M. MIYAGO, M. MASUI, Y. OHYABU, A. KOBAYASHI, H. IGARASHI ・・・（231）Thermogravimetric and Mass-Spectrometric Analyses

The co-firing of coal with biomass is a promising method for reducing net CO2 emissions from existing coalfired power plants. This present study examined the effect of the co-firing of coal with biomass on the produced fly ash and the fouling tendency under condition representative of reheater region of pulverized-coal (PC) boiler. The fouling tests were conducted in a drop-tube furnace by inserting a water-air-cooled deposition probe to the point where the inner furnace temperature was 800-900 °C and probe’s metal temperature was kept at 500 °C. Bituminous coal was mixed with up to 50% (energy basis) of three types of biomass, namely; Palm Kernel Shell (PKS), Japanese cedar (without bark) and bark of cedar respectively. Fouling tendency was evaluated by determining the ash deposition ratio during co-firing tests. The properties of fly ashes and ash deposits for each sample were analyzed in detail by XRF and CCSEM analysis. Compared to coal firing, PKS or bark co-firing significantly increases the fouling tendency, whereas cedar co-firing does not affect the fouling tendency. The increase of minerals with low melting point, particularly Ca-Fe-Al-Si and K/Na-Al-Si, in fly ash accelerated the fouling tendency during co-firing.

Biomass combustion is the most traditional method for its utilization to obtain heat energy as a global source. However, combustion of biomass fuels has been associated with air pollution and emission of toxic pollutants such as particulates, if sufficient appropriate technology was not used. This study focuses on the comparative assessment of particulate matter (PM) of 10, 4, 2.5 and 1.0 µm. Real-time measurement of particulate matter was conducted in laboratory scale, using a Dust-track II aerosol counter and a Yamato F100 fixed bed combustion chamber, attached with a fabricated heat exchanger for reducing the temperature of the exhaust point for sampling. Combustion experiment was conducted for 3 min duration for each 1 g sample of rice husk for each temperature category (600, 700, 800, 900 and 1000 °C). A mean value of 5 tests for each of the temperature category was carried out. Maximum PM₁₀ mass concentration was recorded at 600 °C and 1000 °C as 150.0 mg/m³ and 71.53 mg/m³ respectively, compared to 121.6 mg/m³ and 87.6 mg/m³ of PM_2.5. However, PM_2.5 mass concentration for temperatures of 700 °C, 800 °C, and 900 °C, was apparently higher than that of PM₁₀.

Lignocellulosic biomass has a recalcitrant structure, with hemicellulose and lignin bound tightly to cellulose. Furthermore, lignin might be an inhibitor factor in enzyme reaction. In our earlier study, a vibration mill with ring media was developed to obtain Japanese cedar fine powder, which reached high saccharification efficiency in enzyme reaction. Nevertheless, the influence of lignin was not examined. This study used a lignin quantification test and ESR analysis to assess the influence of lignin in Japanese cedar powder pulverized using a vibration mill with ring media. Lignin quantification test results show that the Klason lignin content of Japanese cedar remained unchanged irrespective of the pulverization time. The ESR analysis results of the radical amount of Japanese cedar revealed that the radical concentration of Japanese cedar was maximized at the pulverization time of 20 min. Results suggest that improvement of the saccharification efficiency of pulverized powder cleaved the lignin binding in the particle, easing access of the enzyme to cellulose.

In this study, an original small-scale demonstration plant was manufactured to produce upgraded wood fuel by torrefaction. The plant consists of a rotary-kiln type oven and a ring-die type pelletizer, and they were optimized for torrefaction based on the commercial models. We succeeded in more than 240 h operation of the torrefaction oven and produced 2.3 t of torrefied chips from raw Japanese cedar chips without drying. The energy yield of the torrefied chips was more than double the energy yield of conventional charcoal chips. The average length of the torrefied pellets was 7.4 mm, which is shorter than the length of the normal wood pellets. In the combustion test using a cone calorimeter, no delay in ignition time and small decease in heat release rate were seen for torrefied pellets in comparison with the results of normal pellets.

Thermal weight change of Japanese cedar wood (Cryptomeria japonica) in helium with steam or steamoxygen was measured and temperature dependences of produced compounds were analyzed by means of a thermogravimetric-mass spectrometric analyzer. Weight loss increased when adding oxygen. It suggested that oxygen accelerated gasification reactions. Decomposition of holocellulose started at around 200 °C, and ended at around 390 °C or 380 °C, at which corresponding curve of the thermal weight change bent. Decomposition of lignin started around 250 °C. Simultaneous decompositions of holocellulose and lignin caused rapid weight loss in temperature range of 250-380 °C or 250-390 °C.

In this paper, we fabricated spherical molybdosilicic acid-silica composite particles via sol-gel based method, and their ability for acid promoted hydrolytic dehydrogenation of ammonia borane. The morphological homogeneity of the spherical particles slightly increased with increasing amount of ammonia using in the preparation process. The intensity of IR bands assigned as Mo-O bond in the spectrum of the spherical particles prepared with highest amount of ammonia after calcination was relatively high compared with the intensity in the spectra of the particles prepared with lower amount of ammonia from the results of Fourier transform infrared spectroscopy (FTIR), indicating that parts of immobilized molybdsilicic acid molecules in the solution with high pH value were broken after calcination. The amount of hydrogen evolution from aqueous ammonia borane solution depends on the samples, and the morphologically homogeneous spherical particles stably immobilizing molybdsilicic acid molecules showed high activity for hydrogen evolution from aqueous ammonia borane solution.

This study aims to clarify the barriers and obstacles to the development of mini-hydro energy in Japan through participant observation, and interviews and questionnaires to the practitioners active in the field. Despite of the great potential of mini-hydro energy in Japan, various barriers and obstacles hinder the development. In total, 8 factors were identified as important factors, and these factors are classified into 3 broad categories: political, technologies and infrastructure, implementation body and finance & development plan. Based on the questionnaires conducted with the practitioners in the field, the relative importance of each identified factor is clarified using analytic hierarchy process method. Adding to the problem of access to electricity grid that has been observed in renewable projects in general, mini-hydro energy projects face various issues related to permits and licenses, community engagement, and slow-development of domestic technology. In order to facilitate the development of mini-hydro energy in Japan, these issues need to be addressed in the formation of the implementation body, financing, and engagement with the local community and other stakeholders. This study adds to the existing knowledge with the clear focus on the perspectives of project developers.

Since it is difficult to generate electricity in small to medium sized MSW treatment facilities less than 100 t/day from an economic point of view, it is important to increase recycling ratio and recovery of unused energy through waste-to-fuel technologies such as RDF or carbonized fuel. In July 2015 when Saikai city carbonization center was completed, carbonization fuel system was introduced. It is a facility of 30 t/day capacity and adopts the first domestic system that converts MSW into carbonized fuel and utilizes it as an alternate fuel of coal in power companies. The properties of carbonized fuel obtained in 2 years operation were 16,000 kJ/kg or more of calorific value, approximately 3,000 mg/kg-DB of chlorine concentration, and 224 of HGI, which showed high crushability compared with coal. Also the leaching and contents tests, and dioxin concentrations were within the regulation values. In addition, during the spontaneous ignition tests at 100 degrees C, carbonized fuel did not ignite. The estimation of energy recovery ratio from actual data showed that 18% of the power generation by carbonized fuel was equivalent to 16 to 21% of power generations by RDF, which were superior to 1 to 13% of simple incinerations.