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

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 line3-3 ofFIG. 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 continuousslag removal system10. As shown inFIG. 1, the continuousslag removal system10 may include a partial oxidation system, such as agasifier12, aslag slurry14, a depressurization system16 (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 acontroller18.
• The partial oxidation system, orgasifier12, may further include areaction chamber20, a quenchchamber22, and adownstream end portion62. Aprotective barrier24 may enclose thereaction chamber20, 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 theprotective barrier24 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 theprotective barrier24 may be in the form of bricks, a castable refractory material, coatings, a metal wall, or any combination thereof. In general, thereaction chamber20 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, acarbonaceous feedstock26 may be introduced to thereaction chamber20 withoxygen28 to produce anuntreated syngas30 and amolten slag32. Thecarbonaceous feedstock26 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. Theoxygen28 introduced to thereaction chamber20 may be replaced or supplemented with air or oxygen-enriched air. In certain embodiments, an optionalslag slurrying agent34 may also be added to thereaction chamber20. Theslag slurrying agent34 may be used to maintain the viscosity of theslag slurry14 within a suitable range and thus may aid in transporting theslag slurry14 through the continuousslag removal system10. In yet other embodiments, an optional moderator36 (e.g., water or steam) may also be introduced into thereaction chamber20. The chemical reaction within thereaction chamber20 may be accomplished by subjecting thecarbonaceous feedstock26 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 ofgasifier12 utilized. Under these conditions, and depending upon the composition of the ash in thecarbonaceous feedstock26, the ash may be in the molten state, which is referred to as molten ash, ormolten slag32.
• The quenchchamber22 of the partial oxidation system, orgasifier12, may receive theuntreated syngas30 and themolten slag32 as it leaves thereaction chamber20 through the bottom end38 (or throat) of theprotective barrier24. Theuntreated syngas30 and themolten slag32 enter the quenchchamber22 at a high pressure and a high temperature. In general, the quenchchamber22 may be used to reduce the temperature of theuntreated syngas30 and to disengage themolten slag32 from theuntreated syngas30, and the quenchchamber22 may be used to quench themolten slag32 to at least partially solidify themolten slag32. In certain embodiments, a quenchring40 arranged at thebottom end38 of theprotective barrier24 is configured to provide a quench liquid42 (e.g. water) to the quenchchamber22. The quench liquid42 may be directed through a quenchinlet44 and into the quenchring40 through aline46. In general, the quench liquid42 may flow through the quenchring40 and down the inner surface of adip tube47 into a quenchchamber sump48. Thecontroller18 may control the flow rate of the quench liquid42 through the quenchinlet44. For example, thecontroller18 may control the flow rate of the quench liquid42 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).
• Theuntreated syngas30 and themolten slag32 may also flow through thebottom end38 of theprotective barrier24, and along the inner surface of thedip tube47 into the quenchchamber sump48. As theuntreated syngas30 passes through the pool of quench liquid42 in the quenchchamber sump48, themolten slag32 is solidified and disengaged from the syngas, the syngas is cooled and quenched, and the syngas subsequently exits the quenchchamber22 through asyngas outlet50, as illustrated byarrow52.Syngas54 exits through thesyngas outlet50 for further processing in agas treatment system56, where it may be further processed to remove acidic gases, particulates, etc., to form a treated syngas. Solidifiedslag58 may accumulate at the bottom of the quenchchamber sump48 and may be continuously removed from thegasifier12 as theslag slurry14. In certain embodiments, a portion of the quench liquid42 may also be continuously removed from the quenchchamber sump48 for treatment through a quenchoutlet60. For example, particulates, soot, slag, and other matter may be removed from the quench liquid42 in a black water treatment system, and the treated quench liquid42 may be returned to the quenchchamber sump48 through the quenchinlet44. In such embodiments, the removed quench liquid42 may have properties similar to theslag slurry14 and thus, may be transported and depressurized using a liquid expansion system separate from or shared with thedepressurization system16 for theslag slurry14.
• Theslag slurry14 may have various compositions of solids suspended in the quenchliquid42, including, but not limited to, fuels (e.g., coals), dry char, catalysts, plastics, chemicals, minerals, and/or other products. Theslag slurry14 entering thedownstream end portion62 of thegasifier12 may have a high pressure and a high temperature. For example, the gage pressure of theslag slurry14 may be between approximately 1000 to 10,000 kPa, 2000 to 9000 kPa, or 3000 to 8000 kPa, and the temperature of theslag slurry14 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, thedownstream end portion62 is narrower than the quenchchamber22.
• Acooling system64 controls a flow of a coolingfluid66 into thedownstream end portion62 via one or more nozzles68 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more nozzles). In some embodiments, thecooling system64 includes a heat exchanger, evaporation system, or refrigerant system to cool the cooling fluid to between approximately 10 to 70 degrees C. The coolingfluid66 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 coolingfluid66 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 coolingfluid66 may be less than approximately 15 percent (e.g., 3 to 10 percent) of the flow rate of the quench liquid42 into the quenchchamber22. For example, the quench liquid42 flow rate may be approximately 7570 LPM, the coolingfluid66 flow rate may be approximately 300 LPM, theslag58 may flow through thedownstream end portion62 of thegasifier12 with a flow rate of approximately 75 LPM, and the slag slurry14 (e.g., the coolingfluid66 and the slag58) may flow through thedownstream end portion62 with a flow rate of approximately 375 LPM. The flow rate of theslag slurry14 may be between approximately 2 to 15% of the flow rate of the quench liquid42 into the quenchchamber22. In some embodiments, the temperature of the coolingfluid66 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 coolingfluid66 may include, but is not limited to, gray water, boiler feed water, raw makeup water, condensate, other water streams, or any combination thereof.
• Thecooling system64 dispenses the coolingfluid66 into thedownstream end portion62 to directly cool theslag slurry14 that will be discharged from thegasifier12. One or more streams (e.g., jets) of the coolingfluid66 interface withslag58 in theslag slurry14, thereby decreasing the temperature of theslag slurry14. While the quenchliquid42 cools thesyngas30 and theslag32 that enters the quenchchamber22 from thereaction chamber20, the coolingfluid66 primarily cools the solidifiedslag58 in theslag slurry14. Thecooling system64 may be integrated with thedownstream end portion62 of thegasifier12 and/or coupled directly to thedownstream end portion62 of thegasifier12. In some embodiments, thenozzles68 of thecooling system64 may be arranged among and/or upstream of one ormore slag crushers70 that receive theslag slurry14 from thedownstream end portion62.
• As may be appreciated, certain designs of continuousslag removal systems10 may include a cooler72 (e.g., heat exchanger) for theslag slurry14 and/or may dispensecold water74 into theslag slurry14 between thegasifier12 and a depressurization system16 (e.g., one or more let down devices). Presently contemplated embodiments of the continuousslag removal system10 may cool theslag slurry14 to less than approximately 70 degrees C. (e.g., approximately 160 degrees F.) without the cooler72 orcold water74 injection shown in the dashedbox78 downstream of thegasifier12. Moreover, the coolingfluid66 directly cools the solidifiedslag58 and theslag slurry14 in thedownstream end portion62 of thegasifier12 rather than indirectly, such as when theslag slurry14 is cooled via a cooler72 (e.g. heat exchanger) downstream of thegasifier12. The removal of the cooler72 from the continuousslag removal system10 may reduce the height and/or foot print of the continuousslag removal system10. Furthermore, the removal of the cooler72 from the continuousslag removal system10 may reduce operational and/or installation costs. The tubes of the cooler72 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 cooler72.
• Thecontroller18 may receive signals from various sensors disposed throughout the continuousslag removal system10. For example, flowrate sensors80 measure flow rates of the quenchliquid42, the coolingfluid66, and theslag slurry14. One ormore pressure sensors82 and/ortemperature sensors83 may provide information regarding characteristics of theslag slurry14, operating conditions within the continuousslag removal system10, temperatures of theslag slurry14, pressures of theslag slurry14 at various sites, and so forth. In some embodiments, thecontroller18 may receive additional sensor information about theslag slurry14 as it exits thegasifier12, such as, but not limited to, viscosity, particle size, and so forth. Furthermore, thecontroller18 may adjust operational conditions of the continuousslag removal system10 in response to received sensor information, as described in detail below.
• In certain embodiments, one ormore slag crushers70 coupled to a slag crusher driver84 (e.g., a steam turbine, thedepressurization system16, a motor, or other source of power) may optionally receive theslag slurry14 before it is directed through thedepressurization system16. The one ormore slag crushers70 may crush the solidifiedslag58 in theslag slurry14 in order to attain a desired particle size distribution or a desired average particle size of particles in theslag slurry14. The one ormore slag crushers70 may be arranged in one or more stages, and the one ormore slag crushers70 may be arranged in series or in parallel with one another. The one ormore slag crushers70 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 theslag slurry14 to flow, for increasing the effectiveness of thecooling system64, or for a desired flow through thedepressurization system16, or any combination thereof. Furthermore, the one ormore slag crushers70 may reduce the average particle size of the solids suspended in the quenchliquid42 and coolingfluid66 of theslag slurry14 to an appropriate range.
• In certain embodiments, the one ormore slag crushers70 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, asingle slag crusher70 may be sufficient to establish this average particle size, and in other embodiments, two ormore slag crushers70 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 theslag slurry14, while a second slag crusher may provide a finer crushing of theslag slurry14. In one embodiment, thecontroller18 may control theslag crusher70 by controlling theslag crusher motor84. Thecontroller18 may adjust theslag crusher motor84 based on information received from other sensors. In certain embodiments, aflow control valve86 may be disposed downstream of theslag crusher70 to adjust the flow rate of theslag slurry14 flowing to theliquid expansion system16. In one embodiment, thecontroller18 may receive information about the flow rate of theslag slurry14 from aflow rate sensor80. In response to the information received by theflow sensor80, thecontroller18 may control the flow rate of theslag slurry14 by adjusting theflow control valve86. In other embodiments, thecontroller18 may adjust the flow rate of theslag slurry14 based on signals fromother sensors82,83.
• Theslag slurry14 may be fed into thedepressurization system16 to decrease the pressure of theslag slurry14. In some embodiments, thedepressurization system16 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 theslag slurry14 exiting thedepressurization system16. In some embodiments, the depressurization system16 (e.g., turbine) may generate power (e.g., drive an electric generator) while depressurizing theslag slurry14 from the pressure at pressure sensor “P1” 82. For example, the first gage pressure of theslag slurry14, 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 thegasifier12. In contrast, the second gage pressure of theslag slurry14, 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 thedepressurization system16, theslag slurry14 may travel further downstream to aslag processing system88, such as for dewatering of theslag slurry14, before theslag slurry14 is disposed of.
• FIG. 2 illustrates an embodiment of thedownstream end portion62 of thegasifier12 and an embodiment of thecooling system64. The quenched and solidifiedslag58 may settle from the quenchchamber22 into thedownstream end portion62. Within thedownstream end portion62, the solidifiedslag58 forms theslag slurry14 with the quenchliquid42 and the coolingfluid66. Thecooling system64 may have one or more nozzle sets100 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) to dispense the cooling fluid66 (e.g., water) into thedownstream end portion62, and each nozzle set100 may have one or more nozzles68 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more). For example, a first nozzle set102 may have 2nozzles68, and a second nozzle set104 and a third nozzle set106 may each have 4nozzles68.
• FIG. 3 illustrates a cross-sectional view of an embodiment of the first nozzle set102, taken along line3-3 ofFIG. 2. Thenozzles68 of each nozzle set100 may extend through awall108 of thedownstream end portion62 of thegasifier12. Each of thenozzles68 may be oriented toward acenter110 of thedownstream end portion62, in a firsttangential direction112, or a secondtangential direction114, or any combination thereof. For example, afirst nozzle116 may be oriented toward thecenter110 and a second nozzle118 may be oriented in the firsttangential direction112. In some embodiments, one ormore nozzles68 of a nozzle set100 may extend through thewall108 to thecenter110 and be oriented towards thewall108 in aradial direction120 from thecenter110, to induce counter-clockwise swirl, and athird nozzle116 may be oriented in the secondtangential direction114 to induce clockwise swirl. Each of the one ormore nozzles68 may dispense the coolingfluid66 in a jet or stream that penetrate the flow of theslag slurry14, thereby enabling the coolingfluid66 to directly interface and contact theslag58 in theslag slurry14. In some embodiments, one or more of thenozzles68 may dispense the coolingfluid66 into theslag slurry14 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 sets100 depicted inFIGS. 2 and 3 may have various arrangements of the one ormore nozzles68. In some embodiments, arrangements of thenozzles68 in each nozzle set100 may be rotationally symmetric about thecenter110, thereby enabling thecooling system64 to cool theslag slurry14 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 nozzle118 may be spaced by approximately 180° from thefirst nozzle116, as illustrated inFIG. 3. As may be appreciated, the term “approximately” as used herein to describe arrangement of thenozzles68 may be within 10° or less. Other arrangements of the one or more nozzle sets100 may include, but are not limited to, an arrangement withnozzles68 spaced from one another by approximately 90° (e.g., thefirst nozzle116, athird nozzle120, the second nozzle118, a fourth nozzle122) or by approximately 60° (e.g., the fourth nozzle122, a fifth nozzle124, and a sixth nozzle126), as illustrated inFIG. 3. In some embodiments, multiple nozzle sets100 may be arranged on thewall108 such that thenozzles68 are circumferentially offset about thecenter110 to enable thenozzles68 to dispense the coolingfluid66 to cool different portions of theslag slurry14. For example, the first nozzle set102 may have fournozzles68 spaced by approximately 90° from each other starting at afirst point128, and the second set104 may have fournozzles68 spaced by approximately 90° from each other starting at asecond point130.
• Returning toFIG. 2, each nozzle set100 dispenses (e.g., injects) the cooling fluid66 (e.g., water) into thedownstream end portion62. The coolingfluid66 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 theslag slurry14, thereby enabling the coolingfluid66 to readily flow into theslag slurry14. In some embodiments, substantially all (e.g., greater than 75 percent) of the coolingfluid66 may cool theslag slurry14 and flow through anexit132 of thedownstream end portion62 rather than through thesyngas outlet50 or the quenchliquid outlet60. Accordingly, the coolingfluid66 primarily cools theslag slurry14 downstream of the quenchchamber22.
• In some embodiments, thedownstream end portion62 may include one ormore slag crushers70 to establish a desired average particle size. As discussed above, a first slag crusher134 may provide a coarse crushing of theslag slurry14, while a second slag crusher136 may provide a finer crushing of theslag slurry14. Eachslag crusher70 may include one ormore elements138 for breaking up the solidifiedslag58 in theslag slurry14, although other types of slag crushers may be used alone or in combination withslag crushers70 havingelements138. Additionally, or in the alternative to one ormore slag crushers70 in thedownstream end portion62, some embodiments may include one ormore slag crushers70 downstream of theexit132.
• The one or more nozzle sets100 may be arranged among the one ormore slag crushers70 of thedownstream end portion62. In some embodiments, a nozzle set100 (e.g., the second nozzle set104) is arranged between the first and the second slag crushers134,136. Additionally, or in the alternative, a nozzle set100 (e.g., the first nozzle set102) may be arranged upstream of theslag crusher70 and/or a nozzle set100 (e.g., the third nozzle set106) may be arranged downstream of theslag crusher70. Thecooling system64 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 sets100. Thecooling system64 may differentially control the flow of the coolingfluid66 to each of the nozzle sets100. For example, thecooling system64 may directmore cooling fluid66 to the second or third nozzle sets104,106 while directing less coolingfluid66 to the first nozzle set102. In some embodiments, thecooling system64 may differentially control the flow of the coolingfluid66 to eachnozzle68 of a respective nozzle set100. For example, thecooling system64 may directmore cooling fluid66 to anozzle68 proximate to a warm component of the continuousslag removal system10 andless cooling fluid66 to anozzle68 proximate to a cooler external ambient environment.
• In some embodiments, thedepressurization system16 may include one or more let down devices including, but not limited to, one ormore orifice plates140, one or more let downvalves142, one ormore expansion turbines144, or one or more reverse-acting centrifugal pumps, or any combination thereof. The one or more let down devices may depressurize theslag slurry14 based at least in part on the flow rate of theslag slurry14 and/or the particle size of the solidifiedslag58 within theslag slurry14. For example, the one ormore orifice plates140 and/or the one or more let downvalves142 may depressurize the slag slurry14 a greater amount when theslag slurry14 flows at a first flow rate (e.g., approximately 380 LPM) than when theslag slurry14 flows at a decreased second flow rate (e.g., approximately 300 LPM). Accordingly, thecontroller18 may control the flow rate of theslag slurry14 to control the depressurization of theslag slurry14. In some embodiments, thecontroller18 may control the flow rate of theslag slurry14 via controlling the flow rate of the coolingfluid66 from thecooling system64. For example, increasing the coolingfluid66 flow rate may increase the flow rate of theslag slurry14 and increase the pressure drop across thedepressurization system16. Conversely, decreasing the coolingfluid66 flow rate may decrease the flow rate of theslag slurry14 and decrease the pressure drop across thedepressurization system16. Controlling the flow rate of the coolingfluid66 may enable thecontroller18 to exercise a fine control of the flow rate of theslag slurry14 to satisfy any minimum flow specifications of thedepressurization system16 relative to control of the flow rate of the quenchliquid42. For example, adjusting the flow rate of the coolingfluid66 by about 10 percent (e.g., from 380 LPM to340 LPM) may affect the flow rate of theslag slurry14 less than adjusting the flow rate of the quench liquid42 by about 10 percent (e.g., from 7570 LPM to 6800 LPM). Additionally, or in the alternative, thecontroller18 may control the flow rate of theslag slurry14 directly via controlling aflow control valve86.
• Adjusting the flow rate of theslag slurry14 via controlling the flow rate of the coolingfluid66 from thecooling system64 may enable thecooling system64 to accommodate a flow rate specification of thedepressurization system16 without adding fluid between thedownstream end portion62 and thedepressurization system16. In some embodiments, thecontroller18 may control the flow rate of theslag slurry14 and/or the flow rate of the coolingfluid66 based at least in part on feedback from apressure sensor82 downstream of thedepressurization system16. Thecontroller18 may also control the flow rate of theslag slurry14 and/or the flow rate of the coolingfluid66 based at least in part on a temperature of theslag slurry14. For example, thecontroller18 may control the flow rate of theslag slurry14 and/or the coolingfluid66 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, aprocessor146 of thecontroller18 may execute instructions (e.g., code) stored in amemory148 of thecontroller18 to control the coolingfluid66 flow rate and/or theslag slurry14 flow rate. Accordingly, thecooling system64 coupled to thedownstream end portion62 may reduce the complexity of the flow path of theslag slurry14 from thegasifier12 to thedepressurization system16. Thus, the coolingfluid66 may be utilized to cool theslag slurry14 and to control the flow rate of theslag slurry14 to sufficiently depressurize theslag slurry14 without vapor flash.
• FIG. 4 is a flowchart illustrating aprocess180 for continuously handling theslag slurry14. In some embodiments, theprocess180 begins when carbonaceous fuel reacts (block182) in thegasifier12. As described above, the carbonaceous fuel may react with an oxidant and optionally additional water. Upon reaction within thegasifier12, the continuousslag removal system10 adds (block184) a quench liquid to a quenchchamber22 in thegasifier12 at a first flow rate, and quenches (block186) the reacted products, such as a gas product and a slag byproduct. Thegasifier12 then separates (block188) the gas from the slag, and conveys (block190) the gas to the gas treatment system. As described above, the continuousslag removal system10 adds (block192) the cooling fluid to thedownstream end portion62 of thegasifier12 at a second flow rate, thereby cooling (block194) the slag and forming (block196) 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 ormore slag crushers70 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 continuousslag removal system10 conveys (block198) the slag slurry at a third flow rate to adepressurization system16 that depressurizes (block200) the slag slurry. The third flow rate is based at least in part on the second flow rate. The continuousslag removal system10 may control the third flow rate to depressurize (block200) 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 (20)

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 ofclaim 1, comprising one or more slag crushers configured to receive the slag slurry.

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

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

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

8. The system ofclaim 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 ofclaim 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 ofclaim 10, comprising one or more slag crushers configured to continuously receive the slag slurry.

12. The system ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 18, wherein the cooling fluid is dispensed upstream, downstream, or between the one or more slag crushers.

20. The method ofclaim 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.

Images