WU Yongfu^1a,3 , LI Zhi^1a , ZHAO Shuang^1a , LIU Zhongxing^1b,3 ,WANG Zhenfeng^1b,3 , DONG Yunfang^1b,3 , LIU Yubao² , MA Shouying^1a

(1a. Faculty of Energy and Environment, 1b. Faculty of Materials and Metallurgy, Inner Mongolia Universityof Science and Technology,Baotou 014000, China; 2. State Key Laboratory of Baiyunebo Rare Earth Resources Research and Comprehensive Utilization,Baotou Rare Earth Research Institute, Inner Mongolia, Baotou 014000, China; 3. Clean extraction and application of light rare earth Inner Mongolia Autonomous Region Engineering Research Center, Baotou 014000, China)

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 pyrolysis 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 pyrolysis 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 temperature, 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 HCl 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 ℃ .

Keywords: spray pyrolysis; cerium zirconium solid solution; numerical simulation

Corresponding Author:刘中兴(1963—),男,教授,博士,内蒙古自治区跨世纪、 新世纪 321 人才、 包头市“5512”工程领军人才,硕士生导师,研究方向为稀土绿色冶金技术开发。 E-mail: liuzx@imust.edu.cn。

DOI:10.13732 / j.issn.1008-5548.2024.02.001

CLC No:TB4; TQ051. 8          Type Code:A

Serial No:1008-5548(2024)02-0001-11