Ultra-low circulation ratio in delayed coking
Thread Content
Are there coking units that operate with a recycle ratio below 0.12, and is it possible to achieve this stably? What are the key points and challenges in fractionation and furnace operation after implementation? Everyone is welcome to discuss.
There seem to be many abroad. In China, 0.2 seems to be quite low, right?
The value currently seen in China is 0.15 in terms of cycle ratio; it’s very difficult for us to reduce it below 0.12； I’ve heard that the coking value at Guangxi Petrochemical is 0.10; I wonder what the performance in actual operation is like?
If the quality of the raw materials is good, the design of the heating furnace is modern, and it is possible to carry out online coking or coke removal, then an ultra-low circulation ratio should be achievable! I heard that abroad, zero-cycle ratio operation is now used; heating furnaces don’t require water or steam to be injected.
Theoretical analysis is possible, but in practice there are a series of issues such as excessively high temperatures of the strainer plates, difficulty in controlling the liquid level at the bottom of the fractionation tower, an increase in the carbon residue content of heavy wax oil, and a relatively low final temperature after heat exchange with the raw materials. Everyone is welcome to continue the discussion.
Reply to 5# North of the City North: You make a good point! I believe that the value of the circulation ratio is determined by the design, rather than being adjustable on the device! If the design cycle ratio is 0.4 and you want to reduce it to below 0.2, then a whole range of problems are likely to arise, such as coking in the heating furnace, increased metal content in the wax oil residue, coking in the evaporation section of the distillation tower, and other equipment-related issues as well. Currently, institutions such as the Luoyang Institute and the East China Institute are promoting a coking process with an adjustable circulation ratio. I believe it is essential to examine this carefully during the design review. By adjusting the circulation ratio from 0 to 1, the flexibility of such equipment indeed increases, but it is necessary to carefully consider the design of the raw materials and the equipment itself, as well as to verify whether true wide-ranging adjustments are possible Otherwise, once it’s in operation, the management won’t care about such things; they just want you to follow the design, and that will cause problems for the workshop!
Reply to 6# Snow removal at the north gate: Currently, flexible control of the circulation ratio is used throughout China, but it’s actually very difficult to achieve this. Our target is a circulation ratio of around 0.06–0.08, and we’re working hard to reach that level. It’s difficult to achieve a ratio lower than 0.05 using existing domestic technologies, unless deep integration between various devices is employed.
Reply to 7# North of the City North: I’m envious of you guys; it seems like your crude oil is of good quality!
We mainly import oil and crude oil from the western region; its residue content is around 23%, while the proportion of resinous and asphaltenic components is close to 50%. It’s not considered high-quality oil. We plan to use an ultra-low circulation ratio when the residue content is between 18% and 20%.