DD122368B1 - PRACTICE FOR THE RECOVERY OF ARGON - Google Patents

Description

VEB Leuna-Werke Leuna, 10. 04. 1981

"Walter Ulbricht"

LP 7561

Title of the invention

Process for obtaining argon

Field of application of the invention

The process can be used in the recovery of argon while recovering hydrogen, nitrogen and methane from residual gases of the ammonia synthesis. It is particularly suitable to avoid argon losses if, in addition to an ammonia synthesis plant, other synthesis gas consumers, for example a metanol synthesis and / or a hydrogenation and / or other oxygen consumers, are operated simultaneously. It fits well into existing technologies of air separation, synthesis gas production and processing ·

- 2 - 189718

Characteristic of the known solutions

It is well known that the upper column of an air separation plant, a relatively large amount of a side stream fraction gaseous decreases, this side stream fraction undergoes a cryogenic distillation, which incurred in the 1st stage of this cryogenic distillation in the sump relatively large amount of condensate in the upper column of the air separation plant recycled and the top product of the 1st stage used as crude argon for further treatment and recovery of pure argon. With such a process it is not possible to produce argon in the cryogenic distillation plants of the ammonia synthesis residual gases and at the same time to recover hydrogen, nitrogen and methane since the relatively large amount of sidestream fraction is processed in direct connection with the air separation plant.

It is also generally known to generate synthesis gas autothermally by gasification of solid, liquid and / or gaseous fuels by using oxygen and / or air as a gasification agent, to supply the synthesis gases thus generated after their purification of the ammonia synthesis and from the residual gas of the ammonia Synthesis to separate the argon with simultaneous recovery of hydrogen, nitrogen and methane by cryogenic distillation. In this method, the recoverable amount of argon is limited by the argon content of the gasification agents oxygen and / or air. In particular, the limitation of the argon content in the oxygen is given when the oxygen is passed to other consumers in addition to the production of synthesis gas for ammonia synthesis and these consumers make high purity demands on the oxygen. In this process, it is not possible to enrich the argon in the synthesis gas or to adjust it to an operationally prescribed value. «

In addition, it is well known to adjust the hydrogen-nitrogen ratio in the gasification

-z- 189718

solid, liquid or gaseous fuels produced ammonia synthesis gas such as 3: 1 by admixing pure nitrogen into this synthesis gas and / or produce a part of the synthesis gas generated for the ammonia synthesis by means of air as a gasifying agent and / or in a secondary reformer air for the production of ammonia synthesis gas. In this process as well, the amount of argon recoverable from synthesis residual gases is limited by the argon content of the gasification agent oxygen and / or air. An enrichment and control of the argon content is not possible.

Finally, it is known to recover argon from gas mixtures, which are purified by freezing supplied to the ammonia synthesis. For this, the argon-containing condensates obtained in the synthesis gas purification by deep-freezing of oxygen, carbon dioxide and optionally methane contained therein are largely freed, the synthesis gas again mixed and the argon from the recirculated in the ammonia synthesis gas obtained (DE-PS 1 076 098). The method is only applicable when the syngas cleaning is done by deep cooling, in which, among other components, the argon has been largely removed from the synthesis gas. In this case too, the amount of argon recoverable from the synthesis residual gases is limited by the argon content of the gasification agent oxygen and / or air, since in the described process at most as much argon can be admixed with the synthesis gas for the ammonia synthesis as in the synthesis gas produced therefor is included. An enrichment of the synthesis gas with argon is not possible.

In all processes, the mentioned wax parts occur the more, the more diverse the synthesis gas production and processing plants used are. In particular, this is the case when, for example, synthesis gas production plants operated in parallel by the coal, oil and Erdga3vergasungsverfahren with air and oxygen as a gasifying agent

- 4 - 189718

be present at the same time synthesis gas processing plants for the production of ammonia and methanol and still other consumers of pure oxygen and / or synthesis gas occur. Then, the introduced by the oxygen and / or air in the synthesis gas amount of argon can be introduced only partially into the ammonia synthesis gas and recovered in the residual gas separation plant of the ammonia synthesis.

Finally, it is also known to recover noble gases, especially cypron and xenon, in conjunction with syngas production and processing equipment by recovering a high degree of krypton and xenon depleted technological oxygen in an air separation plant, one or more arbitrary syngas production facilities, and optionally supplied to other consumers and at the same time an enriched with krypton and xenon oxygen is withdrawn from the air separation plant. This oxygen enriched with krypton and xenon is fed directly or indirectly to the synthesis gas of an ammonia synthesis, and the synthesis residual gas resulting from the ammonia synthesis is separated into its components in a synthesis gas decomposition plant. (DD-PS 84 628) Such a supply, however, is technically and economically possible only if the amounts of inert gas in the entire synthesis gas path do not exceed operationally predetermined values due to the noble gases supplied to the synthesis gas.

Object of the invention

The aim of the invention is to eliminate the disadvantages of limiting the argon content in the gasification agent, the loss of argon while coexisting other oxygen and / or syngas consumers and the impossibility of adjusting the argon content to an operationally predetermined value.

- 5 - 189 7 18

Explanation of the essence of the invention

It was therefore the task of developing a method by which the argon production can be increased while simultaneously obtaining hydrogen, nitrogen and methane, or its decline can be compensated for any existing technological changes in the ammonia synthesis upstream plants.

The object is achieved by the enrichment of the synthesis gas for the ammonia synthesis with noble gases, processing of the synthesis gas to ammonia including the adjustment of the hydrogen-nitrogen ratio and synthesis test gas decomposition by cryogenic separation according to the invention that one enrichment of the Argongebaltes is made in the synthesis gas for ammonia synthesis, by deducting an argon-rich sidestream fraction, which is 1.2 to 4 % of the decomposition air supplied to the air separation plant and containing up to 10 % argon, to this fraction, synthesis gas generators in which fuels are autothermally gasified, as a gasification agent, optionally in admixture with pure oxygen and / or air, the inert gas content in the synthesis gas, which consists essentially of the content of argon and methane, to a value of at most 3 % and the argon content to at least 0.3 times de Inertgasgehaltes is regulated, and from the resulting in the processing of the ao.mit argon-enriched synthesis gas synthesis residual gas in a known manner, the components argon, hydrogen, nitrogen and methane are obtained by cryogenic separation »

Due to the existing fuel bed, it is particularly advantageous for safety and control technical reasons to produce the argon-enriched synthesis gas by autothermal gasification of solid fuels and to use as gasification the argon-rich side stream fraction, optionally in admixture with pure oxygen and / or air.

- 6 - 18 9 7 18

To achieve a high argon yield and avoidance of exceeding an operational inert gas content in the synthesis gas, it has proven to be beneficial to make a control of the argon content in the synthesis gas. It is particularly economical if the control is carried out by mixing several types of synthesis gas, which were generated with and without the argon-rich side stream fraction.

In addition to optimum argon production, one obtains high economic effects in the air separation when the argon-rich side stream fraction drawn off at the air separation plant is regulated to 2 to 3 % of the air quantity supplied to the air separation plant.

The process has a particularly favorable economy when the inert gas content in the synthesis gas is adjusted to a value between 1 and 2 % .

embodiments

The invention will be explained in more detail below with reference to 3 examples and the accompanying drawings and a comparative example.

Figure 1 shows the flow chart of a process for recovering argon, hydrogen, nitrogen and methane, in which the synthesis gas for ammonia synthesis is produced by means of the argon-enriched sidestream fraction and the nitrogen component to produce the ratio of hydrogen to nitrogen 3 to 1 by supplying pure nitrogen "from 'an oxygen plant is introduced into the ammonia synthesis gas.

FIG. 2 shows the flow chart of a process for the production of argon, hydrogen, nitrogen and methane, in which the synthesis gas for the ammonia synthesis by means of a mixture of the argon-enriched side stream fraction and pure lignite coke liquor in a vat.

- ч - 189718

plant is produced and the nitrogen component by parallel operation of a Winkleranlage in the lignite coal coke is gasified using air, and this synthesis gas is mixed with the argon-rich synthesis gas.

Pigur 3 shows the flow chart of a process for the production of argon, hydrogen, nitrogen and methane, in which the synthesis gas for the ammonia synthesis is produced by gasification of lignite coke with a mixture of air and the argon-enriched side stream fraction as a gasifying agent and the hydrogen Nitrogen ratio is produced by admixing pure hydrogen from a parallel gas generating plant.

example 1

According to FIG. 1, 20 Tm (N) / h of oxygen with a purity of SO % are withdrawn from an air separation plant 1 through the line 2 for further use. Through the line 3500 m (N) / h of an argon-enriched oxygen concentrate are withdrawn from the top column as a side stream fraction. The composition of this side stream fraction is about 10% argon and 3 % nitrogen, the rest is oxygen.

The side stream fraction is fed to the pressure gasifier 4 in which the fuel oil from line 5 is reacted with vapor from line 6 and the side stream fraction. The pressure gasification operates at a pressure of 35 at. The synthesis gas produced has the following composition: 46.8 % hydrogen, 45.5 % carbon monoxide, 3 % carbon dioxide, 1.5% nitrogen, 2.9 % argon and 0.3 % methane ,

It is introduced through the line 7 in the conversion unit 8, where the carbon monoxide contained in the synthesis gas with water vapor at temperatures above 370 ⁰ C catalytically converted to 3 % in carbon dioxide and hydrogen and introduced this gas via the line 9 in the pressurized water wash 10. This is where the removal takes place

- 8 - 189 7 18

of carbon dioxide from the gas up to about 1.6%. The gas purified in this way is fed via the line 11 to the compressor system 12, where it is compressed to about 240 atm and introduced via the line 13 into the copper wash 14. This removes the remaining carbon monoxide and carbon dioxide with ammoniacal copper acetate solution. The purified gas is passed through the conduit 15. At the same time 3,7 Tnr (li) / h of nitrogen are withdrawn from the air separation plant 1 through the line 16 and mixed with the purified synthesis gas of the line 15. The thus mixed gas is fed as ammonia synthesis gas through the line 17 of the ammonia plant 18 and has the following composition: 73.0 % hydrogen, 24.3 % nitrogen, 2.45 % argon and 0.25 % methane · In the ammonia plant 18 is the catalytic conversion to ammonia withdrawn through line 19 for further use. In the ammonia production technology, the inert argon and methane accumulate in the recycle gas. In order to maintain the inert gas level, strip venting gas having the following composition is withdrawn from the circulating gas line 20 through the line 21: 52.5 % hydrogen, 17.5 % nitrogen, 27.2 % argon, 2.8% methane. The cycle expansion gas is fed to the Ammoniaks.yntheserestgas decomposition plant 22 and decomposed there by cryogenic separation into its components hydrogen, nitrogen, argon and methane. In this case, 250 m (N) / h of argon, based on 1 Tnr (N) / h of cycle expansion gas, are withdrawn through line 23 for further use. The fractions of hydrogen, nitrogen and methane leave through the lines 24, 25 and 26 the AmmoniaksyntheserestgasZerlO gungsanlage 22 for further use.

Example 2

According to FIG. 2, oxygen with a purity of 99 % is withdrawn from the air separation plant 1 through the line 20 Tnr (N) / h. Of these, 10 Tm (N) / h are the

18 9 7 18

Line 27 is supplied to other oxygen consumers for further use while 10 Tnr (N) / hr is introduced through the line into the mixing tube 29.

At the same time 3500 nr (N) / h of an argon-enriched oxygen concentrate are withdrawn as a side stream fraction through line 30 from the air separation plant and introduced in varying amounts depending on the operating conditions via the line 31 into the mixing tube 29. The side stream fraction contains approx. 10 % argon and 3 % nitrogen, remainder oxygen. "The amount of side stream fraction fed into the mixing tube is adjusted with the regulating valve as a function of the oxygen concentration on the analyzer 33 and can be adjusted according to the specifications between 0 and 3500 m (FIG. N) / h vary. The specifications may be influenced by the production level of argon production, the demands of other consumers on oxygen purity, the type and number of co-operating syngas plants, and the production ratios in parallel, other syngas processing plants. If, by default, for example, an argon-to-methane ratio of 1 to 1 in the synthesis gas to be present, and should the concentration of Inertanteile argon plus methane in the synthesis gas for ammonia synthesis 1.7 % are not exceeded, the amounts of the line 28 as well as through the control valve 32 and the line 31 into the mixing tube 29 introduced partial streams in the ratio of 10 to 2.3 set. If, on the other hand, the inert fraction argon plus methane in the synthesis gas is only 1.3 % , the admixture of the quantity introduced through the control valve 32 and the line 31 into the mixing tube 29 is equal to zero. The amount of Seitenstromfraktion the air separation plant not used in the mixing pipe 29 is generally supplied through the line 34 to other consumers or roof over, «It may also be the amount of withdrawn through the line 30 from the air separation plant 1 side stream fraction to the through the control valve 32nd the mixing tube 29 supplied amount reduced

- ю - 18 9 7 18

be, with the Llindestmenge of 2200 m (N) / h to comply with the parameters of the other products of the air separation plant 1 may not be exceeded. The gasification oxygen produced in the mixing tube 29 is fed through the line 35 to a Winkler plant 36 and produced there by gasification of brown coal coke together with steam synthesis gas with the analyzes listed in Table 1. The values apply to the inert gas fraction argon plus methane equal to 1.7 % or "1.3% with an argon-methane ratio of about 1 to 1 or 2 in the synthesis gas for the ammonia synthesis (see Table 2). ,

TABLE 1 Composition of the synthesis gas from the Winkler plant 36

Amount of side stream fraction based on the amount of total oxygen H _P CO CO ₉ N ₂ Ar CH ₄

C. C

23 % 39 , 6 32 ,8th 24 , 9 1 , 0 0 , 7 1 C \ (rf ) \ J / O 0 % 39 ,8th 33 , 0 25 , 0 1 , 0 0 2 1 r \ c / »U / 0

The synthesis gas thus generated is removed from the Winkleranlage 36 through line 37. In parallel to this gas production 38 38 Tm (N) / h of synthesis gas are generated by gasification of Schwelkoks with air and steam in another Winkleranlage. This synthesis gas contains 14% hydrogen, 54 % nitrogen, 22 % carbon monoxide, 9 % carbon dioxide and is added to the synthesis gas in line 37 for delivery of the nitrogen component through line 39. Through the line 40, the mixed S-ynthesegas the desulfurization unit 41 and 42 supplied via the line 42 of the conversion unit 43, there converted at atmospheric pressure, the carbon monoxide to 4 % to carbon dioxide and hydrogen. Finally, the gas is fed through the line 44 to the compression system 45, where it is compressed to 28 atm, through the line 46 of the pressurized water wash 10.

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out and therein carbon dioxide to about 1.6% removed The synthesis gas is then fed via line 11 of the compressor system 12, in which the compression to 240 at is done "Analogously to Example 1, the synthesis gas is passed through line 13 of the copper liquor washing 14 to the Removal of residual carbon monoxide and carbon dioxide fed and introduced with the composition given in. Table 2 through the line 17 in the ammonia plant 18.

Table 2 Composition of the synthesis gas fed to the ammonia plant 18

Amount of side stream fraction relative to the amount of total oxygen H ₀ N ₂

23 % 73 , 7 24 б 0 85 0 85 % О % 74 , 0 24 7 0 45 0 85 %

From the ammonia plant, the ammonia produced is withdrawn through line 19 for further use. In the cycle gas of the ammonia plant 18, the inert gases enrich argon and methane. From the recycle gas line 20, therefore, recirculation vent gas having the composition shown in Table 3 is withdrawn through the line 21

Table 3 Composition of the cycle vent gas

Amount of sidestream 52 H ₂ N ₂ 5 Ar CH ₄ fraction based 52 , 5 17 5 15 15 % on amount of sour , 5 17 10.4 19.6 % total material 23 % 0 %

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The recirculation de-aeration gas is fed to the ammonia synthesis gas decomposition plant 22, where it is decomposed by its cryogenic decomposition into its components hydrogen, nitrogen, argon and methane and, depending on the specifications, between

3 3

see 135 and 95 m (N) / h argon based on 1 Tm (N) / h venting cycle gas withdrawn through line 23. The hydrogen, nitrogen and methane fractions leave the ammonia synthesis gas separation plant 22 through lines 24, 25 and 26 for further use.

Example 3

According to FIG. 3, in the air separation plant 1, 20% Tirr (N) / h of oxygen with a purity of 99 % are withdrawn through line 2 for further use. Through line 3, 3,500 m (N) / h of an argon-enriched oxygen concentrate are withdrawn as side stream fraction from the top column of the air separation plant 1 and fed into the mixing tube 29, the side stream fraction contains about 10 % argon and 3 % nitrogen, balance Oxygen. At the same time 47 27 Tm (li) / h of air are fed through the line 47 into the mixing tube 29 and the gasification agent thus prepared by mixing supplied through the line 48 of Winkleranlage 38. There, a synthesis gas is generated, which has the following composition: 20.4% hydrogen, 24.5 % carbon monoxide, 13.0 % carbon dioxide, 40.4 % nitrogen, 1.1% argon, 0.6 % methane. It is fed through the line 40 of the desulfurization system 41, through the line 42 of the conversion unit 43 and through the line 44 of the compression system 45 and compressed here to a pressure of 2 * 8 at. Through the line 49, the compressed synthesis gas leaves the compression system 45. Parallel to the line 2 10 Tm ^ (N) / h withdrawn oxygen with a purity of 99 % via line 28 and fed to the pressure gasifier 4, in the fuel oil line 5 with vapor of the line б and the oxygen of the line 28 is converted to synthesis gas. The pressure gasification

189 7 18

operates at a pressure of 35 at. The generated synthesis gas has the following composition:

48.3% hydrogen, 47.3 % carbon monoxide, 3.1 % carbon dioxide, 0.75 % nitrogen, 0.25 % argon and 0.3 % methane and is introduced through line 7 in the conversion unit 8, which in the synthesis gas contained carbon monoxide is catalytically converted into carbon dioxide and hydrogen analogously to Example 1 with Wasserdempf and fed through line 9 into line 49. This ensures the production of the hydrogen-to-nitrogen ratio required for the ammonia synthesis from 3 to 1. This synthesis gas suitable for the ammonia synthesis is passed through the line 46 of the pressurized water wash 10 to remove the carbon dioxide and the line 11 of the compressor system Finally, this synthesis gas is fed, as in Example 1, through line 13 of copper wash 14 to the remainder of carbon monoxide and carbon dioxide, and leaves through line 15 with the following composition: 73.9 % V / hydrogen, 24.6 % nitrogen, 0.95 % argon, 0.55 % methane, this gas is fed into the ammonia plant 18. The ammonia leaves the ammonia plant 18 through the conduit 19 for further use Due to the conditional circulation of the ammonia plant 18, the inert gases argon and methane accumulate, which is why this cycle is replaced by the line 21 withdrawn recirculation release gas, which consists of 52.5 % hydrogen, 17.5 % nitrogen, 19.0 % argon and 11.0 % methane. It is introduced into the Ammoniaksyntheserestogaszerlegungsanlage 22, there decomposed by cryogenic decomposition into its components hydrogen, nitrogen, argon and methane, while 170 m (N) / h argon, based on Tm (N) / h recirculation, recovered by the line 23 leaves the Argon and through the lines 24, 25 and 26 of the hydrogen, nitrogen and methane the ammonia synthesis residual gas decomposition plant 22 for further use

1897 18

Example 4

As a comparison for the effectiveness of the method, comparative values are given in this example if in the combinations according to FIGS. 1 and 3 the side stream action of the air separation plant 1 is not used for the production of synthesis gas for the ammonia production but in the example according to FIG and in the example according to FIG. 3 only air and pure oxygen are used as the gasification agent.

Then the following compositions for the synthesis gas result:

FIG. 1, example 1

Sy-gas KH -, - Gas Kreislaufent 21 0f in Ltg. 7 in ^J Ltg. 17 Voltage gas in Ltg. ql / Q H _? 48.3 74.65 52.5 co 47.3 - - % CO ₂ 3.1 - - % nj, 0.75 24.9 17.5 Ar 0.25 0.2 13.3 CH ₄ 0.3 0.25 16.7

FIG. 3, example 3

Sy-gas

in Ltg. 40 in ^ Ltg. 15

NH ..- gas

-5 τ

Kreislaufentspanηungsgas in Ltg. 20

H ₂ 20.5 74.2 CO 24.7 - CO ₂ 13.0 - H ₂ 40.6 24.8 0.6 0.45 CH, 0.6 0.55

52.5

17.5 13.5 16.5

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The composition of the synthesis gas according to the combination of FIG. 2 without the use of the side stream fraction for the production of synthesis gas is already indicated in the tables of the example in the row zero % side stream fraction based on the amount of oxygen in total.

In the exemplary embodiments, in comparison with example 4 (prior art), the following amounts of argon can be obtained (in m.sub.ql) of argon per Tm (N) cycle vent gas):

Example 1 Example 2 Example 3

According to the invention 250 95 to 135 170 according to the state of

Technology according to 120 95 120

Example 4

Claims (5)

- іб - 18 invention claim 1. A process for the production of argon while obtaining hydrogen, nitrogen and methane from residual gases of ammonia synthesis by enrichment of the synthesis gas for ammonia synthesis with noble gases, processing the synthesis gas to ammonia including the adjustment of the hydrogen-nitrogen ratio and synthesis residual gas decomposition by cryogenic separation, characterized characterized in that an enrichment of the Argongehaltes in the synthesis gas for the ammonia synthesis is made by an air separation plant is withdrawn an argon-rich Seitenstromfraktion which is 1.2 to 4 % of the air fractionation supplied 'air amount and contains up to 10 % argon, this fraction synthesis gas generators in which fuels are autothermally gasified, as a gasification agent, optionally in admixture with pure oxygen and / or air, the inert gas content in the synthesis gas, which is composed essentially of the content of argon and methane Ammensetzt, to a TVert of at most 3% and the argon content is adjusted to at least 0.3 times the inert gas content and from the obtained in the processing of the synthesis gas synthesis residual gas in a known manner by cryogenic separation, the components argon, hydrogen, nitrogen and methane. 2. The method according to item 1, characterized in that the argon-enriched synthesis gas is generated by autothermal gasification of solid fuels, wherein the argon-rich Seitstromfraktion, optionally in admixture with pure Sauastoff and / or air, is used as the gasification agent. 3. The method according to item 1 and 2, characterized in that the control of the argon content in the synthesis gas is carried out by mixing a plurality of synthesis gas species, which were produced with and without the argon-rich side stream fraction. - 17 - 189718 4. The method according to item 1 bia 3> characterized in that the withdrawn at the air separation plant argon-rich Seitenstromfraktion is regulated to 2 bia 3 % of the air separation plant supplied amount of air. 5. The method according to item 1 Ьіэ 4, characterized in that the inert gas content in the synthesis gas is adjusted to a value between 1 and 2 % . This includes 3 sheets of drawing