Ljungstrom Air heater 1

[tool32]

The sootblowers on the ljungstrom air preheaters are located on the gas side and blow in the opposite direction of the flue gas.My question is why couldn't we place the sootblowers on the air side and blow the heater in the same direction as the fd fan discharge into the secondary air duct and reburning the carbon buildup in the furnace? It would be like a second carbon reinjection system.Any thoughts on this idea?

 

[ccfowler]

It seems unlikely that this would be a good way to burn up much of the residual carbon for at least two reasons:

1) The amount of carbon-rich ash involved in air heater accumulations is very small compared to the amount that can be recovered from the precipitator or baghouse.

2) The particle sizes involved are not primarily very fine, so they are not likely to be effectively consumed by another trip through the furnace.

Unfortunately, this does seem to be a way to increase crud accumulations in the combustion air ducts.

 

[Jesse52]

What is the correct clearance between the pinion and the drive gear on a Ljungstrom air heater gear box?

 

[raustaman]

For a large air heater, (size 20 or larger, normally about 3/4" root gap clearance. remember that the heater is probably not round and the gap should be taken after you find the high point on the pin rack.

Also remember that the rotor deflects with the heat, don't run the gear too close to the hot end of the pin rack rail! (3/8" gap between the gear and the cold side of the rail ought to do it)

 

[raustaman]

Regarding sootblowing on the air inlet side, remember that what you clean from the heater must pass though the hot end element too, and any large buildup may get caught in the tighter openings of the hot end. If the beposits fly though OK< remeber also that the scanners on the burners may not like the additional dust/debris floating by...

 

[rmw]

If you did such a thing, you soon would have a real mess of a build up of crud in the ductwork to/in/around and through the secondary windboxes.

Blowing the deposits loose is one thing, but being able to transport them all the way back to the furnace through the burners in another.

Look in the ductwork down stream of the APH and ask yourself if you want your windboxes looking like that.

rmw

 

[norbertrudolf]

who can explain the naming of Ljungström AHs.

for example 28,5 VIT 88
or 32 H 63 and so on and so on.

There must be any system. please explain

 

[davefitz]

The floor of the windbox on many coal fired units already is knee-deep in flyash, just from the small amount of ash that is entrained by the secondary air flow up thru the air heater. If you added sootblowers on the air side of the AH, the windbox ash accumulation would be horrendous.