KR19990077362A - Of removing sulfur-containing impurities, aromatics and hydrocarbons from gas - Google Patents

Abstract

The present invention relates to a method for removing impurities containing mercaptans and H ₂ S form sulfur from natural gas which may contain CO ₂ and higher aliphatic and aromatic hydrocarbons and recovering the sulfur element, Sulfur-containing impurities from the gas to form a purified gas stream on the one hand and an acid gas on the other, which is then passed through a Klaus device followed by selective oxidation of H ₂ S in the tail gas with sulfur element Reducing H ₂ S-enriched and mercaptan-depleted first gas stream, and, if desired after further processing, a second gas stream to reduce the H ₂ S-exposure to selective oxidation of the sulfur compound to the sulfur element and Is fed to a second absorption stage which is separated by a mercaptan-enriched second gas stream.

Description

Of removing sulfur-containing impurities, aromatics and hydrocarbons from gas

In the purification of the purification and the synthesis gas in the purification of natural gas, refinery gas, a sulfur-containing gas, in particular the H ₂ S will there is a glass, wherein H ₂ S is in particular formed from this combustion of sulfur compounds SO ₂ Should be removed to limit emissions to the atmosphere. For example, the limit of the sulfur compounds to be removed from natural gas depends on the desired use of the gas and the set of quality requirements. When the gas must meet the so-called "pipe specification", the H ₂ S content should be reduced to a value of less than 5 mg / Nm ³ . In addition, the requirements are adjusted in consideration of the maximum content of other sulfur compounds. Most methods in the prior art are known as methods capable of reducing the amount of sulfur compounds in gases such as natural gas.

In order to remove the sulfur-containing components from the gas, the following process is commonly used. In the first step, the gas to be treated is purified, thereby removing the sulfur-containing component from the gas, followed by recovery of the sulfur from these sulfur-containing components, followed by a subsequent sulfur removal step of the residual gas. In the sulfur purge step, the residual gas is recovered through the stack to the remaining percent of sulfur before it is released into the atmosphere.

In the purification step, a step using mainly an aqueous solvent (absorbent) is used. These processes are five main groups namely, chemical solvent processes, physical solvent processes, physical / chemical solvent process, the H ₂ S oxidation reduction process is oxidized directly to the sulfur in the aqueous solution, and finally with H ₂ S is chemically or physically Or adsorbed to or adsorbed to the catalyst, or selectively oxidized to the catalyst with a sulfur element.

The first three groups described above are generally used in factories to remove large amounts of sulfur-containing components, which are predominantly present in large quantities of gases. The other two groups are limited in terms of the amount of sulfur to be removed and the concentration of the sulfur-containing component. Thus, these processes are rarely suitable for removing high concentrations of sulfur in large industrial gas purifiers.

The chemical solvent process includes a so-called amine process in which an aqueous solution of an alkanolamine or an aqueous solution of potassium carbonate is used.

Other chemical agents are used in the physical solvent process. For example, methanol known as polyethylene glycol (DMPEG), known under the trade name Selexol, N-methyl-pyrrolidone (NMP), also known under the trade name Purisol, or trade name Rectisol, .

Sulfinol processes are well known in physical / chemical processes. In this process, a mixture of alkanolamine with sulpholane dissolved in a small amount of water is used.

In the three methods mentioned above, absorbers and regenerators are used. In the absorber, the sulfur-containing component is chemically or physically bound to the solvent. Through pressure reduction and / or temperature rise in the regenerator, the sulfur-containing component can be desorbed from the solvent, after which the solvent can be reused. A detailed description of this method can be found in the Cambell Petroleum Series (1977), al. &Quot; Gas and Liquid Sweetening " of RN Medox. In addition to the sulfur-containing components in this process, CO _{2 is} also almost or partially removed depending on the selected solvent.

The removed sulfur component is sent from the regenerator to the sulfur recovery unit along with CO ₂ to recover sulfur from the H ₂ S and other sulfur compounds. The process frequently used to recover sulfur from the thus obtained sulfur components, particularly H ₂ S, is the Klaus process. The process is as follows. Quot; Capability of the modified Claus process " (HG Paskall, Western Research Development, Calgary, Alberta, Canada, 1979).

The Klaus process consists of a temperature step followed by a typical two or three reactor steps. In the temperature step, 1/3 of H ₂ S is burned to SO ₂ according to the following reaction.

_{H 2 S + 1.5 O 2 →} SO 2 + H 2 O

The remainder, that is 2/3 of H ₂ S, reacts with the formed SO ₂ and forms sulfur and water according to the Klaus reaction.

2 H ₂ S + SO ₂ ? 3 S + 2 H ₂ O

The efficiency of the Klaus process depends on several factors. For example, the equilibrium of the Claus reaction shifts to the H ₂ S with the direction that this increase in water content in the gas. The efficiency of the sulfur recovery apparatus can be increased by the use of a tail gas sulfur recovery apparatus and the known processes are the SUPERCLAUS ( ^TM ) process and the SCOT (SCOT) process. In the SUPERCLAUS ( ^TM ) process, use is made of the catalysts described in the international patent application WO-A No. 95.07856, as well as in European Patent Applications Nos. 242,920 and 409,352, where the catalyst is referred to as "Hydrocarbon Processing" April 1989, pp. 40-42).

Using this method, the remaining residues of H ₂ S present in the process gas stream are optionally oxidized to the sulfur element according to the following reaction.

H ₂ S + 0.5 O ₂ - -> S + H ₂ O

In this method, the efficiency of the sulfur recovery unit can easily be increased to 99.5%. The gas fed to the Klaus unit may sometimes contain a large amount of CO ₂ , for example up to 98.5%, which has a very adverse effect on the flame temperature in the temperature step. A large amount of CO ₂ will cause instability of the flame, and will also reduce the efficiency of the temperature step, resulting in a reduction in the total efficiency of the Klaus device.

Further, the gas may contain a large amount of hydrocarbons. When the sulfur-containing gas is treated in an oil refining gas, the hydrocarbon content is generally lowered to less than about 2% by volume.

In the purification of natural gas in which a physical or physical / chemical process is used, a large amount of hydrocarbons and aromatic systems may be terminated in a gas (Klaus gas) which is sent to the sulfur recovery device, respectively, depending on the absorption result. In the temperature step of the Klaus device, these hydrocarbons are completely burned because the reaction rate of oxygen and hydrocarbon is faster than the reaction rate of oxygen and H ₂ S. If there is a large amount of CO ₂ , the flame temperature will continue to be low, and thus the rate of reaction of the components during burning will also be low. As a result, there is a possibility that soot is formed in the flame of the combustor at the temperature stage.

Soot formation causes the clogging of the catalyst in the Klaus apparatus, especially in the first reactor. In addition, the ratio between the oxygen demand for converting H ₂ S to sulfur and the oxygen demand for hydrocarbons and aromatic combustion can take values that the Klaus device can no longer be suitably controlled. These problems are known in the factory.

In addition, in addition to H ₂ S and the above-mentioned large amounts of CO ₂ , mainly mercaptans are also present in the gas. In factories, chemical processes are used where these mercaptans are not removed from the purge gas, such as, for example, natural gas, and there is no need for post-cleaning with the fixed-bed process. Mainly the molecular sieve is used to remove these mercaptans.

However, when this stationary phase is saturated with mercaptans, the molecular sieve must be regenerated mainly for the purpose of using purified natural gas. The regeneration gas must then be purified in turn. In the regeneration of the molecular sieve, mercaptans are mostly liberated at the beginning of regeneration. There is also a process in which the mercaptan is returned to the Klaus apparatus in the post-purification step. These mercaptans then impart a peak load at the temperature stage of the Claus apparatus, seriously interrupting air conditioning. This process is described in the Oil and Gas Journal 57 (19 August, 1991, pp. 57-59). Moreover, this leads to the loss of natural gas, and can easily reach up to about 10%.

Methods for treating sulfur-containing gases containing carbonylsulfides and / or other organic components such as mercaptans and / or di-alkyl disulfides are known. This method is described in British Patent No. 1563251 and British Patent No. 1470950.

The present invention relates to a process for the purification of hydrocarbon gases, in particular natural gas, contaminated with sulfur compounds in the form of H ₂ S and mercaptans as well as CO ₂ . More specifically, the present invention comprises a method for converting mercaptans to H ₂ S, removing CO ₂ , absorbed hydrocarbons and aromatic systems from the H ₂ S-containing gas to form a sulfur element from H ₂ S.

Figure 1 shows a modification of the additional hydrogenation step of the second low H ₂ S gas flow in the form of a block diagram.

Figure 2 shows a variant without hydrogenation.

As shown in Fig. 1, the acid gas from the first absorption unit (not shown), in which the contaminated natural gas is separated into a gas flow on the one hand corresponding to the required conditions and on the other hand by an acid gas, 1 to the absorber of the selective absorption / desorption device 3. The unabsorbed components of the gas, mainly composed of carbon dioxide, hydrocarbons (including aromatics), mercaptans and a small amount of H ₂ S, are directed to the hydrogenation reactor 18 via line 2. At line 2, the gas becomes the desired hydrogenation temperature before being transferred into the hydrogenation reactor 6 with the addition of hydrogen and / or carbon dioxide.

In the hydrogenation reactor 6, mercaptans and other organic sulfur compounds present in the gas are converted to H ₂ S. The gas from the hydrogenation reactor 6 is cooled and transferred via line 5 to the tail gas desulfurization step 11 of the Claus apparatus 8 to convert the existing H ₂ S to a sulfur element.

The H ₂ S-rich gas mixture emerging from the regeneration zone of the absorption / regeneration unit 3 is fed via line 7 to the Claus unit 8 where the majority of the sulfur compounds are released via line 9 Which is then transformed into a sulfur element.

In order to increase the efficiency of the Claus device 8, the tail gas mainly travels via the line 10 to the tail gas desulfurization step 11. The sulfur removal step may be a known sulfur removal process such as, for example, a dry phase oxidation step, an absorption step, or a liquid oxidation step. Air required for oxidation is supplied via line 12. The formed sulfur is discharged through the line (13).

The gas then travels to the post combustor 15 via the line 14 before the gas is discharged via the stack 16.

As shown in FIG. 2, the acid gas from the first absorption unit (not shown), in which the contaminated natural gas is separated into a gas flow meeting the requirements on the one hand and an acid gas on the other hand, 1 to the absorber of the absorption / recovery device 3.

The H ₂ S-rich gas mixture exiting the regeneration zone of the absorption / regeneration unit 3 is fed via line 4 to the Claus unit 5 where the majority of the sulfur compounds are converted into sulfur atoms, (6).

To increase the efficiency of the Claus device 5, the tail gas travels via line 7 to the tail gas desulfurization step 8. The sulfur removal step (8) operates according to the dry phase oxidation principle.

The unabsorbed components of the gas exiting the absorption region of the absorption / regeneration device, which is mainly composed of carbon dioxide, hydrocarbons (including aromatics), mercaptans and a small amount of H ₂ S, 8) oxidation reactor. The air required for the oxidation of H ₂ S and mercaptans is supplied in the case of line 9. In order to limit the temperature rise in the oxidation reactor, the cooled process gas is recirculated from the line 12 to the line 7 with the aid of the cooler 14. The formed sulfur is discharged in the case of the line 11. The gas is then sent to the post combustor 16 via the line 12 before the gas is discharged via the stack 17.

The invention is illustrated by the following non-limiting examples.

It is an object of the present invention to provide a method for removing mercaptans and H ₂ S-type sulfur-containing impurities from a hydrocarbon gas which may contain CO ₂ and higher aliphatic and aromatic hydrocarbons, In this method, the above disadvantage does not occur. More particularly, it is an object of the present invention to provide a method by which tail gas does not contain a harmful substrate or contains a very small amount, so that these gases can be released into the atmosphere without any problem. Yet another object of the present invention is to provide a method for recovering an amount of sulfur-containing impurities as a sulfur element, for example, 90% or more, particularly 95% or more.

Surprisingly, it has been found that the process according to the invention allows a large amount of gas flow to be purified in a highly effective manner, whilst at the same time meeting the stringent requirements for the release of toxic substrates and the effective recovery of sulfur.

The present invention provides a simple method for purifying contaminated hydrocarbon gas with the recovery of sulfur wherein the first absorption step removes the sulfur-containing impurities from the gas and, on the one hand, On the other hand, an acidic gas which is supplied to the Klaus unit followed by a step of selectively oxidizing H ₂ S in the tail gas to a sulfur element, wherein the H ₂ S-enriched and mercaptan- , And a second absorption step in which the second gas stream is separated into H ₂ S-reduction and mercaptan-enriched second gas streams which are exposed to selective oxidation of the sulfur compounds to the elemental sulfur, if required after further treatment .

According to a preferred embodiment of the present invention, the first absorption step is carried out using a chemical, physical or chemical / physical absorbent to remove all impurities from the natural gas. Preferably, it is a sulfolane-based absorbent in combination with a secondary and / or tertiary amine. As has already been pointed out, such systems have been known and have already been used for purifying natural gas on a large scale, especially when liquefying natural gas after purification. Absorption is typically based on a system in which impurities are absorbed in a solvent in a first column and then the solvent is regenerated in a second column, for example, by heating and / or depressurization, when the solvent is added with impurities. The temperature at which absorption occurs depends mostly on the solvent and the pressure used. At a current pressure of 2 to 1000 bar of natural gas, the absorption temperature is generally 15 to 50 DEG C, although good results can be obtained even outside this range. Natural gas is desirably purified to meet the piping specifications, which means that generally less than 10, in particular less than 5 ppm H ₂ S may be present.

According to the process of the present invention, in the second absorption step, the acid gas is first separated into two gases, H ₂ S-rich gas and CO ₂ -rich gas, which in addition to CO ₂ are hydrocarbons, Absorbed mercaptans are contained. In this way, the concentration of H ₂ S can be increased by 2 to 6 times.

The second absorption step preferably occurs with a solvent based on secondary and tertiary amines, more specifically with an aqueous solution of methyldiethylamine, optionally in combination with an activator therefor or a solvent combined with a sterically hindered tertiary amine. Such processes are known and are described in the literature (MDEA process, UCARSOL, FLEXSORB-SE, and others). The manner of operation of such a process is comparable to the first absorption step. The degree of consolidation is preferably at least 2 to 6 times or more, which depends in part on the initial concentration of H ₂ S. The degree of consolidation can be tailored through an appropriate choice of absorber composition.

The H ₂ S-rich first gas flow can be treated very well in the Klaus unit, while the majority of CO ₂ , hydrocarbons and aromatic deficiencies do not cause any additional gas treatment in the apparatus when burned There is an advantage. In the end, the Klaus device can be made into a smaller design, while still achieving very high sulfur recovery efficiency.

Such Klaus devices are known and the manner in which they are operated with respect to temperature, pressure and others is described in detail in the publication cited in the preamble.

A tail gas still containing residual sulfur compounds from the Klaus unit is fed to the tail gas treatment unit, if required after further hydrogenation, where the sulfur element is formed through the selective oxidation of the sulfur compound, For example, as described in European Patent Application 655,415.

After separating the sulfur, the residual gas can be burned in a later combustor. The heat released can be useful for steam generation.

Selective oxidation is preferably carried out in the presence of a catalyst that selectively converts the sulfur compound to a sulfur element, for example, the catalyst described in the aforementioned European patent and international patent application. The publication is incorporated herein by reference in its entirety and also designates the most suitable process conditions, such as temperature and pressure conditions. In general, however, the pressure is not critical and the temperature may be between about 300 [deg.] C and less than 250 [deg.] C, relative to the dew point of the sulfur.

The CO ₂ -rich second gas stream present in addition to hydrocarbons, aromatics and mercaptans is mixed with tail gas from a Krauss sulfur recovery unit to form a tail gas recovery unit based on selective oxidation of sulfur compounds to sulfur elements . In this case, the tail gas recovery unit is preferably a Super Klaus unit stage, whereby the mercaptans are oxidized to the sulfur element in addition to the oxygen present.

Alternatively, CO ₂ -rich gases can also be treated separately in the Super Claus reactor. When the content of mercaptans in the gas is large, it is necessary to cool the Super Klaus reactor in order to prevent the possibility that the temperature becomes too high and, as a result, the selectivity decreases and too much SO ₂ is formed.

According to another embodiment of the process according to the invention, the CO ₂ -rich gas, which is the second gas stream from the strengthening unit, is hydrogenated with hydrogen containing sulfide group 6 and / or group 8 metal catalyst supported on the carrier Through the reactor.

As a carrier, alumina is preferably used in conjunction with these types of catalysts, in addition to the required temperature stability, as this material also allows good dispersion of the active ingredient. As the catalytically active material, a combination of cobalt and molybdenum is preferably used.

For hydrogenation, the gas stream must be heated to a temperature of 200 to 300 DEG C which is required for hydrogenation from an absorption / desorption temperature of about 40 DEG C. As is conventional, the heating preferably occurs indirectly and without a burner arranged in the gas stream. In fact, the disadvantage of direct heating is that direct heating in this case causes significant soot formation, which can pollute and clog the tube in hydrogenation and simultaneous selective oxidation.

During the hydrogenation step mercaptans in the gas are converted to H ₂ S with the aid of the supplied hydrogen. In the hydrogenation step ₂ CO, CO ₂ a H ₂ S containing, hydrocarbons, and aromatic-rich gas is mixed with the tail gas from the Claus unit, and then moved to the tail gas sulfur removal units, especially super Claus reactor stage.

The gas from the hydrogenation reactor can also be treated in a separate Super Claus reactor.

It will be necessary to cool the Super Klaus reactor to prevent the temperature of the catalyst from rising too high.

As pointed out, the gas from the selective oxidation eventually burns, thereby converting residual organic impurities into water and CO ₂ .

The present invention will be described with reference to the following drawings.

Example 1

The amount of acid gas at 15545 Nm ³ / h from the regenerator of the gas purifier has the following composition at a temperature of 40 ° C and a pressure of 1.70 bar abs.

Composition (unit) ingredient 9.0 vol% H ₂ S 0.01 vol% COS 0.22 vol% CH ₃ SH 0.38 vol% C ₂ H ₅ SH 0.03% C ₃ H ₇ SH 0.01 vol% C ₄ H ₉ SH 81.53% CO ₂ 4.23% H ₂ O 3.51 vol% The hydrocarbons (C ₁ to C ₁₇ ) 1.08 vol% Aromatic (benzene, toluene, xylene)

The acid gas was contacted with a methyl diethanolamine solution in the absorber of the gas purifying device, whereby a part of H ₂ S and CO ₂ was absorbed.

The amount of gas (CO ₂ -rich gas) produced from the absorber was 13000 Nm ³ / h with the following composition.

Composition (unit) ingredient 88.47 vol% CO ₂ 500 ppm volume H ₂ S 70 ppm volume COS 0.26 vol% CH ₃ SH 0.46 vol% C ₂ H ₅ SH 0.04% C ₃ H ₇ SH 0.01 vol% C ₄ H ₉ SH 5.21% H ₂ O 4.2 vol% The hydrocarbons (C ₁ to C ₁₇ ) 1.29 vol% Aromatic (benzene, toluene, xylene)

A reducing gas containing hydrogen and carbon monoxide was supplied to the product gas at 2700 Nm < ³ > / h, followed by heating to 205 DEG C to remove all the mercaptans present on the alumina support with the sulfide group 6 and / , In this case hydrogenation to H ₂ S was carried out in a hydrogenation reactor containing a Co-Mo catalyst.

The temperature of the gas from the reactor was 232 ° C. The acid gas was then cooled to 226 ° C and fed to the tail gas desulfurization stage of the sulfur recovery apparatus. The amount of gas from the hydrogenation reactor was 15700 Nm ³ / h and the following composition was shown.

Composition (unit) ingredient 0.68 vol% H ₂ S 60 ppm volume COS 74.22% CO ₂ 8.14% H ₂ O 3.48 vol% The hydrocarbons (C ₁ to C ₁₇ ) 1.07 vol% Aromatic (benzene, toluene, xylene) 0.86 vol% H ₂ 11.56% N ₂

After desorption in the regenerator, an acidic H ₂ S / CO ₂ gas mixture (H ₂ S-rich gas) was sent to the sulfur recovery unit. The H ₂ S / CO ₂ gas mixture was 2690 Nm ³ / h and had the following composition at 40 ° C, 1.7 bar abs.

Composition (unit) ingredient 51.7 vol% H ₂ S 44.0 vol% CO ₂ 4.3 Volume% H ₂ O

Air was supplied to the combustor at the temperature stage of the sulfur recovery apparatus at 2780 Nm ³ / h, and after the second Claus reactor stage, 1.14% by volume of H ₂ S and 0.07% by volume of SO ₂ were present in the gas. The process gas was then fed to a tail gas desulfurization step consisting of a selective H ₂ S oxidation reactor.

Air was supplied to the gas at 875 Nm ³ / h. The inlet temperature of the selective oxidation reactor was 220 캜 and the outlet temperature was 267 캜. A selective oxidation reactor was charged with catalyst as described in European Patent Nos. 242,920 and 409,353, and International Patent Application WO-A No. 95/07856.

The sulfur formed in the sulfur recovery apparatus was concentrated and discharged after each step. The discharged inert gas was transferred to the stack via post combustion. The amount of sulfur was 2068 kg / h. The total desulfurization efficiency based on the original acid gas containing 9.0 vol% H ₂ S was 96.5%.

Example 2

The amount of acid gas at 15545 Nm ³ / h from the regenerator of the gas purifier has the following composition at a temperature of 40 ° C and a pressure of 1.70 bar abs.

Composition (unit) ingredient 9.0 vol% H ₂ S 0.01 vol% COS 0.22 vol% CH ₃ SH 0.38 vol% C ₂ H ₅ SH 0.03% C ₃ H ₇ SH 0.01 vol% C ₄ H ₉ SH 81.53% CO ₂ 4.23% H ₂ O 3.51 vol% The hydrocarbons (C ₁ to C ₁₇ ) 1.08 vol% Aromatic (benzene, toluene, xylene)

The acid gas was contacted with a methyl diethanolamine solution in the absorber of the gas purifying device, whereby a part of H ₂ S and CO ₂ was absorbed.

The amount of gas (CO ₂ -rich gas) produced from the absorber was 13000 Nm ³ / h with the following composition.

Composition (unit) ingredient 88.47 vol% CO ₂ 500 ppm volume H ₂ S 70 ppm volume COS 0.26 vol% CH ₃ SH 0.46 vol% C ₂ H ₅ SH 0.04% C ₃ H ₇ SH 0.01 vol% C ₄ H ₉ SH 5.21% H ₂ O 4.2 vol% The hydrocarbons (C ₁ to C ₁₇ ) 1.29 vol% Aromatic (benzene, toluene, xylene)

The product gas was then heated to 230 DEG C and fed to the tail gas desulfurization step of the sulfur recovery apparatus.

After desorption in the regenerator, an acidic H ₂ S / CO ₂ gas mixture (H ₂ S-rich gas) was sent to the sulfur recovery unit. The H ₂ S / CO ₂ gas mixture was 2690 Nm ³ / h and had the following composition at 40 ° C, 1.7 bar abs.

Composition (unit) ingredient 51.7 vol% H ₂ S 44.0 vol% CO ₂ 4.3 Volume% H ₂ O

Air was supplied to the combustor at the temperature stage of the sulfur recovery apparatus at 2780 Nm ³ / h, and after the second Claus reactor stage, 1.14% by volume of H ₂ S and 0.07% by volume of SO ₂ were present in the gas. The process gas was then fed to a tail gas desulfurization step consisting of a selective H ₂ S oxidation reactor.

Air was supplied to the gas at 875 Nm ³ / h. The inlet temperature of the selective oxidation reactor was 230 캜 and the outlet temperature was 290 캜. To limit the temperature rise in the oxidation reactor to 60 ° C, 13000 Nm ³ / h of gas cooled after the reactor is recycled through the reactor. A selective oxidation reactor was charged with catalyst as described in European Patent Nos. 242,920 and 409,353, and International Patent Application WO-A No. 95/07856.

The sulfur formed in the sulfur recovery apparatus was concentrated and discharged after each step. The discharged inert gas was transferred to the stack via post combustion. The amount of sulfur was 2050 kg / h. The total desulfurization efficiency based on the initial acid gas containing 9.0 vol% H ₂ S was 95.7%.

Claims (14)

Containing impurities from the gas in the first absorption step to form a purified gas stream on the one hand and an acidic gas on the other, and the acid gas is supplied to the Klaus unit followed by H ₂ S in the tail gas, optionally reinforced H ₂ S- supplied to the oxidizing and mercaptan-reduction of a first gas stream, and, if required after additional processing, the H 2 gas flow which is exposed to selectively oxidize the sulfur compounds into elemental sulfur ₂ S- and reduced mercaptan-enriched second gas stream to the made to be supplied to the second absorption stage is separated CO ₂ and higher aliphatic and aromatic hydrocarbons from a hydrocarbon gas also may contain mercaptans and H ₂ S in the form of sulfur Containing impurities and recovering the elemental sulfur. The method of claim 1, wherein the second gas stream is hydrogenated prior to selective oxidation. The method of any one of claims 1 and 2, wherein the selective oxidation step of the tail gas of the first gas flow and the second gas flow occurs in the same reactor. The method of any one of the preceding claims, wherein the step of selectively oxidizing the tail gas of the first gas flow and the second gas flow occurs in two separate reactors. The method of any one of claims 1 to 4, wherein the first absorption step is performed using a chemical, physical, or chemical / physical absorbent to substantially remove all sulfur compounds and CO ₂ from the gas. 6. The process according to claim 5, wherein the sulfolane as the absorbent is used in combination with a secondary or tertiary amine. A process according to any one of claims 1 to 6, wherein the second absorption step is carried out using an absorbent based on secondary and / or tertiary amines. The method of any one of claims 1 to 7, wherein the first absorption step is carried out in such a way that the purified gas contains no more than 10, in particular no more than 5 ppm sulfur-containing impurities. 9. A process according to any one of claims 1 to 8, wherein the natural gas is used as a gas to be purified which is selectively liquefied after purification. The method according to any one of claims 1 to 9, wherein the second absorbing stage is carried out with at least 2.5-fold, especially how to increase at least four times than the H ₂ S content in the first gas flow H ₂ S content of the acid gases in the How to do it. 10. A process according to any one of claims 1 to 10, wherein the content of mercaptan in the first gas stream is at least 1 ppm. Process according to any one of the claims 2 to 11, characterized in that the hydrogenation is carried out with at least one metal in group VIB of the periodic table of the elements and with a catalytically active component based on a combination of at least one metal, in particular cobalt and molybdenum, In the presence of a supported catalyst. 13. Process according to any one of claims 2 to 12, wherein the hydrogenation takes place in the presence of an amount of water. The method of any one of claims 2 to 13, wherein the second gas stream is indirectly heated prior to hydrogenation.