What is Meant By a Dry Bottom Boiler

http://lmgtfy.com/?q=Dry+bottom+boiler

I have also researched this and concur with Lyn..............no difference

You guys are not very observant...

"What is a Dry bottom boiler and how is it different from a dry bottom boiler."

The difference is obviously capitalization!

Speaking functionally, not grammatically.

I'm sorry. My mistake.

I actually mean difference between a Dry bottom and Wet bottom Boiler.

It might be that one has a dry bottom and the other has a wet one?

I know. I couldn't resist.

Madhusudhana

Can you tell us your understanding of either system?

Have you done some other research on sites such as wikipedia?

If some effort has been shown more knowledgeable people are willing to help.

I have no background in this area and have no desire to look it up.

The first one uses an upper case D.

Thank you John, finally a sensible answer. The others obviously have too much time on their hands.

Tony

Thank you Bob, finally a sensible answer. The others obviously have too much time on their hands.

Ah, thanks Tony saved me all the typing ;-)

Thank you John and Bob.

I work in a power plant and for the purpose of Bottom Ash evacuation, BAH (Bottom Ash Hopper) filled with water is placed below the furnace (Dry bottom boiler) and Ash evacuation is done with the help of Clinker Crushers and flushing the ash water with high pressure water mechanism.

May I know how would be the mechanism of molten ash evacuation? Does the firing has anything to do with Ash fusion temperature and Where exactly do we use Wet bottom boilers.

Your help will be highly appreciated.

Hi Madhusudhana,
This can be a large topic.
Whether you use dry or wet will largely depend on your practice for ash removal and particularly for wet removal whether you have the space for ash disposal and settlement, and the availability of water quantities to use in the process. In both cases and because the furnace combustion zone is running at slight negative pressure, you need to provide a seal between the furnace bottom and the ash hopper which also allow for the thermal expansion (usually downwards) of the furnace. The boiler designer usually has no preference for the type of bottom ash type, it is an owner/operator preference.

You would not normally expect to have molten ash as a flowing medium. The ash particles dropout from the combustion zone and either are quenched or removed. Where you may encounter a molten state is where a blockage or bridging occurs and this is exposed to the high temperature radiation. If it cant be removed while maintained in a viscous state from the furnace temperature conditions, forcing the unit out of service, it becomes a major problem to remove in the cold, solidified state - usually with jackhammers or minor explosives.

The ash fusion temperature is a characteristic of the coal and can't be changed with the firing condition.
It is less of an issue with PF-fired boilers than it is with say grate stokers where the coal may remain in the bed in the combustion process. Although modern power generation boilers use finned-tube membrane waterwalls and a lot less refractory for sealing than earlier designs, refractory is still used for locations like burner throats, sootblower openings and access doors. The refractory surface temperature can be hotter than the surrounding metal and approach the ash fusion temperature for some coals. In this situation ash particles can attach and grow to large deposits in the furnace. The large deposits when dislodged, fall into the ash hopper and may disintegrate on impact or cause removal problems because of abnormal size. The firing process, for efficient combustion, can't avoid this situation, it can only be overcome by minimising the local high temperature contact surfaces.

There has to be a process specialist at the facility that knows all this stuff. Otherwise the facility will eventually break down and stay down.

How about a chat with its Maintenance Manager, for example?