AutoQuiz: How to Minimize the Effect of Feed Upsets to the Top of a Distillation Column

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for information about the CAP program. The following question comes from the CAP study guide, Performance Domain II, Definition: Identify customer requirements and complete high-level analysis of the best way to meet those requirements.

 

To MINIMIZE the effect of feed upsets to the top of a distillation column, the flow feed forward signal should be connected to a tray temperature controller output that then directly manipulates a(n):

a) overhead pressure controller
b) linear reflux valve
c) reflux controller
d) reboiler stream ratio controller
e) none of the above

   

Click Here to Reveal the Answer

A distillation tower has feed upsets that are measured and used to create a feed forward signal. A reflux flow controller remote set point becomes the feed multiplied by a reflux-to-feed ratio that the temperature controller output will correct. This is the most linear and accurate way of maintaining the material balance as long as the flow measurements are above their low range ability limit.

The correct answer is C, reflux controller.

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