wood chip burner

[Breezeblock]

does anybody on here use wood chip for heating on a scale of about 20-40 kw i am looking for some pictures of how its done cheers

[Breezeblock]

am i the only tight sod that wants to burn chip

[bunnybasher100]

worked in a shavings factory which the furnace would burn anything moving grate with draft fans bed was about 30ft long.

other furnace was in a biomass factory and was designed to burn drier product which was feed in from a augar under floor

youtube coal stoker will give you an idear

[openspaceman]

am i the only tight sod that wants to burn chip

 

No but mine's 150kW when burning dryish chip, falls to 40kW when it's too wet to get up to temperature.

[Breezeblock]

whats the definition of dryish chip i tried it in mines with ash chip at 30% moisture and it just sat and smoked also i had problems with the auger blades getting bent with long straggley bits of chip does yours feed all the time or is it timed cheers

[renewablejohn]

Refo have excellent reputation and have been around for a long time but dont expect them to be cheap. Will burn woodchip upto 35% MC

 

REFO Automatic-stoking boilers.

[openspaceman]

whats the definition of dryish chip i tried it in mines with ash chip at 30% moisture and it just sat and smoked also i had problems with the auger blades getting bent with long straggley bits of chip does yours feed all the time or is it timed cheers

 

 

 

I guess 30% mc wwb would be dry for this burner but as you say if it gets too wet for the burner to maintain temperature then the chip smoulders as the char burns but the offgas and moisture just pass to the heat exchanger (firetubes in my case) and clog the system. Essentially the heat is just from burning char, the remaining 50-70% of the wood energy is leaving unburnt. So systems burning moister materials usually control primary and secondary air independently, have increase insulated combustion chambers with longer flame paths and often some means of feeding heat back to the incoming material. You need to keep combustion exit temperatures up to around 800C and the indicator of that for mine is a flue gas exit temperature of 140C, keep it up to this and burn is clean. Unfortunately with 40-50% material it falls below 100 and leads to s significant blue smoke.

 

Yes I have seen flights bent back but not on stokers, this was on a chip transfer system. Mine modulates the feed from the hopper but the stoking auger sweeps itself clean continuously to maintain a fire check.

 

The stoking augers on mine are far more substantial, they pass long straggly bits but these usually trigger a safety hatch and cause a burn out.

 

The problems with non homogeneous feedstocks in the combustion area , on mine at least, are uneven burning and ratholing allowing excess air through the combustion, this is what moving grates control but mines a fixed stepped grate, ideal for joinery waste.

 

I'm used to working on austrian boilers with better engineering and design but this poor british model came at the right price and is usable. I've recently seen another offered for sale as "hardly used" which some wag on another forum suggested was an euphemism for "doesn't work".

[Breezeblock]

my plan was to burn wood chip alongside logs and drip feed the chip into the firebox to do this i have built a geared auger as a prototype but the irregularity off the chip was causing the probs it also needed an adjustable timer so that it was was fed in at a cotrollable rate is it worth the hassle ?

[openspaceman]

my plan was to burn wood chip alongside logs and drip feed the chip into the firebox to do this i have built a geared auger as a prototype but the irregularity off the chip was causing the probs it also needed an adjustable timer so that it was was fed in at a cotrollable rate is it worth the hassle ?

 

I see, the flights look too tight and the metal too thin for chips, ok for pellet or grain. Similarly the round tube won't have any give for slivers, square is better.

 

Also the hopper will need some sealing to decrease the risk of a burn back up the tube into the hopper.

 

A virtual friend of mine, we've been in online discussion for 13 years, has produced this:

 

 

And he has modified it to run on dry woodchip (gasification needs drier material in general). In Canada they have very low temperatures to contend with and in his day job he looks after a large woodchip stoker heating glasshouses and has ingenious remedies for loading poor quality, but dry chip, his is stored outside under a breathable membrane but I get the impression they have low rainfall in winter because it is too cold.

 

 

As you see the wedge fits into a standard stove with a side opening door, the chimney draught then sucks in the gasification air through the venturi at the bottom of the hopper and secondary air is aspirated into the offgas stream with full combustion taking place in the wood stove.

[Breezeblock]

I see, the flights look too tight and the metal too thin for chips, ok for pellet or grain. Similarly the round tube won't have any give for slivers, square is better.

 

Also the hopper will need some sealing to decrease the risk of a burn back up the tube into the hopper.

 

A virtual friend of mine, we've been in online discussion for 13 years, has produced this:

 

 

And he has modified it to run on dry woodchip (gasification needs drier material in general). In Canada they have very low temperatures to contend with and in his day job he looks after a large woodchip stoker heating glasshouses and has ingenious remedies for loading poor quality, but dry chip, his is stored outside under a breathable membrane but I get the impression they have low rainfall in winter because it is too cold.

 

 

As you see the wedge fits into a standard stove with a side opening door, the chimney draught then sucks in the gasification air through the venturi at the bottom of the hopper and secondary air is aspirated into the offgas stream with full combustion taking place in the wood stove.

 

Thanks for that its good to get somebody else slant on it