 1 56 as the coolant, line 165, economizer 101 as the coolant, line 99, and into steam drum 90. From there the BFW is distributed to gas coolers 65 and 66, as previously described.

Other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed on the invention as are indicated in the appended claims.

Claims

1. A process for the partial oxidation of an ash-containing solid carbonaceous fuel for producing a cleaned stream of synthesis gas, fuel gas or reducing gas comprising: (1) reacting particles of said solid fuel with a free-oxygen containing gas and with or without a temperature moderator in a down-flow refractory lined gas generator at a temperature in the range of about 17000 to 31000F and a pressure in the range of about 10 to 200 atmospheres to produce a raw gas stream comprising H2, CO, CO2, and at least one material selected from the group consisting of H2O, H2S, COS, CH4, NH3, N2, and A, and containing molten slag and/or particulate matter;; (2) passing the raw gas stream through a thermally insulated transfer line and first gas inlet into the lower chamber of a gas-solids separation zone comprising a closed vertical cylindrical thermally insulated pressure vessel containing said lower chamber which is coaxial with the central vertical axis of said pressure vessel and in communication with a coaxial upper chamber, said lower and upper chambers being connected by a coaxial choke-ring passage, and wherein a portion of said slag and/or particulate matter settles out by gravity, and falls to the bottom of said lower chamber; (3) passing the mixture of gases from the lower chamber upwardly through said choke-ring into said upper chamber in counter-flow with slag droplets, and then into a gas-solids separation means, if any, located in said upper chamber;; (4) separating slag and/or particulate matter from said gas mixture in said upper chamber and removing same from said vessel by way of an outlet in the bottom of said lower chamber; and (5) removing cleaned gas from said upper chamber and discharging said gas through an outlet at the top of said vertical vessel.

2. A process according to Claim 1 provided with the added step of simultaneously passing an oppositely directed stream of cooled and cleaned recycle gas through a second gas inlet which is coaxial with said first gas inlet and into said lower chamber producing a turbulent mixture of gases when said streams impinge, wherein molten slag entrained in said hot gas stream cools below the initial deformation temperature, settles out by gravity, and falls to the bottom of said lower chamber.

3. A process according to Claim 2 provided with the added steps of introducing a portion of said cleaned gas stream from (5) with further cooling and with or without further cleaning downstream into the lower chamber in (2) as at least a portion of said recycle gas.

4. A process according to Claim 2 or Claim 3 wherein (2) said hot gas stream and said cooled and cleaned recycle gas stream are introduced into said lower chamber by way of a plurality of pairs of first and second coaxial opposed inlets.

5. A process according to Claim 4 wherein the longitudinal axis of said first and second coaxial opposed inlets is in the same plane as the central vertical axis of the vessel and said longitudinal axis makes an angle in the range of about 300 to 1 500 with and measured clockwise from said central vertical axis.

6. A process according to any of claims 2 to 5, with the added step of compressing said clean recycle gas stream to a pressure greater than that in the lower chamber prior to introducing same into the lower chamber in (2).

7. A process according to any preceding claim with the additional step of introducing a portion of cooled and cleaned gas stream into the top of the lower chamber and/or the bottom of the upper chamber by way of tangential inlets.

8. A process according to any preceding claim with the added step of introducing a portion of the cleaned gas stream from (5) into a gas cooler in indirect heat exchange with H20 and producing steam.

9. A process according to any preceding claim wherein the upper chamber in the gas solids separation zone in (2) is provided with at least one gas-solids separation means selected from the group consisting of single and multi-stage cyclones, gas impingement separator, filter, and combinations thereof.

10. A process according to any preceding claim provided with the added steps of passing the raw gas stream from (1) down through the central outlet in the bottom of the reaction zone and into a thermally insulated diversion chamber provided with a side outlet and a bottom outlet; separating by gravity molten slag and/or particulate matter from said gas stream; passing from about 0 to 20 vol. % of said gas stream as bleed gas along with said separated material through the bottom outlet of said diversion chamber and into a slag chamber located below said diversion chamber and passing the remainder of said gas stream through a side exit passage in said diversion chamber directly into said thermally insulated transfer line.

11. A process according to Claim 10 wherein said slag chamber contains a pool of quench water in the bottom.

12. A process according to Claim 11, wherein said separated molten slag and/or particulate matter with or without bleed gas is passed into said quench water by means of a dip tube.

13. A process according to any preceding claim, provided with the additional steps of cooling the gas stream from (5) in a main gas cooling zone and producing by-product steam by passing said gas stream in indirect heat exchange with preheated boiler feed water first upward through the tubes of a vertical high temperature shell-and-straight fire tube gas cooler having refractory lined inlet and outlet sections, one pass on the shell and tube sides and having fixed tube sheets, then passing the gas stream down through the tubes in the first tube-side pass of a vertical low temperature shell-andstraight fire tube gas cooler having two passes on the tube-side and one pass on the shell-side and having fixed tube-sheets, and then upward through the tubes in the second tube-side pass of said second gas cooler; and wherein by-product steam is removed from the shell-sides of said first and second gas coolers.

14. A process according to Claim 13, provided with the additional step of preheating said boiler feed water by indirect heat exchange with the gas stream leaving said second gas cooler.

1 5. A process according to Claim 14 further comprising the steps of scrubbing the cooled gas stream with water in the gas scrubbing zone producing a carbon-water dispersion, mixing together at least a portion of said carbon-water dispersion with or without concentration and addition of solids fuel to produce a solid fuel slurry, preheating, and gasifying said solid fuel slurry in the gas generator in step (1).

1 6. A process according to Claim 1 5 with the step of passing a portion of the cleaned gas stream after de-watering through an expansion turbine for the production of mechanical energy, electrical energy or both.

1 7. A process according to Claim 13 provided with the steps of simultaneously passing separate portions of preheated boiler feed water from a steam drum through the shell-sides of said high temperature and low temperature gas coolers and passing the steam produced thereby into said steam drurn; and removing by-product saturated steam from said steam drum.

1 8. A process according to any of claims 1 to 12 provided with the additional steps of cooling the gas stream from (5) in a main gas cooling zone and producing by-product saturated and superheated steam by passing said gas stream in indirect heat exchange with preheated boiler feed water first upward through the tubes in a first upright high temperature shell-and-straight fire tube gas cooler having refractory lined inlet and outlet sections, one pass on the shell and tube sides and having fixed tube sheets, then passing the gas stream in indirect heat exchange with saturated steam down through the tubes in a second upright shell-and-straight fire tube gas cooler having one pass on the tube-side and shell-side and having fixed tube sheets, and then passing the gas stream in indirect heat exchange with preheated boiler feed water up through the tubes in the first tube-side pass of a third gas cooler comprising an upright low temperature shell-and-straight fire tube gas cooler having two passes on the tube-side and one pass on the shell-side and having fixed tube sheets, and then down through the tubes in the second tube-side pass of said third gas cooler; and wherein saturated steam is produced on the shell-sides of said first and third gas coolers, and at least a portion of which is superheated on the shell-side of said second gas cooler to produce by-product superheated steam while the remainder, if any, is removed as by-product saturated steam; and preheating said boiler feed water by indirect heat exchange with the gas stream leaving said third gas cooler.

1 9. A process according to Claim 1 8 provided with the steps of simultaneously passing separate portions of preheated boiler feed water from a steam drum through the shell-sides of said first and third gas coolers and passing the steam produced thereby into said steam drum; and introducing at least a portion of the saturated steam from said steam drum into the shell-side of said second gas cooler.

20. A process according to Claim 18 wherein about 0 to SO vol. % of the gas stream leaving the first cooler by-passes the second gas cooler and is mixed with the gas stream leaving the second gas cooler.

21. A process according to any preceding claim provided with the step of removing additional solids from the cleaned gas stream from (5) in a second gas-solids separation zone located downstream from said gas-solids separation zone and selected from the group consisting of single and multi-stage cyclones, impingement separators, filters, electrostatic separators, and combinations thereof.

22. A process according to any preceding claim wherein said solid carbonaceous fuel is selected from the group particulate carbon, coal, coke from coal, lignite, petroleum coke, oil shale, tar sands, asphalt, pitch and mixtures thereof.

23. A process according to any preceding claim wherein said solid carbonaceous fuel is subjected to partial oxidation either alone or in the presence of substantially thermally liquefiable or vaporizable hydrocarbon and/or waten

24. A process according to any preceding claim wherein said solid carbonaceous fuel is introduced into the gas generator entrained in a gaseous medium from the group steam CO2, N2, synthesis gas, and air.

25. An apparatus for producing a hot gas stream comprising H2, CO, CO2, H20 and containing entrained solid matter and slag by the partial oxidation of solid carbonaceous fuel and cooling and cleaning said hot raw gas stream and separating therefrom entrained solid matter and siag comprising: (1) a partial oxidation gas generator for producing said hot gas stream; (2) a separate closed vertical cylindrical pressure vessel internally lined with high temperature resistant refractory with a coaxial lower gas-gas quench cooling and solids separation chamber in communication with a coaxial upper chamber; a coaxial choke-ring passage of reduced diameter connecting said lower and upper chambers; (3) a first gas inlet nozzle connected to said gas generator for introducing said hot raw gas stream into said lower chamber; a second gas inlet nozzle directly opposite and coaxial with said first gas inlet nozzle for simultaneously introducing into said lower chamber a cooled and cleaned gas stream; wherein said gas streams impinge, said hot raw gas stream is cooled by direct heat exchange with said cooled and cleaned gas stream to a temperature below the initial deformation temperature of said entrained slag, and solid matter and slag separate out by gravity and fall to the bottom of said lower chamber as the stream of cooled gas leaves the lower chamber and passes up through said choke-ring passage and into said upper chamber where additional solid matter and slag separate out and pass to the bottom of said lower chamber; (4) upper outlet means, in the upper portion of said upper chamber for discharging a cooled and cleaned gas stream; and (5) bottom outlet means in the bottom of said lower chamber for discharging said solid matter and slag.

26. Apparatus according to Claim 25 further including at least one gas-solids separation means supported in said upper chamber for receiving the mixture of gases passing, in use, up the vessel from (3) and removing additional solid matter therefrom and discharging that solid matter into said lower chamber.

27. Apparatus according to Claim 26 wherein said gas-solids separation means is a single-stage, or a multi-stage cyclone separator, or an impingement separator, or a filter or combinations thereof.

28. Apparatus according to any of claims 25 to 27 with at least one tangential inlet located in the upper portion of the lower chamber, or in the lower portion of the upper chamber, or in both locations for introducing a portion of cooled and cleaned recycle gas stream.

29. Apparatus according to any of Claims 25 to 28 where means are provided to introduce as said cooled and cleaned gas stream in (3), at least a portion of the cooled and cleaned gas stream from (4) with additional cooling and with or without additional cleaning downstream from said pressure vessel.

30. Apparatus according to any of Claims 25 to 29 the addition of a gas-solids separation means external to and downstream from said vessel to separate additional solids from the gas stream from (4).

31. Apparatus according to Claim 3Q wherein said gas-solids separation means external to the vessel is a single stage cyclone separator, or a multi-stage cyclone separator, or an impingement separator, or an electrostatic precipitator, or a filter, and/or combinations thereof.

32. Apparatus according to any of Claims 25 to 31 with a plurality of pairs of first gas inlets and coaxial second gas inlets in (3).

33. Apparatus according to any of Claims 25 to 32 wherein the longitudinal axis of said first and second gas inlets in (3) is in the same plane as the central vertical axis of the vessel and said longitudinal axis makes an angle in the range of about 300 to 1 500 with and measured clockwise from said central vertical axis.

34. Apparatus according to any of Claims 25 to 33 with a preliminary solids and slag removal means connected between the outlet of said gas generator in (1) and the inlet to said first gas inlet nozzle in (3).

35. A process for the partial oxidation of an ash-containing solid carbonaceous fuel for producing synthesis gas, fuel gas or reducing gas, the process being substantially as hereinbefore described with reference to any Figure of the accompanying drawings.

36. Apparatus for producing a hot gas stream comprising H2, CO, CO2, H20 and containing entrained solid matter and slag by the partial oxidation of solid carbonaceous fuel and cooling and cleaning said hot raw gas stream and separating therefrom entrained solid matter and slag, the apparatus being substantially as hereinbefore described with reference to, and as illustrated in, any Figure of the accompanying drawings.