日本エネルギー学会大会講演要旨集
第25回日本エネルギー学会大会

Although Paris agreement was adopted last December, it seems most of people in Japan still do not understand the seriousnes of its true meanings. The direction the industrial revolution since 18th century must be completely reversed within this century. All human activities based on fossil fuel will be forced to stop, and we need have completely different social systems.

The purpose of the presentation is to investigate background and prospect of reducing dependence on coal in China’s energy structure. Conclusions are as follows. First, increase in coal price due to coal pricing institutional reform and erased cost competitiveness of coal is the most influential factor. Second, recent decline in coal price due to oversupply accelerated by China’s economy slowdown, coupled with recovery in cost competitiveness of coal is stimulating investment for coal-fired power plants again. Nonetheless, the momentum of increasing share of non-fossil energies supply is projected to be accelerated gradually by China’s commitment in COP21 and increasing share of service sector in economy is assumed to result in low energy demand growth. Therefore, reducing share of coal in China’s energy structure will continue in future, too, but the pace may slow down.

The situations relating to energy resources and world economy are much changing currently. New circumstances or trends such as shale gas/oil revolution in US, low oil price in the world market, global warming agreement in COP21, enlargement of renewable energy and the promise of hydrogen system society have the large impacts for the future energy situations. It is very significant to get information and get the picture about the future energy situations for researchers and developers engaging to the technologies on energy and resources subjects. The reports such as “World Energy Outlook” released by IEA and “BP Energy Outlook” are very helpful to know the outline of energy trends and future situations.

Final energy consumption for residential sector in Japan had increased until around the year 2000. Household energy consumption has been decreasing at an accelerated rate for recent 15 years. This is likely due to not only reduction of household size, but energy efficiency improvement of housing and appliance ande behavior change of residents. According to recent published government statistics, CO₂ emissions of households whose houses were built in and after 2011 were 15% less than the average. The statistics also show energy efficient behavior reduced CO₂ emission. Behavioral aspects of energy coemission will be relatively important in the future.

In recent years, there has been a growing expectation for hydrogen energy. Hydrogen has been described in published Japan's Basic Energy Plan in 2014 and is the future of secondary energy. In ”Energy White Paper” was announced in May this year, the hydrogen has been clearly shown as being in the future of secondary energy. It has been shown to accelerate initiatives with the aim of society to use the hydrogen in daily life and industrial activities. The arrival of the era in which the hydrogen is used as a secondary energy is approaching. In Japan, in 2009, ENE-FARM was the world's first general sale. In addition, in 2015, fuel cell vehicles were also generally sold. In the field of hydrogen energy, Japan has been the world's leading.

Air oxidation treatment at 100-260°C was applied to modify the properties of the so called Soluble, a clean extract having a potential as precursor of carbon fiber, obtained by the degradative solvent extraction of rice straw. At around 160 °C oxygen started to react with the functional groups of Soluble, which prevented the evaporation of smaller molecular weight compounds of Soluble. The changes in the functional groups during the oxidation were investigated by an in-situ FTIR technique. The melting point of Soluble was found to increase after the air oxidation. The oxidation reactions of the functional groups were judged to play the important role on the modification of Soluble.

Low rank coals are susceptible to spontaneous combustion, but they must be heated over a critical temperature of around 70 to 80 °C before spontaneous combustion starts. This work focused on the adsorption of water vapor as a possible mechanism of the temperature increase up to the critical temperature and accurate measurement of oxidation rate of coal at low temperatures. It was found that the oxidation rate is very small below 100°C and that the adsorption of water vapor plays a significant role on the temperature increase even over 100°C and at the relative humidity of as low as 0.01.

We have recently proposed a coprocessing method of heavy oils and a low-grade iron ore consisting of FeO(OH) in order to produce both light oil and a raw material for iron making called iron ore/carbon composite (IOC). In this study the effect of heavy oil type on a gasification reaction rate of the carbon in the IOC was investigated. It was shown that the carbon formed in the pore space of the low-grade iron ore was gasified at as low as 650°C due to low carbon crystallinity as well as a large contact area between the carbon and iron ore which can catalyze gasification reaction. While crystallinity and reactivity of the carbon formed in the pore space of the iron ore did not largely depend on heavy oil type, those of the carbon formed outside the pore space were different depending on the heavy oil type, which caused the dependency of gasification rate of IOC on heavy oil type.

Carbon/carbon composites are prepared in the following manner : COG tar recovered from a commercial coke oven is first mixed with low grade cokes or pyrolyzed chars from lignite and sub-bituminous coals, and the resulting mixtures are then heated in He at 10 °C/min up to 500-900 °C with a flow-type fixed bed quartz reactor. The tensile strength of each composite prepared is investigated with a tensile and compression testing machine. The strength increases with increasing weight ratio of tar to coke or char up to about 2, and it becomes approximately 6.0 MPa at this ratio. The strength also increases with increasing pyrolysis temperature up to 800 °C, it reaches about 7.5 MPa, which is comparable to those (7.0 MPa) of high grade cokes used in commercial blast furnaces. On the basis of the results of pore size distribution measurements, it is likely that the increase in the strength takes place as a results of the infiltration of tar-derived carbonaceous materials into pores in low grade cokes and pyrolyzed chars.

We measured coal gas pressure and oven chamber wall displacement during carbonization on commercial coke oven. Those are thought to be factors of influence on coke cake extrusion behavior. The main findings summarized below.

(1)Gas pressure at coal charging wasn’t influenced by coal blend (internal gas pressure at coal thermoplastic). On the other hand, internal gas pressure at 500mm height from oven sole was 1.5kPa at base coal blend, was 20kPa at high gas pressure coal blend.

(2)Wall displacement at coal charge was about 1mm, wall displacement restored to the initial position with the progress of carbonization.

(3)Wall displacement at coal charge of high internal gas pressure coal blend didn’t restore monotonically. It is thought that restore of wall displacement was suppressed by gas pressure of plastic layer close to oven wall, restore of wall displacement started after 3-4hours from charging coal.

In this study, we investigated the influences of residual carbon and an inorganic compound in coal ash on melting behavior of the coal ash. We prepared the coal ashes with different residual carbon content and with different CaCO₃ amount, and evaluated the melting behavior of the prepared samples based on JIS M 8801. The results indicated that the melting points increased with increasing the carbon content and decreased by CaCO₃ addition.

The Osaki Coolgen Project began in April 2012 as an ”Integrated coal Gasification Fuel Cell combined cycle (IGFC) demonstration project” subsidized by the Ministry of Economy, Trade and Industry. This project aims to realize innovative low-carbon coal-fired thermal power generation that combines IGFC, an extremely efficient coal-fired thermal power generation technology, with innovative CO₂ capture technologies. The first stage of this project, to demonstrate the oxygen-blown Integrated Coal Gasification Combined Cycle (IGCC), is progressing in commission toward demonstration testing start of 1st quarter 2017. The following will explain the project outline.

This work studied the reactivity and morphology change of oxygen carriers during multitude reaction cycles. The purpose of this study is to estimate the reactivity and morphology change of oxygen carriers (Ilmenite and Fe₂O₃/Al₂O₃) during multitude reaction cycles under CO-CO₂ reduction atmosphere.

Chemical looping is a potentially high technology for coal combustion with CO₂ capture efficiently. This paper discussed a three towers circulation fluidized bed, for develop CLC Coal utilization technology into commercialization. A basic model of the CLC process was produced using the AspenPlus software and to analyze the process under the conditions of a 250MWth plant. It found that the volume of circulating CLC carrier is roughly the same as the circulation of CFBC medium, and that inner desulfurization and ultra-low NO_x combustion are possible.

The effect of oxygen supply to the gasifier in a circulating fluidized bed system on the cold gas efficiency was estimated. Oxygen supply with low steam supply resulted in an increase in the cold gas efficiency when the excess heat was recovered by the steam generation and steam gasification of char. When the oxygen supply exceeds a certain amount, the cold gas efficiency decreased almost linearly.

Glycerol decomposition over iron ore was studied. The reaction route was not clear because the decomposition reaction was much complicated. Then decomposition reaction of methanol on the iron ore catalyst is studied. Methanol is usually included in actual bi-product glycerol during BDF production. So the decomposition reaction of the mixture of glycerol and methanol is also tested. The product distributions both from glycerol and the mixture was similar. Especially C₂⁺ compounds from both decomposition reaction had similar yield even the mixture included 25% of methanol. From these results, it is concluded that carbon atom from methanol reacts with intermediate from glycerol.

Solid Oxide Fuel Cells (SOFC) operating at high temperatures are one of the most efficient electrochemical devices for power generation. For the efficient recovery of exhaust heat from SOFC stacks, external steam reforming of hydrocarbon fuels such as methane is generally employed in commercial SOFC systems. In this study, dry reforming reaction (DR) is proposed as the external reforming because it does not need steam generators and enables to use carbon dioxide as reactant in the anode gas. Supported Ni catalysts have been investigated by using several support materials of different oxygen ion conductivity and basicity. Among the prepared catalysts, Ni/La_0.3Sr_0.7TiO_3-δ (LST) was found to exhibit excellent activity for DR. In order to improve the catalytic activity and tolerance to carbon deposition, post treatment and basic additives were examined for Ni/LST.

Methane hydrate has been expected as Japan domestic energy resources. As one of enhanced recovery methods for methane hydrate, we have been doing laboratory experiments using exothermic reaction of carbon dioxide (CO₂) hydrate formation since FY2009. Based on the experimental results, an injection probe is designed based of trial calculation. When injection volume is 400m³ and the thickness of injection layers is 20m, there was a possibility of a small size field tests.

For research of hydrate reformation which may happen in the process of depressurization, it is important to know the mechanism of hydrate formation. Therefore, we made the model of hydrate formation to research the morphology and the chemical parameters of hydrate formation. Phase Field Model was used for hydrate growth. Compared to experimental data, interfacial mobility M used in the model was decided to 1.713×10^-12.

In this work, a model that can be used in large-scale simulations was developed for studying the dissociation of methane hydrate. In the model, two mechanisms were assumed: (i) dissociation of methane hydrate as as a concentration driving force difference and (ii) decomposition of hydrate host cage of the methane hydrate according to a chemical potential driving force ignoring heat effects of the endothermic reaction. Experimental data of decomposition rates at 278 K, 4.39 MPa were correlated by the model assuming that (i) and (ii) occur in parallel using an effective rate constant of decomposition K as a fitting parameter. As a result, the rate constant of decomposition K was estimated to be 1.73 × 10^-9 at 278 K.

Producing gas from methane hydrate in subsea sand-mud alternate layers, there is a concern of mud erosion. It is possibly linked to several problems during gas production such as well instability, making skin and sand production. In order to predict the effect of mud erosion, we have conducted experimental and numerical studies. The experiment obtained primary parameters in terms of mud erosion. Applying them into numerical simulation, we computed long-term mud erosion in numerically generated pore-scale sand-mud layers. The results showed that the erosion of mud decreases and it approaches almost zero in several days.

We study the formation of tetrahydrofuran (THF) clathrate hydrate from polyvinylpyrrolidone (PVP) aqueous solution as a function of growth rate V and adsorbed PVP concentration c using the unidirectional growth technique. This study aims to propose a simple method for evaluating the performance of kinetic hydrate inhibitors (KHIs) for the clathrate hydrate–aqueous solution system.

Our group carried out growth experiments of THF hydrates in a mixture of glass beads and the stoichiometric THF−water solution (THF−17H2O) to elucidate the pattern formation mechanism of methane hydrates in oceanic sediments, and succeeded in the formation of four categories of patterns (layered, nodular, disseminated, massive). In the present study, to elucidate the effect of THF diffusion on the hydrate patterns, diluter THF water solution sample mixed with glass beads were used. Experiments were performed as a function of THF concentration and growth rate under conditions of nodular and massive formation in the case of the stoichiometric THF−water solution. As a result, thinner hydrates than the inner thickness of the sample cell grew, when the THF concentration of the sample was decreased. In addition, the facetted hydrates were observed at the lower growth rates. This might be caused by the morphological instability of hydrates in the thickness direction under the influence of THF diffusion field.

Phase-contrast X-ray imaging technique is suitable for visualizing light-element materials. In this study, diffraction-enhanced imaging (DEI) technique equipped with an originally designed cryogenic cell was used for measurements of THF hydrates grown interparticle pores of silica beads with 2 μm in diameter. The DEI technique using X-ray of 35 keV enabled nondestructive observation of layer structures of THF hydrate.

The migration of the hydrogen molecules (H₂) in structure-II (sII) hydrates has relatively low-energy barrier, while the barrier in the case of other guest molecules is so large that the guest molecules barely migrate into the sII hydrate crystals. Tetrahydrofuran (THF) hydrate, which also attracts attention as an H₂ storage medium, is stable at a temperature below 277.4 K and atmospheric pressure. In the present study, we have regarded the enclathration of H₂ as the absorption into the hydrate crystal formed in advance. The dissociation temperature and enthalpy of THF+H₂ mixed hydrates have been measured under various pressure conditions. From the difference of enthalpies between simple THF hydrate and THF+H₂ mixed hydrate with consideration of temperature differences, the absorption enthalpy of H₂ into the sII THF hydrate was estimated as 13.0±3.4 kJ/mol (THF). The pressure swing method for the H₂ storage in (and release from) THF hydrates is superior (approximately 1/10 for the energy requirement) to the decomposition/reformation of THF+H₂ mixed hydrates.

Naturally occurring gas hydrates in marine or permafrost environments can trap methane and heavier hydrocarbons up to C₇ hydrocarbons within its crystal structure. It is important to reveal the distribution of guest gas molecules in hydrate crystals from viewpoint of assessment of gas capacity. In the present study, we assessed cage occupancies of guest gas molecules in gas hydrate crystals formed from mixed gases including several hydrocarbons. As a result, it revealed that heavier hydrocarbons than ethane are preferentially incorporated into the 16-hedral cages in structure II hydrate framework.

Gas hydrate crystal has the structure which has advantage for generating the micro- and nanobubbles (MNBs) when the crystal is dissociated in water. The freeze-fracture replicas of the gas-hydrate dissociated solution were observed via a transmission electronic microscope (TEM) to confirm that various guest hydrates have such properties. Raman spectroscopic observations on the CH₄ hydrate dissociated solution indicated that the existing MNBs were originated from CH₄ hydrates, and that the inner pressure of MNB was about 7 MPa. Based on the MNB distribution data and the inner pressure, we discuss the role of MNBs on the memory effect of gas hydrate formation.

The effect of both NaCl concentration and storage temperature on the self-preservation of methane hydrate were investigated. Phase contrast X-ray CT and dissociation measurements based on mass fraction were conducted in this study. It revealed that dissociation of methane hydrate with NaCl were restrained by the self-preservation below 252 K: the eutectic temperature of NaCl and water. On the other hand, dissociation advanced in the boundaries between methane hydrate and NaCl at over 252 K.

This paper reports an experimental study of CO₂ + N₂ mixed gas separation based on semiclathrate hydrates of tetra-n-butylammonium bromide (TBAB) and tetra-n-butylphosphonium bromide (TBPB). We used mixed gas with a mole fraction of CO₂ : N₂ = 0.15 : 0.85, which is close to a composition of flue gas. We used a 800 cm³ volume high-pressure cell and performed hydrate formation. We used three different pressure levels: 1, 3 and 5 MPa with 3–4 K of subcooling temperatures. We analyzed the gas phase composition before and after the hydrate formation by a gas chromatograph and determined gas compositions captured in the TBAB hydrates. The highest amount of CO₂ in the hydrate phase was obtained with a TBAB aqueous solution with 32 mass%. The CO₂ amounts in the hydrate phase obtained with 20 mass% of TBAB solution and 20 mass% of TBPB solution were close. The most CO₂ uptake was obtained with the 32 mass% of TBAB solution

In this work, CO₂ sorption by tetra-n-butyl ammonium bromide (TBAB) semi-clathrate hydrate (SCH) slurries in the absence and in the presence of polyvinyl alcohol (PVA) and sodium dodecyl sulfate (SDS) dispersants was investigated. CO₂ sorption was measured with a newly-developed bubble column reactor. CO₂ sorption amount for SCH slurry was about 3.2 mmol-CO₂/mol-water at 0.8 MPa (He/CO₂ = 4) in the absence of dispersants. Rheological behavior of the SCH slurries was studied. SDS caused a reduction in the SCH slurry viscosity, whereas PVA caused an increase in slurry viscosity. The SCH slurries with the dispersants were determined to be Bingham plastic.

The heat and mass transfer characteristics during torrefaction of packed bed of bamboo powder have been investigated. Packed bed of bamboo powder was heated with and without the presence of carrier gas. For the heating without carrier gas, the temperature rise and final temperature varied depends on the locations inside the packed bed. Thus, it is difficult to evaluate the relationship between the chemical reaction and the temperature. Meanwhile, for the heating with carrier gas, the temperature rise were identical, resulting thermal decomposition in every locations occurred simultaneously, resulting the thermal reaction behavior became more obvious. The almost constant gas generation after the peak was considered as the result of thermal decomposition of hemicellulose, which occurred gently at temperature range 400 K < T < 550 K, as shown in the thermogravimetric result.

Torrefaction is an effective pre-treatment technique for improving the co-firing rate and milling capability in coal-fired power plants. In the present work, several degrees of carbonised woody biomasses were prepared at the 4t/d carbonisation facility. The torrefied woody biomasses were subjected to industrial analysis, elemental analysis,Higher heating value and color difference measurement. CRIEPI investigated the relationship between the fuel properties and color difference of torrefied woody biomasses. Moreover, from the results of the analyses, CRIEPI suggested a novel approach using hue angle to control the production process of torrefied biomass.

Torrefaction is one of the upgrading methods to convert biofuels into a form with high heating value under the condition of high energy yield. Torrefaction also performs several functions such as good grindability, hydrophobic property and decay durability. But it is pointed out that the energy required to mold pellets of torrefied biomass is much larger than that of untreated one. In this study, effect of torrefaction degree, that is mass yield of torrefied biomass on the softening temperature and extrusion force of thermo-fluid wood powder is investigated. The results obtained are as follows. The softening temperature increases with decreasing mass yield. The softening temperature of soft wood is larger than that of hard wood. The extrusion force increases with decreasing mass yield. This is due to the increase in the frictional pressure loss of thermo-fluid wood powder.

The combustion properties of torrefied Japanese cedar (Cryptomeria japonica) wood pellets were evaluated using a commercial pellet stove and a cone calorimeter; the latter is usually used to verify the fireproof performance of architectural materials. A cone calorimeter is able to estimate various combustion parameters, such as transition changes of the heat release rate, weight loss, ignition time, flame- and burn-out time, and combustion heat, in the single experimental run. The ignition time of untreated wood pellets slowed down in relation to the increasing volume density of pellets. For torrefied pellets, no significant changes in ignition time and heat release values were seen in comparison with results of untreated pellets, although there was a longer burn-out time and higher torrefaction temperature. When using the commercial pellet stove, no significant delay of ignition time was seen, and there was less smoke during ignition for torrefied pellets compared to untreated pellets.

It is known that the yield of supercritical water gasification is not determined not only by the temperature and residence time, but also by heating rate of feedstock. However, detail of the mechanism has not been discussed in regard with the feedstock decomposition network. In this study, mixture of glucose and guaiacol was gasified in supercritical water, changing the length of pre-heater so that heating rate of the feedstock can be changed. Concentrations of glucose and guaiacol were 0.34 and 0.16 wt%, respectively. Reaction was conducted at 600 °C, 25 MPa. Characterisitics of glucose gasification in supercritical water is largely affected by the existence of guaiacol.

The supercritical water gasification (SCWG) of wet-biomass holds promise as a technology to convert biological waste (wet biomass) into valuable, environmentally, and friendly energy. The improvement of the equipment utilization efficiency of the SCWG facility on-site is important. The 24 h continuous operation with the pilot plant (the treatment capacity is 1 t-wet/d) was successful with stable pressure loss of heat exchanger. However, SCWG plant might be operated by daily start and stop on weekday, because Shochu brewers work on weekday daytime. Therefore, the bad influence to tar characteristic by the rise drop of the temperature and the pressure of daily start and stop was concerned about. Therefore, the daily start and stop gasification tests were conducted during 4 days included 3 days holiday. The heat exchanger tar plugging was concerned, however the result of test indicated no tar plugging sign. The product gas elemental analysis results and the carbon gasification efficiency rates indicated no influence sing of Daily start and stop operation.

The utilization of char and heavy tar is limited in the biomass gasification process, and in fact, their disposal is costly, which is one of reasons that the biomass gasification is still economically difficult to put into practical use. This research aims at the feasibility study on the recycling of char and heavy tar as fuel in the gasifier to improve the gasification efficiency and decrease the cost of waste management.

Huge amounts of biomass wastes is being generated in plantation sites in Indonesia. But there is no appropriate technology for the biomass wastes utilization, which can be acceptable by local communities. While a development of a highly-efficient biomass gasification process is required in Indonesia because of relatively high labor and transportation costs, in Indonesia the direction of development of the appropriate technologies are different due to the completely different situation such as relatively low labor but high catalyst costs. Based on the Indonesian circumstance, the authors proposed a biomass catalytic gasification process by clay catalysts. For this process, the authors aim at a development of gasification catalyst prepared from clay minerals, which has not so high activities but can enough reduce tar formation. The purpose of this study is to evaluate the catalytic activity of various clays which are available in the Indonesian field by lab-scale biomass steam gasification experiments.

Judging from the common sense of today, it seems difficult to define the chemical reaction formula of the pyrolysis of biomass since biomass is a mixture of cellulose, lignin, etc. We think of an idea that a unit compositional formula ”CH_mO_n” can be used as a substitute molecular formula of biomass, where suffix ”m” and ”n” indicate the atomic ratio H/C and O/C determined by ultimate analysis. The substitute molecular formula of char and tar are also defined as CH_jO_k and CH_hO_i by a similar manner. We expressed the reaction formula of the pyrolysis of Mizunara oak using CH_mO_n, CH_jO_k and CH_hO_i, verified the thermal balance of pyrolysis, and estimated its heat of reaction.

The main outcomes of the study are as follows: (1) The volatile yields of woody biomasses can almost be predicted by using H/C ratio, excepting the yield of grass biomass (∈ hemicellulose). (2) The primary tar components obtained from wood/herb biomass are affected by the content of biomass constituents. (3) In case of woody biomass, acetic acid, glucose, phenols, and furfural were revealed as the major bio-tar components. In particular, a prominent increase in the yields of chemical species containing O and OH groups was observed.

Interactions between woody biomasses and plastics during co-pyrolysis of these mixtures have been investigated to recover useful materials. In this work, we researched co-pyrolysis behavior of beech wood (BW) and polyethylene (PE) mixtures at 650 °C. The present work revealed that yield of levoglucosan (LG) and products generated from LG increased because LG condensation was physically suppressed by melted PE. In addition, products generated from PE by BW radical species have lower molecular weight. Furthermore, it implied that PE decomposition was enhanced by water produced from BW.

To develop effective utilization of agricultural residue in biorefinery process, the effects of alkaline peroxide treatment on thermal degradation and enzymatic digestibility of rice straw were investigated. It was possible to prepare high cellulose-content rice straw by the short-time alkaline peroxide treatment under room temperature. The TG curve of the sample was similar with that of crystalline cellulose. Moreover, high glucose and xylose yields were obtained by the enzymatic hydrolysis of the sample. This pretreatment has the potential for application on site because it is simple and high efficiency in the short time.

In a recent decade, many implementations of woody biomass boilers in rural areas proved that its cost balance is often better than that of fossil fuel facilities, resulting in enhancement of local economy from socio-economic point of view. Heat generation by woody biomass boilers, for example, boilers for green-houses, community centers, and hot-spar facilities can be listed as some of such examples. Cost analysis of the practical applications on woody biomass heating facilities indicated that total operation cost of such facilities is sufficiently lower than that of fossil-fuel facilities (Suzuki et al. 2012 and 2014). However, cost balance is different by many factors, such as fuel type (wood chip, wood pellet, fire-wood), facility size, and availability of regional resource. This paper tries to propose best mixture of woody biomass heating facilities on regional use with an approach of sensitivity analysis concerning the factors. The result indicated that wood chip is suitable for larger facilities, wood pellet for smaller ones, while fire wood has intermediate characteristics between the former two fuel types. Cost balance of wood pellet is most sensitive with regard to availability of regional resource. Some implications from LCA (life cycle assessment) approach will follow in order to evaluate and compare environmental load of the facilities.

The innovation is required to production of a large amount of biomass by cultivation of domestic photosynthetic plant and to replace fossil fuels. The author has found that the best crop is sweetpotato cultivated in multilayer system. So far, the 4-layers cultivation method using a triangular shelf showed that it is possible to sweetpotato production of about 20kg/m². This is eight times the amount of domestic average yield (2.5kg/m²). However, the soil hygroscopic level decreased quickly and the production of the sweetpotatoes suppressed significantly, were found by the multi-layer cultivation system. Therefore we investigated the influence of the basic irrigation state to produce sweetpotatoes. As the result the yield of sweetpotatoes cultivated with root zone irrigation system increased to 179% of the amount of the past. In addition, the root zone irrigation system was effective to increase the weight of the mass production of sweetpotatoes by increasing the density of the vine seeding per area.

Operating conditions such as engine speed and load of diesel engines change the combustion state. In addition, the thermal efficiency and PM emission characteristics are greatly affected by the combustion state. On the other hand, Bio Diesel Fuel (BDF) contains a lot of oxygen, but the ignitability is inferior because the viscosity is high compared with gas oil. However, the previous researches found out that while gas oil and BDF are different fuel properties, the operating conditions to lose the remarkable difference of the thermal efficiency and the PM exhaust characteristic when using these with Diesel engines. In this research, operation conditions were examined while paying attention to the PM exhaust characteristic that changed by the combustion state by the performance examination of the diesel engine using BDF.

During verification test on high ratio biomass co-firing using a 150 MW-class pulverized coal boiler last year (2015), we collected the initial stage of ash deposits in wall furnace (near burner) and superheater, and then analyzed their properties. In wall furnace, ash deposits collected during co-firing have four times higher in sulfur than those collected during coal-firing and a moderate level of unburned carbon in ash deposits, indicating a high reducing atmosphere for co-firing condition. Sulfur exists as water-soluble CaSO₄, Na₂SO₄, but mainly as water-insoluble Ca-Mg-Fe-S compound. In superheater, ash deposits collected during co-firing have two times higher in potassium and sulfur than those collected during coal-firing. However, it was found that most of potassium exists as water-insoluble compounds (potassium aluminosilicate) rather than water soluble K₂SO₄.