Some issues regarding the shutdown of the diesel hydrogenation unit

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Dear experts, this is my first time encountering a shutdown of a diesel hydrogenation unit, and I have a few questions I’d like to ask you: 1. During the phase when hot hydrogen carries oil, can the units you work at remove all the oil carried by the hot hydrogen? 2. Does everyone in the distillation system go through the stage of water washing first, followed by steam purging? If so, how can we speed up the rate of water release? We released water at a low level for over a day yet still haven’t emptied it completely. Is there a way to feed oil directly into the steam stream without water first? If so, I was wondering if it’s possible to keep it clean? 3. How does everyone handle the reboiler at the bottom of the distillation tower? It’s of course best to use a reboiling pump to push water in a reboiler, but the water that accumulates inside the furnace tubes is difficult to remove; steam isn’t sufficient to push it out, and water hammer occurs as well. Does anyone have any good solutions for this issue? If steam is introduced directly, our reboiler has only one 10-kilogram steam line on the main pipe for the four feed streams. During plant shutdowns for maintenance, the pressure in the steam network is low, so it’s not possible to clear all the steam completely. If we try to clear it stream by stream, there are no valves at the four outlets, so the steam blown from one stream inevitably returns to another stream; this back-and-forth process also prevents complete cleaning. Does anyone have any good suggestions? 4. After stopping production and opening the container, if ferrous sulfide is present naturally, do you think it is better to use nitrogen or steam? Of course, it’s the distillation system. 5. Does everyone’s unit use purge steam for the distillation air cooling? We have 8 air coolers for distillation; steam is supplied at the pump outlet, but it’s not possible to achieve proper purging at the air cooling section at the bottom of the distillation tower. 6. When the shutdown temperature drops to 250°C, are everyone still feeling hot? 7. It is said that pumps should not be exposed to steam; what effects will exposure to steam have on the pump? Can’t get in at all? When the diesel feed pumps are shut down, is it possible to introduce water to push the oil out? Our facility requires that no water should enter, and a blind flange has been installed at the inlet. Do you think this is necessary? There are quite a few questions; everyone can share as much as they can. I’m a beginner, so I hope you’ll be kind enough to give me some guidance. Thank you!