Selection and quality control of refractory materials for cement kiln

Different types and specifications of cement rotary kilns and their different parts of the process have different requirements for refractory materials must be selected to adapt to the refractory materials. There are differences in raw materials, fuel quality, process parameters, equipment status and operating experience of each plant. It is necessary to continuously improve the material selection and supporting scheme according to their own situation and use effect as well as the development of refractory materials, in order to realize the long life and low heat loss of the lining of the whole kiln and its different parts and the high efficiency of cement production.

At present, according to the scientific research, manufacturing level and actual use experience of refractory materials, the following suggestions are made for the selection and matching of refractory materials:

(1) Magnesium bricks should be used in the parts with stable kiln skin in the firing zone and the transition zone on both sides, including magnesia chrome bricks, low chromium and chromium free, zirconium or zirconium free special magnesia bricks and dolomite bricks. High alumina brick can also be used in the kiln with smaller production capacity, lower kiln temperature and more frequent opening and stopping, mainly phosphate bonded high alumina brick.

(2) Spinel brick should be used in the transition zone with unstable kiln skin and even slightly exposed brick. High alumina brick can also be used in the transition zone of kiln with small capacity and low kiln temperature, mainly phosphate-bonded high alumina brick.

(3) In the decomposition zone, at the hot end of the zone, sulfuric acid, alkali and salt melt and part of the clinker melt have been produced, so the unstable floating kiln skin has been attached. In this part of the large kiln, if the bricks erode quickly and the life is too short, spinel brick can also be used, otherwise high aluminum brick can be used. The rest of the decomposing zone should be made of high aluminum bricks.

(4) The high temperature parts (above 1250℃) in the throat of the large kiln, grate type cooling machine and high temperature zone are generally used as the working layer materials, such as anti-peeling high-alumina brick or chemically bonded high-alumina brick. But these parts of the vault should be used in general calcined high aluminum brick, not chemical combination of high aluminum brick. SiC composite brick or low cement and high strength refractory castable should also be used in the side wall of high temperature area of high air pressure grate cooler. If abrasion in this place is not serious, can use phosphate to combine high aluminum wear-resisting brick. The inner lining of the drum cooler shall be made of high quality wear-resistant materials, including steel fiber reinforced and toughened phosphate combined with high aluminum wear-resistant brick.

(5) In the preheating part of the kiln material, including the end after the decomposition zone in the kiln barrel, the preheater and the decomposition furnace system, the tertiary air pipe and the cooling machine in the medium temperature area, all the parts of the lining surface temperature is not more than 1200℃ should be made of clay refractory materials, including a series of alkali resistant brick, alkali resistant castable and ordinary clay brick.

In NSP kiln and Bohr, alkali resistant brick most appropriate use of the above part of the series, including for preheater ontology and cone parts and Bi cooler temperature regions in ordinary alkali resistant brick, high strength alkali bricks for three times in the duct, alkali resistant and heat insulation bricks for kiln end and type to the vaults of the aluminum dome with alkali bricks and corresponding alkali resistant castables.

(6) The composite lining composed of clay brick working layer and high strength (not less than 9Mpa) insulation brick can be used in the preheating and decomposition part of the long kiln barrel.

(7) in the non-kiln cylinder in the stationary equipment in addition to the work layer material has been seen above, generally use heat insulation materials as heat insulation lining, including calcium silicate board, refractory fiber material, heat insulation brick and light castable material, according to the requirements of the equipment used and the performance of these materials can be selected appropriately.

(8) Firebrick and refractory castables with excellent wear resistance can be used in the kiln opening, such as silicon carbide composite brick, high-quality phosphate combined with high aluminum wear-resisting brick and refractory castables with or without steel fiber reinforcement.

The outer protection lining of the burner is generally made of steel jade refractory castables of low cement type, high aluminum refractory castables and steel fiber reinforced refractory castables.

For the kiln system equipment performance and production management is not very perfect, such as considering the initial production of low operating rate, start and stop more frequently, can also choose another part for the initial production of refractory materials.