Process Design And Laboratory Test Of Power Generation Utilized In Pipeline Cathodic Protection By Pressure Energy Of Natural Gas Pipeline Network

As a kind of clean and efficient green energy resource,natural gas has gradually replaced other highly polluting energy resources and become the main supplied energy resource for urban power generation and civilian use.With the rapid development of economy and society in China,the living standards are increasing day by day,the demand for natural gas is growing,and the construction of urban natural gas pipeline network has entered the period of rapid development.Most natural gas pipelines are laid underground.During the service period of pipelines,due to prolonged exposure to the atmosphere and soil environment,to the environment where water,oxygen and electrolytes exist,the metal pipelines would be corroded,service life of the pipelines would be shortened and serious safety accidents hazard would happen.At present,the method of combination of internal anti-corrosion,external anti-corrosion and cathodic protection is usually applied for pipeline corrosion prevention.The forced current cathodic protection system is a better one,compared with other natural gas pipeline corrosion prevention measures,which usually needs to be connected to the city power to provide protection current for the pipeline.In order to solve the problems of long distance and high cost of power line laying in remote areas,it is necessary to provide a power supply system for the natural gas pipeline corrosion prevention system that does not rely on the city power and can still work normally under bad weather conditions.First of all,the paper compares three power supply modes(solar energy,wind energy and pipe network pressure energy),and determines the feasibility of applying the pipe network pressure energy generation device to generate electricity and prevent corrosion.After the analysis and comparison of five kinds of power supply devices(turbine expansion generator set,piston expansion generator set,screw expansion generator set,fluid motor and pipeline built-in power generation)in terms of applicable conditions and power generation capabilities,it is determined that the pipeline built-in power generation technology and the forced current cathodic protection system are the best match.Secondly,based on the research background of specific working conditions of gas pipeline network of one city,a process of pressure energy power generation and corrosion prevention technology was developed.The technology recovers the pressure energy of natural gas pipeline at a branch line(diameter to be DN50,pipe pressure to be 0.3MPa,operating flow to be550~700Nm~3/h)to generate electric energy.The electrical energy provides cathodic protection for the mains buried pipeline(length to be 16.5Km,outer diameter to be D1000,X70 material,wall thickness to be 17.5mm,buried depth to be 1.5m,design pressure to be 4.0MPa,design flow rate to be 110×104Nm~3/h)without significant pressure drop.Finally,the experimental result of laboratory testing for the built-in power generation set of the pipeline showed that:Under certain conditions(ie.rated power to be 20W,diameter to be DN50,inlet pressure to be 0.2 to 0.3MPa,flow rate to be 600Nm~3/h),the power supply set reached the best power generation capacity.It can be determined that,under such working condition,the designed process program can realize the self-power supply of the pressure energy power generation and corrosion prevention system,the stable quality of generated power and satisfying the needs of corrosion prevention for the designed pipeline sections.