From the current domestic and foreign maintenance content and expression of high furnace lining, it is not consistent. However, from the perspective of the specific content of maintenance, it can be basically divided into three categories:

The first category is a complete repair. We are used to calling it "overhaul": the high furnace is shut down and the lining is completely renewed.

The second category is incomplete repairs. We are used to calling it "medium repair": the blast furnace is shut down, and some refractory materials in the lining are retained, such as: the carbon bricks at the bottom of the furnace or the refractory materials below the tuyere are retained.

The third category is hot maintenance. Partial maintenance of the lining of the blast furnace when the blast furnace is not shut down.

spray method. For high furnace lining, the commonly used gunning methods mainly include ordinary gunning, long gun gunning and remote gunning:

1. Conventional Internal Scaffold Gunning Technique. 

   In this way, after the furnace is completely cooled, the operator enters the furnace with a scaffold or a hanging basket to repair the parts of the furnace lining that need to be repaired. This method is mostly used for lining repair of high furnaces below 2000m3. Its operation features are simple gunning equipment, flexible and effective removal of slag skin and loose remaining bricks, maintenance, replacement or transformation of exposed steel plates, coolers and other metal parts, and easy control of gunning position and thickness. The disadvantage is that the impact on production is large, and the operating environment of workers is poor.

2. Lance-Gunning Technique.

   This method is basically the same as the ordinary gunning method. The difference is that the operator stands outside the furnace and uses a spray gun with sufficient length to carry out the gunning operation on the parts of the furnace lining that need to be repaired. The advantages are that the operating environment of the operator is improved, and the blast furnace can not be restricted by the temperature of the blast furnace, which saves the time of shutting down the furnace and is beneficial to production. The disadvantage is that the scope of repair is limited, and holes need to be made in the furnace shell.

3. Remote Gunning Technique. 

   This method is to put the robot (spray gun combination equipment) into the furnace from the entrance hole or the specially opened hole, and move up and down through the bridge or guide chain; while the operator observes and adjusts the spraying through the TV screen set outside the furnace Operation. The feature of this gunning method is that it does not require personnel to enter the furnace, and the operating conditions of the operators are better. The disadvantage is that the equipment is more complicated, and the investment and maintenance costs are relatively large.

   Since the 1970s, high furnace gunning technology has been widely used in blast furnaces in industrialized countries such as Europe, America and Japan, such as Japan's Kashima No. 3 blast furnace (effective volume 5050m3), with a life span of 13 years and 5 months. It can produce nearly 10,000 tons of iron. The furnace has been gunned for more than 30 times in the past 13 years; steel mills such as ScunthorpeWorks in the UK, Thyssen in Germany, and Dofasco in Canada have all carried out gunning on the high furnace and achieved good results.

    

   The research and application of high-level furnace gunning technology in my country started relatively late. In the past 20 years, my country has made great progress in the field of equipment and refractory materials, and blast furnace gunning technology has been rapidly popularized and applied. It has developed from the initial semi-dry gunning to wet gunning. Depending on the gunning method and the quality and amount of the gunning refractory, the maintenance effect of the blast furnace lining after one shot can be used for 6 months to more than a year. The effect of gunning on furnace maintenance is more obvious.