摘要:

Measurements have been carried out in the developing and fully developed regions of a free, axisymmetric, isothermal, air-water, bubbly jet. Three experiments have been conducted at a fixed jet-exit Reynolds number and gas superficial velocity using three different bubble injector assemblies producing bubbles of moderately different average sizes and size distributions. The volume fraction of the bubbly jet flow examined in this study is low and the resulting dispersed flow is dilute. A one-component Phase-Doppler Velocimetry system has been employed to measure bubble size and velocity non-intrusively. Visual data collected simultaneously with the light-scattering measurements were analyzed with the aid of image processing and used to verify the trends portrayed by the light-scattering measurements and to determine average bubble size. Our measurements show that, even in the dilute flow examined here, differences in initial bubble-size and size distribution can influence the RMS velocity fluctuations of the bubbles, particularly in the jet development region. The average bubble velocities are less sensitive. Evidence that the development pattern of the jet near the exit is affected by the presence of the bubbles is also presented. Near the exit of the jet, bubbles are shown to be ejected laterally outside the jet due to the significant lift force caused by the high velocity gradient in the axisymmetric shear layer. The observed sensitivity of the bubble flow to size-related parameters and initial conditions in this dilute case, indicates that discrepancies in previous measurements of dispersed, bubbly flows could be attributed to different size characteristics and/or initial conditions.

ISSN:0098-6445    

DOI:10.1080/00986449608936431

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Almost quantitative absorption of NO is achieved in nitric acid solutions containing sodium chlorite, sodium hypochlorite, or chlorine gas at temperatures up to 80°C and atmospheric pressure. Experiments are conducted by bubbling various mixtures of NO, NO2and O2, with the balance N2into varying volumes of scrubbing solutions up to one dm3. When scrubbing with acidic NaClO2, a greenish yellow color is observed in the solution when the gaseous mixture is bubbled into the liquid containing the oxidizing compound. The color is due to the presence of ClO2gas, an intermediate active in the oxidation of NO. Results in acidic NaClO or Cl2show similar results, except the intermediate that actually promotes the oxidation is HClO. These intermediates were identified spectroscopically. Material balances, determined using ion chromatography, show that the only anions in solution at NO breakthrough are NO3−and Cl−.

ISSN:0098-6445    

DOI:10.1080/00986449608936432

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The objective of this work is to assess the feasibility of adopting artificial neural networks (ANNs) in fault detection and diagnosis for batch and semi-batch processes. Although there is a large volume of related publications available, most of them used steady-state data to train ANNs and, as such, the task of fault diagnosis can only be implemented in continuous operations. Based upon the concept of analytical redundancy, the framework of a two-stage fault monitoring system is proposed in this paper. In the first stage, a hybrid ANN is adopted to predict the long-term dynamic behaviors of the output variables under normal condition. The occurrence of fault(s) can be detected by inspecting the residuals, i.e. the differences between the measured and the predicted values of outputs. A second feedforward neural network is then used for the purpose of differentiating the residual patterns caused by various faults. In addition to the fact the results of pilot tests are quite satisfactory, it is also demonstrated in our experimental studies that the proposed fault-monitoring system is capable of detecting and diagnosing faults that cannot be described by traditional mathematical models.

ISSN:0098-6445    

DOI:10.1080/00986449608936433

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The feasibility of using a cobalt-molybdenum (Co-Mo) sulfide catalyst that was prepared from a commercial Co-Mo oxide catalyst for the production of elemental sulfur from hydrogen sulfide (H2S) and carbon dioxide (CO2) in a packed bed catalytic reactor was studied. It was demonstrated that the desired sulfide catalyst could be prepared by first reducing, then sulphiding the corresponding oxide. The results showed that the prepared catalyst was capable of producing elemental sulfur from the thermal decomposition of H2S in the presence of CO2over a temperature range of 465–700°C and at atmospheric pressure. A specific rate coefficient was calculated as well as the Arrhenius parameters for the non-equilibrated reaction. The H2S decomposition reaction was found to be a second order reaction and have an activation energy of 114.4kJ/mol(27.3kcal/mol).

ISSN:0098-6445    

DOI:10.1080/00986449608936434

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The permeabilities of CH4, CO2, CH3OH, H2O, O2, and CO through films of Kapton® polyimide were measured at temperatures of 50, 100, 150, 200, and 250°C and pressures below 1 atm. Apparent activation energies for the permeation of the pure components ranged from 31.6kJ mol−1for CH4to nearly 0 for H2O under the conditions studied. The ideal permselectivity for methanol relative to methane decreased from over 100 to under 10 as the temperature was increased from 50 to 250°C.

ISSN:0098-6445    

DOI:10.1080/00986449608936435

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An adaptive optimization algorithm using backpropogation neural network model for dynamic identification is developed. The algorithm is applied to maximize the cellular productivity of a continuous culture of baker's yeast. The robustness of the algorithm is demonstrated in determining and maintaining the optimal dilution rate of the continuous bioreactor in presence of disturbances in environmental conditions and microbial culture characteristics. The simulation results show that a significant reduction in time required to reach optimal operating levels can be achieved using neural network model compared with the traditional dynamic linear input-output model. The extension of the algorithm for multivariable adaptive optimization of continuous bioreactor is briefly discussed.

ISSN:0098-6445    

DOI:10.1080/00986449608936436

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A simple model based on an energy balance which takes into account the friction losses at the gas-liquid interface and the slip velocity of single bubble is used to simulate the gas holdup in bubble columns containing Newtonian and non-Newtonian liquids which circulate in both laminar and turbulent flows. Experimental data available from the literature for bubble columns up to 7 m height and 1 m diameter with water and glycerol as Newtonian liquids and different solutions of CMC in a wide range of concentrations as non-Newtonian liquids are simulated with good agreement despite the simplifications made to describe the gas liquid flow regimes. Most of the differences between experimental and calculated gas holdup are justified on the basis of the simplifying assumptions.

ISSN:0098-6445    

DOI:10.1080/00986449608936437

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

On-line concentration measurements from an isothermal semi-batch system, i.e. the liquidphase acetoacetylation of pyrrole with diketene, are used for identification of a kinetic model. An integrated expert system, containing coupled estimation procedures and statistical analysis tools as well as a kinetic model data bank, chooses the most suitable structure for the kinetic model and subsequently identifies model parameters. With the increased availability of data during the run, refinements or structural changes in the kinetic model are performed automatically and parameter estimates are updated. A recently developed short-cut procedure (the Modified Integral transformation Procedure, MIP, Maria and Rippin, 1995, 1996; Maria, 1995), is compared against classical direct methods. Interactive use of a kinetic model-data bank through a numerical transfer of information strategy allows adaption of the mechanism-based kinetic model structure. Multiple nonlinear state estimators of the Extended Kalman Filter (EKF) type are operated in parallel, while the MIP/kinetic data-bank provides information for switching between the EKFs and concerning mechanism and model structure. This on-line use of parallel direct (short-cut) estimation procedures is particularly suitable for real-time process supervision, control and optimisation purposes.

ISSN:0098-6445    

DOI:10.1080/00986449608936438

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Experiments were carried out to determine the effect of the dispersed phase concentration,.φ, on the Sauter mean drop diameter of xylene in water in a mechanically agitated vessel. In the course of the experiments, the rheology of the dispersions was also measured. It was found that the viscosity of the dispersion exhibited strong viscous non-Newtonian characteristics for dispersed phase concentrations greater than approximately 50% by volume. The increase in the apparent viscosity of the dispersion with increasing dispersed phase concentration changed the flow condition in the tank from turbulent regime to transitional and laminar flow regime. The Sauter mean drop diameter measured as a function of the dispersed phase was successfully interpreted in terms of a turbulent eddy-drop breakage mechanism for φ < 50% and by a boundary layer drop breakage model for φ > 50% by volume.

ISSN:0098-6445    

DOI:10.1080/00986449608936439

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The combining of the two process steps comminution and chemical reaction is realized in a newly developed apparatus, the so-called reaction-mill. It is an up to 450°C heatable vibration-mill, that is resistant to pressures up to 2 MPa and that has a gas inlet and outlet for running heterogeneous chemical reactions during the process of comminution. The possible accelerations of the vibration-mill exceed up to 65 g and relative amplitudes of maximum 0.14 are adjustable. The advantage of the combination of the two process steps is the utilization of the effects of comminution exceeding the changes in the dispersity of the solid. The examined heterogeneous non-catalytic gas-solid reaction is the conversion of metallurgical grade (MG) silicon with gaseous hydrogen chloride to give trichlorosilane and silicontetrachloride. The examinations of the combined hydrochlorination and comminution have shown, that the induction periods in the starting phase of the reaction, carried out singularly, can be reduced to a minimum. Furthermore it could be noticed, that the lower temperature limit, which is necessary to start the reaction, could be lowered from 300°C to 100°C and that the selectivity of the reaction products is influenced by the mechanical energy. On one hand the effects are explained by the changes in the dispersity of the solid during comminution and on the other hand by a mechanical activation of the MG silicon.

ISSN:0098-6445    

DOI:10.1080/00986449608936440

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor