【作者】 张忠杰；

【导师】 毛志怀；

【作者基本信息】 中国农业大学 ， 农产品加工及贮藏工程， 2003， 博士

【摘要】 压力喷雾干燥装置是利用压力雾化装置将原料液分散成细小雾滴，并与热介质在干燥塔内充分进行热量、质量交换，最终达到干燥产品的目的。干燥产品可以根据需要生产成细粉状、颗粒状、空心球状或团聚状。压力喷雾干燥装置其雾化器的结构适用易调，可通过改变喷嘴的内部结构得到所需要的喷液量和雾滴尺寸，目前该型式干燥机已推广应用于食品、化工、医药、建材、环保等行业。作为能源消耗的大户之一的喷雾干燥，如何在保证干燥产品质量的前提下，进一步提高能源利用率，提高干燥塔的体积蒸发强度；减少环境污染，降低运行成本；加强系统的自动化程度以提高劳动生产率；在提高产品质量的同时减小设备尺寸，减少固定投资等都具有重要的研究和应用价值。本文总结了国内外在压力喷雾干燥装置的研究应用状况，并分析了现有喷雾干燥装置设计方面的优缺点，运用流体力学、空气动力学、传热传质学、机械设计和计算机技术等多学科知识，综合研究了传统压力喷雾干燥系统的单喷嘴雾化装置在并流、逆流以及混流干燥中的应用和喷雾干燥塔的不同布风装置以及出风装置的设置情况等，提出了新型旋流式组合压力喷雾干燥技术并对此进行了研究，其主要内容包括： （1） 本文创造性地设计出旋流式组合压力喷嘴的基本结构，并通过对料液的物化特性研究分析以及颗粒度的分布要求，给出了喷嘴的不同结构设计参数。 （2） 对旋流式组合压力喷嘴喷射雾化机理加以分析，建立了旋流式喷嘴雾化的数学模型，采用冷态试验法并借助激光雾滴测试等实验装置对喷嘴的雾化参数（如雾化压力、喷液量、料液温度、雾化角、雾距、雾滴直径和分布以及喷嘴的空芯半径等）进行测量和计算。针对几种不同物化特性的物料，并利用CFD技术模拟分析影响其雾化的关键参数，通过调整喷嘴的结构参数和喷射条件，优化了该型式喷嘴的雾化性能。 （3） 采用κ-ε模型实现了压力喷雾干燥塔的温度场、湿度场、流场的理论建模，利用计算流体力学（CFD）技术来解决喷雾干燥过程中热介质与雾滴间的传热传质以及动量传递和湍流扰动等问题，避免了干燥过程中的设计不合理状况；通过增加双格栅均风装置和旋转出风装置，改善了干燥塔内的热质传递，提高了干燥塔的体积蒸发强度。 （4） 采用旋流式组合压力喷嘴雾化后的液滴直径大都分布在30～150um之间，雾滴分布范围较窄，其雾化的平均液滴直径在50～100um左右，压力喷嘴的雾化角度可在150°～180°范围内。因雾滴的脱水时间与其直径的平方成正比，减小液滴直径有利于缩短干燥脱水时间，可有效降低干燥塔的高度；由于旋流式组合压力喷嘴雾化滴径的减小，脱水速度明显加快，在不影响干燥物料性质的前提下，适当提高进风温度，同时有效地降低排气温度，有利于提高干燥塔的蒸发强度，也有利于提高干燥设备的平均能源利用率。 （5） 本文创造性地设计了新型的双格栅均风装置并设置在压力喷雾干燥塔的上部，强化了干燥塔内气、液两相间的混合，最大限度地消除了干燥塔内的无效区域，对热敏性物料的干燥更显出该结构型式的优越性。 应用结果表明：采用新型的旋流式压力喷雾干燥塔的体积蒸发强度可达12kgH₂O／m³·h，能源利用率可达60％，既提高了产品的质量和产量，又降低了设备投资和土建规模。压力喷雾干燥塔的高度比常规压力式喷雾干燥塔高度降低1/3，总投资要节省1／3以上，具有较高的应用推广价值。更多还原

【Abstract】 The dried powder product was formed in the spray dryer by pressure nozzle which atomized liquid into small droplets and heat and mass transferring was performed between droplets and hot medium in the drying chamber. This type of dryer was fitful for liquid drying in concurrent, counter-current or mixed air-flow. The dryer can produce powders, granules, hollow spherical particles and agglomerates products. The spraying capacity and particle size were changed by altering the parts assembled in the nozzle. Pressure spray dryers have been widely used in foodstuff, chemicals, medicaments, building materials, environmental protection, etc. As one of the most energy consumption, it is quite valuable to study how to make the spray dryer save energy consumption, enhance volumetric evaporation intensity, decrease its environmental pollution and running cost, improve its productivity through automatic controlling system and cut down the investment on equipment. In this dissertation, the author summed up the muti-technique in fluid dynamics, heat and mass transferring, mechanical designing and computational technique and studied the conventional pressure spray dryers with different air disperse structure and outlet equipment, at last put forward the theme i.e. the study on combined spin-flow pressure spray drying technology, the main contents were as follows:(1) The combined spin-flow pressure nozzle was designed whose novel structure has no report at present, and the structural designing parameters were obtained through analyzing the physical characteristic of materials and distribution of particles.(2) Base on the analysis of the atomizing principles of spray nozzle, mathematical model of combined spin-flow pressure spray drying was set up and the essential parameters such as spraying pressure, liquid quantity, temperature, spraying angle, inject distance, particle diameter and distribution, hollow diameter for several materials in normal conditions by experiment and LDV. The key items influent on the characteristics of spraying have been also studied in the dissertation, we can get a good spraying result by adjusting the related parameters efficiently.(3) The theoretical model of the dynamical parameters such as temperature, moisture, pressure and contour for hot medium and particle inside the drying chamber were obtained by model, utilized the Computational Fluid Dynamics technique to solve the problem between spraying droplets medium by arranging the double grid dispersing structure and rotary outlet structure and the developed structure improved the drying efficiency and product quality.(4) The droplets diameter of the combined spin-flow pressure spray drying are between 30um and 150um and the ranges of the droplets are narrow. The average diameter of the droplets is between 50 um and 100 um and the spraying angle can be adjusted from 30 to 180 . The dehydration time is square of the droplets diameter so the small diameters of the droplets can cut down the drying time then reduce the height of the drying chamber. To the combined spin-flow pressure spray drying, the diameters of droplets are small and the dehydration rate is higher so keeping the qualities of the dried products we can increase the speed of the inlet wind and reduce the temperature of the outlet wind thus can improve the evaporation intensity of the drying chamber and the average energy utilization of the drying equipment.A novel type double grid dispersing structure is designed and set on the top of the drying chamberwhich increase the mingling degree of the liquid with the gas and reducing the invalid area of the drying chamber. The combined spin-flow pressure spray drying equipment has more superiority to the thermal sensitive material.The preliminary results obtained from the industrial production showed that the volumetric evaporation intensity and energy consumption efficiency would be up to 12kgH2O/m3.h and 60% respectively to use the combined spin-flow pressure spray dryer. Moreover, the combined spin-flow更多还原