Zinc process

The electrochemical process, commercialized in the late 1980s, is the newest available technology and utilizes only caustic and sulfur dioxide as raw materials (359). Anhydrous or solution product can be manufactured by all processes however, the formate and zinc processes typically produce dry product, the amalgam and electrochemical processes typically produce solution product. 

Economic Aspects. U.S. capacity for production of merchant sodium dithionite (soHds basis) was estimated at 93,000 metric tons in 1994. There are three North American producers of sodium dithionite. Hoechst Celanese is the largest producer (68,000 tons capacity) with two formate production locations and one zinc process location. Olin (25,000 t capacity) produces solution product only at two locations using both the amalgam and electrochemical processes. In 1994, Vulcan started a small solution plant in Wisconsin using the Olin electrochemical process. In addition, it is estimated that 13,000 t/yr is produced at U.S. pulp mills using the Borol process from sulfur dioxide and sodium borohydride. Growth is estimated at 2—3%/yr. The... 

Grades purer than the Prime Western product have been made by vacuum de2incing the Hquid alloy to recover 99.9% 2inc at 0.02% lead. Distillation (New Jersey Zinc process) produces a purer product at a considerable cost in energy. 

Hori ntalEetort. In 1800, the first commercial zinc process made use of the horizontal retort. In 1980, only three such plants remain because they are not competitive in terms of labor and fuel costs. Furthermore, the dust produced presents a serious pollution problem. Nevertheless, in 1956, the tonnage of zinc produced from horizontal retorts was above that of any previous year. The only remaining operation is in Russia with a capacity of 10,000 annual MT. 

Particulate emissions from zinc processing are collected in baghouses or ESPs. SO2 in high concentrations is passed directly to an acid plant for production of sulfuric acid by the contact process. Low-concentration SO2 streams are scrubbed with an aqueous ammonia solution. The resulting ammonium sulfate is processed to the crystalline form and marketed as fertilizer. 

Air Pollution Emissions from Primary Zinc Processing... 

The material inputs and pollution outputs resulting from primary and secondary zinc processing are presented in Table 3.7. 

Primary zinc processing activities generate air emissions, process wastes, and other solid-phase wastes. Air emissions are generated during roasting, which is responsible for more than 90% of... 

Goethite A process for removing iron from leach liquors from hydrometallurgical leaching operations. Used in recovering zinc from the residues of the electrolytic zinc process. See also Jarosite, Haematite. 

Jarosite [Named after the mineral, first recognized at Jarosa, Spain] A process for removing iron from the leach liquors from hydrometallurgical operations. First used in 1964 in processing zinc sulfate liquors at Asturiana de Zinc, Spain. Also used for recovering zinc from the residues from the electrolytic zinc process. See also Goethite, Haematite. 

Electrolytic zinc plants, 12 555 Electrolytic zinc process, 26 565-566 Electrolyzers, industrial, 18 281 Electromagnetic applications, for bulk materials, 23 865-870 Electromagnetic assisted material processing, 23 856-857 Electromagnetic brush (EMB) technology, 7 59... 

ISP (Imperial Smelting Process)—a combined lead-zinc process in which oxidized concentrates are reduced with coke in a shaft furnace and the zinc vapor collected in a lead splash condenser. 

With this demonstration that zinc carbonate does not catalyze the photodegradation of paper in the presence of UV light and high humidity, we feel that the diethyl zinc process, as modified by the final carbon dioxide exposure, is now commercially feasible. 

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