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Flash Tank Design Questions

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January 26, 2015, 03:12 PM
Fourth Way Man
Flash Tank Design Questions
We have installed a dual tank flash methanol recovery setup from a defunct bio company. The operating theory consists of a continuous spray into a vacuum tank, then transferred from the flash tank to a holding tank for centrifuging with an Alfa Laval 207. Continuous operation is the key here.

We're able to flash methanol at 195-205F and 25" vacuum with a Wintek system for vacuum/condensation

The second tank is set up with a different spray orifice for flashing settled glycerols.

We get good soap drop-out after flashing, so much so that it will plug a plate exchanger if we don't keep it hot and flowing.

Keeping it going is problematic in that the Tuthill 4314 gear pump won't always maintain suction and will cavitate and stall, interrupting the continuous flow operation. Initially it was a plate exchanger restriction issue that exacerbated cavitation, but with care we get the flow going and the heat up and it doesn't plug.

If I throttle the Wintek down, I can maintain continuous operation, but where is the efficiency at less vacuum?

Is there a handy chart or formula that will allow me to calculate what we can expect at various temp/ pressures vs. methanol concentration in the bio?

Alternately, is there a way to quickly test for residual methanol for real-time monitoring? If we test and find no water after flash, can we assume the methanol is long gone?

Thanks,
C
January 26, 2015, 06:06 PM
Jon Heron
quote:
Is there a handy chart or formula that will allow me to calculate what we can expect at various temp/ pressures vs. methanol concentration in the bio?
Not that I am aware of, FWIW here is calculator you may find useful. http://www.trimen.pl/witek/calculators/wrzenie.html

Alternately, is there a way to quickly test for residual methanol for real-time monitoring? If we test and find no water after flash, can we assume the methanol is long gone?

Again not that I am aware of. I would say if there is no water and the fuel is clear when cool you are good to go.
I am only speculating though. Smile
Cheers,
Jon


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Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer