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Little_Ghost_again
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Calcium Oxide from sea shells
Hi,
I have been reading and came across a reference to calcium oxide in times gone by, being made from crushed sea shell's. As I live 4 miles from a
deserted fabulous beach full of sea shells, this has me thinking.
Apparently the shells are crushed and heated to above 850C, the time of heating wasnt given however. We have a very small granite stone kiln we built
outside last year, it has been used for melting lead for fishing weights and some Aluminum. The fuel source was dried pine cones (what else  ) that burn very hot and are fairly dense in a way similar to hard wood, they are
also a renewable source.
The kiln is fanned from several small high powered 12V fans run from a leisure battery. I am confident I can reach and maintain the temperature but I
am not sure for how long this needs to be done.
While I would wash the shells well in tap water, I am pretty sure any organic material would simply burn off or at most be converted to carbon.
Calcium oxide looks like a neat desiccant and while not overly expensive 500 grams on ebay with postage is around £7.
So any idea how long the >850c needs to be held for? I might make a 2 KG batch and store in several smallish containers. I also need another
crucible as the last one got broken.
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DJF90
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Plante1999 has done this exact preparation and reported his results in the Prepublications forum.
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Little_Ghost_again
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Quote: Originally posted by DJF90  | | Plante1999 has done this exact preparation and reported his results in the Prepublications forum. |
Ok thank you I will go have a look
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Magpie
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Plante specifies 800°C for one hour. I have made CaO from garden lime [very cheap source of slaked lime, Ca(OH)2] a number of times. IIRC I used
conditions very similar to that of Plante.
This makes a nice experiment for the use of a little chemistry math. Weigh your lime before and after heating. Then see if the weight loss matches
the theoretical loss obtained by calculation using molecular weights.
The single most important condition for a successful synthesis is good mixing - Nicodem
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metalresearcher
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| Quote: Originally posted by Magpie | | Plante specifies 800°C for one hour. I have made CaO from garden lime [very cheap source of slaked lime, Ca(OH)2] a number of times.
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Indeed that worked for me too. Just a bag of garden (?) lime from the hardware shop. I heated 500g in a Kanthal furnace for an hour to 700C and I saw
some plumes of water escape.
I used it for arcing it with bbq charcoal to make CaC2 whcih succeeded.
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aga
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Wow !
What arc did you use ?
A stick welding rig ?
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Little_Ghost_again
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| Quote: Originally posted by Magpie | Plante specifies 800°C for one hour. I have made CaO from garden lime [very cheap source of slaked lime, Ca(OH)2] a number of times. IIRC I used
conditions very similar to that of Plante.
This makes a nice experiment for the use of a little chemistry math. Weigh your lime before and after heating. Then see if the weight loss matches
the theoretical loss obtained by calculation using molecular weights. |
Some of the shells like mussel and razor clam will have organic material, I could burn that off with a bunsen I guess.
But yes it will be interesting to see the results. A couple of questions that have arisen from a cryptic conversation with my dad........
I am assuming that shells are calcium carbonate, I mentioned this to dad and he smiled and asked if I was sure??? Looking at a shell under the
microscope I think I am wrong. So working on an assumption I think there s some magnesium carbonate in there as well, there is definitely something
other than calcium carbonate because I can see two crystal like structures that are different (mag Oil Immersion 1400x with phase contrast no stain).
So if I assume mag carbonate my question is there a test to distinguish magnesium and calcium carbonate?
Its not that I think it will matter, but I would like to know. Not sure what our home built stone kiln/roket stove can do temperature wise,but we have
a IR thermometer that goes upto 1200C and it easily passes that! its pretty efficient on dry large pine cones, I burnt around 30Kg of cones last year
melting a load of aluminum cans! Actually I ended up with 31Kg of aluminum! Mostly cans I picked up on our road verge and the lay by near us, also the
beach had loads and the can recycle bank is full most days, so people just put bags of cans by the side. I pick them up and store until dad gets fed
up falling over cans lol.
Anyway weighed the aluminum in and it paid for a new function generator .
All the ash that was left came to under 500g! The inside of the kiln is lined with lime and fire fibre mix (no idea what it is made of). I want to
build a slightly bigger one this winter.
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careysub
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| Quote: Originally posted by Little_Ghost_again | | Quote: Originally posted by Magpie | Plante specifies 800°C for one hour. I have made CaO from garden lime [very cheap source of slaked lime, Ca(OH)2] a number of times. IIRC I used
conditions very similar to that of Plante.
This makes a nice experiment for the use of a little chemistry math. Weigh your lime before and after heating. Then see if the weight loss matches
the theoretical loss obtained by calculation using molecular weights. |
Some of the shells like mussel and razor clam will have organic material, I could burn that off with a bunsen I guess.
But yes it will be interesting to see the results. A couple of questions that have arisen from a cryptic conversation with my dad........
I am assuming that shells are calcium carbonate, I mentioned this to dad and he smiled and asked if I was sure??? Looking at a shell under the
microscope I think I am wrong. ... |
Biological structural materials usually have nanostructure patterning that make them look different from minerals with similar composition - part of
the evolutionary engineering that gives them superior physical properties .
If you are going to calcine them all of the organic materials (like chitins, proteins, etc) that may be incorporated into the structure are going to
disappear.
Looking at one source that looked at the mineral composition of calcined mussel and oyster shells:
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S...
we see that mussel shells are 95.6% CaO, with roughly similar amounts of seven other minerals (0.4 to 0.9%), while oyster shells are almost pure CaO -
98.2%.
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Zyklon-A
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You can read about it here:http://www.sciencemadness.org/talk/viewthread.php?tid=27475#...
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Bert
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If you are intending to re-create traditional building materials?
http://homescale.wordpress.com/makinglime/
Be sure to wash all the sea salt off the shells, especially if you're going to use steel mesh or bars in concrete work.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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blogfast25
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Have a look at this for a better understanding of the relation between temperature and CO2 partial pressure, when calcining CaCO3 to lime and CO2:
http://en.wikipedia.org/wiki/Calcium_carbonate#Calcination_e...
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Little_Ghost_again
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Thanks guys for the links.
I dont want it to build with, I just thought it would be handy to have and a fun thing to do. It also gives me an excuse to fire up the kiln
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Actinium
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How fast does Ca(O) turn back into Ca(OH)2 ?
Doesn't it re-hydrate quite fast?
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blogfast25
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Not if stored properly.
But the reaction between fresh quicklime (CaO) and actual water can be quite vicious and needs to be done carefully. It was in Roman times one of the
less enjoyable jobs to turn quicklime into slaked lime, allegedly...
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Bert
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| Quote: |
the reaction between fresh quicklime (CaO) and actual water can be quite vicious
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A Mason jar full of quick lime with a few small holes punched in the lid has been used for fishing by resourceful hillbillies without access to
dynamite... Throw it in the water, it sinks to the bottom and water enters. As the lime slakes, it heats, water boils and the holes clog from bits of
lime being forced against them from inside. The eventual steam explosion of the jar may be sufficient to stun fish.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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macckone
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| Quote: Originally posted by Bert |
| Quote: |
the reaction between fresh quicklime (CaO) and actual water can be quite vicious
|
A Mason jar full of quick lime with a few small holes punched in the lid has been used for fishing by resourceful hillbillies without access to
dynamite... Throw it in the water, it sinks to the bottom and water enters. As the lime slakes, it heats, water boils and the holes clog from bits of
lime being forced against them from inside. The eventual steam explosion of the jar may be sufficient to stun fish. |
Have you been spying on my fishing?
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Actinium
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| Quote: Originally posted by Bert |
| Quote: |
the reaction between fresh quicklime (CaO) and actual water can be quite vicious
|
A Mason jar full of quick lime with a few small holes punched in the lid has been used for fishing by resourceful hillbillies without access to
dynamite... Throw it in the water, it sinks to the bottom and water enters. As the lime slakes, it heats, water boils and the holes clog from bits of
lime being forced against them from inside. The eventual steam explosion of the jar may be sufficient to stun fish. |
My friend from W. Va will love this one
See Chemistry has very practical applications.
Now as far as drying the Ca(OH)2 > Ca(O) since I no longer have my kiln, will a torch suffice? If so I would use the bottom of a wine bottle so as
not to ruin my precious glassware for this.
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blogfast25
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| Quote: Originally posted by Actinium | | Now as far as drying the Ca(OH)2 > Ca(O) since I no longer have my kiln, will a torch suffice? If so I would use the bottom of a wine bottle so as
not to ruin my precious glassware for this. |
It'll be borderline as the dehydration of slaked lime only starts at about 512 C.
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Little_Ghost_again
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Maybe you could use the fire bricks (slates) from inside something like a old broken wood burning stove.
Our MK2 kiln will use these to line inside the stone, we have no way to measure such high temps but I know the MK1 got extremely hot as the 1/2 inch
steel sheet that the crucible was stood on melted!
The new Mk2 now under construction is going to use a fan from a kids small bouncy castle.
The air out put is very impressive, for control I am going to add a variac, this way I can control the amount of air going into the kiln.
Sone of the conifer trees in our wood produce huge 10" long pine cones (I use inches on here because most of you do, I prefer metric so if I get the
sizes wrong sorry). When these cones are dry the are extremely dense, they make idea fuel for rocket stoves and kilns like this.
Our kiln designs have a burning chamber that is just behind the main flue, we place the object to be heated 6 inches up inside the flue. Just behind
the fire chamber is the fuel box, this is where we put the cones, we can then poke them into the fire chamber and close the stone lid on the fire box.
What we found was as long as the flue (chimney) was 3 x the height as the fire box is long, then you get a massive updraft through the flue, this
really gives a good draw on the fire. Add in extra air via a fan or whatever and you can get really high temperatures, most the rock around here is
granite with marble here and there, we also have a area with lime stone but for the kiln we use the granite.
Everything is then rendered with cement and the fire fibre mix, then the fire bricks/tiles from wood burners go in front of this.
Hope that helps someone.
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Refinery
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Calcium hydroxide decomposes to oxide at 550-600C, while calcium carbonate needs 850-900C, but practically it is necessary to take the temp over
950-1000C to make the reaction fast. I have made CaO with electric furnace from calcium carbonate, and when temperature reached 1000C, the mass was
fully decomposed to the extent I could measure it.
I made a furnace on a small 60 liter steel drum. I cut it about 1/3, put some pearlite clay on bottom of it, placed two firebricks on top of them, sat
a plastic bucket in the middle and poured calcium sulfate plaster. When it dried, I made holes for nichrome wire and casted the 1/3 drum head full of
plaster with couple of reinforcing bars that act as a handle too, mantled the whole setup in 150mm thick rockwool slab and dumped it into a 208l drum.
It has to be heated very carefully at first time and ideally it should be placed into oven at 60C for 4-6 hours and then for 100C for another 4 hours,
and then slowly heated to operational temperature to drive out the moisture contained in the plaster. It may still crack, but the drum keeps it
together and once it's cracked, thermal expansion wont hurt it anymore. It can withstand 1300c temps continously.
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Little_Ghost_again
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Electric is expensive here, mostly we run from a diesel generator. Also I like the idea of running from a renewable fuel. We have a 8 acre commercial
plantation of spruces etc as part of our woodland. Pine cones litter floor everywhere here! Dried out the are very dense and burn like a really good
hardwood.
Add a good blast of air and 1000C is not hard to achieve. I like the idea of your electric one and if electric was cheap here I would tempted because
I could combine it with my love of electronics to make a control system! But its just easier and cheaper for us to use a granite wood fired kiln.
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blogfast25
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| Quote: Originally posted by Little_Ghost_again | | Add a good blast of air and 1000C is not hard to achieve. I like the idea of your electric one and if electric was cheap here I would tempted because
I could combine it with my love of electronics to make a control system! But its just easier and cheaper for us to use a granite wood fired kiln.
|
Fairly easy: lots of fuel and lots and lots of air. It'll melt copper quite easily if you push it.
But bear in mind that a wood or coal based fire will be quite rich in CO<sub>2</sub>, as one of the sources above indicated. This tends to
push the equilibrium CaCO<sub>3</sub>(s) < === > CaO(s) + CO<sub>2</sub>(g) to left again (while temperature ushes it to
the right).
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Bert
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Pine cones should make for a quite luminous fire- Perhaps you should explore harnessing that?
Reverberatory furnace
Traditional lime burning
[Edited on 22-9-2014 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Little_Ghost_again
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Little_Ghost_again | | Add a good blast of air and 1000C is not hard to achieve. I like the idea of your electric one and if electric was cheap here I would tempted because
I could combine it with my love of electronics to make a control system! But its just easier and cheaper for us to use a granite wood fired kiln.
|
Fairly easy: lots of fuel and lots and lots of air. It'll melt copper quite easily if you push it.
But bear in mind that a wood or coal based fire will be quite rich in CO<sub>2</sub>, as one of the sources above indicated. This tends to
push the equilibrium CaCO<sub>3</sub>(s) < === > CaO(s) + CO<sub>2</sub>(g) to left again (while temperature ushes it to
the right). |
Now thats interesting! Does using charcoal lower the CO2? Although I am not too sure how easy it is to turn cones into charcoal!
Probably the best approach is to go for maximum heat. The other thing is the shells will be in a crucible rather than amongst the fuel, I doubt that
is going to make any difference with CO2 though.
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vmelkon
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| Quote: Originally posted by Little_Ghost_again | | Quote: Originally posted by blogfast25 |
Fairly easy: lots of fuel and lots and lots of air. It'll melt copper quite easily if you push it.
But bear in mind that a wood or coal based fire will be quite rich in CO<sub>2</sub>, as one of the sources above indicated. This tends to
push the equilibrium CaCO<sub>3</sub>(s) < === > CaO(s) + CO<sub>2</sub>(g) to left again (while temperature ushes it to
the right). |
Now thats interesting! Does using charcoal lower the CO2? Although I am not too sure how easy it is to turn cones into charcoal!
Probably the best approach is to go for maximum heat. The other thing is the shells will be in a crucible rather than amongst the fuel, I doubt that
is going to make any difference with CO2 though. |
Charcoal has a lot of carbon of course and as you burn it, it produces CO2. I imagine the ratio CO2 to H2O is higher for charcoal compared to wood
which has moisture and carbohydrates and cellulose.
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