Process Control

Surge Tank Design

CHE4042F Process Dynamics and Control Project 1

20 April 2013

Group 26

Table of Contents

List of Figures ii
List of Tables ii
Glossary iii
A. Analysis of Plant Data 1
B. Simulation of Surge Tank 2
i. Modelling the Surge Tank in Xcos 2 ii. Frequency Fluctuations in Density Data 5 iii. Testing of Model for the Product Density 6 iv. Comparison of Unconstrained and Constrained Output Volume of the Surge Tank 7
C. Control of Surge Tank 8
i. Implementation of Controllers 8
Product Flow Fluctuation 10
Product Density Fluctuation 10
Height Fluctuation 11 ii. Effect of Tightening Limits and Reducing Tank Size 11
References 13
Appendix 13
Derivation of Transfer Functions 13
Sample Calculation 15

List of Figures

Figure 1: Relative density of surge tank feed against time 1
Figure 2: Volumetric flow rate of surge tank feed against time 1
Figure 3: Xcos surge tank simulation 3
Figure 4: Sinusoidal response of the height transfer function 4
Figure 5: Sinusoidal response of the density transfer function 5
Figure 6: Response of density transfer function with a 99% reduction in output amplitude 6
Figure 7: Comparison of the specified amplitude to the actual amplitude 6
Figure 8: Sinusoidal response of density transfer function after increasing size of the tank 7
Figure 9: Xcos model simulating the implementation of a control system 8
Figure 10: Product flow fluctuation vs. time, compared to specified amplitude 10
Figure 11: Product density fluctuation, compared to amplitude 10
Figure 12: Tank height control vs. time, compared to soft and hard constraints 11
Figure 13: Schematic of the surge tank 13

List of Tables

Table 1: Numerical constants used to model plant data 2
Table 2: Density transfer function constants 3
Table 3: Variation of τ with outlet amplitude 5
Table 4: P values used to control output fluctuations 10

Glossary

q_1: Average volumetric flow