Chemical Engineering 3P04

Process Control

Tutorial # 4

Learning goals

1. Discuss some common sensors (Flow already covered in Tutorial #1)

2. Continue to practice formulating and solving dynamic models of processes

Some variables that are measured in nearly all processes. What are they?

BARTEK

Maleic Anhydride Process

Your primary resource for sensor information

with lots of links to detailed information.

Some variables that are measured in nearly all processes. Where do we find information?

Sensors with local indication for technicians working on process equipment

Central control room

Transmission to central computer for displays, plot, history, and calculations used for control.

Measurements are displayed either locally or in a central control room

Temperature: Local display is possible using thermometers and bimetallic sensors

Thermocouples: Specific metal pairs are used in practice for selected accuracies and ranges of

temperature

Thermocouples: Specific metal pairs are used in practice for selected accuracies and ranges of

temperature

RTDs: Electrical resistance depends on temperature, with higher temperature having

higher resistanceThermisters: Electrical resistance depends on temperature, with lower temperature having

higher resistance

Pressure Bourdon Tube for local display of pressure

Pressure using Strain Gauge: A change in strain affects the electrical resistance of a metal.

Pressure using Capacitance: A change in pressure deflects the separating diaphragm,

which affects the capacitance.

Pressure using Potentiametric: Converts the deflection of the arm to a change in resistance.

Level : sight glass for Local display

Level using displacement: Sensors measure the weight of an object suspended in the liquid.

Level using head: Sensors measure the pressure difference to infer level.

Modelling exercises: Perform the following modelling exercises from Tutorials on the PC-Education WEB:

4.2 – Flow as the input (forcing function)

3.3 – isothermal CSTR (solution)

ILM Questions 4.3, 4.4, 4.5, 4.8, 4.13

Modelling flow chart

1. Define Goals

2. Prepare information

3. Formulate the model

4. Determine the solution

5. Analyze Results

6. Validate the model

Modeling: Practice, Practice, Practice!!!

We apply this procedure

• to many physical systems• overall material balance• component material balance• energy balances