Level control of tank V1101
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As shown in the diagram, is the liquid level in tank V1101 controlled by the control valves 1 and 2 indicated in the diagram? If the liquid level in tank 1101 is high, the control valve that sends the mixed naphtha to the tank area will open to allow flow. I’m not sure if this is correct; please share your thoughts
This is a complex control system; there must be a sequence in the operation of these two control valves. If the liquid level is high, the feed valve should be closed first to maintain a stable liquid level, while the discharge valve remains open to keep the operating conditions unchanged. If the liquid level continues to rise even after the feed valve has been closed, then the discharge valve will be opened wider. As for how it is controlled specifically, it needs to be confirmed with your process and instrumentation teams.
Agree with the view of Building 2#. When the feed for catalytic reforming pre-hydrogenation is roughly in balance with the total amount of straight-run naphtha, coker naphtha, and hydrotreated naphtha from fractions, there is no need to supply material from the mixed naphtha tank farm or return material to it ； Supplementary feeding from the mixed naphtha tank farm or returning material to the tank farm is only necessary when it is difficult to maintain balance. In the diagram, the bypass line with a control valve below the pump is the return bypass for the pump outlet.
This diagram is just a PCD diagram (process control schematic), and the labeling is not standardized. Both Valve 1 and Valve 2 have flow detection; obviously, this forms a flow control circuit. How can the signal output by the level controller LIC be sent directly to Valve 1 and Valve 2? What is the relationship between the liquid level control signal and the flow measurement signals of valve 1 and valve 2? Some are hard to tell. It is presumed to be level-flow cascade control, where the switch can be controlled by valve 1 or valve 2; it is not clear from the diagram whether the selection is automatic (based on conditions) or manual.