Anyone try burning loads of wood chips?

SidecarFlip

Minister of Fire
There are quite a few institutional wood chip boilers installed around northern New England. I believe Tarm biomass has a few models and there are several manufacturers. I used to work on occasion on the larger bomasss power plants installed around the region that are slowly dying. The hassle with burning chips is chip uniformity, the smaller the boiler the harder it is to meter the fuel flow to the boiler. Most folks think of nice uniform chips that look like square charcoal briquettes. When I went to the biomass shows and saw the small demo units running in the parking lot I would take a look at the chips and wonder where they got them as they were definitely not what I saw in the plants I worked on.

Unfortunately unless someone pays a premium for uniform chips what they get are whole tree chips which include sticks and leaves plus the typical chipper used in the woods tends to shred the wood instead of chip it. Ideally to make a nice uniform chip the chips should be made from the trunks (bole) the same stuff we want for firewood. The uniform chips are great to deal with and flow almost like water, the whole tree chips are nightmare, they get tangled up and clog things. Many a small biomass system owner has learned early on that who and where they get their chips is the most important thing in keeping the systems running. All sort of stories of having to having to have someone stand there 24/7 trying to keep the chips flowing in a supposedly non attended systems. At least one firm in the region got smart and they take make premium chips and handle the fuel supply for a lot of the institutional burners. They owners pay a premium but it cuts the hassle way down.

The problems with non uniform chips is why wood pellets were invented. They are the ultimate uniform wood chip, they are dry so the storage volume is low and no sticks or leaves. Obviously they cost more but they are the way to go for small unattended home systems.

The pulp mill I worked for had a 6 story chip screening facility that could sort chips from a chipper or purchased chips so that the chips going to the pulping process were uniform. It was a Weyerhaeuser licensed system that put out a very uniform chip. Any over sized chips were sorted out and resized, things like sticks and leaves went to our bark boiler. We went through 1100 tons of green wood chips a day so we didnt want clogs in our storage and conveying systems.

The one I tended had what Hurst calls a 'Clairifier' on it. It 'cleans' the chips before they get to the feed auger. Pulls out all the trash, sticks, big chunks, rocks, chainsaw parts, you name it. We even got stuff like rakes, brooms, stopsign posts and lots of gloves. too.

No such thing as 'clean chips' bulk delivered.
 

jetsam

Minister of Fire
Dec 12, 2015
4,627
Long Island, NY
youtu.be
The one I tended had what Hurst calls a 'Clairifier' on it. It 'cleans' the chips before they get to the feed auger. Pulls out all the trash, sticks, big chunks, rocks, chainsaw parts, you name it. We even got stuff like rakes, brooms, stopsign posts and lots of gloves. too.

No such thing as 'clean chips' bulk delivered.
...anything IN the gloves? _g
 

peakbagger

Minister of Fire
Jul 11, 2008
5,009
Northern NH
Our pulp mill bought three types of wood, logs, purchased chips and bark. We had a big drum debarker and a 2500 horsepower chipper down stream of it. The logs were piled in rows and unloaded by our crews so we didnt have to worry about rocks and junk. There was a metal detector upstream of the chipper that diverted suspect wood away from the chipper. Most of our wood was from industrial forests so junk grown into the trees was rare. The chipper could chip just about anything. We had to notify the utility several hours before it was turned on and on days when power was expensive in New England we would only run it at night and on weekends when the power was cheapest. The chipper was designed to optimize chip size. Everything went to out chip screening system I described previously.

Purchased chips were generally supplied by specific suppliers that chipped what most on this forum would use as fire wood. The loggers would sell the high grade logs and pallet logs for much higher value and set the trunks (sometimes called the bole) and large branches aside and would chip them with s specialized chipper that produced somewhat uniform chips and fines. The chips would be blown into tractor trailer box and in theory the fines would not make it in the truck. The trucks were then driven to the mill and dumped using a truck dumper. For many years we had an attendant at the truck dumper who would sample the load. We had a Gradex chip sorter that would be loaded with a random sample and it would automatically sort the chips by size. Over, undersized and properly sized chips were weighed. If there was too much over and undersized chips in a sample the load might get rejected but normally the supplier was put on notice. The foresters knew all the loggers and knew the good ones and the sketchy ones. The closest buyer of these grade chips was about an hour away so if supplier got on our do not buy list they had to drive an hour away and the cost of diesel ate up their profits. The mill paid when delivered and had done so for over 100 years except for about a one year period where it was owned by some Iranian criminals (one of the biggest frauds in the US that no one seems to have heard of https://www.forbes.com/forbes/2002/1125/070.html#4332c81730bf )

The final product we produced and bought was "bark" which was a mix of fresh and reclaimed bark and low grade chips. It was burned as fuel to generate steam and electricity to run the mill. We didnt need to buy oil to run the plant as long as the bark boiler was running. The "bark" we bought which were claimed to be whole tree chips but usually were mostly the crown wood, twigs and leaves that were too small and dirty to make purchased chips. The chippers used to make them were designed to make a lot of chips for a minimum amount of diesel. The loggers that owned the chippers ran them cheap and tended not to change the knives so they got dull and tended to shred the wood instead of chip it. The resulting chips were mostly strips of wood and branches. On occasion in winter we would get a truck full of mostly ice and snow with some chips mixed in. They were miserable to deal with as they tended to get caught up and clog the transfer and fuel system. The reclaimed bark was odd stuff, the area started out with a sawmill complex in the 1860s and eventually switched to pulp. Up until the 1980s all the bark was dumped in whatever hole needed filling. After the first arab oil embargo the mill built a bark boiler and started digging up all the bark from all the places it had dumped. After about 20 years they dug out all the easy stuff and started buying it from other old bark piles. It was mostly bark but tree trunks and boulders came along for the ride. The bark boiler was a bottom grate design. It had to be raked out while in operation once or more often times a shift by hand. It was backbreaking work by employees who had to wear reflective insulated suits to handle the rakes.

These days there is a market for clean uniform chips for the smaller school and institutional systems. Some suppliers specialize in them. Froling sells Precision Dried Chips made in Peterborough NH, they are partially dried, clean and sized chips and sold as replacement for pellets in commercial and industrial boilers. No doubt they have a reject stream that gets sold to someone else. The term with respect to pork production was that the industry sold "everything but the squeal" a properly functioning wood market should do the same thing but of late the low grade markets do not make economic sense for the logger so they leave it in the woods and see if they can get credits for carbon storage. The big downside is forests need to be "pruned" every 20 to 30 years to ultimately grow high grade logs and without the low grade markets it costs too much out of pocket to prune the woods so the quality of logs produced as long as 80 years from now will be lower.

When I tuned up big power producing biomass boilers I always asked the plant to set aside some "good" chips for about 12 hours of run time. Good uniform chips flow well and spread out over the grate well leading to clean combustion. Chips full of sticks clumps and do not spread over the grate very well. We used to preach to the owners to put in screening systems in their fuel yards but they cost money to install and run. I know of few abandoned systems that did a good job but couldnt get anyone to bite to have them buy them and move them. One of the plants ran for over 25 years without buying any wood, they just reclaimed wood from the bark dump of formerly very large sawmill.They had real ice screening system and top pile reclaimers to keep the rocks boulders and big metal out of the process.
 
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Our pulp mill bought three types of wood, logs, purchased chips and bark. We had a big drum debarker and a 2500 horsepower chipper down stream of it. The logs were piled in rows and unloaded by our crews so we didnt have to worry about rocks and junk. There was a metal detector upstream of the chipper that diverted suspect wood away from the chipper. Most of our wood was from industrial forests so junk grown into the trees was rare. The chipper could chip just about anything. We had to notify the utility several hours before it was turned on and on days when power was expensive in New England we would only run it at night and on weekends when the power was cheapest. The chipper was designed to optimize chip size. Everything went to out chip screening system I described previously.

Purchased chips were generally supplied by specific suppliers that chipped what most on this forum would use as fire wood. The loggers would sell the high grade logs and pallet logs for much higher value and set the trunks (sometimes called the bole) and large branches aside and would chip them with s specialized chipper that produced somewhat uniform chips and fines. The chips would be blown into tractor trailer box and in theory the fines would not make it in the truck. The trucks were then driven to the mill and dumped using a truck dumper. For many years we had an attendant at the truck dumper who would sample the load. We had a Gradex chip sorter that would be loaded with a random sample and it would automatically sort the chips by size. Over, undersized and properly sized chips were weighed. If there was too much over and undersized chips in a sample the load might get rejected but normally the supplier was put on notice. The foresters knew all the loggers and knew the good ones and the sketchy ones. The closest buyer of these grade chips was about an hour away so if supplier got on our do not buy list they had to drive an hour away and the cost of diesel ate up their profits. The mill paid when delivered and had done so for over 100 years except for about a one year period where it was owned by some Iranian criminals (one of the biggest frauds in the US that no one seems to have heard of https://www.forbes.com/forbes/2002/1125/070.html#4332c81730bf )

The final product we produced and bought was "bark" which was a mix of fresh and reclaimed bark and low grade chips. It was burned as fuel to generate steam and electricity to run the mill. We didnt need to buy oil to run the plant as long as the bark boiler was running. The "bark" we bought which were claimed to be whole tree chips but usually were mostly the crown wood, twigs and leaves that were too small and dirty to make purchased chips. The chippers used to make them were designed to make a lot of chips for a minimum amount of diesel. The loggers that owned the chippers ran them cheap and tended not to change the knives so they got dull and tended to shred the wood instead of chip it. The resulting chips were mostly strips of wood and branches. On occasion in winter we would get a truck full of mostly ice and snow with some chips mixed in. They were miserable to deal with as they tended to get caught up and clog the transfer and fuel system. The reclaimed bark was odd stuff, the area started out with a sawmill complex in the 1860s and eventually switched to pulp. Up until the 1980s all the bark was dumped in whatever hole needed filling. After the first arab oil embargo the mill built a bark boiler and started digging up all the bark from all the places it had dumped. After about 20 years they dug out all the easy stuff and started buying it from other old bark piles. It was mostly bark but tree trunks and boulders came along for the ride. The bark boiler was a bottom grate design. It had to be raked out while in operation once or more often times a shift by hand. It was backbreaking work by employees who had to wear reflective insulated suits to handle the rakes.

These days there is a market for clean uniform chips for the smaller school and institutional systems. Some suppliers specialize in them. Froling sells Precision Dried Chips made in Peterborough NH, they are partially dried, clean and sized chips and sold as replacement for pellets in commercial and industrial boilers. No doubt they have a reject stream that gets sold to someone else. The term with respect to pork production was that the industry sold "everything but the squeal" a properly functioning wood market should do the same thing but of late the low grade markets do not make economic sense for the logger so they leave it in the woods and see if they can get credits for carbon storage. The big downside is forests need to be "pruned" every 20 to 30 years to ultimately grow high grade logs and without the low grade markets it costs too much out of pocket to prune the woods so the quality of logs produced as long as 80 years from now will be lower.

When I tuned up big power producing biomass boilers I always asked the plant to set aside some "good" chips for about 12 hours of run time. Good uniform chips flow well and spread out over the grate well leading to clean combustion. Chips full of sticks clumps and do not spread over the grate very well. We used to preach to the owners to put in screening systems in their fuel yards but they cost money to install and run. I know of few abandoned systems that did a good job but couldnt get anyone to bite to have them buy them and move them. One of the plants ran for over 25 years without buying any wood, they just reclaimed wood from the bark dump of formerly very large sawmill.They had real ice screening system and top pile reclaimers to keep the rocks boulders and big metal out of the process.

Thank you for that, as a kid my dad worked at the local pulp mill and many of the processes you described here are the same. The one big thing to note with both is the use of almost every part of the tree. Our pulp-mill was built in the early 80's and utilizes the Kraft process. The mill runs on softwood exclusively and due to our climate produces a high quality pulp due to the long fibers, in fact a portion of the pulp used to be sold to Bounty paper towels to give it strength. The mill consumes 2000 tons of chips a day to produce 1000 tons of pulp. The major difference is under normal conditions raw logs aren't chipped for pulp, the mill is located adjacent to the sawmill so the unmarketable and leftovers are used for pulp. The sawmill doesn't produce enough chips alone to supply the mill so additional chips are hauled in from the surrounding sawmills to makeup the difference.

The bark and fines are sent to the power boiler to produce steam to turn turbines to produce electricity and to heat processes in the plant including the pulp dryers. The lignin and solids in the black liquor are also burnt in the recovery boiler to produce yet more steam for power and process heating. There is also a chemical plant next door that produces chlorate for pulp bleaching and as a byproduct produces hydrogen gas, the pulp mill even burns this hydrogen in the boilers. The biomass portion of the mill produces 48 MW of electricity and also has a 64 MW natural gas turbine onsite with a 36 MW steam turbine heat recovery unit for additional power. The low grade heat from this turbine and heat recovery are also sent to the mill for use.

As far as logging goes only the logs are hauled in to town, all the limbs are left behind in piles and usually burned before spring. Why they are burned I am not sure but it is common practice here. Our shop at work sits on top of a hill overlooking the forests, you can see up to 50 miles away and can always tell where the active logging is by the plume of blue smoke from the burning brush piles.
 

SidecarFlip

Minister of Fire
...anything IN the gloves? _g
If you mean 'fingers'...no. Just gloves. Found a few chainsaws though.... One thing about the clairifier, it 'clairified' about everything. Always a pile of stuff in the bin every day...

Don't know if they even use the unit anymore. I've been retired for almost 10 years now and haven't been over that way in a long time.
 

Touch0Gray

New Member
Feb 8, 2020
45
Wi
all my splitter shavings get tossed in 5'ers and dropped off for my daughter and son in law for kindling. I rarely need kindling since my fire never goes out from October to March usually. Red elm splitter waste is the best kindling ever!