Guozhi Lv

Calcification–carbonation method for red mud processing

Red mud, the Bayer process residue, is generated from alumina industry and causes environmental problem. In this paper, a novel calcification-carbonation method that utilized a large amount of the Bayer process residue is proposed. Using this method, the red mud was calcified with lime to transform the silicon phase into hydrogarnet, and the alkali in red mud was recovered. Then, the resulting hydrogarnet was decomposed by CO2 carbonation, affording calcium silicate, calcium carbonate, and aluminum hydroxide. Alumina was recovered using an alkaline solution at a low temperature. The effects of the new process were analyzed by thermodynamics analysis and experiments. The extraction efficiency of the alumina and soda obtained from the red mud reached 49.4% and 96.8%, respectively. The new red mud with <0.3% alkali can be used in cement production. Using a combination of this method and cement production, the Bayer process red mud can be completely utilized.

Chemical Alumina Preparation by Using High Alumina Content Fly Ash

Processes of chemical alumina preparation of high alumina content fly ash raw materials are put forward in order to solve the problems of bauxite resource shortage in China and high value application of fly ash. High white aluminum hydroxide and Pseudoboehmite can be obtained by sintering process with the precipitation and carbonate decomposition. 4A zeolite is prepared through the pre-roasting and synthesis process, and activated aluminium oxide is prepared through the acid leaching and pyrolysis method. Typical experiments for preparing different kind of chemical alumina products are presented as well. Whiteness, porosity, pore volume, crystalline and other key parameters of chemical alumina products determined by XRD and ASAP match the industry requirements well.

Extraction of vanadium from direct acid leach solution of converter vanadium slag

ABSTRACT Direct acid leaching of converter vanadium slag by titanium dioxide waste is eco-friendly and efficient, but with low selectivity. This novel technique can result in a vanadium solution which contains chromium(III), aluminium(III), magnesium(II), manganese(II) and high amount of iron(II) and iron(III). Bis (2-ethylhexyl) phosphoric acid (D2EHPA) and tri-butyl-phosphate (TBP) diluted with sulphonated kerosene were applied for vanadium extraction from the multi-element leach solution. The effects of the initial pH, concentration of D2EHPA, ratio of organic to aqueous phase, and the extraction time on the extraction efficiency of vanadium were investigated in saponification and unsaponifiable systems, respectively. The results showed that the vanadium extraction percentage can be up to 97% and the iron extraction percentage can be less than 10% in a thirteen-stage counter-current simulation test and the separation coefficient between vanadium and iron can reach to 109.8. Furthermore, vanadium(IV) can also be separated from other impurities such as aluminium(III), magnesium(II), manganese(II), chromium(III) efficiently. The loaded organic phase was stripped by 184 g L−1 sulphuric acid solution in a three-stage counter-current stripping process and with the total vanadium stripping percentage of greater than 99.5%. In the end, the vanadium pentoxide products with a purity of 99.14% were obtained.

Research on sulphur conversion and acid balance from marmatite in pressure acid leaching

In this paper, the kinetics of oxygen pressure acid leaching of marmatite was studied in the low-temperature region (383–413 K). The effects of agitation rate, particle size, temperature, H2SO4 concentration and oxygen partial pressure on the conversion of sulphur (S2− → S0) were investigated. The results showed that the conversion ratio increased with increasing agitation rate, temperature and oxygen partial pressure, and with decreasing particle size and H2SO4 concentration. Moreover, the results demonstrated that sulphur conversion was controlled by an interfacial chemical reaction, with an apparent activation energy of 51.17 kJ mol−1. The calculated reaction orders of sulphuric acid and oxygen were 0.48 and 1.01, respectively. The leaching reaction followed an unreacted shrinking core model. A model kinetic equation was established for sulphur conversion. Orthogonal experiments regarding the acid balance () of the oxygen pressure leaching residue were carried out. Variance analysis showed that temperature had the largest influence on this, so the effect of the temperature region (383–443 K) on acid balance was further investigated. When the temperature exceeded 443 K, the increase in the sulphur oxidation ratio was too large, which tended to increase the acidity of the system.

Processing Diasporic Red Mud by the Calcification-Carbonation Method

The novel calcification-carbonation method was proposed to process the diasporic red mud discharged from Bayer process alumina plant. In this study, Batch experiments were performed to evaluate the potential effects of important parameters such as temperature, amount of CaO added, CO2 partial pressure and carbonation cycles on the recovery of alkali and alumina. The results showed that 78.74% alumina was recovered from the diasporic red mud with decreases in the mass ratios of Al2O3 to SiO2 (A/S) from 1.27 to 0.27. The Na2O content in the processed red mud was less than 0.3 wt%, and it can be used as a construction material.

Cold Water Model Simulation of Aluminum Liquid Fluctuations Induced by Anodic Gas in New Tape of Cathode Structure Aluminum Electrolytic Cell

Compared to the conventional cathode structure electrolytic cell, the new type of cathode structure electrolytic cell can effectively inhibit the fluctuation of liquid aluminum, which can reduce the polar distance, decrease cell voltage, and save energy. A cold water model was designed according to scale of 1:3 with 160KA industrial electrolytic cell to examine aluminum liquid fluctuation induced by anodic gas in the new type of cathode structure electrolytic cell. High-speed photographs of the liquid interface waves show the effect of several cell parameters such as anode-cathode distance, electrolyte level, and gas flow rate. The study shows that in the new type of cathode structure electrolytic cell, the largest interface wave height will be reduced significantly.

Thermodynamics Analysis on Process of Pelletizing Chlorination of Fly Ash

Fly ash, generated during the combustion of coal for energy production, is an industrial by-product which is recognized as an environmental pollutant. In this paper, thermodynamic calculations and experiments in a tubular furnace reactor were conducted to investigate the process of pelletizing chlorination of fly ash. The thermodynamic calculations indicated that with the increase of the chlorination temperature, the Gibbs free energy of the chlorination reaction is negative, and this demonstrates the thermodynamics feasibility of pelletizing chlorination process. Experiments results show that the alumina chlorination efficiency was up to 70% when the pellet diameter was 8 mm and the C/Al was 3:1 at 1050 °C for 30 min. The effect of alumina chlorination efficiency in pelletizing chlorination process mainly depended on the temperature, chlorination time and pellet diameter. These findings provide useful information for understanding the pelletizing chlorination process, facilitating the development of pelletizing chlorination metallurgy in efficient clean utilization of fly ash.

Research on Alumina Preparation from Aluminium Chloride Solution by Electrolysis Process

During the technology of extracting Al2O3 and other valuable elements in high-alumina fly ash by hydrochloric acid method, the process of AlCl3 transformed into Al2O3 has many problems, such as the long technological process and the large investment in equipment. In this paper, a new method of the direct-electricity conversion technology is proposed, for dealing with aluminium chloride solution. Namely, using the method of electrolysis and taking CO2 injection to improve the pH of solution, which make the aluminum precipitate in the form of carboaluminates. Then after roasting, Al2O3 can be acquired. The influences of the initial AlCl3 concentration and the composition of the solution in the cathode side of the cell on the electric conversion process have been studied and the roasting products have been characterized.

Direct Calcification–Carbonation Method for Processing of Bayer Process Red Mud

The highly-alkaline red mud, which is the Bayer process residue generated from the alumina industry, is a severe environmental problem. In this study, a new calcification–carbonation process was proposed for red mud disposal. Red mud was processed by lime to convert the aqueous silicon phase into hydrogarnet, which was then decomposed by CO2 to recover alumina. In the direct carbonation process, the NaOH-containing solution after calcification was directly carbonated without prior liquid–solid separation. The discrete and direct carbonation processes had alumina recovery rates of 34.9 and 35.5%, respectively, with 0.15 and 0.21 wt % Na2O in the final red muds, respectively. The optimum NaOH concentration in the calcification liquor was 30 g/L. Under these conditions, alumina recovery was increased to 44.5% and the Na2O concentration in the processed red mud was reduced to <1 wt %. The final red mud can be used as a construction material.

Oxidative acid leaching of mechanically activated sphalerite

ABSTRACT The pressure leaching kinetics of mechanically activated sphalerite was investigated in this work. X-ray diffraction and scanning electron microscopy were used to characterise the influences of crystalline structure and morphology, respectively. A laser particle size analyser and specific surface area tester were used to determine the particle size and specific surface area, respectively. Compared to the non-activated sample, the activated samples demonstrated distinct physicochemical properties with higher reaction efficiencies and increased Zn recovery ratios. The activation energy of sphalerite decreased from 69.96 to 45.91, 45.11, and 44.44 kJ mol−1 as the activation time increased from 0 to 30, 60, and 120 min, respectively. The reaction orders for the H2SO4 solutions of the sphalerite samples activated for 0, 30, 60, and 120 min were 1.832, 1.247, 1.214, and 1.085, respectively, which indicated that the dependency of the sphalerite leaching process on H2SO4 could be reduced by means of mechanical activation.