Processing Solid Arsenic-containing Waste
Development of Effective Technologies for Processing Solid Arsenic-containing Waste of the Copper Production
Tech Area / Field
- ENV-SPC/Solid Waste Pollution and Control/Environment
3 Approved without Funding
Chemical and Metallurgical Institute, Kazakstan, Karaganda
- Scientific and Analytical Center Biomedpreparat LLC, Kazakstan, Stepnogorsk
- Colorado School of Mines, USA, CO, Golden
Project summaryThe Project aim – conclusion of arsenic from copper dust and comprehensive extraction of valuable components in the form of commercial products.
Current status: World tendency of the market and production of copper are characterized by lower copper content in the raw materials and increased proportion of impurities. The most harmful impurity is arsenic as it is ecologically dangerous for the environment. With pyro metallurgy processing of raw copper large mass of impurities (zinc, lead, bismuth, cadmium, arsenic and others) is concentrated in dust and sublimates melting, converter redistribution and anode refinement. The degree of sublimation of arsenic during melting of copper raw materials is significantly influenced by the content of copper in matte and temperature of the process. Dust collected of the melting units is sent to the boilers-utilizers where cooled by 3500С and entered electrostatic. This is a way accepted in all types of melting processes (process of "Mitsubishi", "Noranda", melting in liquid bath, flash melting furnace). For example, the Balkhash Copper Enterprise of the JSC "Kazakhmys Corporation" with the Vanyukov's technology the relative content of arsenic in dust is the following: in boiler utilizer 30-40% of arsenic sulfide; 10-12% of arsenic oxide; 20-25% of tioarsenat copper; 10-15% of tioarsenat lead; 8-10% of iron arsenide; 2-3% arsenates of nonferrous metals. Dust from boiler utilizer is returned to the melting. Dust from dry electrostatic contains 10-15% of arsenic sulfide, 45-50% of arsenic oxide, 5-10% of tioarsenat copper, 3-5 % of tioarsenat lead, 3-5% of iron arsenide, 15-20% of arsenate non-ferrous metals. As a result at this factory when complex composition of the copper-containing material melted in liquid bath arsenic removal is compiled by 90%. Thin dry dust of electrostatic is realized as a commercial product for the lead enterprises that increase intra-and interplant circulation of arsenic.
With converting copper matte of melting blast about 40% of arsenic remains in blister copper, 20% becomes converter slag, the rest becomes dust. In the process of fire refining 12% becomes slag, overwhelming majority stays in anode copper.
With converting matte of the flash melting arsenic is distributed the following way: 50% into slag, 15% into blister copper, 26% into dust; up to 75% of arsenic is concentrated in anode copper.
With converting matte produced by electrofusion the picture of distribution of arsenic is the following: 6-7% in blister copper, 8-10% in converter revolving slag, 15-18% in dust.
With converting redistribution of copper matte produced by melting in liquid bath the following is obtained: 20% of arsenic becomes blister copper, 25% becomes slag, 55% - dust.
Besides, about 50% of lead, up to 1% of cadmium, up to 0,9 % bismuth become converting dust. Dust of the Kazakhstan companies enriched of rhenium up to 100 g/t.
Thus, those raw materials should be utilized using technologies of complex processing with removal of arsenic at the initial stage in the form of stable compound suitable for long storage. Fused sulphides of arsenic, iron arsenide are those compounds.
At the Chemical Metallurgy Institute theoretical basis is established and technology is developed to preliminary dearsenization of sulphide material with the transfer of arsenic into commercial product in the form of sulphide, in particular in the form of tetrasulfide arsenic, which contains up to 60-70 % of arsenic. The conclusion of Sanitary agencies refers them to substances of minimum (III –IV) danger category. In fused or briquetted state arsenic sulphide can be stored in the usual warehouses and transported as a common chemical reagent. Usage of arsenic sulphide as biocide in antifouling paints for marine and hydraulic structures opens new opportunities for tonnage usage of arsenic waste .
Strategy of solving problem of arsenic-containing waste should include the following key issues:
1. Review and rework existing technological schemes of processing arsenic-containing materials and intermediate products to:
- minimize and terminate conclusion of arsenic in dumps in the form of water-soluble and dust generating highly toxic waste (arsenates and arsenite calcium, magnesium, manganese, antimony slags, etc.);
- receive low-emission and compact products or intermediate products not depending on the scale of the use of arsenic (sulfide, arsenide, scorodite).
2. Master pyro and hydro metallurgical method to process accumulated arsenic-containing waste with extraction of non-ferrous metals, obtain commercial arsenic and low-toxic intermediate products for conservation.
3. Offer to find ways to large scale usage of arsenic and produce refined trioxide, clear metal, antiseptics and other substances of arsenic commercial products.
4. Revise existing ways of arsenic containing waste storage and its stabilization, and conservation to prevent environmental pollution by arsenic.
Goals and objectives of the project fully comply with the second point of the strategy to resolve arsenic problem.
The project’ influence on progress in this area
Current technological methods of processing copper concentrate are accompanied with the formation of large amounts of gases and dusts with non-ferrous and rare metals, impurities in the form of arsenic. Non-reduced production volume requires urgent solution of the related environmental problems, primarily disposal of the accumulated waste. At the same time due to the depletion of mineral reserves, issues arise for complex use of industrial waste. High attention in the world is paid to the question of processing industrial waste as this allows solving some technological, economic and ecological tasks: return precious metals in the sphere of industrial activity; reduce energy consumption for the production of non-ferrous scarce metals; prevent or significantly limit the amount of toxic products getting into the environment. All those issues are included into the project and will definitely influence progress in this area.
The participants’ expertise. Participants of the project from the Institution 1 (Chemical Metallurgy Institute named after Abishev) have prior experience in this area which is proved by the list of important publications during the last years and can be studied at http://www.hmi.kz
Expected Results and Their Application
Utilization of dust of copper production with getting additional commercial products is not only profitable production but also prevention of the ecological harm. Those are expected results of the project implementation. The expected results will have impact for all copper enterprises not only in Kazakhstan but also abroad. Mastering pyro and hydro metallurgical methods to process accumulated arsenic-containing waste in the form of dust with extraction of non-ferrous and rare metals, obtaining commercial arsenic and low-toxic intermediate products for conservation are expected results of the project.
Meeting ISTC Goals and Objectives
The results of the project meet ISTC goals – solving ecological tasks aimed to improve environment of the industrial regions.
Scope of activities.
The following activities will be implemented during the project:
Task 1. Establishment of complex pyro metallurgical way of processing arsenic containing dust of copper production.
Task 2. Establishment of complex hydro metallurgical technology of processing arsenic containing dust of copper production
Task 3. Working out ways of stabilization and disposal of arsenic sulfide – the product of processing dust of the copper production.
Role of Foreign Collaborators/Partners. Mr. Corby Anderson, scientist from USA, has agreed to serve as a collaborator for the project.
Technical approach and methodology. Technical approach and methodology include overview of the well-known methods of processing of technogenic raw materials and upon analysis there will technological tests done to extract non-ferrous and rare metals and conclusion of arsenic in the form of its tetrasulfide. Optimization of parameters of the proposed technological methods will be done with the usage of mathematic planning of the experiment to obtain mathematic model of each method. Results will be obtained with the application of the known methods of physics and chemical analysis. Test analysis will be checked at the National scientific laboratory of the collective use by the priority direction “Technology for Hydrocarbon and Mining and Metallurgical Sectors in the Republic of Kazakhstan and Related Service Industries”.
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