Sulfur dioxide reduction

Claim 1

A continuous process for the reduction of sulfur dioxide in a sulfur dioxide-containing gas stream with a gaseous reducing agent selected from the group consisting of carbon monoxide, hydrogen, normally gaseous hydrocarbons of 1 to 4 carbon atoms, and mixtures thereof, which comprises the steps of: a. admixing said sulfur dioxide-containing gas stream with a portion comprising of from about 10 to about 95 percent of the total stream of gaseous reducing agent fed to the process, and passing of from about 60 to 100 percent of the resultant mixed gas stream through a first reaction chamber containing catalytic material, wherein said mixed gas stream is heated to a temperature of from about 850° to about 2400° F. and wherein a portion of the sulfur dioxide is reduced to form a gas stream comprising sulfur dioxide, hydrogen sulfide, and sulfur, and by-passing the remaining portion of the resultant mixed gas stream around the first reaction chamber; b. admixing said gas stream comprising sulfur dioxide, hydrogen sulfide, and sulfur obtained from said first reaction chamber with (i) the remaining portion of the total stream of gaseous reducing agent fed to the process and, (ii) from 0 to about 40 percent of the mixed gas stream obtained in step (a), above, then passing from about 10 to about 80 percent of the resultant mixed gas stream comprising reducing agent, sulfur dioxide, hydrogen sulfide, and sulfur through a second reaction chamber containing catalytic material, and passing the remaining portion of said mixed gas stream comprising reducing agent, sulfur dioxide, hydrogen sulfide, and sulfur through a third reaction chamber containing catalytic material in parallel with the gas stream being passed through said second reaction chamber, to produce in said second and third reaction chambers a product gas stream comprising hydrogen sulfide, sulfur dioxide, and sulfur, wherein in said third reaction chamber heat is absorbed from the gas stream to reduce the temperature of the product gas stream from said third reaction chamber to from about 500° to about 1000° F.; c. periodically reversing the flow in said first and third reaction chambers, thereby subjecting said first and third reaction chambers to periodically alternating heat absorbing and desorbing cycles while maintaining during the alternating cycles the gas flow through the catalyst bed in said second reaction chamber in the same direction; and d. maintaining the temperature of the gas stream entering said second and third reaction chambers within the range of from about 800° to about 1800° F. by varying the proportion of said mixed gas stream obtained in step (a), above, which is by-passed around the first reaction chamber during the alternating heat absorbing cycles of the first and third chambers so as to maintain the gas inlet temperature of said second and third reaction chamber within the above-stated range.