Addressing fine particle emissions, invitation to brainstorm

[patamos]

Further thoughts..

The manner in which air is drawn into the body (pull created by musculo-skeletal activity on a pleural vapour barrier) is part of the picture. Dividing the larger passageways into smaller ones (bronchi into bronchioles) creates a higher ratio of surface area to volume. Then a gas-liquid (air-blood) perfusion occurs across a semi-permeable membrane. The basic layout of mammalian physiology offers a design template. Kind of like a perforated automobile radiator - except the direction of thermal transfer is reversed.
You wouldn't want to get too small with the tubules, but somewhere in the pressure-volume-surface area-perforation equation i imagine the transfer of pressurized flue gas into and through near-surface water could be made to work.

Perhaps poking many tiny holds on one surface of a prebuilt heat exchanger, plumbing it up to the exhaust flue just above the heat riser and setting on the surface of a shallow pool.... would tell us something

p

[patamos]

Hey Folks,

Well, looks like pushing exhaust gas down into water is not plausible, even spread out across a radiator. Just not enough pressure, as other's have alluded. My theory that expanding the surface area interface between gas and liquid is probably whacked.

Turning the rad over and submerging it just below surface to get the gasses to bubble up might work once the gasses are pumping... But there would be all kinds technicalities in stabilizing that kind of set up.

Another thought: Much natural building literature talks about the slight electro-static charge evoked by unfired clay as it is dehydrating. They say having unfired clay surfaces within a dwelling helps the indoor quality by causing the tiny air-bourne dust and mould particles to clump together and fall to the ground.
Although we are dealing with moving air... what about an unfired clay brick chimney with an inside surface that is purposefully dampened?

Could enough electro-static charge be evoked to at least get the unwanted 2.5 micron and smaller particles to clump together before exiting the stack?

I may be wallowing a little too far down the rabbit hole in this one...


p

[Deleted]

Jan 30, 2014 14:24:04 GMT -8 patamos said:

Another thought: Much natural building literature talks about the slight electro-static charge evoked by unfired clay as it is dehydrating. They say having unfired clay surfaces within a dwelling helps the indoor quality by causing the tiny air-bourne dust and mould particles to clump together and fall to the ground.

Intermolecular forces (dipole-dipole interactions and Van der Waals forces)
will catch or repulse everything that comes close enough.
Intermolecular forces are very weak, but can become strong if there is only enough surface.

The inner surface of clays can be millions times larger than the apparent outer surface
and even the outer surface can be thousands times larger than the apparent surface.

The dew point is a function of vapor pressure temperature and surface area.
Due to capillary action the involved surface area is not only the outer surface,
but also the inner surface.

As a result on unfired clay surfaces water can condense or vaporize at much lower temperatures
as showed in dew point graphs.
The surface will be warmed or cooled respectively, which may affect convection..

Because the vapor pressure in inhabited spaces is usually higher than outside
water condenses inside is transported to the outside and evaporates there.

Intermolecular forces become much weaker at elevated temperatures.

[patamos]

Thanks Kari,
That is very helpful information.
Sounds like there is some potential to this non-fired clay material

Yes i have often heard of clay's amazing capacity to absorb and release water - some varieties can hold up to 30x their own weight before wetting out...
So, although unfired, it could keep stable enough with additions of vapour/mist/w.h.y.

I am thinking now of a mass heater i helped build in which all the flues beyond the fire box were home-made unfired adobe brick. I wonder if something like that (and so many of the old mass heaters through out the world..) would register lower fine particle emissions than similar designs with buried metal flue runs... The owner lives nearby, so i could always go do a test.

Bell chambers lined with a 1/2" of cobb plaster might be an even better set up. And/but if elevated temperatures are a deterrent to potentially beneficial intermolecular forces, then perhaps an unfired flue liner or small bell nearer the exhaust exit would be more effective

??

[mintcake]

How about something like a damp cloth? Maybe a long loop on rollers, so it can be slowly rotated to wash/re-wet it?
Again it's going to limit chimney temperatures etc, but might give better collection than a spray, but not need as much forcing as bubbling through
anything.

Another even crazier idea... sticky surface, like, I don't know, pour some cola down the chimney. That stuff seems to stay sticky for ages if you
spill it.

[Donkey]

Huh.. Adobe bells would be my bet.
I wonder if that, PLUS lowering exhaust temperature to below the condensation point might help do the job.
TO make up for the exhaust being too cold, perhaps a short run of single walled metal could go in somewhere, where it (exhaust) could be reheated to run the chimney.

Imagine a double bell system built with adobe, exhaust from the second, larger bell would be piped back into a smaller first bell for re-heating to climb the chimney. The first bell would be small and maybe insulated, The second bell would be oversized and might need a condensate pan with drain.

[Donkey]

Or use a TEG (or some such) to power the pump for a tiny internal mister system..

[DCish]

Wouldn't the adobe quickly become coated in the particulate that we are trying to collect, and stop collecting? If so, what would be the plan for cleaning the internal walls of the adobe bell? Or, is the idea that the fine particulate would somehow be washed out with the condensate?

[Donkey]

It shouldn't be too hard to install a cleaning hatch of some variety.

It's all entirely fantasy at this point... It needs testing to find out if it would even work at all.

[photoman290]

anyone looked at cyclones to remove the mineral emissions? they may work passively. i don't know enough about them. did a lot of research on hydrocyclones to clean up WMO. would need to know the flow rates to calculate if they would work. easy things to make, well if you can build a RMH you should be able to make a cyclone.

[patamos]

I've been thinking along the lines of adobe bells too. Perhaps embedding soaker hose in the cobb/adobe and having some kind of moisture sensor/control to keep the material from wetting out.

Regarding reheating the exhaust for the sake of draft, having a bypass flue near the initial downdraft could make that work. I've just completed one with the damper installed into the galvy T, and there are enough holes in and around the damper to keep letting a bit of warm exhaust through. Changing the angle at which it meets the downdraft flow can adjust the effect. These bypass flues also resolve many (if not all?) of the cold start issues, which means the system can be tweaked for maximal heat harvesting when warmed up.

With all this wondering we are doing, i am still curious to know how true is the initial assumption that 'the fine particles are bound to the exhaust gas stream'?
Running a comparison between 3 RMHs with identical fire chambers and downdraft arrangements, but one with no mass harvesting, one with metal flue runs in mass, and one with adobe flue runs in mass... could tell us a fair bit

well being

pat

[Vince Runza]

Mar 2, 2014 10:02:54 GMT -8 photoman290 said:

anyone looked at cyclones to remove the mineral emissions? they may work passively. i don't know enough about them. did a lot of research on hydrocyclones to clean up WMO. would need to know the flow rates to calculate if they would work. easy things to make, well if you can build a RMH you should be able to make a cyclone.

They seem to work fine on coarse material. The problem is the stuff below 10μ. Perhaps an electrostatic precipitator, powered by house current or a Peltier junction (TEG, etc.) for those who are off-grid. The question is, after you cut the current (or when the stove cools down and the current drops), does the fine particulate matter waft into the chimney, to be expelled the next time you fire it up?

[doggy1969bc]

if it is wet you can poor it out around the house to keep ants away, or use it to make mortar like the roman's did, mix it with clay
make brick or statues

[chazvan]

Looks like this thread has not been active for a while. I think the issue is still around though.

I am not yet in a position to test anything (no rmh at this time). I have had some experience with semiconductor manufacturing and cleanrooms in the past were fine particulate was of utmost concern for defect reasons, not health concerns.

HEPA then ULPA filters are the primary method of removal. Air flow through them is a function of pressure differential so either a really big filtration area or a boost fan would be needed to filter the exhaust of an rmh.

Electrostatic perciptators were another item commonly used. High voltage was applied to a very sharp point to create corona discharge to generate negative ions that would charge any fine particulate so they would collect on oppositely charged surfaces. No air flow restriction in this case.

I have sold used SMOG HOGs which are industrial sized electrostatic filters like what used to be found in some residential forced air HVAC systems. High voltage applied to really fine wires in the air flow and particulate then collects on oppositely charged plates that are washed clean now and then.

Along the lines of the misting mentioned several times, wet spray scrubbers were used to remove fumes from the air stream that were the result of chemical processes. This was acting at the molecular level. I don't know how it would work on large but still micron sized particulate.

I have equipment that could be used to try some of this once I have a functional rmh.

[DCish]

Exciting stuff, chaz! Great to see someone with your technical and practical knowledge in this area join the conversation.