Effective viscosity and thermal conductivity of slurry in a preheater of the 150 ton/day NEDOL coal liquefaction pilot plant

In order to investigate the influence of coal property and its slurry concentration on the operability of the preheater at the 150 ton/day NEDOL coal liquefaction pilot plant, the pressure drop as well as the temperatures of tube skin and coal slurry was measured along the length of a hairpin-shaped tube (72 mm φ I.D.×94 mm φ O.D., 440 m in length) of the slurry preheater. Different concentration of coal slurry was prepared for three kinds of coal by using their recycle oil. The measurement of pressure drop and temperatures were conducted under the conditions of coal slurry concentration of 40 to approximately 50 wt% and the gas/slurry feed ratio of 0.27 to approximately 0.35 Nm³-gas/kg-slurry. The results showed that the increase in the pressure drop was observed for Ikeshima bituminous coal, probably due to the swelling of coal particle, whereas little increase was for Tanito Harem subbituminous coal and Adaro brown coal. By simplifying the flow in the tube as a two-phase flow of gas and slurry, the effective viscosity and thermal conductivity of the slurry in the preheater were analyzed.