MXPA00004591A - Hydrogen sulfide removal process - Google Patents

Abstract

Hydrogen sulfide is removed from gas streams by reaction with sulfur dioxide to produce sulfur. The reaction is effected in a reaction medium comprising a non-aqueous Lewis base with a pKb value of about 6 to about 11. The reaction medium prossesses a specific combination of properties:a) absorbs sulfur dioxide and reacts chemically therewith to form a reaction product;b) absorbs hydrogen sulfide;c) removes the hydrogen sulfide from the gas stream through contact of the gas stream with the reaction medium in the presence of free sulfur dioxide, and/or the reaction product;d) acts as a catalyst for the overall reaction of the hydrogen sulfide with sulfur dioxide to produce sulfur;and e) has the capacity to absorb sulfur dioxide in sufficient quantity to remove substantially all the hydrogen sulfide from the gas stream, notwithstanding short term variations in the stoichiometric balance between the hydrogen sulfide and the sulfur dioxide in the reaction medium.

Description

PROCESS FOR THE REMOVAL OF HYDROGEN SULFIDE FIELD OF THE INVENTION The present invention relates to the removal of hydrogen sulfide from gaseous streams, using a reaction medium comprising non-aqueous Lewis bases.

BACKGROUND OF THE INVENTION Many natural gas deposits or reservoirs contain hydrogen sulphide and carbon dioxide, which are acid gases, which can be extremely corrosive when combined with each other and with water. Natural gas containing these acid gases or acidified gases must be purified (or "deacidified or sweetened") to eliminate or reduce the concentration of these gases before the purified natural gas ("deacidified or sweetened gas") is sent to the consumer, to industrial markets and other markets. The most commonly practiced process technology for the removal of acid gas is the absorption of the acid gases contained in the natural gas stream by means of an absorbing or absorbing and regenerable solution in a gas processing plant. In these processes, an absorber or absorbent and regenerable solution is passed in a countercurrent contact with the natural gas stream to absorb H2S and CO2 from the natural gas stream, as well as other sulfur compounds, reducing this way its concentration in the stream of natural gas and purifying it. The solution rich or charged with acid gas is then regenerated by extraction or steam stripping at elevated temperature and the regenerated solution is cooled and recirculated back to the stage of contact with natural gas. Acid gases extracted from the solution in the regeneration step are vented from the gas processing plant for further processing, which includes, in some cases, incineration to sulfur dioxide. The present invention relates to a way to process sulfurized natural gas streams. The chemical compounds normally used in these processes include amines, esters and similar regenerable materials in which acid gases can be absorbed. The most commonly used amines for this process include monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA). The present invention provides novel methods for the treatment of gas streams containing hydrogen sulfide. As described in more detail below, the process of the invention includes the step of reacting hydrogen sulfide and sulfur dioxide to form sulfur (sometimes referred to as the Claus reaction) in a reaction medium comprising a base of non-aqueous Lewis, preferably quinoline. The processes described herein can be applied to other gaseous streams containing hydrogen sulfide, including tail gas streams from the Claus process and gas streams from industrial smokestacks.

SUMMARY OF THE INVENTION In accordance with the present invention, a reaction medium comprising Lewis bases is used Non-aqueous, having a pKj- value, from about 6 to about 11, preferably, from about 8 to about 10, particularly, quinoline, to remove hydrogen sulfide from gas streams, particularly, during sweetening or sweetening Sulfurized natural gas streams when conducting the reaction between hydrogen sulfide and sulfur dioxide in the reaction medium.

The reaction of hydrogen sulphide with sulfur dioxide, which may be in the form of a reaction product with the Lewis base, proceeds in accordance with the equation: 2H2S + S02? 3S + 2H20 known as the Claus reaction. It is well known that sulfur dioxide is soluble in many amines, which include quinoline, forming an equimolar solid reaction product, which is soluble in quinoline and in quinoline-water mixtures. The inventors of the present use the reaction product in an original form to provide improved processes for removing hydrogen sulfide from gaseous streams. The present invention utilizes a reaction comprising a Lewis base, which has values of pKj-, from about 6 to about 11, preferably from about 8 to about 10. Although strong Lewis bases (pK ^ less than about 6) tend to react irreversibly with sulfur dioxide, preventing The Claus reaction occurs, weaker Lewis bases (pK] -, greater than about 11) do not seem to catalyze the Claus reaction. Lewis bases with intermediate basicity (pKj-, from about 6 to about 11), as used herein, react reversibly with sulfur dioxide and catalyze the Claus reaction. Quinoline (pKj-, 9) is the preferred amine, but other amines having the required pKj- values may be used, such as 2, 4, 6-trimethyl pyridine (pKj-, 7). Accordingly, in one aspect of the present invention, there is provided a process for removal or removal of hydrogen sulphide from a gas stream by reaction with sulfur dioxide, which comprises carrying out the reaction in a reaction medium comprising a non-aqueous Lewis base having a value of pKj-, in the range of about 6 to about 11 and in which the reaction medium: a) absorbs sulfur dioxide and chemically reacts with it to form a reaction product; b) absorbs hydrogen sulfide; c) removes the hydrogen sulfide from the gas stream by contact with the gas stream with the reaction medium in the presence of free sulfur dioxide and / or the reaction product; d) acts as a catalyst for the overall reaction of hydrogen sulfide with sulfur dioxide to produce sulfur; and (e) has the capacity to absorb sulfur dioxide in sufficient quantity to remove practically all of the hydrogen sulfide from the gas stream, notwithstanding the short-term variations in the stoichiometric balance between hydrogen sulfide and sulfur dioxide in the reaction medium. The reaction medium may consist essentially of the non-aqueous Lewis base or may additionally comprise a miscible diluent with vapor pressure below about 0.39 psi at a temperature of about 120 ° C. The process for the removal of the hydrogen sulfide that is provided herein can be effected in a form in which the sulfur dioxide is continuously absorbed by the reaction medium to react with the hydrogen sulfide of the gas stream at a temperature from about 120 ° to about 155 ° C, preferably from about 120 ° to about 130 ° C to produce liquid sulfur and the liquid sulfur produced in this way is continuously removed from the process. This latter method is particularly useful in a natural gas sweetening operation or for the processing of a gaseous stream containing hydrogen sulfide, where a continuous operation is required. The process for the removal of hydrogen sulfide that is provided herein may be P1040 is carried out in a form in which the gas stream is contacted, continuously or intermittently, with a body of the reaction medium to react the hydrogen sulfide with sulfur dioxide in the reaction product to form sulfur until that the reaction medium depletes its ability to react with hydrogen sulfide. This latter method is particularly useful for debugging operations that remove gaseous streams, which have a variety of origins, minor amounts of hydrogen sulfide on an intermittent operating basis. The process can be operated at a temperature above or below the melting point of the sulfur and up to the solidification point of the reaction medium. Sulfur is normally allowed to accumulate in the mass or volume of the reaction medium until the reaction medium is exhausted. When the reaction medium exhausts its ability to react with hydrogen sulfide, which can be detected by any conventional detection device, it is regenerated to the reaction medium. This regeneration can take a variety of forms including the replacement of the spent reaction medium with a fresh charge of the reaction medium or a charge of the reaction medium which was regenerated from a previous batch.

P1040 Regeneration can be carried out by reforming the reaction product of sulfur dioxide and non-aqueous Lewis base. The sulfur can be removed from the reaction medium, intermittently, as desired.

GENERAL DESCRIPTION OF THE INVENTION In a specific aspect of the present invention, there is provided a continuous process for the removal of hydrogen sulfide from a gaseous stream, which comprises contacting a reaction medium comprising a non-aqueous Lewis base which has a value of pKj-, from about 6 to about 11, which has the capacity to absorb sulfur dioxide in an amount sufficient to virtually eliminate all hydrogen sulfide from the gas stream, notwithstanding the short-term variations in the balance stoichiometric between the hydrogen sulfide and the sulfur dioxide in the reaction medium with the gas stream in the presence of sulfur dioxide in the reaction medium to react with the hydrogen sulfide at a temperature above the melting point of the sulfur to form liquid sulfur, in accordance with the equation: 2H2S + S02? 3S + 2H20 which is carried out in the upper region of a reactor; the liquid sulfur of the reaction accumulates as a layer in P1040 lower region of the reactor, below the reaction medium, ventilating from the reactor a gaseous stream with low content of hydrogen sulfide and removing from it the liquid sulfur of the layer. In this process, the sulfur dioxide and / or gas stream can be passed upwardly through the liquid sulfur layer to remove the dissolved sulfur from the liquid sulfur and then through the reaction medium to produce the product therein. of the reaction for the reaction with hydrogen sulfide. A specific embodiment of the process is carried out in a stream of sulfur-containing natural gas containing hydrogen sulphide. In this specific process, the sulfurized natural gas stream is heated to a temperature close to at least the melting point of the sulfur and, optionally, above its melting point and then passed to the reactor. The hot sulfurized natural gas stream is then dispersed in the liquid sulfur layer and allowed to pass upwards through the liquid sulfur layer and into direct contact with the sulfur dioxide-containing reaction medium in an amount at least enough to convert all of the hydrogen sulfide in the gas stream to sulfur.

The resulting stream of sweetened gas is removed from the reactor as the ventilated gas stream. The sweetened gas stream is cooled to remove condensable compounds therefrom and the resultant cold sweetened gas stream is removed as a process product. The heating of the acidified gas stream to the temperature can be carried out at least partially, by passing the source in a heat exchange relationship with the stream of sweetened gas that was withdrawn, thereby effecting the cooling of the stream of gas. sweetened gas withdrawn. The condensable compounds can be collected and comprise the non-aqueous condensed Lewis base, associated compounds and dissolved sulfur and the collected condensable compounds are recycled to the reactor. In addition, the reaction medium can be recycled into the reactor by mixing a stream of the reaction medium from the reactor with the condensable compounds collected and by recycling or recirculating the mixture to the reactor. The mixture can be heated before its passage to the reactor. The combined heating of the sulfurized natural gas stream and the heating of the mixture can provide the heating required to maintain the reaction temperature in the desired range above the melting point of the sulfur.

P1040 In another specific aspect of the present invention, there is provided a process for removing hydrogen sulfide from a gaseous stream, the process comprising passing the gaseous stream into a mass or volume of the regenerable reaction medium, comprising a base of non-aqueous Lewis, having a pKj- value, of about 6 to about 11, which has the capacity to absorb sulfur dioxide in an amount sufficient to remove practically all of the hydrogen sulfide from the gas stream, notwithstanding the variations in short term in the stoichiometric balance between hydrogen sulphide and sulfur dioxide in the reaction medium and containing a reaction product of sulfur dioxide and non-aqueous Lewis base to absorb sulfur dioxide from the gas stream and for reacting the hydrogen sulphide absorbed with the sulfur dioxide of the reaction product, in accordance with the equation: 2H2S + S02 - > 3S + 2H20 to form sulfur in the reactor, vent the gas stream with reduced content of hydrogen sulphide from the top of the reactor, above the reaction medium and allow the sulfur produced to settle in the lower portion of the reactor . The gas stream containing hydrogen sulfide can be passed into the mass or volume of the reaction medium by a distributor into the mass of the reaction medium to distribute, adjacent to the lower end of the reactor, the gas stream in shape of small bubbles. The procedure can be operated as a continuous or intermittent process and is particularly useful for debugging operations. The depletion of the capacity of the mass or volume of the reaction medium to absorb and convert sulfur to hydrogen sulfide can be detected in any convenient way and the spent reaction medium is then replaced by a regenerated reaction medium containing the product of reaction or is regenerated by the addition of sulfur dioxide. The sulfur can be removed from the reaction medium as required.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic flow chart of a continuous process for the removal of hydrogen sulphide to sweeten a stream of natural gas containing hydrogen sulfide at process operating conditions that can vary widely; and Figure 2 is a schematic flow diagram of a batch purification process for removal of the P1040 Hydrogen sulfide from a gaseous stream containing small amounts of hydrogen sulfide.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Applicants hereby provide two distinct embodiments of the process for the removal of hydrogen sulfide, which are described in more detail below in relation to Figures 1 and 2. In one embodiment of the invention ( Figure 1), a continuous process is provided to sweeten a stream of natural gas containing hydrogen sulfide. In a second embodiment of the invention (Figure 2), a batch process is provided for sweetening natural gas, gas in solution or another industrial gaseous stream contaminated with hydrogen sulfide, which uses regenerable quinoline-sulfur dioxide solutions.

A. Modality of Figure 1: Referring to Figure .1, it shows a continuous process 10 for the removal of hydrogen sulfide from a single reactor, the process is performed on a stream of sulfur-containing natural gas. Typical conditions, concentration, temperature and pressure of wellhead gas are provided, but the process is applicable to a wide range of process conditions, P1040 as will be appreciated by those skilled in the art. The natural gas flows from the well head 12, by means of the standard process equipment (not shown), to a heat exchanger 14, where it is heated to say, approximately 116 ° C and from there it then flows to a heater. gas 16, possibly heated with gas, which further increases the temperature of the gas to, say, about 121 ° C and, preferably, high enough to maintain the temperature of a reactor / contactor 18 to which the heated gas stream is fed above the melting point of the sulfur, to allow the sulfur to be in the molten state. The gaseous stream enters the reactor / contactor 18 by means of a check valve, not shown, which prevents backward flow of gas and the contents of the reactor / contactor 18. In the reactor / contactor 18, which may be a column of bubbles or a packed column, the gas stream is first dispersed through the liquid sulfur layer, removing the dissolved compounds from the sulfur. The gas then flows in direct contact with a reaction medium comprising quinoline, which contains sufficient sulfur dioxide to convert the hydrogen sulfide of the gas to sulfur by the Claus reaction referred to above.

P1040 The sweetened gas then passes through line 19 in a countercurrent flow to the gas inlet through the shell side of heat exchanger 14, where the gas temperature is reduced to say, about 5 ° C above the temperature of the wellhead. Alternatively, when larger amounts of water are involved, the quinoline-water separation can be performed. These procedures ensure that the water produced in the Claus reaction is removed or eliminated. This step is important, since it has been found, in accordance with the data in Table 1, that the dissolved water has a detrimental effect on the efficiency of the liquid Claus reaction in the reaction medium. The sweetened gas, which may have the indicated parameters, is discharged from the heat exchanger 14 via line 20. The condensate that forms on the shell side of the heat exchanger 14, which consists of quinoline, associated compounds and Dissolved sulfur (which is moderately soluble in quinoline) and, in some applications also includes water, flows into tank 21. This step performs the important function of preventing the deposition of condensed sulfur vapor on the heat exchanger tubes. The pump 22 then transfers the condensate back via the line to P1040 the reactor / contactor 18 through a check valve, not shown that prevents return flow. The recycle stream 23 can be heated in the heat exchanger 24 to provide heat to the reactor / contactor 18 together with the gas stream heated in the heat exchanger 16. The pump 22 operates continuously at a constant rate. Replenishment 25 is required to the reaction medium, since the outlet gas is saturated at a temperature of, say, 45 ° C. In view of this, it is desirable to operate the heat exchanger 14 with an approach temperature as low as economically. However, the vapor pressure of quinoline at temperatures below 50 ° C is only 0.00145 psi and, at a total pressure of about 1000 psi, this corresponds to a concentration of 1.45 ppm (v). At a gas flow rate of 5 MMSCFD, the replenishment requirement for quinoline is less than 10 kg / day. The replenishing reaction medium 25 can be pumped from a tank through a check valve (not shown) by a level controlled pump 26, between the appropriate levels of the reaction medium in the reactor / contactor 18. Sulfur dioxide liquid 28 is pumped from a car or other source by the pump 30. The pump is P1040 turns on when a detector 32 detects hydrogen sulfide, typically at a concentration of less than about 1 ppm. The presence of H2S in the outlet stream indicates that S02 has been exhausted in reactor / contactor 18 and hence indicates the need to add new sulfur dioxide reactant. A predetermined volume of sulfur dioxide is then injected into the reactor / contactor 18. Due to the high solubility of the sulfur dioxide in the quinoline, the sulfur dioxide does not escape, even at relatively high loads. The sulfur formed as a melt in the reactor / contactor 18, is discharged through a valve controlled by level (not shown), intermittently, as required, by line 34. Most of the quinoline dissolved in the sulfur is purged by the gaseous current and the sulfur dioxide stream, so that from the system, with the liquid sulfur, little quinoline is lost, if there is such a loss. The reaction medium can be withdrawn from the bottom lower region of reactor / contactor 18 via line 36 and recycled to tank 21 to mix with the condensed materials contained therein and form part of the recycle stream to reactor / contactor 18 of line 23. Although the modality previously discussed with P1040 reference to Figure 1 is preferably operated at reactor / contactor 18 temperatures greater than 120 ° C, the reaction can be performed at lower temperatures and, up to about 155 ° C, although the evaporation of the quinoline (or other Lewis base) non-aqueous) occurs at a much higher rate at higher temperatures, due to the increase in vapor pressure. In general, the Claus reaction process in the reactor / contactor 18 is carried out at a temperature of from about 120 ° to about 155 ° C, preferably from about 120 ° to about 130 ° C.

B. Modality of Figure 2: Referring to Figure 2, there is shown a batching process 50, which is performed on a variety of gaseous streams containing hydrogen sulfide to remove residual amounts of hydrogen sulfide. in a regenerable system. Normally, the known processes of batch cleaning are either regenerable or not regenerable. Several commercial processes depend on regenerable oxides, such as zinc oxide, which is often returned to the supplier for a loan. These systems are frequently used when residual hydrogen sulfide must P1040 be less than a few ppb (v) and are very expensive. Other systems use a non-regenerable absorbent, which can be a solution of chemical compounds, such as sodium hydroxide or aqueous sodium hypochlorite. The cost of these processes can be very high and the disposal of spent chemical solutions can be expensive and difficult. The Sulfatreat commercial process uses a non-regenerable iron compound. Like all non-regenerative batching processes, the operating costs of this system can be very high when there is a significant amount of hydrogen sulfide in the gas. The main economic advantage of the process, in accordance with this embodiment of the invention, lies in the high capacity for hydrogen sulfide, with respect to other processes and the simplicity and ease of regeneration of the absorbent solution, which, again, depends of the liquid Claus reaction in the reaction medium comprising non-aqueous Lewis bases, such as quinoline. Referring now to Figure 2, an industrial gas stream 52, which may be natural gas, gas in solution or other industrial gas, is passed through a heater 54, which is optional. The heater may be necessary if the gas stream is saturated and / or contains a water mist, since the water P1040 dissolved inhibits the process in quinoline, as mentioned above. The gas, optionally heated, flows through a shut-off valve (not shown) to a gas distributor inside the absorption / reaction vessel 56. The gas is distributed in the form of small bubbles thanks to a distributor plate in the lower part of the vessel or reactor 56. The vessel 56 contains a solution of sulfur dioxide and the reaction product of the sulfur dioxide and a non-aqueous Lewis base, preferably quinoline, in the reaction medium. Hydrogen sulfide is absorbed by the solution and reacts with the sulfur dioxide contained in it, producing sulfur and water. The way in which sulfur is obtained depends on the operating temperature of the process. Sulfur agglomerates and settles at the bottom of the reactor. The gas treated, with a reduced content of hydrogen sulfide, flows through a mist eliminator (river shown) and through a shut-off valve (not shown as cleaned or cleaned gas 58. The contact of the gas stream with the The reaction medium also removes particulate matter, including condensed vapors, which can remain in solution or can be absorbed into the sulfur.When the sulfur dioxide reactant is exhausted in the system, P1040 is detected in any suitable manner, such as, for example, a hydrogen sulfide detector 32, as used in Figure 1, all equipment, including reactor 56 and associated valves, can be taken out of service and replaced by an identical newly regenerated system. The exhausted system can then be plugged and sent to a central regeneration facility. Alternatively, the content can be removed from the container 56 and replaced by a freshly regenerated solution or it can be regenerated in itself. In the regeneration plant, the sulfur and the reaction medium can be separated by conventional technology and, if desired, the sulfur can be further processed to remove other impurities. The economic advantages of this process are important, and are related to its simplicity, its ability to absorb sulfur dioxide, its completely regenerable chemistry and the low losses of the reagent.

EXAMPLES Example 1 This example illustrates the removal of hydrogen sulphide and sulfur dioxide from gas streams, using non-aqueous Lewis bases.

P1040 The experiments were carried out in a glass container with a bubble tube having an internal diameter of 45 mm and a height of 380 mm. A tube 6 mm in diameter extends inside the container from the top to 30 mm before the bottom of the container, which was used for the introduction of gaseous mixtures into the liquid contained in the container. Attached to the bottom of this glass tube was a porous glass bubbler that dispersed the gas phase into fine bubbles within the liquid phase. A 6 mm diameter glass tube, placed in the upper perimeter of the container, allowed the ventilation of the contact gases. The results obtained at room temperature and atmospheric pressure are summarized in the following Tables I and ?? P1040 TABLE I Effect of Water on Kinetics of Claus-quinoline Reaction P1040 With respect to the results presented in Table I, it can be observed that the presence of 5 percent by volume of water in the quinoline does not affect the reaction kinetics or the stoichiometry of the H ^ s removal but, that the presence of 20 percent by volume of water drastically reduces the removal of H ^ s, probably as a result of the reaction of S02 with water, at the same time as with H2S.

P1040 tJ o? »TABLE II tO U1 With respect to the results presented in Table II, the following observations can be made: (i) the results of tests 1, 2, 3, 6 and 7 indicate that the total elimination of hydrogen sulphide can be achieved in the reaction medium.; (ii) the results of tests 1, 2 and 6 also indicate (for stoichiometries greater than 2: 1) some absorbent capacity of the reaction medium for hydrogen sulfide; (iii) the results of tests 3, 4, 5 and 7 indicate (for stoichiometries greater than 2: 1) an important absorption capacity of the reaction medium for sulfur dioxide; (iv) the results of tests 4 and 5 indicate that the presence of carbon dioxide in the feed gas can inhibit the absorption of hydrogen sulphide.

SUMMARY OF THE EXPOSURE In the summary of this disclosure, the present invention provides processes for the removal or removal of hydrogen sulfide from a gas stream, using the reaction of the Claus process with sulfur dioxide to form sulfur in a liquid process P1040 using a reaction medium comprising quinoline or other non-aqueous Lewis bases with pK] - values, from about 6 to about 11. Modifications are possible within the scope of this invention.

P1040

Claims (23)

CLAIMS; A process for the removal of hydrogen sulphide from a gas stream by reaction with sulfur dioxide, characterized by carrying out the reaction in a reaction medium comprising a non-aqueous Lewis base with a value of pKj-, range of 6 to 11 and because the reaction medium: a) absorbs sulfur dioxide and chemically reacts with it to form a reaction product; b) absorbs hydrogen sulfide; c) removes the hydrogen sulfide from the gas stream by contact with the gas stream with the reaction medium in the presence of free sulfur dioxide and / or the reaction product; d) acts as a catalyst for the overall reaction of hydrogen sulfide with sulfur dioxide to produce sulfur; and (e) has the capacity to absorb sulfur dioxide in sufficient quantity to remove practically all of the hydrogen sulfide from the gas stream, notwithstanding the short-term variations in the stoichiometric balance between hydrogen sulfide and sulfur dioxide in he
1. P1040 reaction medium. ,
2. 2 . The process according to claim 1, characterized in that the sulfur dioxide is continuously absorbed by the reaction medium to react with the hydrogen sulfide in the gas stream to produce sulfur and where the sulfur produced is removed. The process according to claim 1 or 2, characterized in that the gas stream is contacted intermittently or continuously with a mass or volume of the reaction medium to react the hydrogen sulfide with the sulfur dioxide in the product of reaction and form sulfur, until the reaction medium depletes its ability to react with hydrogen sulfide. 4. The process according to claim 3, characterized in that the spent reaction medium is regenerated. 5. The process according to claim 4, characterized in that the regeneration is effected by the addition of sulfur dioxide. 6. A continuous process for the removal of hydrogen sulfide from a gas stream, characterized by: contacting a reaction medium comprising a non-aqueous Lewis base having a value of P1040 pKj-, from 6 to 11 and having the capacity to absorb sulfur dioxide in sufficient quantity to eliminate practically all the hydrogen sulfide from the gas stream, notwithstanding the short-term variations in the stoichiometric balance between hydrogen sulphide and the sulfur dioxide in the reaction medium, wherein the gas stream in the presence of the sulfur dioxide of the reaction medium reacts with the hydrogen sulfide at a temperature above the melting point of the sulfur to form liquid sulfur, in accordance with the equation: 2H2S + S02? 3S + 2H20 in the upper region of a reactor; accumulate liquid sulfur from the reaction as a layer in the lower region of the reactor below the reaction medium; venting the gas stream from the reactor with reduced content of hydrogen sulphide; and remove liquid sulfur from the liquid sulfur layer. The process according to claim 6, characterized in that the sulfur dioxide is passed upwards through the layer of liquid sulfur to remove the dissolved components therefrom and then the reaction medium, to provide the bioxide therein. sulfur for the reaction with hydrogen sulfide. P1040 8. The process according to claim 6 or 7, which is carried out on an acidulated natural gas stream and characterized in that: the stream of acidulated natural gas is passed to the reactor; the acidified natural gas stream is dispersed in the reactor; and the resulting stream of sweetened gas is removed from the reactor as a ventilated gas stream. 9. The process according to claim 8, characterized in that the acidified gas stream is heated first to a temperature close to at least the melting point of the sulfur and then passed to the reactor. 10. The process according to claim 9, characterized in that the heating of the stream of acidified gas to the aforesaid temperature is effected, at least partially, by passing the current in a heat exchange relationship with the stream of sweetened gas withdrawn, which thereby realizes cooling of the gas. sweetened gas stream withdrawn. 11. The process according to any of claims 8 to 10, characterized in that the acidified gas stream is dispersed in the liquid sulfur layer and the dispersed gas stream is allowed to pass through. P1040 up through the liquid sulfur layer and into direct contact with the reaction medium containing sulfur dioxide in an amount sufficient to at least convert to sulfur virtually all the hydrogen sulfide of the gas stream. The process according to any of claims 8 to 11, characterized in that the stream of removed sweetened gas is cooled to remove the condensable compounds therefrom and the resulting flow of cooled sweetened gas is recovered as the product of the process. The process according to claim 12, characterized in that the condensable compounds are collected and comprise the non-aqueous condensed Lewis base, associated compounds and dissolved sulfur and the collected condensable compounds are recycled to the reactor. The process according to claim 13, characterized in that the reaction medium is recycled into the reactor by mixing a stream of the reaction medium from the reactor with the condensable compounds collected and by recirculating the mixture to the reactor. 15. The process according to any of claims 1 to 14, characterized in that the reaction is carried out at a temperature of 120 ° to 155 ° C. P1040 16. The process according to claim 15, characterized in that the temperature is 120 ° to 130 ° C. 17. A process for the removal of hydrogen sulphide from a gas stream, characterized by: passing the gas stream to a mass of the regenerable reaction medium, which comprises a non-aqueous Lewis base having a value of pKj -, from 6 to 11 and which has the capacity to absorb sulfur dioxide in sufficient quantity to eliminate practically all hydrogen sulfide from the gas stream, notwithstanding the short-term variations in the stoichiometric balance between hydrogen sulfide and the sulfur dioxide in the reaction medium and containing a reaction product of sulfur dioxide and the non-aqueous Lewis base to absorb the hydrogen sulfide from the gas stream and to react the hydrogen sulfide absorbed with the dioxide of sulfur of the reaction product, in accordance with the equation: 2H2S + S02? 3S + 2H20 to form sulfur in a reactor; and venting a gas stream with reduced content of hydrogen sulfide from the upper portion of the reactor, above the reactor medium and allowing the sulfur produced to settle in the lower part of the reactor. P1040 18. The method according to claim 17, further characterized by detecting the depletion of the mass capacity of the reaction medium to absorb and convert hydrogen sulfide to sulfur and the mass or volume of the spent reaction medium is replaced with a medium of regenerated reaction containing the reaction product. 19. The method according to claim 18, characterized in that the regeneration is effected by an in-situ reaction with sulfur dioxide. The process according to any of claims 1 to 19, characterized in that the non-aqueous Lewis base has a value of pK] -, from 8 to 10. The process according to claim 20, characterized in that the non-aqueous base is quinoline 22. The process according to any of claims 1 to 21, characterized in that the reaction medium consists essentially of a non-aqueous Lewis base. 2
3. 3. The process according to any of claims 1 to 22, characterized in that the reaction medium further comprises a miscible diluent with a vapor pressure below 0.39 psi at a temperature of 120 ° C. P1040