Destruction of organic contaminants in water by ozonation is a gas-liquid process which involves ozone mass transfer and fast irreversible chemical reactions. Ozonation reactor design and process optimizing require th...Destruction of organic contaminants in water by ozonation is a gas-liquid process which involves ozone mass transfer and fast irreversible chemical reactions. Ozonation reactor design and process optimizing require the modeling of the gas-liquid interactions within the reactor. In this paper a theoretical model combining the fluid dynamic and reaction kinetic parameters is proposed for predicting the destruction rates of organic pollutants in a semi-batch stirred-tank reactor by ozonation. A simple expression for the enhancement factor as our previous work has been applied to evaluate the chemical mass transfer coefficient in ozone absorption. 2,4-dichlorophenol (2,4-DCP) and 2,6-DCP or their mixture are chosen as the model compounds for simulating, and the predicted DCP concentrations are compared with some measured data.展开更多
A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated fro...A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated from the point of hybrid systems.The proposed scheme makes full use of the modeling power of mixed logical dy- namical(MLD)systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system,and takes advantage of the good control quality of model predictive control(MPC) to design a controller.Thus,this approach avoids oscillation during switching between sub-systems,helps to relieve shaking in transition,and augments the stability robustness of the whole system,and finally achieves optimal(i.e. fast and smooth)transition between operating points.The simulation results demonstrate that the presented ap- proach has a satisfactory performance.展开更多
Continuous Stirred Tank Reactors (CSTR) are used ubiquitously in chemical process industry for mixing, reactions and crystallizations. The purpose of this research is to study the effect of solute concentration (sodiu...Continuous Stirred Tank Reactors (CSTR) are used ubiquitously in chemical process industry for mixing, reactions and crystallizations. The purpose of this research is to study the effect of solute concentration (sodium chloride) on the stirrer speed in a CSTR. The experimental method used in this research is the stop watch and beaker method. The behavior pattern of the fluid in a CSTR can be experimentally verified as an alternative to the mathematical model. The tracer experiments were carried out. The effect of different parameters such as stirring speed, concentration at a steady time interval was analyzed. Experimental data obtained at 0.6 M and 160 rpm gave a curve that is in close agreement to that of theoretical or mathematical model. In other words, the results obtained at a concentration of 0.6 M and 160 rpm are in close agreement with that of early researchers. The paper is divided into five main sections: the first section immediately after the abstract is the introductory section that is basically a review of literature;the second section takes care of the materials and methods;the third section is the experimental procedure and this section takes the shut-down procedure and data processing into consideration;the fourth section is the discussion of experimental results and the last section is the conclusion of the paper.展开更多
Catastrophe theory is a new branch of mathematics regarding the discontinuous phenomena in nature. It classifies the critical points according to the potential function and studies discontinuity near them. Generally s...Catastrophe theory is a new branch of mathematics regarding the discontinuous phenomena in nature. It classifies the critical points according to the potential function and studies discontinuity near them. Generally speaking, the catastrophe is mainly elementary catastrophes. There are seven elementary catastrophes according to Thom’s deducing, namely, fold, cusp, swallowtail,butterfly, elliptic umbilic, hyperbolic umbilic and parabolic umbilic.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 d...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 sarme 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
A study was carried out to evaluate the treatment efficiency of modified model of septic tank(ST)for the treatment of domestic wastewater.The objective was to explore the possibility of increasing the removal efficien...A study was carried out to evaluate the treatment efficiency of modified model of septic tank(ST)for the treatment of domestic wastewater.The objective was to explore the possibility of increasing the removal efficiency,at household level,thereby reducing cost and treatment burden on city level treatment plants.For this purpose,a bench scale model of ST was prepared and operated continuously for 78 days at different detention times i.e.,48,24 and 12 h and at two reactor temperatures viz.15°C and 25°C.Domestic wastewater was fed to the bench scale ST without pre-settling.Research was conducted under two different arrangements.Firstly,by installing baffles in the bench scale ST(called Run-1 setup),and secondly by installing perforated plates between the baffles(called Run-2 setup).Results demonstrated that Run-2 setup is better than Run-1 setup.Temperature significantly affects the efficiency.Detention time of 24 h was found feasible.Run-2 setup demonstrated a percentage BOD removal of 45%with effluent BOD of 113 mg·L^(-1)at 15°C and 85%removal with effluent BOD of 31 mg·L^(-1)at 25°C.It is concluded that if a modified design of ST using Run-2 setup is provided at household level,the effluent coming out of the house will meet the National Environmental Quality Standards(NEQS)when reactor temperature is close to 25°C.Development authorities are suggested to change their by-laws and make modified ST mandatory for all households.This may significantly reduce the cost and footprint of city level wastewater treatment plants being planned.展开更多
文摘Destruction of organic contaminants in water by ozonation is a gas-liquid process which involves ozone mass transfer and fast irreversible chemical reactions. Ozonation reactor design and process optimizing require the modeling of the gas-liquid interactions within the reactor. In this paper a theoretical model combining the fluid dynamic and reaction kinetic parameters is proposed for predicting the destruction rates of organic pollutants in a semi-batch stirred-tank reactor by ozonation. A simple expression for the enhancement factor as our previous work has been applied to evaluate the chemical mass transfer coefficient in ozone absorption. 2,4-dichlorophenol (2,4-DCP) and 2,6-DCP or their mixture are chosen as the model compounds for simulating, and the predicted DCP concentrations are compared with some measured data.
基金Supported by the National Natural Science Foundation of China （No.60404018） and the State Key Development Program for Basic Research of China （No.2002CB312200）.
文摘A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated from the point of hybrid systems.The proposed scheme makes full use of the modeling power of mixed logical dy- namical(MLD)systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system,and takes advantage of the good control quality of model predictive control(MPC) to design a controller.Thus,this approach avoids oscillation during switching between sub-systems,helps to relieve shaking in transition,and augments the stability robustness of the whole system,and finally achieves optimal(i.e. fast and smooth)transition between operating points.The simulation results demonstrate that the presented ap- proach has a satisfactory performance.
文摘Continuous Stirred Tank Reactors (CSTR) are used ubiquitously in chemical process industry for mixing, reactions and crystallizations. The purpose of this research is to study the effect of solute concentration (sodium chloride) on the stirrer speed in a CSTR. The experimental method used in this research is the stop watch and beaker method. The behavior pattern of the fluid in a CSTR can be experimentally verified as an alternative to the mathematical model. The tracer experiments were carried out. The effect of different parameters such as stirring speed, concentration at a steady time interval was analyzed. Experimental data obtained at 0.6 M and 160 rpm gave a curve that is in close agreement to that of theoretical or mathematical model. In other words, the results obtained at a concentration of 0.6 M and 160 rpm are in close agreement with that of early researchers. The paper is divided into five main sections: the first section immediately after the abstract is the introductory section that is basically a review of literature;the second section takes care of the materials and methods;the third section is the experimental procedure and this section takes the shut-down procedure and data processing into consideration;the fourth section is the discussion of experimental results and the last section is the conclusion of the paper.
文摘Catastrophe theory is a new branch of mathematics regarding the discontinuous phenomena in nature. It classifies the critical points according to the potential function and studies discontinuity near them. Generally speaking, the catastrophe is mainly elementary catastrophes. There are seven elementary catastrophes according to Thom’s deducing, namely, fold, cusp, swallowtail,butterfly, elliptic umbilic, hyperbolic umbilic and parabolic umbilic.
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 sarme 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Funding by the University of Engineering&Technology,Lahore and support of lab staff
文摘A study was carried out to evaluate the treatment efficiency of modified model of septic tank(ST)for the treatment of domestic wastewater.The objective was to explore the possibility of increasing the removal efficiency,at household level,thereby reducing cost and treatment burden on city level treatment plants.For this purpose,a bench scale model of ST was prepared and operated continuously for 78 days at different detention times i.e.,48,24 and 12 h and at two reactor temperatures viz.15°C and 25°C.Domestic wastewater was fed to the bench scale ST without pre-settling.Research was conducted under two different arrangements.Firstly,by installing baffles in the bench scale ST(called Run-1 setup),and secondly by installing perforated plates between the baffles(called Run-2 setup).Results demonstrated that Run-2 setup is better than Run-1 setup.Temperature significantly affects the efficiency.Detention time of 24 h was found feasible.Run-2 setup demonstrated a percentage BOD removal of 45%with effluent BOD of 113 mg·L^(-1)at 15°C and 85%removal with effluent BOD of 31 mg·L^(-1)at 25°C.It is concluded that if a modified design of ST using Run-2 setup is provided at household level,the effluent coming out of the house will meet the National Environmental Quality Standards(NEQS)when reactor temperature is close to 25°C.Development authorities are suggested to change their by-laws and make modified ST mandatory for all households.This may significantly reduce the cost and footprint of city level wastewater treatment plants being planned.
