Digitized by Kansas Correctional Industries

In the wake of concerns about the long-term integrity and containment of sub-surface CO₂ sequestration reservoirs, many efforts have been made to improve the monitoring, verification, and accounting methods for geo-sequestered CO₂. This Ph.D. project has been part of a larger U.S. Department of Energy (DOE) sponsored research project to demonstrate the feasibility of a system designed to tag CO₂ with radiocarbon at a concentration of one part per trillion, which is the ambient concentration of ¹⁴C in the modern atmosphere. Because carbon found at depth is naturally free of ¹⁴C, this tag would easily differentiate pre-existing carbon in the underground from anthropogenic, injected carbon and provide an excellent handle for monitoring its whereabouts in the subsurface. It also creates an excellent handle for adding up anthropogenic carbon inventories. Future inventories in effect count ¹⁴C atoms. Accordingly, we developed a ¹⁴C tagging system suitable for use at the part-per-trillion level. This tagging system uses small containers of tracer fluid of ¹⁴C enriched CO₂. The content of these containers is transferred into a CO₂ stream readied for underground injection in a controlled manner so as to tag it at the part-per-trillion level. These containers because of their shape are referred to in this document as tracer loops. The demonstration of the tracer injection involved three steps. First, a tracer loop filling station was designed and constructed featuring a novel membrane based gas exchanger, which degassed the fluid in the first step and then equilibrated the fluid with CO₂ at fixed pressure and fixed temperature. It was demonstrated that this approach could achieve uniform solutions and prevent the formation of bubbles and degassing downstream. The difference between measured and expected results of the CO₂ content in the tracer loop was below 1%. Second, a high-pressure flow loop was built for injecting, mixing, and sampling of the fast flowing stream of pressurized CO₂ tagged with our tracer. The laboratory scale evaluation demonstrated the accuracy and effectiveness of our tracer loops and injection system. The ¹⁴C/¹²C ratio we achieved in the high pressure flow loop was at the part per trillion level, and deviation between the experimental result and theoretical expectation was 6.1%. Third, a field test in Iceland successfully demonstrated a similar performance whereby ¹⁴CO₂ tracer could be injected in a controlled manner into a CO₂ stream at the part per trillion level over extended periods of time. The deviation between the experimental result and theoretical expectation was 7.1%. In addition the project considered a laser-based ¹⁴C detection system. However, the laser-based ¹⁴C detection system was shown to possess inadequate sensitivity for detecting ambient levels of ¹⁴CO₂. Alternative methods for detecting ¹⁴C, such as saturated cavity absorption ring down spectroscopy and scintillation counting may still be suitable. In summary, the project has defined the foundation of carbon-14 tagging for the monitoring, verification, and accounting of geological carbon sequestration.

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活性碳是一種擁有優異吸附能力的材料。與其他活性碳相比，活性碳纖維有以下優點。使首先, 它擁有大量微孔，比表面積大；其次，纖維結構有利於快速吸附；最後，它能編織成氈或者布，不但無阻氣流，而且便於使用後回收。但是，由於缺乏廉價的原材料，它的生產成本遠比其他活性碳高，不利於廣泛使用。所以，我們希望透通過使用廉價的棉花作為原材料，生產出優質的活性碳纖維。 / 在這項研究中，我們成功地用普通的棉花，通過氯化鋅活化，生產出活性碳纖維；我們研究了活化時的燒結溫度，浸潤時的氯化鋅濃度和活化後的後處理對活性碳纖維的影響，而且通過不同表徵方法來分析樣品。結果表明，它們不但保留棉花的纖維結構，而且擁有少量碳氧表面官能基。它的孔結構以微孔為主，BET比表面積和孔體積分別高達~2050m²/g和1 cm³/g，比市場上的活性碳或其他研究的活性碳高。 / 我們測試了棉花活性碳纖維在吸附亞甲基藍的吸附速度和吸附等溫線，發現它有很高的吸附速度，只需大約一個小時，吸附已差不多到達平衡。因為它很高的BET比表面积，它吸附亞甲基藍的最高容量達到597 mg/g，比市場上的活性碳高。我們也研究了溶液的pH值對其吸附能力的影響，發現鹼性環境有利亞甲基藍的吸附，相反，酸性環境不利亞甲基藍的吸附。 / 我們也測試了棉花活性碳纖維對水蒸氣，乙醇蒸氣、甲醇蒸氣和丙酮蒸氣的吸附速度，吸附容量和解吸過程。它只需十分鐘便完成乙醇蒸氣、甲醇蒸氣和丙酮蒸氣的吸附。它在水蒸氣中的吸附也比市場上的矽膠快。所有吸附物只需低於200 °C即可完全解吸。蒸氣吸附的最高容量高達1 cm³/g，較其他研究為高。 / Activated carbon (AC) is an important functional material due to its outstanding adsorption ability. Activated carbon fiber (ACF) has many advantages over other types of AC: It mainly possesses micropores and has large surface area. Its fibrous structure assures fast intraparticle adsorption kinetics. Finally, it can be made into felt and fabric forms, which would not hinder gas flow and could be easily recollected after use. However, ACF is expensive due to the lack of low cost precursor so its application is restricted. This work aims to use low cost cotton fiber as an ACF precursor. / In this work, ACF was successfully synthesized by using raw cotton via ZnCl₂ activation. The effects of the sintering temperature during activation, the ZnCl₂ concentration during infiltration and the post-treatment after activation on our samples were studied. Our ACF products were characterized via various methods. It was found that our samples retained the fibrous structure of cotton. They contained trace of carbon-oxygen surface groups and were mainly composed of micropores. Their BET surface area (S[subscript Bsubscript Esubscript T]) and pore volume (V[subscript psubscript osubscript rsubscript e]) were up to~ 2050 m²/g and 1 cm³/g, respectively. / The adsorption kinetics and adsorption isotherm of our samples in the Methylene blue (MB) adsorption were studied. The adsorption was very fast and almost reached equilibrium after an hour. Because of their high S[subscript Bsubscript Esubscript T], the saturated MB capacity in our ACF was found to be 597 mg/g and higher than other commercial AC. The effect of solution pH value on MB adsorption capacity was studied. We found that the basic condition favored MB adsorption while acidic condition lowered the adsorption ability. / Adsorption kinetics, saturated adsorption volume (V[subscript asubscript dsubscript s]) and desorption process of moisture, ethanol vapor, methanol vapor and acetone vapor by our samples were also evaluated. The adsorption of methanol vapor, ethanol vapor and acetone vapor reached equilibrium within 10 minutes. Our sample also adsorbed moisture faster than commercial silica gel. Less than 200 °C was required for complete desorption of these adsorbed species. V[subscript asubscript dsubscript s] of our samples was up to 1 cm³/g and higher than other related works. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chiu, Ka Lok = 棉花活性碳纖維的製作, 定性分析及其應用 / 趙家樂. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chiu, Ka Lok = Mian hua huo xing tan xian wei de zhi zuo, ding xing fen xi ji qi ying yong / Zhao Jiale. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgment --- p.iv / Table of contents --- p.v / List of figure captions --- p.viii / List of table captions --- p.xii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- What is activated carbon --- p.1 / Chapter 1.2 --- Development of activated carbon --- p.2 / Chapter 1.3 --- Morphology of activated carbon --- p.3 / Chapter 1.4 --- Surface groups on activated carbon --- p.7 / Chapter 1.5 --- Fabrication of activated carbon --- p.8 / Chapter 1.6 --- Applications --- p.9 / Chapter 1.7 --- Activated carbon fiber --- p.10 / Chapter 1.8 --- Raw materials --- p.11 / Chapter 1.8.1 --- Precursors of powdered activated carbon and granular activated carbon --- p.11 / Chapter 1.8.2 --- Precursors of activated carbon fiber --- p.12 / Chapter 1.8.3 --- Cotton as activated carbon fiber precursor --- p.12 / Chapter 1.9 --- Previous work and objectives of current work --- p.13 / References --- p.14 / Chapter Chapter 2 --- Methodology and background theory --- p.19 / Chapter 2.1 --- Samples preparation --- p.19 / Chapter 2.2 --- Characterization methods --- p.21 / Chapter 2.2.1 --- Study of processing --- p.21 / Chapter 2.2.1.1 --- Thermogravimetric analysis --- p.21 / Chapter 2.2.1.2 --- In-situ wide angle X-ray powder diffractometry --- p.22 / Chapter 2.2.2 --- Characterization of samples --- p.23 / Chapter 2.2.2.1 --- Scanning electron microscopy --- p.23 / Chapter 2.2.2.2 --- Transmission electron microscopy --- p.24 / Chapter 2.2.2.3 --- Ex-situ wide angle X-ray powder diffractometry --- p.25 / Chapter 2.2.2.4 --- Small angle X-ray scattering --- p.25 / Chapter 2.2.2.5 --- Raman scattering spectroscopy --- p.26 / Chapter 2.2.2.6 --- Fourier transform infrared spectroscopy --- p.27 / Chapter 2.2.2.7 --- N₂ adsorption surface analysis --- p.27 / Chapter 2.2.2.8 --- Zeta potential analysis --- p.29 / Chapter 2.3 --- Evaluation of Methlyene blue adsorption --- p.29 / Chapter 2.3.1 --- Pseudo second order adsorption model --- p.30 / Chapter 2.3.2 --- Langmuir isotherm --- p.31 / Chapter 2.4 --- Evaluation of vapor adsorption --- p.31 / Chapter 2.4.1 --- Vapor adsorption kinetics --- p.31 / Chapter 2.4.2 --- Saturated adsorption capacity --- p.33 / Chapter 2.4.3 --- Desorption --- p.34 / Chapter 2.5 --- Conclusions --- p.34 / References --- p.35 / Chapter Chapter 3 --- Results of characterization --- p.37 / Chapter 3.1 --- Study of the fabrication processes --- p.37 / Chapter 3.1.1 --- Thermogravimetric analysis --- p.37 / Chapter 3.1.2 --- In-situ wide angle X-ray powder diffractometry --- p.38 / Chapter 3.2 --- Characterization of samples --- p.39 / Chapter 3.2.1 --- Appearance --- p.39 / Chapter 3.2.2 --- Yield of the sample --- p.41 / Chapter 3.2.3 --- Scanning electron microscopy --- p.42 / Chapter 3.2.4 --- Transmission electron microscopy --- p.45 / Chapter 3.2.5 --- Ex-situ wide angle X-ray powder diffractometry --- p.46 / Chapter 3.2.6 --- Raman scattering spectroscopy --- p.48 / Chapter 3.2.7 --- Fourier transform infrared spectroscopy --- p.53 / Chapter 3.2.8 --- Nitrogen gas sorption surface analysis --- p.57 / Chapter 3.2.9 --- Small angle x-ray scattering analysis --- p.61 / Chapter 3.2.10 --- Zeta potential analysis --- p.65 / Chapter 3.3 --- Discussions --- p.66 / Chapter 3.3.1 --- Effects of ZnCl₂ on carbonization --- p.66 / Chapter 3.3.2 --- Pore formation --- p.68 / Chapter 3.3.3 --- Graphitic layers --- p.69 / Chapter 3.3.4 --- Effects of post treatment --- p.70 / Chapter 3.4 --- Conclusions --- p.71 / References --- p.72 / Chapter Chapter 4 --- Methylene blue adsorption --- p.74 / Chapter 4.1 --- Results --- p.74 / Chapter 4.1.1 --- Adsorption kinetics --- p.74 / Chapter 4.1.2 --- Adsorption capacity versus pH level --- p.76 / Chapter 4.1.3 --- Adsorption isotherm --- p.77 / Chapter 4.1.4 --- Adsorption capacity in different synthetic conditions --- p.78 / Chapter 4.2 --- Discussions --- p.80 / Chapter 4.2.1 --- Relationship between adsorption capacity and zeta potential --- p.80 / Chapter 4.2.2 --- Relationship between MB adsorption capacity and SBET --- p.81 / Chapter 4.2.3 --- Comparison with other related works --- p.83 / Chapter 4.3 --- Conclusions --- p.85 / References --- p.86 / Chapter Chapter 5 --- Vapor adsorption --- p.87 / Chapter 5.1 --- Results --- p.87 / Chapter 5.1.1 --- Adsorption kinetics --- p.87 / Chapter 5.1.2 --- Saturated adsorption capacity --- p.93 / Chapter 5.1.3 --- Saturated ethanol vapour adsorption volume --- p.94 / Chapter 5.1.4 --- Desorption --- p.96 / Chapter 5.2 --- Discussions --- p.99 / Chapter 5.2.1 --- Relationship between saturated ethanol vapor adsorption volumes and V[subscript psubscript osubscript rsubscript e] --- p.100 / Chapter 5.2.2 --- Comparison with other related works --- p.101 / Chapter 5.3 --- Conclusions --- p.103 / References --- p.104 / Chapter Chapter 6 --- Conclusions and Suggestions --- p.105 / Chapter 6.1 --- Conclusions --- p.105 / Chapter 6.2 --- Suggestions for future work --- p.106 / References --- p.107

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The safe sequestration of CO2 is pivotal to a successful carbon capture and storage scheme. Saline aquifers and depleted hydrocarbon fields in the North Sea are currently used as storage repositories for captured CO2 from anthropogenic sources. This is because they are deemed safe due to the presence of a sealing cap rock and large storage volume they provide. One such field is the Sleipner field, with over 13 million tonnes of CO2 injected into the Utsira Saline +Formation from 1996 to date. Careful monitoring of the injected CO2 into the formation has revealed growing reflections on nine identified sub-horizontal horizons, referred to as intra reservoir shales. The enhanced reflectivity of the shale layers is mainly caused by the high compressibility of the CO2, trapped beneath them, and by constructive tuning effects of the top and bottom reflections at the CO2 accumulations. Within the same data are chimneys – high permeability pathways that show up in the time lapse seismic images as zones of disturbed layering that cut nearly vertically through the interbedded thin shale layers in the reservoir sands. The presence of these intra-reservoir shales and chimneys affects the distribution pattern of CO2 in the reservoir and distorts the verification of known injected mass of CO2. The aim of the research is to interpret intra-reservoir shales and chimneys on the pre-injection seismic data, these features have previously only been identified in the post-injection time lapse seismic data. The characterisation of the 3D geometry of a reservoir from seismic data is crucial to understanding the parameters that control fluid distribution. The 1994 3D pre injection dataset was interpreted with the help of volumetric seismic attributes tied to a well log. This led to the characterisation of layers from the Utsira top layer to intra-Utsira Shales (IUTS) one to ten and Utsira base layer. A multi-attribute analysis was also used to identify chimneys within the data set. The results from the interpretation workflow were then tested, against the post-injection seismic image data. The CO2 plume visualised across the 4D seismic data set were recreated into geobodies to delineate their form and extent across the reservoir. These geobodies were analysed alongside the interpreted geometry (layers) to understand the effect the layers have in controlling the spatial distribution of the injected CO2. Further analysis was conducted on the geobodies (CO2 plume) to calculate the reservoir volume of CO2 and compare against the known injected amounts of CO2. The interpreted geometry of the plume was used to simulate the impact of the reservoir geometry on injected CO2. Models were created with input parameters derived from well logs and published data. Although limited (real time measurements), results from simulations reveal close resemblance with 4D seismic data set. This study has highlighted the possibility of identifying intra-reservoir shales and chimneys to inform site characterisation that can be performed before any CO2 injection project commences. Attribute and spectral analysis can be used to add resolution to seismic data to enable detailed interpretation of the geometry of a reservoir and the volume of CO2 within a reservoir can be verified using seismic geobodies. The current monitoring techniques can employ the characterisation and verification procedure described in this study to characterise a reservoir, verify and quantify the injected amounts of CO2 to avert and mitigate for CO2 leakage.