Petrochemical plant coke towers suffer from sugar-coated date-like creep deformation over time; it’s not clear why this occurs starting from the lower part, moving from bottom to...
Thread Content
This post was last edited by WANGJIABAO on 2017-7-13 at 13:09. I have a gentle question: long-term use of coking towers in refineries can lead to swelling deformation in a shape similar to that of sugar-coated haws. I don’t understand why this deformation starts from the bottom and progresses upward, forming a structure akin to sugar-coated haws
The connection between the tower and the skirt has high rigidity; if no insulation box is provided for the skirt, significant temperature difference stresses arise at the junction of the skirt and the lower head. This leads to a thermal ratcheting effect, allowing the upper part to expand more freely.
The description is too scary. Are there any pictures?
I’m not aware of the operating conditions of this device; it is likely to be operating under high temperatures, and creep caused by exceeding its service life is probably the issue.
In my opinion, the coke tower operates under high-temperature conditions; the load at the bottom of the tower is greater than that at the top. Under these high temperatures, the material at the bottom undergoes creep (plastic deformation), which strengthens the material and prevents further deformation. The stress conditions in the shell near the upper part of the tower change as a result, leading to deformation – and that’s when problems arise:P. It’s completely based on the opposite of the results; I’m waiting here for an expert to explain it. Just to verify my own idea.
A large axial temperature difference exists above and below the surface of the cold coke water, resulting in high thermal stress. The cyclic effects give rise to a thermal ratchet effect; swelling generally first occurs at the third ring weld at the bottom, which is the location where the cold coke water reaches rapidly through the channels. The weld metal has higher strength and better resistance to ratcheting deformation, while the base material is of lower quality; as a result, the cylinder swells gradually between the welds.