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Rate-based modelling, simulation and optimization of the chilled ammonia process for CO2 capture

In the Chilled Ammonia Process (CAP) ammonia (NH3) is applied as a non-degradable solvent to capture CO2 (Figure 1). CAP is a proprietary technology of Alstom [1-3]. The application of the CAP technology to natural gas and coal-fired power plants has been validated and demonstrated in various facilities of different scale with CO2 flue gases concentrations in a range of 3-16% [4,5]. Nevertheless, it has never been demonstrated for CO2 concentration exceeding 16%mol. The complex thermodynamics of the CAP [6] complicate process simulations, while the slow kinetics of the absorption process make the development of a rate-based model necessary. Both features lead to a relatively large spread in the simulation results found in the literature [7-9].

Figure 1
Figure 1. Chilled Ammonia Process (CAP) layout.

The aim of this project is to develop a rate-based model for the CAP which should be suitable to model CO2 capture from flue gases obtained from different processes, mainly focussing in cement manufacture, where CO2 flue gas concentration may reach up to 30%mol. Additionally, the formation of different solids within the process will be considered, according to the thermodynamic model available in the literature [6]. This rate-based model will be validated and adjusted by means of pilot plant tests. Eventually, a 2nd generation CAP process (Figure 2) will be modelled, simulated and optimized, that intends to exploit the formation of solids. Therewith, the CO2 loading in the rich stream that is regenerated can be increased, thus reducing the overall energy consumption.

Figure 2
Figure 2. 2nd generation Chilled Ammonia Process (CAP) layout.

References

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