Have been reading about mining and mineral processing, and about separating the valuable parts from the rest. Which led me to wonder about the following.

How would you separate a very viscous liquid from a finely-divided suspended solid? You couldn’t simply sieve it because the holes in the sieve would quickly clog with the viscous liquid, and you couldn’t just let it sediment out or centrifuge it because it would take too long.

Let’s make the question more specific. For a thought experiment (or a real experiment if you prefer), mix 50:50 a thick honey with a fine sand. You are not allowed to change the viscosity of the honey by heating or diluting it. How would you go about separating the two as completely as possible?

mollwollfumble said:

Have been reading about mining and mineral processing, and about separating the valuable parts from the rest. Which led me to wonder about the following.

How would you separate a very viscous liquid from a finely-divided suspended solid? You couldn’t simply sieve it because the holes in the sieve would quickly clog with the viscous liquid, and you couldn’t just let it sediment out or centrifuge it because it would take too long.

Let’s make the question more specific. For a thought experiment (or a real experiment if you prefer), mix 50:50 a thick honey with a fine sand. You are not allowed to change the viscosity of the honey by heating or diluting it. How would you go about separating the two as completely as possible?

vibrate them possibly

the sand might settle the sand in stratas within the liquid

mollwollfumble said:

Have been reading about mining and mineral processing, and about separating the valuable parts from the rest. Which led me to wonder about the following.

How would you separate a very viscous liquid from a finely-divided suspended solid? You couldn’t simply sieve it because the holes in the sieve would quickly clog with the viscous liquid, and you couldn’t just let it sediment out or centrifuge it because it would take too long.

Let’s make the question more specific. For a thought experiment (or a real experiment if you prefer), mix 50:50 a thick honey with a fine sand. You are not allowed to change the viscosity of the honey by heating or diluting it. How would you go about separating the two as completely as possible?

Feed it to chooks, then separate the sand from the chook poo.

Not terribly practical perhaps, but the best I can do at the moment.

maybe you could blow air through the mix and turn it into bubbles and try to extract the foam from the sand that way

ants(also an amusing method of getting honey off body parts)

you throw sugar in the grass where vagrants and other undesirables gather (if they are causing trouble)

i think the solution for honey-sand example has to translate into the solution for the “real thing”, so ants and chooks probably wouldn’t work.

centrifuge of some description.

A filter combined with suction from below/pressure from above would probably do the trick.

ChrispenEvan said:

i think the solution for honey-sand example has to translate into the solution for the “real thing”, so ants and chooks probably wouldn’t work.

centrifuge of some description.

he says that’s not an option

you could always spray the stuff into a large chamber

the sand and honey might travel different distances as they separated

electrolysis then. have the suspending fluid neutral if the product can be charged or vice versa.

you could have a candy floss machine

the sprayed mix might separate the honey from the mix

the honey might slow faster than the sand which collects on the side of the container

wookiemeister said:

you could have a candy floss machine

the sprayed mix might separate the honey from the mix

the honey might slow faster than the sand which collects on the side of the container

as

the liquid is sprayed from a rotating nozzle

the sand is sprayed towards the side of a container

the honey spreads and slows in the air

the sand being smaller, denser hits the side of the container

strictly speaking you aren’t changing the density or heating it but you are separating quickly

its the air resistance of the sand and the nature of the honey that separates them

you could have a candy floss machine

the sprayed mix might separate the honey from the mix

the honey might slow faster than the sand which collects on the side of the container

isn’t that like how a centrifuge works?

candyfloss machines heat the material

ChrispenEvan said:

you could have a candy floss machine

the sprayed mix might separate the honey from the mix

the honey might slow faster than the sand which collects on the side of the container

isn’t that like how a centrifuge works?

not really

the difference is that you are using the difference between the air resistances between materials

if you wanted you could have a stationary nozzle and get the same result

Riff-in-Thyme said:

candyfloss machines heat the material

only the stuff that hits the wall

he said that you can’t heat the honey – he didn’t say the sand

wookiemeister said:

Riff-in-Thyme said:

candyfloss machines heat the material

only the stuff that hits the wall

he said that you can’t heat the honey – he didn’t say the sand

how is the honey not going to hit the walls?

same principle though. not all centrifuges work like the ones you see in med labs.

Hydrocyclone”:http://en.wikipedia.org/wiki/Hydrocyclone

Riff-in-Thyme said:

wookiemeister said:

Riff-in-Thyme said:

candyfloss machines heat the material

only the stuff that hits the wall

he said that you can’t heat the honey – he didn’t say the sand

how is the honey not going to hit the walls?

because the honey is less dense than the sand and will turn into a mist the sand continues onwards

strictly speaking the hiney doesn’t change density if you examined each clump of honey it would still be of a certain density

wookiemeister said:

Riff-in-Thyme said:

wookiemeister said:

only the stuff that hits the wall

he said that you can’t heat the honey – he didn’t say the sand

how is the honey not going to hit the walls?

because the honey is less dense than the sand and will turn into a mist the sand continues onwards

strictly speaking the hiney doesn’t change density if you examined each clump of honey it would still be of a certain density

It would need to be a very large candyflosser and the spray would require a high pressure. Still don’t know how effective it would be

ok think of it this way

lets say you pumped up the pressure in a hose with water

as the water leaves the nozzle , assuming its the right nozzle, the water turns into a mist right? any dirt in the water will travel forwards further than the mist

no heating

Riff-in-Thyme said:

wookiemeister said:

Riff-in-Thyme said:

how is the honey not going to hit the walls?

because the honey is less dense than the sand and will turn into a mist the sand continues onwards

strictly speaking the hiney doesn’t change density if you examined each clump of honey it would still be of a certain density

It would need to be a very large candyflosser and the spray would require a high pressure. Still don’t know how effective it would be

well we’re assuming industrial strength here

in powerstations you have huge washing machine arrangements that tumble coal and ball bearings around to crush the coal into powder

either way you’d probably still have some honey on the sand

wookiemeister said:

either way you’d probably still have some honey on the sand

I think this is really a question best answered by morrie, our resident materials handling and materials separation expert. I’d certainly like to see his ideas on this one.

>A filter combined with suction from below/pressure from above would probably do the trick.

Aye, a piston thingy squishing it down through a filter that will trap the sand.

Bubblecar said:

>A filter combined with suction from below/pressure from above would probably do the trick.

Aye, a piston thingy squishing it down through a filter that will trap the sand.

Sounds promising.

any system that requires pressure is heating the honey(piston or candyfloss machine)

Riff-in-Thyme said:

any system that requires pressure is heating the honey(piston or candyfloss machine)

not to any appreciable level

you could always do something crazy like cool the mix before the pressure is applied and thus keep the temp the same as before

as far as I read from the original post NO filters

>as far as I read from the original post NO filters

No, that’s not a rule, he just doesn’t think it would work. But with sufficient pressure and getting all the tolerances and materials right, it would.

My proposal would be to simply stick the mixture in a large container with small outlets at the bottom of said container. If the nozzling of these outlets are pointed upward, the honey will drain and drag a minimum of sand with it. This would require a sequential arrangement to progressively remove the sand.

Bubblecar said:

>as far as I read from the original post NO filters

No, that’s not a rule, he just doesn’t think it would work. But with sufficient pressure and getting all the tolerances and materials right, it would.

in that case you could have a big filter and just pump it in regardless what he thinks

Riff-in-Thyme said:

My proposal would be to simply stick the mixture in a large container with small outlets at the bottom of said container. If the nozzling of these outlets are pointed upward, the honey will drain and drag a minimum of sand with it. This would require a sequential arrangement to progressively remove the sand.

hey you’re trying to nick my idea you bastard

only joking

I imagine how this sort of thing is done industrially (not with honey & sand specifically :)). Filters and pumps.

Sandwich the honey/sand mixture between two large flat surfaces. Apply pressure until the surfaces are only one sand grain apart. Turn the whole lot to vertical so the honey can drain leaving the sand between the plates.

I imagine how this sort of thing is done industrially = I imagine this is how this sort of thing etc

Teleost said:

Sandwich the honey/sand mixture between two large flat surfaces. Apply pressure until the surfaces are only one sand grain apart. Turn the whole lot to vertical so the honey can drain leaving the sand between the plates.

Trouble is, you’d end up squashing sand grains against each other, breaking them into even finer particles.

True, and I think the surface tension of the honey would also present problems with draining.

What if the two plates had slightly spongy bot non porous surfaces? The sand would get trapped and the honey forced out.

bot=but

Teleost said:

True, and I think the surface tension of the honey would also present problems with draining.

What if the two plates had slightly spongy bot non porous surfaces? The sand would get trapped and the honey forced out.

If you’re using filters, why bother with two plates? Just pump the stuff through a filter.

Gotta be a centrifuge, Moll.
If you make the holes small enough to block the sand they’ll still be big enough to pass the honey. Spin it up to make pretty serious G’s on the mesh and it will work.

Some of the larger stationary diesel engines just a centrifugal filter system to pre-filter the oil or particulates/sediments before the oil passes through the regular paper filter and they work quite well. I’ve got one here in fact but it’s off a 19080’s Toyota Landcruiser diesel.

Riff-in-Thyme said:

My proposal would be to simply stick the mixture in a large container with small outlets at the bottom of said container. If the nozzling of these outlets are pointed upward, the honey will drain and drag a minimum of sand with it. This would require a sequential arrangement to progressively remove the sand.

If the interior of this container were lined with horizontal plates that drained the mixture through the container at the sides and center sequentially it would seperate.This would at the very least provide a mixture that could be filtered with less maintenance.

Soap and bubbles…

Scenario 1:

Solid bowl centrifuge for the initial separation. You comment about it being too slow isn’t really correct. At the speed these things run, it will happen very quickly.
That will leave you with a cake that will be about 60% solids by volume. You might be able to get this up a little with a basket centrifuge but not for really fine stuff.

From that point you are going to have to introduce a step to get rid of the remainder of the viscous liquid. Depending on it’s worth, a solvent extraction step with filtration and solvent recovery is probably the most straight forward.

There are various permutations of this overall approach. Or you could do the whole process with solvent extraction/filtration/solvent recovery.

Scenario 2

Depending on the surface properties of the sand in relation to the viscous liquid, it might be possible to introduce a third phase of lower viscosity. Agitate and do a phase transfer operation into the lower viscosity liquid. I did some trials on a process like this once. The use of surface active agents like stearic acid can help this sort of process.

Oh, morrie! I don’t think you were supposed to be sensible about it!

;)

Sorry buffy. I only skimmed through the thread. :)

you could always spray downwards the honey becomes a mist and is drawn away by a fan the sand falls downwards

you’d have this arrangement in a tower

mollwollfumble said:

Have been reading about mining and mineral processing, and about separating the valuable parts from the rest. Which led me to wonder about the following.

How would you separate a very viscous liquid from a finely-divided suspended solid? You couldn’t simply sieve it because the holes in the sieve would quickly clog with the viscous liquid, and you couldn’t just let it sediment out or centrifuge it because it would take too long.

Let’s make the question more specific. For a thought experiment (or a real experiment if you prefer), mix 50:50 a thick honey with a fine sand. You are not allowed to change the viscosity of the honey by heating or diluting it. How would you go about separating the two as completely as possible?

Well, in my mineral processing lab we do use centrifuges. Then we use filters. Then we wash the solids with a solvent, from which we can later recover the heavy liquid for reuse.