Band 17, Heft 2 -

Hydrogen is one of the important non-conventional energy sources because of its high energy content and non-polluting nature of combustions. The water splitting reaction is one of the significant methods for hydrogen generation from non-fossil feeds. In the present paper, the hydrogen generation has been experimentally investigated with water splitting reaction using metal aluminum in presence of potassium hydroxide as an activator under flow conditions. The rate of hydrogen generation was reported in the annular micro- reactor of 1 mm annulus using various flow rates of aqueous 0.5 N KOH ranging from 1 ml/min to 10 ml/min. The complete conversion of aluminum was observed at all the flow rates of aqueous KOH. The hydrogen generation rate was observed to depend on the flow rate of liquid reactant flowing through the reactor. At 1 ml/min of 0.5 N KOH, hydrogen generates at an average rate of 3.36 ml/min which increases to 10.70 ml/min at 10 ml/min of aqueous KOH. The Shrinking Core Model was modified for predicting the controlling mechanism. The rate of hydrogen generation was observed to follow different controlling mechanisms on various time intervals at low flow rates of aqueous KOH. It was observed that chemical reaction controls the overall rate of hydrogen generation at higher flow rates of aqueous KOH.

An advanced gaseous tracer technique and procedures were developed and executed to study for the first time the axial dispersion of the gas phase in a slurry bubble column reactor (SBCR) using air-C 9 C 11 -FT catalyst. Residence time distribution (RTD) curves were obtained by measuring the pulse-input’s response of the gaseous tracer. The gas phase axial dispersion coefficient (D g ) was obtained from minimum square error fit of the one-dimensional axial dispersion model to the measured tracer response data. The effects of solids loading on the axial dispersion of gas phase and the overall gas holdup have been studied. It was demonstrated that increasing solids loading improves the gas axial dispersion while decreasing the overall gas holdup. This work suggests that gas phase axial dispersion is significant in reactor performance evaluation of bubble columns or slurry bubble columns.

Experiments were conducted to investigate fluidization fundamentals of coarse particle using nitrogen as the fluidizing gas at high pressure. The particle under study was falling in Geldart’s group B/D. A 60-mm-dia. cylindrical Perspex model, a two-dimensional jetting fluidized bed, a 200-mm-semicircular jetting fluidized bed and a 200-mm-dia. cylindrical bed were used in the experiments. The fundamentals of high pressure fluidization examined in this study include minimum fluidization velocity and bed expansion. Empirical correlations were developed for determining minimum fluidization velocity and bed expansion. With the same excess fluidizing-gas velocity, bed expansion generally increases with the operating pressure, but the influence of pressure on bed expansion becomes weaker at higher pressure.

The electrically conducting three-dimensional Williamson fluid flow produced by the movement of sheet via porous medium under non-uniform heat sink and source, thermal radiation and convective boundary condition is examined. The system of nonlinear expressions is transformed into nonlinear ordinary differential system of equations. These governing expressions are evaluated numerically with the help of boundary value problem default solver in MATLAB bvp4c package. Pertinent results are demonstrated graphically to execute the effects of various governing parameters on dimensionless fields. The aspects of constraints on skin-friction, mass and heat transport rates are characterized via numerical benchmarks. It is noticed that the transverse and axial velocities are depreciated by respective Williamson fluid parameters, while the opposite trend is noticed on concentration and temperature fields.

Modelling and controlling of Continuous stirred tank reactor (CSTR) is one of the major problems in the process industry. The nonlinear characteristic of CSTR may change the variation of temperature in either direction from the given set value. Chemical reactions within the CSTR depends on the given reference temperature. Such variation from reference values may result in degrading the variety of biomass. Design and implementation of the precise control device in such system are difficult for researchers. This paper proposes the MIT based control scheme as a solution to control problem of CSTR. An improvement of signal synthesis MIT system has been proposed in this study to enhance the steady-state and transient performance of CSTR. Artificial Bee Colony (ABC) based controller parameter tuning technique is applied to get the optimal performance of the controller. This paper shows the design and implementation of conventional PID tuned with the Z-N method, adaptive PID tune with ABC, MIT and ABC-MIT for CSTR. Detailed comparison based on simulation studies is presented which shows that ABC-MIT based control scheme improves the transient and steady state response.

The photolysis of iron(III) organic complexes in the presence of natural and simulated light was a concern for the role it plays within the environment in terms of producing hydroxyl radicals able to degrade organic products. In the present work, the study focused on two iron(III) organic complexes. The characterization of these complexes by spectrometry allowed to show their stability in environment with a stability constant equal to Log β = 13.13 for the complex Fe(III)-malonate, and Log β = 20.85 for the Fe(III)-malate complex. Photolysis of these complexes was carried out using a lamp at 365 nm at different pHs, and followed by several assay Fe(II), H 2 O 2 and •OH. The complexes present different photo-reactivities, in the case of Fe(III)-malate, the photolysis is favored by the Fenton process and generates hydroxyl radicals, contrarily to Fe(III)-malonate photolysis which generates an oxidizing •CH 2 COOH radical without formation of H 2 O 2 nor of •OH. The presence of oxygen and the addition of isopropanol and chloroform show different effects on the complex photolysis. Complexes mineralization at natural irradiation was also studied using chemical oxygen demand (COD).

Polymerization of propylene was performed in a pilot fluidized bed reactor, resembling an industrial unit. In order to detect agglomeration in this reaction process, wall vibration signatures of the bed, which contains useful information about its hydrodynamics, were measured by an accelerometer. This approach is non-intrusive and can be easily applied in industry. Different methods employed to analyze the measured vibration signatures. Average cycle frequency of the signatures showed that agglomerates were formed and settled down in the reactor during the process. Plot of the power spectral density function of vibration signals showed that the peak corresponding to the dominant frequency generated by bubbles is located around 2,000 Hz. Energy of the signal among the three hydrodynamic structures in the bed (i. e., micro, meso and macro-scales) showed a decrease in share of macro-scale and a slight increase in share of micro and meso-scales due to the formation of agglomerates. The principal component analysis was performed to characterize the hydrodynamic changes occurred in bed due to formation of agglomerates during the polymerization reaction. Using the S-statistic test, changes in the hydrodynamics of the bed due to formation of agglomerates were detected about 20 minutes before defluidization.

In this research, the catalytic conversion of methanol to gasoline range hydrocarbons has been studied over CuO (5 %)/ZSM-5 and CuO (7 %)/ZSM-5 catalysts prepared via sonochemistry methods. Conversion of methanol to gasoline (MTG) has been carried out in a fixed bed reactor under atmospheric pressure and 400˚C temperature, over copper oxide on the synthesized ZSM-5 catalyst. The samples were characterized by XRD, SEM, TEM, BET, and FTIR techniques; in which good crystallinity and high specific surface area of synthesized zeolite were proved after impregnation of zeolite with copper. The present investigation suggests that the CuO/ZSM-5 catalyst made by sonochemistry method can increase the yield toward hydrocarbon production. It was concluded that impregnation of zeolite with copper oxide can alter the Brønsted/Lewis acid sites ratio and provide new Lewis acid sites over the surface of the ZSM-5. The main products of methanol to gasoline reaction over the catalyst that prepared via sonochemistry method were toluene, xylene, ethylbenzene, ethyl toluene, tetra methylbenzene, diethyl benzene and butylbenzene. The total amount of aromatics in the products was 80 % by using this catalyst. Our results suggest that catalyst synthesized by using sonochemistry shows better production yield toward hydrocarbons by affecting the distribution of active sites on the surface of the ZSM-5.

In this study, sulfamethoxazole (SMX) was removed by electrochemically activated persulfate using iron anode. Different oxidation processes (persulfate alone, Fe 2+ /persulfate, electrolysis alone, electrochemically/Persulfate) were investigated, the results showed SMX could be more efficiently degraded under the electrochemically/Persulfate system. Central composite design (CCD) based Response surface methodology (RSM) was used to optimize and elucidate the individual and interactive effects of independent variables on the degradation kinetics of sulfamethoxazole. The maximum kinetics was predicted by CCD as pH 3.6, 18 mA applied current and 3.55 mM/L persulfate concentration. The results of free-radical scavenging experiments and electron paramagnetic resonance (EPR) indicated that both SO4⋅−{\text{SO}}_4^{ \cdot - } and HO· were responsible for the degradation of SMX. The inhibition of methanol (MeOH) was lower than tertiary butanol (TBA), due to the generation of methanol radical (·CH 2 OH), which promoted the reduction of Fe 3+ to Fe 2+ . LC-ESI-TOF-MS analysis was done on SMX and its intermediates. The SMX degradation pathway during the electrochemical treatment was proposed. In addition, two typical inorganic anions (Cl−,HCO3−{\text{C}}{{\text{l}}^ - },{\text{HCO}}_3^ -) were investigated and the inhibitory effect of HCO3−{\text{HC}}O_3^ - was more obvious.

A graphene film deposited on titanium substrate was successfully prepared by a facile solution evaporation method, as electrode exhibiting superior electrosorption property toward methylene blue (MB) from aqueous solution. The fabricated graphene film on titanium substrate was characterized in detail by scanning electron microscopy (SEM) and FTIR techniques. As electrode (GTE) for electrosorption of MB, some experimental parameters, such as applied potential, concentration of electrolyte, solution initial pH and temperature, were systematically investigated and discussed. The experimental results demonstrated that the maximum adsorption capacity using GTE can reach 86.06 mg· g −1 under the optimized conditions of −600 mV of applied potential, pH of 7.5, 293 K and 0.01 mg· L −1 Na 2 SO 4 solution, which is 1.40 times of that obtained under open circuit condition in 10 mg· L −1 MB solution. The adsorption isotherm of MB on GTE was analyzed with Langmuir and Freundlich isotherm equations, Pseudo-first-order model, pseudo-second-order model, and intra-particle diffusion model were applied to depict the adsorption kinetics process. The electrosorption of MB preferably fitted Langmuir isotherm, indicating a single-layer adsorption of MB molecules on graphene film followed pseudo-second-order model. Moreover the electrosorption of MB on GTE was found to be spontaneous and endothermic process. This work would be helpful to design and fabricate high performance carbon-based electrodes for high efficiency electrosorption treatment of dye wastewaters.