Abstract: A type of automatically flushing device is suggested to avoid the unreliable closing of the relief valve used in fluid with solid particles, which encounters in coal liquefaction industry. A flushing device of gas-liquid directly contacting accumulator is set up in the pipeline between relief valve and the slurry feeding pipeline. The accumulator is filled with certain amount flushing oil and is connected with inlet pipe of relief valve through flushing oil branch pipe. A control valve is installed in the flushing oil branch pipe and is controlled by signals of the valve clack movement. The valve should be opened automatically when the valve clack is detected to move back to the valve seat. To verify the feasibility of the suggested device, flushing process of coal particles in relief valve is numerically simulated with Eulerian-Eulerian model in FLUENT, in which coal-oil mixture (COM) is the transporting fluid and solvent oil is the flushing oil. The results show that the flushing device can flush away the particles effectively, which promise reliable close of relief valve. Further analysis shows that flushing process is completed instantly, and only a little amount of the flushing oil enters the mainstream. Moreover, the flushing oil is compatible with the COM, so it will not impact the stability of liquefaction process.

Key words: Automatic flush, Coal-oil mixture(COM), Leak-proof, Numerical simulation, Relief valve