Hydrocracked aviation fuel becomes cloudy at 20°C
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The device operates in a single-stage series pass, using a catalyst developed by the Fuyan Research Institute. The reaction oil first enters the main stripping tower, and then goes into the distillation tower to separate diesel, jet fuel, and naphtha. Low-pressure steam is used in the distillation tower, medium-pressure steam is used in the side-stream diesel tower, and waste oil is utilized for heat exchange in the jet fuel tower. The water content in the aviation fuel has been checked and is normal, at 50 mg/kg. Checking the components of the jet fuel tower showed no abnormalities, ruling out internal leakage in the heat exchanger. The jet fuel is extracted at around 45°C; right after extraction, it is clear and transparent. When at room temperature, it becomes slightly cloudy from time to time; when the temperature drops to around 20°C, it often turns white and cloudy, though there are also cases where it remains clear. No cause can be found at the moment; there’s no clue
The distillation tower operates at 0.05 MPa; the kerosene and diesel towers should be the same as the distillation tower
The kerosene samples taken before and after steam extraction remain clear and transparent when stored in the refrigerator. Occasionally, there is a dullness and poor light transmission; whitening occurs less frequently. At present, we can only suspect changes in the properties of the crude oil
It’s best to continuously monitor the water content; I suspect that water separation isn’t occurring properly during stripping. It is best to determine the water content while the sample is still cloudy. The phenomenon you mentioned is still an indication that the amount of water is below the required standard. Substances that generally precipitate during oil refining at around 20 degrees cannot be paraffin-based; such substances only precipitate at temperatures near the freezing point.
We have two sets of catalytic cracking units, and both have the same water content of 50 mg/kg. The jet fuel produced by Unit 1 is normal, while that produced by Unit 2 becomes dark and turbid when the temperature drops to 15°C. It is normal to mix the two types of jet fuel in a 1:1 ratio.
It’s probably a problem that occurs during the distillation of diesel and jet fuel
Jet fuel fraction: 140–245°C. When heated in a water bath to 15°C, it becomes turbid; adding potassium hydroxide makes it clear (it is said to be due to the absorption and dissolution of water). Place it directly in the refrigerator to keep it clear; lowering the temperature of the water bath used for experiments to 5°C is not supported by the device. … So far, all attempts at experimentation and adjustment, such as increasing the cracking temperature rise and reducing the dry point of aviation fuel, have yielded no significant results. I merely suspect that there’s a leak in the tail oil heat exchanger or that the trays in the fractionation tower have flipped. The cause of the turbidity has not yet been determined; do any of you have any ideas or experimental methods?