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The Voidage in a CFB Riser as Function of Solids Flux and Gas Velocity

Procedia Engineering 2015年 102卷 1112-1122页

作者： Huili Zhang Jan Degrève Jan Baeyens Raf Dewil KU Leuven Department of Chemical Engineering Chemical and Biochemical Process Technology and Control Section De Croylaan 46 Heverlee 3001 Belgium University of Warwick School of Engineering Coventry CV4 7AL United Kingdom KU Leuven Department of Chemical Engineering Process and Environmental Technology Lab J. De Nayerlaan 5 Sint-Katelijne-Waver 2860 Belgium

Circulating Fluidised Beds (CFBs) are widely applied in the process industry, for mostly gas-solid and gas-catalytic reactions. The riser is the key component of the CFB being the process reactor. The important design parameters are the operating gas velocity (U) and the solids concentration flux (G). The CFB operation starts at moderate to high superficial gas velocities. Its voidage exceeds ∼ 0.9 and is a function of the solids circulation flux. Different flow modes have been presented in literature, and result in an operation diagram where G and U delineate specific operations, from dilute riser flow, through core-annulus flow, to dense riser upflow (mostly at any U, G exceeding 80 to 120 kg m -2 s -1 ). Increasing G whilst maintaining the gas velocity will cause an increase in suspension concentration. The riser flow can hence be characterized by its apparent voidage, ɛ. In the core-annulus operation, clusters of particles reflux near the wall, thus influencing the local radial voidage in the cross section of the riser, and also extending over a given distance, δ, from the wall to the core . Through measurements in CFBs of 0.1 and 0.14 m I.D., the research has been able to determine the average axial and radial voidages of the dense phase within the different regimes, whilst also determining the thickness of the annulus (in CAF-mode). Experimental results will be illustrated and compared with previous empirical equations, shown to have a limited accuracy only both for ɛ, and for the thickness of the annulus in CAF operation. Within the operating conditions tested, results demonstrate that the annulus thickness is about 15 to 20% of the riser diameter in CAF, and that the voidage in the riser is a function of U and G, with riser diameter and distance along the riser length as secondary parameters.

关键词： circulating fluidized bed riser voidage annulus thickness

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Extending a novel class of predictive models to describe the effect of pH on microbial growth 8

Extending a novel class of predictive models to describe the...

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8th International Conference on Simulation and Modelling in the Food and Bio-Industry 2014, FOODSIM 2014

作者： Akkermans, Simen Noriega, Estefania Logist, Filip Van Impe, Jan CPMF-Flemish Cluster Predictive Microbiology in Foods OPTHC - Centre of Kxcellence Optimization in Engineering BioTeC - Chemical and Biochemical Process Technology and Control Department of Chemical Engineering KU Leuven W. de Croylaan 46 B-3001 Leuven Belgium Belgium

ISBN: (纸本)9789077381847

Despite all EU efforts to tackle food poisoning and spoilage, about 5,400 outbreaks and 1.3 billion tons of food waste are reported annually, with a significant impact on EU economy and public health. Modelling and simulation of microbial dynamics as a function of processing, transportation and storage conditions is a useful tool to guarantee food safety and quality. The goal of this research is to improve an existing methodology in order to build accurate predictive models based on multiple environmental conditions. The effect of multiple environmental conditions on microbial dynamics is often described by combining the separate effects in a multiplicative way (gamma concept). This idea was extended further in this work by including the effects of the lag and stationary growth phases on microbial growth rate as independent gamma factors. A mechanistic description of the stationary phase as a function of pH was included, based on a novel class of models that consider product inhibition. Experimental results on Escherichia coli growth dynamics indicated that also the parameters of the product inhibition equations can be modelled with the gamma approach. This work has extended a modelling methodology, resulting in predictive models that are (i) mechanistically inspired, (ii) easily identifiable with a limited work load and (iii) easily extendable to additional environmental conditions.

关键词： Food safety

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An individual-based model for anaerobic dynamics of Escherichia coli colonies 8

An individual-based model for anaerobic dynamics of Escheric...

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8th International Conference on Simulation and Modelling in the Food and Bio-Industry 2014, FOODSIM 2014

作者： Tack, Ignace Logist, Filip Fernández, Estefanía Noriega Van Impe, Jan CPMF - Flemish Cluster Predictive Microbiology in Foods OPTEC - Center of Excellence Optimization in Engineering BioTeC - Chemical and Biochemical Process Technology and Control Department of Chemical Engineering KU Leuven Willem de Croylaan 46 box 2423 B-3001 Leuven Belgium Belgium

ISBN: (纸本)9789077381847

Traditional models in predictive microbiology describe microbial dynamics in homogeneous liquid food systems. However, most food systems have a semi-solid structure, in which microbial cells grow locally as colonies. Due to the high cell density in these colonies, the environment becomes inhomogeneous as a result of nutrient over- consumption and cell product accumulation. Hence, the individual cells exhibit strongly different behavior according to their position in the colony. Consequently, an individual-based modeling approach, considering the cell as the basic modeling unit, is most appropriate to describe colony dynamics in full detail. In this paper, an individual-based model is developed for anaerobic colony behavior of Escherichia coli K-12. From the simulation, characteristic colony dynamics emerge, such as a linear radius increase. These dynamics result from the pH drop and concomitant cellular stress in the colony center due to accumulation of lactic acid.

关键词： Dynamics

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Modelling of the ultrasonic disintegration of activated sludge 19

Modelling of the ultrasonic disintegration of activated slud...

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19th IFAC World Congress on International Federation of Automatic control, IFAC 2014

作者： Lambert, N. Smets, I. Van Impe, J. Dewil, R. KU Leuven Department of Chemical Engineering Process and Environmental Technology Lab. Jan Pieter De Nayerlaan 5 Sint-Katelijne-WaverBE-2860 Belgium KU Leuven Department of Chemical Engineering Chemical and Biochemical Process Technology and Control Division W. de Croylaan 46 HeverleeBE-3001 Belgium

ISBN: (纸本)9783902823625

Ultrasonic treatment of waste activated sludge is one of the possibilities to reduce excess sludge production through the mechanism of sludge disintegration and cell lysis. In the past, several attempts have been made to model the process of solubilisation of the particulate volatile suspended solid part of the activated sludge (VSS) into soluble COD (sCOD). However, the focus of these models was predominantly on predicting an efficiency factor for the release of sCOD (Disintegration Degree, DDCOD) and provided no information on the release of nutrients and the instantaneous reduction of VSS. Moreover, often insufficient influential variables were included in the model equations, making the models only applicable on the training dataset of their own experimental research. This paper, therefore, seeks to build a simple model, which contains all influential input variables, that can predict not only the sCOD release but also the nutrients release (ortho-PO4-P and soluble Kjeldahl nitrogen) and VSS reduction simultaneously. Therefore, in first instance, a Principal Component Analysis (PCA) is carried out on the input and output data matrix of obtained experimental observations that will be used as training data. In this way, certain correlated input variables and independent output variables can be removed from the model, in order to increase its simplicity and predictive nature. Then, the model is built on the basis of Partial Least Squares Regression (PLS-R) and a part of the observations is used to validate the predictive strength of the model. © IFAC.

关键词： Activated sludge process

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Modelling of the ultrasonic disintegration of activated sludge

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IFAC Proceedings Volumes 2014年第3期47卷 7122-7127页

作者： N. Lambert I. Smets J. Van Impe R. Dewil KU Leuven Department of Chemical Engineering Process and Environmental Technology Lab Jan Pieter De Nayerlaan 5 – BE-2860 Sint-Katelijne-Waver – Belgium KU Leuven Department of Chemical Engineering Chemical and Biochemical Process Technology and Control Division – W. de Croylaan 46 – BE-3001 Heverlee - Belgium

Ultrasonic treatment of waste activated sludge is one of the possibilities to reduce excess sludge production through the mechanism of sludge disintegration and cell lysis. In the past, several attempts have been made to model the process of solubilisation of the particulate volatile suspended solid part of the activated sludge (VSS) into soluble COD (sCOD). However, the focus of these models was predominantly on predicting an efficiency factor for the release of sCOD (Disintegration Degree, DD COD ) and provided no information on the release of nutrients and the instantaneous reduction of VSS. Moreover, often insufficient influential variables were included in the model equations, making the models only applicable on the training dataset of their own experimental research. This paper, therefore, seeks to build a simple model, which contains all influential input variables, that can predict not only the sCOD release but also the nutrients release (ortho-PO 4 -P and soluble Kjeldahl nitrogen) and VSS reduction simultaneously. Therefore, in first instance, a Principal Component Analysis (PCA) is carried out on the input and output data matrix of obtained experimental observations that will be used as training data. In this way, certain correlated input variables and independent output variables can be removed from the model, in order to increase its simplicity and predictive nature. Then, the model is built on the basis of Partial Least Squares Regression (PLS-R) and a part of the observations is used to validate the predictive strength of the model.

关键词： wastewater treatment modelling ultrasonic disintegration excess activated sludge reduction

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The Impact of process Variability on Statistical process Monitoring

The Impact of Process Variability on Statistical Process Mon...

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Conference on control and Fault-Tolerant Systems

作者： Geert Gins Jef Vanlaer Jan Van Impe KU Leuven Department of Chemical Engineering Chemical and Biochemical Process Technology and Control (BioTeC)

ISBN: (纸本)9781479928569

process simulators are widely used to develop and benchmark techniques for Statistical process Monitoring (SPM). Typically, the simulators are deterministic and do not take process variability into account. However, modern processes in (bio)chemical industry focus on bio-based production with the help of microorganisms, and are, therefore, subject to larger inherent process variability. In this work, the influence of process variability on the performance of SPM is demonstrated in two representative case studies by adding different levels of process variability to the well-known PENSIM benchmark simulator. In the first case study, a significant improvement (i.e., decrease) of fault detection times is observed. It is hypothesized that process variability causes a persistent excitation of the process, resulting in better process monitoring. In the second case study, a slightly poorer prediction of the batch-end quality was observed for increasing biological variability. Both case studies clearly illustrate that process variability has a profound influence on the performance of SPM techniques. When employing computer-generated data for development, testing or comparison of techniques, the use of a simulator that includes process variability is highly recommended.

关键词： statistical process monitoring simulator process monitoring Scanning Probe Microscopy development test

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Gasification of plastic waste as waste-to-energy or waste-to-syngas recovery route

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Natural Science 2013年第6期5卷 695-704页

作者： Anke Brems Raf Dewil Jan Baeyens Rui Zhang College of Life Science and Technology The Key Laboratory of Bioprocess of Beijing Beijing University of Chemical Technology Beijing China Department of Chemical Engineering Chemical and Biochemical Process Technology and Control Section Katholieke Universiteit Leuven Heverlee Belgium

The disposal of plastic solid waste (PSW) has become a major worldwide environmental problem. New sustainable processes have emerged, i.e. either advanced mechanical recycling of PSW as virgin or second grade plastic feedstock, or thermal treatments to recycle the waste as virgin monomer, as synthetic fuel gas, or as heat source (incineration with energy recovery). These processes avoid land filling, where the non-biodegradable plastics remain a lasting environmental burden. Within the thermal treatments, gasification and pyrolysis gain increased interest. Gasification has been widely studied and applied for biomass and coal, with results reported and published in literature. The application to the treatment of PSW is less documented. Gasification is commonly operated at high temperatures (> 600℃ to 800℃) in an air-lean environment (or oxygen-deficient in some applications): the air factor is generally between 20% and 40% of the amount of air needed for the combustion of the PSW. Gasification produces mostly a gas phase and a solid residue (char and ashes). The use of air introduces N2 in the product gases, thus considerably reducing the calorific value of the syngas, because of the dilution. The paper will review the existing literature data on PSW gasification, both as the result of laboratory and pilot-scale research. processes developed in the past will be illustrated. Recently, the use of a sequential gasification and combustion system (at very high temperatures) has been applied to various plastic-containing wastes, with atmospheric emissions shown to be invariably below the legal limits. Operating results and conditions will be reviewed in the paper, and completed with recent own lab-scale experimental results. These results demonstrate that gasification of PSW can be considered as a first order reaction, with values of the activation energy in the order of 187 to 289 kJ/mol as a function of the PSW nature.

关键词： Plastic Waste Re-Use Gasification Syngas Char Sustainability Reaction Rate

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Wall-to-Bed Heat Transfer at Minimum Gas-Solid Fluidization

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Journal of Powder technology 2014年第1期2014卷

作者： Huili Zhang Jan Degrève Jan Baeyens Raf Dewil Department of Chemical Engineering KU Leuven Chemical and Biochemical Process Technology and Control Section de Croylaan 46 3001 Heverlee Belgiumkuleuven.be School of Engineering University of Warwick Coventry UKwarwick.ac.uk Department of Chemical Engineering KU Leuven Process and Environmental Technology Lab J.P. De Nayerlaan 5 2860 Sint-Katelijne-Waver Belgiumkuleuven.be

The heat transfer from a fluidized bed to the cooling jacket of the vessel has been studied for various powders at minimum fluidization conditions, by both convection and conduction approaches. These heat transfer characteristics are important as the point of transition between packed and fluidized bed operations and are needed in designing heat transfer operations where bubble-flow is not permitted. The effective thermal conductivity of the emulsion moreover determines the contact resistance at the heating or cooling surface, as used in packet renewal models to predict the wall-to-bed heat transfer. In expressing the overall heat transfer phenomenon as a convective heat transfer coefficient, it was found that the results could be fitted by Nu mf, j = 0.01Ar 0.42 .

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Optimal experimental design for mechanistic nonlinear dynamic models using multisine inputs: application to a Diesel engine.

Optimal experimental design for mechanistic nonlinear dynami...

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American control Conference

作者： I. Stamati D. Telen F. Logist E. Van Derlinden M. Hirsch T. Passenbrunner J. Van Impe Katholieke Universiteit Leuven - Department of Chemical Engineering BioTeC - Chemical and Biochemical Process Technology and Control Leuven Belgium Institute for Design and Control of Mechatronical Systems Johannes Kepler University Linz Austria

ISBN: (纸本)9781457710957

For many applications first-principles nonlinear dynamic models are preferred by practitioners. Parameter estimation for these models is often a non-trivial and time consuming task. The use of optimally designed dynamic inputs can reduce the experimental burden and increase the accuracy of the estimated parameters. Traditionally, piecewise polynomial input sequences are exploited for this purpose. In contrast, this paper proposes optimal experiment design with the use of random phase multisine inputs, which are typically used for black box model identification. The main motivations are (i) the practical requirement that the inputs have to be concentrated around an operating point, and (ii) the fact that fast dynamics have to be included in the input profile without introducing a large number of discretization parameters. Moreover, multisines can be designed to excite exclusively a specific frequency band of interest. As an illustration, optimal inputs are designed and validated experimentally for estimating the parameters important for the dynamical behaviour of a Diesel engine air path model.

关键词： Mathematical model Optimization Atmospheric modeling Parameter estimation White noise Diesel engines Sensitivity

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Simulation of the Anaerobic Digestion of Microwave Pre-Treated Waste Activated Sludge with ADM1

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IFAC Proceedings Volumes 2012年第2期45卷 677-682页

作者： Joost Lauwers Lise Appels Jan Van Impe Raf Dewil Chemical and Biochemical Process Technology and Control section Department of Chemical Engineering KU Leuven (University of Leuven) Heverlee Belgium (Tel:32-16-322675)

Abstract The disposal of sludge originating from municipal waste water treatment is a major issue and represents up to 50% of the operating costs of wastewater treatment plants (WWTP). (Appels et al., 2008) This sludge, a by-product of the treatment processes, however, has the potential to be converted into an energy rich biogas, i.e. a mixture of ca. 65% CH 4 and 35% CO 2 , which can be utilized for the sustainable production of heat and/or electricity. Various pre-treatment methods have been suggested in literature for improving the solids reduction and biogas production rate by enhancing the digestion's rate limiting step, i.e. organic matter hydrolysis. They all induce the solubilization of complex particulate matter so this is more rapidly and completely consumed during the anaerobic digestion process. Methods that have been shown to have a positive effect on anaerobic digestion include chemical, mechanical, biological and thermal processes. Microwave disintegration is one of the more recently applied pre-treatment methods. The disintegration is caused by the combination of thermal and athermal effects and may hence provide superior results compared to a heat treatment (Eskicioglu et al., 2007). The application of mathematical models for the optimization of the digestion process is widely acknowledged. Due to the complexity of the microbial process, accurate modelling of anaerobic digestion is, however, a daunting task. A major stride countering this problem was achieved by the development of the Anaerobic Digestion Model no 1 (ADM1) by the corresponding IWA task group (Batstone et al. 2002). This model is ever since, considered to be the state of the art in modelling of anaerobic digestion and has been the platform for further refinements and numerous applications (Batstone et al. 2006). The main aim of this work is to investigate the ability of ADM1 to describe anaerobic digestion of microwave pre-treated sludge. Compared to untreated sludge, the composition

关键词： anaerobic digestion microwave pre-treatment ADM1

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