Method for promoting secondary pyrolysis polycondensation reaction of semicoke

Abstract

The invention discloses a method for promoting secondary pyrolysis condensation polymerization of semicoke, and belongs to the field of coal utilization and clean energy. The method comprises the following steps: firstly, pre-pyrolyzing raw coal by using a dropper furnace heating reactor to obtain rapid pyrolysis semicoke; in the secondary pyrolysis process, raw coal is placed on the upper section of the two-section furnace heating reactor, the temperature is set to be 500 DEG C, rapid pyrolysis semicoke is placed on the lower section of the two-section furnace heating reactor, the temperature is set to be 700 DEG C, and rapid pyrolysis is carried out. Tar generated by pyrolysis of the raw coal on the upper layer is carried by 200 mL / min N2 to penetrate through a semi-coke bed layer, and in addition, independent secondary pyrolysis is carried out on the fast pyrolysis semi-coke for comparison. Compared with independent pyrolysis, the coal pyrolysis tar obviously promotes the increase of aromatic nucleus stripes in the secondary pyrolysis process, and the semi-coke yield is also increased.

Description

Technical Field

[0001] The present invention provides a method for utilizing the polycondensation reaction between pyrolytic coke and semicoke of coal, which relates to the fields of coal utilization and clean energy, and more specifically, to a method for promoting the polycondensation reaction of semicoke pyrolysis. Background Art

[0002] As an important part of traditional fossil energy, coal has long dominated the global energy system. Coal pyrolysis is an essential stage in various other conversion processes and is of great significance to multiple industrial fields. Advanced pyrolysis technologies can enhance the utilization value of low-rank coal and are the core methods for the efficient and clean utilization of coal resources. The polycondensation reaction is one of the important reaction stages in the coal pyrolysis process. Understanding the polycondensation reaction mechanism helps to construct a coal pyrolysis prediction model and accurately control the distribution of pyrolysis products according to the requirements of downstream industries.

[0003] The coal pyrolysis polycondensation reaction generally occurs under relatively high temperature conditions (>600 °C), and a longer residence time usually favors the occurrence of the polycondensation reaction. Under suitable reaction conditions, the main way of the polycondensation reaction is that the aromatic structural units in coal form larger aromatic structures through free radical coupling, dehydrogenation polycondensation, etc.

[0004] Semicoke with a high degree of polycondensation reaction usually has a higher carbon content, a denser structure and higher thermal stability, and can be used to prepare electrode materials, fireproof materials, etc., with broad application prospects. However, in the current interaction between tar and semicoke structures, semicoke with a relatively high degree of pyrolysis is mostly used as the raw material, and its ability to undergo polycondensation reaction is poor, making it difficult to further expand its aromatic nucleus structure. Summary of the Invention

[0005] In view of the fact that in the traditional coal pyrolysis method, only the way of changing the heating conditions can be used to explore the occurrence path of the polycondensation reaction, the present invention proposes a co-pyrolysis synergistic regulation method for coal pyrolysis tar and semicoke. Using the relatively simply structured fast pyrolysis semicoke as the raw material, a two-stage furnace heating reactor is used. The raw coal is placed in the upper layer, and the fast pyrolysis semicoke is placed in the lower layer. Under the fast pyrolysis conditions, the tar generated by the pyrolysis of the raw coal in the upper layer is carried by N2 through the semicoke bed layer for secondary pyrolysis.

[0006] The technical solution adopted by the present invention is as follows: A method for promoting the secondary pyrolysis polycondensation reaction of semicoke, comprising the following steps: (1) After grinding and drying the raw coal, the raw coal is rapidly pyrolyzed by using a dropping tube furnace heating reactor to obtain fast pyrolysis semicoke; (2) In a two-stage furnace heating reactor, the raw coal is placed in the upper reaction tube, the fast pyrolysis semicoke is placed in the lower reaction tube, and N2 is purged; (3) Heat the upper heating zone and the lower heating zone. After the reaction zone reaches the target temperature, push the reaction tube into the furnace for secondary pyrolysis.

[0007] Further, in the step (1), the temperature of the rapid pyrolysis is 500 - 550 °C.

[0008] Further, in the step (2), the mass ratio of raw coal to rapid pyrolysis semicoke is 1:(2 - 3).

[0009] Further, when purging with N2 in the step (2), the flow rate of N2 is 200 mL / min.

[0010] Further, in the step (3), the target temperature of the upper heating zone is 500 - 550 °C and that of the lower heating zone is 700 - 750 °C.

[0011] Further, in the step (3), the time of the secondary pyrolysis is 20 min.

[0012] Further, the raw material of the present invention is low-rank coal, such as Naomaohu coal in Xinjiang and Hongliulin coal in Shaanxi.

[0013] Further, the present invention has carried out pre-pyrolysis experiments on raw coal, and the preferred pre-pyrolysis temperature is 500 °C.

[0014] Further, the pyrolysis reaction of the present invention is carried out under an N2 atmosphere. Preferably, coal pyrolysis tar is generated at 500 °C, and the preferred co-pyrolysis temperature is 700 °C.

[0015] Further, the heating condition selected by the present invention is rapid heating, and the heating rate is about 1×10 4 °C / min.

[0016] Compared with the prior art, the beneficial effects that can be significantly achieved by the solution of the present invention are as follows: (1) The coal pre-pyrolysis method provided by the present invention performs rapid pyrolysis of coal in a dropping tube furnace with a short residence time. While effectively simplifying the coal structure, it retains a chemical environment similar to that of raw coal and strong thermal reactivity.

[0017] (2) The co-pyrolysis method of coal pyrolysis tar and semicoke provided by the present invention effectively improves the yield and quality of secondary pyrolysis tar. By changing the height of the semicoke bed layer, the tar composition can be regulated, the content of heavy oil in the tar can be reduced, and the utilization value of the tar can be improved, which has important significance for the efficient and clean utilization of coal resources and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a two-stage furnace heating reactor; Figure 2It is a schematic diagram of the size distribution of aromatic nucleus stripes of secondary pyrolysis semicoke; Figure 3 is the yield of secondary pyrolysis semicoke. Specific implementation manner

[0019] The following further illustrates the method through specific embodiments, but does not limit the present invention thereby. The following non-limiting embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0020] In the following embodiments, the test methods are all conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0021] The two-stage furnace heating reactor is as Figure 1 shown, mainly including three parts: a reaction zone, tar collection, and gas collection. After drying and grinding the raw coal to a certain particle size, it is pre-treated by rapid pyrolysis under short residence time. In the secondary pyrolysis experiment, the upper reaction tube is pre-heated to 500 °C, the lower tube is heated to 700 °C, and purged with N2 at a flow rate of 200 mL / min for 15 min to remove the air in the reaction tube. Place 1 g of raw coal in the upper reaction tube and 2 g of rapidly pyrolyzed semicoke in the lower reaction tube. When the temperature of the heating furnace reaches the target temperature, the reaction tube is pushed into the furnace for pyrolysis experiment and kept at a constant temperature for 20 min. The tar generated by the pyrolysis of the upper-layer raw coal at 500 °C follows the carrier gas to the semicoke bed layer in the lower tube, realizing the secondary pyrolysis of rapidly pyrolyzed semicoke in a tar atmosphere.

[0022] The calculation formula for the yield of secondary pyrolysis semicoke (dry ash-free basis) is as follows:

[0023] Where Y is the yield of secondary pyrolysis semicoke, W 0, W 1 are the mass of secondary pyrolysis semicoke and the mass of rapidly pyrolyzed semicoke respectively; A ad is the ash content (air-dried basis) of rapidly pyrolyzed semicoke; M ad is the moisture content (air-dried basis) of rapidly pyrolyzed semicoke.

[0024] The raw coal of the present invention can be low-rank coals such as Xinjiang Naomaohu coal and Shaanxi Hongliulin coal. This embodiment further illustrates the present invention by taking Shaanxi Hongliulin coal as an example. Example 1

[0025] The method for promoting the coal pyrolysis polycondensation reaction provided in this embodiment includes the following steps: (1)Grind and screen raw coal to less than 120 mesh, and dry for standby; (2)Use a drop tube furnace to heat the reactor to pyrolyze raw coal rapidly at 500 °C respectively to obtain rapidly pyrolyzed char with simplified structure.

[0026] (3)In a two-stage furnace heating reactor, place 1 g of raw coal in the upper reaction tube and 2 g of the rapidly pyrolyzed char prepared in step (2) in the lower reaction tube. Purge with N2 at 200 mL / min for 15 min to remove the air in the reaction tube; the sample number is recorded as 1-2.

[0027] (4)Heat the upper heating zone to 500 °C and the lower heating zone to 700 °C. After the reaction zone reaches the target temperature, push the reaction tube into the furnace for secondary pyrolysis experiment. Use N2 at 200 mL / min as the protective gas, and the residence time is 20 min. The relatively high heating rate and long residence time ensure the full occurrence of the polycondensation reaction.

[0028] (5)Perform HRTEM characterization and analysis on the secondary pyrolyzed char prepared in step (4). The results show that the content of 1×1 small aromatic nucleus stripes in the secondary pyrolyzed char is 39.85%, the content of large aromatic nucleus stripes above 4×4 accounts for 17.20%, and the char yield is 71.03%. ( Figure 2 、 Figure 3 ) Example 2

[0029] The difference between this example and Example 1 is that in step (3), 3 g of rapidly pyrolyzed char is placed in the lower reaction tube, and the sample number is recorded as 1-3. The HRTEM characterization results of the secondary pyrolyzed char show that the content of 1×1 small aromatic nucleus stripes is 42.91%, the content of large aromatic nucleus stripes above 4×4 accounts for 15.40%, and the char yield is 72.89%. ( Figure 2 、 Figure 3 ) Comparative Example 1

[0030] The difference between this comparative example and Example 1 is that in step (3), no raw coal is placed in the upper reaction tube, and the sample number is recorded as 0-2. The HRTEM characterization results of the secondary pyrolyzed char show that the content of 1×1 small aromatic nucleus stripes is 46.91%, the content of large aromatic nucleus stripes above 4×4 accounts for 13.10%, and the char yield is 70.67%. ( Figure 2 、 Figure 3 ) Comparative Example 2

[0031] The difference between this comparative example and Example 1 lies in that in step (3), raw coal is not placed in the upper reaction tube, and the sample number is recorded as 0-3. The HRTEM characterization results of the secondary pyrolysis semicoke show that the content of 1×1 small aromatic nucleus stripes is 48.27%, the content of large aromatic nucleus stripes with 4×4 or more accounts for 12.83%, and the semicoke yield is 72.59%. ( Figure 2 , Figure 3 ) The results show that the participation of coal pyrolysis tar significantly promotes the occurrence of the condensation reaction during the secondary pyrolysis of semicoke. Compared with the secondary pyrolysis of semicoke alone, the aromatic nucleus stripe size of the secondary pyrolysis semicoke generated by the co-pyrolysis of tar and semicoke increases significantly, and the semicoke yield increases. ( Figure 2 , Figure 3 ) As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for promoting the secondary pyrolysis and polycondensation reaction of semi-coke, characterized in that: The following steps are involved: (1) After the raw coal is ground and dried, the raw coal is rapidly pyrolyzed in a drop tube furnace heating reactor to obtain rapid pyrolysis semi-coke; (2) In a two-stage furnace heating reactor, the raw coal is placed in the upper reaction tube, and the rapid pyrolysis semi-coke is placed in the lower reaction tube, and N2 is purged; (3) Heat the upper heating zone and the lower reaction zone. After the reaction zone reaches the target temperature, push the reaction tube into the furnace for secondary pyrolysis.

2. The method according to claim 1, characterized in that In the step (1), the temperature of rapid pyrolysis is 500-550°C.

3. The method according to claim 1, characterized in that In the step (1), the raw coal is Xinjiang Naomaohu coal or Shaanxi Hongliulin coal.

4. The method according to claim 1, characterized in that In the step (2), the mass ratio of the raw coal to the rapid pyrolysis semi-coke is 1:(2-3).

5. The method according to claim 1, characterized in that During the N2 purging in step (2), the N2 flow rate is 200 mL / min.

6. The method according to claim 1, characterized in that In step (3), the target temperature of the upper heating zone is 500-550°C and that of the lower heating zone is 700-750°C.

7. The method according to claim 1, characterized in that In the step (3), the secondary pyrolysis time is 20 min.

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