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Activated carbon granules and pellets are cheap. Making them into a useful air filter is tricky. The current commercial methods are:
to fill a honeycomb (an idea I had but found out that it's been patented).
to make a cylindrical filter with granules poured in.
to bind finely ground activate carbon
to a foam substrate.
My new approach is to make a semi-rigid filter that can be used is situations that the foam type filters can be used.
The carbon surface area of my filter would be considerably higher.
1) Pour a single layer of granules into tray. 2) Place on top a sheet of HDPE mesh. Repeat to the desired filter depth. Add a weight on top to compress the granule/mesh stack.
Bake at the HDPE melting point.
The HDPE melts and bonds the granules together.
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Wouldn't the HDPE (when molten) tend to wet the
granules, and then seal them? |
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Two things, one MB just partly covered. |
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First, he "activated" portion of the carbon is
related to it's increased surface area. If you melt
plastic onto it, it's area goes down, losing some of
the benefit. |
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Second, I suspect, without definite information,
that "baking" activated charcoal will cause it to
lose much of it's efficacy, since it will do most of
it's adsorption during that heating. This could
partially be corrected by performing this in an
inert (possibly) or evacuated environment,
except: |
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Second.2: Baking/melting HDPE will out gas all
sorts of molecules of the sort that activated
carbon is used to adsorb, so even the evacuated
environment won't be enough. |
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I'm sure the Odor was one of the Dambuster's targets.. |
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I chose HDPE due to its low melting point (around 130'C - easily achievable in a domestic oven). The baking is a more of a reference to doing this at home.
Controlling the temp is vital, yes. One wants it just soft enough to bond the granules. Blocking some of the pores is inevitable. I'm proposing this more as an alternative to the reticulated foam filter whose carbon has a large portion of its surface bonded to the foam and whose ratio of carbon to substrate is relatively low. Here the ratio would be considerably higher, albeit at the cost of physical robustness. |
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Heating at low temp (105'C) is the first stage in regenerating activated carbon. Heating to 130'C won't affect the carbon's performance.
Some gas will be given off by the plastic but we're moving from solid to liquid and for only as long as it takes to become tacky. I don't believe the gas given off will affect the carbon's performance to any significant degree. |
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Or just stick the charcoal to a thin layer of epoxy? |
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Or just stick the charcoal to the odorous person directly? |
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Filling cardboard tubes is something that the patented filling honeycombs does. The issue this tries to resolve is the settling of the granules due to gravity and abrasion breaking them up.
By holding the granules in a regular, stable matrix we maximise airflow through the filter and contact with open ac pores We also minimise abrasion and allow the filter to be orientated in any direction. |
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I'm going to have to go the whole bakery on this one. I devised this because all the ingredients are freely and cheaply available. (insect meshes of various sizes and thermoplastics, ac granules and pellets for fish filters).
I've sat on the idea for 6 months and done nothing with it so I figured I get it on here to stop someone from patenting it.
I'll probably end up £30 out of pocket with a mess to clear up in the kitchen. |
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Just had a search and found that since I was looking at this another honeycomb type filter has come on the market. This time it's ceramic and carbon extruded then baked at high temp for a prolonged period. |
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I put a handful of activated carbon granules in my
cyclonic vacuum cleaner once, thinking "this stuff will
whizz around the periphery of the clear bit and do
wonderful things for that vague milk smell that's
plagued this inherited vacuum since day 1" What
actually happened was that the carbon smashed itself
to bits, I had to buy a new HEPA filter and my flat
mate gave me a "you've been messing around with
things that work perfectly well again" look. |
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