The mixing performances such as the flow pattern, the mixing time and the velocity profile, were measured in a vessel with bottom baffles. The bottom baffles induced high velocity from bottom to surface at the center of the vessel. The dimensionless mixing time Ntm took the minimum value at the bottom baffle diameter being 0.83 times as large as the impeller diameter, regardless of the baffle plate configurations and width.
The carbon micro-coils were prepared by a ultrasonic wave CVD process, in which ultrasonic waves of 23–65 kHz were irradiated in the growing atmosphere of the carbon micro-coils. The irradiation effects of the ultrasonic waves on the growth, morphology and some properties of the carbon micro-coils were examined. With ultrasonic wave irradiation, the coil yield and the thickness of the coil layers increased by about 1.5 times and 1.3 times higher than that without irradiation, respectively. The coil diameter increased from 3–5 μm without irradiation to 5–9 μm with irradiation. The density increased from 1.8 g/cm3 without irradiation to 2.0 g/cm3 with irradiation by a 23 kHz ultrasonic wave.
The vapor permeation properties of an FAU-type zeolite membrane, which was formed on the outer surface of a porous α-Al2O3 support tube, were determined in the temperature range of 358–413 K. The measurements were carried out using single-component benzene (Bz) and n-alkanes (C4-C7), as well as mixtures of benzene and n-alkanes. The hydrocarbons were diluted with nitrogen, and the partial pressures of hydrocarbons on the feed side were determined to be 7–8 kPa for the single-component systems and 4–5 kPa for each component of the binary systems. The permeate side was swept with a flow of nitrogen. The permeances were dependent on the permeation temperature and, to a greater extent, on the presence of benzene. For the single-component systems, the permeances were dependent on the diffusivities of the permeants, and the diffusivity of benzene through the membrane was the smallest of all the hydrocarbons tested. For the binary systems, however, benzene permeated at faster rates than any of the n-alkanes, and the permeances to n-alkanes were not directly dependent on their chain lengths. This benzene-selective permeation was realized using the FAU-type zeolite membrane with pore openings larger than the molecular size of benzene. The separation factors were affected by the partial pressures of permeants on the permeate side. When the partial pressures on the permeate side were in the range of 100–140 Pa for benzene and 1–4 Pa for n-alkanes, the separation factors at 373 K were 57 for Bz/n-C4, 70 for Bz/n-C5, 63 for Bz/n-C6, and 27 for Bz/n-C7. The adsorption selectivities for the binary systems on the feed-side surface of the membrane were 24 for Bz/n-C4 and 15 for Bz/n-C7, and were much higher than those for the single-component systems. This suggests that the adsorption of the n-alkanes on the FAU-type zeolites was strongly retarded by the selective adsorption of benzene.
Recording media (MD) was subjected to peeling with the disk having well-arranged pins, followed by acid leaching with HCl and HNO3 solutions, respectively, under irradiation of ultrasound to investigate Tb, Co and Fe from the MD sample. The result was compared with those in the leaching conducted at room temperature and 60°C without ultrasound irradiation. The acid leaching of metals is accelerated by irradiating ultrasound, and is accomplished by 100% within 1 hour, irrespective of whether HCl or HNO3 solution (1 N) is used. High yield extraction is not attained at all in the leaching without ultrasound irradiation over the same extraction time. The yield increases with an increase in the acid concentration, but it levels off beyond 1 N. Temperature for the leaching is also an important factor; however, ultrasound irradiation is the most effective means for extracting metals from the sample.
For the purpose of developing new technologies of extraction and separation of metals, we have investigated the way of using microcapsules. In this study, the microcapsules containing several organophosphorus compounds as extractants (HR) were prepared by in situ polymerization technique and their characteristics were investigated. The extractant held within microcapsules was not leaked out at pH below 4, hence the microcapsules are useful for the extraction of cationic metal ions. In this study, we investigate the extraction behavior of gallium and indium as objective metal sources. The extraction equilibria were clarified by a slope-analysis method. Those for gallium and indium using the microcapsules containing di(2-ethylhexyl)phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) were determined as follows:
Ga3+ + 2(HR)2 ↔ GaR3·HR + 3H+
In3+ + 5/2(HR)2 ↔ InR3·2HR + 3H+
The extraction equilibrium for the microcapsule containing diisostearyl- phosphoric acid (DISPA) was determined as follows:
The extraction equilibrium constants and separation factors were also determined for each system. The maximum adsorption capacities of the metals in the microcapsule containing EHPNA were determined with the Langmuir isotherm model and determined as 4.49 × 10–4 and 3.22 × 10–4 mol/g-MC for gallium and indium, respectively.
To investigate the effect of the ammonium concentration on SO2 absorption with a chemical reaction in the wet limestone-gypsum flue gas desulfurization (FGD) process, the SO2 absorption rate in limestone slurry was studied by using a stirred tank reactor at a constant pH, high temperature (50°C) and under the presence of ammonium. An absorption model with a reaction plane and the presence of ammonium in the liquid based on the film model was also proposed for an actual FGD plant. For the SO2 absorption rate depending on the concentration of ammonium, the experimental values agreed quite well with the results calculated with the absorption model, taking the presence of ammonium in the liquid into consideration.
Xylanase recovery from Penicillium janthinellum with a reversed micellar system consisting of a cationic surfactant using a continuous process was evaluated. A statistical approach applied to the results showed the highest xylanase recovery (43.5%), which was indicated by the model and was attained at an ionic strength of 10 mS/cm and a volumetric flow at 0.5 ml/min.
This study is concerned with measurements of vapor-liquid equilibrium (VLE) for 1-butene/1, 3-butadiene/DMF and 1-butene/1, 3-butadiene/DMF with salt. A set of experimental apparatus has been established to measure the VLE of the two systems. Data of T-P-x-y at middle pressures have been obtained. The coincidence of experimental and calculated values, and the consistency of thermodynamics show that the experimental results appear accurate and the experimental apparatus is reliable. In contrast to using DMF only, DMF with salt is a better solvent and increases the relative volatility of 1-butene to 1, 3-butadiene. The UNIFAC models for the two systems have been set up, and a good agreement between the predicted and the experimental is achieved.
The semi-conductor integrated circuit electronic devices process has many re-circulation production paths through the stages of product manufacturing. These kinds of processes can be defined as the multi-purpose batch process with re-circulation products if they produce more than two products. In this paper, we have developed the completion time algorithms for a single line multi-purpose batch process including re-circulation products with consideration of the non-zero set-up times and transfer times. We also developed the optimization method, genetic algorithm, for optimal scheduling of a multi-purpose batch process including re-circulation products. Several randomly generated examples were tested using the proposed algorithm, and the Gantt chart results are presented. We used Genetic Algorithm for solving the scheduling problems, and optimal solutions are also presented.
The purpose of this study is to propose a model structure for plant identification and evaluate its properties. Obtaining a good model for a plant is important to construct a control system and it requires a long time and considerable effort. The model accuracy largely depends on the model structure which provides a means to estimate the plant characteristics. The proposed model structure, which is a fraction of a linear combination of sets of proper transfer functions, is for a linear system, and is practical and reliable. A relatively accurate model can be estimated with the model readily compared with other models even under poor conditions. The obtained model is a continuous-time ARX type and applicable to many controller design methods by transferring the model to appropriate forms.
Unmeasured disturbances usually plague the processes and result in defect products in chemical plants; hence, the identification and control of the process with the presence of disturbances are important. This paper completely develops the neural network model predictive control (NNMPC) from the model design to the controller design for nonlinear MIMO processes with unmeasured disturbances. In the model design, an input-driven output neural network ARX model (NNARX) combining with a disturbance AR model, called NNARX+AR, is proposed. NNARX and AR represent the input-output characteristics without the corrupted disturbances and with disturbances respectively. The Levenberg-Marquardt algorithm for NNARX and the least squares algorithm for AR are synchronously used to train the process model. In the control design, a constrained NNMPC based on NNARX+AR via the successive quadratic programming is developed to search the optimal control actions. To demonstrate the proposed identification and predictive control strategies, a pH neutralization system with the presence of unmeasured disturbances is presented.
This paper deals with a catalytic continuous stirred tank reactor (CCSTR), modeled as a non-minimum phase nonlinear system with two control inputs. Under the adaptive-like methodology, the developed Lyapunov-based linearization strategy can ensure the asymptotic output regulation. It is also shown that the integrated two-input control framework can reinforce the accurate state regulation and robust against the unknown disturbances. For the implementation purpose, we propose a systematic design procedure to synthesize a reduced-order observer plus controller. Our results are illustrated via numerical simulation.
A searching method for the blending ratio of regular coffee with a designed flavor and taste has been developed. A fuzzy neural network (FNN) model was at first constructed for estimation of the sensory scores of various blending ratios. Using the model, the following four methods were attempted in order to estimate the blending ratio with the designed sensory score: 1) an exhaustive search, 2) a method using a genetic algorithm (GA), 3) a method using the GA combined with a reliability index (RIGA), and 4) a reverse FNN model. Among the results of these methods, the RIGA showed a good performance not only on estimation of the known blending ratio but also on the actual blending test in the present study.
The flowing solvent liquefaction of a brown coal was performed at temperatures from 623 to 708 K and a pressure of 10 MPa aiming at experimental definition of the primary conversion, which was measured in terms of the mass yield, Xf, of products dissolved into flowing tetralin or 1-methylnaphthalene as a function of temperature and holding time. In-situ isolation of the products from the solid residue by a forced flow of the solvent at a sufficient rate enabled the definition of Xf as the primary conversion. At each temperature, Xf using tetralin increased with time and leveled off at a conversion, Xfm of 0.96 which was independent of the temperature in a range from 673 to 708 K. The results further revealed that that the intraparticle solvent-to-coal hydrogen transfer enhances the primary conversion. Batch liquefaction experiments were also performed at 623 and 693 K using tetralin in the presence or absence of an iron/sulfur catalyst under 10.1 MPa hydrogen gas atmosphere, and the conversion of the coal, Xb, was determined by a common procedure as the mass yield of product soluble to extraction solvent, tetrahydrofuran (THF). Xb in the non-catalytic liquefaction was appreciably lower than Xf at 623 K, since THF cannot dissolve entirely the product that was dissolved into tetralin during the liquefaction. Due to extensive degradation of the primary product dissolved into tetralin into the catalytic liquefaction at 623 and 693 K and even in non-catalytic one at 693 K, the dissolved product converted into THF-soluble product with molecular mass lower than 2, 000, allowing Xb to be equivalent to Xfm.