The full name of Maerz kiln is Maerz co-current regenerative lime kiln. The main features are the co-current calcination of lime and the regenerative preheating of combustion-supporting air in the kiln system. The connecting channel enters the exhaust pipe, and the high-temperature exhaust gas flows upward in the exhaust pipe, preheating the limestone in the preheating zone to a higher temperature, and the preheated low-temperature flue gas is discharged from the kiln chamber. Store the heat to preheat the limestone. The calcination cylinder and the exhaust cylinder are cyclically reversed at a fixed time to realize continuous production.

1. The phenomenon of falling off of high-alumina castables in the connecting channel of Maerz kiln

The refractory lining is the main working surface of the Maerz kiln. The kiln wall and connecting channel are mainly made of clay bricks, magnesia bricks and high-alumina bricks; the refractory lining at the top of the channel is poured in the form of hanging, and the hanging parts are welded under the steel plate of the channel platform. forming. The refractory lining at the top of the connecting channel is composed of high-aluminum castable, refractory castable, thermal insulation castable and refractory fiber felt, and is hung on the steel platform of the connecting channel by anchors. The design service life of the refractory lining is generally 3 years. However, in recent years, many Maerz kilns will crack or fall off the refractory lining at the top of the connecting channel about 1 year after being put into operation.

Under normal conditions, the high-temperature flue gas circulating between the two kiln chambers runs in the rectangular channel formed by the refractory lining. Due to the protection of the castable and the thermal insulation layer, the surface temperature of the steel platform at the top of the channel is about 90°C. After the top castable cracks or falls off, the high-temperature flue gas will directly burn the steel platform at the top of the channel, and the surface temperature of this area will rise sharply, which will seriously affect the normal operation of the Maerz kiln. When the castable falls off to a certain extent, the high-temperature flue gas directly burns the hanger, causing the hanger to deform and break and lose its hanging effect. Blocking, reducing the cross-sectional area of the connecting channel, seriously affecting the normal working conditions of the Maerz kiln.

2. The main reasons for the falling off of the connecting channel castables are as follows:

(1) Construction quality

When pouring the top of the connection channel, the construction space is very narrow, the distance from the bottom mold to the platform steel plate is only about 740mm, and the middle is full of wrong firmware. It is difficult for the construction personnel to complete the pouring, rapping and other processes with high quality.

(2) Oven temperature

Most domestic Maerz kiln drying kilns are preheated by burning wood, and then the burner of the drying kiln is fed with gas or other combustion media to heat up, and the temperature control of the drying kiln is relatively extensive.

(3) Production conditions

In recent years, the steel industry has developed rapidly, and steel prices have risen. Many steel companies are more concerned about the output of kilns, resulting in over-temperature and over-production. The channel temperature of the 600t/d Myrtz kiln should be controlled at about 950℃. If the channel temperature exceeds 1050℃, it will cause irreversible damage to the refractory lining.

(4) Improper maintenance

Many iron and steel enterprises have insufficient experience in the production of Maerz kilns, and the normal maintenance of the kilns is not in place, resulting in damage to the refractory lining of the kiln body.