DRYING EXPERIMENTS WITH ALO(OH) SUSPENSION OF HIGH PURITY AND FINE PARTICULATE SIZE TO DESIGN AN INDUSTRIAL SCALE DRYER

ABSTRACT

AIO(OH) suspension of high purity and fine particle size was dried in a Mechanically Spouted Bed (MSB) dryer with inert particles. During drying the maximum required moisture content and the mean particle size of the dried product had to be taken into consideration. Also another important aspect was to avoid contamination of the dried solid with metals. PTFE cylinders of 8 mm in diameter and of 8 mm in height were used as inert particles, and also the whole dryer itself was coated with teflon. As a result of the drying experiments the optimum values of the process parameters were used for scaling-up. The specific rate of evaporation in the drying zone of the inert bed was the basis of the calculations. The suspension with capacity of 125 kg/h was successfully dried in the designed industrial scale MSB dryer with inert panicles and the required quality of the material was produced.     

THE DESIGN AND OPTIMIZATION OF AN INDUSTRIAL DRYER FOR SULTANA RAISINS

A mathematical model of a tunnel dryer for sultana grapes is presented and applied for the determination of size and optimal operating conditions of the dryer. The optimum condition is given by the minimization of heat consumption, expressed as the ratio of thermal load to production, with some constraints regarding the production rate of the dryer and the maximum permissible air temperature. The optimization variables are temperature and humidity of the drying air, and product loading thickness on the trays. The optimum condition requires the operation of the dryer on the maximum permissible air humidity, which corresponds to a high degree of recirculation of exhaust air. This can be accomplished using automatic control of fresh air and humid air inlet and exhaust dampers along the length of the dryer, during the entire drying cycle.     

THE DESIGN AND OPTIMIZATION OF AN INDUSTRIAL DRYER FOR SULTANA RAISINS

A mathematical model of a tunnel dryer for sultana grapes is presented and applied for the determination of size and optimal operating conditions of the dryer. The optimum condition is given by the minimization of heat consumption, expressed as the ratio of thermal load to production, with some constraints regarding the production rate of the dryer and the maximum permissible air temperature. The optimization variables are temperature and humidity of the drying air, and product loading thickness on the trays. The optimum condition requires the operation of the dryer on the maximum permissible air humidity, which corresponds to a high degree of recirculation of exhaust air. This can be accomplished using automatic control of fresh air and humid air inlet and exhaust dampers along the length of the dryer, during the entire drying cycle.     

高纯度表没食子儿茶素没食子酸酯（EGCG）的分离与制备

绿茶的乙醇浸提液经过浓缩、脱色和萃取，得到茶多酚粗品。用葡聚糖凝胶ＬＨ－２０层析柱和制备型ＨＰＬＣ分离提纯儿茶素组分ＥＧＣＧ，结构鉴定结果证明所获得的ＥＧＣＧ其纯品达到色谱纯级。     

高容量高密度氢氧化亚镍的制备

研究了制备工艺参数对Ｎｉ（ＯＨ）２放电比容和堆积密度的影响并进行了理论分析，给出了最佳工艺条件范围，分析了氨的加入对Ｎｉ（ＯＨ）２堆积密度及形貌的影响采用ＸＲＤ、ＴＧ－ＤＴＡ等检测手段对样品进行分析，并与进口样品进行了比较     

振动流化床干燥装置性能研究(Ⅰ)——气体动力学、传热与干燥特性

以高粱、活性炭为实验物料,在拟工业实用设备的振动流化床中研究颗粒物料的气体动力学、传热及干燥特性,着重讨论了振动参数的作用。     

DESIGN AND TESTING OF AN AEROSOL/SHEATH INLET FOR HIGH RESOLUTION MEASUREMENTS WITH A DMA

A modified aerosol/sheath inlet was designed for a differential mobility analyzer (DMA) for high resolution measurements based on field model calculations which include fluid flow, electric field, and convective/diffusive transport. To avoid the predicted flow recirculation for the current inlet design at an aerosol-to-sheath flow ratio of 0.05, the slit width is reduced and aerodynamically shaped so that the sheath velocity and aerosol velocity more nearly match. Numerical results are presented comparing the fluid flow of the old and new inlet. Problems associated with the old inlet include: flow unsteadiness at a flow ratio of 0.025, voltage shift at the peak particle concentration as a function of the flow ratio, and the historical observation that, while performing tandem differential mobility analyzer measurements (TDMA), the voltage applied on the second DMA for the peak particle concentration is higher than that for the first. Measurements demonstrate that all these problems are reduced or eliminated with the new inlet design. The TDMA measurements include flow ratios of 0.1, 0.05, 0.025 and 0.0125 at sheath flows of 166 and 333 cm³ s^-1 (10 and 20 l min^-1). The challenge of performing measurements at these low flow ratios will be discussed including flow calibration, flow matching, and pressure monitoring. The new inlet is applied to the measurement of the National Institute of Standards and Technology 0.1 μm Standard Reference Material 1963, and it is shown that the DMA can accurately measure the standard deviation of this narrowly distributed aerosol (σ/D_p=0.02).     

NONLINEAR FINITE ELEMENT ANALYSIS OF COUPLED HEAT AND MASS TRANSFER PROBLEMS WITH AN APPLICATION TO TIMBER DRYING*

A finite element formulation and solution of a set of nonlinear coupled heat and mass transfer equations for porous capillary media is presented. The model considers temperature and moisture dependent material properties and can accomodate diffusion of moisture as either a liquid or a vapor. Application was made to drying of timber and predicted results agreed well with the experimental data.     

NONLINEAR FINITE ELEMENT ANALYSIS OF COUPLED HEAT AND MASS TRANSFER PROBLEMS WITH AN APPLICATION TO TIMBER DRYING*

A finite element formulation and solution of a set of nonlinear coupled heat and mass transfer equations for porous capillary media is presented. The model considers temperature and moisture dependent material properties and can accomodate diffusion of moisture as either a liquid or a vapor. Application was made to drying of timber and predicted results agreed well with the experimental data.     

ACOUSTIC DEWATERING AND DRYING (LOW AND HIGH FREQUENCY): STATE OF THE ART REVIEW

The potential of ultrasonic energy to dry heat-sensitive materials was proven by studies conducted a number of years ago. Ultrasonic irradiation improved the rates of drying and the temperatures seldom exceeded 1 C above ambient. Recent developments in energy related areas of technology have caused a new search for more economical methods of drying.

This paper reviews both past and present literature on acoustic dewatering and drying and discusses the current state of the technology. The studies reviewed represent a broad spectrum including effects at very low sonic to ultrasonic frequencies. The fundamental aspects and applications of the technique to a variety of materials are presented.     

SINGLE-LAYER DRYING BEHAVIOR OF MEXICAN TEA LEAVES (CHENOPODIUM AMBROSIOIDES) IN A CONVECTIVE SOLAR DRYER AND MATHEMATICAL MODELING

Single-layer solar drying experiments were conducted for Mexican tea leaves (Chenopodium ambrosioides) grown in Marrakech. An indirect forced convection solar dryer was used in drying the Mexican tea leaves at different conditions such as ambient air temperature (21° to 35°C), drying air temperature (45° to 60°C) with relative humidity (29 to 53%), airflow rate (0.0277 to 0.0556 m ³/s), and solar radiation (150–920 W/m²). The experimental drying curves showed only a falling rate period. In order to select the suitable form of drying curves, 14 mathematical models were applied to the experimental data and compared according to their statistical parameters. The main factor in controlling the drying rate was found to be the temperature. The drying rate equation was determined empirically from the characteristic drying curve. The diffusion coefficient of the Chenopodium ambrosioides leaves was estimated and varied between 1.0209 × 10^?9 and 1.0440 × 10^?8 m ²·s^?1.The activation energy was found to be 89.1486 kJ·mol^?1.     

钻石对顶砧（Diamond Anvil Cell,DAC）高压产生技术及在高压条件下的光物理和光化学研究

高压作为一个重要的物理参量引入到科学研究的各个领域将会大大扩展研究的范围，本文介绍了一种简单安全的产生高压的技术和在高压条件下进行的一些光物理和光化学研究工作，并指今后在高压光物理和光化学研究领域的若干重要研究方向。     

直接凝胶凝固成型SiC(M,Y)-Al_2O_3复合陶瓷材料的研究(Ⅰ)稳定的低粘度高固相含量悬浮体的制备

本文研究了复相SiC(M ,Y) -Al2 O3系稳定的高固相含量的低粘度悬浮体的流变特性 ,找出了影响流变性的主要因素。在碱性条件下 ,用实验室合成的PMAA -NH4 和CM作为复合分散剂以及引入有机单体制备出固相含量高达 62 (vol) % ,粘度 2 4 5mPa.s的SiC(M ,Y) -Al2 O3浓悬浮体     

INFLUENCE OF PARTICLE SIZE AND STRUCTURAL PROPERTIES OF SORBENTS PREPARED FROM FLY-ASH AND Ca(OH)2 ON THE SO2 REMOVAL ABILITY

Sorbents for SO₂ removal from flue gas were prepared by slurring fly ash and Ca(OH)₂. Four fractions of different particle sizes were obtained by sieving and by grinding. These fractions were characterised by determining mean diameter values, the BET specific surface area and the pore size distribution and tested in the desulfurization reaction for 5 and 60 minutes at low temperature in order to relate the particle size and structural properties of the sorbents to the desulfurization ability. Fractions obtained by sieving showed similar BET specific surface area values and pore size distribution to each other. The conversion values at both reaction times were higher for fractions with the smaller particle size. Fractions obtained by grinding exhibited different structural properties depending on the reduction procedure. These fractions with smaller mean particle sizes than those obtained by sieving, showed smaller conversion values. Results indicated that the influence of the particle size is showed only for sorbents with similar pore size distribution. A quantitative relationship between pore filling (due to the calcium sulfate formed) and conversion values has not been found.     

AUTOADHESION OF HIGH DENSITY POLYETHYLENE (HDPE) TO HDPE BY ULTRAVIOLET GRAFTING OF METHACRYLATES AND ACRYLATES

A study has been made on the effect of the presence of grafted acrylic layers on the autoadhesion of polyethylene. Methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), and butyl methacrylate (BMA) were grafted onto high density polyethylene (HDPE). The grafting reaction was faster at higher temperature and methacrylates graft more easily than acrylates. For methacrylates and acrylates, the grafted amount increases with increasing length of the pendant alkyl chain. The grafting temperature is a crucial factor affecting the adhesion of grafted PE samples. For the samples grafted at lower temperature (in a room temperature water bath), the adhesion is very low (less than 50 N/m), even for very thick grafted layers. But for the samples grafted at higher temperature, much higher adhesion can be obtained. The presence of homopolymer was another factor affecting the adhesion of PE samples. When homopolymer is removed from the surface of the grafted sample, higher adhesion can be obtained. For some samples, the highest peel strength of more than 1000 N/m has been obtained. The low adhesion of the samples grafted at low temperature is attributed to the high branching of grafted chains.     

直接凝胶凝固成型SiC（M,Y）—Al2O3复合陶瓷材料的研究（Ⅰ）稳定的低粘度高固相含量悬浮体的制备

本文研究了复相SiC(M,Y)-Al2O3系稳定的高固相含量的低粘度悬浮体的流变特性,找出了影响流变性的主要因素。在碱性条件下,用实验室合成的PMAA-NH4和CM作为复合分散剂以及引入有机单体制备出固相含量高达62(vol)%,粘度245mPa.s的SiC(M,Y)-Al2O3浓悬浮体。     

CONTRIBUTIONS OF T. K. SHERWOOD AND ASSOCIATES TO THE FIELD OF DRYING (Part 3, Final)

ABSTRACT

Any nonuniformity in local moisture content of paper which develops during drying because of locally nonuniform drying rates provides a driving force for in-plane diffusion of moisture, which in turn acts to reduce this moisture nonuniformity. As no data have appeared for the in-plane diffusivity of moisture during desorption from paper over the range of conditions existing during papermachine drying, an investigation was undertaken to obtain this information.

Moisture diffusivity was determined to he a very strong function of the extent and state of water in the sheet, increasing exponentially with paper moisture content. The presence or absence of liquid water at the sheet boundary would effect moisture difiusivity when there is water in the pores but the direction of moisture transport in paper was found to be of overriding importance. In-plane moisture diffusivity is very much greater than that in the thickness direction, indicating that the non-isotropic nature of paper structure is a key factor. A microscale view of the mechanism of moisture transport in the thickness and in-plane directions was developed, consistent with the enormous difference in effect of moisture content on diffusivity in the two directions.