Author: Lou Heavner
In this 3-part series on distillation column control basics, we’ll look at traditional control and modern approaches to improve control robustness. For background, you can find a good write up on industrial distillation in Wikipedia.
Basic Distillation Components – Click to enlarge
In the distillation process, a feed mixture is separated by volatility or boiling point into 2 or sometimes more component streams. Energy in the form of heat is introduced at the bottom of the column in the reboiler and removed at the top of the column in the overhead condenser.
Closing the material and energy balances mean that at a minimum, the sum of the product flows must equal the feed flow and the enthalpy introduced with the feed and in the reboiler must be removed with the product streams and in the overhead condenser.
The product streams will not be perfectly pure and don’t need to be. Product purity is specified based on the subsequent use of the product stream. Purity is directly related to the amount of energy that is used in the process. Energy, itself, has a cost, so there is the competing objective of meeting purity specifications with minimum use of energy. Continue Reading ▶
I heard a great story about a resins manufacturer who was having some issues in meeting quality specifications due to temperature variability in the process. Emerson’s Gergo Kertesz
, whom you may recall from an Emerson Exchange presentation I liveblogged
, shared this story.
This variability not only impacted the quality of the produced resin, it impacted overall energy usage and the amount of manual efforts required by plant operators to try to keep the produced products within specification limits. Improving the temperature control would mean reduced rework and optimized reaction speed.
The plant contained several reactors which required heating and cooling systems for the jackets surrounding each reactor. The objective was to keep the reactor temperature with 5°C of the setpoint. Additionally, if the temperature exceeded +30°C of the setpoint, the exothermic reaction speed would increase too fast. This would cause a distillation column overload at the top of the reactor. Continue Reading ▶
For many plants and production facilities, instrumentation devices measuring the process were limited to just what was needed for monitoring and control due to installation costs and complexity. Wireless instrumentation has opened up the opportunity to add measurements to increase reliability, improve energy efficiency, reduce emissions and increase overall safety.
Emerson’s Jonas Berge
wrote a follow up article, Beyond the Control Room
, to his earlier Control Engineering Asia article, Second Layer of Automation
. I highlighted some excerpts from the Second Layer article in an earlier post, Business Critical Measurement Instrumentation-Second Layer of Automation
In this Beyond the Control Room article, Jonas builds on how these extra measurements provide pervasive sensing to various groups across the plant:
Some of these measurements collected through pervasive sensing go to the operators in the control room for increased situational awareness, but most new information goes to personnel beyond the control room to the offices of the disciplines responsible for reliability and maintenance, energy efficiency, and health, safety, and environmental (HS&E).
The wireless sensor network can connect with several systems and software platforms: Continue Reading ▶
In March of 2014, API Standard 2000 (Venting Atmospheric and Low-Pressure Storage Tanks), 7th edition
In a whitepaper, Sizing Tank Blanketing Regulators Using the Latest API 2000 7th Edition Guidelines, Emerson’s Steve S. Attri describes how the latest changes affect the sizing of tank blanketing regulators. The whitepaper also includes how backpressure regulators are used for vapor recovery systems.
He opens the paper noting the fundamentals that impact tank pressure remain the same—liquid flow (or pump-in and pump-out) and changes to temperature still form the fundamentals to the sizing calculations.
Steve provides the history of the API Standard 2000 over the last several editions: Continue Reading ▶
Some of the technologies making the Internet of Things (IoT) possible include WirelessHART, radio-frequency identification (RFID), near field communication, barcodes, QR codes and digital watermarking.
I mention this because many process operations require material movements via truck, rail, ship and other discrete forms of transportation. The operations to track these movements have historically been done with manual entry, keycard swipes, and similar methods.
RFID tags have made automating these movements much more possible. In this short, 2:04 video, Using RFID for Vehicle Identification in Syncade Logistics
, Emerson’s Shoyeb Hasanali
explains how using RFID for vehicle identification and monitoring helps prevent contamination and misrepresentation of vehicles.
This improved vehicle identification and monitoring results in reduced trip time and better support for unmanned terminal shifts. Continue Reading ▶