An irreversible first-order reaction is run in equal-volume CSTR and PFR units with identical liquid flow rates. The relative conversion will__________________?
Show answer Hide answer
Answer: B. Be more in PFR than in CSTR
Explanation
Plug flow reactors achieve higher conversions than continuous stirred tank reactors of identical volume. Reactant concentrations remain higher along a plug flow reactor, driving faster reaction rates. Continuous stirred tank reactors dilute fresh feed instantly, lowering average reaction rates. Plug flow reactors operate with no fluid mixing in the axial direction along the tube. Continuous stirred tank reactors feature uniform low reactant concentrations throughout the vessel. Reaction kinetics dictate that higher reactant concentrations yield greater conversion per unit volume.
Reactor selection in chemical plant design depends heavily on achieving desired conversion efficiencies. Tubular PFR units are preferred for high-volume reactions requiring maximum single-pass conversion. CSTR units are chosen when continuous uniform temperature control is paramount. CSTR units yield lower conversions than PFR units for positive-order irreversible reactions. Equal conversions in both reactor types only occur for zero-order reaction kinetics. Conversion depends primarily on reactor type and volume rather than temperature alone.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. An unbalanced chemical equation violates the law of________________?
Show answer Hide answer
Answer: B. Conservation of mass
An unbalanced chemical equation has unequal numbers of atomic species on each side. This numerical inequality directly violates the fundamental law of conservation of mass. Mass conservation requires exact atomic balance...
Q2. An irreversible liquid reaction A + B → P is carried out adiabatically in a mixed flow reactor with a feed containing 4 kmole/m3 of each reactant at 8 m3/h. If the exit stream temperature must not exceed 390 K, what is the maximum permissible inlet feed temperature? (Given: ΔH = –50 kJ/mol, mixture density = 1000 kg/m3, specific heat = 2 kJ/(kg·K), independent of temperature/composition)?
Show answer Hide answer
Answer: B. 290
Adiabatic energy balance and reactor equations relate feed temperature to the heat of reaction. Solving the energy balance with the given thermodynamic parameters yields the inlet temperature. The calculated maximum perm...
Q3. As a chemical reaction progresses, the rate of reaction___________________?
Show answer Hide answer
Answer: B. Decreases
Reactant molecules are continuously consumed as a chemical reaction progresses from initial mixing to completion. Lower reactant concentrations reduce the frequency of productive molecular collisions taking place within...
Q4. An isothermal irreversible reaction proceeding in an ideal tubular reactor will see conversion ______________ as space time decreases?
Show answer Hide answer
Answer: C. Decrease
Decreasing space time reduces the reaction contact time inside an isothermal tubular reactor. Shorter contact times allow less opportunity for reactants to transform into products. Consequently, decreasing the space time...
Q5. The BET method is applied to measure the ___________________ of a porous catalyst?
Show answer Hide answer
Answer: C. Surface area
The BET method uses gas adsorption measurements to determine specific surface area. Porous catalysts are characterized by measuring nitrogen gas uptake at various pressures. Surface area calculations derived from BET the...
Q6. Backmixing is most pronounced within___________________?
Show answer Hide answer
Answer: C. A single CSTR
A single continuous stirred tank reactor assumes perfect and instantaneous mixing throughout its entire internal volume. Incoming fresh feed blends immediately with already reacted fluid, creating maximum backmixing of r...