The development of coal liquefaction technology using a 150t/d pilot plant of NEDOL process has been carried out in Kashima city, Japan. Since December 1996 to September 1998, the pilot plant has been successfully operated without any seri-ous trouble throughout the operations. However a variety of massive solid matters appeared inside the heating coil of vacuum tower heating furnace, especially upper side of the inner wall of the coil. In this paper, these solid matters were analyzed chemically and morphologically to investigate their formation mechanism. The solid products were found to consist of coal minerals and catalyst which were dispersed in the semi-coke block on the upper side of the coil showing zigzagging bound-ary. Coke forming mechanism speculated from our study was as follows. (1) Vaporization of light fraction in coal liquid forms slug flow pattern of coal liquid inside the heating coil. (2) Upper side of the heating coil is heated up above 450°C with high heat flux. (3) Splashes of coal liquid containing coal minerals and catalyst were trapped first on the upper surface of the heating coil. (4) The coal liquid trapped on the upper surface is carbonized quickly, to form semi-coke of high densities. (5) In the next stage, light fraction in the liquid is vaporized to be further trapped among the semi-coke grains produced first on the wall, giving semi-coke of well-developed anisotropy and low mineral content. Steam injection was useful to inhibit development of the coke. Elimination of light fraction in the coal liquid before vacuum distillation and reduction of heat flux of the fur-nace are effective to inhibit development of the coke.
Energy usage in Japanese households sector is increasing, and it is becoming important to analyze household demand in considering the energy systems for Japan. We analyzed the electricity consumption in households through micro data obtained from the National Survey of Family Income and Expenditure conducted by the Management and Coordination Agency of Japan. The dependence of electricity con-sumption on the major factors: ie annual family income, ages of family members and superficies of residence, is evaluated by regression analysis. Electricity consumption is confirmed to increase as household income and superficies of residence increase. It is also shown that the ages of family members have considerable influence on the electrici-ty consumption.
Rapid pyrolysis behavior of a single coal particle in a spot heater apparatus was investigated under various conditions, such as pressure (N2 atmosphere), temperature, heating rate and type of coal. During the heating, temperature-time histo-ry of coal sample was measured directly by a thin thermocouple and recorded automati-cally by a logger, and releasing images of volatile matter from a single coal particle were obtained by a CCD camera. Total weight loss of coal sample by pyrolysis was also meas-ured. Both the total weight loss and images showed that pyrolysis yield of coal depends on pressure, heating rate and temperature. Pressure had a significant impact on coal pyrolysis, which is attributed to secondary reactions and the resistance of volatile trans-fer in the coal particle. At higher temperature and higher heating rate, the amount of releasing volatiles from a coal particle increased, and a large releasing rate of the volatiles may reduce the opportunity for secondary cracking reactions and carbon depo-sition. Based on the analysis of image data, kinetic parameters for coal pyrolysis, such as apparent activation energy and frequency factor were estimated by using a first order reaction model.
Attrition and fragmentation of limestone in a 71MWe pressurized flu-idized bed combustor were estimated. Formation of Ca-containing fine particles due to attrition rate was calculated from the material balance of calcium in fly-ash which was captured at the exit of combustor. The average rate of attrition (rate of reduction of radius) of limestone was estimated to be approximately 1μm/h. A population balance model was established to estimate the particle size distiribu-tion in the bed from the size distribution of fed limestone and attrition rate of bed materi-al in the bed. For some cases, the measured bed material size was far smaller than that of the estimated size distirbution. These results suggest that the fragmentation of lime-stone particle took place in the bed. The size distribution of limestone after fragmenta-tion was estimated so that the difference between estimated bed material size distribu-tion and measured size distribution should be minimized. The results indicates that the large limestone particles (greater than approximately 1mm) were broken into small parti-cles when they were fed into the combusotor.
SO2 capture by limestone was conducted within a 71MWe pressu-rized fluidized bed combustor. Mixtures of high-sulfur petroleum coke and low-sulfur coal with different mixing proportion were used as fuels. The effect of the size distribu-tion of limestone on SO2 removal efficiency was evaluated. The SO2 removal efficiency was well correlated with feed rate of external surface area of limestone greater than the cut size of cyclone that recycled elutriated fine particle into the bed. A semi-theoretical correlation between size distribution of fed limestone and SO2 removal efficiency was proposed. This model assumed the uniform formation of SO2 in the dense bed, SO2 cap-ture in the dense bed by fresh limestone of fractions greater than elutriation size, and SO2 capture in the freeboard by fresh limestone of fractions smaller than the elutriation size but greater than the cyclone cut size.