Smelter acid recovery

The company manufactures lead-acid batteries at a piant in New Mexico. The company also operates a lead smelter that produces lead ingots at another location in New Mexico and ships them to the battery plant. Lead scrap from the battery plant is returned to the smelter for recovery and reuse. 

It has been common practice for many years to collect and recycle spent lead-acid batteries because of their value as a major source of lead units. This has led to highly developed operations whereby batteries are collected, sorted, and delivered to the secondary smelter for recovery of the lead and other materials of value. 

Owing to the cycHc nature of the TBRC operation, waste heat recovery from the off-gases is not practical and the SO2 content of the gas varies with the converter cycle. In order to supply a relatively uniform flow and strength SO2 gas to a sulfuric acid plant, a system has been installed at RonnskAr whereby the SO2 from fluctuating smelter gases is partially absorbed in water. During smelter gas intermption, SO2 is stripped with air and the concentrated gas deflvered to the acid plant. 

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). 

Sulfuric acid is the most commonly used reagent for the recovery of uranium from ores, and vanadium is often recovered as a coproduct. The sulfuric acid used is either the by-product sulfuric acid produced at smelters or sulfuric acid produced from elemental sulfur. 

Tn the last several years, much of the work in sulfur oxide emission - control has been aimed at emissions from power plant stacks. However, there are many other stationary sources of sulfur emissions including non-ferrous smelters, sulfuric acid plants, and petroleum refineries. The papers in this collection are concerned with these other sources of sulfur-bearing off-gases. This volume is intended to be a consolidated reference source for those interested in the latest sulfur recovery methods. 

After Mr. Semrau s introductory chapter follow four papers which present alternative techniques for recovering sulfur dioxide from the more concentrated smelter gas streams in the non-ferrous smelting industry. Presently, the only commercially available recovery techniques produce sulfuric acid or liquid sulfur dioxide. However, two of the discussions present developments in new processes for recovery of the sulfur values as elemental sulfur. 

At the Ronnskar works of Boliden AB in Sweden, which include both a copper and a lead smelter, a cyclic process using water as the absorbent concentrates sulfur dioxide both to produce liquid sulfur dioxide and for feed to acid plants (20, 21). The process is reported to give an absorption efficiency of about 98% on gas containing 2% sulfur dioxide. Water is not normally a favorable solvent for such an application but can be used in this case because it is available at a low temperature, less than 5°C for most of the year. Recovery of sulfur dioxide from the complete smelter is to be increased from 90 to 95% by applying water-cooled collecting hoods and waste heat boilers to all the copper converters (20). 

The common sources of indium are the minerals dark sphalerite, christophite, and marmatite. Indium is also found in small amounts in manganese, tungsten, zinc, and tin ores. Rarely found as a free element, indium is commonly associated with gallium in tin and zinc ores. The main commercial source for indium is from zinc smelter flue dusts (Smith etal. 1977). Enrichment of indium from zinc residues is performed by acid leaching followed by chemical separation processes. Aqueous electrolysis of indium salts yields a final metal of 99.9% purity. Canada has the greatest resources of indium with approximately 27% of the world s reserves (based on estimated indium content of zinc reserves) and the United States has about 12% of the world reserves (Brown 2000). In recent years, there have been major improvements in the recovery, refining and recycling of... 

With the exception of one operation, all carry out some form of sulfiir capture. The majority (six) produces sulfuric acid. One smelter did not ecifically define the desulfurization plant installed, and another is scrubbing the off-gas. The average conversion efficiency of the sulfuric acid plants is claimed to be between 94% and 98.5%. Overall recovery figures of sulfur were not provided. 

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