Research And Design Of Air Cooled Propane Cooling Natural Gas Refrigeration Equipment

In the process of West-East Gas Pipeline in the western development,wellhead raw gas in gas-field natural gas treatment stations often contains a small amount of water and heavy hydrocarbons.Before entering the long-distance pipelines,in order to prevent ice blocking caused by the C5~+heavy hydrocarbon solidification,prevent the formation of hydrate,reduce the corrosion of free water and C5~+heavy hydrocarbon on the pipeline,reduce the transmission resistance,dehydration and dealkylation treatment is needed for the raw gas,called"Shallow Cut".That is,the raw gas is cooled by the temperature drop method through a propane cooling heat exchanger so that the water dew point and the hydrocarbon dew point in the raw gas are reduced to below-5?,meeting the separation requirements,and then the water and heavy hydrocarbons in the natural gas are effectively removed through the low-temperature gas-liquid separation process,the gas quality index of the national second-class commercial natural gas as specified in the standard of"natural gas"(GB17820-2015)is achieved,which increases the external transport efficiency of natural gas.In this paper,a natural gas processing station in the Cainan operation area Xinjiang Zhundong oilfield is taken as an example to conduct a systematic research and design on the air cooled propane cooling natural gas refrigeration unit adopting the temperature drop method for shallow cut treatment process.After desulfurization,compression and pressurization,alcohol injection and other pre-treatment process,the natural gas temperature at the inlet of the propane kettle type evaporator in the air cooled propane cooling natural gas refrigeration unit is about 0 to 5?,the inlet pressure is about 3.0-5.0 MPa.The natural gas at the outlet of the evaporator should be cooled to-15?.The daily processing capacity of natural gas is about 180,000 standard cubic meters/day(18×10~4Nm~3/d).Taking this nominal condition as an example,the design method of air cooled propane cooling natural gas refrigeration unit is described in this paper,including:HCFCs and HFCs phase-out schedule,analysis of the reasons for the selection of HCs environment-friendly refrigerant R290 as a refrigerant,selection of compressor lubricant,design calculation of propane screw compressor,design calculation of U-shaped tube kettle type evaporator(natural gas cooler),design calculation of thermosyphon oil cooler,design calculation of economizer,design calculation of propane air cooler(air-cooled condenser),application of the explosion-proof pneumatic valve(throttle valve for the evaporator),the overall explosion-proof and anti-static treatment principles of the electrical components under harsh working conditions such as outdoor open-air,high temperature,low temperature,wind,sand,rain and snow,PLC automation control and the design selection of main components.At the same time,the strength of cylinder,cone shell,head and other main pressure components in the container is checked,and the safety valve is designed and selected.Based on the theoretical analysis and design calculation,the design and verification of the integrated integral skid block device of ZLLGB12.5 air cooled propane cooling natural gas refrigeration unit is completed.After the completion of unit processing,the full performance test for the air cooled propane cooling natural gas refrigeration unit is carried out,and the test results under the nominal conditions are listed.Aiming at the existing problems,the in-depth performance analysis is conducted and reasonable measures are provided.My own opinions about the research and design of the refrigeration unit are put forward,and the design calculation work is summarized.The general idea for the structural design of the air cooled propane cooling natural gas refrigeration unit is provided,and solution for the main technical key points is given.The subsequent performance test shows that the air cooled propane cooling natural gas refrigeration plant meets the use requirements on site,and all the main technical parameters have reached the design specifications under nominal conditions.