Tail gas sulfur from

Sulfur Dioxide Processing, Repriuts of 1972—1974 Chem. Eng. Prog, articles, AIChE, New York (1975). Contaius thirteen papers on flue gas desulfurization, two on SO2 control iu pulp and paper, one on sulfuric acid tail gas, one on SO2 from ore roasting, and two on NO from nitric acid. 

The acid gas from the Sul find regenerator must be disposed of in an environmentally acceptable manner. The Claus process offers an effective means for converting nearly all of the sulfur in the acid gas to saleable elemental sulfur. The tail gas from the Claus plant still contains some sulfur compounds. To minimize sulfur emissions from the plant, the Claus tail gas can be fed to a Shell Claus ff-gas Jreating (SCOT) unit where most of this sulfur is recovered and recycled to the Claus plant. With use of the SCOT Process, additional marketable sulfur is recovered within the Claus plant while tail gas sulfur emissions are substantially reduced, to typically less than 250 ppmv. 

A number of inoiganic pollutants are removable by TSA processes. One of the major pollutants requiring removal is S02 from flue gases and from sulfuric acid plant tail gases. The Sulfacid and Hitachi fixed-bed processes, the Sumitomo and BF moving-bed processes, and the Westvaco fluidized-bed process all use activated carbon adsorbents for proven S02 removal (58). Zeolites with high acid resistance, such as mordenite and clinoptilolite, have proven to be effective adsorbents for dry S02 removal from sulfuric acid tail gas (59), and special zeolite adsorbents have been incorporated into the UOP PURASIV S process for this application (54). 

H2S released from the stripper is treated in an O2- or air-blown Claus plant that oxidizes H2S to elemental sulfur. The tail gas from the Claus plant, still rich in sulfur compounds, is then treated in a Shell Claus off-gas treatment plant where those elements are catalytically converted to H2S and then recycled back to the absorption column of the AGR unit. 

To measure sulfur losses, check for H2S and SO2 in the final condenser effluent. Drager tubes are a simple and reasonably accurate way to get this data. Don t submit sulfur plant tail gas samples to the lab for analysis. The H2S and SO2 will react in the sample container to form solid sulfur and water. To calculate conversion from these measurements ... 

Theoretically, the increase of sulfur vapors to the first reactor would reduce conversion. In practice, a small shift in the reactor temperature rise from the lead reactor to the second and third reactors was noted. The theoretical reduction in conversion was too small to observe with a Drager tube analysis of the sulfur plant tail gas. 

Tail-gas treating processes are generally unnecessary in coal gasification plants that require less than 95% overall sulfur recovery/reduction (26). A well-designed acid gas removal system can easily and effectively remove most of the sulfur from coal gas, and can readily attain this standard with a Claus plant. 

When the Claus sulfur conversion process was first introduced, it was considered to be a means of air pollution control capable of recovering up to about 97% of the sulfur from acid gas streams that would otherwise be burned and vented to the atmosphere. However, as Claus plants became more common, and air pollution control regulations became more stringent, the unrecovered sulfur compounds in Claus plant tail gas streams became the target of further regulation. As a result, many techniques were proposed and/or developed to increase the overall sulfur removal efficiency of sulfur recovery systems and thereby reduce the amount of sulfur escaping into the atmosphere. 

Other developing or potential appHcations for lime are neutralization of tail gas from sulfuric acid plants, neutralization of waste hydrochloric and hydrofluoric acids and of nitrogen oxide (NO ) gases, scmbbing of stack gases from incinerators (qv), and of course, from small industrial coal-fired boilers. 

Recover sulfur from coke oven gas. Recycle Claus tail gas into coke oven gas system. 

Gas Treatment and Sulfur Recovery SO, NO. and HjS from vent and tail gas emissions. 

LOCAT units can be used for tail-gas clean-up from chemical or physical solvent processes. They can also be used directly as a gas sweetening unit by separating the absorber/oxidizer into two vessels. The regenerated solution is pumped to a high-pres.sure absorber to contact the gas. A light slurry of rich solution comes off the bottom of the absorber and flows to an atmospheric oxidizer tank where it is regenerated. A dense slurry is pumped off the base of the oxidizer to the melter and sulfur separator. 

ATS [Ammonium thiosulfate] A process for removing residual sulfur dioxide from Claus tail gas by absorption in aqueous ammonia to produce ammonium sulfite and bisulfite. Addition of hydrogen sulfide from the Claus unit produces saleable ammonium thiosulfate. Developed by the Pritchard Corporation and first operated by the Colorado Interstate Gas Company at Table Rock, WY. 

Hydrosulfreen A process for removing sulfur compounds from the tail gas from the Claus process. It combines the Sulfreen process with an upstream hydrolysis/oxidation stage, which improves efficiency and optimizes the emission control. Developed jointly by Lurgi and Societe National Elf Aquitaine, and installed in 1990 in the Mazovian Refining and Petrochemical Works, near Warsaw, Poland. See also Oxysulfreen. 

Modop [Mobil Oil Direct Oxidation Process] A process for removing residual sulfur-containing gases from the tail gas from the Claus process. The catalyst is titanium dioxide pelletized with calcium sulfate. Developed in the 1980s by Rhone-Poulenc, Procatalyse, and Mobil Oil. Three plants were operating in Germany in 1995 and one in the United States. European Patents 60,742 78,690. 

Trencor Also called Trentham Trencor. A wet-scrubbing process for removing residual sulfur dioxide and hydrogen sulfide from the tail gas from the Claus process. 

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