Qiuyue Zhao

Computational simulation of fluid dynamics in a tubular stirred reactor

Abstract The flow and concentration fields in a new style tubular stirred reactor were simulated by simulating the fluids dynamics(CFD), in which FLUENT software was used and the standard k—ɛ model and multiple reference frame(MRF) were adopted. The various values of initial rotating speed and inlet flow rate were adopted. Simulations were validated with experimental residence time distribution(RTD) determination. It is shown that the fluid flow is very turbulent and the flow pattern approaches to the plug flow. The velocity increases from shaft to the end of impeller, and the gradient is enlarged by increasing the rotating speed. Comparison between RTD curves shows that agitation can improve the performance of reactor. As the flow rate increases, the mean residence time decreases proportionally, and the variance of RTD lessens as well. When rotating speed increases to a certain value, the variance of RTD is enlarged by increasing rotating speed, but the mean residence time has no obvious change.

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.

Study on Minimum Starting Energy of Self-stirring Reactor Driven By Pressure Energy

Stirring plays an important role in the metallurgical process. Enhancing the agitation of materials can strengthen the turbulence in multiphase flow, which can shorten uniform mixing time and reaction time. In order to improve leaching reaction and heat transfer efficiency, a novel self-stirring tubular reactor driven by pressure energy used in bauxite digestion process is presented originally by Northeastern University, which combines the advantages of autoclaves and conventional tubular digestion equipment. According to the principle of dimensional analysis, the dimensionless equation between input power and various factors is established, and it is corrected to obtain input power, through verified, the calculated values are basically consistent with the experimental results.

Comprehensive Utilization of Red Mud: Current Research Status and a Possible Way Forward for Non-hazardous Treatment

Red mud is an alkaline solid waste produced in the process of alumina extraction from bauxite. Presently, more than 3.0 billion tonnes of red mud are estimated to be stockpiled on land with an annual growth rate of approximately 120 million tonnes. The large amount of red mud has become a very real threat to the environment and human health because its high alkalinity presents a potential pollution to water, land and air. This article provides an overview of current research status for the options of comprehensive utilization of red mud and attempts to review their strengths and weaknesses. Ideally red mud is encouraged to be utilized as an industrial by-product for other applications, leading to a zero-discharge situation. On this basis the review recommends the Calcification-Carbonization Method, a promising technology for non-hazardous treatment, to recover the alkali and alumina and meanwhile transform the red mud into a non-hazardous material available for subsequent use.

Influence Factors of Stirring Speed of Self-Stirring Tubular Reactor Used in Bauxite Digestion Process

Aim at improvement leaching reaction and heat transfer efficiency, A novel self-stirring tubular reactor driven by pressure energy used in bauxite digestion process was presented originally by Northeastern University, which combined the advantages of autoclaves and conventional tubular digestion equipment. Quasi-logarithmic equation between the stirring speed and the various factors was established by dimensional analysis method. The results demonstrated that higher pressure promoted the appearance of more obvious turbulence and improved the mixing effect of media in the reactor. The quasi-logarithmic equation between the stirring speed and the various factors was: N = 356.7053ρ−0.4322μ−0.13546P0.56773H−0.86454

Numerical simulation of fluid dynamics in rare earth chloride solution in jet-flow pyrolysis reactor

Abstract Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) inside the reactor was numerically simulated using a computational fluid dynamics method. The self-produced pressure ( p ) and the fuel inlet velocity ( v ) satisfied a quadratic function, p =0.06 v 2 +0.23 v −4.49. To fully utilize the combustion-generated heat in pyrolysis of rare earth chloride, an appropriate external pressure p = v 2 +3 v −4.27 should be imposed at the feed inlet. The 1.25- and 1.5-fold increase of feed inlet diameter resulted in decline of adsorption dynamic pressure, but the intake of rare earth chloride increased by more than 30% and 60%, respectively. The fluid flow in the reactor was affected by the feeding rate; the fluid flow peaked near the throat of venturi and gradually smoothed down at the jet-flow reactors terminal along with the sharp decline of feeding rate.