Gas holdups of large bubbles and small bubbles were measured by means of dynamic gas disengagement approach in the pressured bubble column with a diameter of 0.3 m and a height of 6.6 m. The effects of superficial gas...Gas holdups of large bubbles and small bubbles were measured by means of dynamic gas disengagement approach in the pressured bubble column with a diameter of 0.3 m and a height of 6.6 m. The effects of superficial gas velocity, liquid surface tension, liquid viscosity and system pressure on gas holdups of small bubbles and large bubbles were investigated. The holdup of large bubbles increases and the holdup of small bubbles decreases with an increase of liquid viscosity. Meanwhile, the holdup of large bubbles decreases with increasing the system pressure. A correlation for the holdup of small bubbles was obtained from the experimental data.展开更多
Two-phase pipe flow occurs frequently in oil&gas industry,nuclear power plants,and CCUS.Reliable calculations of gas void fraction(or liquid holdup)play a central role in two-phase pipe flow models.In this paper w...Two-phase pipe flow occurs frequently in oil&gas industry,nuclear power plants,and CCUS.Reliable calculations of gas void fraction(or liquid holdup)play a central role in two-phase pipe flow models.In this paper we apply the fractional flow theory to multiphase flow in pipes and present a unified modeling framework for predicting the fluid phase volume fractions over a broad range of pipe flow conditions.Compared to existing methods and correlations,this new framework provides a simple,approximate,and efficient way to estimate the phase volume fraction in two-phase pipe flow without invoking flow patterns.Notably,existing correlations for estimating phase volume fraction can be transformed and expressed under this modeling framework.Different fractional flow models are applicable to different flow conditions,and they demonstrate good agreement against experimental data within 5%errors when compared with an experimental database comprising of 2754 data groups from 14literature sources,covering various pipe geometries,flow patterns,fluid properties and flow inclinations.The gas void fraction predicted by the framework developed in this work can be used as inputs to reliably model the hydraulic and thermal behaviors of two-phase pipe flows.展开更多
Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with sev...Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with severely non-uniform local-velocity flow profiles and dispersed-phase concentration（of oil droplets） in oil-water two-phase flow,which makes it difficult to measure water holdup in oil wells.In this study,we use an ultrasonic method based on a transmission-type sensor in oil-water two-phase flow to measure water holdup in lowvelocity and high water-cut conditions.First,we optimize the excitation frequency of the ultrasonic sensor by calculating the sensitivity of the ultrasonic field using the finite element method for multiphysics coupling.Then we calculate the change trend of sound pressure level attenuation ratio with the increase in oil holdup to verify the feasibility of the employed diameter for the ultrasonic sensor.Based on the results,we then investigate the effects of oildroplet diameter and distribution on the ultrasonic field.To further understand the measurement characteristics of the ultrasonic sensor,we perform a flow loop test on vertical upward oilwater two-phase flow and measure the responses of the optimized ultrasonic sensor.The results show that the ultrasonic sensor yields poor resolution for a dispersed oil slug in water flow（D OS/W flow）,but the resolution is favorable for dispersed oil in water flow（D O/W flow） and very fine dispersed oil in water flow（VFD O/W flow）.This research demonstrates the potential application of a pulsed-transmission ultrasonic method for measuring the fraction of individual components in oil-water two-phase flow with a low mixture velocity and high water cut.展开更多
The experiment was conducted to explore the hydrodynamics in a conical column with a height of 3.00 m, and a taper angle of 1.91°. Three regimes occur in succession with increasing superficial gas velocity. Ove...The experiment was conducted to explore the hydrodynamics in a conical column with a height of 3.00 m, and a taper angle of 1.91°. Three regimes occur in succession with increasing superficial gas velocity. Overall gas holdup increases with an increase in gas velocity and a decrease in solid concentration or static slurry height. Axial solid holdup becomes more uniform with increasing gas velocity, while axial gas holdup decreases from the bottom to the top. Both dry and wet pressure drops across the gas distributor increase with an increase in superficial gas velocity.展开更多
Cyclic total reflux(CTR) batch distillation is a promising mode of the process but lacking of appropriate modeling for the period of filling the reflux drum.A new dynamic modeling method for the simulation of CTR batc...Cyclic total reflux(CTR) batch distillation is a promising mode of the process but lacking of appropriate modeling for the period of filling the reflux drum.A new dynamic modeling method for the simulation of CTR batch distillation is proposed in this work,in which the changes in column holdup and liquid flow rate during the filling of the drum,and the consequent change in valid number of theoretical plates are considered.The effect of drum holdup on operation time is investigated and the optimal drum holdup is obtained from the simulation.The dynamic modeling is compared to the conventional modeling without consideration of change in liquid flow rate. The experimental result shows that the present modeling is more reliable and more accurate,especially for the column with large liquid holdup.展开更多
The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracke...The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracked with the results of motion equations. The two-way approach was performed to couple the interphase momentum exchange. The turbulent dispersion of bubbles with a size distribution was modeled using a stochastic tracking model, and the added mass force was involved to account for the effect of bubble acceleration on the surrounding fluid. The predicted gas holdup distribution showed that this method could give reasonable prediction comparable to the reported experimental data when the effect of turbulence was took into account in modification for drag coefficient.展开更多
Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas ...Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas dispersion regime in the hot sparged system is similar to the ambient gassed condition. The gas holdup under the elevated temperature and the ambient gassed operation is successfully correlated. With the same total gas flow rate and power input, the gas holdup in the hot sparged system (say near the boiling point) is only about half of that in the ambient system. The results imply that almost all existing hot sparged reactors have been designed on the basis of incorrect estimates of the gas holdup during operation.展开更多
Systematic experimental work was conducted to investigate the solid acceleration length in a 16m long circulating fluidized bed riser with fluid cracking catalyst particles over a wide range of operating conditions. A...Systematic experimental work was conducted to investigate the solid acceleration length in a 16m long circulating fluidized bed riser with fluid cracking catalyst particles over a wide range of operating conditions. A more feasible method is proposed to determine the acceleration length from the measured axial profiles of pressure gradient (or apparent solid holdup). With this new method and large amount of experimental data, a clear picture on the variation of the acceleration length with both solid circulating rate and superficial gas velocity is obtained.It is found that the acceleration length increases generally with increasing solid flow rate and/or decreasing gas velocity. However, the trend in variation of the acceleration length with operating conditions are quite different in different operation ranges. Reasonable explanations are suggested for the observed variation patterns of acceleration length.展开更多
The new mode of operation for slop cut withdrawal in batch distillation, i.e., draining Column liquid holdup at the end of slop cut period, was proposed. And the stopping criterion for the operation was investigated, ...The new mode of operation for slop cut withdrawal in batch distillation, i.e., draining Column liquid holdup at the end of slop cut period, was proposed. And the stopping criterion for the operation was investigated, Experiments were carded out with isopropanol-n-propanol binary system and isopropanol-n-propanol-n-butanol ternary system in a distillation column with a liquid collector installed between the reboiler and the column section, Experimental results in a Ф 45mm batch column show that the proposed policy can overcome the flywheel effect caused by column liquid holdup and thus cut down operation time and energy consumption 31%-61%.展开更多
In this work, a mathematical model is established to describe the axial variation of the characteristic flow parameters (particle velocity, solid holdup and pressure gradient) in a downer. An empirical correlation is ...In this work, a mathematical model is established to describe the axial variation of the characteristic flow parameters (particle velocity, solid holdup and pressure gradient) in a downer. An empirical correlation is developed to estimate the particle velocity at the constant velocity section. Experimental investigations are made to validate the downer model. The model simulations have a good agreement with experimental data. Moreover, a formula is derived to predict the first acceleration section length and the whole acceleration section length.展开更多
The impeller configuration with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers, identified as PDT + 2CBY, was used in this study. The effect of the impeller diameter D, ranging from0.30...The impeller configuration with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers, identified as PDT + 2CBY, was used in this study. The effect of the impeller diameter D, ranging from0.30 T to 0.40T(T as the tank diameter), on gas dispersion in a stirred tank of 0.48 m diameter was investigated by experimental and CFD simulation methods. Power consumption and total gas holdup were measured for the same impeller configuration PDT + 2CBY with four different D/T. Results show that with D/T increases from 0.30 to 0.40, the relative power demand(RPD) in a gas–liquid system decreases slightly. At low superficial gas velocity VSof 0.0078 m·s-1, the gas holdup increases evidently with the increase of D/T. However, at high superficial gas velocity, the system with D/T = 0.33 gets a good balance between the gas recirculation and liquid shearing rate, which resulted in the highest gas holdup among four different D/T. CFD simulation based on the two-fluid model along with the Population Balance Model(PBM) was used to investigate the effect of impeller diameter on the gas dispersion. The power consumption and total gas holdup predicted by CFD simulation were in reasonable agreement with the experimental data.展开更多
Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inc...Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inclined and even vertical sections of gas wells.To grasp the flow law of slug flow and guide engineering practice,the flow law of slug flow at various inclination angles(30°~90°)is studied by means of the combination of laboratory experiments(including high frequency pressure data acquisition system)and finite element numerical simulation.The results reveal that because of the delay of pressure variation at the corresponding position of pipeline resulting from gas expansion,the highest point of pressure change curve corresponds not to the highest point of liquid holdup curve(pressure change lags behind 0.125 s of liquid holdup change).Thus,the delay of pressure should be highlighted in predicting slug flow using pressure parameter change;otherwise the accuracy of prediction will be affected when slug flow occurs.It is generally known that liquid holdup and pressure drop are the major factors affecting the pressure variation and stable operation of pipelines.Accordingly,the results of finite element numerical simulation and Beggs-Brill model calculation are compared with those of laboratory experiments.The numerical simulation method is applicable to predicting the pressure drop of the pipeline,while the Beggs-Brill model is more suitable for predicting the liquid holdup variation of the pipeline.The research conclusion helps reveal the slug flow law,and it is of a scientific guiding implication to the prediction method of flow parameters under slug flow pattern in the process of gas well exploitation.展开更多
Annular centrifugal contactors (ACCs) have many advantages and are recognized as key solvent-extraction equipment for the future reprocessing of spent nuclear fuel (RSNF). To successfully design and operate ACCs for R...Annular centrifugal contactors (ACCs) have many advantages and are recognized as key solvent-extraction equipment for the future reprocessing of spent nuclear fuel (RSNF). To successfully design and operate ACCs for RSNF, it is necessary to understand the hydrodynamic characteristics of the extraction systems in ACCs. The phase ratio (R = Vaq/Vorg, A/O) and liquid holdup volume (V) of the ACC are important hydrodynamic characteristics. In this study, a liquid-fast-separation method was used to systematically investigate the effects of the operational and structural parameters on the V and R (A/O) of a φ20 ACC by using a 30%TBP/kerosene- HNO3 solution system. The results showed that the operational and structural parameters had different effects on the V and R (A/O) of the mixing and separating zones of the ACC, respectively. For the most frequently used structural parameters of the φ20 ACC, when the rotor speed was 3500 r/min, the total flow rate was 2.0 L/h, and the flow ratio (A/O) was 1, the liquid holdup volumes in the mixing zone and rotor were 8.03 and 14.0 mL, respectively, and the phase ratios (A/O) of the mixing zone and separating zone were 0.96 and 1.43, respectively.展开更多
This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity...This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.展开更多
Using experimental data from a number of pulsed disc and doughnut solvent extraction columns, a unified correla- tion for the prediction of dispersed phase holdup that considers the effects of mass transfer is present...Using experimental data from a number of pulsed disc and doughnut solvent extraction columns, a unified correla- tion for the prediction of dispersed phase holdup that considers the effects of mass transfer is presented. Pulsed disc and doughnut solvent extraction columns （PDDC） have been used for a range of important applications such as ura- nium extraction and nuclear fuel recycling. Although the dispersed phase holdup in a PDDC has been presented by some researchers, there is still the need to develop a robust correlation that can predict the experimental dispersed phase holdup over a range of operating conditions including the effects of mass transfer direction. In this study, dis- persed phase holdup data from different literature sources for a PDDC were used to refit constants for the correlation presented by Kumar and Hartland lind. Eng. Chem. Res.,27 （1988）,131-138] which did not consider the effect of col- umn geometry. In order to incorporate the characteristic length of the PDDC （i.e. the plate spacing）, the unified cor- relation for holdup proposed by Kumar and Hartland based on data from eight different types of columns [Ind. Eng. Chem. Res.,34 （1995） 3925-3940] was refitted to the PDDC data. New constants have been presented for each hold- up correlation for a PDDC based on regression analysis using published holdup data from PDDCs that cover a range of onerating conditions and nhwical nronerties and consider the direction of mass transfer.展开更多
A study on two-phase flow characteristics in a coalescence-dispersion pulsed-sieve-plate extraction column of 150mm in diameter was carried out with a working system of 30% tri-butyl-phosphate (TBP) (in kerosene)-nitr...A study on two-phase flow characteristics in a coalescence-dispersion pulsed-sieve-plate extraction column of 150mm in diameter was carried out with a working system of 30% tri-butyl-phosphate (TBP) (in kerosene)-nitric acid-water. The influence of operation conditions on the holdup of the dispersed phase was investigated. According to the analysis of the experimental data, there was a turning point on the curve of ln(Vs) versus ln(l-Φ) under certain pulse intensity. When the holdup is higher than the value at the turning point, the two-phase flow characteristics can be described with the modified Pratt's equation, otherwise a new relation in the form ofΦ=1/2.75uk(uc + 4ud) may be used, which is proposed by this study.展开更多
Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumpin...Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumping turbine(6ITU))was conducted using computational fluid dynamics(CFD)and population balance model(PBM)(CFD-PBM)coupled model.The local bubble size was captured by particle image velocimetry(PIV)measurement.The gas holdup,bubble size distribution and gas–liquid interfacial area were explored at different conditions through numerical simulation.The results showed that the 4 mm bubbles accounted for the largest proportion of 33%at the gas flow rates Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1) for combined impeller of 6BT+6ITU,while the bubbles of 4.7 mm and 5.5 mm were the largest proportion for 6BT+6ITD combination,i.e.25%at Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1),respectively,which indicated that 6BT+6ITU could reduce bubble size effectively and promote gas dispersion.In addition,the gas holdup around impellers was increased obviously with the speed compared with gas flow rate.So it was concluded that 6ITU impeller could be more conductive to the bubble dispersion with more uniform bubble size,which embodied the advantages of 6BT+6ITU combination in gas–liquid mixing.展开更多
The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas–liquid–solid phase reaction and the extraction rate of valuable metals. ...The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas–liquid–solid phase reaction and the extraction rate of valuable metals. In this paper, a transparent quartz autoclave, a six blades disc turbine-type agitator, and a high-speed camera were used to investigate the gas holdup of the pressure leaching process. Furthermore, experiments determining the effects of agitation rate, temperature, and oxygen partial pressure on gas holdup were carried out. The results showed that when the agitation rate increased from 350 to 600 r/min, the gas holdup increased from 0.10% to 0.64%. When the temperature increased from 363 to 423 K, the gas holdup increased from 0.14% to 0.20%. When the oxygen partial pressure increased from 0.1 to 0.8 MPa, the gas holdup increased from 0.13% to 0.19%. A similar criteria relationship was established by Homogeneous Principle and Buckingham's theorem. Comprehensively, empirical equation of gas holdup was deduced on the basis of experimental data and the similarity theory, where the criterion equation was determined as ε=4.54×10^(-11)n^(3.65)T^(2.08)P_g^(0.18). It can be seen from the formula that agitation rate made the most important impact on gas holdup in the pressure leaching process using the mixed-flow agitator.展开更多
Based on the momentum conservation approach, a theoretical model was developed to predict the superficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular external-...Based on the momentum conservation approach, a theoretical model was developed to predict the superficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular external-loop airlift reactor(AELAR)in the bubble flow and developing slug flow pattern. Experiments were performed by using tap-water and silicone oil with the viscosity of 2.0 mm^2/s(2cs-SiO)and 5.0 mm^2/s(5cs-SiO)as liquid phases. The effects of liquid viscosity and flow pattern on the AELAR performance were investigated. The predictions of the proposed model were in good agreement with the experimental results of the AELAR. In addition, the comparison of the experimental results shows that the proposed model has good accuracy and could be used to predict the gas holdup and liquid velocity of an AELAR operating in bubble and developing flow pattern.展开更多
基金Supported by China Petroleum and Chem ical Corporation(No. 2 0 0 0 5 8)
文摘Gas holdups of large bubbles and small bubbles were measured by means of dynamic gas disengagement approach in the pressured bubble column with a diameter of 0.3 m and a height of 6.6 m. The effects of superficial gas velocity, liquid surface tension, liquid viscosity and system pressure on gas holdups of small bubbles and large bubbles were investigated. The holdup of large bubbles increases and the holdup of small bubbles decreases with an increase of liquid viscosity. Meanwhile, the holdup of large bubbles decreases with increasing the system pressure. A correlation for the holdup of small bubbles was obtained from the experimental data.
基金financial support from the Energize Program between the University of Texas at Austin and Southwest Research InstituteHydraulic Fracturing and Sand Control Industrial Affiliates Program at the University of Texas at Austin for financially supporting this research。
文摘Two-phase pipe flow occurs frequently in oil&gas industry,nuclear power plants,and CCUS.Reliable calculations of gas void fraction(or liquid holdup)play a central role in two-phase pipe flow models.In this paper we apply the fractional flow theory to multiphase flow in pipes and present a unified modeling framework for predicting the fluid phase volume fractions over a broad range of pipe flow conditions.Compared to existing methods and correlations,this new framework provides a simple,approximate,and efficient way to estimate the phase volume fraction in two-phase pipe flow without invoking flow patterns.Notably,existing correlations for estimating phase volume fraction can be transformed and expressed under this modeling framework.Different fractional flow models are applicable to different flow conditions,and they demonstrate good agreement against experimental data within 5%errors when compared with an experimental database comprising of 2754 data groups from 14literature sources,covering various pipe geometries,flow patterns,fluid properties and flow inclinations.The gas void fraction predicted by the framework developed in this work can be used as inputs to reliably model the hydraulic and thermal behaviors of two-phase pipe flows.
基金supported by the National Natural Science Foundation of China(Nos.51527805,11572220 and 41174109)
文摘Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with severely non-uniform local-velocity flow profiles and dispersed-phase concentration（of oil droplets） in oil-water two-phase flow,which makes it difficult to measure water holdup in oil wells.In this study,we use an ultrasonic method based on a transmission-type sensor in oil-water two-phase flow to measure water holdup in lowvelocity and high water-cut conditions.First,we optimize the excitation frequency of the ultrasonic sensor by calculating the sensitivity of the ultrasonic field using the finite element method for multiphysics coupling.Then we calculate the change trend of sound pressure level attenuation ratio with the increase in oil holdup to verify the feasibility of the employed diameter for the ultrasonic sensor.Based on the results,we then investigate the effects of oildroplet diameter and distribution on the ultrasonic field.To further understand the measurement characteristics of the ultrasonic sensor,we perform a flow loop test on vertical upward oilwater two-phase flow and measure the responses of the optimized ultrasonic sensor.The results show that the ultrasonic sensor yields poor resolution for a dispersed oil slug in water flow（D OS/W flow）,but the resolution is favorable for dispersed oil in water flow（D O/W flow） and very fine dispersed oil in water flow（VFD O/W flow）.This research demonstrates the potential application of a pulsed-transmission ultrasonic method for measuring the fraction of individual components in oil-water two-phase flow with a low mixture velocity and high water cut.
文摘The experiment was conducted to explore the hydrodynamics in a conical column with a height of 3.00 m, and a taper angle of 1.91°. Three regimes occur in succession with increasing superficial gas velocity. Overall gas holdup increases with an increase in gas velocity and a decrease in solid concentration or static slurry height. Axial solid holdup becomes more uniform with increasing gas velocity, while axial gas holdup decreases from the bottom to the top. Both dry and wet pressure drops across the gas distributor increase with an increase in superficial gas velocity.
文摘Cyclic total reflux(CTR) batch distillation is a promising mode of the process but lacking of appropriate modeling for the period of filling the reflux drum.A new dynamic modeling method for the simulation of CTR batch distillation is proposed in this work,in which the changes in column holdup and liquid flow rate during the filling of the drum,and the consequent change in valid number of theoretical plates are considered.The effect of drum holdup on operation time is investigated and the optimal drum holdup is obtained from the simulation.The dynamic modeling is compared to the conventional modeling without consideration of change in liquid flow rate. The experimental result shows that the present modeling is more reliable and more accurate,especially for the column with large liquid holdup.
基金Supported by the National Natural Science Foundation of China （No.20776121） and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20050530001）, and the Scientific Research Fund of Hunan Provincial Education Department （No.07C765）.
文摘The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracked with the results of motion equations. The two-way approach was performed to couple the interphase momentum exchange. The turbulent dispersion of bubbles with a size distribution was modeled using a stochastic tracking model, and the added mass force was involved to account for the effect of bubble acceleration on the surrounding fluid. The predicted gas holdup distribution showed that this method could give reasonable prediction comparable to the reported experimental data when the effect of turbulence was took into account in modification for drag coefficient.
文摘Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas dispersion regime in the hot sparged system is similar to the ambient gassed condition. The gas holdup under the elevated temperature and the ambient gassed operation is successfully correlated. With the same total gas flow rate and power input, the gas holdup in the hot sparged system (say near the boiling point) is only about half of that in the ambient system. The results imply that almost all existing hot sparged reactors have been designed on the basis of incorrect estimates of the gas holdup during operation.
基金the National Natural Science foundation of China (No. 29928005).
文摘Systematic experimental work was conducted to investigate the solid acceleration length in a 16m long circulating fluidized bed riser with fluid cracking catalyst particles over a wide range of operating conditions. A more feasible method is proposed to determine the acceleration length from the measured axial profiles of pressure gradient (or apparent solid holdup). With this new method and large amount of experimental data, a clear picture on the variation of the acceleration length with both solid circulating rate and superficial gas velocity is obtained.It is found that the acceleration length increases generally with increasing solid flow rate and/or decreasing gas velocity. However, the trend in variation of the acceleration length with operating conditions are quite different in different operation ranges. Reasonable explanations are suggested for the observed variation patterns of acceleration length.
文摘The new mode of operation for slop cut withdrawal in batch distillation, i.e., draining Column liquid holdup at the end of slop cut period, was proposed. And the stopping criterion for the operation was investigated, Experiments were carded out with isopropanol-n-propanol binary system and isopropanol-n-propanol-n-butanol ternary system in a distillation column with a liquid collector installed between the reboiler and the column section, Experimental results in a Ф 45mm batch column show that the proposed policy can overcome the flywheel effect caused by column liquid holdup and thus cut down operation time and energy consumption 31%-61%.
基金the National Program of Basic Research (No. G1999022103) the National Natural Science Foundation of China (No. 29936090).
文摘In this work, a mathematical model is established to describe the axial variation of the characteristic flow parameters (particle velocity, solid holdup and pressure gradient) in a downer. An empirical correlation is developed to estimate the particle velocity at the constant velocity section. Experimental investigations are made to validate the downer model. The model simulations have a good agreement with experimental data. Moreover, a formula is derived to predict the first acceleration section length and the whole acceleration section length.
基金Supported by the National Natural Science Foundation of China(21121064,21206002,21376016)
文摘The impeller configuration with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers, identified as PDT + 2CBY, was used in this study. The effect of the impeller diameter D, ranging from0.30 T to 0.40T(T as the tank diameter), on gas dispersion in a stirred tank of 0.48 m diameter was investigated by experimental and CFD simulation methods. Power consumption and total gas holdup were measured for the same impeller configuration PDT + 2CBY with four different D/T. Results show that with D/T increases from 0.30 to 0.40, the relative power demand(RPD) in a gas–liquid system decreases slightly. At low superficial gas velocity VSof 0.0078 m·s-1, the gas holdup increases evidently with the increase of D/T. However, at high superficial gas velocity, the system with D/T = 0.33 gets a good balance between the gas recirculation and liquid shearing rate, which resulted in the highest gas holdup among four different D/T. CFD simulation based on the two-fluid model along with the Population Balance Model(PBM) was used to investigate the effect of impeller diameter on the gas dispersion. The power consumption and total gas holdup predicted by CFD simulation were in reasonable agreement with the experimental data.
基金Gratitude is extended to Wei Luo,the corresponding author for the article.The authors would also like to acknowledge the support provided by the National Natural Science Fund Project(61572084)major national projects(2017ZX05030-005,2016ZX05056004-002,2016ZX05046004-003).
文摘Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inclined and even vertical sections of gas wells.To grasp the flow law of slug flow and guide engineering practice,the flow law of slug flow at various inclination angles(30°~90°)is studied by means of the combination of laboratory experiments(including high frequency pressure data acquisition system)and finite element numerical simulation.The results reveal that because of the delay of pressure variation at the corresponding position of pipeline resulting from gas expansion,the highest point of pressure change curve corresponds not to the highest point of liquid holdup curve(pressure change lags behind 0.125 s of liquid holdup change).Thus,the delay of pressure should be highlighted in predicting slug flow using pressure parameter change;otherwise the accuracy of prediction will be affected when slug flow occurs.It is generally known that liquid holdup and pressure drop are the major factors affecting the pressure variation and stable operation of pipelines.Accordingly,the results of finite element numerical simulation and Beggs-Brill model calculation are compared with those of laboratory experiments.The numerical simulation method is applicable to predicting the pressure drop of the pipeline,while the Beggs-Brill model is more suitable for predicting the liquid holdup variation of the pipeline.The research conclusion helps reveal the slug flow law,and it is of a scientific guiding implication to the prediction method of flow parameters under slug flow pattern in the process of gas well exploitation.
基金supported by the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT13026)the National 863 Program for Nuclear Fuel Cycling and Nuclear Safety Technology Project(No.2009AA050703)
文摘Annular centrifugal contactors (ACCs) have many advantages and are recognized as key solvent-extraction equipment for the future reprocessing of spent nuclear fuel (RSNF). To successfully design and operate ACCs for RSNF, it is necessary to understand the hydrodynamic characteristics of the extraction systems in ACCs. The phase ratio (R = Vaq/Vorg, A/O) and liquid holdup volume (V) of the ACC are important hydrodynamic characteristics. In this study, a liquid-fast-separation method was used to systematically investigate the effects of the operational and structural parameters on the V and R (A/O) of a φ20 ACC by using a 30%TBP/kerosene- HNO3 solution system. The results showed that the operational and structural parameters had different effects on the V and R (A/O) of the mixing and separating zones of the ACC, respectively. For the most frequently used structural parameters of the φ20 ACC, when the rotor speed was 3500 r/min, the total flow rate was 2.0 L/h, and the flow ratio (A/O) was 1, the liquid holdup volumes in the mixing zone and rotor were 8.03 and 14.0 mL, respectively, and the phase ratios (A/O) of the mixing zone and separating zone were 0.96 and 1.43, respectively.
基金Supported by the National Natural Science Foundation of China(50974095,41174109,61104148)the National Science and Technology Major Projects(2011ZX05020-006)
文摘This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.
文摘Using experimental data from a number of pulsed disc and doughnut solvent extraction columns, a unified correla- tion for the prediction of dispersed phase holdup that considers the effects of mass transfer is presented. Pulsed disc and doughnut solvent extraction columns （PDDC） have been used for a range of important applications such as ura- nium extraction and nuclear fuel recycling. Although the dispersed phase holdup in a PDDC has been presented by some researchers, there is still the need to develop a robust correlation that can predict the experimental dispersed phase holdup over a range of operating conditions including the effects of mass transfer direction. In this study, dis- persed phase holdup data from different literature sources for a PDDC were used to refit constants for the correlation presented by Kumar and Hartland lind. Eng. Chem. Res.,27 （1988）,131-138] which did not consider the effect of col- umn geometry. In order to incorporate the characteristic length of the PDDC （i.e. the plate spacing）, the unified cor- relation for holdup proposed by Kumar and Hartland based on data from eight different types of columns [Ind. Eng. Chem. Res.,34 （1995） 3925-3940] was refitted to the PDDC data. New constants have been presented for each hold- up correlation for a PDDC based on regression analysis using published holdup data from PDDCs that cover a range of onerating conditions and nhwical nronerties and consider the direction of mass transfer.
基金Supported by the National Natural Science Foundation of China (No. 29236122).
文摘A study on two-phase flow characteristics in a coalescence-dispersion pulsed-sieve-plate extraction column of 150mm in diameter was carried out with a working system of 30% tri-butyl-phosphate (TBP) (in kerosene)-nitric acid-water. The influence of operation conditions on the holdup of the dispersed phase was investigated. According to the analysis of the experimental data, there was a turning point on the curve of ln(Vs) versus ln(l-Φ) under certain pulse intensity. When the holdup is higher than the value at the turning point, the two-phase flow characteristics can be described with the modified Pratt's equation, otherwise a new relation in the form ofΦ=1/2.75uk(uc + 4ud) may be used, which is proposed by this study.
基金supported by the National Natural Science Foundation of China(52176040)Shandong Provincial Natural Science Foundation of China(ZR2018LE015)。
文摘Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumping turbine(6ITU))was conducted using computational fluid dynamics(CFD)and population balance model(PBM)(CFD-PBM)coupled model.The local bubble size was captured by particle image velocimetry(PIV)measurement.The gas holdup,bubble size distribution and gas–liquid interfacial area were explored at different conditions through numerical simulation.The results showed that the 4 mm bubbles accounted for the largest proportion of 33%at the gas flow rates Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1) for combined impeller of 6BT+6ITU,while the bubbles of 4.7 mm and 5.5 mm were the largest proportion for 6BT+6ITD combination,i.e.25%at Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1),respectively,which indicated that 6BT+6ITU could reduce bubble size effectively and promote gas dispersion.In addition,the gas holdup around impellers was increased obviously with the speed compared with gas flow rate.So it was concluded that 6ITU impeller could be more conductive to the bubble dispersion with more uniform bubble size,which embodied the advantages of 6BT+6ITU combination in gas–liquid mixing.
基金financially supported by the Joint Funds of the National Natural Science Foundation of China (Nos.U1402271, 51504058, and 51504059)
文摘The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas–liquid–solid phase reaction and the extraction rate of valuable metals. In this paper, a transparent quartz autoclave, a six blades disc turbine-type agitator, and a high-speed camera were used to investigate the gas holdup of the pressure leaching process. Furthermore, experiments determining the effects of agitation rate, temperature, and oxygen partial pressure on gas holdup were carried out. The results showed that when the agitation rate increased from 350 to 600 r/min, the gas holdup increased from 0.10% to 0.64%. When the temperature increased from 363 to 423 K, the gas holdup increased from 0.14% to 0.20%. When the oxygen partial pressure increased from 0.1 to 0.8 MPa, the gas holdup increased from 0.13% to 0.19%. A similar criteria relationship was established by Homogeneous Principle and Buckingham's theorem. Comprehensively, empirical equation of gas holdup was deduced on the basis of experimental data and the similarity theory, where the criterion equation was determined as ε=4.54×10^(-11)n^(3.65)T^(2.08)P_g^(0.18). It can be seen from the formula that agitation rate made the most important impact on gas holdup in the pressure leaching process using the mixed-flow agitator.
基金Supported by the National Natural Science Foundation of China(No.51478297)Program of Introducing Talents of Discipline(No.B13011)
文摘Based on the momentum conservation approach, a theoretical model was developed to predict the superficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular external-loop airlift reactor(AELAR)in the bubble flow and developing slug flow pattern. Experiments were performed by using tap-water and silicone oil with the viscosity of 2.0 mm^2/s(2cs-SiO)and 5.0 mm^2/s(5cs-SiO)as liquid phases. The effects of liquid viscosity and flow pattern on the AELAR performance were investigated. The predictions of the proposed model were in good agreement with the experimental results of the AELAR. In addition, the comparison of the experimental results shows that the proposed model has good accuracy and could be used to predict the gas holdup and liquid velocity of an AELAR operating in bubble and developing flow pattern.
