Energy-saving heat exchange system and heat exchange method for cast iron smelting

Abstract

The invention provides an energy-saving heat exchange system and method for cast iron smelting. The method comprises the following steps that high-temperature flue gas pretreatment is conducted; carrying out pulsed eddy current enhanced heat exchange; gradient phase change energy storage is carried out; the step of multi-stage waste heat recovery is carried out; carrying out dynamic pressure-regulating spray cooling; a step of carrying out ferrite catalytic conversion; a step of carrying out nanometer membrane filtration; carrying out thermal electrolysis ionization purification; a step of performing intelligent control on the system; and carrying out closed-loop energy reutilization. The energy-saving heat exchange method for cast iron smelting has the following advantages that energy is saved, efficiency is improved, and the waste heat recovery rate is gt; combustion-supporting air is preheated to 400 DEG C, and the consumption of smelting fuel is reduced by 15-20%; the service life is prolonged: scaling of the heat exchange tube is inhibited by pulse current, and the service life of equipment is prolonged to more than 5 years; near zero emission: the heavy metal removal rate gt; 95%, NOxlt; the concentration is 50 mg / Nm, and the ultra-low emission requirement of GB 28664-2012 is met; intelligent regulation and control: the fluctuation of the smelting working condition is dynamically responded, and the system energy consumption is reduced by 25%.

Description

Technical Field

[0001] This invention specifically relates to an energy-saving heat exchange system and method for cast iron smelting. Background Technology

[0002] During the cast iron smelting process, high-temperature flue gas (600–1400℃) carries a large amount of waste heat (accounting for 30–40% of energy consumption), but existing technologies have the following problems:

[0003] Low waste heat recovery rate: Traditional tubular heat exchangers only recover 30-50% of the heat energy, and the flue gas outlet temperature is still as high as 300°C or more, and they are prone to cracking due to thermal stress.

[0004] High-temperature corrosion and blockage: Flue gas contains dust (6–10 kg / ton of molten iron), SO2, CO, etc., which are prone to scale formation on heat exchange surfaces at high temperatures, reducing heat transfer efficiency and shortening equipment life.

[0005] Energy consumption and pollution coexist: Existing spray cooling requires a large amount of cooling water, and subsequent purification equipment (such as bag filters) cannot directly handle high-temperature gases, requiring the addition of a pre-cooling system, which increases energy consumption.

[0006] The industry urgently needs an integrated solution for an energy-saving heat exchange system and method for cast iron smelting that combines high-efficiency heat exchange, corrosion resistance, and low energy consumption. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing an energy-saving heat exchange method for cast iron smelting, which can effectively solve the aforementioned problems.

[0008] To achieve the above requirements, the technical solution adopted by the present invention is: to provide an energy-saving heat exchange method for cast iron smelting, the energy-saving heat exchange method for cast iron smelting comprising the following steps:

[0009] S1: Steps for pretreating high-temperature flue gas;

[0010] S2: Steps for enhancing heat transfer with pulsed eddy currents;

[0011] S3: Steps for gradient phase change energy storage;

[0012] S4: Steps for multi-stage waste heat recovery;

[0013] S5: Steps for dynamic pressure-regulating spray cooling;

[0014] S6: The step of ferrite catalytic conversion;

[0015] S7: Steps for performing nanofiltration;

[0016] S8: The step of performing thermoelectric decomposition purification;

[0017] S9: Steps for implementing an intelligent control system;

[0018] S10: Steps for closed-loop energy reuse.

[0019] The advantages of this energy-saving heat exchange method for cast iron smelting are as follows:

[0020] Energy saving and efficiency improvement: Waste heat recovery rate >80%, combustion air preheated to 400℃, reducing smelting fuel consumption by 15-20%;

[0021] Extended lifespan: Pulsed current suppresses scaling on heat exchange tubes, extending equipment lifespan to more than 5 years (compared to 2-3 years for traditional equipment).

[0022] Near-zero emissions: Heavy metal removal rate >95%, NO x <50 mg / Nm³, meeting the ultra-low emission standard of GB 28664-2012;

[0023] Intelligent control: Dynamically responds to fluctuations in smelting conditions, reducing system energy consumption by 25%. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, use the same reference numerals to denote the same or similar parts. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0025] Figure 1 A schematic diagram of a heat exchange method for energy-saving cast iron smelting according to an embodiment of this application is shown. Detailed Implementation

[0026] To make the objectives, technical solutions and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments.

[0027] In the following description, references to "an embodiment," "an embodiment," "an example," "example," etc., indicate that the described embodiment or example may include a particular feature, structure, characteristic, property, element, or limitation, but not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element, or limitation. Furthermore, the repeated use of the phrase "an embodiment according to this application," while possibly referring to the same embodiment, does not necessarily refer to the same embodiment.

[0028] For simplicity, certain technical features known to those skilled in the art are omitted in the following description.

[0029] According to one embodiment of this application, an energy-saving heat exchange method for cast iron smelting is provided, such as... Figure 1 As shown, it includes the following steps:

[0030] S1: Steps for pretreating high-temperature flue gas;

[0031] S2: Steps for enhancing heat transfer with pulsed eddy currents;

[0032] S3: Steps for gradient phase change energy storage;

[0033] S4: Steps for multi-stage waste heat recovery;

[0034] S5: Steps for dynamic pressure-regulating spray cooling;

[0035] S6: The step of ferrite catalytic conversion;

[0036] S7: Steps for performing nanofiltration;

[0037] S8: The step of performing thermoelectric decomposition purification;

[0038] S9: Steps for implementing an intelligent control system;

[0039] S10: Steps for closed-loop energy reuse.

[0040] According to one embodiment of this application, step S1 of the energy-saving heat exchange method for cast iron smelting specifically includes: when the flue gas outlet temperature of the smelting furnace is ≤1400℃, the flue gas passes through the gravity settling chamber from the outlet of the smelting furnace to remove particles >50μm. By expanding the volume and reducing the velocity (flow rate <1m / s), the coarse particles are settled using Stokes' law to prevent subsequent wear of the heat exchange tubes.

[0041] According to one embodiment of this application, step S2 of the energy-saving heat exchange method for cast iron smelting specifically includes: flue gas entering a pulsed eddy current heat exchanger, applying a pulsed current with a frequency of 20Hz and a voltage of 800V to the outer wall of the heat exchange tube; the pulsed current induces eddy currents on the surface of the cast iron heat exchange tube, disrupting the boundary layer stagnant gas film and improving the heat transfer coefficient (K value increases by 40–60%). Maxwell's electromagnetic field equations are coupled with the heat conduction equations. ;

[0042] in:

[0043] k: Thermal conductivity (unit: W / (m·K)), reflecting the material's thermal conductivity;

[0044] T: Temperature (unit: K), a function of space and time;

[0045] Divergence and gradient operators represent the spatial variation of heat flux density and the spatial distribution gradient of temperature;

[0046] Material density (unit: kg / m³);

[0047] Specific heat capacity (unit: J / (kg·K)), the amount of heat required to raise the temperature of a unit mass of substance by 1 K;

[0048] J: Current density vector (unit: A / m²), the induced current density generated by eddy currents;

[0049] J·E: The dot product of current density and electric field strength (unit: W / m³), representing the Joule heat power generated by eddy currents per unit volume.

[0050] According to one embodiment of this application, step S3 of the energy-saving heat exchange method for cast iron smelting specifically includes: the flue gas after heat exchange (reduced to 600°C) enters the phase change energy storage device and exchanges heat with the Al-Si alloy (melting point 575°C). The latent heat of phase change absorbs the sensible heat of the flue gas, achieving constant temperature heat release (heat release temperature 550°C) to preheat the combustion air.

[0051] According to one embodiment of this application, step S4 of the energy-saving heat exchange method for cast iron smelting specifically includes: the flue gas is cooled to 300°C and then enters a two-stage heat pipe heat exchanger; the first stage preheats the combustion air of the smelting furnace to 400°C; the second stage heats the process water; and the heat pipe working fluid (sodium-potassium alloy) evaporates and condenses in the vacuum tube, achieving a heat transfer efficiency of over 90%.

[0052] According to one embodiment of this application, step S5 of the energy-saving heat exchange method for cast iron smelting specifically includes: after the flue gas is cooled to 180°C, it enters the spray tower; the atomization particle size (50–100 μm) of the 0.5 MPa high-pressure nozzle is adjusted according to the real-time temperature; under the Leidenfrost effect, micro water droplets are suspended and evaporated in the high-temperature flue gas, avoiding wall wetting; the Venturi tube accelerates the airflow and enhances gas-liquid contact.

[0053] According to one embodiment of this application, step S6 of the energy-saving heat exchange method for cast iron smelting specifically includes: after spraying, the flue gas (80°C) passes through the Fe2O3 catalyst bed, and ammonia water (NH3 / NO molar ratio 1.2) is injected, and Fe³⁺ activates NH3 to selectively reduce NO. x (Removal rate > 85%), while also adsorbing heavy metal ions;

[0054] According to one embodiment of this application, step S7 of the energy-saving heat exchange method for cast iron smelting specifically includes: flue gas entering a PTFE nanofiber membrane module (pore size 0.1 μm) to capture PM2.5 and aerosols; electret charges on the membrane surface form an electrostatic barrier to enhance the capture of submicron particles (efficiency > 99.5%).

[0055] According to an embodiment of this application, step S8 of the energy-saving heat exchange method for cast iron smelting specifically includes: applying a 10 kV DC electric field after the membrane module to ionize residual VOCs, generating O and OH free radicals through corona discharge, oxidizing organic compounds such as benzo[a]pyrene, with the reaction pathway being ceC20H12+10O3−>20CO2+6H2O;

[0056] According to one embodiment of this application, step S9 of the energy-saving heat exchange method for cast iron smelting specifically includes: real-time monitoring of flue gas flow rate and composition (O2, CO, NO) by an embedded system. x The sensor dynamically adjusts the parameters in steps S2–S8, using a fuzzy PID algorithm with the flue gas enthalpy as the feedback variable to optimize the pulse frequency and spray volume.

[0057] According to one embodiment of this application, step S10 of the energy-saving heat exchange method for cast iron smelting specifically includes: the purified gas (40°C) is discharged by an induced draft fan, the waste heat of the system drives an absorption chiller to cool the plant area, and the LiBr-H2O working fluid absorbs low-temperature heat (≥70°C) for cooling, with a comprehensive energy efficiency ratio of 0.8.

[0058] According to one embodiment of this application, an energy-saving heat exchange system for cast iron smelting is provided, which uses the above-described energy-saving heat exchange method for cast iron smelting.

[0059] The embodiments described above are merely examples 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 all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. An energy-saving heat exchange method for cast iron smelting, characterized in that, Includes the following steps: S1: Steps for pretreating high-temperature flue gas; S2: Steps for enhancing heat transfer with pulsed eddy currents; S3: Steps for gradient phase change energy storage; S4: Steps for multi-stage waste heat recovery; S5: Steps for dynamic pressure-regulating spray cooling; S6: The step of ferrite catalytic conversion; S7: Steps for performing nanofiltration; S8: The step of performing thermoelectric decomposition purification; S9: Steps for implementing an intelligent control system; S10: Steps for closed-loop energy reuse.

2. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S1 specifically includes: when the flue gas outlet temperature of the smelting furnace is ≤1400℃, the flue gas passes through the gravity settling chamber from the smelting furnace outlet to remove particles >50μm. By expanding the volume and reducing the velocity, Stokes' law is used to achieve the settling of coarse particles and prevent subsequent wear of heat exchange tubes.

3. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S2 specifically includes: Flue gas enters the pulsed eddy current heat exchanger, and a pulsed current with a frequency of 20 Hz and a voltage of 800 V is applied to the outer wall of the heat exchange tube. The pulsed current induces eddy currents on the surface of the cast iron heat exchange tube, destroying the boundary layer stagnant gas film and improving the heat transfer coefficient. Maxwell's electromagnetic field equations are coupled with the heat conduction equations. ； in: k: Thermal conductivity, reflecting the material's ability to conduct heat; T: Temperature, a function of space and time; Divergence and gradient operators represent the spatial variation of heat flux density and the spatial distribution gradient of temperature; Material density; Specific heat capacity: the amount of heat required to raise the temperature of a unit mass of a substance by 1 K. J: Current density vector, the induced current density generated by eddy currents; J·E: The dot product of current density and electric field strength, representing the Joule thermal power generated by eddy currents per unit volume.

4. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S3 specifically includes: After heat exchange, the flue gas is reduced to 600°C and enters the phase change energy storage device to exchange heat with the Al-Si alloy. The latent heat of phase change absorbs the sensible heat of the flue gas, achieving constant temperature heat release. The heat release temperature is 550°C, which is used to preheat the combustion air.

5. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S4 specifically includes: after the flue gas is cooled to 300°C, it enters a two-stage heat pipe heat exchanger. The first stage preheats the combustion air of the smelting furnace to 400°C, and the second stage heats the process water. The heat pipe working fluid evaporates, condenses and circulates in the vacuum tube, with a heat transfer efficiency of over 90%.

6. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S5 specifically includes: After the flue gas is cooled to 180°C, it enters the spray tower. The atomization particle size of the 0.5 MPa high-pressure nozzle is adjusted according to the real-time temperature. Under the Leidenfrost effect, micro water droplets are suspended and evaporated in the high-temperature flue gas to avoid wetting the wall. The Venturi tube accelerates the airflow and enhances the gas-liquid contact.

7. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S6 specifically includes: after spraying, the flue gas passes through the Fe2O3 catalyst bed, and ammonia water and Fe³⁺ are injected to activate NH3 and selectively reduce NO. x It also adsorbs heavy metal ions; Step S7 specifically includes: flue gas entering the PTFE nanofiber membrane module to capture PM2.5 and aerosols; electret charges on the membrane surface form an electrostatic barrier to enhance the capture of submicron particles (efficiency > 99.5%).

8. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, Step S8 specifically includes: applying a 10 kV DC electric field after the membrane module to ionize residual VOCs, generating O and OH free radicals through corona discharge, oxidizing organic compounds such as benzo[a]pyrene, with the reaction pathway being ceC20H12+10O3−>20CO2+6H2O; Step S9 specifically includes: real-time monitoring of flue gas flow rate, O2 composition, CO composition, and NO by the embedded system. x The composition and parameters of steps S2–S8 are dynamically adjusted based on a fuzzy PID algorithm, using the enthalpy of the flue gas as a feedback variable to optimize the pulse frequency and spray volume.

9. The energy-saving heat exchange method for cast iron smelting according to claim 1, characterized in that, The specific steps of step S10 include: the purified gas is discharged by an exhaust fan, the waste heat of the system drives an absorption chiller to cool the plant area, and the LiBr-H2O working fluid absorbs low-temperature heat for cooling, with a comprehensive energy efficiency ratio of 0.

8.

10. An energy-saving heat exchange system for cast iron smelting, characterized in that, The energy-saving heat exchange method for cast iron smelting as described in any one of claims 1 to 9 was used.

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