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Posts tagged freeze drying
Freeze dryer info
Jan 2nd
When ice sublimates in a vacuum (that’s the process where by ice goes directly to water vapor without first melting), it requires heat (just like when you sweat and the sweat evaporates, the process of evaporation removes heat thereby cooling your body). This causes the ice to get colder and colder until it’s so much colder than the surrounding environment that the radiant heat being transferred to the ice equals the amount of heat being consumed by the sublimation process. I’ve seen this effect cause the ice in the freeze dryer to go from being about -5′C down to about -45′C. If you can add additional heat via the heating coils, then the ice stays warmer and sublimates faster. I was worried because the lowest setting for the heater thermostats on the freeze dryer is 60′F (about 15′C). I was afraid that the thermostats wouldn’t allow me to set the temp any lower, and that a temp this high would actually add so much heat that it would cause the ice to melt before it sublimated and thereby screw up the freeze drying process. As it turns out, even though 60′F is the first mark on the thermostats, if you don’t turn them all the way up to that first mark, they still work and they will allow you to set the temperature lower than that. They actually go all the way down to about 23′F (or -5′C). So, I set the thermostats to about 40-50′F (6-10′C), which is above freezing, but due to the laws of thermodynamics and heat transfer principles, the shelf can be slightly above freezing and still not transfer enough heat to the ice to cause it to melt. By being able to set the heat to this setting and then just leave the heat turned on all the time (versus going out once an hour to turn the heat on for 5 minutes or so just to rewarm the shelves from -25′C up to about 0′C), I should be able to speed the drying process. I’m hoping to get the total drying time down from roughly 48 hours to 24 hours. If I can, then I both half my costs per batch, and double my annual capacity (assuming the machine is kept running 24/7). This is important because I can only get somewhere around 2,000 to 8,000 pills worth of product per batch, and with a dosage of 3 to 4 pills per day per, that’s not a whole lot of production capacity should this business take off. So, the faster I can run stuff through, the longer we can make do with this freeze dryer before I have to build the custom freeze dryer I’ve been designing in my mind. BTW, when I’m done building that custom freeze dryer, I’m going to name the specific method of freeze drying that it uses the “Ledford Method” of freeze drying. I’m such an egomaniac 
It worked
Jan 1st
Making little ice cubes instead of big ones solved the “Honey, I destroyed another blender” problem. Another round of freeze drying under way, all four shelves in use this time. I would estimate that the machine is at roughly 50-60% capacity. I didn’t have enough to fill it up 
Freeze drying
Dec 27th
I started another run last night. Only a partial run, 1 tray out of the 4 is all that’s in use (although it was pretty full). I’m controlling the method in which this tray is dried in order to provide a control for some experiments. Although it’s not done yet, I can say with confidence that one of the ideas I had for a freeze dryer is current a definite win and something that will improve the process significantly. If I get to, I’m going to name my method of freeze drying the “Ledford Method” 
To give you an idea…
Nov 9th
just how much water came out of that freeze drying run, here’s the ice chunk from the condenser after several hours of melting
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- From the side
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- From the top
Yes, yes…I know I have webbed toes….shut the hell up.
Freeze drying run complete
Nov 8th
I ended up with just barely a small amount that didn’t get totally dried. All in all, it took 2 days.
How much I managed to do in this partial run
No more itty bitty freeze drying runs…
Nov 6th
Freeze drying is actually an expensive process, energy wise. It consumes large amounts of energy to generate both the cold and the vacuum needed. However, once you’ve got the vacuum and the cold, neither of these items are strongly tied to the amount of stuff you are freeze drying. And the drying process proceeds at a specific speed in the stuff being dried regardless of how much is there. So, the more stuff you can get in your chamber, the less it costs on a per unit basis to do the drying. I’ve been doing very small runs of drying using a bench top freeze drier. It only had a roughly 5 1/2″ diameter tray that could only be piled up with about 1″ deep of stuff. Well, that’s no more. I still have the bench top unit, but I plan on getting rid of it. Instead, I bought and reconditioned a roughly 30 year old unit (that was in fabulous shape for its age…) that has 4 shelves, and each shelf has a 12″ x 17″ x 2″ deep tray for holding material. I fired it up for its first real run tonight. I expect it to take a day or two to complete the run, but instead of having a few tablespoons full of product when it’s done, I’ll literally have multiple cups of stuff.
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- Upper portion of unit with bench top freeze dryer sitting on top for comparison
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- Whole machine
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- Contents of a tray currently being dried
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- An unused tray in my freezer, shows how bif these trays actually are
I’m such a ghetto scientist
Oct 14th
Or trailer trash scientist, call me which ever (I heard that ghetto is now considered a racist term, which is such total bullshit, ghetto is a financial/social slur, not a race slur, there’s lots o’ white folk in the ghetto). I’ve been running my freeze dryer. It requires a cooling water supply to work (the water goes into the vacuum chamber and is used to keep a copper plate cool, and then thermoelectric cooling devices on that plate keep the stuff your are freeze drying 30-40 degrees colder than the water, which is cool enough to maintain a solid, hard freeze, which is needed to freeze dry). Previous to now, I’ve been using a big cooler and I would dump in a bunch of store bought ice, and it would circulate ice water as the cooling water supply. The problem with that is that it can take 24+ hours to freeze dry a sample, and you need the water to stay cool the entire time. That means it sometimes took as much as 6-8 *bags* of ice to keep the water cold the entire time.
So, real scientists use what’s called a circulating chiller in these cases. But, if you go to a scientific shop, they want like upwards of $2,000 for base models. In all fairness, they are intended for exact conditions where the temperature must be maintained to within .1 degree centigrade +- of your target temperature. I don’t need that. I need cold water without bags of ice. So, I went to home depot and bought a $79.99 dorm room refrigerator and a $6 13-liter trash can that had roughly the right shape to fit in this dorm room refrigerator. I brought them home, cut away the molded door panel on the inside of the door of the fridge, disassembled the ice tray so I could reposition it into the trash can, put the trash can inside the fridge, the ice tray (which is where the refrigerant is and is the part that actually cools the inside of the fridge) down into the trash can, then the pump I had from my previous setup inside the ice tray in the trash can, and ran the hoses and the pump power cord out through a notch I cut in the door seal. I now have the worlds lamest, but cheapest, recirculating chiller. Pictures of the slaughter at my personal web server:
Setup from the outside
Trash can, pump, and water/antifreeze mixture (that's why it's purple)
Cut away door panel
Been quiet lately
Oct 10th
It’s not my fault though, I swear. You see, ryeth normally posts about all the day to day things, so I don’t duplicate what she does. That means I only post about unique goings on around our house (or scientific/social diatribes). But, due to our fucked up patent system in America, if you tell people about what you are working on before you patent it, you loose the right to patent it (tell people in a public sense, you can tell individuals privately, but mass dissemination is out). Well, I’m working on some research in my spare time, and some of it appears to possibly be patentable, so I can’t talk about it. That’s why I’ve been so quite lately. However, I can say that I’m now able to freeze dry small samples of things at my home and I can say that I think I’ve come up with a design for equipment that will simplify the mechanical requirements of freeze drying. I just can’t say *how* my design does so or that would kill the patentable part of it