Hiroshi Shimizu, Xingwu Wu, Ikuo Biwasaka

Faculty of Agriculture, Iwate University
(3-18-8, Ueda, Morioka 020 Japan)

Abstract

By using the decrease rate of dry matter u = d[delta]D/d[delta]t, as an indicator, this paper proposes a simulation method for analyzing the aerobic fermentation and drying process of organic wastes in packed bed. The initial decrease rate of dry matter (Fig.1-(1)) as a criteria and its attenuation with respect to time (Fig.1-(2)) according to the increase of ash content (Fig.3) were investigated by elementary experiments. The attenuation constant is represented by a. The initial value of drying rate v = d[delta]W/d[delta]t was also investigated. Based on the decreases of quantity of dry matter and water, the changes in moisture content and ash content with respect to time were simulated using geometrical progression (Equation6) . Close agreements (Figs.4-5 about type A and Fig.10 about type E) were obtained between the calculated values and measured values of actual apparatus. Using the simulation method, we can determine more kinds of changes and details about the aerobic fermentation and drying process of organic materials in packed bed (Figs.6-9, 11) . Five types of experiment apparatus (i.e. type A, B, C, D, and E) were used. By comparing the calculations, the merits and demerits of each devices were discussed (Table1) . For example, if the type C and type D are used the same initial materials, the type D shows high efficiency, because the materials can be compacted to 1/16 of tank volume ƒ°M of type C and also has a product ratio b[beta]' of 1/15. Furthermore, in the case of type E, which was modified from type D, it is possible to get 1/80 of product rate b[beta]'. There are big differences among devices, and it becomes possible and important to select the suitable device to achieve the desired objective.

Key words: aerobic fermentation and drying, organic waste, compost, simulation