Predominance diagrams for Zn(Ⅱ)-NH_3-Cl^--H_2O system

The thermodynamics in zinc hydrometallurgical process was studied using a chemical equilibrium modeling code（GEMS） to predict the zinc solubility and construct the species distribution and predominance diagrams for the Zn（Ⅱ）-NH3-H2O and Zn（Ⅱ）-NH3-Cl--H2O system.The zinc solubilities in ammoniacal solutions were also measured with equilibrium experiments,which agree well with the predicted values.The distribution and predominance diagrams show that ammine and hydroxyl ammine complexes are the main aqueous Zn species,Zn（NH3）24-is predominant in weak alkaline solution for both Zn（Ⅱ）-NH3-H2O and Zn（Ⅱ）-NH3-Cl--H2O systems.In Zn（Ⅱ）-NH3-Cl--H2O system,the ternary complexes containing ammonia and chloride increase the zinc solubility in neutral solution.There are three zinc compounds,Zn（OH）2,Zn（OH）1.6Cl0.4 and Zn（NH3）2Cl2,on which the zinc solubility depends,according to the total ammonia,chloride and zinc concentration.These thermodynamic diagrams show the effects of ammonia,chloride and zinc concentration on the zinc solubility,which can provide thermodynamic references for the zinc hydrometallurgy.

DRAWING PREDOMINANCE DIAGRAM OF M_1—M_2—x—y SYSTEM AND ITS APPLICATION

Discussions were made of the principle,method and computer program for drawing the pre- dominance diagrams of the bi-metal co-existed system M_1-M_2-x-y in which the multi-me- tallic compounds may be produced by interaction between compounds of both metals.The formation of zinc ferrite and its stable region have been analyzed through drawing Zn-Fe-S-O system predominance diagrams.The availability of the diagram is given the di- rection to roast the zinc sulfide ore as well.

Plotting and application of predominance area diagram of In-S-O system based on topological rules

The mathematical topological rule was proposed to plot the predominance area diagram.Based on the phase rules,the components of In-S-O system were analyzed and the coexisting points of three condensed phases were determined.Combined with the topological rules and thermody namic calculation,four relation diagrams between the coexisting points of three condensed phases,which were denoted as α,β stable plane-topological diagram and unstable plane-topological diagram,were plotted for the In-S-O system.The results show that α stable plane topological diagram is in accordance with the predominance area diagram of In-S-O system plotted by traditional methods,which indicates that the new method is feasible to plot the predominance area diagram of In-S-O system.Meanwhile,β unstable plane-topological diagram can be used to elucidate the indium production with the bath smelting process.

Plotting and application of predominance area diagram of Me-S-O system based on topological rules

The mathematical topological rule was applied to plot the predominance area diagram.Based on the analysis of the mutually conjugated,only two diagrams were the best topological embryonic graphs to build the predominance area diagram of Me-S-O system.Combined with topological rules and thermodynamic calculation,four relation-diagrams were denoted asαandβstable and unstable plane-topological diagrams,which were plotted for the Pb-S-O system and Zn-S-O system.The results show thatβstable plane-topological diagram of Pb-S-O system andαstable one of Zn-S-O system are in accordance with the traditional predominance area diagram,which indicates that it is feasible to plot the predominance area diagram based on mathematical topological rules.Meanwhile,αunstable plane-topological diagram of Pb-S-O system can elucidate the phenomenon that metallic lead exists in higher oxygen and sulfur pressure area in modern bath smelting furnace.The mathematical topological rules broaden the application scope of the predominance area diagram and enrich the practice of its plotting.

Feasibility of flue-gas desulfurization by manganese oxides

For the purpose of effective and economic desulfurization of flue-gas, the predominance area diagram of the Mn-S-O system at different temperatures was constructed based on the thermodynamic data obtained from the literatures. It is seen from this figure that flue-gas desulfurization by manganese oxides is feasible from the thermodynamic point of view. Additionally, the most appropriate temperature range for flue-gas desulfurization is between 600 and 800 K, and the reaction is strongly exothermic to maintain the heat balance. The natural manganese ores encompass large tunnels that exhibit large surface areas and highly chemical activity, which can provide a high enough SO2 removing efficiency. From the superposition of the diagrams of Mn-S-O and Fe-S-O systems, it is found that there is a coexistent stability region of MnSO4 and Fe2O3, which provides the possibility of desulfurization by selective sulfation without ferric sulfate forming. A multi-stage desulfurization system has been discussed briefly.