De mething

[oakwoodtv]

When I am de mething at 95 C I have noticed that the temperature of the pipe from the SHHE
 to the condenser goes from to hot to touch at the start to nearly cold as de mething is finished.

Could this temperature drop be used with a senser  to switch of the pump and heater automatically.

Richard.       
 

 

[Tony]

I'd go with that.  I've noticed the same.  If there's no fraction light enough to carry the energy as a phase change, we're done demething.

[Rotary-Motion]

maybe one of these?

http://www.biopowered.co.uk/forum/index.php/topic,326.msg2936.html#msg2936



like my twin tank controller you can switch which way it switches at any given temp on or off...

and if I remember rightly when to switch on or off, meaning you can set a scale say 10 to 30c and swich on or off at 10 or on or off at 30

but would need to check been a while...

[Julian]

Interesting.  I found the same section of pipe just about cold whilst dewatering the other day and couldn't work out why.

If this is always the case (still trying to get my head around the phisics) then surely it's a great contribution to automating the process.

For my part I want to dewater over night on economy 7, so having an indication as to when to stop the process is far better that running a timer and hoping all the water is removed during that period.

[oakwoodtv]

I will fit a digital thermometer on the proseser next batch and monitor the temperature
and rate of methanol recovery.

May plot the results on a graph it could be a bit more informative.
     

[Julian]

Having decided that dumping a portion of the last batch of oil on the floor wasn't a good idea, I've cleaned it up and will be dewatering again later this afternoon.

So I'll do the same.  I can't promise to be very diligent about taking regular readings, but I'll certainly try and catch the point where any changes take place.

[Julian]

Sorry, I wasn't at all diligent, got distracted by people coming round and other things on the go.

So ... I turn on the heater, remembered to return and switch on the pump, water and condensing circuit when the processor temperature was at 71°C, but when I revisited some time later the PID had tripped out at it's preset 92°C and the SHHE outlet was already cold.

I did however record the following figures following round the vapour circuit as follows ...

Ambient shed ... 16.4°C

Processor ... 91°C

SHHE outlet from processor ... 70.7°

SHHE inlet from processor ... 44.4°C ... (the pipe between the processor and SHHE is only about 8" long. I'm guessing that the 70.7°C is largely due to conducted heat from the processor.)

SHHE outlet ... 27.6°C

Condenser inlet ... 24.2°C (difference between this and above may be due to large mass of SHHE conducting heat to pipe work)

Condenser outlet ... 11.9°C ... (cooling water is from the mains and is usually constant somewhere between 10°C and 12°C, any time of year)

SHHE contraflow inlet ... 17.4°C ... (I suspect this is picking up lost heat from adjcent pipework)

SHHE contraflow outlet ... 32.7°C

Venturi suction ... 33.1°C  (measured about 2" from venturi to reduce conducted heat from oil flow.)

At this point the was no flow of condensed water, but the collection jar contained a fairly dense vapour.

Sorry I didn't catch the point of change, but the figures appear to confirm that the vapour circuit can achieve a  greatly reduced temperature once the water is removed.

[Mickindashed]

I put a pipe thermometer on the pipe right below the SHHE about 6" before the condensor today and got 48c consistently while the methanol was condensing in a trickle, and it dropped to 30c when the trickle turned into drips. The 48c was steady from about 60c to 72c in the processor, which was when I had to leave it for a bit. The 30c in the vapour pipe was reached with 90c in the tank. I'm going to leave the pipe thermometer where it is and use it as an indication of when to stop demething. Good idea Richard!

[Chug]

Yep, it is a good indicator of when to stop, I have two temp sensors, one in processor next to the condenser outlet and one on the inlet pipe into condenser, the one outside on the condenser inlet starts dropping then the inside one slowly follows but doesn't drop as much, when the inside one starts dropping I stop demething.