An efficient cyclone device for removing hydrocarbon fog droplets in recycled hydrogen was developed based on experimental studies and industrial application. Conditions for optimal separation efficiency of the gas-liquid cyclone were determined. The device reduced raw material losses and desulfurizer consumption and improved desulfurization efficiency, thereby increasing the purity of the cycled hydrogen and decreasing the mean molecular weight of gas. Energy consumption of the cycled hydrogen compressor as well as the pollution discharge of the hydrogenation unit were also diminished.