دوماهنامه مهندسی شیمی ایران
پیاپی 15 (فروردین و اردیبهشت 1384)

Nowadays, increasing the speed of construction works and applications such as repair of airways and highways have provided a basis for production and use of fast set and high early strength cements. In this paper, methods of producing fast set and high early strength cements are introduced. The parameters influencing cement setting and hardening including chemical and mineralogical composition, burning process, fineness of cement, and curing conditions are briefly studied. Methods discussed include those based on burning a raw mix of specific chemical composition to produce a given mineral composition and those based on preparation of multi-component mixtures. Portland-based fast set and high early strength cements could also be produced by controlling the fineness and mineralogical composition of Portland cement.

Natural gas as one of the most important energy sources is usually saturated with water when produced from the gas well. Water vapor increases the corrosive power of natural gas, especially in presence of sour gases. Of the various possible methods of drying the natural gas, using silica gel as an adsorbent is considered in this work because of its capability in providing very low dew points. The design procedure has been presented and analyzed here for four dehumidification columns that are used for dew point control of 260 MMSCFD of natural gas and the effect of various parameters has been investigated. A spreadsheet has also been presented that can be used for process simulation. The results of the hydraulic design procedure show an error of about 5 percent in adsorbent bed height and almost no error in the column internal diameter as compared with actual values.

The production of nanopowders is one the most noticeable applications of induction plasma. An aim of the work is to extend the thermal plasma technique to the synthesis of nanosize nitride based composite powders and to determine an influence of process parameters on characteristics of produced powders. The nanosize nitride –based composites are prepared by evaporation of coarse commercially available powders of chemical elements such as Mo, Cr, Ti, Zr and subsequent condensation of products into a inductively coupled nitrogen plasma(ICP(.

Gas cleaning the cement industry is an enormous task. The electrostatic precipitator is the appropriate opportunity to clean large mass fluxes of flue gas with appropriate efficiency and economy. In this research, causes of corrosion in electrostatic precipitator (ESP) and main stack of mazandaran cement factory were investigated. Calculation (determination of pH and corrosion rate) and experimental results (metallurgical tests) show that acid formation (sulfuric acid) is the main cause of corrosion.

In this contribution we overview the recent advances on OCM process to overcome process problems. From different problems of this process, low selectivity and yield, high temperature, and exothermic nature of reactions can be mentioned. By using different reactor type and configuration these problems can be reduced. Fluidized bed reactors, membrane reactors, and simulated moving bed chromatographic reactors are good substi tutes for conventional fixed-bed reactors. Fluidized bed rea-ctor suppresses the further oxidation of products by minimizing the oxygen contact time with methane and it can cope with the large amount of heat released by the highly exothermic OCM reactions. It also has the ability to be operated with continuous addition and withdrawn of catalyst from the reactor zone. Membrane reactor can prevent deep oxidation with adjusting oxygen flow to the reaction zone. By using simulated moving bed chromatographic reactors, the desired products will be separated from the mixture as soon as they are produced and unreacted methane can be recycled to reactor.

The object of this research is investigating different sorbents in order to determine their potentials in oil spills cleanup from sea water. Experiments were done about Bagasse with two different mesh and rice hull as natural sorbents and polypropylene non woven as a synthetic sorbent. Results show that polypropylenene non woven has the highest oil sorption capacity among sorbents that are under study and this sorbent is capable to sorb 7-9 grams of different types of oils per each gram of its weight. Bagasse with mesh 18-45 can sorb 5-6 grams of different types of oils per each gram of its weight. The sorption capacities of bagasse with mesh 14-18 and rice hull are comaparable and less than two former sorbents.

Application of Computational Fluid Dynamics (CFD) technique for the prediction and investigation of flow and heat transfer in fluidized beds has been developed recently. In this paper the governing equations on fluidized beds has been reviewed theoretically. A CFD-based design of an experimental fluidized bed dryer for drying of sugar beet particles has been reported. Based on this technique, bed size, flow pattern and velocity vectors in the fluidized bed were investigated. For the designed bed, velocity profiles and pressure drop have been calculated in different regions of the bed.

In this paper, an introduction was made on the heavy oil, extra heavy oil, and natural bitumen resources in the world, as well as in Iran. These mixtures were categorized according to their physical properties and chemical composition. According to existing information, the giant extra heavy oil, and natural bitumen reserves are located in the western hemisphere. However, the Middle East countries, including Iran have considerable heavy oil reserves. In Iran, the major heavy oil resources are located in the south and south-west of the country, and the reserves are reported in this paper. Also, the challenges during development, production, transport, and processing of heavy oil and bitumen are addressed. The common and innovative methods of heavy oil production are introduced.