Nashrieh Shimi va Mohandesi Shimi Iran
Year:2006 | Volume:25 | Issue:3|Papers Count:11

Indigenous rhodococcus P32C1 was immobilized on polymeric supports for gas oil biodesulphurization. Among different kinds of supports used for cell immobilization, alginate and polyethylene were chosen because of their cheaper price, simpler immobilization procedures, better availability and adaptability to bacterium. Early experiments, in the aqueous phase, were used to desulphurize a sulphurinated model compound, DBT; as a result, the DBT conversion rates by immobilized P32C1 cells in the case of alginate and polyethylene were 1.06 mmol.hr-1.kg-1DCW and 0.18 mmol.hr-1, respectively. In order to estimate the desulphurization activity of immobilized cells in organic phase, the decreasing rate in the total sulfur content of sample gas oil was measured: In optimal operational conditions, immobilized P32C1 cells decreased the total sulfur content of this sample by 10 and 4 percent, respectively.

A model for determining radiation heat transfer coefficient in circulating fluidized bed is proposed. The model assumes two phase structure, the flow at the wall dominated by streams of clusters and the phase of dilute suspension. Intensity distribution of radiation assumes one dimensional isotropic in the forward and backward direction. The model studies the effect of different bed parameters such as suspension temperature, wall temperature, wall emissivity, particle emissivity and the suspension density on radioactive heat transfer coefficients. The predictions of model are in good agreement with the experimental results from the literature.

Removal of colour and complex organic substances from industrial wastewaters has always presented a challenge to environmental engineers. Textile effluents rich in colour and complex organics are typical examples. Combination of chemical and biological techniques for treatment and purification of such wastewaters has had mixed success. In this study a combination of activated sludge process and carbon adsorption known as biocarbon process was used for treatment of textile wastewater. Granular Active Carbon (GAC) was used in an activated sludge reactor in pilot plant scale to investigate the combined effects of adsorption and biological reaction. This technology has been referred to as “Granulated Active Carbon Technology” (GACT) previously. The pilot plant consisted of two activated sludge reactors. One of the reactors was a normal activated sludge system while the other included GAC in suspension form. The units were started-up with synthetic wastewater but after microbial growth was observed the feed was changed to textile wastewater gradually. After steady state conditions were prevailed in the reactors, the performance of two units was compared under different conditions. It was observed that the activated sludge unit had the capacity to remove up to 90% of the COD and 88% of the colour, while the GACT reactor removed 96% of the COD and 92% of the colour under similar circumstances. However although at low hydraulic loadings the performance of both units were similar but at high hydraulic loadings there was a vast difference in the behavior of reactors. It was concluded that at low rates GACT and normal activated sludge produce similar results but at high rates GACT's performance is much better. Therefore it appears that GACT system could play as a powerful tool for treatment of industrial wastewaters.

In this research, samples of precipitated silica used as reinforcing in rubber industries, were prepared and then washing and drying operations were investigated by analyzing the dried samples and two commercial precipitated silica samples through determination of parameters such as bulk density, oil adsorption, specific area and particle size. After comparing the results of the tests and optimization of preparation method, the optimized sample was used in a rubber compound of NR/BR and operational tests such as abrasion resistance and tensile strength were carried out on the product. The results show that the optimized sample is comparable with commercial products being used in rubber industries and can be an appropriate replacement for them. As hardness of this optimized sample and external sample are the same (57shore). It’s abrasion loss is smaller than commercial one and it shows a better elongation at break. This produced sample also causes to reduce cure time of rubber compound.

An overall adsorption quantity for a heterogeneous solid is usually expressed by an integral equation, which contains a distribution function that describes heterogeneous properties of a problem. The current article shows that the difficulties arising from the ill posed nature of an adsorption equation can be overcome with the regularization method. This work presents general principles of regularization for solving the ill posed problems without detailed mathematical considerations. The application of the regularization method to calculate a distribution function from any overall adsorption function is illustrated with simulated adsorption isotherms.

Sodium perborat has a great role in industry as bleaching agent and is one of the main components of suntbetic detergent powder formulation. This chemical is produced by a reaction between sodium metaborate and hydrogen peroxide. Sodium metaborate, also, is produced by a reaction between caustic soda and borax. In this investigation, these two reactions were studied. In reaction of preparation of sodium metaborate, effect of addition time of borax powder, as reactant, to caustic soda in presence of three different types of agitators on viscosity of reaction mixture has been investigated. The results show that in presence of anchor agitator variations of addition time of borax, even with variation of temperature, prevents the augmentation of viscosity of reaction mixture. For reaction of prepartion of sodium perborate, effect of addition time of sodium metaborate to oxygen peroxide, in presence of different agitators on sodium perborate crystal size distribution and their porosity has been studied. The results show that increase of addition time of sodium metaborate in presence of anchor agitator, increases precipitation of sodium perborate and consequently, yield of reaction and produce low range of size distribution even thought, porosity of product (sodium perborate) decreases. The high porosity of product be obtained with anchor agitator and augmentation of sodium metaborate addition to the reaction mixture (minimum flow rate 0.5 gr/min).

Black tea is produced by polyphenol oxidation in the tea leaf fermentation step. In this research, the effect of both enzymatic and chemical oxidation by using aluminum sulphate and zeolite on the improvement of the tea leaf fermentation was determined, in terms of oxidation and brewing time of the tea produced. The results show that by adding 200 ppm aluminum sulphate and zeolite in the fermentation step, oxidation time will be reduced respectively 21%, 15%. Also tea solution absorption will be increased respectively 10%, 20% by adding 190 ppm aluminum sulphate and zeolite in the fermentation step.

The Wet Process Phosphoric Acid (WPA) is used to produce fertilizers and alimentary supplies for cattle. In each of these applications, the impurities contained in acid must be in standard range. In this paper purification of WPA by solvent extraction is performed and the effect of the mass ratio of solvent to feed on extraction efficiency is studied. The working solvents are Methyl Iso Butyl Ketone (MIBK), Iso Amyl Alcohol (IAA) and the mixture of them. The results show that the IAA is better than other solvents in extraction of WPA. This solvent can extract 82.2% of acid after two extraction stages but MIBK can extract only 73.5% of acid after three extraction stages. For all of these solvents, the Pb and Cd concentrations go down to trace. The experimental results show that the maximum separation of Mg with MIBK is 87.5% which occurs at the mass ratio of solvent to feed eual to 4. In the case of IAA solvent the percent is 91.7% and the ratio is 8.

The first and formost function of food packaging is to protect the product and to preserve its inherent quality. Most serious problem with plastic packaging material is flavor scalping. The aim of this project was to study flavor absorption into Polyethylene Terephtalate (PET) from orange soft drinks. Three different temperatures (4, 25 and 40 ºC) were chosen. The absorption behavior of D-limonene, myrecene and pinene were monitored until equilibrium was reached. Headspace Solid-Phase Micro extraction (SPME) was used as a technique for extracting the absorbed flavors from PET. The influence of the extraction time on the amount of extracted was studied. To measure the amont of flavor absorption by PET gas chromatography with FID detector was applied. It was seen that temperature and the kind of soft drink in use have an effect on the diffusion of flavors in PET. The only flavor detected with this method in PET was D-limonene (47ng/cm2), and the amount of absorption was increased from 6.94×10-12 m2/s at 4 ºC to 5.207×10-11 m2/s at 40ºC. Taste panel was also used as a method to observe the effect of flavor absorption on it’s quality.

Water and energy are two important used commodities in industrial processes. Researches show that in industrials where spend big amounts of water and energy, separate and independent minimization of the mentioned items doesn’t lead to the global optimality. For simultaneous analysis of water and energy consumption two important studies has been developed. One is based on conceptual method and the other one has used the mathematical programming. In this research, first advantages and disadvantages of two existing approaches are pointed out; and in order to better analysis of water and energy systems, some new and complementary discussions are presented. Concerning above discussions, is showed that mentioned approaches do not guarantee global optimality and then a procedure that achieves optimum targeting is proposed. Finally for targeting and design of water and energy networks, some mathematical models that based on conceptual methods are presented.

In this work, experimental data on the kinetics of methane hydrate formation were measured at constant volume. The experiments were carried out in a batch reactor at three temperatures between 274 and 278 K and at pressure ranging from 44.4 to 87.4 bar. The thermodynamic natural path to chemical reaction kinetics was used for modeling hydrate formation rate in a constant volume process. In this approach, the system was considered as classical thermodynamic or macroscopic view. The results show that this method can predict constant volume experimental data well and further study indicates the parameter of this model can be estimated directly from other experimental data.