Research And Application Of Integrated Technology Of LNG Cold Energy Utilization In Cold Storage And Cold Water

With the rapid development of China’s natural gas industry, LNG satellite stations boomeverywhere. LNG satellite stations are build around bigger gas users in order to facilitate gasuse. Aluminum factory is one of the LNG gasification gas station customers, and during theproduction process, a large amount of gas are consumed, while aluminum oxide workshoprequires a lot of cold water for cooling, and canteen needs cold storage for food preservation.The LNG gasification process will release large amounts of cold energy, if LNG cold energycan be used for aluminum factory canteen food preservation and workshop cooling, it willreduce energy consumption, save energy and bring good economic and social benefits.In this paper, by researching cold storage-cold water combined process that is fit for thecold LNG satellite station, we designed LNG cold utilization technology scheme in whichcold storage heat exchanger and cold water heat exchanger were arranged in paralle, andrefrigerant were used directly for cold storage. Its advantages are that it can achieve aquantitative regulation of LNG cold energy distribution between the cold storage and coldwater according to the needs changes, avoid heat loss during the heat exchange between coldintermediate refrigerant and cold storage refrigerant, and can improve the system cold energyutilization efficiency. By refrigerant comparison,60%ethanol solution was determined as thescheme intermediate refrigerant to exchange heat with LNG. The design of refrigerantcirculating system, can make the system automatically adjust the refrigerant flow according tofluctuations in the amount of LNG gasification, automatically adjust the ethanol flowdistribution between the cold storage and cold water according changes in cold requirement,thus ensures the refrigerant cycle under smooth and safe running. The process used exergyanalysis for the thermodynamic analysis, by exergy calculating the streams and operationalunits, and analyzing two heat exchangers for hot and cold temperature and the temperaturedifference distribution, get the streams exergy value and two heat exchangers exergyefficiency taking1atm,25℃as the equilibrium state.Taking potential cold energy users around Guangya Aluminum LNG gasification stationas the background, engineering design of LNG cold energy used for cold storage and coldwater were studied. When the maximum gasification amount is2000Nm3scale in the station,the cold refrigerant circulating system can provide16kW to the cold storage, produce coldwater22000kg/h of5℃for the oxidation workshop. By using Aspen simulation softwareshows: LNG-ethanol solution heat exchanger area of is64m2, the heat load is325kW, ethanol -water heat exchanger area is320m2, the heat load is305kW. By operating flexibility analysis,the stability and security of the system cooling were determined. The total investment is2.5million yuan, and according to the energy assessment methods and cold energy mathematicalmodel built for the engineering solution, a calculation was carried out to assess the energyefficiency of the program, and the results show that economic benefit of470,000yuan/yearcan be achieved.