Measurement of dissolved hydrogen supersaturation during water electrolysis in a magnetic field

The cathode potential on the gas-evolving electrode in 0.5 M H₂SO₄ solution was measured under a uniform magnetic field. The current interrupter method allowed us to study the IR-drop and the supersolubility of dissolved hydrogen gas. MHD convection by Lorenz force slightly reduced the ohmic resistance between the working and reference electrode, considerably restricted the increase of supersolubility and simultaneously promoted the mass transfer coefficient of the dissolved gas above 50 mA cm⁻². Moreover, the supersolubility peak position displayed a strong dependence on the current density in the intermediate current density region from 5 to 30 mA cm⁻². The peak location shifted toward lower current density with increasing in magnetic flux density. Our data show that applying a magnetic field has a much greater effect on the supersolubility at intermediate current density region than the mass transfer coefficient.     

Iterative learning control for the systematic design of supersaturation controlled batch cooling crystallisation processes

The paper presents an approach to improve the product quality from batch-to-batch by exploiting the repetitive nature of batch processes to update the operating trajectories using process knowledge obtained from previous runs. The data based methodology is focused on using the linear time varying (LTV) perturbation model in an iterative learning control (ILC) framework to provide a convergent batch-to-batch improvement of the process performance indicator. The major contribution of this work is the development of a novel hierarchical ILC (HILC) scheme for systematic design of the supersaturation controller (SSC) of seeded batch cooling crystallizers. The HILC is used to determine the required supersaturation setpoint for the SSC and the corresponding temperature trajectory required to produce crystals with desired end-point property. The performance and robustness of these approaches are evaluated through simulation case studies. These results demonstrate the potential of the ILC approaches for controlling batch processes without rigorous process models.     

Derivation of supersaturation during precipitation from the mixing pattern of an inert tracer in the same device: case of partially premixed feed streams

The average supersaturation field is predicted for precipitations in the case of partially premixed feed streams by a simple mixing model from a couple of successive experiments with the same inert tracer by Planar Laser Induced Fluorescence and using a single camera. Then, the mathematical derivation is different from that one used for the unmixed feed case. The corresponding experiments have been achieved in a 90° impinging jets premixer and the supersaturation field was predicted. Due to the non-simultaneity of tracer experiments, a calculation of the averaged nucleation flux is not possible in the premixed feed case. Nevertheless, a comparison between different premixers can be done on the basis of the generated supersaturation levels and fouling risks.     

Derivation of supersaturation and nucleation flux during precipitation from the mixing pattern of an inert tracer in the same device: case of unmixed feed streams

Inert liquid tracer concentrations in a continuous mixer are analyzed by planar laser induced fluorescence (PLIF). Special attention is paid to the two separated entering feed streams containing the tracer solution or pure solvent. From the instantaneous tracer concentration fields, the method proposed allows one to easily calculate the instantaneous supersaturation fields, which would be obtained in the same mixing device with reagents instead of an inert tracer solution and pure solvent. A typical mixing situation in a stirred tank with separated feed streams is investigated. Maps of averaged supersaturation and averaged nucleation flux are yielded with high spatial resolution of a few tens of micrometers for each pixel. The method gives interesting indications about the ability of a given precipitator geometry to generate coarse or fine particles. However, it cannot be extended straightforward to partially premixed feed streams without the use of a mixing model.     

自动控制设计中调节阀的选型

阐述了在自动控制工程设计中 ,调节阀的选择原则 ,认为调节阀的选择内容 ,应包括结构形式 ,流量特性、流向、执行机构、调节阀的材质和口径等。介绍了各方面选择的要求及各种调节阀的应用场合     

Dynamical behaviour of the Belousov-Zhabotinsky reaction in a fed-batch reactor

In this study, we report the experimental and numerical investigation of the behaviour of a spontaneously oscillatory reaction in a fed-batch reactor (FBR). We use a cerium catalysed BZ model with a modified Oregonator mechanism. In fed-batch mode, we observe phase-locked, quasiperiodic and period-doubling responses, depending on the amplitude and period of the replacement cycle. A series of single pulse experiments is used to construct phase transition curves, from which limit point (Arnold tongues) and period-doubling bifurcation boundaries can be constructed. Experimental boundaries are compared with boundaries determined numerically using a path following analysis. The results are used to determine the variation, in terms of the mean rate of production of the oxidised catalyst, with the operating conditions of the FBR for a fixed residence time.     

A stochastic programming approach for the Bayesian experimental design of nonlinear systems

Several approaches for the Bayesian design of experiments have been proposed in the literature (e.g., D-optimal, E-optimal, A-optimal designs). Most of these approaches assume that the available prior knowledge is represented by a normal probability distribution. In addition, most nonlinear design approaches involve assuming normality of the posterior distribution and approximate its variance using the expected Fisher information matrix. In order to be able to relax these assumptions, we address and generalize the problem by using a stochastic programming formulation. Specifically, the optimal Bayesian experimental design is mathematically posed as a three-stage stochastic program, which is then discretized using a scenario based approach. Given the prior probability distribution, a Smolyak rule (sparse-grids) is used for the selection of scenarios. Two retrospective case studies related to population pharmacokinetics are presented. The benefits and limitations of the proposed approach are demonstrated by comparing the numerical results to those obtained by implementing a more exhaustive experimentation and the D-optimal design.     

Scale-Up Study of Dye RB-19 Ozonation in a New Gas-Inducing Reactor

The purpose of this research was to study the scale-up behavior of dye RB-19 ozonation in a new gas-inducing reactor, which has been used in the NTUST laboratory on various ozonation studies over the past few years. In this scale-up study, three geometrically similar gas-inducing reactors with different diameters (D _t =0.17, 0.29, and 0.51m) were employed. Three common scale-up criteria (i.e., equal liquid surface motion, equal specific power consumption, and equal impeller tip velocity) were investigated in this research. Under the equal liquid surface motion criterion, the scale-up exponent value and constant K of the modified onset Froude number were determined to be 0.5 and 0.61, respectively. The equal specific power consumption criterion was studied under gas input condition and the scale-up exponent was found to be 0.65. The regression equation for the power number of the three different scale reactors was also obtained. The scale-up exponent of equal impeller tip velocity was determined by theory to be 1.0. The scale-up investigation of dye RB-19 ozonation was then carried out in reactors with three different diameters under the same operating conditions (e.g., initial dye concentration, initial dye/ozone molar ratio, superficial gas velocity, temperature and pH value). From the experimental results, the best-fit scale-up exponent was found to be 1.18, resulting in same dye removal rate in reactors with different diameters. The enhancement factors and chemical ozone mass transfer coefficients were also obtained for these sets of ozonation experiments.     

A continuous photocatalysis system in the degradation of herbicide

The performance of both batch and continuous photo-catalytic reactors was studied to evaluate their capabilities in removing the sulfonyl urea herbicide of metsulfuron methyl (MM). It was found in a batch reactor that the addition of a small amount of powder activated carbon (PAC) significantly increased the rate of degradation of MM. The continuous photo-catalytic system resulted in 57% of MM removal. When a small dose of activated carbon was added in the photo-catalytic system, MM removal increased to 78–86% MM removal for retention times between of 5.25–21 min (corresponding to withdrawal rates of 10–40 mLmin⁻¹). In this study, the pseudo first order rate constants of a continuous photo-catalytic system revealed that shorter retention times were associated with lower rate constants. Solid phase micro extraction/gas chromatography (SPME/GC) results showed that high concentrations of MM were broken down to small volatile organic compounds (VOCs) by photo-catalytic oxidation. PAC adsorbed the photo-products and increased the degradation of MM.     

Continuous reaction crystallization of struvite from diluted aqueous solution of phosphate(V) ions in the presence of magnesium ions excess

Continuous reaction crystallization of struvite MgNH₄PO₄·6H₂O from diluted aqueous solution containing phosphate(V) ions of concentration 0.20 wt% PO₄³⁻ was investigated experimentally. The tests were carried out in a continuous DT MSMPR type crystallizer in temperature 298 K assuming 20% excess of magnesium ions at the inlet point in respect to struvite synthesis reaction stoichiometry. Influence of pH (8.5–10) and mean residence time of suspension in a crystallizer (900–3600 s) on the product crystals size distribution, their size-homogeneity and process kinetics were identified. Crystals of mean size from ca. 19 to ca. 73 μm, of diverse size-homogeneity (CV 60–87%) were produced. Struvite particles of the largest sizes and acceptable homogeneity were produced at pH 8.5 for prolonged mean residence time 3600 s. Under these conditions struvite nucleation rate did not exceed 5.3 × 10⁷ l/(s m³) according to SIG MSMPR model predictions. Crystal linear growth rate within the investigated process parameter values varied from 3.62 × 10⁻⁹ to 1.68 × 10⁻⁸ m/s. Magnesium ions excess in a process environment influenced yield of continuous reaction crystallization of struvite advantageously – contrary to product crystals quality. Concentration of phosphate(V) ions in mother solution decreased from inlet 0.20 wt% to 0.9 × 10⁻³ – 9.2 × 10⁻³ wt% (9–92 mg/kg) depending on pH and mean residence time of suspension in a crystallizer, what can be regarded as a very good result of their recovering from solution.     

Application of a novel approach for DMC predictive controller design by response surface analysis in a fed-batch bioreactor

This work presents a novel approach for tuning a predictive DMC controller implemented in a fed-batch penicillin bioreactor in order to stabilize the dissolved oxygen concentration by agitation speed manipulation. The operating process variables were calculated by a deterministic and non-structured model solved by a fourth order Runge-Kutta-Gill numerical technique with variable steps. The parameters of the model were obtained from experiments and the literature. The estimated parameters of the DMC controller were model, prediction and control horizons, suppression factor and reference trajectory. The tuning approach employed complete factorial design in order to estimate the influence of these parameters on the integral of the absolute error between the controlled variable and the set point. Response surface analysis provided the optimal parameters. This study showed negligible influence of model, prediction and control horizons while the suppression factor and reference trajectory were very important for the controller. Another important feature of the DMC controller was the that the parameters had negligible influence on each other making design of the controller easier. The performance of the DMC controller was evaluated using several delay times and sample periods of the controlled variable. The behavior of this predictive controller was better than a PID controller tuned by the Modified Simplex method.     

A novel concept reactor design for preventing salt deposition in supercritical water

Reactor plugging and corrosion are the key problems which hinder commercial applications of supercritical water oxidation and gasification, and can be efficiently overcome by preventing salt deposition on internal surface of reactor. In this work the problems caused by salt deposition and the correspondingly main solutions are further reviewed objectively. A novel reactor is designed and manufactured with a feed rate of about 100 L/h for sewage sludge treatment. The reactor combines the characteristics of Modar reactor and transpiring wall reactor for the first time, which is expected to prevent reactor plugging and corrosion as well as to decrease catalyst deactivation rate. The reactor is the core equipment of the first pilot-scale plant for supercritical water oxidation in China. Further optimizations of reactor configuration and operational parameters need plenty of experiments and/or a long-time test with sewage sludge in the subsequent work.     

耐火制品模具自动化设计的CAD系统

从CAD／CAM出发，结合国内耐火制品模具设计的要求，重点研究了用参数法模具CAD系统解决耐火制品模具的设计问题。系统运用CAD系统设计的基本原理，采用学数化特征造型的方法，集成化的设计环境，实现了耐火制品模具的自动设计及其工程图纸的输出。     

Mathematical Modeling of Theoretical Cryptosporidium Inactivation in Full-Scale Ozonation Reactors

Conditions for theoretical inactivation of Cryptosporidium by ozone could be achieved at full-scale facilities if their design is appropriate. To perform this task correctly the chemical engineer's approach for process design must be applied. This paper discusses the basic equations the estimation of the disinfection efficiency of different ozone reacting systems. Available kinetic data have been integrated in a global model accounting for the hydrodynamics and mass transfer performances of the ozonation reactor. Thus the proposed method allows one to predict Cryptosporidium inactivation level in a given ozonation system. However, if a specified disinfection goal is to be achieved for Cryptosporidium with the developed model it is also possible to choose and optimize the design of the ozone reactor.     

溶解乙炔站自控系统设计

针对乙炔易燃易爆的性质，以安全可靠和经济实用的原则，设计了溶解乙炔站的自控系统     

光催化反应器中管板的结构优化设计

针对中药三七提取液中的脱砷工艺设计的光催化反应器,采用ANSYS软件对其中的管板进行了有限元分析和结构优化设计,得到了管板在满足强度和特殊刚度要求前提下的最优厚度,使石英玻璃管的安装和密封得以实现。     

Recent advances in polymer reaction engineering: Modeling and control of polymer properties

Complex reaction kinetics and mechanisms, physical changes and transport effects, non-ideal mixing, and strong process nonlinearity characterize polymerization processes. Polymer reaction engineering is a discipline that deals with various problems concerning the fundamental nature of chemical and physical phenomena in polymerization processes. Mathematical modeling is a powerful tool for the development of process understanding and advanced reactor technology in the polymer industry. This review discusses recent developments in modeling techniques for the calculation of polymer properties including molecular weight distribution, copolymer composition distribution, sequence length distribution and long chain branching. The application of process models to the design of model-based reactor optimizations and controls is also discussed with some examples. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Optimization of process synthesis and design problems: A modified differential evolution approach

A large number of process synthesis and design problems in chemical engineering can be modeled as mixed integer nonlinear programming (MINLP) problems. They involve continuous (floating point) and integer variables. A common feature of this class of mathematical problems is the potential existence of non-convexities due to the particular form of the objective function and/or the set of constraints. Due to their combinatorial nature, these problems are considered to be difficult. In recent years, evolutionary algorithms (EAs) are gaining popularity for finding the optimal solution of nonlinear multimodal problems encountered in many engineering disciplines. In the present study, a novel modified differential evolution [Angira, R., Babu, B.V., 2005a. Optimization of non-linear chemical processes using modified differential evolution (MDE). Proceedings of the Second Indian International Conference on Artificial Intelligence (IICAI-05), Pune, India, December 20-22, pp. 911-923. Also available at 〈http://discovery.bits-pilani.ac.in/discipline/chemical/bvb/publications.html〉], one of the evolutionary algorithms, is used for solving process synthesis and design problems. To illustrate the applicability and efficiency of modified differential evolution (MDE), seven test problems on process synthesis and design have been solved. These problems arise from the area of chemical engineering, and represent difficult nonconvex optimization problems, with continuous and discrete variables. The performance of MDE is compared with that of Genetic Algorithm, Evolution Strategy, and MINLP-Simplex Simulated Annealing (M-SIMPSA).     

A study on crystallization kinetics of pentaerythritol in a batch cooling crystallizer

The crystallization kinetics of pentaerythritol (PeE) in aqueous solution in the presence of impurity or not in a batch cooling crystallizer was explored. Also, the solubility and the nucleation and crystal growth kinetics of PeE in aqueous solution were investigated. A second-order dependence of PeE growth rate on supersaturation is observed in pure PeE-water system. The crystal growth rate of PeE-water system in the presence of impurity is proportional to the supersaturation to the 3.5 power. The nucleation and crystal growth behaviors for PeE-water system in a batch cooling crystallizer were grasped according to Mersmann's criteria. The nucleation in this crystallizer was found to act with heterogeneous nucleation. In this system, it suggests that the crystal growth is controlled by a complex mechanism behavior of surface integrated and diffusion limited. Simplified relation was derived for calculation of mean crystal size of product crystals from the batch cooling crystallizer. The obtained relation was verified by a set of experiments.