DE3207779A1 - Process for the treatment of water-containing condensate from the cooling of the crude gas of coal pressure gasification - Google Patents

Abstract

Crude gas from the gasification of solid fuels is cooled in a plurality of cooling steps. In this way, condensate is obtained having a temperature of at least 130 DEG C and a pressure of at least 4 bar. This condensate is flashed and the flash vapor thereby produced is burned. The flashed condensate is fed to a separating device from which a condensate phase consisting predominantly of water (gas liquor) is withdrawn. The gas liquor is cooled in direct contact with colder gas before it is used for the cooling of the crude gas. The heated water-vapour-containing cooling gas is fed for combustion. Generally, the gas liquor is cooled in direct contact with the colder gas to a temperature of about 30-90 DEG C. The cooling gas expediently consists primarily of one or more of the gases carbon dioxide, nitrogen, methane or carbon monoxide.

Description

Process for treating water-containing condensate

from the cooling of the raw gas of the coal pressure gasification The invention relates to a method for treating water-containing condensate from cooling of the raw gas of the gasification of solid fuels with oxygen, water vapor and / or Gasifying agents containing carbon dioxide under a pressure of 5 to 150 bar, wherein the raw gas is cooled in several cooling stages and at least part of the condensate accumulating during cooling, which has a temperature of at least 130 ° C and has a pressure of at least 4 bar, relaxes the resulting flash steam dissipates and burns and that the relaxed condensate of a separating device zuftIhrt, from which a condensate phase consisting largely of water is withdrawn, which are used to cool the raw gas.

Such a method is from DE-PS 28 53 989 and the corresponding U.S. Patent 4,295,864 is known; the present invention represents a further development this procedure.

The invention is based on the object, the amount of in the circuit to keep water-containing condensate out and an excess of condensate to be able to burn as little energy as possible. This is done according to the invention in the above-mentioned process achieved in that one largely consists of water existing condensate phase in direct contact with colder gas cools, before use them to cool the.

Raw gas is used and the heated gas, which contains water vapor, burns. On contact, this gas takes considerable amounts of T: water vapor from the condensate phase on what the Reduced amount of condensate. Through the procedure it becomes superfluous to remove excess condensate and waste water purification to have to submit. In the heated water vapor-containing gas go through the direct Contact with flammable substances from the condensate, especially phenols, hydrocarbons, NH3, H2S and HCN, whose calorific value is used in the subsequent combustion will.

The cooling gas can be carbon dioxide, nitrogen, methane or carbon monoxide or use mixtures of these gases. Advantageously, exhaust gases are used that mainly consist of these gas components, e.g. pressurized residual gases or Gases from pressure locks or gas scrubbing h. E.g.

In the case of raw gas cleaning, an exhaust gas containing CO2 is produced, which is based on this Wise use. This cooling gas does not need to have any appreciable overpressure.

It is advantageous to use the condensate phase, which consists largely of water, which is also referred to as gas water, in cocurrent with the colder gas cool. A contact zone that is completely or largely free of internals can be used with which there is therefore no risk of bothersome blockages or caking consists. It is of course also possible to run the condensate phase in countercurrent to cool with the colder gas. However, we recommend a container that is used for Improving the contact between gas and liquid with suitable elements, e.g. Trays or trays.

The condensate phase cooled in direct contact with the colder gas can be used heat one or more stages by raw gas and the condensate phase last with a Pass a temperature of about 710 to 1500C into a washer cooler. This'; ash cooler the raw gas coming from the gasification is usually supplied directly and in ii there is about the same pressure as in the gasification.

Usually the condensate phase is in direct contact with the colder one Gas cooled by about 10 to 600C to a temperature in the range of about 30 to 90 0C. The condensate is then reheated in step-by-step contact with the raw gas.

The drawing shows an example of how the process is carried out.

The gasification reactor 1 is through the line 12 with granular coal abandoned a grain size in the range of about 3-100 mm. Through the lines 13 and 14, water vapor and oxygen are added to the reactor and as gasifying agents withdraws the incombustible components through line 15. To generate the Water vapor in line 13 is passed through water in line 37 through a heat exchanger 11, which is fed with hot exhaust gases from line 35.

In reactor 1, the coal or other suitable solid fuel is used gasified at a pressure of 5 - 150 bar in a fixed bed. Details of the gasification process are e.g. in Ullmann's Encyclopedia of Technical Chemistry, 4th Edition (1977), Volume 14, pages 383-386. The gassing can be carried out so that the incombustible components occur either as solid ash or liquid slag.

The method according to the invention can also be used after a fine-grain gasification, e.g. in entrained flow or fluidized beds.

The raw gas generated in the reactor 1 flows through the line 16 with a Temperature in the range of about 200 - 7i) 00C in a wax cooler 2. There the Raw gas with condensate mainly consisting of water (gas water) from the pipe 19 sprayed.

If necessary, additional water or condensate can be in the line 17 will be brought up. In the washing cooler 2, the raw gas is saturated with water vapor.

Condensate and cooled raw gas arrive in line 18 at temperatures from about 150 - 2600C in a separator 3, which the liquids through the line 21 leaving The raw gas is fed in line 20 to a heat exchanger 4.

The condensate in line 21 is still approximately under pressure, which prevails in the gasification reactor 1. This condensate is in the separator 9 relaxed into about atmospheric pressure. This separator is described below also called Teerscheider 9. The steam produced during the relaxation is in the Line 34 of a combustion chamber 10 abandoned, the additional fuel through line 36 receives. In the combustion chamber 10, the water vapor is heated and above all that in it contained flammable components such as hydrocarbons, phenols and ammonia burned at temperatures of around 800 - 10000C. The burning of this relaxation vapor reduces the effort that would otherwise be required to treat condensate to be repelled heat is generated as waste water, considerably. Part of the sensible heat of the exhaust gas the combustion chamber 10 is in the heat exchanger 11 ill in the manner already explained utilized.

In the tar separator 9, which works on the principle of gravity, falls tar, which is withdrawn through line 37, as the heavy phase. The light, far-reaching The condensate phase consisting of water, the so-called Caswasser, is drawn with help the pump 39 through the line 29 and releases it at temperatures of mostly 90 - 1000C into the direct cooler 6. For cooling, the one from line 30 is colder used, which is e.g. a C02-rich exhaust gas from a gas scrubber can.

The cooled condensate leaves the cooler 6 through line 25, where it has a temperature of usually about 30-90 ° C there. The pump 32 first calls for the condensate to a heat exchanger 8, in which this is done the raw gas coming in line 22 (is cooled and stirred off in line 23 That Raw gas was initially in line 20 in the upper part of the heat exchanger 4 for the Steam generation by indirect heat exchange has been used and is in the judgment 4a of the heat exchanger 4 is sprayed with gas water from the line 24. Afterward the further heated gas water passes under the action of the pump 31 through the line 19 into the washing cooler 2. The cooling gas from line 30, which-in the direct cooler 6 was heated in the co-current with the gas water and besides considerable Quantities of water vapor also include flammable components such as phenols, hydrocarbons, and H2S and HCN has taken up is discharged in line 28 and via the line 34 also burned in the combustion chamber 10.

Deviating from the procedure for the drawing, rtian can direct Cooler 6 also lead the condensate and the colder gas in countercurrent to one another. The cooler 6 can also be designed in several stages. It is also possible to choose between the cooler 6 and the wash cooler 2 the multi-stage heat exchange between the Design condensate (gas water) and the raw gas in various ways, directly or indirectly and, for example, all the place of the heat exchanger 8 a direct heat exchange in To be provided in the form of an injection cooler with direct current flow of gas and condensate.

B e i s .p i e 1 In a procedure corresponding to the drawing coal with a grain size of 3 - 100 mm is placed in a fixed bed in a Lurgi gas generator gassed with rotating grate. When using 1000 kg of coal (water- and ash-free recet), which still contained 94 kg of moisture and 107 kg of ash are used as gasification agents 295 m3 of oxygen and 135 kg of water vapor were used. The gasification pressure in the reactor 1 is at 30 bar.

The raw gas in line 16 has a temperature of 4280C and a Volume of 2108 m³ (calculated dry). This raw gas consists of CO2 31.7% CO 17.2 H 37.7 H2 37.7 CH4 10.2 "CnH m 1.1" H2S 0.5 "N2 1.6" In addition the raw gas still contains 69 kg of tar, oil and naphtha, about 8 kg of phenols, 1.3 kg of fatty acids and 11 kg of ammonia and 1574 kg of water vapor.

The raw gas is intensively extracted in the washing cooler 2 with 6000 kg of gas water the line 19 sprayed. The gas leaves the washing cooler 2 at a temperature from 1930C and is saturated with water vapor, the same temperature points to the separator 3 flowing condensate. In the separator 3 condensate and gas are separated. That Raw gas is fed to the heat exchanger 4, where part of its sensible heat used to generate steam and the gas is cooled to 164 ° C. In the lower part 4a of the heat exchanger is the gas with gas water of 850C from line 24 sprayed and cooled to 141 ° C. The gas water is heated to 129 0C and is pumped into the washing cooler 2 via line 19. The raw gas from the lower part 4a of the heat exchanger is cooled to 95 ° C. in the tube heat exchanger 8, thereby that coming from line 25 is heated in countercurrent through the heat exchanger 8 can water from 74 4 to 85 ° C.

7736 kg of condensate from separator 3 are passed through line 21 placed in the tea table 9 and relaxed to atmospheric pressure; Evaporate in the process 1308 kg of the condensate in the combustion chamber 10 at about 880 0C with additional fuel to be burned. G428 kg of non-evaporated condensate, the so-called gas water, are from the tar separator 9 with a temperature of 99 0C through the line 29 in the direct Condenser 6 passed and in cocurrent with C02 from 500 chilled.

The C02 is brought in in line 30 and comes from the regeneration an absorbent used for gas scrubbing. In zone 6, the C02 is with Saturated water vapor and heated to a temperature of 72 ° C. At the saturation of the C02, 266 kg of gas water are evaporated. The CO2 saturated with water vapor becomes also passed into the combustion chamber 10.

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Claims (5)

P a t e n t a n 5 p r ü c h e 1) Process for treating water-containing Condensate from the cooling of the raw gas of the gasification of solid fuels with oxygen, Gasifying agents containing water vapor and / or carbon dioxide under pressure from 5 - 150 bar, whereby the raw gas is cooled in several cooling stages and at least part of the condensate produced during cooling, which has a temperature of at least 130 0 and a pressure of at least 4 bar, relaxes the resulting Relaxation steam dissipates and burns and that one the relaxed condensate a Separating device feeds, from which one largely consists of water Condensate phase is withdrawn, which is used for cooling the raw gas, characterized in that, that the condensate phase, which consists largely of water, is in direct contact cools with older gas before it is used to cool the raw gas, and that heated gas containing water vapor burns. 2) Method according to claim 1, characterized in that the largely consisting of water condensate phase in cocurrent or countercurrent with the colder gas cools. 3) Method according to claim 1 or 2, characterized in that one the condensate phase cooled in direct contact with colder gas in one or more stages heated by raw gas and the condensate phase Suletzt with a temperature of about 110 - 1500C into a washing cooler, to which the raw gas coming from the gasification is fed directly and in which approximately the same pressure as in the gasification prevails. 4) Method according to claim 1 or one of the following claims, characterized characterized in that the condensate phase is in direct contact with the colder gas by about 10 - 60 ° C to a temperature in the range of 30 - 900C Fekü.h1t. 5) Method according to claim 1 or one of the following claims, characterized characterized in that that for cooling the condensate phase consisting largely of water uses gas mainly from one or more of the gases carbon dioxide, nitrogen, Methane or carbon monoxide.