Combined Calcium Looping and Chemical Looping Combustion Process Simulation Applied to CO2 Capture

Abstract

The new Canadian laws on CO2 emissions aim to lower the emissions of coal-fired power plants down to those of natural gas combined cycle units: 420 kg CO2/MWeh. In order to meet these requirements, calcium looping and two process variants are investigated through process simulations using Aspen Plus V8.2. The combination of calcium looping and chemical looping combustion, replacing the required air separation unit, is a way to reduce the energy penalty of the capture process. The addition of copper as an oxygen carrier in two different process configurations is compared to calcium looping and shown to reduce the efficiency penalty from 7.8% to 4.5% points but at the price of circulations rates up to about 3800 kg/s. The other improvement path studied is the implementation of calcium looping to a pressurized fluidized bed combustion unit. The pressurized carbonator acts as a reheater for the gas turbine and operating the carbonator at temperatures up to 798°C results in a reduction of the energy penalty from 5.1% to 3.1% points.