CA1119007A - Process and arrangement for operating a steam power station - Google Patents
Process and arrangement for operating a steam power stationInfo
- Publication number
- CA1119007A CA1119007A CA000318482A CA318482A CA1119007A CA 1119007 A CA1119007 A CA 1119007A CA 000318482 A CA000318482 A CA 000318482A CA 318482 A CA318482 A CA 318482A CA 1119007 A CA1119007 A CA 1119007A
- Authority
- CA
- Canada
- Prior art keywords
- steam
- fluidized bed
- zone
- turbine
- preheater
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
- F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
- F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
- F01K23/061—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with combustion in a fluidised bed
- F01K23/062—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with combustion in a fluidised bed the combustion bed being pressurised
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- 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
- F02C3/205—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 in a fluidised-bed combustor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B1/00—Methods of steam generation characterised by form of heating method
- F22B1/22—Methods of steam generation characterised by form of heating method using combustion under pressure substantially exceeding atmospheric pressure
- F22B1/24—Pressure-fired steam boilers, e.g. using turbo-air compressors actuated by hot gases from boiler furnace
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Engine Equipment That Uses Special Cycles (AREA)
- Fluidized-Bed Combustion And Resonant Combustion (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method and arrangement are disclosed for operating a steam power plant having a steam generator heated by a fluid-ized bed furnace. The fluidized bed is provided with pressurized combustion air which permits a reduction in the bed dimensions.
Combustion gases heat feedwater passing through a series of heat exchangers in the steam generator to provide a working fluid for a steam turbine. The steam turbine operates an electrical current generator. The electrical current generated by the generator is the product of a purely steam generating process.
The combustion gases are also used for superheating the steam and for preheating recirculated feedwater in a heat exchanger contained within the steam generator. The combustion gases also drive a gas turbine which is connected to a compressor, with the compressor supplying the pressurized combustion air to the fluidized bed. After vaporizing the feedwater, superheating the steam, preheating the feedwater and driving the gas turbine, the combustion gases are at such a low temperature that they can be passed directly into the atmosphere through a chimney. An increase in the thermal efficiency of the system is provided by the use of the combustion gases to preheat the feedwater and drive the gas turbine.
A method and arrangement are disclosed for operating a steam power plant having a steam generator heated by a fluid-ized bed furnace. The fluidized bed is provided with pressurized combustion air which permits a reduction in the bed dimensions.
Combustion gases heat feedwater passing through a series of heat exchangers in the steam generator to provide a working fluid for a steam turbine. The steam turbine operates an electrical current generator. The electrical current generated by the generator is the product of a purely steam generating process.
The combustion gases are also used for superheating the steam and for preheating recirculated feedwater in a heat exchanger contained within the steam generator. The combustion gases also drive a gas turbine which is connected to a compressor, with the compressor supplying the pressurized combustion air to the fluidized bed. After vaporizing the feedwater, superheating the steam, preheating the feedwater and driving the gas turbine, the combustion gases are at such a low temperature that they can be passed directly into the atmosphere through a chimney. An increase in the thermal efficiency of the system is provided by the use of the combustion gases to preheat the feedwater and drive the gas turbine.
Description
~9~07 BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method and arrangement for operating a steam power plant having a fluidized bed furnace.
It is known to burn pulverized coal mixed with an absorbent in a fluidized bed to provide heat for a steam generator or boiler. The exhaust gases of the fluidized bed are relatively sulphur-free, thereby reducing pollution of the environment.
Presently known fluidized bed systems use either conventional steam generating processes in which the combustion occurs at atmospheric pressure or combined gas-steam processes. The steam and the combined gas-steam systems both suffer from both economic and technical disadvantages.
The conventional steam process, in which the combustion occurs at atmospheric pressure, requires a relatively large-dimensioned fluidized bed, since the fluidized bed velocity must be kept low. Therefore, relatively large and expensive equipment is necessary to provide for passing of the entire volume of air through the bed.
The combined gas-steam system, in turn, is disadvantageous because the operating temperature of the fluidized bed must not be substantially greater than 800C to prevent reaction of the fuel sulphur with the absorbent material. The limitation on the operating temperature of the fluidized bed, according to the present state of the art, results in a process which is not economically feasible. The efficiency of the gas-111900~7 steam process is also limited by the necessity of using airpassing through the bed to cool the pipes within the fluidized bed. In order to maintain the pipe wall temperature within reasonable limits, a relatively high pressure drop through the pipes is required. This high pressure drop provides for the substantial heat transfer needed for cooling the pipes. The large pressure drop and the relatively low temperature of the air which flows through the air preheater of the in~tallation ad-versely effect the efficiency of the fluidized bed. In addition, a high pipe wall temperature can lead to corrosion and erosion phenomena. For example, at a pipe wall temperature of approx-imately 750C, the temperature at the inlet of the gas turbine is at most 770C, which is insufficient to prevent corrosion with-in the turbine.
Therefore, it is an object of the present invention to provide a method and an arrangement for operating a power plant using a fluidized bed which is not subject to the limitations of the prior known systems.
The method of the present invention employs a fluidized bed in which combustion takes place under pressure. Pressurized air is introduced into the bed to fluidize the fuel and to pressurize the steam generator. The gases produced ~y the com-bustion of the fuel within the fluidized bed vaporize feedwater passing through the steam generator to provide steam for operating a turbogenerator arrangement. Thus the electrical current gener-ated by the turbogenerator arrangement is the product of a purely steam generating process. The combustion gases are also used for superheating the steam and for preheating the feedwater. Exhaust gase~ exiting the fluidized bed pass through a precipitator to remove flyash, with the gases then used to drive a turbine and compressor arrangement which supplies the pressurized air to the fluidized bed. The gases, which are then at a temperature of ~119007 about 120-150C, are then passed directly into the atmosphere through a chimney.
-3a-~1~9~)07 The apparatus of the present invention consists of a steam generator heated by a fluidized bed furnace. A steam turbogenerator having adjoining feedwater preheater~zones respectively before and after the turbines is employed to generate electricity. The steam generator or boiler is kept under pressure by a compressor which supplies air to the fluidized bed. The compressor is driven by a gas turbine which uses the exhaust gases of the fluidized bed as a working fluid. A feedwater heater, typically a multiple pipe heat exchanger, is arranged within the fluidized bed for generating steam by extracting the heat of the burned fuel. Additionally, a superheater and a feedwater preheater are arranged in the pressure chamber of the steam generator in such a way that they are exposed to the flue gas rising in the fluidized bed.
In one aspect of the present invention there is provided a method of producing steam in a steam boiler fired by a fluidized bed burner to drive a steam turbine, the method comprising the steps of: supplying fuel and pressurized air from a rotary compressor to the fluidized bed burner, combusting said fuel and said pressurized air at said fluidized bed burner to produce heat at a first zone, supplying feedwater to a preheater in a second zone in said steam boiler spaced from said fluidized bed burner; conducting feedwater from said preheater through an evaporator in said first zone to produce steam, conducting steam from said evaporator through a superheater in a third zone in said steam boiler located between said first zone and said second zone; conducting combustion gases from said first zone sequentially through said third zone and said second zone and then through a dust precipitator; driving said rotary compressor by a gas turbine supplied with relatively cool gases under pressure from said dust precipitator, the temperatuxe of the gases in said second zone being substantially less than ~
1~19007 1n said first zone; and driving said steam turbine by steam fromsaid superheater.
In a further aspect of the present invention there is provided a steam power plant comprising: a steam boiler having a fluidized bed burner for generating steam, a rotary air compressor for supplying pressurized air to said fluidized bed burner; a gas turbine for driving said rotary air compres-sor' an evaporator in said steam boiler adjacent said fluidized bed burner, a superheater and a preheater in said steam boiler spaced above said fluidized bed burner, said steam boiler being arranged to conduct gas from said fluidized bed burner sequentially over said superheater and then over said pre-heater; a dust precipitator; conduit means for conducting flue gas from said preheater through said dust precipitator to said gas turbine, and conduit means both for conducting feed-water in sequence through said preheater and said evaporator to produce steam and for conducting said steam through said superheater to a steam turbine, whereby said gas turbine operates at a relatively cool temperature as a result of passing the flue gas over said preheater in said steam boiler before passing the flue gas through said dust precipitator and said gas tur-bine.
BRIEF DESCRIPTION OF THE DRAWING
A preferred embodiment of the present invention is described with reference to the single accompanying drawing wherein like members bear like reference numerals. The single drawing is a schematic illustration of a steam power plant ac-cording to the present invention including a fluidized bed furnace.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the single drawing, a steam gener-ator 1 for a steam power plant contains a fluidized bed fur-nace 2, the details of which are not illustrated. The fluidized bed operates in a conventional manner, having a -4a-1.~19()07 bed of pulverized coal to which an absorbent such as, for example, limestone or dolomite, is added. The fuel is fluidized within the bed to provide for combustion of the coal, thereby generating heat for the steam generator.
Superheated steam is generated within the steam generator 1 and passes from the boiler through a fresh steam line 3 to a steam turbine 4, wherein the steam is expanded to release energy. An electrical generator 5 is coupled to the steam turbine 4 to generate electricity. The spent steam discharging from the steam turbine 4 is precipitated in a condenser 6 and the condensate is conveyed by means of a condensate pump 7 through a preheater zone 8. The pre-heater zone 8, shown in a simplified manner, subjects boiler feedwater to a multi-stage preheating process, as condensed steam is withdrawn through extraction points 9 of the steam turbine 4. A feed pump 10 conveys the boiler feedwater through a feed line 11 back to the steam generator 1.
According to the present invention, the combustion of the pulverized coal within the fluidized bed furnace takes place under pressure. The combustion air required for the burning of the fuel is generated outside of the steam generator 1 in a separate turbine and compressor booster arrangement. A gas turbine 12 drives a compressor 13 in which air that is drawn in from the atmosphere at an intake 14 is compressed to, for example, 8-10 bar. During turbine start-up, a starter motor 16 which can be uncoupled at a coupling 15 from the turbine after start-up is used to drive the compressor 13.
The compressed air provided by the compressor 13 is conveyed through a pressure line 17 to a point below the blower plate 18 of the fluidized bed furnace within the 11~9~)07 steam generator 1. The compressed air flows through the blower plate 18 and forms an upwardly-directed carrier stream which lifts the solid fuel and absorbent particles and thus brings about the fluidized bed state.
The solid particles, typically consisting of pulverized coal together with an absorber material such as limestone or dolomite, are introduced into the furnace at 19 and 20 respectively.
The turbulent movement of the fluidized solids results in the exposure of a relatively large specific surface area. The high heat capacity of the fuel being fluidized and the exposed surface area result in high heat transmission coefficients from the fuel to the heat transfer surfaces within the steam generator 1. The heat transfer surfaces are typically multiple pipe heat exchangers, as illustrated by the pipes of a feedwater heater 21. The operating temperature of the fluidized bed is advantageously selected to be approximately 800C, which minimizes the problems arising from the reaction of the sulphur in the coal with the absorbent.
After passing over the feedwater heater 21, the hot flue gases within the steam generator transfer a portion of their heat content to a superheater 22 and a further portion to a preheater 23, before exiting the steam gener-ator 1. The superheater 22 provides an additional stage for heating the steam generated in the feedwater heater 21 before entering the steam turbine 4, while the preheater 23 heats recirculated feedwater discharged from the turbine.
The series of heat exchangers 21, 22 and 23 within the boiler a~l are in the flow path of the combustion gases of the fluidized bed on the steam turbine side.
The electrical current generated by the generator 5 is the product of a purely steam generating process. The steam process permits maximum use of the heat of the burned fuel by providing for preheating of the steam and feedwater, which results in a relatively high thermal efficiency within the steam power plant. The use of a fluidized bed which is operated under pressure and that is water-cooled permits a reduction in the size and cost of the fluidized bed instal-lation in comparison with the known installations, all of which operate with combustion at atmospheric pressure and with an air-cooled fluidized bed.
After passing over the preheater 23, the flue gases enter a dust precipitator 24. In the present inven-tion, the dust precipitator 24 is typically a simple cen-trifugal precipitator, since the flue gases are at a tempe-rature of only about 400C. At such a temperature, corro-sion and erosion problems are minimized. In the precipi-tator, the flue gases are mechanically separated from ash particles which are entrained in the stream of gas rising in the fluidized bed during the combustion process.
The precipitator apparatus has substantially smaller dimensions compared to that of known installations, because of the relatively simple construction of such a centrifugal device. Additionally, the gas volume which flows through the precipitator is relatively small as a result of the pressurizing operation within the fluidized bed, which reduces the size of the bed and therefore de-creases the volume of combustion air introduced into the bed.
After exiting the dust precipitator 24, the flue gases pass through a gas line 25 to the gas turbine 12. The 1119(:)0'7 gas turbine 12 is a pure expansion turbine and forms part of the booster arrangement. The residual heat content of the flue gases is released within the gas turbine 12 to drive the connected compressor 13. A low entry temperature for the flue gases supplied to the gas turbine (typically less than 400C) is feasible because the expansion turbine only drives the compressor 13 and does not contribute to the generation of electricity. Corresponding to this relatively low entry temperature is an off-gas exit temperature of about 120-150C. These off-gases can be passed directly into the atmosphere, at 26, through a chimney (which is not illustrated~ because of the low temperature. In conven-tional arrangements, the exhaust gases first have to be admitted to a heat exchanger downstream from the expansion turbine before being released into the atmosphere.
The usual downstream heat exchanger is, in the present invention, the preheater 23. Since the downstream heat exchanger in the present invention is incorporated within the pressure chamber of the steam generator 1, an optimum preheating of the steam in the steam turbine circuit becomes possible while the off-gas temperature remains sufficiently low. The steam preheating and the low off-gas temperature results in a correspondingly high efficiency of the installation of the present invention.
The present invention is not to be restricted to what is disclosed in the drawing and in the foregoing speci-fication. For example, the steam turbine circuit could readily be provided with a reheater. Also, a heavy fuel oil furnace could be provided instead of the coal furnace, in which case heavy fuel oil, instead of coal, is burnt with the absorbent in the fluidized bed~ The arrangement of the 1~9007 apparatus in the steam generator and the booster system would be the same and hence the process would remain within the scope of the invention.
The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by those skilled in the art without departing from the spirit of the present inven-tion.
The present invention relates to a method and arrangement for operating a steam power plant having a fluidized bed furnace.
It is known to burn pulverized coal mixed with an absorbent in a fluidized bed to provide heat for a steam generator or boiler. The exhaust gases of the fluidized bed are relatively sulphur-free, thereby reducing pollution of the environment.
Presently known fluidized bed systems use either conventional steam generating processes in which the combustion occurs at atmospheric pressure or combined gas-steam processes. The steam and the combined gas-steam systems both suffer from both economic and technical disadvantages.
The conventional steam process, in which the combustion occurs at atmospheric pressure, requires a relatively large-dimensioned fluidized bed, since the fluidized bed velocity must be kept low. Therefore, relatively large and expensive equipment is necessary to provide for passing of the entire volume of air through the bed.
The combined gas-steam system, in turn, is disadvantageous because the operating temperature of the fluidized bed must not be substantially greater than 800C to prevent reaction of the fuel sulphur with the absorbent material. The limitation on the operating temperature of the fluidized bed, according to the present state of the art, results in a process which is not economically feasible. The efficiency of the gas-111900~7 steam process is also limited by the necessity of using airpassing through the bed to cool the pipes within the fluidized bed. In order to maintain the pipe wall temperature within reasonable limits, a relatively high pressure drop through the pipes is required. This high pressure drop provides for the substantial heat transfer needed for cooling the pipes. The large pressure drop and the relatively low temperature of the air which flows through the air preheater of the in~tallation ad-versely effect the efficiency of the fluidized bed. In addition, a high pipe wall temperature can lead to corrosion and erosion phenomena. For example, at a pipe wall temperature of approx-imately 750C, the temperature at the inlet of the gas turbine is at most 770C, which is insufficient to prevent corrosion with-in the turbine.
Therefore, it is an object of the present invention to provide a method and an arrangement for operating a power plant using a fluidized bed which is not subject to the limitations of the prior known systems.
The method of the present invention employs a fluidized bed in which combustion takes place under pressure. Pressurized air is introduced into the bed to fluidize the fuel and to pressurize the steam generator. The gases produced ~y the com-bustion of the fuel within the fluidized bed vaporize feedwater passing through the steam generator to provide steam for operating a turbogenerator arrangement. Thus the electrical current gener-ated by the turbogenerator arrangement is the product of a purely steam generating process. The combustion gases are also used for superheating the steam and for preheating the feedwater. Exhaust gase~ exiting the fluidized bed pass through a precipitator to remove flyash, with the gases then used to drive a turbine and compressor arrangement which supplies the pressurized air to the fluidized bed. The gases, which are then at a temperature of ~119007 about 120-150C, are then passed directly into the atmosphere through a chimney.
-3a-~1~9~)07 The apparatus of the present invention consists of a steam generator heated by a fluidized bed furnace. A steam turbogenerator having adjoining feedwater preheater~zones respectively before and after the turbines is employed to generate electricity. The steam generator or boiler is kept under pressure by a compressor which supplies air to the fluidized bed. The compressor is driven by a gas turbine which uses the exhaust gases of the fluidized bed as a working fluid. A feedwater heater, typically a multiple pipe heat exchanger, is arranged within the fluidized bed for generating steam by extracting the heat of the burned fuel. Additionally, a superheater and a feedwater preheater are arranged in the pressure chamber of the steam generator in such a way that they are exposed to the flue gas rising in the fluidized bed.
In one aspect of the present invention there is provided a method of producing steam in a steam boiler fired by a fluidized bed burner to drive a steam turbine, the method comprising the steps of: supplying fuel and pressurized air from a rotary compressor to the fluidized bed burner, combusting said fuel and said pressurized air at said fluidized bed burner to produce heat at a first zone, supplying feedwater to a preheater in a second zone in said steam boiler spaced from said fluidized bed burner; conducting feedwater from said preheater through an evaporator in said first zone to produce steam, conducting steam from said evaporator through a superheater in a third zone in said steam boiler located between said first zone and said second zone; conducting combustion gases from said first zone sequentially through said third zone and said second zone and then through a dust precipitator; driving said rotary compressor by a gas turbine supplied with relatively cool gases under pressure from said dust precipitator, the temperatuxe of the gases in said second zone being substantially less than ~
1~19007 1n said first zone; and driving said steam turbine by steam fromsaid superheater.
In a further aspect of the present invention there is provided a steam power plant comprising: a steam boiler having a fluidized bed burner for generating steam, a rotary air compressor for supplying pressurized air to said fluidized bed burner; a gas turbine for driving said rotary air compres-sor' an evaporator in said steam boiler adjacent said fluidized bed burner, a superheater and a preheater in said steam boiler spaced above said fluidized bed burner, said steam boiler being arranged to conduct gas from said fluidized bed burner sequentially over said superheater and then over said pre-heater; a dust precipitator; conduit means for conducting flue gas from said preheater through said dust precipitator to said gas turbine, and conduit means both for conducting feed-water in sequence through said preheater and said evaporator to produce steam and for conducting said steam through said superheater to a steam turbine, whereby said gas turbine operates at a relatively cool temperature as a result of passing the flue gas over said preheater in said steam boiler before passing the flue gas through said dust precipitator and said gas tur-bine.
BRIEF DESCRIPTION OF THE DRAWING
A preferred embodiment of the present invention is described with reference to the single accompanying drawing wherein like members bear like reference numerals. The single drawing is a schematic illustration of a steam power plant ac-cording to the present invention including a fluidized bed furnace.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the single drawing, a steam gener-ator 1 for a steam power plant contains a fluidized bed fur-nace 2, the details of which are not illustrated. The fluidized bed operates in a conventional manner, having a -4a-1.~19()07 bed of pulverized coal to which an absorbent such as, for example, limestone or dolomite, is added. The fuel is fluidized within the bed to provide for combustion of the coal, thereby generating heat for the steam generator.
Superheated steam is generated within the steam generator 1 and passes from the boiler through a fresh steam line 3 to a steam turbine 4, wherein the steam is expanded to release energy. An electrical generator 5 is coupled to the steam turbine 4 to generate electricity. The spent steam discharging from the steam turbine 4 is precipitated in a condenser 6 and the condensate is conveyed by means of a condensate pump 7 through a preheater zone 8. The pre-heater zone 8, shown in a simplified manner, subjects boiler feedwater to a multi-stage preheating process, as condensed steam is withdrawn through extraction points 9 of the steam turbine 4. A feed pump 10 conveys the boiler feedwater through a feed line 11 back to the steam generator 1.
According to the present invention, the combustion of the pulverized coal within the fluidized bed furnace takes place under pressure. The combustion air required for the burning of the fuel is generated outside of the steam generator 1 in a separate turbine and compressor booster arrangement. A gas turbine 12 drives a compressor 13 in which air that is drawn in from the atmosphere at an intake 14 is compressed to, for example, 8-10 bar. During turbine start-up, a starter motor 16 which can be uncoupled at a coupling 15 from the turbine after start-up is used to drive the compressor 13.
The compressed air provided by the compressor 13 is conveyed through a pressure line 17 to a point below the blower plate 18 of the fluidized bed furnace within the 11~9~)07 steam generator 1. The compressed air flows through the blower plate 18 and forms an upwardly-directed carrier stream which lifts the solid fuel and absorbent particles and thus brings about the fluidized bed state.
The solid particles, typically consisting of pulverized coal together with an absorber material such as limestone or dolomite, are introduced into the furnace at 19 and 20 respectively.
The turbulent movement of the fluidized solids results in the exposure of a relatively large specific surface area. The high heat capacity of the fuel being fluidized and the exposed surface area result in high heat transmission coefficients from the fuel to the heat transfer surfaces within the steam generator 1. The heat transfer surfaces are typically multiple pipe heat exchangers, as illustrated by the pipes of a feedwater heater 21. The operating temperature of the fluidized bed is advantageously selected to be approximately 800C, which minimizes the problems arising from the reaction of the sulphur in the coal with the absorbent.
After passing over the feedwater heater 21, the hot flue gases within the steam generator transfer a portion of their heat content to a superheater 22 and a further portion to a preheater 23, before exiting the steam gener-ator 1. The superheater 22 provides an additional stage for heating the steam generated in the feedwater heater 21 before entering the steam turbine 4, while the preheater 23 heats recirculated feedwater discharged from the turbine.
The series of heat exchangers 21, 22 and 23 within the boiler a~l are in the flow path of the combustion gases of the fluidized bed on the steam turbine side.
The electrical current generated by the generator 5 is the product of a purely steam generating process. The steam process permits maximum use of the heat of the burned fuel by providing for preheating of the steam and feedwater, which results in a relatively high thermal efficiency within the steam power plant. The use of a fluidized bed which is operated under pressure and that is water-cooled permits a reduction in the size and cost of the fluidized bed instal-lation in comparison with the known installations, all of which operate with combustion at atmospheric pressure and with an air-cooled fluidized bed.
After passing over the preheater 23, the flue gases enter a dust precipitator 24. In the present inven-tion, the dust precipitator 24 is typically a simple cen-trifugal precipitator, since the flue gases are at a tempe-rature of only about 400C. At such a temperature, corro-sion and erosion problems are minimized. In the precipi-tator, the flue gases are mechanically separated from ash particles which are entrained in the stream of gas rising in the fluidized bed during the combustion process.
The precipitator apparatus has substantially smaller dimensions compared to that of known installations, because of the relatively simple construction of such a centrifugal device. Additionally, the gas volume which flows through the precipitator is relatively small as a result of the pressurizing operation within the fluidized bed, which reduces the size of the bed and therefore de-creases the volume of combustion air introduced into the bed.
After exiting the dust precipitator 24, the flue gases pass through a gas line 25 to the gas turbine 12. The 1119(:)0'7 gas turbine 12 is a pure expansion turbine and forms part of the booster arrangement. The residual heat content of the flue gases is released within the gas turbine 12 to drive the connected compressor 13. A low entry temperature for the flue gases supplied to the gas turbine (typically less than 400C) is feasible because the expansion turbine only drives the compressor 13 and does not contribute to the generation of electricity. Corresponding to this relatively low entry temperature is an off-gas exit temperature of about 120-150C. These off-gases can be passed directly into the atmosphere, at 26, through a chimney (which is not illustrated~ because of the low temperature. In conven-tional arrangements, the exhaust gases first have to be admitted to a heat exchanger downstream from the expansion turbine before being released into the atmosphere.
The usual downstream heat exchanger is, in the present invention, the preheater 23. Since the downstream heat exchanger in the present invention is incorporated within the pressure chamber of the steam generator 1, an optimum preheating of the steam in the steam turbine circuit becomes possible while the off-gas temperature remains sufficiently low. The steam preheating and the low off-gas temperature results in a correspondingly high efficiency of the installation of the present invention.
The present invention is not to be restricted to what is disclosed in the drawing and in the foregoing speci-fication. For example, the steam turbine circuit could readily be provided with a reheater. Also, a heavy fuel oil furnace could be provided instead of the coal furnace, in which case heavy fuel oil, instead of coal, is burnt with the absorbent in the fluidized bed~ The arrangement of the 1~9007 apparatus in the steam generator and the booster system would be the same and hence the process would remain within the scope of the invention.
The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by those skilled in the art without departing from the spirit of the present inven-tion.
Claims (15)
- The embodiment of the invention in which an exclu-sive property or privilege is claimed are defined as follows:
l. A method of producing steam in a steam boiler fired by a fluidized bed burner to drive a steam turbine, the method comprising the steps of:
supplying fuel and pressurized air from a rotary compressor to the fluidized bed burner;
combusting said fuel and said pressurized air at said fluidized bed burner to produce heat at a first zone;
supplying feedwater to a preheater in a second zone in said steam boiler spaced from said fluidized bed burner;
conducting feedwater from said preheater through an evaporator in said first zone to produce steam;
conducting steam from said evaporator through a superheater in a third zone in said steam boiler located between said first zone and said second zone;
conducting combustion gases from said first zone sequentially through said third zone and said second zone and then through a dust precipitator;
driving said rotary compressor by a gas turbine supplied with relatively cool gases under pressure from said dust precipitator, the temperature of the gases in said second zone being substantially less than in said first zone; and driving said steam turbine by steam from said superheater. - 2. The method according to claim 1 wherein the temperature of said first zone is about 800°C.
- 3. The method according to claim 1 wherein the temperature of said second zone is about 400°C.
- 4. The method according to claim 3 wherein said dust precipitator is a centrifugal precipitator.
- 5. The method according to claim 1 wherein the temperature of the gases at the exhaust of said gas turbine is between 120°C and 150°C.
- 6. The method according to claim 1 wherein sub-stantially the entire power produced by said gas turbine drives said rotary compressor.
- 7. The method according to claim 1 wherein the rotary compressor is selectively coupled to a motor which drives the rotary compressor during periods of gas turbine start-up.
- 8. The method according to claim 1 wherein the pressurized fluid supplied by the rotary compressor is at a pressure between 8 bars and 10 bars.
- 9. The method according to claim 1 wherein the fuel is pulverized coal.
- 10. The method according to claim 1 wherein the fuel is a fuel oil.
- 11. A steam power plant comprising:
a steam boiler having a fluidized bed burner for generating steam;
a rotary air compressor for supplying pressurized air to said fluidized bed burner;
a gas turbine for driving said rotary air compres-sor;
an evaporator in said steam boiler adjacent said fluidized bed burner;
a superheater and a preheater in said steam boiler spaced above said fluidized bed burner, said steam boiler being arranged to conduct gas from said fluidized bed burner sequentially over said superheater and then over said pre-heater;
a dust precipitator;
conduit means for conducting flue gas from said preheater through said dust precipitator to said gas tur-bine; and conduit means both for conducting feedwater in sequence through said preheater and said evaporator to pro-duce steam and for conducting said steam through said super-heater to a steam turbine, whereby said gas turbine operates at a relatively cool temperature as a result of passing the flue gas over said preheater in said steam boiler before passing the flue gas through said dust precipitator and said gas turbine. - 12. The steam power plant according to claim 11 wherein said fluidized bed burner includes a blower plate and said rotary air compressor includes means for conducting pressurized air upwardly through said blower plate into said steam boiler to produce a fludized bed of particles at the lower portion of said steam boiler, thereby causing said gas from said steam boiler to flow upwardly first over said superheater and then over said preheater.
- 13. The steam power plant according to claim 11 including an electrical generator, said electrical generator being driven by said steam turbine and wherein said gas turbine drives only said rotary air compressor.
- 14. The steam power plant according to claim 11 wherein said preheater has sufficient capacity to reduce the temperature of said flue gas supplied to said dust precipi-tator to about 400°C when the temperature of said fluidized bed burner is about 800°C.
- 15. The steam power plant according to claim 11 wherein the dust precipitator includes a centrifugal preci-pitator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH15979/77 | 1977-12-23 | ||
| CH1597977A CH625868A5 (en) | 1977-12-23 | 1977-12-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119007A true CA1119007A (en) | 1982-03-02 |
Family
ID=4413521
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000318482A Expired CA1119007A (en) | 1977-12-23 | 1978-12-22 | Process and arrangement for operating a steam power station |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1119007A (en) |
| CH (1) | CH625868A5 (en) |
| DE (1) | DE2802361C2 (en) |
| FR (1) | FR2412691B1 (en) |
| GB (1) | GB2010973B (en) |
| SE (1) | SE438526B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3004848C2 (en) * | 1980-02-09 | 1983-11-10 | L. & C. Steinmüller GmbH, 5270 Gummersbach | Fluidized bed combustion |
| DE3012600C2 (en) * | 1980-04-01 | 1982-12-23 | Brown, Boveri & Cie Ag, 6800 Mannheim | Process for operating a steam power plant provided with a fluidized bed furnace |
| EP0044094A1 (en) * | 1980-07-09 | 1982-01-20 | BBC Aktiengesellschaft Brown, Boveri & Cie. | Method for desulfurization with a fluidized bed in a power plant burning pulverized coal, and power plant working according to this method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3234735A (en) * | 1964-04-10 | 1966-02-15 | Babcock & Wilcox Co | Power plant cycle |
| GB1165537A (en) * | 1966-01-11 | 1969-10-01 | Coal Industry Patents Ltd | Improvements in Gas Turbine Systems |
| GB1311869A (en) * | 1969-12-12 | 1973-03-28 | Foster Wheeler Brown Boilers | Steam boilers |
| GB1388552A (en) * | 1971-05-17 | 1975-03-26 | Foster Wheeler Ltd | Power generation utilising a gas turbine plant |
| SE364756B (en) * | 1972-07-07 | 1974-03-04 | Stal Laval Turbin Ab | |
| AU1723076A (en) * | 1975-09-09 | 1978-03-02 | Coal Industry Patents Ltd | Heat pump system |
-
1977
- 1977-12-23 CH CH1597977A patent/CH625868A5/de not_active IP Right Cessation
-
1978
- 1978-01-20 DE DE2802361A patent/DE2802361C2/en not_active Expired
- 1978-02-15 FR FR7804285A patent/FR2412691B1/fr not_active Expired
- 1978-12-18 SE SE7812998A patent/SE438526B/en not_active IP Right Cessation
- 1978-12-22 GB GB7849753A patent/GB2010973B/en not_active Expired
- 1978-12-22 CA CA000318482A patent/CA1119007A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2010973A (en) | 1979-07-04 |
| DE2802361A1 (en) | 1979-07-05 |
| SE7812998L (en) | 1979-06-24 |
| FR2412691A1 (en) | 1979-07-20 |
| CH625868A5 (en) | 1981-10-15 |
| GB2010973B (en) | 1982-04-15 |
| FR2412691B1 (en) | 1981-12-18 |
| DE2802361C2 (en) | 1983-03-10 |
| SE438526B (en) | 1985-04-22 |
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| MKEX | Expiry |