Volume 17, Issue 4 -

The steam reforming of biomass pyrolysis oil is a well-established means of producing the more useful bio-hydrogen. Bio-oil has a comparatively low heating value, incomplete volatility and acidity, hence upgrading to a more useful product is required. Over the years, the experimental conditions of the process have been studied extensively in the domain of catalysis and process variable optimisation. Sorption enhancement is now being applied to the system to improve the purity of the hydrogen stream. Lifecycle analyses has revealed that bio-hydrogen offers considerable reductions in energy consumption compared to fossil fuel-derived hydrogen. Also, green-house-gas savings from the process can also be as high as 54.5 %. Unfortunately, techno-economic analyses have elucidated that bio-hydrogen production is still hampered by high production costs. Research endeavours in steam reforming of biomass bio-oil is done with an eye for developing added value products that can complement, substitute (and one day replace) fossil fuels whilst ameliorating the global warming menace.

Al 2 O 3 -TiO 2 (AT) mixed oxide with atomic ratio Al/Ti = 25 and Al 2 O 3 (A) supports were prepared by the sol-gel method and impregnated to obtain monometallic Pd and Pt (1 wt % of metal), and bimetallic PdPt (Pd/Pt = 4) catalysts. These catalysts were tested in the gas-phase hydrodechlorination of 1,2 dichloroethane. The materials were characterized by nitrogen physisorption, X-ray diffraction analysis (XRD), temperature-programmed reduction (TPR) and high-resolution transmission microscopy (HRTEM). AT support showed a BET area (422 m 2 /g), slightly higher than A(374 m 2 /g). The specific activity for the AT supported catalysts was higher than that for the A supported catalysts. The order of activity for the AT supported catalysts was as follows: Pd> PdPt> Pt and in terms of selectivity towards non-chlorinated compounds the order was PdPt> Pd> Pt. The differences in the activities and the selectivities can be explained by the presence of different species of Pd in the supported catalysts.

This paper deals with mathematical modeling and simulation of methanol carbonylation reactor in acetic acid production plant that consisted of a continuous stirred tank reactor (CSTR), a flash drum, a Joule-Thomson valve, and a condenser. The model was based on material and energy balances that considered liquid-gas mass transfer, thermodynamics, and reactor hydrodynamics. The most important aspect of the model was the selection of an appropriate correlation for prediction of mass transfer coefficient. Several correlations were examined and comparison of the model results with plant data indicated that the correlation reported by Lemoine was most appropriate. The simulation results were found to be in good agreement with plant data and the effects of various operating parameters on the performance of the model such as temperature of reactor from 186 °C to 183.6 °C, CH 3 I concentration from 3.11 mol% to 2.21 mol% and agitator rotation speed from 62 rpm to 112 rpm were investigated.

The removal of Methylene blue (MB) from aqueous medium using alkaline modified Maclura pomifera (NaOH-MMP) has been studied in this work. Results showed that a pH value of 6 was favorable for the adsorption of MB. Rate constants of pseudo-first-order, pseudo-second-order and nth kinetic model were determined to analyze the dynamic of the adsorption process; they showed that adsorption kinetics followed a pseudo-second-order and nth kinetic models. The Sips isotherm model was found to be the most relevant to describe MB sorption onto NaOH-MMP with a correlation factor R 2 > 0.999. The adsorption capacity of NaOH-MMP was found to be 160 mg g −1 at 25 °C, confirming its biosorbent efficiency for the removal of MB dye from aqueous solutions. Thermodynamic parameters indicated that the MB adsorption onto adsorbent was feasible in nature, spontaneous, and exothermique.

Mixing of a shear thinning fluid was scaled-up by maintaining equal Reynolds number (Re), tip speed, and power per volume. A standard 45° four-blade pitch blade turbine (PBT) and a modified version of the same impeller (DF-PBT) which provided simultaneous upward and downward flow were used. The impellers were located eccentrically, and the effects of scale-up were determined. The distribution of a tracer solution to evaluate mixing progress, power consumption, and flow fields were analyzed to compare the three different scale-up rules. The same endpoint of mixing was achieved in all cases of PBT with noticeable differences in flow profiles. Higher power consumption and less time were necessary to complete mixing with equal power per volume compared to that with equal Re and tip speed rules. For DF-PBT, only equal Re rule resulted in values similar to that obtained at the small scale. At a scale-up ratio of 2, the selection of scale-up rule should be based on the time and power requirements of the process. As the effects of scale-up on eccentrically located impellers do not differ significantly from those of concentrically located impellers, impellers which have complex dynamics such as DF-PBT require further studies to understand scale-up effects.

Ruthenium-palladium (Ru-Pd) and ruthenium-nickel (Ru-Ni) bimetallic nanoalloy particles with various metal compositions were synthesized by microwave irradiated (MWI) solvothermal technique using PVP (poly-N-vinyl-2-pyrrolidone) as capping agent and ethylene glycol as a solvent as well as reducing agent. Synthesized bimetallic nanoalloy particles were subsequently impregenated onto γ-Al 2 O 3 support to obtain supported nanoalloy catalysts. Agglomeration of nanoalloyparticles were restricted by using excess solvent during synthesis, then distilled and recovered after completion of reaction. Hydrogenation of Dibenzo-18-crown-6 ether (DB18C6) was carried out at 9 MPa, 120°C and 3.5 h using synthesized bimetallic nanoalloy catalysts. It was observed that bimetallic nanolloycatalyst synthesized by MWI using Ru:Pd 3:1 % (w/w), exhibited higher catalytic activity and resulted 98.9 % conversion of DB18C6 with 100 % selectivity towards cis-syn-cis dicyclohexano-18-crown-6 ether (CSC DCH18C6).

The hydrodynamics of gas-liquid dispersion process in a stirred tank with rigid impellers, rigid-flexible impellers, and punched rigid-flexible impellers were investigated using a combined computational fluid dynamics (CFD) and population balance model (PBM) approach. A classical Eulerian-Eulerian approach coupled with standard k-e turbulence model was employed to simulate gas-liquid turbulent flow in the stirred tank. The multiple reference frame (MRF) approach was used to simulate impeller rotation. The effects of impeller type, flexible connection piece length, aperture size/ratio, impeller speed and superficial gas velocity on the local gas holdup and bubble size distribution for the gas-liquid dispersion process were investigated. Results showed that a long flexible connection piece length was conductive to the gas-liquid dispersion process. The optimum aperture ratio and aperture diameter were 12 % and 8 mm, respectively, for the gas-liquid dispersion process. Punched rigid-flexible impeller could reduce the differential pressure ahead and behind the impeller blade, decrease the size of low-pressure zone, and improve the water shear strain rate compared with rigid impeller and rigid-flexible impeller at the same P g,v . It was found that punched rigid-flexible impeller was more efficient in terms of gas dispersibility than rigid impeller and rigid-flexible impeller.

Residence-time distribution (RTD) experiments were performed to analyze an industrial scale three-tube series continuous pulping digester’s hydrodynamic performance. An impulse of radiotracer 82 Br (γ energy source) was introduced at the inlet of the first tube. The radiotracer concentration in the liquid phase was traced at the outlet of each tube. The input behavior of the radiotracer converted to a non-ideal pulse tracer input for the second and third tubes of the digester. Numerical convolution is adopted to deal with the non-ideal pulse input of the radiotracer. A modeling procedure for determining the RTD from the outlet tracer concentration data is proposed. A plug flow component followed by axial dispersion model is considered, and is adjusted after its convolution with the inlet tracer concentration data to obtain the RTD of the individual tubes. The obtained RTD data are analyzed to explain the flow behavior, degree of dispersion, and flow abnormalities existing in the digester. The mean residence-time (MRT), and dispersion number are estimated for the model components for the three tubes. The vessel dispersion number is found to decrease from tube 1 to tube 3. Overall, the conversion of the highly dispersed flow regime into the plug-flow regime is observed in the whole digester.

Fir sawdust was liquefied in phenol solvent under acidic catalyst at 135, 150 and 165 °C, respectively; after neutralization, bio-crude was obtained where contained oil-like liquid and tiny powder-like residue. The bio-crude was chemically modified with urea at high temperature (e. g. > 130 °C) to form carbamate so as to improve chemical reactivity of bio-crude in phenolic resin synthesis. The carbamate-containing bio-crude was condensed with paraformaldehyde into thermosetting phenolic resin. Finally, this biomass-derived phenolic resin matrixed silica fabric laminates were processed. The uncured and thermally cured bio-based resins were characterized by the techniques of Differential Scanning Calorimetry (DSC), Fourier Transform Infrared spectrum (FT-IR), rheology and Thermogravimetric Analysis (TGA), and the laminates’ structure and mechanical performances were studied using the methods of Scanning Electron Microscopy (SEM), three point bending mechanical test and Dynamic Mechanical Analysis (DMA). The results showed: (1) the chemical reactivity of bio-crude was highly improved by carbamation; (2) biomass-derived thermosetting phenolic resin was thermally curable at 150–250 °C (with two exothermic peaks at 185 °C and 220 °C); (3) the char yield was about 47 %, which was not in apparent relationship with sawdust liquefaction temperatures; (4) flexural strength of silica fabric laminates at room temperature was around 357 MPa (similar with that of conventional phenolic laminate); (5) glass transition temperature of silica fabric laminate was above 270 °C (much higher than T g of conventional phenolic resin laminate, which is normally at 215 °C). The biomass-derived phenolic resin is expected to be widely used as cost-effective and environment-friendly thermosetting resin in the application of high-performance composites.

Numerical investigations of an anti-corrosion design and the combustion process (original conditions and optimal conditions) were conducted for a 660 MW opposed wall fired boiler. In order to solve high-temperature corrosion of the side wall, a scheme was proposed: slotting in the side wall and introducing air (closing-to-wall air) from the secondary air. The effect of anti-corrosion was disclosed in detail by varying the structures of slotting, gas velocities from nozzles and jet inclination angles. The temperature and NOx distribution in the furnace at optimized conditions were compared with those at the original operating conditions. Simulation results showed that the structures of the slot and gas velocities from the nozzles had a marked effect on anti-corrosion of the side wall. When the gas velocity was 4 m/s, an inclination angle of the gas velocity was not conducive to anti-corrosion of the side wall. When the gas velocity increased at the middle and bottom of the side wall, the anti-corrosion effect increased significantly. When the optimal scheme was adopted, the corrosion area of the side wall decreased obviously, but the furnace temperature and the NOx emission increased slightly. The detailed results of this work promote a full understanding of closing-to-wall air and could help to reduce the corrosive area in pulverized-coal furnaces or boilers.