Retrofit or Adjustment Factors

 

See Retrofit or Adjustment Factor Inputs for an explanation of retrofit costs. The solid sorbents TSA system has the following capital cost process areas:

•CO2 Adsorber Vessel: This area deals with the adsorber. The capital cost of the adsorber will go down with higher MEA concentration and higher CO2 loading level of the solvent, and lower CO2 content in the lean solvent.

•Sorbent Regenerator: This area deals with the sorbent regenerator. The regenerator (or stripper) is a column where the weak intermediate compound (carbamate) is broken down by the application of heat. The result is the release of CO2 (in concentrated form) and return of the recovered sorbent back to the absorber. This process is accomplished by the application of heat using a heat exchanger and low-pressure steam. MEA requires substantial heat to dissociate the carbamate. Therefore, a flash separator is also required, where the CO2 is separated from the moisture and evaporated sorbent to produce a concentrated CO2 stream.

•Heat Exchangers: This area deals with the heat exchangers. The CO2-loaded sorbent must be heated in order to strip off CO2 and regenerate the sorbent. In addition, the regenerated sorbent must be cooled down before it can be recirculated back to the absorber column. Heat exchangers are used to accomplish these two tasks. This area is a function of the sorbent flow rate.

•Sorbent Handling: This area deals with the sorbent handling. The sorbent processing area primarily consists of a sorbent cooler, MEA storage tank, and a mixer. The regenerated sorbent is further cooled with the sorbent cooler and MEA added to make up for sorbent losses.

•Circulation Pumps: This area deals with the circulation pumps. Circulation pumps are required to take the sorbent, introduced at atmospheric pressure, and lift it to the top of the absorber column. This area is a function of the sorbent flow rate.

•CO2 Drying and Compression: This area deals with the CO2 drying and compression. The product CO2 must be separated from the water vapor (dried) and compressed to liquid form in order to transport it over long distances. The multi-stage compression unit with inter-stage cooling and drying yields a final CO2 product at the nominal pressure of 2000 psig. This area is a function of the CO2 flow rate.

•Flue Gas Blower: This area deals with the flue gas blower. The flue gas enters the bottom of the absorber column and flows upward, countercurrent to the sorbent flow. Blowers are required to overcome the substantial pressure drop as it passes through a very tall absorber column. The cost is a function of the volumetric flow rate of the flue gas.

•Sorbent Storing: This area deals with the sorbent storing. A portion of the sorbent stream is distilled in the reclaimer in order to avoid accumulation of heat stable salts in the sorbent stream. Caustic is added to recover some of the MEA in this vessel. The reclaimer cost is a function of the sorbent makeup flow rate.

•Steam Extractor: This area deals with the steam extractor. Steam extractors are installed to take low pressure steam from the steam turbines in the power plant. The cost is a function of the steam flow rate.

•Direct Contact Cooler: This area deals with the direct contact cooler. A direct contact cooler is typically used in plant configurations that do not include a wet FGD. A direct contact cooler is a large vessel where the incoming hot flue gas is placed in contact with cooling water. The cost is a function of the gas flow rate and temperature of the flue gas.

•Cyclone Bank: This area deals with the cyclone bank. The regenerator is connected to a reboiler, which is a heat exchanger that utilizes low pressure steam to heat the loaded sorbent. The reboiler is part of the sorbent regeneration cycle. The cost is a function of the sorbent and steam flow rates.

•Auxiliary Gas Boiler: This area deals with the auxiliary gas boiler. An auxiliary natural gas boiler is typically combined with a steam turbine to generate some additional power and/or low pressure steam. The cost is a function of the steam flow rate generated by the boiler. The boiler cost is lower if electricity is not being produced.

•Auxiliary Steam Turbine: This area deals with the auxiliary steam turbine. The steam turbine is used in conjunction with the natural gas boiler to generate some additional power and/or low-pressure steam. The cost is a function of the secondary power generated by the turbine.

•Steam Compressor: This area deals with the steam compressor. Water and steam are used to transfer heat between the heat exchangers.

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