The document describes the implementation of a ratio controller in Aspen Hysys dynamics for a mixing operation involving two water streams. It outlines a model where the mass flow of 'stream 1' is regulated to be 85% of 'stream 2' using a ratio controller. The required adjustments to maintain this ratio are demonstrated through specific control settings within the Hysys model.

1. RATIO CONTROLLER USAGE IN ASPEN HYSYS DYNAMICS
The use of a Ratio controller in Aspen HYSYS Dynamics can be demonstrated using a Mixing Operation. Two
streams of water, ‘Stream 1’ at 3 bar(a) & 25
0
C and ‘Stream 2’ at 3 bar(a) & 50
0
C need to be mixed with a
mass ratio of 0.85 (85%), i.e., ‘Stream 1’ mass flow is 85% of ‘Stream 2’. A HYSYS model can be built using a
ratio controller which can be used to regulate the flow of ‘Stream 1’ (VLV-100) such that at all points in time,
‘Stream 1’ Mass flow is 85% of ‘Stream 2’.
Figure 1. HYSYS Dynamics Model Setup
Figure 2. Ratio Controller Setup – Page 1
Figure 3. HYSYS Model Setup – Page 2 Figure 4. Ratio Controller Setup – Page 3
VLV-100 opening is corrected by the Ratio
controller (RATO-100) to 42.31% (OP value) to
maintain Stream 1 : Stream 2 mass ratio at 0.85