I am converting my appleseed processor into a methanol recovery unit. It has been recommended to lower the voltage on the heating element to 110v and to use a speed router or some other method to control the current.

I understand dropping the voltage is to keep from driving the heating too hard.
Is this still a factor if the glycerol is being circulated using the HF pump already plumbed in?

Why is an accessory speed router necessary? Is the pot on the heater element too crude to be used to regulate the heat?

Thanks for your input. I know the above questions have been answered in one form or another in other posts. I have searched and read ad naseum but I remain confused. Maybe it is the methanol exposure catching up to me...

Here's how I understand it:

The most critical location to control the temperature is in the "headspace" (not the pot temp). That's the part in the system that's just before the vapors enter the condensing coil. Depending on how pure you want the methanol output, you set this at some point above the boiling point of methanol.

The router speed control comes into play if you're planning on watching the process closely and manually adjusting the heating element to ensure the headspace temp stays at the right temperature. As the methanol is boiled out of the glycerin mixture, it will take more and more energy to keep the headspace at the right temperature...so you need to adjust accordingly.

I don't think a regular thermostat has enough precision to keep the headspace at the right temperature...it would also be a trick to mount a regular thermostat to track the headspace temp.

So...if you don't want to babysit the process, you need a way to sense the temp in the headspace and adjust the heating element accordingly. The best way to do this is with a thermocouple and a PID controller.

A thermocouple is a fancy thermometer that can be read by a PID controller. A PID controller is a fancy thermostat (it's actually way smarter than a thermostat, but look that up later).

Anyway, I found the best way to do it is to have a thermocouple sense the headspace temp, and have a PID controller actuate a relay connected to the heating element in the pot. This sound really difficult, but it's not that hard to make it work.

I'm not sure how the circulation comes into play. I don't circulate mine and have not had any problems. Circulation will prevent hot spots in the pot, so that's a good thing.

Hopefully this makes sense and answers your questions...let me know if you have more. Others will probably chime in and they know a lot more than me.

Dan.

Dan,
Thanks for the informative reply.

What type of a PID and thermocouple are you using?

Where did you get them?

Are you running at 110v?

I would like very much not to have to babysit the process. So if I can use a PID and TC as you have described the extra time needed to run 110v would become less of an issue. I have noticed that 110v controllers are much less expensive than the 240v.

I'm working on the exact same problem that you are. Here is what my research has found.

Most solid state relays can work with 120V, 240V, on up to 480V. Your PID will control the output of the element so there is no need to step it down from 240V to 120V. The PID reads the current temp via a thermocouple and you set the target temp. It observes and computes how much power is required to hit the target without overshooting and reduces the power applied as the temp at the thermocouple reaches the target. The PID puts out a 12V (low voltage) signal to a solid state relay, turning it off and on frequently to reduce the power applied. Its a good idea to purchase an SSR that has a very high amp capacity. If your element is 4500 Watt at 240V, that means that it pulls 18.75 amps. Plan to purchase an SSR with an amp rating of double that or more. Maybe 50. The SSR will need a heat sink (to help the SSR cool down) because it will get hot from operation. If you purchased a 20AMP SSR, you would likely burn it out in a short period of time.

Because the PID puts out a 12v signal to the SSR, you can install a low voltage switch and or timer to interrupt the 12v signal from the PID to the SSR.

Flint Holbrook is a very bright guy when it comes to this stuff. He's a contributor on this forum and he is available to build a PID controller unit for you. His handle here is flint67. http://biodiesel.infopop.cc/eve/personal?x_myspace_page=profile&u=6401027041

Hope this helps.

I'm using a CN9000A PID controller and a Type J thermocouple. I got them from the guy who built the still I'm using...I've seen a lot of them on ebay.

I don't know a lot about thermocouples, but the one I have it just some wire that's twisted together at the end and taped onto the surface of the headspace. I have it really well insulated, but still account for some heat loss and set the PID controller to hold it at 166F. I'm not too worried about the theory...my output is 95% pure methanol, which is more that good enough for biodiesel. Some people are using a different, "probe" type thermocouple that actually goes into the vapor in the headspace. That seems really cool, but I didn't find it necessary.

I'm running at 110V and let it go for 8hrs after getting up to temp. I have a second heating element in the pot that's not controlled (and running from a different circuit). I leave that on for 1hr to get it up to temp, then turn it off manually. I'm going to set that up on a 1hr timer soon.

The main heating element runs through the relay and PID controller and keeps the pot up to temp. It's a 4500 watt 220V element that's running on 110 (so that makes it a 1125 watts). If you have more heat going into the system, you can get the methanol out quicker, but you also risk losing some purity AND you need to provide more cooling capacity to remove the heat you've added.

I have a countdown timer that turns the whole system off after 8hrs...which is enough time to recover about 2 gallons of methanol from 8 to 10 gallons of byproduct.

For cooling water, I use a rain barrel outside my garage and recirculate the water through the cooling jacket on the condensing coil. I'm just using a fountain pump to circulate the water...it's powered through the same countdown timer as the PID controller, so it turns off when the rest of the system does. Now I don't waste any water for the cooling process (I was using water from the hose before...it would take 1 trip through the cooling jacket, then go into the garden. Definitely more water than I needed to use.)

I think most of the controllers can read multiple types of thermocouples. There are many different ways you can make it work.

Good luck! Keep me updated on your progress. I've learned enough to be dangerous, but can probably help a bit...Later, Dan.