The Experts below are selected from a list of 1926 Experts worldwide ranked by ideXlab platform
Narayan S. Tavare - One of the best experts on this subject based on the ideXlab platform.
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Mixing, reaction, and precipitation: Interaction by exchange with mean micromixing models
AIChE Journal, 1995Co-Authors: Narayan S. TavareAbstract:An analysis of interaction by exchange with the mean micromixing model is extended to a process involving elementary chemical reaction between two species and subsequent crystallization of product in a continuous mixed suspension mixed product removal etystallizer. Two specific feed conditions are considered: premixed and anpremixed feeds are considered. The sensitivity of these two cases to several parameterv like the Damkohler number, micromixing parameter, fractional flow rate, and dimensionless inlet concentration of Excess Reactant is explored. Both reaction and crystallizaLion performance characteristics are significantly influenced by the fred conditions. Results for the case of premixed feeds tend to suggest that the model description may be better suited to a nearly segregated configuration.
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mixing reaction and precipitation environment micromixing models in continuous crystallizers i premixed feeds
Computers & Chemical Engineering, 1992Co-Authors: Narayan S. TavareAbstract:Abstract The two-environment micromixing model of Ng and Rippin is extended to a process involving an elementary chemical reaction between two Reactant species and subsequent crystallization of a product in a continuous crystallizer. The model formulation in Part I of this paper deals with the premixed feeds case and assumes that the premixed Reactants first enter a completely segregated entering environment and subsequently transfer to a maximum-mixedness leaving environment at a specified rate as defined by an environment transfer function. The sensitivity of this model to several process parameters lik the Damkohler number, micromixing parameter and dimensionless inlet concentration of Excess Reactant is explored. This computationally efficient two- model appears to characterize satisfactorily the micromixing effects in a continuous reactive precipitator with premixed feeds.
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Mixing, reaction and precipitation: Environment micromixing models in continuous crystallizers—I. premixed feeds
Computers & Chemical Engineering, 1992Co-Authors: Narayan S. TavareAbstract:Abstract The two-environment micromixing model of Ng and Rippin is extended to a process involving an elementary chemical reaction between two Reactant species and subsequent crystallization of a product in a continuous crystallizer. The model formulation in Part I of this paper deals with the premixed feeds case and assumes that the premixed Reactants first enter a completely segregated entering environment and subsequently transfer to a maximum-mixedness leaving environment at a specified rate as defined by an environment transfer function. The sensitivity of this model to several process parameters lik the Damkohler number, micromixing parameter and dimensionless inlet concentration of Excess Reactant is explored. This computationally efficient two- model appears to characterize satisfactorily the micromixing effects in a continuous reactive precipitator with premixed feeds.
Kejin Huang - One of the best experts on this subject based on the ideXlab platform.
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Novel Process Design of Synthesizing Propylene Carbonate for Dimethyl Carbonate Production by Indirect Alcoholysis of Urea
Industrial & Engineering Chemistry Research, 2017Co-Authors: Li Shi, San-jang Wang, David Shan-hill Wong, Kejin HuangAbstract:Dimethyl carbonate (DMC) is a green compound with a broad variety of application. Recently, CO2-based routes to produce DMC have attracted much attention because of the environment benefits of CO2 utilization. In the study, we investigate the process design of synthesizing propylene carbonate (PC) for the DMC production using CO2 as a raw material by indirect alcoholysis of urea. The indirect alcoholysis route of urea shows many advantages because of cheap raw materials, mild and safe operation conditions, and environmentally friendly chemicals. Some different processes for PC synthesis by this route are proposed, designed, and optimized in this work. These processes can be classified in terms of two operation types: near-neat operation and Excess Reactant operation. Reactive distillation (RD) and heat integration technologies are used to intensify PC synthesis processes. Two processes are designed under the near-neat operation. Three RD plus conventional distillation (CD) processes with heat integration ...
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Design and Control of a Thermally Coupled Reactive Distillation Process Synthesizing Diethyl Carbonate
Industrial & Engineering Chemistry Research, 2014Co-Authors: San-jang Wang, Shueh-hen Cheng, Pin-hao Chiu, Kejin HuangAbstract:Diethyl carbonate (DEC) is a versatile material due to its excellent chemical and physical properties. Several chemical routes have been reported for the preparation of DEC. However, they suffer the drawbacks of using poisonous gases or attaining a low yield of DEC. In this study, a promising route by the transesterification of propylene carbonate and ethanol is used to coproduce DEC and propylene glycol. The transesterification reaction offers an excellent green chemical process. However, the reaction is a typically equilibrium-limited one. Reactive distillation (RD) with Excess Reactant is adopted in the study to improve reaction conversion and obtain high-purity products in the DEC synthesis. A base-case design, consisting of a RD column and a DEC purification column with its overhead unreacted ethanol stream recycled back to the RD column, is developed and optimized by minimizing the total annual cost. An alternative thermally coupled RD process is also developed which results in substantially reduced...
San-jang Wang - One of the best experts on this subject based on the ideXlab platform.
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Design and Control of a Reactive Distillation Process for Synthesizing Propylene Carbonate from Indirect Alcoholysis of Urea
IFAC-PapersOnLine, 2018Co-Authors: San-jang Wang, David Shan-hill WongAbstract:Abstract Dimethyl carbonate is a green compound with a broad variety of application. In the study, the process design and control of synthesizing propylene carbonate (PC) for the dimethyl carbonate production by using CO2 as a raw material is investigated by indirect alcoholysis of urea. This attractive indirect alcoholysis route of urea shows many advantages such as environmentally friendly chemicals, cheap raw materials, and mild and safe operation condition. Some reaction distillation (RD)-based processes for PC synthesis by this route are proposed, designed, and optimized in this work. These processes consist of two operation configurations, near neat operation and Excess Reactant operation. The intensified technologies of heat integration in addition to RD are used to design economic PC synthesis processes. Steady-state simulation results indicate that the novel intensified process containing a RD column and a conventional distillation column with internal vapor compression provides the most economical design. This process is operated under Excess Reactant and fully utilizes the special azeotrope characteristic of propylene carbonate and propylene glycol pair. This pair forms a homogeneous minimum-boiling azeotrope near the pure PG end under low pressure. However, this azeotrope vanishes under high pressure. Furthermore, steady-state analysis is used to design a simple temperature control strategy. Different desired temperature profiles can be found in the RD column under various feed flow rates. Set point of the temperature loop for maintaining bottom product purity of the RD column is then reset when throughput rate changes. Dynamic simulation results reveal that the proposed temperature control can maintain product purities at their desired values in face of feed flow disturbances.
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Novel Process Design of Synthesizing Propylene Carbonate for Dimethyl Carbonate Production by Indirect Alcoholysis of Urea
Industrial & Engineering Chemistry Research, 2017Co-Authors: Li Shi, San-jang Wang, David Shan-hill Wong, Kejin HuangAbstract:Dimethyl carbonate (DMC) is a green compound with a broad variety of application. Recently, CO2-based routes to produce DMC have attracted much attention because of the environment benefits of CO2 utilization. In the study, we investigate the process design of synthesizing propylene carbonate (PC) for the DMC production using CO2 as a raw material by indirect alcoholysis of urea. The indirect alcoholysis route of urea shows many advantages because of cheap raw materials, mild and safe operation conditions, and environmentally friendly chemicals. Some different processes for PC synthesis by this route are proposed, designed, and optimized in this work. These processes can be classified in terms of two operation types: near-neat operation and Excess Reactant operation. Reactive distillation (RD) and heat integration technologies are used to intensify PC synthesis processes. Two processes are designed under the near-neat operation. Three RD plus conventional distillation (CD) processes with heat integration ...
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Design and Control of a Thermally Coupled Reactive Distillation Process Synthesizing Diethyl Carbonate
Industrial & Engineering Chemistry Research, 2014Co-Authors: San-jang Wang, Shueh-hen Cheng, Pin-hao Chiu, Kejin HuangAbstract:Diethyl carbonate (DEC) is a versatile material due to its excellent chemical and physical properties. Several chemical routes have been reported for the preparation of DEC. However, they suffer the drawbacks of using poisonous gases or attaining a low yield of DEC. In this study, a promising route by the transesterification of propylene carbonate and ethanol is used to coproduce DEC and propylene glycol. The transesterification reaction offers an excellent green chemical process. However, the reaction is a typically equilibrium-limited one. Reactive distillation (RD) with Excess Reactant is adopted in the study to improve reaction conversion and obtain high-purity products in the DEC synthesis. A base-case design, consisting of a RD column and a DEC purification column with its overhead unreacted ethanol stream recycled back to the RD column, is developed and optimized by minimizing the total annual cost. An alternative thermally coupled RD process is also developed which results in substantially reduced...
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Design and control of an ideal reactive divided-wall distillation process
Asia-Pacific Journal of Chemical Engineering, 2011Co-Authors: San-jang Wang, Hsiao-ping HuangAbstract:Reactive distillation and divided-wall distillation are two promising technologies achieving substantial economical benefits from process intensification. In this study, a novel reactive divided-wall distillation process, procuring technical advantages from both reactive distillation and divided-wall distillation, is designed with different degrees of thermal coupling to achieve possible energy saving for an ideal quaternary reaction system with the least favorable relative volatility ranking under Excess-Reactant design. Simulation results demonstrate that reactive divided-wall distillation can provide better energy efficiency than reactive distillation without thermal coupling. Energy efficiency increases with the degree of thermal coupling. Proper selection and pairing of controlled and manipulated variables chosen for three control objectives are determined by using steady-state analysis. Temperature control in the reactive distillation column is used to maintain Reactant inventory in the process. Product purities are maintained by the temperature control loops in the divided-wall column. Stage temperatures that have modest sensitivity to manipulated variables and have little variations with respect to throughput rate changes are selected as controlled variables. Dynamic tests show that the proposed control scheme can maintain high product purity and stoichiometric balance between the Reactant feeds for throughput rate changes. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Thomas A. Trabold - One of the best experts on this subject based on the ideXlab platform.
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Non-active area water mitigation in PEM fuel cells via bipolar plate surface energy modification
International Journal of Hydrogen Energy, 2018Co-Authors: X. Liu, Thomas A. TraboldAbstract:Abstract The management of liquid water from either internal chemical reactions or externally humidified Reactants is an important design consideration for proton exchange membrane (PEM) fuel cells because of the effects on both cell performance and durability. To achieve proper water management, significant effort has been devoted to developing new fuel cell materials, hardware designs, and appropriate stack operating conditions. However, water management in the region of the channel-to-manifold interfaces has received limited attention. This region covers the ends of the bipolar plate from where liquid water exits the active area to the entrance of the stack exhaust manifolds where Excess Reactant flows from individual cells are combined and leave the stack. For practical applications, there is a small driving force to expel liquid water in this region, especially in the anode flow field. Under severe operating conditions such as freezing temperatures, the buildup of water may cause a channel-scale blockage. In this study, hydrophilic and hydrophobic bipolar plate treatments were investigated to identify the effectiveness of water mitigation through ex-situ experiments performed using a dedicated freeze test rig. Water mitigation behavior with various locations of hydrophilic/hydrophobic coatings was characterized using measurements of differential pressure and gas flow rate. It was found that the hydrophilic coatings provide better performance, as water accumulation can be readily mitigated with less potential to cause full channel-scale blockages.
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Neutron Imaging of Water Accumulation in the Active Area and Channel-to-Manifold Transitions of a PEMFC
ASME 2013 11th International Conference on Fuel Cell Science Engineering and Technology, 2013Co-Authors: X. Liu, Thomas A. Trabold, Jeffrey J. Gagliardo, David L. Jacobson, Daniel S. HusseyAbstract:Management of liquid water formed by the electrochemical fuel cell reaction is a key factor in PEMFC performance and durability. For practical stack applications, an important consideration is the transport of liquid water at the transition between the ends of the bipolar plate channels and the manifolds, where Excess Reactant flows from all the individual cells are combined and directed to the stack exhaust. In this region, gas-phase momentum can be very low, especially on the anode, where there is little driving force to remove liquid water that may accumulate as a result of geometrical or surface energy variations, or due to relatively low temperatures that exist outside of the fuel cell active area. This study seeks to characterize the water accumulated within the active area and at the channel-to-manifold transition regions at both the anode and cathode outlets, as a function of cell operating temperature and current density. The neutron imaging method was applied to directly measure the water volumes within the transition regions, and provide a comparison to simultaneously measured water volume within the cell active area. Transition-region water was found to be weakly dependent on current density, suggesting that once water forms in this area, little driving force exists to extract it entirely by means of gas momentum. Moreover, it was found that the active area water volume is strongly dependent on cell temperature, and temperature variation of as little as 0.5 °C can produce a significant change in water accumulation which is reflected in the cell voltage.Copyright © 2013 by ASME
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Investigation of Channel-to-Manifold Water Transport in Proton Exchange Membrane Fuel Cells
ASME 2012 10th International Conference on Fuel Cell Science Engineering and Technology, 2012Co-Authors: X. Liu, Thomas A. Trabold, Jiefeng Lin, K. M. Mcconnaghy, Jeffrey J. Gagliardo, Jon P. OwejanAbstract:Management of liquid water formed by the electrochemical reaction has received considerable attention and is considered a key factor in proton exchange membrane fuel cell (PEMFC) performance and durability. For practical stack applications, an aspect of the water management problem that is often overlooked is the transport of liquid water at the transition between the ends of the bipolar plate channels and the manifolds, where Excess Reactant flows from all the individual cells are combined and directed to the stack exhaust. In the bipolar plate exit region, gas-phase momentum can be very low, especially on the anode, and thus there is little driving force to remove liquid water. This study seeks to first quantify the characteristics of channel-to-manifold water transport by analysis of in-situ neutron radiography images, and correlation of the volumes of liquid water in the active and non-active regions to the relevant fuel cell operating conditions: temperature, pressure, relative humidity, current density and stoichiometric ratio. This analysis is complimented by new ex-situ experiments that directly control the flow of channel-level water and quantify the attendant increase in two-phase pressure drop in the non-active fuel cell region. The ex-situ apparatus has the additional feature of a simultaneous cross-flow channel at the exit plane of the bipolar plate, which enables simulation of two-phase flow dynamics of a fuel cell positioned anywhere in a stack, from zero cross-flow at the capped end of the stack to maximum cross-flow at the gas connected end of the stack.
David Shan-hill Wong - One of the best experts on this subject based on the ideXlab platform.
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Design and Control of a Reactive Distillation Process for Synthesizing Propylene Carbonate from Indirect Alcoholysis of Urea
IFAC-PapersOnLine, 2018Co-Authors: San-jang Wang, David Shan-hill WongAbstract:Abstract Dimethyl carbonate is a green compound with a broad variety of application. In the study, the process design and control of synthesizing propylene carbonate (PC) for the dimethyl carbonate production by using CO2 as a raw material is investigated by indirect alcoholysis of urea. This attractive indirect alcoholysis route of urea shows many advantages such as environmentally friendly chemicals, cheap raw materials, and mild and safe operation condition. Some reaction distillation (RD)-based processes for PC synthesis by this route are proposed, designed, and optimized in this work. These processes consist of two operation configurations, near neat operation and Excess Reactant operation. The intensified technologies of heat integration in addition to RD are used to design economic PC synthesis processes. Steady-state simulation results indicate that the novel intensified process containing a RD column and a conventional distillation column with internal vapor compression provides the most economical design. This process is operated under Excess Reactant and fully utilizes the special azeotrope characteristic of propylene carbonate and propylene glycol pair. This pair forms a homogeneous minimum-boiling azeotrope near the pure PG end under low pressure. However, this azeotrope vanishes under high pressure. Furthermore, steady-state analysis is used to design a simple temperature control strategy. Different desired temperature profiles can be found in the RD column under various feed flow rates. Set point of the temperature loop for maintaining bottom product purity of the RD column is then reset when throughput rate changes. Dynamic simulation results reveal that the proposed temperature control can maintain product purities at their desired values in face of feed flow disturbances.
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Novel Process Design of Synthesizing Propylene Carbonate for Dimethyl Carbonate Production by Indirect Alcoholysis of Urea
Industrial & Engineering Chemistry Research, 2017Co-Authors: Li Shi, San-jang Wang, David Shan-hill Wong, Kejin HuangAbstract:Dimethyl carbonate (DMC) is a green compound with a broad variety of application. Recently, CO2-based routes to produce DMC have attracted much attention because of the environment benefits of CO2 utilization. In the study, we investigate the process design of synthesizing propylene carbonate (PC) for the DMC production using CO2 as a raw material by indirect alcoholysis of urea. The indirect alcoholysis route of urea shows many advantages because of cheap raw materials, mild and safe operation conditions, and environmentally friendly chemicals. Some different processes for PC synthesis by this route are proposed, designed, and optimized in this work. These processes can be classified in terms of two operation types: near-neat operation and Excess Reactant operation. Reactive distillation (RD) and heat integration technologies are used to intensify PC synthesis processes. Two processes are designed under the near-neat operation. Three RD plus conventional distillation (CD) processes with heat integration ...
