I have a question I don’t understand
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What are the advantages and disadvantages of open-loop and closed-loop cycles during the shutdown and startup of atmospheric and vacuum distillation units? Or what’s the difference if one meets the conditions?
Closed-loop cycle: It mainly involves heating and dehydration, removal of condensate, removal of waste fluids, and thermal tightening (condensate is generated during the purging process, and thermal tightening is required after equipment maintenance). In general, I think it serves as preparation for starting up the oil injection process. In the open-loop cycle, once oil is drawn from the diversion tower, the slurry begins to operate in an open-loop cycle, which is then switched to emergency venting. I believe the main purpose of this is to start gradually bringing the various equipment into operation, as well as to carry out thermal tightening.
Another important role of the closed-loop system during startup and shutdown is to prevent too rapid temperature changes, as well as thermal expansion and contraction, which could lead to leaks at the sealing points. In emergency situations such as short-term power outages, when the system temperature does not drop significantly, production can be resumed by switching to an open circuit mode; we have tried this approach, and there is no need to switch back to a closed-loop cycle.