Copper slag assisted coke reduction of phosphogypsum for sulphur dioxide preparation

The reduction of phosphogypsum(PG)to lime slag and SO_(2)using coke can effectively alleviate the environmental problems caused by PG.However,the PG decomposition temperature remains high and the product yield remains poor.By adding additives,the decomposition temperature can be further reduced and PG decomposition rate and product yield can be improved.However,the use of current additives such as Fe_(2)O_(3)and SiO_(2)brings the problem of increasing economic cost.Therefore,it is proposed to use solid waste copper slag(CS)as a new additive to reduce PG to prepare SO2,which can reduce the cost and meet the environmental benefits at the same time.The effects of proportion,temperature and thermostatic time on PG decomposition are investigated by experimental and kinetic analysis combined with FactSage thermodynamic calculations to optimize the roasting conditions.Finally,the reaction mechanism is proposed.It is found that adding CS to the coke and PG system can increase the rate of PG decomposition and SO_(2)yield while lowering the PG decomposition temperature.For example,when the CS/PG mass ratio increases from 0 to 1,PG decomposition rate increases from 83.38%to 99.35%,SO_(2)yield increases from 78.62%to 96.81%,and PG decomposition temperature decreases from 992.4℃to 949.6℃.The optimal reaction parameters are CS/PG mass ratio of 1,Coke/PG mass ratio of 0.06 at 1100℃for 20 min with 99.35%PG decomposition rate and 96.81%SO_(2) yield.The process proceeds according to the following reactions:2CaSO_(4)+ 0.7C + 0.8Fe_(2)SiO_(4)→0.8Ca_(2)SiO_(4)+ 0.2Ca_(2)Fe_(2)O_(5)+ 0.4Fe_(3)O_(4)+2SO_(2)+ 0.7CO_(2)Finally,a process for decomposing PG with coke and CS is proposed.

Interphase migration and enrichment of lead and zinc during copper slag depletion

An interphase migration and enrichment model of lead and zinc during molten copper slag depletion was established.The occurrence of various components in copper slag was predicted using sulfur-oxygen potential calculations and confirmed through high-temperature experiments.The recovery rate of copper can reach 90.13%under the optimal conditions of 1200°C,an iron to silicon mass ratio of 1.0,3 wt.%ferrous sulfide,and a duration of 45 min.Lead(54.07 wt.%)and zinc(17.42 wt.%)are found in the flue dust as lead sulfate,lead sulfide,and zinc oxide,while copper matte contains lead(14.44 wt.%)and zinc sulfide(1.29 wt.%).The remaining lead and zinc are encapsulated as oxides within the fayalite phase.

Detection of Al, Mg, Ca, and Zn in copper slag by LIBS combined with calibration curve and PLSR methods

The precise measurement of Al, Mg, Ca, and Zn composition in copper slag is crucial for effective process control of copper pyrometallurgy. In this study, a remote laser-induced breakdown spectroscopy(LIBS) system was utilized for the spectral analysis of copper slag samples at a distance of 2.5 m. The composition of copper slag was then analyzed using both the calibration curve(CC) method and the partial least squares regression(PLSR) analysis method based on the characteristic spectral intensity ratio. The performance of the two analysis methods was gauged through the determination coefficient(R^(2)), average relative error(ARE), root mean square error of calibration(RMSEC), and root mean square error of prediction(RMSEP). The results demonstrate that the PLSR method significantly improved both R^(2) for the calibration and test sets while reducing ARE, RMSEC, and RMSEP by 50% compared to the CC method. The results suggest that the combination of LIBS and PLSR is a viable approach for effectively detecting the elemental concentration in copper slag and holds potential for online detection of the elemental composition of high-temperature molten copper slag.

Properties of Sustainable High Strength Concrete with Waste Copper Slag

The present work investigates copper slag as a substitute for river sand in high-strength concrete.The concrete mixtures were manufactured with 10%,30%,50%,70%,and 100%of copper slag to evaluate the mechanical and durability properties.The experimental results indicate that replacing copper slag above 50%affects the performance characteristics of the concrete due to its high angularity and lower water absorption characteristics.The strength of concrete with 50%copper slag is improved by 5.6%,whereas the strength of concrete with 100%copper slag is reduced by 2.75%at 28 days.However,increased curing to 90days improves the strength of the former by 7.16%and reduces the latter by only 0.23%.The water absorption,porosity,and rapid chloride penetration of the concrete mixtures with 100%copper slag are increased by 10.44%,13.20%,and 19.56%compared to control concrete.Micro-structural investigations through SEM infer higher replacement of copper results in higher void formation due to its reduced water absorption.

Recovery of iron from copper slag by deep reduction and magnetic beneficiation

Aiming at recovering iron from high-iron-content copper slag, this article introduced a combination technol- ogy of deep reduction and magnetic beneficiation, investigated the iron recovery efficiency and optimized the technical conditions. When coke powder with 86wt% fixed carbon was used as a reductant, iron was successfully extracted from the copper slag. Under the optimized condition of the coke powder content of 14wt%, the calcium-to-silicon mass ratio （Ca/Si） of 0.2, the roasting temperature of 1300℃, the roasting time of 3 h, the grinding time of 20 min, and the magnetic field intensity of 61 kA-m-1, the iron recovery rate of the copper slag can reach 91.82%, and the extracted iron powder has an iron grade of 96.21%. With the characteristics of high iron grade and low impurity content, the extracted iron powder can be used as high-quality raw materials of weathering steel.

Separation of silicon and iron in copper slag by carbothermic reduction-alkaline leaching process

Approximately 2.0-3.0 t of copper slag(CS) containing 35%-45% iron is generated for every ton of copper produced during the pyrometallurgical process from copper concentrate. Therefore, the recovery of iron from CS utilizes a valuable metal and alleviates the environmental stress caused by stockpile. In this paper, a new method has been developed to realize the enrichment of iron in CS through the selective removal of silica. The thermodynamic analyses and experimental results show that the iron in CS can be fully reduced into metallic iron by carbothermic reduction at 1473 K for 60 min. The silica was converted into free quartz solid solution(QSS) and cristobalite solid solution(CSS). QSS and CSS are readily soluble, whereas metallic iron is insoluble, in NaOH solution. Under optimal leaching conditions, a residue containing 87.32% iron is obtained by decreasing the silica content to 6.02% in the reduction roasted product. The zinc content in the residue is less than 0.05%. This study lays the foundation for the development of a new method to comprehensively extract silicon and iron in CS while avoiding the generation of secondary tailing.

Assessment of selective sequential extraction procedure for determining arsenic partitioning in copper slag

An optimized selective sequential extraction(SSE)procedure was developed to assess the arsenic(As)partitioning in copper slag.The potential As species in copper slag are partitioned into the readily soluble As,dissolvable arsenates,sparingly soluble arsenates,As residing in sulfides,arsenopyrite and metal As,as well as As incorporated into glassy silicates.The inductively coupled plasma atomic emission spectrometry(ICP-AES),scanning electronic microscopy(SEM),transmission electron microscope(TEM),X-ray diffractometry(XRD)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the leachates and residues produced from the operation scheme.The selectivity and recovery of extractants were evaluated through single-phase extraction procedures.Partitioning data of As in slag samples show good agreement with the reported works and the total As recovery of each operation is over 90%.This suggests that the optimized SEE scheme can be reliably employed for As partitioning in As-bearing byproducts from copper smelting.

Iron and copper recovery from copper slags through smelting with waste cathode carbon from aluminium electrolysis

To recover metal from copper slags,a new process involving two steps of oxidative desulfurization followed by smelting reduction was proposed in which one hazardous waste(waste cathode carbon)was used to treat another(copper slags).The waste cathode carbon is used not only as a reducing agent but also as a fluxing agent to decrease slag melting point.Upon holding for 60 min in air atmosphere first and then smelting with 14.4 wt%waste cathode carbon and 25 wt%CaO for 180 min in high purity Ar atmosphere at 1450℃,the recovery rates of Cu and Fe reach 95.89%and 94.64%,respectively,and meanwhile greater than 90%of the fluoride from waste cathode carbon is transferred into the final slag as CaF_(2) and Ca_(2)Si_(2)F_(2)O_(7),which makes the content of soluble F in the slag meet the national emission standard.Besides,the sulphur content in the obtained Fe-Cu alloy is low to 0.03 wt%.

Chemical looping gasification of sewage sludge using copper slag modified by NiO as an oxygen carrier

Chemical looping gasification(CLG) provides a novel approach to dispose the sewage sludge.In order to improve the reactivity of the calcined copper slag,NiO modification is considered as one of the good solutions.The copper slag calcined at 1100℃ doped with 20 wt% NiO(Ni20-CS) was used as an oxygen carrier(OC) in sludge CLG in the work.The modification of NiO can evidently enhance the reactivity of copper slag to promote the sludge conversion,especially for sludge char conversion.The carbon conversion and valid gas yield(V_(g)) increase from 67.02% and 0.23 m^(3)·kg^(-1) using the original OC to 78.34% and 0.29 m^(3)·kg^(-1) using the Ni20-CS OC, respectively.The increase of equivalent coefficient(Ω) facilitates the sludge conversion and a suitable Ω value is determined at 0.47 to obtain the highest valid gas yield(0.29 m^(3)·kg^(-1)).A suitable steam content is assigned at 27.22% to obtain the maximum carbon conversion of 87.09%,where an acceptable LHV of 12.63 MJ·m^(-3) and Vg of 0.39 m^(3)·kg^(-1)are obtained.Although the reactivity of Ni20-CS OC gradually decreases with the increase in cycle numbers because of the generation of NiFe_(2) O_(4-δ) species,the deposition of sludge ash containing many metallic elements is beneficial to the sludge conversion.As a result,the carbon conversion shows a slight uptrend with the increase of cycle numbers in sludge CLG.It indicates that the Ni20-CS sample is a good OC for sludge CLG.

Smelting chlorination method applied to removal of copper from copper slags

In order to reasonably utilize the iron resources of copper slags, the smelting chlorination process was used to remove copper from copper slags. Higher holding temperature and O2 flow rate are beneficial to increasing copper removal rate. However,the Cu2O mode is formed by the reaction of surplus O2 and CuCl with O2 flow rate increasing over 0.4 L/min, causing CuCl volatilization rate and copper removal rate to decrease. The resulting copper removal rate of 84.34% is obtained under the optimum conditions of holding temperature of 1573 K, residence time of 10 min, Ca Cl2 addition amount of 0.1(mass ratio of CaCl2 and the copper slag) and oxygen flow rate of 0.4 L/min. The efficient removal of copper from copper slags through chlorination is feasible.

Effect of Vortex Stirring on the Dilution of Copper Slag

In order to solve the problem that the vulcanizing agent utilization rate is low and the dilution effect of copper slag is poor,the vortex stirring dilution method was used to improve the conditions of the dilution kinetics and copper recovery.The water model was used to simulate the effect of copper slag dilution.Under the premise of keeping the Reynolds number consistent,silicone oil and glass beads were used instead of copper slag and vulcanizing agent.Based on the relationship between voltage and concentration,the PC6D dual-channel particle concentration measuring instrument was used to study the stirring speed and the insertion depth of the stirring paddle in model experiments,and the suitable conditions were speed 250 rpm and insertion depth 70 mm.The fire dilution of copper slag was done under the conditions.After stirring and sedimentation,the Fe_(3)O_(4) in slag decreased from 22.58% to 4.65%,and the copper content of the slag decreased from 2.94% to 0.34%.The copper recovery was 88.44%.

Optimization of Roots and Copper Slag to Reinforce Soft Soil Using Response Surface Method

In this paper,roots and copper slag were used to overcome the weakness and reinforce the mechanical property of soft soil.The experiments were designed by the Response Surface Method(RSM),the content optimizing of the root permeated copper slag mixed soil for achieving appropriate values of shear strength and the final results evaluating were also conducted by RSM.Four independent variables including moisture content(12–21%by dry weight of the mixture),slag content(10–20%by dry weight of the mixture),roots content(0–1.1%by dry weight of the mixture),and aspect ratio of roots L/d(5–40)were studied and a generalized response model was built to predict the experimental results.The optimum contents of the four independent variables were suggested as 15.41%(moisture),16.30%(copper slag),and 0.82%(roots)with an aspect ratio of 28.14,respectively.It can be concluded from the verification experiments that the predicted values of the soil mechanical property are almost equal to the experimental values,which validate the response model.Moreover,a typical subgrade model was built for proving the practical advantages of using the above-mentioned mixture as subgrade fill.

Recovery of copper from copper slag using a microbial fuel cell and characterization of its electrogenesis

The microbial fuel cell, which can convert the chemical energy of organic matter into electricity via the catalytic action of microorganisms, is a novel environmentally friendly technology for wastewater treatment and energy generation. The electrical energy generated by the microbial fuel cell can be used as an alternative to a traditional external power source required to extract copper via electrolytic treatment. A dual-chamber microbial fuel cell(DMFC) for the treatment of copper slag sulfuric acid leach liquor was constructed. The electrogenesis performance of the DMFC and its ability to extract copper from the copper slag leachate were investigated. The results demonstrated that the maximum voltage was 540 mV when the DMFC achieved steady-state operation. The removal rate of copper ions was greater than 80.0%, and the maximum value was 92.1%. Moreover, X-ray diffraction and scanning electron microscopy were used to characterize the cathodal products. The results showed that the product deposited onto the cathode was copper and that its morphology was similar to that of the electrolytic copper powder. The DMFC can generate electricity and recover copper from copper slag simultaneously.

Preparation of Fe_(3)Si and FeSi intermetallic compounds from copper slag by electrochemical method

Fe_(3)Si and FeSi intermetallic compounds were prepared by CaCl_(2)-NaCl melt electrolysis at 800℃from the non-magnetic copper slag compound.The phase transition of the cathode particles with different electrolysis voltages and durations was investigated by X-ray fluorescence spectroscopy,inductively coupled plasma spectroscopy,X-ray diffraction,and scanning electron microscopy.The results showed that Fe_(3)Si and FeSi intermetallic compounds can be obtained by one-step electrolysis for 10 h at 3.2 V and two-step electrolysis of 2.5 V for 4 h and 3.2 V for 6 h.However,the current efficiency increased from 31.70%of one-step electrolysis to 39.87%of two-step electrolysis.The formation of Fe_(3)Si and FeSi intermetallic compounds is a gradual evolution process with the increase in Si content,following the formation law of Fe→FeSi→Fe_(3)Si+FeSi→FeSi.The metallic impurities of the final product were 1.29 wt.%Mg and 3.85 wt.%Al,respectively.

Sorptivity and rapid chloride ion penetration of self-compacting concrete using fly ash and copper slag

This paper represents experimental work on the mechanical and durability parameters of self-compacting concrete(SCC)with copper slag(CS)and fly ash(FA).In the first phase of the experiment,certain SCC mixes are prepared with six percentages of FA replacing the cement ranging from 5%to 30%.In the second phase,copper slag replaces fine aggregate at an interval of 20%to 100%by taking the optimum percentage value of FA.The performance of SCC mixes containing FA and copper slag is measured with fresh properties,compressive,split tensile and flexural strengths.SCC durability metrics,such as resistance against chloride and voids in the concrete matrix,is measured with rapid chloride ion penetration test(RCPT)and sorptivity techniques.The microstructure of the SCC is analyzed by using SEM and various phases available in the concrete matrix identified with XRD analysis.It is found that when replacing cement with 20%of FA and replacing fine aggregate with 40%of copper slag in SCC,higher mechanical strengths will be delivered.Resistance of chloride and voids in the concrete matrix reaches the optimum value at 40%;and with the increase of dosage,the quality of SCC will be improved.Therefore,it is recommended that copper slag be used as a sustainable material for replacement of fine aggregate.

A New Technology for Copper Slag Reduction to Get Molten Iron and Copper Matte

The change of iron composition as well as the removal of copper from iron was investigated in the reduction process, and a new way to deal with copper slag was proposed. The iron in copper slag exists mainly in the form of fayalite, and the copper sulfide content accounts for just about 50%. Therefore, the magnetic separation as well as grinding floatation method is not suitable, and a pyrogenic treatment on copper slag is necessary. The carhurization and desulfurization process is restricted to a degree within the carbon composite pellets, and copper matte phase pre- cipitates from copper slag in the reduction process, which is immiscible with molten iron and slag. The copper con- tent decreases to 0.4% as the carbon content in molten iron reaches 3.84%, and the removal ratio of copper from molten iron approaches to 80%. The reduction and sulfurization process can be eompleted in one step, and the copper is separated from iron based on the ternary system of iron-matte-slag.

Characteristics and Mechanism of Reduction and Smelting-separation Process of Copper Slag

The characteristics And mechanism of the reduction and smelting-separation process of the copper slag were studied by investigating the variation ：rule of metallization ratio, yield as well as carbon content of iron nuggets. The formation of molten slag is necessary for slag-iron separation, And iron is in half-molten state during smelting-separa- tion process, the carbon content of which is about 1.25 %. Carburization occurs through direct contact between car- bon and iron in essence, no matter in solid or molten state. The carburization rate is slow below 1 200 ℃ , which is inhibited by the existence of slag. Residual FeO in molten slag tends to form fayalite with SiOz in the copper slag, which is the root cause for the low mehing temperature of copper slag. The addition of CaO improves the reducibility of the copper slag, but Al2 O3 addition has no obvious effect. The melting temperature of slag affects the carburiza- tion extent in solid state, while the content of FeO in molten slag affects that in molten state, both of which co-de termine the carbon content in iron nuggets.

Smelting Oxidation Desulfurization of Copper Slags

According to the mechanism of sulfur removal easily through oxidation, the process of smelting oxidation desulfurization of copper slags is studied, which supplies a new thinking for obtaining the molten iron of lower sulfur content by smelting reduction of copper slags. Special attention is given to the effects of the holding temperature, the holding time and CaF2, CaO addition amounts on the desulfurization rate of copper slags. The results indicate that the rate of copper slags smelting oxidation desulfurization depends on the matte mass transfer rate through the slag phase. After the oxidation treatment, sulfur of copper slags can be removed as SO2 efficiently. Amount of Ca2＋ of copper slags affects the desulfurization rate greatly, and the slag desulfurization rate is reduced by adding a certain amount of CaF2 and CaO. Compared with CaF2, CaO is negative to slags sulfur removal with equal Ca2＋ addition. Under the air flow of 0.3 U/min, the sulfur content of copper slags can be reduced to 0. 004 67% in the condition of the holding time of 3 min and the holding temperature of 1 500 ℃. The sulfur content of molten iron is reduced to 0. 000 8 % in the smelting reduction of treated slags, and the problem of high sulfur content of molten iron obtained by smelting reduction with copper slag has been successively solved.

Recovery of iron from copper slag via modified roasting in CO-CO2 mixed gas and magnetic separation

A novel technology,modified roasting in CO-CO2 mixed gas and magnetic separation,was presented to recover iron from copper slag.The effects of various parameters such as dosage of flux(CaO),gas flowrate of CO and CO2,roasting temperature,roasting time,particle size of modified slag and magnetic flux density on the oxidized modification and magnetic separation were investigated by comparison of the X-ray diffraction patterns and iron recovery ratio.The optimum conditions for recovering iron by oxidizing roasting and magnetic separation are as follows:calcium oxide content of 25 wt.%,mixed gas flow rates of CO2 and CO of 180 and 20 mL/min,oxidizing roasting at 1323 K for 2 h,grinding the modified slag to 38.5-25.0μm and magnetic separation at 170 mT.The mineralogical and microstructural characteristics of modified slag revealed that the iron-bearing minerals in the copper slag were oxidized,the generated magnetite grew into large particles,and the silicate in copper slag was combined with calcium oxide to form calcium silicate.Finally,the iron-bearing concentrate with an iron grade of 54.79%and iron recovery ratio of 80.14%was effectively obtained.

Copper Slag with High MgO as Pozzolanic Material:Soundness,Pozzolanic Activity and Microstructure Development

The results of investigation to assess the possibility of copper slag with high MgO to be used as a mineral admixture in concrete were reported in this study. The soundness of cement paste containing the slag has been examined by autoclave test. Pozzolanic activity of the slag was studied in comparison to fly ash. The slag was mixed calcium hydroxide and water,and the progress of the pozzolanic reaction was determined by X-ray diffraction,differential thermal analysis-thermogravimetry and scanning electron microscopy from 28 to 90 d. The experimental results showed that the autoclave expansion value of cement paste containing the slag was far below the expansion limit (0.8%). It can be conclude that the slag has little periclase content. The consumption of calcium hydroxide showed the slag exhibits high pozzolanic activity,which was higher than that of fly ash. Hence,use of the copper slag with high MgO but low periclase content as a mineral admixture in concrete seems feasible.