Evaluation and analysis of the performance of dehydration units for CO₂ capture

Publication Overview

The purpose of the study is to examine the characteristics of the various dehydration processes and the way they can be best integrated into the CCS system. Moisture in CO₂ can lead to corrosion and hydrate formation. It is necessary to dehydrate CO₂ streams prior to transporting the product in carbon steel pipelines. Several different types of CO₂ capture processes exist. The type selected for use is dependent upon the basic type of combustion process in operation, e.g. coal or natural gas. The CO₂ produced by the various combustion and associated capture processes is of different quality, containing different inerts and impurities, with varying compositions and conditions. The dehydration process can be significantly affected by these differences; it was therefore necessary to consider the different types of capture process separately within this study.

Publication Summary

• The presence of inerts and impurities can lead to significant changes in the CO₂ physical properties and rates of corrosion. These changes are not well understood and further work is required to adequately quantify the effects
• Equations of state need to be developed which adequately reflect the physical properties of CO₂ containing inerts and impurities
• There are limits to the extent of cooling that can be applied to the wet CO₂ gas before water ice, hydrates or liquid CO₂ form. This must be considered in the selection of cooling medium and wet gas conditions.
• There is a wide range in dry CO₂ moisture specifications used for pipelines in the literature. Although it is not the intention of this study to specify what the target moisture should be guidance is given on the types of issues which should be considered when setting the dry CO₂ moisture specification. It should be noted that this value is not merely determined by downstream pipeline conditions but also by coincident conditions which may occur within the processing plant, which may be very different to those experienced by the pipeline.