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Process Modelling

Process Dynamics and Control

ECP 316

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Need for Dynamic models

Do the Bus and bhasikoro have different dynamics?

Which can make a U-turn in 1.5 meter?

Which responds better when it hits a bump?

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Need for Dynamic Models

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Why Dynamic Models?

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Why Dynamic Models

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Why we need dynamic models

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Why Process Dynamics

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Why we develop mathematical models

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Why we develop mathematical models

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Some uses of mathematical models

Process design

Process Control Design

Operating conditions

What if analysis

Training

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Modelling Procedure

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Modelling Procedure

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Modelling procedure

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Modelling Procedure

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Modelling procedure

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Modelling procedure

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Modelling Procedure

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Modelling Procedure

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Modelling Example

The mixing tank in the figure has been operatingfor a long time with a feed concentration of 0.925kg-mole/m3. The feed composition experiences astep to 1.85 kg-mole/m3. All other variables are

constant.Determine the dynamic response.

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Modelling example

Goal : determine dynamic response of mixing tank to a step change ininlet conc.

Information:

System is liquid in tank. Tank well designed, baffling and impeller sizeshape & speed to achieve uniform conc. in liquid

Assumptions well mixed

- density same for A and solvent

- constant flow in

Data -

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Modelling example

Formulation:

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Modelling example

Material balance on component A

Tank well mixed

Tank and outlet concentrations the same

Acc of A = A in A out + Gen of A

Gen = 0 (no reaction)

Dividing by t and taking limit as t 0 gives

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Modelling example

Variables : CA and F1

External Variables : F0 and CA0

DOF = NV NE = 2-2 =0

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Modelling Example

Solution:

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Modelling example

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Modelling procedure