AMIRKABIR
Year:2003 | Volume:14 | Issue:55-C|Papers Count:9

An-hexane degrading bacterium was isolated and used in a biofiltration system for removal of n-hexane from polluted air. Performance of the system under different pollutant concentrations and airflow rates was investigated. Three months of continuous operation showed that biofiltration is a practical method for reducing emission of pollutants into the atmosphere. Maximum elimination capacity for the biofilter obtained in this research was 18.83g/(m3bed.h)

Large reserves of gold deposits have been reported from different parts of Iran, specially at the Neishaboor area which is very high grade approximately 4 ppm in nature, but the characterization studies must be carry out before beneficiation. For mineralogical composition, the nature of the minerals, type of Gold, chemical characters and the suitable mesh of grind play a vital role in finding out suitable beneficiation techniques. The representative samples were subjected to detailed mineralogical, sieve analysis, chemical analysis and liberation studies. The results show that, the ore is oxidized and gold may be present partly in the form of solution in quartz veins as well as in the form of free particles, in iron hydroxides specially, hematite which is the product of pyrite oxidation. The SEM studies also confirm the mineralogical studies. Quartz, hematite, calcite and feldspar are the main minerals present in the order of abundances. Sieve analysis and distribution of gold particles in different sieve fractions and also sink and float tests show that most of the gold particles are distributed bellow 2000 microns specially between 1500-2000 microns.

The formation constant for charge transfer complexes between electron acceptor (AgNO3) and electron donor benzylcyanide (C6 H5 -CH2 -C º N) in solvent ethylene glycol [(CH2OH) 2] has been evaluated by using the Nuclear Magnetic Resonance (NUR) chemical shifts of aromatic group of benzylcyanide measured against external references, tetrametylsilane (TMS), hexamethyldisilane (HMDS) and cylohexane (CXA) at 20 °C. The external referencing procedure eliminated the interference of internal reference in the course of complexation. The necessary bulk magnetic susceptibility corrections on the measured chemical shifts have been made. The solution nonidealities and their effects on tire formation constant have been considered and a new equation has been suggested to obtain the mean ionic activity coefficient of AgNO3 from NMR results. The mean ionic activity coefficient has been taken into account in the formation constant calculations. I The results indicated that the appropriate formation constant should be expressed in terms of activities Also an equation have been derived to eliminate the undesirable effects on the NMR measured chemical shifts in calculating the formation constant. The selection of concentration domains and its effect on the calculated formation constant has been discussed and the new equation is modified to be independent of the concentration domains. In this equation the solution nonidealities, by considering the activity coefficients, have been taken into account.

A nonlinear predictive model controller was designed to control the temperature of a batch polymerization of methyl methacrylate. Using the mechanistic model of the polymerization, a state space model was derived and converted to transfer function model The coefficients of the transfer Function were calculated along the selected temperature trajectory by sequential linearization. 140 operation points were resulted Model validation showed model ability in process dynamic description. Consequently, DMC algorithm was applied and one objective function was optimized Results of control loop simulation shows a high precision ability of this algorithm in comparison to classic methods.

Applications of grinding aids are known as one of the developed subject of Comminution engineering which is one of the mineral processing branch. The different studies indicated that application of grinding aids could provide some advantages on grinding process. Also these advantages have more effects on non-metallic ores rather than metallic ones. This paper presents results of grinding aids effects on grinding process of Sarcheshmeh copper ore. The effects of Sodium Tri Poly Phosphate (STPP) and Soda (NaOH) as grinding aids were studied on grinding parameters like grind ability, fineness, grinding time and particle size distribution. Results indicated that grinding aids could make considerable changes on grinding parameters. On the other hand the presence of STPP and NaOH caused decrease of consumption energy, increasing of mill product fineness and decreasing of grinding time. In addition the application of NaOH caused more effects on grinding process than STPP. Consequently the application of grinding aids on their optimized concentration provided considerable advantages which could apply in industrial units with respect to results of feasibility study.

Coal is known as one of the most important energy sources in different industries. Coal processing has some identified steps like the other ores. One of these steps is comminution which is one of the most significant steps in mineral processing with wide applications in other engineering branches. One of the important subjects in comminution is known as application of grinding aids to optimize grinding parameters. Grinding aids or chemicals provide different effects on grinding product characteristics. In this work the effect of grinding aids such as Alchohol, Terpantinic Acid, Water, Soda and RGA on particle size distribution, consumption energy and selective grinding of Geliran coal ore samples were studied Results indicated that grinding parameters like size distribution, ash percent and work indices varied with the presence of grinding aids. An optimum percent of each grinding aids was determined on the basis of laboratory tests results. Consequently Terpantinic acid as the best grinding aid in this work reduced the consumption energy and ash percent in finer particle size. Alchohol increased the ash percent of coal in finer particle size and NaOH increased consumption energy and reducing ash percent in the same time. Fresh water did not provide considerable optimization on dry grinding process and made some disadvantages. Finally RGA as an industrial cement grinding aids provided some advantages and disadvantages and the selection of the best grinding aids related .with the strategy of grinding process design.

The nonisothermal nitridation of aluminum powders with different average particle sizes and Morphologies as starting materials were investigated using simultaneous thermal analysis (STA) in the temperature ranging from 800 to 1200°C. The nitriding reaction of both morphologies started around 450°C and completed before melting point (660°C) of aluminum powder for flake-like morphology and after it for equi-axed one

Copper mineralization at Sungun porphyry copper deposit is essentialy associated with potassic and less sericitic alteration. Fluid inclusion and isotopic data from oxygen and sulfer, show that main copper mineralization at Sungun occurred in the temperature range of 300-400 °C (with the mode of 360 °C). These data also indicate that the hydrothermal system involved both magmatic and meteoric waters, and boiled extensively. In this research, thermodynamic data are used to delineate the stability fields of alteration and ore assemblages as a function of fs2, fO2, aCl and pH (in the fixed temperature of 450 °c and the pressure of 500 bars) for the chalcopyrite dissolution and deposition.During critical fluid conditions in higher the temperature (>450 °C), copper solubility is Calculated to have been >100,000 ppm, whereas the copper content of the initial fluid responsible for ore deposition is estimated from fluid inclusion data to have been maximum 3800 ppm. This indicates that the fluid was initially undersaturated with respect to chalcopyrite, which agrees with the observation that veins formed at T>400 °c and contain rare chalcopyrite. Copper solubility drops rapidly with decreasing temperature, and at 400 °c is approximately 1000 ppm, within the range estimated from fluid inclusion data. At temperatures less than 350 or 360 °C, the solubility drops to<25 ppm. These calculations are consistent with observations that the bulk of the chalcopyrite deposited at Sungun is hosted by veins formed at approximate temperatures of 360 ± 60 °C. Other factors that may reduce chalcopyrite solubility are increases in pH, and decreases in F02 and aCl. Based on the calculations done in this paper, it is proposed that the Sungun deposit formed partly in response to the sharp temperature decrease and pH increase. In high temperatures (450 °C) chalcopyrite dissolved rapidly and as it is shown later on, the high temperature could be a very important factor to prevent copper depositition in an economic level within the Sungun system

Interesterification is one of the most important means for substituting hydrogenation of oils, in which the functional, physical and chemical properties of the oils are suitably altered with neither chemical changes in fatty acid composition nor geometrical or positional isomerization and/or reduction in degree of unsaturation. In this research work the possibility of using random chemical interesterification in pilot scale, using three common vegetable oils in Iran (sunflower, soybean and cottonseed oils) as liquid phase and fully hydrogenated soybean oil (soy flakes) as solid phase (25% each), with sodium methoxide as catalyst (0.5 %), at 110 °C and different processing times (10, 20, 30, 45 min) was investigated. Physical and chemical properties of the mixture, before and after interesterification, including slip melting point, acid value, iodine value, peroxide value, remaining soap and moisture content were evaluated In order to study the trend of random equilibrium (1, 2, 3-Random Distribution), before and after interesterification, the followings were determined, the profile of fatty acids, cis and trans (elaidic acid), by gas chromatography (GC), the solid fat content (SFC) by NMR and the structure of triglycerids in 2- position by enzymatic (lipase) hydrolysis, thin layer chromatography (TLC) and GC The results showed that interesterification made significant decrease in slip melting point from 54 °C to 35 °C which made the product suitable for producing shortening and margarine. As expected, the difference between iodine values of the oil mixtures and interesterified product was not significant. As a result of interesterification SFC was lowered, and the SFC curve indicated better plastic properties in the product. Studies on fatty acid profiles showed that this process did not affect the chemical structure of fatty acids and the amount of trans isomers was constant. The interesterified product had trace amounts (0.21%) of trans fatty acids (from flake), and higher amounts of unsaturated and essential fatty acids (PUFA: SAFA= 1.20), implying better nutritional quality of interesterified product, as compared to hydrogenated oil. Studies on the 2 - after 30 minutes of processing. position arrangements of fatty acids showed that the expected random equilibrium: was achieved