Coking in the bottom reboiler of the pentane removal column in the vapor phase unit
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The bottom reboiler of our vapor-phase depentanizer develops fouling every 2 to 3 months; it is necessary to replace the reboiler tube bundle, remove the fouled material, clean it, apply anti-corrosion treatment, and then put it back into use. It wasn’t like this before; somehow, later on, it became necessary to clean it every few months.
What is a heat source? Coking? What kind of burn?
The main reason is estimated to be the presence of degradation products of amine solutions from upstream units in the raw liquefied gas, as well as the prolonged residence time of these degradation products at the bottom of the depentanizer and the low flow velocity there. Solutions: 1. Analyze the coking substances to determine whether they contain components such as MDEA. 2. Analyze whether the dehydration property of the vapor-phase raw material tank is alkaline. 3. Analyze whether the raw material contains high levels of MDEA or NaOH, and also check for the presence of disulfides. If the analysis is correct, then carry out modifications: 4: Modifications to be made (1) Adjust the operations to reduce the temperature at the bottom of the tower. (2) Add a return line at the bottom pump discharge to change the flow pattern at the tower bottom. (3) Optimize the raw material by adding liquefied gas washing tanks and sand filters at the liquefied gas inlet or in upstream units. (4) If processing coked liquefied gas, add a filter before the unit to prevent the carryover of coke dust
It is recommended to analyze the coking object
Add a pipeline circulation pump; increasing the circulation rate will prevent coking
Our factory has also encountered such problems; after inspection, it was indeed an issue with the raw materials. I support the opinion from the 4th floor; I suggest you test it according to that opinion
The owner needs to clarify clearly what the reboiler at the bottom of the vapor dewaxing tower exchanges heat with; this is very important. Another aspect is analyzing the substances that cause coking; we conduct thorough tests every time we remove the core, identify the causes by analyzing the components, and then propose solutions for improvement
Only by knowing the reason can we find a solution. First, find out what substance is causing the coking, and then propose a solution
Thank you all. I’ll collect some data first and upload it when I have time. Coking: It is black in color; when heated to a certain temperature using electricity (I can’t remember the exact temperature), it evaporates completely, leaving no residue. A black liquid is obtained from the raw material buffer tank after desulfurization; this liquid is likely an alkaline solution combined with a deodorant. Heat source: Steam reboiler. This post was last edited by rainghost on 2009-4-10 23:07]