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How can I improve the decomposition rate of preheater system in cement plant - solved

Date:2019-09-04 16:47 Source:cementepcViews:

The kiln tail predecomposition system is mainly composed of cyclone preheater and decomposing furnace.The concrete includes cyclone tube, decomposing furnace, connecting air pipe, discharging pipe and its accessories, feeding box, flap valve and blowdown device.They play an important role in increasing decomposition rate of preheater system.
 

1. Influence of cement mechanical cyclone preheater on decomposition rate


The task of cyclone preheater in the pre-decomposition system of kiln tail is to make full use of a large amount of heat energy discharged from the exhaust gas of kiln tail to heat and raise temperature of raw material powder, and feed it into the decomposition furnace for the next suspended carbonate decomposition after the completion of raw material drying, clay mineral dehydration and partial mineral decomposition.Therefore, the following measures can be taken to improve the decomposition efficiency of raw materials by accelerating the heat transfer rate of materials and hot air flow:
 

(1) appropriately increase the exhaust air of the system.


For the cyclone preheater, the exhaust air rate not only affects the complete combustion degree of the fuel, but also affects the suspension dispersion degree of the material in the preheater.Appropriately increasing the exhaust air at the end of the kiln during operation can improve the calcining condition in the kiln, increase the wind speed of the preheater system, strengthen the suspension and dispersion of materials, speed up the heat exchange rate, and thus improve the decomposition rate of raw materials into the kiln.
 

(2) try to avoid system air leakage.


Preheater system because most of the five level cyclone preheater is made on the spot, the processing quality is poor, especially the pipe connection flange, preheater manhole door, observation hole, material hole and other places are not tightly sealed, resulting in obvious air leakage.Plus preheater cyclone tube, smoke chamber on the blow plug compressed air often open, reduce the temperature of hot air flow.Therefore, in the production process, in addition to strengthening the sealing measures of all parts of the system, under the normal and stable pressure and temperature of the system, the compressed air should be blown and blocked as little as possible to minimize the chance of outside cold air infiltration.

preheater

(3) properly adjust the flap valve.


The flap valve (air lock valve) on the preheater's blanking pipe plays an important role in air lock and blanking.If the flap valve weight of torque and load torque is not balance will appear two situations: the former significantly greater than the latter, the flap valve is not easy to start, until the board broken material accumulation to a certain extent on the moment balance when suddenly greatly open, and open for a long time, cause material on and off, to form a smooth dough into shares into the next level of preheater, cause less material dispersion, uneven heating, both affect the heat transfer effect, easy cause local overheating, produce product of leather.When the former is equal to or less than the latter, the flap valve is prone to open and open, causing serious internal air leakage in the preheater, which causes the material to fly twice, and causes the hot air flow in the heat exchange pipeline to enter the cyclone tube through the bottom of the superior cyclone tube without heat exchange of the same material, causing unnecessary heat loss and reducing heat exchange efficiency.In order to avoid the above situation, the weight hammer of the flap valve should be adjusted correctly according to the installation position of the flap valve and the direction of the blanking tube, so that the weight hammer closing moment is slightly larger than the bearing closing moment. In this way, the barycenter line displacement of the flap valve during operation is small, and the blanking can be guaranteed to be even when working, the wind lock performance is good, giving full play to the heat transfer effect of the preheater.
 

(4) connecting duct plays an extremely important role in heat transfer efficiency of cyclone preheater system.


Theoretically, the most effective heat exchange only needs 0.3-0.5s, and too long heat exchange pipeline has no positive significance to improve heat exchange efficiency. Therefore, on the premise of ensuring heat exchange efficiency, the length of air duct connected at all levels should be reasonably matched.
 

(5) the position of the dispensing box and the insertion depth of the inner tube have a great influence on the preheating and decomposition of materials.


When materials are connected by a tremie pipe into duct, scattered on the material in container, and due to the inertia continue to rush to the next level down cyclone tube in tube, if the inner barrel is shorter, the material thermal couldn't driven float, material will be into the next level cyclone cylinder, shorting materials should therefore be rational allocation of cylinder depth of position of feeding point, and the relationship between the inner cylinder diameter.
 

(6) reasonably set up the spreading device


When the raw material powder enters into the heat exchange pipe, it should be dispersed rapidly and evenly distributed in the hot gas flow to strengthen the function of dispersion and evenly distributed so as to increase the solid heat exchange area in the atmosphere.
 

2. Influence of cement mechanical decomposition furnace on decomposition rate


The main function of the decomposing furnace is to make the exothermal process of fuel combustion and the heat-absorbing process of the decomposition of raw material carbonate be carried out very quickly in the suspended or fluidized state, so as to ensure a high decomposition rate. The raw material after pre-decomposition has been decomposed by 90% ~ 95% after entering the decomposing furnace and being decomposed into the kiln.

Temperature plays a decisive role in the decomposition rate of calcium carbonate in raw materials.The temperature of decomposing furnace depends on the exothermic rate of fuel combustion and the endothermic rate of raw material decomposition.According to the study, at 720°C, the decomposition rate of calcium carbonate in raw cement requires about 136s to reach 80%, at 900°C, it requires about 4s to reach 80%, and at 1000°C, it takes only 1.1s to reach 80%.As can be seen from figure 2, when the average temperature in the furnace is above 950°C, the decomposition rate of calcium carbonate can reach more than 90%.Therefore, temperature control is very important.

In addition to the temperature, the factors influencing the decomposition rate of decomposing furnace is there are many: the appearance of decomposing furnace size, the position of the coal injection decomposition furnace mouth, duct into the perspective of three times, the number and location of discharge point and so on, its purpose is to under the premise of without raising temperature, increasing the time duration of the raw materials in the decomposition furnace, to ensure full combustion of fuel in the furnace, to improve the decomposition rate of kiln material.

Through the above analysis, it can be seen that there are many factors affecting the decomposition rate of the preheater system, and improving the decomposition rate of the preheater system plays a very important role in reducing the heat load of the kiln, improving the running cycle of the kiln and improving the production quality.Jiangsu LVSSN can provide high quality and efficient cement factory, please consult our customer service or leave a message to us, we will reply to you as soon as possible.

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