RU2487158C2 - Method to use coal in combined cycle plant based on pyrolysis process - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: cycle air is heated in two stages: after leaving the compressor, cycle air is supplied for heating into a high-temperature high-pressure heater, then it is additionally heated to rated temperature directly prior to arrival of the heated cycle air into a gas turbine. Fuel for a steam and air boiler with the high-temperature air heater is a solid pyrolysis product - semi-coke. Pyrolysis gas is used to additionally heat air directly upstream the gas turbine. Vaporous products of liquid fraction of pyrolysis products are used for heating of source coal to rated temperature of pyrolysis process in a pyrolysis reactor. Pyrolysis products are exposed to treatment from compounds of sulfur and nitrogen directly in the pyrolysis reactor.

EFFECT: expanded sphere of application of combined cycle plants, their improved cost-effectiveness and environmental compatibility.

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Description

The invention relates to a power system, and in particular to a method for producing high-temperature air for use as a working fluid in a gas turbine.

The development of combined cycle technology in the energy sector is currently limited mainly to the use of natural gas as fuel for the combustion chambers of gas gas turbine units (GTU) as a part of CCGT unit. The creation of coal-fired combined cycle plants (CCGT) is associated with two main areas: coal gasification (conversion of carbon mass into gaseous fuel) and technology with “external” combustion. The essence of the technology is to obtain high-temperature air for use as a working fluid in a gas turbine by heating cyclic air behind a compressor using fuel combustion products as a heating medium. To increase the efficiency of modern CCGT units, the temperature at the inlet to the gas turbine part should be about 1500 ° C. The creation of such thermally stressed structures requires the use of materials that are currently not available. Under such conditions, it is possible to use hybrid technology, which provides for stepwise heating of the working fluid.

A known method of complex thermal processing of solid fuel (patent RU 2340651 C1, C10B 49/22, C10J 3/58, F02C 3/28, publ. 10.12.2008), selected for the prototype. The method includes crushing and drying solid fuel, its pyrolysis in a fluidized bed reactor with a solid heat carrier to produce a gas-vapor mixture and semi-coke, their removal from the reactor and separation. Peat is used as solid fuel. The obtained semi-coke is removed from the pyrolysis step together with a gas-vapor mixture. The gas-vapor mixture is cleaned, part of which is burned in the combustion chamber of a gas turbine with the generation of electricity and the subsequent disposal of waste gases. The semicoke is divided in the semicoke separator into two streams in fractions. A large fraction is sent to an activator to produce activated carbon, and a small fraction is sent to a gas generator to produce generator gas, which is then purified and conditioned with the remainder of the gas-vapor mixture to produce synthesis gas, which is fed to the reactor for the synthesis of liquid hydrocarbons to produce liquid fuels . Activated carbon is sent as a sorption material for purification of a gas-vapor mixture and generator gas, and spent activated carbon is returned to the gasification stage. The solid heat carrier is heated in the technological furnace due to its partial combustion with the formation of flue gases and returned to the pyrolysis stage.

However, this method is limited only by the preparation of fuel and is not associated with combined-cycle technology for the production of electricity.

The closest technical solution, selected as a prototype, is a method of organizing a combined-cycle process based on coal combustion, which includes a two-stage heating of the cyclic air leaving the compressor by feeding it into a high-temperature high-pressure air heater with its subsequent heating in the combustion chamber of a gas turbine due to burning third-party fuels, such as natural gas. (Lipets A.U., Kuznetsova S.M., Dirina L.V. et al. “Gas-coal combined cycle plants”, railway engineer “Energetik”, No. 5, 2004).

The disadvantage of this technology is the need to use a third-party source of auxiliary fuel, for example, natural gas, for heating the cyclic air after a high-temperature air heater to the calculated temperature of the working fluid at the inlet of the gas turbine, which limits the use of this technology in the absence of natural gas.

The use of ordinary coals in a steam-air boiler implies the need for organizing the cleaning of flue gases from sulfur compounds, nitrogen oxides, which are formed largely from nitrogen fuel compounds.

An object of the invention is the development of mono-fuel technology to ensure the combined-cycle process of energy production.

The technical result of the proposed technology is to expand the scope of combined cycle plants, increasing their efficiency and environmental friendliness.

To solve the technical problem and achieve a technical result in combined cycle technology, including two-stage heating of cyclic air: after exiting the compressor, the cyclic air is fed to a high-temperature high-pressure heater for heating, followed by heating the air to the design temperature and supplying heated air to a gas turbine, according to the invention use mono-fuel technology based on where, as fuel for a steam-air boiler with a high-temperature air-heating A solid pyrolysis product, semi-coke, is used by the inventor, and pyrolysis gas is used to heat the air immediately in front of the gas turbine.

Wherein:

- pyrolysis products are subjected to purification from sulfur and nitrogen compounds directly in the pyrolyzer;

- the liquid fraction of the pyrolysis products is used to heat the source coal to the calculated temperature of the pyrolysis process in the pyrolyzer.

The use of coal pyrolysis products as fuel eliminates the need for a combined-cycle plant to use a separate, external source of fuel, for example, natural gas, which greatly expands the possibilities of the proposed technology.

The pyrolysis process during the medium temperature treatment of coal 800-850 ° C allows you to get three products: pyrolysis gas, semi-coke, liquid fractions.

All types of fuels obtained during the pyrolysis process (semi-coke, pyrolysis gas, liquid pyrolysis products) are environmentally friendly, freed from sulfur compounds and nitrogen oxides during the pyrolysis process, which ensures the environmental friendliness of the proposed technology.

The use of the liquid fraction of the pyrolysis products for heating the initial coal to the calculated temperature of the pyrolysis process in the pyrolyzer can significantly save thermal energy and, therefore, increase the efficiency of the proposed technology.

The proposed combined cycle technology based on coal pyrolysis is implemented using the circuit shown in the figure.

The scheme includes three blocks:

A - coal pyrolysis unit; B - gas turbine unit with a high-temperature air heater; B - steam turbine unit with a steam generating path of an air-steam boiler.

The technological scheme of block A contains a pyrolyzer 1 with a gas coolant generation chamber 2, which receives coal dust 3, air 4 and auxiliary fuel 5. In the chamber 2, auxiliary fuel 5 is burned, the combustion products released in this process serve as a heat carrier for heating coal dust 3 to a temperature the pyrolysis process, which develops in the cavity of the pyrolyzer 1. The pyrolysis products at the outlet of the pyrolyzer 1 are distributed as follows: semi-coke 6 enters block B, the gas-vapor mixture 7 is sent for cleaning and eparatsiyu gas in a filter separator 8, wherein the resin is separated, and gasoline fractions of pyrolysis gas. Vaporous liquid products through the channel 9 are fed into the chamber generating the gas coolant 2, where they are used as auxiliary fuel. The pyrolysis gas extracted from the vapor-gas mixture and purified in the filter-separator 8 enters the booster compressor 10, in which the pressure of the pyrolysis gas rises by 1-1.5 kgf / cm ² above the pressure of cyclic air. Under this pressure, pyrolysis gas is supplied to block B.

In the technological block B, the air after the compressor 15 is supplied through the channel 16 to the high-temperature air heater 22 of the steam-air boiler 17. The heated air then enters the heating unit 12 through the high-temperature air duct 20, into which pyrolysis gas enters through the high-pressure gas line 11. Due to the combustion of pyrolysis gas in a stream of hot air, the cyclic air is heated to the required temperature at the inlet to the flow part of the gas turbine 14 (for example, 1400-1500 ° C). Part of the pyrolysis gas through the channel 13 can go directly to the flow part of the gas turbine 13 for intermediate heating of the air. The exhaust gases through the channel 21 are fed into the burners 18 of the air-steam boiler, performing the function of an oxidizing agent for burning semicoke.

In a steam turbine unit, the products of the combustion of the semi-coke from the furnace of the boiler 17 enter the steam generating heating surfaces 19 connected to the steam turbine 23. The steam turbine unit also contains a steam condenser 24, a condensate feed pump 25.

Thus, the proposed technology allows to obtain three products (three types of fuel) - pyrolysis gas, liquid fractions, semi-coke. All products of the process of coal pyrolysis - gas, vapor and solid - are used to produce a working fluid for a gas turbine.

Using the proposed combined cycle technology based on coal pyrolysis allows it to be used in conditions where there are no additional sources of fuel, for example, natural gas, etc.

The proposed technology is cost-effective, because allows you to increase the efficiency of coal thermal power plants by 30-40% and significantly reduce the costs of their own needs.

Pyrolysis products are environmentally friendly, because the semi-coke does not contain bound nitrogen, and the pyrolysis gas does not contain sulfur compounds.

In addition, the proposed technology eliminates the use of heat-resistant materials, which is very important for the current state of technology.

The dimensions of the coal heat treatment apparatus in the pyrolysis mode are much smaller than in the gas generation process, which allows them to be placed directly near the boiler burners, directly transport the heated semi-coke to the burners and further to the furnace without preliminary cooling.

The proposed technical solution meets the criterion of "novelty", because the prior art does not know technical solutions with the proposed set of essential features.

Claims (2)

1. The method of using coal in a combined-cycle plant based on a pyrolysis process, which includes two-stage heating of cyclic air: after exiting the compressor, the cyclic air is fed to the high-temperature high-pressure heater for heating, followed by heating the air to the design temperature directly by the cyclic heated air entering the gas turbine, which differs the fact that they use mono-fuel technology, where as fuel for a steam-air boiler with a high-temperature air heater the solid pyrolysis product - char for reheating the air immediately before the gas turbine - pyrolysis gas and vaporous products of the pyrolysis product liquid fraction is used for heating the original coal to an estimated temperature of the pyrolysis process in the pyrolyzer. 2. The method of using coal in a combined cycle plant according to claim 1, characterized in that the pyrolysis products are purified from sulfur and nitrogen compounds directly in the pyrolyzer.

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