VGB POWERTECH 10 (2020) - International Journal for Generation and Storage of Electricity and Heat

Implementation of a slagging prediction tool to lignite blend fired boilers VGB PowerTech 10 l 2020
larger area on the furnace walls (between
32 m to 70 m), which also matched with
the pictures from the slagging monitoring
system. During the case 3, a blend with
higher ash and sulphur contents was fired,
which resulted in more slagging detected
by the monitoring system, higher FEGT
(TDM) equals 963 o C and an elevated slagging
risk predicted as compared to previous
reference cases.
The results obtained from the online ash
deposition rate measurements carried out
during a full boiler load and at available,
specified locations (elevations 36 m and
48 m) for the three investigated cases are
shown in F i g u r e s 8 . The highest ash
deposition rate was measured for case 3
(48 m, 21.03.17) followed by case 2 and
case 1, which corresponded well with the
slagging risk identified based on other collected
data. The observed differences are
in good agreement with InfraScans pictures
(see F i g u r e 7 ) and correlate well
with the ash content in the coal blends
fired during the investigated days. The performed
further scanning electron microscopy
and elemental analysis (SEM-EDX) of
the collected ash deposits samples confirmed
that the major, dominated mechanism
of observed elevated slagging was the
formation of molten particles during the
transformation of pyrites under reducing
conditions in the furnace.
Summary and conclusions
The developed next generation slagging
prediction tool has been successfully applied
to the large scale Boxberg lignitefired
power plant, Unit Q. Gathered during
boiler measurement campaigns, boiler operational
and process data including InfraScan
pictures from the slagging monitoring
system have been used to validate
the developed engineering modelling approach.
In parallel, the evaluation of the
online ash deposition monitoring probe
performance under full- scale boiler operation
conditions has been carried out. The
performed simulations and root cause
analysis revealed that the most critical
fuel- related factors that affect the elevated
slagging risk in the Boxberg Unit Q, are the
high ash content (>10 %) and increased
sulphur content (>1.3 % ar.) in the fuel associated
with the pyrites presence in the
coal blend. The slagging risk assessment
carried out based on the conventional slagging
indices did not give reliable indications.
A very good agreement has been
found between Slagging Predictor results
and corresponding slagging InfraScan pictures
and other operational data (e.g.
FEGT-TDM) collected from the slagging
monitoring system. The developed slagging
prediction tool combined with the online
ash deposition monitoring probe
can help boiler operators in determining
fuel flexibility windows and operating procedures
to maintain a highly efficient boiler
operation without increased slagging
risk.
Acknowledgments
The support of the BMWi (German Federal
Ministry for Economic Affairs and Energy,
grant no. 03ET7062) and industrial partners
LEAG, Uniper, General Electric and
Clyde Bergemann involved in the pro ject
realization is gratefully acknowledged.
References
[1] P. Plaza: “The Development of a Slagging and
Fouling Predictive Methodology for Large
Scale Pulverised Boilers Fired with Coal/Biomass
Blends”, Doctoral Thesis, Cardiff University
2013.
[2] J. Maier, B. Schopfer, P. Plaza: Vorhersage
von Heizflächenverschmutzungen mittels
thermochemischer und CFD-Simulation (Ver-
Si); Experimente, Modellentwicklung und
Simulation; Schlussbericht, University of
Stuttgart, Institute of Combustion and Power
Plant Technology, Stuttgart, 2019.
[3] G. Couch: Understanding slagging and fouling
in pf combustion, IEA Coal Research
IEACR/72, London, August 1994.
[4] EPRI Report nr. 1019698: Guidelines for
Solving Ash Deposition in Power Boilers,
2010. l
VGB Technical-Scientific Report
Recommendations for the operation and monitoring
of boiler circulating pumps
Based on extensive follow-up examina-tions relating to the damage event in 2014
Technical-Scientific Report
Recommendations for the
operation and monitoring
of boiler circulating pumps
Based on extensive follow-up examinations
relating to the damage event in 2014
Edition 2019 – VGB-TW 530 (German edition) and VGB-TW 530e (English Edition)
DIN A4, 96 pages, price for VGB-mebers € 180.–, for non-VGB-member € 270.–, + postage and VAT
On 12th May 2014 the pressure casing of a boiler circulating pump (BCP) in the hard coal-fired supercritical
power station Staudinger, unit 5, failed which led to considerable damage in the power plant [1/1]. As is
customary following such severe damage events, the topic was discussed by VGB PowerTech e. V. (VGB) –
as the competent international association of power plant operators – who took up the topic, coordinated it
and dealt with it within the scope of its responsibility.
As a prompt reaction to the damage event, VGB distributed first information in the form of a newsletter in mid-
June 2014, and in mid-July 2014 a concrete, detailed member information to the member companies [1/2].
The main task of VGB was pri-marily the coordination of measures on the plant operators side and the provision
of information. For this purpose, the working group (WG) “Boiler Circulation Systems” was installed. In
addition to power plant operators and the manufacturer of the dam-aged BCP, members of this working group
were or are NDT companies for the non-destructive testing of the affected components as well as representatives
of the ac-cepted inspection body (ZÜS) in accordance with the German Ordinance on Industrial Safety and Health (BetrSichV).
In addition to the Working Group “Boiler Circulation Systems”, specific topics were dealt with in affiliated ad-hoc working groups.
- Ad-hoc WG “Process Engineering”
- Ad-hoc WG “Calculation and periodic inspections”
- Ad-hoc WG “Scope and method of inspection”
The primary objective of the WG and the affiliated ad-hoc working groups was to avoid future damage events – such as the one that occurred
on 12th May 2014 – to the best possible extent. The present document therefore describes the main lessons learned in the ad-hoc WG meetings
in individual sections.
VGB-TW 530e
* Access for eBooks (PDF files) is included in the membership fees for Ordinary Members (operators, plant owners) of VGB, www.vgb.org/en/vgbvs4om.html
* Für Ordentliche Mitglieder des VGB ist der Bezug von eBooks im Mitgliedsbeitrag enthalten, siehe www.vgb.org/vgbvs4om.html
VGB PowerTech Service GmbH
Deilbachtal 173 | 45257 Essen |Germany
Verlag technisch-wissenschaftlicher Schriften Fon: +49 201 8128-200 | Fax: +49 201 8128-302 | Mail: mark@vgb.org | www.vgb.org/shop
62