30,962 research outputs found
Robust control of ill-conditioned plants: high-purity distillation
Using a high-purity distillation column as an example, the physical reason for the poor conditioning and its implications on control system design and performance are explained. It is shown that an acceptable performance/robustness tradeoff cannot be obtained by simple loop-shaping techniques (using singular values) and that a good understanding of the model uncertainty is essential for robust control system design. Physically motivated uncertainty descriptions (actuator uncertainties) are translated into the H∞/structured singular value framework, which is demonstrated to be a powerful tool to analyze and understand the complex phenomena
Simplification of detailed rate-based model of post-combustion CO₂ capture for full chain CCS integration studies
As post-combustion CO₂ capture (PCC) technology nears commercialisation, it has become necessary for the full carbon capture and storage (CCS) chain to be studied for better understanding of its dynamic characteristics. Model-based approach is one option for economically and safely reaching this objective. However, there is need to ensure that such models are reasonably simple to avoid the requirement for high computational time when carrying out such study. In this paper, a simplification approach for a detailed rate-based model of post-combustion CO₂ capture with solvents (rate-based mass transfer and reactions assumed to be at equilibrium) is presented. The simplified model can be used in model-based control and/or full chain CCS simulation studies. With this approach, we demonstrated significant reduction in CPU time (up to 60%) with reasonable model accuracy retained in comparison with the detailed model
Optimisation of solvent replacement procedures according to economic and environmental criteria in pharmaceutical industry
During pharmaceutical syntheses, the reaction solvent has often to be switched off from one reaction step to the following one. Because of the standard industrial practices, solvent replacement generally constitutes a slow and high solvent-consuming operation. In this paper, a specific methodology, based on a batch processes optimisation framework, is proposed for the optimisation of solvent replacement procedures. Optimisation may be performed at different levels according to economic and environmental criteria and satisfying safety and waste treatment constraints. In fact, the proposed methodology allows both to design new procedures of solvent replacement and to improve existing industrial processes. Two industrial applications are detailed to emphasize the benefits related to this methodology. In each case, the proposed methodology leads to the suitable recipe from comparison of traditional and empirical replacement procedures generally used in the pharmaceutical industry
Heterogeneous Batch Distillation Processes: Real System Optimisation
In this paper, optimisation of batch distillation processes is considered. It deals with real systems with rigorous simulation of the processes through the resolution full MESH differential algebraic equations. Specific software architecture is developed, based on the BatchColumn® simulator and on both SQP and GA numerical algorithms, and is able to optimise sequential batch columns as long as the column transitions are set.
The efficiency of the proposed optimisation tool is illustrated by two case studies. The first one concerns heterogeneous batch solvent recovery in a single distillation column and shows that significant economical gains are obtained along with improved process conditions. Case two concerns the optimisation of two sequential homogeneous batch distillation columns and demonstrates the capacity to optimize several sequential dynamic different processes. For such multiobjective complex problems, GA is preferred to SQP that is able to improve specific GA solutions
Generalised model for heteroazeotropic batch distillation with variable decanter hold-up
A general model of batch heteroazeotropic distillation is proposed. Both liquid phases present in the decanter can be refluxed or withdrawn as distillate, their hold-up can be increased, decreased or kept constant, as well. By assuming maximal separation, that is, that the composition of the condensate always equals to that of the heteroazeotrope, the still path equation was derived. The still path directions are determined for all the 16 possible operational policies. It is possible to steer the still path in a desired direction by changing the operational parameters, which allows the recovery of a pure component in the still. The still path directions are validated by rigorous simulations for three policies not published yet using the mixture water – formaldehyde – propyl formate. From the 16 operational policies, 11 can be considered as useful in practice. To demonstrate the advantage of using a non-traditional policy, the separation of the mixture aniline – ethylene glycol – water was investigated, as well. By using a non-traditional operational policy with hold-up reduction in the decanter a higher purity of ethylene glycol was obtained in the still
Data-based fault detection in chemical processes: Managing records with operator intervention and uncertain labels
Developing data-driven fault detection systems for chemical plants requires managing uncertain data labels and dynamic attributes due to operator-process interactions. Mislabeled data is a known problem in computer science that has received scarce attention from the process systems community. This work introduces and examines the effects of operator actions in records and labels, and the consequences in the development of detection models. Using a state space model, this work proposes an iterative relabeling scheme for retraining classifiers that continuously refines dynamic attributes and labels. Three case studies are presented: a reactor as a motivating example, flooding in a simulated de-Butanizer column, as a complex case, and foaming in an absorber as an industrial challenge. For the first case, detection accuracy is shown to increase by 14% while operating costs are reduced by 20%. Moreover, regarding the de-Butanizer column, the performance of the proposed strategy is shown to be 10% higher than the filtering strategy. Promising results are finally reported in regard of efficient strategies to deal with the presented problemPeer ReviewedPostprint (author's final draft
Preparation, Proximate Composition and Culinary Properties of Yellow Alkaline Noodles from Wheat and Raw/Pregelatinized Gadung (Dioscorea Hispida Dennst) Composite Flours
The steady increase of wheat flour price and noodle consumptions has driven researchers to find substitutes for wheat flour
in the noodle making process. In this work, yellow alkaline noodles were prepared from composite flours comprising wheat
and raw/pregelatinized gadung (Dioscorea hispida Dennst) flours. The purpose of this work was to investigate the effect of
composite flour compositions on the cooking properties (cooking yield, cooking loss and swelling index) of yellow alkaline
noodle. In addition, the sensory test and nutrition content of the yellow alkaline noodle were also evaluated for further
recommendation. The experimental results showed that a good quality yellow alkaline noodle can be prepared from
composite flour containing 20% w/w raw gadung flour. The cooking yield, cooking loss and swelling index of this noodle
were 10.32 g, 1.20 and 2.30, respectively. Another good quality yellow alkaline noodle can be made from composite flour
containing 40% w/w pregelatinized gadung flour. This noodle had cooking yield 8.93 g, cooking loss 1.20, and swelling
index of 1.88. The sensory evaluation suggested that although the color, aroma and firmness of the noodles were
significantly different (p ≤ 0.05) from wheat flour noodle, but their flavor remained closely similar. The nutrition content of the noodles also satisfied the Indonesian National Standard for noodle. Therefore, it can be concluded that wheat and raw/pregelatinized gadung composite flours can be used to manufacture yellow alkaline noodle with good quality and suitable for functional food
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