Modeling and simulation of flue gas desulfurization over sorbent synthesized from CaO/CaSO4/coal fly ash in a fixed-bed reactor has been studied. A mathematical model was proposed based on the material balance for the gaseous and solid phase using partial differential equations to describe the adsorption of SO2 from a moving gas stream to the sorbent-bed of changing composition. The kinetic parameters of the mathematical model were obtained from a series of experimental desulfurization reactions carried out under isothermal conditions at various operating parameters; initial concentration of SO2 (500 ppm ≤ Co ≤ 2000 ppm), reaction temperature (333 K ≤ T ≤ 373 K) and relative humidity (40% ≤ RH ≤ 70%). The partial differential equations were solved using a finite difference method. The model was found to give a very good description of the experimental data with an error less than 10%. The validated model was then used to predict the reactor performance under different modes of operation. It was found that higher relative humidity in the feed gas and higher reaction temperature increases the desulfurization activity of the sorbent. On the other hand, higher initial concentrations of SO2 reduce the desulfurization activity of the sorbent.
A preliminary study was performed for the extraction of trioxane using supercritical fluids. It is found that carbon dioxide is an effective extractant for trioxane separation and is used as a solvent. The higher is the pressure under the same temperature, the larger amounts of trioxane extracts are obtained. Higher concentrations of trioxane solutions are obtained by supercritical fluid extraction than by common distillation of a trioxane–water.
Kinetic investigations were carried out to evaluate the applicability of used black tea leaves (UBTLs) as a low-cost adsorbent to the removal of chromium(VI) from aqueous solutions. The effects of various kinetic parameters were investigated using a batch process. The adsorption of Cr(VI) on UBTLs occurs rapidly in the first day, followed by a slow process that requires more than 10 days to reach its equilibrium. The initial adsorption rate increases with increasing initial concentration of Cr(VI) in the solution and processing temperature. The adsorption kinetics follows Richie’s pseudo-second order rate equation better than the Lagergren’s pseudo-first order one. The rate constant of the pseudo-second order adsorption is affected by the processing conditions such as the initial Cr(VI) concentration, solution pH, temperature and foreign ions. The results of the kinetic experiments showed that the adsorption of Cr(VI) on UBTLs is an endothermic process and the activation energy of adsorption is 16.3 kJ mol–1.
Recently, the wavelet transform analysis based on the localized functions has been utilized to effectively analyze the pressure fluctuation signals. The pressure fluctuation signals can be decomposed into its approximations and details at different resolutions. By the wavelet transform, the time-frequency distribution of energy was described by the multi-resolution method. The result from the maximum energy of the approximations by wavelet transform analysis agreed with the result of the standard deviation analysis of pressure fluctuations. As seen from this study, the wavelet analysis in comparison with the standard deviation analysis, power spectral density function (PSDF), and the energy of PSDF enabled us to obtain the transition velocities, Uc and Uk, in characterizing the flow regimes of the fluidized bed.
A simple mathematical model for efficient short-term scheduling of non-sequential multi-product-multi-unit batch processes with unit- and sequence-dependent setup/changeover times and mixed intermediate storage policies is proposed. The scheduling objective is to minimize the makespan or the earliness of the completion of orders. When some of the sequence-dependent changeover times are relatively large compared to the processing times, a rigid formulation is provided to achieve optimality, which is seldom attended to in previous studies. Several intermediate storage policies for the batch processes are considered, including unlimited intermediate storage (UIS), no intermediate storage (NIS), finite intermediate storage (FIS), zero wait (ZW), and mixed intermediate storage (MIS). The problem is then formulated as a mixed-integer linear program (MILP). Two numerical examples are supplied to demonstrate the efficiency and the wide applicability of the proposed scheduling model in face of various different environments.
The objective of this paper is to present a framework for assessing and improving safety equipment items performance based on maintainability, reliability and availability. The main idea is to employ Principal Component Analysis (PCA) and Importance Analysis (IA) to provide insight on safety equipment items performance. The validity of the model is verified and validated by Data Envelopment Analysis (DEA). Furthermore, a non-parametric correlation method, namely, Spearman correlation experiment shows a high level of correlation between the findings of PCA and DEA. At first PCA is used for assessing the performance of safety equipment items and ranking them. IA is then performed for the worst safety equipment item which could have most impact on the overall system effectiveness to classify their components based on the Component Criticality Measures (CCM). The analysis of the classified components can ferret out the leading causes and common-cause events to pave a way toward decreasing failure interdependency and magnitude of incidents which ultimately maximize overall operational effectiveness.
In order to enhance the biodegradability of the excess sludge generated from the wastewater treatment, a centrifugal vibration mill was used to mill the activated sludge. The centrifugal vibration mill had a column with a volume of about 10 × 10–3 m3 and the sphere stainless steel balls were used. The operational conditions were changed, and the biodegradability of milled sludge was evaluated by using the BOD. The ball diameter of 7.9 mm was optimum in this experimental condition. The biodegradability of sludge increased with the milling time and became constant beyond 12 minutes. It had a maximum when the effective volume fraction (the ratio of the sludge volume to the void volume in ball bed) was unity.
The interesterification of olive oil with palmitic acid catalyzed by Rhizopus delemar lipase was investigated in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) microemulsions. The maximal reaction rate was obtained at a buffer pH of 5.0–6.5. The reaction rate also attained a maximum at a W (=[H2O]/[AOT]) value of 2–5 and a palmitic acid concentration of 125 mM. The molar percentage of the interesterified product 1,3-dipalmitoyl-3-oleoyl glycerol (POP) in the olive oil was markedly enriched from 2.8 to 22.7 mol% after 24 h of the reaction.
In this work three kinds of N-acetyl-D-glucosamine transferase were purified from the crude extract of pupae of Papilio xuthus Linné through Sephadex G-25 gel filtration chromatography and CM-Sephadex C-50 ion exchange chromatography. Thermal stability of these enzymes were 35–55°C and optimal pH for transferase activity appeared at 6.5–7.0. Each enzyme could react with N-acetyl-D-glucosamine, and produced insoluble deposit suggesting highly polymerized chitooligosaccharides. These catalytic properties somewhat differ from those of chitintransferase purified from pupae of Pieridae belonging to the same order.