In the study of coal gasification, it's necessary to analyze the diffe-rent reactivity for coals. Then we estimated coal gasification reaction in point of macer-al, which was a component of coal, uniformly tried to evaluate the reactivity. We prepared four demineralized coals (Taiheiyo, Datong, Wandoan, Plateau) by the HF-HCl treatment to remove the catalytic effect of ash and carried out density separa-tion of these coals by the ZnCl2 solution (density range; 1.20-1.50) to have some sam-ples with concentrated maceral from same coal. Every fractions were gasified in a CO2 stream under 850°C, using a thermobalance and measured the reaction rate and reaction order from TG-curve. Futhermore, some fractions were characterized by ultimate and proximate analysis, CO2 surface area, chemisorbed oxygen, 13C-NMR, maceral analysis, which showed different values. Apparently, the initial reaction rate based on CO2 sur-face area was proportional to acertain maceral ratio, the rate corrected by CO2 surface area and maceral ratio had an exponential relation to H/C ratio. Also the reaction order was proportional to the vitrinite ratio in maceral groups. Consequently, it was possible that the reaction rate constant and reaction order were estimated uniformly with H/C ratio, CO2 surface area, and maceral ratio.
Coal liquids have a very complex composition including paraffins, naph-thenes, phenols, basic compounds and alkylated aromatics which have so many isomers that it is very hard to separate pure compounds. Thermal dealkylation is one method for simplifying the composition of coal liquid be-cause nearly all isomers decompose to unsubstituted aromatics. In the previous studies the authors tried to use methanol as a hydrogen source in-stead of hydrogen itself. Methanol decomposes thermally to carbon monoxide and hydrogen. This hydrogen produced from methanol in situ acts favourably on the dealkylation of coal liquid. In this study we examined the possibility of recycling excess hydrogen produced as a flow gas and to supply the consumed hydrogen as methanol. Thermal dealkylation of ethylbenzene as a model compound and coal liquid were carried out in the quartz glass tube reactor in H2 flow under normal pressure at 700-950°C varying the H2 flow rate or methanol concentration. The main results are as follows: 1) In the reaction of ethylbenzene with methanol in N2 flow, with increasing the con-centration of ethylbenzene in methanol, the yield of carbon and heavy condensation products increased and that of benzene decreased, because of the increase of the conde-nsation reaction of aromatic nuclei. In the present results with the quartz tube reactor, the yield of benzene was a little higher than the previous ones with the stainless steel tube reactor at same condition. 2) In the reaction of ethylbenzene with methanol in H2 flow with increasing the con-centration of methanol, the yield of carbon and heavy condensation products decreased and that of benzene increased. It was shown that for dealkylation in H2 flow, methanol addition is very effective. 3) After the reaction of coal liquid (naphtha and light oil) at 850°C 24ml/min of H2 flow rate, and 13 wt‰ of methanol addition, almost all paraffins, naphthenes, phenols and alkylated aromatics disappeared. The composition of liquid product became extreme-ly simple. Each main components will be easily separated by simple method.
Chars prepared from 22 kinds of coals and demineralized coals are gasified in an air atmosphere using a temperature-programmed reaction (TPR) technique in which the chars were heated at a constant rate. It was found that 8 kinds of coal chars were gasified in two steps. This phenomenon was called two-step reaction here. There found to be exist at least two types of two-step reaction. Based on the measure-ment of the heat of reaction and the activation energy, the second step reaction observed for the chars prepared from several low rank coals was found to be due to the gasifica-tion of a less reactive carbon produced by the catalytic effect of Ca and/or Mg during the first step reaction, as has been reported in our recent works. On the other hand, the two-step reaction observed for two high rank coal chars was found to derive from the gasification of different maceral groups. It was clarified that the first step is mainly the gasification of vitrinite, and that the second step is mainly the gasification of inertinite.
The equilibrium moisture base of coal at 75‰ relative humidity and at a room temparature has been one of the moisture basis specified in the Japanese Industrial Standards (JISs) related to coal analysis. The abolition of it has been disputed since 1950s with a view of improving precision of the coal analysis and due to necessity of leveling the JISs with those of the ISO (International Organization for Standardization) to reduce the trade friction. The questionnaire was sent among the 80 coal-dealing companies by the Union of Japanese Scientists and Engineers as to establish whether the equilibrium moisture base should be abolished or preserved. 59 companies have answered the questionnaire, 51 of which unconditinally agreed with the abolition of the equilibrium moisture base. Based on the possitive results of the questionnaire, the equilibrium moisture base was decided to be abolished in the JISs at the occassions of their next revision. JIS M8812 and M8814, at present under revision, are the first ones to undergo the equilibrium moisture base abolition in their drafts. M8810 is the one to follow.
The effect of properties of 12 kinds coals such as C‰, H/C ratio, O/C ratio, fuel ratio on liquefaction conversion and product yield has been investigated. The main conclusions from this work are: 1. The linear correlation between carbon contents, fuel ratio of coals and liquefaction conversion did not recognized. 2. The yield of gaseous product are increased with decrease of carbon contents of coals. 3. Produced oil from the coals which have high value of H/C, contains high portion of light fraction (b.p-220°C).