Annual production of sewage sludge in Japan increased to 2.17 million tons (d.b.) in 2004. About 70% of sewage sludge is incinerated. The nitrogen content of the sludge is considerably higher than that of other fuels, such as coal and wood. Thus the emissions of NOx and N2O are anticipated to be high. Our previous studies have been reported the proposed fluidized bed incinerator with the turbocharger (FBIT), which is a new type of incineration plant consisting of a pressurized fluidized bed combustor coupled with a turbocharger, can achieve not only energy recovery but also a low environmental impact. The objectives of this work were to clarify the effect of wide range of operating pressure on flue gas characteristics in a laboratory-scale pressurized fluidized bed combustor (PFBC). As the results, CO and NOx emissions depend on the pressure in the combustor, and these emissions decreased with increasing operating pressure. N2O emission was strongly depended on the freeboard temperature in the combustor.
Recently, the biomass gas is remarked as renewable energy. The practical use for the fuel is reported. Some of biomass gas are produced by the gasification with the gas furnace and the others are collected by sewerage processing. The gas includes various species of components which are such inert gas as Nitrogen N2, carbon dioxide gas CO2 and flammable components as hydrogen H2, methane CH4 and carbon monoxide CO. The fuel calorific value depends on the ratio of each component. In this study, the diffusion flame is formed when the biomass gas spouts from the burner nozzle. The practical biomass gas BG and dilute hydrogen H2 with mixing Nitrogen N2 are used as the fuel. The characteristic of combustion with the low-calorie gas fuel is investigated. As for the practical use, the engine is operated by using the biomass gas. The performance of the engine and the components of exhaust gas are measured. It is found that the biomass gas is effective as renewable fuel.
This paper reports on the relationship between biomass char property and gasification reactivity. The gasification kinetics of biomass char has been revealed by measuring the rate of weight loss during reaction with CO2, as a function of temperature. First-order kinetic rate constants are determined by fitting the weight loss data using a random pore model. The relationship between char structure and CO2 gasification reactivity was investigated in the range of 873 to 1073K (pyrolysis temperature), and 0.1 to 3.0 Mpa (pyrolysis pressure) at 1073K. The experimental results indicate that the reactivity of the biomass char is determined by pyrolysis condition. The gasification rate of biomass char decreases with increasing pyrolysis temperature. This is due to promotions of carbonization and dehydrogenation of biomass char. The CO2 gasification rates in char generated at 0.1 MPa exhibited approximately twice values compared to those at 3.0 MPa. This is because the uniformity of carbonaceous structure rises with increasing pyrolysis pressure. The uniformity of carbonaceous structures would affect the CO2 gasification reactivity, and the decreasing uniformity would lead to the progression of cavities on the char surface during the CO2 gasification process.
From a viewpoint of environmental preservation and resource protection, the recycling of wastes has been promoting. Expectations to new energy resource are growing by decrease of fossil fuel. Biomass is one of new energies with prevent global warming. This study is an attempt to burn pruned branches of plum trees in order to thermally recycle waste products of fruits agriculture. The devolatilization property of pruned branches of plum trees were observed by the thermogravimerty and differential thermal analysis (TG/DTA) to obtained fundamental data of fuel pyrolysis. The thermogravimetric analyzer was used to measure weight loss and temperature difference. It observed that the weight of pruned branches was decreased under three stages with endothermic reaction during water vaporazation and volatile pyrolysis, and with exothermic reaction during combustion of volatile and fixed carbon. The combustion behavior of pruned branches was observed in the electric furnace, where the video-recording and measurement of pruned branches weight were carried out at sequential steps of the combustion process. It observed that the combustion behavior of pruned branches was similar to woody pellets. The effects of furnace temperature and branch size were examined in order to elucidate the combustion characteristics as fuel, such as ignition delay, burning period, char-combustion time and the change of weight decrease. The results indicated that they are influenced at each step of the combustion processes such as devolatilization, ignition, visible envelope flame combustion and char combustion. Pruned branches showed medium values of characteristic time between of cider and woody pellet, and therefore ume plum pruned branches are considered to be promising alternative fuels.
Various conversion technologies of biomass have been created since the development of utilization technology of biomass was worked on in 2000. However, the innovation conversion technologies created by the development still have problems of high water content and low density, which are negative points on usage of biomass. From the viewpoint of density of biomass, we crushed molecular space of biomass without carbonization and semi-carbonization. In this study, we measured internal thermal conduction of high-density solid biomass, closing asymptotically to true specific gravity 1.4 of biomass and investigated the characteristics of internal thermal conduction. It is shown that the value of dT/dr which shows spatial thermal gradient constantly increases with time course and not by depending on conditions. Also, it is shown that the dT/dr takes the ultimate value 380K/m and gradually decreases after taking the ultimate value.
In order to reduce the exhaustion of carbon dioxide, the utilization of unused woody biomass such as forestry biomass and pruned branch has come to attract attention as an alternative fuel of coal. Most of the coal are used at coal-fueled power plants and iron mills. In the present study, bio-solid fuels to alternate coal cokes are investigated. Pruned branches of ume and persimmon which are the typical fruit trees cultivated in Wakayama prefecture are used as biomass resources. To establish a technical basis for the method of manufacturing bio-solid fuel with high hardness, effects of molding temperature, tress species and diameter of pruned branch on compressive strength properties of bio-solid fuel are clarified. The results obtained are as follows. In the case of ume, the compressive strength has a maximum, when the molding temperature is 140-160 degree C. There is no effect of diameter of pruned branch on compressive strength. In the case of persimmon, the compressive strength has a maximum, when the molding temperature is 180 degree C. The compressive strength decreases with decreasing the diameter of pruned branch. The difference in compressive strength between ume and persimmon is considered to be caused by the particle shape.
Sulfur oxides (SOx) are one of the main sources of acid rain. In a fluidized bed combustor, limestone is a directly supplied into the combustor, as a desulfurizer in order to decrease the emissions of SOx from fuel, such as sewage sludge and coal. In our previous studies, NaCl-doped limestone has a good performance on the desulfurization characteristics. In the present study, the effect of alkali metal compounds NaCl, KCl and LiCl-dopings on the formation of CaO crystal structure was simulated by the molecular dynamics method. The result indicates that KCl in KCl-doped CaO deforms more largely the CaO crystal structure than NaCl, because K atom tends to separate from Cl atom at high temperature due to larger ionic radius of K than that of Na. For LiCl-doped CaO, LiCl also deforms the CaO crystal structure, because Li, whose ionic radius is smaller than that of Na, can move freely inside the CaO crystal lattice at high temperature. Based on the results obtained by the molecular dynamics simulations, only the NaCl-doping into CaO has a positive effect on the CaO crystallization. Consequently, this NaCl-doping may enhance the desulfurization efficiency. From this viewpoint, the molecular dynamics simulation can well explain the relationship between the desulfurization efficiency of CaO and the effect of alkali metal compounds addition into CaO.
In order to acquire the relevant creep characteristics such as stress exponent and activation energy, creep strain tests were conducted on Sn-3.5Ag and Sn-5Sb systems of solder alloys in the intermediate temperature regime from 353K to 453K corresponding to the homologous temperatures η=0.715∼0.917 and η=0.699∼0.897 for two alloys, respectively. It was found that an apparent creep-activation energy of both Sn-3.5Ag and Sn-5Sb solder alloys had a changing point at theη=0.82 under the higher stress of 9.8MPa. At the lower stress of 4MPa, the change point was found only for Sn-5Sb alloy. Moreover, under the lower stress level (less than 6MPa), the stress exponent of the both solder alloys indicated n Nearly Equal 1, while under the higher stress region (more than 9.8MPa), the stress exponent of the both solders showed n>7. Determining factors of creep deformation were discussed in relation with the temperature and stress regimes. It was considered that the deformation of the both solder alloys is dominated by the rate of the dislocation climb/dislocation glide at the higher temperature and stress regime.