A roasting furnace flue gas treatment system

Abstract

A flue gas treatment system for a roasting furnace in the technical field of high-temperature flue gas treatment, comprising a cooling device, a purification device, a filtration device, a heat exchange box, a high-temperature furnace box and a low-temperature furnace box; flue gas discharge pipes are provided at the tops of the high-temperature furnace box and the low-temperature furnace box; an interlayer cavity is provided on the box wall of the low-temperature furnace box, and the interlayer cavity is connected with a smoke inlet pipe and a smoke outlet pipe, and the smoke outlet pipe is sequentially connected with the cooling device and the purification device; heat exchange coils are arranged in the heat exchange box, and two ends of the heat exchange coils are respectively connected with the smoke inlet pipe and the flue gas discharge pipe of the high-temperature furnace box; a hot air inlet pipe and a heating air outlet pipe are respectively provided on the top wall and the bottom wall of the heat exchange box, the hot air inlet pipe of the heat exchange box and the flue gas discharge pipe of the low-temperature furnace box are respectively connected with the outlet and the inlet of the filtration device, and the outer end of the heating air outlet pipe is communicated with the low-temperature furnace box through a diffuser pipe; this flue gas treatment system can utilize the temperature difference in use of different process roasting furnaces to comprehensively improve the purification effect of high-temperature flue gas and the waste heat utilization rate.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature flue gas treatment, and in particular to a flue gas treatment system for a roasting furnace. Background Art

[0002] The production process of graphite electrodes includes raw material calcination, extrusion, roasting, impregnation, graphitization, and machining forming; among them, the roasting process can greatly improve the thermal stability, mechanical strength, and conductivity of materials. The main roasting furnace types used are tunnel kilns, inverted flame kilns, box-type roasting furnaces, etc. The roasting fuels include solid fuels and combustion gases. However, regardless of the form of the roasting furnace, a large amount of high-temperature flue gas will be generated after roasting the electrodes. The flue gas contains pollutants such as carbon monoxide, sulfur dioxide, and halogen salts. Therefore, the flue gas of traditional roasting furnaces will be cooled, purified, etc. before being discharged into the atmosphere.

[0003] Due to different requirements for the production quality of graphite electrodes, in the existing production process, graphite electrodes are often roasted more than once. The common production form requires at least two roasts. The temperature of the first roast is relatively high, usually more than 1200 degrees. Then, the electrodes will be impregnated and then roasted a second time at more than 700 degrees. The impregnation is generally asphalt impregnation. Therefore, the second roast can remove the volatile components in the asphalt. To ensure the continuity of production, two separate roasting furnaces are used for the two roasts. Although each roasting furnace works independently, most production plants will collect and directly treat the generated flue gas. This treatment method not only ignores the differences in the composition and content of the flue gas from the two roasts, reduces the treatment efficiency, and increases the purification cost, but also has a low utilization rate of the waste heat after heat exchange and cooling of the high-temperature flue gas. Summary of the Invention

[0004] In order to overcome the deficiencies in the background art, the present invention discloses a flue gas treatment system for a roasting furnace, which can utilize the temperature difference in the use of different process roasting furnaces to comprehensively improve the purification effect of high-temperature flue gas and the utilization rate of waste heat.

[0005] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0006] A roasting furnace flue gas treatment system includes a cooling device, a purification device, a filtering device, a heat exchange box, a high-temperature furnace box, and a low-temperature furnace box. Horizontal heat transfer partition plates are provided inside the boxes of the high-temperature furnace box and the low-temperature furnace box. The heat transfer partition plates divide the corresponding box interiors into an upper material storage chamber and a lower combustion chamber. Feed inlets and flue gas discharge pipes are provided at the tops of the high-temperature furnace box and the low-temperature furnace box. A sandwich cavity is provided in the box wall of the low-temperature furnace box. The sandwich cavity is connected with a smoke inlet pipe and a smoke outlet pipe. The smoke outlet pipe is sequentially connected to a cooling device for cooling the flue gas and a purification device for purifying the flue gas. Heat exchange coils are provided in the heat exchange box. Both ends of the heat exchange coils are hermetically passed through the box wall of the heat exchange box and are respectively connected to the smoke inlet pipe of the sandwich cavity and the flue gas discharge pipe of the high-temperature furnace box correspondingly. A first exhaust fan is installed on the flue gas discharge pipe of the high-temperature furnace box. The top wall and the bottom wall of the heat exchange box are respectively provided with a hot gas inlet pipe and a heating gas outlet pipe. The hot gas inlet pipe of the heat exchange box and the flue gas discharge pipe of the low-temperature furnace box are respectively connected to the outlet and the inlet of the filtering device. The outer end of the heating gas outlet pipe is connected with a second exhaust fan. The air outlet of the second exhaust fan is communicated with the low-temperature furnace box through a diffuser pipe.

[0007] Further, the filtering device includes a filtering box body. A unit box body with a breathable structure is detachably inserted into the filtering box body. An adsorbent is filled in the unit box body. The outlet and the inlet of the filtering box body are respectively arranged on opposite side box walls.

[0008] Further, the purification device includes a purification box body. The purification box body is divided into a right cavity filled with a purification agent and a left cavity filled with water at the lower part by a vertical partition plate. A through hole communicating the left cavity and the right cavity is provided at the top of the vertical partition plate. A purification inlet is provided at the bottom wall corresponding to the right cavity. An insertion pipe is provided at the upper part of the left cavity. One end of the insertion pipe is hermetically inserted into the through hole, and the other end of the insertion pipe extends into the water in the left cavity. A purification outlet is provided at the top wall corresponding to the left cavity.

[0009] Further, the cooling device is set as a heat exchange device with a tube side and a shell side. The smoke outlet pipe is connected to the tube side, and cooling water is introduced into the shell side.

[0010] Further, the sandwich cavity is set as an annular cavity along the side wall of the low-temperature furnace box for one week. The smoke inlet pipe and the smoke outlet pipe of the sandwich cavity are respectively arranged on opposite side walls of the low-temperature furnace box.

[0011] Further, a groove is provided on the inner side wall of the low-temperature furnace box. A heat conduction plate is covered on the groove opening to form a sandwich cavity.

[0012] Further, a perforation is provided at the center of the plate surface of the heat transfer partition plate in the low-temperature furnace box. The outer end of the diffuser pipe is connected to the air outlet of the second exhaust fan. The inner end of the diffuser pipe is upwardly and adaptively passed through the perforation of the heat transfer partition plate from the lower combustion chamber of the low-temperature furnace box, and the inner end port of the diffuser pipe is closed. Air permeable holes are provided on the inner end pipe wall.

[0013] Further, the inner port of the gas diffuser is covered with a distribution cone. A buffer chamber is arranged inside the distribution cone. A central hole communicating the buffer chamber and the inner end of the gas diffuser is arranged at the center of the bottom surface of the distribution cone. A plurality of air permeable holes communicating the buffer chamber and the low-temperature furnace chamber are evenly arranged at the outer edge of the bottom surface of the distribution cone.

[0014] Due to the adoption of the above-mentioned technical solution, the present invention has the following beneficial effects:

[0015] The roasting furnace flue gas treatment system disclosed by the present invention can utilize the temperature difference between the high-temperature furnace chamber used in the primary roasting and the low-temperature furnace chamber used in the secondary roasting. The flue gas generated in the secondary roasting is filtered and then introduced into the heat exchange box for recycling. The high-temperature flue gas discharged from the high-temperature furnace chamber is used to transfer waste heat to the low-temperature furnace chamber, and after heat exchange with the secondary roasting flue gas in the heat exchange box, it is introduced into the sandwich cavity of the low-temperature furnace chamber for heat preservation. The secondary roasting flue gas that is heated after heat exchange can be directly introduced into the low-temperature furnace chamber to provide part of the secondary roasting temperature and fuel. This not only greatly reduces the fuel consumption in the secondary roasting, but also, due to the heat exchange and reuse during the dynamic flow process of gases in the early stage, the waste heat utilization in the high-temperature stage can be more sufficient, with better utilization rate and utilization effect, and it is more suitable for the production process of multiple roastings. In addition, the primary roasting flue gas and the secondary roasting flue gas are separately purified. The secondary roasting flue gas is treated by filtration and re-combustion, and the primary roasting flue gas is treated by multi-stage purification, which also greatly improves the treatment effect and reduces the treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0017] Figure 2 is a schematic structural diagram of the filtering device;

[0018] Figure 3 is a schematic structural diagram of the purification device;

[0019] Figure 4 is a schematic cross-sectional structural diagram of the low-temperature furnace chamber;

[0020] Figure 5 is a schematic structural diagram of the gas diffuser.

[0021] In the figure: 1. High-temperature furnace chamber; 2. First exhaust fan; 3. Filter device; 301. Filter box body; 302. Unit box body; 303. Adsorbent; 4. Low-temperature furnace chamber; 5. Diffuser pipe; 6. Heat conduction plate; 7. Interlayer cavity; 8. Smoke outlet pipe; 9. Distribution cone; 901. Buffer cavity; 902. Central hole; 903. Ventilation hole; 10. Second exhaust fan; 11. Heat exchange coil; 12. Heat exchange box; 13. Heat transfer partition board; 14. Lower combustion chamber; 15. Cooling device; 16. Purification device; 1601. Purification box body; 1602. Purifying agent; 1603. Purification inlet; 1604. Vertical partition board; 1605. Purification outlet; 1606. Insertion pipe. Specific implementation mode

[0022] The following will describe the technical solutions of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. In the description, it should be understood that if there are terms such as "upper", "lower", "front", "rear", "left", "right", etc. indicating the orientation or positional relationship, they are only corresponding to the accompanying drawings of the present invention for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation:

[0023] Combined with the attached Figures 1-5 The described roasting furnace flue gas treatment system includes a cooling device 15, a purification device 16, a filtering device 3, a heat exchange box 12, a high-temperature furnace chamber 1 and a low-temperature furnace chamber 4. The high-temperature furnace chamber 1 is used for primary roasting above 1200 degrees. Generally, the high-temperature flue gas generated in the high-temperature furnace chamber 1 will also be more than 1000 degrees. The low-temperature furnace chamber 4 is used for secondary roasting above 700 degrees; horizontal heat transfer partition boards 13 are arranged in the box bodies of the high-temperature furnace chamber 1 and the low-temperature furnace chamber 4. The heat transfer partition board 13 divides the corresponding box body into an upper material storage chamber and a lower combustion chamber 14. The upper plate surface of the heat transfer partition board 13 is used for placing graphite electrodes. Feed inlets and flue gas discharge pipes are arranged at the tops of the high-temperature furnace chamber 1 and the low-temperature furnace chamber 4. The heat transfer partition board 13 is generally set as a grid-shaped or mesh-shaped plate to facilitate direct heat transfer. The graphite electrodes are placed on the heat transfer partition board 13 from the feed inlet. The fuel in the lower combustion chamber 14 burns to heat up the graphite electrodes for roasting, and the generated high-temperature flue gas will be discharged from the flue gas discharge pipe;

[0024] The wall of the low-temperature furnace chamber 4 is provided with an interlayer cavity 7, which is mainly used to introduce higher-temperature flue gas to heat and keep warm the inside of the low-temperature furnace chamber 4; as required, a groove is provided on the inner side wall of the low-temperature furnace chamber 4, and the groove opening of the groove is covered with a heat-conducting plate 6 to form the interlayer cavity 7. The heat-conducting plate 6 is sealed with the groove opening to prevent leakage, and the heat-conducting plate 6 ensures good heat transfer efficiency; the interlayer cavity 7 is connected with a smoke inlet pipe and a smoke outlet pipe 8, and the higher-temperature flue gas can enter from the smoke inlet pipe and discharge from the smoke outlet pipe 8; as required, the interlayer cavity 7 is set as an annular cavity along the side wall of the low-temperature furnace chamber 4, and the smoke inlet pipe and the smoke outlet pipe 8 of the interlayer cavity 7 are respectively arranged on the opposite side walls of the low-temperature furnace chamber 4, so as to ensure that the flue gas circulates fully in the interlayer cavity 7 and achieve a better heat preservation effect; the smoke outlet pipe 8 is sequentially connected with a cooling device 15 for cooling the flue gas and a purification device 16 for purifying the flue gas; as required, the cooling device 15 is set as a heat exchange device with a tube side and a shell side, the smoke outlet pipe 8 is connected to the tube side, and cooling water is introduced into the shell side. The cold water can be heated and used for other purposes after that; in addition, the purification device 16 includes a purification box body 1601, which is divided into a right cavity filled with a purification agent 1602 and a left cavity filled with water at the lower part by a vertical partition plate 1604. A through hole for connecting the left cavity and the right cavity is provided at the top of the vertical partition plate 1604. A purification inlet 1603 is provided at the bottom wall corresponding to the right cavity, an insertion tube 1606 is provided at the upper part of the left cavity, one end of the insertion tube 1606 is hermetically inserted into the through hole, the other end of the insertion tube 1606 extends into the water in the left cavity, and a purification outlet 1605 is provided at the top wall corresponding to the left cavity. The once-calcined flue gas cooled by the cooling device 15 enters the right cavity from the purification inlet 1603, is purified by the purification agent 1602 in the right cavity, is introduced into the water by the insertion tube 1606, the pollutants are captured by the water, and then discharged into the atmosphere through the purification outlet 1605. The purification effect can be greatly improved through multi-stage purification; in addition, two types of purification agents 1602 can be set according to the flue gas components, and the two purification agents 1602 are arranged diagonally in the right cavity corresponding to the purification inlet 1603 and the purification outlet 1605 respectively, and are purified by making full contact;

[0025] Inside the heat exchange box 12, there is a heat exchange coil 11. Both ends of the heat exchange coil 11 are hermetically passed through the wall of the heat exchange box 12 and are respectively connected to the smoke inlet pipe of the sandwich cavity 7 and the flue gas discharge pipe of the high-temperature furnace box 1. A first exhaust fan 2 is installed on the flue gas discharge pipe of the high-temperature furnace box 1. Through the first exhaust fan 2, the flue gas of the high-temperature furnace box 1 can be extracted, sent into the sandwich cavity 7 after passing through the heat exchange coil 11; the top wall and the bottom wall of the heat exchange box 12 are respectively provided with a hot gas inlet pipe and a heated gas outlet pipe. The hot gas inlet pipe of the heat exchange box 12 and the flue gas discharge pipe of the low-temperature furnace box 4 are respectively connected to the outlet and the inlet of the filtering device 3, ensuring that the secondary roasting flue gas in the low-temperature furnace box 4 can pass through the filtering device 3 to filter out pollutants such as asphalt volatile components and then be recycled for combustion; as needed, the filtering device 3 includes a filtering box body 301. Inside the filtering box body 301, a unit box body 302 with a breathable structure is detachably inserted. An adsorbent 303 is filled in the unit box body 302. The outlet and the inlet of the filtering box body 301 are respectively arranged on the opposite side walls. The filtering box body 301 is provided with a box cover, which is usually hermetically connected. When the adsorbent 303 in the unit box body 302 is saturated and needs to be replaced, the box cover can be opened, and the unit box body 302 can be taken out for quick replacement; the outer end of the heated gas outlet pipe is connected to a second exhaust fan 10. The air outlet of the second exhaust fan 10 is communicated with the low-temperature furnace box 4 through a diffuser pipe 5. After the secondary roasting flue gas enters from the hot gas inlet pipe, it is heat-exchanged in the heat exchange box 12, extracted by the second exhaust fan 10, and then sent into the low-temperature furnace box 4 for secondary temperature-raising roasting, which not only improves the waste heat utilization rate but also can treat the combustible components in the flue gas through secondary full combustion;

[0026] As needed, a perforation is provided at the center of the plate surface of the heat transfer partition 13 in the low-temperature furnace box 4. The outer end of the diffuser pipe 5 is connected to the air outlet of the second exhaust fan 10. The inner end of the diffuser pipe 5 is adaptively passed upward through the perforation of the heat transfer partition 13 from the lower combustion chamber 14 of the low-temperature furnace box 4, and the inner end port of the diffuser pipe 5 is closed. The inner end pipe wall is provided with air-permeable holes 903. Through the air-permeable holes 903, high-temperature air is directly discharged for heat dissipation to the upper material storage chamber. When the temperature reaches the requirement, the combustion chamber of the low-temperature furnace box 4 can not be started. If the temperature does not reach, the combustion chamber of the low-temperature furnace box 4 needs to be started to supplement the temperature and fully combust the secondary roasting flue gas at the same time; in addition, a distribution cone 9 is provided at the inner end port of the diffuser pipe 5. A buffer cavity 901 is provided in the distribution cone 9. A central hole 902 communicating the buffer cavity 901 and the inner end of the diffuser pipe 5 is provided at the center of the bottom surface of the distribution cone 9. A plurality of air-permeable holes 903 communicating the buffer cavity 901 and the low-temperature furnace box 4 are uniformly provided at the outer edge of the bottom surface of the distribution cone 9. The distribution cone 9 is beneficial to the uniform feeding of the low-temperature furnace box 4. At the same time, the downward arrangement structure of the air-permeable holes 903 can prevent solid debris from entering the diffuser pipe 5 through the air-permeable holes 9; when the space of the upper material storage chamber is large and the height of the diffuser pipe 5 is high, a plurality of distribution cone 9 structures can be arranged at intervals along the axial direction of the diffuser pipe 5.

[0027] Implementing the roasting furnace flue gas treatment system of the present invention can utilize the temperature difference between the high-temperature furnace chamber 1 used for primary roasting and the low-temperature furnace chamber 4 used for secondary roasting. Under the action of the first induced draft fan 2, the high-temperature flue gas discharged from the high-temperature furnace chamber 1 is conveyed into the heat exchange coil 11, and then enters the interlayer cavity 7 through the heat exchange coil 11 to heat and keep warm the low-temperature furnace chamber 4, and then is discharged from the smoke outlet pipe 8, and then undergoes high-temperature flue gas treatment through the cooling device 15 and the purification device 16; while at the same time, the secondary roasting flue gas generated by the low-temperature furnace chamber 4 is filtered by the filtering device 3, and after entering from the hot air inlet pipe of the heat exchange box 12, it exchanges heat with the high-temperature flue gas of the primary roasting in the heat exchange coil 11. The heated high-temperature air enters the low-temperature furnace chamber 4 from the air diffuser pipe 5 under the action of the second induced draft fan 10 to perform secondary roasting on the graphite electrode in the low-temperature furnace chamber 4.

[0028] The parts not detailed in the present invention are prior arts. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention; therefore, from any point of view, the above embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention, and any reference signs in the claims should not be regarded as limiting the content of the claimed rights involved.

Claims

1. A roasting furnace flue gas treatment system, characterized in that: It includes a cooling device (15), a purification device (16), a filtering device (3), a heat exchange box (12), a high-temperature furnace box (1) and a low-temperature furnace box (4); horizontal heat transfer partitions (13) are provided inside the boxes of the high-temperature furnace box (1) and the low-temperature furnace box (4), and the heat transfer partitions (13) divide the corresponding boxes into an upper material storage chamber and a lower combustion chamber (14). Feed inlets and flue gas discharge pipes are provided at the tops of the high-temperature furnace box (1) and the low-temperature furnace box (4); an interlayer cavity (7) is provided on the box wall of the low-temperature furnace box (4), and a smoke inlet pipe and a smoke outlet pipe (8) are connected to the interlayer cavity (7). The smoke outlet pipe (8) is successively connected to a cooling device (15) for cooling the flue gas and a purification device (16) for purifying the flue gas; a heat exchange coil (11) is provided inside the heat exchange box (12). Both ends of the heat exchange coil (11) are hermetically passed through the box wall of the heat exchange box (12) and are respectively connected corresponding to the smoke inlet pipe of the interlayer cavity (7) and the flue gas discharge pipe of the high-temperature furnace box (1). A first exhaust fan (2) is installed on the flue gas discharge pipe of the high-temperature furnace box (1); a hot gas inlet pipe and a heated gas outlet pipe are respectively provided on the top wall and the bottom wall of the heat exchange box (12). The hot gas inlet pipe of the heat exchange box (12) and the flue gas discharge pipe of the low-temperature furnace box (4) are respectively connected to the outlet and the inlet of the filtering device (3). The outer end of the heated gas outlet pipe is connected to a second exhaust fan (10), and the air outlet of the second exhaust fan (10) is communicated with the low-temperature furnace box (4) through a diffuser pipe (5). A perforation is provided at the center of the plate surface of the heat transfer partition (13) inside the low-temperature furnace box (4). The outer end of the diffuser pipe (5) is connected to the air outlet of the second exhaust fan (10). The inner end of the diffuser pipe (5) is adaptively passed upward through the perforation of the heat transfer partition (13) from the lower combustion chamber (14) of the low-temperature furnace box (4), and the inner port of the diffuser pipe (5) is closed, and air-permeable holes (903) are provided on the inner end pipe wall; a distribution cone (9) is provided to cover the inner port of the diffuser pipe (5). A buffer cavity (901) is provided inside the distribution cone (9). A central hole (902) communicating the buffer cavity (901) and the inner end of the diffuser pipe (5) is provided at the center of the bottom surface of the distribution cone (9). A plurality of air-permeable holes (903) communicating the buffer cavity (901) and the low-temperature furnace box (4) are uniformly provided at the outer edge of the bottom surface of the distribution cone (9).

2. The roasting furnace flue gas treatment system according to claim 1, characterized in that: The filtering device (3) includes a filtering box body (301). A unit box body (302) with a breathable structure is detachably inserted inside the filtering box body (301). An adsorbent (303) is filled inside the unit box body (302). The outlet and the inlet of the filtering box body (301) are respectively provided on opposite side box walls.

3. The roasting furnace flue gas treatment system according to claim 1, characterized in that: The purification device (16) includes a purification box body (1601). Inside the purification box body (1601), a right chamber filled with a purifying agent (1602) and a left chamber filled with water at the lower part are separated by a vertical partition plate (1604). A through hole communicating the left chamber and the right chamber is provided at the top of the vertical partition plate (1604). A purification inlet (1603) is provided corresponding to the bottom wall of the right chamber. An insertion pipe (1606) is provided at the upper part of the left chamber. One end of the insertion pipe (1606) is hermetically inserted into the through hole, and the other end of the insertion pipe (1606) extends into the water in the left chamber. A purification outlet (1605) is provided corresponding to the top wall of the left chamber.

4. The roasting furnace flue gas treatment system according to claim 1, characterized in that: The cooling device (15) is set as a heat exchange device having a tube side and a shell side. The smoke outlet pipe (8) is connected to the tube side, and cooling water is introduced into the shell side.

5. The roasting furnace flue gas treatment system according to claim 1, wherein: The interlayer cavity (7) is set as an annular cavity along the side wall of the low-temperature furnace box (4) for one week. The smoke inlet pipe and the smoke outlet pipe (8) of the interlayer cavity (7) are respectively arranged on the opposite side walls of the low-temperature furnace box (4).

6. The roasting furnace flue gas treatment system according to claim 1, characterized in that: A groove is provided on the inner side wall of the low-temperature furnace box (4), and a heat conduction plate (6) is covered on the groove opening to form the interlayer cavity (7).

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