Processing Mixed Salts and CO2 Utilization

The chemical industry needs a new technology for extracting chlorine from salt (sodium chloride) and mixed salt systems. The industry has conventionally relied upon the chlor-alkali process and the Solvay process to extract chlorine from salt to produce some of the largest scale chemical commodities, such as chlorine, hydrochloric acid, sodium carbonate, and sodium hydroxide. The chlor-alkali process, however, is too energy intensive, results in excessive greenhouse gas emissions, and supplies products in ratios that are disproportionate to demand. The Solvay and mining approaches to producing sodium carbonate are unearthing carbon dioxide for release into the atmosphere at a time when industry should instead be using captured carbon to produce valuable carbonate products. A new process is undergoing development to profitably extract chlorine from salt systems. This extraction of chlorine enables diverse options for subsequent separations or synthesis of other salable minerals and chemicals. This flexible approach to extracting chlorine has the potential to substantially displace the chlor- alkali process, Solvay process, and mining processes for producing sodium carbonate. The processing options include the opportunity to spontaneously and directly absorb carbon dioxide from air through mineral carbonation on the domestic scale of about 10 million tonnes per year. The Phase I and II projects demonstrated the technical feasibility of the chlorine extraction process. A transport membrane condenser technology can benefit the process by enhancing the collection of hydrochloric acid and heat. The program has also demonstrated the technical feasibility of incorporating the chlorine extraction process into a larger approach to profitably process bitterns and other mixed sea salt systems into salable minerals. These bitterns are a rich mineral resource that is a byproduct of salt production through the solar evaporation of seawater that is presently not being exploited. The techno- economic analysis of the Phase II project, however, quantified a strong potential for the proposed technology to finally enable the profitable processing of bitterns into salable minerals. The efficient extraction of chlorine drives the profitability of the overall process. The Phase IIA project will complete the scale up of the chlorine extraction and membrane-based collection process to a semi-continuous prototype and further develop the techno-economic analyses to substantiate the process profitability and commercialization. The large-scale extraction of chlorine, minerals, and other products central to the chemical industry from previously unusable salt commodities would enhance the productivity of the salt industry, improve resource management, and increase energy efficiency in domestic manufacturing. With potential process scales on the order of several million tons of mixed salt per year, the resulting byproducts of the process will lower the feedstock costs for fertilizer, plastics, water treatment, metal/steel, paper/pulp, and carbon sequestration industries.