First, the process characteristics of the process are as follows:
(1) The same from the conventional process from the ingredients to the first mixing. From a mixed mixture, all or part of the ball into the pelleting workshop for pelletizing, the ball size is 3 ~ 8mm about 80% ~ 90%, less than 3mm particle size less than 15%. Due to the mixture caused by the ball The particle size composition of the mixture is improved, and the gas permeability of the material layer is improved, thereby increasing the yield and improving the quality of the sintered ore.
(2) good pelletizing plant made small pellet enters the secondary mixer, with the ball in front of the outer race into two pulverized coal mixture (typically with the outer 60% to 80% of the total amount of coal), i.e. The ball rolls the pulverized coal inside and outside the secondary mixer, and the small ball of the pulverized coal is fed into the sintering machine for cloth. Since the pulverized coal is wrapped on the surface of the pellet, it has sufficient contact with oxygen in the air, and the combustion effect is good, so the pulverization effect can be greatly reduced. Solid fuel consumption.
(3) The outside is equipped with quicklime, that is, before the small ball made in the pelleting workshop enters the second mixing, the raw coal is also blended with quicklime. The effect is: first, because the quicklime is sticky, it is beneficial to the coal powder. It is formed on the surface of small pellets; secondly, it can be further granulated in the second mixture; thirdly, the small pellets are rolled with lime, the surface of the pellet is high alkalinity, and the core is acidic (the alkalinity is not for the whole pellet) change), since the pellet surface with high CaO, the amount of calcium ferrite increases, i.e., between the ball and the ball is bonded iron, calcium, one can increase the strength of sintered ore pellets, on the other hand, the reduction Sexual improvement is also beneficial.
(4) Cloth device. There are three ways in which the pellets can be sintered onto the trolley, namely wide belt fabric, mud roller reflector fabric and multi-roll fabric.
(5) The size of the outer pulverized coal powder. The particle size of the pulverized coal powder in the pellet sintering process is the same as the particle size of the coal powder used in the ordinary sintering production, that is, the content of the particle size less than 3 mm accounts for more than 85%.
(6) The sintering section may be provided without a drying section before ignition.
(7) Pelletizing equipment can be used in a disc pelletizer or a cylinder pelletizer.
Second, the process flow process is as follows:
(1) All the mixture is pelletized. The mixture from the batching chamber to the primary mixer, after mixing to the disc pelletizer or cylinder mixer to make a ball of 3 to 8 ram, then the second mixed external fuel and quicklime, and then into the sintering machine for sintering, Produced a grape-like pellet sinter. The process has the characteristics of a pellet process and the advantages of a sintering process, so it is called a "spheron sintering process". The process flow is shown in Figure 1.
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(2) Partial mixture pelleting (a two-mixer scheme). From a mixed 1/2 mixture into the pelleting workshop, the ball of 3~8mm is about 90%, the mixing ball enters the secondary mixer, and the remaining 1/2 mixture is mixed from one. Direct access to the second mixer. The above two kinds of mixed materials are pulverized in the inside and outside of the second mixing machine (the pulverized coal powder having a particle size of less than 3 mm after being crushed by the existing pulverized coal crushing chamber accounts for more than 85%), and then sintered into the sintering machine, as shown in Fig. 2.
(3) Partial mixture pelleting (two two mixer schemes). Figure 3 shows a new Ф3m×12m secondary mixer under the condition that the mixing capacity of a two-mixer in a plant is insufficient, and it is juxtaposed with the original secondary mixer. The front part of the ball making room is the same as the previous one. The 3~8mm small ball coming out of the ball making room directly enters the new second mixing machine to roll the pulverized coal (not into the second mixing machine); and the remaining 1/2 from the mixed one The mixture directly enters the original secondary mixer to roll the coal powder (the coal powder is more than 85% when the particle size is less than 3mm after being crushed by the existing coal powder crushing chamber). Then, the mixture from the new two-mixer and the original two-mixer enters the sintering machine for sintering, as shown in FIG.
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Third, the impact of various factors on the sintering index We use the Yuxing concentrate powder (concentrate rate 100%, R = 2.0) for the pellet sintering process sintering cup test and semi-industrial test, the main factors affecting the sintering index Were studied.
(1) The influence of coal powder particle size. Under the condition that the coal blending amount is 0.5% and the external coal blending amount is 2.8% (other conditions are the same as those in No.15 and No.16 in Table 1), the particle size of the pulverized coal is changed to be less than 1 mm, 2 mm, and 3 mm, respectively. A series of experiments.
It can be seen from the test results that the three sizes of the outer rolled coal powder less than 1mm, less than 2mm and less than 3mm have little effect on the sintering index. Therefore, the industrialized production uses less than 3mm (85%) coal powder particle size, which can fully satisfy the production. Claim.
(2) The effect of coal blending. The internal coal blending volume of the test pellets was 0%, 0.5%, and 0.8%, respectively.
It can be seen from the test results that the yield, utilization coefficient and drum strength of the pellet sintered ore with the internal coal blending amount of 0 and 0.8 are lower than the corresponding indexes of the pellet sintered ore with 0.5% coal. Therefore, it can be seen that the inside of the small ball is suitable for 0.5% coal powder.
(3) The influence of the thickness of the layer. A total of three conditions were established for the thickness of the test layer, namely three thicknesses of 500 mm, 550 mm and 600 mm.
When the thickness of the layer is 500mm and 550mm, the effect is better, the utilization coefficient is above 1.5t/(m 2 •h), and other indexes are also good. When the thickness of the material layer is 600 mm, only the utilization factor is decreased, and other sintering indexes are also good.
Fourth, the granulation effect of the raw ball
(1) Particle size composition before pelleting. Taking a factory as an example, the content of the mixer mixture with a particle size of less than 3 mm accounts for more than 45%.
(2) Particle size composition after pelleting. After one mixing, the mixture enters the pelletizing plate for pelletizing. After the pelletizing disc is produced, the content of the mixture with the particle size greater than 3 mm reaches 89.09%.
(3) The particle size composition after the secondary mixer is rolled out of the fuel. The content of the mixture above the pelleting chamber is more than 87%, and the content of the mixture is more than 87%. After the mixture enters the second mixed external fuel, the content of the mixture larger than 3mm is slightly increased to 89.42%.
5. Cloth technology of pellet sintering process
There are three kinds of fabrics for the pellet sintering process. The first one is the mud roller reflector fabric, the second is the multi-roll fabric, and the third is the wide belt fabric.
(1) Mud roll reflector cloth. This kind of cloth is suitable for small sintering machine. The key is to adjust the length and inclination of the reflector. When the mixture falls on the reflector, the large ball has strong rolling force and falls on the lower part of the layer. The second ball is placed on the layer. In the middle, the fine powder is on the surface of the layer to form a natural segregation.
(2) Multi-roll fabric. The mixture falls from the mud roller and falls on the multi-roller, causing segregation. The large ball falls on the bottom of the layer, and the second ball is placed in the middle of the layer. The fine powder is on the surface of the layer to form a natural segregation.
(3) Wide belt fabric. This kind of cloth is suitable for large-scale sintering machine. There is a ore tank on the upper part of the igniter of the sintering machine. Because the output of the large-scale sintering machine is high, if the cloth of the mud roller reflector is used, the upper part of the igniter of the sintering machine must have a mining tank, and the mining tank is too small for the cloth. It does not have a buffering effect. When the ore tank is large, the mixing material in the ore tank is several tens of tons, and it is easy to destroy the finished ball, so a wide belt cloth is used. At present, some manufacturers use very well.
Sixth, the perfection of the ball-making equipment (I) Types of pelletizing discs There are three types of pelletizing discs currently used in China (including oxidized pelletizing plants and pelletizing discs used in cement plants), namely Ф=4200mm, Ф=5500mm and Ф =6000mm disc pelletizer, this is a domestic stereotyped product. From the current point of view, the Ф=4200mm disc pelletizer has a small equipment, a small ball-making ability, a large number of installations, and a large amount of maintenance. In contrast, the Ф=6000mm disc pelletizer has a large ball-making ability (the former) 3 times), the amount of maintenance is small, therefore, the Ф=4200mm pelletizing disk has a tendency to be replaced by the Ф=6000mm pelletizing disk.
(2) Scraper form According to the scraper form, the spheroidal disc can be divided into a fixed scraper rug and a rotary scraper rug.
1. Fixed scraper spheroidal disc (1) Spherical disc scraper installation position. The scraper is fixedly mounted on the horizontal truss above the pelletizing disc, and the scraper position is not more than 30° at the first quadrant of the pelletizing disc and the edge of the platter disc; the central scraper is installed at the junction of the third and fourth quadrants.
(2) Scraper material. The material of the scraper of the ball plate is a difficult problem. It is mainly made of a scraper made of general material. The wear resistance is poor. It will be worn a lot in a few days after continuous use, which will cause the plate material to rise, which not only speeds up the scraper. The wear and tear also increases the transmission load of the pelletizing disc. Through research and production practice, it is proved that the use of high chromium - molybdenum wear-resistant cast iron scraper is better. Carbon materials such as carbides mainly distributed in the matrix metal having good abrasion wear resistance. Practice has proved that the service life of high chromium) molybdenum wear-resistant cast iron is much higher than that of medium manganese steel plate, which is about 6-8 times higher. Although high chromium) molybdenum wear-resistant cast iron is relatively expensive to manufacture, it is actually cost-effective to compare from a cost-effective combination. And because the service life is extended, the number of times of scraping the blade is reduced, and the labor of the operator to clean the material of the disc is reduced, thereby improving the working rate of the pelletizing disc. [next]
(3) The material of the platter disk surface. The disc surface of the spheroidal disc is worn away as a result of the intense scouring of the mixture. In order to prevent the disc surface from being worn through, it is necessary to select a wear-resistant disc surface material. People have used a variety of materials, among which the rubber wear-resistant ceramic liner has high cost but good wear resistance, and the disadvantage is that it cannot withstand a slightly higher temperature, for example in When the repairing of the ball-making disc is close to the lining, the lining of the lining plate may be caused to fall off, and it is difficult to refill the slab at the time of refilling, and the surrounding lining may be peeled off.
In the future, ultra-polymer liners, tile liners, and limestone caststones were used. Through the use of a variety of lining materials, we believe that the limestone cast stone is better, because it is lower in cost and easy to install, and the second is good wear resistance and moderate friction, which is conducive to the rolling growth of the mixture. The general life expectancy is more than 3 months. However, it should be noted that the material is relatively brittle. When repairing the pelletizing disc or cleaning the disc area material, the metal object cannot be used to give a strong impact, so as not to damage the gray-green stone cast stone liner.
2. Rotary scraper spheroidal disc The mechanical transmission structure of this kind of spheroidal disc is introduced from foreign technology. The scraper is a disc rotary scraper (rotary cutter disc diameter Ф1100mm, rotation speed 6r/min), which can effectively scrape the entire disc surface. To prevent the surface from rising, to keep the surface flat, and to improve the efficiency of the pelletizing machine.
(1) The material of the platter disk surface. At present, the most suitable materials are available as follows: 1) Steel mesh backing. A 5mm thick steel mesh is spread on the disk surface of the entire pelletizing disk. The mesh size of the steel mesh is 40mm×60mm. Because of these meshes, the mixture is bonded and fixed on the entire steel mesh to form a mixture. The underlay caused by the material is rubbed against each other during the production of the pelletizing disc. It can be said that the disc surface of the pelletizing disc is not worn. The steel mesh as the lining of the pelletizing plate is not expensive and easy to install, and it is convenient to repair if damaged. 2) Gray-green rock cast stone lining. It has been mentioned in the front of the fixed-type plywood underlay that it is more suitable to use a gray-green cast stone underlay, and the underlay can also be used for the rotary scraper slab, which can reduce the wear on the scraper.
(2) Scraper material. Since the disk surface of the pelletizing disk uses the steel mesh as the backing, the mixture will easily stick and rise, which requires a scraper to scrape off and prevent the rise. The original scraper is made of ordinary material and has a diameter of only 28mm. The wear is very serious. As the scraper rod wears, the mixed material surface gradually rises. After several days of continuous operation, the surface of the material will rise to the surface of the rotating cutter. Not only is the work of cleaning the disk surface heavy, but also greatly reduces the operating rate of the pelletizing disk. For this reason, the scraper blade of the rotary scraper is made of YG6 and YG8 cemented carbide. This material is usually a machined cutting tool with high hardness and good wear resistance. The application practice in blast furnace coal injection proves that the service life of cemented carbide is much higher than other materials. For example, the bush made of 40Cr hardened steel in the pulverized coal conveying pipeline of blast furnace coal injection is used in less than 10 days. Wear through, and bushes made of YG8 carbide can be used for more than two years. The service life of the scraper rod made of YG6 or YG8 cemented carbide can reach more than two months. Try to extend the life of the blade bars while minimizing manufacturing costs, the use of copper welding rod blade thickness partial mix extent by wear, the buried layer mix at a lower portion of the blade bars 6mm, 5mm, 4mm Three sections of carbide sleeve of different thickness, the total length is 105mm. The scraper bar is welded to the rotating cutter head, and after the hard alloy portion is completely worn away, the disc area material is cleaned, and a new scraper rod is welded. The structure and size of the scraper bar are slightly omitted.
(3) The mechanism of mixing the atomizing water nozzle into the ball in the pelletizing disk is to add water to the surface of the mixing material, the surface of the mixture is fully and uniformly wetted by the water, and the capillary bonding force of the water is used to make the ball in the pelletizing plate. The mix of rolling motions is bonded together to create pellets of different size levels. In order to increase the pelleting rate of the pelletizing disc, two pelletizing water jets are installed in each pelletizing disc. Due to the different cutting points of the new and old pelletizing discs, the installation position is different. Usually one is placed in the area of ​​the blanking point, and one is placed in the area of ​​the ball.
The material of the atomizing water nozzle is made of 1CRl8Ni9Ti stainless steel, which has quite good anti-oxidation and corrosion resistance. The structure principle is a kind of spiral nozzle, which is mainly composed of a tangential nozzle shell, a plug and a through needle. The water is inserted from the tangential direction of the circular nozzle shell, after being pressurized and a swirling flow, and then entering the tapered section, the swirling speed is gradually increased, and then the misty water is sprayed through the nozzle, and the atomized scattering angle of the atomized water is 50 ° ~ 60 °. At present, the spray volume of the atomized water jet used in the 4200 pelletizing disk is 150 to 180 kg / h when the water pressure is about 0.2 MPa. The atomized water sprinkler is characterized by a through-needle that can often clear the spout and prevent clogging without stopping the water. After a year of production practice, it is still in normal use. [next]
(4) The external coal blending system is refueled twice, that is, the fuel is added to the batching chamber and mixed into a mixer to make the ball. The mixture of the ball is mixed into the fuel before the second mixer. The proportion of external fueling is (30% to 50%): (70% to 50%)
Blending can be used outside the nuclear scale or electronic weighing scales, using the factory outer nuclear scale blending weighed cesium 137 (Activity value 0.2775 × 1010 Bq) of radioactive sources, after a year of production and use It shows that nuclear scales are more durable if they are properly maintained. The metering and adding of the external coal blending is input into the computer through the nuclear scale installed on the mixing belt, and the weighing signal of the mixing amount of the mixture is input into the computer by the computer, and the computer is designated by the coal blending disc feeder according to the set proportion of coal blending. The corresponding speed is fed to the coal blending belt, and then the nuclear scale is installed on the coal blending belt to approve the coal blending amount and feedback to the computer for adjustment. In recent years, production practice shows that after using the external coal blending technology, the solid fuel consumption per ton of sinter is generally 10kg/t compared with the coal without coal.
(5) The temperature of the steam preheating mixture sinter mixture has a great influence on the sintering production. If the temperature of the mixture is lower than the dew point, the condensation of water vapor on the surface of the lower layer mixture makes The moisture in the lower layer is excessively increased, which affects the gas permeability of the sintered layer, which is not conducive to the thickening of the sintered layer, thereby affecting the improvement of the sintering yield. To this end, a steam nozzle is installed in the secondary mixer to heat the mixture. For the pelletized mixture, although the hot returning of the mixture increases the temperature of the material, because of the open operation of the pelletizing disk, The temperature drops, so steam is added to further increase the temperature of the mixture. The steam pipe is inserted from the inlet end of the mixer, and five steam nozzles are installed side by side along the axial direction of the mixer. The front end of the nozzle is 600-800 mm away from the mixing material in the mixer. The preheating of the steam can make the ball The temperature of the mixture is increased from 45 ° C to nearly 60 ° C.
The steam preheating mixture has a steam pressure of about 0.3 kPa and a steam amount of 4 to 5 kg per ton of sinter.
7. Externally equipped with quicklime technology (1) Advantages of external lime preparation On the basis of the pellet sintering process, that is, the mixture from the first mixer enters the pelletizing workshop to make the ball, and then mixes the coal before the second mixing, and the lime is externally dispensed. The advantages are as follows: First, the outer lime is beneficial to improve the granulation effect and increase the yield; secondly, the surface of the small ball is covered with a layer of quicklime, which is beneficial to the pulverized coal being more wrapped on the surface of the small pellet; third, small The high content of CaO on the surface of the pellet is conducive to the formation of calcium ferrite, that is, the surface of the pellet is high alkalinity, the content of calcium ferrite is high (the internal low alkalinity, the total alkalinity of the mixture is unchanged), the small ball and the small ball. It is bound by calcium ferrite. Because of the high strength of calcium ferrite and good reducibility, it is beneficial to the strength increase and reduction of pellet sinter, which is beneficial to blast furnace smelting.
(II) The best conditions for the distribution of quicklime by the sintering cup of the Baogang Company's sintering mixture (R=1.2) after the ball is made, it can be seen that the effect of the external lime is obvious, the most The best conditions are as follows:
(1) After the mixture is pelletized, the amount of fixed external lime is 1.5%. After the pelletizing of the Baogang Sintering Mixture, the proportion of the lime is 3%, the external content is 1.5% (50% inside and outside), and the proportion of the external coal powder is changed (the coal powder ratio is 5%).
When the proportion of fixed quicklime is 1.5%, the external coal blending powder 2.5% (accounting for 50% of the total) has better sintering index. However, the sintering index of only the external lime-mixed coal and coal powder and quicklime are similar.
(2) After the mixture is pelletized, the proportion of the externally distributed coal powder is fixed, and the proportion of the raw lime is changed. After the pelletizing of Baotou Steel Sintering Mixture, the proportion of fixed external coal blending is 2.5% (5% of total coal blending), and the proportion of changing quicklime is 1%, 1.5%, 2% (total ratio of quicklime is 3%).
When the external coal powder is fixed at 2.5%, the external lime powder is 1.0%, 1.5% and 2.0%. The latter two indexes are better, but the external lime powder is 1.5% compared with the external lime powder 2.0%. The two are generally similar.
From the above two experimental results, it can be seen that the pellet sintering process is better under the external coal blending conditions, and the improvement of the sintering index by the external lime. The proportion of the externally prepared quicklime can be about 50% of the total ratio.
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