Sand Pot, could it be a salt replacement.

Ok guys I have been back at it and I think I actually have some useful information now. I located a company that makes them for labs. Thy don't go high enough in temp for what we need but thy are rated up to 1100°. But the principle is the same and it gives us a starting point. One thing is quite clear, which I have started to discover in my testing and this is the deeper the pot the larger the Diamater needs to be. I noticed that as I moved the bubbler lower and lower into the sand the bubbles changed and at full depth I had just one big bubble. But closer to the top I had lots of tiny bubbles. I think what's happening is the bubbles are merging as thy are raising. I was not able to get any information about there disturber plate from there site. Here is some screen shots I took to show what I found.

First up is there models and specs for them, you will notice 2 important chunks of data in these specs. First is the size of the pot and second is the max flow rate. Thy just use air and I don't know what thy mean by max flow rate besides that's the max it can adjust to. I would think it would run somewhere between none and max but I don't know for sure but it gives us a starting point. But notice the pot size, if you want deep you get larger. This is also shown in the peters heat treat video. So is it just that people want larger pots with depth or is it that deep pots that are skinny don't work well. I'm more inclined to lean towards the latter after my testing.
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Thy have some good videos on there site that explain some things and how it works. It opened my eyes To the fact that I was going after a fluidizing level that is not practical. If you watch these video I link below you will see that it's fluid but not crazy like I was trying to get. It just slowly allows the basket to sink into the sand. This must not be a problem because look at the specs and the amount of heat control thy have.
https://vimeo.com/154776445

Thy also say thy use 90um aluminium oxide which is .0035. Thy also sell the sand in 100lb buckets but it's pricy at $250. I don't know how it's graded or if its just "medical grade" 120grit aluminium oxide.
Here is there sand thy sell
https://www.instrumart.com/products/39876/accurate-thermal-systems-ats1027-aluminum-oxide

Another thing I noticed is thy are using 304 stainless 14ga welded pots. Thy offer 316ss pots but only if you are doing corrosive stuff. In my research it seemed like 304 can handle heat a little bit better but I never actually found tensile strength at high temps.
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Another thing I noticed while watching some of there videos is that it's normal for sand to shoot out and make a mess lol. So in our design that is to be expected but the rased surround should keep the mess to a minimum. One thing thy have that I never really thought of is a cover, there's is insulated. I don't know if we need one or not but it would not be hard to incorporate one. I think there's is mostly used to control the flying sand.

Here is a PDF for the model I think we are best trying to deplacate 7x25" pot and has a way to control flying sand.
http://accuthermal.com/wp-content/u...SL12-FTBSL26-Fluidized-Bath-brochure-rev7.pdf

So that's it for now but I think we need to look at going to around 8" for our pot size but 6" would be better becaus the price for 8" skyrockets.
 
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Thanks for the link , lot of useful information :thumbup: AO here is much cheaper .I just bye 10kg 100 grit Austria made aluminium oxide , 2$ for 1 kg . This winter will be warm in my garage :) But I need to know how thermocouple measure temp , only on the tip or on all surface ? Any recommendation for thermocouple ? I need one just to measure the temperature inside , not to control ...
I will use longer tube than I need to avoid sand to shoot out and make a mess ...?
 
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JTknives said:
But tiny jets can be problematic as thy can weep sand down into the manifold when there is a pressure drop after a bubble forums.
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Even with the jets directed at a downward angle or with small shields above them or merely holes drilled at a downward angle?
Did I miss the post/explaination why something like Marc's idea in post #46 wasn't being pursued?

Been following this with interest, as I like the idea of using it to forge as well...
 
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Ok guys , I'm ready to build this sand pot .I have everything except thermocouple . But ,because I'm doing this for the first time I have some question if somebody like to answer . I know how and where to install torch/burner but I don t know how big and where to position outlet for flame ? Since I do not know how a temperature sensor ...... thermocouple work/measure temp. /I mind , did they measure only on tip or on all surface which is inside flame ? I have no idea where to install thermocouple ? Like 1 or like 2 on picture ? Most likely I will build two sand oven, one on gas and one on electricity.But first on gas ...I have lots of ideas about the distribution of air inside to try . Of course , I will take picture and write here everything I try ............

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Natlek, All I can tell you is thermocouples read the temp. at the tip. I like your placement #1 better if I were building it. If I get around to trying this build I will also run my air line down the inside of the pot like your thermocouple. I can't see having to seal things entering through the side of the pot when it won't hurt anything running down the inside.
 
Another interesting thing about thermocouples is that if you hook a number of them up in parallel they will read an average temperature.

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Also you don't want to run your air inside your heated chamber from the top. Come in from the bottom so only a small fraction of your air lines are exposed to high heat.
 
Jesse Smith said:
Natlek, All I can tell you is thermocouples read the temp. at the tip. I like your placement #1 better if I were building it. If I get around to trying this build I will also run my air line down the inside of the pot like your thermocouple. I can't see having to seal things entering through the side of the pot when it won't hurt anything running down the inside.
Click to expand...

Thanks for help . If thermocouple read temp. only at tip I can install several of them ........Well ,I have one more thing to solve .Outlet for hot gas/flames .......how big opening I need ? Same as torch Dia. or much smaller ?
And I m looking for some clear plexiglass tube .I think that will be easy that way to experiment/observe sand and air mix ...Maybe I find some small balls to put in sand for better visibility what was happening inside ?
 
kuraki said:
Also you don't want to run your air inside your heated chamber from the top. Come in from the bottom so only a small fraction of your air lines are exposed to high heat.
Click to expand...

Why ? Cold air will cool sand ? Is it not better solution hot air ?
 
Natlek said:
Why ? Cold air will cool sand ? Is it not better solution hot air ?
Click to expand...

I think he is just referring to less pipe exposed to high temps so less pipe is going through thermal cycles. Nothing to do with air temp, just less pipe having a chance to fail from the high temps. I was thinking the same thing, running it in from the bottom would be better with less pipe exposed to high temps.

The unit doesn't use a high volume of air, so even in a short distance I would think the air will get very hot very quick.
 
If I build something like this will solve a lot of problems .But need to invest a lot more money to control temp......... :grumpy: For now I will play with cold sand and air .

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Let the build begin. I noticed these in the recycle bin and could not let them go to waste. Thy seam about perfect for our needs. The one with the flange on both ends will be the actual body of the sand pot. It's 23" long and 12" ID. I then will cut the other one off at around 6" and use that as the sand fence. My first thought is use the bolt holes on the flanges to attach the bottom. And the top will be that same diamater as the flange but will have the center cut out to fit the actual sand pot. The sand pot will get welded to this top sheet and set down inside. The bottom of the pot will sit on fire bricks and the top will sit on the flange so it's supported on both ends. Then I will tank the sand fence and set it on top and bolt the flanges togather. Should save me some work in the long run. I will like it with 2" of kaowool on the sides and top and the bottom is 3" of fire brick. I will weld a chimney on the side out of 316 stainless pipe that comes out then up. Burner port will be at the bottom. I'm planing on having between a 1" to 2" gap between the wall insulation and the stainless sand pot.

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Ok guys we are now on mk3 version. Here is the revision around my tube.
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I have noticed a trend with this technology, secrets. Getting any useful detailed information on fludizided beds is like digging for gold. It will take hours and hours of researching and reading to find one little tidbit of useful info. The biggest guarded secret is the defuser and how it's put togather. After about 4hrs of research I came across a blurp about grog onto of a perforated plate. So then I kept digging deeper and came across a patient specifically for heat treating steel. The talked about "grog" and even said it was 10 mesh aluminium oxide. Ok this works, and is easy to aquire. The great thing about this is like thy talk about the thickness of the grog can be changed to adjust the performance of the sand pot. This large "grog" aluminium oxide settles to the bottom because it's so much larger then the fluidizing AO that it would require crazy amounts of air flow to fludize.

I also found another rid bit of info that was helpful in selecting the fluidizing AL size. Thy say 100-120 um is optimum size, but if you go below 100um uniformity of fluidization degrades. But over 250um the use of gas becomes uneconomical. Thy did not say it would not fludize just that the amount if gas needed is to much. So this gets me wondering if going 120 grit is wrong because if you look at how the screening is broken down you end up with a lot of particles smaller then the optimum .004 to .005 size. The standard grit we can get for a decent price is just not refined enough. I think that's a big problem with my testing of my silica gel, lots of it is crazy fine so the fluidizing is drastically degraded. Tomarow I am calling an aluminium oxide manufacture and we are going to have a chat about there tolerances and our needs.

If we set our range from 100um to 250um we now are sitting at a much more achievable gole for a reasonable price. This is a range from .004 to .010 which with current grading standards puts us around a 80 to 90 grit which is (90 grit = .0035 to .0095) (80 grit = .004 to .0115) but if you look at "120 grit" it's .002 to .0065. So all this being said I continue to dig deeper.
 
Ok so looking at the grading of the different grit sizes it becomes a quickly apparent that you don't get very high percentage of what you want. It's understandable because it would be quite costly to give you 100% of the requested grit size. There is a standard for grading so let's look at it.

Let's start with 120
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So the numbers are interesting. You order 120grit and According to the numbers a maximum of 20% will be caught by that size mesh. So that means up to 20% is larger then 120 grit but smaller then 80 grit. What that's sad because that's the size range we are after. So then we look further down which shows 65-100% can be caught by 170 grit. That's the bulk of the media that's larger the 170 grit but smaller then 120 grit. After that there is a small percentage of fines that are caught by 230grit, but a very small percentage. This means that the bulk of what we want or think we are ordering is less then our desired .004 sizes.

If we now look at a corser grit we can see the numbers shift in out favor. We will start with the stated Maxamum of the 250um aka .010 or 60grit. This means zero percent can be caught by a 60 grit mesh for our needs. This points us to 90 grit according to the numbers.
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This grit gives us a very high percentage of grit in the butter zone. With this grit we don't have anything larger then our max standard of .01 and very little fines. In the grand scheme of the big picture I will take a small percent of fines (<.004) then the same percentage over our max of .010.
Now this should be a standard for any grit that fallows the ANSI B74-12-2001 standard but I'm not sure of quality control when it comes to sources on places like eBay. I am going to order my grit for this company, it's more money but I know what I'm getting in the long run. Another reasion is looking at there retention percentages for a measured batch is quite good and seams tighter and more controlled then it could be.
 
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I have been so caught up in having my sights set on aluminium oxide that I completely over looked another media until I saw it mentioned in a patient. This is silica sand, why of corse how dump of me. If you think about it for a sec it could be perfect as it meets our needs in just about every aspect and then some that I had not thought about. First good quality aluminium oxide is around $100 per 50lbs and not super common so shipping can be pricy. Silica sand is allmost everywhere on the planet. So not only is it cheep but I think it also holds another key aspect that is kinda hidden from view. Shape, the shape of aluminium oxide is sharp and irregular which is good for a blast media but what about for particles that need to slide agents each other. If you look at silica sand it's nice tiny smooth round(ish) grains. Also silica sand has a melting point of over 3000° so temp is not a problem.

I will continue to research this avanue of media and let you know my findings.

Silica sand
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Aluminium oxide
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Ok after more research maybe silica sand is not such a good idea, silica is not so great to breath in :(
 
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