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

#This application is the United States national phase of International Application No. PCT/EP2013/003250 filed Oct. 29, 2013, and claims priority to German Patent Application No. 10 2012 021 478.2 filed Nov. 5, 2012, the disclosures of which are hereby incorporated in their entirety by reference.

#The invention relates to a method for removing absorbable gases from pressurized industrial gases contaminated by absorbable gases, without supplying cooling energy, wherein an industrial gas to be purified is purified by means of an absorbent solvent of the gases present therein which can be absorbed by the solvent, and the laden solvent is transferred to a flash stage in which the absorbed gas is desorbed again, and the desorbed gas is compressed so that it is heated as a result of the compression, whereupon it is cooled to normal temperature by means of cooling water or cooling air, is to then expanded so that it cools, and this cooled desorption gas is recycled again into the industrial gas so that this is also cooled by the admixture and a feed of cooling energy, for example by means of a refrigerating machine, is no longer necessary in order to establish the low temperature level which is required for the absorption. The invention also relates to an apparatus by means of which this method can be implemented.

#During the preparation of industrial gases, a gas which is contaminated by sour gases frequently results. A typical example is natural gas which is contaminated by larger proportions of sulfur compounds and carbon dioxide. These sour gases are disruptive during the subsequent use of these industrial gases. The gases to be used have a lower calorific value and undesirable corrosive gases are created during combustion. The admixtures are frequently toxic and interrupt further processing. However, non-sour gases such as heavier hydrocarbons can also be disruptive for the subsequent application. For this reason, purifying of the industrial gases to be used is usually carried out. This is carried out in most cases by bringing the gases into contact with an absorbent solvent.

#The invention is explained more specifically with reference to two drawings, wherein these drawings represent only exemplary embodiments and are not limited to these embodiments.

#FIG. 1 shows an exemplary process implementation with absorption column, high-pressure flash vessel, compressor, cooling device and expansion valve.

#FIG. 2 shows the same apparatus which feeds stripping gas into the high-pressure flash vessel, uses an expansion turbine for generating electric current, and instead of a desorption column is equipped with two high-pressure flash vessels.

#FIG. 1 shows an apparatus which transfers an industrial gas (1) to be purified, which is contaminated by an absorbable gas, via a mixer (2) into an absorption column (3). The mixer (2) adds a cool and expanded desorption gas (4) so that a cooled industrial gas (1a) is introduced into the absorption column (3). There, the gas to be absorbed, which for example is a sour gas, is absorbed by an absorbent solvent. The laden solvent (5) is transferred into a high-pressure flash vessel (6). There, the laden solvent is expanded. Readily desorbable gases (7) are released in the process. According to the invention, the desorbed gas (7), which in addition to the gas components to be absorbed also contains co-absorbed useful gas components, is compressed by a compressor (8). The compressed stream of desorption gas (9) is cooled down to normal temperature by means of a cooler (10) which cools with air or water. Some of the desorption gas is liquefied in the process. The desorption gas (10a), compressed and cooled to normal temperature, is expanded via a throttle valve (11). This cools down in the process as a result of the “Joule-Thomson” effect. Some of the sour gas is liquefied in the process. The cooled and expanded desorption gas (4) is fed back via the mixer (2) into the industrial gas (1). The purified industrial gas (12) is obtained from the absorption column (3). The expanded solvent (13) obtained from the high-pressure flash vessel (6), which still contains sour gas, is transferred into a desorption column (14). There, the solvent is freed of the additional sour gas components by means of a stripping gas (15). The residual sour gas (16) is obtained in the process. The regenerated solvent (17) is received in the sump of the column and by means of a pump (17a) is recycled via a cooler (17b) into the absorption process.

#FIG. 2 shows a comparable apparatus which transfers an industrial gas (1) to be purified, which is contaminated by an absorbable gas, via a mixer (2) into an absorption column (3). The mixer (2) adds a cool and expanded sour gas (4) so that a cooled industrial gas (1a) is introduced into the absorption column (3). There, the gas to be absorbed, which for example is a sour gas, is absorbed by an absorbent solvent. The laden solvent (5) is transferred into a high-pressure flash vessel (6). There, the laden solvent is expanded. A stripping gas (6a) is fed into this for aiding the desorption process. The readily desorbable gases (7) are released in the process. According to the invention, the desorbed gas (7) is compressed by means of a compressor (8) to a pressure which lies appreciably above the pressure of the industrial gas (1). Some of the desorption gas is liquefied in the process. The compressed stream of sour gas (9) is cooled down to normal temperature by means of a cooler (10) which cools with air or water. The sour gas (10a), compressed and cooled to normal temperature, is expanded via an expansion turbine (18). This cools down in the process as a result of the “Joule-Thomson” effect and the work performed in the expansion turbine. The work (18a) performed in the expansion turbine is used in order to assist the driving of the compressor (8). The cooled and expanded sour gas (4) is recycled via the mixer (2) into the industrial gas (1). The purified industrial gas (12) is obtained from the absorption column (3). The expanded solvent (13) obtained from the first high-pressure flash vessel (6), which still contains sour gas, is transferred into a second flash vessel (19) in which further absorbed sour gas (7a) is obtained from the solvent as a result of expansion. A regenerated solvent (20) is obtained from the second flash stage (19) and by means of a pump (20a) is recycled via a cooler (20b) into the absorption column (3),

#1 Industrial gas 1a Cooled industrial gas 2 Mixer 3 Absorption column 4 Cool and expanded desorption gas 5 Laden solvent 6 High-pressure flash vessel 6a Stripping gas 7 Sour gas obtained from the flash stage 7a Sour gas obtained from the second flash stage 8 Compressor 9 Compressed stream of desorption gas 10 Cooler 10a Compressed and cooled desorption gas 11 Throttle valve 12 Purified industrial gas 13 Expanded solvent 14 Desorption column 15 Stripping gas 16 Residual sour gas 17 Regenerated solvent 17a Pump for regenerated solvent 17b Cooler for regenerated solvent 18 Expansion turbine 18a Work performed in the expansion turbine 19 Second flash vessel 20 Regenerated solvent 20a Pump 20b Cooler