Regarding the issue of the amount of stripping steam required for the catalytic reaction position

The basis for this is the amount of oil and gas carried by the catalyst; the more oil and gas it carries, the greater the amount of stripping steam required. The amount of oil and gas carried by the catalyst is determined based on both the properties of the feed material and the temperature of the catalyst bed. If the properties of the feed material change, the bed temperature will definitely rise. If the properties of the feed material remain unchanged and there are no issues with the heat removal system, then it means the catalyst is carrying oil, and in such cases the volume of gas should be increased. At the same time, attention must be paid to the pressure drop in the cyclone separator to prevent an increase in the solid content

In the past, catalytic units were equipped with sampling ports for the raw catalyst, and the amount of stripping steam used was adjusted by analyzing samples of this raw catalyst; however, nowadays the amount of stripping steam is generally adjusted by monitoring the cyclone pressure drop, as well as the bed temperature and lean-phase temperature of the regenerator.

The steam volume for stripping in the settler directly affects the stripping efficiency and the catalyst density in the stripping section. An insufficient amount of stripping steam, along with a catalyst density in the stripping section exceeding 700 kg/m3, may affect the proper delivery of the spent catalyst to the regenerator. An excessive amount of stripping steam increases the energy consumption of the unit and raises operating costs. Generally, the amount of stripping steam is controlled to be about 0.35% (by mass) of the catalyst circulation volume. During normal production, depending on the production load, a larger amount of stripping steam is used first; then this amount is gradually reduced, while monitoring the changes in regeneration temperature. Once the regeneration temperature starts to rise, the amount of stripping steam is increased appropriately. When a gauge failure or an interruption in the supply of steam results in a sudden drop or cessation in the flow rate of stripping steam, it is necessary to immediately reduce the flow rate significantly or, as appropriate, shut off the reaction feed to prevent the catalyst from becoming inactive and causing a disruption in its circulation. A low amount of stripping steam results in inadequate catalyst stripping, which can lead to the presence of oil in the catalyst; on the other hand, an excessive amount of steam affects the density in the stripping section, again causing the catalyst to carry steam into the regenerator and affecting its thermal stability. The steam in the stripping section can also reduce the vapor pressure of oil and gas in the settler, as well as shorten the residence time of oil and gas, thereby reducing coking~~~~~~

It is better to keep the amount of gas vapor at a slightly higher level. Additionally, it should be noted that the effectiveness of stripping is also related to the amount of material present in the stripping section

An excessive amount of stripping steam is not only unnecessary but also harmful. It is determined by the bed temperature of the regenerator. It is written very clearly in the textbooks, and the same is true in production.

A higher amount of stripping steam is beneficial for desorbing oil and gas; the catalyst to be regenerated does not contain oil. However, too high a steam volume can lower the temperature in the settler. In our plant, the feed rate is 64 t/h, so let’s use 3.7 units of stripping steam – a slightly higher amount is better. The catalyst density in the stripping section is unstable in our plant. Another issue we face is that the catalyst density in this section drops from 500 to 250, then rises back to around 500. This cycle repeats every 4 days, but otherwise production remains stable. Could anyone help explain the reasons behind this?

When the raw materials remain unchanged, the amount of stripping steam can be determined by changing the bed temperature