A Process Design For Methane Purification After Nitrogen Replacement On Natural Gas Pipeline

The process of town gas pipe network often involves the replacement of corrosionpipe segment, pipeline etc. The repairing and maintenance work usually involves welding,arc welding and welding operation. For the safety of operating personnel, an inert gassuch as nitrogen is generally used to replace the residual gas in the gas pipeline. Whenthe maintenance action is completed, natural gas must be used to replace the residualnitrogen in the operation pipe segment before the resumption of gas, and then the volumeconcentration of natural gas can be consistent with the urban gas supply requirements. Inaddition, with the advancement of urbanization, the coverage of the city gas pipeline hasbeen increasing year by year. For an example of a coastal city of South China, thestatistics show that the city gas pipeline maintained an average growth rate of nearly12%.These new pipelines are usually filled with compressed air in the completion of theinspection; before operation, the compressed air need to be compressed, then theremaining air can be replaced with inert gas (usually nitrogen).Finally, the valve of thesource of natural gas is open,then nitrogen remaining in the pipeline can be replacedwith natural gas.The two replacement process is often accompanied by a lot of natural gas releasing,which can be used to guarantee the natural gas concentration meet the requirement forgas supply. This process not only increases the levels of green house gases in theatmosphere, but also results in a waste of energy to a certain extent. Therefore, thepurification for natural gas and the recovery of methane during the process ofreplacement operation, which not only has economic benefits, but also conducive to theatmosphere environment, has the good social efficiency.Pressure swing adsorption, as a new type of gas separation technology, has theadvantage of high product purity, working at room temperature, working at low pressure,without heating on bed regeneration, simple equipment, convenient operation, convenientmaintenance, continuous operation, automation etc. After years of development, Pressureswing adsorption technology, which has become mature increasingly, obtained the rapid promotion and application in chemical industry, environmental protection and coalindustry. From the original single tower to Twin-Towers, Three-towers, Four-towers etc.The devices which are becoming more and more complex play a very important role inthe field of chemical industry.According to the characteristics of natural gas pipeline replacement operation, thispaper plan to use an activated carbon as an adsorbent, design and develop a set of process,which can be used for the separation of nitrogen and natural gas. The device, which ismade by means of the process, will have the characteristics of small, skid mounted,portable, automation, simple operation and maintenance. The process design can providea new way of solving the problem of a lot of dissipation during the process of natural gasreplacement for nitrogen in the pipeline.