Metal Recycling Ebook
Note that the CO2 emission factor for EAF steelmaking in this table is based on production of steel from scrap metal, and therefore the EAF emission factor does not account for any CO2 emissions from blast furnace iron making. The Tier 1 CO2 emission factor for EAFs in this table is therefore not applicable to EAFs that use pig iron as a raw material.
The secondary production of refined lead amounts to the processing of recycled lead to prepare it for reuse. The vast majority of this recycled lead comes from scrapped lead acid batteries. The lead acid batteries are either crushed using a hammer mill and entered into the smelting process with or without desulphurization or they are smelted whole (Sjardin, 2003). Traditional blast furnaces, Imperial Smelting Furnaces, electric arc furnaces, electric resistance furnaces, reverbatory furnaces, Isasmelt furnaces, Queneau-Schumann-Lurgi furnaces, and Kivcet furnaces can all be used for the smelting of these batteries and other recycled scrap lead (Sjardin, 2003). As with the furnaces used for primary lead bullion production, these furnaces generate different levels of CO2 emissions from their use of differing types and quantities of reductants. The primary reductants are coal, natural gas, and metallurgical coke, although the electric resistance furnace uses petroleum coke (Sjardin,...
First, the amount of sulfur in the scrap metal varies widely, so the metallurgist never knows exactly what dose is needed to just use up the calcium carbide. Second, there is some inherent inefficiency in contacting the sulfur with the calcium carbide, and some metallurgists contend that an overdose will always be necessary, even if one could predict stoichiometrically exactly how much calcium carbide was needed to reach a desired sulfur content. A typical materials flow diagram for a cupola melting operation is illustrated on Figure 4. As illustrated on this figure, materials input to the melting operation include scrap metal, fluxes, coke (source of fuel for the cupola), and refractory material. Wastes generated by the process include spent refractories, slag, bottom drop and sweepings (for cupola operations), and either baghouse dust or a wet sludge depending on the type of melting emission control system. Typical pouring temperatures for iron range from 2,040...
The first step of the process is performed in a separate, dedicated building. The drums of arsenic trioxide are opened in an air-evacuated chamber and automatically dumped into 50 caustic soda. A dust collection system is used. The drums are carefully washed with water, the washwater is added to the reaction mixture, and the drums are crushed and sold as scrap metal. The intermediate sodium arsenite is obtained as a 25 solution and is stored in large tanks prior to further reaction. In the next step, the 25 sodium arsenite is treated with methyl chloride to produce the disodium salt DSMA (disodium methanearsenate, hexahydrate). This DSMA can be sold as a herbicide however, it is more generally converted to MSMA, which has more favorable application properties 8 .
Electric arc furnaces (EAFs) generally convert 1 to 2 of the charge into dust or fume (Chaubal 1982). Zinc contents of the dust have potentially high commercial value. Many methods have been proposed for flue-dust recycling, including zinc recovery. A good survey of recycling strategies is given by Morris (1985). Most recovery options require the zinc content of the dust to be at least 15 , and preferably 20 for the operation to be economical. Increasing zinc content can be accomplished by returning the dust to the furnace from which it is generated. If the dust is injected into the furnace after the charge of scrap metal is melted, temperatures are high enough for most of the heavy metals to fume off, resulting in high zinc content in the dust collected by the scrubbers and or electrostatic precipitation systems and baghouses.
The common types of metal cutting processes are broaching, cutting, drilling, forging, grinding, milling, planing, polishing, reaming, sawing, shaping, stamping, threading, and turning. In most cases, the cutting tool travels along the surface of the work piece and shaves off the metal in front of it. The high friction at the cutting edge of the blades creates heat. If allowed to become excessive, this heat can permanently deform the part that is being formed, or the cutting tool. To prevent this undesirable effect, some form of coolant is needed. Usually, a liquid is supplied to the leading edge of the blade to create a medium with which the heat can be moved to a coolant sump. The major hazardous wastes from metal machining are waste cutting oils and degreasing solvents. Metal shavings are usually recycled as scrap metal. Metal chips are separated from coolants and recycled as scrap metal (Vardar, 2004).
The metal casting industry, also known as the foundry industry, is one of the largest recyclers in the world. For centuries, this industry has been converting a huge volume (e.g., 15 to 20 million tons in the U.S.) of scrap metal that would otherwise be disposed in landfills, into manufactured useful products. This scrap metal forms the raw material charged into furnaces of the foundry facility and converted into usable castings. The casting categories include many general ferrous and nonferrous metals and their alloys, including iron, steel, aluminum, copper, magnesium, and zinc. Major end-use markets cross all sectors of the global economy, examples being the automotive industry, transportation equipment, construction, mining and oil field machinery, and industrial machinery. As the assembled molds are being placed on the pour-off lines, the scrap metal is melted in the furnace. Molten metal from the furnace is brought to the molds on the pouring lines in a refractory lined pouring...
The foundry industry is a major recycler of waste materials (scrap metal). Unfortunately, the recycling of these materials can result in the generation of hazardous wastes. This article focuses on two potentially hazardous waste types in the ferrous foundry industry - calcium carbide desulfurization slag, (potentially reactive) and melt emission control residuals (potentially EP toxic). An overview is given on how foundries have evaluated different waste management options. The ultimate goal is to minimize the amount and degree of hazardous wastes generated while reducing the cost of managing these wastes.
Equipment manufacturers and engineering companies. The book is written as a training guide. It explains how to monitor and maintain RO systems. This knowledge is critical for the daily evaluation of RO system performance. The book goes on to cover various aspects of membrane cleaning and sanitization. It also discusses most of the common RO system problems that should be investigated when troubleshooting an RO concern. These topics make the book an excellent tool for technicians who maintain RO systems. Some of the more common and some of the more interesting applications of reverse osmosis are discussed in detail. These include two-pass RO for high-purity water production, pharmaceutical water treatment, seawater desalinization, application of RO for juice concentration, plating metal recycling, the treatment of secondary sewage effluent, and the final filtration of deionized (DI) water. For anyone who works with industrial RO systems, the book will provide practical insights into...
The predominant source of lead and cadmium in baghouse dust or scrubber sludge is the scrap metal used for casting. To reduce the level of these contaminants, one must identify the incoming source and arrange to acquire charge material which contains lower concentrations. A charge modification program at a large foundry was successful in reducing the lead and cadmium levels in their waste to below EP-Toxicity values (Stephens 1988). Due to the higher cost of high grade scrap and the difficulty of obtaining a reliable and continuous source, most foundries are not able to economically employ this method.
Electric arc steel-making furnaces produce carbon and alloy steels from scrap metal along with variable quantities of direct reduced iron (DRI), hot briquetted iron, and cold pig iron. Hot metal may also be added if available. The charge is melted in cylindrical, refractory-lined electric arc furnaces (EAFs) equipped with carbon electrodes (one for DC furnaces, three for AC furnaces). During charging, the roof is removed to place scrap metal and other iron-bearing materials into the furnace. Alloying agents and fluxes are added through doors on the side of the furnace. The electrodes are lowered into the furnace to about an inch above the metal and current is applied, generating heat to melt the scrap. Modern electric arc furnaces use an increasing amount of chemical energy to supplement the melting process. The chemical energy contribution is derived by burning elements or compounds in an exothermic manner. Sources that provide chemical energy include3 Oxy-fuel burners are used to...
The objectives sought to be achieved through disposal of refrigeration and air conditioning waste appliances are (a) separate disposal of the CFCs from the circulation system and the insulating material (b) further stripping of hazardous substances (e.g., mercury switches) and (c) recovery of ferrous metals, the priority in metal recycling.
Wastes generated in metal casting operations include those picked up by air pollution control devices, hazardous slags, and spent casting sands. Source reduction methods for hazardous wastes from the operation of baghouses, scrubbers and other emission control systems include 1) using cleaner scrap metal for the casting that does not contain lead, cadmium, zinc, or other hazardous metals, and 2) use of induction furnaces that emit less dust and fumes than electric arc furnaces. Baghouse dust can also be recycled back into the process, and zinc and other salable contaminants can be recovered. When flue dusts cannot be recycled and must be treated, the aim is to stabilize the hazardous components such as lead and cadmium, or remove them through precipitation.
Scrap metal Scrap metal that is disposed of or recycled is a solid waste however, it is exempt from Subtitle C regulation when it is reclaimed (i.e., recycled to recover metal content). This does not apply to processed scrap metal that is excluded from hazardous waste regulation entirely.
A visit was paid to the shipyard in order to see the general situation of the shipyard before the application of BMP. Safety issues, threats to workers' health and environmental risks were obtained. Scrap metal sheets and used paint boxes were lying around the production area (see Fig. 39.4) the used grid blasting abrasives were not removed from the area. Also welding workers were not using necessary protective equipment during their work. When production processes such as painting and blasting, which are main cause of waste and pollutants, were observed, it was seen that there was no waste management policy of the shipyard. As a first step for waste management, a waste material billboard (see Fig. 39.5) was located in the shipyard where workers could easily see.
The nonferrous metals industry encompasses establishments that engage in the following primary and secondary smelting and refining of nonferrous metal from ore or scrap rolling, drawing, and alloying and the manufacturing and casting of basic metal products such as nails, spikes, wire, and cable. Primary smelting and refining produces metals directly from ores, and secondary refining and smelting produces metals from scrap and process waste. Scrap is bits and pieces of metal parts, bars, turnings, sheets, and wire that are off-specification or worn out but capable of being recycled.1 The industry does not include the mining and beneficiation of metal ores rolling, drawing, or extruding metals or scrap metal collection and preliminary grading.2