Blast furnace cooling equipment structure

Blast furnace cooling equipment structure

Blast furnace cooling is an important condition for the formation of protective slag skin, iron shell, and graphite layer. It reduces the temperature of the refractory lining itself and provides direct protection. It also protects the strength of structural parts such as the furnace shell.

The cooling medium used in the blast furnace is: water, wind, and a mixture of soda and water. The most commonly used is water, which has high thermal conductivity, large heat capacity, easy transportation and low cost. Wind has worse thermal conductivity than water, and the cooler is easy to overheat when the heat flow is strong, so it is mostly used in places where the cooling intensity is not too strong. The cost of air cooling is more expensive than water, but it is safe and reliable. Therefore, the bottom of the blast furnace is mostly cooled by air. The advantage of cooling with steam-water mixture is that the latent heat of vaporization is large, which can save a lot of water, and can also recover low-pressure steam. It is being widely used in blast furnaces.
Water cooling equipment has special cooling equipment such as spray water cooling, cooling stave and cooling water tank, as well as special cooling equipment such as tuyere, slag outlet, hot air valve and so on.
The water spray cooling structure is light, simple and easy to implement. Most of the large and medium-sized blast furnaces in our country are used as backup cooling methods, and the small blast furnaces are used more. In foreign countries, in the lower part of large and medium-sized blast furnaces, carbon bricks built in the furnace shell are sprayed with water cooling, and the effect is also good. -The diameter of the water spray hole is generally 58mm, and the spray direction should be inclined upward by 45°60°. The spray water on the furnace web should also be equipped with several circles of splash guards, and the gap between the lower edge and the furnace shell is not more than 1015mm.
Cooling stave is an important cooling device in the blast furnace cooling system. It is mainly used in the blast furnace body, waist, hearth, hearth and other parts. Its use effect and life span are directly related to the normal production and life of the blast furnace. Therefore, various countries generally pay attention to the selection of cooling stave materials and the improvement of the structure. The purpose is to extend the service life of the cooling stave.
The cooling stave is a wall-shaped cooler wrapped around the furnace lining and fixed on the furnace shell with bolts. It uses HT1533 gray cast iron to cast into 20# steel cold drawn seamless steel pipe. The outer diameter of the steel pipe is 3444.5mm and the wall thickness is 4.56mm. The thickness of the surface cooling stave is usually 80110mm. The leading part of the water pipe must be cast into a protective sleeve and welded to the furnace shell to prevent the water pipe from being cut off by the expansion of the cooling wall after the furnace is turned on.
In order to avoid brittle cracks caused by high-temperature molten iron carburization to the steel pipe during casting, the pipe wall should be coated with quartz powder after rust removal, and then placed in the mold. The temperature of the molten iron should be lowered to 1220°C before casting. Due to the good thermal conductivity of cast iron, the cooling stave of the light plate does not need to be arranged too densely.
The light plate cooling stave is generally used in the hearth part, and it can meet the requirements after verification by most blast furnaces.
Compared with the smooth-plate cooling stave, the brick-inlaid cooling stave is abrasion-resistant and erosion-resistant, and it is easy to generate slag skin. Generally, the area of ​​inlaid tiles is about 50%, and the thickness is 150~230mm. If it is too thin, it is easy to fall off. If it is too thick, the casting stress between the cast iron rib and the cast iron plate will be too large and crack, and once the heat flow fluctuates, the iron rib will be burnt. In terms of thermal engineering of brick-mounted cooling stave, the surface temperature of the casting rib is an important parameter. Generally, the temperature should not be greater than 500℃. The greater the heat flow, the thicker the brick and the larger the area of ​​the brick, which will cause the temperature of the cast iron rib to rise. Burn out. The research and development of cooling stave in Japan has gone through the process of the first, second, third and fourth generations.
This improvement promotes the larger furnace where the stave is cooled. From the original (first-generation) stave to the second-generation, Nippon Steel has enhanced angular cooling and forced water cooling instead of steam cooling. Nippon Steel's cooling stave (second generation) has made the following improvements: the bending radius of the water pipe in the cooling stave is minimized; ferritic graphite cast iron is used instead of high chromium cast iron; the material of the inlay brick is changed from clay brick to high alumina brick; The "1"-shaped part of the masonry is cooled with a separate system of water pipes. After practical application, the damage to the four corners of the cooling stave has been improved, but there are still more damages between the upper and lower cooling staves.
The main feature of the third-generation cooling stave is: a short refractory support boss and a spiral tube base are added to prevent the front tube from malfunctioning. At the same time, the corner water pipes were added and the back serpentine pipes were added, and the refractory material cast in the cooling stave was changed to SiC. The fourth generation extends the diagonal ribs from AB line to AC line by 220mm and casts them in place with refractory materials.
For Baosteel's No. 3 blast furnace in my country, except for the 4 cooling staves of the upper part of the web, waist and lower part of the shaft, which are manufactured by Nippon Steel, the other 14 cooling staves are all designed and manufactured by Baosteel. The 18 cooling staves from the bottom to the throat are all designed and manufactured by Baosteel According to the working conditions and process requirements of different regions, different structure types are adopted:
1. The furnace bottom and hearth are built with carbon bricks with good thermal conductivity. Therefore, the cooling equipment of this part adopts the new horizontal cooling stave, iron port cooling stave and tuyere cooling stave with high cooling strength.
2. The furnace belly, the furnace waist and the middle and lower parts of the furnace body have high heat load, large temperature fluctuations, severe thermal shock, and serious alkali metal chip erosion. They are the most cruel areas of working conditions, so Nippon Steel's third-generation cooling stave is adopted. , The third and fourth generation cooling staves with bosses are used in the middle and lower parts of the furnace body.
3. The upper masonry of the furnace body was damaged due to the wear of the furnace material and the temperature fluctuation during charging. Therefore, cooling stave is also used on the upper part of the furnace body.
Inlaid brick cooling stave is versatile and versatile, and it is the main cooling component of most blast furnaces. Therefore, it is highly valued by iron smelting workers, and it has become one of the main contents of people's research.

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