Technical Parallel Session 1
Aquistore: Performance Monitoring for Full-Chain CCS
Chaired by Michelle Bentham (BGS)
The Boundary Dam project, Saskatchewan, is the world’s first commercial power plant CCS project. CO2 capture began at the plant in 2014 and start-up of CO2 injection at the adjacent Aquistore site is planned for Spring 2015. Microseismic monitoring forms an important part of a monitoring and verification program for such a project because the detection of seismic events can be used to verify geomechanical models and provide real-time early-warning of CO2 migration or leakage. The microseismic monitoring set-up at the Aquistore site is unrivalled in this sector with baseline data available since July 2012 from an array of 51 vertical component geophones. In addition, three broadband stations provide data since November 2013. The instruments cover ~2.5kmx2.5km, surrounding the injection well. Preliminary baseline data analysis identifies noise sources associated with activity at the power plant, around the wells and on nearby roads. As part of this analysis we calibrated event detection, location and magnitude estimation procedures using injection well perforation shots and reported regional events. With near real-time passive seismic data analysis we will report and characterise any induced seismicity associated with CO2 injection to improve understanding of the geomechanical response to injection at the site and inform injection activities.
Claire Birnie (University of Leeds) - Passive noise analysis from the permanent surface array at the Aquistore CCS site
A study has been performed on a 3-month period of passive seismic data collected at the Aquistore injection site in 2012 with the aim of identification and characterisation of individual noise sources prior to their recreation within a synthetic dataset. Synthetic datasets are commonly used to aid interpretation, test hypothesis and as a benchmarking tool for evaluating the robustness of seismic imaging algorithms however, noise within these datasets is often modelled as white and/or Gaussian. Our work is aimed at creating more realistic noise models with spatial and temporal variations as observed in noise present within field data. This work defines a noise classification scheme that systematically represents these temporal and spatial variations and trends. Preliminary results of the noise analysis are presented where noise signals identified at the Aquistore injection site are classified using the scheme defined into the noise categories: stationary, non-stationary and pseudo-non-stationary noise. Future studies will focus on creating a mathematical description of the signals focusing on non-stationary and non-linear aspects with the aim to build this into a synthetic seismic dataset as realistic noise.
Material Science for CCS
Chaired by Niall Mac Dowell (Imperial College London)
Stuart Scott (University of Cambridge) - High temperature oxygen donor materials for oxy-fuel combustion
Various solid materials can be used to separate oxygen from the air for use in combustion processes. In chemical looping combustion, a metal oxide is used to provide the oxygen to the fuel, thus produce a stream of CO2 which requires little further separation. In some cases, the metal oxide can be used to produce gas phase oxygen, which is released in the vicinity of the fuel. The oxygen released locally can be used to combust solid fuels more efficiently than if the fuel is only reacted with steam or CO2. The metal oxide could also be kept separate from the fuel and used in a cyclic process to produce a stream of oxygen, something which is now sometimes referred to as chemical looping air separation. This latter process is not new and in fact was one of the first commercial processes used to produce oxygen (i.e. the Brin process) before modern air separation techniques were developed. In all case, the incentive to use a looping process comes from the fact that they operate at temperatures above which the waste heat can be recovered back into a power cycle. In these processes, the properties of the solid oxygen carrier to a large extent determine the performance limits of the process.
While absorption-desorption of gaseous CO2 in alkyl amines such as monoethanolamine (MEA) is a developed technology for concentration and purification of CO2, corrosion remains a significant obstacle to the advancement of amine-based post-combustion carbon capture. While stainless steel remains reasonably impervious to amine solvents in the short term, the use of cheaper steels (e.g. mild) for large scale plants is preferred. However, the understanding of corrosion occurring on the mild steel construction remains problematic. To address this, a study of the corrosion on mild steel has been undertaken under reasonably thermally degrading conditions for MEA and three popular 2nd generation amine solvents. These four amines show two categorical behaviors: corrosion and passivation; additionally the common additive K2CO3 also shows passivation. Interestingly, mixtures of amines can be developed which contain corrosive components while still showing a passivating effect on the metal surface.
Several major factors influence the selection of pipeline materials for CO2 transportation, including the susceptibility to corrosion and the ability to resist ductile and brittle fracture propagation. As part of the ongoing EC FP7 project CO2Quest, measurement of the relevant properties for the materials likely to be used in the construction of pipelines for CCS is being performed, and their sensitivity to the composition of the transported CO2 mixture examined. As part of this effort fracture mechanics tests have recently been completed under both normal conditions and at low temperatures, indicative of those potentially reached in the case of a failure of a CO2 pipeline. In this work, the results of the crack resistance of industrial steels, in particular X65, X70 and X80 grades, will be presented and experiments described which have been designed to investigate the materials behaviour during realistic release scenarios. Of those tested it is found that the X70HIC grade steel has the lowest ductile-to-brittle-transition-temperature, hence providing the most protection from brittle fracture.
Amine scrubbing is the most dominated commercial technology adapted for CO2 capture from fossil fuel power plant. However, significant energy consumption and irreversible solvent degradation are the major unsolved challenges for the conventional amines. It is therefore essential to screen new solvents to overcome these drawbacks. Amines with various molecular structures, such as primary, secondary and tertiary amines containing linear, branched and cyclic chains, have thus been studied according to the selection criteria: (a) reactivity, (b) CO2 capacity, (c) regenerability, (d) thermophysical stability, (e) degradability, (f) toxicity, etc. The influence of amine molecule structures [e.g. alkanolamine vs. alkylamine; primary or secondary vs. tertiary amines; and linear vs. branched or cyclic substituents] on the physical and chemical properties is evident. We observed many interesting phenomena, for example, (i) some of the alkylamines with their switchable polarity can led to a liquid-liquid phase separation behaviour upon heating, (ii) secondary amine has a high potential to achieve rapid absorption rate, (iii) tertiary amine and cyclic structure typically exhibit a good chemical stability against thermal and oxidative degradations, (iv) a branch at α-carbon position is favoured to enhance both the absorption rate and CO2 capacity. These observations can help us select suitable amines or optimise solvent recipes for CO2 absorption.
Novel Capture Technologies
Chaired by Mohamed Pourkashanian (University of Sheffield)
Ca looping is one of the newest carbon capture technologies. However, in the space of two decades it has made impressive strides. Firstly, it has been demonstrated at the 2 MWth level, and has performed flawlessly. Secondly, a feed study is now underway for a 10 MWth demonstration. The use of the technology for applications related to both the cement and steel industry are also now under active exploration. It is however at the pilot and lab-scale that some of the most interesting developments have been made. These developments are in particular focused on enhanced reforming, and sorbent improvement. This presentation will look at the state of the art of Ca looping technology, and highlight a number of the most important developments and provide a road map for anticipated future developments.
Membrane technology offers the potential for energy-efficient and cost-effective gas separations. However, it is challenging to develop membrane materials that exhibit sufficient selectivity and flux for a given separation, and which maintain performance over time under the conditions of use. For post-combustion carbon capture, the challenge is to separate very large volumes of CO2 (a typical coal-fired power station may produce 10,000 tons of CO2 per day) at relatively low concentration (10-15% in N2) at low pressure. The current state-of-the-art will be outlined, and efforts to develop improved membrane materials will be discussed, with particular reference to our experience with “Polymers of Intrinsic Microporosity” (PIMs). PIMs are glassy polymers which possess high free volume and high internal surface area as a consequence of their relatively inflexible, contorted macromolecular backbones. Recent research has sought to tailor the permeability and selectivity of PIM-based membranes, and to improve the ageing behaviour. This includes: (1) bespoke monomer synthesis; (2) chemical post-modification of precursor polymers; (3) thermal or ultraviolet treatment; (4) the preparation of polymer blends; (5) the formation of mixed matrix membranes with a variety of fillers, including: (a) inorganic porous solids, (b) carbons (activated carbons, nanotubes, graphene), (c) metal-organic frameworks, (d) porous organic materials.