Research On LNG Cogeneration Technology Based On HYSYS

With the rapid development of China’s natural gas industry.the annual LNG import volume will continue to increase.During LNG gasification,a large amount of cold energy will be released.Therefore,utilizating cold energy released by the LNG gasification rationally can bring great economic benefits.However,the existing LNG cold energy utilization process still has the following problems:the LNG gasification scale is not matched well with LNG cold energy utilization temperature.Because that the LNG gasification load is up to the needs of the downstream gas pipe network,there is a problem that the LNG gasification load flow fluctuates greatly and the stability of process is poor.LNG temperature is so low that the LNG cold exergy dissipation problem occurs due to the large temperature difference in the LNG exchanger.The high-temperature heat source in the power generation cycle is mainly solar energy,and there is still a phenomenon that the solar energy resource can not be continuously and steadily heated due to changes in the seasons and climate.Considering that LNG satellite station is the core users in China,based on the LNG satellite station scale,temperature range utilization,climate characteristics,solar radiation intensity,seasonal demand of natural gas and other important factors,this paper carried out the research of combined cooling and power(CCP)process for LNG satellite station.The main innovations are as follows:1)Considering that the solar energy resource is limited by the region and seasons,it is impossible to maintain stable heating.The organic Rankine cycle with BOG auxiliary heating is proposed,the solar-BOG heating module is added.Taking the method of BOG combustion to prepare backup heat source not only makes up for the shortcomings of instability of solar energy but also further improves the overall net power generation of the process;2)Taking LNG cold exergy dissipation problem in LNG exchanger into account,intermediate media cycle module is used to heat exchange layer by layer,reducing the heat transfer temperature difference,so as to more effectively utilize the precious ultra-low temperature LNG cold exergy.On the other hand,the LNG gasification load flow fluctuates greatly,whereas the LNG gasification load depends on the demand of the downstream gas pipe network.By the intermediate medium circulation module,the matching between the LNG gasification stream and the LNG cold energy utilization integrated process logistics can be greatly improved,so as to ensure the overall stability of the process.3)Based on the LNG cold energy temperature range utilization and the process gasification scale,the improved power generation-cold storage-cold water integrated process is proposed.The new process is mainly composed of LNG gasification module,medium circulation module for power generation,organic Rankine cycle power generation module,medium circulation module for cooling,cold storage cycle module,air conditioning cooling cycle module and solar-BOG heating module.In view of the station climate characteristics,solar radiation intensity,seasonal demand for natural gas and other factors,LNG cold energy utilization process is optimized and analyzed,the results can provide a scientific basis for cold energy utilization,to better guide the research on combined cooling and power(CCP)process for LNG satellite station.Combining with the actual operating conditions of Zibo LNG satellite station,a feasible process simulation of LNG cold energy utilization was carried out by HYSYS simulation software to optimize the LNG cold energy integrated utilization process and confirm an efficient and practical one,that is,the impro-ved power generation-cold storage-cold water integration process.The main conclusions are as follows:1)the annual power-saving benefits mainly depends on the organic Rankine cycle,which account for 75%in overall power-saving benefits section.On the other hand,the proportion in annual power-saving benefits matches well with the LNG temperature range utilization in each cycle,including process power generation,low-temperature cold storage and air-conditioning cooling.The lower the LNG temperature,the higher the LNG cold exergy.The result also validates the scientific feasibility of LNG cold energy utilization process proposed in this paper.2)according to the related parameter setting,the power-saving of organic Rankine cycle with BOG auxiliary heating and the annual electric heater energy consumption to make up for solar seasonal defects are obtained respectively.Comparing the results,it is found the BOG auxiliary heating method Greatly improve the efficiency of power generation.3)in line with cooling capacity and air-condition COP for air-condition,the annual power-saving of LNG cold energy for air-conditioning cooling cycle is calculated.The results showed that although the LNG cooling energy for air-conditioners is only for a short period of 100 days in summer,the equivalent power-saving is still considerable,indicating that using LNG cold energy in the high-temperature region for air-condition cooling cycles is higher feasibility.4)The net annual process power-saving year exceeds 3O×104kW·h,converted into local industrial electricity price,which can bring about an annual power saving effect of over 250 thousand yuan.recycling environmentally-friendly solar energy resources as well as BOG,the improved process not only saves the fuel cost of generating electricity from coal,but also reduces dust or sulfide caused by coal burning and decreases environmental pollution and energy waste BOG direct venting.