食品残渣の家畜飼料・堆肥化におけるエネルギー利用システム確立の検討

Recently, many projects were carried out on the usage of the biomass energy, for example the usage of methane from the organic wastes. However, until now due to the economic restriction and problems in the energy transfer methods, these techniques were not practically applied. In this research, the new methane fermentation system by using biomass, the energy transfer system and energy using systems were studied to establish the energy recycling system. 1. The methane fermentation system By using the wastes of two growing cattle, changes of the temperature in methane fermentation tank and quantity of gases were measured continuously. The methane fermentation system is a simple structure, which consists of five parts, including ingredients throw tank, adjustment tank, methane fermentation tank, sulfa removing equipment and gas holder. It was simple structure. Amount of cattle waste input was as low as 6 kg/day, and methane production was about 0.1m^3/day. It might be due to low temperature. It was interesting that methane bacteria were active even at low temperature. When fermentation tank was warmed, the production of methane gas increased by 5 to 12 times compared to the untreated condition. Hydrogen sulfide was not detected from the gas holder tank. Amounts of methane and carbon dioxide in the gas holder tank were 63% and 12% respectively. The pH of the ingredients was 7.0, and liquids of methane fermentation tank and methane ingested tank tended to be more alkaline. Ammonia concentrations showed similar pattern to pH. The phosphoric-ion, nitrite nitrogen and nitric nitrogen were not detected in these tanks. 2. The settlement of energy transfer system It is expected that gas including about 60% methane occurs from the methane fermentation tank, which can be combusted at 300 C. the combustion heat can be used to dry garbage processes. The methane fermentation tank was an one-tank equipment produced by P Works Co. Ltd. The novel combustion device was produced by ALCAT Co. Ltd. with the technology of Kameyama Lab., Tokyo University of Agriculture and Technology. It can deal with methane of 24 m^3/day, flow rate of 0.5 m^3/min (3% methane). The catalyst combustion device was applied to burn 60% methane from the fermentation tank. Gas chromatograph results show that the composition of the inlet gas was CH_4 63%, CO_2 22%, (N_2+H_2) 15%. The flow rate was 0.025 m^3/min. The results show that the exit gas temperature can keep at 200℃ when the combustion temperature is controlled at 300℃. Furthermore, the exit temperature can be varied from 200 to 400℃ freely when the air ratio is controlled. In addition, the installed novel catalytic deodorization device was also produced by ALCAT Co. Ltd. with the technology of Kameyama Lab., Tokyo University of Agriculture and Technology. 90% offensive odor can be decomposed by the device at 0.5 m^3/min (concentration of 100 ppb). The result shows that 177 ppb propionic acid can be decomposed completely by the device, which proves the device is promising for the deodorization of a cow house. 3. The feasibility to produce cooling by an advanced adsorption heat pump The objective of this study is to evaluate the feasibility to produce cooling by an advanced adsorption heat pump utilizing the heat released from a fertilizing process. The study investigated the performances of the heat exchanger and the adsorption chiller experimentally. Taking the property of discharged gas from the process and the specification of the machine into account, possible recovered heat of 60℃ was estimated as 190 kW and 50 kW for the beginning stage and the following stage, respectively. The gas at the beginning stage contains much humidity due to drying process. So, heat recovery performs well because it can recover latent heat as well. Experiments that actually recovered heat from humid air of various conditions were conducted to measure the heat transfer performance. The results indicate that heat transfer from humid air is more effective than that from dry air by the factor of 6 to 17. Because produce cooling from 60℃ heat source is difficult for conventional adsorption chillers, the advanced cycle of 2 stage adsorption chiller was examined with various heat source temperatures. The chiller uses Silica-gel and water as the working fluid. The performances of the cooling capacity and COP show that cooling is possible even at 53℃, which implies that the proposed system is technologically feasible. Based on the results, cooling performance is estimated to be 28 kW and 7 kW for the beginning stage and the following stage, respectively.