Air Monitoring 29
Figure 2. Salmisaari pellet power plant sampling locations
been previously described in detail in (Niemela et al., 2019). It is recommended to use a ~ 10 µm cutpoint cyclone between the high temperature probe and eDiluter Pro unit to remove coarse fl yash and potential unburned fuel from the sample fl ow.
Aerosol measurements Dekati®
Electrical Low Pressure Impactor+ (ELPI® +) was used for
particle detection due to its wide concentration and size range Wide size range is needed as corrosive species are formed is ultrafi ne particle size range, while most of other produced aerosol mass is in supermicrometer range. In addition, as the ELPI®
+
measured particles in real-time it can detect quick changes in a dynamic combustion process. ELPI®
+ characteristics and
operation have been previously presented by (Järvinen et al., 2014) It is also recommended to take collect the aerosol samples for subsequent chemical analysis to confi rm the presence of corrosive species. This can also be done with the ELPI®
+ using
analysis collection plates or by using a parallel cascade impactor such as the Dekati®
Low Pressure Impactor (DLPI+).
High temperature sampling probe was used in combination with eDiluter™ Pro and ELPI®
Experimental work Dekati®
+ to measure
combustion zone aerosols in Salmisaari 100MW pellet fi ring biomass power plant. Measurements were made in two locations, right before heat exchangers and directly from the combustion zone (Figure 2). The aim of the measurements was to study the potential formation of corrosive species in different combustion conditions. Power plant was running at 100 MW (optimal), 60 MW and 40 MW loads simulating different
load levels during summer, winter and intermediate conditions respectively. High temperature sampling probe was installed in the facility for more than two weeks with 6 full measurement days. Compared with “typical” aerosol measurements from power plant processes, specifi c safety precautions need to be considered when using the the High temperature Sampling Probe. It is important to ensure continuous availability of cooling air for the probe, and a safe location for the used cooling air output need to be arranged.
Suffi cient space should also be reserved around the measurement area to allow safe handling and cooling of the probe after the measurements.
Results
Number size distribution results showed a repeatable accumulation mode peak @ 100nm with all plant output levels. High number concentrations (10^8#/cc - 10^9#/cc) suggest that the aerosol subsequently agglomerates into larger particles in the fl ue gas stream. Potential corrosive species were detected around 20-30 nm especially during high load and during unstable combustion conditions. This peak was highly dependent on power plant load with signifi cantly lower concentrations during lower loads and lower combustion temperatures. Effect of load on particle concentration and size is shown in Figure 3. Cyclone was found to have collected a signifi cant amount of fl yash from the process (Figure 4).
Conclusions
Aerosol concentration measured from the combustion chamber of a pellet fi red biomass plant was found to correlate directly
Figure 4. Coarse fl y ash in cyclone collection cup
with plant load with highest concentrations detected with highest plant load. There was no adverse effect on emissions even at only 40% of optimal load which shows that this plant type can be used without emission penalty at partial loads. Potential corrosive species were found to form mainly during high combustion temperatures under full load conditions and especially when plant load was changing. This information can effectively be used to control additive or coal co-combustion to mitigate corrosion, and to lengthen the periods between mandatory maintenance operations. High temperature probe and other instruments were found to be suitable for these types of measurements as they operated without issues or need for maintenance operations throughout the measurement campaign.
Climate Change 2022, Mitigation of Climate Change, IPCC working group III, 2022
C. Berlanga, J. A. Ruiz, “Study of Corrosion in a Biomass Boiler”, Journal of Chemistry, vol. 2013, Article ID 272090, 8 pages, 2013.
https://doi.org/10.1155/2013/272090
Aho, M., & Ferrer, E. (2005). Importance of coal ash composition in protecting the boiler against chlorine deposition during combustion of chlorine-rich biomass. Fuel, 84(2-3), 201 - 212.
https://doi.org/10.1016/j.fuel.2004.08.022
Aho, M., & Silvennoinen, J. (2004). Preventing chlorine deposition on heat transfer surfaces with aluminium-silicon rich biomass residue and additive. Fuel, 83(10), 1299 - 1305. https://doi. org/10.1016/j.fuel.2004.01.011
Martti Aho, Antonia Gil, Raili Taipale, Pasi Vainikka, Hannu Vesala, A pilot-scale fi reside deposit study of co-fi ring Cynara with two coals in a fl uidised bed, Fuel, Volume 87, Issue 1, 2008, Pages 58- 69, ISSN 0016-2361,
https://doi.org/10.1016/j.fuel.2007.03.046.
A. Järvinen, M. Aitomaa, A. Rostedt, J. Keskinen, J. Yli-Ojanperä, Calibration of the new electrical low pressure impactor (ELPI+), Journal of Aerosol Science, Volume 69, 2014, Pages 150-159, ISSN 0021-8502,
https://doi.org/10.1016/j.jaerosci.2013.12.006.
Ville Niemelä, Erkki Lamminen, Performance evaluation of the Dekati®
FINLAND, Poster presented at the 29th CRC Real World Emissions Workshop, March 10-13, 2019, Long Beach, CA
eDiluter™ conditioning system, Dekati Ltd., Kangasala,
Figure 3. Particle size and concentration with different plant loads
Author Contact Details Markus Nikka, Oskari Vainio, Erkki Lamminen, Dekati Ltd. • Tykkitie 1, 36240 Kangasala, Finland • Tel +358 3357 8100 • Email:
erkki.lamminen@
dekati.fi • Web:
www.dekati.com
Erkki Lamminen
WWW.ENVIROTECH-ONLINE.COM
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