CN113604662A

CN113604662A - Pellet roasting system and method based on sintering machine

Info

Publication number: CN113604662A
Application number: CN202110910662.2A
Authority: CN
Inventors: 李康; 谢朝明; 代友训; 王春林
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2021-08-09
Filing date: 2021-08-09
Publication date: 2021-11-05
Anticipated expiration: 2041-08-09
Also published as: CN113604662B

Abstract

A sintering machine based pellet firing system, the system comprising: the system comprises a sintering machine, a circular cooler, a circulating air flow unit and a flue gas treatment unit. The discharge hole of the sintering machine is connected with the feed inlet of the circular cooler. The circulating air flow unit is arranged among the sintering machine, the circular cooler and the flue gas treatment unit. A smoke hood is arranged above the sintering machine, and an air box is arranged below the smoke hood. According to the trend of materials, a smoke hood positioned above the sintering machine is sequentially divided into a preheating section, a combustion section and a roasting section. The invention adopts the sintering machine to roast the pellets, improves the air flow system, improves the utilization rate of the flue gas circulation heat, reduces the energy consumption, improves the roasting effect, realizes good cooling effect, reduces the generation of nitrogen oxides through step heat supplement, reduces the cost of desulfurization and denitrification, and protects the environment.

Description

Pellet roasting system and method based on sintering machine

Technical Field

The invention relates to a pellet roasting device and method, in particular to a pellet roasting system and method based on a sintering machine, and belongs to the field of pellet roasting.

Background

The pellet is a method for artificial block raw materials, so that the physical properties and chemical compositions of powdery materials can meet the processing requirements of the next step. The pellet production process is a production process for refining pellet ore, and the pellet is a common process for refining iron ore in the iron and steel smelting industry. The pellet ore is prepared by adding a small amount of additive into fine ground iron concentrate powder or other iron-containing powder, mixing, rolling into pellet by a pelletizer under the condition of adding water for wetting, and roasting and solidifying to obtain the spherical iron-containing raw material with certain strength and metallurgical property. The main processes for pellet production can be classified into a shaft furnace method, a grate-rotary kiln-circular cooler method and a belt type roasting machine method according to the pellet roasting method.

The existing belt type roasting machine method is shown in fig. 2, common magnetite iron ore concentrate containing more moisture is dried firstly, is subjected to roller milling after being dried, is mixed with a binder, is subjected to pelletizing after being added with water, is subjected to green ball screening after pelletizing, is screened out green balls meeting conditions, enters a belt type roasting machine through a material distribution device, and is crushed to obtain green balls not meeting the conditions and then participates in pelletizing again. According to the sequence of heat exchange between the flue gas and the pellets, the belt type roasting machine is divided into a drying section, a preheating section, a roasting section, a soaking section, a cooling section and a cooling section, green pellets entering the belt type roasting machine sequentially pass through the drying section, the preheating section, the roasting section, the soaking section, the cooling section and the cooling section to form qualified finished pellets, then the qualified finished pellets enter a finished product buffer hopper, and then are transported to a blast furnace for iron making through a finished product belt conveyor below the finished product buffer hopper. The air flow system participating in pellet roasting comprises: the same cooling fan blows outdoor air into the first cooling section and the second cooling section of the belt type roasting machine through the air box, high-temperature pellets on the first cooling section and the second cooling section of the belt type roasting machine are cooled, hot air generated by the high-temperature pellets cooled in the second cooling section is blown into the drying section of the belt type roasting machine through the drying fan, green pellets with high water content are subjected to blast drying after passing through the drying section air box, and the hot air passes through the material layer to dry the green pellets and then is discharged to the outside through the drying exhaust fan; the hot air generated after cooling the high-temperature pellets in the first cooling section enters the roasting section and the soaking section of the belt type roasting machine through the hot air hood, the pellets on the roasting section and the soaking section of the belt type roasting machine are heated and roasted, the heated lower-temperature waste gas enters the drying section of the belt type roasting machine through the regenerative fan after passing through the air box, and green pellets in the drying section are further dried; mixing and igniting coke oven gas and air at the preheating section of the belt type roasting machine to generate high-temperature gas for heating and roasting the pellets on the dried preheating section; and the exhaust gas after the ball is heated by the drying section and the preheating section enters an electric dust remover through an air box for dust removal, and is subjected to desulfurization and denitrification treatment after passing through a main exhaust fan, and the exhaust gas after the desulfurization and denitrification treatment is discharged out through a chimney.

The existing chain grate-rotary kiln-circular cooler mainly comprises three parts, namely a chain grate, a rotary kiln and a circular cooler. The chain grate machine is composed of main parts of a closed cast iron chain, a grate plate, side baffles, a driving wheel and the like, wherein the cast iron chain connects the chain grate machine into a whole and drives the chain grate machine to perform directional motion, the chain of the chain grate machine is used as a transmission device, the grate plate bears a ball layer and enables airflow to pass through, the side baffles ensure the height of the ball layer and the sealing of the side surfaces, and the driving wheel is a driving device of the chain grate machine. Because the chain grate is wide and the main transmission shaft is long, and the chain grate works in a high-temperature environment and is easy to deform after being heated and expanded, the chain grate is driven by a double-side chain wheel without gear transmission, and the main shaft is cooled by hollow air, so that the normal operation of the shaft is ensured; according to the sequence of heat exchange between the flue gas and the pellets, the chain grate is divided into a drying first section, a drying second section, a transition preheating section and a preheating section. The rotary kiln consists of kiln body, supporting wheel, rolling ring, transmission unit and other parts, and the kiln body is pellet roasting reactor and the carrier roller is the support unit for the rotary kiln to support the whole kiln body and the pellet weight inside the kiln. The ring cooling machine is composed of a frame, a cooling trolley, a transmission device, a guide rail, a fan and the like, wherein air boxes of the blast ring cooling machine are formed by welding and are connected with the frame under the trolley, the air boxes are divided into a plurality of groups according to the number of the air boxes, the air boxes are not communicated with each other and are separated by using partition plates, the number of the air box groups is the number of the fans, the fans send cold air to the air boxes through air pipes, and the cold air is discharged from the top after heat exchange with hot ores, so that hot air circulation is performed.

In the prior art, the trolley of the belt type roasting machine has high temperature resistance and high manufacturing cost, and meanwhile, the cooling section of the conventional belt type roasting machine is shorter and has poorer cooling effect. The existing chain grate machine, rotary kiln and circular cooler have larger occupied area and poorer sintering effect.

Disclosure of Invention

Aiming at the problems of high cost, poor cooling effect, large occupied area and the like in the prior art, the invention provides a pellet roasting system and method based on a sintering machine. The invention adopts the sintering machine with lower temperature resistance to roast the pellets, reduces the cost of pellet roasting equipment, improves the production efficiency by setting the backing material with certain humidity and thickness to insulate heat,

according to a first embodiment of the present invention, a sintering machine based pellet firing system is provided.

A sintering machine based pellet firing system, the system comprising: the system comprises a sintering machine, a circular cooler, a circulating air flow unit and a flue gas treatment unit. The discharge hole of the sintering machine is connected with the feed inlet of the circular cooler. The circulating air flow unit is arranged among the sintering machine, the circular cooler and the flue gas treatment unit. A smoke hood is arranged above the sintering machine, and an air box is arranged below the smoke hood. According to the trend of materials, a smoke hood positioned above the sintering machine is sequentially divided into a preheating section, a combustion section and a roasting section. The ring cooling machine is sequentially divided into a ring cooling first section, a ring cooling second section and a ring cooling third section. The wind boxes at the bottom of the roasting section, the combustion section and the preheating section are not communicated with each other. The ring cooling first section, the ring cooling second section and the ring cooling third section are provided with a clapboard among each other.

Preferably, the circulating air flow unit includes a cooling fan and a circulating line. The circulating pipeline specifically comprises: the cooling fan is communicated with the air inlet of the annular cooling section through an air inlet pipeline. And the air outlet of the annular cooling three-section is communicated with the air inlet of the preheating section through a first gas pipeline. And an air outlet of the preheating section is communicated with an air inlet of the annular cooling section through a second gas pipeline. And an air outlet of the annular cooling section is communicated with an air inlet of the combustion section through a third gas pipeline. And an air outlet of the combustion section is communicated with an air inlet of the annular cooling section through a fourth gas pipeline. And an air outlet of the annular cooling section is communicated with an air inlet of the roasting section through a fifth gas pipeline. And an air outlet of the roasting section is communicated with an air inlet of the flue gas treatment unit through a sixth gas pipeline.

Preferably, a heat supplementing device is arranged on the fifth gas pipeline. The heat supplementing device comprises a burner and a gas conveying pipeline. The burner is arranged in the fifth gas pipeline. And the air inlet of the burner is communicated with the air outlet of the fuel gas conveying pipeline.

Preferably, the heat supplementing device comprises a plurality of burners. The burners are all arranged in the fifth gas pipeline, and the burners are respectively and independently connected with a gas conveying pipeline. In the fifth gas pipeline, along the trend of the gas flow, the number of the burners is distributed in an increasing mode.

Preferably, the flue gas treatment unit comprises an electric dust collector, a main exhaust fan, a desulfurization and denitrification device and a chimney. The electric dust remover, the main exhaust fan, the desulfurization and denitrification device and the chimney are sequentially connected in series, wherein an air inlet of the electric dust remover is communicated with an air outlet of the sixth gas pipeline.

Preferably, the system further comprises a feed unit. The feeding unit comprises a pelletizing device, a microwave drying device and a distributing device. The pelletizing device, the microwave drying device and the material distributing device are sequentially connected in series, wherein the material distributing device is connected with the feed end of the steel belt machine.

Preferably, the pelletizing device comprises a proportioning machine, a mixer, a pelletizing machine, a green pellet screening machine and a crusher. The batching machine, the mixing machine, the pelletizer and the green ball screening machine are sequentially connected in series. And a qualified discharge port of the green ball screening machine is connected with a feed port of the microwave drying device. The unqualified discharge port of the green ball screening machine is connected with the feed port of the crusher, and the discharge port of the crusher is connected with the feed port of the pelletizer.

Preferably, the system also comprises a pulverized coal heat supplementing system. The pulverized coal heat supplementing system comprises a coal crushing device, a pulverized coal conveying pipeline, a coal injection device and an ignition device. The coal injection device is arranged at the top of the combustion section of the sintering machine and is communicated with the interior of the combustion section. The ignition device is arranged in the combustion section of the sintering machine. The coal injection device is communicated with the coal crushing device through a coal powder conveying pipeline.

Preferably, the system further comprises a pellet screening device. And the pellet screening device is arranged at the discharge port of the circular cooler. The pellet screening device is connected to the upper part of the distributing device through the oversize material conveying device. The screening device is also communicated with a feed inlet of the blast furnace through a screen material conveying device.

Preferably, the system further comprises a sprinkler. The sprinkling device is communicated with the oversize material conveying device through a sprinkling pipeline.

Preferably, a buffer hopper is further arranged between the pellet screening device and the sintering machine.

As a second embodiment of the present invention, a method for pellet firing using a sintering machine-based pellet firing system is provided.

A method for pellet firing using a sintering machine based pellet firing system, the method comprising the steps of:

1) and mixing the iron-containing ores and auxiliary materials to obtain a mixture. And then adding water into the mixture for pelletizing to obtain green pellets.

2) And putting the green pellets into a pellet roasting system based on a sintering machine, roasting the green pellets sequentially through a preheating section, a combustion section and a roasting section according to the trend of logistics, and then cooling the green pellets sequentially through a ring cooling section, a ring cooling section and a ring cooling section to obtain finished pellets.

3) In a pellet roasting system based on a sintering machine, according to the trend of air flow, ambient air sequentially flows through a ring cooling three section, a preheating section, a ring cooling two section, a combustion section, a ring cooling one section and a roasting section to complete heat exchange with green pellets. And finally, the waste gas is treated by a flue gas treatment unit and then discharged.

Preferably, the method further comprises:

and 4) screening the finished pellets, wherein the finished pellets with larger particle size are returned to the material distribution device for bedding material, and the finished pellets with smaller particle size are sent to a blast furnace for treatment.

Preferably, the step 1) is specifically: mixing hematite, anthracite powder, calcium oxide and sodium calcium bentonite according to a proportion to obtain a mixture. And then adding a certain amount of water into the mixture for pelletizing to obtain green pellets. And then screening the green pellets to obtain qualified green pellets. And finally, performing primary drying treatment on the qualified green pellets by adopting microwave to obtain green pellet preparation materials. And the unqualified green pellets are crushed and then participate in pelletizing.

Preferably, the iron content of the hematite is 30 to 55 percent, and preferably 45 to 50 percent. The water content of hematite is 5-10%, preferably 7-9%. The hematite has a particle size of greater than 60% at-0.044 mm content, preferably greater than 70% at-0.044 mm content. The specific surface area of the hematite is 1000-2500 cm²Preferably 1500 to 1900 cm/g²/g。

Preferably, the pulverized anthracite has a particle size of-0.074 mm greater than 90%, preferably-0.074 mm greater than 95%.

Preferably, the calcium oxide is greater than 90% pure, preferably greater than 95% pure.

Preferably, the sodium calcium bentonite is obtained by adding sodium hydroxide solution into calcium bentonite with the particle size of less than 0.074mm for sodium treatment. The water content of the sodium calcium base bentonite is 4 to 9 percent, and the preferred water content is 6 to 8 percent.

Preferably, the mass ratio of the added amounts of the hematite, the anthracite powder, the calcium oxide and the sodium calcium carbonate based swelling is 88-96:2-5:1-3: 1-4. Preferably 90-95:3-4:1-2: 2-3.

Preferably, step 2) is specifically: firstly, paving a bottom material on a sintering trolley, and then paving raw pellet preparation materials on the bottom material. And then the sintering trolley filled with the materials is sequentially processed through a preheating section, a combustion section and a roasting section to obtain roasted pellets. And finally, treating the roasted pellets sequentially through a ring cooling first section, a ring cooling second section and a ring cooling third section to obtain finished pellets.

The thickness of the bedding material is preferably 300mm to 450mm, preferably 350mm to 400 mm. The thickness of the green pellet preparation material is 300mm-400mm, preferably 350mm-380 mm.

Preferably, in the combustion section, coal powder is sprayed in by a coal spraying device, and then the ignition device is used for igniting the coal powder, so that the pellets in the combustion section are heated.

Preferably, the length of the firing section > the length of the combustion section > the length of the preheating section.

Preferably, step 3) is specifically: and the cooling fan introduces environmental wind into the annular cooling three sections to perform heat exchange and cooling treatment on the low-temperature roasted pellets to obtain low-temperature hot wind, and the low-temperature hot wind is continuously conveyed into the preheating section to perform preheating treatment on the green pellets. And continuously conveying the low-temperature hot air after the preheating treatment to the annular cooling second section to perform heat exchange and cooling on the medium-temperature roasted pellets to obtain medium-temperature hot air, and continuously conveying the medium-temperature hot air to the combustion section to perform heating treatment on the green pellets. And the medium-temperature hot air after the heating treatment is continuously conveyed to the annular cooling section to carry out heat exchange and cooling on the high-temperature roasted pellets to obtain high-temperature hot air, and the high-temperature hot air is continuously conveyed to the roasting section to carry out roasting treatment on the green pellets. And after the high-temperature hot air after roasting treatment is sequentially treated by an electric dust collector, a main exhaust fan and a desulfurization and denitrification device, the high-temperature hot air is finally discharged through a chimney.

Preferably, the high-temperature hot air is further heated by the burner to raise the temperature of the high-temperature hot air while the high-temperature hot air is continuously fed to the baking stage. Preferably, the number of the burners is multiple, and the number of the burners is distributed in an increasing mode according to the flow direction of the high-temperature hot air.

Preferably, step 4) is specifically: conveying the finished pellet materials cooled by the circular cooler into a pellet screening device for screening. Wherein, the finished pellets with the grain diameter of more than 14mm (preferably 14mm-16 mm) are returned to the distributing device for bedding. And conveying finished pellets with the particle size of less than or equal to 14mm (preferably 5-14mm) to a blast furnace for iron making.

Preferably, the large-particle finished pellets used as the bedding material are required to be subjected to wetting treatment before the bedding material is paved, and specifically, the large-particle finished pellets are subjected to water spraying treatment by adopting a water spraying device, so that the water content of the large-particle finished pellets is 3% -6%, and is preferably 3.5% -5%.

In the prior art, a belt type roasting machine or a chain grate machine, a rotary kiln and a circular cooler are mainly adopted for roasting pellets. Among them, the straight grate method has the following problems and disadvantages. Firstly, because the temperature required for roasting the pellets from green pellets to finished pellets is very high, and the roasting process of the pellets is completed on the travelling grate, the temperature resistance of the trolley of the travelling grate is required to be high, so that high temperature resistant materials are required to manufacture the trolley, the material cost is high, and the manufacturing cost of the trolley of the travelling grate is also very high. Secondly, among the current air current system, the emission point is many, and direct outer exhaust waste gas is more, need set up a plurality of exhaust-gas treatment points, causes great pollution to the environment when handling the trouble. Thirdly, in the existing belt roasting method, the external heat supplement is performed by using coke oven gas, but the coke oven gas has high price, low heat value and unstable gas source, which easily causes insufficient production supply and low heat efficiency, and leads to insufficient pellet strength and low finished product rate. Fourthly, the existing air flow system has the disadvantages of large equipment quantity, high investment and large occupied area. Fifthly, the existing air flow system has many wearing parts and large maintenance workload. Sixthly, when the pellets are roasted by adopting the existing belt roasting machine, more nitrogen oxides are generated, the environmental pollution is greater, the desulfurization and denitrification cost is high, and the effect is general. Seventh, the conventional belt roasting method can treat high-grade magnetite, but has a poor effect on low-grade hematite.

In the prior art, the grate-rotary kiln-circular cooler roasting method has the following problems. The first, including chain grate machine, rotary kiln and cold machine of ring three parts, area is great, invests in great. Secondly, the number of wind flow system devices is large, and the investment is high. Thirdly, the air flow system has a plurality of wearing parts and large maintenance workload.

In the present invention, pellets are fired by a sintering machine. A bed charge of suitable humidity and thickness is laid on the sintering pallet, and then green pellets are laid on the bed charge in a free-stacking manner. Wherein, the bed charge adopts the large granule finished product pellet (intensity is high) behind the control moisture for the green pellet that bears on the platform truck is more, increases output, improves production efficiency. And igniting after the material distribution is finished, starting the sintering process, operating an air flow system, forming a certain negative pressure below the trolley, pumping air into an air box below the trolley from top to bottom through a sintering material layer, after the fuel on the surface of the material layer is ignited and combusted, gradually transferring the combustion layer from the upper part to a lower material layer, eliminating a combustion zone of the material layer to the bottom, and finishing the sintering process to obtain the finished pellets. And (3) conveying the finished pellets into the annular cooler through a finished product buffer hopper, and fully cooling the finished pellets in the annular cooler through three stages of a high-temperature section, a medium-temperature section and a low-temperature section to obtain qualified pellets.

In the invention, in order to ensure the strength and the yield of the pellets in the sintering process, the sintering temperature of the pellets on the upper layer is higher and the duration is longer, and in order to protect the sintering machine with poor temperature resistance, the moisture content in the bottom material is controlled to be 3-5 percent, the thickness of the bottom material is controlled to be 300-450 mm, and most heat generated by sintering is isolated. In the invention, finished pellets are screened, the pellets with the particle size of 14-16mm are screened and sent to distribution, the particle size difference of the pellets is not large, and the pellet roasting time and the roasting temperature are favorably controlled. The large-particle finished pellets (generally 14-16mm finished pellets) are used as the bottom material, the finished pellets used as the bottom material can improve the air permeability of a material layer after being screened and sprayed with water, and the high-temperature flue gas can penetrate through the material layer to reach a grate plate of a sintering machine trolley, so that the temperature is reduced, the sintering machine trolley is protected, high-temperature damage is avoided, meanwhile, the finished pellets are high in strength and not easy to break, and the ventilation performance of the steel belt machine cannot be influenced when the finished pellets are used as the bottom material.

In the invention, an air flow system is arranged between the sintering machine and the circular cooler, and a cooling fan blows ambient air into the low-temperature section of the circular cooler to cool pellets in the low-temperature section of the circular cooler, and then the pellets enter the preheating section of the sintering machine to preheat green pellets on the preheating section. The preheated flue gas goes to the middle temperature section of the circular cooler to cool the pellets on the middle temperature section and then enters the combustion section of the sintering machine, the high temperature section of the circular cooler cools the pellets on the high temperature section after heat exchange is completed, then the flue gas goes to the roasting section of the combustor, heat and oxygen are provided by the roasting section, and finally the flue gas is led to a flue gas treatment system after heat exchange is completed. The gas among the preheating section, the combustion section and the roasting section of the sintering machine and among the high-temperature section, the medium-temperature section and the low-temperature section of the circular cooler are not communicated, namely, the gas can only be sequentially communicated in series through an air flow system. The air flow system adopted by the invention improves the heat utilization rate and reduces the energy consumption, and meanwhile, the whole air flow system is only provided with one cooling fan and one gas outlet, thereby reducing the emission points and facilitating the tail gas treatment.

It should be noted that the circulating air flow system based on the sintering machine-circular cooler of the invention is different from the air flow system of the traditional grate-kiln-circular cooler process, the air flow system of the traditional belt type roasting process and the traditional sintering machine process. The flue gas circulation heat utilization rate of the sintering machine-circular cooler process is improved, the energy consumption is greatly reduced, the roasting effect is improved, meanwhile, the good cooling effect can be realized, the generation of nitrogen oxides is reduced through step heat supplement, the desulfurization and denitrification cost is reduced, and the environment is protected. The circulating air flow system adopts a fan to blow cold air into the system, and then adopts a main exhaust fan to pump the waste gas out of the system, only one air inlet and one air outlet are provided, so that the air system is optimized, the flue gas is used as a medium to better transfer heat energy in the system, better effects of energy saving and emission reduction are achieved, the heat energy is recycled well in the system, the generation of harmful gases such as nitrogen oxides is reduced, the environment is protected, and the cost is greatly saved.

In the present invention, a modifier, a binder and an internal fuel are added to raw materials. Wherein, the binder selects calcium bentonite with the grain diameter less than 0.074mm, sodium hydroxide solution is added into the calcium bentonite, the water content is controlled to be 6-8 percent, and the viscosity of the calcium bentonite is improvedAnd (4) knotting property. The regulator is alkaline, is selected from one of calcium oxide, calcium hydroxide and calcium carbonate, and can be used for roasting pellets and Fe in hematite₂O₃The particles form a calcium ferrite binding phase with good reducibility, so that the pellets can be subjected to solid-phase reaction, consolidation and hardening at a lower temperature, the roasting temperature is reduced, the alkalinity of the pellets is increased, the performance of the pellets is improved, and the later blast furnace ironmaking is facilitated. The internal fuel is anthracite powder, so that certain heat is generated during pellet roasting to supplement heat, the use of fuel gas is reduced, the cost is saved, and meanwhile, the internal coal can improve the consolidation strength inside the pellet and improve the performance of the pellet.

In the invention, the combustion section of the sintering machine is provided with a pulverized coal heat supplementing system. The fuel coal is crushed into coal powder, and then the coal powder is sprayed into a combustion section of a sintering machine through a coal spraying device, and is ignited through an ignition device to generate high-temperature gas for heating pellets in the combustion section of the sintering machine. The coal is selected as the fuel, so that the cost is saved, the combustion is stable, the heat source is stable, the heat efficiency is high, the pellet roasting effect is better, the production continuity is ensured, the pellet quality is improved, and the pellet yield is also improved.

In the invention, after the sintering pallet passes through the combustion section, because the temperature of the roasting section is easy to drop because the internal fuel in the pellets is basically completely combusted, a step heat supplementing system is arranged on the fifth gas pipeline (the pipeline from the high-temperature section of the circular cooler to the roasting section of the sintering machine). Set up the multiunit nozzle on fifth gas pipeline, by changing more and less along the air current direction of motion, present the step and arrange, the nozzle blowout gas is lighted, carries out the concurrent heating to the flue gas, when maintaining calcination section temperature, still avoids causing the production of nitrogen oxide because of the buggy burning is insufficient.

In the invention, the cooled pellets are screened, part of the pellets with the particle size of 14-16mm are selected as bottom materials and returned to the material distribution (step 4)), the pellets with the particle size of less than 14mm are sent to a blast furnace for iron making, and the pellets with the particle size of more than 16mm are crushed and returned to the pelletizing (step 2)). And the large-particle-size pellets are screened out, so that the problem that the finished product rate is reduced due to incomplete roasting inside the pellets is solved. After being wetted, finished pellets of 14-16mm are paved on a sintering machine as a base material, which is favorable for improving the air permeability of a material layer.

In the invention, the green pellets are pre-dried before distribution, so that the interior of the green pellets is more stable, and the risk of pellet fracture in a preheating section is reduced. The microwave drying device is adopted in the predrying, so that the moisture of the green ball can be accurately controlled, the internal structure of the green ball can be more stable and more solid, and the risk of green ball fracture in the preheating section is reduced.

Compared with the traditional sintering machine for producing sintered ores, the sintering machine for producing sintered ores has the advantages that the hematite is used as a raw material, the hematite is pelletized, an air flow system is improved, a coal powder heat supplementing system and a step heat supplementing device are added, the moisture content of the bottom materials is controlled, the roasting effect is better, and the generated pollution is less.

Compared with the straight-belt roasting method, the method has the advantages that the bedding material with proper humidity and proper thickness is arranged for heat insulation, the sintering machine with lower temperature resistance is used for completing the roasting process of the pellets, the sintering machine is reasonably used for producing the pellets, more green pellets are loaded on the trolley, the productivity is increased, and the production efficiency is improved. Because the trolley of the belt type roasting machine has high temperature resistance and high manufacturing cost, the invention reduces the cost of pellet roasting equipment, saves investment and achieves the purposes of quality improvement and yield increase. In addition, the cooling section of the existing belt type roasting machine is very short, and the cooling effect is poor. Meanwhile, the large flue of the sintering machine is utilized, so that the roasting section can keep certain combustion, the roasting effect is increased, the flow velocity of the flue gas is increased, the air flow is balanced through the air guide pipe on the large flue, the grate plate of the trolley is better protected, and the trolley is prevented from being damaged by high temperature.

Compared with the grate-rotary kiln-circular cooler roasting method, the invention directly reduces the number of rotary kilns, shortens the flow, reduces the investment and reduces the occupied area under the condition of ensuring the yield. The invention adopts the sintering machine for roasting, has better effect than a chain grate machine, and obviously improves the yield by strong air draft of a large flue under the sintering machine. In addition, the sintering machine is additionally provided with a water spraying device, a pulverized coal heat supplementing device, a smoke cover on the sintering machine and the like, so that the structure of the sintering machine is further optimized, and the roasting efficiency is improved. The invention also adds step heat compensation, optimizes the flue gas utilization of the circular cooler, reduces the generation of nitrogen oxides and improves the heat utilization rate.

In the invention, the pellet production is carried out by adopting a sintering machine-circular cooler process, so that lower iron-containing ores (such as hematite) can be used as raw materials for the pellet production, and taking the hematite as an example, because the iron content of the hematite is not high than that of magnetite, and more gangue exists in the hematite, in the traditional process, because more gangue exists in the hematite, the melting point of the gangue is lower, and the liquid phase is further increased after the flux is added, so that the trolley blockage is easily caused in the roasting process, the air permeability is influenced, and the roasting process is unsmooth, so that the effect of conventionally treating the low-grade hematite by adding the flux and other methods is poor. Meanwhile, the invention can also realize the zero emission of the circular cooler, namely all the flue gas is circulated, and meanwhile, the cascade heat supply device is additionally arranged, so that the energy is saved and the generation of nitrogen oxides is reduced; and finally, the flue gas is collected through a large flue below the sintering machine, so that the air draft effect is ensured, a plurality of air guide pipes of the traditional large flue are eliminated, and only the air guide pipe at the tail part of the sintering machine is reserved, so that the produced bulk materials and dust are reduced.

In the present invention, the total length of the sintering machine is 50 to 160 meters, preferably 60 to 150 meters, further preferably 70 to 140 meters, and further preferably 80 to 120 meters.

In the present invention, the length ratio of the preheating section, the combustion section and the roasting section on the sintering machine is 1:1 to 5, preferably 1:1.2 to 3:1.5 to 4, and more preferably 1:1.5 to 2:2 to 3.

In the invention, the length ratio of the first ring cooling section, the second ring cooling section and the third ring cooling section on the ring cooling machine is 1:0.8-3:1-5, preferably 1:1-2:1.5-4, and more preferably 1:1.2-1.8: 2-3.

Compared with the prior art, the invention has the following beneficial effects:

1. compared with the belt roasting method, the method has the advantages that the bedding material with proper humidity and proper thickness is arranged for heat insulation, the sintering machine with lower temperature resistance is used for completing the pellet roasting process, the pellet roasting equipment cost is reduced, the investment is reduced, the productivity is increased, and the production efficiency is improved.

2. Compared with a grate-rotary kiln-circular cooler roasting method, the invention shortens the flow, reduces the investment and the occupied area under the condition of ensuring the yield, further optimizes the structure of the sintering machine and improves the roasting efficiency.

3. The invention improves the air flow system, improves the utilization rate of the flue gas circulating heat, reduces the energy consumption, can realize good cooling effect while improving the roasting effect, reduces the generation of nitrogen oxides by step heat supplement, reduces the desulfurization and denitrification cost and protects the environment.

Drawings

Fig. 1 is a schematic structural diagram of a pellet roasting system based on a sintering machine according to the present invention.

Fig. 2 is a schematic view of a conventional straight grate type roasting machine.

Fig. 3 is a schematic structural diagram of a pellet firing system based on a sintering machine according to embodiment 2 of the present invention.

Fig. 4 is a schematic structural diagram of a pellet firing system based on a sintering machine according to example 5 of the present invention.

Fig. 5 is a process flow diagram of a grate-rotary kiln-circular cooler roasting method in the prior art.

FIG. 6 is a process flow diagram of a conventional straight grate process.

Reference numerals: 1: sintering machine; 101: a smoke hood; 102: an air box; 103: a preheating section; 104: a combustion section; 105: a roasting section; 2: a circular cooler; 201: cooling in a ring for one section; 202: a ring cooling section; 203: ring cooling for three sections; 204: a partition plate; 3: a circulating air flow unit; 301: a cooling fan; 4: a flue gas treatment unit; 401: an electric dust collector; 402: a main exhaust fan; 403: a desulfurization and denitrification device; 404: a chimney; 5: a heat-supplementing device; 501: burning a nozzle; 6: a feed unit; 601: a pelletizing device; 6011: a dosing machine; 6012: a mixer; 6013: pelletizing; 6014: a green ball screening machine; 6015: a crusher; 602: a microwave drying device; 603: a material distribution device; 7: a pulverized coal heat supplementing system; 701: a coal crushing device; 702: a coal injection device; 703: an ignition device; 8: a pellet screening device; 801: an oversize material conveyor; 802: an undersize material conveying device; 9: a watering device; 10: a finished product buffer hopper; g: an air inlet pipeline; l1: a first gas conduit; l2: a second gas conduit; l3: a third gas conduit; l4: a fourth gas conduit; l5: a fifth gas conduit; l6: a sixth gas conduit; l7: a gas delivery pipeline; l8: a pulverized coal conveying pipeline; l9: and a water sprinkling pipeline.

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.

A sintering machine based pellet firing system, the system comprising: the device comprises a sintering machine 1, a circular cooler 2, a circulating air flow unit 3 and a flue gas treatment unit 4. The discharge hole of the sintering machine 1 is connected with the feed inlet of the circular cooler 2. The circulating air flow unit 3 is arranged among the sintering machine 1, the circular cooler 2 and the flue gas treatment unit 4. A smoke hood 101 is provided above the sintering machine 1, and an air box 102 is provided below the smoke hood. The hood 101 located above the sintering machine 1 is divided into a preheating section 103, a combustion section 104, and a roasting section 105 in this order according to the direction of the materials. The ring cooling machine 2 is sequentially divided into a ring cooling first section 201, a ring cooling second section 202 and a ring cooling third section 203. The wind boxes 102 at the bottom of the roasting section 105, the combustion section 104 and the preheating section 103 are not communicated with each other. The ring cooling first section 201, the ring cooling second section 202 and the ring cooling third section 203 are all provided with a clapboard 204.

Preferably, the circulating air flow unit 3 includes a cooling fan 301 and a circulating line. The circulating pipeline specifically comprises: the cooling fan 301 is communicated with the air inlet of the ring cooling three-section 203 through an air inlet pipeline G. The exhaust outlet of the annular cooling three-section 203 is communicated with the air inlet of the preheating section 103 through a first gas pipeline L1. The exhaust outlet of the preheating section 103 is communicated with the air inlet of the annular cooling section 202 through a second gas pipeline L2. The exhaust outlet of the annular cooling section 202 is communicated with the air inlet of the combustion section 104 through a third gas pipeline L3. The exhaust outlet of the combustion section 104 is communicated with the air inlet of the annular cooling section 201 through a fourth gas pipeline L4. The exhaust outlet of the annular cooling section 201 is communicated with the air inlet of the roasting section 105 through a fifth gas pipeline L5. The exhaust outlet of the roasting section 105 is communicated with the air inlet of the flue gas treatment unit 4 through a sixth gas pipeline L6.

Preferably, a heat compensating device 5 is disposed on the fifth gas pipeline L5. The heat supplementing device 5 comprises a burner 501 and a fuel gas conveying pipeline L7. The burner 501 is arranged in a fifth gas duct L5. The air inlet of the burner 501 is communicated with the air outlet of the fuel gas conveying pipeline L7.

Preferably, the heat compensating device 5 comprises a plurality of burners 501. The plurality of burners 501 are all arranged in a fifth gas pipeline L5, and the plurality of burners 501 are respectively and independently connected with a gas conveying pipeline L7. In the fifth gas pipeline L5, the number of the burners 501 is distributed in an increasing manner along the flow direction.

Preferably, the flue gas treatment unit 4 comprises an electric dust collector 401, a main exhaust fan 402, a desulfurization and denitrification device 403 and a chimney 404. The electric dust collector 401, the main exhaust fan 402, the desulfurization and denitrification device 403 and the chimney 404 are sequentially connected in series, wherein an air inlet of the electric dust collector 401 is communicated with an air outlet of a sixth gas pipeline L6.

Preferably, the system further comprises a feed unit 6. The feeding unit 6 comprises a pelletizing device 601, a microwave drying device 602 and a distributing device 603. The pelletizing device 601, the microwave drying device 602 and the material distribution device 603 are sequentially connected in series, wherein the material distribution device 603 is connected with the feed end of the steel belt machine 1.

Preferably, the pelletizing device 601 includes a batching machine 6011, a mixing machine 6012, a pelletizing machine 6013, a green pellet screening machine 6014, and a crusher 6015. The proportioning machine 6011, the mixing machine 6012, the pelletizer 6013 and the green pellet screening machine 6014 are connected in series in sequence. And a qualified discharge hole of the green ball screening machine 6014 is connected with a feed hole of the microwave drying device 602. An unqualified discharge hole of the green pellet screening machine 6014 is connected with a feed inlet of a crusher 6015, and a discharge hole of the crusher 6015 is connected with a feed inlet of a pelletizer 6013.

Preferably, the system also comprises a pulverized coal heat supplementing system 7. The pulverized coal heat supplementing system 7 comprises a coal crushing device 701, a pulverized coal conveying pipeline L8, a coal injection device 702 and an ignition device 703. The coal injection device 702 is disposed at the top of the combustion section 104 of the sintering machine 1 and communicates with the interior of the combustion section 104. The ignition device 703 is provided inside the combustion section 104 of the sintering machine 1. The coal injection device 702 is communicated with the coal crushing device 701 through a coal powder conveying pipeline L8.

Preferably, the system further comprises a pellet screening device 8. And the pellet screening device 8 is arranged at the discharge port of the circular cooler 2. The pellet screening device 8 is connected to the upper part of the distributing device 603 through an oversize material conveying device 801. The screening device 8 is also communicated with the feed inlet of the blast furnace through an undersize material conveying device 802.

Preferably, the system further comprises a sprinkler 9. The sprinkler 9 is communicated with the oversize material conveying device 801 through a sprinkler pipeline L9.

Preferably, a buffer hopper 10 is further provided between the pellet screening device 8 and the sintering machine 1.

2) The green pellets are put into a pellet roasting system based on a sintering machine, according to the trend of logistics, the green pellets are roasted through a preheating section 103, a combustion section 104 and a roasting section 105 in sequence, and then cooled through a ring cooling section 201, a ring cooling section 202 and a ring cooling section 203 in sequence, and finished pellets are obtained.

3) In a pellet roasting system based on a sintering machine, according to the trend of air flow, ambient air sequentially flows through a ring cooling three section 203, a preheating section 103, a ring cooling two section 202, a combustion section 104, a ring cooling one section 201 and a roasting section 105 to complete heat exchange with green pellets. And finally, the waste gas is treated by the flue gas treatment unit 4 and then discharged.

Preferably, the method further comprises:

and 4) screening the finished pellets, wherein the finished pellets with larger particle size are returned to the material distribution device 603 for bottom material paving, and the finished pellets with smaller particle size are sent to a blast furnace for processing.

Preferably, step 2) is specifically: firstly, paving a bottom material on a sintering trolley, and then paving raw pellet preparation materials on the bottom material. And then the sintering trolley containing the materials is sequentially processed by a preheating section 103, a combustion section 104 and a roasting section 105 to obtain roasted pellets. And finally, treating the roasted pellets sequentially through a ring cooling first section 201, a ring cooling second section 202 and a ring cooling third section 203 to obtain finished pellets.

Preferably, in the combustion section 104, pulverized coal is injected by using a coal injection device 702, and then the pulverized coal is ignited by using an ignition device 703, so as to heat the pellets in the combustion section 104.

Preferably, the length of the roasting section 105 > the length of the combustion section 104 > the length of the preheating section 103.

Preferably, step 3) is specifically: the cooling fan 301 introduces ambient air into the environment cooling three-stage 203 to perform heat exchange and cooling treatment on the low-temperature roasted pellets to obtain low-temperature hot air, and the low-temperature hot air is continuously conveyed into the preheating section 103 to perform preheating treatment on the green pellets. The low-temperature hot air after the preheating treatment is continuously conveyed into the annular cooling section 202 to perform heat exchange and cooling on the medium-temperature roasted pellets, so as to obtain medium-temperature hot air, and the medium-temperature hot air is continuously conveyed into the combustion section 104 to perform heating treatment on the green pellets. The medium-temperature hot air after the heating treatment is continuously conveyed to the annular cooling section 201 to carry out heat exchange cooling on the high-temperature roasted pellets to obtain high-temperature hot air, and the high-temperature hot air is continuously conveyed to the roasting section 105 to carry out roasting treatment on the green pellets. The high-temperature hot air after the roasting treatment is treated by an electric dust collector 401, a main exhaust fan 402 and a desulfurization and denitrification device 403 in sequence, and is finally discharged through a chimney 404.

Preferably, while the high-temperature hot air is continuously supplied to the baking section 105, the high-temperature hot air is also heated by the burner 501 to increase the temperature of the high-temperature hot air. Preferably, the number of the burners 501 is plural, and the number of the burners 501 is distributed in an increasing manner according to the flow direction of the high-temperature hot air.

Preferably, step 4) is specifically: the finished pellet materials cooled by the circular cooler 2 are conveyed to a pellet screening device 8 for screening. Wherein finished pellets with the particle size of more than 14mm (preferably 14mm-16 mm) are returned to the distributing device 603 for bedding. And conveying finished pellets with the particle size of less than or equal to 14mm (preferably 5-14mm) to a blast furnace for iron making.

Preferably, the large finished pellets used as the bedding material are subjected to wetting treatment before the bedding material is paved, and specifically, the large finished pellets are subjected to water spraying treatment by using a water spraying device 9, so that the water content of the large finished pellets is 3% -6%, and preferably 3.5% -5%.

Example 1

Example 2

As shown in fig. 2, embodiment 1 is repeated except that the circulating air flow unit 3 includes a cooling fan 301 and a circulating line. The circulating pipeline specifically comprises: the cooling fan 301 is communicated with the air inlet of the ring cooling three-section 203 through an air inlet pipeline G. The exhaust outlet of the annular cooling three-section 203 is communicated with the air inlet of the preheating section 103 through a first gas pipeline L1. The exhaust outlet of the preheating section 103 is communicated with the air inlet of the annular cooling section 202 through a second gas pipeline L2. The exhaust outlet of the annular cooling section 202 is communicated with the air inlet of the combustion section 104 through a third gas pipeline L3. The exhaust outlet of the combustion section 104 is communicated with the air inlet of the annular cooling section 201 through a fourth gas pipeline L4. The exhaust outlet of the annular cooling section 201 is communicated with the air inlet of the roasting section 105 through a fifth gas pipeline L5. The exhaust outlet of the roasting section 105 is communicated with the air inlet of the flue gas treatment unit 4 through a sixth gas pipeline L6.

Example 3

Example 2 was repeated except that the fifth gas line L5 was provided with a heat compensating means 5. The heat supplementing device 5 comprises a burner 501 and a fuel gas conveying pipeline L7. The burner 501 is arranged in a fifth gas duct L5. The air inlet of the burner 501 is communicated with the air outlet of the fuel gas conveying pipeline L7.

The heat supplementing device 5 comprises a plurality of burners 501. The plurality of burners 501 are all arranged in a fifth gas pipeline L5, and the plurality of burners 501 are respectively and independently connected with a gas conveying pipeline L7. In the fifth gas pipeline L5, the number of the burners 501 is distributed in an increasing manner along the flow direction.

Example 4

Example 3 is repeated except that the flue gas treatment unit 4 comprises an electric dust collector 401, a main exhaust fan 402, a desulfurization and denitrification device 403 and a chimney 404. The electric dust collector 401, the main exhaust fan 402, the desulfurization and denitrification device 403 and the chimney 404 are sequentially connected in series, wherein an air inlet of the electric dust collector 401 is communicated with an air outlet of a sixth gas pipeline L6.

Example 5

As shown in fig. 3, example 4 is repeated except that the system further comprises a feed unit 6. The feeding unit 6 comprises a pelletizing device 601, a microwave drying device 602 and a distributing device 603. The pelletizing device 601, the microwave drying device 602 and the material distribution device 603 are sequentially connected in series, wherein the material distribution device 603 is connected with the feed end of the steel belt machine 1.

The pelletizing device 601 comprises a proportioning machine 6011, a mixing machine 6012, a pelletizing machine 6013, a green pellet screening machine 6014 and a crusher 6015. The proportioning machine 6011, the mixing machine 6012, the pelletizer 6013 and the green pellet screening machine 6014 are connected in series in sequence. And a qualified discharge hole of the green ball screening machine 6014 is connected with a feed hole of the microwave drying device 602. An unqualified discharge hole of the green pellet screening machine 6014 is connected with a feed inlet of a crusher 6015, and a discharge hole of the crusher 6015 is connected with a feed inlet of a pelletizer 6013.

Example 6

Example 5 is repeated except that the system also comprises a pulverized coal heat supplementing system 7. The pulverized coal heat supplementing system 7 comprises a coal crushing device 701, a pulverized coal conveying pipeline L8, a coal injection device 702 and an ignition device 703. The coal injection device 702 is disposed at the top of the combustion section 104 of the sintering machine 1 and communicates with the interior of the combustion section 104. The ignition device 703 is provided inside the combustion section 104 of the sintering machine 1. The coal injection device 702 is communicated with the coal crushing device 701 through a coal powder conveying pipeline L8.

Example 7

Example 6 was repeated except that the system further included a pellet screening device 8. And the pellet screening device 8 is arranged at the discharge port of the circular cooler 2. The pellet screening device 8 is connected to the upper part of the distributing device 603 through an oversize material conveying device 801. The screening device 8 is also communicated with the feed inlet of the blast furnace through an undersize material conveying device 802.

Example 8

Example 7 is repeated, except that the system also comprises a sprinkler 9. The sprinkler 9 is communicated with the oversize material conveying device 801 through a sprinkler pipeline L9.

And a buffer hopper 10 is also arranged between the pellet screening device 8 and the sintering machine 1.

Example 9

Example 10

4) And screening the finished pellets, wherein the finished pellets with larger particle size are returned to the material distribution device 603 for bedding material, and the finished pellets with smaller particle size are sent to a blast furnace for treatment.

Example 11

Example 10 was repeated except that the step 1) specifically was: mixing hematite, anthracite powder, calcium oxide and sodium calcium bentonite according to a proportion to obtain a mixture. And then adding a certain amount of water into the mixture for pelletizing to obtain green pellets. And then screening the green pellets to obtain qualified green pellets. And finally, performing primary drying treatment on the qualified green pellets by adopting microwave to obtain green pellet preparation materials. And the unqualified green pellets are crushed and then participate in pelletizing.

Example 12

Example 11 was repeated except that the hematite had an iron content of 45%. The water content of hematite was 8%. The content of hematite with the particle size of-0.044 mm is more than 70 percent. The specific surface area of hematite is 1700cm²/g。

The grain size of the anthracite powder is-0.074 mm and is more than 95 percent.

The purity of the calcium oxide is more than 95%.

The sodium calcium bentonite is obtained by adding sodium hydroxide solution into calcium bentonite with the granularity of less than 0.074mm for sodium modification. The water content of the sodium calcium carbonate-based bentonite is 7%.

The mass ratio of the added amounts of the hematite, the anthracite powder, the calcium oxide and the sodium calcium carbonate based swelling is 93:3:2: 2.

Example 13

Example 12 was repeated except that step 2) specifically was: firstly, paving a bottom material on a sintering trolley, and then paving raw pellet preparation materials on the bottom material. And then the sintering trolley containing the materials is sequentially processed by a preheating section 103, a combustion section 104 and a roasting section 105 to obtain roasted pellets. And finally, treating the roasted pellets sequentially through a ring cooling first section 201, a ring cooling second section 202 and a ring cooling third section 203 to obtain finished pellets.

The thickness of the bedding material is 375 mm. The thickness of the green pellet preparation material is 360 mm.

Example 14

Example 13 was repeated except that in the combustion section 104, pulverized coal was injected by using the coal injection device 702 and then ignited by using the ignition device 703, thereby heating the pellets in the combustion section 104.

The length of the firing section 105 > the length of the combustion section 104 > the length of the preheating section 103.

Example 15

Example 14 was repeated except that step 3) specifically was: the cooling fan 301 introduces ambient air into the environment cooling three-stage 203 to perform heat exchange and cooling treatment on the low-temperature roasted pellets to obtain low-temperature hot air, and the low-temperature hot air is continuously conveyed into the preheating section 103 to perform preheating treatment on the green pellets. The low-temperature hot air after the preheating treatment is continuously conveyed into the annular cooling section 202 to perform heat exchange and cooling on the medium-temperature roasted pellets, so as to obtain medium-temperature hot air, and the medium-temperature hot air is continuously conveyed into the combustion section 104 to perform heating treatment on the green pellets. The medium-temperature hot air after the heating treatment is continuously conveyed to the annular cooling section 201 to carry out heat exchange cooling on the high-temperature roasted pellets to obtain high-temperature hot air, and the high-temperature hot air is continuously conveyed to the roasting section 105 to carry out roasting treatment on the green pellets. The high-temperature hot air after the roasting treatment is treated by an electric dust collector 401, a main exhaust fan 402 and a desulfurization and denitrification device 403 in sequence, and is finally discharged through a chimney 404.

Example 16

Example 15 was repeated except that the high temperature hot air was also heated by the burner 501 to raise the temperature of the high temperature hot air while the high temperature hot air was continuously fed to the firing section 105. The number of the burners 501 is set to be a plurality, and the number of the burners 501 is distributed in an increasing manner according to the flow direction of the high-temperature hot air.

Example 17

Example 16 was repeated except that step 4) specifically was: the finished pellet materials cooled by the circular cooler 2 are conveyed to a pellet screening device 8 for screening. Wherein finished pellets with the particle size of 14-16mm are returned to the distributing device 603 for bedding. And conveying finished pellets with the particle size of 5-14mm to a blast furnace for iron making.

Example 18

Example 17 is repeated, but the large finished pellets as the bedding material need to be moistened before the bedding material is paved, and specifically, the water spraying device 9 is adopted to spray water on the large finished pellets, so that the water content of the large finished pellets is 4.5%.

Claims

1. The utility model provides a pelletizing calcination system based on sintering machine which characterized in that: the system comprises: the system comprises a sintering machine (1), a circular cooler (2), a circulating air flow unit (3) and a flue gas treatment unit (4); the discharge hole of the sintering machine (1) is connected with the feed inlet of the circular cooler (2); the circulating air flow unit (3) is arranged among the sintering machine (1), the circular cooler (2) and the flue gas treatment unit (4); a smoke hood (101) is arranged above the sintering machine (1), and an air box (102) is arranged below the smoke hood; according to the trend of materials, a smoke hood (101) positioned above a sintering machine (1) is sequentially divided into a preheating section (103), a combustion section (104) and a roasting section (105); the ring cooling machine (2) is sequentially divided into a ring cooling first section (201), a ring cooling second section (202) and a ring cooling third section (203); the air boxes (102) positioned at the bottom of each section of the roasting section (105), the combustion section (104) and the preheating section (103) are not communicated with each other; the ring cooling first section (201), the ring cooling second section (202) and the ring cooling third section (203) are provided with clapboards (204) among each other.

2. The system of claim 1, wherein: the circulating air flow unit (3) comprises a cooling fan (301) and a circulating pipeline; the circulating pipeline specifically comprises: the cooling fan (301) is communicated with the air inlet of the annular cooling three-section (203) through an air inlet pipeline (G); the air outlet of the annular cooling three-section (203) is communicated with the air inlet of the preheating section (103) through a first gas pipeline (L1); the air outlet of the preheating section (103) is communicated with the air inlet of the annular cooling section (202) through a second gas pipeline (L2); the air outlet of the annular cooling section (202) is communicated with the air inlet of the combustion section (104) through a third gas pipeline (L3); the exhaust outlet of the combustion section (104) is communicated with the air inlet of the annular cooling section (201) through a fourth gas pipeline (L4); the air outlet of the annular cooling section (201) is communicated with the air inlet of the roasting section (105) through a fifth gas pipeline (L5); and an air outlet of the roasting section (105) is communicated with an air inlet of the flue gas processing unit (4) through a sixth gas pipeline (L6).

3. The system of claim 2, wherein: a heat supplementing device (5) is arranged on the fifth gas pipeline (L5); the heat supplementing device (5) comprises a burner (501) and a fuel gas conveying pipeline (L7); the burner (501) is arranged in a fifth gas pipeline (L5); the air inlet of the burner (501) is communicated with the air outlet of a fuel gas conveying pipeline (L7);

preferably, the heat supplementing device (5) comprises a plurality of burners (501); the plurality of burners (501) are all arranged in a fifth gas pipeline (L5), and the plurality of burners (501) are respectively and independently connected with a gas conveying pipeline (L7); in the fifth gas pipeline (L5), the number of the burners (501) is distributed in an increasing mode along the trend of the gas flow.

4. A system according to claim 2 or 3, characterized in that: the flue gas treatment unit (4) comprises an electric dust collector (401), a main exhaust fan (402), a desulfurization and denitrification device (403) and a chimney (404); the electric dust remover (401), the main exhaust fan (402), the desulfurization and denitrification device (403) and the chimney (404) are sequentially connected in series, wherein an air inlet of the electric dust remover (401) is communicated with an air outlet of a sixth gas pipeline (L6); and/or

The system further comprises a feed unit (6); the feeding unit (6) comprises a pelletizing device (601), a microwave drying device (602) and a distributing device (603); the pelletizing device (601), the microwave drying device (602) and the material distribution device (603) are sequentially connected in series, wherein the material distribution device (603) is connected with the feed end of the steel strip machine (1);

preferably, the pelletizing device (601) comprises a proportioning machine (6011), a mixing machine (6012), a pelletizing machine (6013), a green pellet screening machine (6014) and a crusher (6015); the proportioning machine (6011), the mixing machine (6012), the pelletizer (6013) and the green pellet screening machine (6014) are sequentially connected in series; a qualified discharge hole of the green ball sieving machine (6014) is connected with a feed hole of the microwave drying device (602); an unqualified discharge hole of the green ball sieving machine (6014) is connected with a feed inlet of a crusher (6015), and a discharge hole of the crusher (6015) is connected with a feed inlet of a pelletizer (6013).

5. The system of claim 4, wherein: the system also comprises a pulverized coal heat supplementing system (7); the coal powder heat supplementing system (7) comprises a coal crushing device (701), a coal powder conveying pipeline (L8), a coal injection device (702) and an ignition device (703); the coal injection device (702) is arranged at the top of the combustion section (104) of the sintering machine (1) and is communicated with the interior of the combustion section (104); the ignition device (703) is arranged inside the combustion section (104); the coal injection device (702) is communicated with the coal crushing device (701) through a coal powder conveying pipeline (L8); and/or

The system also comprises a pellet screening device (8); the pellet screening device (8) is arranged at the discharge port of the circular cooler (2); the pellet screening device (8) is connected to the upper part of the distributing device (603) through an oversize material conveying device (801); the screening device (8) is also communicated with a feed inlet of the blast furnace through an undersize material conveying device (802); and/or

The system also comprises a water sprinkling device (9); the water sprinkling device (9) is communicated with the oversize material conveying device (801) through a water sprinkling pipeline (L9);

preferably, a buffer hopper (10) is further arranged between the pellet screening device (8) and the sintering machine (1).

6. A method for pellet firing using the system of any one of claims 1-5, the method comprising the steps of:

1) mixing the iron-containing ores and auxiliary materials to obtain a mixture; then adding water into the mixture for pelletizing to obtain green pellets;

2) the method comprises the steps of putting green pellets into a pellet roasting system based on a sintering machine, roasting the green pellets sequentially through a preheating section (103), a combustion section (104) and a roasting section (105) according to the trend of logistics, and then cooling the green pellets sequentially through a ring cooling section (201), a ring cooling section (202) and a ring cooling section (203) to obtain finished pellets;

3) in a pellet roasting system based on a sintering machine, according to the trend of air flow, ambient air sequentially flows through a ring cooling three section (203), a preheating section (103), a ring cooling two section (202), a combustion section (104), a ring cooling one section (201) and a roasting section (105) to complete heat exchange with green pellets; finally, the waste gas is treated by a flue gas treatment unit (4) and then discharged;

preferably, the method further comprises:

and 4) screening the finished pellets, wherein the finished pellets with larger particle size are returned to the material distribution device (603) for bottom material paving, and the finished pellets with smaller particle size are sent to a blast furnace for processing.

7. The method of claim 6, wherein: the step 1) is specifically as follows: mixing hematite, anthracite powder, calcium oxide and sodium calcium bentonite according to a proportion to obtain a mixture; then adding a certain amount of water into the mixture for pelletizing to obtain green pellets; then screening the green pellets to obtain qualified green pellets; finally, performing primary drying treatment on the qualified green pellets by adopting microwave to obtain green pellet preparation materials; the unqualified green pellets are crushed and then participate in pelletizing;

preferably, the iron content of the hematite is 30-55%, preferably 45-50%; the water content of the hematite is 5-10%, preferably 7-9%; the content of hematite with the particle size of-0.044 mm is more than 60 percent, and the content of-0.044 mm is preferably more than 70 percent; the specific surface area of the hematite is 1000-2500 cm²Preferably 1500 to 1900 cm/g²(ii)/g; and/or

The grain size of the anthracite powder is-0.074 mm and is more than 90 percent, and the grain size of the anthracite powder is preferably-0.074 mm and is more than 95 percent; and/or

The purity of the calcium oxide is more than 90%, and preferably the purity is more than 95%; and/or

The sodium calcium bentonite is obtained by adding sodium hydroxide solution into calcium bentonite with the granularity of less than 0.074mm for sodium modification; the water content of the sodium calcium base bentonite is 4-9%, preferably 6-8%;

preferably, the mass ratio of the added amounts of the hematite, the anthracite powder, the calcium oxide and the sodium calcium carbonate based swelling is 88-96:2-5:1-3: 1-4; preferably 90-95:3-4:1-2: 2-3.

8. The method of claim 7, wherein: the step 2) is specifically as follows: firstly, paving a bottom material on a sintering trolley, and then paving green pellet preparation materials on the bottom material; then, the sintering trolley containing the materials is sequentially processed by a preheating section (103), a combustion section (104) and a roasting section (105) to obtain roasted pellets; finally, the roasted pellets are sequentially processed by a ring cooling section (201), a ring cooling section (202) and a ring cooling section (203) to obtain finished pellets;

preferably, the thickness of the bedding material is 300mm-450mm, preferably 350 mm-400 mm; the thickness of the green pellet preparation material is 300mm-400mm, preferably 350mm-380 mm; and/or

In the combustion section (104), coal powder is sprayed in by adopting a coal spraying device (702), then the coal powder is ignited by adopting an ignition device (703), and then the pellets in the combustion section (104) are heated; and/or

The length of the roasting section (105) is greater than the length of the combustion section (104) is greater than the length of the preheating section (103).

9. The method of claim 8, wherein: the step 3) is specifically as follows: the cooling fan (301) introduces environmental air into the annular cooling section (203) to perform heat exchange and cooling treatment on the low-temperature roasted pellets to obtain low-temperature hot air, and the low-temperature hot air is continuously conveyed into the preheating section (103) to perform preheating treatment on the green pellets; the low-temperature hot air after the preheating treatment is continuously conveyed into the annular cooling section (202) to carry out heat exchange and cooling on the medium-temperature roasted pellets to obtain medium-temperature hot air, and the medium-temperature hot air is continuously conveyed into the combustion section (104) to carry out heating treatment on the green pellets; the medium-temperature hot air after the heating treatment is continuously conveyed into the annular cooling section (201) to carry out heat exchange cooling on the high-temperature roasted pellets to obtain high-temperature hot air, and the high-temperature hot air is continuously conveyed into the roasting section (105) to carry out roasting treatment on the green pellets; after the high-temperature hot air after roasting treatment is sequentially treated by an electric dust collector (401), a main exhaust fan (402) and a desulfurization and denitrification device (403), the high-temperature hot air is finally discharged through a chimney (404);

preferably, in the process of continuously conveying the high-temperature hot air to the roasting section (105), the high-temperature hot air is further heated through a burner (501) so as to increase the temperature of the high-temperature hot air; preferably, the number of the burners (501) is set to be a plurality, and the number of the burners (501) is distributed in an increasing manner according to the flow direction of the high-temperature hot air.

10. The method according to any one of claims 6-9, wherein: the step 4) is specifically as follows: conveying finished pellet materials cooled by the circular cooler (2) into a pellet screening device (8) for screening treatment; the finished pellets with the particle size larger than 14mm (preferably 14mm-16 mm) are returned to the distributing device (603) for bedding; conveying finished pellets with the particle size of less than or equal to 14mm (preferably 5-14mm) to a blast furnace for iron making;

preferably, the large finished pellets as the bedding material are required to be subjected to wetting treatment before the bedding material is paved, and particularly, the large finished pellets are subjected to water spraying treatment by adopting a water spraying device (9), so that the water content of the large finished pellets is 3% -6%, and preferably 3.5% -5%.