Biomass Briquettes for fuel vs coal

[Lopez Mike]

I've been doing more research on presto logs and pellets. I finally found a couple of people who know something AND have some evenhanded opinions and advice. Rare!

Prestologs (and the many imitators):
The price per log in my area in small quantities varies from $1.00 to $1.50 u.s. for a 7-8 lb. log and you get what you pay for. No surprise. The higher density and more expensive ones claim about 9000 B.T.U. per pound. The logs I bought today calculate out to 46000 B.T.U per dollar. As the price goes down, the energy density goes down and they aren't as physically strong. Tend to fall apart and absorb water.

Pellets:
Local price is $5 for 40 lbs. in small quantities. The trick seems to be (for a high intensity fire like we need) a S.S. plate that has as many 1/4" holes as you can drill in it. Maybe one every 3/4". Keep the fire relatively thin, don't pile so much in there that the air can't make it to the top pellets. Be prepared to experiment with secondary combustion. That is, let a bit of air in the firebox door so that some burning of the gasses above the fire bed can take place.

I bought a few of the logs and a 40 lb sack of pellets. I cut out two semicircles of 1/8" plate and tomorrow I grab a handful of 1/4" drill bits and use the mill for a drill press. I've learned over the years that low speed and heavy feed and lubrication make for long drill bit life with S.S.

I'm going for a test steam tomorrow afternoon with my old cast iron grates and the logs. We'll see. If the holes get drilled in time, I'll be doing some more steaming the next day with the new grate plates and pellets. Again, we'll see.

Mike

[stevey_frac]

I'm curious to know how the pellet experiment turns out. I know a local supplier that I could purchase them inexpensively.

[Lopez Mike]

The pellet experiment didn't happen as I ran out of time to drill the new grate.

The more expensive logs ($1.46/ea. as opposed to $1.00 ea.) worked fine. Lots of heat. I was able to steam at about a half a knot higher speeds before any drop of pressure (I'm boiler limited). As good as the Madrona hardwood that has been my best so far. No smell problem. These ones have no wax or added materials. Just smelled like soft wood. Burned with a clear stack with no extra air over the fire in my VFT boiler. Standard wood and coal type grate.

Drawbacks:
Messy. I have to chop up the logs ahead of time and there is no way I'm going to do that on board. Lots of bits flying around. I'm told there are dingbats that have a lever that breaks them up without the use of a hatchet. I'm going to look into that.

Slow to get going. With dry softwood I can steam from cold to usable pressure (80+ psi) in thirty minutes. With these, it takes ten minutes longer to get to 80 and then look out! Have to close things up or I will be popping the safety before I can get the boat launched at the ramp. Why is that?

Requires more anticipation when coming to a dock for a bit. The coals generate an amazing amount of heat. I was a the dock watching the pressure and waiting for things to cool down so I could load up and go home. Closed everything up at 120 with two or three inches of coals. 1.5 hours later I was still at 100 and waiting. Opened up the fire door. This usually lets in some cold air and calms things down a bit. Still took almost two hours to get down to a few coals and 40 psi at which point I blew down dry and was able to unbolt the stack (with a thick coat, gloves and a few mild scorches!) and go home.

The stove store guy was right. The more expensive logs have more heat. Perhaps just lower moisture content. I dunno.

As soon as the mill is free so that I can use it as a drill press to drill a zillion 1/4" holes in my new pellet fuel grates, I will give them a try. My locomotive friends have had a poor experience with pellets and forced draft. Lots of burning debris out the stack. I have a six foot stack and natural draft. We will see.

Mike