Claims
- 1. A process for removing SO.sub.x and particulates from the combustion gases of a combustor, comprising:
- preparing a slurry of an alkaline SO.sub.x -reducing composition effective to reduce SO.sub.x within a defined temperature range;
- defining a primary treatment zone including at least one treatment zone, having a temperature within the defined temperature range, within the combustor;
- introducing the slurry into the combustion gases within the primary treatment zone, the conditions being controlled to reduce the SO.sub.3 concentration to less than 10 miligrams per cubic meter;
- cooling the combustion gases;
- passing the cooled gases to a secondary treatment zone wherein they are first humidified and further cooled by introduction of water to produce humidified gases;
- maintaining contact between the SO.sub.x -reducing composition and the humidified gases for a reaction period of at least 2 seconds;
- passing the gases through a fabric filter to remove particulate solids and provide contact between the gases and particulate solids held thereon to provide cleaned gasses.
- 2. A process according to claim 1 wherein the gases leaving the primary treatment zone are cooled first by water heating means and then by a gas-to-gas heat exchanger.
- 3. A process according to claim 2 wherein the cleaned gases are reheated by the gas-to-gas heat exchanger prior to discharge to the atmosphere.
- 4. A process according to claim 1 wherein the step of cooling and humidifying the gases to produce humidified gases, reduces the temperature of the gases to below 100.degree. C. and increases the relative humidity of the gases to within the range of from 50 to 95%.
- 5. A process according to claim 4 wherein the step of cooling and humidifying the gases to produce humidified gases, reduces the temperature of the gases to from 65.degree. to 80.degree. C.
- 6. A process according to claim 1 wherein solids are recovered from the fabric filter at a rate effective to provide capacity for particulates it must separate from the combustion gases, and a portion of the solids is recycled to the process.
- 7. A process of claim 1 wherein the composition comprises a stabilizer system comprising a hydrophobic surfactant having an HLB of less than 8 and a more hydrophilic surfactant having an HLB of at least 8, wherein the HLB values of the hydrophobic and the hydrophilic surfactants differ by at least 3.
- 8. A process of claim 1 wherein the SO.sub.x -reducing composition includes at least one material selected from the group consisting of the oxides, hydroxides, and carbonates of an alkali metal or alkaline earth metal.
- 9. A process according to claim 1 wherein the slurry further contains a composition effective to reduce NO.sub.x within the defined temperature range.
- 10. A process of claim 9 wherein the NO.sub.x -reducing composition comprises urea, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium hydroxide, or a mixture of any of these in aqueous solution.
- 11. A process for removing SO.sub.x and particulates from the combustion gases of a combustor, comprising:
- preparing a slurry of an alkaline SO.sub.x -reducing composition including at least one material selected from the group consisting of the oxides, hydroxides, and carbonates of an alkali metal or alkaline earth metal, effective to reduce SO.sub.x within a defined temperature range of from 900.degree. to 1300.degree. C.
- defining a primary treatment zone including at least one treatment zone, having a temperature within the defined temperature range, within the combustor;
- introducing the slurry into the combustion gases within the primary treatment zone, the conditions therein being controlled to reduce the SO.sub.3 concentration to less than 10 milligram per cubic meter;
- cooling the combustion gases, first by steam generating means and then by gas-to-gas heat exchanger;
- passing the cooled gases to a secondary treatment zone wherein they are first humidified and further cooled by introduction of water to produce humidified gases, wherein the temperature of the gases is reduced to below 100.degree. C. and the humidity of the gases is increased to within the range of from 75 to 95%;
- maintaining contact between the SO.sub.x -reducing composition and the humidified gases for a reaction period of at least 2 seconds;
- passing the gases through a fabric filter to remove particulate solids and provide contact between the gases and particulate solids held thereon to provide cleaned gases;
- recovering solids from the fabric filter at a rate effective to provide capacity for particulates it must separate from the combustion gases; and
- recycling a portion of the solids recovered to the process to improve utilization of the SO.sub.x -reducing composition.
- 12. A process according to claim 11 wherein the cleaned gases are reheated by the gas-to-gas heat exchanger prior to discharge to the atmosphere.
- 13. A process according to claim 11 wherein the step of cooling and humidifying the gases to produce humidified gases, reduces the temperature of the gases to from 65.degree. to 80.degree. C. without exceeding the dewpoint of any SO.sub.3 therein.
- 14. A process of claim 11 wherein the composition comprises a stabilizer system comprising a generally,hydrophobic surfactant having an HLB of less than 8 and a more hydrophilic surfactant having an HLB of at least 8, wherein the HLB values of the hydrophobic and the hydrophilic surfactants differ by at least 3, preferably at least 5.
- 15. A process of claim 11 wherein the SO.sub.x -reducing composition comprises a material selected from the group consisting of limestone, dolomite, lime hydrate, and mixtures of these.
- 16. A process according to claim 11 wherein the slurry further contains a composition effective to reduce NO.sub.x within the defined temperature range.
- 17. A process of claim 16 wherein the NO.sub.x -reducing composition comprises urea, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium hydroxide, or a mixture of any of these in aqueous solution.
- 18. A process according to claim 11 wherein fresh slurry comprising SO.sub.x -reducing composition is added to the solids recycled.
- 19. A process according to claim 11 wherein: the SO.sub.x -reducing composition comprises a material selected from the group consisting of limestone, dolomite, lime hydrate, and mixtures of these; fresh slurry comprising SO.sub.x -reducing composition is added to the solids recycled; and the step of cooling and humidifying the gases to produce humidified gases, reduces the temperature of the gases to from 65.degree. to 80.degree. C. without exceeding the dewpoint of any SO.sub.3 therein.
- 20. A process for removing SO.sub.x and particulates from the combustion gases of a combustor, comprising:
- preparing a slurry including (i) an alkaline SO.sub.x -reducing composition including at least one material selected from the group consisting of the oxides, hydroxides, and carbonates of an alkali metal or alkaline earth metal, and (ii) a composition effective to reduce NO.sub.x comprising urea, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium hydroxide, or a mixture of any of these in aqueous solution, said slurry being effective to reduce SO.sub.x and NO.sub.x within a defined temperature range of from 850.degree. to 1100.degree. C.
- defining a primary treatment zone including at least one treatment zone, having a temperature within the defined temperature range, within the combustor;
- introducing the slurry into the combustion gases within the primary treatment zone, the conditions therein being controlled to reduce the SO.sub.3 concentration to less than 10 gram per cubic meter;
- cooling the combustion gases, first by steam generating means and then by a gas-to-gas heat exchanger;
- passing the cooled gases to a secondary treatment zone wherein they are first humidified and further cooled by introduction of water to produce humidified gases, wherein the temperature of the gases is reduced to below 100.degree. C. and the relative humidity of the gases is increased to within the range of from 50 to 95%;
- maintaining contact between the SO.sub.x -reducing composition and the humidified gases for a reaction period of at least 2 seconds;
- passing the gases through a fabric filter to remove particulate solids and provide contact between the gases and particulate solids held thereon to provide cleaned gases;
- recovering solids from the fabric filter at a rate effective to provide capacity for particulates it must separate from the combustion gases; and
- recycling a portion of the solids recovered to the process to improve utilization of the SO.sub.x -reducing composition.
RELATED APPLICATION
This application is a continuation in part of copending, commonly-owned U.S. patent application Ser. No. 08/264,864, pending, entitled "Multi-Step Process for Reducing NO.sub.x and SO.sub.x ", filed Jun. 30, 1994, by M. Linda Lin and John E. Hofmann.
US Referenced Citations (11)
Foreign Referenced Citations (4)
Number |
Date |
Country |
0373351 |
Jun 1990 |
EPX |
2627880 |
Nov 1982 |
DEX |
9117814 |
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WOX |
9202291 |
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WOX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
264864 |
Jun 1994 |
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