In addition, the cost of CO emissions avoided through Ca-looping is lower than the cost of emissions avoided via an oxyfuel combustion process (~US$23.8/t). This can be explained by the fact that, despite the capital costs incurred in constructing the carbonator for Ca-looping, CO will not only be captured from the oxy-fired combustion, but also from the main combustor (before the carbonator). The oxygen required in the calciners is only 1/3 that required for an oxyfuel process, lowering air separation unit capital costs and operating costs.
Sensitivity Analysis: Figure 3 shows how varying 8 separate parameters affects the cost/metric ton of CO captured through Ca-looping. It is evident that the dominant variables that affect cost are related to sorbent use, the Ca/C ratio and the CaO deactivation ratio. This is because the large sorbent quantities required dominate the economics of the capture process.
These variables should therefore be taken into account to achieve further cost reductions in the Ca-looping process. The cost of limestone is largely driven by market forces, and is outside the control of the plant. Currently, carbonators require a Ca/C ratio of 4 for effective CO capture. However, if the Ca/C ratio or CaO deactivation is reduced (i.e. the sorbent can be made to work more efficiently), the reduction in material consumption and waste can lower feedstock demand and operating costs.