Method for improving quality of magnetite powder pellets

Abstract

The invention relates to a method for improving the quality of magnetite powder pellets. The method comprises a prehating calcination process in which the lengths of a first calculation section and a second calcination section of a chain grate are transformed, the conventional first calcination section is lengthened, and the conventional second calcination section is shortened; calcination temperature parameters are adjusted; specifically, temperature of the first calcination section is increased and temperature of the second calcination section is reduced; and meanwhile, the particle size of the pellets is correspondingly adjusted to 7-14mm from conventional 9-16mm. The method has the advantages that the temperature of the second calcination section is reduced, the strength of pellet finished products is aslo improved, and meanwhile, the metallurgical performance of the pellet finished products is aslo improved; and by adjusting the particle sizes of the pellets, the problem that the layer-by-layer uniform oxidation of the pellets is affected as the outer layers of the magnetite powder pellets are easy to rapidly solidify is solved.

Description

technical field [0001] The invention relates to a method for improving the quality of magnetite powder pellets. Background technique [0002] Magnetite concentrate powder is an ideal raw material for producing pellets. In the past, because the particle size of magnetite concentrate powder was relatively coarse, the proportion of particle size less than 0.074mm (particle size less than 200 mesh) was less than 60%. On the one hand, it was difficult to make pellets Green balls with qualified strength, at the same time, due to the coarse particle size, higher calcination temperature and longer calcination time are required during calcination. For this reason, the iron ore is further finely ground to further refine the particle size of the iron ore powder. The proportion of the particle size less than 0.074mm is mostly below 100%, and the proportion of the particle size less than 0.044mm (particle size less than 325 mesh) can also reach 80%. %above. However, during the producti...

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Problems solved by technology

However, during the production process, it was found that when the particle size of the iron ore powder becomes too fine, the pelletizing performance is improved, and the quality of the green pellets is improved. However, during roasting, its thermal parameters are not easy to control. The main performance is that the temperature in the second stage of roasting is not good. If the temperature of the second stage of roasting is too low, the strength of the pellets entering the rotary kiln will be low and cannot meet the production requirements. After further increasing the temperature of the second stage of roasting, the strength of the pellets entering the rotary kiln will decrease instead.

After research, it was found that the roasting performance of fine-grained magnetite powder pellets is different from that of coarse-grained magnetite powder. For fine-grained magnetite powder pellets, if the temperature control of the first and second stages of roasting is not suitable, especially When the temperature of the second stage of roasting is increased to increase the strength of the preheated pellets, the outer layer of the pellets is easy to solidify rapidly, which hinders the layer-by-layer oxidation of the pellets in the subsequent process, resulting in the pellets entering the rotary kiln. On the contrary, the strength decreases, and at the same time, due to the formation of different levels of layered oxidation, it will seriously affect the strength of the finished pellets and the metallurgical properties of the finished pellets

[0003] Domestic production of pellets using the grate-rotary kiln process actually started on a large scale after 2000. As the key equipment for pellet preheating and roasting, the grate is generally divided into four sections, namely drum The wind section, the exhaust section, the first stage of roasting, and the second stage of roasting. The design lengths of the first stage of roasting and the second stage of roasting are basically based on the design ideas of the shorter stage of roasting and the longer stage of roasting in foreign countries. This design is suitable for roasting hematite powder. Pellets and coarse-grained magnetite powder pellets are suitable, but when used for roasting fine-grained magnetite powder pellets, due to the short roasting period and short preheating roasting time, such pellets enter After the second stage of roasting, in order to increase the strength of the preheated pellets, it is necessary to rapidly preheat and roast at a high temperature of 900-1100°C to improve the strength of the preheated pellets, so that the outer layer of the pellets is easy to consolidate rapidly , but lead to deterioration of the strength and metallurgical properties of the pellets

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