碳化硅超细粉球团变温热风干燥特性及其干燥模型

摘要

利用先高温后低温的变温干燥工艺对碳化硅超细粉球团进行干燥,以变温干燥的前期温度、前期风速、后期风速、转换干基含水率及后期温度为主要影响因素,通过L16(45)正交实验研究变温干燥特性及其数学模型.研究表明:碳化硅超细粉球团在高温段的干燥特性与恒温干燥特性相同,进入低温段后随着球团由外向内的温度梯度降低,球团内部水分溢出阻力降低,导致内部水分扩散速率与表面气化速率相等,此时干燥速率进入短暂的恒速阶段;碳化硅球超细粉球团变温热风干燥工艺不仅可以降低干燥设备投资和干燥能耗,还具有出球温度低、显热少、冷却时间短的优点;通过实验数据拟合,发现Midilli模型拟合度最好,可以较好反映出碳化硅超细粉球团在变温干燥下的干燥特性.%Ultra-fine SiC powder pellet was dried by variable temperature drying technology which had higher temperature at first and lower temperature afterwards.Early temperature,early wind speed,late wind speed,conversion moisture content,and late temperature are the main influencing factors of this process.To get the drying characteristics and drying model,these factors were studied by the L 16 (45) orthogonal experiment research.Results showed that:variable temperature drying characteristics of ultra-fine SiC powder pellet were the same as constant temperature characteristics during high temperature process,with the decline of temperature gradient from outside to inside,the resistance of water overflow reduced internally,the water diffusion speed inside was equal to the gasification rate on the surface,at this point the drying rate entered transient stage of constant speed;Variable temperature drying process of ultra-fine SiC powder pellet could not only reduce cost of drying equipment and drying energy consumption,but also made the temperature of production lower,loss of sensible heat less,and cooldown time shorter.With fitting to experiment data,the Midilli model was the best and could reflect the drying characteristics of variable temperature drying process on ultra-fine SiC powder pellet.