Sulfur dioxide removal from a gas

Claim 2

The process of claim 1 wherein said initial gas is flue gas.

Claim 3

The process of claim 3 wherein said material used to pretreat said flue gas as the initial gas is said carbonaceous material.

Claim 4

The process of claim 4 wherein said carbonaceous material is coke, said gaseous reducing material used for the catalytic reduction of sulfur dioxide is carbon monoxide, and the catalytic reduction is at a temperature of about 950* to about 1,100* F.

Claim 5

The process of claim 6 wherein said flue, gas as the initial gas, contains about 3.5 percent oxygen, said pretreatment utilizes sufficient carbon monoxide and sufficient time of pretreatment to reduce the oxygen content to less than 1.4 percent.

Claim 6

The process of claim 6 wherein the amount of carbon monoxide and the time of pretreatment are sufficient to reduce the oxygen content to less than 0.1 percent.

Claim 7

The process of claim 3 wherein the material used to pretreat said flue gas as the initial gas is an aliphatic hydrocarbon, the pretreatment and the catalytic reduction are performed on the flue gas, while it still has fly ash entrained with it, at zones between the combination zone of a furnace burning a sulfur-bearing coal and a zone for separating the entrained fly ash from the gas before emitting the latter to the atmosphere, said zones for said pretreatment and said subsequent catalytic reduction being between said fly-ash-separating zone and a cooling zone that cools said fly-ash-entrained flue gas emanating from said combustion zone, only said hydrocarbon being introduced into said pretreatment zone for admixture with said fly-ash-entrained flue gas for said substantial reduction of said oxygen content at said temperature of between about 1,000* and about 1,400* F., said gaseous reducing material being introduced into said catalytic reduction zone for admixture with said fly-ash-entrained flue gas from said pretreatment zone, said catalyst for said catalytic reduction zone consists of said entrained fly-ash, said oxygen-reduced, fly-ash-entrained flue gas from the pretreatment zone being raised in temperature for admixture with the reduction by said gaseous reducing material in said catalytic reduction zone at a temperature of at least 1,600* F. when said gaseous reducing material is an aliphatic hydrocarbon, and admixture of said oxygen-reduced, fly-ash-entrained flue Gas and said gaseous reducing material in said catalytic reduction zone being between about 950* and about 1,100* F. when said gaseous reducing material is carbon monoxide.

Claim 8

The process of claim 8 wherein said aliphatic hydrocarbon, introduced into the pretreating zone, is a gas consisting essentially of methane, and the gaseous reducing material, introduced into the catalytic reduction zone, is a gas consisting essentially of methane.

Claim 9

The process of claim 8 wherein the gaseous reducing material, introduced into the catalytic reduction zone is carbon monoxide.

Claim 10

The process of claim 9 wherein the combustion zone is operated to produce a flue gas containing 3.5 percent oxygen and the amount of methane introduced into the pretreatment zone is sufficient to reduce the content of flue gas to below about 0.1 percent.