Weekly Topic (11.21-11.27): Advantages and Disadvantages of CS and KH for Catalytic Cracking Nozzles

I’ve only used CS, and the results are good. As for what kind of nozzle to use, it depends on the actual circumstances.

It mainly depends on looking at the analysis results of the raw materials and regenerated materials, as well as the specific consumption of catalysts. The analysis results show that, compared to fresh catalysts, a catalyst with a smaller particle size distribution and less damage, as well as lower catalyst consumption, performs better. However, this is just one aspect; the product distribution also needs to be taken into consideration. In any case, it’s really difficult to make a clear comparison. Good atomization results may imply more severe damage to the catalyst.

The KH nozzle is currently one of the most widely used catalytic cracking feed nozzles, while the CS nozzle is also quite common, especially in domestic refining companies. Regarding their use, there are various opinions on aspects such as the atomization effect, liquid yield, and coking behavior; users also hold different views. In terms of application, KH requires high power for atomization, resulting in a relatively large pressure drop. Perhaps once the steam pressure is too low, it will not achieve its designed effect ； CS has less stringent requirements in this regard; slight fluctuations in steam don’t have a very serious impact. KH often vibrates during use. As for the liquid yield using their respective liquids, it is difficult to calculate without long-term testing and observation due to the variations in the properties of the raw materials. Of course, the specific usage and selection depend on the requirements of the device design as well as its suitability for actual production. Please point out any mistakes.

During the first operation of the Haiko reprocessing unit, both the raw material nozzle and the slurry reprocessing nozzle used KH nozzles. As mentioned on floor 3, these nozzles require a high amount of steam for proper operation, and they suffer from severe coking – a problem that may be related to the properties of the raw materials as well as the level of operational skill. When maintenance was carried out, CS nozzles were installed, and the results were good: they provided excellent atomization, with little reliance on steam for this purpose.

In fact, the various types of nozzles available in China, such as KH, BWJ, LPC, and CS, each have their own advantages and disadvantages. Relatively speaking, they all require a relatively large amount of steam for atomization, and they have different effects on coking; the quality of the products produced by these nozzles is more or less similar. Furthermore, the improvement in atomization effect brought about by high-speed nozzles affects the generation of fine catalyst powder to a certain extent. It’s a type of nozzle imported from the UK that I’ve seen; its structure is very simple, the pressure drop is low, and the overall benefits are quite noticeable. (It’s inconvenient to go into too much detail.) ）

Regarding the raw material nozzle, this is likely a matter of personal opinion. As for the effects mentioned by various parties, they all seem a bit far-fetched. Issues such as the device’s yield and coking cannot be simply attributed to the feed nozzle. The most critical parameters should be the efficiency of atomization and the appropriate linear velocity – it is necessary to avoid eroding the catalyst while at the same time ensuring a flow rate through it; however, these two parameters cannot be verified using the equipment available.

The last edit to this post was made by lijianhuai on 2011-11-24 at 00:06. Differences between the two types of nozzles: 1. The linear velocity differs; starting with KH-1, KH nozzles utilize a high linear velocity approach in order to achieve better atomization of the material. Although the linear velocity of these nozzles has decreased somewhat, it remains above 90 m/s, which can easily lead to the fragmentation of the catalyst； The linear velocity of the CS nozzle is only around 60 m/s, so it has little impact on catalyst fragmentation. 2. Their durability varies: CS nozzles can be used for over three years without any problems, while KH nozzles typically show varying degrees of wear after just one year of use, with severe cases resulting in the loss of the nozzle tip. 3. The atomization effects differ: the droplet size produced by the CS nozzle is around 60 um, which is roughly consistent with the average particle size in the catalyst, whereas the droplet size produced by KH is larger. 4. Due to the high linear speed of the KH, it is prone to cause resonance with the lift pipe. 5. The amount of vaporized steam varies, with slight differences among different users. Furthermore, a low nozzle pressure drop is not a good thing. Raw material atomization can be divided into film atomization and explosion atomization; the nozzles produced in China are mainly of the film atomization type, and the energy required for explosion atomization comes from the nozzle’s pressure drop

Professional! I learned it! The unit originally used KH, but now CS is being tried out; a decision has not yet been made. The results will be assessed after the maintenance work, and there will be overall changes. .

I’m a beginner, and I’d like to ask gently: what’s the difference between CS and KH nozzles? Are there any textbooks?

The requirements of KH nozzles regarding steam pressure stem from their unique design concept; they utilize the difference in flow velocity between steam and oil to achieve atomization. There are two constrictions, which correspond to two stages of atomization – the first constriction serves to pull the oil stream into sheets, while the second constriction accelerates this process by using the difference in velocity between the high-speed steam stream and the two-phase flow to push these oil sheets out of the nozzle, thus completing the atomization process. The exit line speed is around 60 to 70 m/s, the particle size is approximately 60 um, and the pressure drop is between 0.3 and 0.4 MPa. The pressure drop is inversely proportional to the particle size; the larger the Yajing value, the finer the particles, but the power consumption increases accordingly. It is precisely due to the requirements of the nozzle throat that it is sensitive to steam pressure; therefore, it is necessary to determine the actual value of the steam pressure in the chamber accurately, ensuring that it does not deviate too much. It is advisable to set a slightly lower value and use nozzle design to compensate for this. The throat is actually a Raoult nozzle, the exhaust nozzle of an aircraft engine. Overall, the KH steam consumption is relatively low, ranging from 3.5% to 4.2%; in our case it was as low as 2.56%, and no coking occurred. Regarding the coking issue that occurred in other manufacturers, I believe it was due to a lack of attention to the requirements of the nozzles regarding steam pressure; the control parameters were not set appropriately, as the optimal performance is achieved when they are at the design values. The concept of CS is different from that of KH; it requires more steam consumption. The total amount of steam used over a 3-year cycle is relatively high, and the cooling requirements after distillation also increase.