Zinc oxide smelting

Roasting. Copper and lead sulfides are direcdy smelted but not zinc sulfide. However, theoretical calculations are encouraging (20) and, if an efficient means of condensing zinc rapidly from 1600 K in the presence of carbon dioxide, sulfur dioxide, and steam can be devised, the process may be feasible. The reaction of zinc vapor to yield zinc oxide or zinc sulfide presents the main difficulty. 

The most significant occupational exposures to zinc would occur during the smelting and refining of zinc ore. The standards for occupational exposure have been estabUshed at a level to prevent the onset of metal fume fever. This temporary condition is caused by excessive exposure to freshly formed fumes of zinc oxide and results in flulike symptoms of fever, chills, headache, muscle pain, nausea and vomiting. 

Zinc melts at a fairly low temperature, 419°C, and boils at 918°C, below the temperature at which zinc oxide is reduced to zinc. If zinc had been smelted in the way described, the metal would have distilled when formed. To prevent its reoxidation when in the gaseous condition, the atmosphere of the furnace would have had to be kept free of oxygen so that the metal could cool and condense. The earliest available information on zinc distillation, however, is from as late as the twelfth century c.e. in India the suggested explanation advanced here does not, therefore, provide an answer as to how zinc was smelt before that time. 

Flicker A process for producing zinc oxide by direct oxidation of zinc vapor. Operated by the Fricker s Metal Company at Luton and Burry Port, UK, in the 1920s and 30s, subsequently acquired by the Imperial Smelting Corporation. Also operated by the Anglo American Corporation, South Africa, after World War II. 

New Jersey A continuous process for extracting zinc from zinc oxide, made by roasting zinc sulfide ore, by reduction with carbon in a vertical retort. First operated by the New Jersey Zinc Company in Palmerton, PA, in 1929, and introduced into the Avonmouth, UK, works of the Imperial Smelting Company in 1934. 

Cadmia, it will be remembered, is the impure zinc oxide, containing sometimes lead and copper oxides, from the furnaces in which brass was smelted. Misy was the partly oxidized iron or copper pyrites, essentially basic sulphates of iron and copper. Synopian red was haematite. This mixture, assuming the reducing action of the fuel in the furnace, or of any other reducing agent not specified in the recipe would yield an alloy of gold and zinc, with some copper and perhaps some lead. 

Historical Aspects. Zinc oxide has long been known as a byproduct of copper smelting. The Romans called it cadmia and used it as such in the production of brass. They also purified it for use in ointments by reduction followed by oxidation. In the Middle Ages, the alchemists thought that cadmia could be converted into gold. 

Zinc oxide is a very old technological material. Already in the Bronze Age it was produced as a byproduct of copper ore smelting and used for healing of wounds. Early in history it was also used for the production of brass (Cu-Zn alloy). This was the major application of ZnO for many centuries before metallic zinc replaced the oxide [149]. With the start of the industrial age in the middle of the nineteenth century, ZnO was used in white paints (chinese white), in rubber for the activation of the vulcanization process and in porcelain enamels. In the following a number of existing and emerging electronic applications of ZnO are briefly described. 

Zinc. Oxidized ores are calcined to drive off water of hydration and carbon dioxide. The sulfide ore is always roasted before smelting. 

Historical Aspects Zinc oxide has long been known as a byproduct of copper smelting. 

Cadmium is obtained mainly as a by-product in the smelting and refining of zinc it occurs to the amount of about one percent in many zinc ores. The sulfide of cadmium, CdS, is called greenockite. Cadmium is more volatile than zinc, and in the reduction of zinc oxide containing cadmium oxide it is concentrated in the first portions of dust collected in the receivers. 

Zinc is commonly found in nature in the form of the mineral sphalerite (ZnS). A step in the smelting of zinc is the roasting of sphalerite with oxygen to produce zinc oxide ... 

Pyrolysis is followed by the smelting of the metallic factions within an induction furnace. The batteries are automatically fed into the introduction furnace, reductant and fluxes are added and the iron and manganese are melted to produce ferromanganese and the zinc evaporates. The liberated zinc then passes through a splash condenser where it is returned as zinc metal. The carhon monoxide produced as a by-product of the zinc oxide reduction is washed and fed back into the pyrolysis as fuel (energy recovery). 

Zinc Oxide. Rowers of zinc philosopher s wool zinc white C.l. Pigment White 4 C.l. 77947. OZn mol wt 81.38. Zn 80.34%, O 19.66%. ZnO. Occurs as the mineral zincite. Prepd by vaporization of metallic zinc and oxidation of the vapors with preheated air (French process) also from franklinite, (American process) or from zinc sulfide Faith, Keyes Clark s Industrial Chemicals. F. A. Lowenheim. M. K. Moran, Eds. (Wiley-In terscience. New York, 4th ed 1975) pp 882-888. Purification Depew, U.S. pat. 2,372,367 (1945 to American Zinc, Lead Smelting). The medicinal grade contains 99.5% or more ZnO technical grades contain 90-99% ZnO and a few tenths of 1% of lead. See also Colour Index vol, 4 (3rd ed., 1971) p 4687. 

Two processes are used to produce metallic zinc from the ore concentrates that are not subjected to caustic soda leaching. In one process, the ore concentrate containing zinc sulfide is roasted in the presence of air to produce zinc oxide, which is combined with coke or coal and retorted to approximately 1,100° C to produce metallic zinc. In the other process, the roasted zinc oxide is leached with sulfuric acid, and the solution is electrolyzed to produce zinc of >99.9% purity. The electrolytic processing of zinc is replacing smelting as the most commonly used process (Lloyd and Showak 1984 Stokinger 1981). 

The experimental program described in this paper confirmed the concept of the process and the thermodynamic analysis. That is, the sulfur in the feed materials can be fixed as a Fe-S-O matte using metallic iron or iron ore while both zinc oxide and sulfide materials can be simultaneously smelted in a single reaction medium. The combustion of carbon with oxygrai inside the matte has been proved to be feasible. 

Before smelting, zinc sulfide is usually concentrated by a float and sink method. The zinc sulfide is then roasted to form zinc oxide, followed by reduction with carbon and/or carbon monoxide. Zinc metal is distilled off. 

Qass II consists of electrically active dusts that lose their charge upon adhesion and may form strong aggregates. These include stack effluents of the zinc oxide type, raw cement, discharges from nickel smelting furnaces, magnesites, chromium ore, wheat starch, powdered sugar, and molybdenum oxide. 

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