Nashrieh Shimi va Mohandesi Shimi Iran
Year:2009 | Volume:27 | Issue:4|Papers Count:10

Dimethyl ether as a clean and alternative fuel especially for gas oil has also other applications and so its production rate is increasing. In this paper pore network model is used to simulate the catalytic reaction of methanol dehydration to dimethyl ether on qama-Alumina catalyst.Reaction kinetics is strongly nonlinear and this is the first time that pore network model is applied on this reaction. A two dimensional pore network is considered and orthogonal collocation method is used to solve the nonlinear differential diffusion-reaction equations. Pore network model is used to study the effect of several parameters such as pore space morphology, temperature and concentration on catalyst effectiveness factor. The results will be used for reactors simulation.

Dimethyl formamide (DMF) as an organic solvent with special properties (such as pulping at mild condition and high selectivity) was used for pulping of rice straw. The most important role of DMF is inhibiting from degradation of cellulose chains during pulping process.Pulping was conducted following a central composite design using three level factorial plans (cooking temperature 190~210 oC, cooking time 120~180 min and DMF ratio 30~70%). Responses of pulping were analyzed using statistical software MINITAB and the models of each variable were developed the optimum values of the variables: pulping yield 65. 64%, holocellulose 75.19 %, beta cellulose 7.4 %, degree of freeness 363 ml and liquor suspended solids 2.47%. Results showed that acceptable properties of pulp could be achieved at 200oC, 150 min and 50 % DMF.

In the present research, a rapid and ease procedure for simultaneous determination of captopril and hydrochlorothiazide of overlapping spectra in tablets using Fourier-transform infrared spectrometry (FT-IR) and multivariate calibration methods has been applied. For all chemometric calibrations, a concentration set of mixture of captopril (Cpt) and hydrochlorothiazide (Hctz) according to Full-Factorial desing in dimethylsufoxide (DMSO) solvent was prepared. Then Number of factors, number of scans and the resolution was optimized and FT-IR transmission spectra were recorded in the spectral region of 4000-800 cm-1. The investigated calibrations were tested for the synthetic mixtures consisting of two drugs using the Omnic Quant IR software. The results of the methods were compared with UV-VIS reference method and a good agreement was found. Among three of the chemometric methods which were used, PLS (partial least-squares) first order derivative spectra method have the best results. The statistical parameters such as RMSEC (root mean square error of calibration), RMSECV (root mean square error of cross validation) and SEP (standard error of prediction) for Cpt and Hctz were obtained 0.134, 0.154, 0.043 and 0.192, 0.224, 0.044 (mg per 10 ml) respectively. Relative standard deviation (RSD) for jive independent analyses and recovery were 1.2%, 98.67% and 1.8%, 98.42% for Cpt and Hctz respectively.Regression coefficient (R2) of calibration curves was excellent. The main advantage of investigated method is the fast and simultaneous analysis for the several components in mixture without any chemical pretreatment as separation in HPLC and derivation in derivative spectrometry.

Soil contamination with Total Petroleum Hydrocarbon (TPH) from the leaking underground storage tanks (LUSTs) and its adverse effects are major problems and more important environmental concerns that we are facing today. In the present research bioremediation method was applied for the remediation of the contaminated soil with TPH using soil composting with organic amendment. Sewage sludge, compost and poultry waste were added as amendments for supplementing the organic matter for composting of the contaminated soil. Target contaminant of this research was the TPH-contaminated soil obtained from the Tehran Refinery Site. The amount of contaminant in soil was 140,000-mg/kg dry weight basis. The major objective of this research was to find the appropriate mix ratio of the organic amendments to soil for enhancing the Petroleum Hydrocarbons degradation during the composting process. The ratios of contaminated soil to organic amendments were 1:0.1, 1:0.3, 1:0.5, and 1:1 as wet weight basis. The degradation of TPH was significantly enhanced by the addition of these organic amendments relative to the straight soil.Degradation rates of the total petroleum hydrocarbons (TPH) were the greatest at the ratio of 1:1 of the contaminated soil to the organic amendments. The first order degradation constant of TPH with Sludge was about twice TPH Soil degradation constant .The reactors were divided into two groups: MCR (Mixed Composting Reactor) and ACR (Aerated Composting Reactor). Total volatilization loss of TPH was only about 2-5 % of initial TPH Lose of TPH mainly due to the slow degradation compounds. High correlations were found among the TPH degradation rate, the amount of CO2 evolved and microbial activity. The rate of elimination for sewage sludge, compost, poultry waste and control soil for MCR reactors are as follows: 60, 40, 30 and 25, respectively and for ACR reactors were: 63, 56, 43 and 38, respectively.

Mass transfer and heat transfer coefficients through a drying period have been determined at a falling rate in this study. A fluidized bed dryer was designed and made to be utilized in the test procedures required To give an assessment of the effects of moisture on mass (heat) transfer coefficient and further to determine the relation between mass (heat) transfer coefficient through a drying period at a constant rate and mass (heat) transfer coefficient through a drying period at a falling rate, we defined mass (heat) transfer coefficient attenuation factor in the form of the ratio of Sherwood (Nuselt) number under the circumstances the moisture content was "X" to the Sherwood (Nuselt) number under the circumstances the moisture content was "Xc" (critical moisture). The results indicated that the relation suggested for the calculation of mass (heat) transfer coefficient attenuation factor taking use of drying characteristic factor would provide greater accuracy.

Due to the complexity and variety of metallic compounds present in crude oil, in this study compounds with physical and chemical properties similar to those found commonly in crude petroleum were used Accordingly protoporphoin disodium, tetra phenyl porphine vanadium oxide, and tetra phenyl porphine nickel for screening of bacteria were selected. From a collection of 80 samples of hydrocarbon-polluted soil, water and sludge about 22 different bacteria with capability of reducing porphyrinic compounds were isolated. Amongst these 2 strains identified as Pseudomonas stutzeri and Provendencia stuartii showed promising results and reduced metal-containing compound by about 28% and 34% respectively. Additionally the activity of the selected strains of bacteria was monitored at the site of contamination with regards to the reduction of model compounds.

In this research, the effect of simultaneous presence of single surfactant (ionic and nonionic) and salt on drop-interface coalescence was studied in the system of water (d)/ toluene (c).Sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) as anionic and cationic surfactants and also 1-decanol as nonionic surfactants were used. Sodium chloride (NaCl) and magnesium sulfate (MgSO4) were used as salts. It was found that mixture of surfactant and salt increased the coalescence time. The effect of CTAB was more obvious in comparison with SDS. Also, MgSO4 caused much more increase in partial and total coalescence time.

According to rheological characteristics related to simultaneous cell growth and bacterial morphology, in this research broth rheological characters and its relation to cell broth and clavulanic acid production by Streptomyces clavuligerus in a complex medium were studied The rheological model of the broth was defined as a pseudoplstic. Significant changes in the rheological parameters consistency index (K) were observed with the fermentation evolution. Consistency index (K) can be used as a quick criteria for cell growth evaluation. In the end of the second day, the maximum value of consistency index (K) with dry cell weight achieved 0.446 (Pa.sn) and 1.83 (g/l) respectively. However, the maximum production of 620 (mg/l) clavulanic acids was obtained in the end of 4th day. Bacterial morphological changes also were in connection with consistency index (K) changes, and the maximum mycelial concentration was obtained in the end of second day of fermentation. The best morphology from the rheological aspect and ca production was dispersed mycelia.

Plate heat exchangers are used extensively in most industries, especially in the food and dairies industries; however, very little basic information has been published on their design, optimization, flow and heat transfer characteristics. In this study, it is extended a new straightforward design for this type of exchangers as known “Rapid Design Algorithm”. The design method is based on full utilization of maximum allowable pressure drop on both the hot and cold streams to achieve the required minimum heat transfer surface area. Using mathematical model of PHEs the temperature profiles in each plate and for all plate are also identified.

In this work new equilibrium hydrate formation conditions for carbon dioxide and mixtures of carbon dioxide and methane in the 20 wt % aqueous methanol solution were measured by constant-volume method For CO2, these data are at temperature and pressure ranges of 264.7-270.7 K and 1.47-3.16 MPa, respectively. For mixtures of carbon dioxide and methane these data are at temperature and pressure ranges of 262.9-273.7 K and 1.37-5.1 MPa, respectively. The data obtained for CO2 in 20 wt % aqueous methanol solution in this work were in disagreement with published data in literature but there is a good agreement between thermodynamic models and our data. The Peng-Robinson equation of state (PR EOS) coupled with the Wong-Sandler (WS) mixing rule was used to obtain the fugacity of components in the gas and aqueous liquid phase. The PREDS was then coupled with van der Waals-Platteeuw (vdW-P) hydrate model and applied to predict the hydrate formation conditions of system containing methanol. The model predictions are compared with experimental data and good agreement is demonstrated