**5. Economic and environmental assessments**

Regarding the results for the chilled and the cooled process, **Table 3** compares the predicted electric consumptions. The exhaust cooling and the absorption-regeneration sections are more penalizing for the chilled process due to the major consumption of the chillers. By contrast, the power island is more penalizing for the cooled process, on one side, because of a large

**Table 4.** Overall performances of the chilled and the cooled processes compared against a reference power plant (without

emission kgCO2/MWh<sup>e</sup> 763 104 141.4 138.9

**Parameter Unit Reference MEA Chilled Cooled** Electric power loss MW<sup>e</sup> NA 198.9 140.1 129.3 Net electric power MW<sup>e</sup> 754.0 562.4 613.9 624.7 Net electric efficiency % 45.5 33.5 37.05 37.70 Specific heat duty MJ/kgCO2 NA 3.70 2.19 2.98

*SPECCA* MJ/kgCO2 NA 4.16 2.86 2.58

carbon capture) and a plant integrated with MEA aqueous solution computed by Bonalumi et al. [36].

tion. On the other, because of another major contribution due to the higher specific heat duty and the higher regeneration temperature that require more steam bleeding at a higher value of pressure and enthalpy from the turbine. In addition, the compression stage is more penalizing for the cooled process since the regeneration pressure is lower. Hence, from the electric

In its turn, **Table 4** summarizes the performances for the chilled and the cooled processes and it compares them against those of the reference power plant (without any carbon capture) and a plant integrated with carbon capture in MEA aqueous solution. From the index *SPECCA*, which is as seen the most consistent perspective for evaluating a capture technology, the cooled pro-

In a recent work, Bonalumi et al. [40] adopt the rate-based approach to assess the same cooled aqueous ammonia process that they investigated earlier with the equilibrium approach [36]. **Table 5** summarizes the main results from the comparison of the performances predicted by the two approaches. The overall energy balance for the kinetic study, compared against the equilibrium study, turns to be only slightly penalized. The authors explain that this penaliza-

lean stream from the regenerator. The differences being moderate, though, the study of an absorption capture plant with the equilibrium approach can be considered a valid method for

tion originates from the larger request of energy to achieve a higher level of CO2

consumption, the chilled process is less penalizing than the cooled one.

cess is less penalizing than the chilled one, by far, than MEA.

**4. Process simulation with the rate-based approach**

a preliminary assessment of an ammonia-based process.

that must be recovered by the water wash sec-

purity in the

contribution due to the higher amount of NH3

Specific CO<sup>2</sup>

118 Carbon Capture, Utilization and Sequestration

The integration of the chilled process and an ultra supercritical power plant is analyzed by Valenti et al. [41] via a parametric analysis from the energy and the economic perspectives. The capture island is simulated with an equilibrium approach. In the parametric investigation, five parameters are varied singularly: (1) ammonia initial concentration in the aqueous solution, (2) ammonia-to-carbon dioxide ratio in the absorber, (3) regeneration pressure, (4) regeneration temperature, and (5) absorber chiller evaporation temperature. The economic analysis, with respect to a reference power plant rated at the net electric production of over 750 MW<sup>e</sup> , shows that the capital investment of the capture island is estimated to be a relatively small portion of that of the power island. However, due to other costs and due to the performance penalties, the cost of electricity increases significantly by 37.5%, from 59.90 to 82.38 €/MWh<sup>e</sup> ; ultimately, the resulting cost of avoided CO2 is approximately 38.64 €/tCO2.

A detailed environmental life cycle analysis for an ultra supercritical power plant with and without carbon capture is proposed by Petrescu et al. [42]. Three capture islands are considered: (1) gas-liquid absorption with MDEA (monodiethanolamine), (2) gas-liquid absorption with aqueous ammonia, and (3) gas-solid absorption with calcium oxide. The environmental evaluation is performed using the "cradle-to-grave" methodology considering several upstream and downstream processes. Eleven environmental impact categories, according to the method CML 2001, are compared using GaBi software. The study highlights that carbon capture technologies decrease the global warming potential indicator, but they may increase other indicators. The amine technology achieves a good performance from the perspective of global warming, but not satisfactory from that of all others. Aqueous ammonia adsorption and calcium looping prove to be better. Some indicators, such as acidification potential, eutrophication potential, or those related to lethal concentrations (e.g., human toxicity potential, freshwater aquatic ecotoxicity potential, and marine aquatic ecotoxicity potential), are better in the case of aqueous ammonia. By contrast, some others, such as abiotic depletion fossil and abiotic depletion elements, are better in the case of calcium looping.
