Q&A on hydrogen production technology, solutions to doubts
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115. Why does the temperature rise gradually at a distance of two to three meters up the upper section of the conversion tube? How is a sudden or rapid, sustained increase caused? How to handle it? Answer: The hydrocarbon steam conversion reaction is a highly endothermic reaction. At the beginning of catalyst use, its activity is high, and the reaction occurs more intensively at the upper two to three meters of the conversion tube. The strong endothermic nature causes the temperature in this area to be low. Over time, as the nickel crystals in the catalyst gradually grow larger and the structure of the catalyst changes, its activity declines slowly, which results in a reduction in the amount of heat absorbed during the reaction. This causes the reaction zone to shift downward; in terms of temperature distribution, this is manifested as a gradual increase in temperature at the two to three meter mark. If there is no carbon buildup, it generally stabilizes after some time of use. After the catalysts that have been poisoned or slightly carbonized are regenerated with steam and reduced again, the temperature at two to three meters above them generally also drops. A sudden or rapid increase in temperature by two to three degrees is an abnormal phenomenon. Catalyst poisoning and deactivation, as well as the deterioration of light oil feedstock and an imbalance in the water-to-carbon ratio, are often the main causes. Additionally, sudden changes in environmental conditions can also lead to this phenomenon. When encountering this phenomenon, it is necessary to immediately analyze and identify the cause, swiftly determine a solution to address it, and prevent further deterioration that could lead to catalyst damage. I would like to know why the reaction is more intense at a distance of two to three meters up the conversion tube; how is the reaction in other areas?
The top burner has the highest temperature at this location, providing excellent conditions for the conversion reaction. It’s just my personal opinion
In my personal opinion, it is within this distance range that more reactions occur, resulting in more heat absorption! This is related to various factors such as the performance of the catalyst, space velocity, feedstock, operating parameters, packing quality, the location of thermocouples, and measurement errors! It can only be used as a reference!
The higher the concentration of the reactants, the faster the reaction rate
Hydrogen production plant operator, conversion reaction mechanism
Personally, I think 2-3 meters is exactly the length at which the flame is longest; the temperature is highest here. Since the steam conversion reaction is an endothermic reaction, the reactions occur more intensely here compared to other sections of the pipe