Comparison of Temperature Field Distribution between Cement Preclinkering Technology and Cement Precalcining Technology

Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology,we studied the characteristics of temperature field distribution of cement preclinkering technology systems including cyclone preheater,preclinkering furnace,and rotary kiln.We used numericalsimulation method to obtain data of temperature field distribution.Some results are found by system study.The ratio of tailcoalof cement preclinkering technology is about 70%,and raw mealtemperature can reach 1070 ℃.Shorter L/D kiln type of preclinkering technology can obtain more stable calcining zone temperature.The highest solid temperature of cement preclinkering technology is higher than 80 ℃,and high temperature region（〉1450 ℃）length is 2 times,which is beneficialfor calcining clinker and higher clinker quality.So cement preclinkering technology can obtain more performance temperature filed,which improves both the solid-phase reaction and liquid-phase reaction.

Numerical simulation of low-concentration CO_(2) adsorption on fixed bed using finite element analysis

Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic adsorption model was established by coupling equations of mass,momentum and energy balance,and solved by finite element analysis.The simulation breakthrough curves fit well with the low-concentration CO_(2) adsorption experimental data,indicating the reliability of the established model.The distributions of concentration and temperature field in the column for CO_(2) adsorption and separation from CO_(2)/N_(2) were obtained.The sensitivity analysis of the adsorption conditions shows that the operation parameters such as feed flow rate,feed concentration,pellet size,and column height-to-diameter ratio produce a significant effect on the dynamic adsorption performance.The multi-physics coupled 2D axisymmetric model could provide a theoretical foundation and guidance for designing CO_(2) fixed-bed adsorption and separation processes,which could be extended to other mixed gases as well.

Theoretical analysis and experimental research on thermal focal length of a YVO_4/Nd:YVO_4 composite crystal

This paper investigates the temperature field distribution and thermal focal length within a laser diode array （LDA） end-pumped YVO4/Nd：YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd：YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd：YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd：YVO4 rectangular crystal for the YVO4/Nd：YVO4 composite crystal and the Nd：YVO4 single crystal are researched respectively. Calculating the thermal focal length within the Nd：YVO4 rectangular crystal was done by an analysis of the additional optical path differences （OPD） caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd：YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd：YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd：YVO4 crystal and the Nd：YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd：YVO4 laser is more advantageous than the laser with Nd：YVO4 single crystal.