What Is a Lime Kiln?

The iron and steel industry, calcium carbide industry, alumina industry, refractories and other industries are all large lime consumers, and these industries have been developing rapidly in the past two years.

Lime Kiln Technology

The iron and steel industry, calcium carbide industry, alumina industry, refractories and other industries are all large lime consumers, and these industries have been developing rapidly in the past two years. Annual output is basically increasing at a rate of more than 20%. However, the main material (auxiliary material) that they need does not have a corresponding increase in lime, so it has caused tension in the lime, which has stimulated a large number of lime kiln in the society to be launched, and the blooming of earth kiln has caused serious pollution to the environment. Under such circumstances, the state and local governments have successively introduced a series of policies and regulations for the improvement of earth-fired kiln, but it is difficult to achieve the expected results because of the stimulus of demand. Therefore, if you want to control the pollution of the earth-fired kiln, you must implement modern new technology lime kiln to solve the problem of demand. The so-called modern new technology lime kiln is a modern lime kiln with environmental protection, energy saving functions, mechanization and high degree of automation. Because it uses modern technology, it can make full use of cheap energy, especially using the gas that has polluted the environment as the main energy source, turning waste into treasure. In this way, not only can the environment be protected, but the lime it produces is not only of good quality and low cost. For enterprises using this new technology, economic benefits will increase significantly. This is the practical significance of promoting new technology lime kiln.

According to fuel, there are mixed burning kiln, that is, burning solid fuel, coke, coke powder, coal, and gas burning kiln. Gas firing kiln includes burning blast furnace gas, coke oven gas, calcium carbide tail gas, generator furnace gas, natural gas and so on. According to the shape of the kiln, there are shaft kiln, rotary kiln, sleeve kiln, West German Weimarst kiln, Maerz kiln (Switzerland), Furcas kiln (Italy) and so on. At the same time, it is divided into positive pressure operation kiln and negative pressure operation kiln. Linzhou Modern Science and Technology Center developed and designed mixed-fired kiln below 300 cubic meters and gas-fired kiln below 140 cubic meters, especially XD energy-saving and environmentally friendly lime kiln for blast furnace gas and coke oven gas combustion. The short burning problem can make full use of the remaining coke oven gas. From the original "lighting" of the coke oven gas, polluting the environment has become a valuable energy source for creating benefits for enterprises. For small and medium-sized iron and steel enterprises, coking enterprises, calcium carbide enterprises and refractories industry are very good effective ways to save energy, environmental protection and efficiency.

The main ingredients of limestone are

The lime kiln is mainly composed of a kiln body, a feeding device, a distribution device, a combustion device, an ash discharge device, an electric appliance, an instrument control device, and a dust removal device. Different forms of lime kiln have different structural forms and calcined forms. The process flow is basically the same, but the equipment value is very different. Of course, the use effect is definitely different.

There are two main requirements for the quality of limestone for industrial lime: First, it requires a high content of calcium carbonate, and generally requires more than 97%. The second is that its structural grains are small, because the small crystal grains of limestone are not compact, and in the case of containing organic matter, the porous form formed by the combustion of organic matter, the carbon dioxide is easy to separate, so it is easy to calcinate. Third, there are few impurities, and especially harmful components such as silica, magnesia, alumina, iron oxide, sulfur and phosphorus. If these ingredients are 1% in limestone, they are 18% in calcined quicklime. One ton of lime is theoretically calculated to require 1.78 tons of limestone, but there is also a certain difference between the "raw" and "over" firing levels and the quality of the limestone during calcination.

The general standards for the quality of lime are: calcium oxide content, raw, over-burned rate, activity, harmful content, etc., but more importantly, different industries, different uses have different standards. For example, in the calcium carbide industry, it particularly emphasizes the activity, that is, soft burnt ash, and the ironmaking industry, it also emphasizes strength, so hard burned ash, and steelmaking, soft burned ash. Therefore, its indicators are also different. General standard quicklime, the content of calcium oxide should reach more than 97%, the raw burn rate is less than 10%, and the active calcium should be more than 300mi.

Lime-burning fuels are widely available. Solid fuels, gas fuels, and liquid fuels are all possible. However, the burning principle of the new technology lime kiln is which fuel is the most economical, which fuel is more environmentally friendly, and which fuel is more energy efficient. The key to technical lime kiln. Coke and gas are commonly used today. As far as new technology is concerned, gas is the best fuel for lime kiln, including blast furnace gas, converter gas, coke oven gas, calcium carbide exhaust gas (gas), and furnace gas. Because these gaseous fuels are all waste-utilizing and circular economy in nature. Especially like coke oven gas is now mostly released, and the resources are very rich, followed by blast furnace gas, and then calcium carbide tail gas. If these gases are used, they can save a lot of energy, and secondly, the environment can be protected, and more importantly, companies can Receive good economic benefits. If these gas-fired lime kilns are developed in large numbers, the environmental pollution problems of earth-fired kilns will naturally be solved. Why the development of such a good project is slow, mainly because the technology of gas-fired lime kiln is relatively short in China, and everything has a process of development. Especially coke oven gas, because of its high heat value, short flame, Lime kiln is easy to burn and burn. As a result, some companies dare not use it boldly. In fact, this problem is not too difficult to solve. Linzhou Modern Science and Technology Center has now researched and manufactured the external mixing long flame burner and lime kiln self-circulating dilution high-calorie gas technology, which can completely solve the lime burning problem of coke oven gas. . The amount of fuel used for burning lime is related to the calorific value of its furnace type and fuel. The heat required for calcining lime is derived from the combustion of fuel. The main component of fuel, the molecular formula of carbon combustion process is C + O = CO, and gas fuel is calculated based on its calorific value. According to actual experience, it takes about 960 kcal to produce one kilogram of lime. However, there are also differences due to the different production equipment and process conditions of each plant. Generally speaking, it takes about 1600m³ to burn one ton of ash for ash, about 300m³ for coke oven gas, about 360m³ for calcium carbide gas, about 120m³ for natural gas, and about 900m³ for generator gas.

The main auxiliary equipment of a lime kiln include a feeding mechanism, a distributor, an air supply device, a combustion device, and an ash unloading device. Relatively speaking, the mixed-fired lime kiln cloth is critical because it is used to load fuel and limestone into the kiln It is necessary to achieve a reasonable distribution of the furnace charge in the kiln through the cloth, eliminate the furnace wall effect, balance the furnace resistance, and strive to uniformly "fire" the entire furnace section. Therefore, the form and effect of the spreader have a great influence on the production efficiency of the lime kiln. There are a variety of distributors, including rotary distributors, conch distributors, fixed distributors, etc. Among them, the three-section bell distributor developed by Linzhou Modern Science and Technology Center uses the "funnel throat effect" and "inverted W stacking The combination of the "angle effect" principle and the adjustable baffle plate has a simple structure and is effective in solving the problems of uniform mixing of raw fuels and reasonable distribution of size and particle size. And has many advantages such as high temperature resistance, wear resistance and easy maintenance. It is especially suitable for small and medium-sized lime kiln configurations. The main auxiliary equipment of the gas kiln is a burner, because its gaseous fuel is mixed by the combustible gas and the required oxygen (air) in the burner through the burner. It is sent to the furnace for combustion, and the amount of air required for different gases is different. Different furnace types and different heating methods require different types of flames. Such as pre-mixed, semi-mixed, outer-mixed and oxidized flame, neutral flame, reducing flame and so on. Therefore, the burner of the gas kiln determines the calcination effect of the lime kiln to a certain extent. Of course, other auxiliary equipment is also very important, such as the hood. It is very simple to look similar, but it is necessary to ensure the distribution of the air volume in the kiln across the kiln cross section to have a good effect.

Both the mixed kiln and the gas kiln need a certain amount of reasonable air supply, because any fuel must have three conditions, namely fuel, air (oxygen), and open flame. Without any of these conditions, it will not burn. . The amount of wind is calculated based on the oxygen demand of the flammable components of the fuel. If the air supply is insufficient, the fuel will not be fully burned, and the excess air supplied to the wind will become a large amount of heat in the flue gas, causing an increase and waste of fuel. Its air volume is generally calculated according to the following formula: (The calculation formula is omitted) Its pressure should be calculated according to different resistances formed by different kiln types and different raw material particle sizes. Generally, the resistance of vertical kiln can be

4070 H2O / effective height (m)

Formula to calculate. But there are also differences in the size of the raw fuel. Therefore, when selecting a fan, it is necessary to select the fan based on the theoretical calculation and based on the specific furnace type and actual experience.

The soot emitted by lime during calcination contains a large amount of harmful gases and dust below 10 microns, and the dust also contains SO; F2O; AIO and so on. These harmful gases and dust are very harmful to the human body. If people inhale for a long time, it will cause respiratory diseases such as bronchus and lungs. Young children are more serious. The dust floating in the air also contains carcinogens. Hazardous dust exceeding 150mg / m³ can cause fatal harm to the human body. The main advantage of the new technology lime kiln is that in addition to low energy consumption, high output and good quality, the biggest advantage is that it is easy to remove dust. Because its entire calcination process is equivalent to being carried out in a sealed container, its flue gas can be discharged from the kiln top flue gas pipe, purified by dust removal, and then achieved harmless and pollution-free discharge.

The maintenance of the machine is an extremely important recurring task. It should be closely coordinated with the operation and maintenance of the machine and should have a full-time job.

Personnel perform on-duty inspection.

Maintenance of lime kiln technology machines

1.Bearing

The shaft of the crusher bears the full load of the negative machine, so good lubrication has a great relationship with the bearing life, it directly affects the machine

The service life and running rate of the machine require that the lubricating oil injected must be clean and the seal must be good.

) Rotary bearings (2) Roller bearings (3) All gears (4) Moving bearings, sliding planes.

2. The newly installed rims are prone to loosening and must be checked frequently.

3. Pay attention to whether the parts of the machine work normally.

4, pay attention to check the wear degree of easy-wearing parts, pay attention to replacing worn parts at any time.

5. The plane of the bottom frame of the movable device should be removed from dust to prevent the movable bearing from being on the bottom frame when the machine encounters unbreakable materials.

Move up, so that a serious accident occurs.

6, bearing oil temperature rise, should immediately stop the inspection to eliminate the cause.

7. If there is an impact sound when turning the gear during operation, it should be stopped immediately for inspection and eliminated.

Installation and commissioning of lime kiln technology

1. The equipment should be installed on a horizontal concrete foundation and fixed with anchor bolts.

2. Please pay attention to the vertical of the main body when installing.

3. After installation, check whether the bolts in all parts are loose and whether the main engine compartment door is fastened. If so, tighten it.

4. Configure the power cord and control switch according to the power of the device.

5. After the inspection is completed, perform a no-load test run, and the test run can be carried out normally.