Increasing the COP of a refrigeration cycle in natural gas liquefaction process using refrigerant blends of Propane-NH3, Propane-SO2 and Propane-CO2.

This paper investigates the feasibility of using inexpensive techniques to enhance the coefficient of performance (COP) of the refrigeration cycle used in the liquefaction of natural gas. The effect of mixing the propane refrigerant with ammonia, sulfur dioxide and carbon dioxide on the performance and the work of the compressor is studied. It is shown that the mixture of ammonia-propane and sulfur dioxide-propane enhances the overall COP by 7% and 9%, respectively. The addition of ammonia and sulfur dioxide to the propane refrigerant reduces the overall compressor work by reducing the overall mass flowrate required to absorb a constant heat from the natural gas. On the other hand, the mixture of carbon dioxide-propane degrades the overall COP by 70%. The addition of carbon dioxide increases the overall mass flowrate required to absorb a constant heat from the natural gas. Interestingly, the proposed method requires small capital and running costs.