Novel integrated structure using solar parabolic dish collectors for liquid nitrogen production on offshore gas platforms (exergy and economic analysis)

Abstract

The purpose of this study is to propose a novel integrated structure for producing and storing the required nitrogen in liquid form for gas platforms as the required power to produce this liquid nitrogen is provided through renewable energy. In this regard, the air separation unit, nitrogen liquefaction cycle and Rankine power generation cycle are used so that the required power of separation and liquefaction cycles is provided from the Rankine cycle and the needed heat for this power generation cycle is provided by solar parabolic dish collectors. The South Pars offshore gas platforms in Iran are chosen as the case study. Since by producing 40.44 kg/h of pure liquid nitrogen, the nitrogen need of these platforms can be covered, in order to produce this amount of nitrogen, the capacity of a power generation cycle must be 32.34 kW and the heat capacity produced by the solar system must be approximately 130 kW. The results obtained from exergy analysis show that overall exergy efficiency and total irreversibility of the proposed system is 46% and 57 kW, respectively. Economic analysis shows that the investment return period and the prime cost of product are equal to 7.309 years and 1.203 $/LN2, respectively.