The ultrasonic technique was used for measuring the interfacial area (a) in a gas–liquid bubble column. In this study, the ultrasonic technique is based on the measurement of the attenuation of the ultrasound pulses propagating through a gas–liquid dispersion system. The characterization of gas–liquid dispersion using ultrasound might prove a very valuable alternative for situations in which conventional techniques such as those based on optical principles cannot be applied. The effects of several parameters such as ultrasound pathlength, bubble diameter, and liquid physical property on the attenuation of ultrasound were studied. Based on the experimental data, a linear correlation for interfacial area prediction is derived. The results of the ultrasonic technique are in good agreement with those of the physical method under the current experimental condition.
Effects of slurry rheology and other operating conditions on the performance of cross-flow filtration are investigated. Aluminum oxide powders with a mean diameter of 34 μm are suspended in polyacrylamide (PAA) aqueous solution to prepare the viscoelastic slurry used in experiments. The filtration rate and the cake properties under various operating conditions, such as PAA concentration, filtration pressure and cross-flow velocity, are measured and discussed. The elastic behavior of permeating fluid plays an important role on the filtration performance as the Reynolds number exceeds a critical value that depends on the fluid rheology. The elastic effect is dominant at the beginning period of a filtration, which results in an extra filtration resistance and an excess cake compression. When the elastic effect vanishes, the permeating flow through the filter cake behaves as a pure viscous fluid, which can be modeled by the power law model. The pseudo-steady filtration rate increases with the increase of filtration pressure and cross-flow velocity, but with the decrease of PAA concentrations. These tendencies can be explained reasonably by the cake properties, e.g., the particle size distribution in the cake, the porosity and the specific filtration resistance of the cake under various conditions. The dynamic analysis method proposed by the authors is employed to estimate the cake properties. The calculated results agree fairly well with the experimental data.
With the aid of the McCabe–Thiele diagram, heuristic synthesis of an internally heat-integrated distillation column is addressed in this work. A new scheme for internal heat integration between a rectifying section and a stripping section is derived with the introduction of double-feed arrangement. The process configuration is characterized by its high thermodynamic efficiency and strong resilience to changes in operating conditions. Separation of a binary close-boiling mixture is conducted and the results obtained corroborate the advantages.
Heat transfer from a high-temperature solid surface to a porous plate, which is separated by a narrow gap and contains water, and the resulting evaporation rate of water from the porous plate are investigated experimentally. The vapor flow induced in the clearance establishes a pressure field, which makes a high-temperature solid hover without contacting the plate, as previously reported by the authors (Kojima and Okuyama, 2004). This hovering phenomenon is expected to be applied to high-temperature material processes such as the fabrication of flat glass. In the present report, the experiment is conducted under fixed clearance conditions. The heat transfer and evaporation rates increase with the increase in the solid surface temperature up to 1273 K and with the decrease in the clearance from 1.0 to 0.25 mm, while the temperature near the upper surface in the plate remains close to the saturation temperature throughout the parameter ranges. These findings imply that the water is sufficiently distributed over the entire thickness of the plate. The resulting heat flux to the porous plate is shown to be much smaller than the maximum heat flux, which is estimated as the limit of the evaporation at the capillary meniscus in pores adjacent to the heated surface. The transferred heat is mainly consumed as the latent and sensible heats of the vapor and as the sensible heat of the liquid taken up for evaporation from the lower surface of the porous plate. Even after the cessation of water supply from the lower surface, the upper surface temperature of the porous plate and the evaporation rate remain close to the values before cessation, until the critical moisture content of the material is reached.
Radiation in near infrared region dominates the heat transfer in high temperature processes including particle dispersion such as coal gasification and pulverized coal combustion. The thermal radiation properties in near-infrared region of 0.8–2.2 μm were studied for a cloud of coal ash particles. The monochromatic absorption as well as the directional behavior of scattering for the sample particles dispersed in liquid paraffin wax were measured spectroscopically at an atmospheric state by using FT-IR. The effect of the particles number density in the cloud and the thickness of the dispersion layer on the spectrum of absorption could be expressed in the property of the extinction efficiency. The spectral distribution of the extinction efficiency is dependent of wavelength in the near-infrared region. The contribution of scattering by ash particles can be ignored, or the forward scattering dominates the particle scattering in the radiative heat transfer in the cloud.
The removal of Cr(III) in an aqueous solution by an alkaline solution was experimentally and theoretically investigated. The experiment was carried out in a batch stirred reactor at room temperature. A mathematical model based on mass and charge balances of reactions in the solution at an equilibrium condition was proposed. The effects of certain parameters, such as pH, initial Cr(III) concentration in the solution, and the ratio of NaOH/Ca(OH)2 added to the solution, were investigated. The removal increased with pH and initial Cr(III) concentration. The use of the NaOH/Ca(OH)2 ratio was the most important variable affecting the removal. The results show that Cr(III) removal about 100% in the solution was achieved when the solution was treated at pH 6.8 under the current experimental condition. It was also shown that the results thus obtained using the model is in good agreement with experimental data.
Accidents caused by the domino effect in chemical plants or the petrochemical industry are generally more serious than any other accidents. Although the factors or mechanisms that might cause the domino effect have been studied, it is difficult to examine the true factor because the domino effect is affected by many nonlinear factors. Hence, it is almost impossible to predict the result. The immediate causes of the domino effect are the peak overpressure, flying objects, and flame, and nonlinearity is inherent in all three causes. However, it is believed that a systematic and mathematical approach can minimize the incidence of the domino effect. This study considered the case where there were N-explosive facilities such as storage tanks, high temperature reactors in the given arbitrary rectangular facility site. This paper suggests the positions that can minimize the domino effect using a nonlinear approach. The well-known method of gradient or steepest descent was adopted in this work. The method initiated an arbitrary number of facilities in addition to the original position, and can search for the position to minimize the domino effect. This paper presents a new computer-aided module, MiniFFECT (MINImization of domino eFFECT), which can simulate the procedure for deciding the position of N-facilities for minimizing the domino effect.
The performance of model-based controller design is strongly influenced by the quality of the underlying model. However, the development of an accurate first-principle model is not a trivial task. In this research, a data-based LQI controller design method directly from plant data is developed. By incorporating the just-intime learning technique, LQI design can be carried out without the need of a first-principle model, which is normally assumed to be available in the traditional LQI design. Simulation results are presented to illustrate the proposed method and a comparison with its conventional counterparts is made.
In this paper an algorithm based on simulated annealing is developed to solve time optimal control problems (t-OCPs). In the beginning, a procedure that a t-OCP is converted into a nonlinear programming problem by parametrizing the control input and the time horizon is demonstrated. Then, all the unspecified parameters embedded in the converted problem, including the discretized control inputs and the associated time grids, are optimized by the proposed algorithm. For demonstrating the efficiency of our algorithm in the optimization, four typical examples are provided.
In the present study, we developed the PART-robustBFCS method modified from PART-BFCS. This modeling was performed by using a bagging algorithm. In this algorithm, boosting result was assessed by using the data except one for model construction in order to repress the overfitting by modeling. We applied this method to the analysis of microarray data for the subclass identification of diffuse large B-cell lymphoma (DLBCL) patients. The results of our methods were superior to those of various other methods. The prediction accuracies were 75% for PART-BFCS and 79% for PART-robustBFCS.
The pharmaceutical industry frequently uses cryogenic conditions for organometallic reactions and for the stereoselective synthesis of active pharmaceutical ingredients. Cryogenic conditions are required for these reactions either because of the thermal instability of the organometallic compound, or in order to improve the selectivity of the reaction. This paper focuses on continuous cryogenic organic reactions using mini-sized multi-stage reactors with volumes ranging from 10–6 to 10–3 m3. Mini-sized reactors have many advantages, such as high heat exchange, and efficient and fast mixing comparable to micro-scale reactors. However, mini-sized reactors are easier to operate than micro-scale reactors. The present study deals with synthesis of spirolactone fragment of neuropeptide Y receptor antagonist which is a potential anti-obesity agent. Currently, production is carried out in a semi-batch manner. Due to limitations in heat transfer, temperature control is maintained by slow addition of reactants, although this leads to poor product yield, especially in the second step of the process. The present results, obtained using a mini-sized multi-stage reactor, are compared with the current production scale approach in terms of the product yield, the amount of by-products and the stereoselectivity of the product.
Soy sauce cakes contain about 5–10 wt% salt; therefore, incineration results in corrosion of the furnace and environmental problems related to, for example, dioxin generation. However, amino and organic acids, and soybean isoflavone, as well as a number of other useful components remain in the soy sauce cakes. The amount of desalination with water was 590 mg/10 g-feed, while that with methanol was about 70% of this value. Desalination could not be performed successfully with acetone or n-hexane. The amounts of flavonoid in the form of daidzein and genistein extracted from 10 g of soy sauce cake were 3.4–7.2 and 7.2–11.0 mg, respectively, while extraction with water was minimal. Moreover, the amount of flavonoids extracted increased while the amount of desalination decreased with aqueous alcohol solutions. The dual cylinder solid–liquid extractor presented here for separation of flavonoids and salt from soy sauce cakes was able to collect 10.2 mg/50 g-feed of daidzein and 18.8 mg/50 g-feed of genistein. The length of time the sample is retained in the mixer can be varied by changing the agitation speed, the number of baffle plates and the diameter of the mixer cylinder outlet. This solid–liquid extractor is therefore applicable in a wide range of food waste recycling processes.