Capital Cost (BEC)

 

The Capital Cost results of the flue gas CO2 capture area are divided into two screens. This first screen, Capital Cost (BEC), presents the Bare Erected Cost (BEC) results. A single table displays the equipment included in the flue gas CO2 capture area:

•Flue Gas Condenser: The flue gas condenser is used to cool the incoming hot flue gas.

•Flue Gas Blower: The flue gas has to overcome a substantial pressure drop as it passes through a very tall absorber column, countercurrent to the sorbent flow. Hence, the cooled flue gas has to be pressurized using a blower before it enters the absorber.

•CO2 Absorber Vessel: This is the vessel where the flue gas is made to contact the MEA-based solvent, and some of the CO2 from the flue gas gets dissolved in the solvent. The column may be plate-type or a packed one. Most of the CO2 absorbers are packed columns using some kind of polymer-based packing to provide a large interfacial area.

•Intercooler (Absorber): The absorber intercooler is used to decrease the solution temperature and then enhance the CO2 removal efficiency.

•Wash Column: It is required to limit the MEA vapor emissions from the flue gas out of the absorber to below 3 ppmv. Each wash column consists of a condenser and a knock-out (KO) drum. The condenser is used to cool down the flue gas. The KO drum is used to separate liquid and gas streams.

•Heat Exchanger: The CO2-loaded solvent needs to be heated to strip off CO2 and regenerate the solvent. On the other hand, the regenerated (lean) solvent coming out of the regenerator has to be cooled down before it can be circulated back to the absorber column. Hence, these two solvent streams are passed through a cross-heat exchanger, where the rich (CO2-loaded) solvent gets heated, and the lean (regenerated) solvent gets cooled.

•Circulation Pumps: This includes solvent circulation pumps and cooling water circulation pumps.

•Solvent Regenerator: This is the column where the weak intermediate compound (carbamate) formed between the MEA-based solvent and dissolved CO2 is broken down with the application of heat, and CO2 gets separated from the solvent to leave reusable solvent behind. In the case of unhindered amines like MEA, the carbamate formed is stable, and it takes a large amount of energy to dissociate. It also consists of a flash separator where CO2 is separated from most of the moisture and evaporated solvent to give a fairly rich CO2 stream.

•Reboiler: The regenerator is connected to a reboiler, which is basically a heat exchanger where low-pressure steam extracted from the power plant is used to heat the loaded solvent.

•Solvent Reclaimer: Presence of acid gas impurities (SO2, SO3, NO2, and HCl) in the flue gas leads to the formation of heat-stable salts in the solvent stream, which cannot be dissociated even on application of heat. To avoid the accumulation of these salts in the solvent stream and to recover some of the lost MEA solvent, a part of the solvent stream is periodically distilled in this vessel. The addition of caustic helps in freeing some of the MEA. The recovered MEA is taken back to the solvent stream while the bottom sludge (reclaimer waste) is sent for proper disposal.

•Solvent Processing: The regenerated solvent has to be further cooled down even after passing through the rich/lean cross heat exchanger using a cooler, so that the solvent temperature is brought back to an acceptable level (about 40 deg C). Also, to make up for the solvent losses, a small quantity of fresh MEA solvent has to be added to the solvent stream. So, the solvent processing area primarily consists of a solvent cooler, an MEA storage tank, and a mixer. It also consists of an activated carbon bed filter that adsorbs impurities (degradation products of MEA) from the solvent stream.

•CO2 Drying & Compression Unit: The CO2 product may have to be carried very long distances via pipelines. Hence, it is desirable that it does not contain any moisture to avoid corrosion in the pipelines. Also, it has to be compressed to very high pressures so that it gets liquefied and can overcome the pressure losses during the pipeline transport. The multi-stage compression unit with inter-stage cooling and drying yields a final CO2 product at the specified pressure (about 2000 psig) that contains moisture and other impurities (e.g., N2) at acceptable levels. The cost of the drying and compression unit includes all equipment required to compress and dehydrate the captured CO₂ streams from both the MDEA and MEA carbon capture systems.

•Bare Erected Cost: This is the total of all technologies listed above. This result is highlighted in yellow.

Copyright © 2022-2026 University of Wyoming. All rights reserved. Visit us at https://www.iecm-online.com/