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Pollution Prevention and Control Technologies for Plating Operations
Section 7 - Off-Site Metals Recycling
7.3 OFFSITE METALS RECOVERY PROCESSES
7.3.1 Horsehead Resource Development Company
7.3.2 Inmetco
7.3.3 RECONTEK
7.3.4 CP Chemicals
7.3.5 World Resources Company
7.3.6 Encycle/Texas, Inc.
7.3.7 Alpha Omega Recycling, Inc.
7.3.8 Cyano Corporation of Michigan
7.3.9 Eticam
7.3.10 Metro Recovery Systems
7.3 OFF-SITE METALS RECOVERY PROCESSES
This section presents a short description of each of the metals recycling companies for which information is available. This is intended to provide the reader with information and data on a cross section of available services. Mention of commercial names is not intended to constitute endorsement for use.
7.3.1 Horsehead Resource Development Company
Horsehead Resource Development Company (HRD) operates six metals recycling operations located in Illinois, Pennsylvania, Tennessee, Oklahoma, and Texas. HRD accepts metal-bearing sludges, filter cakes, bag house dusts and soils and processes them using two kiln technologies: (1) Waelzing (the volatilizing, or fuming of metals in a reducing atmosphere, applied as a first step to all feeds) and (2) calcining (the second refining step that separates the zinc, lead and cadmium in the crude zinc oxide and increases the overall metals values).
Only the Chicago, IL and Rockwood, TN facilities accept electroplating wastes, where they currently process wastes from approximately 100 metal finishing companies. The main business of HRD is processing electric arc furnace dust (RCRA waste K061) from the steelmaking industry and other feed sources (e.g., F006 and F019) with recoverable zinc, lead, cadmium and iron. The technology employed at Chicago and Rockwood is the Waelz kiln technology. The Rockwood facility has an annual waste processing capacity of 90,000 tons and the Chicago plant will bring another kiln on-line early in 1994, boosting itÕs capacity to 180,000 tons/yr.
The Waelz kiln technology was developed in 1910. At the heart of the process is a rotary kiln which is typically up to 180 ft in length and up to 12 ft in internal diameter. Kiln feed consists of blended metal-bearing sludges and oxidic dusts mixed with an appropriate amount of a suitable reducing agent (coal, petroleum coke or metallurgical coke fines). During passage through the kiln, the mixed charge is heated under the resulting reducing conditions to a temperature of 1,300oC, sufficient to volatilize the reduced metal species from the charge. The volatilized metal values are subsequently re-oxidized in the gas stream above the charge, and this product is finally collected in bag houses as an enriched fume product. The process derives its name from the German word, Òwalzen,Ó meaning to trundle or roll. These words accurately describe the movement of the charge through the rotating kiln (ref. Horsehead file).
Two products are generated from the Waelzing process: crude zinc oxide and iron rich material (IRM). The crude zinc oxide produced at the Chicago and Rockwood facilities (i.e., locations of electroplating waste processing) is further processed at other HRD facilities since these plants do not perform the calcining process. The IRM (45-55% Fe, <1% Zn), which typically amounts to 50-60% of the feed rate, reportedly passes the TCLP because the iron fraction encapsulates any other metals present. IRM is valued for itÕs strength, density and high iron content and is marketed for a variety of construction materials (e.g., cement manufacture and asphalt production).
The calcining process generates two products: zinc calcine (55-66% Zn, 4-9% Fe) and lead/cadmium concentrate (35-50% Pb, 15-25% Cl, 5-10% Zn, 1-2% Cd). The zinc calcine product is sold to smelters for zinc metal production. The lead/cadmium product is further refined in an acid leaching process to generate lead cake (50-55% Pb), copper cake (35-50% Cu), cadmium sponge (50-60% Cd), and zinc oxide which are sold for feed materials for primary metal manufacturing.
Inmetco, located in Ellwood City, PA, operates a pyrometallurgical process that is capable of annually processing 56,000 tons of feed material. The market focus for this company is on wastes containing chromium, nickel and iron. They currently process wastes from approximately 150 metal finishing companies as well as other segments of industry.
The Inmetco process utilizes equipment commonly found in the primary metals producing industry. The process consists of three main steps. In the first step, the wastes are blended with coke or coal and water in a disc pelletizer. In the second step, the pellets are processed in a rotary hearth furnace where a portion of the carbon in the pellets reacts with oxygen in the waste to produce reduced metal. A portion of the zinc, lead and halogens contained in the flue dust are exhausted into the off-gas treatment system. The hot, metallic, sintered pellets are transferred to an electric arc smelting furnace where the third operation is performed. In this stage, the pellet is melted and chromium oxides are reduced by the residual carbon in the pellet. Lime, silica, alumina and magnesia separate to form a liquid slag that assists in cleansing the metal bath. Metal and slag are tapped periodically from the furnace. The metal is cast from a refactory lined ladle into pigs which are sold to steel mills. Approximately 42% of the original feed material is contained in the pigs. The slag is treated to obtain a sized material that is used locally as fill or ballast. The process water is treated and yields a filter cake that is recycled in a separate processing plant to recover the zinc values (ref. Inmetco file).
Inmetco's pyrometallurgical process has been modified to recover metals from plating wastes. Inmetco accepts nickel and chromium containing wastewater treatment sludge, nickel strip solutions, waste chromic acid and concentrated rinse waters. In order to produce the quality product known as stainless steel remelt alloy pigs, the concentration of elements such as phosphorus and copper in the wastes must be relatively low. During processing, liquid plating wastes are combined with dry, metal bearing wastes prior to entry into the pelletizing disk. Wastewater treatment sludges (e.g., F006) by-pass the pelletizing disk and are mixed with carbon fines. The various wastes are then delivered to the rotary hearth furnace.
RECONTEK operates a pilot or demonstration recovery plant in Newman, IL, where they are fine tuning their processes in preparation for the construction of six other plants around the country. They have received permits for planned facilities in Gila Bend, AZ and Butler, IN and they are in various stages of permitting in: Athens, TX; Enfield, NC; Richland, WA; and Jefferson, WI.
RECONTEK accepts zinc, copper and precious metal bearing wastes from the electronics and metal finishing industries and recovers these metals using a hydrometallurgical process. Their operations are divided into two lines: copper and zinc. The copper line includes acid distillation for recovery of hydrochloric acid and copper sulfate crystals; alkaline digestion to make copper oxide, sodium chloride and calcium sulfate; and an electrolytic cellhouse which produces cathode copper from waste copper sulfate. The zinc line is not yet operational but is expected to be demonstrated in the near future. This process consists of alkaline digestion, cementation and electrolysis that produces copper and lead concentrates for the smelter, zinc powder, sodium chloride and calcium sulfate.
In addition to the end uses already mentioned, RECONTEK products are used in the production of animal feed, micro nutrient mixes, soaps, wallboard, chlor-alkali products, and for the regeneration of ion exchange resins.
The current processing rate on the copper demonstration line is 300 tons per month of sludges and 500 tons per month of copper sulfate. The zinc demonstration will be initiated with a feed of 250 tons per month and they anticipate increasing this rate up to 2,000 tons per month.
CP Chemicals, a major U.S. producer of inorganic metallic salts in the U.S., accepts metal bearing wastes from over 1,000 clients, through their Environmental Recovery Services Division (ERS), at six U.S. plant locations. All six plants are RCRA permitted (four sites have final Part B permits). CP has been recycling metallic wastes since 1950. Details of their metals recovery methods were not provided during the survey; however, CP Chemicals indicated that their processes include hydrometallurgical steps. CP Chemicals mostly accepts and processes segregated metal bearing wastes of the following types: spent plating baths, etchants, pickling solutions, and strippers containing brass, cobalt, copper, nickel, tin, solder or zinc. The primary EPA waste codes accepted are: D002, D004, D006, D007, D008 and F006. Wastes are accepted in different forms including liquid, solid or slurry. The market focus of CP Chemicals includes both printed circuit board manufacturers and common metals plating shops. They have a processing capability of 120,000 tons per year and currently accept 100,000 tons per year. CP Chemicals indicated that their prices for processing wastes ranges from $75 to $210 per drum, or more depending on the waste type and analyses. The output of CP Chemicals recycling processes are technical grade metallic salts and etchants which are sold to industry on a value-added basis and meet the same purity requirements as non-waste derived products. The end use of their products includes: wood treatment chemicals; algaecides and fungicides; catalysts; and ceramics (ref. CP Chemicals file).
World Resources Company (WRC) operates metals recovery processes at Pottstown, PA and Phoenix, AZ. They have been in the hazardous waste recycling business since 1980. WRC's processing methods are proprietary, as is their capacity. WRC indicated that their recovery methods include hydrometallurgical and pyrometallurgical processes. Their end products were not specified in their survey form. WRC indicted that they have accepted metal bearing wastes from 800 metal waste-generating companies during 1992.
For plating shops responding to the Users Survey, WRC is the most frequently used off-site metals recycling company for F006 sludge. Fifty percent of the respondents using off-site metals recycling for this waste send it to WRC.
Encycle/Texas, Inc. operates a metals recycling facility in Corpus Christi, TX. Their client list for 1992 includes approximately 150 electroplating shops. Encycle accepts liquid and solid wastes containing copper, lead, zinc, nickel and to a lesser extent, other metals. They describe their processes as chemical and hydrometallurgical. Their products are used by primary smelters and others (ref. Encycle file).
For plating shops responding to the Users Survey, Encycle/Texas, Inc. is the second most frequently used off-site metals recycling company for F006 sludge. Thirty percent of the respondents using off-site metals recycling for this waste send it to Encycle/Texas, Inc.
7.3.7 Alpha Omega Recycling, Inc.
Alpha Omega Recycling Inc. operates a metals recycling plant located in Longview, TX. Their client list in 1992 included approximately 100 electroplating companies. They primarily accept wastewater treatment sludges containing chromium, chromium/nickel, and copper. Their recovery process consists of acid leaching and selective precipitation and it has a capacity of approximately 5,500 tons/yr. The end use of their recovered metals includes ferrochrome, material for stainless steel manufacturing and blister copper. Alpha Omega Recycling indicated that their average price for waste processing is $350 per ton (excludes transportation costs) (ref. Alpha Omega Recycling file).
7.3.8 Cyano Corporation of Michigan
Cyano Corporation of Michigan operates recovery processes for cyanide bearing wastes (e.g., F007, F008 and F009) in Detroit, MI. They presently service approximately 50 electroplating shops. Their processes include electrochemical recovery of metal and oxidation of cyanide and they have a capacity of 2,200 tons/yr. The metals that are recovered electrochemically are sold as scrap. Cyano Corporation of Michigan indicated that their average price for waste processing is $2 to $10 per gal (ref. Cyano Corporation of Michigan).
Based on the response to the Users Survey, it is believed that Eticam operates a metals recycling operation in Fernley, Nevada. However, Eticam did not respond to the metals recycling survey and no additional information is available.
A centralized waste treatment (CWT) facility, located in Roseville, MN, is owned by Metro Recovery Systems (MRS), a partnership between Metropolitan Recovery Corporation and the U.S. Filter and Recovery Company (ref. 419). Although this facility did not respond to the metals recycling survey, some information was gathered from the literature and the Users Survey.
The MRS differs from most other off-site metals recycling companies in that it offers an alternative to in-plant conventional treatment of metal bearing wastewaters. The other firms only provide final treatment/recovery for concentrated wastes, particularly sludges. To utilize the MRS system, a plating shop installs sets of modular ion exchange units to capture the metals and cyanides from their wastewaters. Separate sets of ion exchange columns would be used for each type of metal plated so that the metal can be captured in a segregated manner. The facility also accepts bulk loads of concentrated wastes, which are not amenable to ion exchange recovery. Section 6.4.2 describes the ion exchange systems used for this purpose and the costs incurred by two respondents that subscribe to the MRS service. The CWT plant recovers metals from the ion exchange regenerant using electrowinning. Residual wastewaters are treated on-site and the sludge is sent off-site for recovery/disposal (ref. 419).