Heating of iron-molybdenum catalyst
Thread Content
The spare channel steel molybdenum hydrogenation catalyst of our company has been sulfided. We now want to put this sulfided spare catalyst into the system, but it is not possible to raise its temperature using recycled nitrogen in production; can coke oven gas be used for heating instead?
It’s possible; just be careful with the heating rate
If using gas for heating, what should the rate of temperature increase be?
Follow the curve provided by the catalyst manufacturer; this curve is usually established after being reviewed jointly by the reactor manufacturer and the catalyst manufacturer. The catalyst supplier proposes it, the equipment manufacturer gives its approval, and it is recommended that your company consult facilities that have used this type of catalyst. The catalyst manufacturer will provide a list along with contact information.
At our company, a spare tank is currently used for the pre-hydrogenation tank, and heating takes place online; in this case, will the catalyst manufacturer also be responsible for providing the heating curve for the gas?
20-30 per hour is fine
Currently, the system is in operation. During the initial stage of heating, circulating nitrogen was used for this purpose; however, nitrogen can no longer be used. When heating online, the flow rate of gas at the inlet is very low, and due to this low space velocity, the temperature at the upper part of the bed reaches around 250 degrees, while the temperatures in the middle and lower parts remain at 50-60 degrees. I don’t dare increase the air velocity now, for fear that the organic sulfur won’t be completely converted, which could affect the zinc oxide later on.
Currently, the system is in operation. During the initial stage of heating, circulating nitrogen was used for this purpose; however, nitrogen can no longer be used. When heating online, the flow rate of gas at the inlet is very low, and due to this low space velocity, the temperature at the upper part of the bed reaches around 250 degrees, while the temperatures in the middle and lower parts remain at 50-60 degrees. I don’t dare increase the air velocity now, for fear that the organic sulfur won’t be completely converted, which could affect the zinc oxide later on.
It is difficult to control the heating rate of iron-molybdenum catalysts; it is generally kept at 15°C/h. Once this rate exceeds 20°C/h, the temperature can rise rapidly, and the catalyst is prone to caking. During sulfidation, the heating rate for iron-molybdenum catalysts should be controlled at 10–15°C/h, while a higher rate of <30°C/h can be tolerated during the passivation stage
Don’t the catalyst manufacturers come to the site for guidance?
We use gas to raise the temperature, but the backup tank has a temperature rise line outlet that does not go straight backward.