Do all the main fractionation towers in catalytic units have two types of recycle streams?

When No. 2 Unit is in operation, diesel can be used to supply the inlet of No. 1 Unit’s pump; this will help No. 1 Unit to reach a higher flow rate more easily

Heavy oil units generally do not have this; the desorption tower uses steam as a heat source. Distillate oil units do have it, and this is determined by the thermal balance of the unit. At the beginning of operation, diesel is not exported, or it is used to replenish the intermediate system.

Our door factory used to have this feature but later discontinued it; when it starts operating, if the fuel level is low, diesel can be used to top it up.

The second type refers to re-refining oil, which is present in any facility

Because some have secondary fractionation columns for gasoline reprocessing, secondary circulation for heat extraction is generally not required. I am referring to the main fractionation tower where the oil and gas from the heavy oil lift pipe enter; it is generally included in SEI designs, but not always in LPEC designs.

We have two types of fractionation towers, which are connected to the re-refining unit. Rerefined oil can be used for the second process. There is light diesel supply at the inlet of Pump 1. It’s easy to increase the volume.

The number of intermediate sections in a distillation tower is determined by the thermal balance of the entire tower. Different units have varying designs due to differences in the raw materials used, production objectives, and approaches, so there is no universal rule that applies to all cases. The method to increase production at the middle fraction stage as early as possible during the startup phase is, as mentioned in the previous sections, to add feedstocks such as diesel that have a boiling range similar to that of the middle fraction. At the same time, if the middle section serves as a heat source for other heat sinks, heat extraction can only be carried out once the temperature in that section rises to a certain level; otherwise, it is likely to cause pump evacuation.

We have No. 2 Unit providing heat for the stabilizer, as well as for the nozzle and the fractionation tower

Our original old unit had two types of recirculation: heat exchange took place on the second layer, after which the fluid returned to the fifth layer. Our new unit now does not draw from the second stage; instead, the oil recycled from the second stage is pumped back to the third stage of the distillation tower via a recycle pump, where it is used as reflux. In Qingdao, the process also involves pumping the fluid out using a re-refining pump, using it as a heat source in the stabilizer tower, and then sending it back to the fifth stage of the distillation tower

The key is to see whether your device is from the Luoyang Institute or Beijing’s; the two are different

The main and secondary fractionation towers refer to the two lift-column reactor units in the FDFCC system; there are two lift-column reactors and two fractionation towers. In an MIP unit, there is only one lift-column reactor and thus only one fractionation tower. What kind of device is the owner’s? The reflux in distillation column 2 of the MIP unit is essentially re-refining oil; during startup, diesel is fed into column 1, and attention should be paid to dehydration at the inlet of pump 2 – this is not difficult to achieve

Whether to implement secondary reflux is determined based on the plant’s processing capacity and thermal balance; generally, secondary reflux is used when the plant has a high processing capacity and a high slag inclusion ratio.

The term \"main fractionation tower\" comes from delayed coking. Because coking involves several stripping towers, absorption stabilization, and so on. The discussion extended to catalysis. Generally, loops for level one and level two need to be established, and the process of setting them up is not complicated

In our unit, the reprocessed oil is drawn from the third stage; part of it is pumped back to the second stage of the distillation tower as an internal reflux via the reprocessed oil pump, while another part is sent to the stabilizer as a heat source there before being pumped back to the fifth stage of the distillation tower. The third portion is used to replenish the feed tank.

Many units in the secondary distillation and re-refining systems have this feature; the decision is mainly based on the overall heat balance of the distillation column in that particular unit. For example, when the process of a certain unit is changed from MGD to MIP, the degree of reaction increases, the temperature at the exit of the riser decreases, re-refining is reduced, and thus the heat generated by the distillation column also decreases. As a result, the heat extraction from the secondary reflux stream is discontinued (only the re-refining system remains), and the heat is transferred upward. If the flow rate to the primary distillation column is insufficient, light diesel can be used to supplement it. This post was last edited by wangrennan1984 on 2008-10-25 at 14:47

In the catalytic cracking of heavy oil, as designed by the Beijing Design Institute, there is a secondary reflux. This reflux is generally drawn from the third stage of the distillation tower and sent to the reprocessing buffer tank, from where it is pumped out. Part of this reflux is used to maintain the liquid level in the distillation tower; it enters at the second stage of the tower and is known as internal reflux. Another part goes to the lift pipe for reprocessing, thereby increasing the thermal load on the distillation tower – this is referred to as reprocessing reflux. Still another part serves as secondary reflux, returning to the distillation tower from its fifth stage. This flow passes through the heat exchanger at the bottom of the stabilizer, providing heat to that area and ensuring that the saturated vapor pressure of gasoline remains within acceptable levels.