Differences between fluidized-bed hydrogenation and suspended-bed hydrogenation

In the suspended-bed process, fine catalyst powder is pre-mixed with the feedstock, and then both are fed into the reactor along with hydrogen; they flow from bottom to top, where hydrocracking takes place. The catalyst remains suspended in the liquid phase and exits the reactor from the top along with the reaction products. Suspension bed reactors are generally of cylindrical design without a catalyst bed ； In a fluidized bed reactor, the catalyst is located within the reactor; a catalyst supply pipe is provided at the upper part of the reactor, while a catalyst discharge port is located at the lower part (to remove the old catalyst from the bottom and add new catalyst from the top). Hydrogen and feed oil enter the reactor from its lower part; as they pass through the catalyst-packed bed via a grid distributor, the void space between the catalyst particles increases gradually with the rise in flow rate, causing the volume of the catalyst bed to expand. The height of the catalyst bed is controlled by the flow rate of the circulating liquid (a circulation line is provided within the reactor; the reaction products are drawn out from the top of the reactor, pumped to the bottom of the reactor where they mix with the feedstock before entering the reactor again, thereby enabling control of the feedstock flow rate).

There are operational industrial units for fluidized-bed hydrogenation abroad, but no industrially operational units for suspended-bed hydrogenation yet.

A multiphase bed generally contains gas, liquid, and solid phases. The ebullated bed is one of the catalyst beds used in residue catalytic cracking; it is characterized by the catalyst being suspended within the bed (it does not flow out of the reactor with the stream, but there are ports for adding and removing the catalyst), with gas passing through the bed in the form of bubbles. It can be seen that, from the perspective of gas and liquid motion, bubbles move upward from the liquid phase; the bed behaves like boiling water, which is why it is called a bubbling bed. For this reason, the gas-solid two-phase bubble column is also referred to as a bubbling bed. From the perspective of the motion of the solid particles, in a multiphase bubbling bed at this stage the catalyst is suspended within the bed layer; hence it is also called a suspension bed! As for those in China who insist on calling a slurry bed a suspended bed, it is truly a misrepresentation that causes endless harm! In a slurry bed, the solid particles are not suspended within the bed layer; instead, they flow along with the liquid phase in and out of the reactor. A slurry bed is also a multiphase bed, but the solid particles are small in size; as a result, their terminal velocity ut is low, while the liquid velocity is greater than ut. Therefore, the particles are carried along by the liquid and are not suspended! When the size of the solid particles is appropriate and matches the flow rate of the liquid, the particles are carried by the liquid and remain in the fluidized zone; however, at this point the liquid velocity is less than ut, so the particles stay suspended and are not carried out of the reactor. Of course, internal components must be installed within the reactor, as the actual conditions are quite complex.

Thank you very much for the detailed analyses from the 2nd and 4th floors!

In the event of an accident, can it be handled in the same way as a fixed-bed system?

The extended version has been in stable operation for 270 days

What kind of raw materials were used in those 270 days?