Posted by Stateng on February 23, 2000 at 09:08:54:
In Reply to: Boiler capacity posted by Dave on February 23, 2000 at 04:08:37:
: we have a water tube boiler that is rated at 40000lbs/hr @ 100 psi MAWP 250 radiant heating surface 562.32sqft convection heating surface 460.65 sqft. Looking for a formula to determine if we can increase capacity to 50,000 lbs/hr without doing any damage. Boiler is fired with natural gas and #4 fuel oil. If boiler is capable of increased capacity is it only a matter of increasing the turn down ratio?
Dave,
Increasing your turn down ratio will cost you more problems than its worth, here are few of the problems;
1. Reduced efficiency by not having enough combustion air at the higher rate.
2. Reduce efficiency by improper mixing of the fuel, not enough time or turbulence in the combustion chamber, the flame may also become dangerously unstable.
3. The furnace chamber is not large enough; you may have flame impingement on the tubes and refractory causing failure and costly repairs.
4. Over pressure of the furnace causing poisonous gases to escape through the casing.
5. Over heating of the casing causing premature failure.
6. Over heating in the radiant tubes by producing too much steam and causing tube failure.
7. The quality of the steam may decrease at the higher rate.
8. Increase polution.
Before you try meeting the demand by increasing the turn down ratio you may want to look at;
New boiler
An additional boiler
Economizer
Air preheater
Overall plant efficiency trap survey, insulation up grade etc.