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AmitavaBandopadhyay, Scientist National Metallurgical Laboratory (CSIR) Jamshedpur - 831 007 Environmental Challenges and Technological Issues in Battery Manufacturing and Lead Smelting Industry Consultation Workshop on Developing Environmental Compliance Assistance Center (ECAC) for Lead Acid Storage Battery Manufacturing and Secondary Lead Smelting & Processing Industries Kolkata : June 29, 2010
Technological Development andEnvironmental Implications 1850s Onwards - [Abundant Resources, Diverse Market, Unrestricted Development & No Concern for Environment] DRIVER : Concern for Health & Safety 1970-1990 - [Industry & Government Focused on Managing Pollutants] DRIVER : Concern for High Cost 1990 Onwards - [Prevent or reduce pollution by providing help to industry outside the enforcement realm – Era of Green Design]
Advantages of Secondary Processing Conservation of ore resources and fuels Lower energy consumption – 5% for Al, 6-10% for lead, 2-5% for Mg, 20-25% for zinc and 30% for Cu Solution to waste disposal problem Lower emission of noxious and green house gases The outlook for recycling various from country to country but each nation benefits in the long run.
BASIC ISSUES Pollution from metallurgical sectors create significant health hazards Industrial processes are not designed keeping pollution prevention and control as priority Cost effective pollution control technologies are mostly not available Pollution prevention require substantial discipline from industries –However, benefits are significant Psychological obstacles for pollution prevention and control
What is Recycling? • Recycling involves processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution and water pollution by reducing the need for "conventional" waste disposal, and lower green house gas emissions as compared to virgin production. • Recycling is a key component of modern waste reduction and is the third component of the “Reduce, Reuse, Recycle" strategy.
Critical Issues in Recycling of Lead Bearing Wastes The recycling of wastes is one of the most important components of the sustainable development process Wastes are now regarded as unutilized resources Significant efforts are required to recycle wastes irrespective of their type and the source of generation Recycling takes a greater dimension as treatment and disposal of hazardous wastes take significant investment. Recycling of lead bearing hazardous wastes results in conservation of mineral resources and lesser mining resulting in lower environmental pollution. The recycling must be done using Environmentally Sound Technologies (EST) A large gap exists between actual generation and the amount that is being recycled through EST
Production and Uses of Lead Principal application area of lead is Pb-acid batteries – accounts for 60% of total consumption. Other uses are – corrosion resistance surfacing, radiation shielding, cable sheathing, sound proofing, damp proofing, ornamental work etc. Total production in India : ~100000 tons [~40,000 tons from secondary sector]
Sources of Lead Waste Generation Sources of lead bearing wastes are : Used lead acid batteries, rejected materials from battery manufacturing industries, slag from smelters and other lead bearing scrap materials such as bottom dross from galvanizing units, used lead anode sheets from primary and secondary zinc producing units using electrolytic methods, lead scrap from printing press and lead pipes etc.
Developments in Traditional Lead Waste Processing Use of non metallic constituents as fuel is discouraged Primary issue in cleaner technology is separation of all components and subsequent processing A sequence of crushing, screening/washing, heavy media separation and flotation processes are used for separation of components Pretreatment of battery paste to lead carbonate is used now to avoid sulphur problems during smelting Level of sophistication varies from place to place
Recycling of Lead Bearing Wastes The lead bearing wastes as specified in Schedule - 4 are used in the production of lead ingots and lead alloy ingots The main steps involved are : smelting of the lead bearing wastes after addition of fuel and flux, cooling and casting of the molten lead into lead ingots. Alloys are produced by melting and refining of the lead ingots after mixing with alloying elements. Smelting is a thermal metallurgical processing operation in which the metal or matte is separated in fused form from non-metallic materials or other undesired metals with which it is associated.
Technological Options in Lead Recycling • Traditional Mandir Bhatti Furnaces • Blast Furnaces • Rotary Furnaces • Lead Sweat Furnaces • Reverberatory furnaces [More suitable for fine particles]
Typical Values of Pollutant Emissions from Secondary Lead Smelters • Constituents Concentration (mg/Nm3) • Suspended 250 Particulate Matters • SOx 60 • NOx 30 • Lead in Work Area : 0.15 mg/Nm3
Steps to Minimize Fugitive Emissions in Secondary Lead Processing The design of the hood/fume collection system from the smelting/refining operations should be capable of collecting the lead emissions and their transfer to the control systems The storage of all the raw materials, intermediates and products should be in covered area/shed having concrete floors and mechanized equipment should be used to handle these materials as far as possible. The floors in the loading area should be kept wet through sprinklers to reduce the chances of lead particles/dust getting airborne. The movement of vehicles to the administrative/working/production areas should ensure that only the trucks/vehicles involved in the material handling / transportation reach the work areas, and their tyres are washed before they leave these areas.
Pollution Prevention & Control in Lead Recycling Use doghouse enclosures where appropriate; use hoods to collect fugitive emissions. Mix strong acidic gases with weak ones to facilitate production of sulfuric acid from sulfur oxides, thereby avoiding the release of weak acidic gases. Maximize the recovery of sulfur by operating the furnaces to increase the SO2 content of the flue gas and by providing efficient sulfur conversion. Use a double-contact, double-absorption process. Desulfurize paste with caustic soda or soda ash to reduce SO2 emissions. Use energy-efficient measures such as waste heat recovery from process gases to reduce fuel usage and associated emissions.
Pollution Prevention & Control in Lead Recycling Recover acid, plastics, and other materials when handling battery scrap in secondary lead production. Recycle condensates, rainwater, and excess process water for washing, for dust control, for gas scrubbing, and for other process applications where water quality is not of particular concern. Give preference to natural gas over heavy fuel oil for use as fuel and to coke with lower sulfur content. Use low-NOx burners. Give preference to fabric filters over wet scrubbers or wet electrostatic precipitators (ESPs) for dust control. This reduces secondary pollution.
Key Issues for Compliance Give preference to the flash-smelting process where appropriate. Choose oxygen enrichment processes that allow higher SO2 concentrations in smelter gases to assist in sulfur recovery; use the double-contact, double-absorption process. Improve energy efficiency to reduce fuel usage and associated emissions; use low-NOx burners; give preference to natural gas as fuel. Reduce air emissions of toxic metals to acceptable levels. Maximize the recovery of dust and minimize fugitive emissions; use hoods and doghouse enclosures. Reduce effluent discharge by maximizing wastewater recycling. Avoid contamination of groundwater and surface waters by leaching of toxic metals from tailings, process residues, slag, and other wastes.
Cleaner Production (CP) in Metallurgical Sector Cleaner Production (CP) is the continuous application of a preventive environmental strategy applied to processes, products and services to increase efficiency and reduce the risks to humans and the environment. Cleaner Production is aimed at reducing consumption of raw materials, energy and pollution created during the production processes through process optimisation and development of newer technologies.
What Cleaner Technology Tries to Achieve? • Minimise amounts and hazards of gaseous, liquid and solid wastes • Minimise accidental risks from chemicals and processes • Minimise consumption of raw materials, water and energy, and • Substitute chemicals and processes less hazardous to human and ecological health.
Cleaner Production (CP) in Metallurgical Sector - Advantages • CP eliminates toxic raw materials • It reduces the quantity of toxicity of all emissions and wastes at source • It reduces negative impacts along the life cycle of a product, from design to ultimate disposal.
Barriers to Cleaner Technology Applications • Non-availability of Technology: An off-the-shelf cleaner technology which can be readily purchased and installed, is not available. • Incompatibility: The cleaner technology that is available may not be compatible in terms of existing scale of operation, raw materials, process, products, lay-out, legal requirements etc. • Economic Non-viability:There may be a technology that may not be economically viable for the industry. • Other Non-technical Barriers :These include problems arising out of socio-economic conditions, psychological factors, administrative and union problems, fixed mind-sets, lack of awareness, lack of competition, unethical and/or illegal escape routes, legal entanglements, lack of incentives as well as punitive measures.
Characteristics of CP Systems Each system focuses on continuous reduction in raw materials & energy consumption The use of each system results in a series of waste reduction measures : Minimization, reuse, recovery and disposal Each system calls for an integrated approach to design, manufacture, and use of product. In addition to inputs and waste materials, it looks into how products are produced, disposed of and accounted for Each system, over the long-term, is cheaper than conventional “End-of-pipe” technology
Technology Related Issues Process Development & Integration Economies of scale – Advantages & Disadvantages Can we break the general rule of economies of scale to make smaller operation economically viable? Feasibility of integrated waste processing from multiple companies Engineering Issues It is a combination of may techniques rather than use of one fundamental principle More we push technology to its limits, engineering issues become more complex Industrial waste and materials recycling Technology only creates a barrier in 10% cases Waste materials is used to reduce waste handling cost rather than saving in raw materials cost Economy of recycling would improve if design value is utilised
Cleaner Technologies for Secondary Lead Processing Alternative cleaner technologies couple environmental requirements to the energy savings with substantial reduction in cost compared to traditional processes More advanced processes e.g. USBM, RSR, EWS and Placid are based on same philosophy: Conversion of insoluble PbSO4 and PbO2 into leachable products Leaching by a suitable electrolyte to put lead (Pb) into solution Lead electro-winning with a insoluble anode with oxygen evolution
Concluding Remarks An attempt has been made to summarise environmentally sound technologies (EST) for recycling of hazardous wastes containing lead The scale of operation of recycling plants in India is small or tiny as compared to that in advanced nations. Hence implementation of sophisticated technology at small scale of operation is not easy. There is an urgent need to evaluate cleaner technology options in the Indian context and chalk out a plan for the industry. The evaluation process needs to concentrate not only on the technical and environmental aspects but has to focus on scale of operation and economic as well as societal aspects.