Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C3/00—Gas-turbine plants characterised by the use of combustion products as the working fluid
  • F02C3/20—Gas-turbine plants characterised by the use of combustion products as the working fluid using a special fuel, oxidant, or dilution fluid to generate the combustion products
  • F02C3/26—Gas-turbine plants characterised by the use of combustion products as the working fluid using a special fuel, oxidant, or dilution fluid to generate the combustion products the fuel or oxidant being solid or pulverulent, e.g. in slurry or suspension

Definitions

• This invention pertains to a process for pressurized combustion of particulate solid combustible materials to generate power. It pertains particularly to a process for the pressurized combustion of particulate solid waste materials such as wood chips in a cyclonic type burner to produce hot effluent gas, which is cooled, cleaned and expanded through a gas turbine driving an air compressor and an electric generator.
• U.S. Patent 2,625,791 to Yellott describes a process and equipment developed by Bituminous Coal Research, Inc. for pressurized combustion of pulverized coal to pro ⁇ turn a combustion gas which is expanded in a gas turbine to drive an electric generator.
• U.S. 2,735,266 to Atherton discloses a basic process and apparatus for the pressurized combustion of wood wastes in dual vertical combustion cham ⁇ bers to generate hot effluent gas used for driving a gas turbine and electric generator.
• the present invention provided a process for pressu ⁇ rized combustion of particulate solid combustible materials to produce a hot pressurized effluent gas used for producing power, such as by expanding the gas through a gas turbine to drive an air compressor and a shaft load, ususally an elec ⁇ tric generator.
• a particulate "solid combustible material, such as wood chips or coke, is fed by suitable means into an air stream pressurized to 3-at ⁇ . and is pneumatically conveyed through a conduit and fed into the inlet port of a cylindrical cyclonic type burner at superficial gas velocity exceeding about 75 ft/sec.
• Additional combustion air is supplied to the burner tangentially through multiple tuyeres spaced-apart along the burner length at a tangential velo ⁇ city exceeding about 100 ft/sec.
• the par ⁇ ticles are rapidly heated and combusted with the added secondary combustion air to provide a high volumetric heat
• the hot gas from the burner primary combustion chamber passes through a choke section and is quenched and cooled in a secondary combustion chamber to a temperature suitable for expanding in a gas turbine, usually about 1400-
• any remaining particulate solids in the effluent gas leaving the burner are mechanically separated from the gas in a cyclone separator, after which the clean gas is then expanded to a lower pressure through a gas turbine for driving a compressor to provide the pressurized combustion air required in the burner.
• the gas turbine provides net shaft power output for driving a load, which is usually an electric power generator.
• the pressurized-combustion process of the present invention is useful for various combustible solids materials, including but not limited to wood bark, wood chips, sawdust, trim, and shavings, petroleum coke, and mixtures thereof. It is an advantage of the process of this invention that the particulate combustible solids, such as wood chips, are pressurized and burned efficiently at high volumetric heat release rates to provide a clean hot effluent gas at controlled temperature suitable for expanding through a gas turbine for producing power. Because of the burner compact ⁇ ness and high heat release rates, the overall process and equipment is more efficient and cost effective and the process equipment requires less space for a particular power rating than for prior conventional processes.
• Fig. 1 is a schematic diagram of the basic process for the pressurized combustion of particulate combustible solids to produce power.
• a source 10 pro ⁇ vides wood chips having size not exceeding about 0.70 inch major dimension, and preferably smaller than about 0.130 inch, which chips are collected at 11 in the hopper 12 maintained at substantially atmospheric pressure.
• the chips 11 are fed from the hopper 12 by a variable speed screw conveyor 14 driven by motor 14a into a vertically oriented chute 15, and are then passed to a suitable feeder means 16 for delivering the wood particulate solids material into pressurized conveying conduit 18.
• Feeder 16 preferably consists of two rotary valves 16a and 16b connected in series and arranged for transferring the particulate solids material by gravity flow from chute 15 into the conduit 18 at a pressure of about 3-20 atm. absolute, and preferably at 4-15 atm. pressure.
• the pressurized transport air from conduit 17 flows in conduit 18 at 40-120 ft/sec superficial velocity and preferably at 60-100 ft/sec velocity and pneu ⁇ matically conveys the particulate solids material tangen- tially to the pressurized burner 20.
• the particulate solids fuel material is fed pnue- matically into burner 20 at near its inlet end through tangential inlet port 21 at superficial gas velocity exceeding about 80 ft/sec and preferably at 90-150 ft/sec into primary combustion chamber 22.
• Additiona'l combustion air is introduced tangentially into the primary combustion chamber 22 at superficial velocity exceeding about 100 ft/sec, and preferably 110-150 ft/sec, through multiple spaced-apart openings or tuyeres 24a, 24b, 24c, etc., located axially along the length of chamber 22.
• pre ⁇ heating or drying the solids in conduit 18 is desired, such preheating can be provided in heat exchanger 19 using any convenient source of heat such as turbine exhaust gas flowing through a jacket surrounding an elongated heat exchanger.
• the fuel solids are made to swirl around at high rotational velocity exceeding about 80 ft/sec and preferably at 100-150 f /sec and produce high centrifugal forces exceeding about 140 gravitational units 'g', while the particles are rapidly heated by the hot chamber walls and progressively devolatized and burned to produce a hot pressurized effluent gas at a temperature of about 2800° F.
• the particles are also advantageously retained in the primary chamber 22 for prolonged combustion therein, not only by the high centrifugal forces but also by the effect of choke opening 25, located at the exit end of the primary chamber 22.
• the choke opening 25 has a • " smaller cross-sectional opening area than the combustion zone 22 so as to prolong the particle solids combustion time therein and thereby provide for more complete combus ⁇ tion of the particulate fuel solids and produce very high volu etric heat release rates exceeding about 400,000
• the primary combustion chamber 22 should have a length/diameter aspect ratio for the chamber at least about 2.5:1 and usually need not exceed about 10:1 to provide for adequate combustion time for the solids.
• the combustion chamber inside diameter should be at least about 1.5 ft. for achieving a reasonable throughput rate for the combustible solids material and usually should not exceed about 3 ft. diameter to achieve adequate rotational velocity for the solid particles there ⁇ in.
• the hot effluent gas at about 2800° F temperature is mixed with additional combustion air provided through conduit 28, to quench and cool the hot effluent gas to lower temperature such as 1600-1800° F suitable for extended use in a gas turbine.
• the secondary or quench air is introduced in the choke zone through dual openings-26 oriented in a tangential direction opposite to that for tuyeres 24 in the primary combustion chamber 22, thereby producing highly turbulent shear type mixing of the two streams in the choke zone leading to secondary combustion zone 30.
• the flow of supplementary air at conduit 28 is controlled relative to combustion air in conduits 23a, 23b,.23c, etc. to the tuyeres 24a, 24b, 24c, etc. by controller 32, which monitors the air flows at flow meters 31a, 31b, and operates control valve 29 in condiut 28.
• the cyclone separator 34 preferably uses an axial flow type element 35 to provide for a more compact separator overall arrangement.
• TITUTE SHEET separator 34 a clean hot effluent gas stream at 1600-1800° F temperature is removed at 36, while the particulate solids removed are withdrawn through valve 37 for suitable disposal.
• the cleaned effluent gas at 36 at 3-10 atm. pressure is then passed through conduit 38 to the inlet of gas tur ⁇ bine 40, which is connected to drive air compressor 42 for supplying pressurized air source at 44 for the combustion air at tuyers 24 and the quench air at 28. Also, a portion of the compressed air stream at 44 is cooled at 45 against stream 45a sufficient to avoid combustion of the particulate solids such as to about 200° F, usually by heat exchange with ambient air.
• the air at 47 is further compressed at 46, preferably by a positive displacement type compressor, to a differential pressure such as 2-10 psi and preferably 4-8 psi to provide the pressurized air 17 required in conduit 18 for pneumatically conveying the wood chips into the burner 20.
• Turbine 40 also rotatively drives a load device 50, which is usually an electric generator for generating electric power. From turbine 40, exhaust stream 41 at near atmospheric pressure and at 900-1000° F temperature can be passed to a heat recovery step at 52 and used as a heat source for generating steam, for heating another fluid used for heating purp.oses, or as a hot gas for preheating and/or drying the particulate feed material in- heat exchanger 19.
• load device 50 which is usually an electric generator for generating electric power.
• exhaust stream 41 at near atmospheric pressure and at 900-1000° F temperature can be passed to a heat recovery step at 52 and used as a heat source for generating steam, for heating another fluid used for heating purp.oses, or as a hot gas for preheating and/or drying the particulate feed material in- heat exchanger 19.
• the gas turbine unit 40 can be divided into two sepa ⁇ rate turbines each operating at different rotational " shaft speeds, with the first turbine 40a used for driving the compressor 42 at a high rotational speed, and the inter ⁇ mediate exhaust gas stream at 41a from the first turbine 40a being passed to second turbine 40b which is.gear- connected to an electric generator_ ⁇ 50 for driving the gene ⁇ rator at a lower rotational speed.
• a single shaft type turbine-compressor unit can be used in which both the compressor and electric generator are driven by a single turbine.
• an auxiliary burner (not shown) using a hydrocarbon fuel source such as propane is used to initially heat the refractory walls of primary combustion chamber 22 to a temperature sufficient to ignite the particulate solid fuel introduced at 21.
• a hydrocarbon fuel source such as propane is used to initially heat the refractory walls of primary combustion chamber 22 to a temperature sufficient to ignite the particulate solid fuel introduced at 21.
• an auxiliary drive motor 54 is used to drive compressor 42 to provide the hot air source initially needed for combustion.
• air further compressed by compressor 46 is used for initially pneumatically conveying the particulate fuel solids through conduit 18 into the burner 20.
• Wood chips and shavings such as produced from a wood processing mill source and having nominal size of about 1/8 inch, were transferred from an atmospheric pressure col ⁇ lection hopper through tandem rotary feeder valves into a pressurized transfer pipe operating at about 5 atm. pressure.
• the wood chips were pneumatically * conveyed at superficial gas velocity of about 80 ft/sec and fed tan- gentially into the inlet end of a horizontally oriented cylindrical cyclonic burner primary combustion chamber having dimensions as shown in Table I below.
• Pressurized combustion air was also supplied tangentially into the combustion chamber through 6 sets of dual tuyeres spaced- apart axially along the chamber length and at superficial gas velocity of about 100 ft/sec. Numerous observations of burner operation made through viewing ports indicated that the particulate solids were circulated in a swirling he ⁇ lical flow path in the combustion chamber at calculated tangential velocity of about 100 ft/sec until consumed.
• the wood particles being circulated at the high rotational velocity developed high centrifugal forces of about 200 'g' , which provided for prolonged total combustion of the particles at high Reynolds number and produced high volumetric heat release rates of about 1,800,000 Btu/hr ft 3 .
• the solid fuel particles were rapidly devolatized and combusted to produce a hot effluent gas at 2700-2800° .F temperature, which passed through a restricted choke opening at the exit end of the combustion chamber.
• the resulting hot effluent gas at about 2700-2800° F " temperature was quenched by additional pressurized secondary air injected tangentially into the throat portion of the choke opening.
• the quench air was injected tangentially in a direction opposite to that of the swirling effluent gas from the primary combustion chamber, thus producing highly turbulent shear type mixing of the two gas streams so that the hot effluent gas was effectively cooled to about 1700° F and then passed into ' a secondary combustion chamber located immediately downstream from the choke.
• the resulting cooled and cleaned gas -at about 1600° F temperature is then expanded through a gas turbine driving a rotary air compressor to provide the pressurized transport and combustion air-, and also driving an electric generator to produce net electric power. Based on burner operating data and related experience, the projected continuous operating period for this process is in excess of 30,000 hours.
• the present process utilizes improved pressurized combustion of wood chips or other particulate solid combustible material to provide high volumetric heat release rates in the burner.
• the process also utilizes effective quenching and cooling of the hot effluent gas together with gas-solids separa ⁇ tion to provide a clean pressurized effluent gas suitable for extended use in a gas turbine to produce electrical power.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Engine Equipment That Uses Special Cycles (AREA)

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• 1985
  • 1985-06-21 WO PCT/US1985/001189 patent/WO1986000375A1/en not_active Ceased
  • 1985-06-21 EP EP19850903534 patent/EP0189459A1/de not_active Withdrawn

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