Research On Process Flow And Parameters Of Natural Gas Culvert Differential Pressure Power Generation System

At present,the country vigorously promotes the research and development of new energy,the Party’s 20 Congress emphasized that to control fossil energy consumption,actively promote carbon peak,carbon neutrality.In the process of natural gas pipe network transportation,high pressure natural gas can only enter the medium pressure and low pressure pipelines after being depressurized by the regulator station,which ultimately provides security for urban residents’gas needs.Most of the existing regulating stations use traditional regulating equipment such as throttle valve and regulating valve to reduce pressure,which leads to the waste of huge pressure energy generated during regulating pressure.Using this residual pressure to generate electricity,a new energy-pressure energy of natural gas pipeline network is derived.The pipeline pressure energy generation technology is mature and has been successfully applied in several pilot projects.However,at present,most of the pilots use expander to drive the generator for pressure energy generation.There are some problems,such as easy leakage of natural gas,unstable power generation and easy loss of equipment,which lead to the failure to popularize the differential pressure power generation technology.There are differences in the utilization of pressure energy in different regulator stations,and the design of the existing pressure energy power generation process is lacking of pertinence.Therefore,the structural principle of a culvert permanent magnet generator is proposed in this paper to solve the problems of natural gas leakage and power generation system instability when the pressure energy is utilized.This paper takes the working conditions of a city gate station and sub-station in Southwest Petroleum Field of China as the research object,designs the best process flow of the city gate station and sub-station,and determines the main size of the culvert permanent magnet generator,which provides reference for the promotion of natural gas pressure energy power generation technology.The main conclusions are as follows:(1)The structural principle of culvert permanent magnet generator is proposed.The structure of the culvert permanent magnet generator has the advantages of natural gas safety,no leakage,high power generation stability(no need to be connected to the generator can be regulated voltage generation),multistage impeller design,etc.(2)The influence of natural gas operation parameters on the power generation performance of the system is explored.The research object is the working condition of city gate station with pressure drop of 3～0.4MPa and flow rate of 100000Nm~3/d.When the upstream natural gas temperature increases by 2.5k W,the system effective output power increases by about 9.5k W.When the flow rate increases 10000Nm~3/d,the effective output power of the system increases by about 2k W.When the pressure difference increases by 0.5MPa,the effective output power will have a nonlinear negative growth,but the effective output power of the system is always positive.(3)The optimal process design of the city gate station and the general size of the culvert permanent magnet generator are determined.Considering the characteristics of low utilization potential of cold energy in differential pressure power generation system for regulating stations with small flow rate and pressure difference,it is suggested to adopt single-stage expansion process design without considering the utilization of cold energy in such regulating stations from three aspects:construction cost,station electricity demand and power generation efficiency.Based on the simulation results of single-stage expansion process at city gate station,the inner diameter of the stator,the length of the core and the thickness of the air gap are determined to be 158mm,372mm and 0.5mm respectively.(4)Carried out the optimal process design of the sub-delivery station.The research object is the sub-station condition with pressure drop of 8～4MPa and natural gas flow of1000000Nm~3/d.There is great potential of cold energy utilization in differential pressure power generation system for sub-transmission stations with larger flow and pressure difference.Therefore,considering economic benefits and power generation efficiency,it is suggested to adopt two-stage expansion,power generation and ice making combined utilization process design for such large voltage regulating stations as substations.