The thin layer drying characteristics of hazelnuts during roasting

Drying is a complicated process with simultaneous heat and mass transfer, and food drying is especially very complex because of the differential structure of products. In practice, a food dryer is considerably more complex than a device that merely removes moisture, and effective models are necessary for process design, optimization, energy integration, and control. Although modeling studies in food drying are important, there is no theoretical model which neither is practical nor can it unify the calculations. Therefore the experimental studies prevent their importance in drying and thin layer drying equations are important tools in mathematical modeling of food drying. They are practical and give sufficiently good results. In this study first, the theory of drying was given briefly. Next, general modeling approaches for food drying were explained. Then, commonly used or newly developed thin layer drying equations were shown, and determination of the appropriate model was explained. Afterwards, effective moisture diffusivity and activation energy calculations were expressed. Finally, experimental studies conducted in the last 10 years were reviewed, tabulated, and discussed. It is expected that this comprehensive study will be beneficial to those involved or interested in modeling, design, optimization, and analysis of food drying.

A Review of Thin Layer Drying of Foods: Theory, Modeling, and Experimental Results

A thin layer drying model of parboiled wheat

Mathematical modeling of thin layer drying of Golden apples

Optimal experimental design for estimating the kinetic parameters of processes described by the Weibull probability distribution function

The present invention is directed to a biomass gasifier combustor which operates by gasification and combustion of the biomass to produce a clean effluent gas which can be used directly for grain drying or other applications where thermal energy is required. This biomass gasifier combustor burns crop residue clean enough so that the combustion gases can be used directly for grain drying without the need for a heat exchanger to isolate the combustion gases from the drying air. The biomass gasifier combustor includes a screw feeder tube having a screw feeder disposed therein. The screw feeder forces the biomass into a first combustion chamber. Primary combustion of the biomass produces a first combustion gas. A venturi gas pump creates a negative pressure region in the gasifier, drawing the first combustion gas into a second combustion chamber. A secondary combustion takes place, completely oxidizing the organics in the primary combustion gas and producing a clean exhaust gas which can be used directly for grain drying purposes. An improved first chamber includes a manifold section for preventing the biomass from escaping into the secondary combustion chamber, and a variable height grate for allowing the ash product to fall through the holes in the variable height grate. A damper may be provided at the air inlets to control the flow rates or primary and secondary air. A damper may be placed on the exhaust eductor or venturi pump for regulating the thermal output of the system. The level of biomass in the first combustion chamber may also be monitored and automatically controlled.

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Biomass gasifier combustor

RELATIVELY little research has been reported in the literature on the thin-layer drying characteristics of soybeans in comparison to that published on corn and other cereal grains. Lee (1959) investigated the thin-layer drying of rewetted soybeans and fitted his data to a diffu-sion-type drying model. He employed the concept of a dynamic equilibrium moisture content and presented graphical techniques for determining the constants in his drying model as a function of drying temperature, relative humidity, initial moisture content, and soybean size. Alam (1972) used an equilibrium model to simulate the drying of soybeans with natural air at relatively low air flow rates (1-2 mVmin-tonne). Overhults et al. (1973) studied the thin-layer drying characteristics of soybeans with initial moisture contents ranging from 20 percent* to 33 percent and drying air temperatures from 38 ° to 140 °C. Dew point tempera-ture was held constant at 8 °C. A modified form of Page's drying equation (Page, 1949) was employed to describe the experimental data. This equation was of the form.

Thin-Layer Drying Model for Soybeans

THIN-LAYER drying experiments have been carried out to establish a clearer understanding of how dry-ing conditions affect the development of seed coat and cotyledon cracks in soybeans dried with heated air. Dry-ing rate was found to be highly dependent on initial moisture content and the relative humidity of the drying air.

Seed Coat Damage in Thin-Layer Drying of Soybeans

Adiffusion-based drying model has been developed for corn in which the endosperm and germ are modeled as a sphere with the resistance of the pericarp being part of the external resistance. The new diffusion model is more accurate than Page's equation in describing the drying of white shelled corn, yet in terms of application, the difference in accuracy is slight. The diffusion coefficient is an exponential function of the inverse of air temperature.

A Cellular Diffusion-Based Drying Model for Corn

A computer technique has been developed to esti-mate the wall pressures and average bulk densities of materials in bins. The Janssen approach is utilized where the material properties and k-values are allowed to vary within the bin as functions of the vertical pressure on the material and the moisture content.

I. J. Ross

Papers

Biomass gasifier combustor

Thin-Layer Drying Model for Soybeans

Seed Coat Damage in Thin-Layer Drying of Soybeans

A Cellular Diffusion-Based Drying Model for Corn

Grain Bin Loads as Affected by Grain Moisture Content and Vertical Pressure