A useful model, Group-Contribution method based Modified Wilson equation (GC-MW) previously developed, has been extensively adopted to calculate liquid–liquid equilibria (LLE) for quaternary systems consisting of alkane, methanol and aromatics (type I and type II) from pure-component properties alone. Further, its applicability has been evaluated in comparison with UNIFAC widely applied.
The present study mainly investigates bubble behaviors in an agitated vessel. Computational fluid dynamics provides a method for exploring the complex fluid flow in an agitated vessel. A stirred tank model with transport equation for the interfacial area concentration and force equilibrium equation for bubbles under multi-forces is created for a 43-dm3 agitated vessel. The model considers the breakage and coalescence mechanism of the bubbles. The local gas holdup is measured by fiber-optical probe. After this, the bubble size distributions are calculated by the interfacial area concentration model. The simulations with validated models show good agreement with the experiments. From the simulation results, the area in which the gas holdup value is greater than 0.01 extends 37% in the upper circulation region when the rotation speed is increased to 40 rad/s from 20 rad/s. However, in the lower circulation, the gas holdup maintains a low level due to the existence of a “death zone”. The simulations indicate that the bubble breakage mainly occurs in the impeller outflow region and the coalescence occurs in the upper circulation region. For bubble behaviors being in the lower circulation region, bubble coalescence or breakage is determined by the flow field pattern in the vessel. Moreover, it is difficult for the simulation process to converge when the virtual mass force is considered and there is a lack of effective technology to measure it, which has led researchers to generally ignore this force. In order to analyze the virtual mass force, the present study utilizes computer programming which is based on the virtual mass force formula to obtain the force. The results show that at positions close to the impeller tip and the center of the upper region, the virtual mass force value is 0.015 and 0.017, respectively, but the value is approximately zero in the bulk of the tank. Hence, the bubble has two significant stages of acceleration process in the vessel.
Hydrogen production using a Pd membrane reformer from desulfurized kerosene is attractive in view of the portable and domestic use of fuel cells. In the present study, membrane reforming of desulfurized kerosene with a pre-reformer was carried out and compared to that of dodecane, which is the main compound in kerosene. The reactivity of desulfurized kerosene was much lower than that of dodecane, resulting in the low performance of the membrane reformer for desulfurized kerosene. In the pre-reforming and membrane reforming of model kerosene (a mixture of dodecane and m-xylene), the performance of the pre-reformer and membrane reformer exhibited a similar trend to those for desulfurized kerosene. This low performance of the membrane reformer may be ascribed to the lowering of Pd membrane performance. From the evaluation of Pd membrane performance in the presence of co-products in the pre-reforming of desulfurized kerosene and model kerosene, polycyclic aromatics such as naphthalenes, anthracene and pyrene reduced the H2 permeability of Pd membranes.
Optical properties of nano–structured ZnO : Sn powders prepared by means of a one–step micro drop fluidized reactor continuously were investigated. The band–gap edge of ZnO : Sn powder was extended to the visible region due to the formation of the extrinsic levels of interstitial oxygen and oxygen vacancy in the band structure of ZnO. The BET surface area of ZnO : Sn powders increased by up to 300%. The fluidization of micro drops of precursors during thermal decomposition contributed to the formation of porous surface morphology and modification of band gap structure of the ZnO : Sn powders by generating micro shear force and strain at the surface of micro drops. The doping of Sn4+ ions into ZnO reduced the electrical resistivity by generating extra free electrons at the surface of ZnO : Sn powders.
Azo dye waste water is a serious problem because of the high yield, the low biodegradability and the high toxicity. In this work, the heterogeneous Fenton process was employed to degrade methyl orange (MO) using Copper(II)–benzoic acid (CuBA) as the catalyst in the HCO3− solution using H2O2 as the oxidant. CuBA was prepared by a complexing reaction. It was analyzed by FTIR and catalytic activity. The effects of different parameters on the degradation efficiency of the process were studied. The results were found that 90.8% MO degradation efficiency was achieved within 30 min under the best conditions of initial pH 7.0, 1.2 mM of CuBA, 25 mg/L of MO, 10 mM of NaHCO3 and 0.40 g/L (m/V) of H2O2 at 40°C. The kinetics of degradation of MO followed first-order reaction kinetics. A possible pathway of MO degradation was also proposed based on the detected intermediate products by UV-Vis, IR, mass spectrometry. MO was effectively degraded by CuBA/NaHCO3/H2O2 under the neutral and alkalic conditions. The CuBA/NaHCO3/H2O2 system overcomes the two problems faced by the homogeneous Fenton process.
Principal component analysis (PCA) is widely used in chemical process monitoring. It selects the first several principal components (PCs) with the most variances information of normal observations for process monitoring. However, PCA may ignore fault information contained in the subspace spanned by the rejected PCs. In this paper, we propose a novel algorithm called sparse principal component selection (SPCS). SPCS can be formulated as a just-in-time reorganized PCA algorithm that constructs an elastic net regression between all PCs and each sample. SPCS selects PCs according to the non-zero regression coefficients which indicate the compact expression of the samples. This expression is naturally discriminative: amongst all subset of PCs, SPCS selects the PCs that most compactly expresse the samples and reject all other possible but less compact expressions. The case studies on the Tennessee Eastman process demonstrate the effectiveness of SPCS on process monitoring. The performance of SPCS is significantly better than other PCA based algorithms.
For ensuring the production quality and operation stability of chemical batch reaction systems under uncertainty, an operation feasibility analysis framework with production quality and flexibility consideration is proposed. The whole suitable range and the optimization operation point of the manipulated variable in the reaction systems can be found by using the proposed framework. In the proposed strategy/framework, the Nelder–Mead method is combined with the golden section method to solve the operation feasibility analysis problems. A concept of the Operation Feasibility Index problem (OFI) is also introduced to find the exact feasible operation range of the manipulated variable for batch reaction systems under uncertainty. The proposed strategy is investigated by two typical batch reaction systems. All the simulation results demonstrate that the proposed approach may provide an effective tool for the operation feasibility analysis of batch reaction systems under uncertainty.
This paper proposes a novel batch process monitoring method called adjoined time series principal component analysis (AdTsPCA). In this method, a modified GG clustering is used for phase identification and data segmentation and multiple time-ordered overlapping PCA models are constructed from the data segments. The PCA models are then used for statistical process monitoring. The key characteristic of AdTsPCA is that additional information contained in the order of PCA models allows for additional diagnosis by the comparison of known process phase and suspected abnormal situation. The proposed AdTsPCA is applied to an industrial penicillin fermentation process to illustrate the effectiveness of the method. AdTsPCA is able to detect faults in the process and significantly reduces the number of false positive errors in the process monitoring.
A combination of the co-assembling process to fabricate binary colloidal crystals (BCCs) and the successive heat treatment to selectively remove the polymer component from the BCCs was conducted to create double inverse opals (DIOs) in which a movable sphere was embedded within each inorganic compartment of nanoparticles. Micron-sized silica cores coated with polystyrene shell and silica nanoparticles were used as the BCC components in the co-assembling process. According to the residue profile measured in thermogravimetric analysis, the heat treatment at low temperatures of 250, 300 and 350°C was conducted to find a cost-effective process, resulting in finding that 300°C heating for 7 h was suitable for obtaining the high movability of micron-sized cores in the compartment. Application of 1 kHz electric field at strength higher than 100 V/mm could suppress the random motion of cores in a wet-state DIO.
Although small and medium-sized enterprises (SMEs) play an important role in economy and use a significant amount of chemicals in their manufacturing processes, little support has been offered in their process improvement for chemicals management. In this series of two papers, we proposed a design support framework for strategic chemicals management in SMEs, and the supporting mechanisms in the framework were informatized as software tool developed in the case study of metal cleaning. In part 2, a software tool which informatized supporting mechanism in process design was developed for chemicals management in SMEs operating metal cleaning processes utilizing chlorinated organic solvents with an open-top washing machine. The developed tool was reviewed by trial users in cleaning industry. Such highly user-friendly tool dedicated for specific industry can strongly facilitate a strategic chemicals management by firm-level decision makers. An informatization approach through analysis scrutinizing industry-specific conditions can lead to familiarize SMEs with assessment methods of health and environmental impacts through practice of LCA and RA.