I have a question regarding the commissioning of atmospheric and vacuum distillation units

Reply to 1# czh214: During the commissioning phase of the atmospheric and vacuum distillation unit, it is necessary to properly drain and remove water from various towers, heat exchangers, process pipelines, as well as pumps, and to carry out replacement operations. 1. At the beginning of operation, carry out purging of the steam tower, heat exchangers, and process pipelines. The timing must be chosen carefully; it should not be too early, as this will result in the formation of a large amount of condensation water, reducing the effectiveness of heating and preheating while also wasting steam. 2. After feeding the crude oil into the atmospheric and vacuum distillation unit, an open-loop circulation is carried out first to replace any water remaining in the unit—such as from line purging—with crude oil. This prevents issues such as impaired operation of the heater due to excessive moisture content in the feedstock, or the transport of water into subsequent systems, which would otherwise increase the difficulty of operating the pumps at the bottoms of various towers and side-stream pumps, thereby reducing the frequency of pump cavitation. 3. Whenever the crude oil arrives, promptly switch to the standby pump and drain all the water accumulated in it. This prevents any issues during subsequent pump switching, such as insufficient flow rate due to residual water in the standby pump, which could otherwise affect the stable operation of the unit. 4. After the open-loop cycle is completed, the device enters the closed-loop cycle phase of heating and dehydration. During this stage, the water remaining in the trays, packing, oil collection tanks, buffer tanks, etc., of various towers is removed, and further removal of water from the pumps, heat exchange equipment, and pipelines is carried out. Note that the temperature increase at this stage must be slow and gradual, in order to avoid incidents such as boiling over or column flooding. This is to prevent coking of the trays or packing in the distillation section at the top of the tower; furthermore, it avoids the introduction of heavy oil into the condensation system at the top, which could block the outer walls of the condenser tubes and severely impair the cooling efficiency. It has a serious impact on the stable operation of downstream equipment. 5. The switching and dehydration of all standby pumps must be completed during the crude oil circulation dehydration phase; it is advisable to avoid delaying this until the stage of stable plant operation. 6. In cases where there is a tower-top recycle reflux or an interruption in the recycle reflux, promptly restart the recycle reflux so that oil can be produced from the side draw as quickly as possible. 6. Once the liquid level is properly established in each surge tank or in the oil collection tank, promptly start the side-stream pumps to gradually establish reflux. Control the gas-phase temperature at each tray section to ensure stable oil discharge from each side stream and a steady temperature rise across all tray sections. Maintain control over the three major balances to ensure a smooth start. 7. Adhere to one principle: If the light-end content at the head of the distillate on this side stream is too low, increase the temperature of the reflux oil on this side stream while ensuring that the reflux rate remains unchanged. If the reflux rate is too low, it should be increased. If the return flow rate is too high, lower the temperature of the return oil while reducing the return flow rate. The necessary reflux rate and appropriate reflux oil temperature are the most important conditions for achieving product distillation.