Friedman, Y. Z.
Y. Zak Friedman is a Principal Consultant with Petrocontrol. He has practiced APC for most of his career, specializing in using first-principles models for inferential process control and has developed inferential models to fit many hydrocarbon processes. Dr. Friedman’s experience spans more than 50 yr, working with Exxon Research and Engineering, KBC Advanced Technology and Petrocontrol. He holds a PhD degree from Purdue University.
HP Control: Alkylation product separation control
People do not speak much about advanced process control (APC) of alkylation product separation. Why? Precise product separation is crucial to alkylation unit economics. Alky reactor effluent is separa..
HP Control: Condenser hot vapor bypass control
What is the worst mistake? It is the one that is repeated in practically every refinery, and yet, we haven't managed to learn from it. I have chosen to discuss the very simple distillation column pres..
HP Control: Part 2—What happened to simple useful APC techniques?
This is the second part of my interview with Greg Martin about simple control techniques, unjustifiably retired. In this part we address single-input, single-output (SISO) predictors and simple engine..
HP Control: Part 1—What happened to simple useful APC techniques?
Advanced process control (APC) is labor intensive, requiring about one experienced engineer per three major units, a level of effort rarely matched, even in well-run plants. And to do the job right, ..
HP Control: Inferential controls that correlate but do not predict
I recently received a letter from Pavlos Ioakimidis of Hellenic Petroleum responding to my editorial about inferential models that correlate but do not predict.1 That March editorial argued that regr..
HP Control: Controlling the mundane naphtha stabilizer, Part 2
Part 1 of this editorial (September issue) discussed a debutanizer control strategy (Fig. 1). Given that feed composition varies with ambient conditions, one could argue that unless you have advanced ..
HP Control: Controlling the mundane naphtha stabilizer, Part 1
Consider the distillation column in Fig. 1. It is called a "stabilizer" and removes LPG from naphtha. Every refinery has at least three of them, and often five or more, one each in every crude unit, r..
Implementing coker advanced process control
This project resulted in about a half-year payout
HP Control: What about reactor advanced process control?
The premise of advanced process control (APC) is that there is money to be made by pushing a unit against its limits while keeping the product qualities at target. This concept is easy to understand b..
HP Control: Inferential models that correlate but do not predict
A friend has asked me to help solve a dilemma. A neural net model developed in his plant had a near perfect fit against lab values but in spite of that the model's prediction ability was poor. I was s..
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