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 Research subject:
The kinetics of xylene isomerization reaction on Mo-Pt @ZSM5 catalyst has not been investigated so far. In this research, the single reversible reaction of meta-xylene to para-xylene has been studied to model this process. Considering that the feed of the industrial unit has only small amounts of non-xylene compounds, it seems reasonable regardless of other reactions and the results of this research also confirm it.
Research approach:
The desired reaction was carried out in the gas phase and constant temperatures of 375 ^oC and 378 ^oC on Mo-Pt @ZSM5 catalyst. The feed is taken from an industrial unit. In each test, the temperature is considered constant. In this research, in order to obtain a simple model, only the reversible reaction of meta-xylene to para-xylene is considered. The forward speed constant is considered as an adjustable parameter, and the backward reaction speed constant is calculated from the (meta-xylene)-(para-xylene) equilibrium constant reported in the literature. Since other reactions are neglected, the total mole fraction of meta-xylene and para-xylene is assumed to be constant and equal to their sum in the feed, and the mole fraction of ortho-xylene is calculated from the (meta-xylene)-(ortho-xylene) equilibrium constant reported in the literature. Using the mass balance and performance equation of the packed column as well as Ergun's equation to estimate the pressure changes along the column, a suitable differential equation system was proposed in this research and solved numerically using the ode45 function in MATLAB.
Main results: both the experimental data and the simulation results with the Aspen HYSYS software show that the temperature has little effect on the obtained results in the investigated temperature range. The optimal value of the reaction rate constant of metaxylene to paraxylene for the forward reaction is 1340 cm³ of product per gram of catalyst per hour. For the reverse reaction, it is obtained from the equilibrium constant data in terms of temperature. The results and the proposed simple kinetic model give a good prediction of the experimental data.

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Thermal power plants consume near to 50 billion cubic meters of natural gas each year. So, optimization of power plants in terms of fuel consumption has become an important issue because of economic values and environmental effects. More than 50 percent of electricity is produced by CCGT and SCGT. In addition, CCGT efficiency is much higher than that of SCGT. So, in this paper these technologies are compared. The outcomes show benefits over costs ratio is affected by fuel price and utilization time. In subsidy prices (before energy price reform), B/C ratio of this substitution is less than one. If fuel price increases more than 500 Rials per cubic meter, using CCGT is more economical than SCGT for mid load power plants. If fuel prices are more than 1300 Rials per cubic meter, B/C ratio will be greater than one in any utilization time.  But this ratio is not greater than one for all cases. If all SCCTs are substituted with CCGTs, yearly natural gas consumption will reduce near to 3.5 billion cubic meters. These are 7% and 2.5% of yearly fuel consumption in power plants and total yearly natural gas consumption respectively. 

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Entering firms into a business can be a sign of economic dynamism, but to what extent do they enter according to optimal size or converge to it? The answers are given in two approaches. In the first approach, a new- entrant enterprise adjusts its size by learning market and continues to its activity. In the second approach, the enterprise does not adjust its size and exits the market. In this regard, the study of size distribution of new enterprises in Iran’s textile industry is the main purpose of this research. We collect statistical data for new textile businesses during 1997-2005 from Statistical Center of Iran. We use nonparametric method and indicators of employment, output value and value-added for evaluation of the size distribution. The results indicate that the employment size distribution follows an active learning model and does not adapt itself with market conditions. Regarding output value and value-added, the textile businesses follow a passive learning model and converge to the Lognormal distribution. The inability of firms in convergence by employment and their ability in convergence by output and value added criteria are some signs of a rigid labor market in Iran. According to these findings, reconsidering the labor law in order to making it more flexible is essential.

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Due to increasing concerns on environmental problems in current era, this study assesses the eco-efficiency of oil refineries. The oil refineries play essential role in the national economy in one hand, and cause environmental pollution due to high fossil fuel consumption and Co2 emissions in the other hand. Eco-efficiency is calculated using Windeap software, DEA output-oriented method, and inclusion of undesirable outputs. The results suggest that Bandar Abbas Oil Refining Company is the most efficient refinery over the 2003-2009, and growth rates of refineries eco-efficiency are positive. The results of Tobit regression show that fuel oil and gasoil have negative effects on the eco-efficiency, however natural gas, refinery gases, and liquefied petroleum gas (LPG) have positive effects on the eco-efficiency. On the other hand, if a refinery refines crude oil slightly more than nominal capacity rate, refinery eco-efficiency will be further decreased.