Lyu Guozhi

Multi-Steps Carbonation Treatment of Calcified Slag of Red Mud

Aluminum industry is one of the most important industries in China’s nonferrous metallurgy industry. With the development of China’s alumina output, red mud emission get 50 million ton at 2011. Under this condition, “Calcification-Carbonation Method” was put forward to deal with red mud by Northeastern University, the main purpose of this method is to change the balance phase of red mud into 2CaO·SiO2 and CaCO3 with hydrometallurgical process. This paper mainly research on the effect of carbonation conditions and steps on alumina extraction and dealkalize efficiency. The results indicate that: through multi-steps carbonation treatment of calcified slag by the new method, A/S of the new structure red mud lowed below to 0.24 and the Na2O content lowed below to 0.26% at carbonation temperature 120°C, CO2 pressure of 1.2MPa with 5-steps carbonation treatment. The new structure red mud could be used in cement industry directly.

Characterization of Activated Alumina Production via Spray Pyrolysis

A novel method was developed to prepare activated alumina via spray pyrolysis of aluminum chloride solution. In this paper, activated alumina was obtained by spray pyrolysis in tube furnace with aluminum chloride solution as raw materials in different temperatures. X-ray diffraction (XRD), scanning electron microscope(SEM) and the specific surface area analysis were used to characterize the spray pyrolysis products, respectively. XRD results showed that the crystal phase composition of activated alumina can be controlled through adjusting pyrolysis temperature. The crystal structure of γ-Al2O3 in the products conformed to the requirements of the index of activated alumina. Most of pyrolysis products were porous structure which the particle size was around 5 μm under scanning electron microscope. With the activated alumina were examined by specific surface area analysis, the products existed as inkbottle-shaped and parallel-plate pores. Pyrolysis products more conformed to the requirements of activated alumina after examined by XRD, SEM, and the specific surface area.

A Novel Self-Stirring Tubular Reactor Used in Bauxite Digestion Process

A novel self-stirring tubular reactor driven by pressure energy used in bauxite digestion process is presented originally in this paper. This reactor combines the advantages of autoclaves and conventional tubular digestion equipment, it can restrain scale at high temperature and high pressure and intensify mass and heat transfer. Stirring of the novel reactor only needs the pressure energy of the liquid. Performance of self-stirring reactor driven by pressure energy was studied in this paper. High-speed photography was adopted in the paper to research the effects of various factors on rotating speed in the self-stirring reactor driven by pressure energy. The results demonstrated that fluid pressure has the most outstanding effects on stirring speed of the novel reactor, and the effects of fluid density and viscosity on stirring speed are minor.

Research on Mechanically Activated Digestion Performance of Diasporic Bauxite and Kinetics

This paper proposes a “mechanical activation-homogeneous digestion” technology as a strengthening method for diasporic bauxite digestion process of alumina production. Effects of digestion temperature, digestion time and mechanical activation speed on digestion performance of diasporic bauxite were investigated by using “homogeneous digestion” equipment, and the digestion kinetics of diasporic bauxite was studied as well. The results indicate that the mechanical activation can greatly improve the digestion performance of diasporic bauxite, digest mine with larger particle size. The optimal mechanically activated digestion temperature is 20°C lower than that of direct digestion. The relative digestion rate of alumina goes up to above 97% when digested at 245°C for 60 minutes with a mechanical activation speed of 80rpm.The apparent activation energy of mechanically activated digestion is 57.30kJ/mol, 21.09kJ/mol lower than the direct digestion. The kinetic equation of mechanically activated digestion is (1−η)−1/3−1=1.5532x10−4exp(4.764x105/T)t.

Effect of Combined Forms of Al and Si on the Acid Leaching Performance of Fly Ash

Research on the leaching performance of fly ash of Shanxi, Chongqing and Western Inner Mongolia. Analyze the existing forms, crystallinity and package situation of Al-Si phase in fly ash from different areas by using SEM and XRD. Effect of fractionation of Al-Si phase in fly ash on the leaching performance from the view of mechanism was investigated as well. Leaching experiments and analysis indicate that: the leaching rates of Al203 in fly ash from the there different areas are 97.41%, 68.94% and 23.61% respectively, under the conditions of solid-liquid ratio 1:20, rotary speed 500rpm, leaching time 120min, sulfate concentration 20%, particle sizes −74µm. Leaching performance of fly ash in Western Inner Mongolia is better than that in other two areas. The main reason for different leaching performance of fly ash from different areas is the difference in crystallinity, encapsulated glass phase of Al-Si phase in fly ash. The crystallinity for Western Inner Mongolia is 75.98%, while there is no non-crystalline phase in fly ash from other tow areas, The average FWHM of XRD diffraction peak of Al-Si phase are 0.641, 0.3324 and 0.1107, respectively. The crystallinity of fly ash in Western Inner Mongolia is worst among the there areas, and its content of glass phase is also lowest among them, so its activity is obviously higher than that of other two areas.