金属工业的回收利用外文原文以及翻译

Recycling in the Metals IndustryHarry V. MakarIn 1990, scrap was a major feedstock component of U.S. metals production. Steel scrap represented 56% of raw steel production, old lead scrap was 66% of total lead production, and purchased aluminum scrap represented 37% of total production. Copper scrap makes up 44% of total U.S. copper consumption annually. Although some recycling operations, such as past (but now obsolete) lead-acid battery breaking and the use of high salt fluxes on aluminum drosses have created environmental problems, the recovery of obsolete autos, cast or extruded products, appliances, lead-acid batteries, beverage containers, and drosses represents major environmental benefits in terms of reduced litter, landfill wastes, and energy savings. Evolving technologies, marketing concepts, and regulations promise even higher levels of recycling in the future. The cumulative amounts of aluminum, copper, lead, and ferrous scrap that would have had to be absorbed by our environment as discards during the period 1965-1990 had they not been recycled totaled more than 2.2 billion tons, just for the four metal groups. Concurrently, huge energy savings were realized and environmental benefits achieved through reduced emissions associated with generating that energy.KEY WORDS: Recycling; metals production; environmental benefits.INTRODUCTIONMetals recycling has long been an important component of supply and has in many instances provided solutions to environmental problems (Makar, 1992). The energy savings factors and estimated total energy savings for the cumulative metal recycled during the 1965-1990 period (Powell, 1983) are shown in table 1. Also shown are the energy requirements for production from primary ore, recycled scrap, and the percent energy savings from using scrap (ISRI, 1990). Aluminum scrap yields the largest (96%) energysavings of all the commonly recycled metals. A description of the pollution factors associated with this level of energy would involve a detailed study of each of the metal production processes and energy sources involved. However, considering carbon dioxide CO2 emission alone, the energy savings associated with recycling results in major reductions in gaseous emissions. For example, a cursory study in 1990 provided estimates of the quantity of CO2 emitted to the atmosphere as a consequence of metallurgical and nonmetallic mineral processing (Network Con- suiting, 1990). The investigation showed that emissions of CO2 caused by the U.S. production of steel, aluminum, copper, zinc, and lead were 88, 61, 12, 2, and 1 million tons, respectively, in 1987. It can be estimated that, as a consequence of recycling just these five major metals in 1987, the emission of 43 million tons of CO2 was avoided. Had this recycling not been accomplished, the total amount of CO2 emitted to the atmosphere from U.S. sources in order to produce the equivalent amounts of these metals from primary ores would have been 26% higher.In addition to substantial energy savings, there are also other significant environmental benefits realized by using scrap metal. The Institute of Scrap Recycling Industries, Inc. (ISRI, 1990), has quoted the U.S. Environmental Protection Agency (EPA) sources to the effect that it takes 1 million tons of ferrous scrap instead of 1.5 million tons of iron ore and 350,000 tons of coal to make the same amount of steel, and that there are reductions in air pollution effluents of 86%, in water pollution of 76%, in water use of 40%, and in mining wastes of 97%. Different terms are used for the recycling of metals to describe different types of scrap. Terms mentioned in this chapter are old and new scrap, primary and secondary metal, primary ore, and raw materials. Old scrap is derived from any metal articles that have outlived their usefulness. New scrap is the trimmings, filings, cut-out blanks, etc., that occur inthe manufacturing of articles for ultimate consumption. Primary metal is produced principally from ore. Secondary metal is metal recovered from scrap by pyro metallurgical or hydrometaUurgical processing. Raw materials are the ingredients before being processed, which enter into a finished product.ALUMINUMWorld War II brought about many changes in the aluminum industry, including the evolution of the secondary industry from simple remitting to smelting and refining. Secondary smelters emerged from the war years with the technology needed to process huge quantities of aircraft scrap and other partially manufactured aluminum products. Phenomenal growth in the secondary aluminum industry followed during the years after the War. Increased costs for energy and growing concerns over waste management provided the impetus for increased recycling rates. Aluminum recovered from old and new scrap has shown a tenfold increase since 1950. In 1990, the U.S. Bureau of Mines (USBM) estimated that about 2.4 million metric tons of metal were recovered from purchased aluminum scrap. Of this total, nearly 60% was recovered from old scrap. In addition to improvements in recycling technologies, some of the increase in aluminum scrap recovery can be attributed to a changing and growing end use consumption pattern. Aluminum products for the construction, transportation, and electrical industries tend to have a fairly long lifecycle and are slow to enter the scrap supply stream. However, the emergence of the aluminum beverage can in the mid- 1970s, with a lifecycle of substantially less than 1 year, added dramaticaly to the consumption of aluminum and the potential scrap supply. The used beverage can (UBC) component of old scrap consumption has doubled since 1975. Figure 1 shows the UBC component of old aluminum scrap consumption, by percent, on an annual basis between 1975-1990. The driving forces behind the increase in recycling are both economic andpolitical. The increasing cost of suitable land for landfills, the stringent regulations on leachate control, and other costs make resource recovery more attractive. While the aluminum can comprises less than 1% by weight of municipal solid waste, it frequently represents over one-half of the revenue collected by municipal recycling programs. In 1990, almost 64% of the aluminum cans shipped were recycled. Primary aluminum producers are major consumers of aluminum scrap. They have set up literally thousands of collection centers around the country for used beverage cans, adding substantially to the rate of aluminum recovery from old scrap. According to Reynolds Aluminum Recycling Company, about 10,000 recycling sites throughout the country accumulated 55 billion aluminum cans for recycling (McCutcheon, 1991). Between 1972 and 1990, over 416 billion aluminum cans, the equivalent of about 15.7 billion pounds of metal, were recycled in the United States (Aluminum Association, 1990). The calculated volume represented by this quantity of cans is about 2 billion cubic feet for flattened cans, or the equivalent of the total annual landfill requirement for all the garbage of 48 million people. Used beverage can recycling, as shown in figure 2, has grown from about 15% of the total cans produced to about 64% in 1990. The aluminum beverage can has undergone a significant change in the thickness of sheet required. One hundred and sixty-four pounds of aluminum were used to make 1,000 beverage cans in the 1960s; the same number of cans now requires only 35 pounds of aluminum (Wall Street Journal, 1991). These source reductions have all been motivated by the same economic factors that have encouraged the development of the secondary recycling network for metals. The lack of available low-cost ores, combined with increased metals demand, have produced the conditions that make source reduction desirable. The recycling process generates certain residues. Black dross, for example, is a residue formed in the charging well of the furnace. It contains upto 20% aluminum and typically is sold to other recyclers for aluminum recovery. Within the industry there is concern that black dross could be classified as a hazardous waste, hindering or even stopping current recycling operations. Dross processors who generate a high-salt slag for disposal are already under considerable pressure to develop and use nonsuit alternatives.COPPERIn 1990, about 1.6 million tons of copper-based scrap, containing an estimated 1.3 million tons of cop- per, were recycled in the United States. Since World War II, copper from recovered old scrap has provided between 19% and 33% annually of U.S. apparent cop- per demand and, on average, provided about 18% of world copper demand. In the United States, about 44% of total annual copper consumption was from copper in old and purchased new scrap. Copper scrap accounted for a similar percentage, 36%, in the European Community, which is one of the largest sources of copper scrap in the world. The recovery rate of old scrap is limited by copper's long life and its essential uses. On average, the rate of old scrap recovered in the United States, as a percentage of total scrap consumption, declined from 50 to 60% in the 1940s to near 40% in the 1980's. The decline in the old scrap component was the result of an increasing manufacturing base from which to generate new scrap, and of a changing demand pattern now dominated by electrical uses. Electrical items, which now account for more than 70% of copper consumption, are less likely to be substituted, replaced, and scrapped than items in other end-use sectors. The long service life for utility and building cable results in a practical limit to the amount and rate at which old scrap from this source can be recovered. The average life for old copper items has been estimated at about 20 years. Parts of the copper industry are very scrap intensive. For example, nearly all of the copper raw material used to make specialty alloy ingot forfoundries is scrap. Scrap is the dominant feed for brass rod mills and for many copper tube mills. Problems on the horizon for copper recyclers include stricter regulations for emissions, higher costs for waste disposal, legislation limiting the lead content of alloys and in drinking water, and the Basel Convention. The cost for disposing of hazardous materials, such as lead-containing plastic coverings for copper wire, is high. While acceptable in some other nations,Such as in Japan, incineration of the plastic coated wire is a less acceptable solution in the United States. Stringent legislation on emissions has restricted this procedure. As a consequence, mechanical dismantling of cables has become common. An estimated 340,000 tons of cable are chopped every year in the United States, resulting in about 158,000 tons of plastic waste that must be disposed. Legislation limiting the content of lead in copper alloys was also being considered in the United States and may create many problems for both producers of these alloys and their consumers.LEADIn 1991, 28 plants in the United States, with annual capacities of 6000 tons or more, accounted for about 99% of secondary lead production. Total U.S. secondary lead production capacity at year-end 1991 was about 1 million tons, with production for the year about 86% of capacity. Transportation was the major end use of lead, with about 75% consumed in automotive batteries; gasoline additives and tanks; and solders, seals, and beatings. Recovery of lead from scrap batter- ies was approximately 734,000 tons in 1991, compared with 784,000 tons in 1990. Since reaching a peak of 1,433,000 tons in 1977, U.S. demand for lead dropped about 130,000 tons by 1990. Most of the decline was in dissipative uses; use of lead in gasoline additives alone decreased by 200,000 tons. Highly recyclable electrical and transportation uses increased by more than200,000 tons. This is reflected in the old scrap production levels for 1990, which increased about 230,000 tons over the 1977 level. The old scrap share of total metal production has been increasing since 1965 when it was about one-half of total production, including primary and secondary. In 1990, old scrap was about two-thirds of total lead metal production. The environmental pressures regarding lead production and use are very intense, with numerous legislative and regulatory activities, both in the United States and on an international level. In the United States, significantly stricter regulations on producers and consumers are expected over the next several years. Part of the regulatory strategy of the EPA is stricter enforcement of existing laws and regulations. At year-end /991, 37 States had enacted mandatory lead-acid battery recycling or disposal regulations, and similar actions are pending in several other states.A study conducted for the Battery Council Inter- national (BCI) showed that U.S. battery recycling rates for 1987, 1988, and 1989 were about 89%, 91%, and 95%, respectively. Because batteries consume more than three-fourths of the total lead produced in the United States, battery recycling rates are an important concern. The recycling rate should be virtually 100% as mandatory battery recycling laws take effect. Several bills have been introduced in both houses of the Congress and hearings have been held dealing with lead pollution and health-related issues. Concerns included: urban soil and household dust contamination from lead-based paint and solid residues from leaded gasoline exhaust emissions; mandatory Federal lead- acid battery recycling; minimum required content of secondary lead; severely limiting lead content of solders; banning lead from all food packaging and containers; taxation of primary lead and economic incentives for secondary production; and comprehensive documentation of existing uses, with mandatory new productreviews and approvals. The biggest effects on recycling are expected to occur when the Resource Conservation and Recovery Act (RCRA) is reauthorized. Secondary lead plants may get relief in the case of toxic process wastes that are recycled on site. Captive dedicated landfills also may be allowed to solve toxic slag disposal, which currently costs about $330/ton at off-site hazardous waste landfills. How these issues finally get resolved will depend on certain specific regulatory approaches such as mandatory minimum secondary lead content in batteries, a tax on virgin lead, and the BCI type of model presently in effect in many States for battery recycling. The industry will also face stricter ambient air quality standards and new source performance standards for secondary lead plants. The latter will set the tone for costly improvements to new or retrofit fur- naces in the United States. In the near future, costly investments also will be required to reduce process effluents and discharges as required by the new drinking water standard and probable reauthorization of the new Clean Water Act. Lead pollution also is being addressed on an international scale. The program on chemicals use reduction within the Organization for Economic Cooperation and Development (OECD) offers a promising approach that attempts to balance the needs for risk reduction against acceptable uses of lead in society. Under this program, the risks associated with the use of a chemical, such as lead, are studied, along withStrategies that can be implemented to reduce that risk, including safe methods of handling and consumer information programs that can result in safer use and management of the material. Currently, lead, cadmium, and mercury are being studied, as well as methylene chloride and brominated flame retardant chemicals.FERROUS SCRAPFerrous scrap provides a good perspective on the sophistication andcomplexities involved in modem- day recycling. Many of the problems in this industry, including the environmental ones, are common to other metal recycling activities. The scrap industries are highly vulnerable to a wide variety of factors such as price/demand fluctuations, increasing quality requirements, scrap mixture complexity, and environmental regulations that increase processing costs or residue disposal, or both.Junk Auto ProblemThe shredding of automobiles resulted from the problems created in the 1960's when junk autos were littering the U.S. landscape, creating major eyesores. The need to solve the automobile disposal problem led to the "Resource Recovery Act of 1970." It became a national goal to seek solutions to the abandoned automobile problem. The U.S. Bureau of Mines published numerous reports describing various aspects of this problem and research activities devoted to it. A very comprehensive and detailed description of the problem was published in 1967 (Staff, Bureau of Mines, 1967). An economic analysis of the problem was published in 1973 (Adams, 1973). Automobile scrap recovery is a complex system and many factors are involved, including the cost of transporting junk cars, scrap quality and price, salvage potential for reusable parts, etc. The 1967 study identified 85 separate factors that influenced the movement of automobile scrap. Although many elements went into the solution of this problem, the scrap auto shredder system has been a major factor. Development of the portable flattener facilitated economic volume delivery of automobile hulks to efficient shredders which produce a high- quality scrap that is in high demand by steelmakers and foundries. Based on USBM data, figure 3 shows the growth of shredded scrap relative to No. 2 Bundles, the lower grade auto scrap which it replaces. The ratio of consumer receipts for shredded scrap versus that for No. 2 Bundles increased from essentially zero in 1967 to about 7 to 1 in 1988 with a recent decline to about 5 to1.The Flow of Shredded ScrapThe USBM has estimated that there are about 600 shredders worldwide. In the United States, there are approximately 200 shredders with a total annual processing capacity of over 16 million tons. The total number of autos scrapped each year in the United States ranges from 8 to 10 million, representing 12 to 14 million tons of ferrous scrap. Shredders also process appliance scrap (white goods), sheet steel, and light trucks and vans. However, auto hulks are the major feed to the shredders. The prominence enjoyed by shredded scrap is further illustrated in table 2 which shows the amount of shredded scrap consumed in the United States in 1990 relative to the two top premium grades, No. 1 Heavy Melting Steel and No. 1 Bundles. Shredded scrap volume has consistently been third behind these two premium grades, reflecting its quality and desirability by steelmakers and foundries. The major flows of shredded scrap are to manufacturers of raw steel and iron foundries and steel foundries. A sense of the importance of certain regulations and where they may have major impacts can be gained by relating these flows to relevant environmental regulations. A few of the problem areas are highlighted below.The Fluff Problem"Fluff" is the name given to the light material separated from autos during the shredding and cleaning operation by air classification. About 3 million tons of fluff are produced annually from auto shredding operations. Fluff is a mixture of plastics, rubber, glass, and fiber plus fine metals and dirt. Percentages reported by Schmitt (1990) show: sponge and foam, 19.3%; fabric, 33.3%; plastics, 22.2%; metal (larger than 12 mesh), 6.1%; and glass, dirt, and metal (less than 12 mesh), 19.1%. Potential disposal problems for fluff have focused on the possible presence of cadmium and oily sub- stances, particularly PCB. Concern aboutthe latter, in 1988, caused a scrap processing industry moratorium against white goods and essentially stopped the recycling of these items. The recycling market for white goods was estimated at more than 19 million units discarded each year from households and commercial establishments in the United States (Halper, 1989). The disruptions were triggered by Federal and State investigations of shredding facilities under provisions of the Toxic Substances Control Act and the Resource Conservation and Recovery Act. Since the effects on white goods recycling were major, the EPA moved quickly to develop detailed data regarding principal sources of PCB capacitors, the main item of concern regarding appliance recycling. In April 1991, EPA published the results of a pilot study on PCB, lead, and cadmium levels in shredder waste materials (Reinhart, 1991). Data were presented on the concentrations and leachability of PCB, lead, and cadmium found in fluff and other shredder streams. Among the conclusions was the fact that no particular input material could be identified as the source of the PCB, lead, and cadmium found in the shredder streams. EPA emphasized that this study was a preliminary assessment of potential contamination because the sampling was limited to only seven shredder sites. The need for further study was cited. Another important conclusion was the need to better understand the economic viability of the shredder industry and the possible economic impacts from various waste management approaches.A related concern affecting ferrous scrap is the preliminary listing by the EPA of metal shredders as a source of toxic pollutants (Metals Week, 1991). The basis of this listing is the suspected emissions of cadmium during the shredding process and the pressure to relegate it to the same toxic category as mercury and lead. The ferrous scrap industry (Network Con- suiting Inc. 1990) has argued against this claim which would subject the shredders to restrictive provisions of the Clean Air Act emission standards.Electric Furnace DustRegulatory actions aimed at electric arc furnace steelmaking residues have important implications for scrap also since these furnaces are totally scrap-based. For example, the listing of electric arc furnace dust as a hazardous waste has the direct impact of increasing disposal costs because of land disposal restrictions. The listing of this dust as hazardous is based on certain constituents such as hexavalent chromium, lead, and cadmium which are present in the scrap charged to the furnaces. Electric arc furnace dust also containsSignificant amounts of zinc, and processes are available for recovering the zinc and removing the other toxic metals. Stabilization processes are used at some plants to permit landfill disposal of dusts that cannot be economically processed for zinc recovery. Further technical developments may give additional relief to this problem, but interstate transport and favorable economics will continue to be important concerns.ExportsRestrictions on international trade in metal scrap are possible under the Basel Convention agreement. Regarding ferrous scrap, the implications are major. For example, U.S. shredded scrap exports in 1990 totaled about 4.1 million short tons at a value of $482 million. This represented 32% of the total volume of carbon steel and cast iron exports and 35% of the corresponding total dollar Value. The next highest scrap category in 1990 was No. I Heavy Melting Scrap at about 2.7 million short tons and $298 million. For 10 months through October 1991, shredded scrap was the second largest category, although total export tonnage was 2 million short tons, down about 44% compared with that of 1990. The dollar value was $211 million through October 1991. Compared with total carbon steel and cast iron exports, shredded scrap represented 24% of the tonnage and 25 % ofthe dollar value through October 1991.Ferrous Scrap ImpactsTable 3 shows the quantity and percentage of shredded scrap relative to total scrap for each of the streams for 1990. The dollar value is included. These data highlight the potential impact areas and relative severity should major disruptions occur because of regulations. The potential impacts could be severe. In major user industries plus exports, shredded scrap represents about 13% of total scrap. The economic impacts represented by this scrap totals nearly $1.3 billion based on 1990 scrap flows. A major disruption to shredded scrap supply would force scrap users to seek other alternatives. Supply of premium scrap grades are limited and other sources of iron units might be required, including direct-reduced iron, hot briquetted iron, iron carbide (still experimental), and merchant pig iron. Most, if not all of these, are seen as higher cost alternatives which could cause significant cost increases to the steelmaker or foundry and possibly weaken their competitiveness.CONCLUSIONSIt would be an ironic twist to be unable to resolve differences between recycling and environmental concerns and to witness the source of shredded scrap, junk autos, and junk appliances becoming, once again, the landscape eyesores they were in the 1960's.金属工业的回收利用Harry V. Makar摘要：1990年，废料是美国金属生产的主要原料。