DE2554419C2 - Process for the production of synthesis gas by partially burning coal - Google Patents

Description

The invention relates to an improved method for Production of synthesis gas by partial combustion of coal, the tar formed from the gas is separated and allowed to settle the solids contained in the tar. The one enriched in solids Tar is recycled to partially burn the coal.

Any solid, carbonaceous material can be used as a feed for such a process be, d. H. any solid fuel consisting essentially of chemically bound or chemically unbound Carbon. A suitable starting material is e.g. B. lignite, bituminous coal, sub-bttumlnous Coal, anthracite or coke.

The partial combustion of the coal to form tar can be carried out in any desired manner, such as by means of the Lurgl process or the Synthan process. With partial combustion the coal, this is converted into a gas mixture with oxygen, air or with oxygen smelted air, which consists mainly of hydrogen and carbon monoxide.

^{0.2 to 0.4 Nm 3 of} oxygen is suitably used per kg of coal. Steam is preferably fed in as a temperature moderator. Expediently, 2 to 9 kg of steam are added to the reaction mixture per Nm ^{3 of oxygen.}

After the gasification of the coal, which is preferably carried out at temperatures of 700 to 1100 ° C the gas obtained is withdrawn from the gasification reactor. This gas generally has temperatures from 370 to 600 ° C and contains hydrogen and carbon monoxide in addition to the desired components and methane undesirable impurities such as tar, oil, heavy gasoline, phenols, water, ammonia, Hydrogen sulfide, carbon dioxide, and coal and ash dust. To avoid these impurities from Separate synthesis gas, the raw gas is cooled to temperatures of 40 to 200 ° C, which is preferably by means of indirect heat exchange with water, in which steam is generated. Through this Tar, oil, heavy gasoline, phenols become and the water condenses with the coal and ash being absorbed by the condensation liquid will. The condensed liquid is separated from the synthesis gas. Oil, heavy fuel, phenols

ίο as well as the tar containing ashes and coal separated from the separated liquid by means of fractional distillation. The synthesis gas can on known catfish by separating hydrogen sulfide, carbon dioxide and possibly contained therein other contaminants such as carbon oxysulphide, carbon disulfide and hydrocyanic acid.

Corresponding or similar processes are known. The recycling of from the product gas is also known deposited solids, such as soot, or tars enriched therewith.

So is according to DE-OS 22 31669 a solid, liquid or gaseous fuel with an oxygen-containing one Gas gasified in a burner nozzle, with one component as a central jet and the other Component is injected into the reactor as a hollow jet. The soot formed during the gasification or the Hydrocarbons formed can also be used for the production of the soot-fuel dispersion to be injected will.

In DE-OS 20 44 310 a gasification process described in which the formed soot and unburned coal as a slurry in water, the up to 25% liquid hydrocarbon can also be added can, is returned to the gasification reactor.

Furthermore, the use of waste sera is the

are heavily contaminated by dust, known for briquetting tar-free fuels (DE-PS 9 14 537), around these briquettes at a low dump height by means of oxygen containing water vapor at high gas extraction temperatures to gas.

In the gasification process described in DE-AS 10 86 000 the tar separated from the synthesis gas is separated into one with solid particles enriched tar portion and In a low-dust portion. The tar fraction enriched with solids serves to build up a filter and dust-trapping layer above the gasification zone, by acting as a wetting agent acts for the coal charge located there.

A gentle distillation of this tar and wetting layer takes place in the gasification reactor, so that the solid particles adhere to the coal charge bind and the tar component itself becomes dust-free. This catfish should cool down when the

The synthesis gas formed is a suitable product for sale Tar fraction can be obtained.

According to DD-PS 74 071 fluctuations in the needs of the buyer of gases produced by gasification solid fuels are produced by an additive

from Z. B. Waste tars In the zones of degassing and / or the reduction can be compensated.

The object of the invention is to provide a maximized, integrated process of coal gasification to ask where from a given

^b> Injection quantity of coal a maximum quantity of synthesis gas is available.

According to the invention, this object is achieved by a complete Exploitation of the gasification process itself

by-products formed dissolved in the Wsise described below.

In the process for the production of synthesis gas by partial combustion of coal, with from Gas containing tar is separated, its solid ~. substances are allowed to settle and the tar enriched with solids for partial combustion of the Recirculates coal, therefore, according to the invention, the tar from which the solids have settled is through partial combustion at temperatures from 1000 w to 1500 ° C and pressures from 1 to 100 ata in one separate reactor gasified, the resulting soot is separated from the gas, this soot with the Solids-enriched tar is mixed in and this mixture is partially burned together with the coal, π

As described above, tar becomes a by-product formed in the gassing of Kohie. This tar generally contains 1 to 25% solids by weight, namely ash and unconverted or only partially converted coal particles. - ·>

Since a high solids content hinders the partial gasification of the tar, which is then to be carried out according to the invention, part of the solids is separated from part of the tar and the other part of the tar is enriched with it. This can be done in any suitable manner by allowing the solids to settle from one part of the tar to another part of the tar. Preferably, the solids are removed from a proportion of 25 to 75% by weight of the tar by allowing them to settle in an amount of 75 to ¹ % by weight of the tar. Another advantage is to remove the solids The process carried out on the tar, the tar is washed with hot water, which is preferably at a temperature of 125 ° C.

The part of the tar from which the solids have been removed is particularly suitable for gasification by means of partial burn.

The partial combustion of the tar from which the solids have settled is preferably by means of of the Shell gasification process. This procedure is in Chemical Economy and Engineering Review ", December 1973, Volume 5, No. 12, Pages 22-28.

For the partial combustion of the tar, oxygen or, if necessary, is used as the oxidizing gas Oxygen-enriched air is used. The tar is preferably gasified using oxygen.

In the case of partial combustion of the tar, preference is given to Steam used as a temperature moderator. Suitable catfish are 0.5 to 3 kg of steam per kg of tar mixed in.

The oxygen or the oxygen-containing gas is preferably at temperatures of 200 to 500.degree preheated before entering the separate reaction zone, in which the partial combustion of the tar is carried out, is fed. After preheating the hot oxidizing gas is advantageously mixed with the tar and the gas / tar mixture is then preferably atomized under high pressure in a reactor. The pressure is advantageously around 1 to 50 at above the pressure used in the reactor. Reactors for this are known.

In order to gasify the largest possible amount of tar fed into the reactor, the tar ^droplets must remain in the reactor for a sufficient period of time; a residence time of 1 to 15 seconds is very suitable for this purpose.

After the tar has been gasified, the reaction product, which consists essentially of hydrogen, carbon monoxide, carbon dioxide, nitrogen and water, is withdrawn from the reactor. The gas obtained has high temperatures, which are generally above HOO ⁰ C, and it contains ash, soot and hydrogen sulfide. During gasification, 0.05 to 0.20 kg of soot are formed per kg of tar. In order to enable the impurities to be separated off, the gas is first cooled, preferably by injecting water, steam and / or part of the cooled and purified product gas. According to another embodiment which is preferably used, the cooling is carried out completely or partially in a digester in which steam is formed by means of the waste heat.

To separate the soot from the gas, those in GB-PS 8 26 209 and 12 67 896 are advantageously described method used.

The gas is preferably cooled to temperatures of 120 to 250 ° C.

The solids content of the cooled gas is kept low by keeping the conditions in the reactor chooses accordingly. Another reduction in the solids content however, the gas is desirable when the gas is e.g. B. should be desulfurized or if the carbon monoxide contained in the gas can be reacted with water to form carbon dioxide and hydrogen target. For this purpose, the gas is passed through known scrubbers, in which it is preferably mixed with water is washed.

Such a washing treatment leads to a gas which practically no longer contains solids and which has a temperature between 20 and 80 ° C. The solids-free dry gas usually has the following composition:

Table I.

Volume percentage

N ₂ + A

15 to 50
15 to 30

7 to 30

Obis 5

0.05 to 0.50

1 to 55

The gas is preferably welter by separating off the hydrogen sulfide and at least a portion of carbon dioxide Purified in a manner known per se.

That part of the tar that has a larger amount of solids as a result of the sedimentation process described above than originally contains, together with carbon black, which in the above-described partial Combustion of the low-solids tar was formed, returned to the partial combustion of the coal.

According to a preferred embodiment of the method according to the invention, 25 to 75% of the Tar is gasified directly and 75 to 25% percent of the tar is separated out together with that from the tar gasification Soot returned to the partial combustion of the coal, with 3 to 10 weight points of tar each Weight carbon black is added.

The soot can either be mixed directly with the tar, or it can first be taken up in water

and then added to the tar. - In the former case, this is the case with partial combustion a part of the tar obtained raw gas contacted with the other part of the tar, so that the soot in the tar enriched with solids passes over. In this method, the raw gas is preferably on first Temperatures of 50 to 200 ° C cooled down, while the tar, to which the soot is to be mixed, preferably a temperature of 50 to 200 ° C ". - In the latter case, soot-containing water, which preferably has a soot content of 0.5 to 10% by weight and has a temperature of 100 to 150 ° C, with stirring at a temperature of 100 to Contacted tar exhibiting 150 ° C.

In the first-mentioned case, ^{0.001 m 3 of} tar ^{are advantageously used per Nm 3 of} soot-containing gas.

In the latter case, 1 m ^{3 of} water containing carbon black ^{is expediently contacted with 1 m 3 of} tar.

Starting from 1000 kg of coal, by means of the process according to the invention and after the drying and removal of the hydrogen sulfide and the carbon dioxide, it is possible to ^{produce 1500 to 3300 Nm 3 of} a synthesis gas with the following composition:

Table II

Volume percentage

N ₂ + A

30 to 45

19 to 24

8 to 30

1 to 45

The following example illustrates the invention. example

A coal with the following composition is used as the starting material:

Weight percent C. 72.95 H 4.88 O 10.78 S. 1.36 N 1.56 ash 8.47

This charcoal contains 34.7% by weight of volatile components and also 2 % by weight of water. The coal is gasified by means of partial combustion together with tar from the subsequent process stage. 0.06 kg of tar, 0.356 kg of oxygen and 1.524 kg of steam are used per kg of anhydrous and ash-free coal. The oxygen fed in has a temperature of 250 ° C and the steam a temperature of 263 ° C.

The gasification is carried out at temperatures of 700 to HOO ⁰ C and a pressure of 40 at abs. carried out.

After the gas obtained has cooled to 125 ° C., the tar is separated from the gas.

Per kg of coal, 0.10 kg of tar with a solids content of 15% by weight is obtained.

After drying, the gas obtained has the following composition:

Volume percentage H ₂ 29.3 CO 15.5 CO ₂ 31.7 CH ₄ 22.1 H ₂ S 0.5 N ₂ + A 0.9

Per kg of water-free and ash-free coal, 2.08 Nm ^{3 of} the gas described above is obtained.

You can now the solids from 50 wt .-% des Settle the tar into the remaining tar. The two parts of the tar are then separated from each other.

The pure tar is in a separate reactor by means of partial combustion with 1.057 kg of oxygen and 2.5 kg of steam per kg of tar into a soot-containing synthesis gas converted. A temperature of 1100 ° C. and a pressure of 40 at abs. applied.

This raw synthesis gas from tar gasification is cooled to 180 ° C by means of indirect heat exchange with water. The gas is then washed with water, whereby the soot is absorbed by the water. 0.15 kg of soot are formed per kg of tar.
The soot-free synthesis gas demonstrates the

standing composition on:

H ₂ Volume percentage 35 CO CO ₂ 48.0 40 H ₂ S 25.2 N ₂ + A 25.6 0.2 1.0

^{2.57 Nm 3 of} gas are formed per kg of tar.

The part of the tar which contains the settled solids of the tar is intimately with stirring at 125 ° C mixed with the soot-containing water, the soot being absorbed by the tar. The soot-containing tar and the purified water are then separated from each other. The soot and solids-containing tar is returned to the partial combustion of the coal.

The synthesis gas obtained directly from the gasification of the throat is mixed with the synthesis gas obtained from the gasification of the cleaned tar. In the end, 2.228 Nm ^{3 of} dry synthesis gas is obtained per kg of coal, which has the following composition:

Volume percentage H ₂ 30.4 CO 16.1 CO ₂ 31.3 CH ₄ 20.8 H ₂ S 0.5 N ₂ + A 0.9

Claims (2)

Patent claims: 1. Process for the production of synthesis gas by partial combustion of coal, with from Gas solids-containing tar is separated, the solids of which can be settled and with Returns tar enriched in solids to the partial combustion of the coal, characterized in that - That the tar from which the solids are deposited have, through partial combustion at temperatures of 1000 to 1500 ° C and pressures from 1 to 100 ata is gasified in a separate reactor, - that the resulting soot is separated from the gas, - That this soot is mixed with the tar enriched with solids and - That this mixture is partially burned together with the coal. 2. The method according to claim 1, characterized in that the formed in the tar gasification Soot, the tar enriched with solids, in a ratio of 1 part by weight to 3 to 10 parts by weight Tar is added.