The application advantages of low thermal conductivity composite mullite bricks in cement kilns

At present, large and medium-sized cement rotary kiln factories using silicon-mullite bricks for the non-firing zone. However, thermal conductivity of silicon-mullite bricks is relatively large, which lead high surface temperature of rotary kiln and large heat loss.

Low thermal conductivity multi-layer composite mullite bricks, using alumina-based sintered mullite, replace traditional silica mullite bricks to reduce the overall thermal conductivity and effectively improve high-temperature structural strength.

This article we Henan Fireramo share one of examples that customer using low thermal conductivity multi-layer composite mullite bricks in rotary kiln for reference:

1,Existing problems

(1) Customer's cement kiln dimension is Φ4m×60m, refractory bricks thickness in kiln is 200mm, in 18 to 59m section of the kiln use silica mullite bricks, which have high thermal conductivity. Especially the average temperature of the shell between 18 and 38m is 330°C, and dissipates heat is large.

2.Cause analysis and solutions

2.1 Cause analysis

The refractory bricks in 18 to 59m section of the customer's cement kiln use silicon-mullite bricks which have good wear resistance, excellent thermal shock stability, have good use effects. However, because large amount of silicon carbide is added to silica mullite brick to improv  high-temperature mechanical properties, the thermal conductivity has remained high, resulting in a large waste of energy.

2.2 Solutions

We recommend to customer to use low thermal conductivity composite mullite bricks instead of silica-mullite bricks.

Low thermal conductivity composite mullite bricks use an innovative multi-layer composite structure design of working, insulation layer, which greatly reduces thermal conductivity. The working layer of the material uses M70 mullite as aggregate, 80 homogeneous material as fine powder, adds 12% to 15% silicon carbide and 10% to 12% andalusite fine powder, which has high normal temperature compressive strength, higher load softening temperature, good thermal shock resistance; insulation layer design M60 or M70 mullite is used as the main raw material. The appropriate alumina content makes it have a higher mullite phase content and almost no corundum phase. The insulation layer has a lower thermal conductivity than the working layer and is closely related to the working layer. The layer has good bonding, high strength and wear resistance.

3.Usage effects

Our customer replaced silica mullite bricks in the 18-38m section with low thermal conductivity composite mullite bricks. After one year , the thickness of 18-28m section bricks was more than 140mm, and 28-38m thickness was basically intact. The shell temperature was average before use is above 330℃, but the temperature after use composite mullite bricks is below 270℃.

The economic benefits are as follows:

(1) Energy saving

(2) Emission reduction

(3) Extend the service life of refractory materials

(4) Reduce tire wear and cylinder deformation speed