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Highlights • Carbon xerogel electrodes have high adsorption capacity for organic N-nitrosamines. • N-nitrosamines were decomposed in amine-based carbon capture waterwash solutions by an electrochemical process. • Electrochemical reduction of N-nitrosamines with high (>80%) removal efficiency. Abstract N-nitrosamines, as a class of compounds, have been reported to be mutagenic, cytotoxic, genotoxic and carcinogenic. N-nitrosamine formation and emission are a major concern for amine-based CO 2 capture systems. A process using a stationary carbon electrode inside an electrochemical cell was developed and tested in this study to adsorb and decompose two N-nitrosamines, N-nitrosopyrrolidine and N-nitrosodiethylamine, from an aqueous amine solution. The carbon xerogel electrode material has a high N-nitrosamine adsorption capacity and can initiate an electrochemically-mediated reduction of N-nitrosamines to a secondary amine. A greater than 80% reduction of N-nitrosodiethylamine and 90% of N-nitrosopyrrolidine was observed from a simulated amine-based waterwash solution using an applied current up to 300 mA. N-nitrosamine decomposition was effective in solutions with relatively high amine or salt concentrations. [ABSTRACT FROM AUTHOR]

Fundamental properties of nitrosamines, such as their Henry’s law constants, are needed to accurately predict the gas-phase partitioning and mitigate emissions of these volatile compounds from operating CO 2 capture systems. In this work, the Henry’s volatility coefficient of several environmentally relevant nitrosamines were experimentally obtained from water, from a concentrated amine solution and from a CO 2 loaded amine solution using a static headspace solid phase microextraction and gas chromatography mass spectrometry method. The dimensionless Henry’s volatility coefficients of N-nitrosodimethylamine and N-nitrosodiethylamine were found to be range of 0.001–0.1 at CO 2 absorber exit temperatures from 25 to 55 °C. A linear temperature dependency of the Henry’s volatility coefficient for these nitrosamines was observed. CO 2 loading in the amine solvent increases the Henry’s volatility coefficient of the more non-polar nitrosamine while it decreased the Henry’s volatility coefficient of the more polar nitrosamine. Similar to parent amines, the polarity of the individual nitrosamines plays a key role in its Henry’s volatility coefficients and gas phase partitioning from concentrated amine solutions. [ABSTRACT FROM AUTHOR]

An advanced 0.7 MWe small pilot coal-fired post-combustion CO 2 capture system with heat integration combined with two-stage stripping was tested on a slipstream of flue gas by the University of Kentucky Center for Applied Energy Research (UKy-CAER). Evaluation of solvent degradation products was performed to determine the impact of oxygen exposure due to incorporation of the secondary air stripper into the conventional amine absorber/stripper system. The overall degradation rates and products observed during the testing campaign were comparable to previously published reports using 30% monoethanolamine (MEA) as the baseline/commissioning solvent. The rates of heat stable salt accumulation and amine degradation were similar to those from conventional CO 2 capture systems using MEA. Metal accumulation as the result of material corrosion inside the system from an improperly constructed material was observed. The impact of the secondary air stripper appears negligible relative to other published MEA campaigns tested at similar flue gas conditions and system operating hours. [ABSTRACT FROM AUTHOR]

The University of Kentucky Center for Applied Energy Research (UKy-CAER) designed, constructed and tested an advanced 0.7 MWe post-combustion CO 2 capture system on a coal-fired power plant using a heat integration process combined with two-stage stripping to enhance the CO 2 absorber performance and lower the cost of CO 2 capture. Evaluation of emissions from the solvent and degradation products was performed to determine the impact on the amine solvent of coal combustion flue gas contaminants and oxygen exposure due to incorporation of the secondary air stripper into the conventional amine absorber/stripper system. The overall amine, ammonia and aldehyde emission levels observed during the baseline 30% monoethanolamine (MEA) solvent testing campaign were generally comparable to previously published reports tested at similar flue gas conditions and system operating hours. Ammonia emissions were correlated to high levels of iron and copper in the solvent, likely as a result of material corrosion. [ABSTRACT FROM AUTHOR]

The novel small molecule carbonic anhydrase (CA) mimic [Co III (Salphen-COO − )Cl]HNEt 3 ( 1 ), was synthesized as an additive for increasing CO 2 absorption rates in amine-based post-combustion carbon capture processes (CCS), and its efficacy was verified. 1 was designed for use in a kinetically slow but thermally stable blended solvent, containing the primary amines 1-amino-2-propanol (A2P) and 2-amino-2-methyl-1-propanol (AMP). Together, the A2P/AMP solvent and 1 reduce the overall energy penalty associated with CO 2 capture from coal-derived flue gas, relative to the baseline solvent MEA. 1 is also effective at increasing absorption kinetics of kinetically fast solvents, such as MEA, which can reduce capital costs by requiring a smaller absorber tower. The transition from catalyst testing under idealized laboratory conditions, to process relevant lab- and bench-scale testing adds many additional variables that are not well understood and rarely discussed. The stepwise testing of both 1 and the novel A2P/AMP solvent blend is described through a transition process that identifies many of these process and evaluation challenges not often addressed when designing a chemical or catalytic additive for industrial CCS systems, where consideration of solvent chemistry is typically the primary goal. [ABSTRACT FROM AUTHOR]

• Evaluated O 2 solubility in amine solvents with four different additives. • Validated electrochemical DO probe by a modified Winkler method titration. • O 2 solubility not affected by non-ionic surfactant and anti-foam agent. • O 2 solubility increased with NaVO 3 and decreased with MBT. Oxidative degradation in amine based post-combustion carbon capture (PCCC) leads to solvent losses and decreased solvent performance. Oxygen (O 2) in the flue gas is dissolved into the aqueous solvent and can reactively degrade the amine component. Advanced aqueous amine solvents are designed to contain additional surfactant and anti-foam additives as well as two types of corrosion inhibitors. These additives contribute to improve the solvent performance while reducing foaming and corrosion of expensive equipment. This work examines the impact of these additives on oxygen solubility (or dissolved oxygen - DO) in various aqueous amines used in PCCC including ethanolamine (MEA), 1-amino-2-propanol (A2P), 2-amino-1-propanol (2A1P), 2-(methylamino)-ethanol (NMEA), 2-(ethylamine)-ethanol (2EAE), diethanolamine (DEA), methyl-diethanolamine (MDEA), dimethylethanolamine (DMEA), piperazine (PZ), 1,2-ethyldiamine (EDA), and 1,6 hexadiamine (HDA). The impact of carbon loading on oxygen solubility with and without these additives was also examined. The surfactant and anti-foam additives had minimal impact on DO for all the solvents investigated. The two anti-corrosion additives had opposite effects in the measured DO, 2- mercaptobenzothiazole (MBT) decreased the DO concentration, and sodium metavanadate showed an increase. These results indicate that several of these common additives can be expected to minimally affect DO related oxidative degradation in these advance amine solvents. [Display omitted]. [ABSTRACT FROM AUTHOR]

N -Nitrosamines are one of the environmentally significant byproducts from aqueous amine-based post-combustion carbon capture systems (CCS) due to their potential risk to human health. Safely mitigating nitrosamines before they are emitted from these CO 2 capture systems is therefore a key concern before widescale deployment of CCS can be used to address worldwide decarbonization goals. Electrochemical decomposition is one viable route to neutralize these harmful compounds. The circulating emission control waterwash system, commonly installed at the end of the flue gas treatment trains to minimize amine solvent emissions, plays an important role to capture N -nitrosamines and control their emission into the environment. The waterwash solution is the last point where these compounds can be properly neutralized before becoming an environmental hazard. In this study, the decomposition mechanisms of N -nitrosamines in a simulated CCS waterwash with residual alkanolamines was investigated using several laboratory-scale electrolyzers utilizing carbon xerogel (CX) electrodes. H-cell experiments revealed that N -nitrosamines were decomposed through a reduction reaction and are converted into their corresponding secondary amines thereby neutralizing their environmental impact. Batch-cell experiments statistically examined the kinetic models of N -nitrosamine removal by a combined adsorption and decomposition processes. The cathodic reduction of the N -nitrosamines statistically obeyed the first-order reaction model. Finally, a prototype flow-through reactor using an authentic waterwash was used to successfully target and decompose N -nitrosamines to below the detectable level without degrading the amine solvent compounds allowing them to be return to the CCS and lower the system operating costs. The developed electrolyzer was able to efficiently remove greater than 98% of N -nitrosamines from the waterwash solution without producing any additional environmentally harmful compounds and offers an effective and safe route to mitigate these compounds from CO 2 capture systems. [Display omitted] • Investigation of electrochemical decomposition mechanisms for hazardous N -nitrosamines in amine-rich waterwash from CCS. • Low-cost synthesized carbon xerogel electrodes were used for several laboratory-scale electrolyzers. • N -Nitrosamines were decomposed by cathodic reduction without producing any environmentally harmful compounds. • A prototype flow-through reactor was able to remove greater than 98% of N -nitrosamines from authentic waterwash. N -Nitrosamines are an environmentally significant byproducts from CO 2 capture systems but can be safely mitigated by electrochemical decomposition enabling widescale deployment of CO 2 capture systems to reach worldwide decarbonization targets. [ABSTRACT FROM AUTHOR]