1,721,873 research outputs found
A Perspective on PSE in Fermentation Process Development and Operation
Full text linkCompared to the chemical industry, the use of PSE methods and tools is not as widespread in industrial fermentation processes. This paper gives an overview of some of the main engineering challenges in industrial fermentation processes. Furthermore, a number of mathematical models are highlighted as examples of PSE methods and tools that are used in the context of industrial fermentation technology. Finally, it is discussed what could be done to increase the future use of PSE methods and tools within the industrial fermentation technology area
Model-based characterisation of twin-screw granulation system for continuous solid dosage manufacturing
No full textContinuous twin-screw granulation has received increased attention as it can be embedded in a continuous manufacturing line allowing 24/7 production capacity eliminating scale-up requirements and intermediate storage. The screws have a modular structure (interchangeable transport and kneading discs) allowing greater flexibility in equipment design. However, process knowledge should be further developed both under steady state and dynamic conditions. Mechanistic models incorporating the underlying mechanisms are therefore applied. In this study, the principle constitutive mechanisms such as aggregation and breakage are included in a population balance modelling framework. Based on an experimental inflow granule size distribution and mean residence time of the granulator, predictions of the outflow granule size distribution were made. Experimental data was used for calibrating the model for individual screw modules in the twin-screw granulator. The results showed that the successive kneading blocks lead to a granulation regime-separation inside the twin-screw granulator. The first kneading block after wetting caused an increase in the aggregation rate, which was reduced after the second kneading block. The breakage rate increased successively along the length of the granulator. Such a physical separation between the granulation regimes will be promising for future design and advanced control of the continuous granulation process
Model-based optimization of the primary drying step during freeze-drying
Full text linkSince large molecules are considered the key driver for growth of the pharmaceutical industry, the focus of the pharmaceutical industry is shifting from small molecules to biopharmaceuticals: around 50% of the approved biopharmaceuticals are freeze-dried products. Therefore, freeze- drying is an important technology to stabilise biopharmaceutical drug products which are unstable in an aqueous solution. However, the freeze-drying process is an energy and time-consuming process. The use of mechanistic modelling to gather process knowledge can assist in optimisation of the process parameters during the operation of the freeze-drying process. By applying a dynamic shelf temperature and chamber pressure, which are the only controllable process variables, the processing time can be decreased by a factor 2 to 3
A Numerical Procedure for Model Identifiability Analysis Applied to Enzyme Kinetics
No full textThe proper calibration of models describing enzyme kinetics can be quite challenging. In the literature, different procedures are available to calibrate these enzymatic models in an efficient way. However, in most cases the model structure is already decided on prior to the actual calibration exercise, thereby bypassing the challenging task of model structure determination and identification. Parameter identification problems can thus lead to ill-calibrated models with low predictive power and large model uncertainty. Every calibration exercise should therefore be precededby a proper model structure evaluation by assessing the local identifiability characteristics of the parameters. Moreover, such a procedure should be generic to make sure it can be applied independent from the structure of the model. We hereby apply a numerical identifiability approach which is based on the work of Walter and Pronzato (1997) and which can be easily set up for any type of model. In this paper the proposed approach is applied to the forward reaction rate of the enzyme kinetics proposed by Shin and Kim(1998). Structural identifiability analysis showed that no local structural model problems were occurring. In contrast, the practical identifiability analysis revealed that high values of the forward rate parameter Vf led to identifiability problems. These problems were even more pronounced athigher substrate concentrations, which illustrates the importance of a proper experimental designto avoid (practical) identifiability problems. By using the presented approach it is possible to detect potential identifiability problems and avoid pointless calibration (and experimental!) effort
Optimization-based methodology for wastewater treatment plant synthesis – a full scale retrofitting case study
No full textExisting wastewater treatment plants (WWTP) need retrofitting in order to better handle changes in the wastewater flow and composition, reduce operational costs as well as meet newer and stricter regulatory standards on the effluent discharge limits. In this study, we use an optimization based framework to manage the multi-criteria WWTP design/retrofit problem for domestic wastewater treatment. The design space (i.e. alternative treatment technologies) is represented in a superstructure, which is coupled with a database containing data for both performance and economics of the novel alternative technologies. The superstructure optimization problem is formulated as a Mixed Integer (non)Linear Programming problem and solved for different scenarios - represented by different objective functions and constraint definitions. A full-scale domestic wastewater treatment plant (265,000 PE) is used as a case study in order to highlight the use of the framework for generating optimal retrofitting solutions
Extending the benchmark simulation model n<sup>o</sup>2 with processes for nitrous oxide production and side-stream nitrogen removal
No full textIn this work the Benchmark Simulation Model No.2 is extended with processes for nitrous oxide production and for side-stream partial nitritation/Anammox (PN/A) treatment. For these extensions the Activated Sludge Model for Greenhouse gases No.1 was used to describe the main waterline, whereas the Complete Autotrophic Nitrogen Removal (CANR) model was used to describe the side-stream (PN/A) treatment. Comprehensive simulations were performed to assess the extended model. Steady-state simulation results revealed the following: (i) the implementation of a continuous CANR side-stream reactor has increased the total nitrogen removal by 10%; (ii) reduced the aeration demand by 16% compared to the base case, and (iii) the activity of ammonia-oxidizing bacteria is most influencing nitrous oxide emissions. The extended model provides a simulation platform to generate, test and compare novel control strategies to improve operation performance and to meet the new plant performance criteria such as minimization of greenhouse gas (in particular of nitrous oxide) emissions
Optimal Design of Algae Biorefinery Processing Networks for the production of Protein, Ethanol and Biodiesel
Full text linkIn this study, optimal design of algal biorefinery using microalgae with respect to techno-economic criteria is studied. A systematic methodology using superstructure-based optimization is used to this end. A superstructure representing a wide range of technologies developed for processing microalgae to produce end products is formulated. The corresponding technical and economic data is collected and structured using a generic input-output mass balance models. An optimization problem is formulated and solved to identify the optimal designs. The effect of uncertainties inherent in economic analysis such as microalgae production cost, composition of microalgae (e.g. oil content) and biodiesel/bioethanol market prices is considered. New optimal processing paths are found with potential of producing higher amount of biodiesel. Last, the methodology is intended as decision support tool for early-stage concept screening to enhance the future development of algal biorefinery
State Estimation in Fermentation of Lignocellulosic Ethanol. Focus on the Use of pH Measurements.
No full textThe application of the continuous-discrete extended Kalman filter (CD-EKF) as apowerful tool for state estimation in biochemical systems is assessed here. Using afermentation process for ethanol production as a case study, the CD-EKF caneffectively estimate the model states even when highly non-linear measurements such as pH are included. Several configurations of the CD-EKF are tested and it is seen that including pH, which is a readily available measurement in virtually every biochemical process, provides information that significantly improves the performance of the filter
Topology optimization for biocatalytic microreactor configurations
No full textThe aim of this study is to present an innovative strategy for selecting a reactor for a specific process. Instead of adapting the process to a well-known reactor shape, a topology optimization method is used to obtain the best reactor configuration, and is applied to a biocatalyic reaction system as a case study. The Evolutionary Structure Optimization (ESO) method is applied using an interface between Matlab® and the computational fluid dynamic simulation software ANSYS CFX®. In the case study, theESO method is applied to optimize the spatial distribution of immobilized enzyme inside a microreactor. The results allow evaluating which regions in the microreactorhave more importance for the product formation. In fact, it was possible to simulate the improvement of the outlet product concentration per same amount of enzyme by modifying the spatial distribution of the immobilized enzyme
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