How To Solve The Common Problems In Rotary Furnace Process

Firing Method: Direct firing, Indirect firing
Minimum Order Quantity :1 Piece

Lime rotary kiln is an important and common type of rotary kiln.

Lime production is a relatively complicated thermal decomposition reaction process of calcium carbonate to calcium oxide. Due to different kiln types, different equipment configurations, different raw material quality and composition, and different fuel types and calorific values, each will appear Various problems and faults The following are the analysis and treatment methods for common problems and faults.

UNDERFIRING

  1. The particle size is too large: the rate of limestone calcination depends on the temperature of the lime material and the surface of the limestone. But at a certain temperature, the calcination rate of limestone depends on the particle size of limestone. The larger the feed, the slower the calcination rate. Here, because the thermal conductivity of lime is less than that of lime calcination, the thickness of the lime layer gradually increases, the harder it is for heat to enter the inside of the stone, and the calcination speed is also slow. So large pieces of limestone often have sandwiches, and quick-burned lime is the first reason. The particle size of the ordinary shaft kiln should be controlled at 40-80mm, and the large kiln capacity can be relaxed to 50-150mm.
  2. Small fuel ratio or low fuel calorific value: the ratio of fuel used in mixed-fired kilns and the technical performance of the kiln. Because the kiln shape design is relatively scientific and relatively low in coal, coal used in mixed-fired kilns generally requires a calorific value above 5500 kcal. The granularity must be controlled. The use of coal must add water appropriately.
  3. Unreasonable air supply: the stone in the lime kiln is burned by fuel heating and calcination, and the fuel is burned by oxygen (air). The combustion of any fuel must have three conditions including fuel, oxygen, and fire. The wind is strong, the wind is even, except for a certain amount of fuel, it is the rationality of the air supply. Some of the local air volumes on the cross-section of the kiln is large, the air volume is small, and the windy place is burned. There is burning. In order to make the air supply reasonable, in addition to the air supply must be at a certain height, a special hood that can evenly supply air in the kiln has been specially researched and manufactured, which can evenly blast the wind on the entire kiln section to make the fuel burn evenly.
  4. Overburning: the quality of quicklime, depends on the content of calcium oxide and magnesium oxide. Second, it depends on the overburning rate of quicklime. Raw burning is that some of the limestones is not completely decomposed, and overburning is limestone calcination. The transition makes the quick lime dense, also known as overfire lime or dead burned lime. This part of the quicklime has low activity and is difficult to differentiate in the subsequent production. For ordinary limestone, the normal combustion temperature is 1,000-1,200 ° C. Overburned ash is usually too high for a long time, and the surface has cracks or a glass-like shell. Volume The shrinkage is obvious, the color is burned to black, and the block volume is increased, which is naturally overburned. Of course, the treatment of overburning is, first of all, to consider whether the fuel ratio is too large. It should be adjusted to a reasonable batching. Of course, the coal blending quantity must fully consider the quality of the coal, and the supply air should also be adjusted to adapt.

THE CALCINATION ZONE MOVES UP

If the top temperature of the calcination belt of the common shaft kiln is increased in the middle of the kiln body, the ash temperature is reduced, the CO2 content is reduced accordingly, the air volume is large, and the excess oxygen increases. The upper part of the kiln burned early. When the charge is lowered to the calcination zone, the fuel has no firepower, the amount of raw lime burning increases naturally, the top temperature control is too high or the fuel entering the kiln is fragmented and burns prematurely. The wind pressure and air volume are too large, or the size of the limestone is too large, the ventilation is smooth, and the unloading amount is unbalanced, which is also the reason for the upward movement of the calcination area. Eventually, a big burn is formed. In this case, you should:

  • Reduce the wind pressure and air volume to move the fire layer down. If the top pressure is low, the top pressure can be increased appropriately.
  • Increase the amount of ash unloaded, increase the fuel ratio appropriately, and supplement the heat loss caused by the high top temperature when it is not returned to normal, and adjust to the normal value after normal.
  • Check and adjust the raw fuel particle size. If the content of fuel powder is too much, water can be added to saturate it properly, so that it can increase the degree of adhesion with the stone to delay the fuel burning time.

THE CALCINATION ZONE MOVES DOWN

When it is found that the top temperature is low and the ash temperature is increased, the fire and fire are not exhausted when the fuel is serious. Lime also increases the calcination, and the CO2 concentration decreases, which means that the calcination zone has moved down. The main reason for this situation is that the air volume is small, the amount of stone loading is large, and the amount of ash discharge is large, which makes the mixture move down quickly, and the cooling zone is shortened. The air fails to be preheated enough to enter the calcination zone, and the amount of calcium carbonate decomposed Reduced, CO also decreased accordingly. This causes an increase in the amount of lime burned.

In addition, the raw material is fragmented or the particle size deviation is large, and the resistance in the kiln increases. At this time, the air pressure is not low, but the actual air volume is not enough. In this case, the stone loading and ash discharge should be appropriately reduced, and the air volume should be appropriately increased. In this case, if the top pressure is too large, the batch can be appropriately reduced, the raw material can be changed, and the proportion of large particles should be appropriately increased to reduce the particles. The level difference reduces the resistance in the kiln. Adjust the fuel and stone mass to meet the technological requirements.

THE CALCINATION ZONE IS PROLONGED

The extension of the calcination zone will cause the top temperature, the ash temperature will be higher, the CO2 will decrease, and the amount of lime burning will also increase. The formation of nodules or poor local ventilation in the kiln is due to excessive fuel ratio and poor uniformity of limestone, and the formation of nodules or poor ventilation in the kiln. At the same time, there are nodules or kiln wall hanging materials in the kiln, and the ventilation is segregated. The nodules or hanging materials prevent the materials from falling normally and have poor ventilation. Because the nodules fall off under the impact of the material flow, the calcination zone will also be extended for a certain period of time.

When this happens, the production should be properly reduced, the particle size of the raw materials should be adjusted, and the fuel ratio should be reduced to increase the air volume. After temporarily reducing the height of the material layer, the material is restored to the normal material level.