Nashrieh Shimi va Mohandesi Shimi Iran
Year:2008 | Volume:27 | Issue:4|Papers Count:24

In this report, experimental investigation of waste water treatment by reverse osmosis to enable its reuse in cooling tower is presented. A polyamide spiral wound RO membrane followed by three filters as RO pretreatment (two activated carbon and one cartridge filter) and samples of Tehran refinery treated waste water have been used. The effect of operating conditions such as pressure difference, temperature and feed concentration on permeation flux, permeate concentration and fouling have been studied. The results show that continuous operation with a pressure difference of 6 bar and a temperature of 30°C are the best operating conditions. Analysis of the water treated by RO represents 95%, 100%, 93% and 97% reduction in TDS, TH, Cl – and SiO2, respectively. Comparison between the treated wastewater analysis and city water used in cooling tower as make up water shows the suitability of reverse osmosis method for the above mentioned purpose.

In this study, alkaline colloidal silica was prepared by titration of an alkaline solution such as sodium silicate with silicic acid in constant range of pH .This constant range of pH was achieved by using concentrated soduim silicate solutions as pH adjusting solutions during titration.The sodium silicate solutions having a variety of concentrations were passed through ionexchange resin to prepare the silicic acid solutions. Various effective parameters on the method were investigated. In this research, the results show the mean particle size and surface area of prepared colloidal silica are influenced by formation temperature, titration rate, silicic acid and alkaline solutions concentration. Low titration rate of slicic acid, high formation temperature and low concentration of silicic acid and alkaline solution would help the particle growth to form the larger particle size of colloidal silica.

Catalysts with the formula of LaCo(1+x)O(3+d), where 0£x£1, were studied for oxidation of CO and C2H6 in a synthetic exhaust gas, comprising 6.0% CO and 0.2% C2H6 in Ar. Ethane was selected as a model for hydrocarbons in the exhaust gas. The performance of catalysts is correlated to their properties, particularly their redox in oxidizing and reducing atmospheres. XRD patterns show perovskite structure for all catalysts. The Co3O4 crystallite size was calculated using the Scherrer’s equation. TPR results show the reduction of Co3O4 and cobalt oxide in perovskite structure in the range of 330 – 475oC and 550 - 650oC, respectively. Disappearance of the cobalt oxide structure in XRD patterns of LaCo(1£x£1.3)O(3+d) catalysts are attributed to small size of the cobalt oxide crystallites. Redox properties of catalysts were also studied by electrical conductivity measurements. Similar Arrhenius-type electrical conductivity behaviors of catalysts with that of cobalt oxide indicates that the cobalt component is essential for charge carrier mobility in LaCo(1+x)O(3+d) catalysts. Catalyst with 0.3 mole excess cobalt, i.e. LaCo1.3O(3+d), which shows the lowest activation energy of electrical conductivity (Ec) and the lowest ratio of conductivities in reducing to oxidizing atmospheres, has the lowest light off temperatures for oxidation of both CO and ethane. High ability of catalysts in gas phase-lattice oxygen transfer is evidenced by the fast reduction and oxidation behaviors of catalysts in CO and air atmosphere, respectively.

Homogenizer and ultrasonicator that we call as mechanical methods were used in the lab scale production of alcohol free reduced glutathione (alcohol free GSH) from baker’s yeast. The study was done to determine the effects of specific parameters of the methods and the pH of the medium on the production of the GSH. The cell disruptions were run at a wide range of those parameters at the suitable common parameters of the methods. The disrupted cells suspension was then centrifuged at 12,000 rpm for 20 min and the GSH content in the supernatant was analyzed by taking the absorbance (A) value of the solution by spectrophotometer at 412 nm. The results obtained showed that the production of GSH was affected by the adjusted specific parameters of each method and the yield of production by the homogenizing and ultrasonic method was found 3.3 and 4.1 times, respectively, better than the yield of production by the unadjusted parameters. Ultrasonic method which produced 23.2 mg/L product was found 1.3 times better than the homogenizing method (18.5 mg/L) in producing the GSH. The result obtained from the lab scale study of the above mentioned mechanical methods showed that the implementation of them in the large scale production of the alcohol free GSH is possible.

Nitrate is an anion of major importance particularly in biological areas. Excessive amounts in water supplies indicate pollution from sewage or agricultural effluents. The effects of excessive quantities of nitrate in water are well known. In this research structural modification of natural clinoptilolite by isomorphic substitution was performed. Isomorphously substituted zeolite was prepared under melting conditions from natural clinoptilolite. It was characterized by XRD, XRF, DTG and SEM techniques. The characterization process revealed that product is different from AlPo. Ion exchange property of the modified product was studied for NO3-, NO2- and F - ion. The uptake of F - was higher than those of NO3- and NO2-. Anion exchange isotherms were constructed for NO3- and discussed. The ion exchange chromatography and neutron activation technique were used to study the extent of the exchange.

In this paper a new method is introduced and investigated for removing the destabilizing effects of time-delay parameter in control loops. The concept of the method is taken from the knowledge concerning the dynamic behaviour of irrational transfer functions (Ir-TF), which is discussed and investigated elswhere in frequency response domain and is explained briefly here. Ir-TFs, which are well capable of representing the model structure of a wide range of distributed parameter process systems are known o have transcendental characteristics in their frequency responses. The main complexity of these systems is in their phase behavior, which appears to have the capability to represent a complete time-delay characteristic as well as the characteristics in which the effect of time-delay is much limited. The conditions for appearance of the above dual phase characteristics may guide one to synthesise a contol loop in which the non-minimum phase dinamics of the open-loop transfer function is removed. This concept, when used in a simple loop by using a suitable predictor, affects the robustness features of the loop in a desirable manner and improves the stability characteristics of the loop, provided that the required conditions for the predictor is established. In addition to the important robustness property, the proposed time-delay compensator provides some advantages and specific properties in comparison to the conventional Smith predictor. These are the capability to be used for controlling the processes with an irrational transfer function model as well as the integrated processes that include time-delay parameter.

A solid-phase extraction (SPE) method for sample clean-up and preconcentration followed by reversed-phase high-performance liquid chromatography (RP-HPLC) with uv detection is reported for determination of polycyclic aromatic hydrocarbons (PAHs) in the Caspian seawater. A good resolution was obtained using acetonitrile: water (40:60) as mobile-phase for separation of these compounds. The effect of experimental variables, such as breakthrough volume with different concentrations of PAHs, type and volume of solvents for elution step were studied in SPE using C18 cartridge as sorbent. Different solvents (methanol, hexane and chloroform) were used for elution step in SPE. The best solvent for elution was hexane with volume of 3 ml, recoveries over 82 % and relative standard deviations lower than 6 %. Detection limits ranging from 0.02 to 0.14 mgml-1 were obtained for different PAHs using HPLC method. Concentration of PAHs in the Caspian seawater was 0.34 to 14.11 ngml-1.

Protonation of the reactive intermediate produced in the reaction between trimethyl phosphite and dimethyl acetylenedicarboxylate or diethyl acetylenedicarboxylate by resorcinol, 5- methylresorcinol, 2,5-dihydroxyacetophenone, 4-chloro-2-methylphenol, 4-chloro-3,5-dimethylphenol, 4-hydroxypyridine, 2-hydroxypyridine, 3-hydroxypyridine, or 8-hydroxyquinoline leads to vinylphosphonium salts, which undergo Michael addition with the conjugate base of the OH-acid to produce highly functionalized 2-oxo-2H-chromene or azacoumarins in good yields.

The present study has been focused on the acid and base transesterification of animal fats (dairy cow and beef) to produce biodiesel by varying process parameters such as catalyst amount, catalyst nature, reaction time and temperature. The maximum biodiesel yield after acid catalysis was 94.1±2.43 and 98.4±2.3 percent for dairy cow and beef tallow, respectively. The quantity of biodiesel obtained after base catalysis was comparatively lower than obtained in case of the acid catalysis. The optimum conditions for biodiesel production using acid catalysis were: 2.5 g of conc. H2SO4, 24 h of reaction time and 50oC for dairy cow fat and 2.5 g of conc. H2SO4, 6 h of reaction time and 60oC for beef fat. The amount of biodiesel obtained from beef tallow in the present study was much higher than earlier reported yields. The evaluation of transesterification process was followed by gas chromatographic analysis of tallow fatty acid esters (biodiesel) at optimal conditions. The fuel properties of biodiesel thus obtained accomplished the requirements of both the American and European standards for biodiesel.

This paper describes the application of process integration principles to the design of oil refineries hydrogen network. In this regard, a design hierarchy as well as heuristics and required guidelines are proposed. The recommended rules compensate lack of procedure to the design and make the design process easier. The guiding principles of the design are based upon pinch technology and extending the heat integration concepts to mass integration. This research makes a designer able to maximize the amount of hydrogen recovered across the site during the design. Besides, it provides an opportunity for refineries to make most efficient use of hydrogen. The study is illustrated with an industrial case study. The work stages such as targeting, simulation etc. are performed in the REFOPT software environment. It is finally shown that this approach can design a network, which saves the total cost by $ 6.3459 million per year.

In this work the acidity constants of Thiamine in water and water-Triton X-100 micelle media solutions, at 25oC, have been determined spectrophotometrically. To evaluate the pH- absorbance data, a resolution based on the combination of soft-and hard-modeling is applied. The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program was applied for determination of acidity constants. Results showed that the pKa values of Thiamine were influenced as the percentages of a nonionic surfactant, such as triton X-100, added to the solution of this reagent increased. Effect of surfactant on acidity constants and pure spectrum of each component are also discussed.

The macrocyclic ligands 2,3,5,6-Bis{3’-bromo-5’-tert-butyl benzo-5-phenyl benzo} 12C3 (L1), 2,3,5,6-bis{3’-bromo-5’-tert butyl-benzo-5’-phenyl-benzo}15C4 (L2), 2,3,5,6-bis{3’- bromo-5’-tert butyl-benzo-5’-phenyl-benzo}18C5 (L3) have been synthesized and their alkaline metal compounds with NaClO4H2O and KClO4 have been prepared. Chemical formulas of all compounds have been characterized by using elemental analyses and spectroscopic techniques.

Nanoscale science and technology has today mainly focused on the fabrication of nano devices. In this paper, we study the use of lithography process to build the desired nanostructures directly. Nanolithography on polymethylmethacrylate (PMMA) surface is carried out by using Atomic Force Microscope (AFM) equipped with silicon tip, in contact mode. The analysis of the results shows that the depth of scratches increases with the increase of applied normal force. The scanning velocity is also shown to influence the AFM patterning process. As the scanning velocity increases, the scratch depth decreases. The influence of time and number of scratching cycles is also investigated.