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Reactor Design I > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Components of a batch reactor

A
  • lid
  • agitator and motor
  • baffles
  • base
  • jackets
  • Fabrication materials (MOCs)
  • seals
  • probes
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2
Q

The lid of a batch reactor

A
  • configurable
  • many ports but finite amount
  • motor assembly can cause space issues
  • access can be problematic
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3
Q

Agitator and motor of batch reactors

A

Drive system comprises
- drive assembly: motor, speed reducer and shaft support

  • Wetted parts: impeller, shaft and seal
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4
Q

devices used to restrain the flow of a fluid, gas, etc

A

Baffles

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5
Q

Batch reactors - shapes of the base

A
  • rectangular
  • hemispherical
  • torispherical
  • conical
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6
Q

impellor type causes flow in the vessel to move the contents from top to bottom

A

axial flow impellors

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7
Q

impellor type causes flow to be pushed against walls and then move either up or down

A

radial flow impellors

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8
Q

Sucessful scale up of liquid mixing processes in tank reactors rely upon

A
  • similar geometry of the large and small vessel
  • the application of constant power per unit volume
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9
Q

Issues with CFD

A
  • Grid design
  • how to model rotating impeller
  • turbulence models
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10
Q

CFD

A

Computational fluid dynamics (CFD)

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11
Q

Reynolds Number specific to tanks

A

Re = ρ N D^2 / μ

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12
Q

Power number

A

Po = P/ ρ N^3 D^5

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13
Q

Analogous to a friction factor
Proportional to the drag force per unit area of the impeller and the inertial stressed generated
depedent on the impeller type, dimensions, position and liquid properties
strong dependence of power input on N and D

A

Power number

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14
Q

Ratio of inertial forces to viscous forces
Comprises of a phyical properties component, a velocity and a characteristic dimension

A

Reynolds number

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15
Q

must be known for sizing the motor and drive. Large power
demands generally means a large drive

A

Power draw (P)

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16
Q

Power draw

A

P = 2πNΛ

Knowing the power dissipated into the liquid by the impellor is CRITICAL for predicting reactor performance
- micing time
- mass transfer

17
Q

Torque measured at small scale

A
  • mount vessel or motor on frictionless bearing and measure torque using a lead cell dynamometer
  • use a commerical torque meter
  • use a modified rheometer
18
Q

Torque measured at large scale

A
  • strain gauges can be used
  • electrical current can be used by is subject to many errors as estimates of losses in the gearbox and bearing required
19
Q

time taken to achieve desired homogeneity in the vessel

A

mixing time

implies not all parts of the tank are at the same concentration at all times, especially at the start of the reaction

20
Q

A series of conductivity probes all on one probe. The probe can act as the vessel baffle. Much more data can be obtained than a single probe.

A

Electrical resistance tomography (ERT)

21
Q

Accumulation equation

A

In – Out ± Reaction = Accumulation

22
Q

Total batch time is the sum of:

A
  • charging
  • dissolution
  • heating to reaction temperature
  • reaction
  • cooling batch
  • discharge of contents
  • cleaning in place
23
Q

time required to complete all of the operations required to create one batch of product materials

A

batch time

24
Q

minimum time needed to complete all of the operations required to create a batch of product

A

cycle time

25
Q

series of operations that must occur in sequence

A

batch production

26
Q

Considered as the time required to complete one whole batch

A

batch time

27
Q

minimum time needed for all operations to occur

A

cycle time

28
Q

how high impellor sits within a vessel

A

clearance

29
Q

how much reactant is converted to any product

A

yield

30
Q

how much reactant is converted to desired products

A

selectivity

31
Q

Yield equation

A

moles A reacted / total moles A in feed

32
Q

Selectivity equation

A

moles A reacted to desired product/ total moles reacted

33
Q

Design criteria for the scale up of liquid blending processes in a reaction vessel

A

(N^3D^2)large=(N^3D^2)small

34
Q

Design criteria for the scale up of liquid blending processes in a reaction vessel assumptions

A
  • constant power number between scales
  • constant physical properties between scales
  • similar geometry between scales
  • constant power per unit volume between scales
35
Q
A

Reactor Design I (6 decks)

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