Liquid-phase degradation of polyethylene wax over mordenite catalysts with different Si/Al molar ratios

The catalytic liquid-phase degradation of polyethylene wax into fuel oil was studied using mordenite catalysts with various Si/Al molar ratios prepared by dealumination. The total yield of gas and liquid products showed a volcano plot along the Si/Al molar ratio of mordenite. No significant change was observed in the composition of the liquid product for all catalysts used in this study. Fast deactivation was anticipated on the mordenite catalysts with low Si/Al molar ratios such as 5 and 10, due to pore blocking by the carbon deposited on the external surface of the zeolite. A high activity and a long catalyst life were obtained on the mordenite catalyst with a Si/Al molar ratio of 12.     

Effect of ZnO contents at the surface of brass-plated steel cord on the adhesion property to rubber compound

An effect of ZnO concentration at the surface of brass-plated steel cord on the adhesion property between a rubber compound and a brass-plated steel cord was investigated. Cord composition was determined by an Auger microscope with Ar ion sputtering. Two different steel cords were prepared; one (cord A) had higher ZnO concentration at the cord surface compared to the other (cord B). Pull-out force of unaged adhesion sample of cord A was lower than that of cord B. But the adhesion durability of the humidity-aged adhesion sample of cord A was better than the latter. Rubber coverage of the pull out cord for the unaged adhesion samples of cord A was poor, indicating insufficient formation of an adhesion layer. Pull-out force of the thermal-aged adhesion samples decreased with increasing aging time and that of cord A was lower than that of cord B. The enhancement of rubber coverage during initial aging period could be explained by an additional formation of copper sulfide at the adhesion interphase and an increase of modulus of rubber compound adjacent to the adhesion layer. With further increases of aging time, adhesion interphase grew excessively and the physical property of rubber compound deteriorated significantly, such that rubber coverage of adhesion samples decreased markedly with increasing aging time.     

Effect of cathode inlet manifold configuration on performance of 10-cell proton-exchange membrane fuel cell

A 10-cell proton-exchange membrane fuel cell (PEMFC) stack with 10 cathode flow channels is employed to investigate the effect of airflow inlet manifold configuration on the overall performance. Four different types of airflow inlet manifold with a 90° turn are considered. First, the flow patterns according to the manifold configuration are numerically sought. The computational result for the improved inlet manifold predicts about 8.5% increase in the uniformity of the airflow distribution. The experiments are carried out to confirm the numerical predictions by measuring actual airflow distributions through the fuel cell stack. The polarization curve and the power curve for the 10-cell PEMFC are also obtained to determine the effect of inlet manifold configuration on the actual performance. The maximum power output increases by up to 10.3% on using the improved airflow inlet manifold.     

Hydrogen production by steam reforming of liquefied natural gas over a nickel catalyst supported on mesoporous alumina xerogel

Mesoporous alumina xerogel (A-SG) is prepared by a sol–gel method for use as a support for a nickel catalyst. The Ni/A-SG catalyst is then prepared by an impregnation method, and is applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of the mesoporous alumina xerogel support on the catalytic performance of Ni/A-SG catalyst is investigated. For the purpose of comparison, a nickel catalyst supported on commercial alumina (A-C) is also prepared by an impregnation method (Ni/A-C). Both the hydroxyl-rich surface and the electron-deficient sites of the A-SG support enhance the dispersion of the nickel species on the support during the calcination step. The formation of the surface nickel aluminate phase in the Ni/A-SG catalyst remarkably increases the reducibility and stability of the catalyst. Furthermore, the high-surface area and the well-developed mesoporosity of the Ni/A-SG catalyst enhance the gasification of surface hydrocarbons that are adsorbed in the reaction. In the steam reforming of LNG, the Ni/A-SG catalyst exhibits a better catalytic performance than the Ni/A-C catalyst in terms of LNG conversion and hydrogen production. Moreover, the Ni/A-SG catalyst shows strong resistance toward catalyst deactivation.     

Long term operation of high concentration powdered activated carbon membrane bio-reactor for advanced water treatment.

A pilot scale experiment was conducted to evaluate the performance of a membrane bioreactor filled with high concentration powdered activated carbon. This hybrid system has great potential to substitute for existing GAC or O3/BAC processes in the drinking water treatment train. The system was installed at a water treatment plant located downstream of the Nakdong river basin, Korea. Effluent of rapid sand filter was used as influent of the system which consists of PAC bio-reactor, submerged MF membrane module and air supply facility. PAC concentration of 20 g/L was maintained at the beginning of the experiment and it was increased to 40 g/L. The PAC has not been changed during the operational periods. The membrane was a hollow fiber type with pore sizes of 0.1 and 0.4 microm. It was apparent that the high PAC concentration could prevent membrane fouling. 40 g/L PAC was more effective to reduce the filtration resistance than 20 g/L. At the flux of 0.36 m/d, TMP was maintained less than 40 kPa for about 3 months by intermittent suction type operation (12 min suction/3 min idling). Adsorption was the dominant role to remove DOC at the initial operational period. However the biological effect was gradually increased after around 3 months operation. Constant DOC removal could be maintained at about 40% without any trouble and then a tremendous reduction of DBPs (HAA5 and THM) higher than 85% was achieved. Full nitrification was observed at the controlled influent ammonia nitrogen concentration of 3 and 7 mg/L. pH was an important parameter to keep stable ammonia oxidation. From almost two years of operation, it is clear that the PAC membrane bioreactor is highly applicable for advanced water treatment under the recent situation of more stringent DBPs regulation in Korea.     

Effects of anisotropic bending stiffness of gas diffusion layer on the MEA degradation of polymer electrolyte membrane fuel cells by wet/dry gas

The effects of anisotropic bending stiffness of a gas diffusion layer (GDL) on membrane electrode assembly (MEA) degradation were investigated. We prepared GDLs with a fiber direction perpendicular to the major flow (i.e., “90° GDL”) and with a fiber direction parallel to the major flow (i.e., “0° GDL”). To analyze the mechanical durability as a function of GDL anisotropy, we examined cell performances such as the I–V characteristics and impedances and the hydrogen crossover characteristics during wet/dry cycles. The results showed that the 90° GDL fuel cell is superior to the 0° GDL fuel cell in terms of higher I–V performance, lower resistance at high frequency, and lower hydrogen crossover through the MEA. Mechanical degradation of the 0° GDL was investigated using scanning electron microscopy (SEM).     

NUMERICAL COMPUTATIONS OF STEADY AND UNSTEADY,SEPARATING, BUOYANT FLOWS - PART II: COMPUTATIONS WITH A LOW-REYNOLDS-NUMBER k -ε MODEL

Numerical computation has been performed to determine the influence of buoyant effects on convective flows with the standard k- k and the low-Reynolds-number k- k models. Results obtained with both turbulent models are compared with the available experimental data. In this work, Kolmogorov velocity, u k = (v k ) 1/4 , is introduced instead of shear velocity, u = ¡ ( w / 𝜌 ), to avoid the singularity that appears at the separating and reattaching point for both turbulence models. Turbulent Prandtl numbers were allowed to vary in the low-Reynolds-number k- k model to mimic the experimental data. Buoyant effects have been investigated with various Richardson numbers for the backward-facing step flow. Various separation patterns as well as vortex shedding were observed beyond a critical Richardson number. In addition, the required grid configration for accurate results for the low-Reynolds-number k- k model has been discussed for the backward-facing step flows.     

Preenrichment versus direct selective agar plating for the detection of Salmonella Enteritidis in shell eggs

The relative effectiveness of two methods for the recovery of Salmonella Enteritidis (SE) from jumbo and medium shell eggs was compared. The first method used in the comparison consisted of a preenrichment of the sample, and the second method was developed by the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). Three bulk lots of blended, pooled eggs, each containing 220 liquid whole eggs that were thoroughly mixed manually were artificially inoculated with different levels of SE cells between approximately 10(0) and 10(3) CFU/ml. Twenty samples containing the contents of approximately 10 eggs each (by weight) were withdrawn from each of the inoculated bulk lots and incubated for 4 days at room temperature (ca. 23 degrees C). For the APHIS method, each sample was cultured by direct plating onto brilliant green (BG), brilliant green with novobiocin (BGN), xylose lysine desoxycholate (XLD), and xylose lysine agar Tergitol 4 (XLT4) agars. For the preenrichment method, 25-g portions from each pool were enriched in modified tryptic soy broth with 30 mg/liter of FeSO4. After 24 h of incubation, the preenrichments were subcultured to tetrathionate and Rappaport-Vassiliadis broths, and streaked to BG, BGN, bismuth sulfite, XLD, and XLT4 agar plates. SE isolates were confirmed biochemically and serologically. In all of the experiments, the preenrichment method recovered significantly more SE isolates (P < 0.05) of all the phage types and inoculum levels than did the APHIS method. From a total of 539 jumbo egg test portions analyzed, 381 (71%) were SE-positive by the preenrichment method and 232 (43%) were positive by the APHIS method. From a total of 360 medium egg test portions analyzed, 223 (62%) were SE-positive by the preenrichment method and 174 (48%) were positive by the APHIS method. The preenrichment method provided greater sensitivity for the isolation of SE in contaminated egg slurries than did the APHIS method.     

Numerical Study of the Effects of the Face Velocity on Ceramic Filter

INTRODUCTIONTheproductsofcoalcombustionsuchasNOx,SOx,COb,andparticulatehavebeenstronglyregulatedtoreducepollutionintheearthenvironment.TherecentlydevelopedCleanCoalTechnologies(CCT)knownasPressurizedFluidizedBedCombustion(PFBC)[']andintegratedGasificationCombinedCycle(IGCC)I"']providetheimprovementofthermalefficiencywithsignificalltlyreducedenvironmelltalimpacts.ThusthePFBCandIGCChaveincreasingattentiontoachievestringentenvironmentalprotection.Advancingthetechnologyofthehotg…