Preparation method and preparation device for synthesis ammonia prereduction catalyst

Abstract

The invention provides a preparation method and a preparation device for a synthesis ammonia prereduction catalyst. The preparation method comprises the following steps: feeding a synthesis ammonia Fe catalyst into a reduction tower, and introducing mixed hydrogen and nitrogen; then heating at a heating rate of 30-40 DEG C / h, and performing reduction reaction when the temperature raises to 365-380 DEG C; after the reduction reaction is over, discharging the mixed hydrogen and nitrogen out of the reduction tower; when the temperature is reduced to be not higher than 50 DEG C and normal pressure is achieved, introducing oxygen for passivating, wherein the pressure during the passivation process is kept between 0.018MPa and 0.02MPa; and after the temperature is reduced to be not higher than 46 DEG C, finishing passivation, thereby obtaining the synthesis ammonia prereduction catalyst. In the preparation device, in-parallel double towers are adopted for the reduction tower, a passivation groove is omitted, heating reduction and passivation are performed in the reduction tower, and a method of negative pressure extraction by use of a circulating fan is adopted during the passivation process, so that the effective production time is obviously increased, the reducing capacity is greatly improved, the operation difficulty is simplified, power consumption is reduced, and the air inflow stability of a system is ensured.

Description

technical field [0001] The invention belongs to the technical field of catalysts, and in particular relates to a method for preparing a synthetic ammonia pre-reduction catalyst and a preparation device thereof. Background technique [0002] It has been more than 60 years to produce synthetic ammonia by catalytic synthesis in industry, and the catalyst used is an iron catalyst containing various promoters. The synthetic ammonia iron catalyst supplied by the catalyst factory generally exists in the state of iron oxide. In this state, it has no catalytic activity for the synthesis of ammonia. It needs to be heated and reduced for about seven days in the synthesis tower to make it The iron oxide becomes a catalytically active body-centered cubic lattice, porous metallic iron. This not only affects the effective production days, but also consumes a lot of manpower and financial resources. At the same time, in the reduction operation, due to factors such as unsuitable control of...

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Problems solved by technology

As far as the preparation process is concerned, first of all, in the heating and reducing stage, because the heating rate is not easy to control, the water vapor concentration in the system changes frequently, causing the reduced catalyst to be oxidized again in the system, resulting in the increase of the crystal grain of the catalyst itself and affecting its activity; secondly , the change of the water vapor concentration in the system can easily affect the strength of the catalyst, reducing its strength and shortening the service life of the catalyst; moreover, it is also difficult to control the intake air volume in the later passivation process, and the air intake volume control is not good. It is easy to cause the system to overheat and affect the service life of the equipment

[0005] In terms of preparation equipment, due to the design defect of the reduction tower, the distribution of hydrogen and nitrogen in the tower is uneven during the reduction process, so it is easy to form a dead angle at the bottom of the tower, resulting in an incomplete reduction process

The additional consequence of this defect is that the post-passivation process is not in place, so that the catalyst that has not been passivated completely in the process of unloading the tower sees the local air temperature rise sharply, resulting in scarring of the catalyst

Moreover, in the passivation process, most manufacturers use passivation tanks for passivation. The problem is that due to the large inner diameter of the passivation tank, it is easy to cause uneven gas distribution, resulting in incomplete passivation, and easy to catch fire when unloading the tower.

On the other hand, most manufacturers currently use single-tower reduction, which has limited reduction capacity and affects output.

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