Basic Research Of Equipment Design For Carborn Process Of Calcified Residue

With the rapid development of alumina industry in China,the superior bauxite with high alumina-silica ratio exhausted gradually.The contradiction between low-grade bauxite and the production technology was one of the main bottlenecks which restrict the alumina industry in China.Alkali consumption and alumina loss will increased when low-grade bauxite was used to produced alumina,at the same time,a large number of red mud with high alkali will be generated and lead to serious environmental pollution.Aimed at this situation,a novel "calcification-carbonation" process was proposed by our team.In this study,the carbonation process of calcified residue was investigated in the new process,that is gas-liquid-solid reaction of hydrogarnet in the calcified residue reacted with C02 under high-temperature and high-pressure conditions.Firstly,status of bubbles micro refinement was researched at different temperature,pressure,stirring speed and ventilation mode in a 1 L scale transparent autoclave.Secondly,effect of the factors on the carbonation reaction of calcified residue was verified in a 2 L scale autoclave under high-temperature and high-pressure conditions.Carbon content of carbonated residue and alumina-silica mass ratio of final residue as criterions to judge the degree of reaction,and the optimal experiment conditions were obtained.Thirdly,a water model equipment of venturi jet reactor was designed to realize efficient mixing of gas-liquid-solid phases,and fluid flow state in the reactor was studied by PIV technology and Fluent numerical simulation.Finally,effect of liquid and gas velocity,high-diameter ratio and position of the reactor on bubbles micro refinement was investigated by two different size of venture tubes and the water model equipment.Meanwhile,high-temperature and high-pressure venturi jet reactor was designed for "calcification-carbonation" process in industry,conclusions were obtained by experiment study and numerical simulation:The images of transparent kettle captured by high-speed camera,the static picture after application Image-Pro-Plus 6.0 software and Origin software for processing,from the histogram,chart of differential distribution and chart of volume-surface area-mean diameter of bubble,airtight ventilation way under the best experiental condition which are 0.8 Mpa,120?,and 700 r/min.Cyclic aeration mode under the optimal experimental conditions of ventilation,pressure and rotate speed are 1000 L/h,0.8 Mpa and 400 r/min respectively.Compared with bubble number and average diameter which researched by two ventilation modes,the air cycle ventilation was better than airtight ventilation.The effect of bubble refinement and air-liquid mixing was better which avail the increase of heat transfer and mass transfer between gas and liquid and chemical reaction rate.By the 2 L high temperature and high pressure reaction kettle calcified residue slag process experiment indicated:Give priority to with hydrated garnet calcification of slag and carbon dioxide Under the high temperature and high pressure reaction in the process of production of carbide slag,recycled ventilation saved the reaction time under the condition of 100 ? and 1.0 MPa but airtight ventilation can not,the reaction time reduced by 23%.And through the analysis of soluble experiment and detection,the best experiment conditions for calcified residue slag is 120 ? and 1.2 MPa.The leaching rate of soluble experiment is 41%.This paper used PIV technology and Fluent software to study internal fluid flow state in jet reactor.Due to the special reactor structure,the fluid fully mixed by axial and radial.That phenomenon produced by coanda phenomenon.And through the theoretical research and experimental observation analyzed the rule of fluid force.Finally confirmed the use of venturi tube in favour of efficient mixed for three phase of gas-liquid-solid.Through the design of two different size of the venturi tube,after calculation contrast found that when d 1=3 8mm,de=25mm the venturi tube could formed negative pressure,comply with the design requirements;Cold water model experiment can concluded the increase of gas velocity,liquid velocity and high-diameter ratio all good for ultra-micronization bubble.Tthe best fluid speed was 1.548 m/s,gas velocity was 14.15 m/s,high-diameter ratio was 1,the each key point pressure of the design of high temperature and high pressure jet reaction device were P1=1.27MPa,P2=1.2MP,P3=1.2MPa,P4=0.4MPa,P5=0.4MPa,P6=0.4MPa,P7=0.41MPa,Pg8=0.428MPa,P9=1.328MPa,P10=0.428MPa.