How to control the reduction of primary reforming catalyst by heating up to prolong its service life?

NiO can be reduced at a low temperature of 250-300℃, but the active Ni generated by low-temperature reduction is very sensitive to poisons, easy to be poisoned and not easy to be regenerated after being poisoned, and a higher reduction temperature can make the tube inlet temperature increase accordingly, which is favourable to ensure the reduction of the catalyst of primary reforming tube inlet. Therefore, in recent years, most ammonia plants use the reduction operation only when the outlet temperature of the section furnace is close to the operation temperature (about 700℃).

Pressure has no effect on the chemical balance of NiO reduction reaction, and the pressure is generally controlled at 0.5-0.7 MPa during the reduction process. In this way, the gas flow rate of each reforming tube can be made larger and the gas flow distribution is even by using less reducing gas, which is beneficial for the catalysts in each tube to be more consistent in the reduction process.

In addition, if a certain amount of hydrogen is added to the reducing gas, the reduction degree of the catalyst in the upper layer of the reforming tube can be increased, and the activity of the catalyst in the inlet of the reforming tube can be maintained at a high level, which in turn can increase the apparent activity of the catalyst in the whole furnace.