US20150159097A1

US20150159097A1 - System and method for continuous slag handling with direct cooling

Info

Publication number: US20150159097A1
Application number: US14/103,714
Authority: US
Inventors: Hsien-Chin William Yen; Whitney Tolbert Norris; Raymond Douglas STEELE
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2013-12-11
Filing date: 2013-12-11
Publication date: 2015-06-11
Also published as: CN104711040A; AU2014271262A1; KR20150068318A

Abstract

A system includes a quench chamber configured to continuously receive a mixture of a gas and slag, and a downstream end portion coupled to the quench chamber. The quench chamber includes a quench sump configured to continuously separate the gas from the slag in the mixture via a quench liquid. The downstream end portion is configured to continuously convey a slag slurry to a depressurization system. The downstream end portion includes a cooling system configured to directly cool the slag slurry with a cooling fluid, and the slag slurry includes the separated slag and at least a portion of the cooling fluid

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT

This invention was made with Government support under contract number DE-FE0007859 awarded by the Department of Energy. The Government has certain rights in the invention.

BACKGROUND

The subject matter disclosed herein relates to a slag handling system, and, more particularly, to a continuous slag handling system.
An industrial process may utilize a slurry, or fluid mixture of solid particles suspended in a liquid (e.g., water), to convey the solid particles through the respective process. For example, partial oxidation systems may partially oxidize carbon-containing compounds in an oxygen-containing environment to generate various products and by-products. For example, gasifiers may convert carbonaceous materials into a useful mixture of carbon monoxide and hydrogen, referred to as synthesis gas or syngas. In the case of an ash-containing carbonaceous material, the resulting syngas may also include less desirable components, such as heavy ash or molten slag, which may be removed from the gasifier along with the useful syngas produced. Accordingly, the molten slag byproduct produced in the gasifier reactions may be directed into a gasifier quench liquid in order to solidify the molten slag and to create a slurry. Generally, this slurry is discharged from the gasifier at elevated temperatures and high pressures. The slurry discharged from the gasifier is depressurized to enable the disposal of, or the further processing of, the slurry. Unfortunately, heat exchangers that reduce the temperature of the slurry after discharge from the gasifier may have complex flow paths, may have relatively large foot prints, and/or may be susceptible to erosion or blockages due to slag accumulation.

BRIEF DESCRIPTION

Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In a first embodiment, a system includes a quench chamber configured to continuously receive a mixture of a gas and slag, and a downstream end portion coupled to the quench chamber. The quench chamber includes a quench sump configured to continuously separate the gas from the slag in the mixture via a quench liquid. The downstream end portion is configured to continuously convey a slag slurry to a depressurization system. The downstream end portion includes a cooling system configured to directly cool the slag slurry with a cooling fluid, and the slag slurry includes the separated slag and at least a portion of the cooling fluid.
In a second embodiment, a system includes a gasifier configured to react a carbonaceous feedstock into a mixture of a gas and slag. The gasifier includes a quench sump configured to continuously separate the gas from the slag in the mixture via a quench liquid, and the quench liquid is configured to flow through the quench sump at a first flow rate. The gasifier also includes a downstream end portion of the gasifier having a cooling system and a controller. The downstream end portion is configured to continuously convey a slag slurry to a depressurization system at a third flow rate approximately 15 percent or less of the first flow rate, the downstream end portion is configured to add a cooling fluid at a second rate to cool the slag slurry, and the slag slurry includes the slag and the cooling fluid.
In a third embodiment, a method includes separating slag from a gas, dispensing a cooling fluid into a downstream end portion of a gasifier, forming a cooled slag slurry from the slag and the cooling fluid, and conveying the cooled slag slurry substantially continuously through an exit of the downstream end portion. The temperature of the slag is greater than approximately 175 degrees C., and the cooling fluid is configured to decrease the temperature of the slag to less than approximately 70 degrees C.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic diagram of an embodiment of a continuous slag removal system;

FIG. 2 is a schematic diagram of an embodiment of a gasifier having a direct cooling system;

FIG. 3 is a cross-section of an embodiment of the direct cooling system, taken along line 3-3 of FIG. 2; and

FIG. 4 is a flowchart illustrating a process for continuously handling the slurry in accordance with an embodiment.

DETAILED DESCRIPTION

One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
Various industrial processes involve the handling of slurries. A slurry may include particulate solids dispersed in a fluid, such as water. In certain situations, the slurry is transported from a first location, or vessel, to a second location. The slurry may be depressurized and/or cooled during transport from the first location to the second location. For example, the reaction chamber of a partial oxidation system (e.g., a gasifier) may receive a carbonaceous feedstock (e.g., a slurry of carbonaceous particulate solids such as coal or biomass, a pneumatically-conveyed stream of particulate solids, a liquid, a gas, or any combination thereof) and an oxidant (e.g., high purity oxygen). In some embodiments, the reaction chamber may receive water (e.g., water spray or steam) to contribute to the slurry. The partial oxidation of the feedstock, the oxidant, and in some cases, the water, may produce a useful gaseous product and an ash or a molten slag byproduct. For example, a gasifier may receive the feedstock, the oxygen and the water to generate a synthetic gas, or syngas, and a molten slag. In certain cases, the molten slag may flow through the gasifier into a quench liquid, such as water, to create a slag slurry. The slag slurry discharged from the gasifier may be at a high gage pressure between approximately 1000 to 10,000 kilopascals (kPa). The slag slurry within the gasifier may be at a temperature between approximately 80 to 250 degrees C., (e.g., 175 to 475 degrees F.), between approximately 100 to 225 degrees C. (e.g., 212 to 440 degrees F.), or between approximately 150 to 200 degrees C. (e.g., 300 to 400 degrees F.) or more. Before the slag slurry is further processed or disposed of, the slag slurry may be depressurized to a lower pressure (e.g., atmospheric pressure). Depressurization of the slag slurry at elevated temperatures may cause vapor flash where at least a portion of the liquid (e.g., water) in the slag slurry evaporates. The disclosed embodiments discussed below cool the slag slurry to a temperature that substantially reduces the occurrence of vapor flash when the slag slurry is depressurized. For example, the disclosed embodiments may cool the slag slurry to a temperature less than approximately 70 degrees C. (e.g., 160 degrees F.). The slag slurry may be cooled without a heat exchanger or cooler downstream of the gasifier. The slag slurry is cooled upstream of the depressurization system by a cooling fluid (e.g., water). The cooling fluid may be injected into the slag slurry at a gage pressure greater than or approximately equal to the gage pressure of the slag slurry.
The disclosed embodiments convey the slag slurry in a continuous process, rather than a batch process. As may be appreciated, a continuous process may occupy less vertical space than a batch process (e.g., lock hopper) and may have lower costs than a batch process. In some embodiments, a continuous process may utilize less water than the batch process. Furthermore, as discussed in detail below, embodiments of the continuous process may increase control of the amount of water (e.g., cooling fluid) in the slag slurry relative to the batch process. Thus, the disclosed embodiments employ a depressurization system (e.g., liquid expansion system) to continuously remove the slag slurry and reduce the pressure, while also consuming less space. In some embodiments, the depressurization system generates power, such as via an expansion turbine. Therefore, certain embodiments may be referred to as slag slurry depressurizing systems, or more generally as slag slurry handling systems.
With the foregoing in mind, FIG. 1 is a schematic diagram of an embodiment of a continuous slag removal system 10. As shown in FIG. 1, the continuous slag removal system 10 may include a partial oxidation system, such as a gasifier 12, a slag slurry 14, a depressurization system 16 (e.g., liquid expansion system, one or more expansion turbines, one or more centrifugal pumps, one or more reciprocating devices, one or more orifice plates, or one or more let down valves), and a controller 18.
The partial oxidation system, or gasifier 12, may further include a reaction chamber 20, a quench chamber 22, and a downstream end portion 62. A protective barrier 24 may enclose the reaction chamber 20, and may act as a physical barrier, a thermal barrier, a chemical barrier, or any combination thereof. Examples of materials that may be used for the protective barrier 24 include, but are not limited to, refractory materials, non-metallic materials, ceramics, and oxides of chromium, aluminum, silicon, magnesium, iron, titanium, zirconium, and calcium. In addition, the materials used for the protective barrier 24 may be in the form of bricks, a castable refractory material, coatings, a metal wall, or any combination thereof. In general, the reaction chamber 20 may provide a controlled environment for the partial oxidation chemical reaction to take place. A partial oxidation chemical reaction can occur when a fuel or a hydrocarbon is mixed in an exothermic process with oxygen to produce a gaseous product and byproducts. For example, a carbonaceous feedstock 26 may be introduced to the reaction chamber 20 with oxygen 28 to produce an untreated syngas 30 and a molten slag 32. The carbonaceous feedstock 26 may include materials such as biofuels or fossil fuels, and may be in the form of a solid, a liquid, a gas, a slurry, or any combination thereof. The oxygen 28 introduced to the reaction chamber 20 may be replaced or supplemented with air or oxygen-enriched air. In certain embodiments, an optional slag slurrying agent 34 may also be added to the reaction chamber 20. The slag slurrying agent 34 may be used to maintain the viscosity of the slag slurry 14 within a suitable range and thus may aid in transporting the slag slurry 14 through the continuous slag removal system 10. In yet other embodiments, an optional moderator 36 (e.g., water or steam) may also be introduced into the reaction chamber 20. The chemical reaction within the reaction chamber 20 may be accomplished by subjecting the carbonaceous feedstock 26 to steam and oxygen at elevated gage pressures (e.g., from approximately 2000 to 10,000 kPa, or 3000 to 8500 kPa) and temperatures (e.g., approximately 1100 degrees C. to 1500 degrees C.) depending on the type of gasifier 12 utilized. Under these conditions, and depending upon the composition of the ash in the carbonaceous feedstock 26, the ash may be in the molten state, which is referred to as molten ash, or molten slag 32.
The quench chamber 22 of the partial oxidation system, or gasifier 12, may receive the untreated syngas 30 and the molten slag 32 as it leaves the reaction chamber 20 through the bottom end 38 (or throat) of the protective barrier 24. The untreated syngas 30 and the molten slag 32 enter the quench chamber 22 at a high pressure and a high temperature. In general, the quench chamber 22 may be used to reduce the temperature of the untreated syngas 30 and to disengage the molten slag 32 from the untreated syngas 30, and the quench chamber 22 may be used to quench the molten slag 32 to at least partially solidify the molten slag 32. In certain embodiments, a quench ring 40 arranged at the bottom end 38 of the protective barrier 24 is configured to provide a quench liquid 42 (e.g. water) to the quench chamber 22. The quench liquid 42 may be directed through a quench inlet 44 and into the quench ring 40 through a line 46. In general, the quench liquid 42 may flow through the quench ring 40 and down the inner surface of a dip tube 47 into a quench chamber sump 48. The controller 18 may control the flow rate of the quench liquid 42 through the quench inlet 44. For example, the controller 18 may control the flow rate of the quench liquid 42 to be between approximately 4,000 to 10,000 liters per minute (LPM) (e.g., approximately 1,050 to 2,640 gallons per minute (GPM)), approximately 5,000 to 9,000 LPM (e.g., approximately 1,320 to 2,375 GPM), or approximately 6,000 to 8,000 LPM (e.g., approximately 1,585 to 2,110 GPM).
The untreated syngas 30 and the molten slag 32 may also flow through the bottom end 38 of the protective barrier 24, and along the inner surface of the dip tube 47 into the quench chamber sump 48. As the untreated syngas 30 passes through the pool of quench liquid 42 in the quench chamber sump 48, the molten slag 32 is solidified and disengaged from the syngas, the syngas is cooled and quenched, and the syngas subsequently exits the quench chamber 22 through a syngas outlet 50, as illustrated by arrow 52. Syngas 54 exits through the syngas outlet 50 for further processing in a gas treatment system 56, where it may be further processed to remove acidic gases, particulates, etc., to form a treated syngas. Solidified slag 58 may accumulate at the bottom of the quench chamber sump 48 and may be continuously removed from the gasifier 12 as the slag slurry 14. In certain embodiments, a portion of the quench liquid 42 may also be continuously removed from the quench chamber sump 48 for treatment through a quench outlet 60. For example, particulates, soot, slag, and other matter may be removed from the quench liquid 42 in a black water treatment system, and the treated quench liquid 42 may be returned to the quench chamber sump 48 through the quench inlet 44. In such embodiments, the removed quench liquid 42 may have properties similar to the slag slurry 14 and thus, may be transported and depressurized using a liquid expansion system separate from or shared with the depressurization system 16 for the slag slurry 14.
The slag slurry 14 may have various compositions of solids suspended in the quench liquid 42, including, but not limited to, fuels (e.g., coals), dry char, catalysts, plastics, chemicals, minerals, and/or other products. The slag slurry 14 entering the downstream end portion 62 of the gasifier 12 may have a high pressure and a high temperature. For example, the gage pressure of the slag slurry 14 may be between approximately 1000 to 10,000 kPa, 2000 to 9000 kPa, or 3000 to 8000 kPa, and the temperature of the slag slurry 14 may be between approximately 150 to 350 degrees C. (e.g., 300 to 660 degrees F.), 200 to 300 degrees C. (e.g., 390 to 570 degrees F.), or 225 to 275 degrees C. (e.g., 435 to 525 degrees F.) or more. In some embodiments, the downstream end portion 62 is narrower than the quench chamber 22.
A cooling system 64 controls a flow of a cooling fluid 66 into the downstream end portion 62 via one or more nozzles 68 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more nozzles). In some embodiments, the cooling system 64 includes a heat exchanger, evaporation system, or refrigerant system to cool the cooling fluid to between approximately 10 to 70 degrees C. The cooling fluid 66 may be at a high gage pressure of between approximately 1000 to 10,000 kPa, 2000 to 9000 kPa, or 3000 to 8000 kPa, and a flow rate of the cooling fluid 66 may be between approximately 1 to 760 LPM (e.g., 0.25 to 200 GPM), 100 to 475 LPM (e.g., 26 to 125 GPM), or 190 to 380 LPM (e.g., 50 to 100 GPM). The flow rate of the cooling fluid 66 may be less than approximately 15 percent (e.g., 3 to 10 percent) of the flow rate of the quench liquid 42 into the quench chamber 22. For example, the quench liquid 42 flow rate may be approximately 7570 LPM, the cooling fluid 66 flow rate may be approximately 300 LPM, the slag 58 may flow through the downstream end portion 62 of the gasifier 12 with a flow rate of approximately 75 LPM, and the slag slurry 14 (e.g., the cooling fluid 66 and the slag 58) may flow through the downstream end portion 62 with a flow rate of approximately 375 LPM. The flow rate of the slag slurry 14 may be between approximately 2 to 15% of the flow rate of the quench liquid 42 into the quench chamber 22. In some embodiments, the temperature of the cooling fluid 66 may be between approximately 10 to 60 degrees C. (e.g., 50 to 140 degrees F.), 20 to 50 degrees C. (e.g., 70 to 125 degrees F.), or 30 to 40 degrees C. (e.g., 85 to 105 degrees F.). The cooling fluid 66 may include, but is not limited to, gray water, boiler feed water, raw makeup water, condensate, other water streams, or any combination thereof.
The cooling system 64 dispenses the cooling fluid 66 into the downstream end portion 62 to directly cool the slag slurry 14 that will be discharged from the gasifier 12. One or more streams (e.g., jets) of the cooling fluid 66 interface with slag 58 in the slag slurry 14, thereby decreasing the temperature of the slag slurry 14. While the quench liquid 42 cools the syngas 30 and the slag 32 that enters the quench chamber 22 from the reaction chamber 20, the cooling fluid 66 primarily cools the solidified slag 58 in the slag slurry 14. The cooling system 64 may be integrated with the downstream end portion 62 of the gasifier 12 and/or coupled directly to the downstream end portion 62 of the gasifier 12. In some embodiments, the nozzles 68 of the cooling system 64 may be arranged among and/or upstream of one or more slag crushers 70 that receive the slag slurry 14 from the downstream end portion 62.
As may be appreciated, certain designs of continuous slag removal systems 10 may include a cooler 72 (e.g., heat exchanger) for the slag slurry 14 and/or may dispense cold water 74 into the slag slurry 14 between the gasifier 12 and a depressurization system 16 (e.g., one or more let down devices). Presently contemplated embodiments of the continuous slag removal system 10 may cool the slag slurry 14 to less than approximately 70 degrees C. (e.g., approximately 160 degrees F.) without the cooler 72 or cold water 74 injection shown in the dashed box 78 downstream of the gasifier 12. Moreover, the cooling fluid 66 directly cools the solidified slag 58 and the slag slurry 14 in the downstream end portion 62 of the gasifier 12 rather than indirectly, such as when the slag slurry 14 is cooled via a cooler 72 (e.g. heat exchanger) downstream of the gasifier 12. The removal of the cooler 72 from the continuous slag removal system 10 may reduce the height and/or foot print of the continuous slag removal system 10. Furthermore, the removal of the cooler 72 from the continuous slag removal system 10 may reduce operational and/or installation costs. The tubes of the cooler 72 may be susceptible to accumulation of slag particulates that may restrict slag slurry flow, and/or the slag slurry may wear or corrode tubes in the cooler 72.
The controller 18 may receive signals from various sensors disposed throughout the continuous slag removal system 10. For example, flow rate sensors 80 measure flow rates of the quench liquid 42, the cooling fluid 66, and the slag slurry 14. One or more pressure sensors 82 and/or temperature sensors 83 may provide information regarding characteristics of the slag slurry 14, operating conditions within the continuous slag removal system 10, temperatures of the slag slurry 14, pressures of the slag slurry 14 at various sites, and so forth. In some embodiments, the controller 18 may receive additional sensor information about the slag slurry 14 as it exits the gasifier 12, such as, but not limited to, viscosity, particle size, and so forth. Furthermore, the controller 18 may adjust operational conditions of the continuous slag removal system 10 in response to received sensor information, as described in detail below.
In certain embodiments, one or more slag crushers 70 coupled to a slag crusher driver 84 (e.g., a steam turbine, the depressurization system 16, a motor, or other source of power) may optionally receive the slag slurry 14 before it is directed through the depressurization system 16. The one or more slag crushers 70 may crush the solidified slag 58 in the slag slurry 14 in order to attain a desired particle size distribution or a desired average particle size of particles in the slag slurry 14. The one or more slag crushers 70 may be arranged in one or more stages, and the one or more slag crushers 70 may be arranged in series or in parallel with one another. The one or more slag crushers 70 may include, but are not limited to, rotary screw crushers and toothed rotor slag crushers. Establishing an appropriate particle size distribution may be useful for enabling the slag slurry 14 to flow, for increasing the effectiveness of the cooling system 64, or for a desired flow through the depressurization system 16, or any combination thereof. Furthermore, the one or more slag crushers 70 may reduce the average particle size of the solids suspended in the quench liquid 42 and cooling fluid 66 of the slag slurry 14 to an appropriate range.
In certain embodiments, the one or more slag crushers 70 may reduce the particle size such that the average particle size is between approximately 0.5 to 26 mm (e.g., 0.02 to 1.0 inches), 2 to 8 mm (e.g., 0.08 to 0.31 inches), or 4 to 6 mm (0.16 to 0.24 inches. In one embodiment, the average particle size may be less than 2, 3, 4, 5, or 6 mm. In certain embodiments, a single slag crusher 70 may be sufficient to establish this average particle size, and in other embodiments, two or more slag crushers 70 may function together (e.g., in series and/or in parallel) to establish this average particle size. For example, a first slag crusher may provide a coarse crushing of the slag slurry 14, while a second slag crusher may provide a finer crushing of the slag slurry 14. In one embodiment, the controller 18 may control the slag crusher 70 by controlling the slag crusher motor 84. The controller 18 may adjust the slag crusher motor 84 based on information received from other sensors. In certain embodiments, a flow control valve 86 may be disposed downstream of the slag crusher 70 to adjust the flow rate of the slag slurry 14 flowing to the liquid expansion system 16. In one embodiment, the controller 18 may receive information about the flow rate of the slag slurry 14 from a flow rate sensor 80. In response to the information received by the flow sensor 80, the controller 18 may control the flow rate of the slag slurry 14 by adjusting the flow control valve 86. In other embodiments, the controller 18 may adjust the flow rate of the slag slurry 14 based on signals from other sensors 82, 83.
The slag slurry 14 may be fed into the depressurization system 16 to decrease the pressure of the slag slurry 14. In some embodiments, the depressurization system 16 is a turbomachine or expansion machinery, such as, but not limited to, an expansion turbine, a posimetric pump, a rotary screw pump, a modified centrifugal pump, a reciprocating device, a restriction orifice, a let down valve, or any combination thereof. A pressure sensor “P2” 82 may provide information on the pressure of the slag slurry 14 exiting the depressurization system 16. In some embodiments, the depressurization system 16 (e.g., turbine) may generate power (e.g., drive an electric generator) while depressurizing the slag slurry 14 from the pressure at pressure sensor “P1” 82. For example, the first gage pressure of the slag slurry 14, as measured by the first pressure sensor “P1” 82, may be between approximately 1000 to 10,000 kPa, 2000 to 9000 kPa, or 3000 to 8000 kPa, or approximately the high operating pressure of the gasifier 12. In contrast, the second gage pressure of the slag slurry 14, as indicated by the second pressure sensor “P2” 82, may be between atmospheric pressure (0 kPa) to 100 kPa, 20 to 80 kPa, or 40 to 60 kPa. In certain embodiments, the second pressure is approximately equal to atmospheric pressure. After exiting the depressurization system 16, the slag slurry 14 may travel further downstream to a slag processing system 88, such as for dewatering of the slag slurry 14, before the slag slurry 14 is disposed of.
FIG. 2 illustrates an embodiment of the downstream end portion 62 of the gasifier 12 and an embodiment of the cooling system 64. The quenched and solidified slag 58 may settle from the quench chamber 22 into the downstream end portion 62. Within the downstream end portion 62, the solidified slag 58 forms the slag slurry 14 with the quench liquid 42 and the cooling fluid 66. The cooling system 64 may have one or more nozzle sets 100 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) to dispense the cooling fluid 66 (e.g., water) into the downstream end portion 62, and each nozzle set 100 may have one or more nozzles 68 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more). For example, a first nozzle set 102 may have 2 nozzles 68, and a second nozzle set 104 and a third nozzle set 106 may each have 4 nozzles 68.
FIG. 3 illustrates a cross-sectional view of an embodiment of the first nozzle set 102, taken along line 3-3 of FIG. 2. The nozzles 68 of each nozzle set 100 may extend through a wall 108 of the downstream end portion 62 of the gasifier 12. Each of the nozzles 68 may be oriented toward a center 110 of the downstream end portion 62, in a first tangential direction 112, or a second tangential direction 114, or any combination thereof. For example, a first nozzle 116 may be oriented toward the center 110 and a second nozzle 118 may be oriented in the first tangential direction 112. In some embodiments, one or more nozzles 68 of a nozzle set 100 may extend through the wall 108 to the center 110 and be oriented towards the wall 108 in a radial direction 120 from the center 110, to induce counter-clockwise swirl, and a third nozzle 116 may be oriented in the second tangential direction 114 to induce clockwise swirl. Each of the one or more nozzles 68 may dispense the cooling fluid 66 in a jet or stream that penetrate the flow of the slag slurry 14, thereby enabling the cooling fluid 66 to directly interface and contact the slag 58 in the slag slurry 14. In some embodiments, one or more of the nozzles 68 may dispense the cooling fluid 66 into the slag slurry 14 as a stream (e.g., jet) a sheet (e.g., vertical sheet, horizontal sheet, oblique sheet), or a cone, or any combination thereof.
The one or more nozzle sets 100 depicted in FIGS. 2 and 3 may have various arrangements of the one or more nozzles 68. In some embodiments, arrangements of the nozzles 68 in each nozzle set 100 may be rotationally symmetric about the center 110, thereby enabling the cooling system 64 to cool the slag slurry 14 to a substantially uniform temperature (e.g., less than approximately 50 to 95 degrees C., less than approximately 60 to 80 degrees C., or less than approximately 70 degrees C.). For example, the second nozzle 118 may be spaced by approximately 180° from the first nozzle 116, as illustrated in FIG. 3. As may be appreciated, the term “approximately” as used herein to describe arrangement of the nozzles 68 may be within 10° or less. Other arrangements of the one or more nozzle sets 100 may include, but are not limited to, an arrangement with nozzles 68 spaced from one another by approximately 90° (e.g., the first nozzle 116, a third nozzle 120, the second nozzle 118, a fourth nozzle 122) or by approximately 60° (e.g., the fourth nozzle 122, a fifth nozzle 124, and a sixth nozzle 126), as illustrated in FIG. 3. In some embodiments, multiple nozzle sets 100 may be arranged on the wall 108 such that the nozzles 68 are circumferentially offset about the center 110 to enable the nozzles 68 to dispense the cooling fluid 66 to cool different portions of the slag slurry 14. For example, the first nozzle set 102 may have four nozzles 68 spaced by approximately 90° from each other starting at a first point 128, and the second set 104 may have four nozzles 68 spaced by approximately 90° from each other starting at a second point 130.
Returning to FIG. 2, each nozzle set 100 dispenses (e.g., injects) the cooling fluid 66 (e.g., water) into the downstream end portion 62. The cooling fluid 66 may be dispensed at a relatively high gage pressure (e.g., between approximately 1000 to 10,000 kPa) that is greater than or approximately equal (e.g., within 10 percent or less) to the gage pressure of the slag slurry 14, thereby enabling the cooling fluid 66 to readily flow into the slag slurry 14. In some embodiments, substantially all (e.g., greater than 75 percent) of the cooling fluid 66 may cool the slag slurry 14 and flow through an exit 132 of the downstream end portion 62 rather than through the syngas outlet 50 or the quench liquid outlet 60. Accordingly, the cooling fluid 66 primarily cools the slag slurry 14 downstream of the quench chamber 22.
In some embodiments, the downstream end portion 62 may include one or more slag crushers 70 to establish a desired average particle size. As discussed above, a first slag crusher 134 may provide a coarse crushing of the slag slurry 14, while a second slag crusher 136 may provide a finer crushing of the slag slurry 14. Each slag crusher 70 may include one or more elements 138 for breaking up the solidified slag 58 in the slag slurry 14, although other types of slag crushers may be used alone or in combination with slag crushers 70 having elements 138. Additionally, or in the alternative to one or more slag crushers 70 in the downstream end portion 62, some embodiments may include one or more slag crushers 70 downstream of the exit 132.
The one or more nozzle sets 100 may be arranged among the one or more slag crushers 70 of the downstream end portion 62. In some embodiments, a nozzle set 100 (e.g., the second nozzle set 104) is arranged between the first and the second slag crushers 134, 136. Additionally, or in the alternative, a nozzle set 100 (e.g., the first nozzle set 102) may be arranged upstream of the slag crusher 70 and/or a nozzle set 100 (e.g., the third nozzle set 106) may be arranged downstream of the slag crusher 70. The cooling system 64 may include one or more flow control valves and/or manifolds to control the distribution of the cooling fluid to the one or more nozzle sets 100. The cooling system 64 may differentially control the flow of the cooling fluid 66 to each of the nozzle sets 100. For example, the cooling system 64 may direct more cooling fluid 66 to the second or third nozzle sets 104, 106 while directing less cooling fluid 66 to the first nozzle set 102. In some embodiments, the cooling system 64 may differentially control the flow of the cooling fluid 66 to each nozzle 68 of a respective nozzle set 100. For example, the cooling system 64 may direct more cooling fluid 66 to a nozzle 68 proximate to a warm component of the continuous slag removal system 10 and less cooling fluid 66 to a nozzle 68 proximate to a cooler external ambient environment.
In some embodiments, the depressurization system 16 may include one or more let down devices including, but not limited to, one or more orifice plates 140, one or more let down valves 142, one or more expansion turbines 144, or one or more reverse-acting centrifugal pumps, or any combination thereof. The one or more let down devices may depressurize the slag slurry 14 based at least in part on the flow rate of the slag slurry 14 and/or the particle size of the solidified slag 58 within the slag slurry 14. For example, the one or more orifice plates 140 and/or the one or more let down valves 142 may depressurize the slag slurry 14 a greater amount when the slag slurry 14 flows at a first flow rate (e.g., approximately 380 LPM) than when the slag slurry 14 flows at a decreased second flow rate (e.g., approximately 300 LPM). Accordingly, the controller 18 may control the flow rate of the slag slurry 14 to control the depressurization of the slag slurry 14. In some embodiments, the controller 18 may control the flow rate of the slag slurry 14 via controlling the flow rate of the cooling fluid 66 from the cooling system 64. For example, increasing the cooling fluid 66 flow rate may increase the flow rate of the slag slurry 14 and increase the pressure drop across the depressurization system 16. Conversely, decreasing the cooling fluid 66 flow rate may decrease the flow rate of the slag slurry 14 and decrease the pressure drop across the depressurization system 16. Controlling the flow rate of the cooling fluid 66 may enable the controller 18 to exercise a fine control of the flow rate of the slag slurry 14 to satisfy any minimum flow specifications of the depressurization system 16 relative to control of the flow rate of the quench liquid 42. For example, adjusting the flow rate of the cooling fluid 66 by about 10 percent (e.g., from 380 LPM to 340 LPM) may affect the flow rate of the slag slurry 14 less than adjusting the flow rate of the quench liquid 42 by about 10 percent (e.g., from 7570 LPM to 6800 LPM). Additionally, or in the alternative, the controller 18 may control the flow rate of the slag slurry 14 directly via controlling a flow control valve 86.
Adjusting the flow rate of the slag slurry 14 via controlling the flow rate of the cooling fluid 66 from the cooling system 64 may enable the cooling system 64 to accommodate a flow rate specification of the depressurization system 16 without adding fluid between the downstream end portion 62 and the depressurization system 16. In some embodiments, the controller 18 may control the flow rate of the slag slurry 14 and/or the flow rate of the cooling fluid 66 based at least in part on feedback from a pressure sensor 82 downstream of the depressurization system 16. The controller 18 may also control the flow rate of the slag slurry 14 and/or the flow rate of the cooling fluid 66 based at least in part on a temperature of the slag slurry 14. For example, the controller 18 may control the flow rate of the slag slurry 14 and/or the cooling fluid 66 to cool the slag slurry to less than approximately 50 to 95 degrees C., less than approximately 60 to 80 degrees C., or less than approximately 70 degrees C. As may be appreciated, a processor 146 of the controller 18 may execute instructions (e.g., code) stored in a memory 148 of the controller 18 to control the cooling fluid 66 flow rate and/or the slag slurry 14 flow rate. Accordingly, the cooling system 64 coupled to the downstream end portion 62 may reduce the complexity of the flow path of the slag slurry 14 from the gasifier 12 to the depressurization system 16. Thus, the cooling fluid 66 may be utilized to cool the slag slurry 14 and to control the flow rate of the slag slurry 14 to sufficiently depressurize the slag slurry 14 without vapor flash.
FIG. 4 is a flowchart illustrating a process 180 for continuously handling the slag slurry 14. In some embodiments, the process 180 begins when carbonaceous fuel reacts (block 182) in the gasifier 12. As described above, the carbonaceous fuel may react with an oxidant and optionally additional water. Upon reaction within the gasifier 12, the continuous slag removal system 10 adds (block 184) a quench liquid to a quench chamber 22 in the gasifier 12 at a first flow rate, and quenches (block 186) the reacted products, such as a gas product and a slag byproduct. The gasifier 12 then separates (block 188) the gas from the slag, and conveys (block 190) the gas to the gas treatment system. As described above, the continuous slag removal system 10 adds (block 192) the cooling fluid to the downstream end portion 62 of the gasifier 12 at a second flow rate, thereby cooling (block 194) the slag and forming (block 196) the slag slurry. The slag slurry may be cooled to less than approximately 50 to 95 degrees C., less than approximately 60 to 80 degrees C., or less than approximately 70 degrees C. In some embodiments, one or more slag crushers 70 may crush the slag to form the slag slurry, which may include the slag, a first portion of the cooling fluid, and a second portion of the added quench liquid. In some embodiments, the second flow rate of the cooling fluid may be between approximately 2 to 15 percent, approximately 3 to 10 percent, or approximately 3 to 7 percent of the first flow rate of the quench liquid. The continuous slag removal system 10 conveys (block 198) the slag slurry at a third flow rate to a depressurization system 16 that depressurizes (block 200) the slag slurry. The third flow rate is based at least in part on the second flow rate. The continuous slag removal system 10 may control the third flow rate to depressurize (block 200) the slag slurry to a desired pressure, such as approximately atmospheric pressure.
Technical effects of the invention include enabling a continuous slag removal system without a cooler and/or water added between a downstream end portion of a gasifier and a depressurization system. A cooling system dispenses a high gage pressure cooling fluid to cool the slag slurry in the downstream end portion of the gasifier to less than approximately 50 to 95 degrees C. (e.g., 120 to 200 degrees F.), less than approximately 60 to 80 degrees C. (e.g., 140 to 175 degrees F.), or less than approximately 70 degrees C. (e.g., 160 degrees F.), thereby reducing the likelihood of vapor flash in the depressurization system. In addition to cooling the slag slurry, the cooling fluid may be used to control the flow rate of the slag slurry to the depressurization system. The pressure drop across the depressurization system may be based at least in part on the flow rate of the slag slurry through the depressurization system. Accordingly, controlling the slag slurry flow rate via control of the cooling fluid flow rate may control the pressure drop across the depressurization system.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A system comprising:

a quench chamber configured to continuously receive a mixture of a gas and slag, wherein the quench chamber comprises a quench sump configured to continuously separate the gas from the slag in the mixture via a quench liquid; and

a downstream end portion coupled to the quench chamber, wherein the downstream end portion is configured to continuously convey a slag slurry to a depressurization system, the downstream end portion comprises a cooling system configured to directly cool the slag slurry with a cooling fluid, and the slag slurry comprises the separated slag and at least a portion of the cooling fluid.

2. The system of claim 1, comprising one or more slag crushers configured to receive the slag slurry.

3. The system of claim 2, wherein the cooling system is disposed at least partially between a first slag crusher of the one or more slag crushers and a second slag crusher of the one or more slag crushers.

4. The system of claim 2, wherein the cooling system is disposed at least partially upstream of the one or more slag crushers.

5. The system of claim 1, comprising a slag crusher coupled to the downstream end portion.

6. The system of claim 1, comprising a reactor coupled to the quench chamber, wherein the reactor is configured to react a carbonaceous feedstock to generate the gas and the slag.

7. The system of claim 1, wherein the cooling system comprises one or more nozzles configured to dispense the cooling fluid directly into the slag slurry.

8. The system of claim 1, wherein the cooling system comprises a plurality of nozzle sets configured to dispense the cooling fluid, wherein each nozzle set comprises one or more nozzles, and each of the one or more nozzles is configured to dispense the cooling fluid at a different angle than another of the one or more nozzles of the respective nozzle set, at a different axial position than another of the one or more nozzles of the respective nozzle set, at a different circumferential position than another of the one or more nozzles of the respective nozzle set, or any combination thereof.

9. The system of claim 1, wherein the cooling system is configured to cool the slag to less than approximately 70 degrees C.

10. A system comprising:

a gasifier configured to react a carbonaceous feedstock into a mixture of a gas and slag, wherein the gasifier comprises:

a quench sump configured to continuously separate the gas from the slag in the mixture via a quench liquid, wherein the quench liquid is configured to flow through the quench sump at a first flow rate; and

a downstream end portion of the gasifier comprises a cooling system, wherein the downstream end portion is configured to continuously convey a slag slurry to a depressurization system at a third flow rate approximately 15 percent or less of the first flow rate, the downstream end portion is configured to add a cooling fluid at a second flow rate to cool the slag slurry, and the slag slurry comprises the slag and the cooling fluid; and

a controller configured to control the second flow rate.

11. The system of claim 10, comprising one or more slag crushers configured to continuously receive the slag slurry.

12. The system of claim 10, comprising the depressurization system coupled to the downstream end portion, wherein the depressurization system comprises one or more orifice plates, one or more let down valves, one or more expansion turbines, one or more centrifugal pumps, or any combination thereof.

13. The system of claim 12, wherein the controller is configured to control the second flow rate based at least in part on a desired flow rate of the depressurization system.

14. The system of claim 10, wherein the cooling system is configured to directly cool the slag slurry to reduce vaporization of the slag slurry upon depressurization in the depressurization system.

15. The system of claim 10, comprising a plurality of sensors configured to provide feedback to the controller, wherein the feedback comprises temperature data, pressure data, flow data, or viscosity data, or any combination thereof.

16. The system of claim 10, wherein the slag comprises less than approximately 5 percent of the quench liquid.

17. A method, comprising:

separating slag from a gas, wherein a temperature of the slag is greater than approximately 175 degrees C.;

dispensing a cooling fluid into a downstream end portion of a gasifier, wherein the cooling fluid is configured to decrease the temperature of the slag to less than approximately 70 degrees C.;

forming a cooled slag slurry from the slag and the cooling fluid; and

conveying the cooled slag slurry substantially continuously through an exit of the downstream end portion.

18. The method of claim 17, wherein forming the cooled slag slurry comprises crushing the slag into a plurality of particles with one or more slag crushers.

19. The method of claim 18, wherein the cooling fluid is dispensed upstream, downstream, or between the one or more slag crushers.

20. The method of claim 18, wherein separating the slag from the gas comprises supplying a quench liquid at a first flow rate, wherein the cooling fluid is dispensed at a second flow rate, and the second flow rate is less than approximately 15 percent of the first flow rate.