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In our kero minus hydrotreater unit, employing Albemarle catalyst, I witnessed an abnormal behaviour in preheat exchanger and HP separator.
A pressure gauge is installed at downstream of tube side of last preheat exchanger that essentially indicates pressure drop in tube side (Reactor downstream) of exchangers. The said gauge has hunting of approximately about 1 bar. I first wonder why is this happening as there is no chance for continuous pressure fluctuations in the circuit. I also presumed gauge to be faulty and asked maintenance section to replace it, but the problem still prevails.
Then I found the level fluctuations of the approximately same kind in HP separator. The level transmitter in our DCS didn't indicate this rise and fall, but the level glass proves this abnormality.
I am unable to understand this behaviour and seek experts advice.
25/02/2018 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
Pressure fluctuations in reactor circuit is very rare. Some checks to be carried
What is the makeup H2 control valve opening during normal operation and upset conditions? If there is no margin in makeup H2 Control valve and it may open 100% during upset conditions and hence reduction in absolute pressure in reactor circuit. If the pressure drop is constant in reactor circuit which can be checked by compressor differential pressure, it is due to hydraulic constraints like makeup gas H2 valve opening and other constraints.
22/02/2018 A: Wang Tzu Hong, Formosa Petrochemical Corporation, 424606@rffpcc.com.tw
It's an quite strange phenomena for me. Have you checked pressure control valve which is located at cold separator (system pressure)? Theoretically Reactor inlet pressure would have fluctuation when throughput changed (hydraulic effect), but not for reactor outlet.