Utilizing electrochemical impedance spectroscopy and neutron imaging to better understand transport characteristics of fuel cells

Issued as final reportAmerican Chemical Societ

Efficient Conversion of Aqueous-Waste-Carbon Compounds Into Electrons, Hydrogen, and Chemicals via Separations and Microbial Electrocatalysis

Valorization of waste streams is becoming increasingly important to improve resource recovery and economics of bioprocesses for the production of fuels. The pyrolysis process produces a significant portion of the biomass as an aqueous waste stream, called bio-oil aqueous phase (BOAP), which cannot be effectively converted into fuel. In this report, we detail the separation and utilization of this stream for the production of electrons, hydrogen, and chemicals, which can supplement fuel production improving economics of the biorefinery. Separation methods including physical separation via centrifugal separator, chemical separation via pH manipulation, and electrochemical separation via capacitive deionization are discussed. Bioelectrochemical systems (BES) including microbial fuel cells (MFCs), microbial electrolysis cells (MECs), and electro-fermentation processes are reviewed for their potential to generate current, hydrogen, and chemicals from BOAP. Recent developments in MECs using complex waste streams and electro-active biocatalyst enrichment have resulted in advancement of the technology toward performance metrics closer to commercial requirements. Current densities above 10 A/m2 have been reported using BOAP, which suggest further work to demonstrate the technology at pilot scale should be undertaken. The research on electro-fermentation is revealing potential to generate alcohols, diols, medium chain fatty acids, esters, etc. using electrode-based electrons. The ability to derive electrons and chemical building blocks from waste streams illustrate the advancement of the BES technology and potential to push the frontiers of bioenergy generation one step further toward development of a circular bioeconomy

Activated Carbon Composites for Air Separation

In continuation of the development of composite materials for air separation based on molecular sieving properties and magnetic fields effects, several molecular sieve materials were tested in a flow system, and the effects of temperature, flow conditions, and magnetic fields were investigated. New carbon materials adsorbents, with and without pre-loaded super-paramagnetic nanoparticles of Fe3O4 were synthesized; all materials were packed in chromatographic type columns which were placed between the poles of a high intensity, water-cooled, magnet (1.5 Tesla). In order to verify the existence of magnetodesorption effect, separation tests were conducted by injecting controlled volumes of air in a flow of inert gas, while the magnetic field was switched on and off. Gas composition downstream the column was analyzed by gas chromatography and by mass spectrometry. Under the conditions employed, the tests confirmed that N2 - O2 separation occurred at various degrees, depending on material's intrinsic properties, temperature and flow rate. The effect of magnetic fields, reported previously for static conditions, was not confirmed in the flow system. The best separation was obtained for zeolite 13X at sub-ambient temperatures. Future directions for the project include evaluation of a combined system, comprising carbon and zeolite molecular sieves, and testing the effect of stronger magnetic fields produced by cryogenic magnets

Status and Directions in Electroseparations

In this presentation, a summary of research conducted in the area of electroseparations at the Chemical Technology Division of Oak Ridge National Laboratory is presented. Fields-driven processes, including (1) phase equilibria modification by electric fields and (2) magnetically seeded separations, as well as transport-enhancement processes by electric fields,including (1) surface area generation and (2) electroconvection, are discussed.It is shown that electric fields can change the concentration of the vapor phase during the distillation of a binary mixture, which may have applications in separations by distillation that consume significant amounts of energy. It is also shown that addition of colloidal seed particles of high magnetic susceptibility to a suspension of non-magnetic particles and subsequent flocculation between seed and non-magnetic particles form paramagnetic flocs that can be removed by high- gradient magnetic filtration. Inverse electrostatic spraying, which is the spraying of a non-conductive fluid (such as air) into a conductive fluid (such as water), is introduced and compared with normal electrostatic spraying, which is the spraying of conductive fluid into a non-conductive fluid. Applications of normal electrostatic spraying, including the development of a bioreactor for oil desulfurization, and inverse electrostatic spraying, including ozonation of an aqueous system, are discussed. It is also shown that electroconvection, caused by electric fields,may result in simultaneous pumping, spraying, and mixing of fluids. In summary,new phenomena caused by electric fields are introduced and their potential applications in electroseparations are discussed

Phase Equilibria Modification by Electric Fields

This project has been focused on equilibrium and transport properties of gas-liquid, liquid-liquid, and solid-liquid systems under electric fields. The objective was to intensify separations methods that are used or can be used to process liquid waste or contaminated groundwater within DOE sites. Examples of processes that have been investigated are distillation (gas-liquid), extraction (liquid-liquid), and sorption (solid-liquid). Effects of electric fields on phase equilibria and interfacial transport have been investigated. So far, this project was directed at basic research on a broadly crosscutting concept. The results advocate continuation of this research in two directions, with the objective to solve problems related to solvent extraction of tank waste and groundwater treatment

Methane recovery from hydrate-bearing sediments

Issued as final reportUnited States. Dept. of Energ

Carbon Dioxide Absorption Modeling for Off-Gas Treatment in the Nuclear Fuel Cycle

The absorption of carbon dioxide is an important process in many practical applications such as reduction of greenhouse gases, separation and purification processes in the chemical and petroleum industries, and capture of radioactive isotopes in the nuclear fuel cycle The goal of this research is to develop a dynamic model to simulate CO2 absorption by using different alkanolamines as absorption solvents. The model is based upon transient mass and energy balances for the chemical species commonly present in CO2 gas-liquid absorption. A computer code has been written to implement the proposed model. Simulation results are discussed. The reported model simulates well the response to dynamic changes in input conditions. The proposed model can be used to optimize and control the separation of carbon-14 in the form of CO2 in the nuclear industry

Phase Equilibria Modification by Electric Fields

The objective of this project is to use electric fields to favorably manipulate the thermodynamic and transport properties of mixtures so that higher separation efficiencies can be achieved. The main focus is to understand and quantify the influence of electric fields on vapor-liquid, liquid-liquid, and solid-liquid systems. This program will lead to greater separation efficiency in a wide range of environmental treatment processes, including solvent extraction, sorption, distillation, and stripping. Such processes are widely used by DOE for treatment of wastes and sites contaminated with heavy metals, radionuclides, and organic solvents. Particular examples of applications of vapor-liquid-equilibria modification can be found in the separation of volatile organic compounds by either stripping or distillation. Improvements can also be made in liquid-liquid-extraction processes of TRU, Sr, Tc, and Cs by both thermodynamic and transport enhancements. Separations of metal ions by electrosorption can be used to remove such metal ions as Cs, Sr, Co, Pu, Cr, Cd, and Hg