zedzedtop wrote:Isn't the issue with LM that it is difficult to maintain azeotrope throughout the run, especially at the end? I was thinking that this could automate the end of the run. Theoretically, you can reach azeotrope with no reflux at all, and low % boiler charge, but just with extremely low power input.
Wouldn't the LM-E-ARC as described in rikus book cause more of a surging because of the on-off nature of the solenoid?
what riku does is to change the output. what you would do is to change the vapor speed. that is very sensitive. if you use a small intenal heater it will stop boiling in a matter of seconds. when that happens the tower of vapor will collapse very fast and the equilibrium is lost. on/off regulating the power is therefor not a recommended option. it might work with bain marie or possibly a plated still, i dont know.
the other option would be a SSR controlling the power. but i doubt your pid can control the temperature as stable as 0,1-0,2C that is required. The PID would have to work with a 0.01C sensitivity to even have a few fractions to calculate the PID-parameters. and even if its sensitive enough the reading of the temperature inside the column is very hard to get stable within 0,2C so i doubt the PID can make any valid calculations based on that. but i know much to little about PIDs to know for sure. maybe it can be solved with some other kind of sensor. and/or better software (check out the arduino threads).
i dont think LM or VM is a good option for this. you would not be able to set them in full reflux without lowering the power way down until the vapor doesn't even reach the top of the column.