ADSORPTION DRYING OF CORN IN ZEOLITE GRANULES USING A ROTARY DRUM

This study was conducted to evaluate the potential of a natural zeolite (chabazite) as the particulate medium for grain drying. The granular zeolite was heated in an electric oven and mixed with grain corn. Drying experiments were conducted in a rotary batch dryer equipped with a computer and a data acquisition and control unit simulating an adiabatic process. Five initial medium temperatures (140, 160, 180, 200, and 220 °C) were used. Drying curves for grain corn and the values of effective diffusivity are reported. The amount of moisture removed and     

CORN QUALITY AFTER DELYING BY FLUIDIZATION TECHNIQUE AT HIGH TEMPERATURE

ABSTRACT

Corn quality, in terms of stress crack, breakage and colour, after drying by fluidization technique was investigated. Drying air temperatures for this study were 150, 170 and 200°C. Experimental results showed that drying corn of 43% (d.b.) initial moisture content to 16% (d.b.) final moisture content (approximate 9 minutes) with drying air temperature up to 170°C (inlet air relative humidity less than 5%) could be done without significant loss of quality, i.e. no breakage of corn kernel, stress crack less than 12% and just small change of colour of grain surface. Empirical equations describing evolution of multiple stress crack and grain surface colour were developed. Results obtained from the equations are in good agreement with experimental ones.     

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.     

DRYING CHARACTERISTICS OF CORN IN FLUIDIZED BED DRYER

ABSTRACT

A batch fluidized bed dryer was carried out for corn drying. Drying characteristics of corn were investigated The experimental results indicated that moisture transfer inside a corn kernel was controlled by internal diffusion by the following conditions : inlet hot air temperatures of 120 - 200 °C, superficial air velocities of 2.2- 4 m/s, bed depths of 4 - 12 cm, fraction of air recycled of 0.5 -0.9 and initial moisture content of corn of 43 % dry-basis. The Wang and Sing equation could describe in accordance with the results. Inlet hot air temperature and specific air flow rate were independent variables for drying constant model in the Wang and Singh equation.     

PROCESS DRYING PRACTICE

ABSTRACT

Drying experiments were carried out using a special microwave surface to examine the drying kinetics of corn and potato samples. The process of internal moisture and heat transfer was analyzed in the light of the experimental data obtained. The effects of several dielectric field parameters were also studied. It was found that the modified exponential law describes the water removal proc-ess of both materials within an acceptable confidence range when the specific microwave performance is the driving force for the internal moisture movement. Furthermore, the inner composition of the materials determines their reaction to the effect of microwave fields.     

Industrial Experience in Pressurized Steam Drying of Beet Pulp,Sewage Sludge and Wood Chips.

ABSTRACT

Drying in superheated steam under pressure gives possibilities for pollution free drying, energy recovery. reduced drying time and a very compact drying equipment.

Products are dried i n a pressurized cellular fluid bed by super heated steam blown through the cells. Above the fluid bed dust is separated before the steam is reheated and recirculated to the cells by a fan. The evaporated water leaves the dryer as usable steam at e.g. 3 bar g, and full energy recovery is obtained. Today 14 plants have been builtor are under construction, with capacities from 2 to 40t / h water evaporation.

This technology is suited for drying of beet pulp, residues from starch production of corn or wheat. sludge. spent grain. brown coal. wood chips and bark.

The technology shows great options for integration in steam systems in various industries, whereby drying is possible without using primary energy and pollution is avoided.     

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.     

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.     

SOME FUNDAMENTAL ATTRIBUTES OF FAR INFRARED RADIATION DRYING OF POTATO

ABSTRACT

Drying experiments were carried out using a far infrared heater to examine the drying characteristics of potato slices. The effect of several parameters e.g. radiation intensity, inlet air velocity and relative humidity on moisture and temperature history are presented. FIR drying of potato was observed to be a falling rate process. Drying rates were negatively correlated with air velocity. Relative humidity did not influence the drying rate. It was found that the modified exponential law describes the moisture removal of potato within an acceptable range.     

LOW TEMPERATURE MUSHROOM (A. bisporus) DRYING WITH DESICCANT DEHUMIDIFIERS

ABSTRACT

Cultivated mushrooms (Agaricus bisporus) slices of 2·5 and 5 mm thick were dried with dehumidified air at 20°, 30° and 40°C. Rehydration ability of dried mushrooms was used as criteria for the evaluation and determination of optimum conditions. Drying mechanism of the mushroom slices was expressed by unsteady state diffusion and the results were interpreted by Fickian model. Drying temperatures lower than 40°C promoted the production of light coloured mushrooms with high rehydration ratios. Diffusivity constants were in the range of 2·6?12×l0^-11 m²/s and the activation energies varied in the range of 23·5?30·3 kJ/gmol depending on the temperature and sample thickness.     

EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON THE DRYING RATES AND DRYING TIMES OF GREEN BELL PEPPERS (CAPSICUM ANNUUM L)

ABSTRACT

Green bell pepper dices were dehydrated at different dry bulb air temperatures (55°, 60°, 65°, 70° and 75°C) and relative humidities (15, 20, 25, 30, 35 and 40%). The effects of temperature and relative humidity (RH) on the drying rates and drying period of diced green bell peppers were determined. Drying rate curves were characterized by a short induction (heating) phase followed by a falling rate period. Near constant rate drying was observed only at 55°C at 15% RH and at 65°C (15% RH). Drying rates generally increased with increasing temperatures and decreasing RH. The effect of temperature on the drying rates became less pronounced with increasing RH Drying rate maxima at 70°C and RH of 15, 20 25 and 40% exceeded those at 75°C, possibly due to case-hardening.     

CORN QUALITY AFTER DELYING BY FLUIDIZATION TECHNIQUE AT HIGH TEMPERATURE

Corn quality, in terms of stress crack, breakage and colour, after drying by fluidization technique was investigated. Drying air temperatures for this study were 150, 170 and 200°C. Experimental results showed that drying corn of 43% (d.b.) initial moisture content to 16% (d.b.) final moisture content (approximate 9 minutes) with drying air temperature up to 170°C (inlet air relative humidity less than 5%) could be done without significant loss of quality, i.e. no breakage of corn kernel, stress crack less than 12% and just small change of colour of grain surface. Empirical equations describing evolution of multiple stress crack and grain surface colour were developed. Results obtained from the equations are in good agreement with experimental ones.     

APPLICATION OF VARIOUS DRYING METHODS IN SELENIUM-ENRJCHED VEGETABLE DEHYDRATION

ABSTRACT

Some Chinese popular vegetables are very low in the selenium(Se). The Se enrichment on these vegetables is very beneficial to the health of the local people. Drying and preservin¨g Se-enriched vegetables can provide a valuable food source. Preservation tests on sweet pepper, eggplant and cucumber enriched with Se by different drying methods of microwave, low-vacuum, heated airflow, and high-vacuum after freezing were conducted. Affecting curves have been developed for different drying temperatures. Effects of drying methods, initial selenium contents, sample moisture contents and blanching on keeping quality of Se-enriched sweet pepper bars are discussed.     

AUTOMATIC CONTROL OF COMMERCIAL CROSSFLOW GRAIN DRYERS

ABSTRACT

An unsteady state model of crossflow grain drying has been developed. The model has been used to develop several empirical models as process models for a feedforward dryer control system.

The control system consists of an empirical drying model, an on-line moisture meter, a tachometer, data acquisition software, a microcomputer, and the feedforward/feedback control software. It has been tested on several commercial crossflow maize (corn) dryers. With the inlet grain moisture content varying between 16.1% to 34.3% (w.b.), the new control system controlled the outlet grain moisture content to + 0.6% of the set point.     

BATCH DRYING OF SHELLED CORN IN TWO-DIMENSIONAL SPOUTED BEDS WITH DRAFT PLATES

ABSTRACT

Geometrically similar spouted beds with draft plates were used to obtain the drying characteristics of freshly harvested shelled corn with 0.28 to 0.31 kg/kg initial moisture content at different air inlet temperatures and bed heights. Thermal equilibrium between air and grains was achieved at minimum spouting conditions. The drying kinetics of shelled corn in a drafted two-dimensional spouted bed was found to be of the "thin layer" type. Expressions for the model parameters in Page's equation accounting for the bed geometry, grain moisture content, and drying conditions were developed.     

RELATIONSHIP OF PROCESS PARAMETERS AND STACK WIDTH IN TIMBER DRYING

ABSTRACT

Drying schedules applied in kiln drying, especially for hardwood species should be supplemented with values of air velocity. When dryers have no air velocity control their drying schedule can be suitably corrected. The correction should take into account factors related to dried material, i.e. wood moisture content, timber thickness, dried timber volume and primary width of a stack. Drying efficiency may be the criterion of modifications. The applied procedure of drying efficiency calculations lets to determine quantitative relationships between process and material factors.     

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.     

THIN-LAYER DRYING BEHAVIOUR OF VEGETABLE WASTES FROM WHOLESALE MARKET

ABSTRACT

The thin-layer drying behaviour of vegetable wastes (as a mix of lettuce and cauliflower leaves) from wholesale market for a temperature range of 50-150^°C was determined. Drying of this material was found to take part only in the falling-rate period. The experimental data were fitted to the simple exponential model and the Page model. Both models have good prediction capability, Effective diffusion coefficient varied from 6.03*10^-9to 3.15*10^-8m3/s with an activation energy of diffusion of 19.82 kJ/mol. The temperature dependence of the effective diffusion coefficient was expressed by an Arrhenius-type relationship.     

Drying of Fresh and Rewetted Shelled Corn in Microwave Fields

ABSTRACT

Drying of freshly harvested and artificially rewetted yellow dent shelled corn was studied experimentally under microwave conditions. The dehydration rate of rewetted corn was found to be higher than that of freshly harvested corn; the deviation in the dehydration rates was found to be a power law function of the moisture content. under similar conditions, freshly harvested corn has a lower drying rate relative to the rewetted samples. The difference between these drying rates varies by a power law relationship with kernel moisture content.     

顺逆式循环流玉米低温烘干塔的产品介绍及性能分析

为了解决粮食的晾晒烘干问题,“远弘干燥”对玉米烘干塔进行了技术与设备的资源整合,研发了性能更好,更加高效的顺逆式循环流低温玉米烘干塔,并对其系统组成、烘干流程、热风循环流使用、余热利用、技术参数和经济性进行了介绍和分析。