METHOD AND APPARATUS TO PREHEAT SLURRY

Abstract

A method of operating a gasification facility includes channeling steam into a grinding mill via a flow control device and a conduit. The method also includes mixing carbonaceous fuel, preheated water, and steam within the grinding mill, to form a preheated coal slurry stream.

Description

BACKGROUND OF THE INVENTION

The present invention herein relates generally to slurry transport systems, and more particularly, to methods and apparatus for preheating slurries to facilitate operation of synthetic gas production facilities.

At least some known gasification plants include a gasification system that is integrated with at least one power-producing turbine system, to form an integrated gasification combined cycle (IGCC) power generation plant. Such known gasification systems convert a mixture of fuel, air or oxygen, steam, and/or CO₂ into a synthetic gas, or “syngas”. Also, many of such known gasification systems include a gasification reactor that generates syngas therein. The syngas is channeled to the combustor of a gas turbine engine, for use in powering a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator (HRSG) that generates steam for use in driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.

At least some of the known gasification systems also include at least one slurry feed pump that channels a fuel slurry to the gasification reactor. Moreover, some of such known gasification systems also include a slurry heating system that includes at least one shell and tube heat exchanger. Preheating the slurry prior to supplying the slurry to the gasification reactor generally increases an efficiency of gasification. Such heat exchangers are typically positioned downstream from the slurry feed pump and use steam as the heating medium. Many of such heat exchangers may be subject to a potential for fouling, plugging, and erosion. Moreover, because a viscosity of the slurry may be high and because the slurry flow through the heat exchanger tubes generally tends towards laminar flow conditions, a heat transfer coefficient associated with the heat exchanger is generally low, which actually decreases efficiency of the heat exchanger. Other known gasification systems may heat the slurry using direct steam injection and mixing. However, such injection and mixing dilutes the slurry and the efficiency of gasification may be subsequently reduced.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method of operating a gasification facility is provided. The method includes channeling steam into a grinding mill via a flow control device and a conduit. The method also includes mixing carbonaceous fuel, preheated water, and steam within the grinding mill, to form a preheated coal slurry stream.

In another aspect, a slurry preparation system is provided. The slurry preparation system is coupled in flow communication with a carbonaceous fuel source, a makeup water source, and a steam source. The slurry preparation system includes a fuel grinding mill coupled in flow communication with the steam source via at least one conduit.

In yet another aspect, a gasification facility is provided. The gasification facility includes a carbonaceous fuel source, a makeup water source, and a steam source. The gasification facility also includes a slurry preparation system coupled in flow communication with the carbonaceous fuel source, the makeup water source, and the steam source. The slurry preparation system includes a fuel grinding mill coupled in flow communication with the steam source via at least one conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments described herein may be better understood by referring to the following description in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of an exemplary integrated gasification combined-cycle (IGCC) power generation plant;

FIG. 2 is a schematic diagram of an exemplary slurry preparation system that may be used with the IGCC power generation plant shown in FIG. 1; and

FIG. 3 is a flow chart illustrating an exemplary method of operating the IGCC power generation plant shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram of an exemplary chemical production system, and more specifically, an exemplary integrated gasification combined-cycle (IGCC) power generation plant 100. In the exemplary embodiment, IGCC power generation plant 100 includes a gas turbine engine 110 that includes a turbine 114 that is rotatably coupled to a first electrical generator 118 via a first rotor 120. Turbine 114 is coupled in flow communication with at least one fuel source and at least one air source and receives fuel and air from the fuel and air sources, respectively. Turbine 114 mixes the air and fuel, produces hot combustion gases (not shown), and converts heat energy within the gases to rotational energy. That is transmitted to generator 118 via rotor 120. Generator 118 converts the rotational energy to electrical energy (not shown) for transmission to at least one load, such as, but not limited to, an electrical power grid (not shown).

IGCC power generation plant 100 also includes a steam turbine engine 130. In the exemplary embodiment, engine 130 includes a steam turbine 132 that is coupled to a second electrical generator 134 via a second rotor 136.

Moreover, in the exemplary embodiment, IGCC power generation plant 100 also includes a steam generation system 140 that includes at least one heat recovery steam generator (HRSG) 142 coupled in flow communication with at least one heat transfer apparatus 144 via at least one heated boiler feedwater conduit 146. HRSG 142 receives boiler feedwater (not shown) from apparatus 144 via conduit 146. The boiler feedwater is heated into steam (not shown). HRSG 142 also receives exhaust gases (not shown) from turbine 114 via an exhaust gas conduit 148. The exhaust gases also heat the boiler feedwater into steam. HRSG 142 is coupled in flow communication with turbine 132 via a steam conduit 150. Excess gases and steam (both not shown) are exhausted from HRSG 142 to the atmosphere via stack gas conduit 152.

Conduit 150 channels steam (not shown) from HRSG 142 to turbine 132. Turbine 132 receives steam from HRSG 142 and converts the thermal energy in the steam to rotational energy. The rotational energy is transmitted to generator 134 via rotor 136, wherein generator 134 converts the rotational energy to electrical energy (not shown) for transmission to at least one load, including, but not limited to, an electrical power grid. The steam is condensed and returned as boiler feedwater via a condensate conduit (not shown).

In the exemplary embodiment IGCC power generation plant 100 also includes a gasification system 200 that includes at least one air separation unit 202 that is coupled in flow communication with an air source via an air conduit 204. Such air sources may include, but are not limited to, dedicated air compressors and compressed air storage units (neither shown). Unit 202 separates air into oxygen (O₂), nitrogen (N₂), and other components (neither shown) that are either released via a vent (not shown) or channeled and/or collected for further use. For example, in the exemplary embodiment, N₂ is channeled to gas turbine 114 via a N₂ conduit 206 to facilitate combustion.

System 200 includes a gasification reactor 208 that is coupled in flow communication with unit 202 to receive oxygen channeled from unit 202 via an O₂ conduit 210. System 200 also includes a fuel preparation system 211, that in the exemplary embodiment, is, a slurry preparation system 211. Slurry preparation system 211 is coupled in flow communication with a carbonaceous fuel source (not shown), such as, a coal source and a water source, via a coal supply conduit 212 and a water supply conduit 213, respectively. System 211 mixes coal and water to form a coal slurry stream that has a predetermined temperature and viscosity, that is channeled to reactor 208 via a coal slurry conduit 214.

Reactor 208 receives the coal slurry stream and an O₂ stream (not shown) via respective conduits 214 and 210. Reactor 208 produces a hot, raw synthetic gas (syngas) stream (not shown), that includes carbon monoxide (CO), hydrogen (H₂), carbon dioxide (CO₂), carbonyl sulfide (COS), and hydrogen sulfide (H₂S). While CO₂, COS, and H₂S are typically collectively referred to as acid gases, or acid gas components of the raw syngas, CO₂ will be discussed herein separately from the remaining acid gas components. Moreover, reactor 208 also produces a hot slag stream (not shown) as a first gasification by-product resulting from syngas production. The slag stream is channeled to a slag handling unit 215 via a hot slag conduit 216. Unit 215 quenches and breaks up the slag into smaller slag pieces wherein a slag removal stream is produced and channeled through conduit 217.

Reactor 208 is coupled in flow communication with heat transfer apparatus 144 via a hot syngas conduit 218. Apparatus 144 receives the hot, raw syngas stream and transfers at least a portion of the heat to HRSG 142 via conduit 146. Subsequently, apparatus 144 produces a cooled raw syngas stream (not shown) that is channeled to a scrubber and low temperature gas cooling (LTGC) unit 221 via a syngas conduit 219. Unit 221 removes a second gasification by-product, that is, particulate matter entrained within the raw syngas stream, and discharges the removed matter via a fly ash conduit 222. Unit 221 facilitates cooling the raw syngas stream, and converts at least a portion of COS in the raw syngas stream to H₂S and CO₂ via hydrolysis.

System 200 also includes an acid gas removal subsystem 300 that is coupled in flow communication with unit 221 to receive the cooled raw syngas stream via a raw syngas conduit 220. Subsystem 300 removes at least a portion of acid components (not shown) from the raw syngas stream as described in more detail below. Such acid gas components may include, but are not limited to, CO₂, COS, and H₂S. Subsystem 300 also separates at least some of the acid gas components into components that include, but are not limited to, CO₂, COS, and H₂S. Moreover, subsystem 300 is coupled in flow communication with a sulfur reduction subsystem 400 via a conduit 223. Subsystem 400 receives and separates at least some of the acid gas components into components that include, but are not limited to, CO₂, COS, and H₂S. Such acid components removed and separated are channeled into at least one third gasification by-product stream (not shown) that is removed from system 200.

Furthermore, subsystem 400 channels a final integrated gas stream (not shown) to reactor 208 via subsystem 300 and via a final integrated gas stream conduit 224. The final integrated gas stream includes predetermined concentrations of CO₂, COS, and H₂S that result from previous integrated gas streams (not shown). Subsystem 300 is coupled in flow communication with reactor 208 via conduit 224, wherein the final integrated gas stream is channeled to portions of reactor 208. The separation and removal of CO₂, COS, and H₂S via subsystems 300 and 400 facilitates producing a clean syngas stream (not shown) that is channeled to gas turbine 114 via a clean syngas conduit 228.

In operation, air separation unit 202 receives air via conduit 204. The air is separated into O₂, N₂ and other components that are vented to atmosphere via a vent. The N₂ is channeled to turbine 114 via conduit 206 and the O₂ is channeled to gasification reactor 208 via conduit 210. Also, in operation, slurry preparation system 211 receives coal and water via conduits 212 and 213, respectively, forms a coal slurry stream and channels the coal slurry stream to reactor 208 via conduit 214.

Reactor 208 receives O₂ via conduit 210, coal via conduit 214, and the final integrated gas stream from subsystem 300 via conduit 224. Reactor 208 produces a hot raw syngas stream that is channeled to apparatus 144 via conduit 218. The slag by-product formed in reactor 208 is removed via slag handling unit 215 and conduits 216 and 217. Apparatus 144 facilitates cooling the hot raw syngas stream to produce a cooled raw syngas stream that is channeled to scrubber and LTGC unit 221 via conduit 219 wherein particulate matter is removed from the syngas via fly ash conduit 222, the syngas is cooled further, and at least a portion of COS is converted to H₂S and CO₂ via hydrolysis. The cooled raw syngas stream is channeled to acid gas removal subsystem 300 wherein acid gas components are substantially removed to form a clean syngas stream that is channeled to gas turbine 114 via conduit 228.

Moreover, during operation, at least a portion of the acid components removed from the syngas stream are channeled to subsystem 400 via conduit 223, wherein the acid components are removed and separated into at least a third gasification by-product stream (not shown) that is removed from the syngas stream, such that the final integrated gas stream is channeled to reactor 208 via subsystem 300 and conduit 224. In addition, turbine engine 110 receives N₂ and clean syngas via conduits 206 and 228, respectively. Turbine engine 110 combusts the syngas fuel, produces hot combustion gases and channels hot combustion gases downstream to induce rotation of turbine 114 which subsequently rotates first generator 118 via rotor 120.

At least a portion of heat removed from the hot syngas via heat transfer apparatus 144 is channeled to HRSG 142 via conduit 146 for use in boiling water to form steam. The steam is channeled through steam turbine 132 via conduit 150 and induces rotation of turbine 132, which powers second generator 134 via second rotor 136.

FIG. 2 is a schematic diagram of slurry preparation system 211. As described above, slurry preparation system 211 receives coal (not shown) and water (not shown) via respective conduits 212 and 213. Conduit 212 is coupled to any coal supply (not shown) that enables system 211 to operate as described herein. Conduit 213 is coupled to any water supply (not shown) that enables system 211 to operate as described herein. In the exemplary embodiment, makeup water is channeled to slurry preparation system 211 at approximately ambient temperature. Alternatively, makeup water channeled to system 211 is heated to any temperature that enables operation of system 211 as described herein.

In the exemplary embodiment, slurry preparation system 211 includes a mixing tank, or recycle solids tank 502. Recycle solids tank 502 includes at least one mixing apparatus 504 and at least one heating device 506 contained therein. In the exemplary embodiment, mixing apparatus 504 is a motor-driven propeller-type mixer, and heating device 506 is a low pressure steam heating element coupled in flow communication with a low pressure (LP) steam source 505, that, in the exemplary embodiment, is coupled to HRSG 142 (shown in FIG. 1). Alternatively, mixing apparatus 504, heating device 506, and LP steam source 505 are any apparatus, device, and/or steam source, respectively, that enables operation of system 211 as described herein. Heating device 506 preheats the makeup water channeled into tank 502 via conduit 213.

Recycle solids tank 502 is coupled in flow communication with portions of system 200 that include, but are not limited to, acid gas removal subsystem 300 and sulfur reduction subsystem (both shown in FIG. 1) via an acid gas removal (AGR) regeneration conduit 508. Conduit 508 channels gasification by-product materials (not shown) that include, but are not limited to, caustic and regeneration solids. In the exemplary embodiment, materials channeled to tank 502 via conduit 508 are at a temperature that is higher than the ambient temperature, and as such, gasification by-product materials entering tank 502 via conduit 508 preheat the makeup water channeled into tank 502 via conduit 213.

Recycle solids tank 502 is also coupled in flow communication with a slag collection facility (not shown) associated with slag handling unit 215 (shown in FIG. 1) via a slag supply conduit 510. Slag supply conduit 510 channels gasification by-product materials (not shown) that include, but are not limited to, slag fines and other slag-type materials to tank 502 from a slag sump (not shown) that collects fines and slag from slag handling unit 215. In the exemplary embodiment, materials channeled to tank 502 via conduit 510 are at a temperature that is greater than ambient temperatures, therefore, such gasification by-product materials entering tank 502 via conduit 510 preheat the makeup water channeled into tank 502.

Recycle solids tank 502 is also coupled in flow communication with a settling tank (not shown) associated with a bottom portion (not shown) of gasification reactor 208 (shown in FIG. 1) via a settler bottoms conduit 512. Settler bottoms conduit 512 channels gasification by-product materials (not shown) that include, but are not limited to, reusable materials from the bottom portion of gasification reactor 208. In the exemplary embodiment, materials channeled to tank 502 via conduit 512 are at a temperature that is higher than the ambient temperature, and as such, gasification by-product materials entering tank 502 via conduit 512 preheat the makeup water channeled into tank 502 via conduit 213.

In the exemplary embodiment, each of the described heat input mechanisms, including conduits 508, 510, and 512, and heating device 506 preheats the water in recycle solids tank 502 to a range of approximately 54.4 degrees Celsius (° C.) (130 degrees Fahrenheit (° F.)) to approximately 76.6° C. (170° F.), with a target median of approximately 65.6° C. (150° F.). Alternatively, the water in recycle solids tank 502 may be heated to any temperature that enables operation of system 211 as described herein. Such gasification by-product materials as described herein are collectively referred to herein as “entrained solids.”

Also, in the exemplary embodiment, slurry preparation system 211 includes a recycle fluid transfer pump 514 that is coupled to tank 502 via a tank discharge conduit 516. Pump 514 induces a motive force on entrained solids and water within tank 502 to enable such entrained solids and water to be channeled in a recycle fluid stream (not shown) for use within other portions of system 211 via a recycle fluid transfer conduit 518.

Moreover, in the exemplary embodiment, slurry preparation system 211 includes a first LP steam injection system 520 that is coupled in flow communication with LP steam source 505. Alternatively, any steam source may be used that enables operation of system 211 as described herein. In the exemplary embodiment, first LP steam injection system 520 includes a LP steam injection device 522 that, in the exemplary embodiment is a LP steam injection venturi 522 that is coupled in flow communication with a first LP steam flow control device or valve 524. Alternatively, LP steam injection device 522 is any injection device that enables operation of system 211 as described herein. Valve 524 is coupled in flow communication with LP steam source 505 and is coupled in communication with a first temperature control sensor 526, wherein sensor 526 generates and transmits signals (not shown) that are representative of the temperatures of the preheated recycle fluid stream downstream of injection device 522.

First LP steam injection system 520 channels LP steam into the recycle fluid stream within conduit 518. In the exemplary embodiment, the injected steam mixes and condenses within the recycle fluid stream and downstream of system 520, thereby preheating the recycle fluid stream with entrained solids to a predetermined temperature range of approximately 71.1° C. (160° F.) to approximately 93.3° C. (200° F.), with a target median of approximately 82.2° C. (180° F.). Alternatively, the recycle fluid stream may be preheated to any temperature that enables operation of system 211 as described herein.

In the exemplary embodiment, first temperature control sensor 526 and first LP steam flow control valve 524 are coupled to an extensive slurry temperature and viscosity control system (not shown). Alternatively, first temperature control sensor 526 and first LP steam flow control valve 524 use any control architecture that enables system 211 to operate as described herein.

Further, in the exemplary embodiment, slurry preparation system 211 includes a coal transfer apparatus 530 that includes a coal storage bin 532 coupled in flow communication to the coal supply via conduit 212. Coal storage bin 532 includes a plurality of steam coils 534 that are coupled in flow communication with LP steam source 505. Steam coils 534 preheat the coal in coal storage bin 532 to any temperature that facilitates operation of system 211. Coal transfer apparatus 530 also includes a coal conveyor 536 that includes a coal flow control device 538 and a plurality of steam coils 539 that are coupled in flow communication with LP steam source 505. Steam coils 539 preheat the coal on coal conveyor 536 to any temperature that enables operation of system 211 as described herein.

Coal flow control device 538 includes a speed control device 540 and a weight control device 542 that cooperate to control a flow of coal on coal conveyor 536. In the exemplary embodiment, coal flow control device 538 is coupled to a more extensive slurry temperature and viscosity control system (not shown), and devices 540 and 542 generate and transmit signals (not shown) that are representative of a speed of conveyor 536 and a weight of coal on conveyor 536, respectively. Moreover, speed control device 540 facilitates automatic adjustment of speed of conveyor 536 as a function of weight of coal on conveyor 536. For example, a decrease in weight of coal on conveyor 536 causes an increase in speed of conveyor 536 to maintain an approximately constant rate of coal flow at a predetermined or operator-selected value. Alternatively, coal flow control device 538, with or without speed control device 540 and/or weight control device 542, includes any control architecture that enables system 211 to operate as described herein. Coal flow control device 538 cooperates with coal conveyor 536 to generate a coal stream 544.

Moreover, in the exemplary embodiment, slurry preparation system 211 includes a grinding mill 550. Grinding mill 550 includes an intake conduit 552 that receives coal stream 544. Intake conduit 552 is coupled in flow communication with recycle fluid transfer conduit 518 and receives the mixture of preheated recycle water with entrained solids. Intake conduit 552 is also coupled in flow communication with a second LP steam injection system 554 that is coupled in flow communication with LP steam source 505.

Intake conduit 552 is further coupled in flow communication with a slurry viscosity additive system 553. System 553 includes a slurry viscosity additive source 555. System 553 also includes a flow control device 557 coupled in flow communication with source 555 and intake conduit 552 via a slurry viscosity additive conduit 559. Flow control device 557 channels a predetermined amount of slurry viscosity additive (not shown) into grinding mill 550.

In the exemplary embodiment, second LP steam injection system 554 includes a second LP steam flow control device 556 that is coupled in communication with a second temperature control sensor 558. Also, in the exemplary embodiment, device 556 is a second LP steam flow control valve 556. Alternatively, second LP steam flow control device 556 is any flow control device that enables operation of system 211 as described herein. Second LP steam injection system 554 also includes a mill supply LP steam conduit 560 that is coupled in flow communication with valve 556. Second LP steam injection system 554 also includes a conduit 562 that is coupled in flow communication with conduit 560. In the exemplary embodiment, conduit 562 is a flexible conduit, for example, but not limited to, rubber hose. Alternatively, conduit 562 is a rigid conduit, for example, but not limited to, plastic. Also, alternatively, conduit 562 is any device fabricated from any material that enables operation of system 211 as described herein.

Grinding mill 550 also includes a grinding device 564 that, after receiving coal pieces from coal stream 544, grinds the coal into smaller pieces within a predetermined size range. Grinding mill 550 further includes a coal discharge port 566 that is coupled in flow communication with grinding device 564.

In the exemplary embodiment, conduit 562 is positioned within grinding mill 550 to enable LP steam to mix with the preheated coal as it is ground by grinding device 564, and with the preheated recycle fluid as it is mixed with the ground coal. Such mixing facilitates increasing the mixing action of coal, fluid, and steam, while reducing heat losses therefrom.

In the exemplary embodiment, slurry preparation system 211 includes a recycle fluid flow control sensor 568 that is coupled in flow communication with recycle fluid transfer conduit 518 and to a recycle fluid flow control device 570. Any recycle flow control device such as a valve, enables system 211 to operate as described herein may be used. Sensor 568 generates and transmits signals (not shown) that are representative of a rate of flow of the preheated recycle fluid stream entering grinding mill 550. Sensor 568 and valve 570 cooperate to control a flow of preheated recycle water and entrained solids into mill grinder 550.

Also, in the exemplary embodiment, slurry preparation system 211 includes a LP steam flow control sensor 572 that is coupled in flow communication with mill supply LP steam conduit 560 and with LP steam source 505. Sensor 572 generates and transmits signals (not shown) that are representative of a rate of flow of LP steam into grinding mill 550.

Further, in the exemplary embodiment, LP steam flow control sensor 572 is coupled in communication with recycle fluid flow control sensor 568, recycle fluid flow control valve 570, and coal flow control device 538, including speed control device 540 and weight control device 542. Sensor 572, sensor 568, valve 570, and device 538 cooperate to control a flow of preheated recycle water and entrained solids, steam, and coal entering mill grinder 550, and thereby control a temperature, flow, and viscosity of the slurry within mill grinder 550. Moreover, grinding mill 550 mixes steam, ground coal, preheated recycle water and the associated entrained solids to form a preheated slurry stream 574 that is channeled from grinding mill 550 at a predetermined flow rate. Further, sensor 572, sensor 568, valve 570, and device 538 cooperate to control temperature and viscosity of slurry stream 574. Also, the predetermined slurry viscosity additive channeled into grinding mill 550 via slurry viscosity additive system 553, and more specifically, flow control device 557, facilitates decreasing a viscosity of stream 574 as a function of temperature. Therefore, the additive, in conjunction with an increased temperature of stream 574, facilitates an increase in a coal content, or coal density, of stream 554.

Further, in the exemplary embodiment, slurry preparation system 211 includes a mill discharge tank 576 that receives preheated slurry stream 574 from grinding mill 550. Mill discharge tank 576 includes a mixing apparatus 578 that functions similarly to mixing apparatus 504. Second temperature control sensor 558 is coupled with tank 576.

Sensor 558 cooperates with sensor 572, sensor 568, valve 570, device 538, and valve 556 to facilitate control of temperature, rate of flow, and viscosity of preheated slurry stream 574. More specifically, sensor 558 transmits temperature feedback signals (not shown) that are representative of a temperature of the slurry within discharge tank 576. Therefore, in the exemplary embodiment, sensor 558 facilitates control of steam flow into grinding mill 550 via modulation of valve 556. Sensor 572 generates and transmits a signal (not shown) to device 538 and valve 570 via sensor 568 that is substantially representative of steam flow through system 554 into grinding mill 550. Device 538 and valve 570 modulate a flow rate of coal stream 544 and recycle fluid stream via conduit 518, respectively. Such modulation of flows of coal, water, and steam facilitates reducing a potential for undue dilution of slurry stream 574.

In the exemplary embodiment, the temperature range of preheated slurry stream 574 is approximately 71.1° C. (160° F.) to approximately 93.3° C. (200° F.), with a target median of approximately 82.2° C. (180° F.). Alternatively, preheated slurry stream 574 may be preheated to any temperature that enables operation of system 211 as described herein. Mixing apparatus 578 agitates the coal and recycle solids within the water in mill discharge tank 576 to control of the viscosity of preheated slurry stream 574 within tank 576.

In the exemplary embodiment, second temperature control sensor 558, second LP steam flow control valve 556, recycle fluid flow control sensor 568, recycle fluid flow control valve 570, coal flow control device 538, including speed control device 540 and weight control device 542, and LP steam flow control sensor 572 are coupled to a more extensive control system (not shown). Alternatively, sensor 558, valve 556, sensor 568, valve 570, device 538, and sensor 572 may use or be coupled to any control architecture that enables system 211 to operate as described herein.

Moreover, in the exemplary embodiment, slurry preparation system 211 includes a mill discharge pump 580 that is coupled in flow communication to mill discharge tank 576 via a slurry conduit 582. Slurry preparation system 211 also includes a slurry run tank 584 that is coupled in flow communication with mill discharge pump 580 via a slurry conduit 586. Mill discharge pump 580 channels preheated slurry (not shown) from mill discharge tank 576 to slurry run tank 584. Tank 584 includes a slurry flow control device 588 that facilitates flow control of preheated slurry into slurry run tank 584. Slurry run tank 584 also includes a mixing apparatus 590 that functions similarly to mixing apparatus 504 and 578.

Also, in the exemplary embodiment, slurry preparation system 211 includes a slurry booster pump 592 that is coupled in flow communication with slurry run tank 584 via a slurry conduit 594. Further, slurry preparation system 211 includes a slurry charge pump 596 that is coupled in flow communication with slurry booster pump 592 via a slurry conduit 598. Slurry booster pump 592 channels a preheated slurry stream (not shown) from slurry run tank 584 to slurry charge pump 596. In the event that slurry run tank 584 cannot provide a sufficient net positive suction head (NPSH) to slurry charge pump 596, because of elevated temperatures, for example, i.e., lower densities, of the preheated slurry stream, slurry booster pump 592 provides additional NPSH. Alternatively, slurry preparation system 211 does not include a slurry booster pump 592.

Further, in the exemplary embodiment, slurry preparation system 211 includes a slurry recirculation conduit 600 that is coupled in flow communication with conduit 598 and slurry run tank 584. Slurry recirculation conduit 600 enhances flow control of the preheated slurry to slurry charge pump 596 by channeling excess slurry back to tank 584. Slurry charge pump 596 channels the preheated slurry stream into coal slurry conduit 214.

Moreover, in the exemplary embodiment, slurry preparation system 211 includes a third LP steam injection system 602 that is coupled in flow communication with LP steam source 505. In the exemplary embodiment, third LP steam injection system 602 includes an LP steam injection device 604 coupled in flow communication with a third LP steam flow control device 606. In the exemplary embodiment, device 604 is a steam injection venturi 604 and device 606 is a steam flow control valve 606. Alternatively, devices 604 and 606 are any respective injection devices and/or flow devices that enable operation of system 211 as described herein.

Valve 606 is coupled in flow communication with LP steam source 505 and with a third temperature control sensor 608, wherein sensor 608 generates and transmits signals (not shown) that are representative of temperatures of the preheated slurry in conduit 214 downstream of venturi 604. Third LP steam injection device 602 channels LP steam into the preheated slurry stream within conduit 214 and, as the injected steam mixes and condenses within the preheated slurry stream downstream of device 602, facilitates preheating the preheated slurry stream from a temperature range of approximately 71.1° C. (160° F.) to approximately 93.3° C. (200° F.), with a target median of approximately 82.2° C. (180° F.) to a temperature range of approximately 126.7° C. (260° F.) to approximately 148.9° C. (300° F.), with a target median of approximately 137.7° C. (280° F.). Alternatively, the preheated slurry stream is heated to any temperature that enables operation of system 211 and gasification reactor 208 (shown in FIG. 1) as described herein. In the exemplary embodiment, third temperature control sensor 608 and third LP steam flow control valve 606 are coupled to a more extensive slurry temperature and viscosity control system (not shown).

Also, in the exemplary embodiment, mill discharge tank 576, mill discharge pump 580, slurry run tank 584, slurry booster pump 592, slurry charge pump 596, and associated conduits 582, 586, 594, 598, and 214 are sufficiently insulated to facilitate maintaining a temperature and viscosity of the slurry materials channeled therein.

In operation, makeup water via water supply conduit 213 and warm gasification by-products via AGR regeneration conduit 508, slag supply conduit 510, and settler bottoms conduit 512, are channeled into recycle solids tank 502. The make-up water and warm gasification by-products are agitated and mixed by mixing apparatus 504 to form preheated water with suspended solids, or preheated fluid. LP steam is channeled through heating device 506 to facilitate heating the fluid to a temperature range of, in the exemplary embodiment, approximately 54.4 degrees Celsius (° C.) (130 degrees Fahrenheit (° F.)) to approximately 76.6° C. (170° F.), with a target median of approximately 65.6° C. (150° F.).

Recycle fluid transfer pump 514 and tank discharge conduit 516 channel the fluid from tank 502 into recycle fluid transfer conduit 518 to form a preheated recycle fluid stream. LP steam injection system 520 injects LP steam into the recycle fluid stream via LP steam injection venturi 522 and first LP steam flow control valve 524. First temperature control sensor 526 generates and transmits temperature feedback signals that are representative of the temperatures of the preheated recycle fluid stream downstream from injection device 522.

Coal that has been preheated within coal storage bin 532 is channeled to coal conveyor 536, wherein the coal is further heated by LP steam within steam coils 539. Preheated coal stream 544 is channeled to grinding mill 550 and the preheated recycle fluid stream is channeled into grinding mill 550 via conduit 518 and recycle flow control valve 570. LP steam is then channeled into grinding mill 550 via second LP steam flow control valve 556 and conduit 562. Grinding mill 550 grinds the preheated coal into smaller pieces (not shown) with grinding device 564 and mixes the coal, steam, and preheated recycle fluid to form preheated slurry stream 574. Stream 574 is channeled into mill discharge tank 576 to facilitate mixing of the preheated slurry with mixing apparatus 578 and to facilitate controlling the viscosity of the preheated slurry within tank 576.

Moreover, in operation, second temperature control sensor 558 indirectly cooperates with LP steam flow control sensor 572, recycle fluid flow control sensor 568, recycle fluid flow control valve 570, second LP steam flow control valve 556 and coal flow control device 538, including speed control device 540 and weight control device 542, to facilitate control of temperature, rate of flow, and viscosity of preheated slurry stream 574. More specifically, sensor 558 transmits temperature feedback signals that are representative of a temperature of the preheated, mixed slurry within discharge tank 576, such tank slurry temperature being at least partially indicative of a temperature of preheated slurry stream 574.

Also, in operation, speed control device 540 and weight control device 542 cooperate to control a flow of coal on coal conveyor 536. Devices 540 and 542 transmit signals that are representative of a speed of conveyor 536 and weight of coal on conveyor 536, respectively. Moreover, speed control device 540 enables automatic adjustments of the speed of conveyor 536 as a function of weight of coal on conveyor 536.

Further, in operation, sensor 572 generates and transmits signals that are representative of a rate of flow of LP steam into grinding mill 550 to device 538 and valve 570 via sensor 568. Furthermore, sensor 568 transmits signals that are representative of a rate of flow of the preheated recycle fluid stream into grinding mill 550. Sensor 568 and valve 570 cooperate to control a flow of preheated recycle water and entrained solids into mill grinder 550.

Moreover, in operation, device 538 and valve 570 modulate a flow rate of coal stream 544 and preheated recycle fluid stream via conduit 518, respectively, thereby controlling flow rate, temperature, and viscosity of the slurry stream 574 channeled from grinding mill 550. Such modulation of flows of coal, water, and steam facilitates reducing a potential for undue dilution of slurry stream 574. In the exemplary embodiment, temperature of preheated slurry stream 574 is controlled to approximately 82.2° C. (180° F.). Also, in operation, the preheated slurry is channeled from mill discharge tank 576 to slurry run tank 584 via mill discharge pump 580 and slurry conduits 582 and 586. Mixing apparatus 590 agitates the preheated slurry to facilitate recovering a potential for temperature and viscosity stratification. Also, in operation, the preheated slurry is channeled to gasification reactor 208 via slurry booster pump 592, slurry charge pump 596, slurry conduits 594 and 598. Excess preheated slurry may channel excess slurry back to tank 584 via slurry recirculation conduit 600.

LP steam is injected into the preheated slurry channeled into conduit 214 via LP steam injection venturi 604 and third LP steam flow control valve 606. Third temperature control sensor 608 transmits signals that are representative of temperatures of the preheated slurry in conduit 214 downstream of venturi 604. As the injected steam mixes and condenses within the preheated slurry stream downstream of device 602, the preheated slurry stream is further heated.

A plurality of benefits are facilitated by injecting LP steam into a coal slurry and its associated constituents. For example, heating the slurry facilitates reducing oxygen consumption associated with syngas production since less oxygen is needed to combine with the fuel to attain a predetermined temperature. Moreover, heating the slurry facilitates maintaining slurry viscosity such that a spray pattern of the slurry within gasification reactor 208 is enhanced. As such, a droplet evaporation time is provided, while an efficiency of carbon conversion therein is improved. Reducing the oxygen consumption and improving the carbon conversion efficiency facilitates reducing operational costs of IGCC power generation plant 100. Moreover, such improvements in efficiency facilitates broadening a coal envelope, that is, a range of coals that may be used within IGCC power generation plant 100, including lower-cost coals.

FIG. 3 is a flow chart illustrating an exemplary method 700 of operating gasification system, and more specifically, exemplary IGCC power generation plant 100 (shown in FIGS. 1 and 2). In the exemplary embodiment, makeup water is preheated by channeling 702 steam through at least one heating device 506 (shown in FIG. 2) immersed within mixing tank 502. Makeup water is further heated by channeling 704 heated gasification by-product into recycle solids tank 502 and by at least partially mixing the makeup water with the heated gasification by-product. Makeup water is also further heated by channeling 706 the at least partially mixed makeup water and gasification by-product from recycle solids tank 502 to grinding mill 550 (shown in FIG. 2) and by channeling steam into the makeup water and the gasification by-product therebetween. At least a portion of a carbonaceous fuel is preheated by channeling 708 LP steam into coal transfer apparatus 530 (shown in FIG. 2), or more specifically, channeling LP steam through at least a portion of coal storage bin 532 (shown in FIG. 2) and by channeling LP steam through at least a portion of coal conveyor 536 (shown in FIG. 2).

Also, in the exemplary embodiment, the carbonaceous fuel is channeled 710 into grinding mill 550 via fuel flow control device 538 (shown in FIG. 2). The at least partially mixed preheated makeup water and gasification by-product, are channeled 712 into grinding mill 550 via recycle fluid flow control valve 570 (shown in FIG. 2). The slurry viscosity additive is channeled 713 into grinding mill 550 via flow control device 557 (shown in FIG. 2), and steam is channeled 714 into grinding mill 550 via second LP steam flow control valve 556 and conduit 562 (both shown in FIG. 2).

The carbonaceous fuel, preheated water, slurry viscosity additive, and steam are mixed 716 within grinding mill 550, to form preheated coal slurry stream 574 (shown in FIG. 2). Preheated coal slurry stream 574 is discharged 718 from grinding mill 550 with at least one of a predetermined slurry temperature and a predetermined slurry viscosity. Preheated coal slurry stream 574 is further heated 720 by channeling steam into preheated coal slurry stream 574.

Described herein are exemplary embodiments of methods and apparatus that facilitate production of synthetic gas (syngas), specifically, preheating a fuel slurry used to produce the syngas, and more specifically, by injecting low pressure steam into the fuel slurry and its associated constituents. Heating the fuel slurry within predetermined temperature parameters facilitates reducing oxygen consumption associated with syngas production, as less oxygen is required to attain a predetermined temperature within the gasification reactor. Moreover, heating the fuel slurry facilitates maintaining a fuel slurry viscosity within predetermined parameters that facilitates an improvement in a spray pattern of the fuel slurry within the gasification reactor. Such spray pattern improvement facilitates decreasing a droplet evaporation time and improving an efficiency of carbon conversion therein. Such reduction in oxygen consumption and improvement in carbon conversion efficiency reducing lower operational costs associated with syngas production. Moreover, such improvements in efficiency facilitate broadening a coal envelope, that is, a range of coals that may be used within any one gasification facility, including lower-cost coals.

The methods and systems described herein are not limited to the specific embodiments described herein. For example, components of each system and/or steps of each method may be used and/or practiced independently and separately from other components and/or steps described herein. In addition, each component and/or step may also be used and/or practiced with other assembly packages and methods.

While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Claims

1. A method of operating a gasification facility, said method comprising:

channeling steam into a grinding mill via a flow control device and a conduit; and

mixing carbonaceous fuel, preheated water, and steam within the grinding mill, to form a preheated coal slurry stream.

2. A method in accordance with claim 1, wherein the conduit is one of rigid conduit and flexible conduit.

3. A method in accordance with claim 1 further comprising:

channeling carbonaceous fuel into the grinding mill via a fuel flow control device; and

channeling preheated water into the grinding mill via a flow control device.

4. A method in accordance with claim 3 further comprising at least one of:

channeling a slurry viscosity additive into the grinding mill via a flow control device, thereby mixing the slurry viscosity additive within the grinding mill; and

heating the preheated coal slurry stream by channeling steam into the preheated coal slurry stream.

5. A method in accordance with claim 4, wherein mixing carbonaceous fuel, preheated water, slurry viscosity additive, and steam within the grinding mill comprises modulating a rate of flow of each of the carbonaceous fuel, preheated water, slurry viscosity additive, and steam for discharging the preheated coal slurry stream from the grinding mill with at least one of a predetermined slurry temperature and a predetermined slurry viscosity.

6. A method in accordance with claim 5, wherein discharging the preheated coal slurry stream from the grinding mill comprises preheating makeup water by at least one of:

channeling steam through at least one heating device immersed within a mixing tank;

channeling heated gasification by-product into the mixing tank and at least partially mixing the makeup water with the heated gasification by-product; and

channeling at least partially mixed makeup water and gasification by-product from the mixing tank to the grinding mill and channeling steam into the makeup water and the gasification by-product therebetween.

7. A method in accordance with claim 5, wherein discharging the preheated coal slurry stream from the grinding mill comprises preheating at least a portion of the carbonaceous fuel by channeling steam into a coal transfer apparatus comprising at least one of:

channeling steam through at least a portion of a coal storage bin; and

channeling steam through at least a portion of a coal conveyor.

8. A slurry preparation system coupled in flow communication with a carbonaceous fuel source, a makeup water source, and a steam source, said slurry preparation system comprising a fuel grinding mill coupled in flow communication with the steam source via at least one conduit.

9. A slurry preparation system in accordance with claim 8, wherein said at least one conduit is one of a flexible conduit and a rigid conduit.

10. A slurry preparation system in accordance with claim 8 further comprising at least one slurry viscosity additive flow control device coupled in flow communication with a slurry viscosity additive source.

11. A slurry preparation system in accordance with claim 8 further comprising at least one of:

at least one steam flow control device coupled in flow communication with the steam source and said at least one conduit; and

at least one temperature control device coupled in communication with said at least one steam flow control device.

12. A slurry preparation system in accordance with claim 11 further comprising at least one mixing tank coupled in flow communication with the makeup water source and with at least one gasification by-product source.

13. A slurry preparation system in accordance with claim 12 wherein said at least one mixing tank is coupled in flow communication with said grinding mill via a fluid transfer conduit and at least one of:

at least one steam injection device coupled in flow communication with said fluid transfer conduit; and

at least one fluid flow control device coupled in flow communication with said fluid transfer conduit.

14. A slurry preparation system in accordance with claim 13 wherein said at least one fluid flow control device is coupled in communication with said at least one steam flow control device.

15. A gasification facility comprising:

a carbonaceous fuel source;

a makeup water source;

a steam source; and

a slurry preparation system coupled in flow communication with said carbonaceous fuel source, said makeup water source, and said steam source, said slurry preparation system comprising a fuel grinding mill coupled in flow communication with said steam source via at least one conduit.

16. A gasification facility in accordance with claim 15, wherein said at least one conduit is one of a flexible conduit and a rigid conduit.

17. A gasification facility in accordance with claim 15 further comprising at least one slurry viscosity additive flow control device coupled in flow communication with a slurry viscosity additive source.

18. A gasification facility in accordance with claim 15 further comprising at least one of:

at least one steam flow control device coupled in flow communication with the steam source and said at least one conduit; and

at least one temperature control device coupled in communication with said at least one steam flow control device.

19. A gasification facility in accordance with claim 18 further comprising

at least one mixing tank coupled in flow communication with the makeup water source and with at least one gasification by-product source, wherein said at least one mixing tank is coupled in flow communication with said grinding mill via a fluid transfer conduit and at least one of: at least one steam injection device coupled in flow communication with said fluid transfer conduit; and at least one fluid flow control device coupled in flow communication with said fluid transfer conduit.

20. A gasification facility in accordance with claim 19 further comprising a coal transfer apparatus coupled in flow communication with said carbonaceous fuel source, said coal transfer apparatus comprises a fuel flow control device coupled in communication with said at least one fluid flow control device and said at least one steam flow control device.