In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated... more
In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70 degrees C employing 157.04 g catalyst per unit volume of the reactor and 0.21 cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor. (C) 2010 Elsevier Ltd. All rights reserved.
Hydrodynamic parameters in solid foam packings were studied in tubular reactors at a wide operating range. Significant hydrodynamic multiplicity phenomena were observed in solid foams which are highly affected by the foam density. The... more
Hydrodynamic parameters in solid foam packings were studied in tubular reactors at a wide operating range. Significant hydrodynamic multiplicity phenomena were observed in solid foams which are highly affected by the foam density. The pulse regime is indicated at high foam density. A new regime map was proposed. The hydrodynamic performance of solid foams is demonstrated by new correlations, which take multiplicity into account. a b s t r a c t Catalytic active open foam packings are promising to enhance the performance of tubular reactors for gas–liquid–solid reactions. In this paper the hydrodynamics of gas–liquid two-phase flow through foam packings in co-current downflow mode of operation are studied experimentally. In particular, the effects of gas and liquid superficial velocities and the pre-wetting mode of the packing ('LEVEC' and 'KAN-LIQUID') on pressure drop, liquid holdup, and axial liquid dispersion were researched. The experiments revealed multiplicity behavior of the hydrodynamic phenomena in the packed bed. The multiplicity has a significant impact on the forming of upper and lower parameter branches of hydrodynamics. Taking the aforementioned phenomena into account, new correlations are proposed to predict the pressure drop and the total liquid holdup. The occurrence of different flow regimes depending on the foam pore density, namely trickle flow regime and pulse flow regime, was observed. The results can be applied for a better understanding of the heat and mass transfer and overall chemical conversion of tubular reactors with catalytic active foam packings.
We present the numerical analysis of the high order terms in the polynomial series of the Landau density energy. We compare the profiles and hysteresis of three series of Landau equations. First series is up to the only fourth order, the... more
We present the numerical analysis of the high order terms in the polynomial series of the Landau density energy. We compare the profiles and hysteresis of three series of Landau equations. First series is up to the only fourth order, the second and the third series are up to the sixth and eighth terms. The polarisation profile curves are obtained by minimizing the Landau equation and solved it using root finding technique while the hysteresis is obtained by solving Landau-Khalatnikov equation. It is found that those three series of Landau model possese similar polarisation profiles and also similar hysteresis when the system is set near Curie temperature, around 40K to 50 K for the Tc of 50 K. If the temperature of the system is decreased further away from the Curie temperature, we have to consider the high order terms in Landau free energy expression. Keywords— higher order, Landau theory, hysteresis I. INTRODUCTION Landau theory is well known as a suitable approximation to explain the properties of the system in the equilibrium condition near phase transition [1]. The transition between two phases which have different symmetry in their thermodynamic state is described by order parameter, a physical entity which values (non-zero or zero) depend on the symmetry of the state. It has non-zero value in the ordered state, while in disordered phase, the value is zero [2]. This phenomenological theory has been used to study the system with long range interaction, near phase transition such as ferroelectric-paraelectric [3] and ferromagnet-paramagnet [4] using electric polarization P and magnetization M as order parameters, and also phase transitions in magnetoelectric multiferroics using both polarization and magnetization. The free energy of the system is approximated by growing the order parameter in power series. This free energy then becomes the starting point to study other parameters of the system. For example, the value of the order parameter in a certain temperature can be obtained by solving the minimum condition of the free energy of the system [2]. The response of the order parameter to the applied disturbance of such fields is also calculated based on the free energy system using Landau Khalatnikov equation yielding the hysteresis curve [5,6]. In the series of order parameter expressing the free energy, we can also add other terms such as the surface effect, the depolarization term, etc. to complete the behaviour of the system [7].
