Clarification of first test reults:

Posts from Gasification List on 4/21/09


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Questions people asked (and my answers):

How dry were the woodchips you used?
I am guessing between 6% and about 15%, since I dryed them over several days on the floor of a shop heated with a counterflow furnace. That means that the heat from the furnace is directed at the floor. I spread each 5 gallon pail out to a 4 foot X 4 foot layer (always less than 1 inch thick). I swept up everything daily and reweighed until no change for 2 to 3 days. I used wood chips from 2 different roadside sources. After drying, I sorted out both "longs" (over 2 1/2") and "shorts" (fall through 1/2" X 1/2" hardware cloth sieve). During all of that I lost 53% of the initial weight of one batch and 64% of the initial weight of the second batch.
Now we have about 400 pounds drying in an old wood wagon (converted manure spreader for the non-country folk). This will be the last woodchips that we will handle manually.>p>

The black stuff in your cyclone collector, was it goo, or fine dust, or chunks, or....?
I haven't gone out there yet to dissassemble the unit, to check all that stuff, but, that black stuff is definitely a very dark, thin liquid.

After you got the unit going and flaring, what did the output gas look like?
(was it clear, or dusty, or smoky/steamy etc?)

The flaring gas was almost totally invisible, except that, on the rare occassion where the wind went down, we could see a reddish tint.

I'm interested in the initial temperature rise;
So am I . Yes, we'll see if it does that again or not. During this initial start up, we could have caused a bunch of chips to fall through the grate into the bottom or "ash pit". If so, those chips might have caught fire causing the one-time high temp. I'm just surprised that we got "good" gas at the lower temps that we saw later.

I wonder what a post-run internal inspection might show?
I'll let y'all know. -----

Comment from a reader:
You used 15-3/4# of wood (I'll assume 15%m.c.) is 114,000 BTU of fuel, which you burned in 110 minutes., which for me is close enough to call an average fuel consumption rate of 1000 BTU/minute or 60K BTU/hr or 17.5 kW(th).

http://wattpower.com/wpindex6.html says 6-12 m3/hr, at 4600-5200kJ/m3.
Twelve m3 times 5000 kJ/m3 is 60,000 kJ/hr, which is the moral equivalent of 60,000 BTU/hr (1 BTU = 1.055 kJ).
So it looks like you achieved more or less the nominal nameplate rating of the unit.

Well, that's good. We can see that there is a lot of tuning up still to be done. When we visited with Greg Manning in March of 2008, we saw that he was running a Chevy 350 on a grate no bigger than this one. Of course this thing isn't an Imbert.

OK!! Good to see you are "up and running."
You had fire in the ashpit. That is what burned the paint. Most likely, it was due to the ashpit door not being closed properly. Also, it could have been due to serious channeling in the fuel.

The ashpit door was closed pretty tight, but we will check when we tear it down to clean and examine. We had serious bridging. Needed to poke stuff down every 5 minutes or more often until the last half hour of the test. By that time, things settled down for some reason. We have a plan to add a C/A thermocouple into the area just below the grate to get an actual hot gas temp reading.

What is the moisture content of your fuel? Should be below 20% WB, ideally about 15%. Could you post a picture of the chip fuel you are using.
I think I commented on this in an earlier reply, but I think we're at somewhere between 6% and 15% moisture.

NOTE: I JUST ADDED TWO PIX OF THE WOODCHIPS AND A LITTLE TEXT ABOUT THEM. CHECK THE PAGE AGAIN!
http://www.spaco.org/Woodgas/FirstTest42009.htm

The JXQ-10 is intended for producing "Heating Grade Gas", (HGG) where its tar content is advantageous. It is is not intended to produce Engine Grade Gas (EGG). Using it directly is inviting engine problems. However, you may be able to configure a gas cleaning system that would give you an adequately clean gas. I would suggest the following:
1: Cool gas to drop out moisture.
2: Filter.

I Agree. Note from the earlier pix that we added a GEK cyclone separator and it DID gather a fair amount of black something.

For a filter, you might consider using fine sawdust laid out on screens to trap the tars. Then use a dry type automotive air cleaner... if it doesn't plug up, you should be OK.
Excellent Idea. I am looking around for an appropriate filter and filter box for this application. One reason we are fooling around with the stove for now is to get some ideas on acceptable system pressure drops.
I don't want to snuff out the whole program by choking the system down too far.
I wonder who has information of the effectiveness of the oil bath air cleaners like all of my farm tractors have for this application?

I notice that you have a good looking cover with the Gasifier. Do you operate with the cover on, or off?
So far, we operate with the cover on. Note that (in the picture on the webpage in question) there is a 3/4" pipe nipple welded to the top ring just that is just below the cover. This is supposed to be the air inlet.

All air must enter through the fuel (stratified downdraft). Have you tried running with the cover open?
Yes, we have opened the cover to add fuel and to break up bridging.

Running with the cover on will "choke" the system, and convection will cause the pyrolysis gases to migrate upward into the fuel, where the tars can condense out, and stick the fuel chips together.
Probably so. We did see the flames and char moving upward about 4 or 5 inches above the restriction area about half way into the test

The fuel looks OK, and the tar convection to the "cold zone" could be what is causing the bridging.
What about trying a run, where you start off with 1/2 a bucket of chips, and the cover OFF. Note how it runs.
Then dump in the other half of the bucket, and run with the cover ON. Note time of each run. See if you can get both burners working. See if you get fuel hang-up or not.
We could do that.

If it still hangs up with the cover off, the problem is in fuel chip characteristics.
From the photo, the chips look like they are relatively thin in relation to their width and length, and might have a tendency to "interleave". You may have to go for a smaller sized chip.
I like this idea. Later in the run, we were adding our "moldy" chips and they ARE of a definitely smaller size than the 2 earlier pails. And it may have been this change to the smaller chips that made things work better.
The samples of chips that Greg Manning sent back with us last March were of this smaller size.

Now that I think about it, we have a small hammer mill around here somewhere that could be used to reprocess the bigger chips. ---On a small scale, at least. I think it could do about 300 pounds per hour.