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- Balanced Draft system in a CFBC Steam Boiler - Friday, July 23, 2010 - Suresh Mangalore [936]
  In our 50 ton, 3.82 MPa, 450 deg Cel superheat boilers, the passage of the heat energy is as follows :
  furnace, vertical rising flames, superheater,thence vertically downward passage to the economiser, air preheater and thence to a
  horizontal duct about 10 meters long. Therefrom, to a wet scrubber, the ID Fan and lastly to the chimney.
  
  Every 2 weeks, we have to stop the boiler and clean the ash accumulation in the 10 meter horizontal duct, mentioned above.
  Could it be to the unbalanced draft in the system between the ID Fan and the FD Fan ?
  
  Request advice from esteemed forum members on their opinion and a solution so that we do not have to stop the boiler every 2 weeks ?
  
  Regards
  Suresh Mangalore
- - Re: Balanced Draft system in a CFBC Steam Boiler - Sunday, July 25, 2010 - Jim Watts [764]
    Your fly ash is settling due to either low flue gas flow or high ash density or a combination.
    You have previously indicated you turn down turning down during off peak and this will be contributing especially if you sootblow during low flows.
    If sootblow scheduling does not fix your problem you will need on line cleaning of the duct.
    Im sure there are many ways to do this and you should use an experienced consultant.
    I would guess at using air jets directed to keep the ash moving towards the scrubber or even steam or water sprays.
  - - Re: Balanced Draft system in a CFBC Steam Boiler - Sunday, July 25, 2010 - Suresh Managlore [936]
      Mr. Jim Watts
      Respected Sir,
      Many thanks for your valued advice.
      Regarding the ash content, I shall obtain details from the boiler staff and then post the same for your scrutiny.
      Although, earlier we did turn down the generation during off peak hours, we are not resorting to it now, because
      the new tariff which came into force last month, is more favourable regarding peak load consumption.
      There is NO soot blowing equipment provision on these boilers.
      I shall follow your advice regarding jets compressed air / water /steam in the horizontal duct.
      Regards
      Suresh Mangalore
  - Re: Balanced Draft system in a CFBC Steam Boiler - Monday, July 26, 2010 - N.Ramani [965]
    I tend to agree with Jim. If the accumulation is at the bottom of the duct low velocity could be a cause apart from density of ash, design Vs actual..Also Checking ID fan capacity design and how it is functioning now.can throw some light..
  - - Re: Balanced Draft system in a CFBC Steam Boiler - Monday, July 26, 2010 - Suresh Mangalore [936]
      Mr. Ramani,
      Respected Sir,
      Many thanks for your advice.
      Actually, we are already considering
      a higher capacity ID Fan.
      Regards
      Suresh Mangalore
    - - Re: Balanced Draft system in a CFBC Steam Boiler - Wednesday, September 01, 2010 - muthusamy manohar [825]
        suresh,
        could you post the arrangement drawing which shows the duct from last heat transfer equipment air heater to chimney? it will be more helpful to analyse the root cause of ash settling on duct.