Porous high reactivity carbon material, method for producing the same, and use thereof

Abstract

The present application relates to a kind of porous high reactivity carbon material and its preparation method and application, belong to carbonized fuel technical field.The material uses low rank coal as raw material, and is prepared by medium temperature pyrolysis method to obtain medium temperature pyrolysis carbon, then with medium temperature pyrolysis as raw material, after mixing calcium magnesium modifier, under the condition of steam, high temperature activation method is finally prepared.The specific surface area of the material is greater than 30 m 2 / g, total pore volume is greater than 25 cm³ / g, grindability index is greater than 55, CO2 reactivity is greater than 60.The material is mixed with pulverized coal injection into blast furnace after crushing, and is injected into blast furnace tuyere with hot air by using injection device and is burned, which can significantly improve the reaction performance of combustion, improve the stable operation of blast furnace smelting, and can greatly improve the coal ratio of blast furnace.

Description

Technical Field

[0001] This invention relates to a porous, highly reactive carbon material, as well as its preparation method and applications, belonging to the field of carbonized fuel technology. Background Technology

[0002] China's energy structure, characterized by abundant coal, scarce oil, and limited gas, means that coal resources will remain the primary energy source supporting the country's economic development for the foreseeable future. While high-quality anthracite and coking coal constitute a relatively small proportion of my country's coal reserves, low-rank coal with high volatile matter content is abundant. Therefore, how to efficiently utilize low-rank coal has become a key focus for the coal processing and consumption industries.

[0003] Blast furnace ironmaking requires a large amount of high-quality coke and anthracite resources. Applying low-rank coal to ironmaking production is a current technological direction for reducing steel production costs. Currently, most steel companies have applied bituminous coal to blast furnace injection production to replace expensive coke and anthracite. However, due to the high volatile matter content, low ignition point, and strong explosiveness of bituminous coal, its use in blast furnaces is limited.

[0004] To further increase the application rate of high-volatile low-rank coal in steel production, some enterprises are using semi-coke in blast furnace injection. Semi-coke is a product obtained from high-volatile coal under medium- and low-temperature dry distillation conditions, belonging to the category of semi-coke, and is not subject to government restrictions on enterprise coal consumption quotas. The grindability, combustibility, and injection characteristics of semi-coke differ significantly from those of pulverized coal (usually a mixture of anthracite and bituminous coal). Specifically, the grindability of semi-coke is significantly lower than that of anthracite and bituminous coal. Bituminous coal grindability is generally 60–75, anthracite is 55–65, while semi-coke is generally in the range of 45–55. This deterioration in grindability limits its application in ironmaking production.

[0005] Chinese patent CN104411838A discloses a "blast furnace pulverized coal and its manufacturing method". This method only involves improving the combustion performance of semi-coke products, but does not involve improving the grindability of semi-coke products. Summary of the Invention

[0006] The technical problem to be solved by this invention is to produce a porous, highly reactive and highly grindable carbon material from low-rank coal, so as to use it as fuel in blast furnace pulverized coal injection.

[0007] The first technical solution proposed by this invention to solve the above-mentioned technical problems is: a porous, highly reactive carbon material, characterized in that it is prepared by pyrolyzing low-rank coal at medium temperature to generate medium-temperature pyrolytic carbon, then mixing it with a calcium- and magnesium-rich modifier and passing it through high-temperature steam, wherein the specific surface area of ​​the porous, highly reactive carbon material is greater than 30 m². 2 / g, total pore volume greater than 25 cm³ / g, grindability index greater than 55, CO2 reactivity greater than 60.

[0008] Furthermore, the low-rank coal includes one or a mixture of lignite, long-flame coal, and bituminous coal; the calcium- and magnesium-rich modifier is one or a mixture of limestone and dolomite, and the amount of modifier added is 2%-8% of the mass of the medium-temperature pyrolysis carbon.

[0009] The second technical solution proposed by this invention to solve the above-mentioned technical problem is: providing a method for preparing a porous, highly reactive carbon material according to the first technical solution, comprising the following steps: (1) The low-rank coal is crushed and then transported to a drying furnace for dehydration and drying; (2) The dried low-rank coal is transported to a medium-temperature pyrolysis site to prepare medium-temperature pyrolysis char; (3) Using medium-temperature pyrolytic carbon as raw material, after mixing with calcium- and magnesium-rich modifiers, high-temperature steam is introduced for high-temperature activation to prepare porous and highly reactive carbon materials.

[0010] Furthermore, in step (1) of the above technical solution, the proportion of low-rank coal particles with a particle size of less than 5 mm after crushing exceeds 90%; hot flue gas is used as the drying medium, the drying temperature is 150℃-200℃, the drying time is 20min-120min, and the moisture content in the low-rank coal after drying is less than 5%.

[0011] Furthermore, in step (2) of the above technical solution, the temperature of the medium-temperature pyrolysis is 650 ℃-750 ℃, and the heating rate of the pyrolysis process is greater than 20 ℃ / min.

[0012] Furthermore, in step (2) of the above technical solution, the specific surface area of ​​the medium-temperature pyrolysis carbon is greater than 10 m². 2 / g, its total pore volume is greater than 15 cm³ / g, its grindability index is greater than 45, and its CO2 reactivity is greater than 55.

[0013] Furthermore, in step (3) of the above technical solution, the calcium-magnesium-rich modifier is one or a mixture of two of limestone and dolomite, and the amount of calcium-magnesium-rich modifier added accounts for 2%-8% of the mass of medium-temperature pyrolysis carbon.

[0014] Furthermore, in step (3) of the above technical solution, the high-temperature steam is superheated steam with a temperature of 800℃-950℃, and the high-temperature activation time is 30min-120min; after the activation reaction is completed, the steam is cooled and discharged from the furnace when the temperature is below 150℃, and then naturally cooled to the natural temperature.

[0015] The third technical solution proposed by the present invention to solve the above-mentioned technical problems is: the application of a porous highly reactive carbon material in the above-mentioned technical solution one, wherein the porous highly reactive carbon material is mixed with blast furnace pulverized coal, crushed, and then transported to the blast furnace tuyeres for injection and combustion.

[0016] The beneficial effects of the present invention are: 1) The porous high-reactivity carbon material provided by the present invention has a grindability index greater than 55 and a CO2 reactivity greater than 60. Therefore, it can overcome the defects of low grindability and poor reactivity of existing carbon materials prepared from low-rank coal, and is more suitable as fuel for blast furnace pulverized coal. 2) This invention provides a method for preparing porous, highly reactive carbon materials. Because the pyrolysis temperature is in the range of 700℃-750℃, the thermal decomposition reaction proceeds rapidly. The large amount of volatiles released during the thermal decomposition process results in pyrolytic carbon with a high porosity structure. Simultaneously, combined with the activation effect of calcium-magnesium-rich modifiers and high-temperature steam, the prepared porous carbon material has a high specific surface area and pore volume. The large specific surface area and pore volume increase the contact area between the carbon material and the gas during the reaction process. Therefore, when the porous, highly reactive carbon material prepared by this invention is applied to blast furnace pulverized coal injection, it can significantly improve the combustion reaction performance. The higher reaction characteristics facilitate rapid ignition and combustion of pulverized coal in front of the blast furnace tuyeres, reduce the content of unburned coal powder, improve the stable operation of blast furnace smelting, and significantly increase the coal ratio of the blast furnace.

[0017] Further theoretical analysis of the aforementioned beneficial effects of this invention is as follows: Research has found that in the process of upgrading low-rank coal through pyrolysis, controlling the pyrolysis temperature, reaction time, and reaction rate can control the two major reactions of depolymerization and condensation in the coal pyrolysis process. This ultimately affects the porosity and microcrystalline structure of the pyrolytic carbon, and consequently has a significant impact on the grindability, combustion performance, and CO2 reactivity of the pyrolytic carbon. Controlling the pyrolysis carbonization reaction temperature and activation temperature are key process parameters for preparing porous, highly reactive carbon materials. The grindability and reactivity are significantly correlated with the microcrystalline structure of the carbon material. During pyrolysis, as the temperature increases, the side chains of the raw coal molecules break, forming a large number of free radical molecules that escape. When the temperature is controlled within a certain range, the remaining carbon atoms have not yet polymerized to form a dense aromatic ring structure, resulting in highly reactive residual carbon material. Simultaneously, the dense carbon matrix of the raw coal is destroyed during pyrolysis, generating a large number of porous structures, which improves the grindability and reactivity of the carbon material obtained through pyrolysis. Steam activation promotes further expansion of the pore structure of pyrolytic carbon, increasing specific surface area and pore volume, reducing pore wall thickness and strength, and improving grindability and reactivity. Calcium-magnesium modifiers improve the activation effect of pyrolytic carbon and act as catalysts for combustion reactions, promoting efficient combustion of pulverized coal before the tuyeres and improving the combustion efficiency of injected fuel in the blast furnace. Calcium oxide and magnesium oxide are generated during the high-temperature modification process of limestone and dolomite. During cooling, these oxides absorb moisture from the air to form calcium hydroxide and magnesium hydroxide, which adhere to fine pyrolytic carbon powder, reducing dust generated by porous reactive carbon materials. Detailed Implementation

[0018] Example 1 The porous, highly reactive carbon material provided in this embodiment is prepared by medium-temperature pyrolysis of low-rank coal to produce medium-temperature pyrolytic carbon, then mixing it with a calcium- and magnesium-rich modifier and introducing high-temperature steam. The low-rank coal raw material used is lignite with a total water content of 25%, a volatile matter content of 43%, and an ash content of 4.6%. The preparation method is as follows: 1) Jaw crusher was used to crush the lump lignite, and the proportion of particles smaller than 5 mm in the crushed lignite reached 92%. The crushed lignite was then fed into a drying furnace for drying. Boiler hot flue gas was used as the drying medium, the temperature of the drying flue gas was controlled at 170℃, the drying time was 60 min, and the moisture content of the dried lignite particles was 4.2%.

[0019] 2) The dried lignite particles are loaded into a rotary kiln pyrolysis reaction vessel for medium-temperature pyrolysis carbonization reaction. During the pyrolysis process, the temperature is rapidly increased at a rate of 30℃ / min to reach 680℃. This pyrolysis temperature is maintained for 45 minutes to carry out the pyrolysis carbonization reaction and obtain medium-temperature pyrolysis carbon.

[0020] 3) Transfer the medium-temperature pyrolytic carbon generated by the pyrolysis carbonization reaction into the activation reactor, and add limestone powder accounting for 3% of the mass of the pyrolytic carbon; then pass high-temperature superheated steam at 830℃ into the activation reactor for activation reaction, the activation reaction time is 110min, after the activation reaction is completed, cool it, and when the temperature is below 150℃, discharge it out of the furnace, and then allow it to cool naturally to the ambient temperature, finally obtaining a porous high-reactivity carbon material.

[0021] The porous, highly reactive carbon material obtained above was subjected to composition and metallurgical performance tests, and the volatile matter content was 13.5%, the specific surface area was 32.5 m2 / g, the total pore volume was 30.2 cm³ / g, the grindability index was 58, and the reactivity index was 63.

[0022] The specific application of the porous highly reactive carbon material in this embodiment is as follows: The porous highly reactive carbon material is mixed with anthracite and bituminous coal injected into the blast furnace, wherein the porous highly reactive carbon material accounts for 35%, the anthracite accounts for 20%, and the bituminous coal accounts for 45%. The mixed material is pulverized using a medium-speed mill, and the three materials are mixed evenly during the pulverization process. After pulverization, the proportion of particles smaller than 0.074 mm in the mixture is 75%, and the moisture content is 1.5%. The pulverized mixture is then introduced into the blast furnace tuyeres through the coal storage bin and the injection device (injection tank, distributor, and spray gun) to mix and burn with hot blast, thereby providing reducing agent and heat for blast furnace smelting. The blast furnace hot blast temperature is 1200 ℃, the oxygen enrichment rate of the blast furnace hot blast is 3.5%, the blast blast humidity is 1.3%, and the theoretical combustion temperature in the blast furnace hot blast swirl zone is 2130 ℃. The combustion rate of the mixture containing the porous highly reactive carbon material of this embodiment reaches 73% before the blast furnace tuyeres, and the utilization rate inside the blast furnace is 98.3%.

[0023] Example 2 The porous highly reactive carbon material provided in this embodiment is basically the same as that in Example 1, except that: 1) the low-rank coal used is long-flame coal with high volatile matter content, with a total water content of 11.3% and a volatile matter content of 36%; 2) the final porous highly reactive carbon material obtained, after composition and metallurgical performance testing, has a volatile matter content of 11.6%, a specific surface area of ​​41.3 m2 / g, a total pore volume of 35.6 cm³ / g, a grindability index of 71, and a reactivity index of 66.

[0024] The preparation method of the porous highly reactive carbon material provided in this embodiment is basically the same as that in Example 1, except that: 1) The proportion of long-flame coal particles with a particle size of less than 5 mm reached 94% after crushing. The drying flue gas temperature was 195℃ and the drying time was 30 min. The moisture content of the long-flame coal particles after drying was 3.2%.

[0025] 2) During the pyrolysis process, the temperature is rapidly increased to 700℃ at a heating rate of 25℃ / min, and this pyrolysis temperature is maintained for 40min to carry out the pyrolysis carbonization reaction.

[0026] 3) Add limestone powder accounting for 5% of the mass of pyrolytic carbon; then pass high-temperature superheated steam at 890℃ into the activation reactor for activation reaction, and the activation reaction time is 40min.

[0027] The specific application of the porous highly reactive carbon material in this embodiment is basically the same as that in Example 1, except that: The blast furnace hot blast temperature is 1250 ℃, the oxygen enrichment rate is 4%, the blast humidity is 1.2%, and the theoretical combustion temperature in the tuyeres swirling zone is 2230 ℃.

[0028] Example 3 The porous highly reactive carbon material provided in this embodiment is basically the same as that in Example 1, except that: 1) the low-rank coal used is bituminous coal with high volatile matter content, with a total water content of 12.5% ​​and a volatile matter content of 28%; 2) the obtained porous highly reactive carbon material, after composition and metallurgical performance testing, has a volatile matter content of 12.1%, a specific surface area of ​​40.6 m2 / g, a total pore volume of 31.7 cm³ / g, a grindability index of 63, and a reactivity index of 69.

[0029] The preparation method of the porous highly reactive carbon material provided in this embodiment is basically the same as that in Example 1, except that: 1) The proportion of bituminous coal particles smaller than 5 mm after crushing reaches 93%, the drying flue gas temperature is 160℃, the drying time is 90 min, and the moisture content of the bituminous coal after drying is 3.5%.

[0030] 2) During the pyrolysis process, the temperature is rapidly increased to 730℃ at a heating rate of 35℃ / min, and this pyrolysis temperature is maintained for 35min to carry out the pyrolysis carbonization reaction.

[0031] 3) Add 3% dolomite powder and 4% limestone powder, which account for 3% of the mass of pyrolytic carbon; then pass high-temperature superheated steam at 810℃ into the activation reactor for activation reaction, and the activation reaction time is 100min.

[0032] The specific application of the porous highly reactive carbon material in this embodiment is basically the same as that in Example 1, except that: The blast furnace hot blast temperature is 1180 ℃, the oxygen enrichment rate is 5.3%, the blast humidity is 1.1%, and the theoretical combustion temperature in the tuyeres swirling zone is 2280 ℃.

[0033] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. For example, although the above embodiments only give lignite, long-flame coal and bituminous coal as a single type of low-rank coal, it is obvious that mixtures of lignite and long-flame coal, mixtures of long-flame coal and bituminous coal, mixtures of lignite and bituminous coal, or mixtures of lignite, long-flame coal and bituminous coal can all be used as low-rank coal raw materials for pyrolysis. All schemes formed by equivalent substitution or equivalent modification of the above embodiments according to the concept of the present invention should be covered within the protection scope of the present invention.

Claims

1. A porous, highly reactive carbon material, characterized in that, The porous, highly reactive carbon material is prepared by medium-temperature pyrolysis of low-rank coal to produce medium-temperature pyrolytic carbon, which is then mixed with a calcium- and magnesium-rich modifier and passed through high-temperature steam. The specific surface area of ​​the carbon material is greater than 30 m². 2 / g, total pore volume greater than 25 cm³ / g, grindability index greater than 55, CO2 reactivity greater than 60; the calcium-magnesium rich modifier is one or a mixture of two of limestone and dolomite, and the amount of modifier added is 2%-8% of the mass of the medium-temperature pyrolysis carbon raw material.

2. The porous, highly reactive carbon material according to claim 1, characterized in that: The low-rank coal includes one or a mixture of two or more of lignite, long-flame coal, and bituminous coal.

3. The method for preparing the porous, highly reactive carbon material according to claim 1, characterized in that... Includes the following steps: (1) The low-rank coal is crushed and then transported to a drying furnace for dehydration and drying; (2) The dried low-rank coal is transported to a medium-temperature pyrolysis site to prepare medium-temperature pyrolysis char; (3) Using medium-temperature pyrolytic carbon as raw material, after mixing with calcium- and magnesium-rich modifiers, high-temperature steam is introduced for high-temperature activation to prepare porous and highly reactive carbon materials.

4. The method for preparing the porous, highly reactive carbon material according to claim 3, characterized in that: In step (1), the proportion of low-rank coal particles with a particle size of less than 5 mm after crushing exceeds 90%. The drying process uses hot flue gas as the drying medium, with a drying temperature of 150℃-200℃ and a drying time of 20min-100min. The moisture content of the low-rank coal after drying is less than 5%.

5. The method for preparing the porous, highly reactive carbon material according to claim 3, characterized in that: In step (2), the medium-temperature pyrolysis temperature is 650 ℃-750 ℃, the pyrolysis time is 30-50 min, and the heating rate during the pyrolysis process is greater than 20 ℃ / min.

6. The method for preparing the porous, highly reactive carbon material according to claim 3, characterized in that: In step (2), the specific surface area of ​​the medium-temperature pyrolytic carbon is greater than 10 m². 2 / g, its total pore volume is greater than 15 cm³ / g, its grindability index is greater than 45, and its CO2 reactivity is greater than 55.

7. The method for preparing the porous, highly reactive carbon material according to claim 3, characterized in that: The high-temperature steam mentioned in step (3) is superheated steam with a temperature of 800℃-950℃. The high-temperature activation time is 30min-120min. After the high-temperature activation reaction is completed, the steam is cooled and discharged from the furnace when the temperature is below 150℃. Then it is naturally cooled to the natural temperature.

8. The application of the porous, highly reactive carbon material according to claim 1, characterized in that: The porous, highly reactive carbon material is mixed with blast furnace pulverized coal, crushed, and then transported to the blast furnace tuyeres for injection and combustion.

9. The application of the porous, highly reactive carbon material according to claim 8, characterized in that: The percentage of the porous, highly reactive carbon material to the pulverized coal injected into the blast furnace is 5%-90%. After crushing, the proportion of pulverized fuel particles smaller than 0.074 mm is greater than 60%, and the moisture content is less than 1.6%. The hot blast temperature at the blast furnace tuyeres is greater than 1100 ℃, the oxygen enrichment rate is greater than 3%, the blast humidity is less than 1.4%, and the theoretical combustion temperature in the tuyeres swirling zone is 2100 ℃~2300 ℃.