Fixed-bed reactor
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Regarding the direction of material flow in fixed-bed reactors, in some of them the material enters from above and exits from below, while in others it enters from below and exits from above. Why is that? Are there any special regulations regarding the inlet and outlet directions of materials in a fixed-bed reactor? I hope an expert can give some advice. Thank you
It is common for matter to move from top to bottom, while it is rare for it to move from bottom to top; this is related to the catalyst and other process conditions.
What we see is movement from above to below. Entering from below can easily blow the catalyst away. Special fixation is required.
Here, matter enters from below and exits from above; however, a catalyst tube is used to hold the catalyst, with the reaction taking place inside the tube
We have them all here. Those with inlet at the bottom and outlet at the top generally have a lower inlet temperature, and liquid can easily be carried in the gas phase; there is a liquid discharge area at the bottom, equipped with ceramic balls and grids to prevent the catalyst from being blown away； Reactors with material flowing from top to bottom generally have a much higher temperature than those with material flowing from bottom to top, and they are where the main reactions take place. To ensure sufficient residence time and complete reaction, the reaction time is increased; more information on this can be found in other sources. :lol
Our company’s MTBE pre-reactor is a fixed-bed reactor with material entering from the top and exiting from the bottom.
The material flows from top to bottom in a fully liquid phase; the heat generated by the reaction is removed through external circulation, allowing for considerable operational flexibility； The design with material entering from below and exiting from above is suitable for gas-liquid two-phase flow, that is, mixed-bed reactors. Such reactors do not rely on external circulation for heat removal; instead, all the heat is absorbed by the material being vaporized, which prevents overheating. These reactors are designed with energy savings in mind, but they are not suitable for reaction environments that generate large amounts of heat.
A Johnson net is generally installed at the bottom of this reactor, which provides good protection against material loss