Primary Copper Smelter Research Articles

Removal of Cu and Sb from waste acid process of copper smelters for minimizing waste generation

The demand for waste minimization in copper smelters has been attracting widespread interest, particularly in the recent global trend towards ESG (environmental, social governance) standards. The typical waste acid process of primary copper smelters is composed of hydrometallurgical technologies such as valuable Cu recovery by single-stage sulfide precipitation followed by a couple of neutralization steps to remove impurities (including H2SO4 and Sb). In this study, a two-stage sulfide precipitation technique capable of removing > 99% of Sb as Sb2S3 and Sb2O3 was introduced prior to the neutralization with the goal of minimizing the generation of large volume of Sb(OH)3 with CaSO4 as waste. Moreover, SO2 in waste acid was identified as the primary cause for the low efficiency of Sb removal by single-stage sulfide precipitation. In addition, an alternative neutralization method facilitated with a slurry mixing technique under optimum pH ≤ 2.5 was introduced in order to valorize the waste neutralization cake as salable gypsum. The phenomena of changing gypsum particle morphology with pH were elucidated by establishing a gypsum particle settling mechanism, which is associated with drag force and inter-particular force. The technical feasibility of the proposed methods was preliminarily assessed on a laboratory scale and verified on a pilot scale.

Primary Copper Smelter and Refinery as a Recycling Plant—A System Integrated Approach to Estimate Secondary Raw Material Tolerance

The primary production of sulfide concentrates includes smelting to copper matte or blister copper, conversion of matte to blister copper, and refining to copper. Smelting, converting, and fire-refining can use a limited amount of secondary materials. Molten copper can effectively dissolve many metals, from valuable noble metals to harmful impurities such as bismuth. However, some of the impurity metals in copper are valuable in other applications. In this paper, we outline the main material flows in copper smelting and electrorefining and describe how minor metals can be recovered from secondary raw materials using copper as a carrier material. We will use a system integrated approach to define the factors that affect the recovery of different metals and copper quality. Metals typical in copper production are used as examples, like noble metals, As, Bi, Se, and Te, including metals in the EU critical raw materials list like PGM and Sb.

Treatment of Wastewater from New Copper Smelter RTB Bor

RTB Bor smelter and sulfuric acid plant modernization project includes reconstruction of an old wastewater treatment plant (WWTP). The task for a team from the Innovation Center of TMF was technical-technological solution for the reconstruction of WWTP with a new wastewater treatment process. Wastewater from the primary copper smelter is very acidic, with a high content of dissolved heavy metals and arsenic. Treatment of wastewater includes the neutralization of the acid, precipitation of the heavy metals in the form of hydroxides by using hydrated lime, and the arsenic co-precipitation with iron(III) hydroxide. Material and energy balances of the process are determined by simulating the wastewater treatment in Superpro Designer software package with thermodynamic parameters defined in HSC Chemistry program. The simulation results were confirmed by experimental tests at the pilot plant level. The designed process is applied in WWTP exploitation within the new copper smelter RTB Bor. Treatment of 8,7 m2/h of wastewater generates 7,2 m2/h of treated wastewater and 10,3 t/h of wastewater treatment (WWT) sludge. The WWT sludge is characterized as hazardous waste requiring treatment prior to disposal. A proposed treatment for WWT sludge is solidification/stabilization (S/S) using a mixture of fly ash and hydrated lime. Results of laboratory scale tests, which included standard leaching tests EN 12457 and TCLP, as well as the compressive strength testing of obtained solidificates, shows that the S/S treatment leads to stabilization of more than 99% of the heavy metals and more than 90% of arsenic. The treated sludge has the characteristics of non-hazardous waste and is suitable for disposal.

Solidified structure and leaching properties of metallurgical wastewater treatment sludge after solidification/stabilization process

ABSTRACTThe presented study investigates solidification/stabilization process of hazardous heavy metals/arsenic sludge, generated after the treatment of the wastewater from a primary copper smelter. Fly ash and fly ash with addition of hydrated lime and Portland composite cement were studied as potential binders. The effectiveness of the process was evaluated by unconfined compressive strength (UCS) testing, leaching tests (EN 12457-4 and TCLP) and acid neutralization capacity (ANC) test. It was found that introduction of cement into the systems increased the UCS, led to reduced leaching of Cu, Ni and Zn, but had a negative effect on the ANC. Gradual addition of lime resulted in decreased UCS, significant reduction of metals leaching and high ANC, due to the excess of lime that remained unreacted in pozzolanic reaction. Stabilization of more than 99% of heavy metals and 90% of arsenic has been achieved. All the samples had UCS above required value for safe disposal. In addition to standard leaching tests, solidificates were exposed to atmospheric conditions during one year in order to determine the actual leaching level of metals in real environment. It can be concluded that the EN 12457-4 test is more similar to the real environmental conditions, while the TCLP test highly exaggerates the leaching of metals. The paper also presents results of differential acid neutralization (d-AN) analysis compared with mineralogical study done by scanning electron microscopy and X-ray diffraction analysis. The d-AN coupled with Eh-pH (Pourbaix) diagrams were proven to be a new effective method for analysis of amorphous solidified structure.

Improving sustainable recovery of metals from waste printed circuit boards by the primary copper smelter process

In this paper, utilizing the existing primary copper smelter process for the recovery of metals from waste printed circuit boards (PCBs) is proposed as an alternative to the current backyard operations in developing countries. The Model for Evaluating Metal Recycling Efficiency from Complex Scraps (MEMRECS) concept is introduced as a tool for the evaluation of the eco-efficiency of metals recovery from waste PCBs. Based on the MEMRECS approach, the relative contribution of every metal fraction to the recyclability of the whole product is estimated. Thereby, gold content is identified as a key factor strongly influencing the efficiency of metals recovery from waste PCBs. Furthermore, it could be used as an indicator for the categorization of waste PCBs before feeding them into the recycling process. Finally, an integrated process is proposed to optimize the eco-efficiency of metals recovery from waste PCBs in developing countries.

Polychlorinated dibenzo p-dioxins and dibenzofurans emissions in a primary copper smelter in China

Metallurgical production is the largest polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) emission source in China. However, PCDD/F monitoring and research are rarely conducted on primary metallurgical production. In this study, a demonstration primary copper smelter in China was selected to investigate PCDD/F characteristics and control. Samples were collected from major PCDD/F release points in the smelter process (fly ashes and waste water sludge). Specific analysis of PCDD/F congeners was carried out using a high resolution gas chromatography/high resolution mass spectrometry method. The results showed that PCDD/Fs might be unintentionally produced in the primary copper smelter processes, with sample concentrations of 180–6110 pg/g dry wt; highly chlorinated PCDD/F homologues were predominant. The toxicity of all the samples was calculated to be 120 pg WHO TEQ/g, fly ashes from the refining process furnaces air pollution control device and sludge were hazardous waste with higher PCDD/F toxicity. Both precursor formation and de novo synthesis were found to contribute to PCDD/F formation in the smelter process. PCDD/F characteristics and formation were compared with reported secondary copper smelters. Life-cycle control of PCDD/F was proposed for retrofitting of this smelter and for similar plants in China's primary copper production sector, including control at the PCDD/F formation, removal and disposal stages.

A solidification/stabilization process for wastewater treatment sludge from a primary copper smelter

Wastewater treatment sludge from primary copper smelter is characterized as hazardous waste that requires treatment prior disposal due to significant amount of heavy metals and arsenic. The aim of the presented study was to investigate the feasibility and the effectiveness of solidification/stabilization process of the sludge using fly ash and lime as binders. The effectiveness of the process was evaluated by Unconfined Compressive Strength (UCS) testing, leaching tests (EN 12457-4 and Toxicity Characteristic Leaching Procedure (TCLP)) and Acid Neutralization Capacity (ANC) test. All samples reached target UCS of 0.35 MPa. Calcium to silicon concentration ratio (cCa/cSi), determined by X-Ray Fluorescence (XRF) analysis, was identified as main factor governing strength development. Inductively coupled plasma-optical emission spectrometry (ICP-OES) analyses of solutions after leaching tests showed excellent stabilization of Cu, Ni, Pb and Zn (above 99 %) and arsenic (above 90 %) in samples with high Ca(OH)2 content. Results of ANC test indicated that buffering capacity of solidified material linearly depended on Ca concentration in FA and lime. Sample with 20 % of binder heaving 50 % of FA and 50 % of lime met all requirements to be safely disposed.

Characterization and quantification of unintentional POP emissions from primary and secondary copper metallurgical processes in China

Field monitoring was conducted to update and develop unintentional persistent organic pollutant (unintentional POP) emission inventories for the copper metallurgy industry in China. In this study, emissions of six unintentional POPs comprised of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDF), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), hexachlorobenzene (HxCBz) and pentachlorobenzene (PeCBz) in stack gas and fly ash samples from primary and secondary copper smelters using different raw materials and technologies were measured and compared. Different concentrations, congener patterns and emission factors of unintentional POPs among four copper smelters were observed. Variations in unintentional POP emissions from several areas of a primary copper smelter were also investigated. The total emissions of unintentional POPs from primary and secondary copper production in 2010 in China were estimated respectively. These results provide a useful reference for the establishment of unintentional POP emission inventories and for policymakers to formulate control strategies to reduce unintentional POPs resulting from copper metallurgy.

Optimizing Peirce–Smith Converters Using Thermodynamic Modeling and Plant Sampling

The performance of pyrometallurgical slag cleaning furnaces at many primary copper smelters is dependent in part on the quality of the converter slag, commonly produced in the batch-wise Peirce Smith converter (PSC). In order to understand the impact of converter slag chemistry and at the same time help optimize the converter operation, thermodynamic modeling of molten slag (including any contained slag solid fractions) was carried out on slag produced at the Chagres smelter in Chile. Phase characterization studies on actual plant slag samples were also carried out. The results are provided in the present paper. This work is also considered as a case study example to illustrate the type of work that can be performed to fairly quickly diagnose the quality of converter slag and assess the overall condition of the converter operation.

Entropy analysis of metal production and recycling

PurposeThe paper attempts to address both resource consumption and recycling effectiveness, using concepts from thermodynamics: entropy production for evaluating the costs (resource consumption) and statistical entropy for evaluating the benefits (separation of materials) of recycling processes.Design/methodology/approachResource consumption, in this context, is to be understood as the overall thermodynamic devaluation of matter and energy flows. The recycling effectiveness, on the other hand, can be measured by the process's ability to reduce the “mixedness” of the material flows, using statistical entropy (entropy of mixing) as an indicator. Statistical entropy has been used by others as an indicator for the performance of waste separation processes, and its application to metal recycling seems straightforward. Entropy production has been applied as a measure for resource consumption in copper production. Here, the two concepts are combined to reach an expression describing the resource efficiency of recycling.FindingsThe theoretical description of the approach is supported by an example calculation for copper recycling. The findings suggest a near perfect effectiveness of the copper separation when processing medium grade copper scrap in a primary copper smelter. The resource consumption, on the other hand, is quite large when compared to the service of the process, giving rise to a rather small thermodynamic efficiency (in terms of the definition of efficiency as applied in this paper).Research limitations/implicationsBoth measures used here, recycling efficiency and recycling effectiveness, are very demanding concerning the data basis, making applications time consuming. These drawbacks can be overcome by linking material flow tools (e.g. LCA software) with thermodynamic databases. More examples have to be considered to show the practical relevance of the approach.Originality/valueThe paper addresses effectiveness and efficiency using a common denominator, thermodynamic entropy. This unification helps in ranking different recycling options regarding their performance in terms of technical effectiveness and resource consumption.

Differential precipitation of copper and nickel from acidic polymetallic aqueous solutions

During the pyrometallurgical treatment of copper concentrates several wastes (gaseous, solid and liquid) are generated. Wastewaters produced in a primary copper smelter are acidic polymetallic solutions characterized by intermediate to high sulphuric acid concentration. Additionally, they usually contain large quantities of valuable metals, such as Cu and Ni, as well as impurities, such as Pb, Zn, Fe, As, Sb, Bi, etc. Therefore, recovery of valuable metals from acidic polymetallic aqueous solutions is of great importance for every plant. This paper is dealing with the recovery of copper and nickel from the acidic polymetallic solutions generated in the copper smelter at Bor, Serbia. The process of differential precipitation of metals through neutralization with caustic soda was selected as the treatment alternative that combines simplicity, efficiency and reliability with low capital and maintenance costs. The concept was based on the development of a simple and efficient process that could be more attractive for industries located in countries suffering from economic recession. Theoretical analysis and experimental results showed that copper and nickel can be differentially removed from the acidic polymetallic solutions at pH=7 and pH=10, respectively, mainly contaminated by arsenic, which occurs at high concentrations in acidic polymetallic solutions. Both metals were precipitated as hydroxides, although a small portion of copper was removed also as copper sulfate salt. The resulted precipitates are rich in copper and nickel and can be recycled in copper, as well as in nickel smelters.

Increasing the Capacity of Major Process Equipment at Primary Copper Smelters

The domestic primary copper smelting industry traditionally has met increased demand for anode copper by expanding existing facilities. In addition to a general discussion on expansion of the smelter as an entity, this article presents a compilation of results from a literature survey of methods that have been used or are possible for expanding the capacity of major process equipment (roasters, smelting furnaces, and converters) on an individual basis. Achievable levels of expansion are noted, as are possible limitations inherent with each technique. The discussion is limited to technical considerations.

The recovery of non-ferrous metals from primary copper smelter discard slags

Slag from the reverberatory furnace copper smelting is a significant source of solid waste. Samples of such slags from a smelter in the Western United States was reduced with carbon as a method of recovering copper, arsenic, bismuth and antimony as an alloy. Recovery was investigated for varying amounts of carbon and calcium oxide addition, time of reduction and temperatures in the range of 1473 to 1573K. Recovery of Cu, As, Bi and Sb increased with increasing reduction time, temperature and addition of C and CaO to the slags. Commercial scale implications are discussed.

Health risks associated with residence near a primary copper smelter: a preliminary report.

Mortality for three groups of ICD codes covering acute, chronic, and malignant respiratory diseases were studied for adult white women in communities near or adjacent to primary copper smelting facilities in the United States between 1968 and 1975, a period when women had not as yet entered the industrial work force. A previous comprehensive survey, sponsored by the EPA, of all U.S. counties used multiple regression analysis as a method of statistical surveillance to assess the association of mortality with industrial activity. This preliminary study suggested an excess mortality from nonmalignant respiratory diseases in copper mining and smelting counties. We directly examined town mortality rates for white female residents, aged 35 to 74, in eight U.S. copper smelting communities and compared them to demographically and geographically matched communities without industries likely to produce significant air pollution, using death certificates obtained from state sources. Site-specific air quality data were also obtained for these communities. Our direct examination of community death rates for copper smelting towns confirmed the preliminary observation at the county level of an excess risk from acute respiratory diseases but did not detect evidence of an elevated mortality from chronic respiratory diseases or cancer of the respiratory tract.

Arsenic Distribution and Control in Copper Smelters

Arsenic emissions from primary copper smelters are currently being reviewed by the U.S. Environmental Protection Agency to help establish the best available control technology. Relatively little information is available in the literature concerning the actual distribution of arsenic throughout the copper smelting processes. In addition, smelting process parameters which specifically affect arsenic distribution have not been clearly defined. This paper presents a general summary of arsenic distributions based on data from foreign and domestic copper smelters utilizing different smelting processes. The distribution of arsenic is presented on a 100% input basis for the various smelting configurations as well as for the individual process units. The general trends of arsenic volatilization and slagging for different process units are examined and probable effects are discussed. The effectiveness of control devices such as electrostatic precipitators and fabric filters in the control of arsenic emissions from copper smelters is also discussed.