Removal of unwanted matter after the construction phase
Before a power plant can be commissioned, the entire steam and water side must be cleaned (by means of chemical cleaning and / or steam blowing). After completing the construction phase of the power plant, this cleaning is carried out to remove unwanted matter that can affect the steam quality.
Common contaminants, including loose dirt particles, oil / grease and atmospheric contaminants, iron oxides and silicates are removed in this phase. Silicates are only removed when cleaning with hydrofluoric acid.
Acid cleaning or boiling out
To achieve the required surface cleanliness of the different systems, the steam and water cycle is chemically cleaned by means of acid cleaning or boiling out. The chemical cleaning is followed by steam blowing the system.
The advantage of acid cleaning prior to steam blowing is that mill scale and silicates (when using hydrofluoric acid) are removed. As a result, fewer steam blowing cycles are required. A lot of demineralised water and gas are used during steam blowing. Shorter steam blowing can therefore result in enormous savings in both time and money.
The chemical cleaning is performed according to VGB guidelines and depending on the requirements of the (end) customer the following types of cleaning can be applied:
- Boiling out of the water side
Suitable for: carbon steel, stainless steel, alloys with chrome or P91/92
Removes: loose iron oxides (rust), very light oil, grease and atmospheric dirt & loose silicates. - Cleaning based on hydrochloric acid
Suitable for: carbon steel, copper
Removes: iron oxides (rust), welding skin, mill scale and annealing skin - Cleaning based on hydrofluoric acid
Suitable for: carbon steel, stainless steel, alloys with chrome or P91/92
Removes: iron oxides (rust), welding skin, mill scale, annealing skin & silicate compounds. - Cleaning based on citric acid
Suitable for: carbon steel, stainless steel, alloys with chrome or P91/92
Removes: iron oxides (rust), at high temperatures or after adding of additional chemistry, also suitable for removing mill scale and annealing skin. - Cleaning based on EDTA/Demclean 94
Suitable for: carbon steel, stainless steel, alloys with chrome or P91/92
Removes: iron oxides (rust) and very light grease / atmospheric dirt.