Evaluation of Soybean Seedcoat Cracking During Drying:PART I. Using Drying Tests

In this study, seedcoat cracking during heated air drying was investigated in five varieties of Minnesota grown soybeans. Effects of initial moisture contents, drying temperatures and time on cracking levels were evaluated. Digital image analysis (DIA) was employed to measure initial sizes and shapes of soybeans in order to evaluate the influence of physical properties of mature seeds on cracking frequency.

Seedcoat cracking rates increased significantly with increase in initial moisture content of the soybeans. drying temperature and time. Rapid water loss at higher initial moisture contents led to greater seedcoat cracking. Variety.growing location. and sizc of soybeans had significant influence on seedcoat cracking. Statistical analysis indicates that interactions between various factors had significant influence on seedcoat cracking.     

Evaluation of Soybean Seedcoat Cracking During Drying:PART II. Using MRI

ABSTRACT

MRI techniques were developed and employed for non-destructive and noninvasive study of seedcoat cracking in low moisture soybean kernels during heated air drying. Proton density image and transient moisture distribution profile of a single soybean kernel can be obtained using MRI. These MRI techniques proved to be particularly useful for the continuous observation of initiation and propagation of seedcoat cracking during the entire period of drying process without interruption.

The proton density images of soybean kernels showed that seedcoat cracking was initiated perpendicular to the long axis of the kernel near the hilum. The transient moisture distribution profiles in soybean kernels during drying indicate that moisture gradient developed during drying was higher in the seedcoat than in the cotyledon. Drying temperature and initial average moisture content were positively correlated with the soyhean seedcoat crackig. The location of the     

Evaluation of Soybean Seedcoat Cracking During Drying:PART II. Using MRI

MRI techniques were developed and employed for non-destructive and noninvasive study of seedcoat cracking in low moisture soybean kernels during heated air drying. Proton density image and transient moisture distribution profile of a single soybean kernel can be obtained using MRI. These MRI techniques proved to be particularly useful for the continuous observation of initiation and propagation of seedcoat cracking during the entire period of drying process without interruption.

The proton density images of soybean kernels showed that seedcoat cracking was initiated perpendicular to the long axis of the kernel near the hilum. The transient moisture distribution profiles in soybean kernels during drying indicate that moisture gradient developed during drying was higher in the seedcoat than in the cotyledon. Drying temperature and initial average moisture content were positively correlated with the soyhean seedcoat crackig. The location of the     

Soybean Drying by Two-Dimensional Spouted Bed

Abstract

Urease activity, cracking, and breakage are important factors in considering the quality of raw soybean for feed meal industries. A two-dimensional spouted bed dryer was investigated to determine its capability for thermally inactivating the urease enzyme and maintaining its other qualities. The experimental results have shown that the drying kinetics of soybean in a two-dimensional spouted bed dryer are of the form described in the thin layer drying. The expression for the model parameter in Newton's law of cooling equation accounting for the moisture contents and inlet air temperatures was developed. The initial moisture content and inlet air temperature conditions cause cracks in the kernels. The strong collision between kernels and deflector because of high superficial velocity leads to high percentage of broken soybeans in the spout region. However, the velocity of 15.9 m/s can reduce the breakage below 5%. The inactivation of urease at low-to-moderate moisture content is suitably described by the first order kinetics. The modified Monod equation is applied when the moisture content is higher than 26% dry basis due to the inhibitory effect of water content on the inactivation rate. To complete urease inactivation and maintain protein quality, the temperatures of 150°C should be used.     

Variability in Transport Properties Regarding Drying Behavior for Blackbutt Timber in New South Wales

ABSTRACT

Variability is a key issue in the processing of many biological materials, in this case the drying of hardwood timber. This article reports the measurements of variability of the diffusion coefficient (a transport property), the initial moisture content, and the basic density that are relevant to the drying of blackbutt, Eucalyptus pilularis Sm, from northern New South Wales in Australia. The diffusion coefficient was quantified using a mathematical model solving Fick's second law of diffusion for mass transfer, and Fourier's law for heat transfer. The initial moisture content and the basic density were measured using experimental procedures. Specifically, within-tree and between-tree variations are reported. The coefficients of variation of the initial moisture contents and final moisture contents are 0.24 and 0.19, respectively, for within-tree variability. A similar result was found for the amount of between-tree variability. Compensating differences in the diffusion coefficients of the timber boards were a significant reason for the small dispersion of final moisture contents, despite the large variation in initial moisture contents.

An analysis of variance showed that some timber properties were affected by the board positions within trees and between trees. Circumferential and radial effects were significant for the within-tree variability of most transport properties. Moreover, principal components analysis suggested that timber boards with low densities have high initial moisture contents and high diffusion coefficients. A potential reason is that if there is less wood material per unit volume (lower density), then there is more space to be occupied by water (higher initial moisture content), and there is also less resistance to the diffusive transport of moisture (higher diffusion coefficients).     

Microwave Drying of Wood Strands

Abstract

Characteristics of microwave drying of wood strands with different initial moisture contents and geometries were investigated using a commercial small microwave oven under different power inputs. Temperature and moisture changes along with the drying efficiency were examined at different drying scenarios. Extractives were analyzed using gas chromatography/mass spectrometry (GC/MS). The results showed that the microwave drying process consisted of three distinct periods (warm-up period, evaporation period, and heating-up period) during which the temperature, moisture change, and drying efficiency could vary. Most of the extractives were remnant during microwave drying. It was observed that with proper selections of power input, weight of drying material, and drying time, microwave drying could increase the drying rate, save up to 50% of energy consumption, and decrease volatile organic compound (VOC) emissions when compared with the conventional drying method.     

Assessing the Influence of the Drying Schedule on Moisture Variability in the Batch Drying of Timber

Abstract

Timber drying schedules influence the dispersion in moisture content between boards at the end of drying. Both a single set-point schedule and a double set-point schedule are selected to illustrate the concept. A simple deterministic drying model that can predict moisture content as a function of time for a single and double set-point schedule is presented. Given random variability in both the initial moisture content and drying rate of the product, theoretical expressions for the range in moisture content as a function of time are developed. The predictions of these equations are compared with experimental measurements from a laboratory kiln. A general methodology whereby the basis of commercial schedules can be analyzed as to their performance with respect to minimizing product moisture dispersion is constructed. The approach should prove useful in assisting drying process designers, concerned about moisture variability, in distinguishing between otherwise equal schedules.     

HYDROGEN TRAIPB-NUUEAR MAGNETIC RESONANCE FOR INDUSTRIAL MOISTURE 8EN8MG

ABSTRACT

A procedure was developed based on a three-component physical model to simulate the drying characteristics of Laird lentils. In this model, the cotyledons were simplified as a homogeneous slab where moisture transfer was governed by a one-dimensional diffusion equation, and the hilum and seedcoat were considered as two parallel routes for moisture to escape from a seed. The simulation procedure was verified with the experimental data from thin-layer drying testing on samples of 19.0 to 24.5% initial moisture content at temperatures from 23 to 80°C and relative humidities from 5 to 70%. Using previously obtained information on the transport properties of the cotyledons, the seedcoat, and the hilum, the simulation followed the drying data closely over temperatures between 23 and 60°C.     

Operating Conditions for Drying Paddy in a Rotating Drum with Sand Medium

ABSTRACT

Batches of wddv rewened to 18% or 24% moisture content were dried in a sealed rotating drum containing ; preheated sand. For each initial moisture content, all combinations of the following variables were replicated three times: sand patilcle size (0.3 and 0.6mm). residence time (60, 120 and 180 s), sand-to-grain mass ration ( 3:1, 6:1 and 9:1) and initial sand temperture ( 100, 150 and 200°). The dried paddy was shelled and milled and the percentage of whole grain kernels was determined. In general. the paddy starting at 18% mc led to lower final moisture contents than that starting at 24%. For equivalent final moisture contents, milling yields of whole rice were equivalent. Best yields were generally associated with lower energy input (ie. low to intermediate initial sand temperature and sand-to-grain mass ratios below 4.7:1) Residence time was not critical in determining milling yieid. This study indicates that particulate medium drying of paddy is an interesting alternative to traditional drying since it greatly accelerates drying timee without reducing milling yields. Solar preheating of the sand could permit substantial energy savings.     

An Experimental Study and Mathematical Simulation of Wheat Drying

Abstract

A fixed-bed dryer was designed and constructed and drying experiments with fixed beds of wheat were carried out under various conditions of drying air with wheat of several initial moisture contents. The air temperature and moisture content of wheat at various levels within the beds were measured periodically. A computer program based on energy and mass balances was developed to simulate the deep bed drying process. Experimental data from the dryer were compared with the results from this program. The results showed that there was good agreement between the simulated drying rates between the layers and those experimentally observed. In addition, there was a good agreement with respect to the shapes of the drying air temperature profiles.     

Effect of Fluidized Bed Drying Temperature on Various Quality Attributes of Paddy

Abstract

As reported by many researchers, it was found that fluidized bed paddy drying using high drying air temperatures of over 100°C affected the head rice yield and whiteness of dried rice. However, only a few studies on fluidized bed paddy drying with drying air temperatures below 100°C were so far reported. The main objective of this work was therefore to study the effect of fluidized bed drying air temperature on various quality parameters of Suphanburi 1 and Pathumthani 1 Indica rice. Paddy was dried from the initial moisture contents of 25.0, 28.8, and 32.5% dry basis to 22.5 ± 1.2% dry basis using inlet drying air temperatures between 40 and 150°C at 10°C/step. After fluidized bed drying, paddy was tempered and followed by ambient air aeration until its final moisture content was reduced to 16.3 ± 0.5% dry basis. The results showed that the head rice yield of Suphanburi 1 was significantly related to the inlet drying temperature and initial moisture content whilst there was no significant relationship between the head rice yield, drying temperature and initial moisture content for Pathumthani 1. The whiteness of the two rice varieties was slightly decreased with increase in drying air temperature and initial moisture content. It was also found that the hardness of both cooked rice varieties exhibited insignificant difference (p < 0.05) comparing to rewetted rice, which was gently dried by ambient air aeration in thin layer. The thermal analysis by DSC also showed that partial gelatinization occurred during drying at higher temperatures. Using inlet drying air temperatures in the range of 40–150°C therefore did not affected the quality of cooked rice and paddy. The milling quality of paddy was also well maintained.     

Drying and Heat Transfer Characteristics for a Novel Fluidized Bed Dryer

Abstract

The use of a fluidized bed dryer with a lateral air flow and mechanical agitation to the drying of sludge from a wastewater treatment plant was investigated. Experimental curves of moisture content vs. drying time, as well as heat transfer coefficients and the size characteristics of the products, were determined at temperatures between 80°C and 110°C, a stirring rate of 55 rpm and air velocity of 0.9 m/s for 3 kg sludge batches with initial moisture contents of 0.55 and 0.65 (d.b.). Experimental drying kinetics were compared with values derived from three models based on Fick's second law, namely: the constant diffusivity model, the simplified variable diffusivity model, and the modified quasi-stationary model.     

Optimization of Rubber Wood Drying by Response Surface Method and Multiple Contour Plots

Abstract

By adopting the central-composite experiment design, the response surface methodology was used to optimize operating conditions of rubber wood drying. The independent variables are initial moisture content of rubber wood, and three drying environment parameters namely, temperature, relative humidity, and air velocity. The investigating responses are final moisture content, drying time, and energy consumption. The restriction of the optimization is the designated final moisture content, which is not greater than 16%. The third-order polynomial models with transformed responses were developed from experiment data to generate 3-D response surfaces and contour plots. The analysis of variance (ANOVA) was performed to identify the significant parameters affecting the rubber wood drying. Drying temperature and holding relative humidity are those two influential operating parameters that significantly control the final moisture of rubber wood and affect the drying time and energy. The multiple contour plots of drying responses show that the optimum operating regions are located mainly at high temperature drying zone. The high temperature drying practice can save energy and drying time by 44 and 25% respectively, in comparison to the conventional temperature drying.     

Heat and Moisture Transfer Model for Onion Drying

Abstract

Onion slices of 3 mm thick were dried in an atmospheric batch tray dryer in order to investigate the influence of air temperature and drying time on parameters such as sample moisture content and drying rate. A model is proposed which takes into account both moisture and temperature distributions in the sample and is in a fair agreement with the experimental data. The models suggested so far by other workers take only the moisture distributions into account for onion drying.     

Impingement Drying of Paper

ABSTRACT

The complete drying history of paper dried under an array of multiple round jets of air was determined. The drying rate – paper moisture content relations, determined as a continuous function by on–line measurements for about 80 sheets, permitted examination of the following parameters: basis weight 20 to 50 g/m2, which covers the tissue to communication paper range; initial moisture content 1.5 to 3 kg water/kg fibre; nozzle to paper spacing of 5, 7.6 & 8.5 nozzle diameters: nozzle plate open area ratio from 1.4 to 3.1%; jet Reynolds number in the range of 450 to 11.100.

Three methods of quantifying the complete drying rate curves were tested. Use of the common assumption of drying rate linear with moisture content over the falling rate period gave inadequate representation. Secondly, the general method of Churchill for any transport process that has a transition between two asymptotic relations was applied for the fmt time to the drymg of paper. This approach gives     

Effect of Four Drying Methods on the Quality of Osmotically Dehydrated Cranberries

Abstract

Partially dehydrated cranberries (osmotically dehydrated) were dried to low water contents using one of following four methods: hot air drying; microwave-assisted convective drying; freeze-drying; and vacuum drying. Quality evaluation was performed on all samples, including sensory evaluation (appearance and taste), texture, color, water activity, and rehydration ratio. Hot air drying produced dried cranberries with the best visual appearance while freeze-dried cranberries had the highest rehydration ratio. The other methods presented similar rehydration ratios. There was no significant difference in color measurements and water activity. Few differences in texture were found, except for freeze-dried cranberries, which had a lower toughness compared to the other drying methods including commercially available dried cranberries. Microwave-assisted to hot air drying rate ratios increased as the moisture content decreased.     

Effect of Particle Structure on Quality Retention of Bio-Products During Thermal Drying

ABSTRACT

To study the influence of particle structure on quality retention of hioproducts during thermal drying, the porous particles formed of albumin and solid carriers were dried in a vibm-fluidized bed dryn at different inlet air temperatures and different initial bulk porosities. Equations to predict temperature and moishrre content of panicles as well as the kinetics of biomass degradation were developed. The particle bulk porosity was incorporated into concentration-dependent moisture diffusivity model to estimate the erect of particle structure on product quality. The analysis of both calculated and experimental results indicates that the more porous structure promotes moisture diffusion, increases drying rate and finally improves the quality retention of bio-products. An extensive literature survey on quality retention issues during thermal drylng has been done.     

Mathematical Modelling of Solar Kilns for Drying Timber: Simulation and Experimental Validation

Abstract

A complete solar kiln model (including the drying of hardwood timber) has been developed with particular reference to the seasoning of blackbutt (Eucalyptus pilularis) timber. The predicted internal air temperatures, relative humidities, and timber moisture contents have been compared with experimental data. The maximum difference between the actual and predicted moisture contents was 0.05 kg kg^?1. The agreement between the predicted and measured temperatures of the internal air is reasonable, and both the predictions and measurements have a similar cyclical pattern. The generally good agreement between the model prediction of the final moisture content and its measurement may be due to the careful measurement of the boundary conditions such as the solar energy input. The main uncertainties were identified as the heat exchanger output, the measurement of the initial moisture content, and the estimation of sky temperature. The significant uncertainty (18%) in the estimation of the initial moisture content is a key reason for the mismatch between the model predictions and the measurements.     

THIN-LAYER DRYING CHARACTERISTICS OF ROUGH RICE AT LOW AND HIGH TEMPERATURES

Abstract

Thin-layer drying characteristics of rough rice were determined at temperature ranging from 11.8 to 51 °C and for relative humidities ranging from 37.1% to 91.3%, with initial moisture contents in the range of 24.7 to 41.6% dry basis. An oven, a self contain air conditioning unit, recently developed in Japan, was used for this experiments. With this apparatus, very smooth drying curves were obtained. The data of sample weight, and dry and wet bulb temperatures of the drying air were recorded continuously throughout the drying period for each test. The drying process was terminated when the moisture content change in 24 h was less than 0.2 % d.b. (weight change was less than 0.05 g). The final points were recorded as the dynamic equilibrium moisture contents.

The drying data were than fitted to the Page model. The model gave a very good fit for the moisture content with an average standard error of 0.294 % d.b? Both the drying parameters, K and N, are function of drying air temperature and relative humidity. The effect of variable initial moisture content was also described effectively by the empirical Page model. The drying time employed had a large effect on the K and N values. The results presented here, over typically 5 day drying, will be useful in the long term moisture transfer process occurring during ventilated storage.     

Probabilistic Analysis of Timber Drying Schedules

Abstract

Timber drying schedules are primarily chosen to achieve a certain final moisture content accompanied by a minimum amount of board degrade. However the schedule adopted also influences the dispersion in moisture content between boards at the end of drying. A simple double set point schedule consisting of two distinct and sequential equilibrium moisture contents is selected to illustrate the concept. Theoretical expressions that predict mean and standard deviation in board moisture content vs. time are developed. The predictions of these equations are compared with the output of a Monte Carlo model of timber drying and with experimental measurements from a laboratory kiln. The advantages of a double set point over a single set point schedule are explained and an optimum double set point schedule is determined. The behavior of a commercial drying schedule is analyzed and its performance with respect to the optimum schedule is quantified. Finally some inherent characteristics of the variability in timber drying systems are outlined.