A pot-type furnace for calcining needle coke and a method for controlling furnace temperature thereof

Abstract

The present invention relates to a can furnace for calcining needle coke and a furnace temperature control method thereof. The can furnace comprises a furnace core and a furnace body. The volatile avenue above the furnace core is connected to the first-layer fire channel through the lower burner of the volatile avenue. The lower burner of the volatile avenue is surrounded by the top silicon bricks of the first-layer fire channel. The preheating air horizontal channel below the furnace core and the volatile avenue are both built with high-alumina bricks. The hot air duct arranged on the side wall of the furnace body is connected to the preheating air horizontal channel. The first-layer fire channel air inlet of the side wall of the furnace body is connected to the hot air duct through the hot air pipe. The first-layer fire channel air inlet is connected to the external gas pipe. The present invention is improved on the basis of the traditional can furnace to form a can furnace suitable for calcining needle coke, which can meet the high-temperature calcination requirements, comprehensively utilize waste hot air and external gas for auxiliary heating, and introduce an automated temperature control method at the same time. The temperature is stable, meets the standard but does not exceed the standard, avoids high-temperature accidents, and effectively improves the quality of calcined coke.

Description

Technical Field

[0001] The invention belongs to the technical field of calcining equipment, and in particular relates to a pot-type furnace for calcining needle coke and a furnace temperature control method thereof. Background Art

[0002] The calcination temperature of needle coke production is generally required to be 1400-1500℃. Most domestic and foreign companies use rotary kilns or rotary multi-bed furnaces to calcine green coke. The use of rotary kilns for calcination results in high carbon loss, resulting in a large waste of resources and energy. At the same time, the rotary kiln is a rotating equipment, so it has high requirements for refractory performance. Although it is well used in some high-temperature equipment such as blast furnaces, it has not been ideal for use in rotary kilns for calcining needle coke.

[0003] Therefore, using a pot furnace to calcine needle coke has become a development trend. Ordinary pot furnaces such as Figure 1 As shown in the figure, except for the fire channel structure that needs to withstand high temperature, the other structures of the tank furnace are generally built with clay bricks, and the lower fire port of the volatile matter avenue is located at the position of the clay bricks. The calcination temperature of needle coke is more than 150℃ higher than that of ordinary petroleum coke. In addition, the automation degree of furnace temperature control is low, which leads to unstable furnace temperature. If the furnace temperature is often higher than the calcination temperature of needle coke for a period of time, long-term use will easily cause the furnace body and the fire channel to be partially burned, which seriously shortens the service life of the tank furnace. At the same time, the quality of a small amount of finished products is uneven. Therefore, in addition to adjusting some structures of the tank furnace, it is also necessary to introduce an automated furnace temperature control method to calcine needle coke in a tank furnace.

[0004] In addition, the pot furnace calcining petroleum coke requires the volatile matter of raw coke to be between 9.8% and 10.3%, otherwise, the volatile matter is too low to be produced. Therefore, if low-volatile needle coke is used to produce high-quality calcined needle coke, combustion-supporting heating is required, and the gas introduced is automatically controlled to save energy and maintain a stable furnace temperature. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a tank furnace for calcining needle coke and a furnace temperature control method thereof, so as to overcome the problem that the prior art cannot produce due to low volatile matter, so that the tank furnace can adapt to high-temperature calcination of the furnace body, effectively increase the true specific gravity of needle coke, reduce the burn-out rate, and improve the degree of automation.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A tank furnace for calcining needle coke, characterized in that it comprises a furnace core 1 and a furnace body 2, the furnace core 1 is built of silica bricks, and comprises a first-layer fire channel 101, a plurality of intermediate fire channels 102 and a bottom-layer fire channel 103 from top to bottom, the furnace body 2 is built of clay bricks, a volatile avenue 3 is arranged above the furnace core 1, and is connected to the first-layer fire channel 101 through a lower burner 301 of the volatile avenue, the lower burner 301 of the volatile avenue is located at the edge of the first-layer fire channel 101, and is surrounded by silica bricks on the top of the first-layer fire channel 101, a preheated air horizontal channel 4 is arranged below the furnace core 1, the volatile avenue 3 and the preheated air horizontal channel 4 are both built of high-aluminum bricks, a hot air duct 5 is arranged horizontally on the side wall of the furnace body 2, the hot air duct 5 and the preheated air horizontal channel 4 are connected through a vertical channel arranged on the inner wall of the furnace body 2, and a side wall of the furnace body 2 is arranged horizontally with the first-layer fire channel 101 A horizontal first-floor fire channel air inlet 6 is provided, and the hot air duct 5 is connected to the first-floor fire channel air inlet 6 through a hot air pipe 7. The preheated air after heat exchange with the hot calcined material is collected and enters the preheated air horizontal channel 4, enters the hot air pipe 7 through the hot air duct 5, and enters the first-floor fire channel 101 through the first-floor fire channel air inlet 6. The first-floor fire channel air inlet 6 is connected to an external gas pipe 8. The external gas is transported through the gas pipe 8 and enters the first-floor fire channel 101 through the first-floor fire channel air inlet 6.

[0008] In the present technical solution, further, a hot air flow meter 9 and a frequency modulation motor 10 are arranged on the hot air pipe 7, and the hot air flow meter 9 and the frequency modulation motor 10 are connected to a DCS automatic control system.

[0009] Furthermore, a gas flow meter 11 and a solenoid valve 12 are provided on the gas pipe, and the gas flow meter 11 and the solenoid valve 12 are connected to a DCS automatic control system.

[0010] Furthermore, the solenoid valve 12 is a pulse solenoid valve.

[0011] Furthermore, a photoelectric pyrometer 13 is provided inside the middle fire channel 102 , and a K-type thermocouple 14 is provided inside the bottom fire channel 103 .

[0012] A method for controlling the temperature of a can furnace comprises the following steps:

[0013] (1) The required temperature of a certain layer of the middle fire channel 102 is set as the control temperature and input into the DCS automatic control system. At the same time, the alarm temperature is set and the temperature is measured in real time using the photoelectric pyrometer 13;

[0014] (2) The measured temperature signal is transmitted to the DCS automatic control system in the central control room for display and processing;

[0015] (3) The DCS automatic control system processes the measured temperature and the controlled temperature according to the automatic fuzzy control algorithm program edited in the system, and outputs a switch signal to the solenoid valve 12 for control;

[0016] (4) Outputting different frequencies according to the calculation results to control the switch of the solenoid valve 12, thereby controlling the injection amount of the fuel gas to reach the control temperature;

[0017] (5) If the measured temperature exceeds the alarm temperature, the DCS automatic control system will issue an audible and visual alarm, and automatically cut off the algorithm operation, stop outputting the switch signal, and stop auxiliary heating until the measured temperature is lower than the temperature setting value, then resume the operation and start outputting the switch signal;

[0018] (6) On the basis of steps (1) to (5), the required ratio of hot air to gas is input into the DCS automatic control system, and the real-time monitoring data of the hot air flow meter 9 and the gas flow meter 11 enter the DCS automatic control system. When the gas flow changes, the DCS automatic control system processes the proportional operation and outputs a signal to control the frequency modulation motor 10 to adjust the hot air volume so that the flow rates of hot air and gas reach a corresponding ratio.

[0019] Furthermore, in step (3), the automatic fuzzy control algorithm is implemented by the following method:

[0020] (a) According to the actual production situation on site, the opening cycle of the solenoid valve 12 is pre-set in the algorithm program of the DCS automatic control system, and a matrix table consisting of the rate of change of the measured temperature per minute as the horizontal axis, the deviation value of the real-time measured temperature and the controlled temperature as the vertical axis, and the output value as the opening time of the solenoid valve 12 within an opening cycle is formed;

[0021] (b) Based on the real-time measured temperature, the program pre-edited by the DCS automatic control system calculates the deviation value between the real-time measured temperature and the control temperature and the rate of change of the measured temperature per minute. Based on these two variables, the program automatically searches the matrix table in the algorithm to obtain the output value when running;

[0022] (c) The output value controls the opening time of the solenoid valve 12 within an opening cycle. The stop time is equal to the cycle time minus the opening time. After the switching cycle ends, the next cycle will automatically continue.

[0023] In the present technical solution, improvements are made to the weak points in the tank furnace body that are subjected to high temperatures, and high-alumina bricks are used to build the volatile matter avenue and between the tank furnace body and the water jacket to replace the clay bricks used in the traditional tank furnace. The partial replacement can save the cost of the tank furnace to the greatest extent, and at the same time ensure that the furnace body can withstand the high temperature in the production process during the high-temperature calcination of needle coke, thereby extending the service life of the tank furnace.

[0024] In the present technical solution, the position of the traditional tank furnace is improved, and the clay bricks on the outside of the tank furnace body are moved forward to the edge of the first-layer fire channel, and are surrounded by silica bricks on the top of the first-layer fire channel. This will avoid the phenomenon that the fire mouth under the volatile matter avenue is burned due to high temperature due to increasing the furnace temperature.

[0025] The air volume adjustment method in the traditional tank furnace is as follows: the size of the air volume in the fire channel is obviously related to the negative pressure of the system. To increase the temperature, fuel combustion must be increased. If the fuel is sufficient, the temperature cannot be increased due to insufficient air entering the fire channel. Therefore, the air volume can only be increased by increasing the negative pressure of the system. This method can meet the increase of furnace temperature, but since the negative pressure of the system needs to be increased, the flue gas volume will inevitably increase, more fuel will be consumed, more heat will be taken away, and more flue gas will be generated to be processed. Therefore, the thermal efficiency is low and the economy is poor. In this technical scheme, the hot air obtained by heat exchange with high-temperature calcined coke is transported to the first-layer fire channel by using the preheating air horizontal channel and the hot air pipeline, and the waste hot air is comprehensively utilized to achieve the effect of energy saving. In addition, a frequency modulation motor is added to the hot air pipe, and flow meters are respectively set on the gas pipe and the hot air pipe. The frequency modulation motor is used to control the preheating air volume, which can ensure the appropriate amount of hot air, increase the utilization rate of hot air, make the volatile matter fully burned, and ensure that the air-fuel ratio is automatically adjusted, so as to achieve the best combustion state and reduce heat energy loss. Compared with the traditional mode, adding a frequency-modulated motor is more convenient, accurate and efficient than manual adjustment, consumes less fuel, has a smaller system negative pressure, produces less smoke, and burns more effectively, increasing the combustion rate of volatile matter. Through testing, it was found that when the same furnace temperature is achieved, after using a frequency-modulated motor and increasing the amount of preheated air, the amount of additional fuel can be saved by 15-20%.

[0026] In this technical solution, a pulse solenoid valve is used to automatically adjust the gas intake volume, and the gas supply volume is controlled according to the length of the solenoid valve opening and closing time. The opening and closing length of the solenoid valve is calculated based on factors such as the continuous real-time measurement of the furnace temperature and the maximum temperature calcination requirement, and then adjusted in real time through the DCS automatic control system, thereby achieving precise temperature control and timely over-temperature alarm.

[0027] In this technical solution, according to the actual production situation on site, the calculation program and related data are input into the fuzzy algorithm program of the DCS automatic control system in advance, and the frequency modulation motor and solenoid valve can be controlled by measuring the real-time monitoring data of temperature, hot air flow and gas flow, and then the flow of gas and hot air can be adjusted to achieve the control temperature. This temperature control method has a high degree of automation. On the one hand, it can be raised to the required calcination temperature in a short time, and the furnace temperature is accurately controlled to achieve the standard without exceeding the standard, protect the furnace body, and avoid high temperature accidents caused by human factors. On the other hand, the stable calcination temperature can effectively increase the true specific gravity of needle coke, reduce the burn loss rate, and improve the quality of calcined coke. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0029] Figure 1 It is a structural schematic diagram of a tank furnace in the prior art.

[0030] Figure 2 It is a structural schematic diagram of the tank furnace in the present invention.

[0031] In the attached figure:

[0032] 1. Furnace core 101, first-layer fire channel 102, middle fire channel 103, bottom-layer fire channel

[0033] 2. Furnace body 3. Volatile matter avenue 301. Lower burner of volatile matter avenue 4. Horizontal channel for preheated air

[0034] 5. Hot air duct 6. First floor fire channel air inlet 7. Hot air pipe 8. Gas pipe

[0035] 9. Hot air flow meter 10. Frequency modulation motor 11. Gas flow meter 12. Solenoid valve

[0036] 13. Photoelectric pyrometer 14. K-type thermocouple DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Example:

[0039] A pot-type furnace for calcining needle coke, characterized in that it comprises a furnace core 1 and a furnace body 2, the furnace core 1 is built of silica bricks, and comprises a first-layer fire channel 101, a plurality of middle fire channels 102 and a bottom-layer fire channel 103 from top to bottom, the furnace body 2 is built of clay bricks, a volatile avenue 3 is arranged above the furnace core 1, and is connected to the first-layer fire channel 101 through a volatile avenue lower burner 301 The volatile avenue 3 and the preheated air horizontal channel 4 are both built with high-aluminum bricks. A hot air duct 5 is horizontally arranged on the side wall of the furnace body 2. The hot air duct 5 is connected to the preheated air horizontal channel 4. A horizontal first-layer fire channel air inlet 6 is arranged at the horizontal position of the side wall of the furnace body 2 and the first-layer fire channel 101. The hot air duct 5 is connected to the first-layer fire channel air inlet 6 through a hot air pipe 7. The first-layer fire channel air inlet 6 is connected to the external gas pipe 8.

[0040] A hot air flow meter 9 and a frequency modulation motor 10 are arranged on the hot air pipe 7, and the hot air flow meter 9 and the frequency modulation motor 10 are connected to a DCS automatic control system.

[0041] A gas flow meter 11 and a solenoid valve 12 are provided on the gas pipe, and the gas flow meter 11 and the solenoid valve 12 are connected to a DCS automatic control system.

[0042] The solenoid valve 12 is a pulse type solenoid valve.

[0043] A photoelectric pyrometer 13 is arranged inside the middle fire channel 102 , and a K-type thermocouple 14 is arranged inside the bottom fire channel 103 .

[0044] In this embodiment, the furnace temperature control method of the tank furnace is as follows:

[0045] (1) The required temperature of the third layer fire channel is set as 1450°C as the control temperature and input into the DCS automatic control system. At the same time, the alarm temperature is set as 1500°C and the temperature is measured in real time using the photoelectric pyrometer 13;

[0046] (2) The measured temperature signal is transmitted to the DCS automatic control system in the central control room for display and processing;

[0047] (3) The DCS automatic control system processes the measured temperature and the controlled temperature according to the automatic fuzzy control algorithm program edited in the system, and outputs a switch signal to the solenoid valve 12 for control;

[0048] The automatic fuzzy control algorithm is implemented by the following methods:

[0049] (a) According to the actual production situation on site, the opening cycle of the solenoid valve 12 is pre-set in the algorithm program of the DCS automatic control system. Two opening cycles are set in total. The opening cycle time of the first gear is set to 100 seconds, and the opening cycle time of the second gear is set to 200 seconds. At the same time, a matrix table consisting of the rate of change of the measured temperature per minute as the horizontal axis, the deviation value of the real-time measured temperature and the controlled temperature as the vertical axis, and the output value as the opening time of the solenoid valve 12 within an opening cycle is set, as shown in the following table;

[0050]

[0051] Note: The unit of deviation is ℃, the unit of rate is ℃ / min, and the unit of output value is s (seconds).

[0052] (b) Based on the real-time measured temperature, the program pre-edited by the DCS automatic control system calculates the deviation between the real-time measured temperature and the control temperature and the rate of change of the measured temperature per minute. Based on these two variables, the program automatically searches the matrix table in the algorithm to obtain the output value when it is running. For example, the deviation between the temperature measurement value and the set value = -6°C, the rate of change = -4°C / min, and the output value = 8s, that is, within one opening cycle, the opening time of the solenoid valve is 8s.

[0053] (c) The output value controls the opening time of the solenoid valve 12 within an opening cycle (100s) to be 8s, and the stop time is equal to the cycle time minus the opening time, which is 92s. After the 100s opening cycle ends, it automatically continues to the next cycle. If the output value is when the output value = 1s (for example, the deviation between the temperature measurement value and the set value = +1°C, the rate of change = -1°C / min, and the output value = 1 s), the DCS automatic control system will automatically switch to the second gear opening cycle. When the output value is ≥2, it will automatically switch to the first gear opening cycle.

[0054] (4) Outputting different frequencies according to the calculation results to control the switch of the solenoid valve 12, thereby controlling the injection amount of the fuel gas to reach the control temperature of 1450°C;

[0055] (5) If the measured temperature exceeds the alarm temperature of 1500°C, the DCS automatic control system will issue an audible and visual alarm, and automatically cut off the algorithm operation, stop outputting the switch signal, and stop auxiliary heating until the measured temperature is lower than the temperature setting value, then resume the operation and start outputting the switch signal;

[0056] (6) On the basis of steps (1) to (5), the required ratio of hot air to gas is set, and the hot air flow / gas flow = 1.5 is input into the DCS automatic control system. The real-time monitoring data of the hot air flow meter 9 and the gas flow meter 11 enter the DCS automatic control system. When the gas flow changes, the DCS automatic control system performs proportional calculation processing and outputs a signal to control the frequency modulation motor 10 to adjust the hot air volume so that the flow rates of hot air and gas reach the corresponding ratio.

[0057] The working process of the pot furnace for calcining needle coke is as follows:

[0058] The raw coke is lifted by buckets and enters the pre-calcination bin. It is then lifted by the pre-calcination loading bucket and continuously fed to the tank furnace by belt conveyors. The raw materials are indirectly heated by the fire channels on both sides of the tank furnace. By adjusting the negative pressure of each fire channel, the pre-heating zone of the tank furnace is gradually heated from a low temperature state to remove volatiles and moisture. Then, the raw coke enters the calcination zone. By adjusting the negative pressure of the calcination zone, the volatiles produced by the raw coke in the pre-heating zone are fully burned and utilized. During calcination, since the volatiles of needle coke are low and insufficient to reach the required calcination temperature, fuel gas needs to be introduced to assist combustion so that the calcination zone reaches the required calcination temperature. After the raw coke is calcined at this high temperature, it enters the calcination zone. The volatile matter is reduced in one step, and the structure is rearranged to undergo physical and chemical changes, so that the density, strength and conductivity are improved, and finally the green coke is transformed into calcined needle coke with qualified indicators. After the calcined material has indirect heat exchange with the air through the cooling belt, the hot air is transported to the first-layer fire channel for auxiliary heating, and the still hot calcined material falls into the cooling cylinder with a cooling water jacket for rapid cooling to avoid oxidation; the cooled calcined material is continuously discharged out of the furnace in appropriate amounts through the closed crushing and discharging mechanism, and is transported to the calcined petroleum coke storage bin via a vibrating conveyor, a belt conveyor and a bucket elevator.

[0059] The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A pot furnace for calcining needle coke, characterized in that: The invention comprises a furnace core (1) and a furnace body (2), wherein the furnace core (1) is built of silica bricks and comprises, from top to bottom, a first-layer fire channel (101), a plurality of middle fire channels (102) and a bottom-layer fire channel (103), and the furnace body (2) is built of clay bricks. A volatile avenue (3) is arranged above the furnace core (1) and is connected to the first-layer fire channel (101) through a lower burner (301) of the volatile avenue. The lower burner (301) of the volatile avenue is located at the edge of the first-layer fire channel (101) and is surrounded by silica bricks on the top of the first-layer fire channel (101). The furnace core (1) A preheating air horizontal channel (4) is arranged below the furnace body (2); the volatile matter avenue (3) and the preheating air horizontal channel (4) are both built of high-aluminum bricks; a hot air duct (5) is arranged transversely on the side wall of the furnace body (2); the hot air duct (5) and the preheating air horizontal channel (4) are connected; a transverse first-floor fire channel air inlet (6) is arranged at a position horizontal to the side wall of the furnace body (2) and the first-floor fire channel (101); the hot air duct (5) and the first-floor fire channel air inlet (6) are connected via a hot air pipe (7); and the first-floor fire channel air inlet (6) is connected to an external gas pipe (8).

2. The can furnace according to claim 1, characterized in that: A hot air flow meter (9) and a frequency modulation motor (10) are arranged on the hot air pipe (7), and the hot air flow meter (9) and the frequency modulation motor (10) are connected to a DCS automatic control system.

3. The can furnace according to claim 2, characterized in that: The gas pipe is provided with a gas flow meter (11) and a solenoid valve (12), and the gas flow meter (11) and the solenoid valve (12) are connected to a DCS automatic control system.

4. The can furnace according to claim 3, characterized in that: The solenoid valve (12) is a pulse type solenoid valve.

5. The can furnace according to claim 4, characterized in that: A photoelectric pyrometer (13) is arranged inside the middle fire channel (102), and a K-type thermocouple (14) is arranged inside the bottom fire channel (103).

6. The method for controlling the temperature of a can furnace as claimed in claim 5, comprising the following steps: (1) The required temperature of a certain layer of the middle fire channel (102) is set as the control temperature and input into the DCS automatic control system. At the same time, the alarm temperature is set and the temperature is measured in real time using a photoelectric pyrometer (13); (2) The measured temperature signal is transmitted to the DCS automatic control system in the central control room for display and processing; (3) The DCS automatic control system processes the measured temperature and the controlled temperature according to the automatic fuzzy control algorithm program edited in the system, and outputs a switch signal to the solenoid valve (12) for control; (4) outputting different frequencies according to the calculation results to control the switch of the electromagnetic valve (12), thereby controlling the injection amount of the fuel gas to reach the control temperature; (5) If the measured temperature exceeds the alarm temperature, the DCS automatic control system will issue an audible and visual alarm, and automatically cut off the algorithm operation, stop outputting the switch signal, and stop auxiliary heating until the measured temperature is lower than the temperature setting value, then resume the operation and start outputting the switch signal; (6) On the basis of steps (1) to (5), the required ratio of hot air to gas is input into the DCS automatic control system, and the real-time monitoring data of the hot air flow meter (9) and the gas flow meter (11) enter the DCS automatic control system. When the gas flow changes, the DCS automatic control system performs proportional calculation processing and outputs a signal to control the frequency modulation motor (10), thereby regulating the amount of hot air so that the flow rates of hot air and gas reach a corresponding ratio.

7. The furnace temperature control method of a can furnace according to claim 6, characterized in that: In step (3), the automatic fuzzy control algorithm is implemented by the following method: (a) according to the actual production situation on site, the opening cycle of the solenoid valve (12) is pre-set in the algorithm program of the DCS automatic control system, and a matrix table is formed with the value of the rate of change of the measured temperature per minute as the horizontal axis, the value of the deviation between the real-time measured temperature and the controlled temperature as the vertical axis, and the output value as the opening time of the solenoid valve (12) within an opening cycle; (b) Based on the real-time measured temperature, the program pre-edited by the DCS automatic control system calculates the deviation value between the real-time measured temperature and the control temperature and the rate of change of the measured temperature per minute. Based on these two variables, the program automatically searches the matrix table in the algorithm to obtain the output value when running; (c) The output value controls the opening time of the electromagnetic valve (12) within an opening cycle, and the stop time is equal to the cycle time minus the opening time. After the switching cycle ends, the next cycle will automatically continue.

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