Abstract
The conversion of brown coals and sapropelic coal in toluene containing mixtures with co-solvents (water, ethanol and tetralin) was studied under sub- and supercritical conditions within the temperature range of 375-550°C and at pressures from 7 to 40 MPa. It was found that the extent of coal extraction in the toluene solvent medium, at 400°C, was significantly increased by the addition of small amounts of hydrogen-donor tetralin or ethanol co-solvents. The extract yield from sapropelic coal reached 79-83%, with the gas yield being small. The effect of process variables on extract yields under sub- and supercritical conditions was monitored. Coal extraction in the toluene-tetralin mixtures was found to depend mainly on the hydrogen donor ability of the tetralin co-solvent irrespective of sub-or supercritical toluene states. According to the composition, the bitumen extracted from coals can be used as a feedstock for pitch production. In the water containing mediums, aside from coal liquefaction, coal methanation, hydrolysis and oxidation reactions occurred resulting in the generation of large amounts of methane, hydrogen and carbon dioxide.
Highlights
The non-fuel use of coals includes mainly the high temperature carbonization of bituminous and sub bituminous coals to make metallurgical coke
The yield of bitumen extracted from brown coals by boiling toluene in a Soxhlet apparatus did not exceed 2
Chaidakh brown coal showed higher conversion as compared to Borodino coal. Low extractability of the latter may be due to enhanced amount of calcium which was found (Kuznetsov et al, 1997) to be a strong cross-linking agent in organic coal matter resulting in restricted accessibility for the solvent molecules
Summary
The non-fuel use of coals includes mainly the high temperature carbonization of bituminous and sub bituminous coals to make metallurgical coke. This process produces coal tar as a by-product. The future of the coal tar production far seems dim, despite a growing demand in both the aluminum industry and in many other industries for the production of modern highvalue-added products. These differently directed trends in tar demand in the aluminum industry and in tar production in the metallurgical industry are faced with the problem of needing to search
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