Secondary lead processing technology

Smelting is a proeess whereby metals, sueh as lead, iron, or eopper, are recovered from a feedstock by the ehemieal reduetion of their eompounds. These reactions occur in various processes and take place at temperatures up to 1400°C in some lead blast furnaces, and to over 1800°C in iron blast furnaces. Various types of furnace are utilized worldwide for the smelting lead. These include the blast, reverberatory and Isasmelt/Ausmelt technologies [6] (see also Chapter 16), and the QSL [7] and Kivcet [8] processes. Not all secondary lead producers use modern technology such... 

Nevertheless, both hazardous and inert residues are solid wastes and require landfill. Dumping solid waste to landfill, even non-hazardous clean wastes, is not sustainable and is not entirely green . An ideal green technology is one that consumes all materials involved in the production process to produce only re-useable or new products, without generating solid waste that requires disposal to landfill. Such smelters can be found in Trail, British Columbia, Canada at the Cominco lead and zinc primary smelter and in Malaysia in Kuala Lmnpur at the Metal Reclamation primary and secondary lead smelter [21]. 

A life-cycle inventory analysis [4] has examined the performance of lead production and battery manufacturing facilities in North America. This study collected data descriptive of industrial emissions in the base year of 1995-1996. The mass flows indicated that the estimates offered by Socolow and Thomas [24] are indeed characteristic of the industry. Secondary lead production was associated with losses to air and water of the order of 0.009%. Lead losses during battery production amounted to 0.002% of material processed. These estimates are some three orders of magnitude lower than those made by Lave et al. [23]. Levels of lead release continue to decrease with improvements in technology and operating practice. 

The need for a different approach to overcome the environmental constraints of pyrometallurgical processes led to the CX-EWS technology, which is the direct electrorefining of metallic lead (grids and poles) obtained from the CX breaker. It is based on fluoborate technology, and when introduced into primary and secondary lead operations, can eliminate all the drawbacks present in lead production. 

This process was developed in the 1980s to address environmental problems associated with secondary lead smelting at that time. It extended the Betts electrorefining technology nsing flnosihcate electrolytes to process desnlfnrised battery pastes and produce a dense cathode deposit of pnre lead metal. 

Other refining technologies, such as hydrometallurgical or aqueous processes, using chemical treatment or solvent extraction and electrolysis, are still in the development phase in the primary sector. They have made some inroads in secondary lead recovery, however, and are discussed in Chapter 6. 

Clearly actual capital costs for each individual project partly depend on chosen scale, process technology and a range of site-specific factors. However, on the basis of recent or planned new greenfield developments, capital costs for new primary lead smelting focilities can be reasonably estimated at between US 2-3000 per annual ton of capacity, with new secondary lead capacity about one half to two-thirds of this. Where smelter refits or modifications are involved, and infrastructure already exists, the capital cost will clearly be much lower. 

The decomposition of the catalyst beads can cause a secondary air pollution emission consisting of the particulate dust generated by abrasion of the surface of the catalyst. Operating cost for catalyst replacement varies directly with catalyst attrition rate. The system can process waste streams with VOC concentrations of up to 25% of the lower explosive limit (LEL). The proprietary catalyst contains up to 10% chromium, including 4% hexavalent chromium. This could lead to the emission of hexavalent chromium in some applications of the technology. 

The vendor states that MBS stabihzes heavy metals in soil, slndges, slag, ash, baghonse dnst, and sediment. Among the heavy metals treatable by the MBS process are arsenic, cad-minm, chrominm, copper, lead, mercnry, nickel, silver, and zinc. MBS technology is applicable in the following indnstries primary and secondary smelters, battery mannfactnrers and recyclers, ferrons and nonferrons fonndries, mnnicipal solid waste incinerators, anto and metal scrap recyclers, electronic mannfactnrers, electroplaters, ceramic prodnct mannfactnrers, and mineral refiners and processors. 

MBR technology is probably the membrane process that has had most success and has the best prospects for the future in wastewater treatment. Trends and developments also indicate that this technology is becoming accepted and is rapidly becoming the best available technology (BAT) for many wastewater-treatment applications. The cost of an MBR plant for secondary treatment is still higher than that for a CAS plant, but as the numbers of MBR plants increase, and as membrane costs fall, the life cycle cost differential will soon disappear, and the process advantages should lead to rapid uptake of the MBR system by the... 

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