Abstract
This work compares three postcombustion CO2 capture processes based on mature technologies for CO2 separation, namely, (i) absorption using an aqueous piperazine solution, (ii) adsorption using Zeolite 13X in conventional fixed beds (either vacuum swing adsorption or temperature swing adsorption), and (iii) multistage membrane separation using a polymeric material (with CO2/N2 selectivity of 50 and permeability for CO2 of 1700 GPU). All three capture plants are assumed to be retrofitted to a generic industrial CO2-emitting source with 12% CO2 v/v (with 95% relative humidity at the inlet temperature and pressure of 30 °C and 1.3 bar, respectively) to deliver CO2 at 96% purity. In the cases of adsorption and membranes, the flue gas is dried before feeding it to the CO2 capture unit. In a first step, the capture processes (i.e., components and design parameters) are optimized based on their technical performance, defined through process exergy requirement and plant productivity; exergy–productivity Pareto fronts are computed for varying CO2 recovery rates. Second, the economic performance of the processes is assessed through a cost analysis. Estimates of CO2 capture costs are provided for each process as a function of the plant size and CO2 recovery rate. The comparative assessment shows that, although the adsorption- and membrane-based processes analyzed may become cost competitive at the small scale (i.e., below sizes of 100 tons of flue gas processed per day) and low recovery rates (i.e., below ca. 40%), the absorption-based process considered is the most cost-effective option at most plant sizes and recovery rates.
Highlights
Postcombustion capture (PCC) systems constitute a technically and economically viable solution to reduce emissions in a variety of sectors for which decarbonization might be possible but costly in the near term
There are the main industrial emitters relying on fossil-fuel combustion and secondary emitters and emitters potentially generating negative emissions.[1,2]
For 90% recovery, the two Pareto fronts extend within comparable ranges of exergy consumption, but the VSA9 cycle allows for a 20% higher maximum productivity
Summary
Postcombustion capture (PCC) systems constitute a technically and economically viable solution to reduce emissions in a variety of sectors for which decarbonization might be possible but costly in the near term. Among such emitters, there are the main industrial emitters relying on fossil-fuel combustion (e.g., power generation, steel making, cement industry) and secondary emitters (e.g., waste incinerators and chemical plants) and emitters potentially generating negative emissions (e.g., bioenergy with carbon capture and storage, BECCS).[1,2] For all these applications, retrofitting existing plants with postcombustion capture units may be the only effective and economic way to reduce emissions at the stack without affecting the process upstream,[2,3] advancing the transition toward net-zero-CO2emission industrial sectors. For effective process design, it is convenient to consider multiple technologies and select the most efficient and economically viable option to serve the purpose
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