Everyone, should the coking design use a high circulation ratio or a low circulation ratio?

It’s not that the higher or lower the value is, the better. Obviously, having a cycle is better than having none; but if there are cycles everywhere, then no material will be fed in, which is even worse. One should ask everyone what percentage the circulation ratio should be controlled at. . Let’s clear things up a bit, and everyone can go ahead. .

^_^What they say makes sense. . . In fact, the choice of circulation ratio during the design phase – the difference between high and low values – depends on the amount of coker wax oil to be circulated back in, as well as several other factors such as the selection of the feed pump. . . Considerations regarding the flux and sectioning of the heating furnace tubes. . . The impact on the yields of gases and liquids, etc. . . :Lol, I think it’s better to operate according to a large cycle ratio rather than designing and arranging production based on an adjustable cycle ratio. . . :lol Last edited by wangsc on 2009-2-3 17:02 ]

The current design trend is to reduce the cycle ratio, increase the processing volume, shorten the coking cycle, and improve the utilization rate of the coke tower.

It depends on what the objective function being pursued is: equipment investment, energy consumption, product yield, and product quality. . .

In recent years, the development trend in coking processes has been to minimize the recycle ratio. The goal is to increase the amount of feed oil available for catalytic cracking and hydrocracking by producing more coking wax oil, and then to boost the production of finished gasoline and diesel by increasing the processing capacity of the cracking units.

In coking designed based on a high circulation ratio, what should be considered when operating at a lower circulation ratio?

It is better to design based on the large circulation ratio: if the quality of the raw material is poor, a large circulation ratio ensures an adequate processing capacity; when the raw material quality is good, the circulation ratio can be reduced appropriately to increase the plant’s processing capacity, thereby resulting in better economic and technical performance for the plant； The currently designed units are quite demanding; if the actual conditions change, their adaptability is very low. For example, our units were designed with a 20-hour coking cycle, which makes it difficult to increase the processing capacity, and it is hard to operate the heating furnaces and coke towers when dealing with lower-quality raw materials

A low circulation ratio with a large processing volume is the current standard for coking units; however, a low circulation ratio leads to an increased yield of wax oil, and without facilities for further processing of this wax oil, it becomes economically unviable. If the circulation ratio is too low, the gas yield will also decrease; especially for small plants, this can easily lead to a shortage of gas, making it difficult to maintain stable production.

1. Sometimes, the choice between a high and a low circulation ratio is determined by the requirements of processing a particular feedstock. For example, when processing Tahe oil, a low circulation ratio leads to a very rapid coking rate in the furnace tubes; therefore, a high circulation ratio is generally used. In the case of other feedstocks, increasing the circulation ratio raises the aromatic content of the material fed into the furnace tubes, which helps to prevent the formation of pellet coke. 2. The choice between a high and a low circulation ratio directly affects the processing capacity and energy consumption of the facility. 3. It also influences the yield of wax oil, thereby affecting the production balance of subsequent units

Regarding whether a higher or lower circulation ratio is better in coking design, it depends on the specific circumstances of the company. First is the issue of raw materials: if the raw materials are of good quality, a lower circulation ratio should be chosen; if the raw materials are of poor quality, a higher circulation ratio is preferable. Another key factor related to the circulation ratio is the yield of coking wax oil – if there are ways to utilize this wax oil (such as in catalytic blending or wax oil hydrogenation), then a lower circulation ratio can be adopted. If the raw materials are of poor quality and there are no subsequent treatment methods available, a higher circulation ratio can be used in the design. Finally, cost is also a consideration; the design should take into account both the cost of producing products through coking and the cost of producing them through catalytic processes. It should also be noted that there is a certain ratio for the feed of coker wax oil into the catalytic and hydrogenation processes, and not all of it will be converted into products.

Coking wax oil contains alkaline nitrogen and a high amount of gums; generally, about 10% is subjected to catalytic cracking, and up to about 30% can be processed through hydrocracking. Additionally, there are significant side effects such as catalyst deactivation, so these factors need to be taken into consideration during design.

The trend is a low cycle ratio. This is mainly because many refineries have increased the processing capacity of their atmospheric and vacuum distillation units; in order to eliminate bottlenecks and reduce investment in coking facilities such as heaters, reducing the cycle ratio is the preferred option. Of course, the factors mentioned by those upstairs must be taken into consideration.