(514b) CO2 Utilization Based on Post-Treatment of Desalinated Reject Brine and Structural Properties of Alkanolamine Type Absorbents for MgCO3 Pseudopolymorph Control

First, according to global CO2 concentration statistics, the amount of CO2 emitted from power plant using fossil fuels gets out of general flow. The excessive amount of CO2 contributes to global warming which induced lots of problems in earth. Also, lots of metal cations in desalinated reject brine induced many problems in discharged location. Therefore, in this study, simultaneous disposal and utilization process of desalinated reject brine and CO2, or brine-based carbon capture and utilization (CCU) was proposed. According to conventional researches which dealt with crystallization process, when crystallization reaction occurs, the surrounding including solvent, materials and ions affect rate and product of the crystallization process. Using metal cations in desalinated reject brine, the feasibility of alkanolamine type absorbents, pseudopolymorph controller of magnesium carbonate formation was investigated in this study. Mg2+ ions were separated from desalinated reject brine in a salt refining plant by using a pH swing method and used for MgCO3 pseudopolymorph formation. Through this process, disposal of the large amount of metal cations in the desalinated reject brine was achieved. CO2 was selectively captured by alkanolamine type CO2 carriers and carried into the separated Mg(OH)2 to generate MgCO3. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR) were used to investigate crystal shape and pseudopolymorph of the product. Additionally, thermogravimetric/derivative thermogravimetric analysis (TG/DTG) was used for purity analysis. The results demonstrated that crystallization inhibition depending on structural properties of alkanolamine type absorbent was possible, leading to successful MgCO3 pseudopolymorph control. The results of this research can be applied to process where the industrial production of metal carbonates based on inorganic CCU and disposal of the desalinated reject brine were involved.