- Time:Feb 11, 2023
The role of the preheater is to use the waste heat of the rotary kiln and the grate cooler to cool the cement clinker, and to preheat the waste heat utilization system of the cement raw meal. The preheater generally has 4-6 levels (the highest level is the first level). After the homogenized cement raw material enters from the highest level, it enters the preheater step by step through the material pipe to complete dehydration and preheating. The tertiary air duct preheats the cooling air and introduces it into the last stage preheater, the material flows downwards, the hot air is discharged upwards, and the heat exchange is carried out step by step to realize the preheating process of the cement raw meal. Making full use of waste heat is the main function of the preheater, but the surface area of the preheater is large. In order to reduce energy consumption, a variety of heat insulation materials and refractory materials must be used to form a composite lining to reduce the surface temperature of the equipment and make full use of the waste heat.
The thermal system of preheater and precalciner has the following characteristics:
The temperature of preheater and precalciner kiln (mainly refers to the temperature measured by the thermocouple installed on the wall of the equipment), from the first stage preheater to the fifth stage preheater and precalciner furnace is as follows: not high At 450°C, 650°C, 750°C, 900°C, 1000°C and 1100°C.
At this calcination temperature, there is basically no liquid phase in the calcined material, and there is no agglomeration and sintering. In addition, the thermal state of the system is relatively stable, so the configuration of refractory materials in the preheater and calciner does not require excessive refractoriness and strength. Since the preheater and calciner are located at the end of the entire hot air flow, the temperature change The frequency and amplitude are small, so there is no need for excessive thermal shock stability.
Since both the preheater and the calciner are static equipment, larger equipment shells can be used to accommodate more refractory materials, so insulation materials with low thermal conductivity can be used to reduce the temperature of the equipment shell and achieve the purpose of energy saving. Some preheaters and calciners have complex shapes, and refractory castables with more flexible molding can be selected.
The range of 800°C to 1200°C is the temperature zone where condensation and deposition of alkali metal oxides occurs. Therefore, under the raw and fuel materials with high alkali content, the preheater is in a wide range, and the refractory material is eroded by heat. , but also to withstand the chemical attack of alkali metal oxides.
In the preheater, because the flue gas containing alkali-sulfur gas is discharged from the preheater, the erosion of the refractory by alkali-sulfur gas should be considered. Since the cement raw meal can gradually reach about 800°C from normal temperature, the relative temperature is relatively low. Therefore, when choosing refractory materials, the erosion, wear and erosion of materials should be considered. In order to reduce heat loss, the kiln lining structure is configured with two layers of materials. The outer layer is an insulating material with low thermal conductivity and low strength. The working surface is A refractory material that has a certain strength and can better resist the erosion of alkaline substances.
ZHENJIN REFRACTORIES has been focusing on the R&D and production of refractory materials for 38 years, based on the high-temperature industry, and its ingenious craftsmanship has created a benchmark for the refractory material industry. A series of high-end refractory materials for the cement industry have been developed to meet the needs of various refractory materials in the cement industry. The products have created a number of safe use records in the cement industry, and have been widely recognized by many well-known domestic cement group companies.
