OH treatment for drum boilers
Technical Report
·
OSTI ID:50699
- Consultant, Leicestershire (United Kingdom)
High concentrations of sodium phosphate and sodium hydroxide were used for conditioning drum boilers in the 1950`s. However, corrosion occurred in the new high pressure plant, due to hydrogen damage and caustic gouging. This led to sodium hydroxide being abandoned in the USA in favour of phosphate treatment (PT). Problems of control and corrosion with PT led to a search for alternative methods of conditioning in other countries. Limiting chloride ingress and the use of low concentrations of sodium hydroxide ({open_quotes}OH{close_quotes} treatment) was developed and now is used successfully for more than 50,000 MWe of plant. The benefits of {open_quotes}OH{close_quotes} treatment over all volatile treatment (AVT), include a higher tolerance to chloride in the boiler water and a reduced risk of acid attack. Compared with PT, it avoids phosphate hide-out and problems with monitoring and control. {open_quotes}OH{close_quotes} treatment is simpler. It is still necessary to limit the chloride in the boiler water to prevent hydrogen damage. Some sodium hydroxide needs to be present in the boiler water to achieve the full benefits of {open_quotes}OH{close_quotes} treatment, but the concentration has to be strictly limited to reduce the risk of caustic gouging in the boiler, carry-over into the steam and damage to superheaters, reheaters and turbines. This is achieved by continuous monitoring the feedwater, boiler water and steam. The chemical guidelines for {open_quotes}OH{close_quotes} treatment adopted overseas are reviewed, together with the evidence gained from operating plant, the problems that occurred and how these were overcome, EPRI guidelines are proposed for coal fired plant.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 50699
- Report Number(s):
- EPRI-TR--104502; CONF-940982--
- Country of Publication:
- United States
- Language:
- English
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