Process Characteristics of Bioga Production System with Feeding of CO_2

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The practice use of H_2/CO_2 utilizing biogas production system which can fix CO_2 into the system is in the huge demand however no useful information on the biogas system with gas substrate is available. In this study, some experiments on the heating characteristics and process stability owing to the anaerobic sludge of the gas utilizing digester is conducted to have fundamental data to design and develop the biogas production system to fix carbon dioxide from the gas substrate.In order to develop the economical methane fermentation system with gas substrate feeding, a pilot scale fermentor with a rotational gas discharge system composed of a pivot and rotational bar was constructed. The heat exchange is conducted by direct contact between the hot biogas from the bar and the slurry in the fermentor. By use of water and air instead of waste slurry and biogas in this study, the rotational and heating characteristics of the system were investigated in the points of enemy and material bal … More ance analysis. The rotation of the bar corresponding to the airflow rate and the heat transfer from the inlet air to the water were observed in the system without the gasbag or the open-air system. In the heating with the gasbag or the closed system, the water temperature increased gradually and the simulated temperature increase by the heating model fitted to the actual temperature rise. The new heating system was concluded to be feasible in practical use.The effects of leachate from a methanogenic process on acidogenic performance in a cascade process of rotational drum fermentation system (RDFS) were evaluated under mesophilic condition and a total HRT of 20 days. Using fresh soybean meal or okara as substrates, two process configurations-Cascade process 1 and 2-were employed to perform the experimental estimation. An apparent first-order hydrolysis rate constant of 15.8×10^<-3>/d for Cascade process 1 at pH values of 4.6〜5.1 and 14.7×10^<-3>/d for Cascade process 2 at pH of 5.2, which were higher than that obtained by a previous study (9.0×^<-3>/d), were obtained. The apparent VS degradation ratio ranged from 21.1 to 25.5% and total VA (as acetic acid) from 14.5 to 18.6 g/L. Occupying ratios for ionized VA increased from 30.8% to 68.5% for Cascade process 1 and to 73.3% for Cascade process 2. However, occupying ratios of acetic acid decreased from 94.3 to 72.6% for Cascade process 1 and to 43% for Cascade process 2 whereas propionic acid and butyric acid ratios increased in both acidogenic processes. Although the addition of leachate promoted hydrolysis of substrate in both processes, the adverse effects of high VA concentration on hydrolysis rate were observed in Cascade process 2, where apparent hydrolysis rate constant was slightly less than that of Cascade 1. Less