Advanced Materials Research Vols. 881-883

Abstract: The absorption performance of CO₂ using MDEA-PZ-TETA ternary absorbent in a rotating packed bed was investigated. The effects of the concentration of the ternary absorbent, the absorbing liquid temperature, the rotating speed, the liquid flow rate and gas flow rate on the absorption performance of CO₂ were discussed in detail. The experimental results showed that the optimum absorption condition was the absorbent concentration of 0.05 mol/L, the absorption temperature of 290 K, the rotating speed of 454 rpm and the ratio of gas to liquid of 1.2, which could provide a molar absorption saturated capacity of 1.3688 molCO₂/molAm and a satisfying CO₂ absorptivity of 93.18%.

Abstract: The volume content of water vapor in ammonium phosphate exhaust gas is about 12-20%, and the temperature is about 70-80°C. If the exhaust gas are directly discharged through the chimney, the water vapor in it will easily condense and fog because of local supersaturation, resulting in some energy and water losing. The cool water spray condensing can be used to recover water vapor from exhaust gas, and it can recover most of the water vapor and the sensible heat and the latent heat of the water vapor in the exhaust gas. Carrying out the energy balance and material balance calculations quickly and accurately is one of the major concerning problems for project design. This paper presents a calculation method for the heat balance by calculation the enthalpy difference of the water in the exhaust gas, compared with the method by directly calculating the heat in water vapor condensing process. Both the results are in good agreement, but the enthalpy difference method is more concise. The calculation methods and procedures are of practical engineering application values.

Abstract: In this paper, a cryogenic air separation process with LNG cold energy utilization is proposed to produce liquid nitrogen and high pressure pure oxygen gas economically. To reduce the electric energy consumption of air separation products, liquid nitrogen have been produced by condensing the separated pure nitrogen gas with LNG cold energy utilization, and the recycled nitrogen is served to transfer cold energy from LNG stream to cool off air stream in the proposed cryogenic air separation process. The specifications of streams and the major equipments of the air separation process are simulated with Aspen Plus software and the main parameters analysis are performed. The results show that the energy consumption of the proposed air separation process with LNG cold energy utilization decreased about 58.2% compared with a conventional cryogenic air separation process. The compressed pressure of recycled nitrogen has a big impact on the cost of air separation products and utilization efficiency of LNG cold energy. The LNG cold energy could be fully utilized when the recycled nitrogen has been compressed to above 6.5MPa.

Abstract: Through analyzing and comparing the treatment of fracturing fluid flowback at home and abroad, it can be found that fluid derived organic waste water can be handled by micro electrolysis economically and efficiently. But there are also some shortages of traditional micro electrolysis. So this paper discusses a new micro-electrolysis technology, namely cavitation-impinging stream electrolysis technology which has several advantages in high concentration organic wastewater treatment. The technology can not only solve the problems that the passivation of process and the plugged equipment in the treatment of fracturing fluid flowback fluid by traditional micro electrolysis, but also can better promote the reaction from the reaction kinetics with the help of Coupling application about cavitation and impinging stream technology, so as to realize the purpose of improving the reaction rate and efficiency.

Abstract: Red mud is a solid waste which is generated in the process of alumina production and is of highly alkaline. Red mud has very complex compositions, but contains a variety of rare and valuable metals. In addition, its high alkalinity is a severe pollution to water, land, air and environment, which has been one of the main factors to affect the sustainable development of aluminum industry. The characterization of red mud, the extraction of valuable metals from red mud, the utilization of red mud in construction materials, environmental restoration materials and other fields are introduced in this paper.

Abstract: The reason of comprehensive utilization of red mud is that it contains recycled oxides and a variety of valuable metals. In this paper, the basic characterization of red mud is described. The current developments of extraction of Fe, Ti, Sc, rare earth and valuable metals from red mud are summarized with some emphasis. In addition, the technological features of each process route are analyzed briefly. It can be concluded that it is practiable to extract Fe, Ti, Sc, rare earth and valuable metals from red mud. However, in order to realize recycling of red mud, the key is that an economic, energy saving, environment friendly and widely applicable process has to be found.

Abstract: Mg was extracted from boron mud through calcining method. The technological process is that the boron mud was calcined at 700 °C for 3 h then uniformly mixed with (NH₄)₂SO₄ in proportion and calcined. The reaction process was studied by TG-DTA and XRD, which is that MgO in calcined boron mud reacts with (NH₄)₂SO₄ to produce (NH₄)₂Mg₂(SO₄)₃ at low temperature, then with increasing the temperature, (NH₄)₂Mg₂(SO₄)₃ decomposes into MgSO₄. The effects of calcination temperature, mol ratio of reaction substrates and calcination time on conversion rate of Mg were studied. The results indicate that the conversion rate of Mg increases with the increasing of calcination temperature first then decreases, increases with the increasing of calcination time and mol ratio of (NH₄)₂SO₄ and MgO. When the calcination temperature is 500 °C, the calcination time is 3 h, the mol ratio of (NH₄)₂SO₄ and MgO is 0.9:1, the conversion rate of Mg is 81.9 %.

Abstract: The extraction kinetics and mechanism of La (III) by P204-kerosine from phosphoric acid were investigated by constant interfacial cell with laminar flow. The effects of stirring speed, temperature, specific interface area on extraction rate were studied. The results indicated that a plateau region is appeared at the stirring speed of over 115r/min. The extraction apparent activation energy was calculated to be-13.40kJ/mol and the extraction process is controlled by a mixed mechanism of diffusion and chemical reaction. The rate equation of extraction was deduced. Under conditions of 25°C and interfacial area 19.64cm2, the extraction rate constant was 2.08×10-6 m·s-1·. Through the derivation of the reaction mechanism the reaction zone is at the liquid-liquid interface.

Abstract: The brine from La Guocuo was pretreated with adding magnesium chloride hexahydrate, and it evaporated at 5°C. The salt precipitation law is obtained by evaporation experiment of this pretreated brine. In the evaporation concentration process, the salts precipitate phases are successively: magnesium carbonate, sodium sulfate, borate salts, sodium chloride and glaserite.

Abstract: The hydrodynamics of a two-dimensional gas-solid fluidized bed with 0.03 m diameter and 0.3 m height were studied experimentally and computationally. The slugging fluidization of large particles was experimentally investigated and simulated using the Fluent 6.3 computational fluid dynamics (CFD) package. By a series of cold-model test, characterization of gas-solid fluidization with large particles was studied. These results can be used to research slugging characteristics. A multifluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady-state behavior and momentum exchange coefficients were calculated by using the Syamlal-OBrien drag functions. These results of the transfer of fluidization state, maximum bed expansion ratio and pressure fluctuation were systemically simulated in a gas-solid fluidized bed. The modeling predictions compared reasonably well with experimental data and qualitative slugging regime. The simulation results can better predict the slugging fluidization characterization of large particles.