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Vivek V Ranade - One of the best experts on this subject based on the ideXlab platform.
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Solid Suspension and liquid phase mixing in Solid liquid stirred tanks
Industrial & Engineering Chemistry Research, 2009Co-Authors: Madhavi V Sardeshpande, Aparna R Sagi, Vinay A Juvekar, Vivek V RanadeAbstract:Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of Solids, crystallization, and so on. In designing and optimizing such processes, Suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and Solid loading. Most of the earlier work on Solid Suspension focuses on identifying critical impeller speed for just Suspension of Solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in Solid−liquid Suspensions were also studied. A new way of characterizing Solid−liquid Suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of Solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications...
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cfd simulation of liquid phase mixing in Solid liquid stirred reactor
Chemical Engineering Science, 2008Co-Authors: Gopal R Kasat, A R Khopkar, Vivek V Ranade, Aniruddha B PanditAbstract:A comprehensive CFD model was developed to gain an insight into Solid Suspension and its implications on the liquid-phase mixing process in a Solid-liquid stirred reactor. The turbulent Solid-liquid flow in a stirred reactor was simulated using a two-fluid model with the standard k-e turbulence model with mixture properties. The multiple reference frames (MRFs) approach was used to simulate impeller rotation in a fully baffled reactor. The computational model with necessary sub-models was mapped on to a commercial solver FLUENT 6.2 (of Fluent Inc., USA). The predicted Solid concentration distribution was compared with the experimental data of Yamazaki et al. [1986. Concentration profiles of Solids suspended in a stirred tank. Powder Technology 48, 205-216]. The computational model was then further extended to simulate and understand the implications of the Suspension quality on liquid-phase mixing process. The computational model and the predicted results discussed here will be useful for understanding the liquid-phase mixing process in stirred slurry reactors in various stages of Solid Suspension.
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computational fluid dynamics simulation of the Solid Suspension in a stirred slurry reactor
Industrial & Engineering Chemistry Research, 2006Co-Authors: A R Khopkar, Gopal R Kasat, And A B Pandit, Vivek V RanadeAbstract:A comprehensive computational fluid dynamics CFD model was developed in the present study to gain insight into the Solid Suspension in a stirred slurry reactor. The preliminary simulations highlighted the need for the correct modeling of the interphase drag force. A two-dimensional model problem was then developed using CFD to understand the influence of free stream turbulence on the particle drag coefficient. The proposed correlation was then incorporated in a two-fluid model (Euler−Euler) along with the standard k−e turbulence model with mixture properties to simulate the turbulent Solid−liquid flow in a stirred reactor. A multiple reference frame approach was used to simulate the impeller rotation in a fully baffled reactor. A computational model was mapped on to a commercial CFD solver FLUENT6.2 (of Fluent Inc., USA). The model predictions were compared with the published experimental data of Yamazaki et al. [Powder Technol. 1986, 48, 205] and Godfrey and Zhu [AIChE Symp. Ser. 1994, 299, 181]. The pre...
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computational fluid dynamics simulation of the Solid Suspension in a stirred slurry reactor
Industrial & Engineering Chemistry Research, 2006Co-Authors: A R Khopkar, Gopal R Kasat, And A B Pandit, Vivek V RanadeAbstract:A comprehensive computational fluid dynamics CFD model was developed in the present study to gain insight into the Solid Suspension in a stirred slurry reactor. The preliminary simulations highligh...
Yoshinori Kawase - One of the best experts on this subject based on the ideXlab platform.
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Dispersion of Floating Solid Particles in Aerated Stirred Tank Reactors: Minimum Impeller Speeds for Off-Surface and Ultimately Homogeneous Solid Suspension and Solids Concentration Profiles
Industrial & Engineering Chemistry Research, 2006Co-Authors: Atsushi Tagawa, Naoki Dohi, Yoshinori KawaseAbstract:Effects of impeller design, baffle, and gas flow rate on distributions of floating Solid particles were examined in a stirred tank of 0.2 m i.d. for Solid concentrations up to 50 vol %. Dual small cross-section impeller systems, i.e., dual four-flat blade disk turbines and dual four-pitched blade downflow disk turbines, and large cross-section impellers, i.e., Maxblend impeller and Fullzone impeller, were used. The minimum impeller speeds for off-surface floating-particle Suspension decreased with aeration because bubbles rising near the tank wall enhanced the breakup of the floating-particle stagnant layer formed on the liquid surface and then the dispersion of floating particles into the liquid. The minimum impeller speeds for ultimately homogeneous floating-particle Suspension also decreased with aeration. These results are contrary to those for the settling particles. The local Solid particle concentrations at different heights in the stirred tank were measured. The axial Solid particles concentration...
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power consumption and Solid Suspension performance of large scale impellers in gas liquid Solid three phase stirred tank reactors
Chemical Engineering Journal, 2004Co-Authors: N. Dohi, Takanori Takahashi, K Minekawa, Yoshinori KawaseAbstract:Abstract An experimental investigation into power consumption and Solid Suspension performance of large-scale impellers was carried out under turbulent conditions. Two types of large-scale impellers, i.e. Maxblend and Fullzone impellers, were employed. For reference, a triple-impeller system, i.e. two four-pitched blade downflow disk turbines (DTs) at middle and upper positions and one Pfaudler type impeller at lower position, was also used. The power consumption and the minimum impeller speeds for off-bottom Solid Suspension and minimum impeller speeds for ultimately homogeneous Solid Suspension were measured in unaerated and aerated systems. At a given rotational speed, the power consumption of the Maxblend impeller was roughly half of that of the Fullzone impeller. The decrease in power consumption due to aeration for large-scale impellers was smaller as compared with that for the triple-impeller system. The proposed correlation for power consumption of large-scale impellers in three-phase systems fit the experimental data reasonably well. Interesting and unexpected Solid movements caused by the large-scale impellers in the vessels having oval bottom were observed. Since the large-scale impellers create strong axial liquid recirculation flowing downward near the impeller shaft and upward near the wall, usually particles are expected to move outward on the tank bottom. On the contrary, however, Solid particles near the bottom moved to the center of the base from the side along the oval tank bottom. The large-scale impellers were found to be more efficient for Solid Suspension than the triple-impeller system. The Maxblend impeller provided the best Solid Suspension ability among the three impellers used in this work. We proposed a correlation for power consumption of large-scale impellers in gas–liquid–Solid three-phase systems. Empirical correlations were also proposed for the minimum impeller speeds for off-bottom Solid Suspension, minimum impeller speeds for ultimately homogeneous Solid Suspension and power consumption at the minimum impeller speeds for ultimately homogeneous Solid Suspension.
Hairui Yang - One of the best experts on this subject based on the ideXlab platform.
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A semi-empirical model to estimate the apparent viscosity of dense, bubbling gas-Solid Suspension
Powder Technology, 2021Co-Authors: Chen Shujie, Runxia Cai, Yang Zhang, Hairui Yang, Hai Zhang, Junfu LyuAbstract:Abstract A semi-empirical model was proposed to estimate the apparent viscosity of gas-fluidized Suspensions. This new model was derived by assuming that a Suspension consisted of the bubble phase and the emulsion phase. A set of experimental measurements were also conducted to verify the validity of the proposed model as well as the models in the literature. The results indicated that none of the tested literature models provided satisfactory predictions for the fluidized gas-Solid Suspension over the mentioned target particle volume fraction range. The estimation using the newly proposed model generally well agreed with the experimental apparent viscosity values of the gas-Solid Suspensions composed of gas-fluidized Geldart Group A or B particles, as most of the estimated values situated within the ±25% error bars. The proposed model is of special significance as it provides a quick estimation method of the apparent viscosity of a gas-Solid Suspension flow in the engineering calculation.
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effect of furnace pressure drop on heat transfer in a 135mw cfb boiler
Powder Technology, 2015Co-Authors: Man Zhang, Junfu Lu, Hairui YangAbstract:Abstract The effect of the pressure drop across the furnace on heat transfer inside large scale CFB boilers was investigated with a 1-D CFB combustion model developed at Tsinghua University. The results from the 1-D model agree well with the field test data carried out in a 135 MW e CFB boiler. It was found that, at a certain load and with fixed size distribution of the coal particles fed to the boiler, a decrease in furnace pressure drop yields an increase in furnace temperature and reduced heat transfer coefficient. According to the heat balance, when the pressure drop decreases by 1 kPa, the heat transfer coefficient is expected to decrease approximately by 2%. The increase in temperature with decreasing pressure drop is less steep, when the boiler load increases or smaller sized coal particles are fed to the boiler. In both cases, more fine particles are carried to the upper parts of the furnace which results in a more uniform Solid volume fraction distribution along the furnace height. The influence of the pressure drop on heat transfer by changing the Solid Suspension density weakens. Operation of the bed at relatively low pressure drop by reducing the size of coal particles will ensure adequate heat transfer.
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effect of bed pressure drop on performance of a cfb boiler
Energy & Fuels, 2009Co-Authors: Hairui Yang, Hai Zhang, Shi Yang, Jun Su, Zhiping FuAbstract:The effect of bed pressure drop and bed inventory on the performances of a circulating fluidized bed (CFB) boiler was studied. By using the state specification design theory, the fluidization state of the gas−Solids flow in the furnace of conventional CFB boilers was reconstructed to operate at a much lower bed pressure drop by reducing bed inventory and control bed quality. Through theoretical analysis, it was suggested that there would exist a theoretical optimal value of bed pressure drop, around which the boiler operation can achieve the maximal combustion efficiency and with significant reduction of the wear of the heating surface and fan energy consumption. The analysis was validated by field tests carried out in a 75 t/h CFB boiler. At full boiler load, when bed pressure drop was reduced from 7.3 to 3.2 kPa, the height of the dense zone in the lower furnace decreased, but the Solid Suspension density profile in the upper furnace and Solid flow rate were barely influenced. Consequently, the average ...
H Y Sohn - One of the best experts on this subject based on the ideXlab platform.
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flowsheet development process simulation and economic feasibility analysis for novel Suspension ironmaking technology based on natural gas part 3 economic feasibility analysis
Ironmaking & Steelmaking, 2013Co-Authors: Haruka Pinegar, Michael S Moats, H Y SohnAbstract:A novel gas–Solid Suspension ironmaking process with much less energy consumption and carbon dioxide emissions than the current blast furnace technology is under development at the University of Utah. The proposed process is based on flash reduction of iron ore concentrate with a gaseous reagent, such as hydrogen, syngas and/or natural gas. This Part 3 deals with economic feasibility analysis of a commercial scale novel ironmaking process based on natural gas, the flowsheet and process simulation of which are described in Parts 1 and 2. To evaluate economic feasibility, the net present value for 15 year operation was calculated for each process, using capital and operating costs estimated from available open references. The sensitivity of the estimated net present value to the variation in item costs was also analysed.
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flowsheet development process simulation and economic feasibility analysis for novel Suspension ironmaking technology based on natural gas part 2 flowsheet and simulation for ironmaking combined with steam methane reforming
Ironmaking & Steelmaking, 2013Co-Authors: Haruka Pinegar, Michael S Moats, H Y SohnAbstract:AbstractA novel gas–Solid Suspension ironmaking process with much less energy consumption and carbon dioxide emissions than the current blast furnace technology is under development at the University of Utah. The proposed process is based on flash reduction of iron ore concentrate with a gaseous reagent, such as hydrogen, syngas and/or natural gas. This series of papers reports on the results of process simulation for the proposed process operated with natural gas. This Part 2 deals with simulation of a commercial scale ironmaking process combined with a steam methane reforming process. The steam methane reforming process was simulated to produce hydrogen or syngas to provide fuel/reductant for ironmaking. Ironmaking was simulated in one-step configuration. The results indicated that the proposed process would reduce carbon dioxide emissions by 31–35%, but energy consumption would be larger by 0–6%, based on the higher heating value of natural gas (28–29% lower, if the lower heating value is used), compar...
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flowsheet development process simulation and economic feasibility analysis for novel Suspension ironmaking technology based on natural gas part 1 flowsheet and simulation for ironmaking with reformerless natural gas
Ironmaking & Steelmaking, 2012Co-Authors: Haruka Pinegar, Michael S Moats, H Y SohnAbstract:AbstractA novel gas–Solid Suspension ironmaking process with much less energy consumption and carbon dioxide emissions than the current blast furnace technology is under development at the University of Utah. The proposed process is based on flash reduction of iron ore concentrate with a gaseous reagent, such as hydrogen, syngas and/or natural gas. This series of papers reports on the results of process simulation for the proposed process operated with natural gas. This Part 1 deals with simulation of a commercial scale reformerless ironmaking process with heat recovery and hydrogen recycling steps. Ironmaking was simulated in one-step and two-step process configurations. The results indicated that the proposed process would, depending on the process configuration, reduce carbon dioxide emissions by 39–51% and energy consumption by 32–44% compared with the average blast furnace process (61–66% if the lower heating value of natural gas is used). The sensitivity of the energy requirement to operating condit...
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process simulation and economic feasibility analysis for a hydrogen based novel Suspension ironmaking technology
Steel Research International, 2011Co-Authors: Haruka Pinegar, Michael S Moats, H Y SohnAbstract:A novel gas-Solid Suspension ironmaking process is under development at the University of Utah, which would greatly reduce energy consumption and carbon dioxide emission compared with current blast furnace technology. The proposed process is based on the flash reduction of iron ore concentrate using a gaseous reagent, such as hydrogen, syngas, natural gas or a combination of thereof. A process flow sheet of the proposed ironmaking process using purchased hydrogen was constructed and then simulations were performed at several potential operating conditions. Ironmaking was simulated using two different process configurations. The simulation results show that the required fresh hydrogen would increase with higher excess driving force and operating temperature, but not greatly when hydrogen is preheated. Compared with the average blast furnace process, the proposed process would reduce energy consumption by 57 - 60%, using the higher heating value of hydrogen (71 – 73%, if the lower heating value is used), when hydrogen and coal are considered as the starting materials in the respective processes. The economic feasibility analysis using net present value (NPV) indicates that the proposed process could be economically feasible at elevated hot metal prices and/or if reduction in carbon dioxide emissions has a significant value in a cap and trade scenario.
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development of green Suspension ironmaking technology based on hydrogen reduction of iron oxide concentrate rate measurements
Ironmaking & Steelmaking, 2010Co-Authors: M E Choi, H Y SohnAbstract:AbstractA novel ironmaking technology is under development at the University of Utah. This technology produces iron directly from fine iron oxide concentrate by a gas–Solid Suspension reduction, utilising hydrogen as the main reducing agent for high reactivity, for the elimination of carbon dioxide release during ironmaking operations and also pursuing the direct use of concentrates to bypass the problematic pelletisation/sintering and cokemaking steps in the steel industry. This paper is mainly focused on the kinetic feasibility tests of the proposed process showing that the reduction rate was fast enough to obtain 90–99% reduction within 1–7 s at 1200–1500°C, depending on the amount of excess hydrogen supplied with the iron oxide. This indicates that the reduction rate of concentrate particles by hydrogen containing gases is sufficiently fast for a Suspension reduction process and forms the most important basis for the new technology.
Gopal R Kasat - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation of liquid phase mixing in Solid liquid stirred reactor
Chemical Engineering Science, 2008Co-Authors: Gopal R Kasat, A R Khopkar, Vivek V Ranade, Aniruddha B PanditAbstract:A comprehensive CFD model was developed to gain an insight into Solid Suspension and its implications on the liquid-phase mixing process in a Solid-liquid stirred reactor. The turbulent Solid-liquid flow in a stirred reactor was simulated using a two-fluid model with the standard k-e turbulence model with mixture properties. The multiple reference frames (MRFs) approach was used to simulate impeller rotation in a fully baffled reactor. The computational model with necessary sub-models was mapped on to a commercial solver FLUENT 6.2 (of Fluent Inc., USA). The predicted Solid concentration distribution was compared with the experimental data of Yamazaki et al. [1986. Concentration profiles of Solids suspended in a stirred tank. Powder Technology 48, 205-216]. The computational model was then further extended to simulate and understand the implications of the Suspension quality on liquid-phase mixing process. The computational model and the predicted results discussed here will be useful for understanding the liquid-phase mixing process in stirred slurry reactors in various stages of Solid Suspension.
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review on mixing characteristics in Solid liquid and Solid liquid gas reactor vessels
Canadian Journal of Chemical Engineering, 2008Co-Authors: Gopal R Kasat, Aniruddha B PanditAbstract:Mechanically agitated reactors with single and multiple impeller systems are used in the industry for the various three-phase mixing processes such as crystallization, fermentation, and hydrogenation, etc. The paper reviews the experimental work reported in the literature along with different techniques used for the measurement of the specific quantities such as minimum or critical impeller speed for Solid Suspension. The work critically surveys the literature and makes specific recommendations for the use of appropriate correlations and conditions to be used for the success of such equipment. This assessment will put all the relevant literature on a common footing and will help to validate work reported earlier.
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computational fluid dynamics simulation of the Solid Suspension in a stirred slurry reactor
Industrial & Engineering Chemistry Research, 2006Co-Authors: A R Khopkar, Gopal R Kasat, And A B Pandit, Vivek V RanadeAbstract:A comprehensive computational fluid dynamics CFD model was developed in the present study to gain insight into the Solid Suspension in a stirred slurry reactor. The preliminary simulations highlighted the need for the correct modeling of the interphase drag force. A two-dimensional model problem was then developed using CFD to understand the influence of free stream turbulence on the particle drag coefficient. The proposed correlation was then incorporated in a two-fluid model (Euler−Euler) along with the standard k−e turbulence model with mixture properties to simulate the turbulent Solid−liquid flow in a stirred reactor. A multiple reference frame approach was used to simulate the impeller rotation in a fully baffled reactor. A computational model was mapped on to a commercial CFD solver FLUENT6.2 (of Fluent Inc., USA). The model predictions were compared with the published experimental data of Yamazaki et al. [Powder Technol. 1986, 48, 205] and Godfrey and Zhu [AIChE Symp. Ser. 1994, 299, 181]. The pre...
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computational fluid dynamics simulation of the Solid Suspension in a stirred slurry reactor
Industrial & Engineering Chemistry Research, 2006Co-Authors: A R Khopkar, Gopal R Kasat, And A B Pandit, Vivek V RanadeAbstract:A comprehensive computational fluid dynamics CFD model was developed in the present study to gain insight into the Solid Suspension in a stirred slurry reactor. The preliminary simulations highligh...