Why does catalytic cracking diesel change color?
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Please, experts, help me understand why the diesel in my distillation column changes color. The diesel comes out of the stripping tower, passes through a heat exchanger as well as water and air coolers before leaving the plant. Now that the heat exchanger has also been removed, why does the diesel still change color?
Have there been any changes to the specific operational parameters, etc.? Including the properties of the raw materials, etc.
What color has it become? What are the conditions? It takes a few more words to make a judgment
Does it change color after sampling? Catalytic cracking diesel contains highly active sulfur and nitrogen compounds as well as unsaturated hydrocarbons, which result in poor stability; its color darkens when exposed to air.
The antioxidant stability is poor – has the properties of the raw material changed?
Determine whether there have been any changes in the properties of the catalytic feed. Normally, catalytic diesel has a high content of unsaturated hydrocarbons and poor oxidation stability, causing it to darken easily when exposed to air. The heavier the catalytic feed, the higher the content of unsaturated hydrocarbons in the catalyzed fuel, and the more likely it is to change color.
If the properties of the feed and the reaction temperature remain unchanged, check the heat exchanger used for heating the fuel to see if there is any internal leakage.
If the raw materials are fine, the only explanation is that the high temperature causes discoloration when it comes into contact with air; in other words, the cooling effect of the cooling system after leaving the stripping tower is insufficient.
If Cuichai is not subjected to hydrogenation refining, it tends to discolor easily when stored!
The main thing to check is whether there are any internal leaks; if the fuel is left to sit for too long, it will change color.
Catalytic coal has poor oxidation stability and tends to change color easily; it requires hydrogenation refining