Enhancement of claus tail gas treatment by sulfur dioxide-selective membrane technology

Abstract

A method for increasing sulfur recovery from an acid gas feed comprising the steps of introducing the acid gas feed and a sulfur dioxide enriched air stream to a Claus process to produce a product gas stream, introducing the product gas stream to a thermal oxidizer to produce a flue gas stream, cooling the flue gas stream to produce a cooled take-off stream, separating the cooled take-off stream into a saturated gas stream, heating the saturated gas stream to produce a membrane gas stream, introducing the membrane gas stream to a membrane sweeping unit, the membrane sweeping unit comprises a membrane, the sulfur dioxide in the membrane gas stream permeates the membrane of the membrane sweeping unit, introducing a sweep air stream, the sweep air stream collects the sulfur dioxide to create the sulfur dioxide enriched air stream.

Claims

1. A method for increasing sulfur recovery from an acid gas feed, the method comprising the steps of: introducing the acid gas feed and a sulfur dioxide enriched air stream to a Claus process to produce a product gas stream and a recovered sulfur stream, wherein the acid gas feed comprises hydrogen sulfide, wherein the hydrogen sulfide is present in a hydrogen sulfide concentration, wherein the sulfur dioxide enriched air stream comprises sulfur dioxide and air; introducing the product gas stream to a thermal oxidizer to produce a flue gas stream, the thermal oxidizer configured to convert sulfur containing compounds in the product gas stream to sulfur dioxide; introducing the flue gas stream to a membrane sweeping unit, wherein the membrane sweeping unit comprises a membrane, wherein the membrane sweeping unit is configured to produce a sulfur dioxide depleted stream, wherein the sulfur dioxide in the flue gas stream permeates the membrane of the membrane sweeping unit to a permeate side; and introducing a sweep air stream to the permeate side, wherein the sweep air stream collects the sulfur dioxide that permeates the membrane of the membrane sweeping unit to create the sulfur dioxide enriched air stream.

2. The method of claim 1, further comprising the step of feeding the sulfur dioxide depleted stream to an incinerator stack.

3. The method of claim 1, further comprising the steps of heating the sulfur dioxide depleted stream in a reheater to produce a heated stack feed, wherein the heated stack feed is at a stack temperature; and feeding the heated stack feed to an incinerator stack.

4. The method of claim 1, wherein the membrane is an [emim][BF4] ionic liquid supported on a polyethersulfone.

5. The method of claim 1, wherein the membrane is selected from the group consisting of polydimethylsiloxane (PDMS), polyphosphazenes, PEBAX (polyether block amide), polyamide-polyether block copolymers, cellulose acetate, cellulose acetate impregnated with TEG-DME, cellulose diacetate, cellulose triacetate, Nafion 117 (perfluorosulfonic acid), rubbery Nafion (perfluorosulfonic acid), sulfonated polyimides, sulfonated polymers, supported ionic liquid membranes (SILMs), polycarbonate, membrane contactors, polyethylene glycol (PEG), polyacrylate, sulfolane, polytrimethylsilyl methyl methacrylate (PTMSMMA), and 3-methylsulfolane blend membranes.

6. The method of claim 1, wherein the hydrogen sulfide concentration is greater than 25%.

7. The method of claim 1, wherein a sulfur recovery is greater than 99.2 wt %.

8. An apparatus for increasing sulfur recovery from an acid gas feed, the apparatus comprising: a Claus process, the Claus process configured to receive the acid gas feed and a sulfur dioxide enriched air stream to produce a product gas stream and a recovered sulfur stream, wherein the acid gas feed comprises hydrogen sulfide, wherein the hydrogen sulfide is present in a hydrogen sulfide concentration, wherein the sulfur dioxide enriched air stream comprises sulfur dioxide and air, wherein the product gas stream comprises sulfur containing compounds; a thermal oxidizer, the thermal oxidizer configured to convert the sulfur containing compounds to sulfur dioxide to produce a flue gas stream, wherein the flue gas stream comprises sulfur dioxide, water vapor, oxygen, nitrogen, and carbon dioxide; and a membrane sweeping unit, wherein the membrane sweeping unit comprises a membrane, wherein the membrane sweeping unit is configured to produce a sulfur dioxide depleted stream, wherein the sulfur dioxide in the flue gas stream permeates the membrane of the membrane sweeping unit to a permeate side, wherein a sweep air stream fed to the permeate side of the membrane sweeping unit is operable to collect the sulfur dioxide that permeates the membrane of the membrane sweeping unit to create the sulfur dioxide enriched air stream.

9. The apparatus of claim 8, further comprising an incinerator stack, the incinerator stack configured to disseminate the sulfur dioxide depleted stream to the atmosphere.

10. The apparatus of claim 8, wherein the membrane is an [emim][BF4] ionic liquid supported on a polyethersulfone.

11. The apparatus of claim 8, wherein the membrane is selected from the group consisting of polydimethylsiloxane (PDMS), polyphosphazenes, PEBAX (polyether block amide), polyamide-polyether block copolymers, cellulose acetate, cellulose acetate impregnated with TEG-DME, cellulose diacetate, cellulose triacetate, Nafion 117 (perfluorosulfonic acid), rubbery Nafion (perfluorosulfonic acid), sulfonated polyimides, sulfonated polymers, supported ionic liquid membranes (SILMs), polycarbonate, membrane contactors, polyethylene glycol (PEG), polyacrylate, sulfolane, polytrimethylsilyl methyl methacrylate (PTMSMMA), and 3-methylsulfolane blend membranes.

12. The apparatus of claim 8, wherein the hydrogen sulfide concentration is greater than 25%.

13. The apparatus of claim 8, wherein a sulfur recovery is greater than 99.2 wt %.

14. The apparatus of claim 8, wherein the Claus process comprises a thermal stage and a catalytic stage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of the present invention will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

(2) FIG. 1 is a process flow diagram of the process of the invention.

(3) FIG. 2 is a process flow diagram of the process of the invention.

(4) FIG. 3 is a process flow diagram of the process of the invention.

(5) FIG. 4 is a process flow diagram of the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(6) While the invention will be described with several embodiments, it is understood that one of ordinary skill in the relevant art will appreciate that many examples, variations and alterations to the apparatus and methods described herein are within the scope and spirit of the invention. Accordingly, the exemplary embodiments of the invention described herein are set forth without any loss of generality, and without imposing limitations, on the claimed invention.

(7) According to a method of the invention, SO.sub.2 is removed from a tail gas stream containing CO.sub.2, H.sub.2O, N.sub.2 and O.sub.2 using a SO.sub.2-selective membrane. In at least one instance of the present invention, the air feed supplied to the reaction furnace of the Claus unit sweeps the permeate side of the SO.sub.2-selective membrane prior to being supplied to the Claus furnace, in doing so the air feed becomes a SO.sub.2-enriched air feed to the reaction furnace. Sweep as used herein means that the stream passes continuously by the membrane, such that the permeate does not sit statically against the permeate side of the membrane, such that the sweep provides the driving force of the permeate. The air sweep lowers the SO.sub.2 concentration on the permeate side of the membrane, thereby causing more SO.sub.2 to be drawn into the membrane from the flue gas stream and sent, along with the air sweep, to the Claus unit. With the air sweep, the SO.sub.2 concentration on the permeate side is lower than the SO.sub.2 on the feed side of the membrane. The air sweep and the SO.sub.2-enriched air feed recovers a fraction of the SO.sub.2 that would otherwise have been released to the atmosphere through an incinerator stack, and by recovering the SO.sub.2 and directing the SO.sub.2-enriched air feed to the Claus furnace, the process provides controlled slippage of SO.sub.2 to the atmosphere at the incinerator stack in order to meet environmental regulations or other process targets. In at least one instance of the present invention, the use of the SO.sub.2-selective membrane minimizes SO.sub.2 emissions from an incinerator stack. In one instance of the invention, the SO.sub.2-selective membrane recovers sulfur dioxide from the exhaust gas of the thermal oxidizer before the exhaust gas is fed to an incinerator stack. The recovered sulfur dioxide is collected by sweeping the permeate side with an air stream, which creates a sulfur dioxide rich air stream. The sulfur dioxide rich air stream can be fed to the reaction furnace of the Claus process, along with a raw air feed, and an acid gas stream. In at least one instance of the present invention, the use of the SO.sub.2-selective membrane improves the Claus unit operability and efficiency to maximize elemental sulfur recovery and minimizes SO.sub.2 emissions from an incinerator stack. In at least one instance of the present invention, the SO.sub.2-selective membrane can be retrofitted to an existing Claus unit or modified Claus process, regardless of the Claus unit and tail gas treatment unit. In at least one instance of the present invention, the SO.sub.2-selective membrane can be a substitute for a tail gas treatment unit, being installed between the thermal oxidizer and the incinerator stack, and has the advantage of minimizing additional mechanical features by avoiding the need for additional rotating equipment, such as blowers.

(8) The use of the SO.sub.2-selective membrane is based upon gas component separation with membranes that exhibit durable high SO.sub.2/CO.sub.2 and SO.sub.2/N.sub.2 selectivity. These selective membranes minimize recirculation of inert gases potentially present in the flue gas, such as CO.sub.2 and N.sub.2. The membrane produces a SO.sub.2-concentrated permeate fraction, which is fed to the reaction furnace of the Claus unit along with the air supply. The membrane also produces an SO.sub.2-depleted reject (retentate) fraction, mainly containing inert gases, which are released to the atmosphere.

(9) Referring to FIG. 1, acid gas feed 1 is introduced to Claus process 100 along with sulfur dioxide enriched air stream 5. Acid gas feed 1 can be any source of acid gas or sour gas, containing H.sub.2S, CO.sub.2, and combinations thereof. Acid gas feed 1 contains H.sub.2S in an amount greater than 25% by weight on a dry basis, alternately greater than 40% by weight on a dry basis, alternately greater than 55% by weight on a dry basis, alternately greater than 70% by weight on a dry basis, greater than 75% by weight on a dry basis, alternately greater than 80% by weight on a dry basis, and alternately greater than 99% by weight on a dry basis. As used herein on a dry basis means as calculated without water or water vapor.

(10) Claus process 100 is a Claus process or modified Claus process, a known process for recovering elemental sulfur from H.sub.2S, through combustion and catalytic reactions that includes a thermal stage, such a reaction furnace (not shown), and a catalytic stage, such as catalytic reactors (not shown). Claus process 100 produces recovered sulfur stream 7 and product gas stream 8. Recovered sulfur stream 7 is a liquid stream of elemental sulfur sent to storage or a sulfur pit for further use or processing. Without being bound to a particular theory, it is believed that the stable form of sulfur that can be separated as a liquid from the process is S.sub.8. Product gas stream 8 includes sulfur containing compounds SO.sub.2, CO.sub.2, air (O.sub.2, N.sub.2, and Argon (Ar)), and water vapor (H.sub.2O). As used herein, sulfur containing compounds includes H.sub.2S and other sulfur containing compounds. Product gas stream 8 enters thermal oxidizer 200 along with thermal oxidizer air feed 9 to generate flue gas stream 10.

(11) Thermal oxidizer 200 can be any thermal oxidizer capable of providing a combustion temperature to convert the sulfur containing compounds, including H.sub.2S, in product gas stream 8 into SO.sub.2. Thermal oxidizer air feed 9 can be any source of air, oxygen, or oxygen-enriched air. Thermal oxidizer air feed 9 can be the same source of air as air feed 2. Thermal oxidizer air feed 9 is fed to thermal oxidizer 200 in excess of the volume necessary to combust the remaining H.sub.2S and other sulfur containing compounds in product gas stream 8, such that flue gas stream 10 contains SO.sub.2, O.sub.2, N.sub.2, CO.sub.2, H.sub.2O, and combinations thereof. Flue gas stream 10 can contain other inert gases present in air. Flue gas stream 10 is introduced to membrane sweeping unit 700.

(12) Membrane sweeping unit 700 is any membrane capable of separating sulfur dioxide from flue gas stream 10. Polymeric membranes are able to separate one or more gases from a feed mixture generating a permeate containing a specific gas enriched stream. Membrane permeability characterizes performance and is dictated by flux and selectivity for a specific gas molecule. Separation is dependent on the physical-chemical interaction of gases with the polymeric membrane. Permeability is expressed in GPU (Gas Permeation Units) or barrer. Exemplary membranes include membranes made from polydimethylsiloxane (PDMS), polyphosphazenes, PEBAX (polyether block amide), polyamide-polyether block copolymers, cellulose acetate, cellulose acetate impregnated with TEG-DME, cellulose diacetate, cellulose triacetate, Nafion 117, rubbery Nafion, sulfonated polyimides, sulfonated polymers, supported ionic liquid membranes (SILMs), polycarbonate, membrane contactors, polyethylene glycol (PEG), polyacrylate, sulfolane, polytrimethylsilyl methyl methacrylate (PTMSMMA), and 3-methylsulfolane blend membranes.

(13) Ionic liquid membranes are membranes that are doped with liquid ionic compounds. Preferably, the liquid ionic compounds have non-nucleophilic anions, such non-nucleophilic anions increase the SO.sub.2 content in the permeate by preferential solubility, permeability and selectivity of the components in the LICs. The use of LICs in membrane sweeping unit 700 takes advantage of low vapor pressure which avoids the loss of the liquids due to evaporation from the pores of the membrane and the preferential solubility of SO.sub.2 in ionic liquids. Exemplary SILM membranes include membranes impregnated with carboxylate-based ILs (including mono-carboxylates and dicarboxylates), membranes impregnated with 1-butyl-3-methylimidazolium 2-formylbenzenesulfonate (BMIM OFBS), membranes impregnated with 1-allyl-3-methylimidazolium 2-formylbenzenesulfonate (AMIM OFBS), [N222] [dimalonate] IL supported on polyethersulfone (PES), and [emim][BF4] IL supported on polyethersulfone (PES).

(14) In at least one embodiment of the present invention, membrane sweeping unit 700 is a [emim][BF4] ionic liquid supported on a polyethersulfone. An [emim][BF4] ionic liquid supported on a polyethersulfone type membrane has increased SO.sub.2 permeability due to the presence of the active carrier, [emim][BF4] ionic liquid.

(15) One of skill in the art will appreciate that the size, permeability, and selectivity of membrane sweeping unit 700 are design features based on the requirements of the system. While in general the larger the surface area, the greater the recovery, there is a tipping point at which the economics make it unfeasible to increase the surface area of the membrane. The type of membrane selected is in consideration of the desired permeability and selectivity of the membrane and the acid gas feed composition.

(16) Flue gas stream 10 contacts membrane sweeping unit 700. SO.sub.2 in flue gas stream 10 permeates through membrane sweeping unit 700 to the permeate side of membrane sweeping unit 700. Air feed 2 provides a continuous stream of air to sweep the permeate side of membrane sweeping unit 700.

(17) Air feed 2 is any source of air, oxygen, or oxygen enriched air. In at least one embodiment of the present invention, an oxygen enrichment membrane system (not show) can be utilized to create oxygen enriched air from a raw air stream, where oxygen enrichment membrane system uses an oxygen selective membrane to separate oxygen from an air stream. The oxygen enrichment membrane system can be any system of membranes capable of extracting oxygen from an air stream to provide enriched air or a pure oxygen stream. The oxygen enrichment membrane system can be those known to one of skill in the art. The oxygen enriched air can be used as air feed 2 to sweep membrane sweeping unit 700. Alternately, the oxygen enriched air can be used as a direct feed to Claus process 100 or thermal oxidizer 200, or both. Oxygen enrichment of the combustion air to the reaction furnace of Claus process 100 improves (increases) capacity and improves the ability to handle contaminants. Without being bound to a particular theory, it is believed that the capacity of the reaction furnace is increased with oxygen enrichment due to the need for less gas flow (the more oxygen in the stream, the lower the overall flow needed) into the Claus furnace. Expanding capacity with oxygen enrichment can be used for handling extra acid gas loading at significantly reduced capital expense. Increased oxygen content in the reaction furnace of Claus process 100 increases flame temperature, which helps destroy contaminants and increase sulfur recovery. An oxygen selective membrane system is advantageous over other types of oxygen recovery units because it does not require significant operating costs due to high energy demands.

(18) The SO.sub.2 that reaches the permeate side of membrane sweeping unit 700 is collected and exits membrane sweeping unit 700 as sulfur dioxide enriched air stream 5. Sulfur dioxide enriched air stream 5 is fed to the thermal reaction stage of Claus process 100. Sulfur dioxide enriched air stream can include sulfur dioxide and air. Oxygen is a component of air. Sulfur dioxide is a reactant in the Claus reaction to recover elemental sulfur.

(19) In at least one embodiment, sulfur dioxide enriched air stream 5 can increase the flame temperature within the reaction furnace of the thermal stage of Claus process 100. In at least one embodiment, sulfur dioxide enriched air stream 5 can decrease the flame temperature within the reaction furnace of the thermal stage of Claus process 100. The decrease in flame temperature can be between about 65 C. and about 10 C., alternately between about 60 C. and about 10 C., alternately between about 50 C. and about 10 C., alternately between about 40 C. and about 10 C., alternately between about 30 C. and about 10 C., and alternately between about 20 C. and about 10 C. In at least one embodiment, sulfur dioxide enriched air stream 5 has a minimal impact (less than 10 degrees) on the flame temperature within the reaction furnace of the thermal stage of Claus process 100. In at least one embodiment, sulfur dioxide enriched air stream 5 can be preheated in a heating unit (not shown) to maintain or increase the temperature in the reaction furnace. The impact on flame temperature is due to overall mass flow rate, overall composition of the feed to the reaction furnace. The overall composition of the feed is influenced by the amount of sulfur recovered and the amount of sulfur dioxide recycled to the reaction furnace.

(20) The remaining gases from flue gas stream 10 form the retentate and exit membrane sweeping unit 700 as sulfur dioxide depleted stream 17. Sulfur dioxide depleted stream 17 contains less than 1 vol % sulfur dioxide, alternately less than 0.5 vol % sulfur dioxide, alternately less than 0.1 vol % sulfur dioxide, alternately less than 0.05 vol % sulfur dioxide, and alternately less than 0.01 vol % sulfur dioxide. Sulfur dioxide depleted stream 17 is introduced to incinerator stack 300. In at least one embodiment of the present invention, the method of the present invention is in the absence of recycling sulfur dioxide depleted stream 17 to the membrane sweeping unit, such as, for example mixing sulfur dioxide depleted stream 17 with flue gas stream 10. Without being bound to a particular theory, it is understood that recycling sulfur dioxide depleted stream 17 will reduce the SO.sub.2 concentration, and as a result the partial pressure of sulfur dioxide. Reducing the SO.sub.2 concentration reduces emissions from a Claus Unit, which are linked to SO.sub.2 concentration and flow.

(21) Incinerator stack 300 can be any type of incinerator stack capable of heating the remaining gases in sulfur dioxide depleted stream 17 for dissemination in the atmosphere as stack vent stream 19. All species in sulfur dioxide depleted stream 17 are oxidized to their final oxidation state in incinerator stack 300.

(22) The overall sulfur recovery can be greater than 99.0%, alternately greater than 99.2%, alternately greater than 99.4%, alternately greater than 99.6%, and alternately greater than 99.8%.

(23) With the use of instrumentation, the entire system can be monitored to minimize the SO.sub.2 being discharged in stack vent stream 19. Instrumentation can be used to measure the SO.sub.2 in sulfur dioxide enriched air stream 5 and air demand in Claus process 100 to adjust the flow rate of air feed 2. Instrumentation can be used to adjust the flows of the streams based on the amount of SO.sub.2 in stack vent stream 19. In one instance, a tail gas analyzer can be used to measure SO.sub.2 in any of the process streams associated with FIG. 1.

(24) Referring to FIG. 2, an embodiment of the invention is described with reference to FIG. 1. Flue gas stream 10 is fed to cooler 400.

(25) Cooler 400 lowers the temperature of flue gas stream 10 to a temperature below the dew point of water to produce cooled take-off stream 13. Cooler 400 can be any type of heat exchanger capable of cooling a gas stream. In at least one embodiment of the present invention, cooler 400 is a quench tower. Cooled take-off stream 13 is at a temperature at or just below the dew point of water, such that any water vapor present in flue gas stream 10 is condensable.

(26) Liquid-gas separation unit 500 is any type of separation unit capable of separating the vapor from the liquid in cooled take-off stream 13 to produce condensed water 14 and saturated gas stream 15. In at least one embodiment, liquid-gas separation unit 500 is a knock out drum. Condensed water 14 contains the water condensed from cooled take-off stream 13. Condensed water 14 can be sent to be further processed or collected for storage. Saturated gas stream 15 contains those gases from flue gas stream 10 that were not condensed in liquid-gas separation unit 500. Saturated gas stream 15 is introduced to heater 600 to produce membrane gas stream 16.

(27) Heater 600 heats saturated gas stream 15 above the dew point of the gases present in saturated gas stream 15 to ensure no liquids are present in membrane gas stream 16. Heater 600 can be any type of heat exchanger capable of heating a gas stream. Membrane gas stream 16 is fed to membrane sweeping unit 700. Sulfur dioxide present in membrane gas stream 16 permeates through membrane sweeping unit 700 and is collected in sweep air stream 3 to produce sulfur dioxide enriched air stream 5. Sweep air stream 3 drives the sulfur dioxide from membrane gas stream 16 across the membrane of membrane sweeping unit 700. In at least one embodiment, sweep air stream 3 enhances the separation and collection of the sulfur dioxide that permeates through the membrane of membrane sweeping unit 700.

(28) Air feed 2 is split into sweep air stream 3 and air bypass stream 4. The flow rate of air bypass stream 4 can be determined based on the composition of acid gas feed 1, the membrane characteristics of membrane sweeping unit 700, the flue gas composition, the target rate for SO.sub.2 in stack vent stream 19, the mandated rate of emissions of SO.sub.2 in stack vent stream 19, or combinations of the same. Sulfur dioxide enriched air stream 5 is combined with air bypass stream 4 to produce combined air feed 6. Combined air feed 6 is fed to Claus process 100 along with acid gas feed 1.

(29) The retentate of membrane sweeping unit 700 can be depleted of sulfur dioxide and forms sulfur dioxide depleted stream 17. Sulfur dioxide depleted stream 17 is fed to incinerator stack 300. Incinerator stack 300 burns the components present in sulfur dioxide depleted stream 17 before releasing them into the atmosphere as stack vent stream 19.

(30) Referring to FIG. 3, a method of the invention is provided. In embodiments where the temperature of the feed to incinerator stack 300 needs to be increased to meet or exceed dispersion requirements, sulfur dioxide depleted stream 17 can be fed to reheater 800 to produce heated stack feed 20. Dispersion requirements refers to the need for the gas exciting incinerator stack 300 to be hot to ensure good sulfur dioxide dispersion from the tip of the stack. Reheater 800 can be any heat exchanger capable of increasing the temperature of sulfur dioxide depleted stream 17. Heated stack feed 20 has a stack temperature. In at least one embodiment, the stack temperature is 480 C. Heated stack feed 20 is fed to incinerator stack 300.

(31) Referring to FIG. 4, a method of the invention is provided that includes a bypass stream to bypass the membrane and is described with reference to FIG. 1 and FIG. 2. Flue gas stream 10 can be split into membrane bypass stream 11 and effluent take-off stream 12. The flow rate of membrane bypass stream 11 can be determined based on the composition of acid gas feed 1, the membrane characteristics of membrane sweeping unit 700, the flue gas composition, the target rate for SO.sub.2 in stack vent stream 19, the mandated rate of emissions of SO.sub.2 in stack vent stream 19, or combinations of the same. In certain embodiments, effluent take-off stream 12 includes the entire volumetric flow rate from flue gas stream 10. Effluent take-off stream 12 is introduced to cooler 400. In certain embodiments of the invention, sulfur dioxide depleted stream 17 can be combined with membrane bypass stream 11 to form stack feed stream 18. Stack feed stream 18 is fed to incinerator stack 300. In at least one embodiment, membrane bypass stream 11 is used when cleaning or maintenance is being performed on membrane sweeping unit 700 and the flow rate of sulfur dioxide depleted stream 17 is zero and membrane bypass stream 11 becomes stack feed stream 18. In at least one embodiment, membrane bypass stream 11 is used when the concentration of sulfur dioxide in flue gas stream 10 is below a threshold, such that only a partial stream from flue gas stream 10 is sent to membrane sweeping unit 700 and is adequate to maintain overall system sulfur dioxide emissions below regulated levels.

(32) Membrane sweeping unit 700 is in the absence of adsorbent. Without having adsorbent to replace, membrane sweeping unit 700 has lower operating costs. Advantageously, the absence of adsorbent eliminates the need to shut down the entire process as each membrane module runs on a bypass, which can be purged and that membrane replaced without having to take any of the other modules offline. Membrane sweeping unit 700 is in the absence of solvent. Without having solvent, there is not solvent to replace, without having a solvent to replace, membrane sweeping unit 700 has lower operating costs. Membrane sweeping unit 700 is in the absence of catalyst.

(33) Advantageously, the use of membranes in the process of the invention reduces or eliminates the need for rotating equipment, including for rotating equipment used in gas compression. The membranes do not require rotating equipment for their operation, beyond what is being used in other parts of the process, such as compression of the air used in the air sweep. In addition, as the driving force of the membrane is provided by the air sweep, the gas in the membrane gas feed does not need to be compressed. The use of membranes lowers waste gas content by increasing the overall sulfur recovery efficiency over systems that are in the absence of membranes. The permeate side of the membrane is in the absence of vacuum suction or low pressure conditions. The membrane gas feed is in the absence of a compression step, such as in a compressor. In at least one embodiment, the membrane sweeping unit is in the absence of a recycle around the membrane sweeping unit, that is where a portion of the permeate is recycled to the feed side of the membrane.

EXAMPLES

(34) Throughout the examples, references will be made to types of membranes for use in the various separation units. Table 1 includes a list of selected properties for exemplary membranes useful in the separation units of the present invention. The data in Table 1 was collected from independently developed data.

(35) TABLE-US-00001 TABLE 1 Properties of exemplary membranes Membrane Properties Cellulose Properties Polyvinylidene Acetate Kinetic fluoride (w/18 wt. impregnated PEI/Pebax Gas NBP, Diameter, Pebax 1657 PEI/Pebax 1657 % sulfone) with TEG-DME 3353 (HFM) Components C.[1] [1] .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU H.sub.2S 60 3.6 1.42.sup.b 141.57 0.93.sup.e 93.5 CO.sub.2 78 3.3 1 100.00.sup.a 1 100.00.sup.a 1 100.00.sup.a 1 100.00.sup.a 1 100.00.sup.a H.sub.2O 100 2.65 146.4.sup.d 14640 O.sub.2 183 3.46 0.03.sup.c 3.19 N.sub.2 196 3.64 0.01.sup.b 0.02.sup.b 1.76 0.05.sup.f 4.65 0.03.sup.g 3.05 0.02.sup.h 1.64 SO.sub.2 157.65 3.60 336.81.sup.b 33680.9 264.23.sup.e 26422.76 215.sup.f 21500 95.24.sup.g 9523.81 66.3.sup.h 6630 Ar 186 3.40 Membrane Properties Ionic Liquid Ionic Liquid [N.sub.222] Properties [emim] [BF4] [dimalonate] Kinetic Cellulose supported on supported on High Flux Gas NBP, Diameter, Triacetate polyethersulfone polyethersulfone Polyacrylate-35 Polycarbonate Components C.[1] [1] .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU .sub.i/co.sub.2 GPU H.sub.2S 60 3.6 0.86.sup.d 86.00 CO.sub.2 78 3.3 1 100.00.sup.a 1 100.00.sup.a 1 100.00.sup.a 1 100.00.sup.a 1 440.sup.r H.sub.2O 100 2.65 238.7.sup.d 23870.00 O.sub.2 183 3.46 0.16.sup.j 16 0.19 82.sup.r N.sub.2 196 3.64 0.04.sup.f 3.57 0.09.sup.m 8.74 0.03.sup.m 3.00 0.043.sup.n 4.3 0.03 12.sup.r SO.sub.2 157.65 3.60 48.21.sup.f 4821.43 19.48.sup.m 1947.92 18.00.sup.m 1800.00 20.40.sup.n 2040.05 0.91 400.sup.r Ar 186 3.40 0.25 250 1 GPU = 10.sup.6 cm.sup.3 (STP)/cm.sup.2 .Math. s .Math. cmHg, or 3.35 10.sup.10 mol/m.sup.2 .Math. s .Math. Pa in SI unit. Permanence (Pressure Normalized flux) Unit .sub.i/co.sub.2: Selectivity of the i-component to CO.sub.2

(36) The Examples were based on the configuration embodied in FIG. 2 and described herein. The Examples illustrate the contribution of the membrane, the air feed, and the acid gas feed to the sulfur dioxide enriched air stream and to sulfur recovery. The variations between Examples were the membrane material, the membrane area and the composition of the acid gas feed. The membrane area was determined based on the membrane characteristics, the acid gas feed composition, and the temperature and the flow rate of membrane gas stream 16. The membrane simulated design was calculated to provide the highest feasible recovery for a fixed flowrate of air feed 2. The operating conditions for acid gas feed 1 were the same for all examples. Acid gas feed 1 was at 41.85 C. (315 K) and 28.117 psia.

(37) The examples that follow include one of five feed streams characterized in the following table. Feed streams A-D are the feed concentrations of Claus process with no Tail Gas Treatment Unit. Feed stream E assumes a Claus process with a Tail Gas Treatment Unit.

(38) TABLE-US-00002 TABLE 2 Feed Stream Compositions H.sub.2S (dry basis) CO.sub.2 (dry basis) Feed Stream A 100% Feed Stream B 80% 20% Feed Stream C 40% 60% Feed Stream D 25% 75% Feed Stream E 45% 55%

Example 1

(39) Example 1 was simulated based on the configuration embodied in FIG. 2 and described above. Membrane sweeping unit 700 was modeled as a Pebax 1657 type membrane with the properties as shown in Table 1 and a membrane area of 12522 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream B in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 3.

(40) TABLE-US-00003 TABLE 3 Stream Conditions and Flowrates for Example 1. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 126.8 213.0 482.2 25 25.0 25.0 Pressure 28.117 29.40 29.4 29.4 23.76 23.766 28.9 28.9 28.9 28.9 (psia) Flow Rate 3581.7 6664.3 6495.7 6562.8 2736.4 8786.6 9135.6 6206.0 6139.0 6139.0 (Kg-mol/ hr) H.sub.2S 0.770 0.000 0.000 0.000 0.000 0.004 0.000 0.000 0.000 0.000 CO.sub.2 0.190 0.000 0.000 0.005 0.000 0.081 0.078 0.115 0.111 0.111 H.sub.2O 0.040 0.013 0.013 0.013 0.000 0.336 0.328 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.205 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.763 0.000 0.570 0.579 0.852 0.862 0.862 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.006 0.000 0.002 0.006 0.009 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.007 0.010 0.010 0.010

(41) Table 4 is a comparison of a process as shown in FIG. 3 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 1. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(42) TABLE-US-00004 TABLE 4 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.88 99.20 1.32 Produced Sulfur, 2045.09 2072.63 27.54 long tons/day

Example 2

(43) Example 2 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a Pebax 1657 type membrane with the properties as shown in Table 1 and a membrane area of 11126 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream C in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 5.

(44) TABLE-US-00005 TABLE 5 Stream Conditions and Flowrates for Example 2. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 197.6 482.2 25 25 25 Pressure 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 (psia) Flow Rate 3581.7 3334.3 3269.1 3384.1 1364.3 6286.3 6477.7 4966.7 4851.6 4851.6 (Kg-mol/ hr) H.sub.2S 0.385 0.000 0.000 0.000 0.000 0.003 0.000 0.000 0.000 0.000 CO.sub.2 0.577 0.000 0.000 0.030 0.000 0.345 0.335 0.437 0.426 0.426 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.245 0.241 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.744 0.000 0.401 0.413 0.538 0.551 0.551 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.004 0.000 0.001 0.004 0.006 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.006 0.007 0.007

(45) Table 6 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 2. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(46) TABLE-US-00006 TABLE 6 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.91 98.91 1 Produced Sulfur, 1022.90 1033.37 10.47 long tons/day

Example 3

(47) Example 3 was simulated based on the configuration embodied in FIG. 2 and described above. Membrane sweeping unit 700 was modeled as a Pebax 1657 type membrane with the properties as shown in Table 1 and a membrane area of 2855 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream E in Table 2. The Tail Gas Treatment unit (part of Claus Process 100) reaches 99.24% recovery. The resulting concentrations of components % vol for selected streams are shown in Table 7.

(48) TABLE-US-00007 TABLE 7 Stream Conditions and Flowrates for Example 3. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 200 482.2 25 25 25 Pressure 28.11 29.4 29.4 29.4 22.67 22.67 28.9 28.9 28.9 28.9 (psia) Flow Rate 2680.8 2798.0 2777.8 2806.6 1152.3 4912.2 4999.5 3740.5 3711.9 3711.9 (Kg-mol/ hr) H.sub.2S 0.431 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 CO.sub.2 0.530 0.000 0.000 0.009 0.000 0.295 0.290 0.387 0.383 0.383 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.263 0.259 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.205 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.763 0.000 0.436 0.442 0.591 0.595 0.595 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.002 0.000 0.001 0.002 0.002 0.001 0.001 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.007 0.007 0.007

(49) Table 8 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 3. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(50) TABLE-US-00008 TABLE 8 Comparison of systems Without membrane With membrane Delta Process Recovery, % 99.24 99.60 0.36 Produced Sulfur, 869.64 872.82 3.18 long tons/day

Example 4

(51) Example 4 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a Pebax 1657 type membrane with the properties as shown in Table 1 and a membrane area of 3960 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream D in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 9.

(52) TABLE-US-00009 TABLE 9 Stream Conditions and Flowrates for Example 4. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 186.3 482.2 25 25 25 Pressure 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 (psia) Flow Rate 3581.7 3334.3 2057.2 2114.7 851.9 5270.9 5403.1 4419.2 4361.6 4361.6 (Kg-mol/ hr) H.sub.2S 0.241 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.000 CO.sub.2 0.721 0.000 0.000 0.025 0.000 0.500 0.488 0.596 0.592 0.592 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.193 0.190 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.201 0.000 0.000 0.002 0.002 0.002 0.002 N.sub.2 0.000 0.771 0.771 0.750 0.000 0.301 0.313 0.383 0.388 0.388 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.003 0.000 0.001 0.003 0.004 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.004 0.004 0.005 0.005 0.005

(53) Table 10 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 4. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(54) TABLE-US-00010 TABLE 10 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.94 98.68 0.74 Produced Sulfur, 640.44 645.30 4.86 long tons/day

Example 5

(55) Example 5 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose acetate impregnated with TEG-DME (Liquid Membrane TEG-DME supported in Cellulose Acetate) type membrane with the properties as shown in Table 1 and a membrane area of 13950 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream B in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 11.

(56) TABLE-US-00011 TABLE 11 Stream Conditions and Flowrates for Example 5. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 204.9 482.2 25 25 25 Pressure 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 (psia) Flow Rate 3581.7 6664.3 6509.7 6576.8 2734.2 8799.8 9146.7 6217.1 6150.0 6150.0 (Kg-mol/ hr) H.sub.2S 0.770 0.000 0.000 0.000 0.000 0.004 0.000 0.000 0.000 0.000 CO.sub.2 0.190 0.000 0.000 0.005 0.000 0.081 0.078 0.115 0.111 0.111 H.sub.2O 0.040 0.013 0.013 0.013 0.000 0.335 0.327 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.205 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.763 0.000 0.570 0.579 0.852 0.862 0.862 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.005 0.000 0.002 0.006 0.009 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.007 0.010 0.010 0.010

(57) Table 12 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 5. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(58) TABLE-US-00012 TABLE 12 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.88 99.12 1.24 Produced Sulfur, 2045.09 2070.91 25.82 long tons/day

Example 6

(59) Example 6 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose acetate impregnated with TEG-DME (Liquid Membrane TEG-DME supported in Cellulose Acetate) type membrane with the properties as shown in Table 1 and a membrane area of 11257 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream C in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 13.

(60) TABLE-US-00013 TABLE 13 Stream Conditions and Flowrates for Example 6. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.07 127 197.5 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 3334.3 3273.5 3388.0 1363.450 6290.2 6481.6 4970.6 4855.3 4855.3 (Kg-mol/hr) H.sub.2S 0.385 0.000 0.000 0.000 0.000 0.003 0.000 0.000 0.000 0.000 CO.sub.2 0.577 0.000 0.000 0.030 0.000 0.345 0.335 0.436 0.426 0.426 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.245 0.241 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.744 0.000 0.401 0.413 0.539 0.551 0.551 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.004 0.000 0.001 0.004 0.006 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.006 0.007 0.007

(61) Table 14 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 6. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(62) TABLE-US-00014 TABLE 14 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.92 98.85 0.93 Produced Sulfur, 1022.90 1032.68 9.78 long tons/day

Example 7

(63) Example 7 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose acetate impregnated with TEG-DME (Liquid Membrane TEG-DME supported in Cellulose Acetate) type membrane with the properties as shown in Table 1 and a membrane area of 2944 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream E in Table 2. The Tail Gas Treatment unit (part of Claus process 100) reaches 99.24% recovery. The resulting concentrations of components % vol for selected streams are shown in Table 15.

(64) TABLE-US-00015 TABLE 15 Stream Conditions and Flowrates for Example 7. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 200.4 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 22.67 22.67 28.9 28.9 28.9 28.9 Flow Rate 2680.8 2798.0 2781.2 2809.9 1151.6 4915.5 5002.8 3743.7 3715.1 3715.1 (Kg-mol/hr) H.sub.2S 0.431 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 CO.sub.2 0.530 0.000 0.000 0.009 0.000 0.295 0.289 0.387 0.383 0.383 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.262 0.259 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.205 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.763 0.000 0.436 0.442 0.591 0.596 0.596 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.001 0.000 0.001 0.002 0.002 0.001 0.001 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.007 0.007 0.007

(65) Table 16 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 7. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(66) TABLE-US-00016 TABLE 16 Comparison of systems Without membrane With membrane Delta Process Recovery, % 99.24 99.54 0.3 Produced Sulfur, 869.64 872.29 2.65 long tons/day

Example 8

(67) Example 8 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose acetate impregnated with TEG-DME (Liquid Membrane TEG-DME supported in Cellulose Acetate) type membrane with the properties as shown in Table 1 and a membrane area of 5218 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream D in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 17.

(68) TABLE-US-00017 TABLE 17 Stream Conditions and Flowrates for Example 8. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 179.5 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 2088.0 2059.8 2131.8 851.6 5287.9 5419.6 4435.8 4363.3 4363.3 (Kg-mol/hr) H.sub.2S 0.241 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.000 CO.sub.2 0.721 0.000 0.000 0.031 0.000 0.501 0.489 0.597 0.592 0.592 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.192 0.190 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.002 0.002 0.002 N.sub.2 0.000 0.771 0.771 0.744 0.000 0.300 0.312 0.382 0.388 0.388 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.003 0.000 0.001 0.003 0.004 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.004 0.004 0.005 0.005 0.005

(69) Table 18 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 8. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(70) TABLE-US-00018 TABLE 18 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.94 98.63 0.69 Produced Sulfur, 640.44 645.02 4.58 long tons/day

Example 9

(71) Example 9 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose triacetate type membrane with the properties as shown in Table 1 and a membrane area of 89491 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream B in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 19.

(72) TABLE-US-00019 TABLE 19 Stream Conditions and Flowrates for Example 9. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 212.1 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 6664.3 6492.8 6722.2 2737.0 8945.9 9296.7 6368.8 6140.0 6140.0 (Kg-mol/hr) H.sub.2S 0.770 0.000 0.000 0.000 0.000 0.004 0.000 0.000 0.000 0.000 CO.sub.2 0.190 0.000 0.000 0.029 0.000 0.098 0.094 0.137 0.111 0.111 H.sub.2O 0.040 0.013 0.013 0.013 0.000 0.330 0.322 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.744 0.000 0.559 0.569 0.831 0.861 0.861 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.005 0.000 0.002 0.006 0.009 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.007 0.010 0.010 0.010

(73) Table 20 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 9. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(74) TABLE-US-00020 TABLE 20 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.80 99.22 1.42 Produced Sulfur, 2045.09 2073.07 27.98 long tons/day

Example 10

(75) Example 10 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose triacetate type membrane with the properties as shown in Table 1 and a membrane area of 11404 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream C in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 21.

(76) TABLE-US-00021 TABLE 21 Stream Conditions and Flowrates for Example 10. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.07 127 197.5 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 3334.3 3278.4 3392.9 1362.4 6295.1 6486.5 4975.5 4860.1 4860.1 (Kg-mol/hr) H.sub.2S 0.385 0.000 0.000 0.000 0.000 0.003 0.000 0.000 0.000 0.000 CO.sub.2 0.577 0.000 0.000 0.030 0.000 0.345 0.335 0.436 0.425 0.425 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.245 0.241 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.745 0.000 0.401 0.413 0.539 0.552 0.552 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.003 0.000 0.001 0.004 0.006 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.006 0.007 0.007

(77) Table 22 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 10. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(78) TABLE-US-00022 TABLE 22 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.92 98.77 0.85 Produced Sulfur, 1022.90 1031.92 9.02 long tons/day

Example 11

(79) Example 11 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose triacetate type membrane with the properties as shown in Table 1 and a membrane area of 3026 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream E in Table 2. The Tail Gas Treatment unit reaches 99.24% recovery. The resulting concentrations of components % vol for selected streams are shown in Table 23.

(80) TABLE-US-00023 TABLE 23 Stream Conditions and Flowrates for Example 11. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 200.3 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 22.67 22.67 28.9 28.9 28.9 28.9 Flow Rate 2680.8 2798.0 2783.9 2812.6 1151.0 4918.2 5005.7 3746.7 3718.0 3718.0 (Kg-mol/hr) H.sub.2S 0.431 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 CO.sub.2 0.530 0.000 0.000 0.009 0.000 0.295 0.289 0.387 0.383 0.383 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.262 0.259 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.207 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.763 0.000 0.436 0.443 0.591 0.596 0.596 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.001 0.000 0.001 0.002 0.002 0.002 0.002 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.007 0.007 0.007

(81) Table 24 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 11. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(82) TABLE-US-00024 TABLE 24 Comparison of systems Without membrane With membrane Delta Process Recovery, % 99.24 99.49 0.25 Produced Sulfur, 869.64 871.84 2.2 long tons/day

Example 12

(83) Example 12 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a cellulose acetate impregnated with TEG-DME (Liquid Membrane TEG-DME supported in Cellulose Acetate) type membrane with the properties as shown in Table 1 and a membrane area of 5218 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream D in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 25.

(84) TABLE-US-00025 TABLE 25 Stream Conditions and Flowrates for Example 12. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 186.2 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 2088.0 2062.5 2134.9 850.8 5291.1 5423.4 4439.7 4367.1 4367.1 (Kg-mol/hr) H.sub.2S 0.241 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.000 CO.sub.2 0.721 0.000 0.000 0.032 0.000 0.501 0.489 0.597 0.591 0.591 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.192 0.190 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.002 0.002 0.002 N.sub.2 0.000 0.771 0.771 0.744 0.000 0.300 0.313 0.382 0.388 0.388 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.002 0.000 0.001 0.003 0.004 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.004 0.004 0.005 0.005 0.005

(85) Table 26 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 12. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(86) TABLE-US-00026 TABLE 26 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.94 98.55 0.61 Produced Sulfur, 640.44 644.46 4.02 long tons/day

Example 13

(87) Example 13 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as an ionic liquid [emin][BF4] supported on polyethersulfone-PES type membrane with the properties as shown in Table 1 and a membrane area of 35076.88 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream B in table 2. The resulting concentrations of components % vol for selected streams are shown in Table 27.

(88) TABLE-US-00027 TABLE 27 Stream Conditions and Flowrates for Example 13. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 293.3 127 482.2 25 25.026 25.026 Pressure (psia) 28.11 29.40 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 6664.3 6522.3 6635.2 2730.6 8859.1 9210.4 6281.2 6168.4 6168.4 (Kg-mol/hr) H.sub.2S 0.770 0.000 0.000 0.000 0.000 0.004 0.000 0.000 0.000 0.000 CO.sub.2 0.190 0.000 0.000 0.013 0.000 0.086 0.083 0.122 0.111 0.111 H.sub.2O 0.040 0.013 0.013 0.013 0.000 0.333 0.325 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.203 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.757 0.000 0.567 0.577 0.846 0.861 0.861 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.005 0.000 0.002 0.006 0.009 0.005 0.005 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.007 0.010 0.010 0.010

(89) Table 28 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 13. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(90) TABLE-US-00028 TABLE 28 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.80 98.99 1.19 Produced Sulfur, 2045.09 2068.21 28.12 long tons/day

Example 14

(91) Example 14 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as an ionic liquid [emin][BF4] supported on polyethersulfone-PES type membrane with the properties as shown in Table 1 and a membrane area of 11723 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream C in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 29.

(92) TABLE-US-00029 TABLE 29 Stream Conditions and Flowrates for Example 14. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.069 127 197.4 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 3334.3 3288.2 3402.8 1360.2 6305.1 6497.2 4986.1 4870.4 4870.4 (Kg-mol/hr) H.sub.2S 0.385 0.000 0.000 0.000 0.000 0.003 0.000 0.000 0.000 0.000 CO.sub.2 0.577 0.000 0.000 0.031 0.000 0.345 0.334 0.436 0.424 0.424 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.244 0.240 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.745 0.000 0.402 0.414 0.539 0.552 0.552 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.003 0.000 0.001 0.004 0.006 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.006 0.007 0.007

(93) Table 30 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 14. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(94) TABLE-US-00030 TABLE 30 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.92 98.62 0.70 Produced Sulfur, 1022.90 1030.29 7.39 long tons/day

Example 15

(95) Example 15 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as an ionic liquid [emin][BF4] supported on polyethersulfone-PES type membrane with the properties as shown in Table 1 and a membrane area of 3152 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream E in Table 2. The Tail Gas Treatment unit reaches 99.24% recovery. The resulting concentrations of components % vol for selected streams are shown in Table 31.

(96) TABLE-US-00031 TABLE 31 Stream Conditions and Flowrates for Example 15. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 200.3 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 22.67 22.67 28.9 28.9 28.9 28.9 Flow Rate 2680.8 2798.0 2789.1 2818.0 1150.0 4923.6 5010.9 3751.9 3723.2 3723.2 (Kg-mol/hr) H.sub.2S 0.431 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 CO.sub.2 0.530 0.000 0.000 0.010 0.000 0.294 0.289 0.386 0.382 0.382 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.262 0.259 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.205 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.763 0.000 0.436 0.443 0.591 0.596 0.596 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.001 0.000 0.001 0.002 0.002 0.002 0.002 Ar 0.000 0.009 0.009 0.009 0.000 0.005 0.005 0.007 0.007 0.007

(97) Table 32 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 15. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(98) TABLE-US-00032 TABLE 32 Comparison of systems Without membrane With membrane Delta Process Recovery, % 99.24 99.41 0.17 Produced Sulfur, 869.64 871.07 1.43 long tons/day

Example 16

(99) Example 16 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as an ionic liquid [emin][BF4] supported on polyethersulfone-PES type membrane with the properties as shown in Table 1 and a membrane area of 5405 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream D in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 33.

(100) TABLE-US-00033 TABLE 33 Stream Conditions and Flowrates for Example 16. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 186.1 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 2048.0 2068.1 2140.9 849.6 5297.2 5430.0 4446.2 4373.4 4373.4 (Kg-mol/hr) H.sub.2S 0.241 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.000 CO.sub.2 0.721 0.000 0.000 0.032 0.000 0.501 0.488 0.596 0.591 0.591 H.sub.2O 0.038 0.013 0.013 0.013 0.000 0.192 0.189 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.200 0.000 0.000 0.002 0.002 0.002 0.002 N.sub.2 0.000 0.771 0.771 0.744 0.000 0.301 0.313 0.383 0.389 0.389 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.002 0.000 0.001 0.003 0.004 0.003 0.003 Ar 0.000 0.009 0.009 0.009 0.000 0.004 0.004 0.005 0.005 0.005

(101) Table 34 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 16. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(102) TABLE-US-00034 TABLE 34 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.94 98.40 0.46 Produced Sulfur, 640.44 643.52 3.08 long tons/day

Example 17

(103) Example 17 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as an ionic liquid [emin][BF4] supported on polyethersulfone-PES type membrane with the properties as shown in Table 1 and a membrane area of 99705 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream A in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 35.

(104) TABLE-US-00035 TABLE 35 Stream Conditions and Flowrates for Example 17. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 215.7 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 8660.8 8427.9 8663.8 3553.2 10482.9 10928.3 7302.2 7066.5 7066.5 (Kg-mol/hr) H.sub.2S 1.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 0.000 0.000 CO.sub.2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 H.sub.2O 0.000 0.013 0.013 0.013 0.000 0.348 0.339 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.201 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.771 0.000 0.637 0.645 0.965 0.971 0.971 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.006 0.000 0.002 0.007 0.010 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.007 0.011 0.012 0.012

(105) Table 36 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 17. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(106) TABLE-US-00036 TABLE 36 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.87 99.22 1.35 Produced Sulfur, 2654.77 2691.24 36.47 long tons/day

Example 18

(107) Example 18 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as an ionic liquid [N.sub.222] [dimalonate] supported on polyethersulfone-PES type membrane with the properties as shown in Table 1 and a membrane area of 103854 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream A in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 37.

(108) TABLE-US-00037 TABLE 37 Stream Conditions and Flowrates for Example 18. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 216.3 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 8660.8 8429.7 8546.1 3552.8 10365.2 10809.7 7182.5 7066.2 7066.2 (Kg-mol/hr) H.sub.2S 1.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 0.000 0.000 CO.sub.2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 H.sub.2O 0.000 0.013 0.013 0.013 0.000 0.352 0.342 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.204 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.768 0.000 0.633 0.641 0.964 0.971 0.971 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.006 0.000 0.002 0.007 0.011 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.008 0.011 0.012 0.012

(109) Table 38 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 18. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(110) TABLE-US-00038 TABLE 38 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.87 99.22 1.33 Produced Sulfur, 2654.77 2690.91 36.14 long tons/day

Example 19

(111) Example 19 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a polyacrylate-35 type membrane with the properties as shown in Table 1 and a membrane area of 95245.23 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream A in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 39.

(112) TABLE-US-00039 TABLE 39 Stream Conditions and Flowrates for Example 19. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 216.2 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 8660.8 8428.8 8565.2 3553.0 10384.4 10829.0 7201.9 7065.0 7065.0 (Kg-mol/hr) H.sub.2S 1.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 0.000 0.000 CO.sub.2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 H.sub.2O 0.000 0.013 0.013 0.013 0.000 0.351 0.342 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.203 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.768 0.000 0.634 0.641 0.965 0.971 0.971 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.006 0.000 0.002 0.007 0.011 0.004 0.004 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.008 0.011 0.012 0.012

(113) Table 40 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 19. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(114) TABLE-US-00040 TABLE 40 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.87 99.21 1.34 Produced Sulfur, 2654.77 2691.05 38.34 long tons/day

Example 20

(115) Example 20 was simulated based on the configuration embodied in FIG. 3 and described above. Membrane sweeping unit 700 was modeled as a polycarbonate type membrane with the properties as shown in Table 1 and a membrane area of 77965 m.sup.2. Acid gas feed 1 was modeled with the composition of feed stream A in Table 2. The resulting concentrations of components % vol for selected streams are shown in Table 40.

(116) TABLE-US-00041 TABLE 41 Stream Conditions and Flowrates for Example 20. Stream 1 Stream 2 Stream 3 Stream 5 Stream 7 Stream 8 Stream 10 Stream 16 Stream 17 Stream 18 Phase Vapor Vapor Vapor Vapor Liquid Vapor Vapor Vapor Vapor Vapor Temp ( C.) 41.8 25 25 25.0 127 215.5 482.2 25 25 25 Pressure (psia) 28.11 29.4 29.4 29.4 23.76 23.76 28.9 28.9 28.9 28.9 Flow Rate 3581.7 8660.8 8488.7 8726.4 3536.9 10545.6 10993.0 7366.8 7129.3 7129.3 (Kg-mol/hr) H.sub.2S 1.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 0.000 0.000 CO.sub.2 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.001 0.000 0.000 H.sub.2O 0.000 0.013 0.013 0.013 0.000 0.346 0.337 0.010 0.010 0.010 O.sub.2 0.000 0.207 0.207 0.201 0.000 0.000 0.002 0.003 0.003 0.003 N.sub.2 0.000 0.771 0.771 0.772 0.000 0.639 0.647 0.965 0.969 0.969 Sulfur 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 SO.sub.2 0.000 0.000 0.000 0.004 0.000 0.002 0.007 0.010 0.006 0.006 Ar 0.000 0.009 0.009 0.009 0.000 0.007 0.008 0.011 0.012 0.012

(117) Table 42 is a comparison of a process as shown in FIG. 2 with a membrane unit and air sweep and a process that does not include a membrane (not shown). The table provides a comparison between the baseline state of the art (no membrane) and the improvement in sulfur recovery in a system of the present invention (membrane) according to the conditions and streams of Example 20. Process recovery percent (%) refers to the sulfur recovery of the system, that is the percent of sulfur recovered from the acid gas feed. The delta is a measure of the improvement in terms of additional sulfur recovered (produced sulfur in long tons/day) of the system with a membrane over a system without a membrane. Each 0.1% additional sulfur recovery can mean a significant reduction in sulfur emissions from the system.

(118) TABLE-US-00042 TABLE 42 Comparison of systems Without membrane With membrane Delta Process Recovery, % 97.87 98.76 0.88 Produced Sulfur, 2654.77 2678.86 24.09 long tons/day

(119) TABLE-US-00043 TABLE 43 Comparison of Furnace Temperatures in the Examples Temp. Difference between Feed Estimated no membrane system and Composition Membrane Furnace Temp. system with membrane (Table 2) Material ( C.) ( C.) No Membrane All No Membrane 1050.00 0 Compositions Example 1 B PEBAX 1657 1007.41 42.59 Example 2 C PEBAX 1657 1018.29 31.71 Example 3 E PEBAX 1657 1040.04 9.96 Example 4 D PEBAX 1657 1032.38 17.62 Example 5 B Cellulose acetate 1010.14 39.86 with TEG-DME Example 6 C Cellulose acetate 1019.16 30.84 with TEG-DME Example 7 E Cellulose acetate 1041.29 8.71 with TEG-DME Example 8 D Cellulose acetate 1030.29 19.71 with TEG-DME Example 9 B Cellulose triacetate 987.83 62.17 Example 10 C Cellulose triacetate 1020.15 29.85 Example 11 E Cellulose triacetate 1042.30 7.7 Example 12 D Cellulose triacetate 1031.01 18.99 Example 13 B Emin-BF4 1008.48 41.52 Example 14 C Emin-BF4 1022.56 27.44 Example 15 E Emin-BF4 1043.48 6.52 Example 16 D Emin-BF4 1032.50 17.5 Example 17 A Emin-BF4 989.78 60.22 Example 18 A [N.sub.222][dimalonate] 997.25 52.75 Example 19 A Polyacrylate-35 995.72 54.28 Example 20 A Polycarbonate 1008.70 41.3

(120) Table 43 shows that for a given air feed the furnace temperature is reduced in the presence of a sulfur dioxide enriched air stream from the membrane sweeping unit. Final design of the system can take into account the effect or potential effect on flame temperature and other parameters can be used to account for the decrease in flame temperature due to the presence of sulfur dioxide.

(121) Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents.

(122) The singular forms a, an, and the include plural referents, unless the context clearly dictates otherwise.

(123) Optional or optionally means that the subsequently described event or circumstances can or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(124) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(125) As used herein and in the appended claims, the words comprise, has, and include and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.

(126) As used herein, terms such as first and second are arbitrarily assigned and are merely intended to differentiate between two or more components of an apparatus. It is to be understood that the words first and second serve no other purpose and are not part of the name or description of the component, nor do they necessarily define a relative location or position of the component. Furthermore, it is to be understood that that the mere use of the term first and second does not require that there be any third component, although that possibility is contemplated under the scope of the present invention.