Recycle solvents obtained from 150t/d NEDOL coal liquefaction pilot plant were hydrotreated over sulfided Ni-Mo/γ-Al₂O₃ by using an experimental downflow fixed bed reactor at 325°C under 8MPa to examine an influence of composition of solvent on the solvent hydrotreatment. The hydrotreated solvents were divided into seven fractions (compound classes) by HPLC, and the hydrogenation reactivity of each compound class was investigated.
The hydrogenation reactivity of the compound classes was in the following order, mono-aromatics << di-aromatics < tetra-aromatics < tri-aromatics < polar fraction. When Adaro or Ikeshima coal was processed in the pilot plant, as compared with an operation for Tanito-harum coal, the reaction rate constant for solvent hydrotreatment decreased owing to smaller content of polar fraction.
The increase of partially hydrogenated aromatic compounds, naphthenic compounds, in the solvent lowered the hydrogenation reactivity of the non-polar aromatic fractions. The decrease of the reaction rate constant for solvent hydrotreatment in an operation with higher coal concentration slurry (40→50wt%) resulted from the increase of the partially hydrogenated aromatic compounds due to the enhancement of degree of solvent hydrotreatment to promote the hydrogen donating ability.
Results of a series of our researches for the solvent hydrotreatment are useful in identifying the nature of feedstock for solvent on the basis of the properties of coal employed and the operating conditions, which helps to design the solvent hydrotreater.

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It can be supposed that introduction of MGT-CGS to small-medium size buildings will increase in future from the view point of energy saving and global environment because of its suitable capacity to such buildings and high efficiency. In this paper environmental burden of MGT-CGS was evaluated in terms of CO₂ emission in both production and operation stages of the system. Investigation was proceeded for the case in which MGT-CGS was applied to an apartment house (floor space 12, 000 m²) and a super market (floor space 3, 000 m²) as an example. The result was compared with that of grid electricity and heat supply system with absorption chiller-heaters. The possibility of CCO₂ emission reduction was clearly illustrated when the MGT-CGS was installed for an apartment house and a supermarket in common, on the contrary CCO₂ emission was increased in the case of application to each building respectively.
MGT-CGS was more energy saving and less CCO₂ emission system in operation stage, although in production stage MGT-CGS emits more CCO₂ than the ordinary system. This CCO₂ difference in production stage can be compensated in short time by the large annual CCO₂ emission reduction in operation. The time was 0.43 years in terms of CCO₂ pay back.

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