EP2914366A1

EP2914366A1 - Method and device for removing absorbable gases from pressurized industrial gases contaminated with absorbable gases, wihout supplying cooling energy

Info

Publication number: EP2914366A1
Application number: EP13794803.0A
Authority: EP
Inventors: Johannes Menzel
Original assignee: ThyssenKrupp Industrial Solutions AG
Current assignee: ThyssenKrupp Industrial Solutions AG
Priority date: 2012-11-05
Filing date: 2013-10-29
Publication date: 2015-09-09
Also published as: CA2890037A1; DE102012021478A1; US20150273386A1; US9844751B2; CN104918680A; WO2014067649A1; CN104918680B

Abstract

The invention relates to a method for removing absorbable gases from pressurized industrial gases contaminated with absorbable gases, without supplying cooling energy, wherein an industrial gas that is to be purified is purified by an absorbent solvent, the absorbable gases situated therein being removed by the solvent, and the loaded solvent is passed to a stripping stage in which the absorbed gas is desorbed again, and the desorbed gas is compressed, in such a manner that it is heated by the compression, whereupon it is cooled to standard temperature by means of cooling water or cooling air, then expanded, in such a manner that it cools and this cooled desorption gas is again returned to the industrial gas, in such a manner that said industrial gas is also cooled by the admixture and a supply of cooling energy, for example by a refrigeration machine, is no longer necessary, in order to establish the low temperature level necessary for the absorption. The invention also relates to a device with which this method can be carried out.

Description

Method and apparatus for removing absorbable gases from pressurized, gas-contaminated industrial gases without supplying cooling energy

The invention relates to a process for the removal of absorbable gases from pressurized industrial gas contaminated with absorbable gases without supplying cooling energy, whereby an industrial gas to be purified is purified by an absorbing solvent from the gases absorbable by the solvent, and adding the loaded solvent to a flash stage in which the absorbed gas is desorbed again, and the desorbed gas is compressed so that it is heated by the compression, whereupon it is cooled to normal temperature by means of cooling water or cooling air, then expanded is, so that it cools, and this cooled desorption gas is recycled back into the industrial gas, so that this is cooled by the admixture and a supply of cooling energy, for example by a refrigerator, is no longer necessary to the erforderl for absorption I adjust low temperature level. The invention also relates to a device with which this method can be carried out.

In the provision of industrial gases often falls to a gas which is contaminated with acid gases. A typical example is natural gas, which is contaminated with larger amounts of sulfur compounds and carbon dioxide. These oxygen gases interfere with the subsequent use of this industrial gas. The gases to be used have a lower calorific value and combustion produces undesirable corrosive gases. The admixtures are often poisonous and interfere with further processing. But also non-acidic gases such as heavier hydrocarbons can interfere with subsequent use. For this reason, a cleaning of the industrial gases to be used is usually carried out. This is usually done by incontacting the gases with an absorbing solvent.

The absorption of the added unwanted acid gases is typically carried out with an absorbing solvent. Physically or chemically acting solvents are used. Typical physical solvents are methanol, alkylated polyethylene glycol ethers, or morpholine derivatives. Typical chemical solvents are alkanolamines or alkali salt solutions. Physically acting solvents are typically used at low temperatures because the desired uptake of this type of solvent for components to be absorbed increases at lower temperatures. To provide the appropriately cooled

CONFIRMATION COPY Solvents require chillers that require an amount of energy that is proportional to the amount of gas to be cooled. Since many industrial gases are treated with large amounts of cooled solvents for the absorption of acid gases, this is associated with a considerable cost factor. A typical process for the absorption of associated gases in industrial gases teaches WO 2004105919 A1. This document teaches a process for sour gas removal from pressurized sulfur-contaminated natural gas, wherein the natural gas to be desulphurised is first passed into an acid gas absorption stage where the sulfur compounds and optionally other components are absorbed with a physico-acting solution which heats the absorbate and the sorbate is placed in a high pressure flash stage where the mixture of acid lean absorbent and desorbed sour gas separates, and the desorbed sour gas is cooled and the vaporized absorbent is condensed out of the sour gas stream is removed, and the sauergasarme absorber from the "high pressure flash stage" is freed in a further stage by means of stripping of Sauerergasresten and the resulting laden stripping gas is cooled and passed into the acid gas absorption stage, and the resulting absorbent cooled and recycled in the cycle in the acid gas absorption stage. The regenerated absorption solution is returned to the absorption process after the heat exchange in a heat exchanger and the cooling in a cooler which cools the absorbent to a temperature suitable for absorption by means of cooling or cooling medium.

As one seeks to improve the economics of the process for sour gas absorption, work is then being done to reduce the cost of cooling the solvent. Since refrigeration systems work especially in countries with a high average temperature with a high proportion of total operating costs, a reduction of this proportion contributes greatly to the economy of the entire process.

In physically acting absorption processes there is also inevitably also a Mitabsorption of gas components that should not be removed from the gas, such as hydrocarbons from natural gas or hydrogen (H ₂ ) and carbon monoxide (CO) from synthesis gas. This is undesirable because these ingredients often represent valuable components whose loss reduces the economics of the entire process. For the recovery of these recyclable components, in the case of physically acting absorption processes, an example of a operating stage to be used for recovery. By means of a compressor, the recovered valuable components are then fed back into the absorption. This procedure is therefore an integral part of almost all physical absorption processes. A reduction in the operating costs for the cooling of the solvent should therefore be such that a recovery of valuable components is possible.

It is therefore an object to provide a process in which the cooling down of the industrial gas for an acid gas absorption by an absorbing solvent is possible without the use of an energy-intensive refrigeration system, so that a cooled industrial gas is provided, which produces a effective absorption of the gases to be absorbed at sufficiently low temperature.

The invention solves this problem by a method which compresses the recirculated gas stream from a gas scrubbing with a physically acting solvent after spewing in a downstream spouting stage to a pressure which is significantly higher than the pressure of the industrial gas, which by the compression heated and compressed gas is cooled down again to ambient temperature by means of cooling water or cooling air and then expanded to the industrial gas pressure, so that the gas cools strongly by the "Joule-Thomson" effect, and this cooled gas admixes the industrial gas, so that the mixture of the two gases adjusts to a temperature suitable for absorption, thus eliminating the otherwise required refrigerating machine and eliminating the heat exchangers required to transfer the low temperature level of the refrigerant to the recirculated gas, which reduces the investment costs ng the process of the invention further reduced. Likewise, the use of the method according to the invention leads to systems with a correspondingly smaller space requirement.

In an advantageous embodiment, the compressed recycle gas can also be cooled down so far that it can be liquefied at a sufficiently high recycle compressor end pressure, and this liquefied recycle gas is admixed or added to the industrial gas in liquid form, which is the quenching fluid - significantly increased. This is particularly advantageous if the sour gas is to be injected back into a deposit. Often, sour gases are injected back into underground reservoirs to ensure safe storage of this sour gas. In this case, however, a further compression of the acid gases is required, since the acid gases from a desorption stage are produced under relatively low pressure.

In particular, a method for the removal of absorbable gases from pressurized, contaminated with absorbable gases industrial gases without the supply of cooling energy, wherein

An industrial gas to be purified, which is contaminated by an acid gas, is first led to an absorption stage, in which the gases to be absorbed are absorbed under pressure by means of an absorbing solvent, and

The absorbent is placed in a high pressure flash tank in which the absorbate separates into a solvent depleted in absorbed gases and a desorbed gas,

and which is characterized in that

The desorbed gas is compressed by a compressor to a pressure at which a portion of the sour gas contained therein liquefies, and the compressed and desorbed gas is cooled by means of cooling water or cooling air via an indirect heat exchanger, and

The cooled compressed gas is expanded by a relaxing device so that it cools further, and this gas is added to the industrial gas to be purified, and

• the solvent depleted in absorbed gases is fed back to the absorption stage for further purification.

The remaining laden solvent from the high-pressure flash tank contains the remaining sour gases and is generally fed to a further purification. This can be, for example, a desorption column or a further Austriebsbehälter. During further purification, the remaining sour gases which are obtained during the purification of the industrial gas and can be discharged from the process are also obtained.

The cooling of a raw gas with a cooled condensate from a cooling stage belongs to the prior art. DE 2853989 B1 describes a process for treating hydrous condensate from the cooling of a raw gas from the gasification of solid fuels with oxygen, water vapor, and / or carbon dioxide. the gasification agents, wherein the raw gas is cooled in at least one cooling stage, wherein a condensate is obtained, which is expanded, the expansion steam dissipates, the relaxed condensate feeds a separator, and deducted from the separator substantially consisting of water condensate phase and as a cooling medium for the Raw gas reused. However, the invention does not disclose any additional compression of the vapor, which by suitable means enables the cooling down of the raw gas to a temperature suitable for absorption of gases from gas mixtures with absorbing solvents. Also, the technical conditions under which a hot raw gas from a fuel gasification is cooled with water are different as compared to an absorption process with an absorbing solvent at low temperatures.

The compression of desorbed gases from a high-pressure flash stage is also found in the prior art. The US 3266219 A discloses a process for removing acid gases from mixtures with gaseous C ^ C ₃ - alkanes, through which the said gas mixture containing a carbon dioxide and hydrogen sulphide-containing sour gas is brought into contact with a sauergasabsorbierenden solvent and the absorbing solvent consists essentially of dimethoxyacetate, wherein the absorption conditions are adjusted so that the sour gas is completely absorbed by the absorbing solvent and the unabsorbed gases from the gas mixture are completely separated from the solvent. In one embodiment of the invention, the carbon dioxide content of the acidic gas with the non-acidic gases contained therein is withdrawn from the solvent in a high pressure flash stage, compressed, and returned to the starting gas mixture. A relaxation of this carbon dioxide content with the non-acidic gases contained therein for the purpose of cooling the industrial gas to make the absorption process more efficient, is not listed.

In an advantageous embodiment of the invention, the desorbed gas is expanded in the process of cooling and relaxation to the absorption pressure or a slightly higher pressure. As a result, no recompression of the desorbed industrial gas is required in the absorption process. In one embodiment of the invention, the desorbed gas is compressed to a pressure at least 10% higher than the pressure of the industrial gas.

The desorbed gas condenses in the process of cooling and relaxation at least partially or completely. The admixture of the returned th gas to the industrial gas is advantageously carried out by a mixer, but can also, depending on the state of aggregation, via a gas valve or via a gas tank. The liquid desorbed gas is added via a nebulizer, a carburetor or similar type of mixer in the starting gas. In one embodiment of the invention, the desorbed gas is added in liquid or partially in liquid form to the industrial gas. In a further embodiment of the invention, the industrial gas to be purified is first cooled prior to introduction into the absorption stage, before the cooled and expanded desorption gas is added. Finally, the desorbed gas may be further cooled after expansion and prior to introduction into the absorption stage before being added to the industrial gas to be purified.

The cooling of the industrial gas before the addition of the cooled and expanded desorption gas can be done by any type of device. It is also possible, instead of the industrial gas to be purified, to cool the cooled and expanded desorption gas still further. This can also be done by any type of device. These may be, for example, heat exchangers, air or water coolers. It is also possible to use an additional chiller, although this is not usually required to practice the invention.

The compression and expansion of the desorbed gas, which comes from the Austriebsstufe, can be done arbitrarily. The compression can be done by way of example via a compressor. This can be, for example, a turbocompressor or a reciprocating compressor. The relaxation can also be done in any way. This can be done by way of example via a throttle valve as expansion valve. However, this can also take place via an expansion turbine, which generates rotational energy from the pressure energy. This in turn can be used as an example for generating electricity.

The Austriebsbehälter in turn may be of any kind. These are widely known in the art. US Pat. No. 4997630 A teaches an example of a method in which flash tanks are used. In a flash tank, easily desorbable gases are released by a sudden expansion from a pressure of 5 to 110 bar to a pressure of 0.3 to 1.0 bar relaxed. This relaxation takes place at temperatures of 35 to 100 ° C. The relaxed solvent is freed of easily desorbable gases. Typical temperatures at which absorption of the gas to be absorbed takes place in an absorption column are -40 ° C to 20 ° C and preferably -20 ° C to 0 ° C. The pressures during absorption are typically 20 to 200 bar. Typical pressures at which desorption of the absorbed gas takes place in a high pressure flash tank are 10 to 100 bar. The temperatures here are typically -10 ° C to 80 ° C and preferably 0 to 60 ° C. The Austriebsbehälter may be provided in an exemplary embodiment also with packing. The Austriebsbehälter can also be supplied to a Austriebsgas. Suitable flue gases are inert gases such as hydrocarbons or nitrogen. In one embodiment of the invention, the flue gas can also be wholly or partly recycled to the industrial gas to be purified.

The industrial gas to be purified may be of any kind insofar as it is to be cleaned by an absorbing solvent. This can be, for example, natural gas or a synthesis gas. The absorbable gas can also be of any kind. These may be, for example, sour gas components or the absorbable gas may contain them. The absorbable gas may be exemplified by carbon dioxide (CO ₂ ) or contain carbon dioxide. The absorbable gas may also be hydrogen sulfide (H ₂ S) or contain hydrogen sulfide. The absorbable gas may also contain both gases in any proportion. Finally, the absorbable gases may also be non-acidic gases, such as heavier hydrocarbons. But it may also contain other admixtures, insofar as they do not interfere with the absorption process by the absorbing solvent.

The present invention purified industrial gas can be used freely after cleaning and providing. Also, the desorbed and discharged from the plant sour gas can be used arbitrarily. This can also be reinjected by way of example after recompression into a deposit.

Also claimed is a device with which this method is executable. In particular, a device is claimed for removing absorbable gases from pressurized industrial gases polluted with absorbable gases without supplying cooling energy

An absorption column equipped with a feed pipe for an industrial gas to be cleaned and a discharge pipe for the purified industrial gas, A high pressure flash tank equipped with a desorbed sour gas bleed port and a sour gas absorbent bleed port connected by a conduit to the absorption tower;

• a compressor,

A cooler that cools a pressurized heated gas by indirect heat exchange with cooling air or cooling water,

A relaxing device suitable for relaxing and cooling a pressurized gas,

A mixer which is suitable for returning the cooled and expanded desorbed gas to the industrial gas,

and which is characterized in that

The outlet port for the desorbed sour gas of the high pressure flash tank in the gas flow is sequentially piped to the compressor, the cooler, the relaxing device and the mixer into the industrial gas to be purified prior to the absorption step, so that the cooled and expanded desorbed sour gas enters the industrial gas to be purified is traceable.

In one embodiment of the invention, the device contains as a relaxing device on or immediately behind the Austriebsbehälter at least one expansion valve. In one embodiment of the invention, the device includes as a relaxing device on or immediately behind the Austriebsbehälter instead of the expansion valve or throttle valve, an expansion turbine. The expansion turbine can be used by way of example for generating electricity or for operating a compressor. The high-pressure Austriebsbehälter may be associated with various auxiliary equipment and other system components. These are, for example, compressors, pumps, heat exchangers, heaters or coolers. This may also be a desorption column in which the absorbing solvent is heated or distilled under reduced pressure.

The invention has the advantage of an energy-saving method for absorbing absorbable gases from an industrial gas. The method comes in a favorable embodiment without chiller and thereby saves a considerable amount of energy compared to the methods of the prior art. Also is a considerable reduction in the size of the equipment required due to the saving of chillers.

The invention will be explained in more detail with reference to two drawings, these drawings represent only exemplary embodiments and are not limited to these embodiments.

FIG. 1 shows an exemplary process with absorption column, high-pressure discharge container, compressor, cooling device and expansion valve. FIG. FIG. 2 shows the same apparatus that supplies flash gas into the high pressure flash tank, uses an expansion turbine to generate electricity, and is equipped with two high pressure flare tanks instead of a desorption column.

FIG. 1 shows an apparatus which transfers an industrial gas (1) to be purified, which is contaminated with an absorbable gas, via a mixer (2) into an absorption column (3). The mixer (2) mixes a cool and relaxed desorption gas (4), so that a cooled industrial gas (1a) is introduced into the absorption column (3). There, the gas to be absorbed, which is an example of sour gas, is absorbed by an absorbing solvent. The loaded solvent (5) is transferred to a high pressure Austriebsbehälter (6). There, the loaded solvent is released. Easily desorbable gases (7) are released. According to the invention, the desorbed gas (7), which in addition to the gas components to be absorbed also contains absorbed useful gas components, is compressed by a compressor (8). The compressed stream of the desorption gas (9) is cooled down to normal temperature by a cooler (10) which cools with air or water. In this case, a part of the desorption gas liquefies. The compressed and cooled to normal temperature desorption gas (10a) is released via a throttle valve (11). This is cooled by the "Joule-Thomson" effect whereby a portion of the acid gas liquefies, The cooled and expanded desorption gas (4) is returned via the mixer (2) in the industrial gas (1). The purified industrial gas (12) obtained from the high-pressure discharge container (6), which still contains sour gas, is transferred to a desorption column (14) where the solvent is removed by means of a flash gas The regenerated solvent (17) is obtained in the bottom of the column and returned to the absorption process by a pump (17a) via a condenser (17b). FIG. Fig. 2 shows a comparable apparatus which transfers an industrial gas (1) to be purified, which is contaminated with an absorbable gas, via a mixer (2) into an absorption column (3). The mixer (2) mixes a cool and relaxed sour gas (4), so that a cooled industrial gas (1a) is introduced into the absorption column (3). There, the gas to be absorbed, which is an example of sour gas, is absorbed by an absorbing solvent. The loaded solvent (5) is transferred to a high pressure Austriebsbehälter (6). There, the loaded solvent is released. In these a Austriebsgas (6a) is supplied to support the desorption process. The easily desorbable gases (7) are released. According to the invention, the desorbed gas (7) is compressed by a compressor (8) to a pressure which is significantly higher than the pressure of the industrial gas (1). In this case, a part of the desorption gas liquefies. The compressed stream of the sour gas (9) is cooled down to normal temperature by a cooler (10) which cools with air or water. The compressed and cooled to normal temperature oxygen gas (10a) is expanded by an expansion turbine (18). This is cooled by the "Joule-Thomson" effect and the work done in the expansion turbine The work done in the expansion turbine (18a) is used to assist the drive of the compressor (8) .The cooled and relaxed Sour gas (4) is returned to the industrial gas (1) via the mixer (2), and the purified industrial gas (12) is obtained from the absorption column (3).) The expanded solvent obtained from the first high-pressure flash tank (6) (FIG. 13), which still contains sour gas, is transferred to a second flash tank (19), in which further absorbed sour gas (7a) is obtained by depressurization from the solvent, from the second flash stage (19) a regenerated solvent (20) is obtained. which is returned by a pump (20a) via a cooler (20b) in the absorption column (3).

[0030] List of Reference Numerals

1 industrial gas

1a Refrigerated industrial gas

2 mixers

3 absorption column

4 Cool and relaxed desorption gas

5 Loaded solvent

6 high-pressure discharge containers

6a expulsion gas Sour gas produced from the extraction stage Sour gas compressor designed from the second extraction stage

Compressed stream of desorption gas

0 cooler

0a Compressed and cooled desorption gas

1 throttle valve

2 Purified industrial gas

3 Relaxed solvent

4 desorption column

5 expulsion gas

6 Remaining sour gas

7 Regenerated solvent

7a Pump for regenerated solvent

7b Cooler for regenerated solvent

8 relaxation turbine

8a Work done in the expansion turbine

9 Second expulsion tank

0 Regenerated solvent

0a pump

0b cooler

Claims

Patent claims

1. Process for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy, wherein

• an industrial gas (1) to be purified, which is contaminated by an acid gas, is first passed into an absorption stage (3), in which the gases to be absorbed are absorbed under pressure using an absorbing solvent, and

• the absorbate (5) is placed in a high-pressure expulsion container (6), in which the absorbate (5) separates into a solvent (13) depleted in absorbed gases and a desorbed gas (7),

characterized in that

• the desorbed gas (7) is compressed by a compressor (8) to a pressure at which part of the acid gas contained therein liquefies, and the compressed and desorbed gas (9) by means of cooling water or cooling air via an indirect heat exchanger (10) is cooled, and

• the cooled compressed gas (10a) is expanded via a relaxing device (11, 18), so that it cools down further, and this gas (4) is mixed with the industrial gas (1) to be cleaned, and

• the solvent (13) depleted in absorbed gases is fed back to the absorption stage (3) for further purification (14,19).

2. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to claim 1, characterized in that the desorbed gas (4) in the process of cooling (10) and relaxation ( 1,18) is relaxed to the absorption pressure or a slightly higher pressure.

3. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to claim 1, characterized in that the desorbed Gas (4) is compressed to a pressure that is at least 10% higher than the absorption pressure of the industrial gas (1).

Method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 3, characterized in that the desorbed gas

(4) is added to the industrial gas (1) in liquid or partly in liquid form.

5. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 4, characterized in that the industrial gas (1) to be purified before being introduced into the absorption stage (3) is first cooled before the cooled and expanded desorption gas (7) is added.

6. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 5, characterized in that the desorbed gas (4) after expansion and before introduction is further cooled in the absorption stage (3) before it enters the industrial gas to be cleaned

(I) is added.

7. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 6, characterized in that the relaxing device (11, 18) is a relaxation valve

(I I) acts.

8. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 6, characterized in that the relaxing device (11, 18) is a Expansion turbine (18) acts, and the turbine (18) generates usable energy.

9. Process for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying Cooling energy according to one of claims 1 to 8, characterized in that the absorbable gas is an acid gas or contains acid gas.

10. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to claim 9, characterized in that the absorbable

Gas contains hydrogen sulfide (H ₂ S), carbon dioxide (C0 ₂ ) or both gases.

11. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 10, characterized in that the industrial gas (1) to be cleaned is natural gas.

12. A method for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to one of claims 1 to 10, characterized in that the industrial gas (1) to be cleaned is a synthesis gas.

13. Device for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy, comprising

• an absorption column (3), which is equipped with a feed connection (1a) for an industrial gas (1) to be cleaned, and a discharge connection (12) for the cleaned industrial gas (12),

• a high-pressure expulsion container (6), which is equipped with a discharge connection (7) for desorbed acid gas (7) and a discharge connection (13) for the low-acid absorbent (13), and which is connected through a pipeline (5) to the absorption column ( 3) is connected, · a compressor (8),

• a cooler (10) which cools a pressurized, heated gas (9) through indirect heat exchange (10) with cooling air or cooling water,

• a relaxing device (11, 18) which is suitable for relaxing and cooling a pressurized gas (10a),

a mixer (2), which is suitable for returning the cooled and expanded desorbed gas (4) into the industrial gas (1), characterized in that

• the discharge connection (7) for the desorbed acid gas (7) the high-pressure expulsion container (6) in the gas flow successively through pipelines (7) with the compressor (8), the cooler (10), the relaxing device (11, 18) and the mixer (2) into the industrial gas (1) to be purified before the absorption stage (3), so that the cooled and relaxed desorbed acid gas (4) can be recycled into the industrial gas (1) to be purified.

14. Device for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to claim 13, characterized in that the device contains an expansion valve (11) as a relaxing device (11, 18).

15. Device for removing absorbable gases from pressurized industrial gases (1) contaminated with absorbable gases without supplying cooling energy according to claim 13, characterized in that the device contains an expansion turbine (18) as a relaxing device (11, 18).