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Process Modeling of Combustion and Digesters for On-line Applications
Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi. (FEC/MERO)ORCID-id: 0000-0001-8191-4901
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The use of biomass has increased in recent years due to the efforts to reduce the high emissions of greenhouse gases, primarily carbon dioxide from combustion of fossil fuels. At the same time industrial processes have become more complex because of increased production rates and profitability requirements. A higher degree of automation is needed when the processes are too complex to be handled manually. There is a need to find modeling strategies that can automatically handle the challenges that the conversion of biomass in an industrial process entails, such as operational changes, decreasing component and overall system efficiency, drifting sensors, etc. The objective of this thesis is to develop a methodology for on-line applications in industrial processes. Dynamic process models have been developed for continuous digesters and boilers. Process models have been evaluated for their use in continuous industrial process. Applications that have been studied are monitoring and diagnostics, advanced control and decision support. The process models are designed for on-line simulations. The results shows that the use of mathematical simulation models can improve the use of both process data and process understanding, to achieve improved diagnostics, advanced control and process optimization. In the two examples of industrial processes covered in this thesis, we can see that similar types of models can be used for completely different types of processes, such as pulp digesters and boilers. It also demonstrates the ability to combine soft sensors and hard sensors with physical models to take the information to a higher level of utilization.

Ort, förlag, år, upplaga, sidor
Västerås: Mälardalen University , 2015.
Serie
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 194
Nationell ämneskategori
Energiteknik
Forskningsämne
energi- och miljöteknik
Identifikatorer
URN: urn:nbn:se:mdh:diva-29462ISBN: 978-91-7485-244-8 (tryckt)OAI: oai:DiVA.org:mdh-29462DiVA, id: diva2:868788
Disputation
2015-12-15, R2-025, Mälardalens högskola, Västerås, 08:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2015-11-12 Skapad: 2015-11-11 Senast uppdaterad: 2015-11-25Bibliografiskt granskad
Delarbeten
1. Use of combined physical and statistical models for online applications in the pulp and paper industry
Öppna denna publikation i ny flik eller fönster >>Use of combined physical and statistical models for online applications in the pulp and paper industry
2009 (Engelska)Ingår i: Mathematical and Computer Modelling of Dynamical Systems, Vol. 15, nr 5, s. 425-434Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This paper discusses the accuracy of different types of models. Statistical models are based on process data and/or observations from lab measurements. This class of models are called black box models. Physical models use physical relationships to describe a process. These are called white box models or first principle models. The third group is sometimes called grey box models, being a combination of black box and white box models. Here we discuss two examples of model types. One is a statistical model where an artificial neural network is used to predict NOx in the exhaust gases from a boiler at Mlarenergi AB in Vsters, Sweden. The second example is a grey box model of a continuous digester. The digester model includes mass balances, energy balances, chemical reactions and physical geometrical constraints to simulate the real digester. We also propose that a more sophisticated model is not required to increase the accuracy of the predicted measurements.

Nyckelord
statistical models; physical models; pulp digester
Nationell ämneskategori
Teknik och teknologier
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-7590 (URN)10.1080/13873950903375403 (DOI)000274741800003 ()2-s2.0-75349089565 (Scopus ID)
Tillgänglig från: 2009-11-29 Skapad: 2009-11-29 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
2. New Methods for Adaptation to Degeneration in Process Models for Process Industries
Öppna denna publikation i ny flik eller fönster >>New Methods for Adaptation to Degeneration in Process Models for Process Industries
2009 (Engelska)Ingår i: Chemical Product and Process Modeling, Vol. Vol. 4, nr : Iss. 1, s. , Article 25.-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The implementation of model-based control and diagnostics suffer strongly from the fact that models deteriorate as a function of process and sensor deterioration. Also, changes in the raw material (i.e. wood) may occur and often the process control is not addressing these variations in reality. It is thus vital for the model system to be robust in the sense that it is transparent and easy for the operator to maintain. Robustness is essential in many parts of the system, including measurement, process model validation, the ability of the model to adapt to changes in the process, optimization algorithms, and of course the model itself. In this paper, we first show three real-life applications of the utilization of models for diagnostics and control. Thereafter conditions for on-line adaptation of the models are discussed. The challenges when designing such a system are in achieving operator confidence, filtering of misleading measured data, adaptation of process parameters when the process parameters change, and combining validation of measurements and process models. These challenges are met by using a combination of physical and statistical models and methods based on them such as model predictive control (MPC) and parameter estimation. The model should be maintained by a qualified engineer who should be able to explain the system to the operator so that it is understood and confidence can be maintained.

Ort, förlag, år, upplaga, sidor
Berkley Electronic Press, 2009
Nyckelord
simulation, model based control, MPC, power boiler
Nationell ämneskategori
Kemiska processer Annan elektroteknik och elektronik
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-8011 (URN)10.2202/1934-2659.1127 (DOI)2-s2.0-77954559066 (Scopus ID)
Projekt
Värmeforskproject on model based control of boiler
Tillgänglig från: 2010-02-10 Skapad: 2010-02-10 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
3. On-line simulation of continuous pulp digester
Öppna denna publikation i ny flik eller fönster >>On-line simulation of continuous pulp digester
2009 (Engelska)Ingår i: TAPPSA JournalArtikel i tidskrift (Refereegranskat) Published
Abstract [en]

Continuous cooking is the dominant process in the kraft pulping industry.  Our general knowledge and understanding of process conditions inside the digester is limited. Process control systems comprise of groups of measurements, which give information about conditions at the outer shell of the digester.  These measurements mostly tell about cooking liquor inflows and outflows, temperature and it is also possible to measure pressure or pressure difference at the screen section of the digester shell.  But ultimately process conditions inside the digester are based on measurements at the shell and intelligent approximations.

 

The aim of this paper is to describe more accurately the cooking conditions and phenomena inside the digester.  A model of a continuous digester was developed as an extension of the well known Purdue model [Bhartiya, 2003].  The model was adapted to simulate an industrial Lo-Solids pulp digester as well as an ITC digester.  The models were then used to do online predictions and these predictions were compared with the actual plant performance.

Nyckelord
modelling, simulation, on-line, pulp digester
Nationell ämneskategori
Pappers-, massa- och fiberteknik
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-8005 (URN)
Projekt
KKS Use of statistical and physical models for on-line optimization
Tillgänglig från: 2010-02-10 Skapad: 2010-02-10 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
4. Dynamic simulation of fouling in a circulating fluidized biomass fired boiler
Öppna denna publikation i ny flik eller fönster >>Dynamic simulation of fouling in a circulating fluidized biomass fired boiler
2011 (Engelska)Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 88, nr 5, s. 1813-1824Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A dynamic model is presented for a biomass-fired circulating fluidized bed boiler. The model is based on energy and mass balances for the components in the boiler and on a combustion model for the fluidized bed. The main purpose of the model is to simulate how deposits affect the boiler efficiency and performance. The model is verified against the municipal circulating fluidized bed boiler in Vasteras, Sweden, which produces 157 MW. The distribution of deposits on the surfaces in the boiler is well known from inspections. These observations are used as inputs to the model to simulate their effects on boiler performance. The heat exchanger most affected by fouling is Superheater 2, which is the first heat exchanger in the flue gas channel. Deposits typically reduce the heat transfer rate by half over a season despite soot blowing. This and other fouling scenarios are simulated and presented in this article. The simulations show that fouling on superheaters redistributes the heat transfer rate from the superheaters to Reheater 1 and partially redistributes turbine power from the high pressure turbine to the intermediate pressure turbine. If the boiler is running at maximum load, water injection to Reheater 1 has to increase to maintain temperatures below the permitted limit. The dynamic effects of fouling are small and the total efficiency of the boiler is only marginally affected. Fouling on evaporating surfaces has major dynamic effects and dramatically decreases the boiler efficiency. A decrease in fuel rate flow is needed to maintain temperatures in the fluidised bed and in the flue gas channel within acceptable limits.

Nationell ämneskategori
Teknik och teknologier
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-13209 (URN)10.1016/j.apenergy.2010.12.006 (DOI)000288360500038 ()2-s2.0-79551537174 (Scopus ID)
Tillgänglig från: 2011-10-28 Skapad: 2011-10-28 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
5. Use of modelica for “multi phase flow” in complex systems, with application for continuous pulp digesters
Öppna denna publikation i ny flik eller fönster >>Use of modelica for “multi phase flow” in complex systems, with application for continuous pulp digesters
2009 (Engelska)Ingår i: Proceedings of APMMCT. Kleminski, Ukraine,  May 17-18, 2005., 2009Konferensbidrag, Publicerat paper (Refereegranskat)
Nationell ämneskategori
Teknik och teknologier
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-23763 (URN)
Konferens
APMMCT. Kleminski, Ukraine, May 17-18, 2005.
Tillgänglig från: 2013-12-19 Skapad: 2013-12-19 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
6. Moisture content determination of biomass fuel supported by Bayesian network
Öppna denna publikation i ny flik eller fönster >>Moisture content determination of biomass fuel supported by Bayesian network
2006 (Engelska)Ingår i: Proceedings of  IFAC conference at Bali, ASCC 2006. July 2006., 2006Konferensbidrag, Publicerat paper (Refereegranskat)
Nationell ämneskategori
Teknik och teknologier
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-23999 (URN)
Konferens
IFAC conference at Bali, ASCC 2006. July 2006.
Tillgänglig från: 2013-12-23 Skapad: 2013-12-23 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
7. Applications of simulation models for diagnostics and model based control in pulp and paper and power plant applications
Öppna denna publikation i ny flik eller fönster >>Applications of simulation models for diagnostics and model based control in pulp and paper and power plant applications
2009 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
Nationell ämneskategori
Teknik och teknologier
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-23765 (URN)
Konferens
Mathmod 2009, February 4-7 in Vienna
Tillgänglig från: 2013-12-19 Skapad: 2013-12-19 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
8. Time based data reconciliation and decision support for a CFB boiler
Öppna denna publikation i ny flik eller fönster >>Time based data reconciliation and decision support for a CFB boiler
2009 (Engelska)Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline), 2009 / [ed] Yrjö Majanne, Tampere: Tampere University Press , 2009, s. 338-343Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

This paper covers a method for operator decision support, where physical simulation models are used to connect different physical variables to each other. By comparing energy and material balances for a larger process area inconsistencies in single process parts and sensor measurements can be detected, by following the development between single measurements and values predicted from the simulations. This information then can be used as input to e.g. a BN, Bayesian Network, for decision support. The application has been for a CFB boiler at Mälarenergi AB. The simulators have been made in Modelica respectively a more advanced model in APROS.

Ort, förlag, år, upplaga, sidor
Tampere: Tampere University Press, 2009
Nyckelord
Dynamic data-reconciliation, sensor diagnostics, process performance monitoring, decision support
Nationell ämneskategori
Annan elektroteknik och elektronik Energiteknik Reglerteknik
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-8013 (URN)
Konferens
IFAC Symposium on Power Plants and Power Systems Control, PP and PSC 2009; Tampere; Finland; 6 July 2009 through 8 July 2009
Tillgänglig från: 2010-02-10 Skapad: 2010-02-10 Senast uppdaterad: 2015-11-12Bibliografiskt granskad
9. Fluidized bed combustion and gasification modeling and utilization of the models for diagnostics, control and decision support
Öppna denna publikation i ny flik eller fönster >>Fluidized bed combustion and gasification modeling and utilization of the models for diagnostics, control and decision support
2009 (Engelska)Ingår i: Proceedings Mathmod 2009, February 4-7 in Vienna., 2009Konferensbidrag, Publicerat paper (Refereegranskat)
Nationell ämneskategori
Teknik och teknologier
Forskningsämne
energi- och miljöteknik
Identifikatorer
urn:nbn:se:mdh:diva-24000 (URN)
Konferens
Mathmod 2009, February 4-7 in Vienna.
Tillgänglig från: 2013-12-23 Skapad: 2013-12-23 Senast uppdaterad: 2015-11-12Bibliografiskt granskad

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