(290g) The NETL Aqueous Process: History and Recent Developments

An aqueous mineral carbonation process was developed at the NETL with emphasis on the utilization of calcium and magnesium silicate ores as the primary reactants.  The studies included cursory regional resource assessments, process development, and a process evaluation for the carbonation of flue gas-derived CO₂ at the industrial scale.  While successful demonstration of the aqueous process was achieved, several opportunities for further process optimization were identified.  For example: 1) inclusion of a magnetic separation step in the serpentine process flow sheet could produce an iron oxide by-product while limiting deleterious iron oxidation during heat treatment; 2) utilization of a pipeline reactor in place of the high-pressure stirred tank reactor was demonstrated at the bench-scale, and could dramatically reduce plant costs at scale; and 3) studies by other researchers indicate that ~75% of the heat required for thermal treatment of serpentine ore could be recovered and utilized for additional operations in the plant by efficient integration of the overall plant operations.  While each of these process modifications was investigated with positive results, they are but a few examples of the potential for overall process integration and improvement.

While the recent NETL focus has been on geological sequestration, mineral carbonation research has continued.  These efforts have included the investigation of alternative feedstock materials, such as coal fly ash, electric arc furnace (EAF) dust, and steel grinding swarf.  Results indicate that the reactivity of the various materials is highly dependent on their phase composition, which can be used as a predictive tool when considering such materials as suitable feedstock.  Finally, modification of the carrier solution, namely removal of the NaCl addition, was demonstrated successfully, which could reduce corrosion of the process equipment and eliminate the detrimental impact of chloride on the potential commercial applications for the final carbonate product.