Refractory Bricks

The Inner Side of the Hot Blast Furnace

Jan 25,2019

The Inner Side of the Hot Blast Furnace

1 Overview
According to the textbook, the blast furnace column is divided into a block zone, a soft melt zone, a drip zone, a tuyere zone and a dead iron layer. There may be a big difference between the real distribution of each zone and the theoretical description. For example, the mixing of the block zone gradually increases from top to bottom; the coke window morphology of the remelted zone is affected by the coke quality and ore performance, and the actual distribution is not uniform. The drip zone is not like the conversion of ice water, more like the gradual growth of the droplets; the tuyere of the tuyere is not empty, there are many fine coke particles inside; the dead iron layer, the dead coke heap, the slag iron mixed layer does not The naked eye can clearly distinguish the boundaries.

The damage forms of different parts of the blast furnace are different, from the throat steel brick, the furnace cooling wall, the furnace carbon brick, the bottom sediment layer, etc., in addition to the mechanical, high temperature and chemical reasons, there are also iron The influence, the impact of the impact of the charge, and other forms.

2. The actual column shape of the blast furnace
2.1 Block area
The block area exhibits a mixture of raw materials and coke, and the deeper the feed line, the more obvious the degree of mixing. The main reason is that in the process of the falling of the charge, in addition to the downward movement of the coke layer and the ore layer, there is a radial motion caused by the cross section becoming larger. Judging from the movement of the charge itself, there is also the collapse and compaction of the charge due to erosion, damage, and the like.
2.2 Soft Melt Belt
The iron-containing charge in the soft-melt zone gradually softens, and the coke particle size is rubbed by the charge in the soft-melt zone, and the particle size becomes smaller and becomes more regular. At this time, the mixing of coke and ore is more sufficient.
2.3 Drip zone
The iron-containing charge in the drip zone exhibits a transition from a solid state and a soft-melt state to a liquid state due to an increase in temperature. The low process includes the transition from reflow to liquid, droplet growth, and dripping. The figure below shows the drop zone in the case of quenching.
2.3 tuyere
There are many factors affecting the size of the tuyere of the tuyere, in addition to the influence of the blast parameters, it is also affected by the shape of the charge. The gyration zone presents an upward "bucket type". The coke in the maneuvering zone exists in the form of fine-grained coke powder, and the more the periphery, the larger the coke grain size.
2.4 slag iron and iron layer
The distribution of the slag-iron interface is not obvious, and the transition zone where the slag-iron mixture is gradually separated is presented. Therefore, the slag-iron interface in the strict sense exists only at the microscopic interface, and macroscopically, the slag iron is mixed in a certain area of the blast furnace hearth. On-site dissection can find that the material form strength of the slag area is small, and the cleaning of the slag iron mixed zone and the dead iron layer is troublesome, mainly because of the high hardness and the mixture, similar to the cement structure, the coke acting as the skeleton, and the bonded solid state. Slag iron and so on.
3. Damage to the wall of the blast furnace
The cooling wall of different parts of the blast furnace is damaged in different forms. There are many types of staves. According to the form, it can be divided into boss cooling wall, brick cooling wall and smooth surface cooling wall. According to the material, it can be divided into copper cooling wall, ductile iron cooling wall, cast steel cooling wall and so on.
The shape of the throat steel brick in the early stage of the blast furnace can be basically maintained. In the middle and late stages of the furnace operation, it is affected by mechanical impact, high temperature, alkali metal, etc., and the shape changes, deformation, burning and abrasion occur.
After the blast furnace is opened, the refractory material at the front end of the furnace body to the front end of the cooling wall of the furnace is quickly detached, and the cooling wall is mainly formed by the formation of a self-protection system. From this point of view, the damage of the blast furnace stave is susceptible to the instability of the edge airflow.
4. Blast furnace anatomy
Common phenomena of blast furnace anatomy are as follows:
(1) Compounds of alkali metals and Zn
The alkali metal (K, Na) and zinc oxides exhibit different colors in different oxidation states, as shown in the figure below, which are oxide solid solutions of Na and Zn.
(2) Furnace sediment layer
(3) After the press slurry is driven into the middle of the cooling wall and the furnace shell, a layer of refractory material having protective properties is formed.
(4) The carbon brick ring crack in the hearth zone can occur simultaneously in the radial direction, as shown in the following figure. Therefore, the calculation and speculation for ring cracking under normal circumstances is mainly a comprehensive effect. The occurrence of multi-layer ring cracks greatly reduces the strength of the furnace wall, so the hot surface of the cooling wall is very dangerous for the fragile furnace wall.
5 Summary
There is still a lot of mystery in the actual situation inside the blast furnace; the safety and longevity of the blast furnace body, in addition to the influence of masonry and other conditions, play a key role in the full play of self-protection.

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