Air pollution control of oxides of nitrogen

Claim 2

A process for removing nitrogen oxide and nitrogen dioxide from a waste gaseous mixture containing up to 1% by volume of nitrogen oxides, comprising adjusting the oxygen concentration of said waste gaseous mixture to at least 10 times greater than the nitrogen dioxide and nitrogen oxide concentration of said mixture, countercurrently contacting said mixture with a liquid selected from the group consisting of water and dilute aqueous alkaline solutions, said liquid having a flow rate of from 10 to 60 gallons per minute per 1000 cubic feet of said gaseous mixture, in the presence of a knitted wire mesh packing material of stainless steel containing at least 8% Ni and having a diameter of from 0.003 to 0.015 inches, said packing material having from 180 to 800 square feet of surface area per cubic foot of volume, and maintaining a residence time of from 3.5 to 15 seconds for said gaseous mixture in the presence of said packing material.

Claim 3

The process of claim 1 wherein said residence time is maintained from 3.5 to 6 seconds.

Claim 4

The process of claim 1, wherein said initial waste gaseous mixture contains at least one water-soluble acid gas, further comprising first contacting said gaseous mixture with a liquid selected from the group consisting of water and dilute aqueous alkaline solutions in the presence of a plastic packing material to remove water-soluble acid gases before removing the nitrogen oxides.

Claim 5

In the process for removing nitrogen dioxide and nitrogen oxide from a mixture of waste gases containing oxygen and up to 5,000 ppm of nitrogen oxides, comprising contacting said mixture of gases with a countercurrent flow of an aqueous liquid in the presence of a packing material, the improvement which comprises maintaining an oxygen concentration in said mixture of waste gases of at least 10 times greater than the said nitrogen oxides concentration of said mixture, providing a liquid flow rate of from 10 to 60 gallons per minute per 1000 cubic feet per minute of said gaseous mixture, utilizing as said packing material a knitted wire mesh packing material of stainless steel containing at least 8% Ni and having a diameter of from 0.003 to 0.015 inches, said packing material having from 180 to 800 square feet of surface area per cubic foot of volume, and maintaining a residence time of from 3.5 to 6 seconds for said mixture of gases in the presence of said packing material.

Claim 6

In the process for removing nitrogen dioxide and nitrogen oxide from a mixture of waste gases containing oxygen and up to 5,000 ppm of nitrogen oxides, comprising contacting said mixture of gases with a countercurrent flow of an aqueous liquid in the presence of a packing material, the improvement which comprises maintaining an oxygen concentration in said mixture of waste gases of at least 10 times greater than the said nitrogen oxides concentration of said mixture, providing a liquid flow rate of from 10 to 60 gallons per minute per 1000 cubic feet per minute of said gaseous mixture, utilizing as said packing material a knitted wire mesh packing material of stainless steel containing at least 8% Ni and having a diameter of from 0.003 to 0.015 inches, said packing material having from 180 to 800 square feet of surface area per cubic foot of volume, and maintaining a residence time of from 3.5 to 6 seconds for said mixture of gases in the presence of said packing material.