Turbine technology|Maintenance


The performance of the gas turbines was measured in April 2024 prior to cleaning and May 2024 after the foam cleaning.


In summary, large masses of deposits were removed from the gas turbine blades (see Table 4).


The small accumulated amount of iron and chromium detected in the liquified foam outlet is a strong indication that gas turbine materials were not attacked by the foam.


Similar results were observed during the foam cleaning of the turbine of a biomass fired district heating power plant.


The deposits there were composed of hardness scale (principally calcium carbonate), silica and mainly iron oxides.


After cleaning, the efficiency of the steam turbine returned from 90% of nominal to design values, and the swallowing capacity, which had been reduced by 20% also went back to 100% (see pictures 8 and 9).


Table 3.


MW recovery, 7A gas turbines Unit 1 Unit 2 11.7 9.7


Initial MW loss MW recovery from exfoliation 3.0


MW recovery from foam cleaning 5.0 Total MW recovery


8.0


In this case, 7.3 kg of silicates (as SiO2 of hardness scale (as CaCO3 (as Fe2


O3


by the foam cleaning process. A proven method


In summary, foam cleaning is a proven method for removing deposits from gas and steam turbine blades without jeopardising turbine integrity. The method has been used for over 40 years in the United States. It can compete with mechanical


Daily electricity production MWh


140 120 100 80 60 40 20 0


3.0 6.5 9.5


), 5.9 kg ) and 4.3 kg of iron ) was removed from the steam turbine


Table 4. Mass of deposits removed from gas turbine blades


Silica


Calcium Iron


Chromium


Unit 1 Unit 2 28.5 kg 39.9 kg 59.9 kg 53.0 kg 0.45 kg 0.10 kg 0.05 kg 0.01 kg


cleaning in terms of efficiency restoration. However, foam cleaning requires much less time because the turbine casing does not need to be opened and the rotor does not need to be removed from the machine. Compared with water wash and wet steam washing, foam cleaning can do a much more thorough job of removing scale and deposits because the foam reaches all parts of the machine and because the foam mixture can be adapted to the expected or known composition of the deposits.


Picture 8. Power output before and after foam cleaning Daily heat production MWh


700 600 5000 400 300 200 100 0


Picture 9. Heat output before and after foam cleaning


Literature:


[1] F U Leidich, Some basics of power plant chemistry – corrosion and deposition, PPChem 2023, 25(01), 38 [2] State-of-knowledge on deposition, Part 2: Assessment of Deposition Activity in Fossil Plant Units, 2003, Electric Power Research Institute, Palo Alto, CA, USA, EPRI 1004930


[3] F U Leidich, The economic impact of power plant chemistry in regard to maintenance and lifetime, presented at IMechE Steam Turbine and Generator User Group meeting, 2016, Manchester


[4] F U LeidichPPChem 2024, 26(01), 4 [5] Monica Nielsen, Handling sea water ingress cases at Avedøre power station 2022, presented at vgbe conference 2023, Ingolstadt [6] C Holl, Hydro Engineering GmbH, Mülheim an der Ruhr [7] F U LeidichPPChem 2024, 26(01), 18 [8] W Majka, Ecol SP. z.o.o., Rybnik


30 | July/August 2025| www.modernpowersystems.com


MWh


MWh


01.09.2024 08.09.2024 15.09.2024 22.09.2024 29.09.2024 06.10.2024 01.09.2024 08.09.2024 15.09.2024 22.09.2024 29.09.2024 06.10.2024 13.10.2024 20.10.2024 27.10.2024 03.11.2024 10.11.2024 17.11.2024 24.11.2024 01.12.2024 08.12.2024 15.12.2024 22.12.2024 29.12.2024 13.10.2024 20.10.2024 27.10.2024 03.11.2024 10.11.2024 17.11.2024 24.11.2024 01.12.2024 08.12.2024 15.12.2024 22.12.2024 29.12.2024


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