Nashrieh Shimi va Mohandesi Shimi Iran
Year:2008 | Volume:27 | Issue:1|Papers Count:16

The purpose of this paper is to introduce a new process for hydrolysis of methyl acetate (M.A). Methyl acetate is produced as a by-product in chemical plants such as, polyvinyl alcohol and terephthalic acid. Hydrolysis of M.A results in producing the value added products i.e. acetic acid and methanol. The process eliminates the needs to a complicated design as well as high investment and operating costs in comparison to the reactive distillation process. In fact in this experimental study the fixed bed reactor is used as the reflux drum of the distillation column. In the present research, the experiments have been conducted in an experimental set up and different operating parameters such as the mole ratio of water to M.A. in the feed (Rm), reactor temperature (Tr) and volumetric flow rate of feed to catalyst volume (LHSV) have been investigated. The experimental results are in accordance with the simulated process results obtained by Hysys.

The present paper discusses development of a high current density (2 A.cm-2) electrodissolution system of Rh metal that allows the solubilisation of rhodium fragments, powder and pieces of foils and wires in the presence of hydrochloric. A cylindrical, graphite centrifugal electrodissolution mini-reactor was prepared. Feeding 12N hydrochloric acid into the system operated at 85oC and 3000 rpm rotation speed and applying a 30 amperes ac-current.

This study is about the non-uniform electric field (Dielectrophoretic) with sinusoidal current for splitting of colloidal particles from wastewater of Alborz Carpet factory in Babolsar. Then this method was compared to the other methods. The study is considered the effect of temperature, time, and voltage on the separation efficiency of colloidal particles. The results show that the non-uniform electric field method can be one of efficient methods for removal of colloidal particles from wastewater. Turbidity was measured by turbidity meter (FNU=Formazine Nephelometry unit) in the present study. Using the non-uniform electric field with 7500-volt intensity and 50-hertz frequency and 40 degree centigrade temperature, the splitting is done 96%.

Optimum operating conditions of a single - step synthesis of dimethyl ether (DME) from synthesis gas has been determined. The bifunctional catalyst has been prepared by physical mixing of a commercial methanol catalyst (KMT, Russia) and a dehydration catalyst (H-MF-90) and has been characterized by XRD, XRF and BET techniques. Catalytic synthesis of dimethyl ether from synthesis gas was evaluated in agitated slurry micro reactor at different ranges of operating conditions which have been determined by experimental design according to Taguachi algorithm. The range of operating conditions were chosen as follows: H2 /CO mole ratio in feed varying from 0.26 to 1.5, the pressure varying from 10 to 50 bar, the temperature varying from 200 to 240 °C. Nine experiments have been conducted with different operating conditions at fixed impeller speed equal to 1600 rpm and space velocity equal to 500 ml/gcat.h. By using the results of experiments, optimum conditions for direct synthesis of DME were predicted as follows: T= 2400C, P=33.3 Bar, H2 /CO=1.5 and weight ratio of methanol catalyst to dehydration catalyst equal to 3.

Addition small amounts of specific compound, which is called additives can to lubricating oils enhance wax crystallization in the oil and improve pour point of the lubricants. In this research effect of such compounds on the pour point were investigated. Results show addition of specific additive (in this research Dodecilpolymethacrylate and Tetra do decilpolymethacrylate) is improved pour point of the oil but the relation between pour point decrease and additive concentration is not linear. Also simultaneously effect of dilutant and additive was studied. Use of a dilutant and an additive simultaneously is more efficient than additive.

In present paper a new decomposition algorithm is introduced to reduce energy consumption. In this algorithm, some rules and assumptions are considered to minimize the costs of fluid transmission such as piping costs, associated pumping costs and the plant's complexity. The algorithm has a good flexibility to be applied for vast majority of industrial process plants. The algorithm is consisted of two steps. At first, by using the concept of zoning in grassroots design, the existing HENs divided into two or more primary substructures (sub-networks) with considering the limitations of fluid transmission. At primary substructures, each heat exchanger could be belonged to one or more substructures. The second step is to decrease the substructure components by applying plant's constrains such as operability, layout of components and heat exchanger's materials in each substructure. Eventually, the final substructures achieved, are independent and there is no heat transfer across the different substructures due to the limitation of the fluid transmission. The existence of path in each substructure is led to opportunities for heat recovery in retrofit design. Path analysis in each substructure is a beneficial tool to identify the streams which have capability to adapt process to process heat transfer. These streams may cross different substructure simultaneously. Each substructure could be modified by retrofit methods. Also, in this a new algorithm of retrofitting HENs which is useful when there is no process to process heat exchanger is introduced. The case-study which is chosen is Acetic Acid plant of FPC (Fanavaran Petrochemical Company). The HENs of FPC has been divided into substructures and each one has been retrofitted by use of new retrofit method.

In present paper two agricultural residues, rice hull, sawdust and a soil sample were examined as sorbents to remove heavy metals Pb(II), Cd(II), Cu(II), Zn(II) and Ni(II) from synthetic solutions. The sorbents were analyzed for some physico-chemical characteristics as CEC, surface area and elemental composition using ammonium acetate method, N2-BET and SEM-EDX respectively. The effect of initial pH and concentration of solutions, type of sorbents, equilibrium time and particle size of sorbents were studied in removal of heavy metals from metal solutions. The sorption experiments were carried out in 1:100 suspensions of sorbent to synthetic solutions. The sorption of the heavy metals from the synthetic solutions was increased with pH for all sorbents, significantly (p< 0.01). pH=5 was selected as the lowest pH with highest mean sorption. At this pH, among the heavy metals, Pb(II) and Cd(II) showed the highest sorption with the average of 0.87 and 0.77 mg/g and then Cu, Zn and Ni, respectively. The increase of metal concentration in the solution increased the sorption. The sorption isotherms of the natural sorbents and the soil sample were best described by the Freundlich model. The highest sorption capacity was observed for the soil sample, followed by the rice hull and the sawdust samples, respectively. The sorption of the heavy metals from the synthetic solutions was increased with increasing of shaking time. Shaking time of 60 minutes was considered as equilibrium time. Decreasing of sorbent particle size increased the sorption. The smallest diameter of particles (< 0.5 mm) showed the highest sorption capacity.

A study on the removal of sulfur components from gasoline by carbon nanotubes for use as support in catalysis was conducted in batch conditions. Kinetic data and equilibrium removal isotherms were obtained. The influence of different experimental parameters such as contact time, initial concentration of sulfur components, catalyst mass and temperature on the kinetics of sulfur components removal was studied. Results showed that the main parameters that played an important role in removal phenomena were initial sulfur components concentration and catalyst mass. The necessary time to reach equilibrium was between 7 and 11 hours depend on the initial concentration of sulfur components. We used differential and integral method for computing rate equation. Equation order that was computed from these two methods is 2.85 and there isn’t many difference is changing in different temperature. Temperature changes in the range of -2-40 °C (for solution with initial concentration of 1000 ppm, removal yield changed from 76 % to 81 %) increased removal of sulfur components. Sulfur components uptake of carbon nanotube catalyst supported was quantitatively evaluated using adsorption isotherms. Results indicate that the Longmuir model fits better with experimental data in comparison with Freundlich equation.

A batch extraction of an essential amino acid, Phenylalanine, from an aqueous solution of different concentrations by an Emulsion Liquid Membrane (ELM) was developed using D2EHPA as a cationic carrier, Span 80 as the surfactant, paraffin and kerosene as the diluents, and HCl as the internal electrolyte. All effective parameters such as pH of initial aqueous external phase, electrolyte concentration in aqueous internal phase, carrier and surfactant concentration in emulsion, volume ratio of the organic to aqueous internal phase (Roi), volume ratio of the W/O emulsion to aqueous external phase (Rew) and time were examined and optimized using Taguchi method which was the first time of optimizing such number of factors by Taguchi method in ELM process. Appling Taguchi method to analyze the experimental results, we obtained the effects and contribution of each of the factors on the extraction efficiency. The results obtained from the experiments illustrated that with a stable emulsion by optimizing all the effective parameters, a considerable amount of phenylalanine can be extracted in a short time with an acceptable ratio of swelling and breakage.

In this research, a systematic investigation was carried out to determine kinetics of HDS reaction of Iranian gas condensate using a commercial catalyst (Co-Mo/  g -Al2O3). In this way, process conditions were optimized. Experiments were carried out in a trickle bed micro reactor (10 cc catalyst) at 280-3400C, 40-50 bar, Liquid hourly space velocity (LHSV) of 1-5 h –1, H2/Oil ratio of 125 nl/l. Prior to the kinetics tests, by some basic tests, mass transfer effects on chemical reactions were evaluated, and it is found that pore diffusion and film diffusion resistances have a slight effect on the kinetics of chemical reaction, within the operating conditions. Hence, kinetics of HDS reaction was determined by using thiophene as a reference sulfur component, in the form of power low model. The results indicated that thiophene HDS reaction order in gas condensate feed was 1.3. Also, HDS reaction activation energy was determined to be 77.55 kj/mol. The results of this kinetics model and its simulation can use in optimization of HDS units process conditions and prediction of product specifications with new feeds and different process conditions. It is also useful for designing the reactor of new HDS plants.

Montmorillonite, layered silicates, are used widely for preparing polymer nanocomposites. In present paper, domestic clays containing montmorillonite mineral were used. Firstly, mines related to these types of soils were studied and then 20 types of samples were supplied from extractor companies. After optimizing purification conditions, the best clay was selected and then ion exchange process was carried out for synthesizing suitable organoclays. The organoclay, a coupling agent compound and polypropylene with different ratios were mixed and nanocomposite plates were fabricated. Finally, the properties of these nanocomposites were compared with that of a standard sample. Characterization techniques such as XRD, XRF, SEM, AFM, mechanical strength, HDT, impact strength were used in this work. The tensile strength, impact strength and HDT of the best prepared nanocomposite, containing 5 wt % organoclay and 10 wt % coupling agent compound, in comparison with polypropylene were improved to 24 %, 17 % and 55 % respectively.

During the electrolytic copper refinery, anodic copper is dissolved and deposited on the cathode. The copper anode slimes are made up of those components of anodes which are not soluble in the electrolyte. They contain gold, silver, selenium, tellurium and the other metals such as copper, lead, nickel and etc. There are several hydrometallurgical and pyrometallurgical methods to recover valuable elements. As a route, initially, copper is removed and returned back to the electrolysis process. Tellurium is cemented from leaching solution by copper powder as Cu2Te. In this research, at first, anode slimes were analyzed and then leached in sulphuric acid. Leach solution contained 103.6 ppm tellurium. Tellurium was cemented and the effects of time, temperature and amount of copper powder were considered on tellurium cementation. Suitable conditions of cementation of tellurium were as follow: Time: 90 minutes, temperature: 105 degrees centigrade and amount of copper powder: 3 times of stoichiometry amounts. In these conditions, the cementation of tellurium was around 90 percent.

As the temperature of oil transfer pipeline walls is reduced to cloud point, wax tends to deposit on internal side of tubes. Wax deposition may be prohibited by mechanical, chemical and thermal methods. As the period of oil recovery proceeds and volumetric flow of oil production decreases, the holding time of oil in pipe would increase, thereby wax deposition may increase. In this research using a designed dynamical set up, the extent of wax deposition was studied for four oil samples (B, C, D, E) provided from Iran reservoirs. The oil samples contain wax weight percent in range of 2-3 %. The result of studies, presents that the discrepancy between fluid temperature and pipe temperature is the most important factor influencing the extent of wax deposition. Increasing the volumetric flow of the fluid leads to expulsion the majority of wax from the fluid, but it decreases the tendency of deposition on pipe surface. The physical properties of the fluid exclusively could not evaluate the amount of deposition and wax deposition is affected by operational conditions too. The deposition issue is not excluded only to wax precipitation; rather the deposit has to be studied from general view considering overall oil constituents.

Considering improved heat transfer, uniformity of catalyst distribution and virtual elimination of diffusion limitations as the major advantages of fluidized beds, it seems preferable to employ such a reactor for reforming of natural gas. In this study, by considering the presented simulators and hydrodynamic structure of the fluidized beds, a simulation model is developed in order to predict the performance of the fluidized bed reactor of steam methane reforming in a complex process. The results obtained from the simulation of this model in Hysys 3.1 environment are compared with other models and experimental data. Better agreement is found between the model predictions and experimental data than the recent studies.