Simulations and process analysis of the carbonation–calcination reaction process with intermediate hydration

Abstract

Several technologies are currently being developed to separate carbon dioxide from large point sources, such as coal-fired power plants. An emerging technology that shows great potential is a calcium oxide–calcium carbonate cycle. A major drawback is the calcium carbonate decreases in reactivity over multiple cycles. The Ohio State University demonstrated in 2008 the first carbonation–calcination reaction (CCR) process that includes intermediate hydration for sorbent regeneration and its feasibility over multiple cycles at the 120kWth scale with actual flue gas from coal combustion. The CCR Process utilizes a calcium-based sorbent to react with the carbon dioxide and sulfur dioxide in a flue gas stream to form calcium carbonate and calcium sulfate, respectively. The carbon dioxide is subsequently released from the calcium carbonate to produce a high-purity, sequestration-ready carbon dioxide stream while regenerating the calcium oxide sorbent. The sulfur dioxide is fixated as calcium sulfate and removed through a purge stream. An intermediate hydration step restores reactivity to the calcium oxide sorbent. Process analysis from computer simulations shows the CCR Process to be highly effective and efficient in removing both carbon dioxide and sulfur dioxide at low energy penalties under realistic conditions. A 20–22% decrease in electricity generation efficiency with the CCR Process is expected, compared with amine scrubbing around 27% and oxy-combustion around 25% energy penalty. A 25–28% increase in thermal energy with the CCR Process is expected to maintain a constant electrical output. Further, the CCR Process consumes half the oxygen necessary for an oxy-combustion plant and 25% less steam necessary for amine scrubbing.