SU1729296A3 - Coal gasification method - Google Patents

Abstract

In gasifying coal in a preferably allothermally heated gas generator, the hot product gas taken off from the gas generator is used as the heating medium for generating high-pressure and/or low-pressure steam, and the condensate water obtained from the product gas on cooling is separated off, freed of any volatile or organic impurities present therein and then evaporated in an evaporator and returned as process steam into the gas generator. The high-pressure and/or low-pressure steam is used as the heating medium for the evaporator, if appropriate after previous utilisation in a steam turbine. This leads to environmentally friendly recycling of the condensate water from the product gas.

Description

The invention relates to a method for coal gasification, wherein the produced gas in one or several heat exchangers is cooled to a temperature below the dew point of the water vapor contained in it, and the condensate water that falls out of the gas is separated, enriched and returned to the process.

The purpose of the invention is to reduce energy costs.

The drawing shows a flow chart for the implementation of the proposed method. - the path of passage of the produced gas is indicated by a double line, the path of passage of the produced steam is a thick line, thin lines show pipelines for water or the like).

In the gas generator 1, which with the help of the coil 2 is heated by an external heat source, from the supplied

the fine coal pipeline 3 and a fluidized bed are created through the water vapor pipeline 4, the superheated water vapor serving as the reaction and liquefying medium.

The gas generated in the gas generator 1 or the crude gas is directed through the raw gas cooling pipeline 5 and is cooled in the heat exchanger 6 of the high-pressure steam generator 7. In this case, high pressure steam is generated, the pressure of which is more than 100 bar, and the superheat temperature is more than 450 ° C.

The cooled coal gas through the pipeline 8 is directed through the scrubber 9, equipped with a pipe. Venturi, and enters the tank separator 10, where the pollutants contained in the gas are separated: dust, salts (e.g. NH / iCI) and partially organic components.

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The carbon dioxide thus purified from the separator 10 is cooled further in heat exchangers 11 and 12, and low pressure steam (2-4 bar) is generated in the steam generator 13. At the same time, condensate-to-condensate water, which contains mainly organic contaminants, is used in the heat exchangers 11 and 12, is used as wash water in the scrubber 9 and with the gas enters the separator 10. From the separator 10 condensate water valve 14 is withdrawn and supplied to distillation column 15. In this column, when the low-pressure steam is supplied, the gaseous components, such as NHa, H2S and also volatile organic components, are removed in the condensate water, and are fed after cooling in the heat exchanger 16 through conduit 17 to the combustion stage.

The condensate coming out of the column 15 is fed through a pump to one or more coke fines filters 18, in which soluble and insoluble hydrocarbons still contained in the condensate water are separated.

In filters 18, residual coke and / or volatile dust, which falls during gasification in the gas generator 1 and is discharged as a residue through the lock system, can be used as absorption aids and auxiliary filter layer. The use of coke breeze filters for separating hydrocarbons from wastewater is known.

After passing through the filter 18, the condensate water through line 19 is directed to the evaporator 20 and is evaporated there. The heat source for the partial evaporation of condensate is superheated high-pressure steam generated in the steam generator 7, which is previously sent through a steam turbine 21 (back pressure steam turbine) to perform work, in particular, to drive the generator 22 in order to generate electricity. The steam turbine exhaust steam is directed through the tubular heat exchanger 23 of the evaporator 20 and is cooled to a temperature below the condensation point, so that the heat of condensation of the exhaust steam serves to evaporate the condensate water coming from the filters 18.

The steam produced in the evaporator 20 by evaporating the condensate water is supplied through pipelines 24 and A as process steam to the gas generator 1. If the pressure and temperature of the exhaust steam of the steam turbine 21 are high enough for the vapor generated in the evaporator 20 pressure than pressure in

gas generator 1, then steam can be supplied through conduit 4 directly to gas generator 1. If the pressure and temperature of the exhaust steam from the steam turbine 21 are so low that the pressure

0, the vapor produced in the evaporator 20 is lower than the pressure in the gas generator 1, then it may be necessary to compress the vapor from the evaporator 20 using a compressor 25 to the pressure required for

5 supply to the gas generator, the compressor 2.5 being able to be driven by a steam turbine.

Water condensed in heat exchanger 23 evaporator 20 from exhaust steam

0 turbines 21, through pump 26 and heat exchangers 27 and 28 returns to high pressure steam generator 7.

If the amount of condensate evaporated in the evaporator 20 is not enough to cover the need for process steam in the gas generator 1, additional water for feeding the evaporator 20 can be supplied from the outside via pipeline 29. This feeding with outside water can also be carried out in another location, such as above filter 18.

The remaining water in the evaporator 20 is discharged through line 30, cleaned from solid particles in filter 31 and then returns to evaporator 20 through pump 32. The solid particles separated in filter 31 can be dried and removed as a filter cake.

0 The condensation heat contained in the exhaust steam from the steam turbine 21 can be used to evaporate the condensate water, i.e. to produce process steam, so it does not disappear. Then, due to the evaporation process in the evaporator 20, there is no need to use external cooling power. The entire gasification process can be carried out almost without receiving wastewater, which is particularly important for the interface of the gasification process with the operation of gas and steam turbines, therefore, in the field of operation

5 power plants.

The heating of the gas generator 1 with the help of a tubular coil 2 is carried out by means of a hot heat transfer medium supplied through a conduit 33. This heat-carrying medium can be provided.

for example, from an atomic reactor. The process, which is closed and independent of external heat sources, is obtained when at least part of the product gas discharged through pipeline 34 is burned, and the resulting flue gas with a temperature of, for example, 850 ° C or higher is fed through pipeline 33 to a coil 2. Before entering The flue gas coil 2 can be further channeled through the heat exchanger 35 so that the process steam obtained in the evaporator 20 can be heated to temperatures above 800 ° C. The flue gas leaving the coil 2 can also be used in the heat exchanger 36 to overheat and the steam supplied to the steam turbine 21.

Heat exchangers 16, 27 and 28 are used to heat the boiler water used in steam generators 7 and 13.

For heating the evaporator 20, low pressure steam produced in the steam generator 13 can be used. In this case, the steam discharged through conduit 24 is only under pressure and must be compressed by means of compressor 25 to a high pressure, for example 35 bar, required to be supplied to gas generator 1. Column 15 for distillation and / or filter 18 provided for pre-cleaning condensate by evaporation, theoretically, they can also be eliminated, and then the corresponding contaminants remain in the condensate water and together with the vapor produced in the evaporator 20 are returned to the gas generator 1. certain contaminants, such as ammonia, removed in the distillation column 15, or phenols separated in the filters 18, and the like, enrich the moving circulating condensate water and under certain conditions can reach a concentration critical to operation of the plant and / or for the materials used. Therefore, the inclusion of a distillation column 15 and a filter 18 is a preventive measure.

Claims (5)

1. The method of coal gasification, including heating the coal by indirect heat exchange in the presence of water vapor, cooling the obtained gas in heat exchangers to a temperature below the condensation point of water vapor contained in the gas to produce high and / or low pressure steam supplied to the steam; the turbine, separation of condensate water from the gas, its treatment and return, a process that, in order to reduce energy costs, the condensate water is subjected to evaporation by heat exchange with high and / or low pressure steam and as a process steam is fed to the stage of heating coal. 2. A method according to claim 1, characterized in that the condensate water is freed from gaseous or volatile contaminants and / or filtered and free from soluble and insoluble hydrocarbons before the evaporation step in the stripping stage. 3. Method according to claim 1 or 2, characterized in that the exhaust steam from the steam turbine is used to evaporate the condensate water. 4. A method according to claim 3, characterized in that the process steam obtained as a result of evaporation of condensate water is burned in a compression stage driven by a steam turbine. : 5. A method according to claim 1, characterized in that water is supplied to the evaporation stage in addition to condensate water.