Common Problems And Solutions of Lime Kiln

Common Problems And Troubleshooting Methods In Lime Kiln Production

Lime production is a relatively complicated thermal decomposition reaction process from calcium carbonate to calcium oxide. Due to different kiln types, equipment configurations, raw material quality and composition, fuel types and calorific values are also different, so there will be various occurrences during calcination. Various problems and faults The following are the analysis and treatment methods for common problems and faults:

Causes and treatment of burning

1. The particle size is too large: The speed of limestone calcination depends on the size of lime and the temperature at which the limestone surface is in contact. But at a certain temperature, the calcination rate of limestone depends on the particle size of limestone. The larger the material density, the slower the calcination speed. Here, because the thermal conductivity of lime is smaller than that of lime calcination, the thickness of lime layer gradually increases, the more difficult it is for heat to enter the inside of the stone, and the calcination speed is also slower. Therefore, large pieces of limestone often have a sandwich, and raw burnt lime is the reason for this. The particle size of ordinary vertical kiln should be controlled at 40-80mm, and the kiln capacity can be relaxed to 50-150mm. In order to save the cost of limestone, small stones can also be specially used.

2. The proportion of fuel is small or the calorific value of fuel is low. The ratio of the fuel used in the mixed firing kiln is related to the technical performance of the kiln. The coal used in the mixed firing kiln generally requires a calorific value of more than 5500 kcal. The particle size of the fuel must be controlled to a certain extent, and water should be added appropriately when using fine coal.

3. The air supply is unreasonable. The stone in the lime kiln is heated and calcined by fuel combustion, and the fuel is burned by oxygen (air). The combustion of any fuel must meet three conditions including fuel, oxygen, and fire. , and the wind is strong, the fire is even, and the fire is even. Except for a certain proportion of fuel, it is the rationality of the air supply. On the cross section of the kiln, some local air volumes are large and some are small. Raw burning will naturally appear in small places. The kiln type designed by Great Wall Machinery Co., Ltd. pays special attention to the air supply design. In order to make the air supply reasonable, in addition to the air supply at a certain height, a computer simulation hood that can evenly supply air in the kiln is specially researched and manufactured. The air equalizing pressure and the equalizing drum are used to burn the fuel evenly on the entire section of the kiln. In order to improve the productivity of the shaft furnace lime kiln and the activity of the lime produced, the company applies a two-dimensional mathematical model to the shaft furnace lime kiln. A simulation study was carried out, and the results showed that the low productivity of the shaft furnace lime kiln and the activity of the produced lime were caused by the unreasonable distribution of the air flow in the furnace, and the unreasonable distribution of the air flow reflected the structure of the original lime kiln computer simulation air cap of the shaft furnace. In response to this problem, the company combined with many domestic experts to transform the hood structure of the shaft furnace lime kiln. The measures adopted are to set up a special air duct on the top of the hood to open up the central air flow, with the purpose of eliminating or inhibiting the shaft furnace lime kiln. The raw burning phenomenon caused by entrainment in the center of the kiln, the airflow distribution in the lime kiln after the modification of the hood structure is greatly improved, and the activity of the produced lime is higher than that of the lime produced by the same type of lime kiln without the modification of the hood structure Got 15 or more.

4. Overburning, the quality of quicklime depends on the content of calcium oxide and magnesium oxide in it, and the raw over burning rate of quicklime. Raw burning means that part of the limestone is not completely decomposed, and overburning is Limestone is calcined to make quicklime dense, also known as burnt lime orburnt lime. This part of quicklime has low activity and is difficult to differentiate in subsequent production. The normal combustion temperature of ordinary limestone is 1000-1200°C. Over burned ash usually has too high a burning temperature and a long time, and cracks or glassy shells appear on the surface. The shrinkage is obvious, the color is burnt to black, and the block volume increases, which is naturally overburned. The treatment of over burning is of course first to consider whether the proportion of fuel is too large, and it should be adjusted to a reasonable proportion. Of course, the quality of coal should be fully considered in the amount of coal blending. The main method of uniform internal distribution is to use the rotary distributor reasonably. The multi-point rotary distributor designed by Great Wall Machinery Co., Ltd. fully absorbs the principle of blast furnace distribution. The designed and manufactured rotary distributor can realize single-point, multi-point, forward and reverse And other material distribution operations, especially the designed furnace material distribution spreader can realize the control of material flow and material volume like the seeder in agriculture, so that the fuel material layer is thin and evenly distributed, so that the fuel and raw materials are fully mixed and the material is uniformly distributed and burned full.

In addition to the above-mentioned situations, there are several reasons and solutions for operational problems.

5. The calcination zone moves upwards. If the calcination zone of an ordinary shaft kiln is found in the middle of the kiln body, the top temperature rises, the ash temperature decreases, and the CO2 content,the air flow is reduced accordingly, the air volume is large, and the excess oxygen increases. This means that the calcination zone has moved up.Burn early. When the furnace material falls to the calcination zone, the fuel has no firepower, the amount of lime burning will naturally increase, and 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 limestone particle size is too large, the ventilation is smooth, and the ash discharge is uneven Balance is also the reason for the upward movement of the calcination zone. In the end, a large raw fire is formed. When encountering this situation, you should: reduce the wind pressure and air volume to make the fire layer Move down, if the top pressure is low, you can increase the top pressure appropriately.

1) Increase the amount of ash unloading, increase the fuel ratio appropriately, and supplement the heat loss caused by the high top temperature before returning to normal.

Adjust to normal value.

2) Check and adjust the particle size of raw fuel. If the limit content of fuel powder is too much, it can be properly saturated with water to increase

The degree of cohesion with the stone can delay the burning time of the fuel.

6. The calcination area moves downward, when the top temperature is found to be low, the ash temperature rises, and in serious cases, the fuel is not burned out due to wind and fire. lime same raw

Calcination increases, while 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 and the amount of rocks

Large amount of ash unloading, so that the mixed material moves down quickly, and the cooling zone is shortened, and the air enters the calcination zone without sufficient preheating.

The amount of calcium carbonate decomposition is reduced, and the CO is also reduced accordingly. Causes the amount of lime burning to increase. In addition, the raw materials are broken or grainy

If the temperature deviation is large, the resistance in the kiln will increase. At this time, the air pressure is not low, but the actual air volume is not enough. In this case, it should be appropriately reduced

The amount of stone loading and ash unloading should be increased appropriately. If the top pressure is too large at this time, the batch of materials can be appropriately reduced to change the partial crushing of raw materials.

In this case, appropriately increase the proportion of large grains, reduce the difference in grain size, and reduce the resistance in the kiln. Adjust the fuel and stone lumpiness to match Process requirements.

7. The extension of the calcination zone will cause the top temperature and ash temperature to be high, the CO2 will decrease, and the lime burning amount will also increase.

In addition, when it is serious, red ash will appear from the fire on the top of the kiln, that is, red at both ends. Tumors are formed in the kiln or local ventilation is poor, the reason is

If the fuel ratio is too large, the uniformity of limestone is poor, and nodules are formed in the kiln or local ventilation is poor. At the same time, there are nodules in the kiln or hanging on the kiln wall

Material, ventilation segregation, nodules or hanging material prevent the material from falling normally and poor ventilation. Due to the lump in the material flow

Falling off under impact will also prolong the calcination zone for a certain period of time. When this happens, production should be appropriately reduced, and the granularity of raw materials should be adjusted.

Reduce the fuel ratio and increase the air volume appropriately. Temporarily reduce the height of the material layer and then re-feed to return to the normal material level.

Nodules, nodules are the biggest failure of co-fired kilns including gas fired kilns, which can be found at this time 

8. The ash temperature remains high all the time, raw burning occurs at the same time when the lime is unloaded, and the CO2 content of the kiln gas is low for a long time (2) Material

The surface height does not match the ash discharge volume, the residence time of the material in the kiln is shortened, but the ash discharge time is prolonged, and the ash is mixed with unburned

Fuel and uncalcined limestone appear to form fly ash. Its main reason is (1) The fuel ratio is too high, or the impurities in the fuel

Excessive ingredients produce fusibles.

1) Although the proportion is not high, the fuel is locally concentrated, and the calcination is strong to form the hanging material on the kiln wall

2) Normal production is not possible due to a power outage or a long period of time, and the high-temperature zone stays in the kiln for too long or when there are impurity components, it is easy to form Tumors. When this happens you should Fuel ratio, adjust wind pressure and top pressure, reduce raw fuel impurity content.

3) Reduce the amount of feeding or increase the amount of ash unloading, reduce the height of the material surface, and expose the lumps or hanging materials. After cooling down and feeding impact make it fall off. Take small blasting measures in severe cases.

4) Change the mixing of raw materials and uneven distribution of fuel to avoid excessive local fuel.

5) Increase the frequency of feeding and ash unloading to increase the flow of materials and avoid the phenomenon of sticking and hanging materials.

6) Partial kiln, from the top of the kiln, it can be found that the material surface is inclined and the material is cut quickly on one side. Observe that the fire layer is dark on one side of the fire layer, indicating that the material surface is inclined.

The surface fire layer has a large temperature difference. It can be seen from the bottom of the kiln that the ash comes out quickly locally or on one side when the ash is unloaded, and sometimes red ash comes out when the ash temperature is high here. Forming

The reason is mainly

7) Uneven distribution of mixed materials or uneven ash discharge, local nodules in the kiln, resulting in local ventilation segregation. This case solves the cloth

(1)It is very important to fully and rationally use the multi-point rotary distributor to have a good distribution effect and have a good effect on avoiding partial kiln.

(2) Improper adjustment of ash unloading equipment causes unbalanced ash unloading.

(3) The kiln structure is unreasonable. The angle from the cooling section to the lower ash section is too small to form a dead corner and the feeding is not smooth.

8) In this case,

(1) change the mixing of raw materials and uneven ash discharge, and when it is judged that there is local nodulation in the kiln, it should be

Take measures first. In severe cases, modification of the kiln structure can also be considered.

(2) Most of the debris is distributed in the fast feeding part, dark fire part,There are many large pieces of cloth, so that the parts that get angry quickly increase the wind resistance.

Common problems of gas fired kiln:

In addition to the above common problems, the gas-fired kiln is almost the same as the mixed-fired kiln. Its key is the adjustment of the combustion flame temperature. Gas burning flames generally need to adjust the ratio and pressure of air and gas according to the composition and calorific value of different gases. The common problem of high calorific value gas is overburning, while the common problem of low calorific value gas is raw burning, but the occurrence of raw burning and overburning must also be analyzed in detail. When the value is high, the flame will form a very high temperature as soon as it exits the burner.

The sintering around the burner prevents the flame from penetrating in, which inevitably causes raw burning in the center of the kiln. Or because of improper adjustment of the calcination temperature, the surface of the limestone is first sintered into a hard shell. It's raw.

These problems are directly related to the type of kiln and the burner used. Great Wall Machinery Co., Ltd. designed a high-calorific-value long-flame burner for the use of high-calorific gas such as coke oven gas, calcium carbide tail gas, and natural gas. A variety of specific kiln types have been developed, such as dumbbell-shaped, beam-induced air type, and designed for high-calorific-value gas.

The carbon dioxide produced by this kiln has a good effect on diluting high-calorific-value gas and reducing over-burning. The company is using the gas generator to produce hot gas. The flame generally needs to adjust the ratio and pressure of air and gas according to the composition and calorific value of different gases.

The common problem of high calorific value gas is overburning, while the common problem of low calorific value gas is raw burning, but the occurrence of raw burning and overburning must also be analyzed in detail. As soon as the flame comes out of the burner, the temperature becomes very high, so that the sintering around the burner prevents the flame from penetrating in, which inevitably causes raw burning in the center of the kiln, or because of improper adjustment of the calcination temperature, the surface of the limestone is first sintered into a hard shell.

From the surface it looks like burnt, but the inside is actually burnt. These problems are directly related to the type of kiln and the burner used. Great Wall Machinery Co., Ltd. designed a high-calorific-value long-flame burner for the use of high-calorific gas such as coke oven gas, calcium carbide tail gas, and natural gas. A variety of specific kiln types have been developed, such as dumbbell-shaped, beam-induced air type, and designed for high-calorific-value gas. The carbon dioxide produced by this kiln has a good effect on diluting high-calorific-value gas and reducing over-burning.

The company is using the gas generator to produce hot gas. A breakthrough has also been made in the technology of lime production.