烟丝干燥特性实验研究

目前烟草热质传递过程的研究,均采用静态实验研究方法,得出的实验结果与生产实际有一定程度的偏差.针对这种情况,为了使研究结果更加贴近生产实际,模拟了烟丝在转筒内的热质交换规律,自行设计、安装、调试了一座实验台.在该实验台进行了烟丝干燥过程动态试验研究,重点考察了湿烟丝增温减湿条件下的热质迁移的规律,以及该过程对烟草填充力的影响.结果表明,烟丝干燥过程分为恒速和降速两个阶段,恒速阶段干燥速率主要取决于外部干燥条件,提高风温或风速可大大缩短干燥周期.因而在保证烟丝干燥质量的前提下,应该改善流动和传热条件,争取在恒速阶段就把烟丝干燥到工艺要求.烘丝方式、来料温度和水分、干燥介质状态参数等对烘后烟丝的填充力有显著影响.对于转筒式烘丝机,采用顺流烘丝方式,较高的来料温度和水分,较大的热风流速,可获得较高的烘丝填充力.

Experimental Investigations on the Drying Characteristics of Cut Tobacco

At present,the researches on the mass and heat transfer mechanism of cut tobacco are in the static process.These experiment results have a certain degree of deviation from the industrial practice.In response,we designed,installed and put up a dynamic experimental facility,so as to simulate industrial reality.A dynamic experiment of cut tobacco drying was made on this facility.The mass and heat transfer mechanism of wet cut tobacco and the filling power changes in heating or humidifing processes were also researched.The research results show that the drying process includes constant rate period and falling rate period.The drying rate corresponding to the constant stage depends on the drying conditions. Increasing the temperature or velocity of airflow greatly shorten the drying process.From the perspective of improving tobacco's drying properties,it is suggested that the air flow and heat transfer rate should be increased in the constant rate period.The filling power of dried cut tobacco is significantly influenced by drying methods,the temperature and moisture content of entrancing cut tobacco and drying medium conditions.For rolling dryer,the higher filling power value corresponds to downstream quickly drying way,higher inlet temperature and moisture content.