Whats causing my 2nd pass vacuum to be higher than 1st? WFE

Recent patch of biomass we are working through i’m seeing higher 2nd pass vacuum levels than my 1st pass. Running a single stage stainless WFE and extracting CBD Hemp biomass

Cold ethanol extracted -40C denatured ETH
Decarb in 50L jacketed reactor taking it up to 138C @ which point light terpenes are coming off.
1st pass on the wiped film running evap:132-135C/condenser:100C 375RPM. Vacuum ~35-40 micron -75 CT
-1st pass I’m pulling about 6-7% volatiles off and about about another 6% as heads.
2nd pass on the wiped film running evap:162-165C/condenser:100C 425RPM. Vacuum 42-46 micron -75 - -80 CT yielding 73-76% to distillate from start material here.

been playing around with increasing the 1st pass temp from 132-135 but doesn’t change anything on the 2nd pass and just creating more SPD cleanup of the heads coming off which yield pretty high to distillate already.

Been keeping it in the mid 20’s for the 2nd pass in the past but for the past month or so we are just seeing it climb way past there when begin feeding. I’m happy with the output overall… i’m thinking the obvious answer is some fraction in the 140-160 range coming off but cold traps are bone dry. Anyone got any experience with this ?

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I dont have much experience with CBD but I would terp strip a bit differently and see if it helps

1st pass
425rpm
250-300 mtorr
148C
50C condenser

2nd pass looks good, you could try to lower your condenser temp if you want to experiment

how would one raise vacuum in that sceanrio?

Turn your turbo pump off and use a needle valve with the roughing pump

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Word no turbo just using a single rotary

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Your second pass material will be thicker than the first pass which in turn will give you a higher vacuum. I get 200-350mtorr on first and 100mtorr or less on second pass.

Sounds like you mean lower vacuum?

“Deeper” avoids that pit fall

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Yes! Just need better pump!

Yes I’m describing a scenario with deeper 1st pass vac than 2nd.

We run a chemtech kd10 and we terp strip @:
180 evap
45 Cond
800-900um vac
Roller/wiper full rpm
Vols/Terps are clean

1st pass:
165 evap
90 cond
Low as she’ll go vac
Roller/wiper 50% rpm
Disty @ 80% on low end

Our vac ways drops after each pass. Nothing in there getting in the way at that point.

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I use nearly the same settings on mine lol. Or used to.

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