US 5,658,547 A · Simplified efficient process for reducing NO.sub.x, SO.sub.x, and particulates

Abstract

The removal of SO.sub.x and particulates, and preferably also NO.sub.x, from the combustion gases of a large boiler, is simplified while efficiency is improved. In a primary treatment zone, a slurry comprising an alkaline SO.sub.x -reducing composition and preferably a nitrogen-containing composition effective to reduce NO.sub.x, is introduced into combustion gases at a temperature of from about 900.degree. to about 1300.degree. C. The gases are cooled by initial contact with steam-generating means, and then by contact with an gas-to-gas heat exchanger. Cooled gases are then subjected to a secondary treatment in which they are first humidified and further cooled by introduction of a water spray or aerosol to reduce the temperature to 100.degree. C. or below. Contact between the SO.sub.x -reducing composition and the humidified gases is maintained for a reaction period of at least 2 seconds. Particulate solids are then separated from the gases with a fabric filter. The cleaned gases are reheated by the gas-to-gas heat exchanger prior to discharge to the atmosphere. Reductions of SO.sub.x of greater than 80% are achieved, preferably 90 to 95%.

Claims20

Dependent claims

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.

4 more elements

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.

7 more elements

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.

7 more elements

Dependencies are inferred from the claim text.

Simplified efficient process for reducing NO.sub.x, SO.sub.x, and particulates

Life of this patent

Simplified efficient process for reducing NO.sub.x, SO.sub.x, and particulates

Life of this patent

Abstract

Claims20