DE3112761C2 - - Google Patents

Description

The invention relates to a method for producing a methanol synthesis gas, in the raw coke oven gas with extensive tar separation cooled and then in the presence of pure oxygen of a partial oxidation is subjected.

It is known coke oven gas by partial oxidation in its composition to change so that it produces a gas, which after appropriate Gas treatment for different uses, eg. B. as a reducing gas or as a synthesis gas can be used. So will 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 13 67 720 a method for further processing of coke oven gas described by partial oxidation to synthesis gas. In both cases However, it is considered that it is not appropriate to use the raw coke oven gas contained by-products by special measures before separating the gas into the partial oxidation. It is therefore proposed in each case, coming from the coke oven battery hot coke oven gas directly, that is without prior cooling and Purification to supply the partial oxidation. Purpose of this proposal It should be there, on the one hand, the systems for separation and Obtain 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 the partial oxidation. In practice, the realization prepares This proposal, however, difficulties because it is not without Another is possible, coming from the coke oven battery hot coke oven gas to convert into the partial oxidation serving carburetor, without this leading to the deposition of condensates. also always provides the tar contained as a by-product in the raw coke oven gas still a valuable and quite salable product, which  as a starting material for the production of a variety of chemical Connections serves. The separation of the tar from the raw coke oven gas is therefore still useful today and of economic Interest.

In the journal "Technische Mitteilungen", 73 (1980), page 835, is in this context a process for the production of hydrogen, Synthesis gas and / or reducing gas pointed to the Kokereirohgas cooled to 150 ° C and then in a swing tube reactor is partially oxidized with oxygen. That this procedure especially suitable for the production of methanol synthesis gas, can not be deduced from this citation.

The process, the raw coke oven gas in the tar separation and gas treatment typically passes, for example, in Winnacker-Kuchler, "Chemische Technologie", Vol. 3, pages 63-64. On the reuse of coke oven gas, in particular its reaction by partial oxidation is described in this reference but nothing stated.

From DE-AS 20 65 892 finally a method for simultaneous Production of two synthesis gas streams of different composition known in which the one for performing the oxo synthesis and the other suitable for carrying out the methanol synthesis should be. Here is a by partial oxidation of Hydrocarbons, in particular of refinery gas, recovered feedstock went out. This gaseous feedstock is doing further treated in two separate process strands. So far the further implementation of the feed gas to methanol synthesis gas provided is, the gas is first in a non-catalytic water gas converter initiated, in which the gas with additional water vapor is reacted so that it then has a lower CO / H₂ molar ratio has as the starting gas. Subsequently, this gas  After appropriate cooling in a waste heat boiler soot deposition subjected to a CO₂ scrubbing. After that it will be his next Used in the synthesis of methanol.

If the resulting gas in the partial oxidation of coke oven gas as Synthesis gas used for methanol synthesis, that is namely to take into account that in the production of so-called. Methanol synthesis gas in terms of the ratio of hydrogen to carbon oxides (CO + CO₂) are to be observed in the synthesis gas special conditions. in this connection should at a CO₂ content in the synthesis gas of more than 2 vol .-% the relationship

be.

The object of the present invention is therefore to provide the method for Extraction of so-called Methanol synthesis gas by partial oxidation of To further simplify coke oven gas and make it cheaper. This should at the same time to a recovery of raw coke oven gas contained tar and the environmental impact be minimized by the process as possible.  

This is according to the invention in a method of the type mentioned achieved in that one up to a temperature of 20 to 70 ° C pre-cooled coke oven gas at a temperature of 1100 to 1600 ° C. and a pressure of 1 to 2 bar subjected to the partial oxidation, wherein per Nm³ Koksofengas be added to 0.3 Nm³ of oxygen and that the resulting in the partial oxidation gas of dust-like impurities freed and desulfurized and then after Compressed without further treatment of the methanol synthesis plant supplied becomes.

While in a process where the coke oven gas without upstream Cooling and purification of the partial oxidation is subjected to this Methanol synthesis gas required above ratio of hydrogen to carbon oxides (CO + CO₂) only by a downstream CO conversion with subsequent CO₂ scrubbing can be achieved has in the implementation of the method according to the invention in a surprising Way shown that so that a gas can be generated at the above-mentioned ratio of hydrogen to carbon oxides (CO + CO₂) can be achieved without CO conversion and CO₂ scrubbing can. Therefore, in the process of the invention in the partial oxidation accumulating gas only from its dusty impurities free and to a sulfur content of <1 ppm desulfurized and then readily after appropriate compression be introduced into the reactor for the synthesis of methanol.

The coke oven gas may optionally tar during the partial oxidation in an amount up to 0.1 kg per Nm³ Koksofengas be added. However, this addition of tar is only required if the CO and CO₂ content in Partialoxidationsgas is too low, to the above specified ratio of hydrogen to carbon oxides to achieve. The amount of coke oven gas added tar is therefore all the more larger, the greater the deficit of CO and CO₂ in Partialoxidationsgas  is. In any case, however, the tar addition remains within the range above limits. Normally, tar addition is however not mandatory.

Further, the coke oven gas may vaporize during the partial oxidation in an amount up to 0.4 kg per Nm³ Koksofengas be added.  

In carrying out the method according to the invention fall in the various gas treatment stages condensates or wastewater to, which contain H₂S and / or especially NH₃. would this wastewater without further treatment from the process dismissed, this would be a significant environmental burden to lead. Therefore, according to another embodiment of the inventive method provided in the individual Gas treatment stages accumulating condensates and / or wastewater to collect and a common H₂S and / or NH₃ output to submit, with the case arising H₂S and / or NH₃-containing vapors coke oven gas before the partial oxidation be added. After the output of H₂S and / or NH₃-containing Ingredients can collect the collected wastewater without concern be fed to a normal wastewater treatment plant.

Further details of the method according to the invention are intended in the following with reference to the flow diagrams shown in the figures be explained at the same time the description serve the method examples.

It show here:

Fig. 1 is the flow diagram for the process according to the invention, when the coke oven gas is to be processed in its entirety to methanol synthesis gas and

The flow scheme for the inventive method to be when diverted from the resulting coke oven gas, a partial flow and is used as the coke oven battery for the undergrate FIG. 2.

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

In the flow scheme shown in Fig. 1, the coming of the coke ovens 1 coke oven gas is to be processed in its entirety into methanol synthesis gas, while for Unterfeuerung the coke ovens 1 another gas such. B. lean gas is used. The deduction of the raw coke oven gas from the coke ovens 1 and its direct cooling in the template correspond to the usual in coking technology procedures. Details on this are not shown in the flow chart. The raw coke oven gas coming from the coke ovens 1 passes via the lines 2 and 3 into the collecting line 4 , through which in the present case 75,000 Nm³ / h of coke oven gas are supplied for further treatment. The coke oven gas has a temperature of about 75-85 ° C in the front part of the manifold 4 . In the course of this line, the condensate 5 is arranged, which serves to separate the tarry condensates from the gas stream. These condensates pass via the line 6 to the condensate treatment 7 , in which the tar is separated by phase separation of the aqueous condensate components. For this purpose, of course, known from the coking technology devices apply.

Meanwhile, the freed from the tarry condensates coke oven gas enters the precooler 8 , in which it is cooled to a temperature of about 20-70 ° C. Also for the pre-cooling of coke oven gas known for this purpose from the coking technology cooler constructions with liquid cooling (water cooling) are used. Optionally, however, it is also possible to work with air coolers here.

In the pre-cooling falls on more condensate, which is withdrawn from the precooler 8 via line 11 and also introduced into the condensate treatment 7 . The tar formed there is transported via the line 12 into the tar collection container 13 , while the liberated from the tar aqueous condensate constituents via the line 14 into the collection container 15 , in which all accumulating in the process aqueous condensates and wastewater are collected.

If it has been said above that the raw coke oven gas is before the The partial oxidation is largely freed from the tar, this means that the degree of tar separation depends on from the gas temperature in the precooling in the coking plant generally common degree of deposition corresponds. This means, in the cooled coke oven gas can be on average about 1-5 g of tar per Nm³ gas may be contained in mist form.

After exiting the precooler 8 , the coke oven gas is pressed by the sucker 9 into the gasifier 10 , in which its partial oxidation (gasification) takes place. Before entering the gasifier 10 , the coke oven gas has the following composition:

H₂ 59.0% by volume CH₄ 23.6 vol.% C _n H _m 3.4% by volume N₂ 4.7% by volume CO 5.5% by volume CO₂ 2.0 vol.% O₂ 0.3% by volume rest 1.5 vol.%

The partial oxidation (gasification) is in the present case under following conditions:

Print: 1.04 bar Temperature: 1300 ° C adding @ a) oxygen: 0.3 Nm³ / Nm³ coke oven gas b) tar: no tar addition c) Water vapor: 0.03 kg / Nm³ coke oven gas

The carburetor 10 is a Koppers Totzek carburetor, which has proven well for the purpose mentioned. Optionally, but could also be used here another carburetor design. The oxygen required for the partial oxidation is recovered in the air separation plant 16 and passed via line 17 into the gasifier 10 . The tar optionally required for the partial oxidation is removed from the tar collection container 13 and fed via the line 18 to the gasifier 10 . With regard to the system of tar addition during the partial oxidation, reference is made to the remarks made above. Since no tar is added during the partial oxidation in the present case, the total tar can be fed in an amount of 6600 kg / H via line 41 to the tarry distillation not shown in the flow scheme. Optionally, a line not shown in the flow scheme may also be provided, through which the required reaction water vapor is introduced into the gasifier 10 . The accumulated in the cooling of the gas after the partial oxidation wastewater (condensate) is withdrawn via line 19 and also transferred to the collection container 15 .

The gas leaving the gasifier 10 after the partial oxidation has the following composition:

CO₂ 2.6% by volume CO 27.4% by volume H₂ 65.5% by volume N₂ / Ar 4.1% by volume H₂S / COS 0.4% by volume

This gas first passes into the gas container 20 and subsequently into the electrostatic gas cleaning 21 , in which it is freed from its dust-like impurities. Then, the gas is compressed in the compressor 22 to a pressure of 30 bar and introduced at this pressure in the desulfurization device 23 , in which a desulfurization of the gas is provided to a sulfur content of <1 ppm. The desulfurization is carried out in a conventional manner by washing with methanol at a temperature of -30 to -40 ° C (so-called methanol cold washing).

The loaded essentially with H₂S methanol passes via the line 24 from the desulfurization device 23 in the associated regeneration device 25 , in which the sulfur compounds taken up by methanol are driven off. These are fed via the line 26 of the Claus plant 27 , in which they are after the so-called. Claus process to elemental sulfur be worked up. This is deducted in the present case in an amount of about 14 t / d via the line 28 from the process. The regenerated methanol is introduced back into the desulfurization device 23 through the line 29 , while the wastewater obtained during the methanol regeneration passes via the line 30 into the collecting tank 15 . The resulting in the methanol regeneration CO₂-containing exhaust gases are simultaneously withdrawn through line 31 and can be repelled through the fireplace, not shown in the atmosphere.

Of course, the inventive method is not on the application of the methanol cold wash described above limited. Rather, other desulfurization processes can be used be used, provided that they have the required Achieve desulfurization. Besides, it is basically also possible, instead of generating elemental sulfur To produce sulfuric acid.

After exiting the desulfurization device 23 , the desulfurized and purified gas is compressed in the compressor 32 to the synthesis pressure of 50-80 bar in order to be catalytically converted to methanol at this pressure in the synthesis plant 33 . In the Koksofengasmenge specified above, the methanol yield is 45 tons per hour. This methanol can be withdrawn via line 34 from the process.

The combined in the sump 15 aqueous condensates and wastewater are introduced via the line 35 continuously or discontinuously in the Abtreiber 36 , are aborted in the H₂S and / or NH₃ at a temperature of 100-120 ° C from the liquid. The case arising H₂S and / or NH₃ vapors are withdrawn through line 37 and added in their entirety to the coke oven gas between the nipple 9 and the carburetor 10 , so that they participate in the partial oxidation of coke oven gas with. The freed from H₂S and / or NH₃ wastewater flow via line 38 to the wastewater treatment device 39 , from which they can be discharged after appropriate workup via the line 40 into the receiving water.

In the flow scheme shown in FIG. 2, the process flow is basically the same as in the flow scheme according to FIG. 1. Corresponding reference symbols therefore have the same meaning in both flowcharts. In the method of Fig. 2 is also assumed that a Koksofengasmenge of 75 000 Nm³ per hour. However, since in this case the underfiring of the coke ovens 1 to be operated with coke oven gas, a partial flow of 28 500 Nm³ / h coke oven gas is diverted from the manifold 4 between the precooler 8 and the sucker 9 and withdrawn via the line 42 . However, before this partial flow can be used for undercutting the coke ovens 1 , it must be cleaned to the required extent. Therefore, in the course of the line 42, the electrostatic gas cleaning with naphthalene 43 , the H₂S-wash 44 and the NH₃-laundry 45 are provided. Only after the coke oven gas has passed through these devices in the line 42 can it be fed to the subfire burners of the coke ovens 1 . The sucker 46 is the required compression of the gas stream before entering the H₂S-laundry 44th The H₂S-wash 44 and the NH₃-wash 45 are carried out in this case as ammoniacal cycle wash, the coke oven gas from the accompanying substances - in essence H₂S and NH₃ - are also added to the coke oven gas before the carburetor 10 .

From the Abtreiber 36 here is a part of the effluent liquid via the line 47 as a washing liquid on the NH₃-laundry 45 abandoned. The effluent from the NH₃ wash 45 ammoniacal solution is then supplied via the line 48 of the H₂S wash 44 and used there as a washing liquid. The effluent from the H₂S wash 44 liquid then contains both the recorded from the Koksofengas H₂S and the NH₃ and passes back via the line 49 in the Abtreiber 36 , in which further processing takes place in the manner already described above.

In the process variant described above, of course, correspondingly less gas enters the synthesis plant 33 , so that the methanol yield in this case is only 27.5 tons per hour.

Claims (6)

1. A process for producing a methanol synthesis gas, cooled in the crude coke oven gas with extensive tar separation and then subjected to partial oxidation in the presence of pure oxygen, characterized in that the pre-cooled to a temperature of 20 to 70 ° C coke oven gas at a temperature of 1100 to 1600 ° C and a pressure of 1 to 2 bar subjected to the partial oxidation, wherein per Nm³ Koksofengas be added to 0.3 Nm³ of oxygen and that the resulting in the partial oxidation gas is freed from dust-like impurities and desulfurized and then after compression without further After treatment of the methanol synthesis plant is supplied. 2. The method according to claim 1, characterized in that in Dependence on the content of carbon oxides (CO + CO₂) of the the partial oxidation of gas generated coke oven gas during the Partial oxidation tar in an amount up to 0.1 kg per Nm³ coke oven gas can be added. 3. Process according to claims 1 and 2, characterized in that that the coke oven gas during the partial oxidation steam in an amount up to 0.4 kg per Nm³ Koksofengas is added. 4. Process according to claims 1 to 3, characterized that the gas obtained in the partial oxidation except for one Sulfur content of <1 ppm is desulfurized.   5. Process according to claims 1 to 4, characterized that incurred in the individual gas treatment stages condensates and / or sewage collected and a common H₂S- and / or NH₃-driven are subjected, the case arising here H₂S- and / or NH₃-containing vapors before the coke oven gas Partial oxidation can be added. 6. Process according to claims 1 to 5, characterized that when using a partial flow of Koksofengases for Unterfeuerung the coke ovens for the H₂S and NH₃ wash this partial flow required washing liquid the common abortion is removed, wherein the loaded washing liquid for the purpose of regeneration is returned to the abortor, where this accumulating vapors also the coke oven gas before the partial oxidation be added.