decomposition furnace endothermic rate of materials and its influencing factors

Endothermic decomposition rate of materials in the decomposition furnace and its influencing factors

In the actual production process, many factors influencing the decomposition rate of material is very complex, but the main factor is that the physical and chemical properties, temperature, and the materials for the different reaction vessel, such as rotary kiln and decomposing furnace, the situation is not the same, for decomposing furnace, the factors that affect the decomposition velocity in the furnace are the following:

1. The temperature

Temperature is one of the main factors influencing the decomposition of raw speed, the reaction between all substances is based on a certain temperature, with the increase of temperature, material molecules between relative speed to speed up the reaction rate increases, for CaCO3 decomposition reaction, with the increase of temperature, decomposition rate constant increase, the decomposition in a shorter time, decomposition speed, the higher the temperature, the faster decomposition.

2. Physical and chemical properties of materials

Dense structure, large crystal limestone, due to the ionic bond between the crystals of the interaction force, the ability to resist foreign destruction is strong, the required force is large, so the decomposition rate is slow, and for the relatively loose structure of limestone, due to its resistance to foreign destruction is relatively weak, so the decomposition reaction is easier to proceed.

3. Fineness of raw materials

The fineness of raw material powder is large, the surface area of gas-solid contact is small, the heat and mass transfer speed is slow, and the decomposition time is long, while the fineness of raw material is fine, the particles are uniform, the situation is the opposite.

4. Degree of suspension and dispersion of raw materials

Suspension dispersion, relatively increases the particle size of raw powder, reduced the heat transfer area, changed the nature of the decomposition process, reduce the decomposition rate, raw suspension dispersion degree is influence on the speed of decomposition of raw powder and a very important factor, we know that in the traditional rotary kiln CaCO3 decomposition rate mainly depends on the heat transfer process, but due to material is state exists in the bottom of the rotary kiln, the heat flow from the bed surface, heat flow and refractory heat transfer area is very small for the material, the heat transfer coefficient is not high, and because the material exists in the stack state. The powder in the material layer absorbs heat from the upper and lower material layer and substrate by conduction only, and the heat transfer rate is very slow. And particles in the material layer is surrounded by a CO2 gas film, CO2 partial pressure is very big, decomposition temperature relative to the demand is higher, so that the carbonate decomposition is difficult, and in the decomposition furnace, material exists in the suspended state in the stream, basically can be regarded as a single particle, its heat transfer coefficient is very large, especially the heat transfer area is very large, it is will increase the contact area and heat flow, the powder have data points out that in the preheater and calciner, because material is a state of suspension, its heat transfer coefficient of 2.5-10 times higher than the rotary kiln and the heat transfer area is 1300 ~ 4000 times larger than that of rotary kiln, In a rotary kiln, the decomposition of CaCO3 usually takes more than 15 minutes at a temperature ranging from 800℃ to 1100℃, while in a decomposition furnace, the apparent decomposition rate of raw material reaches 85 ~ 95% in a suspended state of 850℃, and only takes a few seconds. This is also the modern cement production technology why widely used calciner the most fundamental reason.

5. CO2 concentration

The lower the CONCENTRATION of CO2 and the lower the fraction, the better the decomposition of carbonate. The lower the concentration of CO2 in the decomposition furnace, the faster the decomposition reaction will proceed. Therefore, good ventilation should be ensured in the decomposition furnace during the production and operation.