Technical summary of chaeng lime kiln

Modern lime kiln compared with the traditional soil kiln with environmental protection, energy saving; mechanization, a higher degree of automation advantages, it can make full use of cheap energy, in particular, and can use the original pollution of the environment as the main energy, turning waste into treasure, not only The environment can be protected, and it produces lime,it not only good quality and low cost, the enterprise economic benefits will be significantly increased.

First, the type of lime kiln

1, according to the fuel points: a mixed kiln (ie, burning solid fuel, coke, coke powder, coal, etc.) and gas kiln (ie, 2 blast furnace gas, coke oven gas, calcium carbide tail gas, gas furnace, natural gas, etc.).

3, according to kiln shape: a vertical kiln, rotary kiln, sleeve kiln, double kiln, double-beam kiln and so on.

4, according to the operating pressure points: a positive pressure operation kiln and negative pressure operation kiln.

Second, the basic principles and thermal process

Limestone is the main component of calcium carbonate, and lime composition is mainly calcium oxide. The basic principle of burning lime is by means of high temperature, the limestone in the decomposition of calcium carbonate into calcium oxide and carbon dioxide.

Reaction style

CaCO3 = CaO + CO2-42.5 Kcal

Process: limestone and fuel into the lime kiln (if the gas fuel through the pipeline and burner into) preheated to 850 ℃ began to break down to 1200 ℃ to complete the calcination, and then after cooling, unloading the kiln. That is to complete the production of lime products. Different kiln shapes have different preheating, calcining, cooling and unloading methods. However, there are several principles of the process is the same: high quality raw materials, lime quality is good; fuel calorific value is high, the number of consumption less; limestone particle size and calcination time is proportional to; lime activity and calcination time, calcination temperature is inversely proportional.

Third, fuel and burning

The lime fuel is very broad, solid fuel, gas fuel, liquid fuel can be. New technology lime kiln combustion principle is: which fuel the most economical, which fuel is more conducive to environmental protection, which fuel is more energy conservation.

Now the use of the general mainly coke and gas, the most ideal or gas, including blast furnace gas, converter gas, coke oven gas, calcium carbide tail gas (gas) furnace gas is the best fuel lime kiln. Because these gas fuels are waste use, the nature of circular economy, especially as coke oven gas is now most of the scattered, very rich in resources, followed by blast furnace gas, and then is the calcium carbide tail gas, these gases if used, one can save a lot of energy, Second, the environment can be protected, more importantly, companies can receive very good economic benefits.

The amount of fuel used for lime is related to the calorific value of its furnace type and fuel. The heat required for the calcination of lime is derived from the combustion of the fuel. The molecular formula of the main component of the solid fuel is C + O2 = CO2 and the gaseous fuel is calculated from its calorific value. According to the actual experience of production of one kilogram of lime about 960kcal calories, but because the plant production equipment and process conditions are different. In general, burn a ton of ash with blast furnace gas to be about 1600m3, coke oven gas to be about 300m3. Calcium carbide tail gas to be about 360m3, natural gas to be about 120m3, the furnace gas to be about 900m3.

Fourth, the basic structure and equipment

Lime kiln mainly by the kiln body, feeding device, cloth device, burning device, ash removal device, electrical appliances, instrument control devices, dust removal devices and other components. Different forms of lime kiln, its structure and the form of calcination are different, the process is basically the same, but the value of the equipment is very different, the use of the effect is different.

Blended lime kiln fabric is very critical, because it is in the fuel and limestone into the kiln at the same time, must be achieved through the fabric charge in the kiln reasonable distribution, to eliminate the furnace wall effect, balanced furnace resistance, and strive to the entire furnace section "on Fire "uniform, so the form of cloth and the use of the effect of lime kiln production efficiency has a great impact. The distributor includes a rotary distributor, a conch-type dispenser, a fixed cloth, and the like.

The main auxiliary equipment of the gas kiln is the burner because its gaseous fuel is fed through the burner to mix the combustible gas and the required oxygen (air) into the furnace at a certain rate in the burner and burn The amount of air required for gas is also different. Different furnace type, different heating methods, it needs the type of flame is not the same, such as premixed, semi-mixed, mixed and oxidation flame, neutral flame, flame reduction and so on. So that the gas burner burner to a certain extent determines the lime kiln calcination effect.

Of course, other ancillary equipment is also very important, such as the hood, look similar to very simple, but to ensure that it is for the kiln air volume in the kiln section of the distribution of good results.

Five, limestone quality requirements and quantity consumption

1, containing calcium carbonate content is high, the general requirements to be more than 97%.

2, the structure of grain to be small, the general size of 30mm-60mm, because the small grain of limestone between the strong, and in the case of organic matter containing organic matter formed porous, carbon dioxide easily separated to facilitate calcination.

3, less impurities, especially harmful components such as silica, magnesium oxide, alumina, iron oxide, sulfur and phosphorus, these ingredients in limestone if one percent, to calcined into lime, Eighteen.

4, calcined "Health" "over" the level of the quality of the limestone is also good or bad there is a certain difference.

Burn 1 ton of lime according to the theoretical calculation to be 1.78 tons of limestone.

Six, the quality of lime standards

Lime quality of the general criteria are: calcium oxide content, raw, over-burning rate, activity, harmful ingredients, etc., different industries, different uses have different standards. Such as the calcium carbide industry, especially the emphasis on the degree of activity that is soft burning ash, iron and steel industry has stressed the strength, so hard to burn ash, steel and then have soft burning ash. So its indicators are not the same. General standard lime, calcium oxide content to reach more than 97%, raw birth rate of less than 10%, the degree of activity to 300ml or more.

Seven, for the wind and fan selection

Whether the mixed kiln or gas kiln is required to be reasonable for the wind, because any fuel combustion must have three conditions, namely fuel, air (oxygen), and open flame, the lack of any one condition is not burning The The amount of the wind is calculated based on the amount of oxygen required for the flammable component of the fuel. If the fuel is insufficient, the fuel will not be sufficiently fueled. The excess air will become a flue gas and a large amount of heat will be lost, resulting in fuel increase and waste. Air volume is generally calculated according to the formula, but the original fuel particle size is also different. So the choice of the fan should be based on theoretical calculations and specific furnace and practical experience as the basis to select the fan in order to have a good effect.

Eight, lime kiln dust and environmental protection

Lime in the calcined emissions of dust contains a lot of harmful gases and 10 microns below the dust, dust and contains SO2, F2O3, AlO3, etc., these harmful gases and dust on the human body is very harmful, and the use of new technology, modern lime Kiln in addition to low energy consumption, high yield, good quality, the biggest advantage is easy to dust. Because the entire calcination process is equivalent to a sealed container, its flue gas can be discharged from the kiln flue gas pipeline, through the dust purification, and then to harmless, non-polluting discharge standards.