**Acknowledgements**

**6. Future developments**

120 Carbon Capture, Utilization and Sequestration

A highly promising solvent-based CO2

and removal reaction is as follows:

where the CO2

**7. Conclusions**

higher level of CO2

MWh<sup>e</sup>

gation and optimization process.

and a cost of avoided CO2

capture process, named the mixed-salt technology, is

absorption

being currently developed, as reported by Jayaweera et al. [43]. This technology adds potassium carbonate to the system in order to exploit the advantages of both ammonia-based and

*K*<sup>2</sup> *C O*<sup>3</sup> · *N H*<sup>3</sup> · *H*<sup>2</sup> *O* · *xC O*<sup>2</sup> ⇆ *K*<sup>2</sup> *C O*<sup>3</sup> · *N H*<sup>3</sup> · *H*<sup>2</sup> *O* · *yC O*<sup>2</sup> (6)

the equilibrium represent the lean and rich solutions, respectively. Despite the system being characterized by the presence of several ionic species that could form a solid phase, precipitation is avoided by operating the absorber at relatively high temperatures and at concentrations below the solid-forming conditions. The expected advantages are a limited heat duty at

This chapter covers the chemical absorption of carbon dioxide by an aqueous solution of ammonia for coal- and natural gas-fired power plants and industrial processes. It reports the literature review, the simulation by equilibrium- or rate-based approach, the economic as well as environmental assessments, and the future developments. Conclusions are as follows:

**1.** The ammonia-based technology confirms to be attractive compared to conventional amines. It can be implemented in a chilled as well as in a cooled process depending upon

**2.** The predicted specific heat duty, in the equilibrium approach, is 3.0 for the cooled process and 2.2 MJ/kgCO2 for the chilled one. Moreover, the index *SPECCA* is 2.6 for the cooled and 2.9 MJ/kgCO2 for the chilled. Overall, the cooled process combines the advantage of a mod-

**3.** The predicted performances in the rate-based approach, compared against those in the equilibrium approach, result slightly penalized. The difference is due to the need of a

changes from 2.6, as seen in the equilibrium, to 2.8 MJ/kgCO2, in the rate-based approach, yielding an increase of the prediction of about 6%. Hence, the study of an absorption capture plant with an equilibrium approach is a valid methodology for a preliminary investi-

**4.** From an economic perspective, the carbon capture via chemical absorption by aqueous ammonia is a feasible retrofitting solution, yielding a predicted cost of electricity of 82.4 €/

purity in the lean stream from the regenerator. The index *SPECCA* value

of 38.6 €/tCO2, both for the chilled process (those for the

the temperature and, consequently, the precipitation of salts in the absorber.

erate energy requirement with the absence of solid formation.

cooled process are not reported yet in the open literature).

loading is the numerical difference between *y* and *x*. The left and right side of

potassium carbonate-based technologies. The simplistic representation of the CO2

the regenerator and a limited load for the water wash on top of the absorber.

The authors gratefully acknowledge Mr. Stefano Lillia of Politecnico di Milano for his help in investigating carbon capture alternatives as well as in reviewing this chapter.
