A waste heat utilization method of adopting steam and electricity dual drive for an aluminum carbon plant

Abstract

The application discloses a waste heat utilization method for an aluminum carbon factory adopting steam-electric dual drive, and the method is based on four subsystems of waste heat recovery, steam-electric dual drive, feed water circulation and intelligent control: the waste heat recovery subsystem captures 850-1100 DEG C high-temperature flue gas of a carbon calcining furnace, and converts the high-temperature flue gas into high-temperature and high-pressure steam through a waste heat boiler; the steam-electric dual drive subsystem realizes flexible switching of four modes of motor driving, combined driving, steam driving and driving and power generation through three clutch combinations; the feed water circulation subsystem realizes closed loop circulation of a working medium; and the intelligent control subsystem automatically regulates and controls based on multi-sensor data, so that the application improves waste heat comprehensive utilization efficiency, guarantees production continuity and is suitable for power driving scenes of key fan equipment of the aluminum carbon factory.

Description

Technical Field

[0001] This invention relates to the field of energy-saving technology in aluminum carbon production, specifically to a waste heat utilization method for aluminum carbon plants using a dual-drive steam and electric system. This method is applicable to the power drive of key equipment such as induced draft fans, cooling fans, and raw material conveying fans in aluminum carbon plants, achieving synergistic optimization of efficient utilization of waste heat resources and reduction of production energy consumption. Background Technology

[0002] Carbon for aluminum (such as prebaked anodes) is the core raw material for electrolytic aluminum production. During its production process, the carbon calcining furnace needs to complete the calcination of raw materials such as petroleum coke at a high temperature of 1200-1400℃. This process generates a large amount of high-temperature flue gas (temperature 850-1100℃). The huge amount of waste heat contained in the flue gas is the most important waste heat resource for aluminum carbon plants.

[0003] Currently, aluminum carbon plants face the following prominent problems in utilizing waste heat from calcining furnaces: Waste heat utilization efficiency is low. Existing technologies mostly use waste heat boilers to generate electricity or preheat raw materials. The electricity generated needs to be connected to the grid before driving production equipment. There are many energy conversion links (waste heat → steam → electricity → mechanical energy), and the comprehensive utilization efficiency is only 35-40%. A large amount of waste heat is lost in the conversion process. Carbon production line equipment has high energy consumption. Key equipment such as induced draft fans and cooling fans in carbon plants mostly adopt a single motor drive mode, which consumes a lot of industrial electricity and has high operating costs. Insufficient operational stability makes it difficult to fully match steam drive with waste heat steam, which makes it hard to guarantee the stable operation of equipment such as fans, thus affecting the continuity of the carbon calcination process.

[0004] Therefore, developing a dual-mode technology that can directly convert waste heat steam from carbon calcining furnaces into equipment driving power and use excess steam for power generation has become the key to solving the above problems. Summary of the Invention

[0005] To address the problems of low waste heat utilization efficiency, high equipment drive energy consumption, and unstable system operation in existing aluminum carbon plants, this invention provides a waste heat utilization method using a steam-electric dual-drive system. The core objectives are: to shorten the waste heat energy conversion path, directly converting waste heat steam into mechanical energy for equipment drive, thereby improving the overall efficiency of waste heat utilization; to construct a multi-mode system of "steam drive + waste steam power generation," flexibly switching operation according to waste heat fluctuations to ensure stable equipment operation; and to significantly reduce the power consumption of key equipment such as fans, thereby reducing the production and operating costs of the carbon plant. To achieve synergistic adaptation between waste heat utilization and carbon calcination processes, reduce energy waste and carbon emissions, and improve the energy conservation and consumption reduction level of enterprises.

[0006] To address the problems existing in the prior art, the present invention adopts the following technical solution: A waste heat utilization method for an aluminum carbon plant using a steam-electric dual-drive system is disclosed. This method is based on a waste heat recovery subsystem, a steam-electric dual-drive subsystem, a feedwater circulation subsystem, and an intelligent control subsystem. The input end of the steam-electric dual-drive subsystem is connected to the waste heat recovery subsystem, and its output end is connected to the feedwater circulation subsystem. The steam-electric dual-drive subsystem includes a steam turbine 21, a first clutch 22, a generator 23, a second clutch 24, a fan 25, a third clutch 26, and a drive motor 27. The intelligent control subsystem controls the operation mode of the steam-electric dual-drive subsystem based on data transmitted from sensors S01, S02, and S03 installed on the pipeline, realizing an integrated operation process of waste heat recovery, equipment drive, and waste electricity generation. Specifically, the four operation modes are described in detail below: Motor Drive: Since the waste heat from the production line is used to generate steam for driving or power generation, and waste heat is only generated after the production line is running, the important equipment, the fan, needs to be driven by a motor first. This is the motor drive mode. In this mode, the intelligent control subsystem controls the first clutch 22 and the second clutch 24 to disengage, and the third clutch 26 to open, so that the drive motor 27 drives the fan 25 alone; at this time, the fan speed sensor S03 monitors the fan speed, and the fan speed r ≤ 2940 rpm; Combined Drive: When the waste heat of the production line increases, the steam turbine generator set completes the start-up procedure according to the program, generates steam, and is ready for operation and regulation. It can drive the fan together with the motor. This working condition is the combined drive mode. At this time: In this mode, the intelligent control subsystem controls the first clutch 22 to disengage, and the second clutch 24 and the third clutch 26 to open. The steam turbine 21 and the drive motor 27 work together to drive the fan 25. At this time, the fan speed is monitored by the fan speed sensor S03. In this working mode, the fan speed r is: 2940≤r≤2960rpm. Steam Driven: As the amount of waste heat steam increases, the contribution of steam to the drive also increases. As a result, the fan speed gradually increases. When the fan speed r ≥ 2960 rpm, the waste heat has the ability to drive the fan independently, and at this time, the steam driven mode is entered. That is, the intelligent control subsystem controls the first clutch 22 and the third clutch 26 to disengage, and the second clutch 24 to open, so that the steam turbine 21 drives the fan 25 independently. Drive + Power Generation: As the amount of waste heat steam continues to increase, the steam drive capacity also exceeds the contribution of the blower, resulting in a gradual increase in blower speed. When the blower speed r ≥ 2980 rpm, it enters the drive + power generation mode. The intelligent control subsystem controls the third clutch to disengage, while simultaneously opening the first and second clutches. The steam turbine drives the blower to run, and at the same time, it drives the generator to generate electricity.

[0007] In actual operation, it can be operated and controlled as follows: When the steam pressure / temperature sensor S02 fails to meet the requirements, steam cannot drive the turbine, thus preventing power generation. In this case, the fan operates in motor drive mode. At this time, the fan speed is monitored, and the fan speed r ≤ 2940 rpm. When the steam pressure / temperature sensor S02 meets the requirements and the drive requirement is met, the steam turbine and the motor drive the fan together, entering the combined drive mode. At this time, the fan speed is monitored and controlled to be 2940 ≤ r ≤ 2960 rpm. When the fan speed increases to r≥2960rpm, it has the conditions to drive the fan independently, and at this time it enters the steam drive mode; When the rotational speed continues to increase and r≥2980rpm, it indicates that there is still surplus waste heat after meeting the requirements of the wind turbine drive. At this time, the drive + power generation mode is activated.

[0008] Furthermore, the feedwater circulation subsystem includes a turbine exhaust pipe 31, a condenser 32, a condensate pump 34, a deaerator 36, a feedwater pump 38, and supporting pipes. The turbine 21 exhaust port is connected to the condenser 32 through the exhaust pipe (31), the condenser 32 is connected to the deaerator 36 through the condensate pump 34, and the deaerator 36 is connected to the feedwater inlet of the waste heat boiler 12 through the feedwater pump 38, forming a closed-loop circulation. The intelligent control subsystem controls the operation of the first condensate pump motor M21, the second condensate pump motor M22, the first feedwater pump motor M31, and the second feedwater pump motor M32 respectively based on the flue gas temperature sensor S01, thereby adjusting the feedwater circulation subsystem to meet the requirements of the waste heat boiler 12.

[0009] Furthermore, the power output end of the steam turbine 21 is connected to the generator 23 through the first clutch 22, to the fan 25 through the second clutch 24, and then connected in series with the drive motor 27 through the third clutch 26.

[0010] Furthermore, the first clutch 22, the second clutch 24, and the third clutch 26 are all electromagnetic clutches with a response time of ≤0.5s.

[0011] Furthermore, the steam pressure / temperature sensor (S02) is located on the main steam pipeline, and the fan speed sensor (S03) is located on the fan drive shaft.

[0012] Furthermore, the waste heat recovery subsystem includes a carbon calcining furnace 11, a waste heat boiler 12, a flue gas duct 13, and a main steam duct 14; the flue gas outlet of the carbon calcining furnace 11 is connected to the flue gas inlet of the waste heat boiler 12 through the flue gas duct 13, and the steam outlet of the waste heat boiler 12 is connected to the steam-electric dual-drive subsystem through the main steam duct 14.

[0013] Furthermore, the wear-resistant and corrosion-resistant coating on the inner wall of the flue gas passage of the waste heat boiler 12 is made of SiC-Si3N4 ceramic material, with a coating thickness of 0.8-1.5mm.

[0014] Furthermore, the high-temperature and high-pressure steam output parameters of the waste heat boiler 12 are: pressure 2.45-3.82MPa, temperature 380-450℃; the flue gas emission temperature of the waste heat boiler 12 is controlled at 180-200℃.

[0015] Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Significantly improved waste heat utilization efficiency: By adopting a direct conversion path of "waste heat → steam → mechanical energy", the intermediate link of "electrical energy transmission" is omitted, and the comprehensive utilization efficiency of waste heat is increased to more than 65%; after the high-temperature flue gas is heat exchanged by the waste heat boiler, the emission temperature is reduced to 180-200℃, and the waste heat loss is greatly reduced.

[0016] 2. Significantly reduced driving energy consumption: Under normal operating conditions, the steam turbine uses waste heat to drive equipment such as fans, which can significantly or even completely replace the power consumption of the motor; when the waste heat increases or the fans are running at low load, the surplus power can be used to generate electricity, significantly reducing the electricity cost during operation.

[0017] 3. Strong operational stability: Through the dual-drive mode of steam and electricity and intelligent control, the drive mode can be switched in real time according to the waste heat fluctuation, avoiding the defects of a single drive mode being affected by external factors; the fault emergency mode ensures the continuous operation of the load equipment and guarantees the stability of the carbon calcination process.

[0018] 4. High adaptability and flexibility: The multi-clutch design enables flexible switching between four working modes: motor drive, combined drive, steam drive, and drive + power generation, adapting to the waste heat fluctuations caused by load changes (50%-110%) in aluminum carbon plant calcining furnaces; the generator can convert excess waste heat into electrical energy, realizing the cascade utilization of energy.

[0019] 5. Significant energy-saving and environmental protection effects: No additional fossil energy consumption is required, industrial waste heat is fully recovered and utilized, and the carbon emission pressure on enterprises is reduced.

[0020] 6. Extended equipment life: The waste heat boiler adopts a wear-resistant and corrosion-resistant coating, and the feedwater circulation system is equipped with a pressure deaerator, which effectively solves the problems of carbon flue gas corrosion and equipment oxygen erosion. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the waste heat utilization method of the aluminum carbon plant using a dual-drive steam and electric system according to the present invention.

[0022] Figure label: 11-Carbon calcining furnace; 12-Waste heat boiler; 13-Flue gas duct; 14-Main steam duct; 21-Steam turbine; 22-First clutch; 23-Generator; 24-Second clutch; 25-Wind fan; 26-Third clutch; 27-Drive motor; 31-Exhaust steam pipe; 32-Condenser; 33-Condenser drain pipe; 34-Condensate pump; 35-Condensate pipe; 36-Deaerator; 37-Deaerator outlet pipe; 38-Feed water pump; 39-Main feed water pipe; 40-DCS master station; S01 - Flue gas temperature sensor; S02 - Steam pressure / temperature sensor; S03 - Fan speed sensor; M11 - First clutch electromagnetic drive device; M12 - Second clutch electromagnetic drive device; M13 - Third clutch electromagnetic drive device; M21 - First condensate pump motor; M22 - Second condensate pump motor; M31 - First feed water pump motor; M32 - Second feed water pump motor. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] A waste heat utilization method for an aluminum carbon plant using a steam-electric dual-drive system, the method being based on a waste heat recovery subsystem, a steam-electric dual-drive subsystem, a water supply circulation subsystem, and an intelligent control subsystem; The waste heat recovery subsystem includes a carbon calcining furnace 11, a waste heat boiler 12, a flue gas duct 13, and a main steam duct 14. The flue gas flow is as follows: carbon calcining furnace 11 — flue gas inlet of waste heat boiler 12 — heat exchange with superheater, evaporator, and economizer in sequence within waste heat boiler 12 — flue gas outlet of waste heat boiler 12. The flue gas outlet of carbon calcining furnace 11 is connected to the flue gas inlet of waste heat boiler 12 via flue gas duct 13, and the steam outlet of waste heat boiler 12 is connected to the steam-electric dual-drive subsystem via main steam duct 14. The wear-resistant and corrosion-resistant coating on the inner wall of the flue gas passage of waste heat boiler 12 is made of SiC-Si3N4 ceramic material with a coating thickness of 0.8-1.5mm. The high-temperature and high-pressure steam output parameters of waste heat boiler 12 are: pressure 2.45-3.82MPa, temperature 380-450℃; the flue gas emission temperature of waste heat boiler 12 is controlled at 180-200℃.

[0025] The steam-electric dual-drive subsystem includes a steam turbine 21, a first clutch 22, a generator 23, a second clutch 24, a fan 25 (load device), a third clutch 26, and a drive motor 27. Through the above equipment setup and the intelligent control subsystem, the drive mode of the fan 25 can be adjusted according to the waste heat situation. The input end of the steam-electric dual-drive subsystem is connected to the waste heat recovery subsystem; its output end is connected to the feedwater circulation subsystem. That is, the power output end of the steam turbine 21 is connected to the generator 23 through the first clutch 22, to the fan 25 through the second clutch 24, and then connected in series with the drive motor 27 through the third clutch 26. The three clutches (24, 24, 26) are driven by their respective electromagnetic drive devices (M01, M02, M03). The first clutch 22, the second clutch 24, and the third clutch 26 are all electromagnetic clutches with a response time ≤0.5s. Data from steam pressure / temperature sensor S02 is collected. When the steam pressure / temperature sensor S02 fails to meet the requirements, steam cannot drive the turbine, thus preventing power generation. In this case, the blower operates in motor-driven mode. The intelligent control subsystem disengages the first clutch 22 and the second clutch 24, and opens the third clutch 26, allowing the drive motor 27 to drive the blower 25 independently. At this time, the blower speed is monitored; the blower speed r ≤ 2940 rpm. Continue collecting data from steam pressure / temperature sensor S02. When the steam pressure / temperature sensor S02 meets the requirements and the driving requirements are met, the turbine and motor drive the fan together, entering a combined drive mode. The intelligent control subsystem controls the first clutch 22 to disengage and the second clutch 24 and third clutch 26 to engage. The turbine 21 and drive motor 27 work together to drive the fan 25. At this time, the fan speed is monitored and controlled to be 2940 ≤ r ≤ 2960 rpm. Data from the fan speed sensor S02 is collected. Increased waste heat leads to increased steam volume, which in turn increases the fan speed. Therefore, when the speed r ≥ 2960 rpm, the conditions for steam to drive the fan independently are met, and the system enters steam drive mode. The intelligent control subsystem controls the first clutch 22 and the third clutch 26 to disengage, and the second clutch 24 to engage, allowing the turbine 21 to drive the fan 25 independently. Continue collecting data from the wind turbine speed sensor S02. When the speed continues to increase and r ≥ 2980 rpm, it indicates that there is surplus waste heat beyond meeting the wind turbine drive requirements. At this point, the system enters the drive + power generation mode. The intelligent control subsystem controls the third clutch to disengage, while simultaneously opening the first and second clutches. The turbine drives the wind turbine and drives the generator to generate electricity.

[0026] The feedwater circulation subsystem includes a turbine exhaust pipe 31, a condenser 32, a condenser drain pipe 33, a condensate pump 34, a condensate pipe 35, a deaerator 36, a deaerator outlet pipe 37, a feedwater pump 38, and a main feedwater pipe 39. The exhaust port of the turbine 21 is connected to the inlet of the condenser 32 through the turbine exhaust pipe 31. The exhaust steam after the turbine 21 has done its work enters the condenser 32 to be cooled and condensed into condensate. The outlet of the condenser 32 is connected to the inlet of the condensate pump 34 through the condenser drain pipe 33, and the outlet of the condensate pump 34 is connected to the inlet of the deaerator 36 through the condensate pipe 35, so as to transport the condensate to the deaerator 36. The deaerator 36 is used to remove oxygen from the condensate to prevent oxygen corrosion of the equipment. Its outlet is connected to the inlet of the feed water pump 38 through the deaerator outlet pipe 37. The outlet of feedwater pump 38 is connected to the feedwater inlet of waste heat boiler 12 via main feedwater pipeline 39, delivering treated feedwater to waste heat boiler 12 for reheating to generate steam, completing a closed-loop cycle. Control logic: The controller automatically switches the drive mode based on flue gas temperature, steam parameters, and fan 25 load. The intelligent control subsystem, in addition to cooperating with the steam-electric dual-drive subsystem to adjust the drive mode of the fan 25, can also adjust the automatic regulation and operation of the waste heat boiler 12 and the feedwater circulation subsystem according to the waste heat of the flue gas of the carbon calcining furnace 11. Through the DCS, it controls the operation of the first condensate pump motor M21 and the second condensate pump motor M22 of the condensate pump 34, and the first feedwater pump motor M31 and the second feedwater pump motor M32 of the feedwater pump 38, thereby meeting the normal operation of the waste heat boiler 12.

[0027] The above description is only a preferred embodiment of the invention patent, but the invention patent is not limited to the specific embodiments described above. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the invention patent.

Claims

1. A waste heat utilization method for an aluminum carbon plant using a dual-drive steam and electric system, characterized in that, The method is based on a waste heat recovery subsystem, a steam-electric dual-drive subsystem, a water supply circulation subsystem, and an intelligent control subsystem, wherein the input end of the steam-electric dual-drive subsystem is connected to the waste heat recovery subsystem. Its output end is connected to the water supply circulation subsystem; the steam-electric dual-drive subsystem includes a steam turbine (21), a first clutch (22), a generator (23), a second clutch (24), a fan (25), a third clutch (26), and a drive motor (27); the intelligent control subsystem controls the operation mode of the steam-electric dual-drive subsystem based on the data returned by the set flue gas temperature sensor S01, steam pressure / temperature sensor S02, and fan speed sensor S03, realizing the integrated operation process of waste heat recovery, equipment drive, and waste electricity generation, including: When the steam pressure / temperature sensor S02 fails to meet the requirements, the steam cannot drive the turbine. At this time, the fan adopts the motor drive mode. The intelligent control subsystem controls the first clutch (22) and the second clutch (24) to disengage and the third clutch (26) to open. The drive motor (27) drives the fan (25) alone. The fan speed sensor (S03) monitors the fan speed. In this working mode, the fan speed r is: r≤2940rpm. When the steam pressure / temperature sensor S02 meets the requirements, the steam turbine and the motor drive the fan together, and at this time, the combined drive mode is entered; the intelligent control subsystem controls the first clutch (22) to disengage, and the second clutch (24) and the third clutch (26) to open, and the steam turbine (21) and the drive motor (27) work together to drive the fan (25); at this time, the fan speed sensor (S03) monitors the fan speed. In this working mode, the fan speed r is: 2940≤r≤2960rpm; When the available waste heat increases, the power generated by the steam turbine increases, which will increase the fan speed. When the speed r≥2960rpm, the conditions for driving the fan independently are met, and the steam drive mode is entered. The intelligent control subsystem controls the first clutch (22) to disconnect from the third clutch (26) and opens the second clutch (24), so that the steam turbine (21) drives the fan (25) independently. As the residual heat continues to increase, causing the fan speed to continue to increase, when r≥2980rpm, the drive and power generation mode is entered; the intelligent control subsystem controls the third clutch to disengage, and simultaneously opens the first and second clutches, so that the turbine drives the fan and drives the generator to generate electricity.

2. The method according to claim 1, characterized in that: The feedwater circulation subsystem includes a turbine exhaust pipe (31), a condenser (32), a condensate pump (34), a deaerator (36), a feedwater pump (38), and supporting pipes. The turbine (21) exhaust port is connected to the condenser (32) through the exhaust pipe (31), the condenser (32) is connected to the deaerator (36) through the condensate pump (34), and the deaerator (36) is connected to the feedwater inlet of the waste heat boiler (12) through the feedwater pump (38), forming a closed loop. The intelligent control subsystem controls the operation of the first feedwater pump motor M31 and the second feedwater pump motor M32 according to the data of the flue gas temperature sensor S01, thereby adjusting the feedwater circulation subsystem to meet the requirements of the waste heat boiler 12.

3. The method according to claim 1, characterized in that: The power output end of the steam turbine (21) is connected to the generator (23) through the first clutch (22), to the fan (25) through the second clutch (24), and then connected in series with the drive motor (27) through the third clutch (26).

4. The method according to claim 2, characterized in that: The first clutch (22), the second clutch (24), and the third clutch (26) are all electromagnetic clutches with a response time of ≤0.5s.

5. The method according to claim 1, characterized in that: The flue gas temperature sensor is installed on the flue gas duct, the steam pressure / temperature sensor is installed on the main steam duct, and the fan speed sensor is installed on the fan drive shaft.

6. The method according to any one of claims 1-5, characterized in that: The waste heat recovery subsystem includes a carbon calcining furnace (11), a waste heat boiler (12), a flue gas duct (13), and a main steam duct (14). The flue gas outlet of the carbon calcining furnace (11) is connected to the flue gas inlet of the waste heat boiler (12) through the flue gas duct (13), and the steam outlet of the waste heat boiler (12) is connected to the steam-electric dual-drive subsystem through the main steam duct (14).

7. The method according to claim 6, characterized in that: The wear-resistant and corrosion-resistant coating on the inner wall of the flue gas passage of the waste heat boiler (12) is made of SiC-Si3N4 ceramic material with a coating thickness of 0.8-1.5mm.

8. The method according to claim 7, characterized in that: The steam parameters output by the waste heat boiler (12) are: pressure 2.45-3.82MPa, temperature 380-450℃; the flue gas emission temperature of the waste heat boiler (12) is controlled at 180-200℃.

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