Thermodynamic Modeling And Process Optimization On Oxygen-enriched Bottom Blowing Continuous Copper Smelting Process

With the increasing complexity of copper resources,and the enhancement of the people consciousness of environment protection,conventional copper smelting processes are being eliminated due to poor raw material adaptation and environment pollution.Some large scale and continuous new copper smelting processes have been developed.Oxygen-enriched bottom blowing continuous copper smelting（OBCS）process is one of them.Because of its strong adaptability of raw materials and low comprehensive energy consumption,several industrial production lines have been built in China.Because of the lack of systematic theoretical research on OBCS process,the production practice lacks guidance,which limits the popularization and application of the process.In this paper,the thermodynamic modeling and process optimization of OBCS process were carried out by combining theoretical research,computer simulation and production practice.The basic theoretical system of OBCS process was established,the optimization measures were introduced,the directional separation and enrichment of accessory elements were realized.The research results provide guidance for efficient and clean treatment of copper complex resources and comprehensive recovery of polymetallic resources.The main conclusions are as follows:（1）The thermodynamic model of the OBCS process was optimized and an efficient solution algorithm was developed.1)The model can be used to study the distribution of multi-element（Cu,Fe,S,O,Si,Au,Ag,Pb,Zn,As,Sb,Bi）between multiple phases（matte,metal,Cu₂O,slag,and gas）under complex conditions（matte grade,oxygen potential,sulfur potential,temperature,Fe/Si O₂ ratio）.2)For the above complex model,the multi-thread particle swarm optimization algorithm（MTPSO）was developed,and the algorithm speed and position perturbation mechanisms were established to improve the global search capability and local exploration capability of the algorithm.3)The thermodynamic simulation of OBCS process was carried out under actual production conditions.Compared with the single-threaded particle swarm optimization algorithm（STPSO）,the time required for a single calculation of the MTPSO was shortened by 60%.The calculated results were in good agreement with the industrial production data,proving the reliability of the model and algorithm.（2）The regulation mechanism of the large-scale oxygen-enriched bottom-blowing copper smelting（OBBS）process was established.1)Compared with the small OBBS process,the oxygen-rich concentration and oxygen/ores ratio are higher in the large-scale OBBS process,so the smelting temperature and oxygen partial pressure are higher(T=1542K,P_O2=10^-2.42Pa).At the same time,the dissolution and mechanical inclusion loss of copper in the slag are increasing,and the copper content in the slag is 3.37wt.%in the large-scale OBBS process.2)Under stable operation conditions,Au 93.74%and Ag 93.29%enter the copper matte,As 66.15%and Bi 66.59%volatilize into the gas phase,Pb 53.03%enters the copper matte,Zn 68.03%is oxidized into slag,Sb 35.95%enters the slag and37.28%enters the gas.3)The P_S2 in the system increases with increasing the content of Fe and S in the concentrate,which is beneficial to the enrichment of Au and Ag into the copper matte and the volatilization of As and Bi into the gas phase.Increasing the content of Cu in concentrate,oxygen/ores ratio,and oxygen-enriched concentration result in higher P_O2and the smelting temperature,which are beneficial to the removal of Pb and Zn into slag.4)By optimizing the process parameters,the enrichment rates of Au and Ag in copper matte are increased to 95.66%and 95.26%,the removal rates of Pb and Zn slagging are 52.63%and 75.51%,and the removal rates of As and Bi volatilization are 85.02%and 87.79%.（3）The mechanism of the oxygen-enriched bottom-blowing continuous converting（OBCC）process was revealed.1)High-grade copper matte is directly converted to anode copper in one OBCC furnace,in which the Cu goes through the evolution process of copper matte→blister copper（high sulfur/oxygen blister copper）→Cu₂O→anode copper.The OBCC process is divided into the oxidation period and the reduction period.2)In the early stage of the oxidation period,high-sulfur blister copper（S 1.00wt.%）saturated with Cu₂S coexists with copper sulfonium.With the decrease of copper matte,the oxygen partial pressure and sulfur partial pressure of the system remains unchanged(P_O2=10^-1.90Pa,P_S2=10^-0.90Pa).In the middle stage of the oxidation period,copper matte disappears,and Cu₂S dissolved is oxidized to Cu₂O and the high-oxygen blister copper is formed.At this time,the P_O2 increases rapidly,and the P_S2decreases sharply,accompanied by a large loss of Cu in the slag.In the later stage of the oxidation period,the Cu₂O is saturated in high oxygen blister copper（O 1.14wt.%）,and a single phase of Cu₂O begins to precipitate.The P_O2 in the system is maintained at about 9Pa,and the P_S2decreases slowly with the decrease of P_SO2.（4）The optimization measures for the OBCC process were formed.1)The product in the oxidation period of the OBCC process is high oxygen blister copper（O 0.50wt.%,S 0.07wt.%）.The converting temperature（T=1523K）,oxygen partial pressure(P_O2=10^-0.50Pa),and Cu content in slag（Cu 32.29wt.%）are higher than conventional copper matte converting process.2)Under stable operation conditions,the enrichment rates of Au and Ag in the copper phase are 96.48%and 95.90%,the removal rates of Pb and Zn into slag are 68.28%、85.97%,and the slagging removal rate of Sb,and Bi into slag is less than 4%.3)Increasing the content of S in copper matte and converting temperature can reduce the mechanical entrainment loss of blister copper in the slag,which are beneficial to improving the direct yield of precious metals.Improving the copper matte grade,oxygen/ores ratio and oxygen-enriched concentration results in the higher P_O2 in the system,which are conducive to the oxidation slagging of impurity elements.4)By optimizing the process parameters,the enrichment rates of Au and Ag in the copper phase are increased to 98.86%and 98.71%,the removal rates of Pb and Zn into slag are increased to 78.74%and 92.73%,and the removal rates of Sb and Bi into slag are increased to38.10%,29.31%.（5）The key factors affecting the removal of impurities in the OBCS process were investigated.1)The removal reaction thermodynamics of typical impurity in the copper smelting process was studied.From the aspects of furnace structure and process parameter,the OBBS process was compared with the flash smelting,the top blowing smelting,the side blowing smelting process,and the OBCC process was compared with the PS converting process.2)Compared with the OBBS process,the P_O2 in the flash smelting reaction shaft is higher.Therefore,Sb is difficult to volatilize.After falling into the settler,Sb is reduced into copper matte.The gas is blown into the slag layer in the side-blowing process and in the top-blowing process,Sb is reduced and volatilized into the gas phase with the addition of the reducing agent.Without the addition of fuel in the OBBS process,it is not conducive to the volatilization of Sb.Reducing the smelting temperature and oxygen partial pressure and increasing the amount of slag can promote the removal of Sb into slag in the OBBS process.3)Compared with the PS converting process,the migration path of impurity is long,and impurity is easy to react with the Cu in the metal phase,resulting in a low removal rate of As,Sb and Bi impurities in the OBCC process.In addition,the P_O2 is higher in the OBCC process,and the amount of gas is less.So,the volatilization of impurity elements is less.The impurities can only be removed by oxidation slagging in the OBCC process.In this paper,the thermodynamic modeling of the large-scale OBBS process and the OBCC process was carried out.The directional separation and enrichment of accompanying elements were realized.The research results provide a theoretical basis and technical support for the clean and efficient treatment of complex copper resources and the recovery of valuable metals in the OBCS process.