Biomass fuel for iron ore sintering and application method

Abstract

The invention relates to the technical field of iron ore sintering, in particular to a biomass fuel for iron ore sintering, which is prepared by the following steps: 1) biomass carbonization: crushing biomass, putting the crushed biomass into a carbonization furnace, and introducing nitrogen shielding gas for carbonization to prepare biomass carbon blocks; 2) crushing the biomass charcoal blocks, fully and uniformly mixing the crushed biomass charcoal blocks with limestone powder, magnesite powder and carboxymethyl cellulose according to the mass percentage content of (92-94.5%): (3-5%): (2-3.5%): (0.2-0.5%), and pressing the mixture into biomass charcoal mixed pellets; and 3) secondary carbonization: putting the biomass charcoal mixed pellets into a carbonization furnace, and introducing nitrogen shielding gas for carbonization to prepare the biomass fuel. The biomass fuel which is high in fixed carbon content, low in porosity, good in strength and excellent in performance is prepared, the purpose that the biomass fuel replaces fossil fuels such as coke powder in a large proportion is achieved, and the problem that when existing biomass fuel serves as sintering fuel, the combustion speed is too high, and consequently the quality of sintered ore becomes poor is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron ore sintering, and particularly relates to a biomass fuel for iron ore sintering and an application method thereof. Background Art

[0002] Sintered ore, as the main iron-containing raw material charged into the blast furnace for smelting, plays a dominant role in blast furnace production. High-quality sintered ore is the basis for high-quality and high-efficiency blast furnace ironmaking. At the same time, it is also an important guarantee for energy conservation, emission reduction, environmental friendliness in the ironmaking process, and the sustainable development of iron and steel enterprises.

[0003] Biomass is formed through photosynthesis and is a general term for all organisms derived from animals and plants except fossil fuels. It is a renewable substance. Biomass can be converted into other forms of fuel, such as solid, liquid, and gaseous, according to specific needs. Biomass includes trees, crops, aquatic plants, and the wastes formed by them.

[0004] Biomass has the following characteristics:

[0005] (1) Abundant resources and wide distribution

[0006] Biomass not only exists in various forms but also is widely distributed, covering both land and water. In the world's energy, biomass energy is an indispensable energy source and also accounts for a large proportion in the world's energy consumption. With the increasing consumption of fossil energy and the emphasis on environmental protection, in the future energy development, the proportion of biomass energy in the world's energy will gradually increase, and biomass energy will become an important part of the future world's sustainable energy.

[0007] China is rich in biomass energy resources, which are an important part of China's primary energy, accounting for about one-third of the primary energy, ranking second only to coal in the total energy proportion. Among biomass resources, various crops and the wastes formed by them account for a large proportion. Among them, rice straw, corn straw, and wheat straw account for 31.3%, 27.7%, and 16.0% respectively. In addition, China's plant biomass resources are also relatively rich, such as reeds, bamboos, etc. As an important part of plant biomass, their annual output is huge.

[0008] (2) Clean and renewable

[0009] Biomass fuels mainly contain three elements: carbon, hydrogen, and oxygen, especially carbon and oxygen. The content of other elements harmful to the environment, such as sulfur and nitrogen, is very low. Since biomass contains almost no sulfur and very little nitrogen (nitrogen content is 0.5%-3%, sulfur content is generally only 0.1%-0.5%), when using biomass as fuel, the generation of NOx is extremely low, and the emission of SOx is also much lower than that of fossil fuels such as coke powder and coal powder. In addition, due to the relatively low calorific value of biomass, during the combustion process, considering the temperature, the generation rate of NOx is lower than that of other fossil fuels. Therefore, using biomass as fuel can reduce the emissions of SOx and NOx.

[0010] The formation and utilization of biomass are through the photosynthesis of green plants and the combustion process of biomass. During this process, a cycle of carbon dioxide absorption and emission is formed. In this cycle, the absorption and emission amounts of carbon dioxide are almost equal. Therefore, considering from the perspective of the life cycle, when using biomass as fuel, near-zero emissions of CO2 can be achieved in total. Therefore, from the perspective of low SOx and NOx emissions and near-zero CO2 emissions, biomass is a clean energy source.

[0011] The application of biomass fuel in iron ore sintering can not only relieve the tense situation of China's energy supply but also significantly reduce the emissions of various pollutants. It is an important development direction for clean production in sintering in the future. However, the fast combustion speed of biomass during the sintering process increases the overall incomplete combustion degree of the fuel, shortens the high-temperature holding time, and enhances the reducing atmosphere, which is not conducive to sintering ore formation. This reduces the generation amount of calcium ferrite in sintered ore, generates some low-strength minerals, and forms some large-pore thin-wall structures, thus reducing the drum strength of sintered ore and the yield of sintered ore also decreases accordingly. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a biomass fuel for iron ore sintering and its preparation method, which solves the problems of low fixed carbon content, high porosity, and poor strength of ordinary biomass fuel when used as sintering fuel.

[0013] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0014] A biomass fuel for iron ore sintering is prepared by the following steps. The specific steps include:

[0015] 1) Biomass carbonization: After the biomass is crushed, it is put into a carbonization furnace, and nitrogen protective gas is introduced for carbonization to make biomass carbon blocks;

[0016] 2) After the biomass carbon blocks are crushed, they are fully mixed with limestone powder, magnesite powder, and carboxymethyl cellulose in a mass percentage of 92% - 94.5%: 3% - 5%: 2% - 3.5%: 0.2% - 0.5%, and then pressed into small balls of biomass carbon mixed material.

[0017] 3) Secondary carbonization: The small balls of biomass carbon mixed material are put into a carbonization furnace, and nitrogen protective gas is introduced for carbonization to produce biomass fuel.

[0018] The biomass in step 1) is any one or more of corn straw, corn cob, and sorghum straw, and the crushing particle size of the biomass is controlled at 15 - 30 mm.

[0019] The carbonization furnace in step 1) is heated to 300 - 500 °C at a heating rate of 2 - 5 °C / min, the carbonization time is 15 - 25 min, and the nitrogen flow rate is 1 - 3 L / min.

[0020] The crushing particle size of the biomass carbon blocks in step 2) is less than 0.1 mm, the particle sizes of the limestone powder and magnesite powder are less than 0.074 mm, and the particle size of the prepared small balls of biomass carbon mixed material is 1 - 3 mm.

[0021] The carbonization furnace in step 3) is heated to 650 - 800 °C at a heating rate of 5 - 15 °C / min, the carbonization time is 10 - 20 min, and the nitrogen flow rate is 2.5 - 4 L / min.

[0022] Performance indicators of the biomass fuel: The calorific value of combustion is 28 - 35 MJ / kg, the fixed carbon content is 88% - 91%, the ash content is 4% - 6%, the volatile content is 5% - 6%, the porosity is 10% - 20%, the specific surface area is 5 - 15 m 2 / g, and the density is 1.8 - 1.95 g / m 3 .

[0023] The application method of the biomass fuel, and the application method includes the following steps:

[0024] 1) Prepare small balls of fuel mixed material with the biomass fuel, magnetite concentrate powder, limestone powder, and magnesite powder in a pelletizer; the small balls of fuel mixed material take the biomass fuel balls as the pelletizing core, and are wrapped with magnetite concentrate powder, limestone powder, and magnesite powder on the outside.

[0025] 2) Mix hematite powder, limestone powder, magnesite powder, and coke powder through a mixer to prepare coke powder mixture;

[0026] 3) Granulate the small balls of fuel mixed material in step 1) and the coke powder mixture in step 2) through a granulator. During the granulation process, the small balls of fuel mixed material are used as the granulation core, and are wrapped with the coke powder mixture on the outside to make sintering mixture, and the sintering mixture is fed onto a sintering trolley for the production of sintered ore.

[0027] Step 1) The pelletizing time of the pelletizer is 5 - 8 min. After pelletizing, continue to compact for 2 - 4 min.

[0028] In step 1), the proportion of particles with a size less than 0.074 mm in the magnetite concentrate powder exceeds 90%; the proportion of particles with a size less than 3 mm in the limestone powder is 80% - 85%; the proportion of particles with a size less than 3 mm in the magnesite powder is 75% - 80%; the size of the prepared fuel mixed material pellets is 3 - 6 mm.

[0029] In step 2), the proportion of particles with a size of 1 - 8 mm in the hematite powder is 45% - 55%; the proportion of particles with a size less than 3 mm in the limestone powder is 80% - 85%; the proportion of particles with a size less than 3 mm in the magnesite powder is 75% - 80%; the proportion of particles with a size less than 0.5 mm in the coke powder is 13% - 16%, the proportion of particles with a size of 0.5 - 3 mm is 70% - 73%, and the size of the remaining particles is greater than 3 mm.

[0030] In step 3), the mass ratio of the fuel mixed material pellets to the coke powder mixture is (2 - 7)∶(3 - 8).

[0031] Compared with the existing technology, the beneficial effects of the present invention are as follows:

[0032] 1. The biomass fuel of the present invention is carbonized twice to prepare a biomass fuel with excellent performance of high fixed carbon content, low porosity, and good strength, solving the problem of poor properties of ordinary biomass fuels as sintering fuels, and providing a more valuable way for the further rational use of agricultural wastes such as corn straws, corn cobs, and sorghum straws.

[0033] 2. In the sintering mixture of the present invention, since Fe3O4 in the magnetite concentrate reacts with O2 to form Fe2O3, part of the oxygen is consumed during the oxidation process, reducing the combination rate of oxygen and the biomass fuel, slowing down the combustion rate of the biomass fuel, prolonging the mineralization process of the sintered ore, achieving the purpose of improving the quality of the sintered ore, and at the same time making full use of the heat released during the oxidation process of the magnetite concentrate. The released heat can be used for the sintering reaction of the mixture mainly composed of hematite powder in the outer layer, thereby reducing the consumption of solid fuel during the sintering process and significantly reducing the sintering production cost.

[0034] The present invention prepares a biomass fuel for sintering production by treating agricultural production wastes. Through process optimization, the purpose of large - scale substitution of fossil fuels such as coke powder by biomass fuel is achieved, overcoming the problem of poor quality of sintered ore caused by the too - fast combustion rate of existing biomass fuels as sintering fuels, and achieving the effect of reducing the emissions of SO2, NOx, and CO2 during sintering production. Specific embodiments

[0035] It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The mention of "embodiment" in this text means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0036] A biomass fuel for iron ore sintering is prepared by the following steps, and the specific steps include:

[0037] 1) Biomass carbonization: After the biomass is crushed, it is put into a carbonization furnace, and nitrogen protective gas is introduced for carbonization to make biomass carbon blocks;

[0038] 2) After the biomass carbon blocks are crushed, they are fully mixed with limestone powder, magnesite powder, and carboxymethyl cellulose according to the mass percentage content of 92% - 94.5%: 3% - 5%: 2% - 3.5%: 0.2% - 0.5%, and then pressed into biomass carbon mixed material small balls; The limestone powder provides CaO to make the biomass fuel have a certain alkalinity, the magnesite powder provides MgO, and the carboxymethyl cellulose is used as a binder to improve the strength of the biomass fuel.

[0039] 3) Secondary carbonization: The biomass carbon mixed material small balls are put into a carbonization furnace, and nitrogen protective gas is introduced for carbonization to make biomass fuel. The recarbonization of the mixed material containing biomass carbon can increase its fixed carbon content, reduce the ash content and volatile content, thereby increasing the calorific value of combustion.

[0040] The biomass in step 1) is any one or more of corn straw, corn cob, and sorghum straw, and the crushing particle size of the biomass is controlled at 15 - 30 mm.

[0041] The carbonization furnace in step 1) is heated to 300 - 500 °C at a heating rate of 2 - 5 °C / min, the carbonization time is 15 - 25 min, and the nitrogen flow rate is 1 - 3 L / min.

[0042] The crushing particle size of the biomass carbon blocks in step 2) is less than 0.1 mm, the particle sizes of the limestone powder and magnesite powder are less than 0.074 mm, and the particle size of the prepared biomass carbon mixed material small balls is 1 - 3 mm.

[0043] In step 3), the carbonization furnace is heated to 650 - 800 °C at a heating rate of 5 - 15 °C / min, with a carbonization time of 10 - 20 min and a nitrogen flow rate of 2.5 - 4 L / min.

[0044] Performance indicators of the biomass fuel: calorific value of combustion is 28 - 35 MJ / kg, fixed carbon content is 88% - 91%, ash content is 4% - 6%, volatile matter content is 5% - 6%, porosity is 10% - 20%, specific surface area is 5 - 15 m 2 / g, and density is 1.8 - 1.95 g / m 3 .

[0045] Application method of the biomass fuel, and the application method includes the following steps:

[0046] 1) Prepare fuel mixed material small balls of the biomass fuel, magnetite concentrate powder, limestone powder, and magnesite powder in a pelletizer; the fuel mixed material small balls take the biomass fuel ball material as the pelletizing core and are wrapped with magnetite concentrate powder, limestone powder, and magnesite powder on the outside.

[0047] 2) Mix hematite powder, limestone powder, magnesite powder, and coke powder through a mixer to prepare coke powder mixed material;

[0048] 3) Granulate the fuel mixed material small balls in step 1) and the coke powder mixed material in step 2) through a granulator, and the mass ratio of the fuel mixed material small balls to the coke powder mixed material is (2 - 7)∶(3 - 8); in the granulation process, the fuel mixed material small balls are used as the granulation core and are wrapped with the coke powder mixed material on the outside to make sintering mixed material, and the sintering mixed material is fed onto a sintering trolley for the production of sintered ore. The core of the sintering mixed material is the fuel mixed material small ball, and there is biomass fuel in the core. Since Fe3O4 in magnetite concentrate is easy to oxidize, Fe3O4 reacts with O2 to generate Fe2O3. In the oxidation process, part of the oxygen is consumed, reducing the combination speed of oxygen and biomass fuel, slowing down the combustion speed of biomass fuel, prolonging the mineralization process of sintered ore, and improving the quality of sintered ore. At the same time, make full use of the characteristic that heat is released during the oxidation process of magnetite concentrate. The released heat can be used for the sintering reaction of the mixed material mainly composed of hematite powder in the outer layer, thereby reducing the consumption of solid fuel in the sintering process.

[0049] The limestone powder and magnesite powder in the biomass fuel provide CaO and MgO for the core of the sintering mixed material; the limestone powder and magnesite powder in the fuel mixed material small balls provide CaO and MgO for the middle layer of the sintering mixed material; the limestone powder and magnesite powder in the coke powder mixed material provide CaO and MgO for the outer layer of the sintering mixed material; making the alkalinity and MgO content of the core, middle layer, and outer layer of the sintering mixed material uniform and improving the quality of sintered ore.

[0050] Step 1) The pelletizing time of the pelletizer is 5 - 8 minutes. After pelletizing, it is further compacted for 2 - 4 minutes. The water content of the fuel mixed pellets is 4.5% - 6% by mass fraction.

[0051] In step 1), the proportion of particles with a size less than 0.074 mm in the magnetite concentrate powder exceeds 90%; the proportion of particles with a size less than 3 mm in the limestone powder is 80% - 85%; the proportion of particles with a size less than 3 mm in the magnesite powder is 75% - 80%; the size of the prepared fuel mixed pellets is 3 - 6 mm.

[0052] In step 2), the proportion of particles with a size of 1 - 8 mm in the hematite powder is 45% - 55%; the proportion of particles with a size less than 3 mm in the limestone powder is 80% - 85%; the proportion of particles with a size less than 3 mm in the magnesite powder is 75% - 80%; the proportion of particles with a size less than 0.5 mm in the coke powder is 13% - 16%, the proportion of particles with a size of 0.5 - 3 mm is 70% - 73%, and the size of the remaining particles is greater than 3 mm.

[0053] The chemical composition of the limestone powder by mass fraction is: CaO: 50% - 55%, MgO: 2% - 4%, SiO2: 1% - 3%, Al2O3: 0.2% - 1.5%, and the balance is impurity elements.

[0054] The chemical composition of the magnesite powder by mass fraction is: CaO: 1.5% - 4%, MgO: 43% - 46%, SiO2: 9% - 11%, Al2O3: 0.3% - 2.5%, and the balance is impurity elements.

[0055] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0056] Example 1:

[0057] Preparation of a biomass fuel for iron ore sintering:

[0058] 1) Combine corn cobs and sorghum straws in a mass percentage ratio of 1:1, and perform crushing treatment with the particle size controlled within the range of 15 - 20 mm to obtain biomass blocks. Put the biomass blocks into a carbonization furnace, and introduce nitrogen into the furnace as a protective gas with a nitrogen flow rate of 1 L / min. The carbonization furnace is heated to 300°C at a heating rate of 2°C / min, and the carbonization time is 25 minutes to obtain biomass carbon blocks.

[0059] 2) Finely grind limestone powder and magnesite powder respectively to obtain finely ground limestone powder and finely ground magnesite powder, and the mass percentage of the two powders with a particle size less than 0.074 mm after fine grinding is 100%. The chemical composition mass fraction of limestone powder is: CaO: 50%, MgO: 2.5%, SiO2: 2.3%, Al2O3: 0.8%, and the remainder is impurity elements. The chemical composition mass fraction of magnesite powder is: CaO: 2.44%, MgO: 43.5%, SiO2: 9.3%, Al2O3: 0.8%, and the remainder is impurity elements.

[0060] 3) The biomass carbon block is crushed and the particle size is controlled to be below 0.1 mm. The crushed biomass carbon block, limestone powder, magnesite powder and carboxymethyl cellulose are fully mixed according to the mass percentage of 92%: 5%: 2.8%: 0.2%, respectively, and transported to a roller ball press to be pressed into balls to obtain biomass carbon mixed pellets. The particle size of the biomass carbon mixed pellets is controlled within the range of 1 to 3 mm, the water content is 4.5%, the alkalinity is 2.15, and the MgO mass fraction is 1.4%.

[0061] 4) The biomass carbon mixture pellets were placed in a carbonization furnace, and nitrogen was passed through the furnace as a protective gas with a nitrogen flow rate of 2.5 L / min. The carbonization furnace was heated to 800°C at a heating rate of 5°C / min, and the carbonization time was 10 min to obtain biomass fuel.

[0062] The performance indicators of biomass fuel are: fixed carbon 88.9%, ash 5.2%, volatile matter 5.9%. The porosity of the biomass fuel is 12%, and the specific surface area is 8m 2 / g, density is 1.93g / m 3 .

[0063] Application of biomass fuel for iron ore sintering:

[0064] 1) Magnetite concentrate powder, limestone powder, magnesite powder and biomass fuel are used in a pelletizing machine to prepare fuel mixture pellets. The fuel mixture pellets are made of biomass charcoal as the pelletizing core and are coated with magnetite concentrate powder, limestone powder and magnesite powder. The pelletizing time is 5 minutes, and the particle size of the fuel mixture pellets is controlled to be 3-6 mm. After the pelletizing time is over, continue to compact for 3 minutes. The proportion of particles with a particle size of less than 0.074 mm in the magnetite concentrate powder exceeds 95%; the proportion of particles with a particle size of less than 3 mm in the limestone powder is 82%-85%; the proportion of particles with a particle size of less than 3 mm in the magnesite powder is 75%-78%.

[0065] 2) Prepare a coke breeze mixture from hematite powder, limestone powder, magnesite powder, and coke breeze through a mixer. Its basicity is 2.15, and the mass fraction of MgO is 1.4%. The proportion of particles with a size of 1 - 8 mm in the hematite powder is 50% - 55%; the proportion of particles with a size less than 3 mm in the limestone powder is 80% - 82%; the proportion of particles with a size less than 3 mm in the magnesite powder is 78% - 80%; the proportion of particles with a size less than 0.5 mm in the coke breeze is 13% - 15%, the proportion of particles with a size of 0.5 - 3 mm is 70% - 72%, and the remaining particles have a size greater than 3 mm.

[0066] 3) Transport the fuel mixture pellets to a cylindrical pelletizer, and add the coke breeze mixture for secondary mixing and pelletizing. The ratio of the mass percentage of the fuel mixture pellets to the coke breeze mixture is 2:8. Prepare a sintering mixture, and distribute the sintering mixture onto a sintering trolley for the production of sinter ore.

[0067] To compare the application effect of the present invention, Comparative Example 1 uses a conventional sintering production process, with all sintering fuels being coke breeze, and other process parameters remaining the same.

[0068] Table 1: Comparison of the reduction amounts of SO2, NOx, and CO2 emissions in the sintering flue gas between Example 1 and Comparative Example 1

[0069]

[0070] It can be seen from the comparison results that, compared with Comparative Example 1, the reduction amounts of SO2, NOx, and CO2 emissions in the sintering flue gas of Example 1 are significantly reduced. The SO2 emissions in the sintering flue gas are reduced by 25.3%, and the NOx emissions in the sintering flue gas are reduced by 40.2%. Due to the improvement and innovation of the process, the overall consumption of sintered solid fuel is reduced, resulting in a 15.8% reduction in CO2 emissions in the sintering flue gas, and the emission reduction effect is obvious.

[0071] Table 2: Comparison of the sintering economic and technical indicators between Example 1 and Comparative Example 1

[0072]

[0073] After the application of the present invention, the drum strength of the sinter ore is increased from 79.8% to 81.6%, the consumption of sintered solid fuel is reduced from 52.3 kg / t to 47.2 kg / t, the low-temperature reduction degradation index RDI+3.15mm of the sinter ore is increased from 87.6% to 89.8%, and the improvement effect of the sinter ore quality and the reduction degree of solid fuel consumption are significant.

[0074] Example 2:

[0075] Preparation of a biomass fuel for iron ore sintering:

[0076] 1) Combine corn stalks, corn cobs, and sorghum stalks in a mass percentage of 1:1:1, and crush them to obtain biomass blocks with a particle size of 15 to 30 mm. Put the biomass blocks into a carbonization furnace, and pass nitrogen as a protective gas in the furnace with a nitrogen flow rate of 3 L / min. The carbonization furnace is heated to 500°C at a heating rate of 5°C / min, and the carbonization time is 15 minutes to obtain biomass carbon blocks.

[0077] 2) Finely grind limestone powder and magnesite powder respectively to obtain finely ground limestone powder and finely ground magnesite powder. After fine grinding, the mass percentage of the two particles with a particle size less than 0.074 mm is 100%. The chemical composition (mass fraction) of limestone powder is: CaO: 55%, MgO: 2.3%, SiO2: 1.6%, Al2O3: 0.3%, and the remainder is impurity elements. The chemical composition (mass fraction) of magnesite powder is: CaO: 3.6%, MgO: 45.8%, SiO2: 9.8%, Al2O3: 0.6%, and the remainder is impurity elements.

[0078] 3) The biomass carbon block is crushed and the particle size is controlled to be below 0.1 mm. The crushed biomass carbon block, finely ground limestone powder, finely ground magnesite powder and carboxymethyl cellulose are fully mixed according to the mass percentage of 94%: 3%: 2.6%: 0.4% respectively, and transported to a roller ball press to be pressed into balls to obtain biomass carbon mixed pellets. The particle size of the biomass carbon mixed pellets is controlled within the range of 1 to 3 mm, the water content is 6%, the alkalinity is 1.9, and the MgO mass fraction is 1.5%.

[0079] 4) Place the biomass charcoal mixture pellets into the carbonization furnace, and pass nitrogen as a protective gas in the furnace, with a nitrogen flow rate of 4L / min. The carbonization furnace is heated to 650℃ at a heating rate of 10℃ / min, and the carbonization time is 20min to obtain biomass fuel. The performance indicators of biomass fuel are: fixed carbon 90.5%, ash 4.1%, volatile matter 5.4%. The porosity is 17%, and the specific surface area is 12.5m 2 / g, density is 1.85g / m 3 .

[0080] Application of biomass fuel for iron ore sintering:

[0081] 1) Prepare fuel - mixed pellets in a pelletizer with magnetite concentrate powder, limestone powder, magnesite powder, and biomass fuel. The fuel - mixed pellets have biomass fuel as the granulation core, wrapped with magnetite concentrate powder, limestone powder, and magnesite powder. The pelletizing time is 8 min, and the particle size of the fuel - mixed pellets is controlled at 3 - 6 mm. After the pelletizing time ends, continue to compact for 2 min. The proportion of particles with a size less than 0.074 mm in the magnetite concentrate powder exceeds 92%; the proportion of particles with a size less than 3 mm in the limestone powder is 83% - 85%; the proportion of particles with a size less than 3 mm in the magnesite powder is 78% - 80%.

[0082] 2) Mix hematite powder, limestone powder, magnesite powder, and coke powder in a primary mixer to prepare a coke - powder mixture with an alkalinity of 1.9 and an MgO mass fraction of 1.5%. The proportion of particles with a size of 1 - 8 mm in the hematite powder is 50% - 52%; the proportion of particles with a size less than 3 mm in the limestone powder is 83% - 85%; the proportion of particles with a size less than 3 mm in the magnesite powder is 75% - 77%; the proportion of particles with a size less than 0.5 mm in the coke powder is 14% - 16%, the proportion of particles with a size of 0.5 - 3 mm is 73% - 75%, and the rest of the particles have a size greater than 3 mm.

[0083] 3) Transport the fuel - mixed pellets to a cylindrical pelletizer, and add the coke - powder mixture for secondary mixing and pelletizing. The mass - percentage ratio of the fuel - mixed pellets to the coke - powder mixture is 7:3. Prepare a sintering mixture, and distribute the sintering mixture onto a sintering trolley for the production of sintered ore.

[0084] To compare the implementation and application effects of the present invention, Comparative Example 2 uses a conventional sintering production process, with all sintering fuels being coke powder, and other process parameters remaining the same.

[0085] Table 3: Comparison of the reduction amounts of SO2, NOx, and CO2 emissions in the sintering flue gas between Example 2 and Comparative Example 2

[0086]

[0087] It can be seen from the comparison results that compared with Comparative Example 2, the reduction amounts of SO2, NOx, and CO2 emissions in the sintering flue gas of Example 2 are significantly reduced. The SO2 emissions in the sintering flue gas are reduced by 78.6%, and the NOx emissions in the sintering flue gas are reduced by 85.3%. Due to the improvement and innovation of the process, the overall consumption of sintered solid fuel is reduced, resulting in a 20.6% reduction in CO2 emissions in the sintering flue gas, and the emission reduction effect is obvious.

[0088] Table 4: Comparison of the sintering economic and technical indicators between Example 2 and Comparative Example 2

[0089]

[0090] After the implementation of the present invention, the drum strength of sinter increased from 79.8% to 82.8%, the solid fuel consumption of sinter decreased from 52.3 kg / t to 45.3 kg / t, and the low-temperature reduction degradation index RDI of sinter +3.15mm increased from 87.6% to 90.3, and the improvement effect of sinter quality and the reduction degree of solid fuel consumption were significant.

[0091] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biomass fuel for iron ore sintering, characterized in that, It is prepared by the following steps, and the specific steps include: 1) Biomass carbonization: After the biomass is crushed, it is put into a carbonization furnace, and nitrogen protective gas is introduced for carbonization to make biomass carbon blocks; 2) After the biomass carbon blocks are crushed, they are fully mixed with limestone powder, magnesite powder, and carboxymethyl cellulose according to the mass percentage of 92% - 94.5%: 3% - 5%: 2% - 3.5%: 0.2% - 0.5%, and then pressed into biomass carbon mixed material small balls; 3) Secondary carbonization: The biomass carbon mixed material small balls are put into a carbonization furnace, and nitrogen protective gas is introduced for carbonization to make biomass fuel.

2. The biomass fuel for iron ore sintering according to claim 1, wherein The biomass in step 1) is any one or more of corn straw, corn cob, and sorghum straw, and the crushing particle size of the biomass is controlled at 15 - 30 mm.

3. The biomass fuel for iron ore sintering according to claim 1, wherein, The carbonization furnace in step 1) is heated to 300 - 500 °C at a heating rate of 2 - 5 °C / min, the carbonization time is 15 - 25 min, and the nitrogen flow rate is 1 - 3 L / min.

4. The biomass fuel for iron ore sintering according to claim 1, wherein The crushing particle size of the biomass carbon blocks in step 2) is less than 0.1 mm, the particle sizes of the limestone powder and magnesite powder are less than 0.074 mm, and the particle size of the prepared biomass carbon mixed material small balls is 1 - 3 mm.

5. A biomass fuel for iron ore sintering according to claim 1, characterized in that, The carbonization furnace in step 3) is heated to 650 - 800 °C at a heating rate of 5 - 15 °C / min, the carbonization time is 10 - 20 min, and the nitrogen flow rate is 2.5 - 4 L / min.

6. The application method of the biomass fuel according to claim 1, wherein, The application method includes the following steps: 1) Prepare fuel mixed material small balls with the biomass fuel, magnetite concentrate powder, limestone powder, and magnesite powder in a pelletizer; The fuel mixed material small balls take the biomass fuel ball material as the pelletizing core, and are wrapped with magnetite concentrate powder, limestone powder, and magnesite powder on the outside. 2) Mix hematite powder, limestone powder, magnesite powder, and coke powder through a mixer to prepare coke powder mixture; 3) Granulate the fuel mixed material small balls in step 1) and the coke powder mixture in step 2) through a granulator. During the granulation process, the fuel mixed material small balls are used as the granulation core, and are wrapped with the coke powder mixture on the outside to make sintering mixture, and the sintering mixture is fed onto a sintering trolley for the production of sintered ore.

7. The application method of the biomass fuel according to claim 6, characterized in that, The pelletizing time of the pelletizer in step 1) is 5 - 8 min. After pelletizing, it is compacted for another 2 - 4 min.

8. The application method of the biomass fuel according to claim 6, characterized in that, In step 1), the proportion of particles with a particle size less than 0.074 mm in the magnetite concentrate powder exceeds 90%; the proportion of particles with a particle size less than 3 mm in the limestone powder is 80% - 85%; the proportion of particles with a particle size less than 3 mm in the magnesite powder is 75% - 80%; the particle size of the prepared fuel mixed material small balls is 3 - 6 mm.

9. The application method of the biomass fuel according to claim 6, wherein In step 2), the proportion of particles with a particle size of 1 - 8 mm in the hematite powder is 45% - 55%; the proportion of particles with a particle size less than 3 mm in the limestone powder is 80% - 85%; the proportion of particles with a particle size less than 3 mm in the magnesite powder is 75% - 80%; the proportion of particles with a particle size less than 0.5 mm in the coke powder is 13% - 16%, the proportion of particles with a particle size of 0.5 - 3 mm is 70% - 73%, and the remaining particles have a particle size greater than 3 mm.

10. The application method of the biomass fuel according to claim 6, wherein, The mass ratio of the fuel mixed material small balls to the coke powder mixture in step 3) is (2 - 7):(3 - 8).

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