thread794-210028 Hi MJCronin,

[Charliebos]

thread794-210028

Hi MJCronin,

What was your outcome on the auxiliary design?
We have a similar situation; I am investigating to find method and/or process to keep the existing 150K "D" tube boiler at hot standby and minimize the cycling of the flame on's and off's during startup.

charlie

 

[MJCronin]

Well, this was quite some time ago ...

And this was for a brand new aux boiler to replace a worn out startup aux boiler at a coal plant

But as I remember, i talked a bit with the sales department at B&W

They said that the following features would be an advantage for boilers used for intermittent service: (as i recall)

1) Superheater coils constructed from premium chrome moly material: Even though the operating temperature of the steam would allow carbon steel tubes, B&W suggested use of ASME A213-T22 (?) (chrome molly material) as it would endure more thermal transients

2) Slightly larger steam Drum: This larger drum size would help during fluctuations in startup demand

3) Flue gas guilottene duct dampers: This would keep heat in the boiler

4) VFD on Combustion air fan: This would enhance control

5) Mud drum heating coil: If steam is available from another source, this will cut down on startup time

Good luck .... Please tell us about your challenges and how you overcame them !!!

MJCronin
Sr. Process Engineer

 

[Charliebos]

MJCronin,

Thank you for your response.
The site has a 12 years old 150,000 lb, 390 psig, 660F, "D" tube boiler. The startup process required the auxiliary boiler to cycle the flame ON's and OFF's until it meets the specified steam conditions. This cause thermal and fatigue stresses to the waterwall tubes and steam drums. There have been pin hole leak at various locations on the water tubes. In additional to the startup stress concern, we are considering continuously keeping the boiler in the hot standby to allow operators to quickly put the auxiliary boiler back into service.

Some of the suggestions are installing a center-fire pilot burner that operates continuously keeping the boiler hot and at pressure ready to go. Another approach is to add a second pilot.

I was wondering if there is other method that can keep the boiler hot and at pressure? No steam is available on site, this is the startup boiler for the larger unit. Is there electric coil that can be install in the lower drum to keep the temperature? Maybe some type of electrical heating blankets/coils?

I am looking for ideas.

Charlie