This paper presents a new multi-scale kinetic model built upon the multi-stage growth Hypothesis for predicting biohydrogen production. The proposed model represents the significant factors affecting ...biohydrogen production using a sum of first-order kinetic terms with varying dynamics from slow to fast one. The current work investigates 52 case studies of biohydrogen production that show the double first-order kinetic model provides the best modeling fitness (R2 > 0.99). This result suggests two prevalent pathways or microbial groups with distinct dynamics (i.e., fast and slow modes) in biohydrogen production. An increase in temperature (30 °C–43 °C) or substrate concentration (10 g/L to 40 g/L) and the use of simple substrates or mixed cultures can increase the fast-mode dominance up to 100% contribution. Model analysis suggests that the fast mode corresponds to the butyrate production pathway, the growth-associated hydrogen-producing activity, the easily-biodegradable substrates, or the quick hydrogen-producing groups.
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•New multi-scale kinetic model based on multi-stage growth hypothesis.•Reveal two factors with distinct dynamics affecting hydrogen production.•Provide excellent data fitting in 52 case studies of dark and photo fermentations.•Elucidate the impacts of operating conditions on fermentation performance.
Open-loop unstable systems with time-delays are often encountered in process industry, which are often more difficult to control than stable processes. In this paper, the stabilization by PID ...controller of second-order unstable processes, which can be represented as second-order deadtime with an unstable pole (SODUP) and second-order deadtime with two unstable poles (SODTUP), is performed via the necessary and sufficient criteria of Routh-Hurwitz stability analysis. The stability analysis provides improved understanding on the existence of a stabilizing range of each PID parameter. Three simple PID tuning algorithms are proposed to provide desired closed-loop performance-robustness within the stable regions of controller parameters obtained via the stability analysis. The proposed PID controllers show improved performance over those derived via some existing methods.
•Stabilization of second-order unstable systems with time-delays.•New theorems to construct stabilizing PID controller parameter regions.•Three different tuning algorithms with guaranteed closed-loop stability.•Improved PID controller performance-robustness.
•New decentralized multi-scale controller design for MIMO processes.•Multi-scale control (MSC) scheme leads to PID controller with augmented filter.•Effective approach to synthesize PID controllers ...for MIMO processes.•Numerical examples demonstrate the usefulness of the proposed approach.
Based on the recently proposed (SISO) multi-scale control scheme, a new approach is introduced to design multi-loop controllers for multivariable processes. The basic feature of the multi-scale control scheme is to decompose a given plant into a sum of basic modes. To achieve good nominal control performance and performance robustness, a set of sub-controllers are designed based on the plant modes in such a way that they are mutually enhanced with each other so as to optimize the overall control objective. It is shown that the designed multi-scale controller is equivalent to a conventional PID controller augmented with a filter. The multi-scale control scheme offers a systematic approach to designing multi-loop PID controllers augmented with filters. Numerical studies show that the proposed multi-loop multi-scale controllers provide improved nominal performance and performance robustness over some well-established multi-loop PID controller schemes.
•New control scheme for stable and integrating/unstable time-delay processes.•The design principle is to decompose a given plant into a sum of basic modes.•An individual sub-controller is ...specifically designed to control each mode.•The sub-controllers are combined to enhance cooperation among the plant modes.•Numerical study demonstrates the applicability and effectiveness of the scheme.
This paper presents a new multi-scale control scheme which is applicable to both stable and integrating/unstable time-delay processes. The salient feature of the proposed scheme is to decompose a given plant into a sum of basic modes, where an individual sub-controller is specifically designed to control each of these modes. An overall multi-scale controller is then synthesized by combining all the sub-controllers in such a way to achieve good cooperation among the different plant modes as to achieve good nominal performance and performance robustness. Extensive numerical study shows that the proposed multi-scale control scheme provides substantial improvement in control performance/robustness over the classical Smith predictor and some of its well-established variants.
The current energy supply depends on fossil fuels which have increased carbon dioxide emissions leading to global warming and depleted non-renewable fossil fuels resources. Hydrogen (H2) fuel could ...be an eco-friendly alternative since H2 consumption only produces water. However, the overall impacts of the H2 economy depend on feedstock types, production technologies, and process routes. The existing process technologies for H2 production used fossil fuels encounter the escalation of fossil fuel prices and long-term sustainability challenges. Therefore, biohydrogen production from renewable resources like biomass wastes and wastewaters has become the focal development of a sustainable global energy supply. Different from other biohydrogen production studies, this paper emphasizes biohydrogen fermentation processes using different renewable sources and microorganisms. Moreover, it gives an overview of the latest advancing research in different biohydrogen process designs, modeling, and optimization. It also presents the biohydrogen production routes and kinetic modeling for biohydrogenation.
•Review on biohydrogen process design, modelling, and optimization.•Comparison of biohydrogen process designs including continuous, batch, or semi-batch processes.•Kinetic equations with optimized parameters are hard to be converted into universal predictive models.•Identification of some possible future research directions.
Fed-batch fermentation processes are commonly used in bioprocessing industry. A fed-batch fermentation process often exhibits integrating/unstable type of dynamics with multiple right-half plane ...zeros. A class of fourth-order integrating model can be used to adequately represent such a complex dynamics of the fed-batch fermentation process. In this paper, rigorous stability analysis of proportional-integral-derivative (PID) controller based on the Routh-Hurwitz criteria for the fourth-order integrating system is presented. A set of all stabilising PID controller parameter regions is established. Based on these stabilising regions, a general PID controller tuning procedure is proposed for the fourth-order integrating system with two right-half plane zeros. Numerical study shows that based on the proposed tuning procedure, a low-order PID controller can outperform a fifth-order optimal LQG controller in terms of servo and regulatory controls.
The fruit wastes of Mangifera pajang were found to exhibit excellent antioxidant capacity. However, its application can be limited by its poor stability. Therefore, this study aims to improve its ...stability by solubilizing them in a novel choline chloride/ascorbic acid natural deep eutectic solvent (CHCL/AA NADES) system. The degradation of the antioxidant extracts in the aqueous and NADES system under effects of temperature (25 °C, 40 °C, 60 °Cand 80 °C) and pH (3.0–8.0) were studied by modeling the degradation kinetics. For both systems, the degradation process followed the first-order kinetics. Remarkably, a lower degradation rate constant was found for the antioxidant-CHCL/AA NADES system, suggesting the ability of CHCL/AA NADES in protecting the antioxidant against extreme temperature and pH. Moreover, the half-life values for the antioxidant-CHCL/AA NADES was higher by 4.17–25% as compared to the antioxidant-aqueous system, suggesting that the CHCL/AA NADES is feasible to improve the stability of antioxidants.
•CHCL/AA NADES was formulated to enhance the stability of antioxidant from M. pajang.•CHCL/AA NADES protects the antioxidants against extreme temperature and pH.•Antioxidant-CHCL/AA NADES exhibited lower rate constant and higher half-life value.
•Generalized cascade multi-scale control (CMSC) scheme is proposed.•The scheme is applicable to stable and integrating/unstable dead-time cascade processes.•The scheme provides improved nominal ...performance/performance robustness.•Numerical studies show the applicability and usefulness of the CMSC scheme.
The cascade control is a well-known technique in process industry to improve regulatory control performance. The use of the conventional PI/PID controllers has often been found to be ineffective for cascade processes with long time-delays. Recent literature report has shown that the multi-scale control (MSC) scheme is capable of providing improved performance over the conventional PID controllers for processes characterized by long time-delays as well as slow RHP zeros. This paper presents an extension of this basic MSC scheme to cascade processes with long time-delays. This new cascade MSC scheme is applicable to self-regulating, integrating and unstable processes. Extensive numerical studies demonstrate the effectiveness of the cascade MSC scheme compared with some well-established cascade control strategies.
Nonminimum-phase (NMP) processes are frequently encountered in chemical plants, where the presence of right half-plane zeros and time delays often imposes limitations on the achievable control ...performance. In this article, a new multiscale control scheme for controlling NMP processes is introduced. The novelty of the proposed scheme is to decompose a given plant into a sum of basic factors/modes having distinct speeds of responses. Then, an individual subcontroller is specifically designed to control each of these plant modes. Finally, an overall multiscale controller is synthesized by combining all of the subcontrollers in a way that enhances good cooperation among the different modes, which is an essential feature for good control performance and robustness. Extensive numerical studies demonstrate that the proposed scheme can provide better nominal performance and performance robustness than some well-established control schemes.
This paper formalizes a new multi-scale kinetic model for a process influenced by several limiting factors which are multi-scale in nature. The multi-scale kinetic model incorporates all of the ...dominant factors which can be expressed in the form of first-order kinetics where some of the factors could have delayed effects on the process. The applicability of this new model is demonstrated using a case study of Mangifera pajang antioxidant degradation modelling. The results show that the multi-scale kinetic model can provide improved modelling accuracy, with a Root Mean Square Error (RMSE) of 1.32%. Interestingly, the analysis of the multi-scale model suggests the presence of two groups of antioxidant compounds based on the degradation dynamics in the M. pajang extract. The dominant group of antioxidant compounds contributes about 87% to the total antioxidant concentration, and the degradation of this group is much slower than the non-dominant antioxidant compounds at pH 3. At a high temperature above 60 °C and pH above 7, the fast-degrading group of antioxidants becomes dominant in the extract. Significantly, the proposed multi-scale kinetic model is generic and flexible which can be applied to data-driven modelling of many different processes.
•New generalized multi-scale kinetic model for improved modelling accuracy.•Antioxidant degradation modelling over broad range of experimental conditions.•Reveals two groups of antioxidants in the extract.•Provides more accurate half-life value of antioxidants.
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