During the fluidized bed fast pyrolysis/ gasification of woody biomass, a few characteristic phenomena were observed. In our small scale fluidized bed fast pyrolysis, agglomerates were found in the bed, which will cause serious engineering problems, such as plugging and defluidization. In the present study, the agglomerates formed were recovered and weighed after pyrolysis of Japanese cypress with different particle diameters using two bed materials of porous alumina and silica sand. The agglomeration was found to be observed mainly between 500-900 °C. Then soluble organic compounds were extracted and the agglomerates were again weighed. The reduction in weight of agglomerates was correlated with the weight of recovered organic compounds. In all of the results, some effects of bed particle and biomass particle diameter were observed. Then the in-situ gasification of biomass char produced was conducted at between 800-1100 °C for different bed materials. The progress of the gasification was different between two bed materials. The different behavior observed in pyrolysis and gasification was explained by the difference in volatile release behavior between large and small biomass particles and by the difference in adsorption/decomposition behavior of volatile between two bed materials.
Microalga Botryococcus braunii produces and stores liquid hydrocarbons. The oil extraction residue of the microalga is a good substitution for anaerobic digestion. However, hexane used as extraction solvent inhibits anaerobic digestion. In this study, the degree of inhibition from hexane and carbohydrate were measured in the continuous experiments. It was found that the hexane concentration and the remained carbohydrate should be kept under upper limits for success of the anaerobic digestion.
In Japan, the main feedstock for city gas is imported natural gas. In a city gas production process, the calorific value of natural gas is adjusted upward to regulated value of city gas by addition of LPG. In recent years, the method of adding LPG directly in the liquid phase has become the main stream in calorific value adjustment, where all of the added LPG must be securely vaporized. Otherwise, the LPG that does not contribute to increasing the calorific value flows out to the downstream side of the calorific value adjustment system, where the system is not functioning properly. Atomization of added LPG is the KEY for stable calorific value adjustment. In addition, demand for city gas varies greatly depending on the season and time of day, where a turndown, operating flow rate / rated flow rate, of natural gas reaches as small as 1/20, and that of LPG becomes even less than 1/500. The newly developed calorific value adjustment system realized complete and reliable atomization of added LPG over such a wide flow rate range without increasing pressure loss, resulting in a wide possible operating range and excellent calorific value controllability.
LNG stored in a tank is always subject to heat input because the temperature of LNG, at approximately –160°C, is far below the ambient temperature. The LNG is partly evaporated by the heat, and this evaporated gas is the BOG (boil off gas). Processing BOG is a challenge for the industries importing LNG such as city gas industry or electric power industry. The industries have been addressing the issue by installing BOG recondensing systems, which reduce power consumption by the BOG compressor. To further minimize the lifecycle cost of BOG processing, the authors developed a new BOG recondensing system utilizing gas-liquid direct mixing technology, which enables to substantially reduce the size of the BOG recondenser. In a course of developing the gas-liquid mixer, as a key device of the recondensing system, several technical features have to be taken into account and confirmed, such as, high recondensing performance, low pressure loss, prevention of internal cavitation-erosion, and, reduction of thermal stress due to large temperature difference of BOG and LNG. The paper describes the confirmed recondensing performance and features of the system. This paper also introduces the first commercial system utilizing developed mixer with a volume of only 2% of conventional system.