Sulfur hydrogen sulfide with absorbed

Apart from this, a number of side reactions take place. In the gas absorber polysulfides (Sx, with x<6) can be formed by reaction of hydrogen sulfide with sulfur ... 

The performance of the Champlin SCOT unit has been tested by the Los Angeles APCD emission source test team. They found that the emission level was considerably below the statutory limits of 500 ppm sulfur dioxide. The plant has also been subject to a lengthy test by the mobile laboratory of the EPA with similar findings. Performance tests made by Shell Development Co. proved that the Champlin Plant met and exceeded its guarantee level of 500 ppm hydrogen sulfide in absorber offgas and that the selectivity of the solvent for hydrogen sulfide exceeded expectations. 

The quinone-based processes utilize the redox cycle illustrated in Figure 9-8 to convert hydrogen sulfide to elemental sulfur. In these processes hydrogen sulfide is absorbed into an aqueous solution containing a quinone in the oxidized state. The absorbed hydrogen sulfide is then oxidized to elemental sulfur by the quinone, which is reduced to hydroquinone in the reaction. The hydroquinone is reoxidized to quinone by contact with air in a separate step to complete the cycle. 

Carbonate is measured by evolution of carbon dioxide on treating the sample with sulfuric acid. The gas train should iaclude a silver acetate absorber to remove hydrogen sulfide, a magnesium perchlorate drying unit, and a CO2-absorption bulb. Sulfide is determined by distilling hydrogen sulfide from an acidified slurry of the sample iato an ammoniacal cadmium chloride solution, and titrating the precipitated cadmium sulfide iodimetrically. 

NKK s Bio-SR process is another iron-based redox process which instead of chelates, uses Thiobacillusferroidans )2iQ. - 2i to regenerate the solution (9). This process absorbs hydrogen sulfide from a gas stream into a ferric sulfate solution. The solution reacts with the hydrogen sulfide to produce elemental sulfur and ferrous sulfate. The sulfur is separated via mechanical means, such as filtering. The solution is regenerated to the active ferric form by the bacteria. 

Holmes-Maxted A process for removing organic sulfur compounds from coal gas. The gas, mixed with hydrogen, is passed over a metal thiomolybdate catalyst at 300 to 380°C, which converts the sulfur compounds to hydrogen sulfide which is then absorbed by iron oxide. Developed by E. B. Maxted at W. C. Holmes Company, UK, based on an invention made in 1937. More than 50 units were in operation by 1985. 

The Bio-FGD process converts sulfur dioxide to sulfur via wet reduction (10). The sulfur dioxide gas and an aqueous solution of sodium hydroxide are contacted in an absorber. The sodium hydroxide reacts with the sulfur dioxide to form sodium sulfite. A sulfate-reducing bacteria converts the sodium sulfite to hydrogen sulfide in an anaerobic biological reactor. In a second bioreactor, the hydrogen sulfide is converted to elemental sulfur by Thiobacilh. The sulfur from the aerobic second reactor is separated from the solution and processed as a sulfur cake or liquid. The process, developed by Paques BV and Hoogovens Technical Services Energy and Environment BV, can achieve 98% sulfur recovery. This process is similar to the Thiopaq Bioscrubber process for hydrogen sulfide removal offered by Paques. 

Twenty-five milliliters of concentrated ammonia are saturated with hydrogen sulfide gas while cooling in ice. When no more gas is absorbed 25ml more of the ammonia water is added. The ammonium sulfide solution is warmed to about 35°C and then 25g of finely powdered roll sulfur are stirred in. When no more dissolves (Vfc-l hour), the yellow solution is filtered into 60ml of 95% alcohol and allowed to stand in a stoppered flask overnight in the refrigerator. The crystals are filtered by suction and washed with alcohol and ether. They are dried in vacuo over lime covered with a very small amount of solid ammonium chloride. 

The CNG process removes sulfurous compounds, trace contaminants, and carbon dioxide from medium to high pressure gas streams containing substantial amounts of carbon dioxide. Process features include 1) absorption of sulfurous compounds and trace contaminants with pure liquid carbon dioxide, 2) regeneration of pure carbon dioxide with simultaneous concentration of hydrogen sulfide and trace contaminants by triple-point crystallization, and 3) absorption of carbon dioxide with a slurry of organic liquid containing solid carbon dioxide. These process features utilize unique properties of carbon dioxide, and enable small driving forces for heat and mass transfer, small absorbent flows, and relatively small process equipment. 

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