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Chemical Reaction Engineering
Ideal Reactor Design
GATE 2009
Hard

The liquid-phase reaction A→B is conducted in an adiabatic plug flow reactor. Inlet concentration of A=4.0 kmol/m³, density of reaction mixture (independent of T)=1200 kg/m³, average heat capacity of feed (independent of T)=2000 J/kg.K, heat of reaction (independent of T)=−120 kJ/mol of A reacting. If the maximum allowable temperature in the reactor is 800K, then the feed temperature (in K) should not exceed

  • A400
  • B500
  • 600
  • D700

Explanation

Adiabatic temperature rise at complete conversion: ΔTad=(−ΔHrxn)×CA0/(ρ×Cp)=(120,000 J/mol)(4000 mol/m³)/(1200×2000)=480,000,000/2,400,000=200K. Since the maximum temperature (at X=1, for an exothermic adiabatic PFR) must not exceed 800K: Tfeed+200≤800 ⟹ Tfeed≤600K.

Source: GATE CH 2009 (2009)

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