Material for baghouse filter socks

Hello fellow wood gasers .
Can any body tell me what kind of material is being used for the socks when building a bag house filter for the gasifiers that we are using? And where to get it .
How many square inches of filter would be needed on a WK gasifier. Needle felt meterial they say is good up to 500 f What would work?
How about it Max?

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I think @Patrick1 has some good experience with baghouse filters. Hopefully he’ll chime in.

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For reference, here’s Patrick’s filter socks. He didn’t mention the material though.

From his pictures and description, he’s got 43 tubes, 2.375" dia, 3 ft long. This to feed a Chevy 350.

By the math, that’s roughly 12,000 sq in of filter space.


Hi, Calvin!
The most popular material over here is chineese fine-wowen SS and Acid-proof “canvas” 15 – 30 microns mesh. It is sold by Alibaba.

As usual, a good formula for area is:

l X n X 0,5 – 1 = m2


l = liters of displacement

n = RPM : 1000

It needs no help structure, it i sturdy enough to keep cylindrical form. ~1" diameter.

Easy to clean with internal blowing pressurized air or water spray. From inside – out.

Point- or roll-welded on a round compact copper bar with a diameter = the design diameter for the mesh-tubes.

No troubles with heat after a cyclone.

But this is nothing for “nitti-gritti” small, small dreamers!

It neads a full barrel, well insulated, weatherproof.

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Shure you mean filter surface!

l had great resaults with a thick cotton towel on my charcoal powered Seat arosa.

After about 2 or 3 thousant km the original paperfilter was just mildly gray. It did a exelent job at cleaning the soot and ash out, while it was wery breathable. All the knots add to its surface area. For cleaning, just pull the sack out (like seen on the picture) and shake the soot cake off.

But that is relatively dry chargas. For wet woodgas, l have no idea how the towel will perform.
l am planning to test it out thugh. l have all prepared but hadnt yet got time to assemble it.
If that doesent work, l “borrowed” a sack from a original sack filter used to filter air from pneumatic transported lime and limestone powder at wotk, its a wery thick artificial pabric, similar to vacuum cleaner bags. So, if the towel doesent work, this gets in.

But it is a lot less breathable!

Thanks ,Chris , Max & Kristijan.
I phoned a felt store in Toronto
& what they have is called needle felt which can be used as a filter in high temp dry applications
Will start to decompose at around 700 F
8 oz meterial
1/8 inch thick
72 inch wide
Sold by the lineal foot @ 14.55 US
The name is Meta Arimid.
On Patrick Johnsons site this is what I believe he said he used (Meta Arimid)
Kristijan ,how many filter tubes do you have ,how often do you have to clean them & how much restriction does it create before & after you clean them?

Hello Max
I didn’t understand the last half of your formula
I have 318 cu inch ( 5.2 litre). Engine running 2000 rpm highway speed, how many square inches filter surface area wood be needed?
Max about how much does the cychone lower the temp & what temp is that fabric good for.
My temp cumming out of my heat exchanger & going into my cyclone wood be between 500 & 600 f maximum?

Hi, Calvin!

l X n X 0,5 – 1 =

liters X RPM:1000 X (0.5 – 1) =

l = liter(s) displacement

n = RPM : 1000 = RPM divided by 1000

l = 5.2

n= 2000 : 1000 = 2

In the “lower” end

l X n X 0,5 – 1 = 5,2 X 2 X 0,5 = 5,2 m2

0r in the “upper” end

l X n X 0,5 – 1 = 5,2 X 2 X 1 = 10,4 m2

That means over 100 tubes of deacent length… if 20 mm in diameter…

No heat problems; but the service intervalls are ~ 8 – 10 times longer if
you use a deacent cyclone ahead of the filter, and empty it daily!

Oh, 1m2 = 1550,003 inch2

1m2 = 1,19599 yard2

What he might be confused about as well as myself, what is this → (.5–1) ?

Hi, Bill!

(.5 – 1) = from 0,5 to 1,0 plainly.

Value “band” = from one value up or down to another value level.

All intermediate values in the “band” are acceptable, or concidered.


Hi Calvin
Sorry to come in so late.
I used Nomex filter cloth, handles temps up to 230c -446 f . But the needle felt that goes up to 700f -371 c would be much better, I often get my bag house temps up to 230c on long up hills then I back off or blend in some petrol.
I used 2" pipe nipples and sockets, but you could use 1" just as easy, give you more cloth area.
I haven’t had a problem with my Chevy with the 2" socks, but the stationary unit does block up after 5 hrs of solid running, then I have to shut down the gasifier for 5 min and give the bag house filter barrel a few blows with a rubber mallet to knock the soot cake off, then open it up again and it’s ready for a few more hours of hard work!

Hope this helps


Hi Patrick,You are a very busy man, you did very well by answering me this soon.
Do you use a cyclone precleaner on your truck?
I have a problem finding enough space on the Dakota for a 55 gallon barrel.
How many inch water restriction do you have on a clean filter & how many kilometres do you get befor you have to clean it?
Do you think it could have less surface area & maybe rig up a internal bag shaker that would operate on a timer or manually.

Maxg base formula is for a FOUR-Stroke (one intake suck in every other full crankshaft rotation). Why the divide in half step.
THEN a factor DOWN multiplier for a range of realistic actual cylinder filling rate of air and fuel(gasses). From an only idle/low power needed; to a full engine capability power need.

Natural Aspiration (sucking in) never reaches 100% cylinder filling.
And even if woo-woo forced induction like exhaust turbo charging, or gear/belt/electric motor driven supercharging makes you think you can overachieve a greater than 100% filling rate equivalency - this only occurs at a full load (for the RPM) power demand. With a range of air fuel ratios that must be maintained at an engine idle and low power needs still not the need for 100% cylinder filling rate even with a forced induction boosting system.
You can only over air cylinder stuff-in for some fuels like diesel in a compression ignition engine. Different critters

Never, ever trust a math-jonney who does not put in an in-real-world-use factoring down step relevancy on each and every power conversion step.
100 kW/mechanical will never make 100 kW/electrical. Factor range down of times .4 to .9
100 energy units of fuel heat value will never make 100 units of mechanical to make 100 units of electrical power.
You must pay the energy conversion trolls crossing over each and every conversion bridge.

Practice. Patience. Persistence.
J-I-C Steve Unruh


Hi Calvin
Yes I have a cyclone pre cleaner, but it’s not that effective.
I can’t help with the space, all you can try is make a custome box for your bag house filter, to fit the vehicle. On a mobile unit I don’t think it’s necessary to fit any form of shaker. The vehicle movement will take care of that. There is a difference of about 1-2 in before and after the bag house, when it blocks it can go to about 6 in, my blowers are after the bag house filter so on start up I blow back and forward this usually knocks off most of the soot cake build-up.

Hope this helps



With due respect, but!

Here is no need to boil a soupe on a nail!

The filter formula gives room for squeese-minded and liberal constructors to meet their demand for service times. Preceeded by a decent cyclone.

Be it a one cylinder, 2,3,4,5,6 or a 8cyl one. Assuming 4-stroke.

The Surface aims to be satisfying for a calcuable gas-flow, nothing more…

I always have much respect for your maths-proofs Maxgasman. They are true Engineering practical, useable.

Do realize though that we live in a world/culture that too many worship the genius/prophet/wizard model. One of these jabber-encourage-you-to-support-them’s always anymore using baffling math “proofs” to sell their philosophies.
And then there are the true idealists who will not accept entropy, diminishing-returns, inputs versus output ratios wanting to believe as my friend BenP says, “they can power an aircraftcarrier on a handful of wood-chips”.
I recently watch a video presentation where a for-sell gasifier system builder here in USA was claiming 100 pounds of fuel wood could replace 60 gallons (US) of pump grade fuel! No way Jose! And he was not try to spin-make-believe people. He believed this himself.
ChrisKY says 16 pounds woodfuel for each one gallon USA gasoline. I use found needed 20 to 30 pounds per gallon gasoline replacement conversion ratio as a from cold start to next cold start best. Smaller systems with less possible “scale” possibilities.

Again. Much Respect for your real usable maths presentations.
YES. How often as PatrickJ’s input says, do you want to do system shut down baghouse filter service? Undersize and make an interrupting, beasty, operational choke point.
J-I-C Steve Unruh


Post deleted by me K.


Hi, Steve!
That is an embarrasing exaggeration for just a bit of a schoolboy’s rule of three.
Just fundamentals.
Trying to live in the process.

Ahhh. There you go MaxG.
“live in the process (daily)” as really the only way to learn.

I dusted off two old late1970’s books about earth sheltered home building as superior in many ways. Not really. Not for where we have 122+ inches a year of rain fall. Build up, off of the ground! Up, above the wet soils.
One of these books has an excellent appendix chart of the annual heating fuel costs savings living-earth-sheltered, comparing using wood, versus fuel oil, versus natural gas.
WITH mathematical by % comparison charts.
The wood stove of the 70’s maths used 50% effective wood low heat values to heat made inside of the houses by the then current woodstoves. Factor of .5
Still good comparisons IF that 50% is upgraded to real-in-this-century min 72% to 80% effectiveness of the spec woodstoves mandated here since the 1990’s. Upgraded factors of .72 to .8
By two different stove/chimney up grades for my annual 200 to 250 days of needed woodheating I now use 40% LESS fuel wood annually 1996 to now.

Rural living in a very green growing climate is gasses and weeds mowing demanded.
In the 1970-1980’s this took a ~180 days/21 weeks mowing season of at least 100 gallons of gasoline. 1990’s by engine equipment upgrades I got this down to 70-80 gallons a season. By 2005 semi-retired using more walk behind mowing versus rider mower got this down to 50 gallons gasoline a season. And then mowing twice the area.
Post 2010 over the course of 3 years by going with the best world class Honda OHC engined walk behinds. Then a new spec Kawasaki V-twin ridermower, 2013 to 2016 I got this annual mowing fuel used down to only 35 gallons for that 21 weeks needed doing.
So far this year the .65 gallons an hour rider mower is still unused. Done some areas three times, other’s twice, the last to be done now once over six weeks on only 1 1/2 gallons gasoline using the Honda engined power walk behind.
Ha! Sweating work still. 12 pints of gasoline. At least 12 pints of local crafts beers. Less fuel used is good for the atmosphere CO load added. But add in the out-of pocket cost for the sweats-out-beer-refueling and I am far behind in the pocket book!!
Diminishing Returns. Inputs versus Outputs ratios now gone unfavorable. Time to put the rider mower back to work.
(and asked why I must mow such a large area? the local powers-that-be have made it illegal to animal graze this down since the year 2000. grass weeds fire suppression, and noxious weeds department would then fine us. local powers-that-be strive to force our properties into high density suburban cookie cutter housing. of the once eight adjacent families who once cow/horse/donkey/goat graze managed - we are down to just three who have not given up to the banker/builder/real estate developers.)

2007 out annual Grid-buy electricity was an annualized 21 kW/hrs a day.
Now, today that is 12 kW/hrs per day. Grid storm/speeding-drunk-drugged-out, power pole taken out and we fall-back live handily on the 3-4 kWhrs I can generated daily on one GGE am willing to sweat-of-brow make and expend daily.
Taken years of doing it daily, living in these processes, to get to here.

Hey man. I do live this stuff each, and every day. Have for decades.
Simple systems, doing improvements step by step, can be improved just as well by try-three-times cut-and-fit as by the very best math proofs.
DO first. Observe. Honestly; without idealism as your bias; judge your results. Go a bit more, next time. Or: back off a bit, having found an adverse edge of possibility.
e.g.- compact florescent suck. Die early deaths, and dimout age too fast. Fourth generation LED’s replacements work just fine and are cost effective.
A 1960’s/70’s Rainbow, FilterQueen carpet vacuum will clean just as well as the latest, greatest multi-mini-cyclone Dyson.
And our Kenmore/Panasonic filter bag canister vacuum “Better” does just as fine much cheaper than theses Bests gotcha’ systems.

In a Good, Better, Best in all things world culture now . . . . always chose Better. Avoid extremes. Avoid purists.

J-I-C Steve Unruh