Claims
- 1. A process for removing SO.sub.2 from a gas mixture comprising SO.sub.3 in an amount greater than zero and less than or equal to 15% by volume, SO.sub.2 in an amount greater than zero and less than or equal to 5,000 ppm by volume and a volume ratio of SO.sub.3 to SO.sub.2 greater than 1 which process comprises introducing said gas mixture into an SO.sub.3 absorber at a temperature between about 50.degree. and about 150.degree. C., contacting the gas mixture with aqueous sulfuric acid containing more than 90% by weight H.sub.2 SO.sub.4 and also with 1 to 25 parts of a peroxide compound per million parts based on said aqueous sulfuric acid; converting SO.sub.2 to H.sub.2 SO.sub.4 in said absorber; converting SO.sub.3 to H.sub.2 SO.sub.4 in said absorber; removing a stream of purified gas from an upper portion of the absorber; and removing a stream of sulfuric acid from a lower portion of the absorber, wherein said peroxide compound is introduced into said absorber in the form of a mist.
- 2. The process according to claim 1, wherein said gas mixture comprises nitrogen and oxygen in addition to SO.sub.2 and SO.sub.3.
- 3. The process according to claim 1, wherein said gas mixture comprises about 4 to about 15% by volume SO.sub.3 and about 1,000 to about 5,000 ppm by volume SO.sub.2.
- 4. The process according to claim 1, wherein said gas mixture comprises about 0.2 to about 1.5% by volume SO.sub.3 and about 200 to about 800 ppm by volume SO.sub.2.
- 5. The process according to claim 1, wherein the peroxide compound is either H.sub.2 O.sub.2 or peroxymonosulfuric acid and is supplied to the absorber in an amount corresponding to between about 0.53 and 2 parts by weight H.sub.2 O.sub.2 per part by weight of SO.sub.2 to be removed.
- 6. The process according to claim 1, wherein said mist introduced into said absorber comprises 1-40 parts acid per one part peroxide.
- 7. The process according to claim 1, wherein said mist comprises aqueous particles having a size less than 100 .mu.m.
- 8. The process according to claim 1, wherein said mist is introduced into a vapor space in said absorber in an amount which does not exceed 500 mg of mist per cubic foot of vapor space.
- 9. The process according to claim 1, wherein said mist contacts an SO.sub.2 containing gas in a vapor space in said absorber and the treated gas is subsequently introduced into a mist eliminator.
- 10. The process according to claim 9, wherein said mist eliminator is a fiber bed mist eliminator.
- 11. A process for the commercial manufacture of sulfuric acid in a sulfuric acid manufacturing plant in which a sulfur dioxide containing gas and an oxygen-containing gas are reacted in a catalytic oxidation zone into a mixture comprising sulfur trioxide and sulfur dioxide having a volume ratio of SO.sub.3 to SO.sub.2 greater than 1, which process comprises introducing said mixture of sulfur trioxide and sulfur dioxide into an SO.sub.3 absorber containing an aqueous sulfuric acid medium possessing an H.sub.2 SO.sub.4 concentration greater than 90%, introducing 1 to 25 parts of a peroxide compound per million parts of said aqueous sulfuric acid medium into said SO.sub.3 absorber, absorbing sulfur trioxide in said medium to produce H.sub.2 SO.sub.4 ; dissolving and oxidizing the sulfur dioxide in said medium to produce additional sulfuric acid and reducing the SO.sub.2 concentration in said mixture such that the sulfur dioxide content in the remaining gas phase is maintained at a concentration of less than 4 lb SO.sub.2 per short ton of H.sub.2 SO.sub.4 produced; and removing a stream of sulfuric acid and a stream of emission gas from said absorber, wherein said peroxide compound is introduced into said absorber in the form of a mist.
- 12. The process according to claim 11, wherein the gas from said catalytic oxidation zone contains unconverted SO.sub.2 in excess of 4 lb SO.sub.2 per short ton of H.sub.2 SO.sub.4 produced and said unconverted SO.sub.2 is reduced by addition of the peroxide into the absorber in an amount which effectively reduces SO.sub.2 plant emission to less than 4 lb SO.sub.2 per short ton of H.sub.2 SO.sub.4 produced without an increase in the pressure drop of the plant.
- 13. The process according to claim 11, wherein catalytic conversion efficiency is less than 99.7%.
- 14. The process according to claim 11, wherein said peroxide compound is hydrogen peroxide, peroxymonosulfuric, peroxydisulfuric acid, or peroxymonophosphoric acid.
- 15. The process according to claim 14, wherein said peroxide compound is hydrogen peroxide.
- 16. The process according to claim 11, wherein said sulfuric acid in said SO.sub.3 absorption zone is recirculated through a recirculating loop.
- 17. The process according to claim 11, wherein said peroxide compound is premixed with sulfuric acid before introduction in the SO.sub.3 absorption zone.
- 18. The process according to claim 11, wherein the concentration of sulfuric acid in said SO.sub.3 absorber is above 95% by weight.
- 19. The process according to claim 18, wherein the concentration of sulfuric acid produced in said SO.sub.3 absorber is between 96 and 99.9% by weight.
- 20. The process according to claim 19, wherein the temperature in said SO.sub.3 absorber is above 50.degree. C. and up to 150.degree. C.
- 21. The process according to claim 11, wherein said peroxide compound is introduced directly into said absorber.
- 22. The process according to claim 11, wherein said peroxide compound is introduced into said absorber in the form of a mist comprising a mixture of peroxide and sulfuric acid.
- 23. The process according to claim 22, wherein said mist comprises 140 parts acid per one part peroxide.
- 24. The process according to claim 22, wherein said mist comprises aqueous particles having a size less than 100 .mu.m.
- 25. The process according to claim 22, wherein said mist is introduced into a vapor space in said contacting zone in an amount which does not exceed 500 mg of mist per cubic foot of vapor space.
- 26. The process according to claim 22, wherein said mist contacts an SO.sub.2 containing gas in a vapor space in said contacting zone and the treated gas is subsequently introduced into a mist eliminator.
- 27. The process according to claim 26, wherein said mist eliminator is a fiber bed mist eliminator.
- 28. A process for the manufacture of sulfuric acid in a sulfuric acid manufacturing plant, which process comprises:
- introducing a sulfur-containing feed material into a reaction zone maintained at conditions suitable for producing gaseous sulfur dioxide;
- introducing at least a portion of the gaseous sulfur dioxide in the presence of an oxygen-containing gas into a catalytic conversion zone maintained at conditions suitable for converting the gaseous sulfur dioxide into a gas mixture containing sulfur trioxide and sulfur dioxide;
- introducing the mixture of sulfur dioxide and sulfur trioxide into a lower portion of an SO.sub.3 absorber containing a downwardly moving sulfuric acid absorption medium maintained at a temperature above 50.degree. C. and up to about 150.degree. C.;
- introducing 1 to 25 parts of a peroxide compound per million parts of said sulfuric acid absorption medium into said SO.sub.3 absorber;
- removing a stream of purified emission gas from an upper portion of the absorption zone, and removing a stream of sulfuric acid product from a lower portion of the absorption zone while keeping SO.sub.2 emissions from the process no more than 4 lbs SO.sub.2 per short ton of H.sub.2 SO.sub.4 produced;
- wherein said peroxide compound in said SO.sub.3 absorber is introduced in the form of a mist.
- 29. A processing according to claim 28, wherein the peroxide compound is hydrogen peroxide, peroxymonosulfuric acid or peroxydisulfuric acid and is added into the absorber to provide therein the equivalent of between about 0.53 and 2 part by weight of H.sub.2 O.sub.2 per part by weight of SO.sub.2 to be removed therein.
- 30. A process according to claim 29, wherein the peroxide compound is introduced into the SO.sub.3 absorption zone in an amount to maintain SO.sub.2 emissions from the process at no more than 4 lb SO.sub.2 per short ton of sulfuric acid produced when the catalytic conversion zone is not capable of providing 99.7% conversion efficiency.
- 31. A process according to claim 29, which comprises only one SO.sub.3 absorber.
- 32. A process according to claim 31, wherein the gas mixture introduced into the SO.sub.3 absorption zone comprises about 4 to 15% by volume of SO.sub.3 and about 1,000 to 5,000 ppm by volume of SO.sub.2, plus oxygen and nitrogen.
- 33. A process according to claim 29, which comprises two separate SO.sub.3 absorbers and in which process:
- the gas mixture containing sulfur dioxide and sulfur trioxide from a first catalytic conversion step is passed into a first SO.sub.3 absorber containing sulfuric acid for the absorption of sulfur trioxide therein in the substantial absence of any peroxide compound;
- a stream of sulfuric acid and a stream of sulfur dioxide-containing gas are removed from said first SO.sub.3 absorber;
- said sulfur dioxide-containing stream is passed through a second catalytic conversion step under conditions suitable for converting a major portion of the sulfur dioxide present into sulfur trioxide;
- passing the resulting mixture of sulfur trioxide and residual sulfur dioxide into and upwardly through a second SO.sub.3 absorption zone, said second SO.sub.3 absorption zone containing a sulfuric acid absorption medium maintained at a temperature above 50.degree. C. and up to about 150.degree. C. and comprising sulfuric acid having an H.sub.2 SO.sub.4 content greater than 90% by weight;
- introducing 1-25 parts of a peroxide compound per million parts of said sulfuric acid absorption medium into said second SO.sub.3 absorber so as to keep SO.sub.2 emissions in the tail-gas from the plant no greater than 4 lbs per short ton of sulfuric acid produced; and
- removing a stream of purified tail gas from an upper portion and a stream of sulfuric acid product from a lower portion of said second SO.sub.3 absorption zone.
- 34. A process according to claim 33, wherein the gas mixture introduced into the SO.sub.3 absorption zone comprises about 0.2 to 1.5% by volume SO.sub.3 and about 200 ppm to 800 ppm by volume SO.sub.2, plus oxygen and nitrogen.
- 35. The process according to claim 34, wherein catalytic conversion efficiency is less than 99.7%.
- 36. The process according to claim 34, wherein said second SO.sub.3 absorber contains a mist eliminator.
- 37. A process for removing SO.sub.2 from a gas mixture comprising SO.sub.3 in an amount greater than zero and less than or equal to 15% by volume, SO.sub.2 in an amount greater than zero and less than or equal to 5,000 ppm by volume and a volume ratio of SO.sub.3 to SO.sub.2 greater than 1 which process comprises introducing said gas mixture into an SO.sub.3 absorber at a temperature between about 50.degree. and about 150.degree. C., contacting the gas mixture with aqueous sulfuric acid containing more than 90% by weight H.sub.2 SO.sub.4 and also with 1 to 25 parts of a peroxide compound per million parts based on said aqueous sulfuric acid; converting SO.sub.2 to H.sub.2 SO.sub.4 in said absorber; converting SO.sub.3 to H.sub.2 SO.sub.4 in said absorber; removing a stream of purified gas from an upper portion of the absorber; and removing a stream of sulfuric acid from a lower portion of the absorber, wherein said peroxide compound is introduced into said absorber in a stream separate from another stream which introduces aqueous sulfuric acid.
- 38. The process according to claim 37, wherein said gas mixture comprises nitrogen and oxygen in addition to SO.sub.2 and SO.sub.3.
- 39. The process according to claim 37, wherein said gas mixture comprises about 4 to about 15% by volume SO.sub.3 and about 1,000 to about 5,000 ppm by volume SO.sub.2.
- 40. The process according to claim 37, wherein said gas mixture comprises about 0.2 to about 1.5% by volume SO.sub.3 and about 200 to about 800 ppm by volume SO.sub.2.
- 41. The process according to claim 37, wherein the peroxide compound is either H.sub.2 O.sub.2 or peroxymonosulfuric acid and is supplied to the absorber in an amount corresponding to between about 0.53 and 2 parts by weight H.sub.2 O.sub.2 per part by weight of SO.sub.2 to be removed.
- 42. The process according to claim 37, wherein said stream containing hydrogen peroxide introduced into said absorber comprises 1-40 parts acid per one part peroxide.
- 43. The process according to claim 37, wherein said stream containing hydrogen peroxide is introduced into the absorber as a mist comprising aqueous particles having a size less than 100 .mu.m.
- 44. The process according to claim 43, wherein said mist is introduced into a vapor space in said absorber in an amount which does not exceed 500 mg of mist per cubic foot of vapor space.
- 45. The process according to claim 37, wherein said mist contacts an SO.sub.2 containing gas in a vapor space in said absorber and said SO.sub.2 containing gas is subsequently introduced into a mist eliminator.
- 46. The process according to claim 45, wherein said mist eliminator is a fiber bed mist eliminator.
- 47. The process according to claim 46, wherein the fiber bed allows for additional contact between said peroxide and said sulfur dioxide.
- 48. The process according to claim 45, wherein a reaction between the peroxide in the mist phase and sulfur dioxide in the gas phase is completed in the mist eliminator.
Parent Case Info
This application is a continuation-in-part of U.S. patent application Ser. No. 08/495,396 filed Jun. 28, 1995, now U.S. Pat. No. 5,593,652.
US Referenced Citations (8)
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Jan 1939 |
DEX |
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Entry |
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Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
495396 |
Jun 1995 |
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