Environmental risk assessment on slag and iron-rich matte produced from reducing-matting smelting of lead-bearing wastes and iron-rich wastes

A new process for utilization of hazardous lead-bearing wastes and iron-rich wastes by reducing-matting smelting has been developed.The slag（SG） and the iron-rich matte（IRM） are the main by-products from reducing-matting smelting of lead-bearing wastes and iron-rich wastes.The environmental risk of heavy metals（Cd,Zn,Pb and As） in the main by-products versus the charging material for reducing-matting smelting（CM） has been systematically assessed using leaching toxicity test,the three-stage sequential extraction procedure of European Community Bureau of Reference（BCR） and Hakanson Potential Ecological Risk Index Method（PERI）.The results demonstrate that the ecological risk level of heavy metals for SG and IRM is significantly reduced after the reducing-matting smelting process compared with that for CM.

Numerical investigation of sinusoidal pulsating gas intake to intensify the gas-slag momentum transfer in the top-blown smelting furnace

The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essential aspects of the fluid phase(e.g.,splashing volume,dead zone of copper slag,and gas penetration depth)were explored together with the effect of sinusoidal pulsating gas intake on the momentum-transfer performance between phases.The results illustrated that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance,respectively.The expansion of larger ones as well as the shrinking of smaller ones combine to cause the contraction of the bubble waist.Compared to the results of the case with a fixed gas injection velocity(V_(g)=58 m/s),the splashing volume and dead zone volume of the slag under the V_(g)=58+10sin(2πt)condition are reduced by 24.9%and 23.5%,respectively,where t represents the instant time.Gas penetration depth and slag motion velocity of the latter are 1.03 and 1.31 times high-er than those of the former,respectively.

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting(SCS)dust using a sulfating roasting−water leaching process were investigated.The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl.Under the sulfating roasting conditions of the roasting temperature of 250℃ and the sulfuric acid excess coefficient of 1.8,over 74 wt.%of F and 98 wt.%of Cl were volatilized into flue gas.Approximately 98.6 wt.%of Zn and 96.5 wt.%of Cu in the roasting product were dissolved into the leaching solution after the water leaching process,while the leaching efficiencies of Pb and Sn were only 0.12%and 0.22%,respectively.The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.

Rapid detection and risk assessment of soil contamination at lead smelting site based on machine learning

A general prediction model for seven heavy metals was established using the heavy metal contents of 207soil samples measured by a portable X-ray fluorescence spectrometer(XRF)and six environmental factors as model correction coefficients.The eXtreme Gradient Boosting(XGBoost)model was used to fit the relationship between the content of heavy metals and environment characteristics to evaluate the soil ecological risk of the smelting site.The results demonstrated that the generalized prediction model developed for Pb,Cd,and As was highly accurate with fitted coefficients(R^(2))values of 0.911,0.950,and 0.835,respectively.Topsoil presented the highest ecological risk,and there existed high potential ecological risk at some positions with different depths due to high mobility of Cd.Generally,the application of machine learning significantly increased the accuracy of pXRF measurements,and identified key environmental factors.The adapted potential ecological risk assessment emphasized the need to focus on Pb,Cd,and As in future site remediation efforts.

CFD modeling of gas−liquid flow phenomenon in lead smelting oxygen-enriched side-blown furnace

A validated numerical model was established to simulate gas−liquid flow behaviors in the oxygen-enriched side-blown bath furnace.This model included the slip velocity between phases and the gas thermal expansion effect.Its modeling results were verified with theoretical correlations and experiments,and the nozzle-eroded states in practice were also involved in the analysis.Through comparison,it is confirmed that the thermal expansion effect influences the flow pattern significantly,which may lead to the backward motion of airflow and create a potential risk to production safety.Consequently,the influences of air injection velocity and furnace width on airflow behavior were investigated to provide operating and design guidance.It is found that the thin layer melt,which avoids high-rate oxygen airflow eroding nozzles,shrinks as the injection velocity increases,but safety can be guaranteed when the velocity ranges from 175 to 275 m/s.Moreover,the isoline patterns and heights of thin layers change slightly when the furnace width increases from 2.2 to 2.8 m,indicating that the furnace width shows a limited influence on production safety.

Clean production of Fe-based amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore and apatite

Separated preparation of prealloys and amorphous alloys results in severe solidification-remelting and beneficial element removal-readdition contradictions,which markedly increase energy consumption and emissions.This study offered a novel strategy for the direct production of FePC amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore(HPIO)and apatite.First,the thermodynamic conditions and equilibrium states of the carbothermal reduction reactions in HPIO were calculated,and the element content in reduced alloys was theoretically determined.The phase and structural evolutions,as well as element migration and enrichment behaviors during the smelting reduction of HPIO and Ca_(3)(PO_(4))_(2),were then experimentally verified.The addition of Ca_(3)(PO_(4))_(2)in HPIO contributes to the enrichment of the P element in reduced alloys and the subsequent development of Fe_(3)P and Fe_(2)P phases.The content of P and C elements in the range of 1.52 wt% -14.63 wt% and 0.62 wt% -2.47 wt%,respectively,can be well tailored by adding 0-50 g Ca_(3)(PO_(4))_(2)and controlling the C/O mole ratio of 0.8-1.1,which is highly consistent with the calculated results.These FePC alloys were then successfully formed into amorphous ribbons and rods.The energy consumption of the proposed strategy was estimated to be 2.00×10^(8) kJ/t,which is reduced by 30% when compared with the conventional production process.These results are critical for the comprehensive utilization of mineral resources and pave the way for the clean production of Fe-based amorphous soft magnetic alloys.

The new green smelting process of CNREG commissioned

A demonstration project of the major scientific and technological project in Inner Mongolia Autonomous Region-"Industrialization Test of New Green Smelting Technology for Rare Earth Concentrate produced from Baiyun Obo ore"was commissioned on November 20th.This project adopts the"new green smelting process for rare earth concentrate"independently developed by China Northern Rare Earth Group(CNREG),and has achieved a new breakthrough in rare earth smelting technology.

钒钛矿PLCsmelt工艺冶炼技术

钒钛磁铁矿的成分和结构复杂,是世界公认的难选冶矿种。与普通铁精矿相比,钒钛磁铁矿的品位偏低,有价组元分散于各矿相中,采矿和选冶都具有较大的难度,钒钛矿资源的有效利用是钢铁行业的关注问题之一。基于此,依据攀西钒钛磁铁矿特性,提出了PLCsmelt炼铁新工艺。首先介绍了PLCsmelt炼铁工艺流程,以气基竖炉-电炉工艺为参照,从工艺流程、成本、资源利用率、碳排放和能耗等方面对两种工艺进行了分析对比,并与高炉工艺进行了碳排放及能耗对比。研究表明,PLCsmelt的工艺成本、钒资源回收率、碳排放及能耗分别为1943.1元/t、75.9%、1009.6 kgCO_(2)/tHM及370.9 kgce/tHM,各参数较高炉及气基竖炉-电炉工艺均有明显优势,证明PLCsmelt炼铁新工艺更有利于钒钛磁铁矿资源综合高效利用。同时对PLCsmelt工艺技术的发展前景进行了展望,也对该技术存在的问题及未来研究的方向进行了讨论。

Recovery of valuable metals from spent lithium ion batteries by smelting reduction process based on FeO-SiO_2-Al_2O_3 slag system

NA novel smelting reduction process based on FeO-SiO2-Al2O3 slag system for spent lithium ion batteries with Al cans was developed, while using copper slag as the only slag former. The feasibility of the process and the mechanism of copper loss in slag were investigated. 98.83% Co, 98.39% Ni and 93.57% Cu were recovered under the optimum conditions of slag former/battery mass ratio of 4.0：1, smelting temperature of 1723 K, and smelting mass ratio of time of 30 min. The FeO-SiO2-Al2O3 slag system for the smelting process is appropriate under the conditions of m（FeO）：m（SiO2）=0.58：1？1.03：1, and 17.19%？21.52% Al2O3 content. The obtained alloy was mainly composed of Fe-Co-Cu-Ni solid solution including small amounts of matte. The obtained slag mainly consisted of fayalite and hercynite. Meanwhile, the mechanism of copper loss is the mechanical entrainment from strip-like fayalite particles in the main form of copper sulfide and metallic copper.

Soil vanadium pollution and microbial response characteristics from stone coal smelting district

A field investigation was performed to study the content, speciation and mobility of vanadium, as well as microbial response in soil from a stone coal smelting district in Hunan province of China. The results showed that the contents of soil V ranged from 168 to 1538 mg/kg, which exceeded the maximum permissible value of Canadian soil quality for V. The mean soil V content from wasteland area reached 1421 mg/kg, and those from the areas related with slag heap, ore pile and smelting center were 380, 260 and 225 mg/kg, respectively. Based on the results of the modified BCR sequential extraction procedure, V contents in the mobile fractions varied from 19.2 to 637 mg/kg accounting for 7.4%-42.3% of total V, and those of V(+5) species were between 21.9 and 534.0 mg/kg. Soil enzyme activity and microbial basal respiration were adversely affected by high level of soil V. More attention should be paid to soil V pollution and potential hazardous surrounding the stone coal smelting district.

Recovery of cobalt from converter slag of Chambishi Copper Smelter using reduction smelting process

The reduction smelting process for cobalt recovery from converter slag of the Chambishi Copper Smelter in Zambia was studied. The effects of reducing agent dosage, smelting temperature and time and the addition of slag modifiers （CaO and TiO2） were investigated. In addition, the depleted slag and cobalt-bearing alloy were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Under the determined conditions, 94.02% Co, 95.76% Cu and less than 18% Fe in the converter slag were recovered. It was found that the main phases of depleted slag were fayalite and hercynite; and the cobalt-bearing alloy mainly contained metallic copper, Fe-Co-Cu alloys and a small amount of sulfide.

Furnace structure analysis for copper flash continuous smelting based on numerical simulation

According to the innate characteristic of four types of furnace, the copper flash continuous smelting （CFCS） furnace can be considered a synthetic reactor of two relatively independent processes： flash matte smelting process （FMSP） and copper continuous converting process （CCCP）. Then, the CFCS thermodynamic model was proposed by establishing the multi-phase equilibrium model of FMSP and the local-equilibrium model of CCCP, respectively, and by combining them through the smelting intermediates. Subsequently, the influences of the furnace structures were investigated using the model on the formation of blister copper, the Fe3O4 behavior, the copper loss in slag and the copper recovery rate. The results show that the type D furnace, with double flues and a slag partition wall, is an ideal CFCS reactor compared with the other three types furnaces. For CFCS, it is effective to design a partition wall in the furnace to make FMSP and CCCP perform in two relatively independent zones, respectively, and to make smelting gas and converting gas discharge from respective flues.

Effect of moderately thermophilic bacteria on metal extraction and electrochemical characteristics for zinc smelting slag in bioleaching system

The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied. The results show that the extraction rates of Fe, Cu and Zn from the slag reach 86.7%, 90.3% and 66.7% after adsorbed bacteria sterilize, while those with adsorbed bacteria are 91.9%, 96.0% and 84.5% in conditions of pulp density 2%, pH 1.0, temperature 65 °C and stirring rate 120 r/min, respectively. Some stretching peaks of functional groups from bacterial secretes on the bioleached residue surface, such as 1007 cm-1 and 1193 cm-1, turn up through FI-IR analysis and indirectly reveal the presence of the adsorbed bacteria on the slag particles surface. Besides, the corrosion of zinc smelting slag is enhanced by bacteria according to the characteristics of cyclic voltametry and Tafel curves in bioleaching system.

RESEARCH ON SMELTING LOW-CARBON FERROCHROME IN A PLASMA FURNACE

By a non-transformed arc plasma torch whose gas is nitrogen,scrap of high-carbon ferrochrome was heated and melted in a sealed furnace. When the liquid bath was at 1600℃,top blowing of oxygen began to decrease the bath's carbon without stopping plasma operation for its temperature addition and maintennace of at least 1750 ℃. The liquid bath was agitated by bottom-blowning nitrogen. In the experiments low carbon Fe-Cr have been obtained whose composition respectively was 0.45% carbon,50.75% chrome and 0.42% carbon, 70.25% chrome. Loss of chrome could be less than 5%.

Risk assessment of heavy metals in soils and vegetables around nonferrous metals mining and smelting sites,Baiyin,China

A field survey was conducted to investigate the metal and arsenic contamination in soils and vegetables on four villages （Shuichuan （SCH）, Beiwan （BWA）, Dongwan （DWA） and Wufe （WFE）） located along, Baiyin, China, and to evaluate the possible health risks to local population through foodchain. Results show that the most significantly contaminated soils occurred upstream at SCH where Cd, Cu and As concentrations exceeded maximum allowable concentrations for Chinese agricultural soil. Further downstream the degree of contamination semi-systematically decreased in concentrations of metal. Generally, the leafy vegetables were more heavily contaminated than non-leafy vegetables. Chinese cabbage is the most severely contaminated, the concentrations of Cd exceeded the maximum permit levels （0.05 mg/kg） by 4.5 times. Bio-accumulate factor also shows that an entry of Cd to food chain plants is the greatest potential. Furthermore, the estimated daily intake amounts of the considered toxic elements （Cd, Pb and Cu） from the vegetables grown at SCH and BWA and DWA have exceeded the recommended dietary allowance levels. Thus, the vegetables grown in three villages above, which affected by Baiyin mining and smelting have a health hazard for human consumption.

COMPUTER MODEL OF COPPER SMELTING PROCESS AND DISTRIBUTION BEHAVIORS OF ACCESSORY ELEMENTS

A computer model has been developed to simulate the distribution behaviors of Ni, Co. Sn. Ph,Zn, As, Sb, Bi, An and Ag in copper smelting process. The model assumes that the copper smelting furnaceis in thermodynamic equilibrium. As many as 21 elements (Cu. S, Fe. Ni, Co. Sn, As, Sb. Bi, Ph. Zn.An. Ag. O, N, C, H, Ca, Mg, Al, and St) and 73 compounds are considered. This model accounts forphysical entrainment in the melts. The predictions by the present computer model are compared with theknown commercial data from Guixi Smelter in China, Home Smelter in Canada and Naoshima Smelter inJapan. The agreements between the computer predictions and the commercial data are excellent, so that thepresent computer model can be used to monitor and optimize the actual industrial operations of copper smelting. It is applicable to simulation of almost all copper pyrometallurgical processes.

Numerical simulation analysis of Guixi copper flash smelting furnace

A numerical simulation analysis for reactions of chalcopyrite and pyriteparticles coupled with momentum, heat and mass transfer between the particle and gas in a flashsmelting furnace is presented. In the simulation, the equations governing the gas flow are solvednumerically by Eular method. The particle phase is introduced into the gas flow by theparti-cle-source-in-cell technique (PSIC). Predictions including the fluid flow field, temperaturefield, concentration field of gas phase and the tracks of particles have been obtained by thenumerical simulation. The visualized results show that the reaction of sulfide particles is almostcompleted in the upper zone of the shaft within 1.5 m far from the central jet distributor (CJD)type concentrate burner. The simulation results are in good agreement with data obtained from aseries of experiments and tests in the plant and the error is less than 2%.

Effects of smelting parameters on the slag/metal separation behaviors of Hongge vanadium-bearing titanomagnetite metallized pellets obtained from the gas-based direct reduction process

Smelting separations of Hongge vanadium-bearing titanomagnetite metallized pellets（HVTMP）prepared by gas-based direct reduction were investigated,and the effects of smelting parameters on the slag/metal separation behaviors were analyzed.Relevant mechanisms were elucidated using X-ray diffraction analysis,FACTSAGE 7.0 calculations,and scanning electron microscopy observations.The results show that,when the smelting temperature,time,and C/O ratio are increased,the recoveries of V and Cr of HVTMP in pig iron are improved,the recovery of Fe initially increases and subsequently decreases,and the recovery of Ti O_2 in slag decreases.When the smelting Ca O/Si O_2 ratio is increased,the recoveries of Fe,V,and Cr in pig iron increase and the recovery of Ti O_2 in slag initially increases and subsequently decreases.The appropriate smelting separation parameters for HVTMP are as follows：smelting temperature of 1873 K;smelting time of 30–50 min;C/O ratio of 1.25;and Ca O/Si O_2 ratio of 0.50.With these optimized parameters（smelting time：30 min）,the recoveries of Fe,V,Cr,and Ti O_2 are 99.5%,91.24%,92.41%,and 94.86%,respectively.

Relationship between copper content of slag and matte in the SKS copper smelting process

In the newly developed oxygen-enriched bottom-blowing copper smelting process(also known as the SKS copper smelting process), Cu loss in slag is one of the most concerning issues. This paper presents our research results concerning the relationship between the Cu content of the matte and slag in the SKS process; the results are based on actual industrial production in the Dongying Fangyuan copper smelter. The results show that the matte grade strongly influences Cu losses in slag. The dissolved and entrained losses account for 10%–20% and 80%–90% of the total SKS industrial Cu losses in slag, respectively. With increasing matte grade, the dissolved and entrained Cu losses in the SKS slag both increase continuously. When the matte grade is greater than 68%, the content of Cu in the smelting slag increases much more dramatically. To obtain a high direct recovery of copper, the matte grade should be less than 75% in industrial SKS copper production.

Reductive smelting of spent lead–acid battery colloid sludge in a molten Na_2CO_3 salt

Lead extraction from spent lead–acid battery paste in a molten Na2CO3 salt containing Zn O as a sulfur-fixing agent was studied. Some influencing factors, including smelting temperature, reaction time, Zn O and salt dosages, were investigated in detail using single-factor experiments. The optimum conditions were determined as follows: T = 880°C; t = 60 min; Na2CO3/paste mass ratio = 2.8:1; and the Zn O dosage is equal to the stoichiometric requirement. Under the optimum conditions, the direct recovery rate of lead reached 98.14%. The results suggested that increases in temperature and salt dosage improved the direct recovery rate of lead. XRD results and thermodynamic calculations indicated that the reaction approaches of lead and sulfur were Pb SO4→Pb and Pb SO4→Zn S, respectively. Sulfur was fixed in the form of Zn S, whereas the molten salt did not react with other components, serving only as a reaction medium.