MVR-耙式干燥系统设计及其性能研究

发布时间：2018-05-06 02:16

本文选题：MVR + 耙式干燥　；参考：《浙江工业大学》2017年硕士论文

【摘要】：干燥一般是指通过直接或间接的方式传递能量(通常是热量)给湿物料,使其中的湿分(大多数情况下为水)产生相变与物料分离,从而获得一定湿含量固体产品的过程。干燥过程的能耗与湿分的相变热、传热传质和能量回收方式等因素有关。由于湿分(尤其是水)的相变热较大,导致脱湿需要消耗的能量较大。运用MVR(机械蒸汽再压缩)技术,回收干燥过程脱除的湿分(二次蒸汽)的相变热(冷凝热),有显著的节能效果。传统的耙式干燥系统用蒸汽等为热源间接加热物料并在真空条件下脱湿,尾气经过滤、冷凝除湿后由真空泵排出。本文将MVR技术应用于耙式干燥系统,提出用罗茨蒸汽压缩机替换该系统中的真空泵,将干燥过程脱出的湿分(二次蒸汽)压缩以提高压力和温度,再经增湿(消除过热)和补充少量生蒸汽后作为热源使用。不仅节省了大量热能,还节省了冷量,节能效果显著。该系统特别适合热敏性、易氧化和湿分须回收的物料的干燥。被干燥物料可以是粉粒状、膏状、浆状,也可以是溶液(此时包含蒸发、结晶和干燥过程)。本文提出了MVR耙式干燥系统工艺流程;设计了实验装置的工艺流程,进行了物料热量衡算和主要设备工艺计算,绘制了带控制点工艺流程图、耙式干燥机和丝网除沫器装配图和设备管道布置图,搭建了MVR耙式干燥实验装置。分别以水和碳酸钠溶液为对象,实验研究了干燥压力、压缩比、耙轴转速、过热度、物料初始含水率、填充率等对过程COP和SMER的影响。结果表明:在实验条件范围内,选择适当低的干燥压力、适当小的压缩比、适中的转轴速率、控制蒸汽过热度均有利于提高系统的运行效率。以水为对象时,COP为4.4~8.8,SMER为2.0~3.4 kg/(kW·h);以碳酸钠溶液为对象时,COP为3.1~7.3,SMER为1.2~2.8 kg/(kW·h)。节能效果明显优于传统耙式干燥机。研究结果对MVR耙式干燥系统的应用有参考意义。
[Abstract]:Drying generally refers to the process of transferring energy (usually heat) directly or indirectly to the wet material, which makes the wet fraction (in most cases water) produce phase transition and material separation, thus obtaining a certain amount of wet solid product. The energy consumption of drying process is related to the heat of phase change, heat and mass transfer and energy recovery. Due to the large phase change heat of wet fraction (especially water), the dehumidification needs a large amount of energy. By using MVR( Mechanical Vapor recompression) technology, the phase change heat (condensation heat) of wet fraction (secondary steam) removed during drying process is recovered, which has remarkable energy saving effect. In the traditional rake drying system, steam is used as heat source to heat the material indirectly and dehumidify under vacuum condition. The tail gas is filtered, condensed and dehumidified, then discharged by vacuum pump. In this paper, the MVR technology is applied to the rake drying system. The vacuum pump in the system is replaced by a Roots steam compressor, and the wet fraction (secondary steam) released from the drying process is compressed to increase the pressure and temperature. After humidifying (eliminating overheating) and adding a small amount of steam, it can be used as heat source. Not only save a lot of heat energy, but also save the cooling capacity, energy saving effect is remarkable. The system is especially suitable for drying materials with heat sensitivity, easy oxidation and moisture separation to be recovered. Dried material can be powdered, paste, paste, or solution (this includes evaporation, crystallization, and drying processes). In this paper, the process flow of MVR rake drying system is put forward, the process flow of the experimental device is designed, the heat balance of material and the technological calculation of main equipment are carried out, and the process flow chart with control point is drawn. The assembly drawing of rake dryer and screen defoaming device and the layout drawing of equipment pipe were used to build MVR rake drying experimental device. The effects of drying pressure, compression ratio, speed of rake shaft, superheat, initial moisture content of material and filling ratio on COP and SMER were studied. The results show that, in the range of experimental conditions, choosing proper low drying pressure, proper compression ratio, moderate rotating shaft rate and controlling steam superheat are all beneficial to improve the operation efficiency of the system. The cop of water and sodium carbonate solution was 4. 4 and 2. 4 kg/(kW / h, respectively, and that of sodium carbonate solution was 3. 1 7. 3 and 1. 2. 8 kg/(kW / h respectively. The energy saving effect is obviously superior to the traditional rake dryer. The results are useful for the application of MVR rake drying system.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.892

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