Biomass boiler settings

[rollestonpark]

Sorry, for this being a long one,
But I could do with some advice from someone with good experience of biomass boilers.

I have a Froling TM250 boiler (250kw), but alot of these biomass boiler operate in a similar manner.
It's running well, but I'm only managing about 180/190kw on the current fuel and would like to try and push the boiler harder, even if it reduces the fuel efficiency a bit.

On other fuels I have had it at/or close to 250kw

The fuel:
It's Class A waste wood (which the boiler is certified to burn), very dry and smashed up with lots of fines/dust and small pieces.

The boiler has many settings you can change:
Fuel infeed
Primary air flap
Secondary air flap
Flue gas re-circulation (FGR) fan speed
Primary air reduction from FGR
Grate speed
etc etc

The FGR basically pulls flue gases from the chimney and put them back into the primary air, the FGR fan speed can be altered as can the proportion of fresh primary air against flue air.

The boiler has a combustion chamber temperature (CCT) sensor and flue gas temperature (FGT) sensor.
If the CCT reaches 1000c or the FGT reaches 190c the boiler will back off the infeed to protect itself, thus reducing output.

So it seems to be a matter of balancing these temperatures to get max output.

The boiler has graphing software continuously collecting data on everything and showing graphs in realtime on a PC

Findings/views (could be wrong) (please comment):
Increasing secondary air reduces the CCT, so for dry fuel run lots as this increases output
Increasing FGR reduces the CCT, but increases the FGT, which helps improve fuel consumption/efficiency
Increasing primary air increases the CCT and FGT so reduce with dry fuel
Reducing primary air and replacing with FGR air seems to increase output with this fuel to a point.
Running the grate slow seems necessary to ensure the fuel has time to burn out before going to the ash auger

There is a lot of complex settings I can change and most/all work on a gradual basis, in that, as temperatures change in the boiler the flaps/fans alter on a gradual basis.

Also a setting change can take many hours to show an outcome, which makes life hard.
Chris

 

[Daniel king]

I have the same boiler I think your problem is the fines in the wood chip , the fuel quality / moisture makes a huge difference I used to burn poor quality chip but now buy more expensive chip and the heat out put has gone up hope that helps

 

[Daniel king]

Plus you can increase the fuel supply which again pushes the boiler on

 

[rollestonpark]

Yeah am fairly sure it's the chip, your right.
Am up to about 210kw now. Not sure if it'll stay there though.

Thing is I can get this fuel locally for £35/Ton and it's really dry, so not paying for water.
So am prepared to put up with lower output, but would like to try and max the boiler out.
Chris

 

[rogeriko]

Dont change any of those settings you will just make matters worse. There is one setting that sets the max fuel feeding its in the installer menu. its probably set to around 30% to get 250kw. All you have to do is turn that one setting up to get whatever output you want.

 

[rollestonpark]

Yeah thanks for that.
Did that first and the CCT goes very high and boiler backs off.
Max output is about 120kw doing this.
So going to stick with the adjustments I've made for now.
Think I'll get 1 of the Froling factory engineers to set it when the weather gets colder and it's working flat out 100% of the time.
Chris

 

[A1an]

As above.

I have the TM 500. It was only putting out 320-380 and we found that the end of the burning material was 2ft short of the end of walking grate, we slowly upped the feed and grate speed and now almost the whole grate is being used, we now regularly see 520kw.

Your flue gas seems a touch high?

 

[rollestonpark]

Yeah the fuel is too dry, but this is how it comes.
I have actually reduced the grate speed slightly because the fuel was going off the end before burn out.
Getting the flue gases higher temperatures seems to be the only way to get close to the target output.

Think it's mostly a fuel problem, but was trying to understand what the settings did to the output.
The Froling standard infeed for this boiler is 22%, but I can't get to that, maybe 18-20%
The chamber is quite full and running at 1000c

I suppose if I can get 205kw continuous then I should be happy with that on this fuel.
Was just trying to get the last bit.

 

[turbofarming]

What if you burnt a couple days worth of CHP chip instead just to see if the output shoots right up?

 

[rollestonpark]

Cheers Tommy,
After some gentle tweaking this morning, I got it to 250kw.
But it has had to back off now as the morning temperatures warm up and the load has started to drop.
Currently sitting at 220kw, so think it'll do it on the waste wood, just needs the right settings.
Chris