Pre-cooling type heavy hydrocarbon recycling system and technology for offshore natural gas extraction

The invention relates to a pre-cooling type heavy hydrocarbon recycling system and technology for offshore natural gas extraction. The pre-cooling type heavy hydrocarbon recycling system is characterized by comprising a refrigerator, a pre-cooling system and a heavy hydrocarbon separation system, wherein three-level cooling is adopted by the pre-cooling system for supplying cooling energy to the heavy hydrocarbon separation system for processing natural gas and LPG (Liquefied Petroleum Gas). According to the technology, the cooling energy of a pre-cooling unit and the pressure of the high-pressure natural gas can be fully utilized to fully recycle heavy hydrocarbon in the natural gas, so that the propane recovery rate is increased, and better economical efficiency is achieved. The backflow of top gas phase to a contact tower is adopted by a deethanizer of the pre-cooling type heavy hydrocarbon recycling system, so that the heavy hydrocarbon is more fully removed from the natural gas in the heavy hydrocarbon separation system, and the efficiency of removing the heavy hydrocarbon from the natural gas is effectively increased. The inner equipment of the pre-cooling system and the heavy hydrocarbon separation system is compact and simple, process valves are fewer, and the mounting is convenient, so that the pre-cooling type heavy hydrocarbon recycling system is easily applied to the offshore operation. The pre-cooling type heavy hydrocarbon recycling system provided by the invention can be widely applied to a heavy hydrocarbon recycling technology for the high-pressure natural gas under an ocean production environment.