Does coking dry gas crystallize in winter at low temperatures in front of valves with flow restrictions?

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Under normal feeding conditions, the hydrogen production unit using coking dry gas experienced a gradual decrease in the feed rate at noon. Even after increasing the size of the control valve, the feed rate did not improve. Upon inspection, the flow meter was functioning properly, the pressure of the coking dry gas entering the unit remained unchanged, and the valves were not frozen; the valve stem could move as intended when adjusted. Eventually, an experienced technician resolved the issue by heating the valve seat with steam. The experienced technician said that it might be the case that the coking dry gas causes crystallization at the valve stem under low temperatures, leading to blockage of the valve stem. So the question is, what components in coking dry gas can cause crystallization? Does it contain salt? Please analyze it