Density of Settled Solids

[TexasCHe]

I have a sluice line carrying solids out to a dewatering lagoon. The water containing the solids circulates in and out of the lagoon slow enough to allow the solids to drop out. I am looking for a method of estimating the desnity of the settled solids in the bottom of the lagoon so I can carry out some additional calculations. Any helo would be welcome.

Thanks

 

[btrueblood]

Depends on the composition of the solids, doesn't it? I.e. lithium carbonate would have a different density than uranium sulfate...

Can you not scoop up a measured volume of the solids and weigh them?

 

[TexasCHe]

Sorry, CaSO4 sludge

 

[btrueblood]

Well, at full hydration CaSO4*2H2O (Gypsum) has a density of 2.32 g/cc according to my copy of the CRC Handbook. Density increases for the crystalline solids as the salt dehydrates, up to anhydride crystal at 2.96 g/cc.

Obviously, the density of a precipitate will depend on the packing as well, so you can safely estimate the 2.32 g/cc as a maximum. A scoopful of whatever is on the bottom will range between that value (full dense solid) and the value for water (i.e. no solids at all) at 1.0.

 

[TexasCHe]

At 145lbs/ft3 that's pretty dense material. I now have a sample and see if we get close to this published density. Thanks for the information!

 

[btrueblood]

"I now have a sample and see if we get close to this published density".

There you go, now you can calculate the packing for your sample. You'll probably find the density increases as the layer size and settling time increases....but only slightly.

 

[bimr]

The density of concrete is 145 lbs/cu.ft. The density of gypsum is probably about 75 lbs/cu.ft.

http://www.fgdproducts.org/Presentations_Indy_11_09/Tue_1330_Larrimore.pdf

 

[TexasCHe]

Okay I'm impressed. Granted this was a down-and-dirty analysis but we collected a sample, cooked it in a 105 C degree over for several hours (ran out of time), and determined the weight to be 325 grams. Transferred it to a graduated cylinder and the dry volume was 270 ml or 75 lbs/ft3. I then added water, created a slurry, and allowed solids to settle. The volume of the settled solids was 260 ml or 78 lbs/ft3.

I'm thinking the CRC test, if I read it, may show to be for packed material to some (large) extent. I have no reason to beleive it would be off but the 2.32 g/cc seems way high at least for my application. Thanks to both of you!

 

[bimr]

If you want to see what it looks like from the air, type:
4832 industrial drive, calvert city, ky
into google maps. That auqamarine color is from a calcium sulfate settling pond.

 

[NDTaware]

Hello: density vs specific gravity.
Just to make things right: density is a number without unit, being a ratio between, say, the mass of a given volume of a liquid and the same volume of water, at a given temperature.
Specific gravity is written as kg/cubic meter, or grams/liter, etc.
Have a look to the document titled "PT-MT units: stop the mess" in

http://www.ressuage-magnetoscopie-penetranttesting-magnetictesting-dpc.info

PATRICK DUBOSC NDT CONSULTANT

 

[TexasCHe]

Aeronautics guys must use a different book.

 

[TexasCHe]

I see it. It looks like there's some segregation of materials. Are yall recycling materials? Our lagoon is at:

30.538037°, -97.075185°

 

[btrueblood]

Tex,

Yes, sorry, thought I was being clearer - CRC handbook lists values for crystalline (or as close as a chemist can get) solids. Thus, it is an upper bound only.

 

[TexasCHe]

That makes sense. In that form I'll bet the density is close to that of concrete.

A little more settling occured over the weekend and I'm at 83 lbs/ft3.

Thanks again

 

[bimr]

At that site, there is a hydrofluoric acid plnat, an HCL plant, and a refrigerant plant. It is the old Pennwalt plant.

The pond is waste products from acid neutalization, mostly calcium sulate. Waste acid from the refrigerant pant is reacted with a waste lime from an adjacent carbide plant. The pond allows the calcium sulfate to settle out. THe gypsum is added to one end of the pond and water is taken off on the other end.

I understand that the locat road crew is recycling the calcium sulfate.