The steam-assisted calcination of limestone and dolomite for energy savings and to foster solar calcination processes

CaO and MgO are important industrial raw materials commonly produced by either the decomposition of calcium carbonate at about 900 degrees C, or the calcination of dolomite, a mixed calcium and magnesium carbonate, calcined either to MgO.CaCO3 at about 750 degrees C, or to MgO.CaO at 900 degrees C. In this research, the decomposition reaction of 104-147 nm dolomite and limestone particles was investigated, both without and with steam added to the reaction. A series of experiments was performed in terms of relevant parameters such as time, temperature and amount of H2O added. Reactants and reaction products were fully characterized and demonstrate the different morphology and specific surface area of the raw carbonate ores and the calcined oxides. Adding H2O during calcination has a significant positive effect. The calcination shows that steam can significantly accelerate the reaction rate, and reduce the decomposition temperature by similar to 100 degrees C, thus reducing the cost of the decomposition by increasing the yield for a given reaction time, while also reducing the required sensible heat of the feedstock and combustion air. This ultimately reduces the amount of fossil fuel or alternative energy carriers, thus reducing the CO2 footprint of the system. The improved operating conditions foster the use of concentrated solar calcination. The CO2 footprint of the carbonate decomposition can be reduced by -4% in traditional kilns, and by as much as 20% if concentrated solar kilns are used. Both applications are currently investigated in pilotscale operations.

Automated summary

The decomposition of dolomite and limestone particles with the addition of steam has been investigated, showing that steam can significantly accelerate the reaction rate and reduce the decomposition temperature, leading to cost reduction and reduced CO2 emissions.