Techno-economic assessment of upfront nitrogen removal in a baseload LNG plant

Abstract

As the world's energy demand grows, the LNG industry is gaining popularity as a cleaner fossil fuel source. Studies on process enhancement have proposed that retrofitting upfront nitrogen removal (UNR) technologies like the lithium cycle to the cold section, increases the process efficiency, and plant capacity and decreases power consumption. In this paper, an economic evaluation is conducted for varying percentages of UNR to study its profitability compared to the conventional cold section (base case) by calculating the grass-root capital expenditure (CGR) and cost of manufacturing (COM). The cost incurred to produce one million BTU LNG (COE) is used as a basis to compare the cases and calculate the increment in profit. While the techno-economic impact was studied for a range of UNR percentages, the specific results for 87.5 % UNR are as follows. The CGR and COM for the cold section alone decrease by 3.2% and 2.3% respectively compared to the base case. The CGR and COM of the lithium cycle increase linearly with the UNR percentage. The total annual cost (TAC) and LNG energy content increased by 12.3% and 4.5% respectively over the base process. This leads to a 7.4% COE increment over the base case for 87.5% UNR. The profit calculation for LNG price of 15$/MBTU showed a 4.27% or 101.74 million $/year increase in profit for 87.5% UNR case as compared to the base case.