Morphological changes and caking properties during the carbonization of eight slightly-and non-caking coals (SNCC) were studied in their single and co-carbonization with a caking coal to evaluate them as a blending component. The coals were classified according to their petrographic analyses and coking properties into four categories (1) high rank (2) low rank (3) high inert content (4) weathered. The morphological examination revealed that vitrinites of their reflectance ranging 0.58 to 2.04% Ro except for weathered ones exhibited softening whatsoever in the carbonization. The fluidity of blended coal was estimated from the amouts of vitrinite of this range and inert, allowing the estimation of coke strength. It is noted that the carbonization above 200°c developed fissures in the most grains of non-fusible vitrinites in low ranking SNCC due to large amount of volatile matter, which reduced the strength of cokes obtained by the co-carbonization. Such vitrinites should be carefully distinguished from inerts of low volatile content at their blenging.
For evaluation of solvent involving coal derived liquids during coal liquefaction, reaction mechaninsm and rate of coal dissolution and semi-coke formation were examined at 723 K under 10 MPa of nitrogen or hydrogen with tetralin, naphthalene and creosote oil for Taiheiyo and Illinois No.6 coals. Semi-coke was defined on the basis of kinetics as pyridine insolubles obtained by rehydrogenating reaction residue at 723K and 10 MPa of hydrogen with an excess amount of tetralin and its fromation reaction was decelerated in the presence of hydrogen donor solvent. The reaction rate of coal dissolution to pyridine solubles can not represent as a n-th order reaction with respect to concentration of hydrogen donor solvent under the conditions in which semi-coke formation is observed at the same time with formation of lighter liquid products during coal liquefaction. Pyridine solubles contained inherently in original Illinois No.6 coal seemed to be not concerned with the semi-coke formation even under nitrogen atmosphere. The semi-coke formation, however, occurred with mixed solvent such as creosote oil even under 10 MPa of hydrogen. These results suggested that the semi-coke formation reaction depended on the concentration of transferable hydrogen in solvent, and mass transfer in the solvent and coal particles was also not ignored to evaluate solvent for coal liquefaction as well as chemical parameters such as the hydrogen donating ability, the amount of transferable hydrogen in solvent.
A single particle of coal char was gasified with CO2/Ar atmosphere at the temperature of 1273 to 1773K. The pore structure and the ash properties in a gasified char particle were investigated. Two kinds of reacting zone (B, C zone) were observed in the char. Primary gasification occurred in inner shell (B zone) and the thickness of the shell decreased with temperature. The thickness of C zone which consists of ash and unreactive residue (carbon content is below 30 wt%) maximized at the temprature range of 1473 to 1573K. This suggests that the residue is surrounded by cohered ash or high viscous melting ash and that gasification reaction is prevented. Above 1673K, ash was completely melted and the thicknese of C zone, therefore, decreased. Small sphere ash particles were observed within unreactive char.
In order to reduce NOx and the ignition loss generated by the pulverized coal combustion, the secondary gas fuel injection method is investigated at the pulveried coal combustion test facility (standard load: 6.54×105kcal/h). The secondary gas fuel injection method is to inject the gas fuel (H2, CH4, C3H8) in the flame for the NOx reduction. In the case of using CH4 or C3H8 as a secondary fuel, the NOx concentration is reduced for both combustion conditions of non-two stage combustion and stage combustion. But, H2 doesn't have any effect for NOx reduction. For CH4 or C3H8 injection, the NOx reduction effect is different for the location of the injection point. At the case of non-two stage combustion condition, the better injection location for Nox reduction is distant from the burner and C3H8 is more effective at many points for injection than CH4. On the contrary, at the case of two stage combustion the location near the burner is suitable for NOx reduction in both CH4 and C3H8 injection.