IMPROVING SULFUR RECOVERY OPERATIONS WITH PROCESSES BASED ON NOVEL CO2 OVER SO2 SELECTIVE MEMBRANES AND ITS COMBINATIONS WITH SO2 OVER CO2 SELECTIVE MEMBRANES
20230001349 · 2023-01-05
Assignee
Inventors
- Milind Vaidya (Dhahran, SA)
- Sebastien Duval (Dhahran, SA)
- Feras Hamad (Dhahran, SA)
- Richard Baker (Newark, CA, US)
- Tim Merkel (Newark, CA, US)
- Kaaeid Lokhandwala (Newark, CA, US)
- Ahmad Bahamdan (Dhahran, SA)
- Faisal Al-Otaibi (Dhahran, SA)
Cpc classification
B01D2258/0291
PERFORMING OPERATIONS; TRANSPORTING
B01D2317/08
PERFORMING OPERATIONS; TRANSPORTING
B01D2311/25
PERFORMING OPERATIONS; TRANSPORTING
B01D53/228
PERFORMING OPERATIONS; TRANSPORTING
Y02C20/40
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
Abstract
Methods and systems for recovering sulfur dioxide from a Claus unit process emissions stream are provided. The method comprises the steps of generating a process emissions stream from a thermal oxidizer or other combustion device, introducing the emissions stream to an SO.sub.2 removal system, introducing the SO.sub.2 rich stream from the SO.sub.2 removal system to a CO.sub.2 removal system, and introducing an enriched SO.sub.2 stream back to the Claus unit. The SO.sub.2 removal system can include one or more SO.sub.2 selective membranes. The CO.sub.2 removal system can include one or more CO.sub.2 selective membranes.
Claims
1. A method for processing sulfur dioxide emissions from a sulfur removal unit for improved operating conditions when treated streams are recycled to the sulfur removal unit, the method comprising the steps of: introducing an SO2 emissions stream to an SO2 removal system, the SO2 removal system comprising an SO2 selective membrane, operable to separate sulfur dioxide and carbon dioxide, wherein the SO2 emissions stream is saturated with water and further comprises sulfur dioxide and carbon dioxide; separating sulfur dioxide and carbon dioxide in the SO2 removal system by the SO2 selective membrane; generating a CO2 removal system feed stream from the SO2 removal system; generating a low SO2 discharge stream from the SO2 removal system; introducing the CO2 removal system feed stream to a CO2 removal system, the CO2 removal system comprising a CO2 selective membrane, operable to separate carbon dioxide and sulfur dioxide; separating carbon dioxide and sulfur dioxide in the CO2 removal system by the CO2 selective membrane; generating an SO2 rich recycle derived from the CO2 removal system, such that the SO2 rich recycle has a higher concentration of sulfur dioxide than the SO2 emissions stream, and further such that the SO2 rich recycle has a lower concentration of carbon dioxide than the SO2 emissions stream; and generating a CO2 waste gas from the CO2 removal system.
2. The method of claim 1, further comprising the step of recycling the SO2 rich recycle to the sulfur removal unit, such that the introduction of the SO2 rich recycle to the sulfur removal unit allows for additional sulfur recovery while assisting in maintaining a proper temperature profile in the sulfur removal unit due to the lower concentration of carbon dioxide in the SO2 rich recycle, and further such that an amount of a fuel gas introduced to the sulfur removal unit is reduced.
3. The method of claim 1, wherein the SO2 emissions stream is generated from a combustion device in the sulfur removal unit.
4. The method of claim 1, wherein the sulfur removal unit is selected from the group consisting of: a Claus plant, a sulfur scrubber, a metallurgical smelting process, a FCC catalyst regeneration process, and combinations of the same.
5. The method of claim 1, wherein the low SO2 discharge stream comprises less than 150 ppm sulfur dioxide.
6. The method of claim 1, wherein the low SO2 discharge stream comprises less than 100 ppm sulfur dioxide.
7. The method of claim 1, wherein the SO2 removal system comprises a rubbery polar membrane.
8. The method of claim 1, wherein the CO2 selective membrane comprises a perfluoropolymer.
9. The method of claim 8, wherein the perfluoropolymer is a monomer, copolymer, block copolymer, terpolymer, or block terpolymer generated by a combination of monomers selected from the group of monomers: CYTOP™ polymer material; HYFLON™ polymer material; TEFLON™ polymer; TEFLON™ polymer AF2400; TEFLON™ polymer AF1400; TEFLON™ polymer AD60; TEFLON™ polymer AD80; perfluoro(2-methylene-4,5-dimethyl-1,3-dioxolane); perfluoro(2-methylene-1,3-dioxolane); perfluoro-2,2-dimethyl-1,3-dioxole (PDD); and perfluoro-3-butenyl-vinyl ether (PBVE).
10. The method of claim 8, wherein the perfluoropolymer is a homopolymer, a copolymer, a block copolymer, a terpolymer, a block terpolymer, or any other combination of the monomers selected from the group of monomers consisting of: ##STR00010## ##STR00011## and combinations of the same.
11. The method of claim 1, wherein the SO2 removal system comprises an SO2 selective membrane unit, the SO2 selective membrane unit comprising an SO2 selective membrane unit retentate side and an SO2 selective membrane unit permeate side, and the CO2 removal system comprises a CO2 selective membrane unit, the CO2 selective membrane unit comprising a CO2 selective membrane unit retentate side and a CO2 selective membrane unit permeate side, and the method further comprising the steps of: introducing the SO2 emissions stream to the SO2 selective membrane unit retentate side, the SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the SO2 selective membrane unit to produce the CO2 removal system feed stream from the SO2 selective membrane unit permeate side; removing the low SO2 discharge stream from the SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the CO2 selective membrane unit retentate side, the CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing the carbon dioxide to pass through the CO2 selective membrane in the CO2 selective membrane unit to produce the CO2 waste gas from the CO2 selective membrane unit permeate side; and removing the SO2 rich recycle from the CO2 selective membrane unit retentate side.
12. The method of claim 11, further comprising the step of recycling the CO2 waste gas to the SO2 selective membrane unit retentate side, such that additional sulfur dioxide is recovered in the SO2 rich recycle.
13. The method of claim 11, further comprising the step of recycling the SO2 rich recycle to the sulfur removal unit, such that the introduction of the SO2 rich recycle to the sulfur removal unit allows for additional sulfur recovery while assisting in maintaining a proper temperature profile in the sulfur removal unit due to the lower concentration of carbon dioxide in the SO2 rich recycle, and further such that an amount of a fuel gas introduced to the sulfur removal unit is reduced.
14. The method of claim 13, further comprising the step of providing an air sweep to the SO2 selective membrane unit permeate side, such that the SO2 rich recycle provides an oxygen source to substitute a portion of air introduced to the sulfur removal unit.
15. The method of claim 1, wherein the SO2 removal system comprises an SO2 selective membrane unit, the SO2 selective membrane unit comprising an SO2 selective membrane unit retentate side and an SO2 selective membrane unit permeate side, and the CO2 removal system comprises a CO2 selective membrane unit, the CO2 selective membrane unit comprising a CO2 selective membrane unit retentate side and a CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a polishing SO2 selective membrane unit, the polishing SO2 selective membrane unit comprising a polishing SO2 selective membrane unit retentate side and a polishing SO2 selective membrane unit permeate side, and the method further comprising the steps of: introducing the SO2 emissions stream to the SO2 selective membrane unit retentate side, the SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the SO2 selective membrane unit to produce the CO2 removal system feed stream from the SO2 selective membrane unit permeate side; removing the low SO2 discharge stream from the SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the CO2 selective membrane unit retentate side, the CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing carbon dioxide to pass through the CO2 selective membrane in the CO2 selective membrane unit to produce the CO2 waste gas from the CO2 selective membrane unit permeate side; removing a CO2 membrane retentate stream from the CO2 selective membrane unit retentate side; introducing the CO2 membrane retentate stream to the polishing SO2 selective membrane unit retentate side, the polishing SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the polishing SO2 selective membrane unit to produce the SO2 rich recycle from the polishing SO2 selective membrane unit permeate side; and removing a polishing SO2 selective membrane retentate stream from the polishing SO2 selective membrane unit retentate side.
16. The method of claim 15, further comprising the step of recycling the CO2 waste gas to the SO2 selective membrane unit retentate side, such that additional sulfur dioxide is recovered in the SO2 rich recycle.
17. The method of claim 15, further comprising the step of recycling the polishing SO2 selective membrane retentate stream to the SO2 selective membrane unit retentate side, such that additional sulfur dioxide is recovered in the SO2 rich recycle.
18. The method of claim 15, further comprising the step of recycling the SO2 rich recycle to the sulfur removal unit, such that the introduction of the SO2 rich recycle to the sulfur removal unit allows for additional sulfur recovery while assisting in maintaining a proper temperature profile in the sulfur removal unit due to the lower concentration of carbon dioxide in the SO2 rich recycle, and further such that an amount of a fuel gas introduced to the sulfur removal unit is reduced.
19. The method of claim 18, further comprising the step of providing an air sweep to the SO2 selective membrane unit permeate side, such that the SO2 rich recycle provides an oxygen source to substitute a portion of air introduced to the sulfur removal unit.
20. The method of claim 1, wherein the SO2 removal system comprises a first SO2 selective membrane unit, the first SO2 selective membrane unit comprising a first SO2 selective membrane unit retentate side and a first SO2 selective membrane unit permeate side, and the SO2 removal system further comprises a second SO2 selective membrane unit, the second SO2 selective membrane unit comprising a second SO2 selective membrane unit retentate side and a second SO2 selective membrane unit permeate side, and further wherein the CO2 removal system comprises a first CO2 selective membrane unit, the first CO2 selective membrane unit comprising a first CO2 selective membrane unit retentate side and a first CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a second CO2 selective membrane unit, the second CO2 selective membrane unit comprising a second CO2 selective membrane unit retentate side and a second CO2 selective membrane unit permeate side, the method further comprising the steps of: introducing the SO2 emissions stream to the first SO2 selective membrane unit retentate side, the first SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the first SO2 selective membrane unit to produce the CO2 removal system feed stream from the first SO2 selective membrane unit permeate side; removing an SO2 membrane retentate stream from the first SO2 selective membrane unit retentate side; introducing the SO2 membrane retentate stream to the second SO2 selective membrane unit retentate side, the second SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the second SO2 selective membrane unit to produce an SO2 membrane permeate stream from the second SO2 selective membrane unit permeate side; removing the low SO2 discharge stream from the second SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the first CO2 selective membrane unit retentate side, the first CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing carbon dioxide to pass through the CO2 selective membrane in the first CO2 selective membrane unit to produce the CO2 waste gas from the first CO2 selective membrane unit permeate side; removing a CO2 membrane retentate stream from the first CO2 selective membrane unit retentate side; introducing the CO2 membrane retentate stream to the second CO2 selective membrane unit retentate side, the second CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing carbon dioxide to pass through the CO2 selective membrane in the second CO2 selective membrane unit to produce a CO2 membrane permeate stream from the second CO2 selective membrane unit permeate side; and removing the SO2 rich recycle from the second CO2 selective membrane unit retentate side.
21. The method of claim 20, further comprising the step of providing an air sweep to the second SO2 selective membrane unit permeate side.
22. The method of claim 20, further comprising the step of recycling the SO2 membrane permeate stream to the sulfur removal unit, wherein the carbon dioxide concentration of the SO2 membrane permeate stream is lower than the concentration in the SO2 emissions stream, such that the introduction of the SO2 membrane permeate stream to the sulfur removal unit allows for additional sulfur recovery while assisting in maintaining a proper temperature profile in the sulfur removal unit due to the lower concentration of carbon dioxide in the SO2 rich recycle, and further such that an amount of a fuel gas introduced to the sulfur removal unit is reduced.
23. The method of claim 20, further comprising the step of recycling the SO2 rich recycle to the sulfur removal unit, such that the introduction of the SO2 rich recycle to the sulfur removal unit allows for additional sulfur recovery while assisting in maintaining a proper temperature profile in the sulfur removal unit due to the lower concentration of carbon dioxide in the SO2 rich recycle, and further such that an amount of a fuel gas introduced to the sulfur removal unit is reduced.
24. The method of claim 20, further comprising the step of recycling the CO2 waste gas to the first SO2 selective membrane unit retentate side, such that additional sulfur dioxide is recovered in the SO2 rich recycle.
25. The method of claim 20, further comprising the step of recycling the CO2 membrane permeate stream to the first SO2 selective membrane unit retentate side, such that additional carbon dioxide is removed in the CO2 waste gas, and further such that additional sulfur dioxide is recovered in the SO2 rich recycle.
26. The method of claim 20, further comprising the step of recycling the CO2 membrane permeate stream to the first CO2 selective membrane unit retentate side, such that additional carbon dioxide is removed in the CO2 waste gas, and further such that additional sulfur dioxide is recovered in the SO2 rich recycle.
27. The method of claim 20, further comprising the step of recycling the CO2 waste gas to the second SO2 selective membrane unit retentate side, such that additional sulfur dioxide is recovered in the SO2 rich recycle.
28. The method of claim 20, further comprising the step of recycling the low SO2 discharge stream to the first SO2 selective membrane unit permeate side, such that the low SO2 discharge stream creates a gas sweep of the SO2 selective membrane in the first SO2 selective membrane unit permeate side.
29. The method of claim 1, wherein the SO2 removal system comprises a first SO2 selective membrane unit, the first SO2 selective membrane unit comprising a first SO2 selective membrane unit retentate side and a first SO2 selective membrane unit permeate side, and the SO2 removal system further comprises a second SO2 selective membrane unit, the second SO2 selective membrane unit comprising a second SO2 selective membrane unit retentate side and a second SO2 selective membrane unit permeate side, and further wherein the CO2 removal system comprises a first CO2 selective membrane unit, the first CO2 selective membrane unit comprising a first CO2 selective membrane unit retentate side and a first CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a second CO2 selective membrane unit, the second CO2 selective membrane unit comprising a second CO2 selective membrane unit retentate side and a second CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a third CO2 selective membrane unit, the third CO2 selective membrane unit comprising a third CO2 selective membrane unit retentate side and a third CO2 selective membrane unit permeate side, the method further comprising the steps of: introducing the SO2 emissions stream to the first SO2 selective membrane unit retentate side, the first SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the first SO2 selective membrane unit to produce the CO2 removal system feed stream from the first SO2 selective membrane unit permeate side; removing an SO2 membrane retentate stream from the first SO2 selective membrane unit retentate side; introducing the SO2 membrane retentate stream to the second SO2 selective membrane unit retentate side, the second SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; causing sulfur dioxide to pass through the SO2 selective membrane in the second SO2 selective membrane unit to produce an SO2 membrane permeate stream from the second SO2 selective membrane unit permeate side; removing the low SO2 discharge stream from the second SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the first CO2 selective membrane unit retentate side, the first CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing carbon dioxide to pass through the CO2 selective membrane in the first CO2 selective membrane unit to produce a first CO2 membrane permeate stream from the first CO2 selective membrane unit permeate side; removing a first CO2 membrane retentate stream from the first CO2 selective membrane unit retentate side; introducing the first CO2 membrane retentate stream to the second CO2 selective membrane unit retentate side, the second CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing carbon dioxide to pass through the CO2 selective membrane in the second CO2 selective membrane unit to produce a second CO2 membrane permeate stream from the second CO2 selective membrane unit permeate side; removing the SO2 rich recycle from the second CO2 selective membrane unit retentate side; introducing the first CO2 membrane permeate stream to the third CO2 selective membrane unit retentate side, the third CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; causing carbon dioxide to pass through the CO2 selective membrane in the third CO2 selective membrane unit to produce the CO2 waste gas from the third CO2 selective membrane unit permeate side; and removing a second CO2 membrane retentate stream from the third CO2 selective membrane unit retentate side.
30. The method of claim 29, further comprising the step of recycling the SO2 rich recycle to the sulfur removal unit, such that the introduction of the SO2 rich recycle to the sulfur removal unit allows for additional sulfur recovery while assisting in maintaining a proper temperature profile in the sulfur removal unit due to the lower concentration of carbon dioxide in the SO2 rich recycle, and further such that an amount of a fuel gas introduced to the sulfur removal unit is reduced.
31. The method of claim 29, further comprising the step of providing an air sweep to the second SO2 selective membrane unit permeate side.
32. The method of claim 29, further comprising the step of recycling the second CO2 membrane retentate stream to the first CO2 selective membrane unit retentate side, such that additional CO2 is removed in the CO2 waste gas, and further such that additional sulfur dioxide is recovered in the SO2 rich recycle.
33. The method of claim 29, further comprising the step of recycling the second CO2 membrane retentate stream to the first CO2 selective membrane unit retentate side, such that such that additional carbon dioxide is removed in the CO2 waste gas, and further such that additional sulfur dioxide is recovered in the SO2 rich recycle.
34. The method of claim 1, wherein the SO2 removal system comprises an SO2 selective membrane unit, the SO2 selective membrane unit comprising an SO2 selective membrane unit retentate side and an SO2 selective membrane unit permeate side, and the CO2 removal system comprises a CO2 selective membrane unit, the CO2 selective membrane unit comprising a CO2 selective membrane unit retentate side and a CO2 selective membrane unit permeate side, and the method further comprising the steps of: introducing the SO2 emissions stream to the SO2 selective membrane unit retentate side, the SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the SO2 selective membrane unit permeate side with an SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the SO2 selective membrane unit to produce an SO2 selective membrane permeate vacuum stream from the SO2 selective membrane unit permeate side; passing the SO2 selective membrane permeate vacuum stream through the SO2 selective membrane vacuum to generate the CO2 removal system feed stream; removing the low SO2 discharge stream from the SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the CO2 selective membrane unit retentate side, the CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the CO2 selective membrane unit permeate side with a CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the CO2 selective membrane unit to produce a CO2 selective membrane permeate vacuum stream from the CO2 selective membrane unit permeate side; passing the CO2 selective membrane permeate vacuum stream through the CO2 selective membrane vacuum to generate the CO2 waste gas; and removing the SO2 rich recycle from the CO2 selective membrane unit retentate side.
35. The method of claim 1, wherein the SO2 removal system comprises an SO2 selective membrane unit, the SO2 selective membrane unit comprising an SO2 selective membrane unit retentate side and an SO2 selective membrane unit permeate side, and the CO2 removal system comprises a CO2 selective membrane unit, the CO2 selective membrane unit comprising a CO2 selective membrane unit retentate side and a CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a polishing SO2 selective membrane unit, the polishing SO2 selective membrane unit comprising a polishing SO2 selective membrane unit retentate side and a polishing SO2 selective membrane unit permeate side, and the method further comprising the steps of: introducing the SO2 emissions stream to the SO2 selective membrane unit retentate side, the SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the SO2 selective membrane unit permeate side with an SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the SO2 selective membrane unit to produce an SO2 selective membrane permeate vacuum stream from the SO2 selective membrane unit permeate side; passing the SO2 selective membrane permeate vacuum stream through the SO2 selective membrane vacuum to generate the CO2 removal system feed stream; removing the low SO2 discharge stream from the SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the CO2 selective membrane unit retentate side, the CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the CO2 selective membrane unit permeate side with a CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the CO2 selective membrane unit to produce a CO2 selective membrane permeate vacuum stream from the CO2 selective membrane unit permeate side; passing the CO2 selective membrane permeate vacuum stream through the CO2 selective membrane vacuum to generate the CO2 waste gas; removing a CO2 membrane retentate stream from the CO2 selective membrane unit retentate side; introducing the CO2 membrane retentate stream to the polishing SO2 selective membrane unit retentate side, the polishing SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the polishing SO2 selective membrane unit permeate side with a polishing SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the polishing SO2 selective membrane unit to produce a polishing SO2 selective membrane permeate vacuum stream from the polishing SO2 selective membrane unit permeate side; passing the polishing SO2 selective membrane permeate vacuum stream through the polishing SO2 selective membrane vacuum to generate the SO2 rich recycle; and removing a polishing SO2 selective membrane retentate stream from the polishing SO2 selective membrane unit retentate side.
36. The method of claim 1, wherein the SO2 removal system comprises a first SO2 selective membrane unit, the first SO2 selective membrane unit comprising a first SO2 selective membrane unit retentate side and a first SO2 selective membrane unit permeate side, and the SO2 removal system further comprises a second SO2 selective membrane unit, the second SO2 selective membrane unit comprising a second SO2 selective membrane unit retentate side and a second SO2 selective membrane unit permeate side, and further wherein the CO2 removal system comprises a first CO2 selective membrane unit, the first CO2 selective membrane unit comprising a first CO2 selective membrane unit retentate side and a first CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a second CO2 selective membrane unit, the second CO2 selective membrane unit comprising a second CO2 selective membrane unit retentate side and a second CO2 selective membrane unit permeate side, the method further comprising the steps of: introducing the SO2 emissions stream to the first SO2 selective membrane unit retentate side, the first SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the first SO2 selective membrane unit permeate side with a first SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the first SO2 selective membrane unit to produce a first SO2 selective membrane permeate vacuum stream from the first SO2 selective membrane unit permeate side; passing the first SO2 selective membrane permeate vacuum stream through the first SO2 selective membrane vacuum to generate the CO2 removal system feed stream; removing an SO2 membrane retentate stream from the first SO2 selective membrane unit retentate side; introducing the SO2 membrane retentate stream to the second SO2 selective membrane unit retentate side, the second SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the second SO2 selective membrane unit permeate side with a second SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the second SO2 selective membrane unit to produce a second SO2 selective membrane permeate vacuum stream from the second SO2 selective membrane unit permeate side; passing the second SO2 selective membrane permeate vacuum stream through the second SO2 selective membrane vacuum to generate an SO2 membrane permeate stream; removing the low SO2 discharge stream from the second SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the first CO2 selective membrane unit retentate side, the first CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the first CO2 selective membrane unit permeate side with a first CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the first CO2 selective membrane unit to produce a first CO2 selective membrane permeate vacuum stream from the first CO2 selective membrane unit permeate side; passing the first CO2 selective membrane permeate vacuum stream through the first CO2 selective membrane vacuum to generate the CO2 waste gas; removing a CO2 membrane retentate stream from the first CO2 selective membrane unit retentate side; introducing the CO2 membrane retentate stream to the second CO2 selective membrane unit retentate side, the second CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the second CO2 selective membrane unit permeate side with a second CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the second CO2 selective membrane unit to produce a second CO2 selective membrane permeate vacuum stream from the second CO2 selective membrane unit permeate side; passing the second CO2 selective membrane permeate vacuum stream through the second CO2 selective membrane vacuum to generate a CO2 membrane permeate stream; and removing the SO2 rich recycle from the second CO2 selective membrane unit retentate side.
37. The method of claim 1, wherein the SO2 removal system comprises a first SO2 selective membrane unit, the first SO2 selective membrane unit comprising a first SO2 selective membrane unit retentate side and a first SO2 selective membrane unit permeate side, and the SO2 removal system further comprises a second SO2 selective membrane unit, the second SO2 selective membrane unit comprising a second SO2 selective membrane unit retentate side and a second SO2 selective membrane unit permeate side, and further wherein the CO2 removal system comprises a first CO2 selective membrane unit, the first CO2 selective membrane unit comprising a first CO2 selective membrane unit retentate side and a first CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a second CO2 selective membrane unit, the second CO2 selective membrane unit comprising a second CO2 selective membrane unit retentate side and a second CO2 selective membrane unit permeate side, and the CO2 removal system further comprises a third CO2 selective membrane unit, the third CO2 selective membrane unit comprising a third CO2 selective membrane unit retentate side and a third CO2 selective membrane unit permeate side, the method further comprising the steps of: introducing the SO2 emissions stream to the first SO2 selective membrane unit retentate side, the first SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the first SO2 selective membrane unit permeate side with a first SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the first SO2 selective membrane unit to produce a first SO2 selective membrane permeate vacuum stream from the first SO2 selective membrane unit permeate side; passing the first SO2 selective membrane permeate vacuum stream through the first SO2 selective membrane vacuum to generate the CO2 removal system feed stream; removing an SO2 membrane retentate stream from the first SO2 selective membrane unit retentate side; introducing the SO2 membrane retentate stream to the second SO2 selective membrane unit retentate side, the second SO2 selective membrane unit operable to allow sulfur dioxide to permeate the SO2 selective membrane in preference to carbon dioxide; generating vacuum pressure on the second SO2 selective membrane unit permeate side with a second SO2 selective membrane vacuum; causing sulfur dioxide to pass through the SO2 selective membrane in the second SO2 selective membrane unit to produce a second SO2 selective membrane permeate vacuum stream from the second SO2 selective membrane unit permeate side; passing the second SO2 selective membrane permeate vacuum stream through the second SO2 selective membrane vacuum to generate an SO2 membrane permeate stream; removing the low SO2 discharge stream from the second SO2 selective membrane unit retentate side; introducing the CO2 removal system feed stream to the first CO2 selective membrane unit retentate side, the first CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the first CO2 selective membrane unit permeate side with a first CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the first CO2 selective membrane unit to produce a first CO2 selective membrane permeate vacuum stream from the first CO2 selective membrane unit permeate side; passing the first CO2 selective membrane permeate vacuum stream through the first CO2 selective membrane vacuum to generate a first CO2 membrane permeate stream; removing a first CO2 membrane retentate stream from the first CO2 selective membrane unit retentate side; introducing the first CO2 membrane retentate stream to the second CO2 selective membrane unit retentate side, the second CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the second CO2 selective membrane unit permeate side with a second CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the second CO2 selective membrane unit to produce a second CO2 selective membrane permeate vacuum stream from the second CO2 selective membrane unit permeate side; passing the second CO2 selective membrane permeate vacuum stream through the second CO2 selective membrane vacuum to generate a second CO2 membrane permeate stream; removing the SO2 rich recycle from the second CO2 selective membrane unit retentate side; introducing the first CO2 membrane permeate stream to the third CO2 selective membrane unit retentate side, the third CO2 selective membrane unit operable to allow carbon dioxide to permeate the CO2 selective membrane in preference to sulfur dioxide; generating vacuum pressure on the third CO2 selective membrane unit permeate side with a third CO2 selective membrane vacuum; causing carbon dioxide to pass through the CO2 selective membrane in the third CO2 selective membrane unit to produce a third CO2 selective membrane permeate vacuum stream from the third CO2 selective membrane unit permeate side; passing the third CO2 selective membrane permeate vacuum stream through the third CO2 selective membrane vacuum to generate the CO2 waste gas; and removing a second CO2 membrane retentate stream from the third CO2 selective membrane unit retentate side.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] These and other features, aspects, and advantages of the present disclosure 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 disclosure and are therefore not to be considered limiting of the scope as it can admit to other equally effective embodiments.
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[0054]
[0055] In the accompanying Figures, similar components or features, or both, can have a similar reference label. Similarly numbered streams and units have the same composition and operational conditions as described above unless otherwise noted. For the purpose of the simplified schematic illustrations and descriptions of the figures, the numerous pumps, compressors, valves, temperature and pressure sensors, electronic controllers, and the like that can be employed and well known to those of ordinary skill in the art are not included. Transfer lines between the various components of the system can include pipes, conduits, channels, or other suitable physical transfer lines that connect by fluidic communication one or more system components to one or more other system components. Further, accompanying components that are in conventional industrial operations are not depicted. However, operational components, such as those described in the present disclosure, can be added to the embodiments described in this disclosure. Optional recycle lines are shown in dashed lines.
[0056] It should further be noted that lines and arrows in the drawings refer to transfer lines which can serve to depict streams between two or more system components. Additionally, lines and arrows that connect to system components define inlets or outlets in each given system component. The arrow direction corresponds generally with the major direction of movement of the materials of the stream contained within the physical transfer line signified by the arrow. Furthermore, lines and arrows which do not connect two or more system components signify a product stream which exits the depicted system or a system inlet stream which enters the depicted system. Product streams can be further processed in processing systems or can be end products. System inlet streams can be streams transferred from accompanying processing systems or can be processed or non-processed feed streams.
DETAILED DESCRIPTION
[0057] While the disclosure 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 systems and methods described are within the scope and spirit of the disclosure. Accordingly, the embodiments of the disclosure described are set forth without any loss of generality, and without imposing limitations, on the claims.
[0058] As used in this disclosure, a “membrane” refers to a structure through which mass transfer can occur under a variety of driving forces. The driving forces can be a pressure differential between the two sides of the membrane generated by a positive pressure on the feed side of the membrane, a vacuum pressure on the permeate side of the membrane, stream component concentration differential between the permeate and retentate sides of the membrane, or combinations of the same. Driving forces that facilitate the transport of one or more components from the inlet gas stream through the selectively permeable membrane can be pressure, concentration, electrical potentials or combinations thereof across the membrane. Membrane operation can be in any mode such as high pressure at the feed side or vacuum pressure on the permeate side. The membrane allows a “penetrant” (a “penetrant” is an entity from a phase in contact with one of the membrane surfaces that passes through the membrane) to pass through the membrane from the retentate into the permeate. As used in this disclosure, the “retentate” is the stream that exits the membrane module without passing through the membrane, and has been depleted of penetrants. The membranes can be single or multilayered. As used in this disclosure, the “permeate” used as a noun can refer to the stream containing penetrants that leaves the membrane module, or can refer to the liquids and gases that have permeated the membrane of a membrane unit. Permeate can also be used in this disclosure as a verb, and means to spread through or flow through or pass through a membrane of a membrane unit. As an example, liquids and gases can permeate a membrane.
[0059] As used in this disclosure, “selective layer” refers to the membrane layer that is active in allowing the penetrant to pass through the membrane generating the permeate stream. As used in this disclosure, when a membrane is “selective for” a gas, that refers to the property of the membrane that allows more mass transport across the membrane material of one component as compared to the other component. For example, a CO.sub.2 over SO.sub.2 selective membrane preferentially transports CO.sub.2 through the membrane in the presence of SO.sub.2 and other components in the process stream to produce a CO.sub.2-enriched permeate and a CO.sub.2-depleted retentate. A membrane that is selective for one compound over another, such as a CO.sub.2 over SO.sub.2 selective membrane can be depicted as the following: CO.sub.2 over SO.sub.2, CO.sub.2/SO.sub.2, or CO.sub.2 vs. SO.sub.2.
[0060] As used in this disclosure, “thin-film, composite membranes” refers to membranes that consist of a thin polymer barrier layer formed on one or more porous support layers. The polymer barrier layer determines the flux and separation characteristics of the membrane; the porous backing serves only as a support for the selective layer and has no effect on membrane transport properties. As used in this disclosure, a reference to a membrane containing a specific material refers to the material used in the selective layer. The support structure can be made of any material.
[0061] As used in this disclosure, a “membrane module” refers to a manifold assembly containing a membrane or membranes to separate the streams of feed, permeate, and retentate. The membrane module can be any type of membrane module, including hollow fiber membrane modules, plate-and-frame membrane modules, capillary fiber membrane modules, spiral wound membrane modules, or potted hollow-fiber modules. Membranes can be arranged in the membrane module in a variety of configurations. Membranes can be in a flat-sheet configuration, a plate and frame configuration, or can be arranged to increase packing density, for example in a hollow-fiber or a capillary configuration or a spirally-wound configuration.
[0062] As used in this disclosure, a “sweep” refers to a nonpermeating gas stream that passes continuously by the downstream membrane face such that the permeate does not sit statically against the permeate side of the membrane, but is collected by the gas stream. The sweep can provide a driving force for the separation.
[0063] As used in this disclosure, “air” refers to the collective gases that constitute earth's atmosphere. Air contains nitrogen, oxygen, argon, carbon dioxide, water vapor, and other components. Unless otherwise indicated, the use of the term air includes all of the gases listed.
[0064] As used in this disclosure, a “stage” refers to a membrane process configuration where an additional membrane is positioned on the permeate discharge of a first membrane. Generally, additional compression is needed between the first membrane and the additional membrane because the permeate discharge is at a lower pressure than what is required to provide a driving force for separation. A multi-stage configuration can also have multiple recycles between membranes.
[0065] As used in this disclosure, a “step” refers to a membrane process configuration where an additional membrane is positioned on the retentate discharge of a first membrane. Generally, no additional compression is needed between the first membrane and the additional membrane, because the retentate discharge stream is at almost the same feed pressure. A multi-step configuration can also have multiple recycles between membranes.
[0066] The description may use the phrases “in some embodiments,” “in an embodiment,” or “in embodiments,” which can each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “containing,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.
[0067] For the purposes of describing and defining the present disclosure, a composition that “substantially contains” a particular compound includes at least 51% by weight of that particular compound.
[0068] As used in this disclosure, the term “about” is utilized to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term “about” is also utilized in this disclosure to represent the degree by which a quantitative representation can vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.
[0069] Embodiments of methods and systems to increase sulfur recovery and separate SO.sub.2 and CO.sub.2 from the tail gas and SO.sub.2 emissions streams from industrial processes, including the Claus sulfur recovery systems, are provided herein. The methods and systems use CO.sub.2 and SO.sub.2 selective membranes which selectively permeate CO.sub.2 and SO.sub.2 respectively over other components. An emissions stream containing SO.sub.2 emissions is sent to a membrane separation unit which includes an membrane selective for SO.sub.2 over other compounds, including CO.sub.2. The SO.sub.2 enriched permeate or SO.sub.2 depleted retentate can then be sent to additional membrane units that can contain membranes selective for SO.sub.2 to further concentrate or remove the SO.sub.2, or can be treated in a membrane selective for CO.sub.2 over other compounds, including SO.sub.2. The treatment in the membrane units results in a concentrated SO.sub.2 stream that can be recycled with a 3 to 5 fold enrichment in SO.sub.2, and a CO.sub.2 enriched stream that includes a low concentration of SO.sub.2, such as less than 150 ppm.
[0070] The concentrated SO.sub.2 stream has a lower concentration of CO.sub.2 than the emissions stream, so that when the concentration SO.sub.2 stream is recycled to the sulfur removal unit, the reduced CO.sub.2 content assists in maintaining a proper temperature profile in the sulfur removal unit and results in requiring less fuel in the sulfur removal unit. Increased CO.sub.2 content requires additional fuel use in the reactors and heaters in the sulfur removal unit since CO.sub.2 has no heating value and does not contribute to the reactions. Due to the reduced CO.sub.2 content, the operability of the sulfur removal unit is improved. Therefore, reducing CO.sub.2 content in the SO.sub.2 concentrated streams recycled to the sulfur recovery units results in significant advantages.
[0071] If the SO.sub.2 rich permeate from the SO.sub.2 over CO.sub.2 selective membrane has more than 50% CO.sub.2, then additional CO.sub.2 removal and SO.sub.2 purification to further reduce the amount of gas and the amount of CO.sub.2 recycled to the sulfur removal units. Thus, the SO.sub.2 concentrated streams can have 5% to 20% more SO.sub.2 than the original tail gas and SO.sub.2 emissions stream treated with the membrane units. Additionally, the SO.sub.2 enriched stream recycled to the sulfur recovery unit is less than the 10% of the original stream volume, and can be less than 5% of the original stream volume, so that the SO.sub.2 enriched stream can be recycled to multiple points within the sulfur removal unit without affecting or disrupting plant operations. If the SO.sub.2 rich permeate from the SO.sub.2 over CO.sub.2 selective membrane has less than 25% CO.sub.2, then SO.sub.2 purification can be used to further concentrate the gas stream.
[0072] Advantages to the methods and systems include those stated above, as well as additional advantages in increased sulfur recovery, reduced emissions, increased cost-effectiveness, and ability to retrofit existing systems. The addition of an air sweep improves efficiency of the membranes. Additionally, when an air sweep is utilized along with the SO.sub.2 selective membrane, the SO.sub.2 enriched recycle stream has oxygen that can replace some or all of the air introduced to the sulfur removal units. When the permeate from the SO.sub.2 selective membrane is further treated with CO.sub.2 selective membranes, the SO.sub.2 enriched stream recycled to the sulfur removal units is also oxygen enriched.
[0073] The SO.sub.2 over CO.sub.2 selective membrane, referred to as an SO2 selective membrane herein, can be a rubbery polar membrane. The SO2 selective membrane can be a composite membrane containing one or polymers. The SO2 selective membranes can have a selectivity of 3 and above. In some embodiments, the SO2 selective membrane is performed in a relatively low pressure process, such as membrane processes at 1 bar of pressure or less where the mass transfer is driven by concentration differentials or sweep gases, and not by pressure differential. In these embodiments, the membranes are housed in plate-and-frame membrane modules, or in capillary fiber membrane modules. In some embodiments, portions of the SO.sub.2 concentration utilizing the SO2 selective membranes are performed in a higher pressure process, such as 10 to 15 bar, and therefore the SO.sub.2 selective membranes are house in spiral wound membrane modules.
[0074] The SO2 selective membrane can be made from PEBAX™ (a registered trademark of Arkema) 4011. The permeation properties of a membrane containing PEBAX™ 4011 is included in Table 1, below. The properties of the membrane in Table 1 were tested at 23° C., with a gas mixture at 2.5 psig pressure containing 82.6% N.sub.2, 7.0% O.sub.2, 10.0% CO.sub.2, and 0.4% SO.sub.2. The permeating gas was kept at 22 mmHg absolute pressure. The resulting permeate contained 13.2% N.sub.2, 2.5% O.sub.2, 72.5% CO.sub.2, and 11.8% SO.sub.2.
TABLE-US-00001 TABLE 1 Properties of PEBAX ™ 4011 Composite Membrane Flux (1 × 10.sup.−6 cm.sup.3 Gas (STP)/cm.sup.2 .Math. s .Math. cmHg) Selectivity over N.sub.2 N.sub.2 5.0 gpu 1 O.sub.2 11 gpu 2.2 CO.sub.2 280 gpu 56 SO.sub.2 3,500 gpu 700
[0075] The SO.sub.2 selective membrane can be made from PEBAX™ 2533 material. A membrane containing PEBAX™ 2533 material can have an SO.sub.2 permeance of 2,000 gpu, a CO.sub.2 permeance of 200 gpu, an N.sub.2 permeance of 10 gpu, and an O.sub.2 permeance of 20 gpu.
[0076] The CO.sub.2 over SO.sub.2 selective membrane, referred to as a CO2 selective membrane herein, can be a composite membrane containing one or more polymers. The CO2 selective membrane can contain a glassy polymer. The glassy polymer can be hydrophobic. The glassy polymer can include a glassy perfluoropolymer. Glassy perfluoropolymer containing membranes can exhibit high CO.sub.2 selectivities. The CO2 selective membrane can have a selectivity for CO.sub.2 over SO.sub.2 of 5 or more, alternately 10 or more, alternately 20 or more, and alternately 30 or more. In some embodiments, the CO2 selective membranes are performed in a higher pressure process, such as 10 to 15 bar, and therefore the CO2 selective membranes are house in spiral wound membrane modules.
[0077] The CO2 selective membrane can contain commercially available amorphous perfluoropolymers such as CYTOP™ (a registered trademark of Asahi) material, HYFLON™ (a registered trademark of Solvay) material, TEFLON™ (a registered trademark of DuPont) AF material, or combinations of the same. These materials are commercially available amorphous perfluoropolymers.
[0078] CYTOP™ material is a polymer made of the monomer having the chemical structure of:
##STR00003##
[0079] The variable m can be repeated to generate the polymer. Membranes containing CYTOP™ material are CO.sub.2/SO.sub.2 selective. Acceptable grades of CYTOP™ material include CYTOP-A and CYTOP-M. CYTOP-A includes an R structure of —COOH between or at the end of the repeating monomers. CYTOP-M includes an R structure of —CONH—SI(OR′).sub.3 between or at the end of the repeating monomers. All grades of CYTOP™ material are acceptable for use in the membranes.
[0080] HYFLON™ material is a copolymer made of the monomer having the chemical structures of:
##STR00004##
[0081] The variables m or n can be repeated to generate the polymer. Acceptable grades of HYFLON™ material includes HYFLON HD40, where m=0.4 and n=0.6; HYFLON HD60, where m=0.6, and n=0.4; and HYFLON HD80, where m=0.8 and n=0.2. The CO.sub.2/SO.sub.2 selectivity of HYFLON™ containing membranes are in the range of 4 to 5. Additional information on the properties of HYFLON™ containing membranes can be found in Table 1.
[0082] TEFLON™ AF material is a copolymer made of the monomers having the chemical structures of:
##STR00005##
[0083] The variables m or n can be repeated to generate the polymer. Various grades of TEFLON™ AF material can be used, such as TEFLON™ AF2400 and TEFLON™ AF1400. TEFLON™ AF material is made of copolymers of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole (PPD), shown as monomer m above, and tetrafluoroethylene (TFE), shown as monomer n above, where m=0.87 and n=0.13. Membranes containing TEFLON™ material have a typical selectivity for CO.sub.2/SO.sub.2 of 4 to 5. Other grades of TEFLON™ material can be used in the CO2 selective membrane, including TEFLON™ AD60 and TEFLON™ AD80.
[0084] The CO2 selective membrane can contain homopolymers of CYTOP™ material, HYFLON™ material or TEFLON™ material; or copolymers of CYTOP™ material, HYFLON™ material or TEFLON™ material; or block copolymers of CYTOP™ material, HYFLON™ material or TEFLON™ material; or terpolymers of CYTOP™ material, HYFLON™ material or TEFLON™ material; or block terpolymers of CYTOP™ material, HYFLON™ material or TEFLON™ material; or copolymers of combinations of CYTOP™ material, HYFLON™ material or TEFLON™ material; or block copolymers of combinations of CYTOP™ material, HYFLON™ material or TEFLON™ material. For example, the material can be a terpolymer of the CYTOP™ monomer and the TEFLON™ monomers.
[0085] The CO2 selective membrane can contain materials made from homopolymers, copolymers, block copolymers, terpolymers, or block terpolymers generated from the monomers perfluoro (2-methylene-1,3-dioxolane) (PFMD); perfluoro (2-methylene-4,5-dimethyl-1,-dioxolane) (PFMDD); perfluoro-2,2-dimethyl-1,3-dioxole (PDD); and perfluoro-3-butenyl-vinyl ether (PBVE).
[0086] PDD has the following chemical structure:
##STR00006##
[0087] PBVE has the following chemical structure:
##STR00007##
[0088] Properties and selectivities of CO2 selective membranes containing different polymer materials are listed in Table 2. Perfluoro Polymer A is a copolymer of PFMD and PFMDD.
TABLE-US-00002 TABLE 2 Mixed Gas Selectivities with a Feed Gas of 1-5% SO.sub.2, 10% O.sub.2, and 78.5% N.sub.2 Saturated with Water at 50 psig and 25° C. N.sub.2 CO.sub.2 SO.sub.2 permeance permeance permeance CO.sub.2/SO.sub.2 Polymer (gpu) (gpu) (gpu) selectivity Hyflon 40 22 150 34 4.5 Hyflon 60 86 540 125 4.3 Perfluoro 29 220 19 12 Polymer A Perfluoro 200 2,000 200 10 Polymer B
[0089] The CO2 selective membrane can contain a glassy hydrophobic perfloropolymer. The CO2 selective membrane can be made of a homopolymer, copolymer, block copolymer, terpolymer, or block terpolymer of a combination of monomers A through H, pictured below:
##STR00008## ##STR00009##
[0090] For example, the membrane can contain a homopolymer of monomer C. The membrane can contain a copolymer of monomer C and B, or the membrane can contain a block copolymer of monomers C and B. The membrane can contain a terpolymers of monomers C, B and G, or can be a block terpolymer of monomers C, B, D, G and H. The membrane can contain copolymers of monomers B and H, or can be a block terpolymers of monomers C, B, D, E, and G. The membrane can contain multiple materials made of the various polymer generated from the homopolymers, copolymers, block copolymers, terpolymers, or block terpolymers of monomers A through H. For example, the membrane can contain a layer containing a material made of a block copolymer of monomers A and E, and the membrane my further contain a layer containing a material made of a terpolymer of monomers D, F, and H. Any combination of the above monomers generating a polymer is envisioned as a possible use for the membrane material in this disclosure.
[0091] In some preferred embodiments, the CO2 selective membrane contains a random amorphous polymer made from homopolymers or copolymers made from monomers B, D, and H. The CO2 selective membrane can contain copolymers with the compositions shown in the table below:
TABLE-US-00003 TABLE 3 Typical Tg for Possible Copolymer Compositions Monomer D Monomer H T.sub.g Polymer component mol % component mol % (° C.) 1 100 0 165 2 74 26 155 3 58 42 145 4 43 57 125 5 20 80 106 6 0 100 228 (T.sub.m)
[0092] Referring to
[0093] SO2 removal system 20 separates SO.sub.2 from the SO2 emissions stream 10 by membrane separation processes. SO2 selective membrane 25 preferentially allows SO.sub.2 to permeate the membrane. CO.sub.2 and water vapor also permeates SO2 selective membrane 25. SO2 removal system 20 generates low SO2 discharge stream 30 and CO2 removal system feed stream 50. Low SO2 discharge stream 30 contains less SO.sub.2 than SO2 emissions stream 10. Low SO2 discharge stream 30 can contain SO.sub.2 in a concentration less than 150 ppm, alternately less than 140 ppm, alternately less than 120 ppm, alternately less than 100 ppm, alternately less than 90 ppm, alternately less than 75 ppm, and alternately less than 50 ppm. CO2 removal system feed stream 50 has a greater concentration of SO.sub.2 than SO2 emissions stream 10. CO2 removal system feed stream 50 contains CO.sub.2, SO.sub.2, air, and water vapor.
[0094] CO2 removal system feed stream 50 is introduced to CO2 removal system 60. CO2 removal system 60 includes a membrane module with CO2 selective membrane 65. CO2 selective membrane 65 can have any of the characteristics and compositions as any of the CO2 selective membranes discussed herein. CO2 removal system 60 separates CO2 and SO2 from the CO2 removal system feed stream 50. CO2 selective membrane 65 preferentially allows CO.sub.2 to permeate the membrane. CO2 removal system 60 generates SO2 rich recycle 80 and CO2 waste gas 90. SO2 rich recycle 80 has a higher concentration of SO.sub.2 than CO2 removal system feed stream 50 and SO2 emissions stream 10. SO2 rich recycle 80 can substantially contain SO.sub.2. SO2 rich recycle 80 can have an SO.sub.2 concentration greater than 10 mol %, alternately greater than 15 mol %, alternately greater than 20 mol %, and alternately greater than 50 mol %. Advantageously, SO2 rich recycle 80 can have a reduced volume compared to SO2 emissions stream 10. CO2 waste gas 90 contains a higher concentration of CO.sub.2 than the CO2 removal system feed stream 50. CO2 waste gas 90 substantially contains CO.sub.2. Additional compression can be provided to increase pressure of the streams being introduced to the membrane modules.
[0095] Referring to
[0096] Low SO2 discharge stream 30 is removed from SO2 selective membrane unit retentate side 225A, and exits SO2 removal system 20. CO2 removal system feed stream 50 is removed from SO2 selective membrane unit permeate side 225B. CO2 removal system feed stream 50 contains SO.sub.2, CO.sub.2, water vapor, and additional air introduced from the air sweep.
[0097] CO2 removal system feed stream 50 is introduced to CO2 removal system 60. CO2 removal system 60 includes CO2 selective membrane unit 265. CO2 selective membrane unit 265 includes CO2 selective membrane 65 which separates CO2 selective membrane unit retentate side 265A and CO2 selective membrane unit permeate side 265B. CO2 selective membrane 65 preferentially allows CO.sub.2 to permeate the membrane. SO2 rich recycle 80 is removed from CO2 selective membrane unit retentate side 265A and exits CO2 removal system 60. CO2 waste gas 90 is removed from CO2 selective membrane unit permeate side 265B and exits CO2 removal system 60. CO2 waste gas 90 can be recycled to SO2 removal system 20 and introduced to SO2 selective membrane unit retentate side 225A to improve SO.sub.2 recovery. Additional compression can be provided to increase pressure of the streams being introduced to the membrane units.
[0098] Referring to
[0099] SO2 emissions stream 10 is introduced to SO2 removal system 20. SO2 removal system 20 includes SO2 selective membrane unit 225. SO2 selective membrane unit 225 includes SO2 selective membrane 25 which separates SO2 selective membrane unit retentate side 225A and SO2 selective membrane unit permeate side 225B. SO2 emissions stream 10 is introduced to SO2 selective membrane unit retentate side 225A. SO2 selective membrane 25 selectively allows SO.sub.2 to permeate the membrane. Air sweep 238 is introduced to SO2 removal system 20. Air sweep 238 is introduced to SO2 selective membrane unit permeate side 225B.
[0100] Low SO2 discharge stream 30 is removed from SO2 selective membrane unit retentate side 225A, and exits SO2 removal system 20. CO2 removal system feed stream 50 is removed from SO2 selective membrane unit permeate side 225B.
[0101] CO2 removal system feed stream 50 is introduced to CO2 removal system 60. CO2 removal system 60 includes CO2 selective membrane unit 265 and polishing SO2 selective membrane unit 375. CO2 selective membrane unit 265 includes CO2 selective membrane 65 which separates CO2 selective membrane unit retentate side 265A and CO2 selective membrane unit permeate side 265B. Polishing SO2 selective membrane unit 375 includes SO2 selective membrane 25 which separates polishing SO2 selective membrane unit retentate side 375A and polishing SO2 selective membrane unit permeate side 375B. CO2 selective membrane 65 preferentially allows CO.sub.2 to permeate the membrane. CO2 membrane retentate stream 368 is removed from CO2 selective membrane unit retentate side 265A. CO2 membrane retentate stream 368 contains a lower concentration of CO.sub.2 than CO2 removal system feed stream 50. CO2 waste gas 90 is removed from CO2 selective membrane unit permeate side 265B and exits CO2 removal system 60. CO2 waste gas 90 can be recycled to SO2 removal system 20 and introduced to SO2 selective membrane unit retentate side 225A to improve SO.sub.2 recovery.
[0102] CO2 membrane retentate stream 368 is introduced to polishing SO selective membrane unit retentate side 375A of polishing SO2 selective membrane unit 375. SO2 selective membrane 25 preferentially allows SO.sub.2 to permeate the membrane. SO2 rich recycle 80 is removed from polishing SO2 selective membrane unit permeate side 375B and exits CO2 removal system 60. SO2 rich recycle 80 has a lower concentration of CO.sub.2 and a higher concentration of SO.sub.2 than CO2 membrane retentate stream 368. Polishing SO2 selective membrane retentate stream 378 is removed from polishing SO2 selective membrane unit retentate side 375A. Polishing SO2 selective membrane retentate stream 378 can be recycled to SO.sub.2 removal system 20 and introduced to SO2 selective membrane unit retentate side 225A to improve SO.sub.2 recovery. Polishing SO2 selective membrane retentate stream 378 has a higher concentration of CO.sub.2 than the CO2 membrane retentate stream 368. Additional compression can be provided to increase pressure of the streams being introduced to the membrane units.
[0103] Referring to
[0104] SO2 emissions stream 10 is introduced to SO2 removal system 20. SO2 removal system 20 includes first SO2 selective membrane unit 425 and second SO2 selective membrane unit 427. First SO2 selective membrane unit 425 includes SO2 selective membrane 25 which separates first SO2 selective membrane unit retentate side 425A and first SO2 selective membrane unit permeate side 425B. Second SO2 selective membrane unit 427 includes SO2 selective membrane 25 which separates second SO2 selective membrane unit retentate side 427A and second SO2 selective membrane unit permeate side 427B.
[0105] SO2 emissions stream 10 is introduced to first SO2 selective membrane unit retentate side 425A. SO2 selective membrane 25 selectively allows SO.sub.2 to permeate the membrane. CO2 removal system feed stream 50 is removed from first SO2 selective membrane unit permeate side 425B and exits SO2 removal system 20. SO2 membrane retentate stream 426 is removed from first SO2 selective membrane unit retentate side 425A. SO2 membrane retentate stream 426 contains a lower concentration of SO.sub.2 than SO2 emissions stream 10. SO2 membrane retentate stream 426 is introduced to second SO2 selective membrane unit retentate side 427A. SO.sub.2 preferentially permeates SO2 selective membrane 25 in second SO2 selective membrane unit 427. SO2 membrane permeate stream 440 is removed to second SO2 selective membrane unit permeate side 427B. SO.sub.2 membrane permeate stream 440 contains CO.sub.2, SO.sub.2, and water vapor. SO2 membrane permeate stream 440 has a higher concentration of SO.sub.2 than SO2 membrane retentate stream 426. SO2 membrane permeate stream 440 can be recycled to first SO2 selective membrane unit retentate side 425A to improve SO.sub.2 recovery. Low SO2 discharge stream 30 is removed from second SO2 selective membrane unit retentate side 427A, and exits SO2 removal system 20. Low SO2 discharge stream 30 contains a lower concentration of SO.sub.2 than SO2 membrane retentate stream 426.
[0106] CO2 removal system feed stream 50 is introduced to CO2 removal system 60. CO2 removal system 60 includes CO2 selective membrane unit 265. CO2 selective membrane unit 265 includes CO2 selective membrane 65 which separates CO2 selective membrane unit retentate side 265A and CO2 selective membrane unit permeate side 265B. CO2 selective membrane 65 preferentially allows CO.sub.2 to permeate the membrane. SO2 rich recycle 80 is removed from CO2 selective membrane unit retentate side 265A and exits CO2 removal system 60. CO2 waste gas 90 is removed from CO2 selective membrane unit permeate side 265B and exits CO2 removal system 60. Additional compression can be provided to increase pressure of the streams being introduced to the membrane units.
[0107] Referring to
[0108] SO2 emissions stream 10 is introduced to first SO2 selective membrane unit retentate side 425A. SO2 selective membrane 25 selectively allows SO.sub.2 to permeate the membrane. CO2 removal system feed stream 50 is removed from first SO2 selective membrane unit permeate side 425B and exits SO2 removal system 20. SO2 membrane retentate stream 426 is removed from first SO2 selective membrane unit retentate side 425A.
[0109] SO2 membrane retentate stream 426 is introduced to second SO2 selective membrane unit retentate side 427A. SO.sub.2 preferentially permeates SO2 selective membrane 25 in second SO2 selective membrane unit 427. Air sweep 238 is introduced to second SO2 selective membrane unit permeate side 427B. SO2 membrane permeate stream 440 is removed to second SO2 selective membrane unit permeate side 427B. SO2 membrane permeate stream 440 contains CO.sub.2, SO.sub.2, water vapor, and additionally air. SO2 membrane permeate stream 440 exits SO2 removal system 20 and can be recycled to the sulfur recovery system. Since air sweep 238 is introduced to second SO2 selective membrane unit permeate side 427B, SO2 membrane permeate stream 440 contains air which can be used to substitute a portion of the air stream used in the sulfur recovery units such as the heaters or furnaces. Low SO2 discharge stream 30 is removed from second SO2 selective membrane unit retentate side 427A, and exits SO2 removal system 20. Alternately, a portion or all of the low SO2 discharge stream 30 can be used as a sweep for SO2 selective membrane 25 in first SO2 selective membrane unit 425 by introducing low SO2 discharge stream 30.
[0110] CO2 removal system feed stream 50 is introduced to CO2 removal system 60. CO2 removal system 60 includes first CO2 selective membrane unit 565 and second CO2 selective membrane unit 578. First CO2 selective membrane unit 565 includes CO2 selective membrane 65 which separates first CO2 selective membrane unit retentate side 565A and first CO2 selective membrane unit permeate side 565B. Second CO2 selective membrane unit 578 includes CO2 selective membrane 65 which separates second CO2 selective membrane unit retentate side 578A and second CO2 selective membrane unit permeate side 578B.
[0111] CO2 removal system feed stream 50 is introduced to first CO2 selective membrane unit retentate side 565A. CO.sub.2 preferentially permeates CO2 selective membrane 65. CO2 membrane retentate stream 368 is removed from first CO2 selective membrane unit retentate side 565A. CO2 waste gas 90 is removed from first CO2 selective membrane unit permeate side 565B and exits CO2 removal system 60. CO2 waste gas 90 can be recycled to first SO2 selective membrane retentate side 425A to improve SO.sub.2 recovery.
[0112] CO2 membrane retentate stream 368 is introduced to second CO2 selective membrane unit retentate side 578A of second CO2 selective membrane unit 578. CO.sub.2 preferentially permeates CO2 selective membrane 65. CO2 membrane permeate stream 589 is removed from second CO2 selective membrane unit permeate side 578B and exits CO2 removal system 60. CO2 membrane permeate stream 589 has a higher concentration of CO.sub.2 than CO2 membrane retentate stream 368. CO2 membrane permeate stream 589 can be recycled to first SO2 selective membrane unit retentate side 425A or can be recycled to first CO2 selective membrane unit retentate side 565A to improve SO.sub.2 recovery. SO2 rich recycle 80 is removed from second CO2 selective membrane unit retentate side 578A and exits CO2 removal system 60. Additional compression can be provided to increase pressure of the streams being introduced to the membrane units.
[0113] Referring to
[0114] SO2 emissions stream 10 is introduced to first SO2 selective membrane unit retentate side 425A. SO2 selective membrane 25 selectively allows SO.sub.2 to permeate the membrane. CO2 removal system feed stream 50 is removed from first SO2 selective membrane unit permeate side 425B and exits SO2 removal system 20. SO2 membrane retentate stream 426 is removed from first SO2 selective membrane unit retentate side 425A. SO2 membrane retentate stream 426 contains a lower concentration of SO.sub.2 than SO2 emissions stream 10.
[0115] SO2 membrane retentate stream 426 is introduced to second SO2 selective membrane unit retentate side 427A. SO.sub.2 preferentially permeates SO2 selective membrane 25 in second SO2 selective membrane unit 427. Air sweep 238 is introduced to second SO2 selective membrane unit permeate side 427B. SO2 membrane permeate stream 440 is removed to second SO2 selective membrane unit permeate side 427B. SO2 membrane permeate stream 440 exits SO2 removal system 20 and can be recycled to the sulfur recovery system. Since air sweep 238 is introduced to second SO2 selective membrane unit permeate side 427B SO2 membrane permeate stream 440 contains air which can be used to substitute a portion of the air stream used in the sulfur recovery units such as the heaters or furnaces. Low SO2 discharge stream 30 is removed from second SO2 selective membrane unit retentate side 427A, and exits SO2 removal system 20.
[0116] CO2 removal system feed stream 50 is introduced to CO2 removal system 60. CO2 removal system 60 includes first CO2 selective membrane unit 565, second CO2 selective membrane unit 578, and third CO2 selective membrane unit 685. First CO2 selective membrane unit 565 includes CO2 selective membrane 65 which separates first CO2 selective membrane unit retentate side 565A and first CO2 selective membrane unit permeate side 565B. Second CO2 selective membrane unit 578 includes CO2 selective membrane 65 which separates second CO2 selective membrane unit retentate side 578A and second CO2 selective membrane unit permeate side 578B. Third CO2 selective membrane unit 685 includes CO2 selective membrane 65 which separates third CO2 selective membrane unit retentate side 685A and third CO2 selective membrane unit permeate side 685B.
[0117] CO2 removal system feed stream 50 is introduced to first CO2 selective membrane unit retentate side 565A. CO.sub.2 preferentially permeates CO2 selective membrane 65. First CO2 membrane selective permeate stream 670 is removed from first CO2 selective membrane permeate side 565B. First CO2 membrane selective permeate stream 670 has a higher concentration of CO.sub.2 than CO2 removal system feed stream 50. First CO2 membrane retentate stream 668 is removed from first CO2 selective membrane unit retentate side 565A. First CO2 membrane retentate stream 668 has a lower concentration of CO.sub.2 than CO2 removal system feed stream 50.
[0118] First CO2 membrane retentate stream 668 is introduced to second CO2 selective membrane unit retentate side 578A of second CO2 selective membrane unit 578. CO.sub.2 preferentially permeates CO2 selective membrane 65. CO2 membrane permeate stream 689 is removed from second CO2 selective membrane unit permeate side 578B and exits CO2 removal system 60. CO2 membrane permeate stream 689 has a higher concentration of CO.sub.2 than first CO2 membrane retentate stream 668. CO2 membrane permeate stream 689 can be recycled to first CO2 selective membrane unit retentate side 565A to improve SO.sub.2 recovery. SO2 rich recycle 80 is removed from second CO2 selective membrane unit retentate side 578A and exits CO2 removal system 60.
[0119] First CO2 membrane permeate stream 670 is introduced to third CO2 selective membrane unit retentate side 685A of third CO2 selective membrane unit 685. CO.sub.2 preferentially permeates CO2 selective membrane 65. CO2 waste gas 90 is removed from third CO2 selective membrane unit permeate side 685B and exits CO2 removal system 60. CO2 waste gas 90 contains a higher concentration of CO.sub.2 than first CO2 membrane selective permeate stream 670. Third CO2 membrane retentate stream 688 is removed from third CO2 selective membrane unit retentate side 685A. Third CO2 membrane retentate stream 688 has a lower CO.sub.2 concentration than first CO2 membrane permeate stream 670. Third CO2 membrane retentate stream 688 can be recycled to first CO2 selective membrane unit retentate side 565A to improve SO.sub.2 recovery, or can exit CO2 removal system 60. Additional compression can be provided to increase pressure of the streams being introduced to the membrane units.
[0120] The addition of a vacuum or a compressor and vacuum on the permeate side of a membrane can result in an additional driving force for the separation of the components. The additional vacuum and compression provided on the permeate sides of the membrane modules in the system allow for a reduction of required membrane surface area and increased SO.sub.2 recovery. The vacuum or compressor used on the permeate side of a membrane module can be any type of vacuum or compressor used to generate a vacuum (less than atmospheric pressure) on a feed stream or used to increase the pressure of the produced stream (greater than atmospheric pressure). Types of vacuum generators that can be used include vacuum pumps, such as gas transfer vacuum pumps like diaphragm pumps or rotary piston pumps. Types of compressors that can be used include reciprocating, rotary, centrifugal, and axial compressors.
[0121] Referring to
[0122] CO2 removal system 60 depicted in
[0123] Referring to
[0124] CO2 removal system 60 depicted in
[0125] Referring to
[0126] CO2 removal system 60 depicted in
[0127] Referring to
[0128] CO2 removal system 60 depicted in
[0129] Referring to
[0130] CO2 removal system 60 depicted in
EXAMPLES
[0131] Process simulations were performed using computer software to illustrate potential operations of the methods and systems disclosed herein.
[0132] Examples 1, 2, and 3 show that when using only an SO2 selective membrane, significant amounts of CO.sub.2 are still captured in the SO2 rich recycle 80 being directed back to the sulfur recovery unit. Additional reductions in CO.sub.2 amounts recycled to the sulfur recovery units are needed to improve efficiency and prevent upsets, which supports the need of the additional CO.sub.2 removal system of the methods and systems disclosed herein.
Example 1
[0133] As a comparative example, a process simulation was performed utilizing a membrane unit including an SO2 selective membrane. The SO2 selective membrane used in this example has the characteristics as shown in Table 4, below.
TABLE-US-00004 TABLE 4 SO2 Selective Membrane Properties SO.sub.2 CO.sub.2 N.sub.2 O.sub.2 H.sub.2O Membrane 2,000 200 20 40 5,000 Permeance (gpu) Selectivity SO.sub.2/ SO.sub.2/ CO.sub.2/ SO.sub.2/ SO.sub.2/ N.sub.2 = CO.sub.2 = N.sub.2 = O.sub.2 = H.sub.2O = 100 10 10 20 0.4
[0134] The process simulation was set up to represent a configuration as shown in
[0135] The process simulation was performed with the air sweep 238 flow rate set equal to the SO2 emissions stream 10. The area of the SO2 selective membrane in the SO2 selective membrane unit 225 was adjusted until the SO.sub.2 concentration in the low SO2 discharge stream 30 was 50 ppm SO.sub.2. The resulting membrane area was 4,350 m.sup.2. No compression or vacuum was used. The results of the process simulation are shown in Table 5.
TABLE-US-00005 TABLE 5 Example 1 Results Stream Number 10 30 238 80 Composition SO.sub.2 0.1 50 ppm — 0.083 (mol %) CO.sub.2 35.0 19.7 — 15.9 N.sub.2 60.9 72.7 79.0 67.9 O.sub.2 4.0 7.6 21.0 16.1 Flow (mmscfd) 2.0 1.7 2.0 2.3 Pressure (bar) 1.0 1.0 1.0 1.0
[0136] The results of Example 1 show that although 95% of the SO.sub.2 is removed from the SO2 emissions stream 10 to the SO2 rich recycle 80, an additional 52% of the CO.sub.2 content also was disposed in the SO.sub.2 rich recycle 80, resulting in a significant amount of CO.sub.2 that could result in operational upsets and difficulties in the sulfur recovery units if recycled.
Example 2
[0137] Another process simulation was performed utilizing the same membrane unit setup and same membrane characteristics as in Example 1, except that additional compression was provided on the SO2 emissions stream 10 so that the pressure was higher. The pressure increased from 1.0 bar to 6.0 bar.
[0138] Similar to in Example 1, the area of the SO2 selective membrane in the SO2 selective membrane unit 225 was adjusted until the SO.sub.2 concentration in the low SO2 discharge stream 30 was 50 ppm SO.sub.2. The resulting required membrane area was 244 m.sup.2. The theoretical power that would have been supplied to a compressor necessary to raise the pressure of the SO2 emissions stream 10 was calculated to be 167 kWe. The results of the process simulation are shown in Table 6.
TABLE-US-00006 TABLE 6 Example 2 Results Stream Number 10 30 238 80 Composition SO.sub.2 0.1 50 ppm — 0.085 (mol %) CO.sub.2 35.0 28.2 — 9.1 N.sub.2 60.9 67.3 79.0 72.0 O.sub.2 4.0 4.5 21.0 18.8 Flow (mmscfd) 2.0 1.8 2.0 2.2 Pressure (bar) 6.0 6.0 1.0 1.0
[0139] The addition of raising the pressure of the SO2 emissions stream 10 with a compressor results in a 0.1 mmscfd in the SO2 rich recycle 80 as compared to Example 1 and a 4,095 m.sup.2 required membrane area decrease as compared to Example 1. Additionally, the compression produced a useful reduction in CO.sub.2 recycled from 52% to 29%.
Example 3
[0140] Another process simulation was performed utilizing the same membrane unit setup, including compression, and same membrane characteristics as in Example 2, except that the air sweep 238 was reduced to 0.2 mmscfd instead of matching the gas flow rate of the SO2 emissions stream 10. Sweep ratios (sweep gas flow/feed gas flow) of 0.1 to 0.2 produce a large reduction in membrane area as compared to no sweep flow.
[0141] Similar to in Example 1, the area of the SO2 selective membrane in the SO2 selective membrane unit 225 was adjusted until the SO2 concentration in the low SO2 discharge stream 30 was 50 ppm SO.sub.2. The resulting required membrane area was 511 m.sup.2. The theoretical power that would have been supplied to a compressor necessary to raise the pressure of the SO2 emissions stream 10 was calculated to be 167 kWe. The results of the process simulation are shown in Table 7.
TABLE-US-00007 TABLE 7 Example 3 Results Stream Number 10 30 238 80 Composition SO.sub.2 0.1 50 ppm — 0.319 (mol %) CO.sub.2 35.0 24.0 — 52.8 N.sub.2 60.0 71.4 79.0 38.9 O.sub.2 4.0 4.6 21.0 8.0 Flow (mmscfd) 2.0 1.6 0.2 0.6 Pressure (bar) 6.0 6.0 1.0 1.0
Example 4
[0142] Examples 1-3 above show that even with separation, significant amounts of CO2 are recycled to the Claus furnace. The following examples utilize both CO.sub.2 and SO.sub.2 selective membranes used together to reduce the CO.sub.2 recycled to the SRU.
[0143] In example 4, the set up in
[0144] The SO2 selective membrane simulated in the computer model was a PEBAX™ 4011 composite membrane with the properties as described in the following Table 8.
TABLE-US-00008 TABLE 8 Permeation Properties of PEBAX ™ 4011 Composite Membrane Gas Flux Selectivity over N.sub.2 N.sub.2 5.0 gpu 1 O.sub.2 11 gpu 2.2 CO.sub.2 280 gpu 56 SO.sub.2 3,500 gpu 700
[0145] The CO2 selective membrane simulated in the computer model was a perfluoropolymer membrane with the properties as described in the following Table 9.
TABLE-US-00009 TABLE 9 Permeation Properties of CO.sub.2/SO.sub.2 Selective Membrane SO.sub.2 CO.sub.2 N.sub.2 O.sub.2 H.sub.2O Permeance 50 500 20 40 2,000 (gpu) Selectivity SO.sub.2/ CO.sub.2/ CO.sub.2/ SO.sub.2/ H.sub.2O/ N.sub.2 = N.sub.2 = SO.sub.2 = O.sub.2 = SO.sub.2 = 2.5 25 10 1.25 40
[0146] The operational conditions for the simulation were as follows. The air sweep ration for the SO2 selective membrane was set at 0.1. The optional recycle of CO2 waste gas 90 was sent to SO2 selective membrane unit retentate side 225A. In this example, the SO2 selective membrane vacuum 234 was a compressor that generated CO2 removal system feed stream 50 at a pressure of 9 bar, and the CO2 selective membrane vacuum 267 was a compressor that generated CO2 waste gas 90 at a pressure of 6.0 bar for recycle.
[0147] The results of the simulation are shown in the following Table 10.
TABLE-US-00010 TABLE 10 Example 4 Results Stream Number 10 30 238 233 50 90 80 Composition SO.sub.2 0.096 50 ppm — 0.374 0.374 0.227 0.766 (Mol %) CO.sub.2 61.4 34.6 — 67.4 67.4 88.7 10.0 N.sub.2 35.2 60.8 79.0 26.6 26.6 8.1 76.5 O.sub.2 4.6 4.6 21.0 5.6 5.6 2.9 12.8 Flow (mmscfd) 2.67 1.95 0.2 0.91 0.91 0.67 0.25 Pressure (bar) 6.0 6.0 1.0 1.0 9 6.0 6.0
[0148] The membrane area of the SO2 selective membrane was calculated to be 700 m.sup.2. The membrane area for the CO2 selective membrane was calculated to be 384 m.sup.2. The calculated power required for SO2 selective membrane vacuum 234 was 219 kWe, and the calculated power required for CO2 selective membrane vacuum 267 was 74 kWe.
[0149] SO2 rich recycle 80 has a very low flow rate with very little CO.sub.2 concentration, and so can be easily incorporated into the recycle to the sulfur recovery unit. The results of this example show that only 3.6% of the CO.sub.2 was recycled in SO2 rich recycle 80, and SO2 rich recycle 80 was only 12.5% of the original emissions stream, SO2 emissions stream 10.
Example 5
[0150] In Example 5, the set up in
[0151] The results of the computer simulation are shown in the table below:
TABLE-US-00011 TABLE 11 Example 5 Results Stream Number 10 30 238 233 50 266 376 368 378 Composition SO.sub.2 0.1 50 ppm 0.558 0.558 0.410 10.0 1.121 0.327 (Mol %) CO.sub.2 35 31.9 69.3 69.3 86.2 21.2 5.0 3.5 N.sub.2 60.9 62.6 79.0 24.9 24.9 10.0 53.5 81.6 84.1 O.sub.2 4.0 5.5 21.0 5.3 5.3 3.4 15.3 12.3 12.1 Flow (mmscfd) 2.0 2.2 0.2 1.1 1.1 0.88 0.02 0.23 0.21 Pressure (bar) 6.0 6.0 1.0 1.0 6.0 1.0 1.0 20 20
[0152] The membrane area for the membrane in SO2 selective membrane unit 225 was calculated to be 924 m.sup.2. The membrane area for the membrane in CO2 selective membrane unit 265 was calculated to be 590 m.sup.2. The membrane area for the membrane in polishing SO2 selective membrane unit 375 was calculated to be 14 m.sup.2. The calculated power required for SO2 selective membrane vacuum 234 was 90 kWe, and additional compressors were calculated to require 253 kWe and 12 kWe. The additional compression between membrane modules was used to increase the pressure feed. SO2 rich recycle 80 had the same composition as polishing SO2 membrane permeate vacuum stream 376. SO2 rich recycle 80 has 10 mol % SO.sub.2 and 15 mol % O.sub.2, so the impact of the recycle on the sulfur recovery unit was minimal.
[0153] Although the present disclosure has been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the principle and scope of the disclosure. Accordingly, the scope of the present disclosure should be determined by the following claims and their appropriate legal equivalents.
[0154] The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise.
[0155] 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.
[0156] Ranges may be expressed throughout as from about one particular value, 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 or to the other particular value, along with all combinations within said range.
[0157] As used in the specification and in the appended claims, the words “comprise,” “has,” “contain” 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.
[0158] As used throughout the specification and claims, 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 disclosure.