栲胶喷雾干燥条件对粉胶粒度影响的初步研究

<正> 有关喷雾干燥的文献中介绍了坚木、荆树皮、柯子栲胶液体的喷雾干燥条件:进风温度低于250℃,出风温度80—85℃,粉胶含水分4—8％;还指出了咖啡浸提液(与栲胶溶液相近似)喷雾干燥时进风温度、进料浓度对咖啡松密度的影响,以及单个咖啡液滴干燥时咖啡液滴形态的变化和最终形态。我国栲胶工作者做了大量工作。在保证粉胶质量的前提下,合理分配热风和应用旋转风,适当提高进风温度和进胶浓度,已使离心喷雾干燥装置(离心喷雾盘直径300毫米,转速7000转/分左右)生产能力提高到日产粉胶10—13吨。 关于喷雾干燥条件对粉胶粒度及其分布的影响,迄今未见文献报导。但是,在讨论栲胶液体喷雾干燥的基本原理、设计和计算时,都需要知道喷雾干燥条件、粉胶粒度及其分布,以及它们之间的关系,我们特对此进行了初步探讨。 一、试验方法与设备、仪器 本试验包括栲胶液体喷雾干燥试验和粉状栲胶粒度的测定。 1、栲胶溶液喷雾干燥试验 (1)喷雾干燥装置 为使试验条件尽可能接近生产情况,本试验采用丹麦制造的小型离心式顺流喷雾干燥装置。它包括压缩空气机(自配)、空气电加热器、干燥塔(ф800×600,

A PRELIMINARY STUDY ON THE INFLUENCE OF SPRAY PRYING CONDITIONS ON THE SIZE OF POWDER EXTRACTS

Spray drying experiments of the lipuid extracts from cups of Quercus spp. and bark of Larix gemelini were designed by the cross experiment method. By means of a small centrifugal spray drier, all samples of the two powder extracts were prepared under definite conditions. Accumulative subsidence curves of all powder extract samples were drawn following the determining of their sizes by an automatic record subsidency balance. Based on the Stocks law and the regression formulae from the accumulative subsidence curves, a program was made and the sizes, distributive functions, percentage of contents and volume-area average diameters of all powder extract samples were calculated in a micro-computer. Results showed that particle diameters of the two powder extracts were less than 344 microns, their volume-area average diamters ranged from 21 to 36 microns, and the particle diameters corresponding to the highest points of the distribution curves of all powder extract samples ranged from 14 to 44 microns, with a content percentage of 71-75%. The rotary speed of the centrifugal atomizer was the main factor to influence the particle diameters of the two powder extracts. With the increase of the rotary speed of the centrifugal atomizer, the particle diameters of the two powder extracts soon became smaller. The inlet temperature of heated air, the feed temperature and concentration were secondary factors influencing their particle diameters, of which the inlet temperature of heated air exerted cardinal influence on the particle diameters of the powder extracts of the cups from Quercus spp. The particles rapidly became smaller in diameter with the increase of the inlet temperature of heated air.