Current Research Projects
CARBON DIOXIDE CAPTURE
Numerical Simulation and Optimization of Carbon Capture in
Chemical Looping Solid or Gaseous Fuel Reactors
Ramesh K. Agarwal (PI), Dept. of Mechanical Engineering and Materials Science
It is increasingly recognized that high temperature Chemical Looping Combustion (CLC) is an energy efficient combustion technology for both gaseous and solid fuels that can potentially be utilized for power generation. This process also inherently produces a concentrated CO2 stream, thereby substantially reducing the costs of CO2 capture for geologic sequestration. The CLC system generally consists of two fluidized bed reactors, an air reactor and a fuel reactor. The fuel is oxidized in the fuel reactor by contacting hot granular metal oxides. There have been many experimental studies on CLC, however numerical simulations of CLC have been very few and none takes into consideration the optimization. For scale up and further development of CLC, multi-phase CFD simulations have a strong potential to suggest pathways for economical capture of CO2. An Eulerian multi-phase continuum model will be used to describe both the gas and solid phases (this model is available in commercial CFD software Fluent). Initially the CFD solutions will be validated against the available experimental data. Then a multi-objective genetic algorithm based optimizer will be integrated with the CFD solver. It will be used to optimize the concentration of released CO2 by changing the parameters such as superficial velocity, metal oxide concentration, reactor temperature etc. Such a capability currently does not exist anywhere and will have significant impact in determining the most economical and efficient approach for CO2 capture.
Advanced Oxyfuel Combustion Concepts for CO2 Capture
Richard Axelbaum (PI), Dept. of Energy, Environmental and Chemical Engineering
Pratim Biswas, Dept. of Energy, Environmental and Chemical Engineering
Shuiqing Li, Dept. Thermal Engineering, Tsinghua University
Presently, the costs associated with the capture of carbon dioxide from coal-fired power plants using first-generation oxyfuel combustion technology are prohibitively high. The U.S. Department of Energy has set a goal of developing technologies that can lead to 90% capture of carbon dioxide, with an increased cost of electricity of no more than 35%, as compared to a similar plant without carbon capture. In this project, we aim to demonstrate the technical feasibility of a unique fuel-staged oxy-combustion approach that is capable of meeting the DOE’s goals. By staging the fuel injection and transferring some of the heat between stages, the temperature and heat transfer can be controlled. This allows for the elimination of other temperature control processes, such as flue gas recycle or water/steam injection. The potential benefits which result in increased plant efficiency are: reduced process gas volume, increased radiative heat transfer, reduced oxygen demands, increased CO2 purity entering the carbon compression and purification unit (CPU), and reduced auxiliary power demands. Computational fluid dynamics (CFD) modeling will be utilized to evaluate and optimize the staged combustion process, and for design of experiments. Experiments will be conducted at the lab scale, and at the pilot scale in the ACERF test facility. These experiments will focus of the first and second stages of the process, which involves the combustion of fuel in high concentrations of oxygen, with high stoichiometric ratio.
Carbon Dioxide Capture Using Nanostructured Materials Enhanced Adsorbents
Pratim Biswas (PI), Dept. of Energy, Environmental and Chemical Engineering
A. K. Suresh Department of Chemical Engineering, Indian Institute of Technology Bombay
This project aims to reduce the costs associated with post-combustion capture of carbon dioxide. Studies are conducted to enhance the mass transfer rates and overall rates of carbon dioxide absorption, thereby reducing the materials and operation cost. This is achieved with the addition of nanostructured materials and enzyme-enhanced sorbents to enhance adsorption of CO2. As an alternative to amines, other lower-cost solvents such as carbonates are examined. This will significantly reduce the cost of the CO2 capture in conventional coal combustion systems. Enhanced surface areas are developed by using novel spray systems for the amines and various carbonate/bicarbonate sorbents.
GEOLOGIC CARBON SEQUESTRATION
Coupled Geochemical and Transport Processes in Geologic Carbon Sequestration:
Evolution of Geochemical Gradients and Flow Properties in Diffusion-Limited Zones
Daniel Giammar (PI), Dept. of Energy, Environmental and Chemical Engineering
Sophia E. Hayes (Co-PI), Department of Chemistry
Anurag Mehra, Department of Chemical Engineering, Indian Institute of Technology Bombay
Catherine A. Peters, Department of Civil and Environmental Engineering, Princeton University
The project objective is to advance our understanding of the coupling of chemical reactions and transport processes in diffusion-limited carbon sequestration systems. The multidisciplinary project builds on knowledge that we have gained in our previous project for well-mixed systems and on research relationships developed during that project. While well-mixed systems have been valuable for identifying reaction mechanisms and quantifying reaction rates, actual carbon sequestration systems are poorly mixed, and transport processes can be closely coupled with chemical reactions. Limitations of transport can lead to the development of geochemical gradients and conditions very different from those in well-mixed solutions. The objective will be pursued in an approach focused on two important systems for geologic carbon sequestration: (1) magnesium-rich rocks with high potential for mineral trapping and (2) carbonate-rich cap rocks that overlay storage zones. For both systems we will work with model minerals and intact rock materials. The approach will integrate bench-scale experiments, advanced characterization techniques, and reactive transport modeling. The characterization work will (a) apply an in situ nuclear magnetic resonance high-pressure, high-temperature probe developed with CCCU support to follow reaction progress in real-time, and (b) use a computed tomography scanner optimized for carbon sequestration research at the National Energy Technology Laboratory.
Understanding and Controlling Chemical Reactions and Dynamics
for Safer Carbon Dioxide Sequestration by Mesoscale Engineering Approaches
Young-Shin Jun (PI), Dept. Energy, Environmental and Chemical Engineering
Dongxiao Zhang, Peking University
Yun Moon Lim, Yonsei University
Ruben Juanes, Dept. Civil and Environmental Engineering, Massachusetts Institute of Technology
Due to recent global climate-change concerns, geologic carbon dioxide sequestration (GCS) has received considerable attention. Two promising GCS injection sites are deep saline reservoirs, and oil reservoirs where CO2 storage and CO2-enhanced oil recovery (CO2-EOR) can occur. While the pure fluid dynamics of the injected CO2 in GCS operations are well understood, we still do not have a full systematic understanding of the potential impact of chemical reactions on the fluid dynamics of both GCS injection site options. In addition, we need effective engineering solutions for potential fractures of seals in GCS. Therefore, this study investigates chemical reactions among, supercritical CO2, brine, organics (from simple carboxylic compounds to complex hydrocarbons), and formation rock under conditions related to these two GCS sites. The broader objectives are (1) to develop engineered solutions for inhibiting fracture propagation and strengthening caprock structures and to predict CO2 transport, and (2) to identify how chemical reactions affect fluid dynamics in CO2-EOR. Our highly interdisciplinary approach will investigate the chemical reactions and dynamics of multiple fluid phases in heterogeneous porous environments. The project will be conducted from the nanoscale to continuum scale. The experimental results will be utilized as input parameters into numerical simulations to predict fluid transport in EOR sites. Our expected results will provide information for designing more efficient and safer geologic CO2 sequestration operations by developing effective engineering solutions to arrest fracture propagation in GCS sites.
Evaluation of Mercury and Other Heavy Metals (Fine Particles)
Capture Methodologies in Coal Combustion Systems
PI: Pratim Biswas (PI), Dept. of Energy, Environmental and Chemical Engineering
Jiming Hao, Dept. of Environmental Engineering; Tsinghua University
This project will evaluate options for control of mercury and heavy metals from coal combustion systems using different sorbents. The performance of various sorbent methodologies under different combustion conditions will be evaluated. A key objective will be to minimize the carbon in the fly ash mix to ensure its salability. This will be tested by strategies that reduce the amount of carbon used, or by use of non-carbonaceous sorbents. The objectives will be met through four integrated tasks: Task 1. Develop a fine carbonaceous particle sorbent method and test its effectiveness for Hg capture (to lower C-fly ash ratios); Task 2. Evaluate the efficiency of various non –carbon based sorbents for multi-pollutant removal (Hg and heavy metal fine particles). The sorbents tested will include TiO2-based, halogen-containing materials (such as KI and KBr) and selective catalytic reduction (SCR) catalysts (such as vanadium, molybdenum, tungsten oxides and zeolites); Task 3. Perform a techno-economic evaluation by developing a model to determine the most effective sorbent (the model will account for the salability of the fly ash); and Task 4 – conduct pilot scale studies with a couple of optimal sorbents identified in the studies.