Measurement and prediction of oxygen solubility in post-combustion CO2 capture solvents

Vanja Buvik,Ida M Bernhardsen,Roberta V Figueiredo,Solrun J Vevelstad,Earl Goetheer,Peter Van Os,Hanna K Knuutila

doi:10.1016/j.ijggc.2020.103205

Abstract

This work aims to understand oxygen solubility in pure and aqueous amine solvents for CO2 capture. Commercially available dissolved oxygen sensors were studied to evaluate whether these can be used for measuring oxygen solubility in the carbon capture processes. It also aims to understand the possible discrepancies from realistic concentrations of oxygen when using a dissolved oxygen sensor. Two independent measurement principles were used for this purpose, both electrochemical and optical. Furthermore, a Winkler titration method was used to aid the validation of the sensors as well as understanding salting-out effects. A simple model for predicting oxygen solubility in CO2-loaded ethanolamine solutions was made, which also has potential for predicting oxygen solubility in other loaded amine solutions.The results of the study show that dissolved oxygen sensors may be applied for measurement of oxygen concentrations in amine solutions and that different amines and different concentrations in water only show small variations in oxygen solubility. The sensors may also be used in CO2-loaded amine solutions, but here the increased conductivity of the solution may give a higher measured concentration of oxygen, than it is in reality. In ethanolamine, the consumption of oxygen is faster than the mass transfer of oxygen from gas to liquid phase, giving lower concentrations of oxygen than it should be in absence of a chemical reaction between oxygen and amine.

Highlights

The capture and storage of CO2 from large emission sources (CCS) has to play a key role for reaching the target of not exceeding 1.5 ◦C increase of global average temperatures, concludes the Intergovern mental Panel on Climate Change (IPCC) in their report from 2018 (Rogelj et al, 2018)
The solubility of oxygen was measured using two different electro chemical dissolved oxygen sensors and one optical oxygen sensor, all designed for measurement of oxygen concentrations in water
The electrochemical dissolved oxygen sensors used are based on galvanic probes that give a measurable current proportional to the chemical reduction of O2 on a cathode

Summary

Introduction

The capture and storage of CO2 from large emission sources (CCS) has to play a key role for reaching the target of not exceeding 1.5 ◦C increase of global average temperatures, concludes the Intergovern mental Panel on Climate Change (IPCC) in their report from 2018 (Rogelj et al, 2018). There are many studied technologies for CO2 capture and of those, flue gas scrubbing with liquid amine solvents is one of the most mature technologies (Kohl and Nielsen, 1997; Leung et al, 2014; Rochelle, 2009). Liquids have inherent gas absorption properties and can physi cally absorb gases to some extent (Battino and Clever, 1966). The amines can more selectively, and in higher concentrations than physical gas absorption, bind the gas molecules. In this process, a solvent reversibly binds CO2 at low temperatures in an absorber column and is released at high temperatures in a desorber column

Objectives

Methods

Results

Conclusion