So this process is biomass gasification. We take waste wood, we chip it and the
product I use is about a 2 and a half inch minus type of product.
It provides the necessary surface area that I need in my reactor.
I don't use something that's too big, it causes problems with my material-handling
systems or something that's really small and fine like a sawdust type of thing
cause that doesn't provide me any useful surface area so this is a chip product.
It's a material that currently I brought with me from Montana, but we have our
second drying bin full of local product with opinion juniper material that was
chipped here on site and we'll be running that shortly.
So the system has two feedstock bins. One as I said was filled with dry material
this material is dried to a moisture content of about 11 percent, probably this
was 40 percent plus when I loaded it and I have a second feedstock bin filled with
this local material that looked to be about 35 percent moisture content.
And so when we process this one dried bin we recover the heat and we use that
recovered heat to dry the moist bin. And then when we're done with the dried
bin we have a new dry bin that we swap the process, fill up the empty now with a
moist material and repeat the process.
And in any kind of woods-handling system, the big issue is solids handling.
I have a system that's configured optimized for woodchips.
You can optimize them for pellets or someone was mentioning cherry pits.
You can optimize it for almost any type of biomass, but once you optimize it for that
particular biomass, obviously you've reduced your flexibility.
So we've tried to make this as flexible as possible, but it's still optimized for
wood. We've used some pretty ugly slash in it,
we've had clay, rocks, metals, all sorts of things go through it.
So it does a fairly good job of handling it, but still if we were to switch our
feedstocks to say, pellets, or cherry pits as one of your colleagues
recommended, the clearances and the auger systems are too great I think to conduct
that material efficiently through the system.
So, most of my headaches are in the front part of the system with handling, drying,
conveying wood chips into the reactor.
[grinding noise]
This is the gasification reactor. It's basically just a big pipe.
And the pipe is full of woodchips, there's about a six to eight inch layer of fresh
wood. There's a small flame front at the bottom
of that and the whole rest of the length of that reactor is full of hot char.
The char is about 800 degrees C and we control that through differential
injection of oxygen. That's what these rings are around this
gasification vessel. So I've measured - monitored temperatures
in 5 different levels and if I don't like what I see I can inject additional oxygen
to raise the temperature or extract - or limit the oxygen to reduce the
temperature. So that's my method of process control.
There's a number of reactions that occur in a gasification process.
Some are endothermic, some are exothermic so the temperature profile through the
reactor is not constant. It's high and then it goes a little bit
lower and then it comes back high again, but we exit at about 600 degrees C.
That's too hot to throw into an engine so we cool it down.
The heat exchange is on the other side we'll take a look at that in a minute.
We cool it down to about 50 degrees C then we take that cooled gas and we filter
it in this baghouse filter system, it's a simple system there's just four individual
inverted 55 gallon drums that have filter bags in there.
The gas is entrained with a fine char pellet.
This is what the char looks like. Most of it's very fine particulate, some
of it's a little bit larger, but that's entrained in the gas it's blown through
the tube side of the heat exchanger and is extracted out at the filter system.
The char is collected in the bottom of the filter system and there's an auger that
augers this material out and in the back there's a larger drum that contains and
collects this char. As I mentioned in my spiel before this is
called a biochar. It has properties that it can be used as a
soil amendment so we are working with researchers at the university of Montana
where they reapply this material and they're actually using it in that
particular instance as a defense against invasive species.
They find that an application of this char around invasive species helps mitigate
some of the chemicals that the invasive species give off to give it unfettered
access to the land. So by removing some of those chemicals the
natives are allowed to crowd in and perhaps control and manage the invasive
species.
So if we want to walk around the back here
This is our control area where we have our PLC.
You can see it up there on the big screen. This is my assistant Mike Bergman.
So we monitor our operations here we have a webcam that's looking down at the
gasification system so we can see what's happening at the top of the gasifier
just by our position here.
This is the barrel where the biochar is collected.
Again, this material is being examined for commercial uses in agriculture or as I
said before in potential management strategies for invasive species.
Let's walk up this way and we'll come back down.
So this is what we loaded up this is the local material that we loaded up with
yesterday. This is in the process of being dried in
our second feedstock bin and when we run out probably later today with the primary
bin we'll switch over to start using this stuff.
I find that if I have a lot of needles, I get clinker formation, there's a lot of
phosphorus - you know most of the minerals are concentrated in the leaves and the
needles, also the bark. If I have a high percentage of those
materials in my feedstock, I tend to have more maintenance issues because they
form clinkers, they clog up the bottom of my gasifier and it requires me to take
the system down and clean that material out.
From the other side I mentioned we have the gasifier, the hot gas comes out, it
goes through this heat exchanger, this heat exchanger is just a tube and shell.
The hot gas and the entrained char goes through the tube side.
We just use ambient air as a coolant. The ambient air comes in the middle of the
heat exchanger and is pushed out to either end.
At either end the hot air is recovered and is traveled overhead back into the bin
area where I can choose which bin to dry it with.
We have three potential sources of recovered heat.
First is the one I just showed you, this heat exchanging with the hot gas.
The second one is in the engine compartment.
We have a spark engine that's running over there, we'll show you that in a minute.
There's also a heat exchanger in there. And I can recover heat off the exhaust gas
I can also recover heat off the coolant. So I have three potential sources.
Right now I'm only recovering heat off the hot producer gas and that gives me a
thermal efficiency of about 70 percent. If I recover heat from all three sources
that thermal efficiency would go north of 90 percent.
This is basically the control system.
This is where all the sensing elements and the PLC is located - the computer.
This is a portable unit obviously and it's been especially ruggedized for portable
travel and whenever I find occasionally especially on accesses such as this
bouncing down a road any number of these flyers can pop loose and then you have
probably a one to two day trouble-shooting session trying to figure out which bloody
thing went wrong and how to fix it. So there's always issues with these
systems, but this has performed remarkably well.
And then here is mostly an off-the-shelf genset.
We're using a Chevy V6 that can run on propane or gasoline and producer gas
that's been modified and I'll show you the engine side and then we have it attached
to a generator. This system produces 25 kilowatts of
electricity and I'm recovering about 200,000 BTUs per hour of waste heat.
Chevy V6 operating on woodgas.
25 kilowatt electricity. 480 volt 3-phase electricity is being
produced by this.
Since we don't have electrical load right here we're only running our parasitic
systems which run between 2 and 4 kilowatts so we have additional gases left
over. What we do is we flare up this top within
the stack.
We do have an onboard transformer and I can transform that 483 phase into
208 3-phase and from that we can get 120 single phase which would power normal
household appliances.
We've used this system before in remote powering applications in Missoula, Montana
there's a - we're coming into our festival season where we often have every weekend
some kind of music festival downtown. And they often invite me to come down and
run their sound stage with the output from this system.
It's a difficult load because it's a very dynamic load.
This system would prefer to see a nice, steady grid load.
But we have been able to manage it. We get on sound stages anywhere from a
5 kilowatt usage up to a 15 or 17 and back down.
So in order to follow that system you need a fairly flexible, robust generator.
Sometimes if we have too big of an excursion it will fall down, but normally
we can follow those kind of loads.
Yeah, so a couple other examples of this technology that I'm familiar with.
There's a similar system, it's a little bit larger, this is 25 kilowatts, there's
a system in California that's 50 - twice as large - it's 50 kilowatts.
And it's on the property of an organic walnut farmer.
So this walnut farmer has his back 40 full of spent walnut shells, right?
So he's bought a big one of these things, he's converting that waste into
electricity and heat. He uses the processed heat for drying his
product and electricity for running it. He's not completely off-grid, but he's
close to it. Another option or another example is the
U.S. Army and overseas they've deployed a couple of these systems that are
contained in shipping ISIL containers. Two or three containers the system is
contained in. And they use spent trash, they shred up
paper, plastic, cardboard, all those materials and they compress it into a
plug, a pellet type plug, and they gasify it and make their own heat and
electricity and they power a tactical quiet generator.