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Aug
18

Post Retirement Key Points – Part 4 (2009 Articles)

My articles in 2009 are focused on pH and wireless measurement and control. Not listed below is an article planned for later this year on the use of wireless pH for inferential measurement of solvent concentration at the University Texas Research Campus pilot plant for carbon dioxide capture.

Virtual Plant Provides Real Insights“, Chemical Processing, Jan, 2009

ImprovingpHSystemDesignandPerformance.pdf

(1) Modeling and control in a virtual plant showed that the size of the neutralization vessels could be reduced from 40,000 to 10,000 gallons reducing the project capital costs by more than $500K for a strong acid and base system. The virtual plant was also able to detail mixing, reagent injection, and valve requirements

(2) Translation of the controlled variable from pH to percent reagent demand (X axis of the titration curve), provided faster recovery from upsets.

(3) It was expected that the resolution of the reagent valves needed to be exceptional. It was surprising how important resolution was for the feed valves. What would be normally considered a good resolution for the feed valves caused excessive deviations in the vessel pH. Stick-slip in the feed valves showed up as short term deviation rather than a limit cycle in the pH because of the feedback correction by the pH loop

(4) Innovative Methods of continuous and semi-batch mode offered maximum operational flexibility.

Is Wireless Process Control Ready for Prime Time“, Control, May, 2009

My time in spent building and starting up chemical plants, working in process labs, and dealing with pH measurement noise gave me a greater appreciation for the significance of being able to eliminate instrument wiring. This article offers my take on the value wireless and shows incredibly tight wireless bioreactor pH control. Some biopharmaceutical processes require control within 0.02 pH of set point for optimum operation. The pH control demonstrated in this wireless pH test on a bioreactor with a disposable liner (single-use-bioreactor) was an order of magnitude better than required, the tightest pH control I have ever seen. Most of the credit goes to new wireless PID algorithm and the exceptional capability of the pH electrode and wireless pH transmitter. Finally, the wireless measurement did not have the spikes exhibited by the wired pH transmitter from ground noise, showing that wireless can eliminate a significant source of noise.

The Essentials of pH Measurement Design, Installation, Maintenance, and Improvement“, ISA 55th International Instrumentation Symposium, League City, 2009

This paper is a chapter out of “The Essential Book” scheduled to be published in time for ISA Expo 2009 in Houston.