New Technique And Equipment On Arsenic Control In Cleaner Production Of Complex High Arsenic Gold-copper Concentrate Smelting

The development and utilization of global gold and copper resources accelerated with the increasing demand for gold and copper,resulting in the decreasing of high-quality gold and copper concentrates.Complex gold and copper concentrate resources all over the world attract more and more researchers.Among them,gold and copper concentrates containing arsenic are one of the important sources of gold and copper resources in many countries.Arsenic-containing gold and copper concentrates is treated with Pyro-metallurgical technology including oxygen-enriched bottom-blown smelting and oxygen-enriched side-blown smelting.The quality of smelted products is affected by arsenic which causes some problems in dust collection,acid production,during the smelting process.Therefore,it is of great significance to study the technology and equipment for arsenic control in clean smelting of arsenic-bearing gold copper concentrate.A new process of arsenic control at source and control is proposed—dry arsenic collection and control—wet arsenic collection and control—safety arsenic control in the end product,and studied and optimized the corresponding equipment based on the study of the mineralogy characteristics of arsenic source,existent state and flow distribution in the process of oxygen-rich side-blown smelting.The following results is gotten and a series of innovative research results are carried out:The occurrence and flow behavior of arsenic in the process of oxygen-enriched side-blown smelting of arsenic-bearing gold-copper concentrate are analyzed.The results show that as content of two arsenic-containing gold-copper concentrates are 0.89%and 1.72%respectively,arsenic is mainly in arsenopyrite（Fe As S）,realgar（As₄S₄）,enargite（Cu₃As S₄）,arsenate,scorodite（Fe As O₄·2H₂O）,tennantite(Cu₁₂As₄S₁₃),mimetite（Pb₅（As O₄）₃Cl）.The As content in copper matte is0.17%,and As is mainly present in the form of arsenic-lead-antimony alloy.The As content of slag is 0.34%.As consist the glass phase and slag in the form of arsenate or arsenic-containing copper matte phase in the form of alloys and sulfides.The As content of boiler ash is 1.35%,the As content in the electric dust is 3.87%,the As content in the environmental protection dust is 22.96%,and As smoke and dust is mainly in the form of arsenate and arsenic oxide.The main source of arsenic in oxygen-enriched side-blown smelting process is mixed arsenic-containing gold and copper concentrates,accounting for about 96%.The other about 4%of arsenic come from returned slag concentrates and cold feed.about 81%arsenic is mainly concentrated in smoke and dust,the distribution coefficient of arsenic in copper matte is about 3%,and the remaining about 16%of arsenic is distributed in the slag during the smelting process.The oxygen-enriched concentration is reduced from 82%to 80%,the copper grade of matte is controlled at 45%～50%,and the residual oxygen in the flue gas is controlled less than 4%.After continuous counting the production data of oxygen-enriched side-blown smelting system for one month,it is found the distribution rate of arsenic in smoke and dust increased from 81%to85.07%.By setting up a side-blown water model experimental platform and carrying out experimental research,the sloshing liquid level of molten pool in the side-blown furnace would increase about 15%～45%compared to the static liquid level by the treatment of side-blown air jets.The stirring state of molten pool in the side-blown furnace is mainly divided into turbulent agitation and macro-unstable agitation.The macro-unstable state is divided into three different types which called“left and right shaking type”,“center tearing type”and“forward and backward shaking type”according to the type of shaking.The“swaying type”only existed in the initial stage of blowing.The occurrence of macroscopic instability and the type of macroscopic instability are related to the height of liquid level on the arrangement and number of spray guns,technical optimization of side-blown furnace protection measures and side-blown furnace roof.Grilled slag mouth,air-driven sample feeding device and air supply time is carried out according to the study of hydraulic model of macroscopic instability phenomenon,combined with the actual production situation.Important support basis is provided for preventing furnace leakage and smoke leakage,reducing production costs,increasing the rate of start-up.The effect of oxygen utilization on arsenic collection in flue gas of side-blown furnace is studied,and the inlet device of side-blown furnace is optimized.The results show that SO₃in flue gas of side-blown furnace mainly came from the conversion of SO₂,and the conversion rate is most affected by temperature.400-600℃is the optimal temperature for the conversion of SO₂into SO₃,followed by the catalytic effect of oxides such as ferric oxide.The key technology affecting dry arsenic collection is the control of residual oxygen in flue gas and absorbent of quench tower.Optimal process parameters were found by the studying on the optimization research of secondary air and flue gas pressure.The secondary air volume of oxygen-enriched side-blown furnace smelting system is controlled at 500～1500 Nm³/h,the flue gas pressure is controlled at-50～50 Pa.The optimal dosage of absorbent for quench tower is 6.75 t/h according to the theoretical calculation and production practice.The utilization rate of oxygen of oxygen-rich air in the oxygen-rich molten pool is improved significantly and the residual oxygen is controlled stably less than 3%,and arsenic in the smelting flue gas is efficiently recovered by optimizing and reforming the inlet device of side-blown melting pool melting furnace.Side-blown smelting electric dust（As grade 4.65%）is used as raw material,and acid leaching-oxidation leaching process is studied.The optimal leaching parameters are H₂O₂/As 2.8,reaction time 2.4 h,reaction temperature 67℃,acidity 17%,arsenic removal rate 86.81%,arsenic content 0.79%.The optimal conditions for arsenic sulfide precipitation of leaching solution are Na HS/As 1.3:1,reaction time 30min,stirring speed 110 r/min,arsenic precipitation rate 99.99%,arsenic content 0.89 mg/L.The optimal conditions for iron removal and zinc precipitation are p H 4.0,reaction time 2.0 h,reaction temperature 60℃,iron removal rate 99.64%,zinc loss rate 2.58%.Sodium carbonate is selected as the zinc precipitation agent,the p H of solution is adjusted to7.5,the reaction time is 2.0 h,the reaction temperature is 60℃,and the zinc precipitation rate reaches 99.72%.The main components of arsenic removal slag from electric dust are Pb SO₄,Pb S and Zn S,and the main components of arsenic sulfide slag is As₂S_3.The purity of basic zinc carbonate is 55.92%.The experimental equipment is designed,which mainly composes of a material heating furnace,a material holding furnace,a water-cooling collection device and a vacuum system.The crude arsenic trioxide（As₂O₃content 89.74%）collected by the side-blown smelting flue gas dry method is used as the raw material,and the oxidation roasting process is adopted.The single factor experiment results show the best process parameters,crude arsenic trioxide 15g,the roasting temperature is 338℃,the roasting time is 80 min,the amount of lime is 1.35 g,the vacuum degree is-0.08 MPa,the arsenic recovery rate is 95.84%,and the arsenic trioxide grade is 99.59%,which meets the requirements of As₂O₃-1 in the national standard GB 26721-2011.