Effect of solvent on the viscosity changes of coal-oil slurry under high temperature-high pressure during preheating

摘要

Coal-oil slurry preheating is an important step during coal direct liquefaction, and some physical and chemical changes will occur that will affect the viscosity of coal-oil slurry. The project is necessary for the building coal direct liquefacation demonstration plant and has a good application prospect. A rotary viscometer that can measure the viscosity of coal slurry at high pressure-high temperature was designed and manufactured by self. Two kinds of solvent including anthracene oil, Shenhua recycle oil (coming from Shenhua coal direct liquefaction pilot plant) and Yanzhou coal were used. The coal-oil slurry is prepared by mixing the solvent with the coal powder (<200 mesh) according to coal/anthracene oil and recycle oil weight ratio equal to 2/3 and 11/9 respectively. The slurry was putted into the high temperature and high pressure viscometer and heated under 5MPa initial hydrogen pressure at the rate of 5 ℃/min till the different setting temperature. At the same time the viscosity changes with increasing temperature of coal-oil slurry was investigated under atmosphere. The results show that the viscosity of Yanzhou coal-anthracene oil and Shenhua recycle oil slurry decrease firstly for the decreasing of solvent viscosity, then increase with measuring temperature for the absorption and volatilization of solvent under atmosphere. Both of them have a viscosity peak with increasing measuring temperature under atmosphere. However, the Yanzhou coal-anthracene oil slurry has a viscosity peak at about 310 ℃ under high pressure during preheating, the Yanzhou coal-Shenhua recycle oil slurry has not a viscosity peak but coke deposit appearance above 350 ℃ under high pressure during the whole preheating. In addition, the viscosity-temperature characteristics of preheated coal-oil slurry through different temperature are same that both of them have a peak appearance with increasing preheating temperature at the same measuring temperature except the viscosity values.