Learning about the process: Gas phase balances Sef Heijnen, - PowerPoint PPT Presentation

Learning about the process: Gas phase balances Sef Heijnen, Department of Biotechnology, Faculty of Applied Sciences

Completing the picture Broth-Balances Substrate [mol s/h]: d(V L c s )/dt = R s +F in c s,in – F out c s,out F in c s,in Product [mol p/h]: O 2 d(V L c p )/dt = R p +F in c p,in – F out c p,out c p,in c x,in Biomass [mol x/h]: V L d(V L c x )/dt = R x +F in c x,in – F out c x,out c s c p c X F out c s,out c p,out c x,out

The oxygen balance for the broth (mol O 2 /h) System boundary T N,O [mol/h] (Transfer term) Gas c O,out [mol/m 3 ] c O,in [mol/m 3 ] Broth F in [m 3 /h] c O [mol/m 3 ]·V L [m 3 ] = N O [mol] F out [m 3 /h] (Transport term) (Transport term) R O [mol/h] Broth oxygen balance: (mol O 2 /h) d(V L c O )/dt = R O + F in c O,in - F out c O,out + T N,O

The oxygen balance for the gas phase (mol O 2 /h) System boundary y O,in [mol/mol] y O,out [mol/mol] y O [mol O 2 /mol gas] · N G [mol gas] = N O [mol O 2 ] F N,in [mol air/h] F N,out [mol gas/h] T N,O [mol O 2 /h] (Transport term) (Transport term) (Transfer term) Gas Broth Gas phase oxygen balance: 0 d(N G y O )/dt = 0 + F N,in y O,in – F N,out y O,out - T N,O

Combined broth/gas O 2 -balances (mol O 2 /h) 0 = R O + F in c O,in - F out c O,out + T N,O Broth balance: - R O = F in c O,in - F out c O,out + F N,in y O,in – F N,out y O,out Combined balance: Measurements needed to calculate R O: F in , c O,in , F out , c O,out , F N,in , Y O,in , Y O,out , F N,out 0 = 0 + F N,in y O,in – F N,out y O,out – T N,O Gas phase balance:

F N,out y C,out N G y C F in c C,in T N,C V L c C F N,in F out y C,in c C,out Combined broth/ gas balances CO 2 : R C = - F in c C,in + F out c C,out - F N,in y C,in + F N,out y C,out

How to determine F N,out -R O = F in c O,in – F out c O,out + F N,in y O,in – F N,out y O,out Combined broth/gas balances O 2 : N 2 gas balance: F N,in (1 - y O,in - y C,in ) = F N,out (1 - y O,out - y C,out ) Combined broth/gas R C = -F in c C,in + F out c C,out - F N,in y C,in + F N,out y C,out balances CO 2 :

Understanding and improving the fermentation process CO 2 C 6 H 12 O 6 C-conservation 6R s = 3R p + 1R x + 1R C R s R p R x R C C 1 H 1.8 O 0.5 N 0.2 (Biomass) C 3 H 8 O 2 (PDO)

Understanding and improving the fermentation process CO 2 C 6 H 12 O 6 C-conservation 6R s > 3R p + 1R x + 1R C R s R p R x R C C 1 H 1.8 O 0.5 N 0.2 (Biomass) C 3 H 8 O 2 (PDO)

Understanding and improving the fermentation process CO 2 C 6 H 12 O 6 • Unknown by product R s • Volatile product/substrate R p R x • Product is degraded R C C 1 H 1.8 O 0.5 N 0.2 (Biomass) C 3 H 8 O 2 (PDO)

Understanding and improving the fermentation process CO 2 C 6 H 12 O 6 C-conservation 6R s < 3R p + 1R x + 1R C R s R p Measurements Are Wrong R x R C C 1 H 1.8 O 0.5 N 0.2 (Biomass) C 3 H 8 O 2 (PDO)

Wrap up: Learning about the process: Broth and Gas phase balances Rates Cannot be measured, but are calculated from proper • compound balances and measurements Compound Balances System boundaries (gas, broth,..) • Tells you what to measure • Broth and Gas balances • Learning about the process Conservation of element • Unknown mechanisms working on product/substrate • Faulty measurements • Easy opportunities to improve process economy •

See you in the next unit!