Cement kiln system work zone classification

Date: 2019-07-24 Views:

Generally speaking, according to the temperature of materials in cement kiln, the working belt of rotary kiln system (including kiln tail preheating and kiln head cooling machine) is divided into the following: drying belt, preheating belt, decomposition belt, exothermic reaction belt, firing belt and cooling belt.

1. Dry zone

For the traditional cement rotary kiln, the material temperature in the dry zone is 20 ~ 150℃, and the gas temperature is 250 ~ 400℃.For the new-style dry cement kiln, the materials into the kiln are heated to more than 150℃ at the moment when they enter the level-i cyclone cylinder at the end of the kiln.Therefore, the dry zone is only a short distance from the raw material entrance.There is almost no dry zone in the end system of new dry cement kiln.

2. The preheating zone

For the traditional cement rotary kiln, the temperature of the material in the preheating zone is 150 ~ 800℃, and the gas temperature is 450 ~ 850℃.For the new dry kiln, the first stage up to the last last stage cyclone dust collector is pre-tropical.In the pre-tropical zone, the organic components in the raw materials begin to dry distillation and decomposition, and the clay begins to dehydrate, creating conditions for the decomposition of calcium carbonate.

3. The decomposition zone

For the traditional cement rotary kiln, the material temperature in the decomposition zone is 800 ~ 1000℃, and the gas temperature is 1000 ~ 1400℃.For the new dry cement kiln, the decomposition zone is from the decomposing furnace to the inner distance of the kiln head 7D(D is the steel plate diameter of the kiln).NSP kiln, for example, the size of the rotary kiln to Φ 4 m by 60 m, from the kiln head is 28 ~ 60 m is decomposed with;The size of the NSP kiln kiln to Φ 4.7 m by 74 m, from the kiln head is 33 ~ 74 m are decomposing zone.

In the new dry cement kiln, the main reaction of decomposition zone is the decomposition of calcium carbonate.Generally speaking, the calcium carbonate in raw materials decomposing at the end of kiln is about 90%, and the remaining 10% of calcium carbonate decomposing in the rotary kiln.The advantage is that 10% calcium carbonate is used as a coolant to control the temperature at the end of the kiln.If the proportion of wind coal changes, only the decomposition rate of calcium carbonate into the kiln will have little effect on the temperature of the kiln tail.

4. Exothermic reaction zone

Exothermic reaction zone is also called transition zone or upper transition zone.For traditional cement kilns, the material temperature of exothermic reaction zone is 1000~1300℃, and the gas temperature is 1400~1600℃.Generally speaking, the calculation from the head of the new-type dry cement kiln from 7D to 4D is a transition zone.For example, when the size of the rotary kiln of the new dry kiln is 4m×60m, 16 ~ 28m from the kiln head is a transition zone.The size of the NSP kiln kiln to Φ mx 4.7 74 m, from the kiln head is 19 to 33 m is a transition zone.

5. Calcining zone

The material temperature of the firing belt is 1300~1450~1300℃, and the highest flame temperature can reach 1700℃.When the material is close to 1300℃, flux minerals C3A and C4AF begin to melt and produce liquid phase. Calcium oxide and dicalcium silicate are melted and C3S are precipitated when the saturated concentration is reached.Under the premise of not damaging the kiln skin, appropriately increasing the temperature of firing zone can promote the formation of liquid phase, increase the melting of f-cao and C2S, promote the formation of C3S, and improve the yield and quality of clinker.Generally, the length of the burned band is (4 ~ 5)D.In fact, the length of the firing zone and the length of the flame are also affected by the pre-firing.

6. The cooling zone

The cooling zone is also called the lower side transition zone.In the cooling zone, the temperature of kiln material is 1300 ~ 1100℃.After the clinker is fired into the belt, it is cooled to solidify or preliminary solidify in the cooling belt, and then further cooled to the gray-black solid near-round particles in the cooling machine.If the temperature is high, the main damage of clinker to the refractory is erosion and high temperature wear.After entering the cooling machine, because the clinker has not been completely solidified, there may be problems such as building "snowman" in the cooling machine entrance.If the temperature decreases, the damage of clinker to the refractory is mainly the wear at high and high temperature.

If the temperature of kiln mouth changes rapidly, the main damage of clinker to kiln mouth refractory is thermal shock.Therefore, the kiln mouth refractory damage is quite complex, the specific kind of damage is the main reason for forensics, analysis, analysis and determination on the basis of facts.

As a matter of fact, the length of each belt in cement rotary kiln is influenced by such factors as the quality of kiln prefiring, the length of flame and the flammability of raw materials.The specific length of decomposition zone, transition zone, firing zone and cooling zone in cement rotary kiln varies with different production conditions.Even for the same manufacturer, it will change with the change of production conditions.Therefore, the length of each belt of cement rotary kiln, the selection and configuration of refractory materials in the kiln can be obtained through repeated exploration and trial and error, and necessary adjustments should be made at any time according to the changes of production conditions.

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