Browsing by Author "Parchei Esfahani, Mehrshad"

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    Kinetic and Mass Transfer of Peroxone Oxidation of Toluene Using Ultra Sonic Spray: Ab Initio Quantum Calculations and Numerical Modeling
    (2020-01-16) Parchei Esfahani, Mehrshad; Gates, Ian Donald; De Visscher, Alex; Kibria, Md Golam; Lu, Qingye Gemma; Soltan, Jafar; Achari, Gopal
    The application of ozone along with hydrogen peroxide, commonly referred to as peroxone oxidation, is a widely investigated advanced oxidation technique to treat waste gas or wastewater. Degradation of ozone in water is a key step in the pollutant degradation mechanism, particularly in peroxone oxidation. However, the degradation of ozone in water is not well understood. In the research documented here, peroxone treatment is studied in detail via reaction and transport phenomena modeling, as well as computational chemistry simulation. Ab initio studies, using the coupled cluster calculations method, were conducted to investigate the kinetics of ozone degradation in gas and aqueous phases considering the ozone-hydroperoxyl radical reaction and the dissociation equilibrium of the hydroperoxyl radical. The predictions of the ozone degradation rate at low pH (<6) is improved by up to two orders of magnitude over existing models. For peroxone oxidation of toluene, the results from the research reveal that dissolution of ozone in water is the rate determining step in the pollutant degradation mechanism. However, the major issue that limits widespread application of peroxone oxidation for waste gas treatment arises from high energy demands, stiff costs, and deteriorating efficiencies over time due to mass transfer limitations. This research also uncovers that creating small droplets and thus, increasing surface area, significantly raises mass transfer rates from gas to aqueous phases, thus making peroxone oxidation of toluene more efficient. Small droplets increase the effectiveness of the peroxone technique when the diffusion rate of ozone is enhanced in ultrasonic-based aerosol mist systems compared to traditional liquid-gas multiphase reactors e.g. bubble column devices.
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    Life Cycle Assessment of Using Biomass-Based Activated Carbon for Water Treatment in Oil Sands Operations in Alberta
    (2015-01-28) Parchei Esfahani, Mehrshad; Hill, Josephine M.
    The recovery of bitumen through steam-assisted gravity drainage in Alberta produces about 2.7 m3 of water per one m3 of bitumen, resulting in about 118 million m3 of water per year having high levels of organic compounds. When this water is recycled to the boilers, the organic compounds contribute to fouling and corrosion, thus, the energy companies are interested in finding a cost-effective strategy to remove the organics before recycling the water. In mining operations, approximately 3 m3 of water are produced per one m3 of bitumen, resulting in 148 million m3 of water per year flowing into tailings ponds. While the majority of this water is reused, the organics in water can be metabolized and produce methane, a potent greenhouse gas. Laboratory studies have shown that activated carbon from forestry residues (aspen wood) could remove the organics, create a carbon sink, reduce emissions from tailings and provide a new market for the residual biomass from the local forestry industry. This study compares the cost, energy requirement, and greenhouse gas (GHG) emissions associated with four scenarios: two scenarios for activated carbon production, pyrolysis and activation of biomass in mobile units in the field or transporting the residual biomass to a central location where it is both pyrolyzed and activated, and two scenarios for using the produced activated carbon for removal of organics from the produced water in either SAGD operations or tailings ponds in mining operations. Field pyrolysis of biomass for both SAGD and mining operations was calculated to have lower emissions (approximately 75% lower GHG emissions), but higher economic costs (approximately 20% higher cost) compared to the centralized processing. The net emissions of the systems were calculated to be between 0 to 16 kgCO2e/m3. Furthermore, at 75% removal level, the maximum feasible amount for the systems used in this study, the net emissions range between -55 to -76 kgCO2e/m3. Hence, the ultimate GHG emissions range achievable by these systems is 16 to -76 kgCO2e/m3. The sensitivity analysis showed pyrolysis and activation yields as well as removal level are the main parameters that should be the focus of future research in order to reduce energy requirements, emissions, and cost of the entire process.