The main goal of this paper is to generate a complete phase envelope for natural gases based on a exponential decay distribution for C6+. Using this technique, a single dew point measurement provides enough information to generate an accurate phase envelope. Using the single dew point measurement, appropriate distribution for C6+ is determined. The distribution will contain normal alkanes ranging from nC6H14 to nC17H36. Once the distribution is determined, a complete phase envelope containing the bubble point curve, dew point curve, retrograde curve, and hydrate curve can be generated. We have verified that the exponential decay or logarithmic distribution of hexane plus will improve the accuracy of PHLC (Potential Hydrocarbon Liquid Contenet) prediction by using a hexane plus molecular weight to match a single dew point. This approach enables the generation of full and accurate phase envelopes. This technique may be applied with any EoS of state so long as proper binary interaction coefficients are employed.
The potential of simple fluidic circuits, based on oscillators and laminar resistance, for the smart metering of fluids is examined. If fluid properties are unknown a single fluidic oscillator is only capable of volumetric metering if it has a constant Strouhal number, which is often not the case. With known viscosity, flowrate and density can be determined by measuring both frequency and the pressure drop across a meter with variable Strouhal number. A fluidic oscillator in parallel with a laminar resistance is known to have a significantly extended flow range, but it is shown to be unable to measure flowrate, density and viscosity. This is, however, achieved by placing a further oscillator in series, forming a two meter by-pass system. This is shown to have potential both as a Reynolds number meter, by measuring two frequencies, or with the additional measurement of a pressure drop, as a smart system simultaneously measuring flowrate, density and viscosity. Two target type fluidic oscillators and a laminar resistance are built and calibrated experimentally using air. These are then combined to form a two meter by-pass system which is again tested with air. The tests confirm the operation of the system both as a Re meter and for simultaneous measurement of flowrate and gas properties. The options in designing the system including component matching are briefly discussed and the potential of the technology for application at the micro-scale is highlighted.
Three-dimensional direct numerical simulations of the motion of a Newtonian drop rising in Carreau–Yasuda model fluids were carried out by a coupled level-set/volume-of-fluid (CLSVOF) method. Our numerical approach simulated faithfully the physical shear-thinning properties and 3D-nonlinear dynamics that are observed in experiments. Three-dimensional computational results showed that the local change in viscosity around a drop greatly depended on the drop shape and the shear-thinning properties of the quiescent liquid. We quantitatively considered the drop rise motion based on the modified dimensionless numbers (ReM and MM) and the effective viscosity.
Various aspects of crystallization of THF hydrate have been studied. It has been found that formation of THF hydrate is possible between solution concentrations of 9 and 46% by weight. Induction time for nucleation in various solutions has been determined. The results indicate that the lowest induction time for nucleation corresponds to solutions with a THF concentration of 19% by weight. This solution concentration matches with the THF composition in the crystalline hydrate. The metastable zone for primary nucleation has been investigated and concluded that for each stirrer speed, THF hydrate forms at a higher temperature when the solution concentration is 19% by weight. The next conclusion is that the higher the stirrer rate, the narrower the metastable zone. Nucleation and growth rates have been evaluated from a series of experiment by s-plane analysis. Compared with the growth rate, nucleation rate has been found to be a stronger function of the stirrer speed. Both rates increase with subcooling but in the case of the growth rate, only a slight increase has been observed at high levels of subcooling and stirrer speeds. A regression analysis resulted in derivation of kinetics correlations between the significant process variables and the consistency between the correlations and the experimental data has been examined.
The Distinct Cell Model (DCM) for the contact detection in the algorithm of the Discrete Element Method was proposed to improve the calculation speed when particles have a large size ratio. This model has several grids, which are overlapped three-dimensionally, and the particles having different size are boxed in a suitable grid cell. The contact detection time of this model was measured and compared with that of the conventional cell model in the simulation of a rotating dram. The contact detection using the DCM was extremely faster than that of the conventional cell model; e.g. when particles had a size ratio of dmax/dmin = 15, the speed-up was about 25. The speed-up ratio increases with increasing particle size ratio, regardless of the number of grids. This model has an advantage of being able to set optimum cell sizes for all particles, thus, the number of searching cells and contact check can be minimized. The optimum cell size of the DCM is the size that each cell has about 1 particle in it when two grids are used, 0.3–0.6 particles in the case of more than three grids. The large-scale simulation of granular flow having a large particle size ratio will be possible by using the Distinct Cell Model.
This paper reports on the performance of an internally Heat-Integrated Distillation Column (HIDiC) in separation of ternary mixtures. Separation of two ternary mixtures, benzene–toluene–p-xylene and n-pentane–cyclopentane–2-methylpentane, are studied to determine the effect of the span of boiling points on the performance and the energy savings of the HIDiC. For the former mixture, the HIDiC consumes about 30% less energy than a conventional distillation column, while for the latter mixture, even a higher degree of about 50% reduction of energy consumption is achieved. Although the efficiency of the HIDiC depends heavily upon the mixtures to be separated, it has been found that the HIDiC can be a very efficient alternative for the separation of ternary mixtures provided the span of boiling points is narrow enough to allow feasible application of heat pump techniques. The internal heat integration design and system performance were also evaluated by sensitivity analysis.
A model for predicting the cooling profile used in the batch cooling crystallization was introduced. The model includes the supersaturation- and suspension density-dependent secondary nucleation rate, the supersaturation-dependent growth rate, the seeding condition and the batch time. The cooling profile was predicted by numerically solving the model equation when the constant supersaturation was chosen to be the control target. For the different sets of operating conditions, i.e. seeding condition and batch time, different cooling profiles together with the control target, i.e. different constant levels of supersaturation, were predicted. The predicted supersaturation levels were verified experimentally in the crystallization of potassium dihydrogen phosphate (KDP). The product crystals with mono-modal size distribution were obtained with a cooling mode of reducing secondary nucleation predicted by the model.
As an important approach to improve the fuel economy of lean-burn engines, cutting down the thermal loss will lower the exhaust temperature. In response to this technical challenge, the enhancement of the low temperature performance turns out to be an imperative issue with the NOx storage and reduction (NSR) catalysts. Targeted at gaining technical information on upgrading practical NSR catalysts, NOx storage reactions over a model NSR catalyst under a series of lean-burn exhaust atmospheres and a corresponding thermodynamic analysis were conducted in this research. It was found that, below 400°C, the residual reducing agents of CO and C3H6 in the lean gas reduced NO2 to NO over the NSR catalyst; hence, the outlet NO2 concentration fell lower than the value derived merely from thermodynamic equilibrium with NO oxidation reaction. With CO and C3H6 existing in the reaction atmosphere, it did not matter if NO2 or NO was used as the inlet NOx species; the outlet NO2 concentration would turn out the same. Thus, the NOx storage amount with NO2 as an inlet NOx species is approximately the same as that with NO. If no CO and C3H6 are present in the reaction atmosphere, the outlet NO2 concentration equaled the thermodynamic equilibrium value with NO oxidation reaction, while an increase in the NOx storage amount with NO2 as an inlet NOx species had been observed. These results indicated that the enhancement of NO oxidation to NO2 and the removal of the residual reducing agents from the exhaust gas are both necessary for improving the NOx storage performance at low temperatures.
Methane steam reforming (MSR) over a Rh-loaded Ce0.15Zr0.85O2 catalyst in a membrane reactor was investigated. An yttria-stabilized zirconia (YSZ) membrane used in the membrane reactor showed an ideal H2/N2 selectivity of 6.6 at a H2 permeance of 3.3 × 10–6 mol m–2 s–1 Pa–1 at 500°C. Methane conversions in the membrane reactor were higher than those in a packed bed reactor due to the sufficient permeation rate of hydrogen, which shifted the equilibrium, reaching 82% at 550°C. To evaluate the stability of a membrane reactor, the methane conversion was measured as a function of time. As a result, no significant change in methane conversion was evident at 500°C for 7 h.
Process asymmetry often introduces severe difficulties to process modeling and worsens control system performance. In this work, a simple modeling framework is proposed, which can effectively trade-off the difference between positive and negative process dynamics. It is characterized by small modeling effort in the consideration of process asymmetry. Modeling and control of a nonlinear high-purity ideal heat-integrated distillation column is conducted and the results obtained demonstrate the effectiveness of the modeling method proposed.
The biofilm formation of the cyanobacterium Synechococcus sp. strain PCC 7942-SPc-BF, an isolate from the culture of Synechococcus sp. strain PCC 7942-SPc, has been investigated in terms of growth kinetics and superficial gas velocity of the bioreactor. Initial attachment of the cells in planktonic growth to the bioreactor surface took place steeply in the situation where the nitrate concentration dropped beyond the critical value. Kinetic analysis showed that the specific growth rate of the population was higher in biofim growth than in planktonic growth. In addition it was observed that biofilm formation was strongly influenced by the detachment rate that has a positive relation with superficial gas velocity. Cells in biofilm growth showed higher hydrophobicity than those in planktonic growth.
Conversion of hot coke oven gas (COG, containing tarry material) into light fuel gas over a Ni/Al2O3 catalyst was studied. Laboratory scale tests were carried out in a two-stage fixed-bed reactor at ambient pressure. The nickel catalyst promoted the hydropyrolysis reaction of tarry materials. High yields of total product gas and methane were obtained at high hydrogen concentrations. If the hydrogen supply was adequate for hydropyrolysis of the tarry material, conversion of coal volatiles was high, at more than 95% on carbon balance, even with a gas residence time as short as 0.15 s in the catalyst bed. The product gas yield depended on catalytic temperature. At 923 K, the maximum conversion of coal volatiles into the light gas was achieved at 95.0% on carbon balance, with methane 86.7 vol% of the carbonaceous gas product. Although carbon deposits deactivated the catalyst after a long period of use, the catalyst could be regenerated by treatment with oxygen at 800 K, providing high activity in subsequent decomposition of tarry material. The influence of sulphide on the tarry material decomposition reaction was small even in a 2000 ppm H2S atmosphere.
Co-grinding of monochlorobiphenyl (BP-Cl) with rare earth oxides has been conducted and the mechanochemical decomposition of BP-Cl on the oxides has been investigated by a suite of analytical methods including X-ray diffraction (XRD), thermogravimetry (TG), Raman spectroscopy, electron spin resonance (ESR), gas chromatography/mass spectrometry (GC/MS). The experimental results have been compared with the use of CaO as additive and the differences have been discussed. It has been found that the use of rare earth oxides allows an efficient decomposition of BP-Cl and the time required to complete the decomposition reaction is much shorter than that by the use of CaO.
The metallic semiconductor of TiO2 was immobilized in thin-film during UV photodegradation of AY-36. Immobilizing the catalyst allowed H2O2 to be present at the start of photodegradation without fear of recombination, electron band competition, and destruction of immobilized photocatalyst. The photodegradation of AY-36 was improved by 90%. Decolorization in the present method was begun more slowly but by 75 min, no difference was observed. An enzymatic method has been conducted to accurately measure the formation of extra-H2O2 concentration and its decomposition. The pH needed no adjustments; it increased slightly instead of decreasing as was seen in the previously tried AOP methods. This method has the potential of both increasing degradation and slightly reducing costs in practice.
The organic carbon (DOC) leachability of bottom ash samples obtained from two different sources, municipal solid waste (MSW) and industrial solid waste (ISW) incineration facilities, were investigated aiming at enhancing the washing efficiency of DOC. The relationship of DOC leaching with minerals in bottom ash was also studied as a tool for the prevention of their impact on the environment. Furthermore, ultrasound was applied to enhance the efficiency of the conventional washing method and shorten the washing time of DOC from bottom ash. MSW incinerator bottom ash (M-ash) showed a DOC leaching pattern dependent on pH; the higher DOC leaching was observed at the lower pH, while ISW incinerator bottom ash (I-ash) showed DOC leaching independent of pH. DOC leaching in M-ash appeared to be trapped in the solid matrix by stable soluble calcium-aluminosilicate mineral species, identified by X-ray diffraction (XRD) measurements. Approximately 50% of additional DOC leaching could be achieved when pH was lowered from alkaline-neutral to the acid range due to the dissolution of these mineral species in acid pH. Calcium-aluminumsilicate species were not detected in I-ash and therefore ratified the liability of these species for blocking the DOC leaching from M-ash. Ultrasound significantly increased the efficiency of the conventional washing method as well as shortened the washing time of DOC from 60 to 5 min in M-ash. Moreover, ultrasound would be considered as a feasible treatment method to minimize environmental impacts of landfill sites over short- and long-term considerations.