The hydrogenation of coal model compounds using molten potassium and ethanol was carried out with and without ultrasonic irradiation. Aromatic ethers and ploynuclear hydrocarbons were employed as coal model compounds. The cleavage of carbon-oxygen bonds was dominant for the aromatic ethers, whereas main products obtained from the polynuclear hydrocarbons were compounds derived from hydrogenation of the aromatic nucleus. The reaction mechanism was affected by the structure of the substrate: one-electron and/ or two-electron reaction. The effect of ultrasonic irradiation is very small in the reaction of the hydrocarbons. On the other hand, striking effect caused by the ultrasonic irradiation, such as an inccrease of the rate, an increase of the final conversion, and the promotion of sidereactions, ware observed for the reaction of the ethers.
Characteristics of coke deposition onto the inner surface of a coal liquefaction preheater tube were experimentally simulated in an autoclave reactor for a range of industrial operating variables. A test piece with a tubular baffle was installed in the autoclave to generate artificial heat spots in slurry by controlling the heatflux from the piece to the slurry as well as the slurry velocity near the piece. No coke deposition was found to occur under conditions with a bulk slurry temperature of ca. 700K, oil/coal weight ratios from 55/45 to 60/40 and slurry velocities from 0.5 to 1.0m/s. On the other hand, an appreciable coke deposition was observed at bulk slurry temperatures over approximately 720K and slurry velocities below about 0.1m/s. Surface temperature of the test piece increased with a progress of the coke deposition. Within the present experimental conditions, the deposition rate was in a range about 1.5×10-6 to 2.3×10-6g·cm-2·min-1·g-1-coal. Also, amount of coke deposited increased with S/C and O/C atomic ratios of parent coal while decreasing with the increase of H/C atomic ratio of parent coal.
The emission behaviors of fuel-N from coal were studied by pyrolyzing 6 different coals of which the fuel ratio ranged from 0.9 to 6.6, under various heating conditions in He atmosphere. The experiments were made by changing the temperature (573K-1273K), the coal particle diameter (37-4500 μm) and the heating rate (5-1000K/min). As the results: 1) Fuel/N started to be released from coal when the temperature reached about 673-773K, which was about 50-100°C higher than the temperature where the main volatile components like C and H started to be released. 2) Two different emission behaviour of fuel-N from coal were observed below and above 1173K. 3) The conversion of fuel-N increased with decrease in fuel ratio at the same heating temperature. The conversion of fuel-N, the fuel ratio and the temperature were well correlated. 4) There was no influence of coal particle size on the conversion of fuel-N below 1173K. However, when the temperature became higher than 1173K, the conversion of fuel-N tended to decrease with increase in coal particla diameter.