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Effects of calcium in ash on the corrosion performance of Ni-based alloys in simulated oxy-fuel environment
Increasing the efficiency of coal power plants requires raising the operating temperature above 650°C. However, coal ash can severely attack alloy materials at high temperature. For example, the corrosion rates of commercial Fe- and Ni-based alloys are generally greater than 2 mm/year at 750°C in the gas environment of oxy-fuel combustion. Thus, a critical study is needed to determine the effect of the constituents in the ash on corrosion and find an approach to reduce the corrosion rates in an ash-laden environment at high temperature. The role of CaO in the ash (typical of U.S. Western coal ash) has been investigated in laboratory exposure environments with various structural alloys. Detailed results are presented on weight change, scale thickness, internal penetration, microstructural characteristics of corrosion products, and the cracking of scales for the alloys after exposure at 750°C. The thermal stability of K3Al(SO4)3 under the environment of oxy-fuel combustion was determined by thermogravimetric analysis and differential thermal analysis. The reaction of this low melting temperature salt with the CaO-containing ash is discussed. In addition, we performed synchrotron nanobeam X-ray analysis to study the phase and chemical composition of the oxide layers on the alloy surface. Results from these studies are used to address the role of CaO in ash in the long-term corrosion performance of alloys.
Modeling and simulation of cross-flow transport membrane condenser heat exchangers
Not Available
Development of an analytical simulation tool for storage capacity estimation of saline aquifers
Not Available
Modeling and simulation of CO 2 capture using semipermeable elastic microcapsules
Very high rates of CO2 absorption have been demonstrated using semipermeable microcapsules filled with environmentally benign sodium carbonate solutions (Vericella et al., Nature communications 6, 2015). However, such capsules have also exhibited several traits, including water loss/uptake, elastic swelling and buckling, and precipitation of solids, which make them more complicated to engineer as a carbon capture material. To address this, a mechanistic model for mass transfer and chemical reaction has been developed, which accounts for these behaviors, and can be used as a predictive tool to explore capsule performance under different CO2 capture scenarios. The model uses a modified film theory to describe CO2 and H2O mass transfer rates, a concentration based description of vapor-liquid-solid equilibrium inside the capsule, and an elastic description of the capsule shell. Model predictions compare favorably to literature data for precipitating carbonates, as well as recent data for microcapsule CO2 absorption. The model was used to assess practical issues of capsule water transfer during a temperature swing CO2 absorption/desorption cycle. Model predictions indicate that capsules filled with high weight percent, precipitating sodium carbonate solution could be significantly or completely dehydrated during CO2 absorption. Subsequent rehydration of lean capsules at elevated temperature showed strong sensitivity to both gas humidity, and capsule shell elasticity.
Numerical simulation of falling film flow hydrodynamics over round horizontal tubes
Not provided.
Discrete element simulations of powder-bed sintering-based additive manufacturing
Not Available