Synthetic Calcium Carbonate Production by Carbon Dioxide (CO₂) Mineralization of Industrial Waste Brines

Technical Report · Mon May 15 00:00:00 EDT 2023

DOI:https://doi.org/10.2172/1974173· OSTI ID:1974173

Wang, Bu ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)

The global scale of CO₂ emission has crossed 36 B tons, and the United State represents 14% of the total emissions. In light of the high cost associated with current CO₂ capture processes ($60-to-150 per ton of CO₂), carbon capture and utilization (CCU), wherein CO₂ is converted to beneficial products, provides a pragmatic path to overcome the economic barrier for CO₂ emissions control. In particular, CO₂ mineralization offers an attractive route as it produces high-value mineral carbonates that sequester CO₂ in a stable form. For instance, fine precipitated calcium carbonate, a valuable product with unit price in the range of $230-280/t and a global market projected to reach 99 M tons in 2020, can be produced by capturing CO₂ within aqueous Ca²⁺ solution. However, two critical challenges need to be overcome—(i) the need for costly processes such as electrolysis or addition of alkali hydroxides to maintain alkalinity during mineralization, and (ii) the geographic availability of Ca-rich solutions (or brines) which often renders efficient integration with power plants impractical. To simultaneously address these challenges, this project developed two novel routes to enable carbonate production based on efficient CO₂ mineralization. In one variation, the project developed a new alkaline carbonation process to capture CO₂ and produce calcite precipitates from coal ashes. Herein, coal ash is carbonated first in a sodium carbonate solution. The carbonation reaction produces sodium hydroxide and raises the solution pH. This high-pH hydroxide solution is then used for CO₂ capture, which converts the sodium hydroxide solution back to sodium carbonate to repeat the carbonation cycle. The carbonated ash residue is refined with a CO₂ pressure swing step to produce high-purity precipitated calcium carbonate. In another variation, Ca-rich produced water brine serves as the Ca-source to mineralize CO₂. An H⁺/Na⁺ ion-exchange cycle was designed to provision alkalinity during mineralization and regenerate the ion-exchange reagent in brines with high salinity. Ca-depleted brines can then be treated within a centralized water treatment facility. Both variations beneficially utilize reject streams—such as coal ashes and brines from oil and gas extraction or CO₂ storage operations—that are available at substantial quantities in the vicinity of coal power plants within the U.S. In addition to technology development, this project included techno-economic and life-cycle analysis to identify technically and economically appropriate solutions for power plants in different geographic locations. Taken together, the project provides a unique route to integrate CO₂ emissions control and waste handling/treatment for coal power plants, while producing a high-value product to offset the economic burden associated with waste management. The developed processes utilize post-desulfurization flue gas from coal-fired power plants as is. The CO₂ conversion reactions are performed in alkaline brines at ambient pressure from the flue gas, thereby minimizing the energy burden. By beneficiation of industrial waste streams with low energy input, the processes offers significant technical advantages in energy and CO₂ footprint over the current paradigm of precipitated calcium carbonate production, which involves calcination of limestone at processing temperatures in excess of 800 °C. Overall, this project developed viable CO₂ mineralization processes while strategically maximizing the economic benefit.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE), Clean Coal and Carbon Management
• DOE Contract Number: FE0031705
• OSTI ID: 1974173
• Report Number(s): DOE-UWMADISON-0031705
• Country of Publication: United States
• Language: English

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