A sintering waste gas in-situ modified lump ore under-screen powder paving method

Abstract

The present application relates to the technical field of steel metallurgy sintering process, and particularly relates to a lump ore screen-under powder bottoming method based on in-situ modification of sintering waste gas, which comprises the following steps: screening lump ore with a water content of 4% to 7% through two-stage screening to obtain small lump ore with a size of 3 to 8 mm; laying a 10 to 18 mm sintering ore lower layer and a small lump ore upper layer on a pallet grate; using 300 to 450 DEG C waste gas at the head of a sintering machine to penetrate the upper layer of lump ore from below the material layer under negative pressure for 1 to 3 min, so that the water content is reduced to less than or equal to 1.0%, and a 20 to 50 mu m Fe2O3 shell layer is formed on the surface; and the modified lump ore layer is used as a gas permeable skeleton and a filter layer to participate in sintering. The present application solves the problems of lump ore bottoming explosion, control hysteresis and material imbalance, and realizes the synchronous improvement of waste heat resource utilization and sintering ore quality.

Description

Technical Field

[0001] This invention relates to the field of sintering technology in iron and steel metallurgy, specifically to a method for laying underfill powder from lump ore screens based on in-situ modification of sintering waste gas. Background Technology

[0002] As the steel industry faces increasing pressure to reduce costs, the proportion of lump ore in blast furnace feed has been rising year by year, currently reaching 15% to 25%. Lump ore has the advantages of low procurement costs and short process flow, but it generally suffers from high physical water content (4% to 7%), high crystal water content (such as limonite FeO(OH)·nH2O), and is prone to breakage and powdering during transportation.

[0003] To address the utilization of undersize powder from lump ore, existing technology CN115612832A discloses a method for preparing a double-layer bottom layer material using undersize powder from lump ore. This method involves screening lump ore into small-sized 3-8mm lumps and combining them with 10-18mm sintered ore as a bottom layer to achieve material recycling. However, this method has several problems: it only treats the lump ore as a physical filler, ignoring the tendency of high-moisture-content lumps to explode in subsequent high-temperature environments. This leads to the lumps exploding after ignition due to the rapid vaporization of crystal water, generating a large amount of new dust, which not only pollutes the environment but also exacerbates grate blockage and dust collection load. Furthermore, the thickness adjustment relies solely on simple production and consumption calculations, lacking a dynamic compensation mechanism for fluctuations in the on-site screening flow rate. This makes it difficult to precisely control the bottom layer thickness, and the fixed-ratio bottom layer method often results in lump ore accumulation or uncontrolled bottom layer thickness due to fluctuations in screening output, affecting the operational stability of the sintering machine.

[0004] Furthermore, the exhaust gas temperature at the head of the sintering machine (wind boxes 1-3 after ignition) often reaches 350-450℃, containing a large amount of sensible heat. Currently, waste heat recovery systems mainly target the high-temperature section at the tail end (>450℃), while the low-temperature exhaust gas at the head end is mostly directly discharged, and sensible heat resources are not effectively utilized. For example, CN103484661B discloses a sintering waste heat utilization technology that uses the high-temperature exhaust gas (>450℃) at the tail end of the sintering machine to preheat the mixture to reduce solid fuel consumption. Although this technology involves a heating range of 300-500℃, it is fundamentally mismatched with the sintering bottom-laying process: First, the high-temperature exhaust gas at the tail end is usually accompanied by strong positive pressure injection. If it directly acts on the freshly laid bottom-laying material layer, it is very easy to cause the surface of the material layer to be blown away and the structure to be damaged; second, the excessively high temperature will cause the surface of fine-particle ore to be over-sintered, forming a dense thick shell layer, which will block the internal pores of the particles and lose the permeability and filtration function that the bottom-laying material should have.

[0005] Therefore, how to utilize waste heat to reduce energy consumption while simultaneously addressing the issues of crack prevention and permeability of high-moisture-content ore paving materials through reasonable airflow organization and temperature control, and how to achieve dynamic regulation of the paving process, has become an urgent technical challenge. Summary of the Invention

[0006] To address the problems of increased energy consumption, dust generation from cracking, and material imbalance caused by the solidification of sintering parameters in existing lump ore bottom-laying technologies, this invention provides a method and system for bottom-laying lump ore undersize powder based on in-situ modification of sintering waste gas. By constructing a double-layer bottom-laying structure, in-situ dehydration and weak oxidation modification are achieved by utilizing the negative pressure penetration of waste gas at 300-450℃ through the No. 1 to No. 3 wind boxes at the head of the sintering machine. A dense Fe2O3 shell layer is generated on the particle surface to prevent cracking and form a porous filter layer. At the same time, a PID closed-loop control strategy is used to dynamically adjust the bottom-laying thickness, achieving synergistic effects of full-quantity disposal of lump ore undersize powder, efficient utilization of waste heat, and stable bottom-laying process.

[0007] The technical solution of this invention is as follows: This invention provides a method for spreading undersize powder from lump ore based on in-situ modification of sintering waste gas, comprising the following steps: S1. Cascade Screening and Material Monitoring: The raw lump ore undergoes a first-stage screening to separate the ore from the primary screen oversize and the ore from the primary screen undersize. The primary screen oversize is directly supplied to the blast furnace lump ore bin. The primary screen undersize is subjected to a second-stage screening to separate the powder ore <3mm and small-sized lump ore. The powder ore <3mm enters the sintering batching room to participate in mixing and granulation, while the small-sized lump ore is transported to the second bottom material bin. S2, Dynamic double-layer material distribution: A double-layer material structure is laid on the grate bars of the sintering trolley along the thickness direction. The lower layer is the finished sintered ore, and the upper layer is the small-particle block ore obtained in step S1. S3. In-situ heat treatment and mineral phase modification: In the exhaust sintering stage after the igniter of the sintering machine, the high-temperature exhaust gas generated by the wind box at the head of the sintering machine is introduced from below the double-layer bottom material layer through the wind box branch pipe. The negative pressure generated by the main exhaust system penetrates the upper small-particle lumps of ore to carry out in-situ dehydration and weak oxidation treatment, and the modified small-particle lumps of ore are obtained. S4. Co-sintering mineralization: The modified small-sized ore is used as a permeable skeleton and filter layer, and sintered together with the sintering mixture placed on top of it.

[0008] Furthermore, the particle size of the small-sized lumps is 3-8mm, and the particle size of the finished sinter is 10-18mm. By using the 3-8mm small-sized lumps and the 10-18mm finished sinter as upper and lower layers respectively, the porous filter layer formed by the heat treatment of the upper-layer lumps works in synergy with the supporting framework of the lower-layer large-sized sinter. This ensures both the overall permeability of the material layer and the effective interception of fine dust, thus resolving the contradiction that a single-size bottom material cannot simultaneously achieve both permeability and filtration functions.

[0009] Furthermore, in step S1, the moisture content of the raw material lump ore is 4% to 7%, and the raw material lump ore is limonite or highly hydrated hematite.

[0010] Furthermore, in step S1, the second-stage screening process also includes real-time monitoring of the instantaneous processing volume Q of the second-stage screening. screen The oversize yield η is specifically determined by the instantaneous throughput Q collected in real time by the weighing belt conveyor below the second-stage screening. screen The sieving processing volume Q is collected at a sampling frequency of 1Hz. screen The arithmetic mean of N consecutive sampled values ​​is used as the actual processing quantity Q. real N is 6~10; calculate the real-time output Q of small-sized lump ore based on the oversize yield η of the second-stage screening. ore =Q real ×η.

[0011] Furthermore, the dynamic double-layer fabric also includes features based on real-time output Q. ore Adjust the ratio of the thickness of the upper layer to the total thickness of the base material.

[0012] Furthermore, the specific method for adjusting the ratio of the upper layer thickness to the total base layer thickness is as follows: real-time monitoring of the sintering machine speed V and effective width W, and calculation of the theoretical total base layer amount Q required to maintain the baseline base layer thickness H0. need ; Introducing a thickness adjustment coefficient K, the calculation formula is: K=Q ore ÷(Q need ×α), where α is the target proportion of the upper layer of base material to the total base material, with a value ranging from 40% to 70%; When K>1.2, the control system automatically locks the opening of the second bottom material bin gate at the upper limit, so that the upper layer thickness ratio is maintained at 70%, and the excess ore is transferred to the blast furnace ore bin via the bypass belt, and triggers an audible and visual warning. When 0.3≤K≤1.2, the thickness ratio of the upper layer is maintained to fluctuate around the set value α; When K < 0.3, the control system automatically locks the opening of the second bottom material bin gate at the lower limit, so that the upper layer thickness ratio is maintained at 40%, and sends a material supply interruption alarm signal to the central dispatch system. The insufficient thickness is automatically supplemented by the lower layer of sintered ore, ensuring that the total bottom material thickness is always maintained within the range of H0 ± 5mm. Furthermore, in step S3, the temperature of the high-temperature exhaust gas is 300~450℃; the time for in-situ dehydration and weak oxidation treatment is 1~3 minutes.

[0013] Furthermore, the modified small-sized lump ore has a moisture content of ≤1.0%. An in-situ Fe2O3 shell is formed on the surface of the ore particles, with a thickness of 20~50μm. In-situ heat treatment reduces the moisture content of the lump ore to ≤1.0% and forms an Fe2O3 shell on the particle surface. This shell prevents the rapid vaporization of internal crystal water during the high-temperature sintering stage, eliminating the driving force for cracking. Simultaneously, it imparts higher strength and thermal shock resistance to the particle surface, solving the problem of newly generated dust and deteriorated permeability of the material layer caused by cracking during the sintering process of untreated high-moisture lump ore.

[0014] Furthermore, the method is implemented using the following system: the system includes: a cascade screening module, a material distribution module, a waste heat coupling module, a detection module, a central control module, and a bypass transfer module, wherein the cascade screening module includes a first vibrating screen and a second vibrating screen arranged in series; The material feeding module includes a first bottom material bin and a second bottom material bin arranged sequentially along the running direction of the sintering machine trolley, and the second bottom material bin is located behind the igniter along the trolley's direction. The waste heat coupling module includes at least one wind box branch pipe, through which the exhaust gas of the first wind box of the sintering machine is guided to the bottom of the double-layer bottom material layer. The wind box branch pipe is equipped with a regulating valve. The detection module includes a laser rangefinder located behind the second base material silo and in front of the igniter, and a weighing belt conveyor located between the first vibrating screen and the second vibrating screen. The central control module has a built-in PLC or DCS controller; it is used to receive Qscreen, V, W and Hact signals and execute the dynamic adjustment algorithm, and output a 4~20mA current signal to the gate actuator of the first and second base material silos. The bypass transfer module includes a belt conveyor connecting the outlet of the second bottom material bin to the blast furnace ore bin, used to transfer excess ore blocks when K>1.2.

[0015] Furthermore, the first vibrating screen has a screen aperture of 6-8 mm, and the second vibrating screen has a screen aperture of 3-5 mm; the discharge port of the second bottom material hopper is equipped with a sealing device. The sealing device is used to prevent sintering exhaust gas from escaping.

[0016] The beneficial effects of this invention are as follows: (1) This invention uses a stepped screening method to finely classify the undersize material of the lump ore, return the fine powder ore to the batching and granulation, and use the small-sized lump ore as the bottom material to realize the resource utilization of intermediate materials; adopting a double-layer bottom material structure, the lower layer provides air-permeable support, and the upper layer has both filtration and reaction functions, which solves the problems of poor air permeability and easy blockage of traditional bottom material layers. At the same time, the high-temperature exhaust gas from the head of the sintering machine is used to perform in-situ dehydration and weak oxidation treatment on the upper small-sized lump ore, which greatly reduces the moisture content and avoids sintering cracking, and improves its high-temperature strength and reactivity through surface mineral phase modification; the modified small-sized lump ore serves as an air-permeable skeleton and active filter layer, and works with the sintering mixture to form minerals, improve the air permeability and heat transfer efficiency of the material layer, promote the generation of liquid phase and mineral phase reconstruction, improve the quality of sintered mineral products, reduce solid fuel consumption and return rate, realize the internal recycling of waste heat, and have both economic benefits and environmental protection value.

[0017] (2) This invention collects the instantaneous processing volume in real time through a weighing belt conveyor, calculates the real-time output of small-sized lump ore based on the actual processing volume and the oversize yield, introduces a thickness adjustment coefficient K and uses a laser rangefinder to measure the thickness feedback, adopts incremental PID and first-order inertial filtering to dynamically control the gate opening, and sets boundary locking, bypass transfer and lower layer replenishment mechanisms for K>1.2 and K<0.3, which solves the problem of thickness loss due to the lack of adaptive compensation capability for screening flow fluctuations in the existing bottom layer thickness control, and improves the accuracy of the total bottom layer thickness from ±15mm to ±5mm, enhancing the system's anti-interference capability and operational stability.

[0018] (3) By setting the second bottom material silo behind the igniter, the upper layer of ore is immediately subjected to waste gas heat treatment after ignition. The negative pressure penetration method of the main exhaust is used to replace the positive pressure injection. At the same time, the temperature is controlled by the high temperature regulating valve to avoid overburning. This solves the problem that the high temperature waste gas positive pressure scheme can easily cause the material layer to be blown away and the particles to be overburned and block the pores. The modified bottom layer forms a porous filter layer with a porosity of 35%~45%. While maintaining the function of the air-permeable skeleton, it intercepts fine dust and sends <3mm powder ore into the batching room, bypasses the excess ore to the blast furnace, and makes up the insufficient thickness by the lower layer. This realizes the synergistic effect of waste heat resource utilization, pre-dust removal and material cascade utilization. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The image shows the XRD pattern of the ore particles after in-situ heat treatment in Example 1.

[0021] Figure 2 This is a schematic diagram of the sintering substrate system of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0023] Example 1 This embodiment uses 550m 2 The sintering machine was used as the target material, and the raw material selected was Australian limonite with a moisture content of 6.5% and a crystal water content of 8.2% (Al2O3 / SiO2=0.35).

[0024] 1. Cascade screening and material monitoring The raw materials are screened by a 7mm first vibrating screen. Particles larger than 7mm are directly supplied to the blast furnace lump ore bin; particles smaller than 7mm enter the 4mm second vibrating screen. Small lump ore particles of 4-7mm are intercepted and sent to the second bottom material bin; powder ore smaller than 4mm enters the sintering batching room.

[0025] To address the issue of signal jitter on-site, the system collects the instantaneous processing quantity Q at a frequency of 1Hz via the weighing belt conveyor below the second vibrating screen. screen The central control module employs a sliding time window averaging filtering algorithm (window N=6, corresponding to 30 seconds) to filter out flow spikes caused by screen sticking, and calculates the actual processing capacity Q. real =95t / h, combined with the oversize yield η=68%, the real-time output Qore=64.6t / h.

[0026] 2. Dynamic double-layer fabric A double-layer structure is laid on the sintering trolley grate: the lower layer is 12-16mm of finished sintered ore (30mm thick), and the upper layer is 4-7mm of limonite. The baseline total thickness H0 is set at 80mm, and the target proportion of the upper layer is α=55%.

[0027] The system monitors the machine speed V=3.0m / min and width W=5.0m in real time, and calculates the theoretical material requirement Q. need The flow rate is approximately 141.8 t / h, with an adjustment coefficient K≈0.83. The actual thickness H is detected in real time using a laser rangefinder located above the base layer. act=79.5mm, and an incremental PID algorithm is introduced to calculate the deviation. To prevent mechanical impact on the pneumatic gate, the system performs first-order inertial filtering (τ=3s) on the output 4~20mA control signal, and finally stabilizes the total thickness precisely within the range of 80±2mm.

[0028] 3. In-situ heat treatment and mineral phase modification The second bottom material silo is located behind the igniter along the trolley's path. After ignition, the system utilizes the 380℃ high-temperature exhaust gas generated by the 1#~3# air boxes at the head of the sintering machine, which is introduced from below the bottom material layer through the air box branch pipes. With the help of the negative pressure of the main exhaust system, it penetrates the upper layer of lump ore, and the heat treatment time is 1.5 minutes.

[0029] During this process, the free water on the surface of the lump ore is removed to 0.6%, and a dense Fe2O3 shell with a thickness of 20-50 μm is formed in situ on the particle surface (XRD pattern of the lump ore particles after in-situ heat treatment is shown in [reference]). Figure 1 This shell effectively blocks the rapid vaporization of internal crystal water, and the irregular particles form a porous filter layer with a porosity of 38% due to water removal.

[0030] 4. Co-sintering ore formation The small-sized ore particles after in-situ heat treatment and mineral phase modification are used as a permeable skeleton and filter layer, and together with the subsequently laid sintering mixture, they undergo the sintering mineralization process.

[0031] The system used in this embodiment includes: a cascade screening module, a material distribution module, a waste heat coupling module, a detection module, a central control module, and a bypass transfer module. The cascade screening module includes a first vibrating screen and a second vibrating screen arranged sequentially along the material conveying direction. The first vibrating screen has a screen aperture of 6-8 mm, and the second vibrating screen has a screen aperture of 3-5 mm. The material distribution module includes a first bottom material bin and a second bottom material bin arranged sequentially along the sintering machine trolley's running direction. The discharge port of the second bottom material bin is equipped with a sealing device, and the second bottom material bin is located along the trolley's direction from the igniter. The waste heat coupling module guides the exhaust gas from the first section of the sintering machine's air box to below the double-layer bottom material layer through the branch pipes of the 1#~3# air box. A regulating valve is installed on the branch pipe of the air box. The detection module includes a laser rangefinder located behind the second bottom material silo and in front of the igniter, and a weighing belt conveyor located between the first and second vibrating screens. The central control module has a built-in PLC or DCS controller. The bypass transfer module includes a belt conveyor connecting the outlet of the second bottom material silo to the blast furnace ore bin (see schematic diagram of the sintering bottom material system). Figure 2 (As shown).

[0032] 5. Implementation Effect Analysis Compared with the untreated condition, this embodiment achieved significant results: ① No cracking occurred in the base material layer, and no visible dust escaped from the trolley surface; ② The dust concentration at the electrostatic precipitator inlet decreased by 13.2%; ③ The strength of the sinter drum increased by 0.24%; ④ Throughout the entire treatment process, even when encountering instantaneous flow fluctuations, the fluctuation range of the base material thickness was controlled within ±2mm, demonstrating significant application effects.

[0033] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for spreading undersize powder from lump ore screens based on in-situ modification of sintering waste gas, characterized in that, Includes the following steps: S1. Cascade Screening and Material Monitoring: The raw lump ore undergoes a first-stage screening to separate the ore from the primary screen oversize and the ore from the primary screen undersize. The primary screen oversize is directly supplied to the blast furnace lump ore bin. The primary screen undersize is subjected to a second-stage screening to separate the powder ore <3mm and small-sized lump ore. The powder ore <3mm enters the sintering batching room to participate in mixing and granulation, while the small-sized lump ore is transported to the second bottom material bin. S2, Dynamic double-layer material distribution: A double-layer material structure is laid on the grate bars of the sintering trolley along the thickness direction. The lower layer is the finished sintered ore, and the upper layer is the small-particle block ore obtained in step S1. S3. In-situ heat treatment and mineral phase modification: In the exhaust sintering stage after the igniter of the sintering machine, the high-temperature exhaust gas generated by the wind box at the head of the sintering machine is introduced from below the double-layer bottom material layer through the wind box branch pipe. The negative pressure generated by the main exhaust system penetrates the upper small-particle lumps of ore to carry out in-situ dehydration and weak oxidation treatment, and the modified small-particle lumps of ore are obtained. S4. Co-sintering mineralization: The modified small-sized ore is used as a permeable skeleton and filter layer, and sintered together with the sintering mixture placed on top of it.

2. The method as described in claim 1, characterized in that, The particle size of small-sized lump ore is 3~8mm, and the particle size of finished sintered ore is 10~18mm.

3. The method as described in claim 1, characterized in that, In step S1, the moisture content of the raw material lump ore is 4%~7%, and the raw material lump ore is limonite or highly hydrated hematite.

4. The method as described in claim 1, characterized in that, In step S1, the second-stage screening process also includes real-time monitoring of the instantaneous processing volume Q of the second-stage screening. screen The oversize yield η is specifically determined by the instantaneous throughput Q collected in real time by the weighing belt conveyor below the second-stage screening. screen The sieving processing volume Q is collected at a sampling frequency of 1Hz. screen The arithmetic mean of N consecutive sampled values ​​is used as the actual processing quantity Q. real N is 6~10; calculate the real-time output Q of small-sized lump ore based on the oversize yield η of the second-stage screening. ore =Q real ×η.

5. The method as described in claim 1, characterized in that, Dynamic double-layer fabric also includes based on real-time output Q ore Adjust the ratio of the thickness of the upper layer to the total thickness of the base material.

6. The method as described in claim 5, characterized in that, The specific method for adjusting the ratio of the upper layer thickness to the total base layer thickness is as follows: monitor the sintering machine speed V and effective width W in real time, and calculate the theoretical total base layer amount Q required to maintain the reference base layer thickness H0. need ; Introducing a thickness adjustment coefficient K, the calculation formula is: K=Q ore ÷(Q need ×α), where α is the target proportion of the upper layer of base material to the total base material, with a value ranging from 40% to 70%; When K>1.2, the control system automatically locks the opening of the second bottom material bin gate at the upper limit, so that the upper layer thickness ratio is maintained at 70%, and the excess ore is transferred to the blast furnace ore bin via the bypass belt, and triggers an audible and visual warning. When 0.3≤K≤1.2, the thickness ratio of the upper layer is maintained to fluctuate around the set value α; When K < 0.3, the control system automatically locks the opening of the second bottom material bin gate at the lower limit, so that the upper layer thickness ratio is maintained at 40%, and sends a material supply interruption alarm signal to the central dispatch system. The insufficient thickness is automatically supplemented by the lower layer of sintered ore, ensuring that the total bottom material thickness is always maintained within the range of H0 ± 5mm.

7. The method as described in claim 1, characterized in that, In step S3, the temperature of the high-temperature exhaust gas is 300~450℃; the time for in-situ dehydration and weak oxidation treatment is 1~3 minutes.

8. The method as described in claim 1, characterized in that, The moisture content of the modified small-sized lump ore is ≤1.0%.

9. The method as described in claim 1, characterized in that, The method is implemented using the following system: the system includes a cascade screening module, a material distribution module, a waste heat coupling module, a detection module, a central control module, and a bypass transfer module; The cascade screening module includes a first vibrating screen and a second vibrating screen arranged in series. The material feeding module includes a first bottom material bin and a second bottom material bin arranged sequentially along the running direction of the sintering machine trolley, and the second bottom material bin is located behind the igniter along the trolley's direction. The waste heat coupling module includes at least one wind box branch pipe, through which the exhaust gas of the first wind box of the sintering machine is guided to the bottom of the double-layer bottom material layer. The wind box branch pipe is equipped with a regulating valve. The detection module includes a laser rangefinder located behind the second base material silo and in front of the igniter, and a weighing belt conveyor located between the first vibrating screen and the second vibrating screen. The central control module has a built-in PLC or DCS controller. The bypass transfer module includes a belt conveyor connecting the outlet of the second bottom material silo to the blast furnace ore bin.

10. The method as described in claim 9, characterized in that, The first vibrating screen has a screen aperture of 6-8 mm, and the second vibrating screen has a screen aperture of 3-5 mm; the discharge port of the second bottom material silo is equipped with a sealing device.

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