DE3112761A1 - Process for generating a synthesis gas suitable for the synthesis of methanol - Google Patents

Abstract

The invention relates to a process for generating a synthesis gas suitable for the synthesis of methanol by partial oxidation of coke furnace gas, the crude coke furnace gas, before the partial oxidation is carried out, being largely freed of tar and being precooled to a temperature of from 20 to 70 DEG C. Following the partial oxidation, which is preferably carried out in the presence of oxygen and/or air enriched with oxygen at a temperature of from 1100 to 1600 DEG C and a pressure of from 1 to 2 bar, the partial-oxidation gas generated is dedusted and desulphurised, whereupon this gas, after appropriate compression, is used as a synthesis gas for the synthesis of methanol without further secondary treatment.

Description

Process for the production of a suitable for the methanol synthesis

th synthesis gas.

The invention relates to a method for producing one for methanol synthesis suitable synthesis gas by partial oxidation of coke oven gas.

It is known that coke oven gas is composed by partial oxidation to change in such a way that a gas is produced, which after appropriate gas treatment for different purposes, e.g. as a reducing gas or as a synthesis gas, can be used. For example, in DE-OS 26 38 348 a method for further processing of coke oven gas by partial oxidation to reducing gas and in the FR-PS. 1 36-7 720 a method for the further processing of coke oven gas Partial oxidation to synthesis gas described. In both cases, however, it will assumed that it was not expedient to use those contained in the raw coke oven gas By-products by special measures before the gas enters the partial oxidation to separate.

It is therefore suggested in each case that from the coke oven battery incoming hot coke oven gas directly, i.e. without prior cooling and cleaning, to be fed to the partial oxidation. The purpose of this proposal is to be on the one hand on the plants for the separation and recovery of the by-products from the raw coke oven gas and on the other hand the sensible heat of this gas as much as possible to use in partial oxidation.

In practice, however, the implementation of this proposal prepares Difficulties because it is not easily possible to use the coke oven battery to transfer incoming hot coke oven gas into the partial oxidation gasifier, without condensates being cut off. In addition, the The tar contained as a by-product in the raw coke oven gas is still a valuable one and a completely salable product, which is used as the starting material for production serves a variety of chemical compounds. The separation of the tar from The raw coke oven gas is therefore still useful today and of economic importance Interest.

Should the gas resulting from the partial oxidation of coke oven gas be used as Synthesis gas is used for methanol synthesis, it must be taken into account that in the production of so-called. Methanol synthesis gas in terms of ratio from hydrogen to carbon oxides (COSCO in synthesis gas, special conditions must be observed are. With a C02 content in the synthesis gas of more than 2 vol. - 7o the ratio is 2 ~ ~~~ 2.0 to 2.2 CO + 1.5 CO2.

It has now been found that with a gas which according to the next proposal discussed above by partial oxidation of crude coke oven gas, which none has been subjected to upstream cooling and cleaning, the given above Ratio of hydrogen to carbon dioxide (CO + CO2) cannot be easily achieved. In this case it is rather required that the partial oxidation raw gas in addition to a generally customary cleaning and desulphurisation is also subjected to a CO conversion and subsequent CO2 scrubbing will.

Of course, this is caused by the last two procedural steps mentioned not inconsiderable investment and operating costs.

The aim of the present invention is therefore the method for the extraction of so-called. Methanol synthesis gas through partial oxidation of coke oven gas to further simplify and make them more cost-effective. This should be at the same time the extraction of the tar contained in the raw coke oven gas is not omitted and the environmental impact of the process is reduced as much as possible.

This is done according to the invention in a method of the type mentioned at the beginning achieved in that the crude coke oven gas before the partial oxidation is carried out largely freed from tar and pre-cooled to a temperature of 20 to 70 "C. and that the gas resulting from the partial oxidation by dry and / or wet gas cleaning freed from its dusty impurities as well as one Desulfurization is subjected, whereupon this gas after appropriate compression is used as synthesis gas for methanol synthesis without further treatment.

That is to say, it was the case when the method according to the invention was carried out Surprisingly, it has been shown that the6 Tar off the raw coke oven gas before the partial oxidation this supplies a gas in which the ratio of hydrogen to carbon dioxide (CO + CO2) given above without CO conversion and CO2 scrubbing can be achieved. Therefore, the inventive Process the gas resulting from the partial oxidation only from its dusty Contaminants are freed and desulphurized down to a sulfur content of <1 ppm and, after appropriate compression, can easily be put into the reactor for the methanol synthesis be initiated.

The partial oxidation of the coke oven gas in the presence of oxygen and / or oxygen-enriched air is preferably at one temperature carried out from 1100 to 1600 ° C and a pressure of 1 to 2 bar, with per Nm3 Coke-3 oven gas until 0.3 Nm oxygen can be added.

Tar can be added to the coke oven gas during the partial oxidation be added in an amount of up to 0.1 kg per Nm coke oven gas. This encore of tar is only necessary if the CO and CO2 content is in the partial oxidation gas is too low to reach the ratio of hydrogen to carbon oxides given above to reach. The amount of tar added to the coke oven gas is therefore the same The greater the deficit of CO and CO2 in the partial oxidation gas.

In any case, however, the addition of tar remains within the range limits given above. Normally, however, the addition of tar is not necessary.

Furthermore, the coke oven gas can water vapor during the partial oxidation coke oven gas can be added in an amount of up to 0.4 kg per Nm3.

When carrying out the method according to the invention fall into the different gas treatment stages condensates or wastewater, the H2S and / or mainly contain NH 3. Would this wastewater from without further post-treatment Dismissed from the process would result in significant environmental pollution to lead. Therefore, according to a further embodiment of the method according to the invention provided, the condensates occurring in the individual gas treatment stages and / or To collect waste water and subject it to a joint H2S and / or NH3 output, whereby the H2S and / or NH3 -containing vapors are added to the coke oven gas be added before the partial oxidation. After the removal of the H2S and / or NH3 -containing components can be the collected sewage without a normal concern Waste water treatment plant are fed.

Further details of the method according to the invention are to be found below are explained on the basis of the flow diagrams shown in the figures at the same time also serve to describe the process examples.

In this case: FIG. 1 shows the flow diagram for the one according to the invention Process when the coke oven gas produced in its entirety leads to methanol synthesis se gas is to be processed and FIG. 2 shows the flow diagram for the inventive Procedure when a partial flow is branched off from the coke oven gas and as Sub-firing gas is to be used for the coke oven battery.

The flow diagrams only show those for the process description absolutely necessary equipment or system parts, while all other ancillary equipment, which have nothing to do directly with the method according to the invention, in particular also the facilities and components of the coking plant and the methanol synthesis plant, are not shown.

In the case of the flow diagram shown in FIG. 1, this should be done by the coke ovens 1 incoming coke oven gas is processed in its entirety into methanol synthesis gas, while for the underfiring of the coke ovens 1 another gas, such as z, 3rd lean gas, is used.

The withdrawal of the raw coke oven gas from the coke ovens 1 and its direct cooling in the receiver corresponds to the working methods customary in coke oven technology. Details of this are not shown in the flow diagram. That from the coke ovens 1 incoming raw coke oven gas reaches the collecting line via lines 2 and 3 4, 3 by the 75,000 Nm / h coke oven gas of the further treatment in the present case are fed. The coke oven gas is in the front part of the collecting line 4 a temperature of approx. 75-85 ° C. In the course of this line is the condensate separator 5 arranged, which serves to separate the tar-containing condensates from the gas stream.

These condensates reach the condensate treatment via line 6 7, in which the tar stood by phase separation from the watery condensate ilen is separated. Of course, those from coking technology are used for this purpose known facilities for use.

In the meantime, the tar-containing condensate is released Coke oven gas in the pre-cooler 8, in which it is down to a temperature of approx. 20-70 ° C is cooled. Also for the pre-cooling of the coke oven gas are used for this Purpose known from coking technology Cooler constructions with Liquid cooling (water cooling) is used. If necessary, however, can also air coolers are used here.

During pre-cooling, additional condensate is produced, which comes from the pre-cooler 8 withdrawn via line 11 and also in the / 7 ~ ~ condensate treatment ' is initiated. The tar accumulating there is via line 12 into the tar collection container 13 transported, while the tar freed aqueous condensate constituents reach via line 14 in the collecting container 15, in which all in the process accumulating aqueous condensate and waste water are collected.

If it was said above that the raw coke oven gas before implementation the partial oxidation is largely freed from tar, this means that the Degree of tar separation depending on the gas temperature during pre-cooling corresponds to the degree of separation generally used in coking technology. This means, In the cooled coke oven gas, an average of about 1-5 g tar per 3 Nm gas can still be in the form of a mist be included.

After exiting the pre-cooler 8, the coke oven gas is released from the sucker 9 pressed into the carburetor 1G, in which its partial oxidation (gasification) takes place. Before entering the gasifier 10, the coke oven gas has the following composition to: H2 59.0 vol. -7o CH4 23.6 vol. -7o C H 3; 4vol .-% n m N2 4.7 vol. -CO 5.5vol .-% CO2 2.0 vol. -70 O2 0.3 vol. -7o remainder 1.5 vol .-% The partial oxidation (gasification) is carried out in the present case under the following conditions: Pressure: 1.04 bar Temperature: 1,300 cc Addition of a) oxygen: 0.3 Nm3 / Nm coke oven gas b) tar: none Tar addition 3 c) Steam 0.03 kg / Nm coke oven gas. The gasifier 10 is is a Koppers-Totzek carburettor, which has proven itself well for the stated purpose Has. If necessary, however, a different carburetor construction could also be used here will. The oxygen required for the partial oxidation is in the air separation plant 16 and passed into the carburetor 10 via the line 17. The one for partial oxidation any tar required is removed from the tar collection container 13 and is fed to the carburetor 10 via the line 18. Regarding the system of tar addition during the partial oxidation, reference is made to the statements made above. Since in the present case no tar is added during the partial oxidation, can the total tar accruing in an amount of 6600 kg / h via the line 41 led to tea rde stillation, not shown in the flow diagram. Possibly A line not shown in the flow diagram can also be provided be, through which the necessary steam of reaction is introduced into the gasifier 10 will. The wastewater resulting from the cooling of the gas after the partial oxidation (Condensate) is drawn off via line 19 and also into the collecting container 15 convicted.

The gas emerging from the gasifier 10 after the partial oxidation has the following composition: CO2 2.6 vol .-% CO 27.4 vol .-% H2 65, 5 vol. -N / Ar 4, 1 Vol. - 7o 2 H S / COS 0,4Vol.-70 2 This gas first enters the gas container 20 and then into the electrostatic gas cleaning 21, in which it is of its dusty impurities is freed.

Then the gas in the compressor 22 is up to a pressure of 30 bar compressed and introduced with this pressure into the desulfurization device 23, in which a desulphurisation of the gas down to a sulfur content of <lppm The desulfurization is carried out in a manner known per se a wash with methanol at a temperature of -30 to -400C (so-called methanol cold wash).

The methanol, which is essentially loaded with H2S, passes through the line 24 from the desulfurization device 23 into the associated regeneration device 25, in which the sulfur compounds absorbed by the methanol are driven off. These are fed via line 26 to the Claus plant 27, in which they are after the so-called Claus process for elemental sulfur worked up will. This is in the present case in an amount of approx. 14 t / d over the Line 28 withdrawn from the process. The regenerated methanol is through the Line 29 is fed back into the desulfurization device 23, while the Waste water resulting from the regeneration of methanol via line 30 into the collecting tank 15 reached. The CO2-containing exhaust gases resulting from the methanol regeneration are withdrawn at the same time through the line 31 and can be accessed via the not shown Chimney to be repelled into the atmosphere.

Of course, the process according to the invention is not open the use of the methanol cold wash described above is limited. It can Rather, other desulphurisation processes can also be used, provided that these are the achieve the required degree of desulfurization. Besides, it is basically too possible to produce sulfuric acid instead of producing elemental sulfur.

After the exit from the desulfurization device 23, the desulfurized and purified gas in the compressor 32 up to the synthesis pressure of 50-80 bar compressed to catalytically to methanol with this pressure in the synthesis plant 33 to be implemented. With the amount of coke oven gas specified at the outset, the methanol yield is 45 tons per hour. This methanol can via line 34 from the process subtracted from.

The combined in the collecting tank 15 aqueous condensates and waste water are continuously or discontinuously into the abortion via line 35 36 initiated, in the H2S and / or NH3 at a temperature of 100-120tc from the liquid be aborted. The resulting H2S and / or NH3 vapors are carried through the line 37 withdrawn and in its entirety the coke oven gas between the sucker 9 and the gasifier 10 added so that they participate in the partial oxidation of the coke oven gas participate with. The wastewater freed from H2S and / or NH3 flows through the pipe 38 to the wastewater treatment facility 39, from which, after appropriate processing can be drained via line 40 into the receiving water.

In the flow diagram shown in FIG. 2, the process sequence is basically the same as in the flow diagram according to FIG. 1.

Corresponding reference symbols therefore also have in both flow diagrams the same meaning. In the method according to FIG. 2, 3 is also a quantity of coke oven gas assumed 75,000 Nm per hour. In this case, however, the underfiring the coke oven 1 is to be operated with coke oven gas, is from the manifold 4 between the pre-cooler 8 and the sucker 9, a partial flow 3 of 28,500 Nm / h coke oven gas branched off and withdrawn via line 42. Before this substream, however, to Underfiring of the coke ovens 1 can be used, it must be in the required Scope to be cleaned. Therefore, in the course of the line 42 are electrostatic Gas cleaning with naphthalene separation 43, the H2S scrubbing 44 and the NH3 scrubbing 45 provided. Only after the coke oven gas has these facilities in line 42 has happened, it can be fed to the underfiring burners of the coke ovens 1. The suction device 46 is used to compress the gas flow required before it enters into the H2S wash 44. The H2S wash 44 and the NH wash 45 are in this case executed as ammoniacal cycle scrubbing, the removed from the coke oven gas Accompanying substances - mainly H2S and NH - also 3 the coke oven gas be added before the carburetor 10.

In this case, part of the draining liquid becomes part of the drainage device 36 Abandoned via line 47 as washing liquid on the NH3 scrubbing 45. From the ammoniacal solution running off the NH3 scrubber 45 is then poured over the Line 48 supplied to the H2S scrubbing 44 and used there as washing liquid. The liquid running off from the H2S wash 44 then contains both that from the Coke oven gas absorbed H2S as well as the NH3 and enters via line 49 the aborter 36 back, in which the further work-up in the above described manner takes place.

Of course, the method variant described above succeeds correspondingly less gas in the synthesis plant 33, so that the methanol yield in this case is only 27.5 tons per hour.

Claims (9)

Claims: 1.) Process for the production of a for the methanol synthesis suitable synthesis gas by partial oxidation of coke oven gas, characterized in that that the crude coke oven gas before the partial oxidation is carried out largely from Tar is freed and pre-cooled to a temperature of 20 to 70 ° C and that Gas produced during partial oxidation by dry and / or wet gas cleaning freed from its dusty impurities and then one Desulfurization is subjected, whereupon this gas after appropriate compression used as synthesis gas for methanol synthesis without further treatment will . 2.) VerfahrennachAnspruch 1, characterized in that the partial oxidation of the coke oven gas in the presence of pure oxygen and / or enriched with oxygen Air at a temperature of 1100 to 1600 ° C and a 3 pressure of 1 to 2 bar is carried out, with up to 0.3 Nm oxygen being added per Nm 3 coke oven gas. 3.) Process according to claims 1 to 3, characterized -net, that depending on the content of carbon oxides (C; O + C02) of the partial oxidation generated gas the 2 coke oven gas during the partial oxidation tar in an amount up to 0.1 kg per Nm coke oven gas can be added. 4.) Process according to claims 1 to 3, characterized in that that the coke oven gas during the partial oxidation water vapor in a quantity up to 0.4 kg per Nm coke oven gas is added. 5.) Process according to claims 1 to 4, characterized in that that the gas resulting from partial oxidation is subjected to electrostatic gas cleaning and / or gas cleaning in a cyclone and / or wet gas cleaning (gas scrubbing) is subjected. 6.) Process according to claims 1 to 5, characterized in that that the gas resulting from the partial oxidation up to a sulfur content of <1 ppm is desulfurized. 7.) Process according to claims 1 to 6, characterized in that that the condensates and / or waste water occurring in the individual gas treatment stages collected and subjected to a common H S and / or NM 3 output, with the resulting H2S and / or NH3-containing vapors to the coke oven gas before the Partial oxidation can be added. 8.) Process according to claims 1 to 7, characterized in that that when using a partial flow of the coke oven gas to fire under the coke ovens the scrubbing liquid required for the H and NH3 scrubbing of this substream common aborter is removed, the loaded washing liquid for the purpose Regeneration is returned to the abortionist, with the resulting Vapors can also be added to the coke oven gas before the partial oxidation. 9.) Process according to claims 1 to 8, characterized in that that for the pre-cooling of the raw coke oven gas, liquid coolers and / or air coolers be used.