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
  • F01K23/067—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 the combustion heat coming from a gasification or pyrolysis process, e.g. coal gasification
• • 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
  • F02C3/28—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 using a separate gas producer for gasifying the fuel before combustion
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
  • Y02E20/18—Integrated gasification combined cycle [IGCC], e.g. combined with carbon capture and storage [CCS]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E50/00—Technologies for the production of fuel of non-fossil origin
  • Y02E50/10—Biofuels, e.g. bio-diesel

Definitions

• the present invention relates to a method according to the preamble of claim 1 for using biomass fuel, solid waste or other -solid fuel as the secondary fuel for an oil- or gas-fired gas turbine.
• the solid fuel may have an extremely high total moisture content, or when slurried with water, even have a negative caloric value.
• the invention also concerns a -connection based on said method for producing energy.
• biomass is used in conjunc ⁇ tion with paper mills, because these plants produce large amounts of biomass suited for energy production, and rather abundant quantities of combustible byproduct waste are left over from the paper and pulp process.
• a particularly interesting target is to use the biomass arising in paper mills maximally efficiently in energy generation, since a majority of paper mills today already have generating plants which provide the plant with both electric power and heat distributed in the form of pro ⁇ cess steam.
• reaction turbines are used for generating electric power in paper and pulp mills.
• the process steam needed in the plant is taken from the backpressure section, and even if the steam consumption would be substantial, the amount of electric power gener ⁇ ated remains low.
• the ratio of generated electric energy to heat energy used is rela ⁇ tively low, typically below 0.3. For instance, in district heat cogeneration this ratio reaches 0.5.
• topping combustion One method of using solid fuel in conjunction with a gas- turbine cycle is so-called topping combustion.
• the gas turbine is fired with product gas made from solid fuel by means of a gasification system and the inlet gas temperature to the gas turbine is then elevated sufficiently high by supplementary firing using a liquid or gaseous topping fuel such as natural gas.
• topping fuel such as natural gas.
• a two-stage gasification process is employed in which the volatile components of the fuel are gasified and the non- gasified char residue is combusted in either the bottom part of the gasifier or a separate combustion chamber.
• the firing process of the solid fuel is crucial to the operation of the plant and extremely crucial to the total economics of the plant.
• the main fuel is the solid fuel taken to the gasifier and the topping fuel is used to operate the gas turbine with maximum possible efficiency.
• the combus ⁇ tion of the char remaining from the solid fuel gasifica ⁇ tion at a sufficiently high temperature is also restrict ⁇ ed by other factors including the evaporation of alkali compounds which are most damaging to the blades of the gas turbine wheels.
• the goal of the invention is achieved by gasifying the solid fuel to be fired at least partially by virtue of the heat content of the gas turbine main fuel and taking the product gas into the fuel circulation of the gas turbine.
• the gas turbine is fired by natural gas and the solid fuel is biomass.
• connection according to the invention is characterized by what is stated in the characterizing part of claim 12.
• a benefit of the invention is that the side-stream gasi ⁇ fication connection offers high power-to-heat ratio in plant designs partially fired by solid fuel and having a combined-cycle process as its main process. Small amounts of biomass and waste can be utilized at the efficiency rates of the large and efficient main process, partially drawing upon the existing system resources of the large main process.
• the gasifica ⁇ tion equipment is smaller and the gasification and pro- duct gas clean-up processes proper are simpler in design and less costly than full-scale gasification systems fired by product gas alone.
• the heating values of the secondary fuel and the product gas may be selected more freely, because a portion of the main fuel may be intro ⁇ cuted into the side-stream gasifier.
• the heating value of the product gas exiting the gasifier may be very low and even negative, because the proportion of the side-stream gas in the total fuel firing rate remains small.
• the heating value of the gas mixture can be kept sufficiently high by combusting the main fuel of the gas turbine.
• Another significant benefit is the improved availability of the process according to the invention over a conven ⁇ tional IGCC (Integrated Gasification Combined Cycle) process, because the production of the side-stream gas flow in the gasifier does not cause a similar nonavail ⁇ ability risk and need for keeping a reserve fuel storage as is the case with a conventional IGCC process.
• IGCC Integrated Gasification Combined Cycle
• the present invention offers a significant simplification of the gasification plant design.
• it is also possi ⁇ ble to omit the erection of a dryer in conjunction with the gasifier of solid fuel of high moisture content.
• the control of the gasifier will become easier as the inlet flow of the external energy is principally used for gasifier control.
• the product gas cooler may be replaced by an arrangement of simpler design and lower cost such as water spray cooling.
• the side-stream gasification arrangement according to the invention improves significantly the electric-to-thermal energy ratio and the power-to-heat ratio of the power plant with respect to boiler plants fired by solid biomass fuel.
• the gasification technique By virtue of the gasification technique, the use of biomass fuels of high moisture content in a gas-turbine plant achieves a more economical outcome than what is possible using a conventional steam cycle.
• a high-pressure steam dryer may advantageously be connected to a pressurized gasifier. Using a proper connection, the dryer, the gasifier and the gas turbine can be economically combined together, simultaneously maximizing the electric power generation capacity.
• the invention makes it possible to increase the firing percentage of renewable fuels with respect to fossil fuels.
• the clean-up of the product gas is easy as the gas may be cooled down to temperatures at which the gas may be cleaned free from obnoxious substances by means of metal or ceramic filters, whereby alkali compounds contained in the gas are condensed in the filters on the separated particulate matter. Cooling may be performed using water or steam spraying, whereby the generated steam acts as an auxiliary expanding medium in the gas turbine. Alterna ⁇ tively, clean-up of the product gas may be performed using water-spray washer equipment.
• the method according to the invention is well suited for incinerating materi ⁇ als containing extremely toxic substances, since the high temperature in the combustion chamber of the gas turbine disintegrates efficiently such toxic compounds.
• topping combustion the fuel being gasified is used for elevating the temperature of the inlet gas flow to the gas turbine sufficiently high to permit economical operation of the gas turbine.
• the gas turbine may be operated at maximum efficiency also without the gasifier.
• topping combustion could be performed without the product gas from the gasifier, but not without significantly compromising the total efficiency of the power plant.
• topping combustion gasifies the main fuel, while the process according to the invention can use almost any available fuel in the gasifier.
• topping combustion requires a solid fuel of relatively easy gasification in order to achieve a sufficiently high temperature for the gasifier discharge gases taken to the gas turbine, while the heating value of the product gas from the gasifier in the process according to the invention is not crucial to the total energy balance of the power plant, in the pro- cess according to the invention, a natural-gas combustor placed in front of the gasifier can be used in order to ensure gasification of extremely problematic fuels, or alternatively, to aid the gasification step of reasonably easily gasifiable fuels. Without significantly degrading the efficiency of the plant, the process employed in the invention can use even such fuels that have a negative heating value.
• topping combustion the quality of the product gas delivered from the gasifier can affect the plant total efficiency crucially, thus requiring the use of a complicated and therefore expen ⁇ sive system in order to achieve a good gasification effect, while the process according to the invention can be built on less expensive arrangements based on, e.g., cooling the product gas with water-spray coolers.
• a sufficiently high gasification temperature can be obtained only by burning the fuel proper to be gasified in order to make gasification possible at all, while in the process according to the invention, a significant fraction of the gasification heat can be introduced by burning externally fed supple ⁇ mentary fuel in either the gasifier or the inlet air to the gasifier.
• FIG. 1 shows a connection according to the invention
• Figure 2 shows a second alternative connection according to the invention
• Figure 3 shows a third alternative connection according to the invention.
• Figure 4 shows a fourth alternative connection according to the invention
• connection incorporates a gas turbine 2 to which air is fed by a compressor 1.
• the exhaust gas of the gas turbine 2 is taken to a boiler 3 in which steam is generated for a steam turbine 4.
• steam is taken to a process or condenser 5 using the steam.
• the main fuel of the gas turbine 2 is natural gas, which is taken to a combustor 9 of the turbine over a gas line 12.
• a side line 13 is taken from the compressor 1 of the gas turbine 2 to the combustor 11, and therefrom further to the gasifier 6.
• the com ⁇ bustor 11 is operated on the gas turbine main fuel.
• the side line 13 is provided with a booster fan 10 for blowing air into the combustor 11 and the gasifier 6.
• the air is heated in the combustor, wherefrom the heated air is taken together with the gas turbine exhaust gases to the gasifier 6, into which the solid fuel is taken along a feed line 14.
• the solid fuel is gasified in the gasi- bomb under air-lean conditions, thus forming combustible product gas.
• the product gas is taken first to a cooler 7 and subsequently cleaned in a water-spray washer 8.
• the purified product gas is passed into a natural gas feed line 12, mixed therein with the natural gas and the mixture is fed into the combustor 9 of the gas turbine 2.
• the gasifier 6 can be operated with a plurality of fuels having different heating values, and although the connec- tion described herein is not provided with a separate dryer, the fuel may have a relatively high moisture con ⁇ tent, since the energy balance of the gasifier may be adjusted by elevating the inlet air temperature to the gasifier prior to its introduction into the gasifier.
• the gasification process itself may be enhanced by taking a fraction of the main fuel into the gasifier proper.
• Water spraying is well suited for cooling the product gas, because the steam generated herein can be used as injec ⁇ tion steam into the gas turbine 2. Cooling may also be implemented with the help of heat exchanger walls, whereby steam can be generated for the steam turbine or industrial processes.
• the heat recovered from cooling may be used for preheating the inlet air to the gasifier.
• an alternative approach is to replace the water-spray washer with mechanical filters.
• the use of water-spray washing permits the omission of the cooler 7 in some cases provided that the gas is cooled with suffi ⁇ cient efficiency by the water spray in the washer.
• FIG. 2 another connection is shown having the gasification step complemented with drying of the solid fuel.
• the fuel to be fed to the gasifier is first taken a high-pressure dryer 15, and the fuel is next separated from the mixture of the circulating steam and dried fuel in a cyclone 16, whereafter the fuel is routed via a fuel feed nozzle 14 to the gasifier 6.
• From the circulating steam flow is separated that portion of the steam which corresponds to the amount of water evaporated from the fuel and this portion of the steam is added along a line 18 to the product gas flow prior to the cooler 7.
• the energy used for drying the fuel can be recovered in the form of injection steam mixed in the fuel flow of the gas turbine 2. Simultaneously, the injected steam cools the product gas flow.
• the separated steam can be taken to another point in the fuel circuit of the gas turbine, obviously the most advantageous arrangement is to introduce the steam into a pressurized section of the system prior to the gas turbine or to directly inject the steam into the turbine.
• the steam can be used in the steam circulation of the plant.
• the circulating steam of the dryer 15 is taken along a line 17 blown by a fan 19 into the combustor 20 of the dryer, where the circulating steam is reheated prior to its return into the dryer.
• the combustor 20 may have a design of the heat-exchanger type, wherein the energy of combustion is transferred through heat-exchanger walls into the circulating steam, or alternatively, the flue gas of the combustor 20 can be mixed into circulating steam.
• the heating energy required by the dryer 15 by means of the main-fuel-fired combustor 20 of the gas turbine 2
• at least a fraction of this heating energy can be generated in the exhaust heat recovery boiler 3 of the gas turbine 2 or in the cooler of the product gas.
• One further technique of altering the energy balance sheet of the dryer 15 is to fire main fuel directly into the dryer 15.
• the gasi ⁇ fication of the solid fuel is supported by introducing the required supplementary energy into the solid fuel contained in the dryer 15 either in the form of heat, or alternatively, by combusting the main fuel.
• the connec ⁇ tion is suited for such fuels whose heating value may be elevated so high by drying that gasification may be carried out simply by feeding air from the compressor 1 of the gas turbine 2 into the gasifier 6.
• the supplementary energy introduced by combusting the main fuel is in this embodiment brought via the dryer to the gasification step, whereby the dryer and the gasifier form an integrated gasification unit.
• the embodiment shown therein can use fuels of extremely low caloric value.
• a combustor 21 fired with the main fuel of the gas turbine 2.
• the dryer circuit 15 - 17, 19 is provided with a combustor 20 in the same fashion as in the embodiment of Fig. 2.
• these combustors With the help of these combustors, a substantial amount of energy can be introduced into the solid second ⁇ ary fuel, making this connection suitable for fuels of extremely high moisture content and/or low caloric value.
• the connection could be used for burning of waste which is problematic to dispose of and difficult to in ⁇ cinerate.
• connection is also most flexible as the ex ⁇ ternal heat added to the process by means of the supple ⁇ mentary combustors of the dryer and the gasifier is easy to control according to the properties of the solid fuel, in some cases even permitting operation with only one of the combustors 20, 21.
• FIG. 4 shows a connection for atmospheric-pressure gasi ⁇ fication.
• the inlet air to the gasifier 6 is fed to the combustor 11 of the gasifier 6 with the help of a fan 22, whereby the internal pressure in the gasifier 6 is approximately equal to the ambient pressure.
• the product gas exiting the gasifier is at the ambient pressure, and any possible increase of internal pressure in the gasifier due to the compression heating of the inlet air is cancelled by the pressure drop that occurs when the temperature of the product gas falls in the cooler 7.
• the cooled product gas is taken via the washer 8 to a compressor 23.
• a compressor driven by an electric motor -24 is required for compressing the product gas, the pressure elevation of the product gas consumes electric power.
• the present invention may have alternative embodiments. -
• the heat required by the dryer was produced by combusting the main fuel. At least a fraction of this energy could be generated in the waste heat recovery boiler 3 of the gas turbine 2.
• the connection of Fig. 3 could be provided with a heat exchanger, which is connected to said waste heat recovery boiler 3, in parallel with or replacing the combustor 20 of the dryer 15.
• the following calculation is based on the assumption that a plant to be erected is required to supply a given heat load for which a combined-cycle power plant has to be designed.
• the main product of this combined-cycle plant is process steam with electric power generated as a by-product.
• the size of this plant is dictated by the required steam output, to which a gas turbine of optimal size is adapted dimensioned on the basis of the steam consumption.
• a power plant of the above-outline type could be erected in conjunction with, e.g., a pulp and paper mill, whereby the solid fuel would be obtained as the sludge of a wastewater treatment plant.
• a sludge chiefly com ⁇ prises extremely fine fiber material collected from manu- facturing steps of fiber from wood and a certain amount of bacterial biomass escaping the treatment process plus some other components carried over along the process waters.
• the size of the gas turbine in the comparative process can be made smaller as a por ⁇ tion of the generated steam is obtained from a separate solid-fuel-fired boiler.
• the present invention makes it possible to select a larger gas turbine to supply the same given heat load than is possible in con- ventional connections, since the application of the in ⁇ vention makes it possible to generate the entire steam output in the exhaust gas heat recovery boiler of the gas turbine.
• the gas turbine selected for the comparative example is type GE F5 (made by General Electric), whose nominal output power (26 MW e ) is approx.
• the solid-fuel- fired boiler combusts the sludge using natural gas as supplementary fuel so that the fraction of natural gas combustion is approx. 40 % of the boiler overall output. Then, approx. 3.3 % (0.66 kg/s) of the overall steam output reaches the condenser, corresponding to a genera ⁇ tor output power of approx. 0.3 MW e .
• the gasification of the solid fuel can be per ⁇ formed using approx. 0.5 - 1.0 MJ/s of natural gas energy to heat the gasification air prior to the gasifier.
• the main difference is in the gas turbine unit used for electric power gener ⁇ ation.
• Both steam turbine units have approximately iden ⁇ tical capacities, namely, about 11 MW e gross electric power output and slightly below 60 MJ/s process steam, while in the gas turbine units, the difference between the gross electric power outputs is about 15 MW e , corre ⁇ sponding to approx. 56 % increase of power output in the gas turbine unit operated using the side-stream gasifica- tion connection with regard to operation according to the comparative example, and a 37 % increase in the total electric power output of the entire plant. Simultaneous ⁇ ly, the firing rate is increased 15 %, that is, 17 MJ/s.
• the internal acquisition cost of such solid fuel can be assumed to be essentially zero. Then, the generated output of additional electric power should cover all extra costs incurred by the side-stream gasification connection. If the additional electric power is valued at 200 FIM/MWh e , the annual value of the additional electric power generation according to the invention at 7000 h/a peak demand is 18.6 MFIM/a, of which the increased con ⁇ sumption of natural gas shaves off about 8.6 MFIM/a if the purchase cost of natural gas is estimated at a thermal energy level of 65 FIM/MWh th .
• the addi ⁇ tional electric power generation leaves about 10 MFIM per annum to be divided between the extra investment costs and higher operating margin.
• the difference between the discounted values of electric power generation and fuel costs will be 75 MFIM.
• the procurement cost difference between the gas turbine units F6B vs. F5
• the remaining discounted difference 60 MFIM
• the investment into the side ⁇ stream gasifier can replace the solid-fuel-fired steam generator in the comparative process.
• the money saved from such a boiler of the fluidized-bed type for instance, can be diverted to the investment into the side-stream gasifier.

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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)
• Hydrogen, Water And Hydrids (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Combustion Of Fluid Fuel (AREA)

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• 1995
  • 1995-10-12 FI FI954847A patent/FI102630B1/fi active IP Right Grant
• 1996
  • 1996-10-10 HU HU9802914A patent/HUP9802914A3/hu unknown
  • 1996-10-10 EP EP96933459A patent/EP0854970A1/en not_active Withdrawn
  • 1996-10-10 PL PL96326198A patent/PL326198A1/xx unknown
  • 1996-10-10 WO PCT/FI1996/000537 patent/WO1997013962A1/en not_active Application Discontinuation
  • 1996-10-10 AU AU72184/96A patent/AU7218496A/en not_active Abandoned

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