Year:2008 | Volume:42 | Issue:2 (112)|Papers Count:13

Iran is rich in mineral resources such as Celestine. On the basis of estimations, the capacity of mineral Celestine is over two million tons with 75-95% strontium sulfate purity. Strontium sulfate directly is not a major feed in industries, but it has a huge consumption in the form of strontium carbonate in many industries such as Color cathode Ray Tubes (CRT), pyrochemical process, ceramics, paint production, zinc purification process. Two conventional methods are used to produce strontium carbonate from strontium sulfate including direct reaction method and black ash method. In this work, the second method was analyzed and optimum condition of many operational condition and process parameters were determined. In the black ash method, firstly, mineral Celestine was reduced with coke at high temperature and strontium sulfate was reduced to strontium sulfide. In according to high solubility of sulfide in hot water, strontium sulfide was separated by leaching process. Then, strontium sulfide was reacted with sodium carbonate and strontium carbonate was produced. One isolated system was designed and prepared properly to analyze operational condition and process parameters including process temperature, residence time, feed particle size distribution and the effect of excess coke on conversion. The results showed that the reduction reaction occurred for temperature more than 800 °C. Also, smaller particle size led to better reaction conversion which is related to more surface provided. It was found that using more than 20% excess coke in the process, increases the efficiency by 4%. However, using more than 25% excess coke has not any positive effect on reaction process and conversion. Mass transfer resistance analysis showed that the most important resistance to reaction is diffusion throughout black ash layer which is controlling phase to reduction reaction. Thus, black ash layer is the most important parameter to control the rate of reaction. Finally, optimum condition is determined at temperature 1100°C, residence time 2 hours in reduction furnace, particle size distribution including coke and Celestine substance in 100 to 500 mesh, excess coke 25% with 75% reaction efficiency and high reliability and economical explanation.

Templated silica membrane is prepared on a-alumina annular as support by sol-gel polymerization rout, using cationic surfactant, cetyl pyridinium bromide (CPB), as template agent. Gas transport mechanisms through porous membranes as well as influences of main parameters in each mechanism have been reviewed individually. Membrane characteristics have been studied, using nitrogen absorption isotherms. The membrane surface morphology and cross sectional views have been presented using electron microscopy (SEM). Gas permeation properties through support as macro-porous membrane as well as silica membrane have been studied using experimental set up at the temperature range of 25-200oC and pressure range of 1-2bar. Permeation through a-alumina support increased with mean pressure and decreased with rising the temperature and results showed good agreement with viscous flow model, whereas permeation on silica templated membrane increased with temperature and showed no dependency with the mean pressure and followed configurational model. Values of permselectivity in binary mixtures of H2/CH4, H2/CO2 and CO2/CH4 were nearly pressure independent and very close to the values of separation factor, while both values were significantly higher than the Knudsen selectivities. Permeation measurements and membrane characterization were also carried out with pure silica membrane (with no template agent); also using polymerization rout and comparison between the two silica membranes have been done. It was found that the characteristics of the membrane as well as gas permeation properties are so affected by using template agent in preparation of the sol-gel silica membranes. Permeation of hydrogen and methane through the templated membrane were approximately twice of those for the non-templated membrane, while in the case of carbon dioxide it was vice versa; permeation of carbon dioxide increased in the non-templated membrane. The increase of permeation for hydrogen is due to the larger pore size of the templated membrane in comparison to the non-templated membrane. For methane in addition, this is due to more tendency of adsorption of methane on the templated membrane surface. Increase of carbon dioxide permeation through non-templated membrane is related to the control of permeation more from the molecular size dCO2< dCH4

In this investigation, the performance of a tower for absorption of sulphur dioxide gas into calcium carbonate solution has been studied. The trays had no downcomer and the tower itself was a scaled down pilot from industrial equipment. The industrial scale tower was used for clean up of 110000 m3/hr gas using 40 m3/hr alkaline solution. The study was composed of two parts. In the first section, hydraulic experiments were carried out and the pressure drops both for dry and wet trays were measured. The measured data were in good agreement with the correlations found in literature. In the second part of the study, the effect of operating parameters such as liquid flow rate, gas flow rate, alkaline solution concentration and sulphur dioxide concentration on the separation efficiency were investigated. Overall, it has been concluded that the separation of sulphur dioxide from air in this tower is always above 80% complete and the equipment offers fairly good efficiency in all the operating conditions considered. The main operating parameters were alkaline solution flow rate 500 – 2000 Lit/hr, alkaline solution concentration 0.1 – 3%, air/sulphur dioxide flow rate 0.15 – 0.4 m3/s and sulphur dioxide concentration in inlet air 100ppm.

In this paper, a batch hydrogenation reactor performance was modeled using a hydrodynamic and reaction sub-models. The reaction expressions were obtained from the information reported in literature. Experimental studies were conducted in order to generate the experimental data needed to validate the model. The comparison between the experimental data and model predictions seems quite satisfactory considering the hydrodynamic limitations and simplifications made on the reaction scheme. The results of this study could be considered as framework in developing new process equipment and also soya oil product design for new applications.

In this paper, the effect of flow rate on relative permeability curves was investigated in Iranian carbonate rocks. Core samples were prepared from outcrop of Asmari formation. The dynamic displacement experiments were performed at 2.55, 3.55, 4.55 and 5.55cc/hr during waterflooding and oilflooding. Relative permeabilities have been calculated with the Jones and Roszelle method and then the flow rate effect was investigated. The end-points and crossover saturations in the relative permeability curves indicate water wetness. In the waterflooding process, water relative permeability curves and end-point were not affected by the flow rate. It was observed that the oil curves vary with the flow rate, decreasing with its decrease. This variation vanishes at the middle saturations. Also, in the oilflooding, water relative permeabilities behave the same as it observed in waterflooding. It was not possible to find any trend in kro and end-point saturation with the flow rate. In contrast to sandstone, hysteresis was observed in both krw and kro curves. With increasing the flow rate, this phenomenon increases in water curves and decreases in oil curves.

Corn steep water as effluent which arrives in environment from starch processing industry has adverse effects on the environment and also large volume of fresh water is wasted. Corn step water is composed of high concentration of proteins, sugar, starch, vitamin and minerals, so it can be used as substrate for production of biological products. Hence, corn steep water concentration is important task both in environmental consideration and reuse of water. In this study, reverse osmosis membrane was used for concentration of steep water. The pilot consisted of two parts: pretreatment and reverse osmosis membrane. Pretreatment section contains ceramic filter with pore size of 50 micron and polypropylene filter which operates at 3-7 bar pressure. Surface area of reverse osmosis membrane was 1.11 m2 and operating pressure is 250 psi. Results showed that permeate flux is reduced exponentially over time and transmission through the polyamide membrane of calcium ions are less than sodium and potassium ions. For membrane cleaning, at first acid solution (pH= 3.5) and then soda solution (pH= 11-11.5) were used. For removal of microorganism like bacteria from polyamide membrane, acetic acid solution (4000ppm) or hydrogen peroxide (2000ppm) could be used. In general, reverse osmosis system with polyamide membrane is suitable process for concentration of steep water.

Cinnamon is the bark the cinnamomi cassia that exhibits many medical properties such as anti-cancer effect and anti-diabetic effect. Moreover, because of its antioxidant activity; it can be used in food industries. Many studies have already reported biological and chemical properties of the cinnamon extracted essential oil such as their antimicrobial, antifungal, antimosquito, free radical scavenging activity, antioxidant and antipathogenic properties. In this article, the result of treatments for extraction cinnamon oil with high quality or in the other words with higher percentage of cinnamon aldehyde in different thermal powers, different solvent ratios and different solvent pH have been done. For extraction of the essential oil, the water distillation in atmospheric pressure was used. All the essential oils were analyzed with GC and in the same conditions. According to the results the cinnamon oil is not sensitive to the heat power, the best solvent ratio to cinnamon bark is 25 to 1 and the best water pH is 4.11.

In this research, effect of bicomponent mixed surfactant was studied on drop interface coalescence phenomenon in ambient temperature. First basic chemical system was water and toluene and 0.01 gr of sodium dodecyle sulfate (SDS) and the second basic system was water and toluene and 0.01 gr of cethyl trimethy amonium bromide (CTAB). Various weight fractions of second surfactant including 2-heptanol (non-ionic) and aniline (cationic) added to each of these systems, respectively, in order to study the effect of mixed surfactant on coalescence time. It was shown that chemical systems including mixture of nonionic/anionic surfactant increased coalescence time. However, chemical systems including mixture of nonionic/cationic surfactant decreased coalescence time. If a mixture of anionic/cationic surfactant was considered, in terms of being weak or powerful cationic surfactant, coalescence time would have been decreased in the later and for mixture of ctionic/ctionic surfactant, coalescence time increased in small diameter and decreased in further diameter. Effect of sodium chloride (NaCl) on selected systems, including 40% CTAB in the basic system of water and toluene and SDS, 40% 2-heptanol in basic system of water and toluene and CTAB and 40% 2-heptanol in basic system of water and toluene and SDS was considered and it was shown that in general, coalescence time decreases

Mixing is an important unit operation in many chemical engineering applications. Nowadays, the jet mixing is widely used and going to be replaced with conventional mixers as a result of its simplicity, high performance and low costs. Jet mixing in tanks has been investigated by many researchers. However, no comprehensive literature review exists. In the present review detailed investigation of previous studies which are categorized into two general classes: experimental and simulation based on CFD techniques were stressed. The influence of geometrical and operational parameters is discussed and a general explanation about existing information was presented. In spite of some differences in data from various sources, general conclusions and guidelines for optimum design selection were obtained

Beginning with a discussion of energy and exergy analysis definitions, the presented study provides a descriptive mathematical model for energy and exergy analysis for a co-current gas cooling tower. For this purpose using conservation laws of mass, energy and momentum, the variation of temperature and enthalpy of gas and liquid streams are predicted along the tower length and are used in order to calculate the energy and exergy efficiencies. The model validity in prediction of gas and liquid characteristics changing along the tower length was examined against some operating data measured in a commercial cement plant. As a result, it was concluded that in spite of high energy efficiency, the cooling tower has a relatively low exergic efficiency which is because of thermodynamic irreversibilities and entropy production during heat and mass transfers. Also, the effect of some operating parameters including tower diameter, tower length, liquid drops size distribution and water flow rate was investigated on amount of exergy destruction. In all cases the results showed that the exergy of water does not completely absorbed by gas and a notable portion of the exergy is destructed. The result of these investigations may be employed to inform about the true energy potential caring by fluids.

In the present research work, the flexural modulus and strength of glass fiber-epoxy resin and carbon fiber-epoxy resin composites have been enhanced through fiber tension during curing of the polymeric resin. This study showed that the tension applied on the fibers increased the flexural modulus of the glass-epoxy composites up to 12% and the flexural strength up to 19%. The flexural modulus and strength of carbon-epoxy were also increased up to 25% and 13%, respectively. It was shown that the optimum fiber tension to obtain the maximum flexural properties depends on the fiber the composite is made of. The mechanism through which the improvement has been achieved was also presented.

In this contribution, two approaches are followed to predict the saturated liquid density of liquefied natural gas (LNG) mixtures. In one approach, 12 cubic equations of state (EoSs), comprising the popular Peng-Robinson (PR) and Redlich-Kwong-Soave (RKS), are employed to predict the saturated liquid density of 20 LNG mixtures. In the other approach, these EoS are used in conjunction with a recently developed correlation to predict the liquid density of the same LNG mixtures. This correlation takes the advantages of the EoSs functions and is remarkably accurate for LNG mixtures. The results for both approaches are presented and the best predicting methods are ranked. Also the liquid density of 3 gas condensate mixtures are predicted using 10 EoSs and the results are compared with experimental data. The method employed is discussed and the best EoSs are ranked. Our evaluation indicates that in general, the EoSs used in this study are not accurate enough for predicting the liquid density of gas condensate mixtures. The PR, Patel-Teja (PT) EoSs or one of their variant are recommended, however