Fine ore sintering machine

1. no The height of the bed has little to do with this. Theoretically, the heat storage of the thick bed can save the amount of coke. At present, the fuel remains unchanged, the return ore increases and the sinter strength decreases. There are many reasons for this, such as ignition temperature control, holding time, iron ore ratio, etc. the first reason should not be the height of material layer. The basic reason for this situation is that the temperature of the burning zone of the material layer is not enough, so find out the reason accordingly.

2. Sintering is a method of heating powdery materials (such as fine ore and concentrate) at high temperature and sintering them into blocks under the condition of incomplete melting. The proct is called sinter, and its shape is irregular and porous. The heat energy required for sintering is provided by the combustion of the carbon in the sintering material and the excess air, so it is also called oxidation sintering. Sinter mainly depends on liquid phase bonding (also known as melting sintering), solid phase bonding only plays a secondary role
modern sintering proction is a process of exhaust sintering, in which the mixture (iron ore powder, fuel, flux and return ore) is mixed with an appropriate amount of water, mixed and granulated, and then spread on the grate of belt sintering machine. After ignition, a certain negative pressure is used to exhaust air, so that the sintering process can be carried out from top to bottom. The sinter is unloaded from the sintering trolley. After crushing, cooling, granulation and screening, the finished sinter, return ore and bedding material are separated< The typical sintering proction process can be divided into eight process systems:
1) the receiving process system mainly includes mper system, receiving tank, concentrate warehouse, flux warehouse, fire extinguishing warehouse, etc., which is responsible for the receiving, transportation and storage of incoming raw materials
2) raw material preparation process system includes neutralization of iron containing raw materials, crushing of fuel, crushing and screening of flux. Its task is to prepare raw materials, flux and fuel that meet proction requirements for batching process
3) batching process system, including ore trough, disc feeder, weighing facilities, etc; According to the specified sinter chemical composition and the type of raw materials used, through calculation, each raw material is fed according to the calculated weight, so as to ensure the stability of chemical composition of mixture and sinter and the adjustment of fuel quantity
4) mixing and granulating process system mainly includes cold and hot return plate and primary mixing; Mixture ore tank, secondary mixing and other processes. Its task is to add water and wet the mixture, then mix the mixture evenly with the primary mixer, and preheat the pellets with the secondary mixer
5) sintering process system includes bedding, distribution, ignition, sintering, etc. The main task is to sinter the mixture into qualified sinter
6) the ventilation system includes bellows, st collecting pipe, st collector and fan. Chimneys, etc
7) the finished proct processing system includes hot crushing, hot screening, cooling, cold crushing, cold screening and finished proct transportation system. The task of this process is to separate 5 ~ 50mm finished sinter, 10 ~ 20mm bottom material, less than 5mm cold return ore
8) the environmental protection st removal process system is mainly to use the electrostatic precipitator system to purify the waste gas from the st points of the sintering machine tail discharge, hot screen, cooling, ore return and whole grain system. After being purified by the precipitator, the waste gas is discharged into the atmosphere. After being wetted, the st is added into the sintering mixture for sintering. Its task is to protect the environment of sintering proction
in some sintering plants in our country, the process is not perfect, some of them have no cooling, cold crushing and cold screening operations (called hot ore plants); Some of them have cooling effect, but no cold breaking, cold screening and bedding effect. In the more advanced sintering process of Baosteel, the raw material receiving, flux crushing, screening and neutralization of iron bearing raw materials are carried out in the raw material yard, and the iron bearing raw materials are mixed into a single and stable mixture by the raw material yard and directly sent to the sintering batching tank.

3. The manganese ore used in the process of procing silicon manganese alloy by submerged arc furnace should be screened. The screened ore powder can not be directly fed into the furnace, but can be converted into sinter by sintering and briquetting with sintering machine. In this way, the reasonable utilization of ore powder can improve the structure of ore fed into the furnace, and the sinter is clinker fed into the furnace, which can rece the power consumption of smelting in submerged arc furnace and speed up the smelting process. If there is sintering machine in the raw material system of submerged arc furnace smelting, manganese ore powder can be directly imported from abroad for sintering, which not only reces the cost of raw materials, but also benefits the furnace condition.

4. Sintering machine is suitable for sintering operation of large-scale ferrous metallurgy sintering plant. It is the main equipment in the process of air extraction sintering. It can sinter concentrate powder and rich ore powder with different composition and particle size into blocks, and partially eliminate sulfur, phosphorus and other harmful impurities in ore. According to the sintering area, the sintering machine can be divided into several specifications of different length and width, which can be selected by users according to their output or site conditions. The larger the sintering area, the higher the output.

5. The function of using nine roller cloth is to control the degree of segregation to the minimum, not to cause segregation. So it's important to control the size of the fuel< When the particle size of
coke powder is too coarse,
the particle size of
more than 2mm in the coke powder increases. Due to the distribution segregation, the fuel is unevenly distributed along the height of the material layer, and the gas flow in the sintering material layer is unevenly distributed. During the sintering process, the temperature near the coarse fuel is too high, while the position far away from the coarse fuel is insufficient e to the rection of fuel,
the lower sintering temperature
leads to the decrease of sinter bonding phase and sinter strength, resulting in the increase of powder and the decrease of yield. Because fuel combustion is controlled by
diffusion,
the larger the particle size is, the longer the combustion time is, the thicker the combustion layer is, and the more sufficient the combustion is, the stronger the oxidation atmosphere is, and the better the utilization of
chemical energy is. Properly increasing the particle size of fuel can improve the utilization rate of fuel chemical energy and save the amount of sintering fuel
when the sinter
basicity
,
SiO2
content is fixed, the amount of calcium ferrite depends on the amount of carbon. Appropriately increasing the particle size of the fuel can improve the utilization rate of the fuel, rece the amount of carbon, enhance the
oxidizing atmosphere
, and create favorable conditions for the formation of calcium ferrite. At the same time, e to the appropriate increase of fuel particle size, the combustion speed and vertical sintering speed are reced, and the amount of liquid phase in the sinter bed is increased, which improves the sinter strength and
improves the sinter quality
considering the composition of sintering raw materials, material structure, coke powder
fixed carbon
and solid unit consumption, the coke powder particle size should be controlled between 80% and 85% in the case of large proportion of coarse powder in sintering mixture, and 75% to 80% in the case of small proportion of coarse powder in sintering mixture, In this way, the quality of sinter minerals can be guaranteed and the unit consumption of sinter solids can be reced appropriately.

6. 1. The concept of sintering

a series of physicochemical changes are made on the sintering equipment after mixing and pelletizing all kinds of powdery iron containing raw materials with appropriate amount of fuel and flux and adding appropriate amount of water< At present, the belt type suction sintering machine is widely used to proce sinter. The technological process of sintering proction is shown in Fig. 2-4. It mainly includes the preparation of sintering material, proportioning and mixing, sintering and proct treatment<
process flow of exhaust sintering

> preparation of sintering raw materials

① iron containing raw materials

high iron content, particle size & lt; 5mm ore powder, iron concentrate, blast furnace st, steel sheet, steel slag, etc

it is generally required that the raw material containing iron should have high grade, stable composition and less impurities

② flux

it requires high content of effective Cao, less impurities, stable composition, about 3% water content and more than 90% particle size less than 3mm in flux

adding a certain amount of dolomite into the sinter can make the sinter contain appropriate MgO, which has a good effect on the sintering process and can improve the quality of sinter

③ the fuel

is mainly coke powder and anthracite

the requirements for fuel are high fixed carbon content, low ash content, low volatile matter, low sulfur content, stable composition, water content less than 10%, and more than 95% of the particles with particle size less than 3mm

see table 2-2 for general requirements of raw materials for sintering<

General requirements of raw materials for sintering into the plant

● proportioning and mixing

① proportioning

proportioning purpose: to obtain sinter with stable chemical composition and physical properties to meet the requirements of blast furnace smelting

commonly used batching methods: Volume batching method and mass batching method

Volumetric Batching method is based on the condition that the bulk density of materials is constant and the mass of raw materials is proportional to the volume. The accuracy is poor

the quality batching method is based on the quality of raw materials. The specific volume proct method is accurate and easy to realize automation

② mixing

mixing purpose: to make the composition of sinter uniform, the moisture content appropriate, and easy to pelletize, so as to obtain the sinter mixture with good particle size composition, so as to ensure the quality of sinter and improve the output

mixing operation: wetting with water, blending and pelletizing

according to the different properties of raw materials, one mixing or two mixing processes can be used

the purpose of one-time mixing: wetting and mixing, and preheating the material when heating the return ore

the purpose of secondary mixing is to continue mixing and pelletizing, so as to improve the permeability of sinter layer

when sintering with rich ore powder with particle size of 10-omm, because its particle size has reached the requirement of pelletizing, one-time mixing is adopted, and the mixing time is about 50s

when fine grinding concentrate powder is used for sintering, because the particle size is too fine and the permeability of material bed is poor, in order to improve the permeability, pelletizing must be made in the mixing process, so the secondary mixing is adopted, and the mixing time is generally not less than 2.5 ~ 3min<

most sintering plants in China adopt secondary mixing< Sintering operation is the central link of sintering proction, which includes feeding, ignition, sintering and other main processes

① distribution

the operation of laying the bottom material and mixture on the sintering machine trolley

when the bedding material process is adopted, a layer of small sinter with particle size of 10-25 mm and thickness of 20-25 mm is laid as bedding material before the mixture is laid. The purpose is to protect the grate, rece the st removal load, prolong the service life of the fan rotor, and rece or eliminate the slag on the grate

after the bottom material is laid, the cloth is distributed. The size and chemical composition of the mixture should be evenly distributed along the vertical and horizontal direction of the trolley, with certain looseness and smooth surface

at present, the round roller distributor is widely used

② ignition

ignition operation is to ignite the material layer surface on the trolley and make it burn

sufficient ignition temperature, suitable high temperature holding time and uniform ignition along the trolley width are required for ignition

the ignition temperature depends on the melting temperature of sintering procts. It is usually controlled at 1250 ± 50℃ < The ignition time is usually 40-60s

ignition vacuum is 4-6kpa< The ignition depth is 10-20 mm

③ sintering

accurately control the air volume, vacuum degree, material layer thickness, machine speed and sintering end point

sintering air volume: the average air volume required per ton of sinter is 3200m3, which is (70-90) m3 / (cm2. Min) according to the sintering area

Vacuum Degree: it depends on the capacity of the fan, the resistance of the exhaust system, the permeability of the material layer and the air leakage loss

material layer thickness: appropriate material layer thickness should combine high yield with high quality. The thickness of material layer is 250-500mm

machine speed: the proper machine speed should ensure that the sinter is thoroughly burned at the predetermined sintering end point. In actual proction, the speed of the machine is generally controlled at 1.5 ~ 4 m / min

judgment and control of sintering end point: control the sintering end point, that is, control the position of the trolley when the sintering process is completed. The end point of small and medium sintering machine is generally controlled at the penultimate bellows, while that of large sintering machine is controlled at the penultimate bellows

the sintering process of belt sintering machine is carried out from top to bottom. The temperature change along the height of the material layer can be generally divided into five layers, and the reaction change in each layer is shown in Fig. 2-5. After ignition, sinter layer, combustion layer, preheating layer, drying layer and over wet layer appear successively. Then the last four layers disappear one after another, and finally only the sinter layer is left< After ignition at high temperature, the fuel in the sinter gives off a lot of heat, which makes the minerals in the sinter melt. With the combustion layer moving down and cold air passing through, the molten liquid phase is cooled and recrystallized (1000-1100 ℃) to solidify into sinter with mesh structure

the main change of this layer is the solidification of the melt, accompanied by crystallization and precipitation of new minerals, the cold air inhaled is preheated, and the sinter is cooled at the same time, and the low valent oxides may be reoxidized when contacting with the air

② combustion layer

the fuel burns in this layer, and the temperature is as high as 1350 ~ 1600 ℃, which makes the minerals soften, melt and bond into lumps

in addition to the combustion reaction, the melting, rection and oxidation of solid materials and the decomposition of limestone and sulfide occur in this layer

③ preheating layer

the mixture in the lower part is preheated to the ignition temperature quickly by the high temperature exhaust gas from the combustion layer, which is generally 400 ~ 800 ℃

solid state reaction begins in this layer, crystal water and part of carbonate and sulfate decompose, and magnetite is oxidized locally< (4) the drying layer is heated by the waste gas from the preheating layer, and the temperature of the drying layer quickly rises to above 100 ℃. A large amount of free water in the mixture evaporates, and the thickness of this layer is generally 10-30mm

in fact, it is difficult to separate the drying layer from the preheating layer, which can be collectively referred to as the drying preheating layer

the pellets in this layer are heated rapidly and dried rapidly, which is easy to be damaged and worsen the permeability of the layer

⑤ over wet layer

the hot waste gas from the dry layer contains a lot of water. When the material temperature is lower than the dew point temperature of the water vapor, the water vapor in the waste gas will re condense, which makes the water in the mixture increase greatly and form over wet layer

too much water in this layer will deteriorate the permeability of the material layer and rece the sintering speed

basic chemical reactions in sintering process

① combustion reaction of solid carbon

the combustion reaction of solid carbon is as follows:
after reaction, C0 and C02 are generated, and part of resial oxygen is proced, which provides oxidation-rection gas and heat for other reactions

the composition of the exhaust gas proced by combustion depends on the sintering raw material conditions, fuel consumption, the development of rection and oxidation reactions, and the composition of the gas pumped through the combustion layer

② decomposition and mineralization of carbonates

the carbonates in sinter are CaC03, mgc03, fec03, mnc03, etc., among which CaC03 is the main one. Under sintering conditions, CaC03 begins to decompose at about 720 ℃, and chemical boiling begins at 880 ℃. The decomposition temperature of other carbonates is lower

the decomposition proct Ca0 of calcium carbonate can react with other minerals in the sinter to form new compounds, which is mineralization. The reaction formula is:

CaCO3 + SiO2 = CaSiO3 + CO2

CaCO3 + Fe2O3 = Cao · Fe2O3 + CO2

if the mineralization is not complete, there will be resial free Ca0. During storage, it will digest with the water in the atmosphere:

CaO + H2O = Ca (OH) 2

make the volume of sinter expand and pulverize<

③ decomposition, rection and oxidation of iron and manganese oxides

under sintering conditions, Fe203 can decompose when the temperature is higher than 1300 ℃

Fe304 can decompose when the sintering temperature is lower than 1300 ℃

I don't know if it can meet your needs?

7.

Blast furnace raw materials (iron ore: natural lump ore, sinter, pellet, flux) are the material basis of blast furnace smelting, and concentrate is the basic guarantee for stable operation, high yield, high quality, low consumption and long life of blast furnace. At present, the burden structure of high basicity sinter + acid pellet + lump ore or high basicity sinter + acid pellet ore is basically used in large and medium blast furnace ironmaking

First, sintering proction process

blending ore → (belt) → ore tank → first mixing → second mixing → distributor → sintering combined car (ignition, ventilation, sintering) →

crushing → whole grain → blast furnace

concentrate powder, rich ore powder (less than 8mm), flux powder (less than 3mm limestone powder, dolomite powder, etc.) and fuel powder (coke powder or anthracite powder) are mixed, At the same time, a certain amount of water is added to make the mixture into small balls. Then, the mixture which is basically small balls is laid on the sintering machine through the distributor, and the thickness is 400-800mm. Under the negative pressure proced by the suction of the windbox, the heat is transferred downward, which makes the lower material layer graally warm up and burn. When the trolley moves to the end of the sintering machine, the sintering process ends. The red hot agglomerates slide onto the crusher and are sheared. The hot sinter discharged from the sintering machine needs to be crushed and sieved after passing through the cooler

Pelletizing is another method of briquetting iron concentrate or other iron bearing powder. It is a mixture of concentrate powder, flux (sometimes binder and fuel), rolled into green pellets with a diameter of 8 ~ 15mm (larger for steelmaking) in a pelletizing machine, then dried, roasted and consolidated into fine iron bearing raw materials with good metallurgical properties to meet the needs of steel and iron smelting

8. To put it simply: after the iron ore powder is mixed and sintered by adding flux, the finished procts pass through four stages of screening (the screening level is not necessarily) which are large finished proct, small finished proct, bedding material and reverse ore (that is, the one with the least strength). The percentage of reverse ore amount in the total amount of finished sinter is the reverse ore rate.