Efficient configuration/design of solvent-based post-combustion carbon capture

https://doi.org/10.1016/B978-0-444-59507-2.50155-4Get rights and content

Abstract

In this study, we analyze two design configurations for post-combustion carbon capture (PCC) namely inter-stage cooling and split flow. The results show that inter-stage cooling configuration has notable impact on improving PCC performance. It is found that, for a flue gas with 13.0 mol% of CO2, and with objective of capturing 90% of CO2 at purity of 98%, base case configuration imposes a 4.7GJ/ton-CO2 reboiler duty. This energy burden decreases (about 34.8%) to 3.1 GJ/ton-CO2 with single-stage cooling configuration. Two-stage-cooling configuration further improves the efficiency but only incrementally. Similarly, split flow design configuration shows considerable improvement in efficiency (3.8GJ/ton-CO2 vs. 4.7GJ/ton-CO2 for base case).

Introduction

Solvent based PCC was evaluated by Metz et al. (Abu-Zahra, Schneiders, et al., 2007, 2011, 1995, 2011, 2005, 2007) and described as the most mature technology for commercial scale industrial carbon capture from power plants' flue gas. The standard carbon capture process is illustrated in Fig.1. A stream of amine solution is continuously recycled between absorption and desorption units where the lean stream removes the CO2 from the bulk flue gas in an absorber column and the rich stream is regenerated in the stripper column.

Despite recent progress in solvent-based PCC, the implementation of this technology still burdens a notable energy penalty mainly due to solvent regeneration. The energy penalty though varies by the type of power plant and by different techno-economic studies, is estimated to be above 20% (Khalilpour and Abbas Khalilpour and Abbas, 2011). This inevitably leads to a significant reduction in the power plant's load. The critical parameters influencing the efficiency are solvent type, solvent concentration, operating conditions of absorption/desorption columns, percentage of CO2 avoided, captured CO2 purity and amount of regeneration. There are extensive research to study the impact of these parameters and their potential process improvements.

Configuration of absorption-desorption processes is also an important factor. In a conventional PCC scenario, gas enters at the bottom of the column and exists from the top. This traditional design does not exploit potential heat integration possibilities of the exothermic/endothermic absorption/desorption operation. Therefore, application of conventional simple column coupling configurations results in inefficient performances of both absorber and desorber. This leads to higher capital and operating costs. Recent studies see great potential for energy savings by introducing flow sheet innovations. Cousins et al. made an overview of several proposed configurations for PCC (Cousins, Wardhaugh, et al., 2011). The purpose of this paper is to assess two improved flow schemes: Interstage cooling and split flow, validating their potential in relieving the energy penalty on a basis of 30wt% MonoEthanolAmine (MEA) being employed as the absorbent. Process flow diagrams of inter-stage cooling and split flow are presented in Fig.2. Aspen HYSYS V7.1 is used in this study.

Section snippets

Fluid package

A reliable fluid package is the basis of simulation and its competency can be verified by comparing the predicted solubility of CO2 with experimental data. Jou, et al. (1995)) experimentally measured the solubility of CO2 in 30 wt% MEA solution by relating the CO2 loading to its partial pressure. Case studies of CO2 solubility were carried out using Amine pkg, Electrolyte NRTL respectively.

. Validation of simulation fluid packages in terms of CO2 solubility in 30 wt% MEA solution at (left) 60°C,

Temperature profile along the absorber

From Fig. 4, it is observed that the inter-stage cooling configuration significantly levels the parabola-shaped temperature profile of the base case. It extends almost horizontally throughout the first four plates since the hot solution to be cooled down is withdrawn from the third plate. The process target is to achieve 90% of carbon capture and the ratio of amine solution to flue gas (L/G) in wt./wt. was set to be around 20. Similarly, but not as significant as inter-stage cooling,

Conclusion

Alternative process flowsheet models were simulated and analyzed for PCC operations. The performances with and without design changes were evaluated and analyzed on a consistent basis (90% of CO2 removal and 98% purity of CO2 captured). From the simulation results, we found great potential for reducing the energy consumption in PCC via the process design configurations of inter-stage cooling and split flow. Compared to the base case, both inter-stage cooling and split flow schemes successfully

References (0)

Cited by (6)

  • Status and perspective of CO<inf>2</inf> absorption process

    2020, Energy
    Citation Excerpt :

    Combination of these actions was also reported in the literature. Among these modifications, the process of ICA attracted a lot of attention and researchers investigated its application [14,15]. ICA is withdrawing a portion of the solvent in the absorber and sending it back to the absorber.

  • Post-combustion CO<inf>2</inf> capture technologies — a review of processes for solvent-based and sorbent-based CO<inf>2</inf> capture

    2017, Current Opinion in Chemical Engineering
    Citation Excerpt :

    Absorber intercooling (AIC): Absorber intercooling helps reject the heat of absorption, enabling higher CO2 loadings. In one configuration, solvent is withdrawn from the absorber, and it is sent through an interstage cooler before being returned to a stage immediately below where it was withdrawn, as shown in Figure 3a [6–14]. In another variation, the cooled solvent is returned to an upper stage, which enables increased residence time, as shown in Figure 3b [13,15,16].

  • Process modifications for solvent-based post-combustion CO<inf>2</inf> capture

    2014, International Journal of Greenhouse Gas Control
    Citation Excerpt :

    The split flow arrangement has initially been designed for H2S removal but the concept is technically cogent for adaptation in CO2 capture applications. The general principle is to regenerate the solvent at two, or more, loading ratios: one lean solvent stream which is fed to the top of the absorber and one, or more, semi-lean solvent stream which are fed in the middle of the absorber (Fig. 3d) (Iijima et al., 2007; Oyenekan and Rochelle, 2007; Aroonwilas and Veawab, 2007; Cousins et al., 2011a,b; Le Moullec and Kanniche, 2011a; Amrollahi et al., 2012; Li et al., 2012; Ahn et al., 2013). This process modification has been designed for deep removal of acid gas in order to increase the absorption driving force at the top of the absorber.

View full text