Just an incomplete answer: The small stuff acts like a filter in the low end towards
the grate. A typical Imbert property, when using a fine stationary sieve instead of
a proper grate.
Still, you use a grate with about 1/2" slots! This tells, that the reduction volume is
too big (passage area big and draft velocity low) for the small fuel size and driving style.
After the restriction, one has to keep up the gas velocity to avoid the “filter effect”.
Preferably slightly increase it!
This is of course against the talk about residence time, but what good is there with
residence time, if the char is clogged by ash? Ash-clogged char cannot act chemically,
as the active surface is “insulated” by ash!
I think you need an active sieving + self cleaning angle-bar grate,
operated manually at about every time you bunker, if you insist to have a “lazy”
reduction volume after the restriction.
The “lazy” wide reduction volume will then work with big size fuel too… with heat.
Allso, l forgot to mention the fact that l usualy dont get much powdered ash in the reduction, l get clumps of partly melted ash in size of about a walnut. All the dust flows right trugh the gate.
I do burn wood trat grows from quarz sand. Culd it be l have a lot of silica in the ash? Molten quarz gets wery sticky when hot, culd this produce those slagy ash clumps?
Allso, while on the topic, l almost always find molten metal droplets the size of beans in the reduction charcoal. They are goldish colored. I know l use only wood 100% free of nails and metal, so where culd they come from? Has anyone experianced that before?
I’d say it all depends on what kind of fuel you have on hand or want to handle and what kind of maintenace your want to do.
Personally I like fuel easy to make and handle and low maintenace, especially in the winter. I’d hate crawling in the snow emptying the gasifier and sifting char with frozen fingers.
I find it’s usually enough to tap or wiggle the grate a little bit with the poker at every lightup. I do that after light up with the blower running. Any ash will fall/get sucked down.
Ain’t woodgasing fun!!??
Again. Depends. Depends. Depends.
I use exclusively conifer “sappy” wood inputs.
I will only use an command active grate anymore.
Conifer trunk/stem wood make a very fragile char in the reduction zone.
ANY upward grate movements (like a swinging chain hanger); ANY top-of-grate sweeping arm; ANY wiggling slat grate crushes my reduction char causing flows clogging; and crushed char drop-through wasting.
For fragile chars a center post supported; selected slotted flat plate grate; with a 15-20 degree, back and forth sifting action had proven to be be the best compromise. Grate plate with a low perimeter “save-char” fence. Yet still allowed up and over the edge gasses bypass flow.
Lots of Depends, Depends, Depends with woodgasing.
NO ONE SOLUTION CAN EVER FIT ALL
J-I-C Steve Unruh
Yes I have seen this twice now.
Brass filler, brazed jointing too close to the oxidization/reduction temperature zones. Great way to join outside of these areas. Corrosion resistant. No electricity needed.
Brass and bronze pipe air nozzles tips melting.
The historic units using these were specialized castings with water cooling passages.
That would need a reversing switch aswell, or a crank and connecting rod!
You only need one flip-flop at tanking or once a day, some fuels very seldom.
Perhaps for stationary, automated equipement?
Hi MaxG
I think you are asking if a radial, versus spiraled out flat plate grate slot pattern is used??
I do not think it matters.
Slots need to be constant width.
Center post supported with a back and forth sifting action then does promote a center stacked up less moved Cone of material. GOOD for post/support heat insulating.
This less active area why it’s important to have an up/over/the outer edge flow capability too.
Not be just dependent on flow down through the grate slots.
Give a wider range of system works flow rate possibilities. From low drawn flow to high drawn flows.
On my use systems I want no individual system built-in use choking points.
Let the engine, and operator, decide use limits. YOU low use cold-tar it up - YOU DID IT. YOU overdraw/overheat damage things - YOU DID THAT TOO. Make the working human operator the control points.
J-I-C
These have already been posted up often.
GEK II’s and early III’s
Victory model hearth systems and later. BenP clearly shows this in his book.
Pegasus “book system” illustration number 54. On the DOW here is in the library section as a pdf.
More reference illustrations been put up of center post flat plate rotating grate systems been used if a fellow wants to look.
The WHY is often not explained. Why make up a more difficult to fabricate grate support/movement system?? Because it works better for a wider range of woods fuels inputs and gas drawn-out conditions.
Perimeter edge grate supporting is a manufacturing convenience. Just like a “flat-head”, “side-valve”, valves-in-block engine.
You want better performance change over to overhead valve engines.
And forcing all gas flow down through the grate grid with no over the grate edge flow possibility is like insisting ALL engines must be an overhead CAM arrangement as “the Best”. Overhead cam better at high RPM’s. All flow through grates make you velocity, and fuel ash type and % range-use dependent.
Good conversation you and others doing on the other topic about reduction gases recirculating under some conditions. Give a 2nd, 3rd chance for more HOT CO2 to CO reduction conversion.
Ha! But then I only drink three-pass, triple distilled Irish whiskey. Never the strong nasty tasting single-pass stuff.
Hi Steve,
I saw a new design somewhere (maybe Ben’s site) with a very high screen type basket grate and it made sense to me so I upgraded mine as seen below. Gas production is very good. Although I have no way to quantify my results, if you’re starting out, start this way, I don’t think it can hurt gas production. I’ll try to find the picture that inspired this and post it back here.
Pepe
EDIT: found the source- GEK
Max, you might be interested in the ash scroll plate and auger drive here.
I think the elongated slots at the bottom probably do more for gas production without plugging than the open grate sides if my 2 cent opinion is worth anything. Where did you get that nice slotted grate?
What is the perpose of the screen on the sides of the grait? I am suposeing cleaner fuel forceing the gas through more coals?imbert design. PS that slotted grait looks like some type of drain cover?
Hi All,
I laid out a bunch of parallel lines approx 3/8" wide on a 1/4" thick 10" d circle, then laid out the ends of the slots and cut them out with the oxy-acetylene torch. Takes steady hands.
I’m thinking the open sides present less overall resistance of the gas flow through the system helping maintain a high char bed temp. It might even open up more surface area through the sides for the reduction reaction. It’s something I saw and wanted to try. It certainly hasn’t hurt the gas production or quality as far as I can tell.
Edit: Actually it was 5/16" thick and has held its shape well, a major concern I’ve had since day one.
