Published August 2003
Calcium formate is being tested by the U.S. DOE as a third generation "clean" technology approach for flue gas desulfurization (FGD) of coal and high sulfur fuel oil fuel combustion for steam generation. For high sulfur fuel oil, SOX emissions are abated if the fuel oil is emulsified with a solution containing calcium formate before burning. For coal combustion, a calcium formate solid may be more easily shipped to power plants instead of limestone and formic acid as FGD reagents. The product is produced from quicklime and CO generated by natural gas reforming. The type of FGD system that will consume calcium formate produces gypsum as a combustion gas desulfurization by-product, which is a preferred salable product form. This new generation of FGD system may allow for fuel switching from coal to heavy fuel oil as dictated by local economics and fuel supply sources.
This review presents a conceptual process design and economics for the large-scale industrial production of calcium formate from CO and quicklime, based on a review of patent and technical literature. The CO is produced by steam reforming of natural gas to maximize hydrogen production. Calcium formate is produced by gas/liquid contacting of lime slurry with CO to produce a slurry from which solid calcium formate is recovered.
Total battery limits capital costs for a large scale 551 million lb/yr (250,000 metric tons/yr) production facility located on the U. S. Gulf Coast is $95.8 million on a grass roots basis. The calculated product value of calcium formate for this lime carbonylation process, based on production cost plus a 25% return on total fixed capital, is 15.25¢/lb, assuming by-product value can be sold at chemical value. Under these conditions, production of calcium formate by the direct carbonylation of hydrated lime process is technically and economically feasible.
Since there is no one strategy that is a unique answer to the sulfur emissions problem, a more detailed market study should be made to determine the potential demand for calcium formate, and to explore new potential applications that would create new markets. For Flue gas desulfurization, site-specific factors such as proximity to reagent source, space availability, and the extent of sulfur removal required must be determined on a plant-by-plant basis for both retrofits and new power plant installations. This study should also determine whether additional calcium formate can be made from existing production processes and the effect on market price if world demand or supply for calcium formate expands.