Gas Treatment and Energy Recovery
The flue gas treatment and energy recovery section of the flowsheet performs on water removal and compression of the flue gas and expansion of the N2-enriched product of the separator. Ideally, these expansion and compression systems will share a joint driveshaft to reduce mechanical efficiency losses. The compression of the flue gas feed to the target condition is carried out via two-stage compression, with pressure ratios between 3 and 5. Multiple intercoolers are used to make the compression more efficient while also providing boiler feed-water (BFW) preheating for the plant. Further discussion of BFW integration can be found in the Supporting Information S1.2. Using just the first stage of compression, the heat for the first three boiler feed-water preheaters is provided as modeled in comparison to DOE Base Case 11a.34 Cooling water can then be used to cool the feed gas. The compressed gas can be further cooled between compression stages using excess low quality (> 0 °C) cooling available from the product and byproduct gas. Following the second compression stage, the gas is cooled to 2 °C to further dehydrate the gas prior to the complete drying necessary to enter the sub-ambient heat exchange system.