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: APC designs for minimum maintenance—Part 2
My last month's editorial proposed that since our advanced process control (APC) applications are by and large under-maintained, these applications should be designed in the simplest possible way. The..
HP Control: APC designs for minimum maintenance—Part 1
I, and others, have written much about the difficulties of maintaining advanced process control (APC) applications.1–5 It is a problem to be tackled on many levels. There are issues of manning, t..
HP Control: CDU overhead double-drum configuration
Fig. 1 shows one of many CDU overhead configurations, with naphtha cutpoint control accomplished by a column top temperature controller manipulating a top pumparound (TPA) circuit heat removal. This c..
HP Reliability: To b(ias) or not to b(ias)? This is the question
How often would you bias an inferential model? Given the propensity of instruments to go off calibration, "never" is not a valid answer. "Every day upon receiving lab information" is an equally bad an..
HP Control: Where do you take those inferential models from?
Charts shown in my editorials, illustrating the performance of select first-principles models, have attracted much e-mail feedback. While mostly positive, some question why the editorials do not provi..
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..
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