US2707148A

US2707148A - Process for pyrolytic cracking of hydrocarbons and gasification of coal

Info

Publication number: US2707148A
Application number: US210075A
Authority: US
Inventors: Kollgaard Reyner
Original assignee: Houdry Process Corp
Current assignee: Houdry Process Corp
Priority date: 1951-02-08
Filing date: 1951-02-08
Publication date: 1955-04-26
Anticipated expiration: 1972-04-26

Description

April 26,

R. PROCESS FOR PYROLYTIC CRACKING OF HYDROCARBONS KOLLGAARD 2,707,148

AND GASIFICATION OF COAL Filed Feb. 8. 1951 ATT N'EY United States Patent O PROCESS FOR PYROLYTIC CRACKING OF HYDROCARBONS AND GASIFICATION OF COAL Reyner Kollgaard, Media, Pa., assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application February 8, 1951, Serial No. 210,075

2 Claims. (Cl. 48-201) This invention relates to a process for the pyrolytic cracking of hydrocarbons, combined with gasification of coal.

In pyrolytic non-catalytic cracking of hydrocarbons the heat required for cracking the hydrocarbons is generally produced by combustion of a portion of the hyn drocarbons with air or the like, this portion of the hydrocarbon charge thus being lost for the production of gasoline or other cracking products desired.

It is an object of the invention to avoid such loss in hydrocarbon charge. It is another object of the invention, while avoiding such loss, to produce at the same time gaseous fuels as useful by-products of a combined pyrolytic cracking operation. Further objects and advantages of the invention will appear from the follow ing specification and the claims.`

According to the present invention the pyrolytic noncatalytic cracking of hydrocarbons is combined with gasification of coal in such a manner that on the one hand the heat required for cracking the hydrocarbons is furnished by burning the coal, while on the other hand water-gas is produced by treatment of the incandescent coal with steam. Preferably, this combined process is carried out in a semi-continuous system. For this purpose, fresh coal is passed through a combustion zone, ash being formed which is continuously or periodically re moved. Air is blown into this zone to form an incandescent layer or zone and to burn the coal, followed by steam blown in for producing water-gas and for purging. Thereafter, a hydrocarbon feed is passed counter-currently through the incandescent bed to crack the hydrocarbons, until the temperature of the bed reaches a practical minimum. On raising the temperature again by air blowing, the cycle of operations is resumed and repeated.

The invention will be more clearly understood by the Y.

subsequent detailed description of an example of execution, in connection with the accompanying drawing.

The single gure of the drawing shows a somewhat diagrammatic View, partly in section, of an apparatus suitable for carrying out the new process.

A cylindrical vertically elongated refractory lined reaction chamber 1 is provided at its lower end with an ash removal grate 2. Below the grate 2 the reaction chamber 1 ends in a funnel-shaped chamber 3 forming an ash pit. The funnel 3 ends in a solids-discharge pipe 4 provided with a valve 5 to control removal of the ashes. A pipe 6 is provided for steam to be blown into and through ash pit 3 controlled by a valve 7.

A manifold 8 communicates with the ash pit 3 proximate to its upper end below grate 2. Manifold 8 is connected with branch pipes 9, 10 and 11, which are adapted to be opened and closed by valves 12, 13 and 14, respectively, which may be suitably coupled with one another in such a manner that only one of them can be open at a time. Pipe 9 serves for introducing the hydrocarbon feed into the apparatus, pipe 10 for blowing steam to purge manifold 8 and pipe 11 for introducing air from a blower.

A pipe 15 near the upper end of reaction chamber 1, provided with a control valve 16, forms an outlet for the hydrocarbon cracking eiuent, while another similarly arranged pipe 17, controlled by valve 18, forms an out* let for the flue and water-gas.

Coal is introduced into reaction chamber 1 by gravity from a funnel, or the like chamber 19 through a conduit` 20, forming a seal leg to prevent escape of vapors and gases from chamber 1 to chamber 19. A pipe 21 opening in the dome 22 of chamber 1 allows the introduction of seal steam into the top of this chamber above a partition 23. The coal charge introduced through seal leg 2) gravitates from partition 23 through a number of vertical open pipes 24 circularly arranged at said partition 23 and depending from it into reaction chamber 1 to a level below the mouths of pipes 15 and 17.

1n a typical operation of the process according to the invention, the lower portion of reaction chamber 1 below the lower ends of pipes 24 is filled with coal from funnel 19 through seal leg 20 and pipes 24 while all

valves

12, 13, 14 and 16 are closed and valve 18 only is open. Seal steam is then introduced through pipe 21 above partition 23.

Ignition and combustion of the coal in chamber 1 can be started in any suitable manner, e. g. by means of gas burners (not shown) arranged above grate 2, or by means of an electric heating device (not shown), which may be arranged correspondingly; or, if desired, by introducing pre-heated air through pipe 11, said air being at a temperature high enough to ignite the coal. Such ignition will start, for example, at a temperature of at least about 800 F., depending on the type of coal employed. Once started, the whole process can be generally run automatically, Without further requiring any interior heating devices or the like.

The combustion of the ignited coal in the incandescent zone 25 of reaction chamber 1 by air blown in through pipe 11 and valve 14 proceeds for a predetermined time, for example for l() minutes, while valve 18 of pipe 17 is open to allow the gases of combustion to escape. The heat of these gases can be used for pre--heating the air to be blown into chamber 1 and/or the steam'to be employed, or for heating a waste-heat boiler, and/ or for preheating the hydrocarbon charge to be cracked. After initial start-up of the operation, producer gas formed by subsequent passage of air through reactor Il, may be separately collected as a valuable byproduct.

At the end of the coal combustion period, valve 14 is closed and valve 13 of pipe 10 is opened to purge manifold 8 by steam. After closing valve 13, valve 7 of pipe 6 is opened to blow steam through ash pit 3, upward through the ash layer 26 resting on grate 2, and through the incandescent zone 25 above the ash layer 26. The steam pre-heated by the hot ashes reacts with the glowing coal in zone 25 to produce water-gas which passes through the coal layer 27 and through pipe 17, and. can be utilized for any desired purpose, e. g. in part for heating coal to ignition in the reaction chamber of an identical apparatus operated in parallel, and/ or for pre-heating the hydrocarbon feed.

When the water-gas producing period comes to an end after a predetermined time, say after 5 minutes, valves 7 and 18 of pipes 6 and 17 are closed, while valve 12 of pipe 9 and valve 16 of pipe 15 are opened. Hydrocarbons to be cracked are now passed from below grate 2, if desired pre-heated by the flue gases of combustion or by the sensible heat of hot water-gas produced, through reaction chamber 1 and are cracked while passing the incandescent Zone 2S under suitable cracking conditions, i. e. at a temperature of about 1000 to 1300 F. or more. While passing the zone 27 of fresh coal in reaction chamber 1, the cracking effluent formed is cooled and said fresh coal is simultaneously preheated.

At the end of the cracking period, say after about minutes, valve 12 of pipe 9 is closed again, while Valves 7 and 13 of pipes 6 and 10 respectively, are re-opened to purge the apparatus by steam, say for about 5 minutes, and valve 16 is closed while valve 18 is opened during this period.

Thereafter, valves 7 and 13 are closed and the cycle resumed with opening valve 14 of pipe 11 to re-heat the hot coal in zone of chamber 1 to incandescence by blowing air. Generally, no re-heating of the coal in this chamber by external heat will be required for this purpose, the temperature of the coal in zone 25 being still high enough at the end of the cracking period to effect its ignition and incandescence by the airblowing. The air may, however, be preheated in the afore-mentioned manner, if desired. Ashes formed above grate 2 are discharged to the pit 3 below, by actuating the grate in any suitable manner.

By arranging at least two identical apparatus of the described type parallel to each other and by suitably coupling them, care can be taken, that the cracking of hydrocarbons can proceed continuously without any interruptions, one of these parallel apparatus being switched, for example, for a minutes coal combustion period succeeding a 5 minutes steam flush and followed by another 5 minutes steam flush combined with water-gas production, while the other apparatus is switched for the pyrolytic cracking of hydrocarbon charge during 20 minutes, for example, and vice versa. On using three such apparatus coupled with one another and correctly predetermining the periods of combustion, repeated steam flushing, and cracking, care can be taken that the water-gas production, too, may go on continuously and without interruption.

Any suitable type of coal can be employed in the process, including hard and soft coal, as Well as de-gasified coal, or coke.

Practically all kinds of hydrocarbons or hydrocarbon mixtures can be employed as the hydrocarbon charge material, such as normally gaseous hydrocarbons, gasolines, light and heavy gas-oil fractions, petroleum residua, and the like; also fractions containing or composed of tar, so far as they are sufficiently uid or sufficiently fluidized or liquefied by pre-heating with the aid of the sensible heat of the flue-gases or the water-gas escaping through pipe 17, or in any other suitable manner.

The type of cracked products obtained will mainly depend on the type of hydrocarbon charge used and on the cracking conditions, particularly the temperature of the incandescent coal zone and the rate of flow of the hydrocarbon charge through this zone. Thus, gasoline, furnace oil, and the like can be produced and separated from the cracking effluent withdrawn from the reaction chamber.

Solid hydrocarbonaceous or carbonaceous deposits, called coke, which in known processes are generally formed by pyrolytic cracking of hydrocarbons and/ or tar, will not interfere in the present process. Any coke formed in the present process, will deposit on the coal in chamber 1 and will be burnt with this coal during a subsequent airblowing or water-gas producing period. Besides, steam can also be admitted to reaction chamber 1 during the cracking periods, if so desired, in order to reduce coke formation in vapor-phase cracking of the hydrocarbons.

The cracking effluent or a portion thereof, can be recycled for further cracking, if so desired.

Obviously many 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 as are indicated in the appended claims.

1. A combination process for effecting successively the gasification of coal and the pyrolitic, noncatalytic cracking of hydrocarbons in the presence of said coal which comprises the steps of: maintaining a confined treating zone partially filled with a grid-supported bed of said coal including an upper region containing fresh coal, an intermediate region containing incandescent coal derived from the combustion of said coal in the presence of oxygen-containing gas, and a lower region containing coal ash resulting from said combustion, uniformly distributing fresh coal over the surface of said bed from a distributing zone maintained immediately above said treating zone, maintaining a continuous supply of fresh coal to said distributing zone from a supply Zone located a substantial distance above said distributing zone, said fresh coal being conveyed between said supply and distributing zones as an elongated compact moving column forming a seal leg, removing coal ash from the bottom of said treating zone through said grid, the removal of said coal ash and the supply of said fresh coal being regulated to maintain a constant bed level within said treating zone, passing the coal ash discharged through said grid by free fall to the surface of a bed of coal ash partially filling a confined ash-receiving Zone located directly beneath said treating zone, discharging coal ash from the bottom of said ashreceiving zone at a rate adapted to constantly maintain said bed of coal ash therein, the foregoing steps being simultaneously accompanied by the sequential steps of: passing oxygen-containing gas upwardly through said gridsupported bed under conditions suitable for effecting the combustion of said coad, and removing the gaseous combustion products collected in the upper region of said treating zone above said grid-supported bed; passing steam upwardly through said ash-receiving and treating zones to purge the same of said gaseous combustion products and to form water-gas while passing through said intermediate region, said water-gas being removed from said gas-collecting region of said treating zone; passing hydrocarbons upwardly through said treating zone to pyrolytically crack the hydrocarbons, and removing the gaseous cracking products separately from said gas-collect ing region; again passing steam upwardly through said ashreceiving and treating zones to purge the same of said gaseous cracking products; and thereafter again passing oxy gen-containing gas upwardly through said grid-supported bed to reheat said coal to the desired stage of incandescence in preparation for a repeated cycle of operation.

2. A process as defined in claim 1, including the step of continuously introducing seal steam into said distributing zone in an amount sufficient to prevent the migration of gaseous material from said treating zone into and through said elongated compact moving column.

References Cited in the file of this patent UNITED STATES PATENTS 1,762,100 Odell June 3, 1930 1,875,923 Harrison Sept. 6, 1932 1,902,747 Yunker Mar. 21, 1933 1,947,339 Galusha Feb. 13, 1934 2,194,574 Snyder Mar. 26, 1940 2,406,810 Day Sept. 3, 1946 2,426,848 Tuttle Sept. 2, 1947 2,445,328 Keith July 20, 1948 2,514,371 Caldwell July 1l, 1950 2,547,015 Kirkbride Apr. 3, 1951 2,561,419 Schutte July 24, 1951 2,596,610 Shabaker May 13, 1952

Claims

1. A COMBINATION PROCESS FOR EFFECTING SUCCESSIVELY THE GASIFICATION OF COAL AND THE PYROLITIC, NON-CATALYTIC CRACKING OF HYDROCARBONS IN THE PRESENCE OF SAID COAL WHICH COMPRISES THE STEPS OF: MAINTAINING A CONFINED TREATING ZONE PARTIALLY FILLED WITH A GRID-SUPPORTED BED OF SAID COAL INCLUDING AN UPPER REGION CONTAINING FRESH COAL, AN INTERMEDIATE REGION CONTAINING INCANDESCENT COAL DERIVED FROM THE COMBUSTION OF SAID COAL IN THE PRESENCE OF OXYGEN-CONTAINING GAS, AND A LOWER REGION CONTAINING COAL ASH RESULTING FROM SAID COMBUSTION, UNIFORMLY DISTRIBUTING FRESH COAL OVER THE SURFACE OF SAID BED FROM A DISTRIBUTING ZONE MAINTAINED IMMEDIATELY ABOVE SAID TREATING ZONE, MAINTAINING A CONTINUOUS SUPPLY OF FRESH COAL TO SAID DISTRIBUTING ZONE FROM A SUPPLY ZONE LOCATED A SUBSTANTIAL DISTANCE ABOVE SAID DISTRIBUTING ZONE, SAID FRESH COAL BEING CONVEYED BETWEEN SAID SUPPLY AND DISTRIBUTING ZONES AS AN ELONGATED COMPACT MOVING COLUMN FORMING A SEAL LEG, REMOVING COAL ASH FROM THE BOTTOM OF SAID TREATING ZONE THROUGH SAID GRID, THE REMOVAL OF SAID COAL ASH AND THE SUPPLY OF SAID FRESH COAL BEING REGULATED TO MAINTAIN A CONSTANT BED LEVEL WITHIN SAID TREATING ZONE, PASSING THE COAL ASH DISCHARGED THROUGH SAID GRID BY FREE FALL TO THE SURFACE OF A BED OF COAL ASH PARTIALLY FILLING A CONFINED ASH-RECEIVING ZONE LOCATED DIRECTLY BENEATH SAID TREATING ZONE, DISCHARGING COAL ASH FROM THE BOTTOM OF SAID ASHRECEIVING ZONE AT A RATE ADAPTED TO CONSTANTLY MAINTAIN SAID BED OF COAL ASH THEREIN, THE FOREGOING STEPS BEING SIMULTANEOUSLY ACCOMPANIED BY THE SEQUENTIAL STEPS OF: PASSING OXYGEN-CONTAINING GAS UPWARDLY THROUGH SAID GRIDSUPPORTED BED UNDER CONDITIONS SUITABLE FOR EFFECTING THE COMBUSTION OF SAID COAD, AND REMOVING THE GASEOUS COMBUSTION PRODUCTS COLLECTED IN THE UPPER REGION OF SAID TREATING ZONE ABOVE SAID GRID-SUPPORTED BED; PASSING STEAM UPWARDLY THROUGH SAID ASH-RECEIVING AND TREATING ZONES TO PURGE THE SAME OF SAID GASEOUS COMBUSTION PRODUCTS AND TO FORM WATER-GAS WHILE PASSING THROUGH SAID INTERMEDIATE REGION, SAID WATER-GAS BEING REMOVED FROM SAID GAS-COLLECTING REGION OF SAID TREATING ZONE; PASSING HYDROCARBONS UPWARDLY THROUGH SAID TREATING ZONE BY PYROLYTICALLY CRACK THE HYDROCARBONS, AND REMOVING THE GASEOUS CRACKING PRODUCTS SEPARATELY FROM SAID GAS-COLLECTING REGION; AGAIN PASSING STEAM UPWARDLY THROUGH SAID ASHRECEIVING AND TREATING ZONES TO PURGE SAME OF SAID GASEOUS CRACKING PRODUCTS; AND THEREAFTER AGAIN PASSING OXYGEN-CONTAINING GAS UPWARDLY THROUGH SAID GRID-SUPPORTED BED TO REHEAT SAID COAL TO THE DESIRED STAGE OF INCANDESCENCE IN PREPARATION FOR A REPEATED CYCLE OF OPERATION.