Abstract
Solid accumulation characteristics was examined in a 240mm dia. and 2720mm high reactor of 2.4ton/day NKK direct coal liquefaction process. The characteristics was largely influenced by gas flowrate. No solid accumulation was observed at gas feedrates higher than 400Nm3·h-1. At a low gas feedrate of 300Nm3·h-1, the axial temperature profile in the reactor was not uniform and solid accumulation occurred due to insufficient fluid mixing. The accumulated solids were found to be mainly composed of two types of compound, which were small pieces of metal iron generated from ball mill for coal slurry prearation and agglomerates of sulfides of liquefaction catalyst and metal iron. The composition of solids obtaind in the present reactor was diffrent from those in other coal liquefaction plants, which mainly arised from formation and agglomeration of mineral matter such as CaCO3. The characteristics of solid accumulation was well simulated by a sedimentation-diffusion model with densities and linear velocities of gas and liquid under coal liquefaction condition, which were estimated on the basis of gas-liquid equilibrium. It was suggested from the model that ash accumulation is more hardly to occur in the present reactor under the conventional operating conditions than in the other coal liquefaction reactors.
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