Abstract
Slurry viscosity in the preheater of the NKK 2.4 ton/day direct coal liquefaction process was estimated from observed results of pressure-drop and temperature distributions through the preheater. The estimation of slurry viscosity was performed by utilizing the modified Lockhart-Martinelli (L-M) method for gas-liquid two-phase flow at normal temperature and pressure. In this method, the relationship between the fluid parameter, X, and the square root of the pressurd drop ratio, φg, for the gas phase was modified for estimated results to fit those observed for a cold hydrogen-gas/creosote oil system and for a hot hydrogen-gas/anthracene oil system. On the basis of the modified relationship, the slurry viscosities were estimated for hydrogen rich gas/Illinois No. 6 coal particles-anthracene oil slurry system under liquefaction conditions. The estimated slurry viscosity was found to increase with the initial volume concentration of coal particles in the slurry. The viscosity also increased monotonouly with temperature for slurries having lower coal concentrations, while exhibiting a maximum for those with higher coal concentrations, implying that the viscosity change was caused by swelling of coal particles. The difference of temperature ranges for viscosity peak appearance in the preheater and in a batch viscometer was recognized and attributed to differences in the slurry heating rates between the two apparatus.
