Iranian Journal of Chemical Engineering (IJChE)

Abstract Deposition of colloidal particles onto surfaces is usually assumed to follow the Derjaguin-Landau-Verwey-Overbeek (D.L.V.O.) theory for colloidal stability. In the work presented here the D.L.V.O theory is extended to include the case where the surface is electronically conducting. The effect of application of an electric field to the surfaces on the rate of deposition of 5.4 µm colloidal particles is simulated.

Abstract Prediction of particle removal efficiency in all kinds of dust collectors includes mathematical modeling of particle-laden flow. One of the main problems for such modeling is to find particle velocity distribution which can he predicted using a particle momentum balance equation. A common simple alternative is to use equilibrium or settling velocities. In this work, a comprehensive mathematical model for particle removal in double-stage electrostatic precipitators was developed. Analysing the results of this model shows that the equilibrium assumption can be considered as a reliable method for a Stokes number less than 0.001. Atm for a higher Stokes number, an explicit Eulerian method was developed for the evaluation of particle velocities explicitly. This method eliminates solving particle momentum balance equations which is a relatively time-consuming step in mathematical modeling of dust collectors. 

Abstract
In well fractured carbonate reservoirs the gas/oil gravity drainage from the gas-invaded zone Ls the dominating oil producing process. When the gravitational forces exceed the capillary forces, the matrix blocks, which are surrounded by gas, will release their oil. The results of our experimental works reveal that, depending on the interfacial tension, spreading coefficient, rock wettability, and surface roughness, there is a critical fracture aperture size, tjrk. Rock wettability, surface roughness and spreading coefficient play their rules in formation of oil droplets, while the maximum size of the droplet is controlled by the amount of surface tension. When the fracture aperture is more than tie, the continuity is via solid compressed spacers and/or oil film around them, which at actual reservoir conditions may he considered as non-effective capillary continuity. Whereas for the case that the fracture aperture is less than its critical value, the capillary continuity is mainly through liquid bridges, which due to their high transmissibility will result in an effective capillary continuity between blocks. Two new definitions for horizontal fracture capillary pressure based on the type of capillary continuity have been presented. The Laplace formula and pressure difference between the fracture gas and the matrix oil may be used for the calculation of fracture capillary pressure for non-effective and effective continuity, respectively. 

Abstract A study on coke deposition and coking inhibitors during naphtha pyrolysis was made in a jet stirred reactor system. This system is noted for its simple structure, easy alteration of operating parameters, small volumes of feedstock used for pyrolysis, high accuracy of coke formation measurements, and short operating cycle. It is also particularly suitable for identifring coking inhibitors over a wide range of conditions. The effect of the addition of CS2, DMS, DMDS and Disulfideoil in the naphtha feed was investigated. It was found that for a given concentration of sulfa. in the feed, the asymptotic coking rate decreases in the order: Dimethyl disulfide > Disulfideoil > Dimethyl sulfide > Carbon disulfide. Scanning electron microscope (SEM) was used for the microstructure of deposited coke and energy dispersive X-Ray spectroscopy (EDAX) for the surface elemental composition of coke formed on the surface of stainless steel coupons. It was found that in the presence of inhibitors, deposited coke has a porous structure and small amounts of Ni, Cr, and Fe elements. Based on our results, this paper aims to provide a closer insight into the coking problem in industrial steam crackers. 

Abstract In this paper, a simplified formulation for a compositional reservoir simulator is presented. These type of simulators are used when interphase mass transfer depends on phase composition as well as pressure. The procedure for solving compositional model equations is completely described. The Peng Robinson equation of state is used for preparing a compositional thermodynamic program for equilibrium calculation, property estimation and pseudo component determination. Another purpose of this paper is to prepare an experimental apparatus for the displacement of oil by gas injection. In each test, oil recovery as a function of injected pore volume was measured. The application of the developed simulator to simulate the results of the oil recovery from slim tube experiments is also presented. Finally, the model was run for a 2-D reservoir. Acceptable trends were obtained from the model predictions.

Abstract  In this paper, an affine neural model is used to model the unknown part of SISO processes with un-modeled actuator dynamics. It is assumed that a partially known first principlesbased model of the process, which is invertible with respect to the unknown part, is available. Using this available knowledge, I/O training data of the process, and affine neural networks, a serial gray-box model is generated which is suitable for applying feedback linearization. Hence, the resulting nonlinear controller works in a large operating region. The superiority of the gray-box over the black-box approach is investigated for a fermentor using the experimental data borrowed from the literature. Simulation results of our case study show that the proposed affzne gray-box method is superior to the conventional agfine black-box method and preserves extrapolation property.

Abstract The application of the Taguchi analysis to the experimental results of the extraction of gold (III) ions by a three-phase W/O/W emulsion liquid membrane system has been studied. Experiments were performed using alkaline aqueous sodium sulfite as the internal phase and LK-80 as a novel emulsifier for the first time in emulsion liquid membrane technology. The effects of various operational and compositional parameters were studied. Results showed that nearly all of the Au (III) ions in the aqueous phase were extracted in a few minutes. The analysis determined the effects and contribution of each of the parameters on the extraction efficiency, interaction between the parameters and also the optimum parameters to achieve the best extraction efficiency. The analysis showed that the pH of the external phase with a contribution of 65% is the highest, and the concentration of carrier with a contribution of 2% is the least effective in the final system response.