Contents lists available at ScienceDirect International Journal of Greenhouse Gas Control journal homepage: www.elsevier.com/locate/ijggc Combined carbon capture cycles: An opportunity for size and energy penalty reduction Luis M. Romeo a, ⁎ , Pilar Lisbona a , Yolanda Lara b a Escuela de Ingeniería y Arquitectura, Departamento de Ingeniería Mecánica, Universidad de Zaragoza, Campus Río Ebro, María d9e Luna 3, 50018 Zaragoza, Spain b Research Center for Energy Resources and Consumption (CIRCE), Campus Río Ebro, Mariano Esquillor Gómez 15, 50018 Zaragoza, Spain ARTICLE INFO Keywords: Ca-Looping Amine impregnated solid sorbents Energy integration Combined carbon capture cycles ABSTRACT One of the main technical difficulties in the design and dimensioning process of carbon capture and storage (CCS) systems is the proper utilization of the low temperature energy streams within the process. Rejecting these energy streams has a negative effect on both the process energy efficiency and the penalty of the CCS in industry or power plants. This is particularly important in oxyfuel and some post-combustion technologies such as amine scrubbing or Calcium-Looping. With the objective of reducing dimensions, energy penalty and capital costs of the CO 2 capture systems, this study analyses and demonstrates the beneficial effects of splitting the CO 2 capture in two cycles which operate at high (Ca-looping, Ca-L) and low temperature (amine impregnated solid sorbent, AISS). The latter (bottoming- carbon cycle) makes use of the waste energy from the high temperature capture cycle (topping-carbon cycle). Flue gas flow is split and each capture system treats a percentage of flue gas stream. This study quantifies the energy improvements derived from the combination of a topping and a bottoming CO 2 capture system and analyses the required dimensions and the optimum flue gases split between both sys- tems. Results show a reduction of energy penalty when 20–30% of the flue gas is diverted from the Ca-L to the AISS system if the AISS specific energy consumption for CO 2 captured is between 2000 and 3000 kJ/kgCO 2 . 1. Introduction A large number of research papers and project reports have in- vestigated the reduction of energy penalties caused by CCS systems when applied to industry or power plants for carbon capture. This en- ergy consumption is required to trigger the separation of CO 2 from the flue gas. The reduction of net efficiency, energy penalty or specific primary energy consumption for both avoided and captured CO 2 allow quantifying this effect. This energy necessity has a significant role in the economic feasibility of the process through the operating costs but also through the amortization of the capital costs. Published works propose the integration of available energy streams in the industry and power plants or even into the CCS process itself to cover part of the requirement and minimize the effect of energy con- sumption of the carbon capture. Unfortunately, after heat integration, streams with large amounts of low-temperature energy are usually difficult to exhaust in the global system. This is particularly important in oxyfuel and some attempts have been done to take advantage of this energy through the use of Organic Rankine Cycles (ORC) to produce extra power and reduce the ASU power consumption (Romeo et al., 2011). Besides oxyfuel technology, another CCS option with an important amount of heat to be integrated in the system or in an additional power plant (Romeo et al., 2008) is the Ca-L technology. Recent literature has demonstrated the advantages of Ca-L as a low penalty and mature technology for post-combustion CO 2 capture. For power plants, the efficiency penalty of Ca-L is lower than other alternatives for CCS. Lara et al. reported a minimum energy penalty of 5.1–5.7% after a sys- tematic approach of heat integration for high temperature looping cy- cles in power plants (Lara et al., 2016, 2014). Ortiz et al. (2016) and Martínez et al. (2011) obtained similar values. Ortiz et al. reported an efficiency penalty between 4–7% points while Martínez et al. found energy penalties somehow higher between 7.5–8.3% (Martínez et al., 2011). Rolfe et al. (2018) developed a steady-state model of the Ca-L process integrated with a 600 MW power plant and performed a techno- economic analysis. The net efficiency of the integrated system (power plant and carbon capture plant) was calculated as 33.8% LHV for a CO 2 capture efficiency of 94%. The energy penalty of the combined system with respect to the reference plant without CO 2 capture was 7.4% https://doi.org/10.1016/j.ijggc.2019.06.023 Received 15 February 2019; Received in revised form 20 June 2019; Accepted 24 June 2019 ⁎ Corresponding author. E-mail address: luismi@unizar.es (L.M. Romeo). International Journal of Greenhouse Gas Control 88 (2019) 290–298 1750-5836/ © 2019 Elsevier Ltd. All rights reserved. T