Combined carbon capture cycles: An opportunity for size and energy penalty reduction

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 CO2 capture systems, this study analyses and demonstrates the beneficial effects of splitting the CO2 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 CO2 capture system and analyses the required dimensions and the optimum flue gases split between both systems. 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 CO2 captured is between 2000 and 3000 kJ/kgCO2.