Volume 21, Issue 11

The present work focuses on obtaining optimal operational policies of an industrial scale penicillin fed-batch fermentation process using dynamic optimization (DO). The three process objectives considered in this work include, maximization of total penicillin formed ( J 1 ), minimization of total biomass formed ( J 2 ), and minimization of fed-batch operation time ( J 3 ). The control variables for the optimization study include, the feed flowrates of sugar, soyabean oil, and phenylacetic. We perform a single-objective optimization study with J 1 as the objective function and showcased the importance of DO. Consequently, we solve three multi-objective optimization (MOO) problems corresponding to all the pairwise combinations of the aforementioned three objectives. Outcomes of MOO problems are presented in terms of several non-dominated Pareto-optimal solutions. Furthermore, descriptive analysis of three representative Pareto points for all the MOO problems is presented, which highlights the importance of MOO study of the penicillin bio-reactor.

In this work, the application of multiscale analysis to evaluate the sensitivity of the dynamic responses of the trays in a distillation column exposed to external disturbances is explored. This sensitivity allows for the identification of the tray where the temperature sensor improves the performance of a composition-temperature type cascade controller. To implement the proposed methodology, synthetic time series are generated for each plate of the column, which is subsequently analyzed using the multiscale rescaled range (R/S) analysis. Three case studies were evaluated (binary mixtures, azeotropic mixture and ternary mixture), finding that the highest values of the Hurst exponent correlate with the areas of greatest sensitivity of the column. To corroborate this result, a composition-temperature cascade control scheme was implemented, evaluating the temperature sensor in each plate of the column, identifying that the zone of greatest sensitivity determined with the multiscale analysis corresponds to the best performance of the controller. Therefore, our results show that the proposed methodology represents an easy-to-implement alternative that provides information on the most suitable zone for the placement of temperature sensors to improve the performance of cascade control in a pre-designed distillation column.

In the study, carbon fiber as porous media, water and vapor as liquid and gas phases, respectively, the evaporation process of multiphase fluid in carbon fiber was explored based on the pore network model. The Micro-CT technology was adopted to reconstruct the structure of carbon fiber. The applicability of the CFD model adopted in the simulation was validated by experiment. Effect of heating temperature and porosity on the evaporation process was investigated in detail. The study found that at various heating temperatures, fluid temperature increases gradually with time, and tends to be constant when it reaches a certain temperature. When heating temperature is high, the constant temperature is large, the time to arrive the constant temperature is short. The liquid evaporation rate V e and the heat absorbed by the fluid every 0.5 s Q 0.5 increase first, and decrease gradually when a maximum value is reached. When the heating temperature is high, the maximum that V e and Q 0.5 can be obtained is also large, the required time is also short. In porous media with different porosity, fluid temperature rises to an approximate constant. V e and Q 0.5 increase first, and decrease gradually after reaching a certain maximum value. The maximum values of V e and Q 0.5 in porous media with porosity of 0.598 are the largest.

As a product of oil extraction from Moringa seeds, Moringa seed meal contains a large amount of flocculant active substances, which are not effectively utilized at present. The concentration of 50 mg L −1 Moringa seed meal extract could be prepared by the mixture of Moringa seed meal defatted powder (100 mesh) and NaCl solution (0.5 mol L −1 ). According to the share ratio, a novel natural flocculant was formed from 10 mL Moringa seed meal extract (50 mg L −1 ), 11.94 mg cactus powder (60 mesh) as well 2 mL sodium alginate solution (5 mg L −1 ). The experimental result suggested that for 400 mL of 100 NTU kaolin suspension, the turbidity removal effect of flocculant was 93.1 % with no increase in turbidity during the resting process, testifying to its biodegradability and ecological safety.

Aiming at the problems of low mixing efficiency and poor uniformity of solid–liquid dispersion caused by double-layer 4-pitched blades turbine, a new impeller is obtained by optimizing the structure of the traditional blade. In order to efficiently apply the improved double-layer 4-pitched blades impeller to the mixing process of DNAN-based explosives, this paper takes the new impeller as the research object, investigating the solid–liquid suspension characteristics of the stirred tank through computational fluid dynamics (CFD). A stirring experiment is designed, and a conductivity probe is employed to measure the local solid particle concentration. After validating the CFD model by experimental results, numerical analysis is successfully used to examine the impacts of stirring speed, layer spacing, impeller height from the bottom and impeller inclination angle on the solid–liquid mixing quality. Results show that the increase of rotational speed can significantly enhance the solid–liquid dispersion efficiency. Meanwhile, the blade structure parameters have an important influence on the homogeneity of solid phase distribution, and the appropriate blade structure can make the particles have a better suspension effect. Moreover, the improved blade has obvious advantages in solid–liquid space homogenization in comparison to the traditional blade under the same stirring conditions.

The tetrafluoroethylene (TFE) polymerization process is an essential industrial process to produce polytetrafluoroethylene (PTFE), which is extensively utilized in aerospace and medical domains. A precise mechanism model is a prerequisite for comprehensively understanding this process. However, significant uncertainties in the kinetic model parameters may hinder attaining an optimal reaction rate. This study proposes a hybrid polymerization reaction model that integrates process mechanism modeling and data-driven modeling to address this challenge. In the hybrid modeling approach, the mechanism model for the polymerization reaction is developed based on reaction kinetic and thermodynamic assumptions. Additionally, a long short-term memory (LSTM) neural network is employed to predict the reaction rate for chain initiation by leveraging temporal relationships derived from archived measurements. The proposed methodology is implemented using a PTFE polymer reactor system, and experimental comparisons affirm its superior performance and effectiveness.

To achieve good servo and regulatory responses, a generalized fractional-order tilt-integral-derivative (FOTID) control is developed in this study for time-delayed fractional-order processes. To enhance the closed-loop robustness, the controller parameters are calculated based on maximum sensitivity ( M s ). To check the performance and robustness of the suggested control law, several case studies on industrial processes like DC servo systems, Level-loop, Bio-reactors, Fuel cells and CSTR are performed and compared with existing designs. The robustness of the proposed controller is analysed by employing 20 percent perturbation in plant parameters. Lastly, a comparison of the closed-loop response on different error indices is included.

With the rapid economic development, PET (polyethylene terephthalate) plastic is widely used in various fields, i.e., clothing, food, housing and transportation. However, PET has a very strong chemical inertia, which makes it difficult to be degraded by microorganisms, thereby occupying a lot of space. Therefore, the recycling of waste PET has become one of the most important topics of environmental protection. Glycolysis requires the most mild and safe reaction environment among chemical recycling methods, and the ethylene glycol used in the reaction can be reused. Using glycolysis to recycle PET undoubtedly conforms to the green and sustainable concept, and glycolysis recycling is undoubtedly a low-cost, low-consumption and low-harm path for PET recycling. The heating and glycolysis characteristics of microwave-assisted PET glycolysis, and the energy analysis of glycolysis were studied. The aim was to produce BHET (bis(2-hydroxyethyl) terephthalate) as the target product from PET waste. In this study, the effects of reaction temperature, reaction time, and PET particle size on the performances of PET conversion rate, oligomeric BHET yield, and BHET yield were examined, and the energy efficiency and recovery efficiency also were presented. The results showed that the optimal conditions for microwave-assisted PET glycolysis were reaction temperature of 180 °C, reaction time of 30 min, and PET particle size of 75 μm, and the maximum PET conversion rate was 66.71 ± 9.71 wt%, the maximum yield of BHET was 48.08 ± 0.68 wt% and the maximum BHET yield was 19.83 ± 5.40 wt%. The energy efficiency and recovery efficiency were 11.88 % and 17.89 %, respectively.

Insufficient reaction between dust and sulfuric acid during leaching of zinc oxide dust containing germanium is a major reason for the low leaching efficiency of germanium. This paper makes use of the unique physical effect of ultrasonic wave to play an important role in strengthening the leaching process. Research found that with ultrasonic enhanced leaching, on the one hand, the surface tension and viscosity of the leaching solution decreased by 5.94  and 32.73 %, respectively; on the other hand, for the leached mineral, the contact angle decreases, the surface free energy increases by 9.43 %, the particle size decreases 40.92 %, and the specific surface area and pore volume respectively increase 94.10  and 54.05 %, which reduces the contact resistance between sulfuric acid and dust, making the reaction between them more completely and in-depth. Therefore, the leaching rate is accelerated and the germanium leaching efficiency is increased. Under ultrasonic condition, the leaching efficiency of germanium is enhanced by 3.94 % and the time to reach equilibrium is shortened by about 40.00 %. The above findings can provide theoretical guidance for the extended application of ultrasound in hydrometallurgy and the efficient leaching of germanium-containing zinc oxide dust.

Microchannels are small-scale channels with unique properties that make them useful in various fields, such as electronics, biomedical engineering, and chemical engineering. This research paper investigates the effect of microchannel geometry on fluid flow behavior at different values of the Reynolds number. A rectangular microchannel with a pattern of obstructions and water as the working fluid was used in this study. Computational fluid dynamics (CFD) simulations were used to investigate the impact of different channel geometrical configurations and different values of the Reynolds number on fluid flow behavior. The results showed that the channel geometrical configuration and the Reynolds number significantly affect fluid flow behavior. A geometry with increasing obstruction heights led to higher values of pressure drop than the geometry with decreasing obstruction heights. This study provides valuable insights into microchannel flow behavior and can be used for the development of optimized microchannel designs for diverse applications.