Mega Leaf & Twig Incinerator

[TNGP]

Fall is coming and there's no better time to build a mega PTO powered incinerator to save myself a lot of pain and suffering.

Here's the idea -
48" high pitch 700rpm fan attached to the PTO via shaft and chain drive.
Wide swath vacuum collector at 72"x4".
Snail shell collector with top exhaust to keep unburnt bits low in the can.
Possible propane injection.

Now for the problems -
At zero static pressure the CFM of the fan is 43,400. The fan has a face of 1080ish square inches which makes its exhaust 51mph. For the intake if the 72"x4" is used, the intake velocity would be 190mph assuming the 43,400cfm remains constant. However, since that opening is 360 sq.in. the static pressure would be greatly increased for the fan. The problem then is the actual intake speed bottoming out and if there would be enough left to vacuum leaves, twigs and possibly grass clumps and force them into the burn chamber. To note the pitch of the fan is 38 degrees and it requires 8.5hp to turn it at 700rpm.

Here is the static pressures for the fan up to .5
@ 0.000-In. SP 43,400 CFM
@ 0.125-In. SP 41,957 CFM
@ 0.250-In. SP 40,294 CFM
@ 0.375-In. SP 38,364 CFM
@ 0.500-In. SP 36,102 CFM

My calculations bring the SP to about 9.5ish if sucked through a 360 sq.in. opening, but I have no idea if thats right. If anyone reading this knows about this, PLEASE let me know.

As for the propane, I don't want t turn the burn chamber into a giant shrapnel producing death trap, but I do want to keep it close to 1,800F to burn up the twigs and not produce any smoke.

Give me your opinions...

 

[zzvyb6]

I have a Woods trailer vac, industrial version of a Trac-Vac. Once I rolled over a 'dead' leaf fire on the road, but, it still had some hot embers. The blower nicely fed the combustion of leaves, grass and weeds. The only downside was that it burned all the paint off my metal containment box. A bit smokey, but so what.

I think you are over thinking it. Heck, a leaf blower feeding a fire in any trailer ought to be enough IMHO.

 

[roadhunter]

I'd recommend the KISS Keep It Simple Stupid method along with watching lots of you tube videos to get ideas. As was mentioned before I think you might be overthinking this.

I play around building stuff like this making biochar. Here is a kiln I built,Fed with a leaf blower. When it gets hot it only takes a small amount of air to keep hot, like less than 10% of the leaf blower flow.


Here are a couple of videos I'd recommend.
Incinerator- Induced Draft - YouTube

Burnwell Micro Air Curtain Incinerator - YouTube

Burnboss Mobile Trailer Air Burner / Airburner - YouTube

 

[TNGP]

KISS is the goal, but the problem with low air flow is that it won't vacuum up the debris from the lawn. A simple incinerator would be perfect, but I'm trying to combine it with the lawn vacuum. The other idea is that it will save thousands over just a massive leaf sucker.

 

[roadhunter]

KISS is the goal, but the problem with low air flow is that it won't vacuum up the debris from the lawn. A simple incinerator would be perfect, but I'm trying to combine it with the lawn vacuum. The other idea is that it will save thousands over just a massive leaf sucker.

Ahh. I see. A chipper shredder with vacuum attachment would probably do a good job of sucking up leaves and feeding enough air to create massive amounts of heat. Essentially you are just wanting to use the vacuum fan portion for leaves.
ECHO Bear Cat | Products

I would imagine if your fan creates anywhere close to that much suction it would work quite well. Not sure how it would handle the debris but there is only one way to find out.



What are you going to use for the burn chamber?

 

[TNGP]

Basically yes. The burning part is the fun and easy part...15.5:1 or air to propane. So I'll be able to get good heat with any fan. The real problem is the vacuum part.

For the burn chamber imagine this. A rectangle with the proper square inch opening area. This is the entry point for the air into the chamber. On the outter edge of the rectangle will be a flat sheet of steel that is rounded to come in and meet the otherside of the rectangle. The idea is to make a vortex of **** fire. The bottom will be flat. The top will be flat too but will have an appropriately size stack in the center for the exhaust. This was the unburnt debris will remain in the bottom. Propane injection might be just after of the fan or just in the entrance port so there's no flameouts.