Chemical Engineering

The present study investigates the oxidative-conversion of propane-butane (C3–C4) fraction to methanol via a proposed vapor–gas system: C3–C4 + O2 + h?/HN?3 ? 2??3?? + C2H4 + C3H6. Experiments were performed by feeding propane-butane fraction, oxygen, and nitric-acid into a photo-chemical reactor under mild conditions at a temperature of 100oC, an atmospheric pressure (P = 1 atm.), and under the influence of electromagnetic radiation using visible-light excitation at a wavelength ? = 420 nm, and at reaction-times (tr) between 2 – 120 minutes. The major oxidation-products are methanol, ethylene, and propylene. From this approach, methanol with 90 % selectivity can be achieved at a single-pass C3–C4 conversion level of 10 %. Quantum-chemical calculations for the oxidation reaction of C3–C4 by hydroxyl radical (via HN?3 photo-dissociation) were performed using the density functional theory (DFT) method at the B3LYP/6-311++G(3df,3pd) level, and the calculation-results are broadly consistent with the experimental data. In a strict sense, the applied technique herein for the oxidation of C3–C4 to methanol, and the valuable semi-products (alkene), as well as to enhances the regeneration of nitric-acid, apparently finds physico-chemical justification.

The failures of the bituminous pavements are not only due to increase in traffic but also due to extreme climatic conditions prevailing in the country. The addition of sulphur to the bitumen can improve the quality of bitumen and enhance its properties as far as its use in the road construction is considered. In this paper the effect of addition of sulphur on the physical properties of the bitumen is studied and the optimum dose of sulphur to be added to the bitumen is also determined. The effect of Aging on the physical properties of Sulphur modified bitumen is also discussed in this paper.

Direct Methanol Fuel Cells (DMFC) offers one of the most promising alternatives to the replacement of fossil fuels. However effective the design of the fuel cell may be, it cannot perform effectively without proper modelling and simulation. The importance and the need for the modelling of a DMFC are discussed in detail. The modeling of the key components such as the gas diffusion layer, MEA, flow distribution, catalyst thickness which contributes to the performance of the fuel cell are discussed.

Design of proportional integral and derivative (PID) controllers for unstable SOPTDZ (Second Order Plus Time Delay with a Zero) system with a negative/positive zero is difficult. If zero is positive, it shows an inverse response. A simple method is proposed to design proportional integral and derivative controllers for such systems. The proposed controller is applied to the various unstable transfer function models of exothermic CSTR, an isothermal CSTR carrying out an autocatalytic reaction and crystallizer. Simulation results on linear model equations of exothermic CSTR, an isothermal CSTR carrying out an autocatalytic reaction and crystallizer are given to show the effectiveness of the proposed PID controller. The performance of proposed controller in terms of integral square error (ISE), integral absolute error (IAE) and integral time weighted absolute error (ITAE) is compared with the literature reported data.

The present paper involves the application of chemical and photochemical homogeneous advanced oxidation processes on the decolourization of textile effluent and Methyl Orange (MO) Dye. The decolourization efficiency of various oxidants such as hydrogen peroxide (H₂O₂), fenton reagent i.e. hydrogen peroxide and hydrated ferrous sulphate (H₂O₂/Fe²⁺), sodium hypochlorite (NaClO), UV/H₂O₂/Fe²⁺, Solar/H₂O₂/Fe²⁺, UV/NaClO and Solar/NaClO has been investigated. The effect of process parameters viz., oxidant dose, pH, concentration of dye and source of light (UV/Solar) for decolourization and COD reduction of dye effluent and MO has been studied. The decolourization efficiency was estimated from residual concentration spectrophotometrically. The experimental results show that the maximum decolourisation (more than 95 %) and COD reduction (40 %) of effluent occurred using combined Solar/NaClO (20 mg/L) system at pH 6 within 20 minutes. The decolourization efficiency of MO dye with H₂O₂ or UV alone was found to be negligible but more than 95% efficiency could be achieved either with UV/H₂O₂/Fe²⁺ (450 mg/L /150 mg/L) at pH 2 or Solar/NaClO (120 mg/L) at pH 6 within 30 minutes.

This study presents a computational fluid dynamics (CFD) model for modelling gas evolution and current distribution in a direct methanol fuel cell (DMFC). The improved two-phase model includes a new sub-model for estimating the interface mass transfer without empirical correlations. Simulation results in a horizontal channel of the DMFC agree with typical trends reported in the literature for bubbly flows. The increase in inlet flow rate is found to lead to a decrease in the gas content in the outlet of the anode channels. A case study illustrates applications of the CFD model for modelling gas evolution and current distribution in a DMFC with a parallel flow-field design. Simulation results with a improved two-phase model provide an explanation of experimental observations of a transparent DMFC with parallel channels. An improved three-dimensional CFD model includes all relevant phenomena and is valuable for gas management in a DMFC design.

This paper attempts to design a vane type feed inlet device to study the flow of vapour in vacuum column containing feed inlet device. The flow of inlet feed has been analysed for pure vapour and mixture streams. The primary function of the flash zone is to separate the entrained liquid feed from the vapour. This is achieved with a feed entry device that changes the direction and reduces the feed velocity as well as by providing adequate height between the wash and the flash zones. Liquid flow behaviour, such as velocity distribution, in the feed inlet device is of considerable importance in determining column performance. Using the volume-average method, a computational fluid dynamics (CFD) model was proposed to describe the liquid flow behaviour in a structured vane type feed inlet device. The values of the geometrical parameters and operation Reynolds number that mark the transitions of flow regime in the inlet device and column are reported. The model of inlet device in column has been developed and meshed in Gambit and the velocity distribution of the flow has been studied at different sections of the column. The proposed study of flow in a column containing feed inlet device has been done in Fluent.

A fluidized bed reactor with a perforated draft tube was employed to obtain hydrodynamic data for different Geldart’s particle group A, B, C & D by using various operating condition. The stability and hydrodynamics properties of a fluidized bed are determined primarily with respect to minimum fluidization velocity, pressure drop, minimum bubbling velocity, fluidization quality with a perforated draft tube by changing the total gas flow rate through the column. The result of calculation showed that, the pressure drop through the column increases with the increase in gas flow rate. At about 1.7 Ums some bed instability was observed which is characterized by fluctuation in pressure drop, with increase in gas flow rate this phenomenon disappeared. The effects of perforated draft tube on fluidization can be evaluated by comparing the experimental results by using the Geldart’s correlation with the correlation derived. Moreover the various correlations are derived by using the multiple regression analysis method (Polynomial method) for fluidized bed with perforated draft tube.

The demand for petroleum is increasing with each passing day. This may be attributed to the limited resources of petroleum crude. In that case, it becomes utmost necessity to search for alternative fuels, which are renewable, and in that biodiesel emerges as a real solution. Because of diminishing petroleum reserves and the deleterious environmental consequences of exhaust gases from petroleum diesel, biodiesel has attracted attention during the past few years as a renewable and environmentally friendly fuel. Since it is made entirely from oils, it is renewable and biodegradable. Biodiesel is a cleaner burning fuel than diesel and a suitable replacement. It is made from non-toxic, biodegradable, renewable resources. It can be produced in many ways.

The transesterification reaction is actually replacement of alcohol group from an ester by another alcohol. The reaction was carried out by varying different parameters, like amount of catalyst in reaction, ratio of methyl alcohol to oil, temperature and stirring on the reaction; to find the best conversion of oil to biodiesel. Alkali catalysed transesterification is considered to be the best amongst all methods available for the production of biodiesel from fresh oil. Our aim is to establish the parametric dependency of the reaction from the experiments.