Liquid-Amine Infused Surfaces for Carbon Capture

Author

Pedro Bertolini, CUNY City CollegeFollow

Date of Award

2024

Document Type

Dissertation

Department

Chemical Engineering

First Advisor

Charles Maldarelli

Keywords

Carbon capture, Transport, Modeling, Liquid Infused Surfaces

Abstract

The release and accumulation of carbon dioxide in the atmosphere during the burning of fossil fuels is considered the primary contributor to climate change. Efficient and high-capacity technologies that can remove CO₂ from (i) point sources (e.g. exhaust streams) and (ii) directly from air (i.e. direct air capture (DAC)) are the key towards reversing the elevated levels of atmospheric CO₂.

Here, we study a novel technology (solid with infused reactive liquid (SWIRL)) which integrates liquid infused surfaces in flow-through geometries to form systems that have large interfacial surface areas per unit volume. The chemistry of the surfaces are designed to be readily wet by pure amine liquids to form wetting infused layers, retained by capillary forces, of order tens of microns in thickness. These stationary wetting layers capture CO₂ via a reaction to form carbamate. The large interfacial areas per unit volume far exceed the values for commonly used amine scrubbing towers. In addition, the large thickness and the use of pure amines in SWIRL, provides an increase in capacity for CO₂ capture per unit volume relative to other sorbents and mesoporous materials in literature which display reactive amines either as single (i.e. grafted) or multiple molecular layers.

The focus of this study is to develop a transport model to describe the CO₂ capture for the flow-through geometry of SWIRL. As the thickness of the amine wetting infused layers is much smaller than the characteristic dimension of the gas passageways, a model is developed in which CO₂ flows over a planar thin film, partitioning and diffusing into the film and reacting to form carbamate. The principal effect which governs the capture of CO₂ as a function of time is the development of a highly viscous layer of carbamate at the gas/amine liquid interface. This viscous interfacial layer acts as a barrier that prevents further CO₂ diffusion into the layer and reaction with fresh amine diffusing to the surface. As the system evolves from that of pure amine into one of pure carbamate, the physical properties, in particular the diffusion coefficients and solubility, change in composition in time as capture proceeds and carbamate accumulates. MD calculations are used to determine the composition dependence of the CO₂ solubility, and a Stefan-Maxwell framework is used to evaluate the composition dependence of the diffusion through the mixture viscosity which is measured. The reaction of CO₂ and amine is assumed to be a single step reversible reaction with forward and backward reaction constants

This study is divided into three parts: First, data on the capture of CO₂ in a SWIRL device using TEPA amine is fit to the transport model for two inlet concentrations of CO₂ (50 and 500 mbar) equal to or above characteristic flue gas (point source) concentrations and four temperatures (48°C-105°C) with the unknown parameters being only the two reaction constants at the different temperatures. The transport model shows precise, quantitative agreement with experiments, providing a deeper understanding of the balance between the parameters that determines the dynamics of SWIRL capture and explains non-thermodynamic behavior such as the increase in conversion with temperature and regressive behavior in capture at high temperatures and 50 mbar.

The second part models the regeneration process which is implemented by flowing an inert gas through the structure at an elevated temperature which causes the CO₂ to diffuse out of the amine/carbamate liquid mixture, driving the conversion of carbamate back to amine. The simulated regeneration agrees with experiments following a capture at 50 mbar. The validated transport model is then used to model multiple capture/regeneration cycles.

The last part models SWIRL capture under DAC conditions (400 ppm). In this case, the dynamics of the transport becomes less constrained by diffusion due to the lower rate of accumulation of carbamate. Additional simulations demonstrate that the use of less reactive amines can still provide viable capture which can be improved further by using thicker films, distinguishing SWIRL from other capture technologies based on monomolecular layers.

Recommended Citation

Bertolini, Pedro, "Liquid-Amine Infused Surfaces for Carbon Capture" (2024). CUNY Academic Works.
https://academicworks.cuny.edu/cc_etds_theses/1291