Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
Issue link: https://emj.epubxp.com/i/70939
PROCESSING SOLUTIONS ton of material. With the Hydro-Clean and rinse screen, the producer uses a maximum 4,000 l of water per ton, reducing the operation's water con- sumption by up to 70%. In addition to water savings, the Hydro-Clean 700 saves up to 1.8 kW of energy for every ton of cleaned material when compared with the washing drum system. HSG also noted that the Hydro- Clean's compact size and lighter weight keep overall operating and structural costs considerably lower than with tra- ditional washing systems—which also require more equipment and a greater footprint. In addition, the Haver unit experiences little wear with a low-main- tenance design that allows for simple replacement of the few standard com- ponents that are subject to wear. Following its initial success with the Hydro-Clean 700 test unit, the producer plans to authorize an investment program that will allow the installation of a larger washing operation with several HSG Hydro-Clean 1000 units. This operation would be capable of washing up to 4 mil- lion tons of auriferous ore each year. Innovative Technologies for Treating Mine Effluents Mining activities in Peru are subject to strict environmental requirements in terms of Maximum Permissible Limits (LMP). Currently, the principal technolo- gy used by the mining industry in Peru for effluent treatment involves the use of lime to cause precipitation of metal hydroxides by modification of pH. However, this method has deficiencies that include the necessity to have access to a large supply of lime, substantial generation of sludge that must be dis- posed, of, low process thermodynamic efficiency, and inability to achieve the levels of LMP required by Peruvian law. ARCADIS has developed new tech- nologies for abatement of heavy metals concentrations (Fe2+, Fe3+, Pb2+, Cu2+, Zn2+, MoO42-, AsO33-, AsO43- and oth- ers), as well as well as removal of ultra- fine solids and soluble compounds (SO42-, Cl-, Ca2+, and others) that may be present in mining effluent. Included in these technologies are two of inter- est: Recirculation and Source Reduc- tion through Process Optimization, and Precipitation with Sulphides followed by Dissolved Air Flotation (DAF). ARCADIS believes these technologies— 152 E&MJ; • JUNE 2012 This effluent treatment plant at the Los Pelambres mine in Chile employs ARCADIS technology for reduc- tion of heavy metals content. already proven at operations in Chile— would be successful at Peruvian opera- tions as well. The first technology is designed to optimize the water management process throughout the circuit in order to decrease the volume of effluent to be treated, which helps to reduce the size of the treatment plant and improves effluent quality control. This can be accomplished by preparation of a detailed model of the entire process, describing mass and ionic flow behavior using a tool developed by ARCADIS in Matlab-Simulink, a software environ- ment for multidomain simulation and model-based design for dynamic and embedded systems. This tool can model, with proven precision, all system units in steady state; test changes and modifica- tions such as variations in water quality, flow separation or union, as well as changes in dosage and replacement of reagents; simulate the effect of recircu- lation or reuse in water quality; and can even be used to estimate total opex and capex of the alternative process. This approach has been successfully applied at several mining projects. One project called for study of water man- agement at a copper mine to abate dis- solved sulphate in the effluent from the concentrate pipeline. The technology was demonstrated to be effective for sulphate reduction (from 2,000 to 300 mg/l) by incorporating pulp washing to improve water quality and redistribute water flow without a need to treat the effluent. This allowed a reduction in capex for the treatment plant, and improved water quality by generating an effluent with low concentrations of sul- phate and dissolved solids, less con- ductivity and reduced hardness. In the DAF approach, effluent is ini- tially treated to achieve precipitation- coagulation of metallic sulphides. This is possible due to the high reactivity of used sulphides (reagents) and the low solubility of the formed solids (clots) in a wide pH range. Once the clots are formed, a second stage (Dissolved Air Flotation) of solid-liquid separation uses flotation by micro bubbles (smaller than those used in flotation of mineral con- centrates) generated by a process involving compression-decompression of water. The main advantages of this tech- nology in comparison with precipitation with lime are that it can provide lower contaminant values in the final effluent and less generation of sludge—but that sludge also can be sold because of its high metal content. This method also requires less residence time in the reac- tor, a smaller area required for installa- tion and fewer elements to be con- trolled. Sludge generated by conven- tional lime addition produces highly sol- uble hydroxides, creating an additional problem for its disposal. DAF technology has been success- fully tested in effluent treatment plants at Chilean mines including Collahuasi, Los Pelambres and Esperanza, and at Codelco's Ventanas refinery. In each case, the technology was able to achieve precipitation of almost all diva- lent metallic ions, producing concen- tration levels lower than that stipulated by local regulations. Information for this article was provid- ed by ARCADIS, an international com- pany providing consultancy, design, engineering and management services in the fields of infrastructure, water, environment and buildings. Contribu- tors to the article include: Carlos Morillo, project manager, Water Management Area, Arcadis Chile; Omar Gaete, project manager, Water Manage- ment Area, Arcadis Chile; Kathia Tabra, effluent project leader, Arcadis Peru; and Giulliana Tiravanti, effluent project leader, Arcadis Peru. New Pump Saves Copper Mine Downtime, Energy Costs GIW Industries, a supplier of heavy-duty centrifugal slurry pumps, reported that installation of its MDX pump technology at a major Chilean copper mine resulted in a significant reduction of total cost of ownership (TCO) for those pump appli- cations, amounting to millions of dollars in savings for the customer. www.e-mj.com