(266f) Techno-Economic Analysis of Gas Purification for CO2 Transport in Pipeline Networks and Injection for Storage

Techno-economic analysis of gas purification for CO₂ transport in pipeline networks and injection for storage

Clea Kolster*^1,2 , Evgenia Mechleri^1,2, Sam Krevor³, Niall Mac Dowell^1,2

*Presenting author’s e-mail: clea.kolster10@imperial.ac.uk

¹ Centre for Environmental Policy, Imperial College London, South Kensington Campus, SW7 1NA, UK

² Centre for Process Systems Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, UK

³ Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, UK

Abstract

The IEA Energy Technology Perspectives 2014 stated that Carbon Capture and Storage (CCS) is a crucial component in capping the world’s average surface temperature increase by 2 °C (IPCC, 2014) and, if applied to the power generation and heavy industry sectors, could reduce cumulative emissions by 14% in 2050 (IEA, 2014). In addition, when considering the decarbonisation of the heavy industry sector, CCS is currently the only available option. Therefore, it is imperative that the CCS process be optimised to run smoothly through each stage of operation and that its costs be minimised in order to accelerate its global financial and political acceptance. In view of these issues, this paper focuses on the operational modelling of a CO₂ capture process, modelling and quantifying the economic benefits resulting from a CO₂ transport network system and the cost reduction ensuing from CO₂ capture plant clusters.

Oxy-combustion capture comprises of two energy intensive sections: the air separation unit (ASU) and the CO₂ purification and compression unit (CO₂CPU). The CO₂CPU brings the raw flue gas from a low purity atmospheric CO₂ stream to a high purity, high pressure CO₂ stream suitable for transport. So far little has been discussed regarding the optimal design and operation of the CO₂CPU (Boot-Handford et al., 2014). This work focused on minimising the capital and operational costs involved in the CO₂CPU while prioritising an EOR suitable end product. Three CO₂ compression and purification units processing flue gas from a pulverised fuel oxy-combustion plant were modelled in Aspen HYSYS. These CO₂CPU models build on similar separation processes presented by Posch et al. (Posch & Haider, 2012) and Pipitone et al. (Pipitone & Bolland, 2009).

It was established that, as the CO₂CPU models increased in complexity and purity of the produced CO₂ stream, they increased in operational and capital costs but decreased in capture efficiency i.e. increase the amount of CO₂ vented to the atmosphere. The capital and operational costs for each process model were translated into a price for each stream of CO₂ marketed for EOR. A non-monotonic and non-linear relationship between CO₂ price and CO₂ purity was observed. A CO₂-EOR suitable product stream, requiring a very high purity, led to a price of £20 per tonne, while the least complex system provides a stream that is suitable for transport, but not for injection, at a price of £11 per tonne.

In addition, this paper discusses the possibility of having one CO₂ capture plant for a cluster of power and/or industrial plants as opposed to several smaller capture plants. Modelled in Aspen HYSYS, it was found that instead of having 4 CO₂CPUs with a 5 Mt.CO₂ yearly capacity, having one large CO₂CPU with a yearly capacity of 20Mt.CO₂ reduces capital expenditure by 16% and yearly operational expenditure by 4%.

As CCS is deployed on a large scale, we will deploy transport networks, as opposed to a large number of single point-source to sink links. It is therefore vital to understand how these complex networks will behave, and indeed contribute to the flexibility of these systems. Therefore, a second part of this work considers a hypothetical UK-based network of CO₂ sources connecting to a single sink in the North Sea (Prada, Konda, & Shah, 2010). The CO₂ sources considered include combined cycle gas turbine (CCGT) plants, coal fired power plants and industrial plants. The CO₂ transport network allows for high purity sources of CO₂ derived from post-combustion capture power plants to be combined with less expensive, lower purity sources of CO₂ using oxy-combustion capture, to produce a CO₂ stream which is suitable for injection, i.e., a CO₂ stream composed of >96 wt.% CO₂. This led to a 19% reduction in the price of CO₂.

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