Iranian Journal of Chemistry and Chemical Engineering
Volume:27 Issue: 3, May-Jun 2008

Methoxy poly(ethylene glycol) (mPEG) with molecular mass of 5 kDa activated with succinimidyl carbonate and cyanuric chloride, separately was covalently attached to human red blood cells (RBCs). Inhibition of agglutination by blood-type specific antisera (anti-D) was employed to evaluate the effect of the polymer coating. The remaining single cells after incubation with anti-D sera were counted using a simple hemocytometer (Improved Neubauer Ruling). The extent of surface coating was evaluated by addition of FITC labeled-anti-D to the cells and recording the fluorescence intensity ratio of FITC-anti-D bound cells of the PEG-RBCs versus control (uncoated) RBCs. The morphology of RBCs was evaluated by scanning electron microscopy (SEM). The effect of polymer coating, based on the immunological response of RBCs, using two kinds of activated mPEG, at optimum conditions of PEGylation was compared. It was found that succinimidyl carbonate at its optimum condition (pH=8.7, temperature =14C and reaction time =60 min) is more effective than cyanuric chloride at its optimum condition (pH=8.7, temperature =14 C and reaction time =30 min) for RBC coating with mPEG.

This paper presents a methodology for design of instrumentation sensor networks in non-linear chemical plants. The method utilizes a robust extended Kalman filter approach to provide an efficient dynamic data reconciliation. A weighted objective function has been introduced to enable the designer to incorporate each individual process variable with its own operational importance. To enhance the evaluation accuracy of the weighted objective function, a true relative standard deviation measure has been employed in the presented formulation. A Genetic Algorithm (GA) has been used to solve the resulting constrained optimization problem due to cost-optimal and performance-optimal design objectives. The proposed method has been tested on a non-linear continuous-stirred tank reactor (CSTR) benchmark plant, illustrating its effective design capabilities.

pH control is a challenging problem due to its highly nonlinear nature. In this paper the performances of two different adaptive global linearizing controllers (GLC) are compared. Least squares technique has been used for identifying the titration curve. The first controller is a standard GLC based on material balances of each species. For implementation of this controller a nonlinear state estimator is used. Some modifications are proposed to avoid the singularity of the observer gain. The second controller is designed based on the reduced state equation. Through computer simulations, it has been shown that the performances of the second GLC is superior and it is more robust to process model mismatch. It should be also noted that the design of reduced state-based GLC is much easier and dose not need observer for implementation.

Alumina-supported Cs3[Re(C2O4)3] precursor has been synthesized for preparation of Re-Cs/-Al2O3 catalyst. Cs3[Re(C2O4)3] has been prepared from the reaction of ReCl3 with H2C2O4.2H2O and CsCl in water. The complex has been characterized by elemental analysis and various spectroscopy techniques such as FT-IR, UV-Vis and 13C-NMR. The complex was supported on γ-Al2O3 by column chromatography. Cs3[Re(C2O4)3]/Al2O3 was calcined at 600 °C for 6 h. Characterization of both precursor and calcined catalyst were carried out using XRD, BET specific surface area and thermal analysis methods (TGA/DSC).

The direct sulfation of three high purity Iranian limestones and one precipitated calcium carbonate from different sources, containing more than 97 % CaCO3, were studied in a specially designed fixed bed reactor under atmospheric pressure, in the presence of excess CO2 to prevent decomposition of CaCO3. Experiments were carried out over a range of particle sizes from 1.6-2.5 m at four temperatures (750, 800, 850, 900 °C), and SO2 concentration of 2400 ppm. The particle size and temperature showed a dominant influence on the variation of conversion with time. The results of experiments show that the Shrinking Unreacted Core Model can be used to predict the behavior of sulfation of limestone. This simple model reveals that the reaction rate is the controlling step. The parameter of model, chemical rate constant (Ks), was obtained as: Ks = 0.1 exp (-6.2/RT) cm/s. Model predictions are in good agreement with expeimental data.

In this study, gas evolution in a vertical electrochemical cell is investigated numerically with a modified two-fluid model. The mathematical model involves solution of separate transport equation for the gas and liquid phases with an allowance to inter-phase transfer of mass and momentum. The governing equations are discreted via the finite volume technique and then are solved by the SIMPLE algorithm in both the natural and forced convection states. In order to increase the accuracy of calculations, the power-law scheme is employed to approximate the convection-diffusion terms. Void fraction distribution of chlorine gas and velocity of both the gas and liquid phases are calculated. Also the effect of current density, electrolyte flow rate and space between the electrodes on the gas release are investigated. To verify this model, numerical simulations of a bubble-driven flow caused by the bottom injection of gas into a liquid bath is conducted. Comparisons between the predictions and the literature numerical datas illustrate that the predicted results satisfactorily agree with data available in the literature for both the liquid and gas phases.

In the present paper Electrical Conductivity (EC) of Colloidal Gas Aphron (CGA) suspensions was measured for anionic and cationic surfactants (Sodium Dodecyl Sulfate (SDS) and Tetradecyl Trimethyl Ammonium Bromide (TTAB)). Experiments were made for different concentrations of SDS (6, 8.1, 10 mM) and TTAB (2, 3.51, 5 mM). CGA drainage behavior was observed and measured using 1 liter measuring cylinder while recording EC. Studying the results, CGA drainage process was observed as four-phase mechanism, instead of three conventional phases. Regardless of surfactant concentration and type, the drainage process is divided in to absorption, macroscopic, bubble, and microscopic phases. Drainage rate did not change at the end of bubble phase, with the maximum value at the end of absorption phase. Results showed that electrical conductivity is a more sensitive property for studying CGA characterization.

Steel slags are the by products of steel industries, which forms during reduction process of iron melting. The chemical composition of it changes depending to the melting procedure. Its mineralogical composition also varies based on the cooling procedure. Two different types of steel slag were used as absorbing bed for various concentrations of Pb2+ ions in the form of lead chloride, and the concentrations of lead ions were measured in the effluent by atomic absorption spectroscopy. When Electric Arc Furnace slag (EAFS) which is a basic crystalline slag was used in the presence of various concentrations of Pb2+, ranging from 2mg/lit up to 10 mg/lit. The concentration of lead ions dramatically decreased in the first thirty 30 minute and the remaining ions were absorbed up to 48 hours that the reaction was continuing but with slower rate. Almost the same thing happened when granulated blast furnace slag (GBFS) which is also a basic slag but in the amorphous mineralogical form, was used as the absorbing bed. The extent of ion removal from the solution was much lower compared to EAFS. Based on the results of this study, both types of slags can be used as industrial filters for reduction of lead ions from industrial waste waters.

Petroleum contamination of soil is a serious problem throughout the oil producer countries. Vegetation may play an important role in the biodegradation of toxic organic chemicals in soil. For petroleum compounds, the presence of rhizosphere micro flora may accelerate biodegradation of the contaminants. In a greenhouse study, petroleum contaminated soil were treated using phytoremediation. The C/N ratios and microbial populations were assessed in the beginning and the end of trials. The results showed that Puccinellia distance could tolerate the harsh condition of the soils. As MPN increases, C/N ratios decrease among trials. N, as a nutrient, had effects on both microbial populations and decreasing of organic carbon. Among six C/N ratios, organic carbon content of soil was lower at the end of the study in the vegetated pots compared with the non-vegetated ones. For the most part, the presence of plants enhanced the dissipation of the contamination. Our findings show that in level of 12.9 g crude oil per kg of dry soil we have critical point and for successful pyhtoremediation operation pollution must be below this amount. Microbial activity in loam texture had greater numbers and seedling pots had better efficiency in comparison with planting seed pots.

In present paper, dynamic behavior and control of a fluidized bed reactor for polyethylene production has been considered. A double active sites model for Ziegler-Natta catalysts is used for simulation of polymerization reaction. Hydrodynamic behavior of the bed is modeled using a two phase model including bubble and emulsion phases in which bubble phase has plug flow pattern with differentially variable velocity and size through the bed and emulsion phase has the CSTR flow pattern. The reactor model is validated using industrial data. Conventional PID controllers with anti-windup are considered for control purposes. It has been shown that the control system has satisfactory performances either for setpoint tracking or load rejection. To improve the performance of the control system for load rejection the cascade control strategy has been considered.

The experimental study and modeling of gravity drainage during Water Alternative Gas Injection, WAG process, in carbonate rock for one of the Iranian off-shore reservoir at lab-scale were carried out. The mechanism of gravity drainage during the WAG process, and its contribution to the oil recovery in the fractured carbonate reservoirs were also studied. In the WAG process alternatively gas is injected during the process and gravity drainage could be happened. Changes in the block dimensions, rock properties, oil properties, gas properties, and fractures properties and their effect on the amount of oil recovered during the gravity drainage mechanism were studied. It would be worth mentioning that Methane, as major constituent of natural gas, was used as injection fluids within the experiments. Also carbonate rock was used as block sample in the physical model within the experiments. The results obtained from the experiments were compared with those obtained from the simulation and the comparison confirmed fair agreement between the results. It was found out that from 1 to 6 percent of oil can be recovered by gravity drainage during WAG process

Abstract: Waste heat recovery is very important, because not only it reduces the expenditure of heat generation, but also it is of high priority in environmental consideration, such as reduction in greenhouse gases. One of the devices is used in waste heat recovery is heat pipe heat exchanger. An experimental research has been carried out to investigate the hydrodynamic and thermal performance of a gas- liquid thermosyphon heat exchanger THE in a pilot plant. The ε –NTU method has been used. The pressure drop has been calculated across tube bundle of the thermosyphon heat exchanger. Its module is composed of 6rows and 15columns copper pipes with aluminum plate fins with dimensions of 130cm height, 47cm width and 20cm depth. The tubes have been filled by water with filling ratio of 30%, 50% and 70%. The density and thickness of fins are 300 fin/m and 0.4mm, respectively. The configuration of tubes is in-line with 30mm pitch. The results show that as the ratio of Ce/Cc raises the amount of heat transfer increases. The effectiveness of heat pipe heat exchanger remains constant as the temperature of hot stream rises, but the amount of heat transfer increases. Filling ratio in normal region (30-70%) has no effects on experimental results. A new correlation for thermosyphon heat exchanger with individual finned tubes and in-line geometry has been proposed for calculating pressure drop across tube bank of a THE. The error in pressure drop for 40 experimental points in the new correlation is less than %15. This indicates that the new correlation possesses an acceptable accuracy predicting pressure drop.

Adsorbed natural gas has various advantages and is relatively more economical than liquefaction and compression. Carbon nanotubes can be introduced as a new candidate for natural gas storage. In this study, adsorption of methane was firstly studied on the as-prepared multi-walled carbon nanotubes, and then chemical and physical treatment of MWCNTs was performed to enhance the methane adsorption. Treatment by acid washing and annealing with air improved purity, surface area and methane adsorption. The adsorption and equilibrium isotherm data of T-MWCNTSs, were measured by a static volumetric technique at different temperatures of 298, 291, 273 and 263 K and pressures up to 7 MPa. The maximum value of methane storage at normal temperature of 298 K was achieved to 2.81 mmole/g in our experiments. This amount of methane adsorption is equal to 108 v/v, meanwhile the target value of the adsorbed natural gas is 120 v/v to become as the accepted material for ANG process. The isosteric heat of adsorption of T-MWCTs was determined in the studied range of pressures and temperatures. The results revealed an energetically heterogeneous surface in methane adsorption. Furthermore, different isotherm models were fitted on the experimental adsorption data and the model parameters were correlated. Within the different studied isotherms, Sips equation provided best fitting to the experimental data.

Waste heat recovery is very important, because not only it reduces the expenditure of heat generation, but also it is of high priority in environmental consideration, such as reduction in greenhouse gases. One of the devices is used in waste heat recovery is heat pipe heat exchanger. An experimental research has been carried out to investigate the hydrodynamic and thermal performance of a gas- liquid thermosyphon heat exchanger in a pilot plant. The ε-NTU method has been used. The pressure drop has been calculated across tube bundle of the thermosyphon heat exchanger. Its module is composed of 6 and 15 copper pipes with aluminum plate fins with dimensions of 130 cm, 47 cm and 20 cm. The tubes have been filled by water with filling ratio of 30 %, 50 % and 70 %. The density and thickness of fins are 300 fin/m and 0.4 mm, respectively. The configuration of tubes is in-line with 30 mm pitch. The results show that as the ratio of Ce/Cc raises the amount of heat transfer increases. The effectiveness of heat pipe heat exchanger remains constant as the temperature of hot stream rises, but the amount of heat transfer increases. Filling ratio in normal region (30-70 %) has no effects on experimental results. A new correlation for thermosyphon heat exchanger with individual finned tubes and in-line geometry has been proposed for calculating pressure drop across tube bank of a. The error in pressure drop for 40 experimental points in the new correlation is less than 15 %. This indicates that the new correlation possesses an acceptable accuracy predicting pressure drop

Agaricus bisporus and Agaricus bitorquis are among most favorite mushrooms of the world. Mineral contents, proximate composition and fatty acid profile of these mushrooms were determined for evaluation of their dietary value. Na, K and Li contents were high, while Cr, Cu, Pb, Co, Zn, Mn and Ni concentrations were low in both Agaricus bisporus and Agaricus bitorquis. Proximate analysis showed that both mushrooms have sufficient quantity of protein, lipids, carbohydrates and cellulose. Gas chromatographic analysis of fatty acid methyl esters revealed that linoleic acid (44.19 %) and oleic acid (40.13 %) were the dominant fatty acids in Agaricus bisporus and Agaricus bitorquis respectively.