How to operate when changing the hydrorefining unit to a full long-cycle mode
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When changing the cycle length, should only the manual valve be moved and not the control valve? How should the manual valves on the product outlet device and the long-cycle manual valves be operated, and what are the precautions? Thank you everyone
The outlet control valve doesn’t need to be touched for now; for the outlet manual valve and the long-cycle manual valve, one of them is opened to a certain extent while the other is closed to a corresponding extent. A long-cycle line usually has two manual valves, with one being opened first. Even if the switching is not done promptly, the problem won’t be severe; the raw material tank has a sufficient liquid level (at least 50%), and the distillation tower can also hold a certain amount of liquid for some time (usually also 50%). Therefore, it is relatively safe to switch between these processes. Here, we usually turn one on and the other off, making sure that the degrees of opening are roughly similar~~~ After making adjustments to the main circulation system, the liquid levels in each container are balanced; at that time, the external delivery valve may move~~~
Should the outlet valve be closed slightly before opening the long-cycle manual valve, in order to build up some pressure in the product line and prevent raw materials from flowing back into it?
First, confirm whether the large-circulation control valve is in operation; once it is confirmed to be working properly, open the large-circulation control valve first and reduce the flow rate controlled by the product discharge control valve, so as to ensure normal circulation. Gradually close the discharge valve to regulate the circulation level in the buffer tank. If there is leakage from the product discharge, contact the field operator to take corrective action on-site
1. Some large circulation lines are equipped with check valves (some have control valves). 2. Generally, by the time a circulation line needs to be modified, there are already problems with the product; in such cases, it has usually already been switched to an unqualified production line by then. 3. Generally, when the circulation rate is increased, the feed material has already been cut off, and intermittent feeding is usually employed. Since the closed-loop backwashing is still in operation, the fuel consumed for backwashing is also a reason for the decrease in the liquid level in the tower within this closed loop; therefore, a supply of straight-run diesel feedstock is needed periodically to maintain the liquid level. 4. What circumstances of the device are taken into account for the situation you are asking about?