Ratio control

Ration Control System

1. Ratio Control Adnan Akhtar 2017-Ms-Ch-05

2. Ratio Control Scheme Ratio Control scheme is a special type of feed-forward control scheme where two disturbances (loads) are measured and held in a constant ratio to each other. Mostly used to control the Flow rates of two streams. Wild stream Controllable stream

3. Configuration of Ratio Control

4. Configuration of Ratio Control

5. Applications of Ratio Control Hold Constant Reflux ratio in a distillation column Control the ratio of two reactants entering a reactor at a desired value Keep the ratio of Fuel/Air in a burner at it’s optimum value

6. Fuel/Air Ratio

7. Advantages Allows user to link two streams to produce and maintain a defined ratio between the streams . Ratio control scheme is very simple to use. It does not require a very complex model.

8. Disadvantages Often one of the flow rates is not measured directly and the controller assumes that the flows have the correct ratio through the control of only the measured flow rate . Requires a ratio relationship between variables that needs to be maintained. Not as useful for variables other than flow rates.