Conceptual study of hydrogen donor solvent in the NEDOL coal liquefaction process

A 150 ton/day coal liquefaction pilot plant (PP) of the NEDOL process, supported by New Energy and Industrial Technology Development Organization (NEDO), was operated successfully for a total of 269 days at Kashima, Japan. With a great number of data obtained through the operation, the design procedure for the NEDOL process was studied. Middle and heavy oils from the coal employed were recycled as a hydrogen-donor solvent after hydrotreatment over Ni Mo/gamma-Al2O3 in a trickle bed reactor. The hydrogen donating ability of the solvent was high enough to obtain higher oil yield (50-58 wt%) at the aromaticity of ca. 0.45. Life expectancy of solvent hydrotreatment catalyst, requisite to the hydrotreater design, was estimated under PP operating conditions. In addition, physical properties of the solvent required for process design were determined, and hydrodynamics in the liquifaction bubble column reactors were examined. Taking the obtained hydrodynamics and thermal behavior into consideration, we established a design procedure of the liquefaction bubble column reactors using a process simulator (CARD) validated by the product yields of PP. The Simulation including distillation and solvent hydrotreatment showed that the content of heavy oil fraction (b.p. 350 - 538 C in the solvent was a determinant factor in the design of a large scale plant based on the NEDOL process.