折射窗干燥装置设计与试验

Design and drying test of refractance window drying equipment

分别以热水和碳纤维红外板为热源,设计并制作折射窗干燥(RW)装置、红外板折射窗干燥(IR-RW)装置,利用胡萝卜浆进行干燥试验验证,并与热风干燥结果进行对比。结果表明,RW和IR-RW干燥装置设计方案可行;当干燥温度为95℃时,二者均可在5 min内实现2mm厚胡萝卜浆的快速脱水;干燥初期,二者的物料温度均迅速上升至60~75℃并保持恒定,且物料最高温度始终比干燥热源温度低约15~25℃;预热阶段,IR-RW装置仅需约2min即可达到设定温度,而RW干燥中热水需约30min达到设定温度;RW和IR-RW干燥样品的色差值、胡萝卜素含量无显著性差异(P<0.05),分别约为17,10%,二者均未出现明显褐变和黏结现象;95℃热风干燥(HA)时间约为13min,胡萝卜素损失约32.58%,干燥产品色差值为37.5。

In order to explore a suitable drying device and method for heat-sensitive pulp materials,a refractance window dehydration(RW)device and an infrared refractance window dehydration(IR-RW)device were designed and manufactured with hot water and carbon fiber infrared plate as heat sources,respectively.The drying experiments were carried out with carrot pulp and also compared with the hot air drying.Both of the RW and IR-RW device were composed of feeding system,heating system,cooling system and unloading system.The control system was made of touch screen and a series of slave controllers.A control network was formed base on Modbus protocol to precisely control the parameters of drying process.The experimental results showed that the design scheme of RW and IR-RW drying devices was feasible and the work program was also reliable.When the drying temperature was 95 ℃,both of IR and IR-RW drying devices can achieve rapid dehydration,and the 2 mm thick carrot pulp can be dried in 5 min.The material temperature raised rapidly to 60~75℃at the initial drying stage,and then gradually became stable in the middle drying stage,and decreased in the later drying stage.The maximum temperature of the material was 15~25 ℃lower than that of the heating source of drying.In the preheating stage,it took about 2 minutes for the IR-RW device to reach the set temperature,while it took about 30 minutes for the hot water to reach the set temperature in the RW drying process.The quality attributes of the RW and IR-RW dried samples were not significantly different(P<0.05),and had the color difference(△E)and loss of carotene are about 17,10%respectively.The required time for hot air drying at 75℃ was nearly 13 min,and the loss of carotene was 32.58%.The HA drying samples had obvious browning and bonding phenomenon,and the color difference(△E)of HA samples was 37.5.The research results provided important information about pulp drying with RW and IR-RW drying technologies.