摘要
[目的]为了探究喷雾热解过程中加热壁温对铈锆固溶体生产过程的影响,分析热解炉内的流量场和浓度场的变化情况,实现对热解炉的设计优化.[方法]采用数值模拟的方法,建立喷雾热解炉的物理模型,分别探讨加热壁温对铈锆固溶体在热解炉的不同阶段及热解炉中水蒸气分布和HCl分布的影响.[结果]当热解温度为850℃时,液滴的反应主要分2个阶段,在炉膛高度为0～0.05 m处,为加热蒸发阶段,在炉膛高度为0.05～0.6 m处,为稳态热解阶段.当炉壁温度为550～650℃时,在炉膛高度为0.9 m处温度变化放缓,喷雾处于稳定热解阶段;而壁温在750～850 ℃时,在炉膛高度为0.6 m处温度变化放缓;当壁温为850℃时,在炉膛高度为0.1～0.6 m处的温度曲线斜率最大,液滴达到稳定蒸发阶段的时间缩短,水分蒸发变快,热解时间变短.[结论]炉壁加热区的温度越高,HCl生成的速度越快,速度的最大值越小,在炉膛高度为0.4 m处速度变化最大,达到1.6m/s左右;并且整体HCl生成的量随温度的升高而增大,平均速度变化随着热空气温度的升高而减小.
Abstract
Objective During spray pyrolysis,a series of complex chemical reactions and physical changes occur,most of which occur at high temperatures.Therefore,it is difficult to directly observe the velocity field and various concentration fields in pyrolysis furnaces,but the velocity field,temperature field and various concentration fields have a crucial impact on the design optimization of pyrol-ysis furnaces and the study of pyrolysis processes.In order to investigate the effect of the heating wall temperature on the solution of cerium-zirconium solids during spray pyrolysis,the temperature field,flow field and concentration field variations in the pyroly-sis furnace were analyzed and further design and optimization of the pyrolysis furnace was implemented.Methods A hydrodynamic numerical simulation method was used to simulate the spray pyrolysis furnace and a physical model of the spray pyrolysis furnace was developed.The influence of heating wall temperature on the reaction process was studied,and on the premise of verifying the correctness of the model,it was hoped that the changes of various fields during the reaction process of spray pyrolysis furnace could be accurately reflected,and the simulation results could be used to guide the optimization of the experiment.The thermal and velocity fields in the pyrolysis furnace were calculated quantitatively.The distributions of the tem-perature,velocity and concentration fields in the furnace at different heating wall temperatures were described qualitatively and quantitatively and compared.Results and Discussion In the process of spray pyrolysis,when the temperature of spray pyrolysis is 850 ℃,the reaction of spray pyrolysis droplets is mainly divided into two stages,respectively:at 0-0.05 m in the furnace,it is the spray pyrolysis heating evaporation stage.Within 0.05-0.6 m of the furnace,the steady-state pyrolysis phase of the spray pyrolysis occurs.When the spray pyrolysis furnace wall temperature rises from 550 ℃ to 650 ℃,the spray pyrolysis temperature in the furnace changes slowly at 0.9 m,and the spray pyrolysis process is in the stable pyrolysis stage.When the furnace wall temperature is in the range of 750-850 ℃,the change of spray pyrolysis temperature in the furnace slows down at 0.6 m.When the wall temperature is 850 ℃,the temperature slope of the furnace is the largest at 0.1-0.6 m,and the time required for droplets to reach the stable evaporation stage of spray pyrolysis is shortened.At the same time,the rate of evaporation of water is accelerated and the total time required for pyrolysis is shortened.Conclusion The higher the temperature in the heating zone of the furnace wall during the spray pyrolysis,the faster the HC1 formation rate and the smaller the maximum air velocity.At a height of 0.4 m in the furnace,the velocity changes most,reaching about 1.6 m/s.Moreover,the amount of produced HCl increases with temperature because the reaction is facilitated at high temperatures.Since the viscous resistance of the air increases with the increase of temperature and the average velocity decreases with the increase of the heating wall temperature,the velocity is minimum at the temperature of 850 ℃.
基金项目
国家自然科学基金(51964039)
内蒙古自治区自然科学基金(2022LHMS05004)
内蒙古自治区应用技术研究与开发项目(2021GG0103)
维普
万方数据