Sulfur pilot plant, elemental

Reduction of Sulfur Dioxide to Sulfur The Elemental Sulfur Pilot Plant of ASARCO and Phelps Dodge Corp. 

The El Paso elemental sulfur pilot plant is designed to permit reduction of 12—100% sulfur dioxide in gas streams. In the reduction of pure sulfur dioxide, stoichiometric proportioning of reformed gas to sulfur dioxide may be defined by ... 

S02 emissions from sulfuric acid plants are controlled in spray towers. Effluent gases contain less than 0.5 percent S02. The S02 emissions have to be controlled (or recovered as elemental sulfur by, for example, the Claus process). An approach is to absorb the S02 in a lime (or limestone) slurry (promoted by small amounts of carboxylic acids, such as adipic acid). Flow is in parallel downward. The product calcium salt is sent to a landfill or sold as a by-product. Limestone is pulverized to 80 to 90 percent through 200 mesh. Slurry concentrations of 5 to 40 percent have been used in pilot plants. 

Attempts to separate thorium and uranium from sulfuric acid solution of monazite by solvent extraction with TBP were unsuccessful because distribution coefficients of uranium and thorium from monazite solutions were too low, as these elements are complexed by phosphate ion. Development of extractants with higher distribution coefficients for these metals has made solvent extraction a practical process for recovering uranium and thorium from monazite sulfate solutions and from sulfuric acid solutions of other thorium ores. This section describes processes tested on a pilot-plant scale by Oak Ridge National Laboratory [C5]. 

A consortium of Japanese electric utilities is developing the IGC process with financial support from the Japanese government. A large (200 t/d) pilot plant is operating at the Nakoso Power Station in Iwaki City, Japan. This plant includes a hot gas cleanup system and a 13 MW combustion turbine with a combustor outlet temperature of 2,300°F. The hot gas desulfurization system recovers elemental sulfur which is a better form of sulfur... 

The process was operated (with the exception of the conversion of elemental sulfur to hydrogen sulfide) in a pilot plant processing 400 cfin of reveibaatory furnace gas, located at the San Manuel, Arizona, smelter of Magma Copper Company. Opmnting data collected over a period of several months indicate sulfur dioxide removal efficimicies exceeding 90%. 

A number of processes based upon the absorption of sulfur dioxide in aqueous solutions of ammonia have been proposed, and several have been developed to commercial or advanced pilot-plant operations. The processes differ primarily in the method of removing the sulfur dioxide from the ammonia-containing solution. Techniques used include steam or inoct-gas stripping, oxidation to sulfate, reduction to elemental sulfur, and displacemmit by a stronger acid. Three processes do not remove the sulfur dioxide from the ammonia-containing solution, but rather produce ammonium-based fertilizer. 

Commercialization of the ammonia process was pioneered by the Consolidated Mining Smelting Company, Ltd. (Cominco), which operated a 3 ton/day sulfur-producing pilot unit at their Trail plant in 1934 and placed a 40-ton/day commercial plant in operation in 1936 (King, 1950). The sulfur dioxide recovered in these early units was reduced to elemental sulfur. Later changes in the market picture made it more economical to use the concentrated sulfur dioxide streams as feed to sulfuric acid plants. Sulfur dioxide-absorption processes using both heat and acid neutralization were developed at Trail. Present operations use the neutralization process. 

The RESOX process, developed by Foster Wheeler, uses anthracite coal to reduce gaseous SO2 to elemental sulfur. Development work began on the process in the late 1960s. It was tested at the Scholtz Plant (a 42 MW demonstration unit) in the 1970s and at the Lunen plant (a pilot plant) in Germany in 1974 (Rush and Edwards, 1977). The process or variations of it have been used at three plants in Japan (Steiner, 1992). 

Direct catalytic oxidation of hydrogen sulfide to elemental sulfur in the presence of gaseous paraffinic hydrocarbons or other gases has been reported by Grekel (1959). Although pilot-plant work indicated good conversions and no effect on the hydrocarbons, the process has so far not been successfully commercialized. 

A process using synthetic zeolites for recovery of sulfur from sour gases under pressure has been described by Haines et al. (1961). In this process, which has been tested in a pilot plant, but which has not been commercialized, hydrogen sulfide is adsorbed on the zeolite which is then regenerated with sulfur dioxide containing gas at high temperatures. The elemental sulfur formed is condensed, and residual hydrogen sulfide and sulfur dioxide are vented to atmosphere. 

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