Reactor residuum concentration control in hydroconversion of coal

Abstract

A process for the hydrogenation of coal at elevated temperature is disclosed, wherein particulate coal having an average particle size of less than 1000 microns is admixed with a liquid hydrocarbon to form a slurry containing about 30-50 weight percent solids, and the slurry is passed to an ebullated bed reactor wherein the coal is catalytically hydrogenated at reactor pressure of about 100 to 300 atmospheres to produce hydrocarbon products including a liquid residuum containing unconverted processed coal solids. The improved process includes the steps of removing the hydrocarbon products from the reactor; reducing the pressure of the hydrocarbon products not more than 10% below reactor pressure to separate the hydrocarbon products by phase separation of the gaseous components from the liquid component containing residuum and unconverted coal solids; dividing the liquid into a stream for liquid-solids separation and a bypass stream; passing a portion of the liquid residuum to a liquid-solids separator at substantially the same temperature as the phase separating step; recovering from the separator a purified liquid product stream containing a substantially reduced concentration of unconverted coal solids combining a sufficient amount of the bypass stream with the solids reduced stream to maintain the desired levels of solids and residuum in the reactor; recycling the purified liquid product stream to the ebullated bed reactor in a liquid handling system wherein the pressure throughout the process is maintained at least 90% of the reactor pressure; and recovering from the cyclonic separator a second liquid product stream containing 25 to 45 weight percent unconverted coal solids.