EP2552569A1

EP2552569A1 - Process for workup of a carbon dioxide-rich gas to be freed of sulfur components

Info

Publication number: EP2552569A1
Application number: EP11712170A
Authority: EP
Inventors: Johannes Menzel
Original assignee: ThyssenKrupp Uhde GmbH
Current assignee: ThyssenKrupp Industrial Solutions AG
Priority date: 2010-03-29
Filing date: 2011-03-22
Publication date: 2013-02-06
Also published as: EP2552570B1; RU2012142710A; US20130017144A1; KR20130057975A; CN102802767A; CN102821830A; TW201202124A; CA2793638A1; DE102010013279B3; RU2012138294A; US8568676B2; KR20130008600A; WO2011120647A1; CA2792812A1; AU2011234876A1; ZA201207560B; US20130022534A1; EP2552570A1; RU2545273C2; AU2011238134A1

Abstract

The invention relates to a process for workup of an industrial carbon dioxide-rich gas to be freed of sulfur components, in which an industrial gas to be freed of sulfur components is purified by a gas scrubbing, and the laden solvent is freed of carbon dioxide and hydrogen sulfide by a regeneration to obtain at least one acid gas fraction having a relatively high content of sulfur components, and the fraction with the highest hydrogen sulfide (H₂S) content is supplied to a Claus plant with downstream Claus process gas hydrogenation, and at least one carbon dioxide-laden, low-hydrogen sulfide acid gas fraction from the regeneration device, which has a reduced sulfur content compared to the fraction with the highest hydrogen sulfide (H₂S) content, is combined with the hydrogenated Claus process gas to give a combined process gas stream, which is supplied to further processing or to recycling into the process.

Description

A method of processing a carbon dioxide-rich gas to be purified from sulfur components

The invention relates to a method for processing a technical component of carbon dioxide-rich gas to be purified from sulfur components, in which a technical component of sulfur components to be purified technical gas is purified by a gas scrubber, and the loaded solvent is freed by a regeneration of carbon dioxide and hydrogen sulfide, said at least one acid gas fraction is obtained, which has a higher content of sulfur components, and the fraction with the highest hydrogen sulfide (H ₂ S) content is fed to a Claus plant followed by Claus process gas hydrogenation, and at least one carbon dioxide laden, low-sulfur acid sour gas fraction from the Regeneration device, which compared to the fraction with the highest hydrogen sulfide (H ₂ S) content has a reduced sulfur content, is brought together with the hydrogenated Claus process gas to a common process gas stream, the further processing or a he is fed back into the process.

Many industrial gases, such as natural gas, synthesis gas, refinery gases or coking gas must be freed prior to the use of acid gases contained therein, because these substances interfere with further processing. Typical acid gases that interfere with further processing and therefore have to be separated from the desired gases are hydrogen sulfide (H ₂ S), carbonyl sulfide (COS), organic sulfur compounds, ammonia (NH ₃ ) or hydrogen cyanide (HCN). These gases are corrosive and toxic. One way to remove them from the desired gases is by gas scrubbing with physically absorbing solvents. Suitable acid gas absorbing solvents are, for example, propylene carbonate, N-methylpyrrolidone, alkylated polyethylene glycol ethers and methanol. Chemically absorbing solvents can also be used, but they have only a low absorption capacity for organic sulfur compounds. Examples of chemically absorbing solvents are ethanolamines or alkali salt solutions.

To recover the sulfur compounds contained in the acid gases, originating from the regeneration device of the gas scrubbing process acid gases are usually fed to a Claus plant in which a partial flow of the separated hydrogen sulfide to Sulfur dioxide is burned and this is then converted according to the Claus reaction with the residual stream of hydrogen sulfide to sulfur. The sulfur can be used in many different ways.

The technical gases to be cleaned often contain in addition to the sulfur components, such as hydrogen sulfide (H ₂ S), carbon dioxide (COS), mercaptans and higher levels of carbon dioxide (C0 ₂ ). High levels of carbon dioxide arise, for example, in synthesis gas processes, in which the carbon monoxide formed in the synthesis gas production is converted by a CO conversion into carbon dioxide, so that these technical gases often contain large amounts of carbon dioxide. The proportion of carbon dioxide can be up to 50% by volume (% by volume) in the converted synthesis gas. On the other hand, on the other hand, the content of sulfur components in the converted synthesis gas can be very low, depending on the starting material for synthesis gas production, with levels below 0.1 vol .-% are possible.

In the prior art, there are methods that allow separation of the carbon dioxide from the sulfur-containing acid gases. DE 10332427 A1 teaches a process for the removal of hydrogen sulfide and other sour gas components from under pressure technical gases by means of a physical detergent and the recovery of sulfur from hydrogen sulfide using a Claus plant. The technical gases to be purified are freed in the process by gas scrubbing with suitable absorbent solvents from the acid gases contained therein and the loaded absorbent fed to a regeneration. The gas scrubbing is carried out in several stages, wherein the individual regeneration stages have pressure levels which are different from each other and also lower pressure relative to the absorption, so that an acid gas enriched in sulfur components is obtained. This gives various fractions of sour gas, which may also differ in the content of sour gas and the type of sour gases.

In many Claus plants, a hydrogenation is carried out behind the actual Claus process, is hydrogenated by the sulfur dioxide present in the process and converted into hydrogen sulfide. This hydrogenation is usually a necessary process step to prepare the Claus process gas for the so-called Claus process gas treatment. In a gas scrubbing, whether physically or chemically, it can not be avoided that in addition to the sulfur components, which must be removed from the synthesis gas, and a significant proportion of the carbon dioxide to be cleaned in the scrubbed gas is washed out of the feed gas, so that the acid gases released again in the regeneration device of the gas scrub often consist to a large extent of carbon dioxide. This interferes with the further processing of the acid gas in a Claus plant, because the combustible acid gases because of the dilution with the inert carbon dioxide have only a low calorific value and thus not or only very difficult for a stable Claus furnace operation high temperature of at least 850 - 900 ° C can be achieved.

For this reason, it is often not possible to supply the sour gas fraction with a reduced content of hydrogen sulfide without further addition in the Claus burner of the Claus plant.

This is undesirable, for example, when the sour gas fractions, which have a reduced sulfur content compared to the fraction with the highest hydrogen sulfide (H ₂ S) content, have an exceptionally high carbon dioxide content. An addition of this fraction into the Claus reactor or the Claus reaction space can cause the reduced hydrogen sulphide content to hinder or prevent further reaction of the sulfur dioxide with the remaining hydrogen sulfide.

There is therefore the task of providing a method that supplies as little as possible of the absorbed carbon dioxide to the Claus process, as this leads to a discharge of the entire Claus plant and, accordingly, lower investment costs. The invention solves this problem by a method in which, on the one hand, only the hydrogen sulfide-rich sour gas fraction is fed into a Claus plant and the still contained in the Claus plant leaving Claus residual sulfur compounds contained by subsequent hydrogenation almost completely to hydrogen sulfide (H ₂ S) are hydrogenated, so that a hydrogenated Claus residual gas is obtained, and on the other hand, at least one of the carbon dioxide-rich, low-sulfur sour gas fractions from the regeneration device, which compared to the fraction with the highest hydrogen sulfide (H ₂ S) content a reduced Have sulfur content, with the hydrogenated Claus process gas to a common process gas stream is brought together, which is fed to a further processing or a return to the process.

The further processing of the merged fractions can be arbitrary.

In particular, a method for the distribution of a carbon dioxide-rich acid gas in a Claus process is claimed, wherein

(A) a technical gas to be purified of sulfur components, which contains at least hydrogen sulfide and carbon dioxide as Sauerergaskomponenten, first by a gas scrubbing with a sour gas absorbing solvent which sulfur components more strongly than carbon dioxide, is passed, and

(B) the loaded solvent is fed to a regeneration device for regeneration, and

(c) separating the sour gas released in the regeneration, consisting of sulfur components and carbon dioxide (C0 ₂ ), into at least two sour gas fractions, and recovering at least one sour gas fraction having a higher content of sulfur components, and

(D) the fraction with the highest hydrogen sulfide (H ₂ S) content is fed to a Claus plant in which most of the contained hydrogen sulfide (H ₂ S) is converted to sulfur (S), and

(e) the sulfur compounds present in the Claus plant leaving the Claus plant are hydrogenated almost completely to hydrogen sulphide (H ₂ S) by a subsequent hydrogenation so that a hydrogenated Claus process gas is obtained, and

(F) at least one carbon dioxide laden, low-sulfur acid sour gas fraction from the regeneration device, which compared to the fraction with the highest hydrogen sulfide (H ₂ S) content has a reduced sulfur content is merged with the hydrogenated Claus process gas to a common process gas stream, which further processing or returned to the process. The number of carbon dioxide-laden, low-hydrogen sulfide fractions from the regeneration device, which compared to the fraction with the highest hydrogen sulfide (H ₂ S) content have a reduced sulfur content, can be arbitrary in principle. In principle, all carbon dioxide-laden, low-hydrogen sulfide fractions from the regeneration device, which compared to the fraction with the highest hydrogen sulfide (H ₂ S) content have a reduced sulfur content, the hydrogenated Claus process gas can be supplied. According to the invention, at least one sour gas fraction from the regeneration device, which has a reduced sulfur content compared to the fraction with the highest hydrogen sulfide (H ₂ S) content, must be combined with the hydrogenated Claus process gas to form a common process gas stream which is subject to further processing or recycling the process is fed.

In a preferred embodiment, the separation is carried out in at least two sour gas fractions in that the laden with acid gas from the gas scrubber before being fed into a regeneration column is first led to carbon dioxide depletion in at least one Austriebsstufe in which a carbon dioxide rich sour gas fraction and a with the in the regeneration column, a further depleted in carbon dioxide and enriched in sulfur components sour gas fraction is obtained, which is performed for combustion with an oxygen-containing gas in the Claus burner.

The depletion of the loaded solvent to carbon dioxide is preferably carried out in two to four flash stages, which are upstream of the regeneration column in the flow direction made. However, any number of flash stages can be used. The process of absorption, expansion in the flash stage, and regeneration may be arbitrary and is known in the art. The amount of sulfur components in the sulfur component-enriched substream supplied to the burner of the Claus reactor is typically 20 to 40 percent of the total sulfur removed from the feed gas.

In one embodiment of the invention, the recombined from the Claus residual gas and the carbon dioxide laden, low-sulfur sour gas residual gas stream is returned by means of a compressor for gas recirculation in the absorption column located in the main gas flow. This will do that Returned carbon dioxide in the first absorption column and finally carried out with the product gas from the process.

In a further embodiment of the invention, the hydrogen sulfide (H ₂ S) still present in the combined process gas stream is passed into at least one further gas scrubber with an absorption column, so that a virtually sulfur-free Claus residual gas is obtained.

The solvent used for the absorption is preferred in at least one sour gas scrubbing a physical solvent with a high selectivity for sulfur components, in particular hydrogen sulfide (H ₂ S), compared to carbon dioxide (C0 ₂ ). Examples of suitable physical solvents are Morphysorb ^® (mixture containing N-formylmorpholine and N-acetylmorpholine), Selexol ^® (mixture containing dimethyl ether of polyethylene glycols), N-methylpyrrolidone (NMP), methanol or propylene carbonate. This can be used in at least one of the absorption columns for gas scrubbing or hydrogenation subsequent absorption columns, or for several or ultimately for all absorption columns.

It can also be used in at least one acid gas scrubbing a selectively acting chemical solvent, which is suitable for a selective removal of sulfur components to carbon dioxide (C0 ₂ ), in aqueous solution. Examples of chemical solvents include methyldiethanolamine (MDEA), Flexsorb ^® (mixture containing hindered amines), or alkali metal salt solutions (for example potash solutions). This can also be used in at least one of the absorption columns for gas scrubbing or the hydrogenation subsequent absorption columns, or for several or ultimately all absorption columns.

The carbon dioxide content of the technical gas to be purified may be arbitrary. Thus, the content of carbon dioxide in the feed gas may be 30 to 50% by volume. The application of the method according to the invention is particularly advantageous when the sulfur component content is small compared to the carbon dioxide content. Thus, gases can be purified whose content of sulfur components at 0.1 to 1 volume percent hydrogen sulfide (or molar equivalent). The technical gas to be purified may also contain ammonia. The technical gas for desulfurization to be purified may be, for example, synthesis gas from a CO conversion. At the zu Purification technical gas for desulfurization may also be, for example, natural gas.

The number of sour gas fractions into which the sour gas released in the regeneration, consisting of sulfur components and carbon dioxide (C0 ₂ ), is separated, can be arbitrary. According to the invention, the fraction with the highest hydrogen sulfide (H ₂ S) content is fed to the Claus burner of a Claus plant, so that the number of fractions, compared to the fraction with the highest hydrogen sulfide (H ₂ S) content a have reduced sulfur content, may also be arbitrary. These can in principle all be combined with the hydrogenated Claus residual gas and fed to a use which does not lie in the region of the Claus plant. The number of selected fractions, which are used in a non-Claus plant, can ultimately be arbitrary.

When used, it may be an example of disposal. It may also be a reuse that uses the gases contained in the depleted fractions. However, the further use can in principle be of any kind. In a further embodiment of the invention is behind the hydrogenation and the merger of the hydrogenated Claus residual gas with the low-sulfur, carbon dioxide-rich fraction, another gas scrubbing, so that one obtains a desulfurized Claus process gas or Claus residual gas, which led by way of example in an afterburning becomes. This contains a burner, which burns the remaining sulfur compounds with an oxygen-containing gas or air to sulfur dioxide (S0 ₂ ), which is passed into the atmosphere. For this purpose, an additional fuel gas can be used. For use in the further process flow is an example of processing of the combined fractions by means of an additional Claus plant and downstream of the Claus plant hydrogenation.

The invention has the advantage that acid gas fractions with a reduced content of hydrogen sulfide need not be fed into the Claus burner a Claus plant or reaction chamber of a Claus plant, but combined with the residual gas of a Claus plant and fed to further use can be. This contributes accordingly to an improved economy of the entire process. The device of the invention will be explained with reference to two drawings, these drawings are only exemplary embodiments of the construction of the device according to the invention.

FIG. 1 shows an embodiment according to the invention in which hydrogenated Claus residual gas from a Claus process is combined with the carbon dioxide-rich sour gas fraction from a gas scrubber and the combined gas stream is returned to the gas scrubbing process. FIG. Figure 2 shows an embodiment of the invention in which the hydrogenated Claus residual gas is combined with the carbon dioxide-rich sour gas fraction from a gas scrubber and the combined gas stream is re-gas scrubbed with post-combustion.

FIG. 1 shows a process flow according to the invention in which a feed gas (1a) to be cleaned is fed to a gas scrubber (2). A sulfur-containing feed gas (1a) is passed to a absorption column (2) for gas scrubbing in which it is brought into contact with an absorbent solvent cooled by a heat exchanger (2a). This gives a purified product gas (1b) which is free or nearly free of sulfur compounds, the greater part of the carbon dioxide contained in the feed gas (1a) also remaining in the product gas (1b), and the solvent laden with sour gases (3). The loaded solvent is inventively preheated by heat exchangers (4a, 4b), and in a Austriebsbehälter (5) out. During expansion in the flash tank (5), a carbon dioxide-laden, low-sulfur acid sour gas fraction (6) and a carbon dioxide-depleted laden with sulfur components loaded solvent (7). This is passed into a regeneration column (8), which is heated here by way of example with a reboiler (8a), and freed from the sour gas enriched in sulfur components by heating and venting. This gives a carbon dioxide depleted, enriched with sulfur components sour gas (9), and a regenerated solvent (10). The sour gas (9) is passed through a condenser (9a) in a Claus plant (11). Condensed vapors (9b) are recycled to the regeneration column (8). The carbon dioxide laden, low sulfur acid sour gas fraction (6) coming from the flash tank (5) has a lower

Sulfur component concentration (Xi (H ₂ S)) as the sour gas fraction (9) richer in sulfur components from the regeneration column (8) (X ₂ , (H ₂ S)). In the Claus plant (11), the carbon dioxide depleted, enriched with hydrogen sulfide acid gas (9) by partial combustion with an oxygen-containing gas (11a) to sulfur dioxide (S0 ₂ ) and by its subsequent reaction with the remaining hydrogen sulfide (H ₂ S) in sulfur (11 b, S), which is discharged and reused. The Claus process gas (12) obtained from the Claus process (11) contains residual sulfur mainly as sulfur dioxide (S0 ₂ ). This Claus process gas (12) is passed into a hydrogenation stage (13) in which the remaining sulfur compounds in the Claus process gas (12) are hydrogenated with hydrogen (13a, H ₂ ) to hydrogen sulfide (H ₂ S). The hydrogenated Claus process gas (14) is combined via a valve (6a) with the carbon dioxide-laden, low-sulfur sour gas (6) and via a compressor for the gas recirculation (14a) and a heat exchanger (14b) in the feed gas (1a) and thus in returned the process. The carbon dioxide (C0 ₂ ) is discharged from the process with the product gas (1b).

FIG. 2 shows an embodiment according to the invention in which the hydrogenated Claus residual gas (14) is combined with the carbon dioxide-rich sour gas fraction (12) from a gas scrubber (2) and fed to a further gas scrubber (15) with an afterburning (16). As in FIG. 1, the feed gas (1 a) to be purified is first freed of sulfur compounds by gas scrubbing (2) with subsequent regeneration (6,9), whereby a carbon dioxide-laden, low-sulfur sour gas (6) and a carbon dioxide-depleted, enriched with hydrogen sulfide Sour gas (9) can be obtained. The enriched in carbon dioxide, enriched with hydrogen sulfide acid gas (9) is passed into a Claus process (11) in which the carbon dioxide depleted enriched with hydrogen sulfide acid gas (9) by partial combustion to sulfur dioxide (S0 ₂ ) and its subsequent post-reaction is converted with the remaining hydrogen sulfide (H ₂ S) into sulfur (11b, S), which is discharged and reused. The Claus process gas (12) obtained from the Claus process (11) contains the remaining sulfur mainly as sulfur dioxide (S0 ₂ ). This Claus process gas (12) is passed into a hydrogenation stage (13) in which the remaining sulfur compounds in the Claus process gas (12) are hydrogenated with hydrogen (13a) to hydrogen sulfide (H ₂ S). In this case, a hydrogenated Claus process gas (14) is obtained which, according to the invention, is combined with the carbon dioxide-laden, low-sulfur sour gas (6) and is passed through a gas scrubber (15) with a subsequent regeneration device (16). The sour gas (15e) depleted in sulfur compounds from the additional gas scrubber (15) is passed to afterburning (17) in which the remaining sulfur compounds are burned with an oxygen-containing gas (17a) and optionally with a fuel gas (17b) and the exhaust gas (18 ) is conducted into the atmosphere. The hydrogen sulfide-rich Claus residual gas (19) from the regeneration device (16) is recycled to the carbon dioxide-depleted hydrogen sulfide enriched sour gas (9) prior to the Claus process (11).

[0031] List of Reference Numerals

1a Sulfur-containing technical gas to be cleaned, feed gas

1 b Purified product gas

2 absorption column

2a heat exchanger

3 loaded solvent

4a, 4b heat exchangers

5 flask ("flash tank")

6 carbon dioxide laden, low sulfur hydrogen sour gas

7 Carbon dioxide-depleted, sulfur-enriched, loaded solvent

8 regeneration column

8a reboiler

9 Carbon dioxide depleted hydrogen sulfide enriched

sour gas

9a capacitor

10 Regenerated solvent

10a pump

11 Claus process with burner and Claus reaction space

11a Oxygen-containing gas, air

11b sulfur

12 Claus process gas

13 hydrogenation

14 Hydrogenated Claus process gas

14a Compressor for gas recirculation

14b heat exchanger

15 absorption column of the additional gas scrubber

15a Loaded solvent

15b pump

15c heat exchanger

15d heat exchanger

15e Sour gas depleted in sulfur compounds

16 regeneration device

16a heat exchanger

16b pump

16c reboiler 17 afterburning

17a Oxygen-containing gas, air

17b fuel gas

18 exhaust

19 recycled high-sulfide-rich Claus residual gas

X (H ₂ S) concentration of H ₂ S in the carbon dioxide-rich sour gas

X ₂ (H ₂ S) Concentration of H ₂ S in the H ₂ S-enriched sour gas fraction

Claims

claims

A process for processing a technical carbon dioxide-rich gas to be purified from sulfur components (1a), wherein

(A) a technical component to be purified of sulfur components (1a), which at least hydrogen sulfide and carbon dioxide as

Contains acid gas components, first by a gas scrubber (2) with an acid gas absorbing solvent (10), which sulfur components more strongly than carbon dioxide, is passed, and

(B) the loaded solvent (3) for regeneration in a

Regeneration device (5) is guided, and

(C) in the regeneration (5) liberated sour gas, consisting

Sulfur components and carbon dioxide (C0 ₂ ), in at least two sour gas fractions (6.9) is separated, and at least one sour gas fraction having a higher content of sulfur components

(9) is won, and

(d) the fraction with the highest hydrogen sulphide (H ₂ S) content (9) is fed to a Claus plant (11) in which most of the hydrogen sulphide contained (H ₂ S) is converted to sulfur (S, 11a) is implemented, and

(e) the still in the Claus plant (11) leaving Claus process gas

(12) sulfur compounds are hydrogenated by a subsequent hydrogenation (13) almost completely to hydrogen sulfide (H ₂ S), so that a hydrogenated Claus process gas (14) is obtained, and

(f) at least one carbon dioxide laden, low hydrogen sulfide

Sauerergasfraktion (6) from the regeneration device (5), which compared to the fraction with the highest hydrogen sulfide (H ₂ S) - content (9) has a reduced sulfur content, with the hydrogenated Claus process gas (14) to a common process gas stream (14c ), which is fed to a further processing or a return to the process.

2. Process for processing a technical component of carbon dioxide-rich gas (1a) to be cleaned of sulfur components according to claim 1, characterized in that all carbon dioxide-laden, low-hydrogen-fracking fractions (6) from the regeneration device (5) are compared to the fraction with the highest hydrogen sulfide ( H ₂ S) content (9) have a reduced sulfur content, the hydrogenated Claus process gas (14) are supplied.

Process for processing a technical carbon dioxide-rich gas (1a) to be cleaned of sulfur components according to one of claims 1 or 2, characterized in that the residual gas stream (14c) combined from the Claus residual gas and the carbon dioxide-laden, low-sulfur sour gas (6) is compressed by means of a compressor for the gas recirculation (14a) is returned to the absorption column (2) located in the main gas stream.

Process for processing a technical carbon dioxide-rich gas (1a) to be cleaned of sulfur components according to one of Claims 1 or 2, characterized in that the hydrogen sulfide (H ₂ S) still present in the combined process gas stream (14c) is subjected to at least one further gas scrubbing with an absorption column ( 15), so as to obtain a nearly sulfur-free Claus residual gas (19).

Process for processing a technical carbon dioxide-rich gas (1a) to be cleaned of sulfur components according to one of Claims 1 to 4, characterized in that a selectively acting chemical washing agent is used for at least one acid gas scrubbing (2, 15, 16).

A method of processing a technical carbon dioxide-rich gas to be purified from sulfur components (1a) according to any one of claims 1 to

5, characterized in that for at least one sour gas scrubbing (2, 15, 16) and a physically acting detergent is used.

A method of processing a technical carbon dioxide-rich gas (1a) to be cleaned of sulfur components according to any one of claims 1 to

6, characterized in that it is in the technical Gas (1 a) for the desulfurization of synthesis gas from a CO conversion is.

8. A method for processing a technical component of carbon dioxide-rich gas to be cleaned of sulfur components (1 a) according to one of claims 1 to 6, characterized in that it is to be cleaned technical gas (1a) for desulfurization is a natural gas.