【JST-027】One-on-one assistance office for catalytic units (focusing on reactions, distillation, and units)
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This post was last edited by Firefly on 2015-4-10 08:27. It was created with the intention of challenging oneself, learning together, and sharing experiences. Work experience: 19 years of experience in catalytic cracking, having worked in areas such as distillation, reaction, and unit operations; currently engaged in hydrocracking production. 1. Questions are welcome regarding catalytic production operations. II. Due to work hours and limited energy, I may not be able to respond promptly; please understand. III. For issues I am not sure about, I will communicate with you and discuss them in a timely manner. IV. After all, my capabilities are limited; having worked on the front line for many years, my perspectives are largely those of someone who handles operations on the ground. I would be very grateful if you could point out any mistakes.
Hehe, Brother Dao, since you’re giving a lecture now, I won’t post a request for help. Here’s a simple question: Use elbows with a large radius of curvature at the reactor outlet, and elbows with a small radius of curvature at the inlet of the distillation tower, so as to minimize the distance between the elbows and the distillation tower inlet. Why does this method reduce coking? Thank you first!
Bro Dao, there’s another question: I’ve just started learning about catalysis and don’t have a deep understanding of reverse regeneration units. I’d like to ask what methods can be used to increase the catalyst-to-oil ratio?
Bro Dao, it seems that among the new units being put into use these days, catalytic cracking isn’t used very often; most of them are for hydrocracking or hydrorefining and similar processes. Could you please tell us about the current status of catalytic cracking and hydrocracking, as well as their future development directions? Thank you very much
There are many ways to increase the catalyst-to-oil ratio, but the considerations mainly fall into two categories: first, reducing the preheating temperature of the feed oil; second, reducing the temperature of the catalyst before it enters the nozzle. The first approach is relatively simple to implement, but due to considerations related to atomization, the range of adjustments available is limited； The latter is a relatively popular method these days; most installations involve modifications, such as pre-cooling the catalyst before it enters the nozzle. This approach requires significant investment and presents difficulties in operation, and the gasification efficiency also needs to be taken into consideration. Studies suggest that the temperature of the catalyst before it enters the nozzle should not be lower than 640 degrees. Just my humble opinion; please feel free to offer your corrections while enjoying the drink. I hope you can forgive any mistakes.
This post was last edited by liaifeng on 2014-9-16 11:27. During the training, the people from the design institute mentioned this issue and provided various theoretical explanations; I then summarized it in one sentence: Increase the line speed to reduce the probability of coking! ;P
Regarding the coking issue of oil and gas lines mentioned by the original poster, as far as I know, the current level of catalytic technology in China is not sufficient to completely resolve this problem; only improvements can be made. The key approaches to implementing this are mainly as follows: first, reduce the residence time and increase the flow rate. II. Reduce temperature drop. III. Appropriate steam supply volume. However, with regard to the sharp curve radius and gentle curve radius mentioned by the original poster, from the perspective of preventing coking, the scouring force is certainly greater on the outside of sharp curves, while it is smaller in the case of gentle curves. However, I don’t know whether the unit used by the original poster is of the cold-wall type, hot-wall type, or a combined cold-hot oil and gas type. Given the large vertical height of such oil and gas lines, design considerations must take into account factors such as process requirements, material selection, thermal expansion stresses, as well as construction difficulties and costs. The devices designed by different design institutes vary; there may be differences. In other words, the design considerations go beyond just the issue of coking, as factors such as thermal stress, material requirements, construction difficulties, and cost also play a role in the design process ； In my personal opinion, the factor of heat stress should play a more significant role in the issue mentioned by the original poster. These are just my humble opinions; I welcome any corrections. Please forgive any mistakes.
May I ask the original poster: what is your method for switching between the primary and backup units? I’ve heard that when they switch systems, they raise the outlet pressure of the unit that is to take over (such as 1#) to a value that is higher by a certain amount than the outlet pressure of the unit that is being switched out (such as 2#), by 5–10 KPa. They then fully open the electric valve at the outlet of 1#, adjust the vent valve associated with 1#, and finally fully close the electric valve at the outlet of 2# while opening its vent valve. Is such a method feasible? Our standard procedure is to, once pressure has built up, gradually open and close the four valves—namely the electric valves at the outlets of units 1 and 2, as well as the vent valves—in sequence, in small increments, to reverse the operation of the machines
Thank you for your support. Catalysis and hydrogenation both fall under the category of secondary petroleum processing (hydrogenation of crude oil is practiced abroad, but not yet in China as far as I know). Catalysis is an ideal process for producing olefin-rich liquid hydrocarbons and high-octane gasoline, while hydrocracking is used to produce high-quality aviation fuel, high-quality diesel, and lubricant base oils; however, the octane rating of naphtha is not satisfactory. With **increasingly strict environmental regulations, unclean products cannot be released directly from the facility; therefore, hydrogenation has become the preferred option. However, catalysis does have many advantages: low energy consumption and high amounts of by-product steam, which are essential for matching production capacity. For new oil refineries, in an environment where crude oil is scarce and the feedstock becomes heavier, hydrocracking is undoubtedly a relatively ideal process. These are just my humble opinions; I welcome any corrections. Please forgive any mistakes.
Thank you for your support. Please, the original poster, explain what device is used and how the primary and backup machines are switched between, thank you.
They are the main fans for catalytic cracking, along with the backup main fans; there is a triple-unit configuration for these fans, all of which are axial flow compressors.