| The alumina production process has developed rapidly in recent years.However,due to low mining efficiency and low efficiency of alumina extraction,the amount of alumina resources in China has been greatly reduced.So far,China’s recoverable reserves are 830 million tons.It accounts for 3%of the total global reserves.At the same time,due to the imperfect manufacturing technology of alumina in China,the high sodium and alkalinity of red mud has caused a series of economic problems and environmental pollution problems.In order to follow the national bauxite resource development plan and solve a series of derivative problems brought about by the production of alumina process,Northeastern University Special Metallurgy and Process Engineering proposed a new process of calcification carbonization with back feeding CaO technology to produce alumina.The thermodynamics of the carbonation transformation process was analyzed,and the effects of various reaction conditions on the dissolution rate of alumina and the sodium-alkali content in red mud were studied by calcification and carbonization transformation process,and the industrial scale simulation was carried out under laboratory reaction conditions.The new process of adding calcium calcification process carries out material balance and energy balance.The specific findings are as follows:(1)The results of thermodynamic analysis show that the standard Gibbs free energy change value of the calcification reaction process of the gibbsite is negative in the temperature range of 323～573 K,indicating that the reaction can occur in this temperature range,and as the temperature rises,the standard Gibbs free energy variable decreases.For the carbonization reaction process,the standard Gibbs free energy variable value is negative in the temperature range of 323～573 K,indicating that the reaction can occur in this temperature range,but unlike the calcification process,with the increase of temperature The standard Gibbs free energy variable value increases,the value is the smallest of 323 K,and the maximum value of 573 K.(2)The calcification transformation experiment of gibbsite shows that the optimal conditions are calcification temperature 200℃,calcium-to-silicon ratio 3.5:1,reaction time 120min;with industrial production considerations,the optimal calcification conditions are calcification temperature of 180℃,calcium to silicon ratio of 3.0:1,and reaction time of 60 min.The final dissolution rate of the alumina in the reaction is 70.10%,and the sodium content of the carbonized residue is 0.96%using the calcified slag with carbonation treatment under the conditions of carbonation temperature 100℃ for 90min holding time.(3)The calcification-carbonization method with back feeding CaO process can reduce the solid content of the dissolution reactor,thereby reducing the problem of poor fluidity of the crucible slurry formed by the dissolution of the alkali solution.The material balance and energy balance were calculated according to the industrial scale simulation using the Indonesian gibbsite as raw material.Producing 1 ton alumina needs to be equipped with 3594.36 kg bauxite,18514.08 kg sodium aluminate solution,and the amount of quicklime is 1041.35 kg with back feeding CaO process;according to each part of the heat of reaction,bauxite and lye warming required the heat of 281.71 MJ,the heat required for the mixing reaction is 194.01 MJ,the heat required for the calcium oxide heating during the calcification transformation is 113.19 MJ,and the heat released during the calcification process is 98.60 MJ.From this,the total heat added to the process is 490.31 MJ. |
