A mini review on the separation of Al,Fe and Ti elements from coal fly ash leachate

The electricity demand is increasing rapidly with the development of society and technology.Coal-fired thermal power plants have become one of the primary sources of electricity generation for urbanization.However,coal-fired thermal power plants produce a great amount of by-product coal fly ash every year.Coal fly ash disposal in landfills requires a sizable space and has negative environmental impacts.Therefore,it is crucial to develop new technologies and methods to utilize this enormous volume of solid waste in order to protect the environment.In this review,the fundamental physical and chemical character-istics of coal fly ash are introduced,and afterward the disposal policies and utilization ways of coal fly ash are discussed to gain a comprehensive understanding of the various ways this waste.The leaching of valuable metals in coal fly ash and the extraction of metal elements in leachate under different conditions are also summarized.Furthermore,the possibility of coal fly ash to serve as a supplementary source for mineral resources is analyzed,providing a basis for its extensive use as a raw material in the metal industry in China and worldwide.

Tensile Behavior of SiC Fiber-Reinforcedγ-TiAl Composites Prepared by Suction Casting

The process of preparing SiC_(f)iber-reinforced y-TiAl composites by the conventional methods is difficult and complicated due to the high reactivity,high melting point and poor deformability of y-TiAl alloys.In this work,suction casting,a promising method for preparing SiC_(f)/TiAl composite,had been attempted.In the process,y-TiAl alloy melt was introduced rapidly into a mold within pre-arranged fibers that were coated with additional layer of titanium alloy.This simple method successfully prevented serious reactions between the alloy melt and the fibers which remained intact during the solidification process.The interfacial reaction layer was observed by optical microscopy,scanning electron microscopy(SEM).The interfacial reaction products were identified by transmission electron microscopy(TEM).Tensile tests of the matrix alloy and composites were performed at room temperature and 800℃.The results exhibited that the tensile strength of SiC_(f)/γ-TiAl composite was higher than that of the matrix alloy at both room temperature and 8000 C.At room temperature,tensile strength of SiC_(f)/γ-TiAl composite was increased by about 7%(50 MPa),whereas a double increase in tensile strength 14%(100 MPa)was obtained at 800℃.The titanium alloy coating on the fiber not only prevented the serious interfacial reaction between the y-TiAl alloy melt and the SiC_(f)iber,but also played a role in delaying the propagation of cracks in the matrix to the fiber at 800℃.The fracture mechanism of the composite was analyzed by fracture metallographic analysis.

Numerical Investigation into the Distributor Design in Radial Flow Adsorber

Air flow distribution in radial flow adsorber was numerically investigated using computational fluid dynamics(CFD)method,which was proved to be applicable to study the problem of non-uniform distribution in radial flow adsorber.Results showed that the degree of non-uniformity was more serious in desorption process than that is adsorption process.Therefore,it was considered that the non-uniform distribution of flow in a radial flow adsorber was mainly manifested in the desorption process.Optimum design of distributor parameters can improve the flow distribution in adsorber.Meanwhile,three different structures of distributor and the effect of breathing valve were analyzed.Results revealed that truncated cone is more effective than tubular and conical distributors in flow distribution.By inserting the truncated cone in central channel,desorption uniformity was increased by 6.56%and the breakthrough time of CO_(2)was extended from 564s to 1138s in the adsorption process.The“dead zone”problem at the top of adsorber during the desorption process was solved by opening breathing valve,which prolonged the working life of adsorber and was proved to have less effect on the uniform of airflow.

Numerical Investigation into the Air Flow Distributions of the Air Conditioning System in the Modular Data Center

Data center plays an increasingly important role in everyday life.As data center is becoming more and more powerful,energy consumption is also increasing dramatically.The air conditioning system occupies at least 50 percent of the total energy consumption.Therefore,delicate analysis on the air conditioning system could help to reduce energy consumption in data center.An advanced Finite Volume Method with RNG k-ε model and convective heat exchange model is used in this paper to study the airflow and the temperature distribution of modular data center under different arrangements.Specifically,the calculation formula of convective heat transfer coefficient for plate flow is adopted to simplify analysis;and fans on the back of racks are simplified to be walls with a certain pressure jump.Simulations reveal that,in the case where air conditioners are arranged face-to-face,the temperature distribution on the back of racks is not uniform,and local high temperature points emerge near the side wall of air conditioners.By analyzing the distribution of air flow and temperature,geometric model is optimized by using a diagonal rack arrangement and drilling holes on the side wall.In the same energy consumption situation,the overall maximum temperature of the optimized model is reduced by 2.3℃ compared with that of the original one,and the maximum temperature on the server surface is reduced by 1℃.Based on the optimized model,the effect of the hot aisle distance on the temperature distribution is studied.By simulating four different cases with various distances of hot aisle of 100cm,120cm,130cm and 150cm,it is found that the temperature is generally lower and distributed more evenly in the case with 120cm hot aisle distance.This demonstrates that the distance of hot aisle has an effect on temperature.