Graphite electrode roasting tunnel kiln with stable combustion chamber temperature

Abstract

The utility model discloses a graphite electrode roasting tunnel kiln with a stable combustion chamber temperature, which belongs to the technical field of graphite electrode production and processing, and comprises a kiln body, a kiln door, a traverse car, a pneumatic system and a combustion system. The traversing car solves the problem that a kiln car cannot be pulled by mechanical force at a section from a loading line to the traversing car, realizes effective management of gas intake and gas exhaust of a combustion kiln by arranging a pneumatic system, and realizes constant temperature in a combustion chamber when the combustion chamber works by adopting two cascade control systems and taking the combustion temperature as a main control variable. The problems that in the prior art, due to the fact that the combustion chamber takes the oxygen content and the combustion temperature as double variables, temperature control in the combustion chamber is unstable, and the production yield and the product quality of graphite electrodes are affected are solved.

Description

Technical Field

[0001] The utility model patent relates to the technical field of graphite electrode production and processing, in particular to a graphite electrode baking tunnel kiln with stable combustion chamber temperature. Background Technique

[0002] In the production of graphite electrodes, it is necessary to bake the baked products. Secondary baking is the process of baking the baked products again after impregnation to carbonize the asphalt immersed in the pores of the baked products. At present, the widely used external combustion type secondary baking tunnel kiln adopts two single-loop closed-loop PID control systems: Loop 1 controls the temperature of the combustion chamber and adjusts the opening of the gas electric valve to control the oxygen content entering the combustion chamber, and Loop 2 controls the oxygen content inside the combustion chamber. Since the combustion-supporting air is transported to the combustion chamber through the heat exchanger to participate in combustion support.

[0003] The above combustion control system has the following deficiencies:

[0004] 1. The oxygen content in the kiln cannot be automatically controlled. Since the volatile asphalt vapor in the kiln participates in combustion as a heating fuel, the oxygen content in the combustion chamber changes greatly. Adjusting the combustion-supporting air volume alone cannot effectively control the oxygen content at the preset value;

[0005] 2. The combustion chamber temperature control loop is easily interfered by the oxygen content control loop. When the temperature of the combustion chamber rises, Loop 1 needs to adjust the gas valve to a smaller opening, so that the oxygen content (percentage) will increase. After the oxygen content (percentage) in Loop 2 increases, the combustion-supporting air valve is adjusted to a smaller opening to reduce the oxygen content, resulting in a decrease in the temperature of the combustion chamber, and vice versa;

[0006] 3. The combustion chamber temperature control loop and the oxygen content control loop operate independently, and the control system cannot be effectively connected;

[0007] Therefore, it is urgent to invent a graphite electrode baking tunnel kiln with stable combustion chamber temperature to solve the above problems. Content of the Utility Model

[0008] The utility model discloses a graphite electrode baking tunnel kiln with stable combustion chamber temperature. Compared with the traditional process, by adopting a double-loop cascade control system with the combustion temperature as the main control variable, when the combustion chamber is working, the air-fuel ratio regulating valve is controlled through the cascade control system to adjust the intake ratio of the combustion-supporting air and the gas, and the temperature in the combustion chamber is controlled to be constant, solving the problem that the existing combustion chamber uses the oxygen content and the combustion temperature as double variables, resulting in unstable temperature control in the combustion chamber and affecting the production output and product quality of graphite electrodes.

[0009] A graphitized electrode baking tunnel kiln with stable combustion chamber temperature disclosed by the utility model comprises: a kiln body, a kiln door, a traversing vehicle, a pneumatic system and a combustion chamber. The kiln body is provided with kiln doors on both sides. The kiln body includes a high-temperature area, a cooling area and a normal cooling area. A traversing vehicle is provided at the kiln mouth of the kiln body. The pneumatic system is connected to the combustion chamber and the kiln body. The temperature in the combustion chamber is controlled by a dual-loop cascade controller.

[0010] Preferably, the pneumatic system includes an air supply pipeline, a temperature reduction pipeline and a recovery pipeline. The air supply pipeline includes a hot air pipeline, a hot smoke pipeline and a gas pipeline. The hot air pipeline is connected to the combustion chamber after being heated by a heat exchanger. The hot smoke pipeline transports the high-temperature flue gas discharged from the combustion chamber. The hot smoke pipeline is connected to the high-temperature area of the kiln body and a chimney. The temperature reduction pipeline includes a pre-cooling pipeline and a normal cooling pipeline. The pre-cooling pipeline is communicated with the cooling area of the kiln body. The normal cooling pipeline is communicated with the normal cooling area of the kiln body. The recovery pipeline is connected to the high-temperature area of the kiln body.

[0011] Preferably, the pre-cooling pipeline cools the hot smoke through a heat exchanger, the normal cooling pipeline cools through normal temperature air, and the recovery pipeline recovers the volatile asphalt vapor in the high-temperature area of the kiln body and sends it into the combustion chamber to participate in combustion.

[0012] Preferably, the combustion chamber is arranged outside the kiln body. A combustion controller is arranged outside the combustion chamber. The combustion controller includes: an air-fuel ratio regulating valve, a dual-loop cascade controller, a PID controller and an igniter. An oxygen content measuring instrument and a temperature measuring instrument are arranged inside the combustion chamber.

[0013] Preferably, the air-fuel ratio regulating valves are respectively arranged at the air outlet of the hot air pipeline and the air outlet of the gas pipeline. The hot air pipeline and the gas pipeline are connected to the combustion chamber. The oxygen content measuring instrument and the temperature measuring instrument are electrically connected to the dual-loop cascade controller. The dual-loop cascade controller is electrically connected to the PID controller. The PID controller is electrically connected to the air-fuel ratio regulating valve.

[0014] Preferably, the temperature value in the combustion chamber is controlled to be 800 °C, and the oxygen content inside the combustion chamber is controlled to be 2.75%-2.85%.

[0015] Beneficial effects

[0016] The utility model monitors the temperature and oxygen content in the combustion chamber in real time by setting a dual-loop cascade controller. The dual-loop cascade controller adjusts the opening and closing amplitude of the air-fuel ratio regulating valve through a PID controller, and adjusts the intake air volume of the combustion-supporting air and the gas respectively, so as to realize the control with the temperature in the combustion chamber as the main variable, make the temperature in the combustion chamber constant, and thus introduce the hot flue gas with controllable temperature into the kiln body to ensure that the temperature in the kiln body is adjustable.

[0017] The utility model realizes precise control of the temperature inside the kiln by setting a pneumatic system, in which the gas supply pipeline heats the high-temperature area of the kiln body and controls the heating temperature inside the kiln body, and the cooling pipeline cools the cooling area and the normal cooling area of the kiln body, meeting the heating requirements of graphite electrodes.

[0018] When the impregnated electrode is heated to a certain temperature in the utility model, a part of the pitch thermally decomposes to generate a large amount of volatile pitch vapor, and another part of the pitch seeps out of the electrode surface in a liquid state and drips on the kiln car tabletop. These large amounts of volatile pitch vapor in the kiln are sent back to the combustion chamber by the circulation fan and reused as fuel, which can save fuel consumption and reduce production costs.

[0019] The utility model is used for the secondary roasting of graphite electrodes, can keep the temperature inside the kiln body constant, meets the processing requirements of graphite electrodes, has a high finished product rate of processed products, excellent product quality, and meets the requirements of continuous batch roasting of graphite electrodes. Brief Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0021] Figure 1 It is a pipeline schematic diagram of a tunnel kiln for roasting graphite electrodes;

[0022] Figure 2 It is a schematic diagram of the burner control process;

[0023] Figure 3 It is a schematic diagram of the temperature change in the combustion chamber;

[0024] Figure 4 It is a schematic diagram of the oxygen content change in the combustion chamber;

[0025] Figure 5 It is a schematic diagram of the burner control pipeline;

[0026] Figure 6 It is a schematic diagram of the cooling pipeline and the normal cooling pipeline of a tunnel kiln for roasting graphite electrodes.

[0027] In the figure: 1. Kiln body, 101. High-temperature zone, 102. Cooling zone, 103. Normal cooling zone, 2. Kiln door, 3. Combustion chamber, 301. Combustion controller, 302. Air-fuel ratio regulating valve, 303. Dual-loop cascade controller, 304. PID controller, 305. Igniter, 306. Oxygen content measuring instrument, 307. Temperature measuring instrument, 4. Gas supply pipeline, 401. Hot air pipeline, 402. Hot smoke pipeline, 403. Gas pipeline, 5. Cooling pipeline, 501. Pre-cooling pipeline, 502. Normal cooling pipeline, 6. Recovery pipeline, 7. Transverse moving vehicle, 8. Heat exchanger, 9. Chimney. Specific implementation mode

[0028] A graphite electrode baking tunnel kiln for maintaining the temperature stability of the combustion chamber 3, comprising: a kiln body 1, a kiln door 2, a transverse moving vehicle 7, a pneumatic system and a combustion chamber 3. The kiln body 1 is provided with kiln doors 2 on both sides. The kiln body 1 includes a high-temperature zone 101, a cooling zone 102 and a normal cooling zone 103. The graphite electrodes to be processed pass through the high-temperature zone 101, the cooling zone 102 and the normal cooling zone 103 in sequence through the kiln car. A transverse moving vehicle 7 is provided at the kiln mouth of the kiln body 1, and the transverse moving vehicle 7 transfers the kiln car. The pneumatic system is connected to the combustion chamber 3 and the kiln body 1. The pneumatic system provides combustion-supporting air, gas and asphalt vapor for the combustion chamber 3, and provides high-temperature heating and cooling for the kiln body 1. The combustion chamber 3 controls the temperature in the combustion chamber 3 through a dual-loop cascade controller 303, and controls the temperature in the combustion chamber to remain stable with the combustion temperature in the combustion chamber 3 as the main variable.

[0029] In some embodiments, the pneumatic system includes a gas supply pipeline 4, a cooling pipeline 5 and a recovery pipeline 6. The gas supply pipeline 4 includes a hot air pipeline 401, a hot smoke pipeline 402 and a gas pipeline 403. The hot air pipeline 401 is connected to the combustion chamber 3 after being heated by the heat exchanger 8. The hot smoke pipeline 402 transports the high-temperature flue gas discharged from the combustion chamber 3. The hot smoke pipeline 402 is connected to the high-temperature zone 101 of the kiln body and the chimney 9. A pressure sensor is provided at the connection of the hot smoke pipeline 402 with the high-temperature zone 101 of the kiln body to detect the gas pressure in the kiln and keep the gas pressure in the kiln body 1 in a slightly positive pressure state. Excessive pressure will cause oxidation of the graphite electrode material. The cooling pipeline 5 includes a pre-cooling pipeline 501 and a normal cooling pipeline 502. The pre-cooling pipeline 501 is communicated with the cooling zone 102 of the kiln body, and the normal cooling pipeline 502 is communicated with the normal cooling zone 103 of the kiln body. The recovery pipeline 6 is connected to the high-temperature zone 101 of the kiln body, and transports the asphalt vapor after evaporation of the asphalt in the high-temperature zone 101 of the kiln body to the combustion chamber 3 for combustion utilization, saving production costs, reducing air treatment costs at the same time, and reducing environmental pollution.

[0030] In some embodiments, a heat exchanger 8 is provided in the precooling pipeline 501. The heat exchanger 8 is connected to an external blower. The external blower cools the heat exchanger 8, and the heat exchanger 8 cools the hot smoke. The constant-cooling pipeline 502 cools the constant-cooling area 103 by introducing normal-temperature air. The recovery pipeline 6 recovers the volatile asphalt vapor in the high-temperature area 101 of the kiln body and sends it into the combustion chamber 3 to participate in combustion.

[0031] In some embodiments, the combustion chamber 3 is provided outside the kiln body 1. The combustion chamber 3 is provided with a combustion controller 301. The combustion controller 301 includes: an air-fuel ratio regulating valve 302, a dual-loop cascade controller 303, a PID controller 304, and an igniter 305. An oxygen content measuring instrument 306 and a temperature measuring instrument 307 are provided in the combustion chamber 3. Both the oxygen content measuring instrument 306 and the temperature measuring instrument 307 are made of high-temperature resistant materials.

[0032] In some embodiments, the air-fuel ratio regulating valve 302 is respectively provided at the air outlet of the hot air pipeline 401 and the gas outlet of the gas pipeline 403. The air-fuel ratio regulating valve 302 adjusts the air output by regulating the size of the valve port. The hot air pipeline 401 and the gas pipeline 403 are connected to the combustion chamber 3. The oxygen content measuring instrument 306 and the temperature measuring instrument 307 are electrically connected to the dual-loop cascade controller 303. The dual-loop cascade controller 303 monitors the temperature and oxygen content in the combustion chamber 3. The dual-loop cascade controller 303 is electrically connected to the PID controller 304, and the PID controller 304 is electrically connected to the air-fuel ratio regulating valve 302. The dual-loop cascade controller 303 takes the temperature in the combustion chamber 3 as the main control quantity. When it is detected that the temperature in the combustion chamber 3 is lower than the preset threshold, after calculation, the PID controller 304 is controlled to increase the intake of combustion-supporting air and the gas volume to intensify combustion and increase the temperature in the combustion chamber 3. When it is detected that the temperature in the combustion chamber 3 is higher than the preset threshold, after calculation, the PID controller 304 is controlled to reduce the intake of combustion-supporting air and the gas volume to reduce combustion and lower the temperature in the combustion chamber 3, so that the temperature in the combustion chamber 3 reaches stability.

[0033] In some embodiments, the main control quantity, the temperature value in the combustion chamber 3, is 800 °C, and the sub-control quantity, the oxygen content inside the combustion chamber 3, is about 2.8%.

[0034] Embodiment 1

[0035] In a specific embodiment provided by the present utility model, as Figures 1 - 4As shown in the figure, before starting the tunnel kiln, it is necessary to set the temperature and oxygen content in the combustion chamber 3 in the dual-loop cascade controller 303 first. After the setting is completed, start the fan and the heat exchanger 8, and blow heated air into the combustion chamber 3 through the hot air pipeline 401. The dual-loop cascade controller 303 controls the PID controller 304 to increase the adjustment command for the air-fuel ratio regulating valve 302 of the hot air pipeline 401 and the gas pipeline 403, and controls the opening size of the air-fuel ratio regulating valve 302. The burner starts the ignition procedure, and the flue gas generated by combustion leads to the high-temperature area 101 of the kiln body 1 through the hot flue gas pipeline 402. A temperature measuring instrument is installed at the end of the hot flue gas pipeline 402, and a pressure sensor is provided on the hot flue gas pipeline 402 to detect the pressure in the kiln body 1, so as to keep the inside of the kiln body 1 in a slightly positive pressure state to prevent the oxidation of the graphite electrode. The graphite electrode is carried on the kiln car and heated by the high-temperature flue gas in the high-temperature area 101 of the kiln body. After reaching the predetermined time and expected effect, it travels to the cooling area 102. The cooling area 102 is cooled by the fan in the normal cooling pipeline 502 to make the graphite electrode reach the normal temperature state. The kiln car is towed out of the kiln body 1 by the traversing vehicle 7 to complete the secondary baking of the graphite electrode.

[0036] In the high-temperature area 101 of the kiln body 1, when the impregnated electrode is heated to above 200 °C, a part of the asphalt thermally decomposes to produce a large amount of volatile components, and another part of the asphalt seeps out of the electrode surface in a liquid state and volatilizes at a high temperature. The high-temperature asphalt vapor is pumped into the combustion chamber 3 through the recovery pipeline 6 to participate in the combustion of the combustion chamber 3, reducing the use of gas and the production cost.

[0037] The combustion chamber 3 is always maintained at the preset 800 °C during the heating process. When the amount of asphalt vapor and gas introduced increases and the amount of combustion-supporting air introduced remains unchanged, the temperature in the combustion chamber 3 will be lower than the preset threshold. The dual-loop cascade controller 303 detects that the temperature detected by the temperature measuring instrument 307 is lower than the preset threshold. After calculation, the dual-loop cascade controller 303 transmits an electrical signal to the PID controller 304. The PID controller 304 sends a valve body adjustment signal to the air-fuel ratio regulating valve 302 on the hot air pipeline 401 to increase the outlet air volume of the combustion-supporting air in the hot air pipeline 401, promoting the combustion in the combustion chamber 3 to increase the temperature. When the temperature in the combustion chamber 3 exceeds the predetermined temperature, after calculation, the dual-loop cascade controller 303 transmits an electrical signal to the PID controller 304. The PID controller 304 simultaneously sends valve body adjustment signals to the air-fuel ratio regulating valve 302 on the hot air pipeline 401 and the gas pipeline 403, reducing the outlet air volume of the combustion-supporting air in the hot air pipeline 401 and at the same time reducing the gas outlet volume of the gas pipeline 403, reducing the combustion condition in the combustion chamber 3 and lowering the temperature in the combustion chamber 3 to keep the temperature in the combustion chamber 3 always at the preset temperature.

Claims

1. A graphite electrode baking tunnel kiln with a stable combustion chamber temperature, characterized in that: include: A kiln body, a kiln door, a traverse vehicle, a pneumatic system and a combustion chamber. Kiln doors are arranged on both sides of the kiln body. The kiln body comprises a high temperature zone, a cooling zone and a normal cooling zone. A traverse vehicle is arranged at the kiln mouth of the kiln body. The pneumatic system is connected with the combustion chamber and the kiln body. The temperature inside the combustion chamber is controlled by a double-circuit cascade controller.

2. A graphite electrode baking tunnel kiln with a stable combustion chamber temperature according to claim 1, characterized in that: The pneumatic system includes an air supply pipeline, a cooling pipeline and a recovery pipeline. The air supply pipeline includes a hot air pipeline, a hot smoke pipeline and a gas pipeline. The hot air pipeline is connected to the combustion chamber after being heated by a heat exchanger. The hot smoke pipeline transports high-temperature smoke discharged from the combustion chamber. The hot smoke pipeline is connected to the high-temperature zone of the kiln body and the chimney. The cooling pipeline includes a pre-cooling pipeline and a normal cooling pipeline. The pre-cooling pipeline is connected to the cooling zone of the kiln body, the normal cooling pipeline is connected to the normal cooling zone of the kiln body, and the recovery pipeline is connected to the high-temperature zone of the kiln body.

3. A graphite electrode baking tunnel kiln with a stable combustion chamber temperature according to claim 2, characterized in that: The precooling pipeline is provided with a heat exchanger and cools down the hot smoke through the heat exchanger. The normal cooling pipeline cools down the normal cooling area by introducing normal temperature air. The recovery pipeline recovers the volatilized asphalt vapor in the high temperature area of ​​the kiln body and sends it into the combustion chamber to participate in combustion.

4. The graphite electrode baking tunnel kiln with a stable combustion chamber temperature according to claim 1, characterized in that: The combustion chamber is arranged outside the kiln body, and a combustion controller is arranged outside the combustion chamber. The combustion controller includes: an air-fuel ratio regulating valve, a double-loop cascade controller, a PID controller and an igniter. An oxygen content measuring instrument and a temperature measuring instrument are arranged in the combustion chamber.

5. The graphite electrode baking tunnel kiln with a stable combustion chamber temperature according to claim 4, characterized in that: The air-fuel ratio regulating valve is respectively arranged at the air outlet of the hot air pipeline and the air outlet of the gas pipeline, the hot air pipeline and the gas pipeline are connected to the combustion chamber, the oxygen content measuring instrument and the temperature measuring instrument are electrically connected to the dual-circuit cascade controller, the dual-circuit cascade controller is electrically connected to the PID controller, and the PID controller is electrically connected to the air-fuel ratio regulating valve.

6. The graphite electrode baking tunnel kiln with a stable combustion chamber temperature according to claim 1, characterized in that: The temperature in the combustion chamber is controlled to be 800°C, and the oxygen content in the combustion chamber is controlled to be 2.75%-2.85%.

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