Research On LNG Satellite Station Cold Energy Used In Cold Water Air Conditioning And Power Generation Integrated Process

In recent years,with the development of China's economy and the enhancement of people's awareness of environmental protection,the demand for liquefied natural gas(LNG)is increasing.LNG satellite stations are rapidly developing due to their miniaturization and flexibility.The traditional gasification process releases LNG cold energy directly into the air,which not only causes waste of cold energy,but also forms cold pollution to the surrounding environment.On the other hand,as people have higher and higher requirements for living and production conditions,the number of air conditioners is rapidly increasing,and the problem of air conditioning energy consumption is becoming more and more serious.This paper aims at the characteristics of the LNG satellite station's small gasification volume and large cooling demand.Design a set of integration process of LNG cold energy with simple process and large operation flexibility for cold water air conditioning and power generation.First of all,combined with the survey results and the actual situation of the LNG satellite station,it is determined that the designed LNG cold energy is used in the cold water air conditioning and power generation integration process parallel with the original gasification process to ensure that the downstream gas is not affected.Due to the small gasification scale of LNG satellite stations and less recoverable cold energy,the once refrigerant method is used to transfer LNG cold energy to air conditioning water,and the direct expansion method is used for cold energy power generation to meet the demand and reduce process costs.Compared with the original electric compression refrigeration process,when the LNG gasification amount is 500kg/h,the cold water air-conditioning system can provide 16730kg/h of cold water,reducing the electricity consumption by 26.16 k W and saving 52320 k W·h of electricity annually;An additional 7.75 k W of power output is added,with a total power saving of 33.91 k W.Secondly,aiming at the problem of low efficiency of the integrated process system of cold water air conditioning and power generation in Chapter 2,the optimization is made from the aspects of refrigerant,process and equipment.Comparing the gasification curves of the refrigerant and LNG,the slope of the propane-isobutane mixed refrigerant curve is closest to that of LNG,indicating that the two have the best heat transfer effect,and further determined propane: isobutane=8:2 mass ratio by Aspen simulation,the exergy efficiency of system reaches 25.06%.After the optimization of the cold water air conditioning system,the cold water volume reached 18120kg/h,an increase of 8.50%,and the system exergy efficiency increased to 26.39%;the optimized cold power generation system reached 8.41 k W,an increase of 6.46%,and the system exergy efficiency increased to 26.39%.The key equipment selected is the winding tube heat exchanger,turbine expansion generator and air temperature type reheater,which is most suitable for this process.Finally,design a systematic plan of LNG cold energy utilization process for the LNG satellite station of metal processing plant.The total project is divided into the first-stage cold water air conditioning project and the second-stage cold energy power generation project for planning.The first-stage cold water air conditioning project has a total equipment investment cost of about 355,000 yuan and an annual power saving benefit of 150,000 k W·h.During the commissioning of the first phase of the project,it was found that the LNG flow adjustment process needs to be slowly increased to ensure uniform heat exchange between the LNG and the refrigerant and improve the heat exchange effect.