Journal of Chemical and Petroleum Engineering
Year:2010 | Volume:44 | Issue:1|Papers Count:10

This paper presents the results of an investigation on the effects of concentration of cations on activated sludge properties and membrane fouling in submerge membrane bioreactors. The working volume of the experimental setup was two liters. The cellulose acetate membrane was immersed in the bioreactor. The flocculability, settling properties and fouling propensity of activated sludge was measured in various concentrations of cations such as sodium, potassium, magnesium and calcium. Results showed that cations bind with biopolymers and induce flocculation in bioreactors. This phenomenon induced in divalent cations so that flocculability of activated sludge in presence of divalent cations was two-fold of flocculability of activated sludge. On the other hand, cations improve settle ability and dewatering properties of activated sludge and especially mitigated membrane fouling, for example, calcium reduced the membrane fouling intensity by 25% of the reference activated sludge.

The nondestructive techniques are applied to identify important data from the internal process of distillation towers, process towers, pressure vessels and etc. In recent, the gamma-ray scanning techniques as diagnostic tools for scanning of tray columns, packed columns, storage tanks, level measurement and density measurement of containing materials has been used widely. This paper has tried to model tray column failures. Also failures identification using real time analysis and scan profile interpretation has been investigated. This suggested model can be used before gamma ray scanning technique, calibration and adjustment of working conditions in industrial scale.

NaY zeolites with different framework Si/Al ratios were synthesized via hydrothermal technique. Structural characteristics of the synthesized zeolites were determined by using XRD, XRF, SEM, BET analyses. The effects of operating conditions of hydrothermal dealumination, i.e. time, temperature and partial pressure of water vapor on dealumination of the Y zeolites framework and their structure were investigated via XRD and BET analyses. According to the experiments, hydrothermal dealumination of the Y zeolite with Si/Al=1.69 was not successful while it was satisfactorily performed for the other one with Si/Al=2.44

Typical production objectives in distillation process require the delivery of products whose compositions meet certain specifications. The distillation control system, therefore, must hold product compositions as near the set points as possible in faces of upset. In this project, inferential model predictive control, that utilizes an artificial neural network estimator and model predictive controller, is developed for an industrial multicomponent distillation column. First, composition control by direct measuring composition is used. This method because of large sampling delay has a poor performance. The selection of the temperature measurement points is done for indirect control of the column. The use of temperature loop leads to an offset in the composition, due to the fact that the temperature set-point must be changed when feed disturbances occurred. An artificial neural network estimator is designed to estimate the product compositions from tray temperature measurements. A model predictive controller is used to control column composition based on composition estimates. The performance of the developed inferential model predictive control system is tested for set-point tracking and load rejection.

In this paper, we studied effect of different parameters including density, viscosity, interfacial tension and solute transfer concentration on phase inversion hold-up. The results showed that change in phase density ratio had no effect on phase inversion hold-up. It also disclosed that the phase viscosity ratio was the most effective parameter affecting phase inversion hold-up and each phase had tendency to increase dispersion by rising viscosity of that phase. When the proportion of dispersed phase viscosity to continuous phase viscosity was more than 1, phase inversion hold-up decreased as the interfacial tension increased or Vice versa. Also, increase in the solute transfer concentration by affecting phases physical properties and electrostatic interaction between drops and continuous phase resulted in increasing the tendency toward both types of inversion and.

Drop size distribution in a mixer-settler is an essential design parameter, as obtaining drop size distribution will result in optimum performance of equipment. In this paper for obtaining drop size, several experiments have been performed with a single stage horizontal mixer-settler. A video technique has been used in order to measure the drop size in the mixer-settler with the help of a digital camera. The present work examines the influence of an anionic surfactant concentration on the variation of drop sizes in the presence of solute. The results show that in low concentration of surfactant, a significant decrease in mean drop size is observed, but at high concentration, increasing of surfactant concentration doesn't change mean drop size more. For different concentration of surfactant, a new empirical correlation is derived for estimation of mean drop size. These correlations have a good agreement with experimental data.

The critical properties of a solute are required for modeling of the solubility by the equation of state. For many compounds, the critical properties are not available. So, group contribution method is utilized as a common method to estimate these properties. But, it leads to the consecutive errors in calculations of the solubility modeling. In this study, Soave-Redlish-Kowang (SRK) and Peng-Robinson equation of states with Huran-Vidal mixing rules were used for modeling of the solubility. A new method for evaluating of C2 (Huran-Vidal mixing rule parameter) is recommended as a function of temperature and pressure. For solubility modeling by semi-empirical correlation, the new forms of Chrastil and Mendez equations were used. Finally, the modeling of solubility for 20 compounds by these methods has been investigated. Results show that the AARD% for the models with semi-empirical equations (Charstil, Aguilera, Gordillo, Mendez, modified Charstil and modified Mendez) are 12.07, 11.71, 34.89, 19.89, 11.17 and 15.70 respectively, and for SRK, PR EOS are 14, 19.85 respectively.

In this study simulation and optimization of an industrial acetylene hydrogenation reactor was studied. Three well known kinetic models were used for a nearly similar catalyst to predict the industrial data. Due to the complexity of the reactions, none of the offered kinetic models could be considered as an exact kinetic model and it is necessary to determine the kinetic parameters. One of the best methods to determine the kinetic of a process is to simulate the process and then minimize the deviations between industrial data and calculated ones. Thus the hydrogenation reactor was simulated at the industrial operating conditions which were taken from an operational petrochemical plant and the optimum kinetic parameters were determined using optimization technique. Since such problem has many local optima, the genetic algorithm (GA) and simulated annealing (SA) methods were used to optimize the kinetic parameters of the three models. Due to the strong dependency of the GA performance on the GA condition, it was tried to investigate the effect of GA parameters on overall GA performance in detail. For this purpose, different GA parameters were used to solve the problem and results were discussed.

The aim of this paper is to study the local Nusselt number of the symmetrical liquid-liquid jets emitting from a nozzle. Equations obtained from theoretical works are arranged in the form of a computerized model. The validity of this model was tested by the data from an experimental paper [1]. After few adjustments the model predicted the experimental data with a reasonable accuracy. Making sure of the model acceptable operation the effects of changes of hydrodynamic and thermal parameters on local Nusselt number were investigated which eventually lead to an equation for predicting numerical values of local Nusselt number as a function of liquid jet length.