دوماهنامه مهندسی شیمی ایران
پیاپی 27 (فروردین و اردیبهشت 86)

Cooling is one of the primary needs of each building in summer that usually meets by mechanical chillers. Cooling storage systems can be used as an efficient way for peak shaving of electrical energy consumption.In this article, the principles of cooling load estimation and design of an ice storage system is described, and a case study calculation is made for building no. 1 of engineering college of Isfahan university.The results of calculations showed that by use of cooling storage systems, the capacity of chiller can be decreased and the fixed capital cost of this system is less than traditional chillers.

Nowadays, with worldwide increasing demands of the high qualitative gasoline, it is necessary to establish the new naphtha reforming units and develop the traditional units to the high efficiency processes. So in this article, first history and overall process scheme was expressed then reactions, catalysts and mechanisms are explained. Further by comparing between operating and economical condition in regular trading processes, such as fixed bed, moving bed and hybrid systems, advantage and disadvantage for each one is presented. It is concluded that in spite of higher capital investment of moving bed processes, the product has higher quality and quantity in comparison to the fixed bed reactors. At the same yield capacity of these processes, the product cost from moving beds is twice more than the fixed beds whereas the total investment is only 40% higher than the other.

Adsorption process is one of important separation processes for recovery of organic acids with ion exchange resins. Generally ion-exchange resins are made on matrix non soluble long polymer, usually polystyrene. The results have indicated among strongly anionic resins, Amberlite IRA-400 is suitable for recovery of Lactic Acid. In the present work, efficiency of lactic acid recovery in 10/40 chromatographic column in 45 °C was studied. Also the effect of volumetric flow rate for washing of resin with distilled water and normal sulfuric acid and the recovery efficiency was obtained. Generally the results have indicated in the best volumetric flow rate, the recovery efficiency was obtained almost 96%.

In present study two different mathematical models consisting of differential equations for energy, momentum and material exchange are developed in order to predict the performance of a fluidized bed dryer. In order to approach a realistic model the existing of surface and internal moisture is considered too. The validity of the models was examined by comparing the results of models by existing data reported in the literature [1]. The predicted final temperature of particles, and final moisture content are in good agreement with the experimental data. Finally the effects of various operating parameters including: gas velocity, gas temperature and gas humidity on final moisture content of the product were investigated.

Currently more than half of used energy in world is supplied by non-renewable energy of fossil fuels. Recovery of energy, optimum energy consumption, recognition and utilization of new energy sources are very important due to economical and environmental protection aspects. In order to reduce costs of gas transfer system from gas refineries to consumption units, the gas flow pressure is increased via compressors. Prior to consumption of gas, its pressure is reduced in gas pressure regulating stations by pressure reduction valves. This form of pressure reduction wastes a considerable amount of energy that contain in high pressure gas flow. For recovery of the pressurized gas flow energy, instead of pressure reduction valves, expansion turbines are implemented. These systems not only reduce the gas flow pressure, but also convert the pressure energy into rotational energy. This energy in the next stage is converted to electrical one via an electric generator. Technology for conversion of gas flow pressure to energy is known as PIP. In this paper, this method is introduced and operation of two pressure reduction systems of the valve and expansion turbine is evaluated and compared. Also based on simulation, the produced electrical power for different range of gas flow rates and pressure is evaluated. By considering efficiency of 96% for power generator, 1600 $/kW as capital cost for gas pressure regulating stations, and 0.12 $/kWh for price of generated electrical power, the capital cost return time is estimated about 2 years.

The work involves experimentation on drying of three natural product (tomato, potato and garlic) in a tray dryer covering different variables like power of heater and air flow velocity. The data are modeled using mathematical models. The drying curves obtained were processed to find the most convenient one among 7 different mathematical models. The empirical constants and coefficient were determined. MRAE were used to determine the consistency of the fit. These values are among 0.953% and 11.95%.

In this paper elimination of Volatile organic compounds(VOC) from polluted air using Platina catalyst has been studied. Toluene which is known as one of the major pollutant has been selected from variety range of volatile compounds in order to conduct the experiment. The process of oxidation of volatile compounds over the Platina catalyst is directly affected by factors such as flow rate of polluted air, concentration of initial Toluene, flow rate of Ozone, temperature and the area occupied by the Platina catalyst. in this study the flow rate of polluted air has been assumed 100 cc/min and the ozone flow rate is 50cc/min.the concentration of the Toluene is assumed constant and also the effect of temperature and concentration of ozone over the level of elimination of toluene has been studied. the results propose that elimination of toluene using ozone is more than the time when the ozone is not used. Considering that the perfect elimination of the ozone in lower temperature is achievable, elimination of volatile compound in existence of ozone due to its high oxidation ability has a considerable importance in terms of the process and being more economical. Also using these method air pollutants will be removed in lower temperature.

In this work, with a simple freeze dryer has been reported drying curve of roses. Powdered dry ice which has -78.5 ºC sublimation temperature, has been used for freezing cycles and vacuum oven as freeze drying chamber. During the process, the pressure of chamber has been kept below the triple point of water (< 0.01 atm). Primary and secondary stages of drying for two samples of roses in drying curve have been specified. The results show in constant drying condition, sample weight affects the drying curve and in constant chamber pressure, increasing of temperature decreases the drying time.

Based on process combinations, kind of technology and product quality, the energy cousumplian is will be evaluated. Energy flow, water and raw material have big share on production cost, thus minimized cost depend on this factor. Although additional refining process cause more energy usage but optimal equipments operation decrease losses. Total industrial energy consumption in Iran is about 30% of total final energy and about 80% of industrial energy consumption allot to large industrial work places. In pulp and paper industries several processes are applied that lead to these manufacture are categorized in severe energy consumption industries as in North America it was ranked third among all industries in energy usage. Here after paper production process studying, Iran energy consumption was compared with others and base on this, kind of production process, stochastic and historical production and finally energy save opportunity, loss placements and pollution reduction are stated.