| As China paying attentions to air pollution,liquefied natural gas(LNG)has developed rapidly in China recently due to its advantages of safety,reliability,high combustion heat value,and favorable environmental protection.The increasing utilization of LNG has created excellent prerequisites for the recycling of high quality cold energy.The development of comprehensive utilization technologies of LNG cold energy is conducive to energy conservation,reduction of carbon emissions,development of recycling economy which has a broad application and development space.This article has carried out interdisciplinary research,including water treatment technology and district cooling technology,starting from energy saving,achieving water saving and reducing carbon emissions.This paper discusses two aspects of LNG cold energy application:Freezing,watering and centrifugal desalination(FWCD)process using LNG cold energy and the feasibility of using LNG cold energy as a basic cold source in a multi-energy district cooling system.In the FWCD process study,according to our group’s research on freezing desalination,Combined with the ion removal rate,TDS removal rate and water production rate,the effect of factors such as the percentage of water,the salinity of water,and the temperature of water during the washing process was studied experimentally.In the study of the district cooling system using LNG cold energy,this paper designed the system flow of using LNG cold energy as the basic cold source in multi-energy district cooling system for offices and data centers.By using Aspen Plus process simulation software,the available cooling capacity of an LNG receiving station in Tianjin,China,was calculated and analyzed.The cooling capacity is transferred from the LNG side to the circulating chilled water system as the basic cold source in the multi-energy cooling system.According to the length of the transmission distance,four cooling schemes were proposed and the actual cooling capacity of each scheme,the cost of the required equipment,and the operating energy consumption were calculated.For these four schemes,the economics were calculated,and the feasible transportation distance for LNG cold energy district cooling system was obtained.It analyzed the economic and environmental benefits of district cooling system utilized LNG cold energy for the office and data center building at various distances from receiving stations.Based on the above experimental and simulation analysis and research,the main conclusions of this paper are as follows:After seawater was treated by FWCD process,Compared with freezing process,the salt removal rate,TDS removal rate,chloride ion removal rate and calcium and magnesium ion removal rate of ice samples were all improved.The addition of water causes the brine channel to open further,which has a significant accelerating effect on desalination,and ultimately improves the desalination effect of seawater.In the FWCD process,when the mass of water is same,the removal rate of each ion when adding fresh water is higher than that of adding seawater,but the increased ice production can not compensate the consumption of fresh water.For economic reasons,the desalination rate can be increased by adding seawater with a higher mass percentage.When the added water quality and salinity are certain,the desalination rate is higher when the water temperature is higher,and the water production rate is reduced.This means that in the summer,the desalinization effect using the FWCD process is better and the ice production is lower,in the winter due to the lower seawater temperature,the amount of added seawater would be more if a higher desalination rate is desired.Compared with the previous research results of the our group,although the TDS and ion removal rate of ice produced by the FWCD process is lower than that of the FGCD(Freezing,gravity-driven and centrifugal desalination)process,the amount of ice production is increased;and the duration of the entire FWCD process is short,this allows FWCD to be used as a pre-treatment process for other desalination methods or as a desalination method without strict water quality requirements.In the study of the district cooling system using LNG cold energy,the simulation analysis shows that when the gasification amount at the receiving station is 300×10~4 t/a,and the minimum external gas transmission capacity of the cold energy utilization facility is160t/h,the maximum available cold energy for the LNG gasification process is30572.3471kW per hour.Due to the heat dissipation of the pump and the cold loss of the pipeline,the actual available cooling capacity at the customer end will decrease with the increasing of the transmission distance.When the transportation distance increases from 5km to 20km,the cooling loss of the circulating chilled water system during the transportation process has increased from 1402.72kW to 5194.88kW.Calculations show that when the transportation distance is below 15km,the district cooling system using LNG cold energy reduces energy consumption,eases local electric power,improves economic efficiency,and has better environmental and social benefits.When comparing the initial investment of district cooling system using LNG cold energy and the conventional electric refrigeration system,it can be concluded that when the user type is office building,when the transmission distance of cold energy is 5km,10km and 15km,the initial investment recovery cycle for office building users is 1.13,5.06 and 15.87 years respectively;for data center users,the investment recovery cycle is 0.25,1.13 and 3.51 years. |
