Iranian Journal of Chemistry and Chemical Engineering
Volume:26 Issue: 2, Mar-Apr 2007

Brass Ferrules have been used as packing in a laboratory- scale glass distillation column approaching pilot plant size because of their availability in all sizes and low cost. The available size range is such that these ferrules could also be used in industry and the results of this study could be scaled up. The performance of the new packing has been compared with the performance of glass packing, and has proven to be more satisfactory with lower HETPs (Height Equivalent to a Theoretical Plate). Three systems were studied in this work, namely, ethanol/water, 1-propanol/water, and 1-butanol/water and the HETP of the brass packing in these systems was experimentally measured. Pressure drop and flooding have been studied together in this work and a new relationship has been presented that relates efficiency in terms of HETP to pressure drop, a parameter that can be measured readily in any column or predicted.

The objective of this research is to find an economically attractive alternative method for hydrodesulfurization of petroleum fractions and to select a suitable adsorbent for this process. Deep desulfurization of transportation fuels (gasoline, diesel, and jet fuels) is being mandated by governments and is also needed for future fuel cell applications. However, it is extremely difficult and costly to achieve with current technology, which requires catalytic reactors operated at high pressure and temperature. Zeolites are a family of crystalline aluminosilicate minerals. About fifty natural zeolites are now known and more than one hundred and fifty have been synthesized. Clinoptilolite is a naturally occurring zeolite, formed by the diversification of volcanic ash in lake and marine waters millions of years ago. It is the most researched of all zeolites and is widely regarded as the most useful. It is an abundant natural zeolite. We show that Hg+2 and Ag+ clinoptilolite can adsorb sulfur compounds from commercial fuels selectively and with high capacities. The desulfurization of 83.60 % by Ag+ clinoptilolite at liquid to solid ratio of 50/100 gr.ml -1, 353 K, and flow rate of 3.0 ml.min-1 was obtained

The aim of this research is to develop a silica gel and alumina column chromatography for separation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) into two groups. This is achieved by optimizing the cut-off volume of eluting solvent and weight ratio of silica gel and alumina. In this process mixture of PAHs and PCBs divide in two groups and simultaneously other interferences like lipids and aliphatic compounds are removed. So the sample is prepared to be analyzed and quantified by HPLC. The main purpose of the research was to find a combination of sorbents for the column chromatography method that would permit the determination of many types of pollutants (PAHs, PCBs and aliphatic compounds) in a single run. Elution profiles for both the analytes and the interfering components were determined for several types of column chromatography sorbents (alumina, silica) and combination of them. The silica: alumina (5:5 g) column is suitable for the separation of PCBs and silica: alumina (5:10 g) is preferred for the separation of PAHs. The efficiency of the developed clean- up method was evaluated using real sediment sample.

Tabas mines in Iran have coal sources which are suitable for use in metallurgy industries as coking coal. But the high sulfur content of this coal imposes severe limitations on its utilization as the sulfur oxide gases evolved from the combustion of high sulfur coals result in acid rains and corrosion of equipments. In this work, attempts have been made to reduce sulfur from high sulfur coal of Tabas by froth flotation. Laboratory tests were carried out in order to investigate the influence of various collectors, frothers, pyrite depressants and their consumption dosages on ash and sulfur reduction of Tabas coal. The use of kerosene as a collector and pine oil as a frother has decreased ash and sulfur content of coal more than other collectors and frothers. Although use of sodium polyacrylic acid as a pyrite depressant improved the total recovery of coal concentrate but did not enhance the reduction of sulfur

Direct orthogonal signal correction(DOSC) and Savitzky-Golay filters (SGF) were applied as preprocessing methods on the original and first derivative absorbance data. Principle component regression (PCR), partial least squares (PLS) and iterative target transformation factor analysis (ITTFA), were used in spectrophotometric simultaneous determination of heavy divalent metal ions, lead, zinc, mercury and cadmium, using 4-(2-pyridylazo) resorcinol (PAR) as metallochromic indicator. The optimum values of the parameters for DOSC and SGF were obtained according to REP, R2 and RMSEP functions for calibration and prediction sets. The concentration for Hg2+, Pb2+, Zn2+ and Cd2+ ions in calibration set were varied between 0 - 12.24, 0 - 9.81, 0 - 0.87 and 0 - 3.96 ppm, respectively. The experimental calibration set was composed of 35 sample solutions and the 7 solutions as prediction set using a simple lattice (4,4) mixture design. The absorption spectra were recorded from 450 to 600 nm and absorbance data were autoscaled. The effect of pH on the sensitivity and selectivity was studied in the range of 1.00 - 11.00 and pH=7.50 was chosen according to net analyte signal (NAS) as a function of pH.

A neuro-fuzzy modeling tool (ANFIS) has been used to dynamically model cross flow ultrafiltration of milk. It aims to predict permeate flux and total hydraulic resistance as a function of transmembrane pressure, pH, temperature, fat, molecular weight cut off, and processing time. Dynamic modeling of ultrafiltration performance of colloidal systems (such as milk) is very important for designing of a new process and better understanding of the present process. Such processes show complex non-linear behavior due to unknown interactions between compounds of a colloidal system. In this paper, ANFIS, Multilayer Perceptron (MLP) and FIS were applied to compare results. The ANFIS approximation gave some advantage over the other methods. The results reveal that there is an excellent agreement between the tested (not used in training) and modeled data, with a good degree of accuracy. Furthermore, the trained ANFIS are capable of accurately capture the non-linear dynamics of milk ultrafiltration even for a new condition that has not been used in the training process (tested data). In addition, ANFIS and Multilayer Perceptron (MLP) are compared and the Matlab software was adopted to implement the method

Based on driving force for crystallization of one-component gas hydrate, in this report an expression for the supersaturation for crystallization of multicomponent gas hydrate is derived. Expressions for the supersaturation are obtained in isothermal and isobaric regimes. The results obtained are applied to the crystallization of hydrates of mixtures of methane plus ethane and can apply to other mixtures.

Calcium aluminates (CA) are the most important hydraulically setting cements used for preparing refractory castables, because they develop high strength at very early ages after placements. The anhydrous phases of this kind of cements are CA, CA2 and traces of C12A7 and alpha-alumina. The major hydraulic phase in all of the CA cements including ciment fondue is CA. Once hydrated, it starts to form the hexagonal crystals of CAH10 and C2AH8 that depending on the time and temperature of hydration converts to the cubic crystals of C3AH6 and AH3. The nature of the calcium aluminate hydrates, their morphology and the way in which they are broken down, play an important roles in determining the properties of fired cement. For this reason a series of investigations has been conducted on the hydration reactions of Secar 71, a commercial cement which can completely represents this type of cements, and hydration products were characterized by DTA, DSC, XRD and SEM. At 12 oC, the only hydration products were a gel phase, CAH10 and gibbsite, while the same hydrates were still predominant phases, C4ACH11 also formed as a result of carbonation of the pastes.

Gas injection into heavy oil reservoirs could result in high ultimate recovery of oil. Experimental studies showed that an application of a combined technology of Gas Assisted Gravity Drainage (GAGD) and Vapor Extraction (VAPEX) could increase final oil recovery of a candidate viscous oil reservoir. In this paper the results of laboratory investigation are presented, including Pressure-Volume-Temperature (PVT) studies, physical model experiments and simulation studies to evaluate the gas injection process for heavy oil reservoirs recovery. The study examined the effect of two different gases on viscosity reduction and oil swelling. Physical model tests were carried out to investigate the effect of gas injection on oil recovery. Another study (simulation model) predicted the performance of the reservoir under gas injection in a model. This simulation study was established on a sector of the reservoir

Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. These reactors have been studied based on Computational Fluid Dynamics (CFD) that can be used in the analysis, design and scale up of these reactors. Most of the researches done in this area are limited to single phase reactors, and a few remaining two phase flow investigations have been done based on MRF (Multi Reference Frame) and Snapshot approach. However, the MRF and snapshot approaches cannot be used in rigorous simulation of unsteady state problems. In order to simulate the unsteady state behavior of the multiphase stirred tank reactors we have used sliding mesh technique to solve the problem rigorously. In this work a 3D CFD model is used to investigate hydrodynamics of a fully baffled cylindrical stirred tank containing air-water in which air is sparged. The tank is equipped with a standard Rushton turbine impeller. This work has been done based on two fluid (Eulerian-Eulerian) model and finite volume method, along with standard k- model to address turbulent behavior of both phases. The results obtained for velocity field show a good agreement with the corresponding data published by researchers in this field for the same case. The effect of gas inlet velocity on the gas holds up distribution has been studied. According to the obtained results, there should be an optimum value for gas inlet velocity in order to achieve appropriate gas distribution in the liquid. The most important parameter affecting the optimum value is impeller rotational speed.

In general, the objective of distillation control is to maintain the desired products quality. In this paper, the performances of different one point control strategies for an aromatic distillation column have been compared through dynamic simulation. These methods are: a) Composition control using measured composition directly. This method sufferes from large sampling delay of measuring devices. b) Composition control by controlling the temperature of a specific tray. In this strategy, the composition-temperature relationship is used to find the temperature setpoint corresponding to the desired composition. Since composition-temperature relation depends on feed condition, an artificial neural network has been proposed which receives the feed specifications and provides the setpoint of the temperature control loop. c) Using temperature measurements for predicting the composition and controlling the composition based on predicted values of composition (inferential contol). Simulation results indicate that controlling the 8th tray temperature and using an artificial neural network for calculating corresponding tray temperature setpoint, has the best performance. Due to negligible pressure drop along the column, controlling the tray temperature difference does not improve the control loop performance.

In a novel dual bed reactor Fischer-Tropsch synthesis was studied by using two diffrent cobalt catalysts. An alkali-promoted cobalt catalyst was used in the first bed of a fixed-bed reactor followed by a Rutenuim promoted cobalt catalyst in the second bed. The activity, product selectivity and accelerated deactivation of the system were assessed and compared with a conventional single bed reactor system. The methane selectivity in the dual-bed reactor was about 18.9 % less compared to that of the single-bed reactor. The C5+ selectivity for the dual-bed reactor was 10.9 % higher than that of the single-bed reactor. Accelerated deactivation of the catalysts in the dual-bed reactor was 42 % lower than that of the single-bed reactor. It was revealed that the amount of catalysts activity recovery after regeneration at 400 oC in the dual-bed system is higher than that of the single-bed system.

The kinetics of molybdenite oxidation was studied by non-isothermal TGA-DTA with heating rate 5 ºC.min-1.The model-fitting kinetic approach applied to TGA data. The Coats-Redfern method used for model fitting. The popular model-fitting gives excellent fit for non-isothermal data in chemically controlled regime. The apparent activation energy was determined to be about 34.2 kcalmol -1 with pre-exponential factor about 108 sec-1 for extent of reaction less than 0.5

Reaction constants and heat release during thermophilic aerobic digestion of typical secondary and mixed sludges were determined. Maximum reaction constant, determined by measuring the amounts of biodegradable volatile suspended solids (bVSS) removed, occurred in the temperature range of 55-60 ºC. Measurement of heat releases were carried out, at the same range, by the aid of a temperature programmable logic controller (PLC). An amount equal to 16.2 KJ/g-cell was measured for secondary sludge digestion. The maximum amount of kinetic constant for secondary sludge (0.45 d –1) was observed at temperature of 55 ºC. Addition of primary sludge to secondary sludges decreased kinetic constants due to stimulate of biomass growth. Cell growth in mixed sludges provided an extra heat equal to 6.7 KJ/g-cell generated. However, it decreased the overall rate of heat release compared to the rate in the secondary sludge digestion