Carbon Capture Solvents Research Articles

Heat requirement for regeneration of aqueous ammonia in post-combustion carbon dioxide capture

The present work evaluates ammonia as a carbon dioxide (CO2) solvent for post-combustion carbon capture, focusing on the thermal performance of the ammonia regeneration process and the operating conditions for the aqueous ammonia process. The main parameters investigated were the CO2-loading of the lean solution (0.2–0.5) and the ammonia concentration (2–20%). An equilibrium-based electrolyte model was used in process simulation software to evaluate the performance of the ammonia regeneration. The heat requirement was approximately 2500kJ/kg CO2 captured. Running conditions in which the precipitation of solids occurred did not enhance the thermal performance. The main reaction pathway for the absorption of CO2 was identified as the formation of bicarbonate through the reaction of ammonia with CO2. The heat of reaction required to desorb CO2 of ammonia was similar to that required for monoethanolamine (MEA). However, significantly less water was evaporated during the regeneration process with ammonia, resulting in a lower heat requirement for regeneration.

Concerted HO2 Elimination from α-Aminoalkylperoxyl Free Radicals: Experimental and Theoretical Evidence from the Gas-Phase NH2(•)CHCO2(-) + O2 Reaction.

We have investigated the gas-phase reaction of the α-aminoacetate (glycyl) radical anion (NH2(•)CHCO2(-)) with O2 using ion trap mass spectrometry, quantum chemistry, and statistical reaction rate theory. This radical is found to undergo a remarkably rapid reaction with O2 to form the hydroperoxyl radical (HO2(•)) and an even-electron imine (NHCHCO2(-)), with experiments and master equation simulations revealing that reaction proceeds at the ion-molecule collision rate. This reaction is facilitated by a low-energy concerted HO2(•) elimination mechanism in the NH2CH(OO(•))CO2(-) peroxyl radical. These findings can explain the widely observed free-radical-mediated oxidation of simple amino acids to amides plus α-keto acids (their imine hydrolysis products). This work also suggests that imines will be the main intermediates in the atmospheric oxidation of primary and secondary amines, including amine carbon capture solvents such as 2-aminoethanol (commonly known as monoethanolamine, or MEA), in a process that avoids the ozone-promoting conversion of (•)NO to (•)NO2 commonly encountered in peroxyl radical chemistry.

Durability of fly ash/GGBFS based geopolymers exposed to carboncapture solvents

This paper examines a series of fly ash and ground granulated blast furnaceslag binders formulated to examine the effects of composition and mix designon performance and durability when exposed to aggressive environments foundin carbon capture facilities (monoethanolamine or concentrated potassiumcarbonate, as well as distilled water). Ordinary Portland cement andordinary Portland cement fly ash blends were examined for comparison. Thesamples are exposed to solvents by immersion under static conditions. Leachingand mechanical strength tests show a wide range of geopolymer performance,depending on the initial mix design and the nature of the aggressive agent.Alkali carbonate solutions are found to be the most aggressive agent amongthose tested in terms of geopolymer mass and strength loss; nonetheless, theresistance to structural degradation upon carbonation of the geopolymer binderstructure is mitigated to a significant extent by the low calcium contentof the geopolymer binder. Less porous materials, or materials with smallerand more tortuous pores, show in many cases a markedly higher durability;porosity is shown to hold the key to durability. In traditional cement basedbinders, strength is lost through chemical attack upon exposure to solvents.

The effect of boric acid on the vapour liquid equilibrium of aqueous potassium carbonate

Aqueous potassium carbonate has seen renewed interest as a viable solvent for pre and post combustion carbon capture and storage. However, slow reaction kinetics may require the addition of a rate promoter such as boric acid to improve efficiency. The vapour liquid equilibrium of 30 weight percent potassium carbonate with 0, 3 and 5 weight percent boric acid was investigated at 50 and 70 °C using a dynamic inert gas stripping method. By estimating the boric acid reactions an Electrolyte-NRTL model was able to fit this data and literature results very closely.

Theoretical Screening of Ionic Liquid Solvents for Carbon Capture

A computational approach that accurately computes CO2 solubilities in ionic liquid solvents is described. A large number of solvents are screened for efficient dissolution of CO2. The approach yields an excellent agreement (within 10–15 %) with recent solubility measurements over a range of temperatures and gas pressures of practical interest.