Volume 16, Issue 6 -

Mixing and segregation characteristics of biomass particles are of practical importance because the in-bed combustion efficiency of volatile matter affects the vertical location of biomass in bubbling fluidized bed combustor. Sesame and broad bean stalk biomass materials mixed with sand used in this study. The superficial gas velocity, biomass chip length, sand particle size and mass fraction of biomass varied as experimental variables. The mixing and segregation behavior of mixtures were analyzed in terms of mixing index. It was found that the variability in the chip-shape made the sesame chips is quantitatively and qualitatively higher homogeneity and mixedness than the broad bean chips. The optimum overall mixing index for the sesame and the broad bean is around 0.96 and 0.84 at dimensionless superficial gas velocity ( U/U mf ) of 2.0 (1.40 m/sec) and 2.1 (1.25 m/sec), respectively. It was found that as the mean diameter increased and the sphericity decreased, the mixing quality decreased. The average sand particle size of 371 µm can keep good mixing with biomass chips of both materials, compared with average particle sizes of sand 550 and 700 µm. Increasing the initial biomass mass fraction yields a poor mixing of the investigated biomass stalks.

This study was carried out to investigate the potential of Pseudomonas aeruginosa for the removal of bisphenol-A (BPA) from synthetic wastewater. To achieve this, BPA removal capability of P. aeruginosa with respect to BPA concentration, and temperature were examined in batch reactors. Experiments were conducted in the presence/absence of glucose, as a carbon source. The first set of experiments consisted of evaluating the kinetic of removal of BPA at different concentrations (5, 10, 20, and 30 mg BPA/L) without glucose. In the second set of experiments, three different glucose concentrations (0.5, 1.0, and 2.0 glucose/L) with BPA concentrations were tested. After settlement of the P. aeruginosa biomass in the shakers, supernatants and control groups were filtered and analyzed for BPA using high performance liquid chromatography. In the biotic study, BPA removal rates were between 63 % and 100 %. All concentrations of BPA under 20 mg/L were completely degraded at 25 and 35 ºC at first step. However, 30 mgBPA/L was decreased to 8.56 mg/L by P. aeruginosa at first step at 25 ºC. At the second step, all concentrations of BPA were completely degraded by the cells at the presence of glucose. Hence, it can be summarized that bisphenol A can be used by P. aeruginosa as an external carbon source in the wastewater environments.

Direct extraction of high purity ethanol from fermentation broth was investigated using a vacuum fractionation technique. Batch and repeated-batch extractive fermentation of ethanol were carried out using concentrated sweet sorghum as a carbon source. The effect of product inhibition was reduced by continuous removing ethanol from the fermented broth. About 60 % relative viability was observed in fermented broth with a higher productivity value. Due to the high value of living cells presented in the medium, repeated-batch extractive fermentation was subsequently performed. The ethanol was continuously fractionated out from the system at the average rate of 10.2 g/h with the concentration of approximately 80 wt%. There were 8 cycles of fermentation using only 1 time inoculation. Nevertheless, the calculated ethanol productivity and relative viability for each fermentation cycle were decreased gradually due to the accumulation of toxic substances in fermented broth. The simulation of 200 liters continuous extractive fermentation system using ASPEN PLUS was studied including process optimization and economical consideration. 18.5 liters of ethanol solutions 82 wt% with insignificant amounts of by-product was produced from a 200 liters extractive fermentation system per day. Production cost including raw material and utilities cost was approximately 0.71 €/liter. The economic and systemic performance process were subsequently analyzed, and including that ethanol loss was recovered using a gas scrubber connected to the vapor exiting the venturi tank as well as in the stillage stream. The calculated utility costs after process modification were 0.5 €/liter of ethanol, approximately 30 % of production cost was reduced.

Although heavy oil is an abundant and promising energy source, its processing and utilization are complicated due to its high density, low hydrogen/carbon ratio, and high asphaltene content. Fortunately, these problems can be mitigated by the application of oxy-fuel combustion. To gain deeper insights into the above technology, the characteristics of heavy oil combustion in an O 2 /CO 2 atmosphere was investigated using non-isothermal thermogravimetric analysis. We demonstrate that the combustion process consisted of four stages. Low-molecular-weight hydrocarbons reacted at low temperature, whereas heavy ones required a higher temperature. Increasing the concentration of oxygen resulted in increased TGA and DSC peak intensities and decreased peak widths, and these peaks were shifted to lower temperatures. Coat-Redfern and Flynn-Wall-Ozzawa methods were used to evaluate the kinetic parameters (E, A) of the oxidation process, showing that the high-temperature activation energy was much higher than the low-temperature one due to the different molecular weights of the oxidized substrates in each region. The reaction was demonstrated to be diffusion-controlled, as reflected by the lower activation energy at high oxygen concentration and high temperature, with the influence of oxygen concentration on QO processes being much more obvious than that on SO ones.

The dynamic process of gas-solid chlorination of high-density polyethylene (HDPE) was revealed using a vibrated-bed reactor, where a UV-Vis measurement system was used to record the kinetics of chlorination online. Thermal and UV-enhanced chlorination at fixed temperature below the melting point ( T m ) of HDPE were firstly investigated. It was observed that UV irradiation could accelerate the reaction rate. However, all of the prepared chlorinated polyethylene (CPE) products had unchlorinated crystal structures and a limitation of chlorine content. Multi-stage chlorination was hence designed for more homogeneous chlorination and decreasing the residual crystallinity. The differential scanning calorimetry (DSC) results showed effective decrease of the melting enthalpy (Δ H m ) while the final reaction temperature was beyond T m . Meanwhile, the presence of -CH = CH- bonds in the polymer chain revealed by solid-state nuclear magnetic resonance (S-NMR) indicated that the final reaction temperature should not be higher than 150 °C.

Homotopy techniques in nonlinear problems are getting increasingly popular in engineering practice. The main reason is because the homotopy method deforms continuously a difficult problem under study into a simple problem, which then can be easy to solve. This study explores several homotopy approaches to obtain semi- or approximate analytical solutions for various cases involving mechanistic phenomena such as aggregation and breakage. The well-established approximate analytical methods namely, the Homotopy Perturbation Method (HPM), the Homotopy Analysis Method (HAM), and the more recent forms of homotopy approaches such as the Optimal Homotopy Asymptotic Method (OHAM) and the Homotopy Analysis Transform Method (HATM) have been used to solve using a general mathematical framework based on population balances. In this study, several test cases have been discussed such as conditions in which the aggregation kernel is not only constant, but also sum or product dependent. Furthermore cases involving pure breakage, pure aggregation and a combined aggregation-breakage have been studied to understand the sensitivity of these homotopy-based methods in solving PBM. In all these cases, the solutions have been analytically studied and compared with literature. Using symbolic computation and carefully chosen perturbation parameters, the approximate analytical solutions are compared with each other and with the available analytical solution. A convergence analysis of the solution methods is made in comparison to the available solution. The case studies indicate that OHAM performs slightly better than both HATM and HPM in solving nonlinear equations such as the PBEs.

The present article deals the entropy generation due to heat and mass transfer of an unsteady MHD flow of a Casson fluid squeezed between two parallel disks. The upper disk is taken to be impermeable and the lower one is porous. The flow field equations are reduced to non-linear ordinary differential equations by using similarity transformations and the resulting ODE problem is solved by shooting technique with Runge-Kutta 4 th order method. The effects of various non dimensional fluid and geometric parameters on the velocity components, temperature, concentration, entropy generation number, Bejan number, skin friction and Nusselt number are illustrated through graphs and tables. It is noticed that the temperature of the fluid is enhanced with Eckert number, whereas the concentration of the fluid decreased with Casson fluid parameter. The present study is applicable to nuclear engineering cooling systems, wire and blade coating, extrusion of polymer fluids, optical fibers, magnetohydrodynamics and optimization of chemical engineering processes.

The liquid phase esterification of butyric acid with benzyl alcohol was studied using homogenous catalyst p-toluenesulfonic acid. The reversible second order rate equation was used to investigate the kinetic parameters of the reaction. The L9 orthogonal array of Taguchi methodology was employed to study the parametric effect independent variables on the responses equilibrium constant ( K eq ) and conversion ( X eq ) of butyric acid. The parameters and their range such as catalyst concentration (0.5–1.5 wt%), temperature (333–363 K) and molar ratio (1–3) was used and considered as independent parameters for parametric sensitivity analysis. Non-ideal behavior of the reaction was studied using UNIFAC group contribution method. The effect of reaction temperature on the overall activity factor was studied. The relative parametric effect on the K eq and X eq was found. In sensitivity analysis, temperature and molar ratio was the most influencing parameter on the K eq and X eq . The regression model was developed and validate by performing unknown experiments.

The supported CoNi/TiO 2 composite oxide catalysts were prepared by impregnation method. The physical and chemical properties of the prepared catalysts were studied by XRD, XPS and H 2 -TPR. The results show that the Co 3 O 4 , NiO and NiCo 2 O 4 species are formed in the CoNi/TiO 2 composite oxide catalysts. The interaction between the Co and Ni species can effectively enhance the properties of the CoNi/TiO 2 oxide catalysts. The introduction of Ni species can effectively enhance the surface hydroxyl oxygen species and adsorbed oxygen species content, and the Co 3+ species content can be enhanced on the surface of the prepared CoNi/TiO 2 composite oxide catalysts. The low temperature reducibility and toluene catalytic combustion activity of the CoNi/TiO 2 composite oxide catalysts can be improved by the Ni species. The toluene catalytic combustion activity of CoNi/TiO 2 composite catalysts can be obviously affected by the Co/Ni molar ratio. The CoNi/TiO 2 composite oxide catalyst, which has a Co/Ni molar ratio of 1.0, has the best toluene catalytic combustion activity and wide scope of the concentration of toluene. The toluene catalytic combustion conversion can exceed 99 % at 340 °C. That is to say, the toluene concentration in air can be decreased to 80 ppm from 8000 ppm.

A two dimensional (2D) boundary layer two-phase MHD (magneto hydrodynamics) flow of Maxwell and Oldroyd-B fluid over a stretching sheet has been explored. Heat and mass transfer phenomena is inspected through Non-linear radiation, viscous dissipation, joule heating, Soret (thermo-diffusion) and Dufour (diffusion-thermo) Impact. The boundary layer governing differential equations are modelled and transformed to a system of ODE’S with the aid of similarity transformations. The final controlled equations along boundary restrictions are resolved numerically by Runge-Kutta Felhberg method. The graphical analysis has been emphasized for the fluid and dust phase velocity, temperature and concentration fields to the influence of sundry dynamical flow quantities. Furthermore, for authentication of the present computation, the achieved results are distinguished with earlier research works in specific cases and marvellous agreement has been noted. The outcomes conveyed here manifest that velocity and boundary layer thickness escalate with boost up the values of K1${K_1}$ . Velocity and boundary layer thickness declines with boost up the values of M$M$ . Opposite trend is seen in temperature and concentration profiles. The specific heat ratio parameter γ$\gamma$ enhances the temperature profile declines. Boost up the values of Soret number Sr$Sr$ temperature profile declines and concentration profile enhances. Skin friction factor declines with increasing values βv$\beta _v$ verses M$M$ .