Conventional vapor compression refrigeration systems, need considerable amount of power specially when they are used in the cryogenic processes. Alternative cooling technologies which can be driven by thermal energy have been considered for introducing new refrigeration systems in the natural gas liquefaction processes. In this study a novel process configuration for production of liquefied natural gas in small scale is proposed and analyzed. In this configuration a conventional single mixed refrigerant (SMR) LNG process is upgraded by using a diffusion absorption refrigeration (DAR) system. DAR is a small-scale cooling technology that can be driven purely by thermal energy without the need for electrical or mechanical inputs. DAR systems use a third fluid component: a low-density inert gas such as hydrogen or helium that aids evaporation of the refrigerant by lowering its partial pressure in the evaporator. DAR is a “single pressure” cycle that necessity for electrical or mechanical energy input can be omitted. Natural gas enters the process at 32 °C and 65 bar. Mass flow rate of the produced LNG is 57.85 ton/h. The process configuration, heat and material balance and designed equipment specifications are presented in the paper. Thermal design of multi stream heat exchangers is evaluated by composite curves. The results show that COP of the DAR system is about 0.157. Also the liquefaction efficiency can reaches to 0.225 kW/kg LNG which is lower than base case SMR process. Next the process is analyzed discussed by energy and exergy methods analysis. Also consequences of effective parameters variations such as ratio of the hydrogen to mixture of water and ammonia, ammonia percentage, DAR operating pressure are intercepted.
|Affiliation of speaker||ITMO University|
|Publication||Impact Factor journals|