颗粒表面料层干燥过程的数值模拟

建立单颗粒表面料层干燥的物理及数学模型,并将方程组无因次化,采用全隐法对该无因次模型方程进行求解,从而分析惰性载体的直径、薄层物料厚度、薄层物料孔隙分布标准方差、均值、干燥气体温度、流速对干燥时间的影响.     

粒状复合肥薄层干燥过程的试验研究

通过实验 ,对复合肥的干燥过程进行研究 ,分析干燥风温和复合肥颗粒大小对干燥速率的影响 ,并对以上 2因素分别进行拟和 ,得出多因素的薄层干燥的半经验公式。     

片状物料滚筒干燥试验研究

针对片状物料玫瑰花瓣滚筒干燥过程中主要干燥介质温度、湿度和滚筒结构及转速等因素的影响,通过试验,结合滚筒干燥过程中物料动力学分析,考察不同干燥温度(60℃、70℃、80℃)下,滚筒内物料含水率、质量、形态、干燥速率、滚筒内部湿度等方面的变化。试验结果表明,片状物料在滚筒干燥过程中,较高的干燥温度不仅有利于缩短干燥时间,而且也有利于提高干燥品质。     

小颗粒“胶乳法”氯化天然橡胶穿透干燥试验

通过氯化天然橡胶(CNR)的穿透干燥试验,探讨风温、风速以及粒径对“胶乳法”CNR干燥速率的影响规律,结果表明,温度和风速对含水量的下降速率影响较大,而粒度对其影响较小。建立了穿透干燥方程,对实验数据进行了拟合,结果显示其吻合性较好。红外光谱分析以及物理性能测试结果表明,“胶乳法”CNR物料的干燥温度应控制在100℃以下。     

氢氧化铝薄层干燥的节能方法探讨

氢氧化铝的洞道式薄层干燥在生产中有重要应用，但要消耗大量的能量。对氢氧化铝的干燥的基础特性进行了研究，并着重探讨了变温干燥的节能方法。试验结果表明：氢氧化铝的洞道式薄层干燥主要由水分内部迁移控制，强化其干燥速率应着重从改善物料状况着手；并采用冷热风交替的干燥方法将取得较好的节能效果。这些工作对改进生产中的氢氧化铝的干燥方法具有一定的指导意义。     

过热蒸汽间歇干燥酒精糟研究

以高湿物料酒精糟为研究对象,进行了过热蒸汽间歇干燥实验研究。利用自行设计的间歇干燥实验台,酒精糟的初始含水质量分数为66.7%,研究了不同实验条件对干燥速率的影响。结果表明:随着干燥介质温度的升高,干燥速率明显加快;被烘物料质量越少,烘干时间越短;随着物料颗粒直径的减小,恒速段的干燥速率基本不变,而降速段的干燥速率明显增加;过热蒸汽质量流量越大,干燥速率越高。因此随着蒸汽过热度的升高、质量流量的增大,过热蒸汽干燥速率加快,干燥效率越高;随着进料质量的增加、颗粒直径的增大,过热蒸汽干燥速率却有所降低。     

城市污泥热风与微波干化特性研究

采用热风和微波加热两种方式对城市污泥进行薄层干化实验研究,分别考察污泥薄层厚度和其他操作条件对污泥干燥特性及能耗的影响。研究发现:在热风干燥过程中,由于污泥的塑性,污泥表面容易结壳,从而严重阻碍了水分向外迁移,使得干燥速率呈阶梯状下降。微波干燥污泥具有时间短、干燥速率大,同时节省能源。     

响应曲面法优化硫酸铵微波干燥工艺

对微波干燥硫酸铵的新工艺进行研究,探讨了干燥温度、微波干燥时间、物料质量、物料厚度等因素对硫酸铵相对脱水率的影响.并在单因素实验的基础上,以硫酸铵的相对脱水率为响应值采用响应曲面中心组合设计,对硫酸铵的微波干燥工艺参数进行了优化.所获得的优化实验条件:干燥温度86.05℃,微波干燥时间190.50 s,物料质量102....     

城市污泥与木屑混合薄层干燥实验及动力学分析

角度研究了比,添加木通过对纯污泥和添加木屑的污泥进行薄层干燥对比实验,分别从混合比例、薄层厚度、干燥温度、风速木屑添加对污泥干燥特性的影响,并引入薄层模型对其干燥过程进行模拟。结果表明：与纯污泥干燥相屑后污泥干燥速率明显加快,且木屑添加比例越大、薄层越薄、干燥温度越高干燥速率越快,风速对干燥速率的影响不大;Wang—singh模型能很好的描述两种污泥薄层干燥,利用费克第二扩散定律导出的无限平板公式求出纯污泥和添加木屑的污泥在温度120℃～170℃时的有效扩散系数分别为6．13×10-6m／s～1．11×10-5m／s、1．07×10-5m／s～1．67×10-5m／s;由阿伦尼乌斯方程分别求得活化能为Es=16．67kJ／mol、Es=12．97kJ／mol。     

硫酸铵微波干燥特性及动力学模型分析

采用微波干燥技术进行了硫酸铵干燥的研究.通过系统实验分析了硫酸铵微波干燥特性,并采用薄层干燥模型进行数值分析.结果表明:修正Page模型(Ⅱ)较之其他模型更适于薄层硫酸铵微波干燥的模拟.应用Fick第二定律得到微波功率230-700 W,物料质量150-300 g条件下薄层硫酸铵微波干燥的有效扩散系数的变化范围分别为:...     

Effects of freezing pretreatment and hygroscopicity of fluidizing particles on drying characteristics of carrots in fluidized bed under reduced pressure

Abstract

A method for low-temperature drying with high drying rate was developed for heat-sensitive foods and agricultural products. A freezing pretreatment was combined with fluidized bed drying under reduced pressure. Cylindrical carrot samples were frozen and then placed without thawing in a fluidized bed of hygroscopic porous silica gel particles that adsorbed water from the sample during the drying process. The effects of the freezing pretreatment and hygroscopicity of fluidizing particles on the drying characteristics of carrots were examined. A higher drying rate was achieved when carrots samples were subjected to freezing pretreatment than without it. At 12?kPa, the volume change was smaller in carrots subjected to freezing pretreatment than in untreated samples. A larger amount of water was absorbed during rehydration by carrots dried at 12?kPa than at 101?kPa within 120?min. The properties of dried carrots were affected not only by freezing pretreatment but also by the pressure applied during the drying process.     

Effect of hysteresis phenomena of cellular plant-based food materials on convection drying kinetics

Water removal rate during drying depends on the microstructural pathways of water migration from inside the food materials. The water removal rate also depends on the mechanical properties of plant tissue. There is no literature that shows the interrelationship between viscoelastic property and transport phenomena during drying. In this study, the influence of viscoelastic property of plant-based food material on transport phenomena during drying has been experimentally investigated. Granny Smith apple, pears, and beet root has been taken as the sample in this study. A 2?kN Instron universal testing machine and ImageJ software were used in order to measure and analyze the viscoelasticity of the samples. Three different fruits Granny Smith apple, pears, and beet root show different viscoelastic properties along with different energy loss due to hysteresis. A positive relationship was found between energy loss due to viscoelastic nature of materials and drying kinetics. This correlation can be explained by the nature of the cell wall stiffness that facilitates or hinders the water migration in mechanical and thermal energy applications.     

微波干燥玉米籽粒的试验研究

针对玉米热风干燥中存在的问题。运用自制的微波干燥试验设备。采用不同的质量比功率和加热时间及配套的工艺流程。研究了玉米微波干燥特性及干燥条件对干燥品质、能耗的影响；分析了微渡干燥玉米过程中单位质量功耗、温度、平均失水速率与玉米籽粒发芽率、爆腰率和淀粉得率的关系；确定了影响微波干燥玉米的工艺参数和玉米微波干燥的合理工艺流程。研究结果表明：玉米微波干燥主要处于恒率干燥阶段，应用微波技术既能快速而经济地对玉米籽粒进行干燥，又能保持其种用价值，且有利于改善其品质。     

Considerations on Drying Frozen Spruce Wood and Effects upon Its Properties

The aricle presents the results of a research performed in order to establish whether drying lumber from frozen state (in winter) has repercussions upon its properties, compared to drying under the same conditions lumber parts originating from the same log and position within the log section but that were not frozen prior to drying. To this purpose, spruce (Picea abies L.) lumber specimens, 35 mm and 55 mm thick, cut from the same log, half frozen at - 30°C and half unfrozen, were dried under the same conditions in a climate chamber. Some mechanical properties (hardness, bending strength, and modulus elasticity in static bending), as well as workability (expressed by means of the absorbed power and specific resistance to cutting during milling), were determined The results revealed slight differences between the frozen and the unfrozen samples both during the drying process and afterwards. It was noticed that a significant amount of water was removed from wood during the very beginning of the heating phase (thawing). With regards to wood properties after drying, a slight lowering of the mechanical properties and better workability could be established for the initially frozen samples.     

A Model to Simulate Chopped Alfalfa Drying in a Fixed Deep Bed

A model to simulate the drying process of chopped alfalfa is presented. The drying profile of a fixed bed dryer has been simulated through a system of five partial and ordinary differential equations, which describe the changes of the physical properties of the product, as well as the thermodynamic data of the drying air. The equations were solved using the thin-layer drying theory. In order to check the accuracy of the model, the drying rate curves at various depths of four deep-bed batches were calculated and the results were compared with experimental measurements, under the same conditions. The proposed model predicts accurately the drying rate of chopped alfalfa under a wide range of drying air conditions, and thus, the drying profile of the batch can be determined at any time.     

超临界C02干燥法工艺条件对氧化锆气凝胶结构性质的影响

以无机盐ZrOCl2·8H2O为原料,采用溶胶-凝胶过程结合超临界CO2干燥法制备了ZrO2气凝胶.采用BET、TG/DTA、XRD、TEM以及SEM等手段对样品进行了表征分析.考察了超临界CO2干燥过程中,操作压力、操作温度、CO2流率及干燥时间等工艺条件对样品比表面积、孔性质等的影响.结果表明利用本方法制备的ZrO...     

Effects of Salting and Drying on Shark (Carcharhinus sorrah) Meat Quality Characteristics

The effect of drying method and pretreatment with salt on the properties of shark meat was investigated. Water loss during the salting step was faster with dry salting than with brine salting; however, both methods led to the same final water content at the end of the drying process. Moisture desorption isotherms showed that addition of salt prior to sun or air drying resulted in lower equilibrium moisture contents at the same water activity levels. Salting and method of drying had significant effects on the microbial load. Osmo-air-dried samples showed better microbial quality than samples treated by other methods. Molds grew on all samples after two months of storage at room temperature. Color and rehydration ratio were affected by the drying method. Higher dehydration ratios were obtained with air drying.     

Experimental study on the effects of drying methods on the stabilities of lignite

The drying processes are always applied prior to the transportation or utilization of lignite, and result in notable changes in the stabilities of lignite. In this paper, the study on the effects of nitrogen and MTE drying process on the physico-chemical properties and stabilities of Zhaotong lignite was carried out. The briquettes produced by MTE drying in this study were 150 mm in dimension, and so had a much larger particle size than nitrogendried samples. Nitrogen adsorption, mercury intrusion porosimetry and scanning electron microscopy all suggested that drying was accompanied by the transformation of larger pores into smaller ones. Compared to nitrogen drying, the pore structures could be stabilized by the MTE process. The soluble salts were removed during MTE drying which resulted in the decrease in ash and the concentrations of some of the major metals.The removal of water enhanced the hydrophilicity of nitrogen dried samples, but did not affect the hydrophilicity of MTE dried samples. The moisture holding capacity of MTE dried samples reduced faster than nitrogen dried samples with the decrease of residual moisture content. Themoisture readsorption processes of MTE dried sampleswere strongly inhibited due to themuch larger particle size of sample produced byMTE drying than nitrogen drying. The susceptibility to spontaneous combustion, indicated by cross point temperature and self-heating tests, of nitrogen and MTE dried samples increased with the decrease of residual moisture content. The MTE dried samples are more liable to spontaneous combustion than nitrogen dried samples with the same residual moisture and particle size. However, the larger particle size of the MTE product made it more stable with respect to spontaneous combustion and also moisture readsorption.     

Considerations on Drying Frozen Spruce Wood and Effects upon Its Properties

The aricle presents the results of a research performed in order to establish whether drying lumber from frozen state (in winter) has repercussions upon its properties, compared to drying under the same conditions lumber parts originating from the same log and position within the log section but that were not frozen prior to drying. To this purpose, spruce (Picea abies L.) lumber specimens, 35 mm and 55 mm thick, cut from the same log, half frozen at ? 30°C and half unfrozen, were dried under the same conditions in a climate chamber. Some mechanical properties (hardness, bending strength, and modulus elasticity in static bending), as well as workability (expressed by means of the absorbed power and specific resistance to cutting during milling), were determined The results revealed slight differences between the frozen and the unfrozen samples both during the drying process and afterwards. It was noticed that a significant amount of water was removed from wood during the very beginning of the heating phase (thawing). With regards to wood properties after drying, a slight lowering of the mechanical properties and better workability could be established for the initially frozen samples.     

Drying Operational Parameters Influence on Chicory Roots Drying and Inulin Extraction

Chicory (Cichorium intybus L.) root is the most important tuberous root for industrial production of inulin. Inulin is a fructooligosaccharide that is not digestible but is selectively utilized by bifidobacteria in the large intestine, being the prototype prebiotic. The inulin has been identified as an ingredient that substitutes fat or sugar. Considering that the chicory root is a highly perishable material, drying is an alternative for storing it for a long period of time. In this work, chicory roots samples were dried in a convective dryer with different temperatures and different air velocities. The dried samples were submitted to inulin extraction by diffusion process using hot water. The results were analysed in order to identify the influence of drying operational settings on effective diffusivity and extracted soluble solids. A response equation has been obtained for the effective diffusivity on chicory roots drying and for the extracted soluble solids on inulin extraction process from dried chicory root.