Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 63 (2014) 2547 – 2556
GHGT-12
Testing of CO2 specifications with respect to corrosion and bulk phase reactions Arne Dugstad*, Malgorzata Halseid, Bjørn Morland Institute for Energy technology, Pb. 40, NO-2027 Kjeller, Norway
Abstract Captured anthropogenic CO2 contains impurities that might react and form solids and separate corrosive phases when the impurity concentrations exceed the limit where the impurity combination becomes thermodynamically unstable. A number of tentative CO2 specifications and recommendations for the maximum acceptable impurity concentrations have been published. The recommendations include impurity combinations and impurity levels that are not found in the published CO2 specifications for pipelines that are or have been in operation. The lack of field experience and the lack of published lab data that support these specifications are a concern. The most referred recommendations have been challenged in the present work. Experiments were performed with dense phase CO2 containing 300 ppmv water, 350 ppmv O2, 100 ppmv SO2, 100 ppmv NO2 and 100 ppmv H2S. The CO2 and the impurities were continuously injected in the test autoclaves and the consumption rate of the impurities was measured. The experiments showed that the carbon steel corroded and that elemental sulfur formed together with a liquid phase containing sulfuric and nitric acid. The paper discusses the experimental technique and the results obtained in four autoclave experiments. The paper also discusses how the lack of fundamental data and understanding makes it difficult to predict corrosion rates and define a safe operation window for transport of dense phase CO2 originating from different sources with different contaminants. © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2013 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of GHGT. of GHGT-12 Peer-review under responsibility of the Organizing Committee Keywords: CCS, CO2 pipeline transport, impurities, corrosion, elemental sulfur
* Corresponding author. Tel.: +47 63 80 62 63 E-mail address:
[email protected]
1876-6102 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Peer-review under responsibility of the Organizing Committee of GHGT-12 doi:10.1016/j.egypro.2014.11.277
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Arne Dugstad et al. / Energy Procedia 63 (2014) 2547 – 2556
1. Introduction Although dense phase CO2 has been transported for more than 40 years, there is limited knowledge about possible corrosion and bulk phase reactions when the CO2 contains flue gas impurities like SOx, NOx, O2 and CO in addition to H2O and H2S. A number of CO2 specifications and recommendations for maximum impurity concentrations have been published (see Table 1). The most referred CO2 quality recommendation has been suggested in the DYNAMIS project1,2. Other frequently referred CO2 specifications have been presented by IPCC3 and Kinder Morgan.4 The National Energy Technology Laboratory (NETL) issued in 2012 and 2013 a Quality Guideline giving recommendations for the impurity limits to be used for conceptual design of carbon steel pipelines.5,6 The recommendations were based on a review of 55 CO2 specifications found in the literature. A large variation in the reported impurity concentrations can be seen and that is reasonable as the impurities in the CCS/CCUS stream will depend on the fuel type, the energy conversion process (post-combustion, pre-combustion or oxyfuel) and the capture process. In addition, with new capturing technologies, new compounds (impurities) can be formed and higher concentrations of impurities can follow the CO2 phase with an unknown effect on corrosion and cross chemical reactions in the bulk phase. 8,9 The justification for many of the proposed recommendations can be questioned as the reported CO2 compositions presently transported in pipelines does not include flue gas impurities like for instance SO2 and NO2, and as concluded in a recent review11 hardly any lab data were found supporting CO2 specifications with these impurities. A CO2 composition (Table 1, last column) with impurity concentrations within the maximum ranges given in the DYNAMIS and NETL recommendations have been tested with respect to corrosion and bulk phase reactions. The experiments were performed in a rocking autoclave system in the dense phase CO2 lab at IFE. The paper presents the results of four experiments performed at 100 bar CO2 pressure, 25 or 45 °C, and with the following impurities: 300 ppmv water, 350 ppmv O2, 100 ppmv SO2, 100 ppmv NO2 and 100 ppmv H2S. Table 1
1,2
Impurity concentrations reported in existing pipelines, CO2 specifications recommended by Dynamis specification tested in the present experiments.
5,6
and NETL
and the CO2
Impurity levels in existing pipelines8,9
Published CO2 recommendations2,5,6
Canyon Reef Carriers
Central Basin Pipeline
Cortez Pipeline
Weyburn
DYNAMIS1,2
NETL5,6
Literature review5
IFE exp.
H2O, ppmv
122
630
630
20
500
7305 / 5006
20-650
300
H2S, ppmv
