CO2 Capture from Flue Gas, Natural Gas, and general Process Gas Streams: Experimental and Simulation Programs
Researcher: Dr Penny Xiao, Research Fellow
Penny leads the research effort on adsorption processes for gas separations and CO2 capture. She leads a number of ongoing projects such as CO2 capture from flue gas streams and IGCC processes, natural gas and biogas purification, and assessment of adsorbents. She is also currently involved in other projects such as CO2 utilisation.
Most projects commence with choosing or synthesizing suitable adsorbents by analysing and screening the adsorption capacity and selectivity of CO2, CH4, N2, water vapour and other components, and then predicting the separation performance with the selected adsorbents by simulation with our adsorption simulator, MINSA; experiments are then carried out to achieve the project’s target. We have two VPSA (vacuum pressure swing adsorption) rigs in our laboratory — GSR2 (two adsorption beds which can be used for both high temperature and high pressure separations) and Four-bed VSA rig (four adsorption beds which can be used to test multi-bed PVSA cyclic designs).
Materials development and testing for Gas Separation Applications
Researcher: Dr Ranjeet Singh, Research Fellow
Microporous and mesoporous materials such as zeolites, inorganic — polymers are promising adsorbents for gas separation (eg. flue gas / natural gas / biogas). In this work, we are synthesizing zeolites and fine-tuning their pore sizes using a number of techniques. These materials are subsequently characterized by X-ray diffraction, Scanning Electron Microscopy, etc. The materials are further tested for their adsorption capacities and selectivities for various gases.
Currently the aim is to find an adsorbent which has high capacity and can be used at high pressure for natural gas separation.
CO2 Recovery from High Pressure Natural Gas Streams
Researcher: Lefu Tao, PhD Candidate
My project investigates CO2 removal from high pressure natural gas sources via pressure swing adsorption (PSA). PSA is a promising technology in this situation as the energy requirement for the process is lower than alternatives such as amine absorption, cryogenic distillation and multistage membrane separations. This may enable the exploitation of sour gas reserves that are currently left unused due to the high costs involved in treating the gas enabling pipeline transport.
The project aims to identify possible adsorbents that will be suitable to the application, as well as address issues such as competitive water adsorption and slow adsorption kinetics. The primary methods employed in this work are materials synthesis, post synthesis modifications, volumetric and gravimetric isotherm measurement, PSA simulation and other analytical methods such as XRD, TGA, FT-IR and TPD.
Adaptive management system for sustainable bioenergy with carbon capture and storage (beccs)
Researcher: Nasim Pour, PhD Candidate
This project concerns the sustainability of bioenergy with carbon capture and storage (BECSS). In BECCS the CO2 derived from conversion of the biomass to energy is not released to the atmosphere but is sequestered, transported and permanently stored in a suitable geological formation. The biomass for energy generation is seen as carbon neutral in that the carbon released to the atmosphere during conversion of plant matter was first taken from the atmosphere during photosynthesis. Thus, a negative flow of CO2 from the atmosphere to the subsurface is established. The potential of BECCS to remove atmospheric CO2 in addition to generating energy makes it one of the more attractive approaches to achieve the ambitious atmospheric temperature targets such as +2°C.
BECCS consists of various variables such as type of biomass resource, conversion technology, CO2 capture process and storage. Each of these pathways has its own environmental, economic and social impacts. The scope of this study is to integrate these impacts into a three pillar sustainability framework. This framework is provided to assist decision-makers to evaluate sustainability of different BECCS options in a transparent and timely manner.
BECCS is an inherently evolving system and fundamentally influenced by ecological, economic and social changes. Accordingly, the sustainability of such system is of an evolving nature as well. For this reason, such system is better to be managed as an adaptive system so that could thrive in an ever-changing environment. An adaptive management system allows its components to interact, react and coevolve. An essential part of an adaptive system is a decision-making tool. Given multi-faceted nature of BECCS, multi-criteria decision making (MCDM) methods are particularly suitable.
The formulation of the MCDM is as follows; first, a set of alternatives for BECCS deployment are defined. To evaluate the sustainability of these alternatives, the most important criteria regarding their technical, environmental, economic and social performances are evaluated. Based on the circumstances and importance of each of these criteria, they are weighted. Then acceptable alternatives are introduced and ranked. A sensitivity analysis to examine the robustness of the alternatives under different circumstances and preferences is executed.
The Analytic Hierarchy Process (AHP) is chosen as the MCDM tool. APH is one of the most widely applied decision making tools, which uses pairwise comparisons of criteria to score and rank the alternatives. In evaluation of all these criteria the whole BECCS supply chain from biomass production to CO2 storage is considered.
The adaptive management system proposed in this study will then be applied to investigate the sustainability of different BECCS options in the Australian energy sector.
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Electrical Swing Adsorption (ESA) for CO2 capture from Flue Gas Streams
Researcher: Qinghu Zhao, PhD Candidate
This project aims to develop process cycles and test materials for electrical swing adsorption (ESA) for CO2 capture from flue and process gas streams. The project is a collaboration with European partners through the MATESA program. In comparison to conventional Temperature Swing Adsorption (TSA), Electric Swing Adsorption (ESA), as an emerging CCS technology, has certain advantages including shorter regeneration time, higher adsorbent regeneration efficiency.
The different nature of ESA requires new cycles and understanding of how efficiency varies with voltage, current, column length, electrification time etc. In this project, ESA experiments will be conducted with different adsorbents to compare their performance. Also, ESA experiments will be conducted different conditions to develop a model for how efficiency varies with different operating conditions. This information will allow the most economic ESA cycles to be developed according to different conditions for different applications.
Encapsulated solvents for CO2 Capture
Researcher: Thomas More, PhD Candidate
While both solvents and adsorbents can be used to separate CO2 from power plant flue gases, each class of materials has its own unique disadvantages. Solvents often have high heats of regeneration (and those that don’t tend to have slow kinetics) and they may be corrosive, toxic or volatile. Adsorbents often have poor stability and capacity in the presence of water, and can be expensive to manufacture.
This project aims to investigate a new hybrid material, microencapsulated solvents (MECS), in which solvents are encapsulated in small (100-500 micron) polymer shells which are highly permeable to CO2. Encapsulating the solvent may allow us to use corrosive, viscous or volatile solvents which we otherwise couldn’t use. Further, the very high surface area of these particles enhances the kinetics of absorption, allowing us to use solvents with low regeneration energies, whose kinetics would otherwise be prohibitively slow.
We will be investigating the industrial application of MECS for post-combustion capture of CO2. By a combination of large-scale process modelling, small-scale transport phenomena analysis and experimental measurements we hope to assess their industrial viability, analyse different process designs, and compare them with existing capture technologies. We also hope to look at improved manufacturing techniques: at present MECS are made using microfluidic devices, but larger-scale techniques like membrane emulsification could reduce manufacturing costs significantly.
Polymer metal-organic framework composite structures for CO2 capture applications
Researcher: Ke Xie, PhD Candidate
Metal-organic frameworks (MOF) are good candidates for gas separation due to their molecular sieving properties. MOFs are cast into membranes (MOF membranes) or blended with polymer matrix to produce mixed-matrix membranes (MMM). Neither of these techniques is optimal as the resultant membranes can have poor mechanical strength, defect-prone features and processing difficulties.
In this study, amino-functionalised MOFs and bromide functionalised MOF nanocrystals (30~50 nm) were successfully prepared and characterised by XPS, XRD, TGA, SEM and TEM. Bromide MOFs were used to initiate the polymerisation of polyethylene glycol acrylate (PEGA) via atom transfer radical polymerisation (ATRP), resulting in a polymer grafted MOF composite (P@MOF). P@MOF was firstly applied as the catalyst carrier by loading Pd nanoparticles. (K. Xie et al. Chem. Comm., 2015, 51, 15566.) Owning to its complete water dispersity and pH-sensitive aggregation-deaggregation nature, Pd loaded P@MOF integrated the advantages of both high activity easy recyclability. Furthermore, the unique core-shell structure of P@MOF suggests its potential for gas separation MMM.