Iranian Journal of Chemistry and Chemical Engineering
Year:2013 | Volume:32 | Issue:4|Papers Count:12

H-Point Standard Addition Method (HPSAM) was applied for the simultaneous determination of V (V) and Fe (III). The method is based on the complex formation of V (V) and Fe (III) with chromazurol S (CAS) in acidic media and in the presence of cetyltrimethylammonium bromide (CTAB) as a micellizing agent. Acidic media and the presence of a micellar system improve selectivity and sensitivity. Fe (III) and V (V) could be determined simultaneously in the range of 0.1-2 and 0.2-2 mg / mL, respectively, and with the ratio 1:20 to 10:1 Fe (III)/ V (V) in the mixed samples. The proposed method was successfully applied to the simultaneous determination of Fe (III) and V (V) in tap, river, saliva and plasma samples.

1, 8-Dioxo-decahydroacridines have been synthesized by the three-component reaction of aromatic aldehydes, aromatic amines (or ammonium acetate), and dimedone in the presence of sulfonic acid functionalized nanoporous silica (SBA-Pr-SO3H) under solvent-free conditions. Excellent yields, short reaction times, mild reaction conditions, and easy work-up procedures are advantages of this green method.

Recovery of gold and other valuable metals from electronic scrap involves a complex metallurgical flow sheet and requires state-of-the-art recovery technologies that are available in large-scale, integrated smelter and refinery operations. At the end of their use, electronic and other electrical product scrap offer an important recycling potential for the secondary supply of gold and silver into the market. With gold concentrations reaching 200-250 g/t for computer circuit boards, this scrap is an ‘urban mine’ that is significantly richer in gold than the sources of the primary ores today. This paper gives methods of gold and silver recovery from printed circular board. The methods of purification are given and they separate gold from the impurities (tin, copper and nickel). The obtained gold and silver have 99.99% quality.

The kinetics of catalyst deactivation and coke formation during dehydrogenation of propane over supported Pt–based catalysts and, in particular, the effect of alkali metal promoters on catalyst activity and stability were studied. The analysis of propane conversion data showed that there is an optimum level of alkali metal promoter loading for both catalyst activity and stability. A model based on individual site poisoning was proposed for coke deposition kinetics. The model showed fair fits for coke formation data with time on stream. While the rate constant of coke formation was slightly affected by loading of Na as the neutralizing promoter, the ultimate coke amount was strongly dependent on the Na loading. It was found that coke formation sites should be different from active sites for the main reaction.

Alkaline hydrolysis of ethyl acetate is essentially an irreversible and second order reaction. Industrial importance of the reaction product, sodium acetate, necessitate for process improvement in terms of maximum conversion and economical usage of raw materials. Statistical design of experiments was utilized to enhance conversion in both batch and plug flow reactors. A full two level factorial design was used to screen out insignificant factors through analysis of variance followed by examining the significant factors in face-centered central composite design. Reaction conversion in plug flow reactor was investigated, and experimental results after analysis were compared with batch reactor. The experimental data of both the reactors was fitted to develop second order model. Furthermore, graphical residual analysis was used to validate the model. The initial concentration of sodium hydroxide and ethyl acetate for the hydrolysis reaction in both the reactors were reported to be the significant factors. The maximum conversion of 96% was achieved for a residence/reaction time of five minutes at optimum initial concentrations of sodium hydroxide (0.01mol/L) and ethyl acetate (0.07mol/L) in batch and plug flow reactor.

In this work, we studied the effect of carboxylic acid on the rheological properties of a high-alumina cement mortar (CH45) produced by the Algerian firm REFRACTAL. The investigated properties are setting time, water consumption, electrical conductivity, pH, density and the compressive strength. The results show a setting time of about 200 min for the acid free, 180 min with 0.1% of carboxylic acid and 18 hours with 2% of this acid. A significant reduction in water consumption was noticed. The water/cement ratio of the acid free-mortar is reduced from 0.24 to 0.16 with 2% acid. The rheological investigations carried out on the mortar-water mixtures with and without carboxylic acid show a Newtonian behavior. The setting of hydrated mortar-water with acid mixtures shows an increase in the apparent density leading to an improvement of the compressive strength.

A moment equations method was performed to study the Reversible chain Transfer Catalyzed Polymerization (RTCP) of styrene in 80oC. To do this, a kinetic scheme containing conventional free radical polymerization reactions and equilibrium reactions of RTCP was assumed. After obtaining mass balance equations, three moment equations were defined for free and dormant radicals and dead chains. Monomer conversion, catalyst and cocatalyst concentrations, molecular weights and polydispersity index profiles were achieved for two different systems and compared with the simulation results of Goto et al. and also with the experimental results of this work. These systems have had different reaction rate constants for equilibrium reactions of RTCP. The results showed the pseudo-linear increase of conversion and molecular weight versus time while a small PDI values were obtained for system 1 while the final PDI value of system 2 was high. Calculating average error of results compared to experimental and simulation results of Goto et al. showed a good agreement of modeling results with others and confirm the accuracy of results obtained in this work.

In this paper, optimization and control of a tubular reactor for thermal bulk post-polymerization of styrene have been investigated. By using the reactor mathematical model, static and dynamic simulations are carried out. Based on an objective function including polymer conversion and polydispersity, reactor optimal temperature profile has been obtained. In the absence of model mismatch, desired product characteristic can also be obtained by applying the corresponding reactor wall or jacket temperature profile. To achieve this temperature trajectory, reactor jacket is divided into three zones and jacket inlet temperatures are used as manipulated variables. Effectiveness of the proposed approach has been demonstrated through computer simulation. Furthermore for a special case of model mismatch, a method has been proposed which results in a near optimal profile.

Computational Fluid Dynamics (CFD) is a computational technology that enables researchers to study the dynamics of things that flow. By using CFD, it is possible to build a computational model that represents a system under study. It not only predicts fluid flow behavior, but also the transfer of heat, mass, phase change, chemical reaction, mechanical movement, and stress or deformation of related solid. In this study, hydrodynamics behavior of a laboratorial fluidized bed dryer containing carrot cubes as well as heat transfer in the dryer was simulated using CFD. In addition, to understand the energy utilization the system was optimized using the Taguchi technique. Simulations were planned based on L9 orthogonal array of Taguchi, and they were conducted at inlet air temperatures 50, 60 and 70oC, bed depths 3, 6 and 9 cm and carrot cube dimensions 4, 7 and 10 mm. Results show that cube size and bed depth have the maximum and minimum contribution on the energy utilization ratio, respectively. According to the results inlet air temperature 70oC, cube size 4mm and bed depth 9cm were obtained as optimum conditions. Finally, a verification test was performed to confirm the validity of the used statistical method.

Complex heat transfer phenomena (including unsteady state conduction, convection and solidification processes) occur in steel belt conveyer sulfur granulating method. Numerical simulation of this technique is performed via a comprehensive and multifaceted one dimensional model. Since the air situated between the adjacent sulfur pastilles is essentially stagnant, therefore, the surface temperatures of neighboring pastilles are actually the same during cooling process and the radial heat transfer can be entirely ignored. Knowing this issue, the axial heat flow is the only remaining mechanism of heat transfer and the one dimensional model would be valid. After solving the partial differential equation of the model, the effects of various operating conditions (such as ambient air temperature, inlet cooling water flow rate and its temperature, initial temperature of the liquid sulfur droplet and steel belt conveyer speed) are studied on the performance of the entire granulation process. According to results, with increasing the cooling water flow rate and steel belt conveyer speed, solidification rate of the liquid sulfur droplet is increased. Furthermore, the solidification process of the sulfur droplet occurs more rapidly when the ambient air temperature, initial liquid sulfur temperature and inlet water temperature are reduced. To the best our knowledge, simulation of steel belt conveyer sulfur granulating process has not been addressed previously.

The impact of installing process control systems can be expected in terms of performance improvements through reduced operating costs. Since these installations impose considerable capital expenditure, the profitability of the new systems should be economically justified. Controlled variable trend was reconstructed by a combination of simple waves, which provided a means to simulate the effect of installing a control system (feedback) by removing disturbance waves with high periods (> one cycle per hour). A method was proposed to evaluate the impact of installing a control system either by a reduction of difference between concentrate target quality and operating quality (i.e., bias reduction) or by reduction of scatter of product quality (i.e., variance reduction). Installing automatic control systems not only reduces operating costs, but also may increase revenue from washed coal sales by maintaining plant performance on designed or desired target. It was found that if an appropriate feedback control system is used at the flotation circuit of the Zarand coal washing plant, the variance of concentrate ash content could be decreased from the current value of 0.38 to 0.06. Based on the predicted metallurgical improvement, the payback time of installing a conventional control system for the flotation circuit of the Zarand plant size with the approximate cost of $1,000,000 was found to be 2 years.

Obtaining samples that represent original fluid of reservoirs optimizes reservoirs management. The optimized management increases recovery. Also, selecting and performing proper Improved Oil Recovery (IOR) or Enhance Oil Recovery (EOR) programs depend on collecting representative samples. Achieving accurate compositions of original in-situ fluid prevents overdesigning surface facilities. Representative samples cannot be collected from wells which are perforated at the gas / oil contact and are producing non-equilibrium gas. In some cases, samples must be or are collected, when gas coning occurs. There is no standard method for determining accurate original compositions in this situation. We want to discover a method that can estimate original in-situ compositions when gas coning is happened for the first time. Real fluid properties of Iranian oil reservoirs are imported to a synthetic reservoir model that is constructed by a compositional simulator for this purpose. Sampling is performed in the model and methods of determining original in-situ fluid compositions are modeled by detailed Equation of State (EOS) characterization in the new scheme. In the result an accurate method is found. In this new approach gas coning is not a limitation in sampling even it is a benefit.