Basis for temperature selection of diesel flushing during hydrocracking shutdown
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What is the basis for selecting the temperature for flushing with diesel when shutting down a paraffin oil hydrocracking unit? Some are 280°C, some are 300°C, and some are 260°C; solve it. Additionally, how should the high-pressure bolts of the device be handled to ensure smooth disassembly? In the past, many bolts would break whenever the device was shut down.
Make sure there is no reaction; otherwise the temperature will rise again
It is generally believed that the reactive temperature of diesel in hydrocracking is 280-300
Rinsing is done to protect the catalyst, that is, to wash away the unwanted oils from it. The key is to determine at what temperature level the oil starts to crack. Apply a little molybdenum disulfide to the bolts; however, it’s normal for them to get damaged over time
Bolts can be coated with a layer of graphite powder; it works very well
Keep it as low as possible; if it’s too high, there will be a reaction
It’s better to keep the temperature low, as diesel is primarily used to flush the catalyst; a slightly higher temperature can cause the diesel to crack, leading to an increase in temperature. Regarding the bolt issue you mentioned, I have the following suggestions: 1. Protect the bolt caps to prevent them from being exposed to wind, sun, and rain. 2. Apply an anti-seize agent during installation. 3. During shutdown, when the pressure is below 3.0 MPa and the temperature is at least 150°C, it is possible to try sending fluid in first and then tightening it up. That is, loosen it when there is a certain level of heat.