ANALYTICAL APPROACH FOR THE ASSESSMENT OF OPTIMUM PERFORMANCE OF PROPANE PRE-COOLING CYCLE WITH AERIAL COOLING IN LNG PLANTS

Abstract

An analytical approach is developed to check the aerial flow rate required for aerial cooler used in a propane pre-cooling mixed refrigerant components cycle operating in a Liquefied natural gas (LNG) plant located at Damietta, Egypt. The presented analytical approach takes into concern the changes in both the ambient air inlet temperature and the aerial mass flow rate. Based on an economic objective function, namely the annual total cost of the aerial cooler, the optimum operating conditions and hence the best performance of the propane pre-cooling mixed refrigerant cycle with aerial cooling was determined for various ambient aerial surrounding temperatures. Two algorithms are presented which can be used effectively with good engineering accuracy to control the process fluid (propane) outlet temperature in the propane precooling cycle through regulation of the air flow rate. The ambient air inlet temperature is modeled analytically by simplifying periodic relations. Numerical results are obtained reflecting the performance of the air-cooled heat exchanger which cools both NG (natural gas) and MR (mixed refrigerant) in the selected LNG plant. The obtained results revealed that the periodic hourly variations of the ambient air inlet temperature in the summertime have a much impact on the required air flow rate, while its influence becomes relatively less pronounced in winter