How much blast furnace gas is needed to produce one ton of burnt iron ore in sintering furnace and one ton of lime in lime kiln?
Sintering furnace:
Sintering furnace is a kind of furnace that makes the solid particles of ceramic body bond with each other at high temperature, and the grains grow, and the gaps (pores) and grain boundaries gradually decrease. Through the transfer of substances, its total volume is reduced and its density is increased, and finally it becomes a dense polycrystalline sintered body with a certain microstructure.
Lime kiln:
1. Significance of developing new technology of lime kiln at present
Iron and steel industry, calcium carbide industry, alumina industry, refractories and other industries are all big lime consumers, and these industries have developed rapidly in the past two years. The annual output is basically increasing by more than 20%. However, the main material (auxiliary material) lime they need has not increased correspondingly, which has caused the tension of lime, thus stimulating a large number of lime kilns in society, and the widespread flowering of lime kilns has caused serious pollution to the environment. In this case, the state and local governments have successively issued a series of policies and regulations to control lime kilns, but due to the stimulation of demand, it is difficult to achieve the expected results. Therefore, in order to control the pollution of earth kiln, it is necessary to implement modern new technology lime kiln to solve the demand problem. The so-called modern new technology lime kiln is a modern lime kiln with environmental protection and energy saving functions and high mechanization and automation. Due to the adoption of modern technology, we can make full use of cheap energy, especially the gas that polluted the environment in the past as the main energy, and turn waste into treasure. This not only protects the environment, but also produces lime with good quality and low cost. For enterprises adopting this new technology, the economic benefits will be significantly improved. This is the practical significance of popularizing the new technology of lime kiln.
Two. Types of new technology lime kiln
According to the fuel, there are mixed burning kilns, that is, burning solid fuel, coke, coke powder, coal and so on. Harmonious kiln burning. Gas kilns include burning blast furnace gas, coke oven gas, calcium carbide tail gas, producer gas and natural gas. According to kiln types, there are vertical kiln, rotary kiln, sleeve kiln, West Weimaster kiln, Maierzi kiln (Swiss), Focas kiln (Italian) and so on. At the same time, there are positive pressure operated kilns and negative pressure operated kilns. Linzhou Modern Science and Technology Center has developed and designed mixed kilns below 300 cubic meters and gas kilns below 140 cubic meters, especially XD energy-saving and environment-friendly lime kilns burning blast furnace gas and coke oven gas. The combustion problems of high calorific value and short flame of coke oven gas are overcome, and the remaining coke oven gas can be fully utilized. From the original coke oven gas "indomitable spirit", polluting the environment has become a valuable energy source to create benefits for enterprises. It is an effective way to save energy, protect environment and increase efficiency for small and medium-sized iron and steel enterprises, coking enterprises, calcium carbide enterprises and refractory industry.
3. Basic principle and thermal technology of lime combustion.
Limestone is mainly composed of calcium carbonate, while lime is mainly composed of calcium oxide. The basic principle of burning lime is to decompose calcium carbonate in limestone into calcium oxide and carbon dioxide quicklime with the help of high temperature. Its reaction formula is
Calcium carbonate, calcium oxide and carbon dioxide-42.5 kg
The technological process is as follows: limestone and fuel are put into a lime kiln (if gas fuel is added through pipelines and burners), preheated, then decomposed at 850℃, calcined at 1200℃, cooled and taken out of the kiln. That is, the production of quicklime products is completed. Different kiln types have different ways of preheating, calcining, cooling and ash discharge. But several technological principles are the same: high-quality raw materials, high-quality lime; Fuel has high calorific value and low consumption; The particle size of limestone is proportional to the calcination time; The activity of quicklime is inversely proportional to calcination time and calcination temperature.
4. Basic structure and main auxiliary equipment of lime kiln
Lime kiln is mainly composed of kiln body, feeding device, distributing device, combustion device, ash unloading device, electrical appliance, instrument control device and dust removal device. Different forms of lime kilns have different structural forms and calcination forms, and the process flow is basically the same, but the equipment value is very different. Of course, the use effect is definitely different.
Verb (abbreviation for verb) Quality and quantity consumption of limestone
There are two main requirements for limestone quality in industrial lime: First, it requires a high calcium carbonate content, which is generally above 97%. Second, its structural particles are small, because the limestone particles with small particles are not compact. In the case of containing organic matter, the organic matter is porous, and carbon dioxide is easy to separate and easy to calcine. Third, there are few impurities, especially harmful components such as silicon dioxide, magnesium oxide, aluminum oxide, iron oxide, sulfur and phosphorus. If there is 1% in limestone, there is 18% in calcined quicklime. According to theoretical calculation, one ton of lime needs to be burned.
1.78 tons of limestone, but the degree of "green" and "overburning" during calcination is different from the quality of limestone.
6. Quality standard of quicklime:
The general standards of lime quality are: calcium oxide content, raw burning rate, activity, harmful component content and so on. But more importantly, different industries have different standards for different purposes. For example, in the calcium carbide industry, it particularly emphasizes activity, that is, soft ash combustion, while in the iron-making industry, it emphasizes strength, so steel-making requires hard ash combustion and soft ash combustion. So its indicators are different. Generally, the content of standard quicklime and calcium oxide should be above 97%, the overburning rate should be less than 10%, and the active calcium should be above 300mi.
7. Fuel and combustion of energy-saving and environment-friendly lime kiln
There are many kinds of fuels for burning lime, including solid fuel, gas fuel and liquid fuel, but the combustion principle of the new technology lime kiln is that which fuel is the most economical, which fuel is more conducive to environmental protection and which fuel can save energy is the key to the new technology lime kiln. Coke and gas are now widely used. As far as new technology is concerned, gas is the best fuel for lime kiln, including blast furnace gas, converter gas, coke oven gas and calcium carbide tail gas (gas) producer gas. Because these gaseous fuels belong to waste utilization and circular economy. Especially now, most coke oven gas is dispersed and rich in resources, followed by blast furnace gas and calcium carbide tail gas. If these gases are used, it can save a lot of energy and protect the environment, and more importantly, enterprises can receive good economic benefits. If these gas lime kilns are developed in large quantities, the environmental pollution caused by earth kilns will naturally be solved. Why is such a good project developing so slowly now? The main reason is that the development of gas-fired lime kiln technology in China is relatively short, and everything has a process of development and understanding. In particular, coke oven gas is easy to burn and burn when used in lime kiln because of its high calorific value and short flame. As a result, some enterprises dare not use it boldly. In fact, this is not too difficult to solve. Linzhou Modern Science and Technology Center has developed the technology of mixing long flame burner outside lime kiln and self-circulating dilution of high calorific value gas. The problem of burning lime in coke oven gas can be completely solved. The amount of fuel used for burning lime is related to the furnace type and the calorific value of the fuel. The heat required for calcining lime comes from the combustion of fuel. The main component of fuel, the molecular formula of carbon combustion process is C+O2 = CO2 gas fuel, calculated according to its calorific value. According to practical experience, it takes about 960kcal to produce one kilogram of lime. However, due to the different production equipment and process conditions of each factory, there are also differences. Generally speaking, it takes about 1600m3 blast furnace gas and 300m3 coke oven gas to burn one ton of ash. Calcium carbide tail gas needs about 360m3, natural gas needs about 120m3, and producer gas needs about 900m3.
Eight. Distributor, burner and other auxiliary equipment of lime kiln
The main auxiliary equipment of lime kiln includes feeding mechanism, distributor, air supply device, combustion device and ash unloading device. Relatively speaking, the distribution of mixed-burning lime kiln is very important, because when fuel and limestone are loaded into the kiln at the same time, it is necessary to realize the reasonable distribution of burden in the kiln through distribution, eliminate the furnace wall effect, balance the resistance in the furnace, and strive for uniform cross section of the whole furnace. Therefore, the form and application effect of distributor have great influence on the production efficiency of lime kiln. At present, there are various distributors, including rotary distributor, conch distributor, fixed distributor and so on. Among them, the three-stage bell jar distributor developed by Linzhou Modern Science and Technology Center uses the principle of "funnel throat effect" and "inverted W heap angle effect" and the combination of adjustable baffles, which has a simple structure and good effect on solving the problems of uniform mixing of raw fuel and reasonable particle size distribution. But also has the advantages of high temperature resistance, wear resistance, convenient maintenance and the like. It is especially suitable for the configuration of small and medium-sized lime kilns, and the main auxiliary equipment of gas kilns is the burner, because its gas fuel is mixed with combustible gas and required oxygen (air) in the burner in a certain proportion and then sent to the kiln for combustion. The air required by different gases is also different, and different furnace types and different heating methods require different flame types. Such as premixing, semi-mixing, external mixing and oxidation flame, neutral flame, reducing flame, etc. Therefore, the burner of gas kiln determines the calcination effect of lime kiln to a certain extent. Of course, other auxiliary equipment is also very important, such as hood, which looks very simple, but it is necessary to ensure the distribution of air volume in the kiln throughout the kiln section to achieve good results.
9. Selection of air supply and fan for lime kiln
Whether it is a mixed kiln or a gas kiln, it needs reasonable air supply, because any fuel combustion must meet three conditions, namely fuel, air (oxygen) and open flame, and it will not burn without any condition. The air volume is calculated according to the oxygen demand of combustible components of fuel. If the air supply is not fuel, the fuel will be insufficient, and the excess air will become a lot of heat in the flue gas, which will increase the 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 the different resistance formed by different kiln types and different raw material particle sizes. Generally speaking, the resistance of vertical kiln can be determined by the following formula
40-70h2o/ effective height (m)
The formula to be calculated. However, the particle size of raw fuel is different. Therefore, the selection of fan should be based on both theoretical calculation and specific furnace type and practical experience. In order to have a good use effect.
X. dust removal and environmental protection of lime kiln
The smoke and dust emitted during lime calcination contains a lot of harmful gases and dust below 10 micron, and the dust also contains SO2. F2O3AIO3, etc. These harmful gases and dust are very harmful to human body. If people inhale them for a long time, it will cause respiratory diseases such as bronchi and lungs, especially for children. Moreover, the dust floating in the air also contains carcinogens. If the 24-hour average concentration of harmful dust is greater than 150mg/m3, it will cause fatal harm to human body. The main advantages of the new lime kiln are low energy consumption, high output and good quality, and the biggest advantage is easy dust removal. Because its whole calcination process is equivalent to being carried out in a sealed container, its flue gas can be discharged from the flue gas pipeline at the top of the kiln, after dust removal and purification, and then discharged up to the standard, which is harmless and pollution-free. XI。 Automatic control
Automatic control is an important feature of new technology lime kiln. Its feeding, batching, air supply, gas supply and ash discharge are all automatically controlled by computer. However, we should also consider the national conditions, factory conditions and value costs. The higher the degree of automation, the better. The final effect should be principle.