Copper smelter sulfuric acid production

However, this paper is primarily concerned with sulfuric acid production from copper smelters where most of the sulfur dioxide is in a gas stream which varies widely and frequently, both in gas volume and in sulfur dioxide concentration. This gas stream presents a real challenge... 

When oxygen-rich air is blown through a copper matte a large amount of SO2 is produced. This is contaminated with dust from the ores and hence it is cleaned by scrubbers and electrostatic precipitators and then fed to the (attached) sulfuric acid plant. This plant consumes all the SO2 and produces sulfuric acid. However, due to copper converter operations, the percentage SO2 and the gas flow vary considerably. External heating sources (oil fired burners) are provided if required and similar workings are used for zinc smelters and to use the SO2 produced for sulfuric acid production. 

For the typical lead smelter the principal by-products will be silver and gold, copper dross, sulfuric acid and antimony metal, usually in the form of antimonial lead alloy. Other possibilities are arsenic compounds and zinc oxide if slag fuming facilities are installed. 

Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

Ill - Alabama, Arkansas, Louisiana, Mississippi, New Mexico, and Texas. IV - Colorado, Idaho, Montana, Utah, and Wyoming. V -Alaska, Arizona, California, Hawaii, Nevada, Oregon, and Washington.] The justification is that for the next decade at least oil and gas are likely to continue as the primary sources of domestic recovered sulfur. Second, the inclusion of Arizona and Nevada in PAD district V roughly corresponds with the present market for acid production from copper smelters. Third, as the districts are established on the basis of an aggregation of states, data compilation is simplified. And fourth, as the districts have been defined ja priori they were not based on present expository requirements. 

Obviously, not all smelter acid capacity is utilized and not all SO2 produced is transformed into acid. For copper, lead, and zinc alone, if it is assumed that only 93.5 percent of the sulfur had been removed, metal production in 1976 implied an acid production of 6 million short tons. Actual acid production was 3.2 million short tons. A doubling of acid output due to abatement... 

Amine salts have been used to recover molybdenum from solutions arising from a variety of sources. Most of the western world s supply of this metal is derived from molybdenite (MoS2) concentrates obtained as a byproduct of copper production in the USA and Chile. Such concentrates are roasted to molybdenum(VI) oxide (volatile Re207 can often be recovered as a valuable byproduct from the roaster gases) and leached with dilute sulfuric acid to remove the copper from the crude M0O3 product. Some molybdenum also dissolves and can be recovered, for example, by the same technique as that practised at Kennecott s Utah Copper Division smelter,213 i.e. by extraction into a solution of a tertiary amine in kerosene at an aqueous pH value of about 1. 

A particle removal method commonly used in industry is electrostatic precipitation. Industrial interest in this very efficient scheme can be traced back to 1911 with the investigation of F. Cottrell. His pioneering studies of sulfuric acid mist removal from copper smelter effluents led to the production of the Cottrell precipitator. 

Smelter acid is not as pure as the acid produced from sulfur combustion, so it fetches a lower price. Nevertheless, this product is quite suitable for uses such as fertilizer phosphate production, which gives a by-product credit to the process. Smelters which exercise this choice produce about 4 tonnes of sulfuric acid for each tonne of copper [36]. Smelter sources contributed about 6% of the sulfuric acid produced in the U.S.A. in 1965 and more than 60% of the Canadian total for 1976 [39]. 

Table III presents the 1999 capacities and productions of the surveyed zinc smelters and refineries. The total capacity for the 20 plants was 3.2 million t/y of zinc, and the production rate was 2.8 million t/y. The average reported plant production was 141,250 t/y. The major byproducts are also given in Table III. Over 90% of the operations produced cadmium and sulfuric acid. Other important by-products include copper and gypsum.

Hnally, sulfuric acid from pyrites, smelter operations, or other byproduct sources may contain impurities that may or may not be deleterious for phosphoric acid production. In at least one case, zinc in smelter acid proved useful since the fertilizer produced from phosphoric add contained enough zinc, mainly derived from the smelter acid, to improve crop yields in zinc-deficient areas. The same benefit applies to another micronutrient, copper. 

Smelter revenues are also boosted by an ability to recover and sell by-products such as sulfuric acid and copper, as weU as some minor elements such as antimony in the form of antimonial lead alloys, mercury and cadmium. In some instances zinc can be recovered from smelter slags by fuming. 

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