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Description of the
heat transfer in the furnace
NTUA provided simplified models for the heat transfer degradation evaluation due
to the ash deposition on the heat exchange surfaces in boilers. Therefore, the
heat transfer properties of the ash deposit layer and the heat transfer
mechanisms were investigated and simulated in a manner to take into account, as
far as possible, the influence of the operating conditions and the ash physical
properties.
The interest was focused on the ash deposit layer thermal properties where, even
though various experimental works have been executed, very poor information for
theoretical formulas with widespread applicability is available. The target was
to produce theoretical formulas for the estimation of the thermal properties of
any ash deposit configuration. The above-mentioned target was achieved and the
formulas were incorporated into the overall online dynamic models.
Subject Descriptors : Biomass, Computer architecture, Expert systems, Neural
networks
Subject Index Codes : Renewable Sources of Energy, Information Processing,
Information Systems
Subject Class : Energy, IT, telecommunications
Market Applications : Liquefied natural gas, Steam distribution, quality
Stage of Development : Scientific and/or technical knowledge (basic research)
Remarks : Results eTIP
Collaboration Sought : Further research or development support, Information
exchange/Training, Private-public partnership
Collaboration Detail : NTUA can help entities dealing with Heat Transfer
Modelling.
Entities dealing with Coal and Biomass.
Sources of Support : CEC
Programmes : EESD
Projects : ERK5-CT-1999-00009
Project Title : Slagging and fouling prediction by dynamic boiler modelling
Contact Details
Contact Name : NANOS, Evangelos
Position : Research Scientist
Contact Organisation : National Technical University of Athens
Address : Heroon Polytechniou St., 9
City : Athens
Region : ATTIKI
Postcode : 15780
Country : GREECE
Telephone Number : +30-210-7723754
Fax Number : +30-210-7723663
Electronic Mailbox :
enanos@central.ntua.gr
On-line model for assessment of heat transfer using standard software
This result consists of the methodology to use power plant data to produce
comprehensive information on the boiler. Boiler instrumentation information is
usually targeted on the water/steam circuit to control the steam properties to
the turbine. The measurements on the flue gas path are more restricted due to
the larger difficulties on measuring reliable flow rates and temperature in
large flue gas cross-sections. The boiler exit gas temperature is usually
registered as it affects directly heat losses and therefore boiler efficiency.
For small boilers based on grate firing and fluidised bed systems, boiling is
carried out not only at furnace walls as well as in tube banks subject to
convection to allow for a flexible boiler operation. In these smaller plants
flue gas temperature is also measured in some positions along the convection
circuit that is built in independent blocks, providing further information on
the boiler.
Two on-line assessment models were developed in parallel by Instituto Superior
Tecnico (IST) and Technical University of Delft
(TUD) , both with a graphical interface to display and consult the
values calculated based on the measured data. For both cases the calculation
procedures implemented were specific for each plant analysed but the graphical
interface from IST is more general as it can import or allows the configuration
of the boiler.
The calculations from TUD are directly based on measured gas temperatures and
convection heat transfer. This model generates calculated values of heat
transfer resistances for the heat exchanger surfaces near to the flue gas
temperature measurement. The graphical application from TUD integrates further
plant data such as the soot blowing operations. The evolution of calculated and
measured properties can be represented along time to analyse the effects of soot
blowing.
The calculations from IST are based on the boiler exit gas temperature, avoiding
the consideration of flue gas temperature measurements in other sections in the
boiler with higher temperature. The calculations consider the convective section
of the boiler as well as the furnace with radiation heat transfer.
Based on this model, temperature along the whole flue gas circuit is calculated
and the comparisons performed in the project with plant data showed that
calculated furnace exit gas temperature is in general higher than the
correspondent plant data but is closer to specific measurement performed in test
campaigns during the project. The IST model can therefore be applied to boilers
with minimum plant instrumentation and may perform virtual instrumentation
located in higher temperature sections. Based on the calculated and measured
values, the heat transfer resistance in all heat exchangers are calculated and
can be represented along time in the graphical interface.
The graphical interface from IST has three main menus to display data in
sketches, tables or trend graphs. The boiler components for both gas and
water/steam circuits are represented by icons where relevant parameters and
properties can be made available. Tables and trend graphs can be configured by
the user and saved in profiles that can be selected from a menu, allowing the
users to configure different types of users, who see information in different
levels of detail.
Subject Descriptors : Biomass, Expert systems, Neural networks, Process control
Subject Index Codes : Renewable Sources of Energy, Information Processing,
Information Systems, Industrial Manufacture
Subject Class : Energy, IT, telecommunications, Materials, industrial
manufacturing technologies
Market Applications : Liquefied natural gas, Steam distribution, quality
Stage of Development : Software code
Stage Description : 'Virtual' temperature sensor
Remarks : Results eTIP
Collaboration Sought : Further research or development support, Joint venture
agreement, Information exchange/Training, Available for consultancy
Collaboration Detail : IST can offer the installation of monitoring software for
a boiler to visualise measured and calculated data covering the whole
water/steam and air/flue gas circuits.
The graphical interface from IST has been constructed in a general form so its
adaptation to a new plant is straightforward and only requires the configuration
of the boiler from components in a drag and drop menu.
The calculations are still based on sequential calculations but a large amount
of functions are available in dll files so the adaptations for a new plant can
be performed in an efficient way. At present IST is developing the use of a
general calculation procedure to solve a set of non-linear equations for boiler
components in order to allow the software code to be fully used in an
interactive mode without the need of programming.
The monitoring model also produces the boiler efficiency and the efficiency of
heat transfer exchangers and heat transfer resistance.
This service may be extended making available a simulator where the effects of
heat transfer parameters and in particular heat transfer resistance can be
changed to evaluate their impact on operation.
There are two profiles for additional partners. Companies providing plant
instrumentation and control system may integrate our software in their package
enhancing the information made available by their systems. The target clients
for the tools developed are owners and operators of boilers spatially in the
case when the fuel supplied can not be continuously characterised in detail. The
tools developed may provide valuable information on flue gas temperature in the
boiler and furnace, that otherwise can only be acquired by expensive
instrumentation that is also not reliable on a long-term operation. The system
may allow the optimization of boiler operation by evaluating the evolution of
boiler efficiency and heat transfer characteristics in different exchangers.
Sources of Support : CEC
Programmes : EESD
Projects : ERK5-CT-1999-00009
Project Title : Slagging and fouling prediction by dynamic boiler modelling
Contact Details
Contact Name : TOSTE DE AZEVEDO, João Luís (Dr)
Position : Assistant Professor
Contact Organisation : Instituto Superior Técnico
Address : Avenida Rovisco Pais
City : Lisboa
Region : CONTINENTE
LISBOA E VALE DO TEJO
Grande Lisboa
Postcode : 1049-001
Country : PORTUGAL
Telephone Number : +351-218-417993
Fax Number : 351-218-475545
Electronic Mailbox :
toste@navier.ist.utl.pt
Dynamic on-line model for assessment of heat transfer - Fortran Code
The purpose of the project was, to predict slagging and fouling behaviour in the
boiler in order to minimise of the soot blowing effort.
This leads to:
- Optimisation of the boiler efficiency,
- Better knowledge of the fuel behaviour,
- Increase of boiler availability,
- Easy to use for operators at plants.
1) Prediction of plant behaviour and efficiency at load changes, fuel changes
etc.
To achieve this goal, the following steps were undertaken:
- Use of easily accessible steam cycle parameters, such as temperature,
pressure, mass flow and geometrical plant parameters, stored on-line in an
access database by VAB,
- Modification of an existing Fortran programme for boiler modelling, including
a model for deposit conductivity calculation,
delivered by NTUA,
- Fuel characterisation of fuel and ash samples analysis to achieve more
detailed information on the ash melting behaviour etc to feed to the NTUA model,
- Set-up of the plant environment (geometry) in the model, definition of
boundary conditions, off-line and on-line testing,
- Calculation of discrete heat transfer coefficients for all boiler sections,
- Additional heat transfer degradation tests with a specially developed probe in
a test facility at USTUTT,
2) Monitoring: Two models (USTUTT and TUD) for two different
power plants (Uppsala and Nyköping) are ready and successfully tested. The
USTUTT model was developed for the pulverised fuel boiler at Uppsala. The heat
transfer degradation can be monitored with real time data, a slag thickness can
be theoretically obtained and a soot blowing policy can be developed.
3) Prediction of heat transfer coefficient transience during desired variation
of plant load or running conditions, as time and duration of soot blowing etc
was realised. The model could follow the heat transfer degradation successfully.
The USTUTT model makes slagging and fouling predictions possible with
restrictions regarding unknown plant operation modes chosen by the operator.
Subject Descriptors : Biomass, Expert systems, Neural networks, Process control
Subject Index Codes : Renewable Sources of Energy, Information Processing,
Information Systems, Industrial Manufacture
Subject Class : Energy, IT, telecommunications, Materials, industrial
manufacturing technologies
Market Applications : Liquefied natural gas, Steam distribution, quality
Stage of Development : Software code
Remarks : Results eTIP
Property Rights : Secret know-how
Collaboration Sought : Further research or development support, Licence
agreement, Information exchange/Training, Private-public partnership, Available
for consultancy
Collaboration Detail : - Improvement of the available model
- Adaptation and Application of the developed models for other
power plants
- Consulting for operational problems in biomass fired plants
- Operators of biomass fired power plants
- Research institutes interested in a further improvement of heat transfer
modelling, heat transfer measurement and combustion technology
Sources of Support : CEC
Programmes : EESD
Projects : ERK5-CT-1999-00009
Project Title : Slagging and fouling prediction by dynamic boiler modelling
Contact Details
Contact Name : LOUX, Jean-Claude
Position : Research Scientist
Contact Organisation : IVD - University of Stuttgart
Address : Pfaffenwaldring 23
City : Stuttgart
Region : BADEN-WÜRTTEMBERG
STUTTGART
Stuttgart, Stadtkreis
Postcode : 70569
Country : GERMANY
Telephone Number : +49-711-685-3487
Fax Number : +49-711-6853491
Electronic Mailbox :
loux@ivd.uni-stuttgart.de
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