Jesse Thompson

Selective Removal of Nitrosamines from a Model Amine Carbon-Capture Waterwash Using Low-Cost Activated-Carbon Sorbents

Nitrosamines generated in the amine solvent loop of postcombustion carbon capture systems are potent carcinogens, and their emission could pose a serious threat to the environment or human health. Nitrosamine emission control strategies are critical for the success of amine-based carbon capture as the technology approaches industrial-scale deployment. Waterwash systems have been used to control volatile and aerosol emissions, including nitrosamines, from carbon-capture plants, but it is still necessary to remove or destroy nitrosamines in the circulating waterwash to prevent their subsequent emission into the environment. In this study, a cost-effective method for selectively removing nitrosamines from the absorber waterwash effluent with activated-carbon sorbents was developed to reduce the environmental impact associated with amine-based carbon capture. The results show that the commercial activated-carbon sorbents tested have a high capacity and selectivity for nitrosamines over the parent solvent amines, with capacities up to 190 mg/g carbon, under simulated amine waterwash conditions. To further reduce costs, an aerobic thermal sorbent regeneration step was also examined due to the low thermal stability of nitrosamines. To model the effect of oxidation on the sorbent performance, thermal- and acid-oxidized sorbents were also prepared from the commercial sorbents and analyzed. The chemical and physical properties of nitrosamines, the parent amine, and the influence of the physical properties of the carbon sorbents on nitrosamine adsorption was examined. Key sorbent properties included the sorbent hydrophilicity and hydrophobicity, surface pKa of the sorbent, and chemical structure of the parent amine and nitrosamine.

Reduction of amine mist emissions from a pilot-scale CO2 capture process using charged colloidal gas aphrons

Abstract In the CO2 capture process from coal-derived flue gas where amine solvents are used, the flue gas can entrain small liquid droplets into the gas stream leading to emission of the amine solvent. The entrained drops, or mist, will lead to high solvent losses and cause decreased CO2 capture performance. In order to reduce the emissions of the fine amine droplets from CO2 absorber, a novel method using charged colloidal gas aphron (CGA) generated by an anionic surfactant was developed. The CGA absorption process for MEA emission reduction was optimized by investigating the surfactant concentration, stirring speed of the CGA generator, and capture temperature. The results show a significant reduction of MEA emissions of over 50% in the flue gas stream exiting the absorber column of a pilot scale CO2 capture unit.

Sensory Odor Evaluation of Trap Grease and Trap Grease Biodiesel

Waste oils and greases from commercial restaurants, also known as trap grease, are potential feedstocks for sustainable biodiesel production. A significant challenge in producing biodiesel from trap grease is the very strong and offensive odor it can possess. The odor can be attributed to several factors including the volatile chemical compounds created during fermentation and biodegradation of oils and fats. Sensory assessment evaluations were performed on several samples of trap grease, trap grease biodiesel, and reference materials to illustrate different aspects of their odor profile and to gain a better understanding of the odor sources so odor mitigation strategies can be developed and evaluated. Short-chain free fatty acids have been identified as a significant component in trap grease and the odor descriptors commonly associated with short-chain free fatty acids were identified in the trap grease samples evaluated. Biodiesel was prepared from trap grease and found to have a similar odor profile as petrodiesel and other commercially available biodiesels blends. The results from this study show that the odor from trap grease can be mitigated during pretreatment and biodiesel conversion steps and does not represent a significant obstacle to commercialization.