rogeryermaw Posted September 27, 2015 Posted September 27, 2015 It is a fairly common practice, at least in amateur chemistry labs, to use chemical desiccation to dry reagents and such. Is this a viable technique for drying finicky charcoal stars? Perhaps in a sealed bag with cup of NaOH Or H2SO4?
Mumbles Posted September 27, 2015 Posted September 27, 2015 I would only use it to finish off drying difficult compositions. Desiccators really aren't designed to do bulk drying. They more commonly keep dry reagents dry, finish off removing water, and help preserve water sensitive chemicals. If you put freshly cut/rolled/pumped stars in a desiccant chamber, there is a decent risk of driving them in due to the rapid effect strong desiccants have. 1
rogeryermaw Posted September 28, 2015 Author Posted September 28, 2015 thanks Mumbles! so such a method may be suited more to helping the last couple days of drying in very humid environments?
Arthur Posted September 28, 2015 Posted September 28, 2015 As fireworks are usually designed for cheapness I'd doubt that desiccator drying is viable as usually the desiccant is used and likely not recyclable. 1
PIL Posted September 28, 2015 Posted September 28, 2015 Anhydrous calcium chloride can be used over and over again .All you need to do is to heat up the hydrated salt . 1
rogeryermaw Posted September 28, 2015 Author Posted September 28, 2015 Anhydrous calcium chloride can be used over and over again .All you need to do is to heat up the hydrated salt .If you can get it out after it turns into a solid block. I use calcium chloride to dry gasses through a wash bottle when appropriate and there have been times I've had to throw the bottle away.
marks265 Posted September 28, 2015 Posted September 28, 2015 There are a couple of ways to dry using desiccant which I think would be a little expensive but doable for a hobbyist. Well, one would be really expensive I guess. Train cars have air dryers that work using just ambient air with little heat which is really hard to imagine but still true. I've installed one for a powder coat paint line which needed dry air. This was really meant for compressed air and an example found here. The one I installed may have had no heating elements, that was a few years ago so don't remember exactly which unit it was. A second way would be to recirculate air through a bed of desiccant that has an electric heating element buried in the media and uses a temperature controller to control the heat to a certain temperature. A small amount of air is allowed to bleed off which would take the moisture with it. So the air would have to circulate through the bed and then the dry box and back to the bed again. Again a small amount of air is allowed to enter the system as well as bleed off. You can easily get down to a dew point of -20 to -30. Some systems such as this use media something close to what resembles clay beads. A large industrial version would cycle between two beds. One media bed removes moisture from the product while the other bed regenerating itself by removing residual moisture with no air circulating through the product that is being dried. An industrial system example can be found here. Mark
MadMat Posted October 7, 2015 Posted October 7, 2015 I made a vacuum chamber using an old compressor from a window air conditioning unit http://www.amateurpyro.com/forums/topic/11050-vacuum-drying-chamber/. Today, I put in a batch of glitter stars that had dried for 5 days, but after cutting one open it was still "gushy" on the inside. I applied the vacuum slowly over a 10 minute period. If I would've hit it with a hard vacuum all at once, I was afraid the water boiling out of the center of the star would "blow up" the stars. (as the vacuum increases the boiling temperature of water goes down). After one hour, the stars were dried throughout.
Arthur Posted October 7, 2015 Posted October 7, 2015 My limited experience using a refrigeration compressor as a vac pump was not good. The fumes carried into the pump locked the works up in one working day -made it a bit expensive.
Col Posted October 8, 2015 Posted October 8, 2015 (edited) I dont think fumes would harm much, maybe all the oil got pumped out or perhaps there wasnt any in it I use them as air compressors not vacuum pumps. Edited October 8, 2015 by Col
MadMat Posted October 8, 2015 Posted October 8, 2015 (edited) Yeah, you got to make sure there's oil in them. that is also another thing you have to be aware of if using them for a vacuum pump; you have to have a diverter valve of some sort to release the vacuum from the chamber before turning off the pump or the chamber will get an oil shower. I've had great results using an old window a/c compressor; it can pull a vacuum up to 27-28 " Hg. Expensive? I paid nothing for mine. It was a throw-away because the evaporator coil had developed a leak, but the compressor was fine. The bonus to that was it wasn't my responsibility that freon had leaked into the atmosphere. Edited October 8, 2015 by MadMat
MrB Posted October 10, 2015 Posted October 10, 2015 The bonus to that was it wasn't my responsibility that freon had leaked into the atmosphere. Actually. While i don't condone it, i wouldn't be losing sleep over spilled freon gas. As far as i know a lot of asthma inhalers still use freon as the pressurizing agent. More gas is dumped from these straight out in to the environment then any refrigerator holds, or any car leaks. Yet they want to replace the car gas with what essential is camping stove gas... but ignore the inhalers. Politicians... They should be kept as far away from important stuff as possible.B! 1
Recommended Posts