Fundamental And Technological Study On Phase Transformation And Selective Extraction Of Valuable Components From Laterite Nickel Ore

As the beginning of the new energy industry chain,the extraction of laterite nickel ore resources determines its development lifeline and plays a key role in the process of low-carbon economic transformation.Aiming at the problems of poor adaptability of raw materials,serious acid corrosion of autoclave and low utilization rate of free acid in traditional high pressure acid leaching process.The main research object of this thesis is limonites or saprolites produced in Indonesia.Concentrated sulfuric acid,ammonium sulfate,ammonium hydrogen sulfate and ammonium chloride were used as mineral transformation agents.The low temperature roasting mineral phase transformation-high pressure water leaching selective extraction of valuable components process was developed to achieve efficient and selective extraction of valuable metals under mild conditions.The main research results and conclusions of this thesis are as follows:（1）Process mineralogy research was carried out to clarify the physical and chemical properties,and element occurrence state of laterite nickel ore,which provided a theoretical basis for the subsequent nickel extraction process.The limonite is mainly composed of Fe O（OH）,Fe₃O₄ and Fe₂O₃,and nickel mainly exists in Fe O（OH）phase in the form of Ni OOH and Ni（OH）₂.The saprolite is mainly composed of Mg₃Si₂O₅（OH）₄,Fe O（OH）,Fe₃O₄ and Fe₂O₃,and nickel mainly exists in Mg₃Si₂O₅（OH）₄ phase in the form of Ni（OH）₂.To achieve efficient extraction of nickel,it is necessary to accurately transform the main nickel-bearing mineral phase into the corresponding soluble salt/double salt in the low-temperature roasting process.（2）The thermodynamic simulation of the phase transformation processof laterite nickel ore was carried out to clarify its reaction process and pathway.To verify the accuracy of the theoretical calculation,the experimental study of mineral phase transformation of laterite nickel ore was carried out.The actual reaction of ammonium sulfate,ammonium hydrogen sulfate and ammonium chloride with the main mineral phases in the ore are different from the theoretical calculation.The products are soluble metal double salts（（NH₄）₃Fe（SO₄）₃ and（NH₄）₂Mg₂（SO₄）₃）.The comparative analysis of the mechanism of mineral phase transformation was carried out to clarify the common mechanism of the reaction between the main mineral phases and the four transformation agents.The Fe O（OH）phase in limonite and saprolite is easily transformed by four mineral transformation agents,and the effect is good.The reaction trend of Fe₃O₄ phase in saprolite and ammonium hydrogen sulfate is small,and the effect of mineral phase transformation is poor.The Fe₂O₃ phase in limonite is difficult to be transformed,while ammonium sulfate and ammonium hydrogen sulfate promote the mineral phase transformation of Fe₂O₃ phase in saprolite.The reaction trend of Mg₃Si₂O₅（OH）₄ phase in saprolite with ammonium sulfate and ammonium hydrogen sulfate is moderate,which is easy to react with concentrated sulfuric acid,but not easy to react with ammonium chloride.（3）The non-isothermal kinetics of the mineral phase transformation process of laterite were studied,and the process limiting reaction and strengthening methods were clarified to provide theoretical guidance for strengthening the mineral phase transformation process.The limiting reaction and strengthening means of the mineral phase transformation process with concentrated sulfuric acid were clarified.The activation energy of the reaction between Fe₂O₃ phase in limonite and concentrated sulfuric acid is higher,and the activation energy is 192.48k J/mol.The activation energy of the reaction of Mg₃Si₂O₅（OH）₄ and iron oxides（Fe O（OH）,Fe₃O₄ and Fe₂O₃）in saprolite with concentrated sulfuric acid are 126.49 k J/mol and 134.37 k J/mol,respectively,which can increase the amount of concentrated sulfuric acid to accelerate the reaction rate.The limiting reaction and strengthening methods of mineral phase transformation process with ammonium sulfate were clarified.The activation energy of the reaction of Fe（OH）and Fe₃O₄ in limonite with ammonium sulfate and the reaction of Fe₂O₃ in limonite with ammonium sulfate are 106.88 k J/mol and 117.90 k J/mol,respectively.The reaction rate can be accelerated by increasing the roasting temperature.The activation energy of the reaction between Mg₃Si₂O₅（OH）₄ phase in saprolite and ammonium sulfate is higher,and the activation energy is139.54 k J/mol.The reaction is a limiting reaction,and the reaction rate can be accelerated by increasing the roasting temperature.The limiting reaction and strengthening methods of mineral phase transformation process with ammonium hydrogen sulfate were clarified.The activation energy of the reaction of Fe O（OH）and Fe₃O₄ in limonite with ammonium hydrogen sulfate and the reaction of Fe₂O₃ in limonite with ammonium hydrogen sulfate are 73.74 k J/mol and 82.21 k J/mol,respectively.The activation energy of the reaction of Mg₃Si₂O₅（OH）₄phase in saprolite with ammonium hydrogen sulfate and the reaction of Fe O（OH）and Fe₂O₃ in saprolite with ammonium hydrogen sulfate are94.22 k J/mol and 90.75 k J/mol,respectively,which are higher than that of the reaction of Fe₃O₄ with ammonium hydrogen sulfate.The limiting reaction and strengthening means of mineral phase transformation process with ammonium chloride were clarified.The activation energy of the reaction between the main mineral phase in limonite and ammonium chloride:E（Fe₃O₄:57.2 k J/mol）>E（Fe O（OH）:43.03 k J/mol）.The activation energy of the reaction between the main mineral phase in saprolite and ammonium chloride:E（Mg₃Si₂O₅（OH）₄:85.07 k J/mol）>E（Fe O（OH）:32.19 k J/mol）.Although the reaction rate of ammonium chloride with the main mineral phase is fast,its thermodynamics determines the degree of reaction is limited.（4）The process of low temperature roasting mineral phase transformation-high pressure water leaching selective extraction of valuable components was studied.The effects of various process parameters on the efficient extraction of valuable metals and the directional removal of impurity metals were investigated.The most suitable process conditions under the four transformation agent systems were clarified,which provided technical support for the accurate transformation of laterite and selective extraction of valuable components.Under the suitable process conditions of low-temperature roasting with concentrated sulfuric acid and high-pressure water leaching,the leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in limonite are99.45%,91.00%,94.20%,98.72%,3.77%,79.72%,34.65%,and 6.32%,respectively.The leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in saprolite are 80.02%,68.16%,77.13%,61.15%,1.42%,55.57%,13.16%,and 2.47%,respectively.The process significantly reduces the conditions of traditional high-pressure acid leaching process,and solves the problem of serious acid corrosion in autoclave.Under the suitable process conditions of low-temperature roasting with ammonium sulfate and high-pressure water leaching,the leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in limonite are 99.47%,86.53%,98.70%,85.90%,3.31%,84.76%,1.46%,and 2.39%,respectively.The leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in saprolite are 71.40%,88.36%,99.98%,80.72%,0.28%,62.52%,3.39%,and 0.70%,respectively.Ammonium salt transformation agents can be recycled and can solve the problem of poor operating environment in the mixing process of concentrated sulfuric acid.Under the suitable process conditions of low-temperature roasting with ammonium hydrogen sulfate and high-pressure water leaching,the leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in limonite are99.79%,89.19%,97.92%,43.48%,2.33%,91.45%,1.46%,and 1.39%,respectively.The leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in saprolite are 97.02%,85.01%,99.99%,99.65%,1.36%,63.43%,4.51%,and 1.16%,respectively.The process has strong applicability of raw materials,good extraction effect,and broad prospects for promotion and application.Under the suitable process conditions of low-temperature roasting with ammonium chloride and high-pressure water leaching,the leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in limonite are 81.06%,82.55%,81.92%,69.81%,0.74%,16.46%,30.78%,and 2.43%,respectively.The leaching efficiencies of Ni,Co,Mn,Sc,Fe,Mg,Al,and Cr in saprolite are 67.56%,90.60%,99.99%,0.64%,0.02%,18.74%,0.47%,and 0.04%,respectively.The hydrolysis residue produced by the process has low sulfur content,which can achieve maximum resource utilization of the waste residue.