Transport and loosening of nitrogen and water vapor in DMTO. . .

Steam and nitrogen contain no O2, or have a low O2 content. After using air, the question is whether it comes into contact with the catalyst? 　 Will there be any other problems after contact? Like it becoming natural, and so on. After using air, does the device need to be purged with N2 again? Olefin plants are designed to prevent O2 from entering the system

Reply 2# douglas: Correct! In Baotou, steam and N2 are used, with switching taking place by moving the valves back and forth!

It’s really funny!

Of course, air cannot be used, as it may cause spontaneous combustion and damage the equipment.

I’d like to ask: with so many people being so certain that air cannot be used, do anyone have any evidence to back this up? Have you seen design drawings? Did you see the actual situation on site? Regarding what was said on the 2nd floor, \"After using air, the question is whether it comes into contact with the catalyst?\" Will there be any other problems after contact? Like it becoming natural, and so on. # L: After using air, does the device need to be purged again with N2? In olefin plants, it is essential to prevent O2 from entering the system. First, consider spontaneous combustion: the horizontal and vertical pipes for the unreacted material definitely carry unreacted material, which is then sent to the regenerator to be burned. So what’s the problem with spontaneous combustion? What’s there to be afraid of? What was said on the 5th floor: “Afraid of damaging the equipment?” Then why wasn’t the regenerator damaged? Moreover, the olefin plant is designed to prevent oxygen from entering the system. First of all, the horizontal and vertical pipes for the unreacted material carry unreacted catalyst, which is sent to the regenerator to be burned. And for burning to take place in the regenerator, oxygen is necessary; otherwise, burning cannot occur. Indeed, the olefin separation unit prevents oxygen from entering the system, but regeneration and reaction are two separate systems: regeneration requires oxygen, while reaction must take place in the absence of oxygen. I’m not sure whether it’s a misunderstanding of the question by everyone or some other reason, but in the case of a regeneration system, including the regeneration horizontal pipes and regeneration vertical pipes, the statement that oxygen should be excluded from olefins is correct!

Hehe, at least for the Baotou project, steam and nitrogen are indeed all that is used for catalyst regeneration: after the catalyst is stripped, it is fed into the regenerator under the action of nitrogen； After burning in contact with air, the regenerated catalyst is stripped, and after stripping it is fed into the reactor ； Coming into contact with air without stripping poses a significant safety risk from a production perspective! Is it clear now if I put it this way?

On our company’s design drawings, nitrogen is also used to transport the raw catalyst to the regenerator; after regeneration, it is then transported to the reactor using 1.0 MPa steam. Why has the use of 1.0 MPa steam for transporting the regenerated catalyst been changed? I don’t understand. . .

This post was last edited by 1681818 on 2011-1-11 00:07. Reply to 8# jinlei198761: Don’t you understand this? From the regenerator to the reactor, if nitrogen is continued to be used, it will enter the reactor and then proceed to the subsequent separation systems. Nitrogen is a non-condensable gas, and it will reach the top of the demethanization tower, thereby increasing the energy consumption of the compression system as well as that of the cold separation processes. If steam is used, it disappears automatically and turns into water in the quenching unit, having no impact on the subsequent separation system. It should be noted that the cost of separating 1 ton of nitrogen is equivalent to the energy consumption of at least 50 tons of steam.

Reply to 9# 1681818: What was said on floor 8 is very accurate; I’ve seen that in practice. But why is nitrogen used from the reactor to the regenerator? Can’t it be done with steam? If it is to prevent thermal degradation caused by contact between the catalyst and water vapor, the regenerator also has a water vapor stripping section, through which water vapor is delivered to the reactor. . .

Reply to 10# jinlei198761: In the catalyst transfer process of the fluidized bed reaction-regeneration system, nitrogen should be used whenever possible. Although its cost is slightly higher than that of steam, the amount of nitrogen used in such a reaction-regeneration system is still very low. This is because water vapor has some effect on the reaction, or more directly, on the performance of the catalysts, as well as on their hydrothermal stability, although this effect cannot yet be described quantitatively. As long as nitrogen is not introduced into the reaction gas, its use is preferred.