旋流闪蒸干燥过程特性的理论及实验研究

发布时间：2018-03-06 04:39

本文选题：闪蒸干燥　切入点：气固两相流　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：旋流闪蒸干燥机是集打散、干燥、收集于一体的气流干燥设备,但其能耗问题一直没有得到很好的解决,因此开展基于数值模拟和实验的闪蒸干燥流场、物料干燥特性的研究,对闪蒸干燥工艺优化、节能降耗及设备改进将具有一定的参考价值。本文成功设计出旋流闪蒸干燥机实验平台,并以之为研究对象。一方面,建立闪蒸干燥数学模型,并借助Fluent软件对其进行气固两相流数值模拟;另一方面,利用旋流闪蒸干燥机实验平台,研究了不同热风进口速度、热风温度、叶片转速等诸多工况下,热风温度分布、物料出口含水量等方面的变化规律,深入探究了干燥区域传热传质机理。得到如下研究成果和结论:(1)在数值模拟方面,连续相压降主要分布在旋流外筒段、环形缝隙段以及干燥筒体段,其中环形缝隙单位长度压降损失最大,达到了3.61Pa/mm;通过对颗粒相轨迹线进行稳态数值模拟分析,得出颗粒停留时间=0.29s;提出采用Multicomponent方式对离散相进行非稳态DPM模拟,得到了颗粒干燥特性曲线。通过改变不同操作参数,深入分析了旋流闪蒸干燥过程。(2)在实验研究方面,将实验结果与模拟结果进行对比分析,发现热量散失、物料组分的混合形式以及打散装置是二者存在一定差别的主要原因,具体结果和差别如下:1)在热风温度随筒体高度变化曲线中,模拟值较实验值存在一定差别,T=400K工况,风温最大差别发生在h=440mm处,温度相差11.3K;2)物料出口含水量随热风温度的升高减小较为明显,T=340K时,物料出口干基含水量的模拟值为8.3%,而实验值为5.4%;3)在物料出口含水量随速度变化曲线中,均存在含水量拐点,在T=400K工况下,(v=22m/s,X=2.88%)为实验值拐点;4)叶片转速相对其他因素,对物料出口含水量影响较小。(3)经过模拟和实验对比,模拟结果和实验结果趋势性符合较好,但具体数值上有一定偏差,因此本文建立的理论模型可以作为一种研究闪蒸干燥过程特性的辅助手段之一。
[Abstract]:The swirl flash dryer is a kind of airflow drying equipment which integrates dispersion, drying and collection, but its energy consumption has not been solved very well. Therefore, the flow field and material drying characteristics of flash drying based on numerical simulation and experiment are studied. It will have some reference value for optimizing the flash drying process, saving energy and reducing consumption and improving the equipment. In this paper, the experimental platform of swirl flash dryer is designed successfully, and taking it as the research object. On the one hand, the mathematical model of flash drying is established. The numerical simulation of gas-solid two-phase flow is carried out with the help of Fluent software. On the other hand, the distribution of hot air temperature under different conditions, such as inlet velocity, hot air temperature, blade speed and so on, is studied by using the experimental platform of swirl flash dryer. The mechanism of heat and mass transfer in drying region is studied in detail. The results and conclusions are as follows: in numerical simulation, the pressure drop of continuous phase mainly distributes in the outer cylinder of swirl flow. The pressure drop per unit length of the annular slot is the largest, which reaches 3.61 Pa / mm.Through the steady state numerical simulation of the trajectory of the particle phase, the pressure drop of the annular slot and the drying cylinder is analyzed. The particle residence time (RTD) is 0.29 s, and the unsteady DPM simulation of discrete phase by Multicomponent is proposed, and the drying characteristic curve of particle is obtained. By changing different operating parameters, the drying process of swirl flash drying is deeply analyzed. By comparing the experimental results with the simulation results, it is found that the heat loss, the mixing form of the material components and the dispersing device are the main reasons for the difference between the two. The specific results and differences are as follows: (1) in the curve of the variation of hot air temperature with the height of the cylinder, there is a certain difference between the simulated value and the experimental value, and the maximum difference of the wind temperature occurs at 440 mm, When the water content at outlet of material decreases obviously with the increase of hot air temperature, the simulated value of moisture content in dry base of material outlet is 8.3, while the experimental value is 5.4%) there are inflection points of water content in the curve of changing water content of material outlet with velocity. Under the operating condition of TX 400K, the speed of the blade is less affected by the rotating speed of the blade than other factors, and the simulation results are in good agreement with the experimental results, but there is a certain deviation in the specific value, compared with the experimental results, after the simulation and the experiment, the simulation results are in good agreement with the experimental results, which is the inflection point of the experimental value. (4) the speed of the blade has a small effect on the water content of the material outlet. Therefore, the theoretical model established in this paper can be used as an auxiliary means to study the characteristics of flash drying process.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.892

【引证文献】