Fly ash treatment device, system and method for electromagnetic heating superheated steam coupling rotary kiln

Abstract

The invention relates to the technical field of environmental protection equipment and solid waste treatment, and discloses a fly ash treatment device, system and method of an electromagnetic heating superheated steam coupling rotary kiln. Superheated steam with precise temperature control (400 + / -0.5 DEG C) is generated through multi-stage electromagnetic induction heating; and injecting into a rotary kiln through a specially designed steam distribution system to form a gas-solid two-phase spiral flow with fly ash, thereby realizing the degradation rate of 99.8% of dioxin and the stabilization of more than 95% of heavy metals. The system comprises an electromagnetic heating superheated steam generator, a rotary kiln pyrolyzing furnace, a cooperative control system and a waste heat recovery device, has the characteristics of low energy consumption (less than or equal to 180kWh / t), high efficiency, no secondary pollution and the like, and is suitable for harmless treatment of household garbage incineration fly ash.

Description

Technical Field

[0001] This invention relates to the field of environmental protection equipment and solid waste treatment technology, and in particular to a fly ash treatment device, system and method for an electromagnetically heated superheated steam coupled rotary kiln. Background Technology

[0002] With the acceleration of urbanization, the treatment of fly ash from municipal solid waste incineration has become a major challenge in the environmental protection field. Fly ash contains high concentrations of organic pollutants such as dioxins and furans, as well as heavy metals such as lead and cadmium, and is classified as hazardous waste (HW18). Traditional fly ash treatment technologies mainly suffer from the following problems:

[0003] 1. Cement solidification method: Although it can stabilize some heavy metals, it is ineffective in degrading organic pollutants and has a large volume increase ratio (1.2-1.5), which poses a long-term risk of pollutant leaching.

[0004] 2. High-temperature melting method: requires a temperature of over 1300℃, has extremely high energy consumption (800-1000kWh / t), and will produce secondary fly ash (accounting for about 3-5% of the processing volume).

[0005] 3. Chemical stabilization: The treatment cost is high (about 500-800 yuan / ton), and the effect on dioxin degradation is limited, achieving only a degradation rate of 50-70%.

[0006] Existing pyrolysis technologies, such as CN223171608U, employ low-temperature pyrolysis systems. While they can achieve 99% dioxin degradation at 350℃, they rely on gas heating, resulting in low temperature control accuracy (±15℃) and insufficient steam utilization. CN222053409U, using an electric arc heater, can reduce pollution, but suffers from severe electrode wear and high maintenance costs. Electromagnetic heating technology in rotary kiln applications (such as CN119681573A) is mostly limited to cylinder heating and is not coupled with a superheated steam system.

[0007] Traditional superheated steam generators (such as CN222824335U) use resistance heating, which has high thermal inertia and slow response speed (5-8℃ / s), making it difficult to meet the precise temperature control requirements of fly ash pyrolysis. While multi-stage electromagnetic induction heating steam generators (such as patent number ZL202321633300.4) can provide a temperature control accuracy of ±1℃, they do not involve a collaborative design with the rotary kiln. Summary of the Invention

[0008] This invention provides a fly ash treatment device, system, and method for an electromagnetically heated superheated steam coupled rotary kiln to solve existing technical problems, thereby addressing issues such as high energy consumption, incomplete pollutant degradation, and poor system stability in existing fly ash treatment technologies.

[0009] To solve the above-mentioned technical problems, according to one aspect of the present invention, more specifically, a fly ash treatment system for an electromagnetically heated superheated steam coupled rotary kiln, comprising:

[0010] 1) Electromagnetically heated superheated steam generation subsystem:

[0011] The heat exchange device, consisting of three sets of electromagnetic coils with different power (power gradient: 20kW / 50kW / 100kW), is adopted with a multi-stage electromagnetic induction heating structure and arranged sequentially along the steam flow direction.

[0012] The lower and upper cylinders (material: 06Cr25Ni20, wall thickness 8mm) made of high-temperature and pressure-resistant seamless steel pipe serve as the heating carrier, with a design pressure of 4.5MPa and a temperature resistance limit of 650℃.

[0013] A gas-liquid separator is used to ensure the dryness of the output gas;

[0014] The intelligent temperature control system adopts a three-variable PID algorithm and achieves precise temperature control of 400±0.5℃ through dual composite detection by a K-type thermocouple (measurement range 0-600℃) and an infrared thermometer (measurement range 200-800℃).

[0015] 2) Rotary kiln pyrolysis subsystem:

[0016] The kiln body has an inclination angle of 1.5-3° and an adjustable rotation speed of 0.5-5 r / min. It is equipped with a spiral guide plate (lead angle of 15°, height of 1 / 8 of the kiln diameter).

[0017] Double-layer structure design: the inner cylinder is made of 310S stainless steel ( =12mm), the outer cylinder is made of Q345R steel plate ( =16mm), with a 150mm thick aerogel insulation layer in the middle (thermal conductivity 0.018W / m·K);

[0018] The steam distribution system includes 12 radial nozzles (8mm orifice) and 1 axial swirl nozzle (45° swirl angle) to ensure full contact between steam and fly ash.

[0019] 3) Pollutant degradation control subsystem:

[0020] a. Employing a three-factor synergistic control approach: temperature, time, and atmosphere.

[0021] Temperature control: 400±0.5℃ (adjusted in real time via electromagnetic heating power);

[0022] nTime control: Residence time 30±0.5min (adjusted by kiln rotation speed and tilt angle);

[0023] Atmosphere control: Maintain a slight negative pressure (-50~-100Pa), with an oxygen content ≤0.5 vol.

[0024] b. Equipped with an online monitoring system, including a dioxin rapid detector (response time 5 min) and a heavy metal flue gas analyzer (detection limit 0.01 mg / m³).

[0025] 4) Waste heat recovery subsystem, adopting a three-stage heat recovery design:

[0026] Level 1: Flue gas-steam heat exchanger (recovery efficiency 65%)

[0027] Level 2: Steam circulation system (transfers heat to the pretreatment drying section)

[0028] Level 3: Heat pipe air preheater (heats the intake air to 150°C).

[0029] This continuous degradation system and method for fly ash pollutants based on the synergistic effect of electromagnetically heated 400℃ superheated steam and rotary kiln achieves:

[0030] 1. Dioxin degradation rate ≥99.5% (detection limit 0.1ng-TEQ / kg);

[0031] 2. Heavy metal curing rate ≥ 95% (calculated as Pb, Cd, Zn);

[0032] 3. Energy consumption ≤180kWh / t (82% lower than traditional melting method);

[0033] 4. The system temperature control accuracy is ±0.5℃ (3 times higher than existing technology).

[0034] A fly ash treatment device for an electromagnetically heated superheated steam coupled rotary kiln includes:

[0035] A multi-stage electromagnetic induction heating superheated steam generator;

[0036] Rotary kiln with a steam distribution system;

[0037] Temperature-time-atmosphere coordinated control system;

[0038] Waste heat recovery device.

[0039] Furthermore, the rotary kiln with a steam distribution system includes: radial nozzles and axial swirl nozzles, with nozzle orifice diameters of 1 / 75 to 1 / 100 of the kiln body diameter;

[0040] The temperature-time-atmosphere coordinated control system includes: a three-variable PID temperature controller, a kiln speed-tilt angle linkage regulator, and a micro-negative pressure atmosphere maintenance device.

[0041] A method for treating fly ash in an electromagnetically heated superheated steam coupled rotary kiln includes:

[0042] S1. Pre-treat fly ash to a moisture content of ≤5-8%;

[0043] S2. Introduce superheated steam at 400±0.5℃, with a superheated steam to fly ash mass ratio of 0.6-1.2:1;

[0044] S3. Control the residence time of fly ash in the rotary kiln to be 30±0.5min;

[0045] S4. Maintain the system oxygen content ≤0.5 vol%, with a slight negative pressure of -50 to -100 Pa.

[0046] Furthermore, the process of generating the superheated steam includes:

[0047] The water supply is heated by three stages of electromagnetic induction heating, with temperature rises of 150℃, 200℃ and 50℃ for each stage, respectively.

[0048] The final steam superheat is ≥120℃.

[0049] Furthermore, the treated fly ash meets the following requirements:

[0050] Dioxin content ≤5ng-TEQ / kg;

[0051] Pb leaching concentration ≤ 0.05 mg / L;

[0052] Cd leaching concentration ≤ 0.01 mg / L.

[0053] The present invention provides a fly ash treatment device, system, and method for an electromagnetically heated superheated steam coupled rotary kiln. Compared with the prior art, the advantages achieved by this method are as follows:

[0054] 1. This invention generates precisely temperature-controlled superheated steam by employing multi-stage electromagnetic induction heating technology, combined with the gas-solid two-phase spiral flow design in the rotary kiln, achieving efficient thermal energy utilization in the fly ash treatment process, significantly reducing system energy consumption, and improving the thermal energy utilization rate of steam, thus achieving a high level of overall energy efficiency.

[0055] 2. This invention achieves the deep degradation of dioxin-like organic pollutants and the effective stabilization of heavy metals through the synergistic effect of thorough mixing of superheated steam and fly ash and precise control of temperature, time and atmosphere. The pollutant content of the treated fly ash is significantly reduced, meeting strict environmental emission standards.

[0056] 3. This invention utilizes the rapid response and low thermal inertia characteristics of electromagnetic heating, enabling the system to start up quickly and maintain stable operation. At the same time, the long lifespan design of the electromagnetic coil reduces maintenance frequency and cost, improving the reliability and continuous operation capability of the equipment.

[0057] 4. This invention reduces the overall cost of fly ash treatment through system integration optimization and the application of waste heat recovery technology. At the same time, the compact equipment layout reduces the floor space required, making this technology have significant advantages in terms of economy and space utilization. Attached Figure Description

[0058] Figure 1 This is a flowchart illustrating the principle of the present invention;

[0059] Figure 2 This is a front view of the electromagnetic heating superheated steam generation subsystem of the present invention;

[0060] Figure 3 This is a side view of the electromagnetic heating superheated steam generation subsystem of the present invention.

[0061] In the diagram: 1. Lower cylinder; 2. Upper cylinder; 3. Heat exchanger; 4. Steam-water separator. Detailed Implementation

[0062] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] like Figure 1 As shown, when the fly ash treatment system of the electromagnetically heated superheated steam coupled rotary kiln is working, the pre-treated fly ash (moisture content ≤5-8%) enters the feed end of the rotary kiln through a sealed conveying device. Simultaneously, 400℃ superheated steam generated by the electromagnetic heating system is injected in multiple directions through the kiln head and radial nozzles. Under the rotation of the rotary kiln, the fly ash and superheated steam form a "gas-solid two-phase spiral flow," achieving the following synergistic effect:

[0064] 1. Heat conduction mechanism: Superheated steam rapidly transfers sensible heat (1674kJ / kg) to fly ash particles, causing them to heat up to the target temperature within 30 seconds;

[0065] 2. Micro-explosion effect: Steam penetrates into the internal pores of fly ash particles, causing capillary rupture at 400℃, promoting the exposure of pollutants;

[0066] 3. Molecular bond breaking: The CO bond (bond energy of about 465 kJ / mol) in the dioxin molecule breaks under thermodynamic conditions at 400℃, and is converted into a low-toxicity hydrocarbon through the Stevens rearrangement reaction;

[0067] 4. Heavy metal stabilization: in steam The molecules form a stable hydroxyapatite structure with heavy metal oxides.

[0068] The treated fly ash is rapidly cooled to below 80°C by a kiln tail water cooling device (such as CN223077266U) to prevent the resynthesis of dioxins.

[0069] Example 1: 200kg / h pilot-scale system

[0070] like Figure 2 , 3 As shown, the equipment parameters are:

[0071] Electromagnetic heater: Three-level power configuration (20kW+50kW+100kW), operating frequency 20kHz;

[0072] Steam pipe: Φ89×8mm, length 4.5m, material 06Cr25Ni20;

[0073] Rotary kiln: Φ600×5000mm, rotation speed 1.8r / min, tilt angle 2°;

[0074] Operating procedures:

[0075] 1. System preheating: Start the electromagnetic heater and raise the steam temperature to 400℃ within 18 minutes;

[0076] 2. Feed control: Fly ash is continuously fed at a rate of 200 kg / h, while steam is injected at a flow rate of 120 kg / h.

[0077] 3. Process monitoring: Infrared thermometers are used to ensure that the temperature in the middle of the kiln is maintained at 400±0.5℃;

[0078] 4. Product collection: The treated fly ash is discharged through a water-cooled screw conveyor (cooled to 80℃);

[0079] Performance testing:

[0080] Dioxin degradation rate: 99.82% (from an initial 1520 ng-TEQ / kg to 2.7 ng-TEQ / kg);

[0081] Energy consumption: 165 kWh / t (including system auxiliary power consumption);

[0082] No coking occurred after 30 days of continuous operation.

[0083] By combining a three-stage gradient power electromagnetic coil with a precision temperature control system, precise temperature control of the small-flow fly ash treatment process was achieved. Its innovative gas-solid two-phase spiral flow design ensured the full mixing of superheated steam and fly ash particles, thereby achieving efficient degradation of dioxins and effective stabilization of heavy metals at a low energy consumption level, verifying the feasibility and superiority of this technical route.

[0084] Example 2: 5t / h Industrial System

[0085] Equipment improvements:

[0086] The electromagnetic heater adopts a modular design (six 50kW modules connected in parallel).

[0087] The rotary kiln is equipped with a double spiral guide plate (with alternating lead angles of 15° and 30°).

[0088] The steam nozzle has been optimized into a swirl-direct current composite structure.

[0089] Economic Analysis:

[0090] Investment cost: approximately RMB 5.8 million (of which the electromagnetic heating system accounts for 35%).

[0091] Operating costs: Including electricity consumption (185kWh / t), labor, maintenance, etc., totaling 305 yuan / ton;

[0092] Investment payback period: 3.2 years (based on a processing fee of 800 yuan / ton).

[0093] Through modular design of electromagnetic heating, double helix guide plate structure and optimization of composite nozzles, the system's processing capacity and operational stability have been significantly improved. Its modular configuration enhances the maintainability and scale adaptability of the equipment, enabling the technology to maintain its comprehensive advantages of low energy consumption, high efficiency and economy in large-scale applications.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A fly ash treatment system for an electromagnetically heated superheated steam coupled rotary kiln, characterized in that, include: The electromagnetic heating superheated steam generation subsystem adopts a multi-stage electromagnetic induction heating structure to generate superheated steam at 400±0.5℃. The rotary kiln pyrolysis subsystem, connected to the electromagnetic heating superheated steam generation subsystem, includes a kiln body and a steam distribution system, and is used to pyrolyze fly ash and superheated steam into a gas-solid two-phase spiral flow. A pollutant degradation control subsystem is connected to the rotary kiln pyrolysis subsystem for coordinated control of temperature, time, and atmosphere. The waste heat recovery subsystem is connected to the rotary kiln pyrolysis subsystem and is used to recover and utilize the system's waste heat.

2. The fly ash treatment system for an electromagnetically heated superheated steam coupled rotary kiln according to claim 1, characterized in that: The electromagnetic heating superheated steam generation subsystem includes: A heat exchange device (3) with at least three electromagnetic coils is arranged sequentially along the steam flow direction, with a power gradient configuration; The lower cylinder (1) and the upper cylinder (2) serve as heating carriers. The material is 06Cr25Ni20, the wall thickness is 8mm, the design pressure is 4.5MPa, and the temperature resistance limit is 650℃. A gas-water separator (4) is used to ensure the dryness of the output gas; The intelligent temperature control system employs a three-variable PID algorithm and utilizes dual composite detection via a K-type thermocouple and an infrared thermometer to achieve precise temperature control of 400±0.5℃.

3. The fly ash treatment system for an electromagnetically heated superheated steam coupled rotary kiln according to claim 1, characterized in that: The rotary kiln pyrolysis subsystem includes: The kiln body tilt angle is 1.5-3°, and the rotation speed is adjustable from 0.5-5 r / min; It has an internal spiral guide plate with a lead angle of 15° and a height of 1 / 8 of the kiln diameter; Double-layer structure design: the inner cylinder is made of 310S stainless steel, the outer cylinder is made of Q345R steel plate, and the middle is filled with a 150mm thick aerogel insulation layer with a thermal conductivity of 0.018W / m·K. The steam distribution system includes 12 radial nozzles and 1 axial swirl nozzle. The radial nozzles have an orifice diameter of Φ8mm, and the axial swirl nozzle has a swirl angle of 45°.

4. The fly ash treatment system for an electromagnetically heated superheated steam coupled rotary kiln according to claim 1, characterized in that: The pollutant degradation control subsystem includes: The temperature control unit adjusts the electromagnetic heating power in real time to maintain the temperature at 400±0.5℃; The time control unit adjusts the kiln rotation speed and tilt angle to control the fly ash residence time to 30±0.5min; The atmosphere control unit maintains a slight negative pressure in the system at -50 to -100 Pa, with an oxygen content ≤0.5 vol%. The online monitoring system includes a dioxin rapid detector and a heavy metal flue gas analyzer.

5. The fly ash treatment system for an electromagnetically heated superheated steam coupled rotary kiln according to claim 1, characterized in that: The waste heat recovery subsystem adopts a three-stage heat recovery design: Primary heat recovery: flue gas-steam heat exchanger, with a recovery efficiency of 65%; Secondary heat recovery: A steam circulation system transfers heat to the pretreatment drying section; Three-stage heat recovery: a heat pipe air preheater heats the intake air to 150°C.

6. A fly ash treatment device for an electromagnetically heated superheated steam coupled rotary kiln, characterized in that, The fly ash treatment system for the electromagnetically heated superheated steam coupled rotary kiln according to any one of claims 1-5, the fly ash treatment device for the electromagnetically heated superheated steam coupled rotary kiln, comprises: A multi-stage electromagnetic induction heating superheated steam generator; Rotary kiln with a steam distribution system; Temperature-time-atmosphere coordinated control system; Waste heat recovery device.

7. The fly ash treatment device for an electromagnetically heated superheated steam coupled rotary kiln according to claim 6, characterized in that: The rotary kiln with a steam distribution system includes: radial nozzles and axial swirl nozzles, with nozzle orifice diameters of 1 / 75 to 1 / 100 of the kiln body diameter. The temperature-time-atmosphere coordinated control system includes: a three-variable PID temperature controller, a kiln speed-tilt angle linkage regulator, and a micro-negative pressure atmosphere maintenance device.

8. A method for treating fly ash from an electromagnetically heated superheated steam coupled rotary kiln, characterized in that, The fly ash treatment system for the electromagnetically heated superheated steam coupled rotary kiln according to any one of claims 1-5, the fly ash treatment method for the electromagnetically heated superheated steam coupled rotary kiln, includes: S1. Pre-treat fly ash to a moisture content of ≤5-8%; S2. Introduce superheated steam at 400±0.5℃, with a superheated steam to fly ash mass ratio of 0.6-1.2:1; S3. Control the residence time of fly ash in the rotary kiln to be 30±0.5min; S4. Maintain the system oxygen content ≤0.5 vol%, with a slight negative pressure of -50 to -100 Pa.

9. The fly ash treatment method for an electromagnetically heated superheated steam coupled rotary kiln according to claim 8, characterized in that: The process of generating the superheated steam includes: The water supply is heated by three stages of electromagnetic induction heating, with temperature rises of 150℃, 200℃ and 50℃ for each stage, respectively. The final steam superheat is ≥120℃.

10. The fly ash treatment method for an electromagnetically heated superheated steam coupled rotary kiln according to claim 8, characterized in that: The treated fly ash meets the following requirements: Dioxin content ≤5ng-TEQ / kg; Pb leaching concentration ≤ 0.05 mg / L; Cd leaching concentration ≤ 0.01 mg / L.

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