Jingsheng Ye

Sorption Drying of Soybean Seeds with Silica Gel in a Fluidized Bed Dryer

Soybean seeds were contacted with silica gel in a fluidized bed, where mass transfer is driven by moisture concentration gradient. It has the advantage of well-mixing the solid adsorbent (silica gel) with the material being dried (soybean seeds) in fluidization state, and thus the dried seeds quality could be improved since they are in a uniform environment of low humidity. The drying kinetics was compared under different mass ratios and fluidization conditions. The drying rate was improved with the gas velocity and mass ratio of silica gel. A scheme of sorption drying in a hybrid process of fluidized/fixed bed is proposed in the viewpoint of energy efficiency and product quality.

Comparison of Microwave Drying of Soybean in Static and Rotary Conditions

A rotary device was built in a home microwave oven, where wet soybean was dried in a dynamic moving state to improve the microwave drying uniformity. Experiments were conducted to investigate the relative water removal ratio which was defined to characterize the electromagnetic field distribution in microwave oven, and to compare the drying characteristics between static and rotary microwave drying. It is concluded that the kernel cracking ratio is lower when microwave drying of soybean was carried out in rotary state. Higher unit microwave power input results in rapid removal of water from soybean but an increase of kernel cracking ratio.

Thin-layer drying of fermentation spent liquor using corn bran adsorbent.

To utilize the spent liquor from yeast fermentation, sorption drying in a thin static layer was proposed in which the corn bran serving as a solid carrier adsorbs the viscid liquor, and wet granules are then dried in a fixed bed by the hot air stream. A parametric study was conducted to investigate the effects of weight ratio, drying air temperature, air velocity, and layer thickness on the drying kinetics. Experimental results show that a low critical moisture content exists in the drying process, so the majority of moisture was removed during the constant drying rate period. Drying air temperature and layer thickness were two important parameters governing the drying process. In addition to expected effects from convective drying of capillary-porous materials, it was found that the conditioning period during which the spent liquor–bran mixture is left for conditioning markedly improves the drying rate. The possible mechanisms leading to this phenomenon were put forward.

Modeling of Diffusion in Ellipsoidal Solids: A Simplified Approach

Abstract A three-dimensional model was applied to rigorously interpret the diffusion phenomena in ellipsoidal solids. The numerical solution of the diffusion equation was obtained by the finite difference method for ellipsoids of various shape factors. Due to its complexity for practical use, the spheroidal model (two-dimensional model) was utilized as a better alternative. In comparison with the numerical results generated by the three-dimensional model, the spheroidal model still fails to give good predictions in some cases, although it was assumed to have the same volume and surface area (i.e., same shape factor) as that of the ellipsoidal model. Consequently, a simplified approach was developed with satisfactory predictions, that is to apply a one-dimensional model to solve the diffusion problem with equivalent diameter as well as equivalent liquid diffusivity, which is a function of the intrinsic diffusivity and geometry factor.

Thin-layer Steam Distillation of Fermented Grains: Effects of Steam Flow Rate and Temperature

Abstract Bioethanol was obtained by distillation of solid-state fermented biomass. In this process, the objective material is ethanol and it is not necessary to consider other contents, like aromatic compounds, as essential in Chinese traditional alcohol distillation. In this paper, the characteristics of steam distillation of fermented grains were investigated and interpreted by means of steam drying. Two criteria were defined to evaluate the process unit energy consumption. The results indicated that the ethanol removal rate is improved with an increase of steam flow rate and the unit energy consumption is higher. But with an increase of inlet steam temperature, the constant distillation rate keeps invariant, and the unit energy consumption is lower.

Numerical Evaluation of the Non-Isothermal Method for Determination of Moisture Diffusivity

A non-isothermal (linearly increasing temperature) procedure was used to determine the moisture diffusivity in mass transfer as a function of temperature with the complex optimization method. The effects of heating rate and experimental errors on the prediction accuracy of the parameters in Arrhenius equation were evaluated through pseudo-experimental data randomly generated on the basis of simulation results. An optimum heating rate of 0.01 K/s was found at which the experimental error less than 15% has negligible effect on calculated liquid diffusivity.