Immersion Drying of Wheat Using Al-PILC, Zeolite, Clay, and Sand as Particulate Media

Wheat (Triticum durum) was dried by immersion in a particulate medium grain dryer using natural clay, pillared aluminum clay (Al-PILC), zeolite 13X, and sand as particulate medium at different initial bed temperatures and residence times in the dryer. Results showed that zeolite caused the highest grain moisture loss for a given drying time, followed by Al-PILC, natural clay, and, finally, the sand. The drying capacity of the Al-PILC was similar to that of the zeolite. The Al-PILC transferred an amount of heat equivalent to 85-94% of the heat transferred by zeolite and evaporated 83-93% of the moisture removed by zeolite. Results also showed that the zeolite and the Al-PILC had the best heat and mass transfer properties of the four particulate materials used and that the Al-PILC can be used as an alternative of the zeolite in particulate medium immersion grain drying.     

Heating/Drying Using Particulate Medium : A Review Part I. General and Heat transfer parameters

This paper presents an Overview of particulate medium drying and heat treating of cereal grains. While the conventional air drying of grains is well documented, studies on the drying of grains using heated granular medium do not appear to exist. The scientific study of the different aspects of drying with a heated granular medium began in the early 1970's. Progress on the utilization of particle-to-particle heat transfer was slow as evidenced by the fact that there is no commercial dryer using the method as of today.

The first section of this paper deals with conduction heating and how it led to the use of granular medium in heating the grain. Starting with the earliest work on conduction heating reported by Kelly ( 1939), the developments in the heating of grain using granular media is discussed. For decades since Kelly's report, work in the subject area dealt mostly with the theoretical aspects of solid-to-solid heat transfer. Thus, in the succeeding section of the paper, heat transfer parameters and mechanisms involved in the process are thoroughly investigated.     

Heating/Drying Using Particulate Medium : A Review Part I. General and Heat transfer parameters

ABSTRACT

This paper presents an Overview of particulate medium drying and heat treating of cereal grains. While the conventional air drying of grains is well documented, studies on the drying of grains using heated granular medium do not appear to exist. The scientific study of the different aspects of drying with a heated granular medium began in the early 1970's. Progress on the utilization of particle-to-particle heat transfer was slow as evidenced by the fact that there is no commercial dryer using the method as of today.

The first section of this paper deals with conduction heating and how it led to the use of granular medium in heating the grain. Starting with the earliest work on conduction heating reported by Kelly ( 1939), the developments in the heating of grain using granular media is discussed. For decades since Kelly's report, work in the subject area dealt mostly with the theoretical aspects of solid-to-solid heat transfer. Thus, in the succeeding section of the paper, heat transfer parameters and mechanisms involved in the process are thoroughly investigated.     

Heating/Drying Using Particulate Medium : A Review Part II. Equipment

This paper presentS an overview of particulate medium dryers developed to evaluate the drying of grains using heated particulate media. Components of particulate medium heating and drying equipments as well as the devices employed to conduct the materials through the machine are described. How these components accomplish the basic processes involved in conduction/particulate medium heating is also explained.

To characterize the performance of these dryers based on criteria developed for farm level dryers was not possible because of the different methods employed by researchers and the various conditions the equipment were subjected to. So in order to assess the operating characteristics of each design. the dryers were compared based on their ability to remove moisture and their thermal and drying efficiency. Comparison was made on the methods utilised by each design to accomplish heating of the medium, mixing the medium with grain, the separation of the medium from grain, and the means of recirculating the medium.

Several studies conducted to evaluate the different parameters which influence drying using heated particulates are discussed. The granular media used in heating the grain and the corresponding types of grains used in the tests are also presented.     

Heating/Drying Using Particulate Medium : A Review Part II. Equipment

ABSTRACT

This paper presentS an overview of particulate medium dryers developed to evaluate the drying of grains using heated particulate media. Components of particulate medium heating and drying equipments as well as the devices employed to conduct the materials through the machine are described. How these components accomplish the basic processes involved in conduction/particulate medium heating is also explained.

To characterize the performance of these dryers based on criteria developed for farm level dryers was not possible because of the different methods employed by researchers and the various conditions the equipment were subjected to. So in order to assess the operating characteristics of each design. the dryers were compared based on their ability to remove moisture and their thermal and drying efficiency. Comparison was made on the methods utilised by each design to accomplish heating of the medium, mixing the medium with grain, the separation of the medium from grain, and the means of recirculating the medium.

Several studies conducted to evaluate the different parameters which influence drying using heated particulates are discussed. The granular media used in heating the grain and the corresponding types of grains used in the tests are also presented.     

玉米干燥中应力裂纹的生成、扩展、检测和预防分析

针对谷物干燥过程中产生裂纹的类型和对粮食品质的影响作了概述。以玉米为例,就干燥工艺中热风温度、湿度、干燥速率、玉米初始含水率及玉米的种类、粒度、大小形状和内部结构以及干燥机的选型、冷却、缓苏等因素对玉米产生应力裂纹的影响进行了分析;介绍了裂纹产生的机理和检测方法,提出了减少裂纹的措施,并介绍了近年来该项技术的最新进展。     

Energy Analysis on Use of Air and Superheated Steam as Drying Media

ABSTRACT

The physical properties of air and superheated steam were analysed in a range of temperature applied in paper and paperboard drying processes. On the basis of tests carried out on a pilot stand the values of energy indices for air and steam drying processes are compared. With the drying media temperature as T_m = 300°C, nozzle velocity v= 60m/s and using the Huang and Mujumdar model as well as relationships given by Chance a compartive analysis of the results has been carried out Variation of several indices in the range of temperatures 100-600°C and various nozzle velocities was studied.     

Corn,Rice, and Wheat Seed Drying by Two-Stage Concept

Corn, rice, and wheat seeds with an initial moisture content (IMC) of 20–25% wb were dried to moisture content below 18% wb at 40–80°C in a fluidized bed dryer (FBD) and spouted bed dryer (SBD) and the seeds with IMC 18% wb were dried to below 14% wb at air temperatures 18–30°C and relative humidity 60–70% by an in-store dryer (ISD). As a result, it appears that a two-stage drying concept is feasible in drying high-moisture-content seeds due to the high germination rate of dried seeds. Nonetheless, the drying temperature must be carefully selected. A drying temperature of 40°C was clearly safe for all samples, whereas more than 90% of wheat seeds still germinated after drying at 60°C in FBD. Furthermore, drying seeds with IMC 18% wb by ISD was safe under specified drying conditions.     

Comparison of Drying Characteristics and Quality of Shiitake Mushrooms (Lentinus edodes) Using Different Drying Methods

The objective of this study was to compare the drying characteristics and the quality of dried Shiitake mushroom (Lentinus edodes) cubes obtained by hot-air drying (HAD), intermediate-infrared drying (IIRD), and vacuum microwave spouted-bed drying (VMSD). Several quality parameters of products, including color, texture, and rehydration capacity, were investigated. Compared to IIRD and VMSD, HAD turn out to be the most undesirable method due to its longer drying time and poor product quality. With similar rehydration capacity, the color of the VMSD product was closest to the original material. In terms of texture, total sugar content, and sensory evaluation, the VMSD product has the best quality.     

Granulation and Drying of Modified Clay Incorporated Pesticide Formulation

The extensive use of chemicals in agriculture, in particular herbicides, is a serious environmental concern. There is an urgent need to develop smart herbicide formulations that combine both optimum bioactivity and minimum dosages. In the current article, an attempt has been made to design the formulation based on one of the most widely used herbicide, Atrazine (AT). This potent herbicide along with “China clay” as the carrier and suitable clay modifiers can be thought as one of the potential way of formulation keeping in view the desired dosage and bioavailability of the same. The China clay was subjected to modification using a surfactant blend of alpha olefinic sulphonate (AOS) and alkyl polyglucosides (APG). The intercalation of the surfactant into the clay was confirmed by XRD and FTIR and the morphology was studied by SEM. The process of granule formulation and the drying was carried out using rapid mix granulator and the fluidized-bed dryer, respectively, at the desired conditions of temperature and relative humidity. These granules were then compared on the basis of key parameters such as dissolution rate, dispersion stability, and other physical properties such as bulk density, angle of repose, and particle size distribution. The study reveals the desired effect of clay modifications on the granules in terms of above-mentioned quality parameters.     

Drying Characteristics and Quality of Restructured Wild Cabbage Chips Processed Using Different Drying Methods

The drying characteristics of restructured wild cabbage chips dried using microwave vacuum (MVD), hot air (AD), and microwave freeze drying (MFD) were compared. Some of the key quality parameters of restructured wild cabbage chips such as fracturability and color and sensory characteristics were measured. Results showed that the drying time was reduced with the increase of microwave power (MVD/MFD) and in the case of air drying by the temperature (AD). Drying time was the shortest in the MVD process. Optimal quality of dried chips was obtained with the MFD process at a microwave power level 2.0 W/g.     

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。     

Simultaneous Drying and Modification of Properties of Starch Using Vacuum Microwave Treatment

The prospect of modifying starch properties while drying was investigated. Potato starch (18% moisture, dry basis) was vacuum microwave treated for different durations (60 to 600 s) with power ratings of 600, 1,000, and 1,500 W at a reduced pressure of 5,000 Pa (absolute). The drying rate was observed to be partially constant but was accompanied by a curious rise in sample temperature. Under a polarized light microscope, reduction in granule size was noticed, which was confirmed from the bulk density measurements, and this shrinkage may be explained by the loss of constituent water. Water absorption capacity of the treated starch samples was further studied at 55°C. The results showed a sudden increase in the capacity, indicating a reduction in gelatinization temperature of starch. This may be attributed to the change in nature of starch from crystalline to amorphous as shown by X-ray diffractograms and to the cracks developed on the granule surface during treatment seen in the scanning electron microscope images. This modified starch can serve well in the paper and food industry.     

干燥机单位热耗和干燥能力折算的研究

热耗和生产能力是粮食干燥机试验的重要指标,但是由于试验时环境条件、粮食条件和干燥介质条件的多变性,试验结果往往没有可比性,因此必须将干燥机的性能试验数据折算到一个公认的标准条件才能进行比较和标定。本文以粮食干燥机的试验数据为基础,参考国内外粮食干燥机试验标准,对粮食干燥单位热耗和生产能力折算系数进行了研究和探索;总结了四种折算方法,分析了粮食干燥机在不同的环境和谷物条件下折算系数的计算方法和步骤,阐述了各种方法的优缺点,提出了折算方法的初步的建议,为干燥机试验数据的可比性和完善干燥机试验标准提供了依据。     

Performance of Single and Multi-stage Spouted Bed Drying Systems

ABSTRACT

A mathematical model is developed to predict the performance of single-stage and multi-stage drying systems using spouted beds. The model uses unsteady state analysis for batch operation to simulate the steady state operation of a continuously fed spouted bed. A parametric study is carried out to study the effect of the following parameters on the performance of a single-stage grain drying system: air flow rate per unit mass of the grain in the bed, ambient air temperature and humidity, initial and target moisture contents, the residence time in the bed, and the effectiveness of the heat exchanger to recover the thermal energy in the exhaust air. The parametric study is also extended to investigate the effect of these parameters (except ambient air temperature and humidity) on the performance of the multi-stage system. In addition, the number of stages is also included in the latter study. The results are presented in terms of charts which may be adopted for the design of such systems.     

Microwave,Vacuum, and Air Drying Characteristics of Collard Leaves

Collard leaves (Brassica oleracea L. var. acephala) with an initial moisture content of 6.65 on percentage dry basis (%db) were dried by three different drying methods: microwave, air, and vacuum. Samples of fresh leaves, 25 g each, were dried until their moisture was down to 0.1 on a dry basis. The following drying levels were used in each of the drying processes: 350, 500, 650, 750, 850, and 1000 W for microwave drying; 50, 75, 100, 125, 150, and 175°C for air drying; and 0.4, 50, and 100 mmHg at 50 and 75°C for vacuum drying, respectively. Drying times ranged between 2.5 to 7.5 min, 8 to 210 min, and 35 to 195 min for microwave, air, and vacuum drying, respectively. The data obtained compared well with a thin-layer drying model. Microwave drying at 750 W provided optimal results with respect to drying time, color, and ascorbic acid content (vitamin C).     

砂率对再生混凝土强度及干燥收缩性能影响

试验以不同砂率为变量,研究了100％再生粗骨料取代率C30再生混凝土的强度及干燥收缩性能,并与普通混凝土试件进行对比.试验结果表明,在相同配比条件下随着砂率的增加,新拌混凝土坍落度值有所降低,含气量有所加大,100％再生粗骨料混凝土与普通混凝土的抗压强度趋于平稳,变化不大;100％再生粗骨料混凝土与普通混凝土对比强度略有降低;在相同配比条件下随着砂率的增加,100％再生粗骨料混凝土与普通混凝土的干燥收缩长度变化率都略有增加,120 d后趋于平稳,180 d混凝土的干燥收缩长度变化率与砂率呈良好的线性关系.     

An Experimental and Modeling Investigation on Drying of Ragi (Eleusine corocana) in Fluidized Bed

Experimental investigation on drying of ragi (Eleusine corocana) in a fluidized bed has been attempted covering the operating parameters such as temperature, flow rate of the drying medium, and solids holdup. The drying rate was found to increase significantly with increase in temperature and marginally with flow rate of the heating medium and to decrease with increase in solids holdup. The duration of constant rate period was found to be insignificant, considering the total duration of drying and the entire drying period was considered to follow falling rate period. The drying rate was compared with various simple exponential time decay models and the model parameters were evaluated. The Page model was found to match the experimental data very closely with the maximum root mean square of error (RMSE) less than 2.5%. The experimental data were also modeled using Fick's diffusion equation and the effective diffusivity coefficients were estimated. The effective diffusion coefficient was found to be within 5.7 to 14 × 10^-11 m²/s for the range of experimental data covered in the present study with RMSE less than 5%.