Gas-solid two-phase flow field optimization device for sintering machine flue gas desulfurization system

Abstract

The application is a kind of sintering machine flue gas desulfurization system gas-solid two-phase flow field optimization device. It includes a desulfurization tower body, which is composed of an inlet section, a square-round section one, a venturi section, a conical section, a straight pipe section, a square-round section two and a top square section along the flue gas flow direction. The inlet section is provided with a flow regulation grid. The square-round section one is used to connect the rectangular inlet section and the circular venturi section. The venturi section is composed of multiple parallel venturi channels, each of which is a contraction-expansion structure. The conical section is provided with a spray water nozzle interface and a lime particle supplement interface on the side wall. The top square section is provided with a tapered outlet structure on the other side of the bottom surface. The application realizes uniform distribution of inlet airflow, uniform air distribution of parallel venturi, efficient mixing of gas-solid-liquid three-phase and stable internal circulation of particles, and has the advantages of uniform flow field, reasonable structure, reliable operation, low particle escape rate, and wide application in large-scale sintering machine flue gas desulfurization.

Description

Technical Field

[0001] This invention belongs to the field of sintering flue gas purification technology in the steel industry, specifically relating to a gas-solid two-phase flow field optimization device for a sintering machine flue gas desulfurization system. Background Technology

[0002] The flue gas generated during the sintering process in the steel industry is characterized by large flow rate, high temperature, and large fluctuations in sulfur dioxide (SO2) concentration. With the implementation of the national ultra-low emission policy, higher requirements have been placed on the desulfurization efficiency, operational stability, and energy consumption level of the sintering flue gas desulfurization system.

[0003] Currently, Venturi spray coupled desulfurization technology is widely used in desulfurization retrofit projects for large and medium-sized sintering machines due to its advantages such as relatively simple structure, sufficient gas-liquid contact, and integrated dust removal and desulfurization. However, the existing system still has the following technical defects in actual engineering operation:

[0004] 1. Uneven inlet flow field: When flue gas enters the desulfurization tower, the flow is severely biased, resulting in an uneven velocity field distribution inside the tower. In some areas, the flow velocity is too high, causing equipment wear, while in other areas, the flow velocity is too low, forming a "dead zone" that affects desulfurization efficiency.

[0005] 2. Poor gas-solid two-phase flow matching: Insufficient coupling between spray droplets and circulating lime particles prevents the particles from forming a stable internal circulation flow, resulting in a high particle escape rate, difficulty in ensuring the calcium-sulfur ratio, and increased operating costs.

[0006] 3. Blind control of key parameters: There is a lack of systematic simulation and precise control methods for the velocity field, temperature field, pressure field and particle residence time in the tower. The design is mostly based on experience and is difficult to adapt to the operation requirements of large flow and variable operating conditions.

[0007] 4. Insufficient synergistic optimization: The three core parameters that determine desulfurization efficiency—flue gas velocity, residence time, and reaction temperature—cannot achieve synergistic optimization, resulting in high system energy consumption and unstable desulfurization efficiency. Summary of the Invention

[0008] The purpose of this invention is to provide an optimized device that can achieve precise control of velocity field, temperature field, pressure field and particle motion trajectory, and solve the technical problems of inlet flue gas deviation, uneven gas-solid two-phase mixing, high lime particle escape rate and lack of scientific and systematic flow field testing and control methods in existing Venturi spray desulfurization systems.

[0009] The technical solution to achieve the purpose of this invention is: a gas-solid two-phase flow field optimization device for a sintering machine flue gas desulfurization system, comprising a desulfurization tower body, which is composed of an inlet section, a square-round section one, a Venturi section, a conical section, a straight pipe section, a square-round section two, and a top square section along the flue gas flow direction.

[0010] The inlet section is used to connect to the upstream flue and introduce flue gas into the tower. The inlet section is equipped with a flow-rectifying grid. The square-round section one is used to connect the rectangular inlet section and the circular Venturi section. The Venturi section is composed of multiple parallel Venturi channels, each of which is a contraction-expansion structure. The cross-sectional area of ​​the conical section gradually increases from bottom to top. The side wall of the conical section is circumferentially arranged with spray water nozzle interfaces and lime particle feeding interfaces. The square-round section two connects the bottom surface of the circular straight pipe section and the rectangular top square section. The other side of the bottom surface of the top square section is equipped with a contracting conical outlet structure facing downward.

[0011] Furthermore, the inlet section is a rectangular cross-section flue with a width of 9.6±0.1m and a height of 5.5±0.1m. The inlet section consists of two straight pipe sections with orthogonal axes and an inclined pipe section connecting the straight pipe sections. A flow-rectifying grid is installed in the straight pipe section near the square-round section one of the inlet section.

[0012] Furthermore, the rectifier grille is composed of multiple parallel grille plates, with a spacing of 0.2-0.3m between adjacent grille plates.

[0013] Furthermore, a flow equalization plate is installed inside the square section.

[0014] Furthermore, the Venturi segment has a seven-channel parallel structure, with each Venturi channel arranged in a rectangular array. Each Venturi channel includes a contraction segment, a throat segment, and a dilation segment. The contraction angle of the contraction segment is 18°-25°, the dilation angle of the dilation segment is 6°-10°, and the cross-sectional area of ​​the throat segment is 35%-45% of the inlet cross-sectional area of ​​the contraction segment.

[0015] Furthermore, the lower cross-sectional shape of the conical section matches the outlet of the Venturi section, and the upper cross-sectional shape matches the straight pipe section. The cone angle of the conical section is 55°-65°, and the height is 6-8m. The sidewall of the conical section is uniformly provided with 4-8 spray water nozzle interfaces and 2-4 lime granule feeding interfaces along the circumference. The spray water nozzle interfaces are located 0.8-1.5m below the lime granule feeding interfaces.

[0016] Furthermore, the straight pipe section is a cylindrical body with a circular cross-section, an inner diameter of 10.8±0.1m, and a height of 11.35±0.1m.

[0017] Furthermore, the top square section is a cuboid structure with two openings on the bottom surface. One opening on the bottom surface connects to the second square section, and the other opening on the bottom surface is the tower outlet. The top of the top square section has a step from the corresponding side of the second square section to the other side, which reduces the cross-sectional area. The far corner of the top square section away from the second square section is replaced with a slope for drainage.

[0018] Furthermore, wear-resistant bushings are installed at the throats of each channel in the Venturi section. The bushings are made of high-chromium cast iron or ceramic composite material and are 20-40mm thick.

[0019] Compared with the prior art, the significant advantages of this invention are:

[0020] (1) Complete flow field control structure: Through the dual flow equalization structure design of inlet section rectifier grid + square and round section flow equalization plate, the inlet airflow deviation is effectively eliminated, and the velocity non-uniformity coefficient of the tower section is reduced from more than 35% to less than 12%, which greatly improves the uniformity of the flow field of the whole tower.

[0021] (2) Uniform air distribution in parallel Venturi: The seven-channel Venturi are arranged in a rectangular array with consistent channel dimensions. Combined with the pre-distribution effect of the front flow equalization plate, the airflow deviation of each channel is ensured to be no more than ±5%, thus solving the problem of flow deviation when multiple channels are connected in parallel.

[0022] (3) High integration of functions in the conical section: The spray water nozzle and lime particle feeding port are integrated and arranged in the conical section. The high-speed airflow zone of the Venturi outlet is used to realize the synchronous mixing of gas-solid-liquid three phases. The cone angle of 55°-65° not only ensures that the particle wall falls back to form an internal circulation, but also avoids excessive material accumulation. The structure is compact and efficient.

[0023] (4) Coordination and optimization of the size ratio of each section: By strictly limiting the height-to-diameter ratio, cone angle ratio and outlet shrinkage ratio of each functional section, the pressure loss of the whole tower is minimized and the particle residence time is maximized. Furthermore, the transition between each section is smooth with square and round joints to avoid local eddies and pressure changes.

[0024] (5) Durable and reliable structure: Wear-resistant bushings are installed at key wear parts (Venturi throat), and the inner wall of the tower is coated with anti-corrosion and wear-resistant coating, which extends the overall service life of the device and reduces the frequency and cost of maintenance. Attached Figure Description

[0025] Figure 1 This is a three-dimensional schematic diagram of the gas-solid two-phase flow field optimization device of the present invention.

[0026] Figure 2 These are three views of the gas-solid two-phase flow field optimization device of the present invention; wherein (a) is the front view, (b) is the left view, and (c) is the top view.

[0027] Figure 3 This is a three-dimensional schematic diagram of the inlet section.

[0028] Figure 4 This is a three-dimensional schematic diagram of a square-round joint.

[0029] Figure 5 This is a three-dimensional schematic diagram of the Venturi section.

[0030] Figure 6 This is a 3D schematic diagram of the top square segment.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1-Inlet section, 2-Square-round section one, 3-Venturi section, 4-Conical section, 5-Straight pipe section, 6-Square-round section two, 7-Top square section. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] As shown in the figure, a gas-solid two-phase flow field optimization device for a sintering machine flue gas desulfurization system has the following overall structure from bottom to top along the flue gas flow direction: inlet section 1, square section 1 2, venturi section 3, conical section 4, square section 2 6, and top square section 7.

[0035] The inlet section is located on one side of the bottom of the tower and is a rectangular cross-section flue. In this embodiment, the cross-sectional width of inlet section 1 is 9600mm and the height is 5543mm. A flow-rectifying grid is installed within inlet section 1. The flow-rectifying grid consists of multiple parallel grid plates made of 12mm thick steel plates, with a spacing of 270mm between adjacent grid plates. The grid plates are arranged perpendicular to the flue gas flow direction. The flow-rectifying grid is used to cut the large-scale vortex brought in from the upstream flue into a smaller, uniform airflow, initially eliminating inlet flow deviation.

[0036] The Fangyuan section 1-2 is equipped with a flow equalization plate, which is a perforated plate structure with a thickness of 16mm and an opening ratio of 40%. The holes are arranged in an equilateral triangle and have a diameter of 150mm. The function of the flow equalization plate is to perform secondary flow equalization before the flue gas enters the Venturi section, ensuring that the airflow velocity distribution at the inlet of the seven Venturi channels is consistent.

[0037] Venturi section 3 is located above square section 2 and is a seven-channel parallel structure. The seven Venturi channels are arranged in a 3-2-2 rectangular array, that is: 3 in the first row, 2 in the second row, and 2 in the third row, arranged in 3 columns in the width direction and 3 rows (staggered) in the depth direction, with a center distance of 3200mm between each channel.

[0038] Each Venturi channel includes a contraction section, a throat section, and a dilatation section, with an overall height of 2150 mm (in this embodiment, the overall height of the seven channels is consistent, but the illustration shows the elevation of the Venturi section; the actual overall structural height of each channel is approximately 2400-2800 mm, and the inlet cross-section of each channel is square with a side length of 2400 mm). The contraction angle of the contraction section is 20°, the ratio of the inlet cross-sectional area to the throat cross-sectional area is 2.5:1, and the throat cross-section is square with a side length of 1520 mm (the area is approximately 40% of the inlet area). The dilatation angle of the dilatation section is 8°, and the outlet cross-section has the same dimensions as the inlet cross-section, being a square with a side length of 2400 mm.

[0039] Each Venturi channel is equipped with a wear-resistant bushing at its throat. The bushing is made of high-chromium cast iron (Cr26) with a thickness of 30mm and an inner wall hardness of ≥HRC58 to resist the erosion and wear of high-speed dust-laden flue gas.

[0040] The conical segment 4 is positioned above the venturi segment 3 and is an inverted frustum-shaped shell structure. Its lower cross-sectional shape and dimensions match the overall outlet of the venturi segment 3 (square, approximately 7200mm on each side, corresponding to the envelope dimensions of the seven channels), while its upper cross-section is circular, with an inner diameter consistent with the third vertical segment 7 (10800mm). The cone angle (i.e., the angle between the sidewall and the vertical direction) of the conical segment 4 is 60°, and its height is 6880mm.

[0041] The sidewall of conical section 4 is evenly equipped with six spray water nozzle interfaces and four lime granule feeding interfaces along its circumference. The spray water nozzle interfaces are located at the lower part of conical section 4, approximately 1200 mm above the outlet of venturi section 3, with the interface angled downwards at a 25° angle to the vertical, and are used to install solid conical spray nozzles. The lime granule feeding interfaces are located in the middle of conical section 6, approximately 1000 mm above the spray water nozzle interfaces, with the interface angled horizontally or slightly downwards, and are used to connect to the lime granule pneumatic conveying pipeline.

[0042] The conical section 4 has a shell wall thickness of 16mm and is made of Q345B carbon steel. The inner wall is overlaid with a wear-resistant layer with a thickness of 4mm to resist the erosion of sprayed water and lime particles.

[0043] Straight pipe section 5 is a circular cross-section cylinder with an inner diameter D3 of 10800 mm and a height H3 of 11350 mm. It is the main area for the three-phase mixing and reaction of flue gas, spray droplets, and lime particles. While its diameter is 10800 mm, the cross-section changes from square to round, allowing for more complete circular motion of the airflow, which is beneficial for extending the particle's flight path and residence time. The cylinder wall is 14 mm thick, made of Q345B carbon steel, and the inner wall is coated with an anti-corrosion and wear-resistant coating.

[0044] The top outlet section 7 is located above the square-round section 6 and has a tapered constriction structure. The outlet cross-section is square, with an inner wall side length L4 of 5600mm. The height of the top outlet section 7 is 8500mm, and the side wall contraction angle (the angle with the vertical direction) is approximately 17°. A flange interface is provided at the outlet of the top outlet section 7 for connecting to the downstream flue gas duct.

[0045] Summary of overall structural dimensions

[0046] Dust- and sulfur-containing high-temperature flue gas enters the tower body through inlet section 1. First, it is cut and homogenized by a rectifier grid to eliminate large-scale flow deviation. Then, it is homogenized again by a flow equalization plate to ensure that the inlet flow of the seven Venturi channels is consistent. In Venturi section 3, each channel contracts and accelerates the flue gas (the throat velocity can reach 30-40 m / s), making the gas-solid turbulence intense and enhancing the subsequent mass and heat transfer processes.

[0047] High-speed flue gas carries lime particles fed in by conical section 4 upwards. In the gradually expanding channel of conical section 4, the velocity gradually decreases. Simultaneously, fine droplets sprayed from the water nozzles exchange heat with the flue gas (cooling it to 75-85℃) and wet the particle surface, providing optimal temperature and humidity conditions for the desulfurization reaction. Due to the combined effects of gravity and airflow in conical section 4 and straight pipe section 5, the lime particles form an internal circulation flow pattern, rising in the central region and falling back near the wall, prolonging the effective residence time of the particles within the tower.

[0048] The flue gas and a small amount of unseparated particles continue to rise after the reaction and are discharged at an accelerated rate in the narrowing channel of the top outlet section 7. Some large particles slide back into the tower along the wall under the action of gravity, thereby controlling the outlet particle escape rate.

[0049] Actual engineering verification shows that using the device described in this invention, the outlet flue gas velocity can be stably controlled within the range of 9-19 m / s, the effective residence time of the flue gas is ≥5.23 s, the outlet temperature is 75-85℃, and the lime particle escape rate is ≤0.17%. All performance indicators meet the process requirements for high-efficiency desulfurization.

Claims

1. A gas-solid two-phase flow field optimization device for a sintering machine flue gas desulfurization system, characterized in that, The desulfurization tower body consists of, along the flue gas flow direction, an inlet section (1), a square-round section one (2), a venturi section (3), a conical section (4), a straight pipe section (5), a square-round section two (6), and a top square section (7). The inlet section (1) is used to connect the upstream flue and introduce the flue gas into the tower. The inlet section (1) is equipped with a rectifier grid. The square and round section (2) is used to connect the inlet section (1) with a rectangular cross section and the Venturi section (3) with a circular cross section. The Venturi section (5) is composed of multiple parallel Venturi channels, and each Venturi channel is a contraction-expansion structure. The cross-sectional area of ​​the conical section (4) gradually increases from bottom to top. The side wall of the conical section (4) is circumferentially arranged with a spray water nozzle interface (13) and a lime particle feeding interface (14). The square section 2 (6) connects the bottom surface of the straight pipe section (5) with a circular cross-section and the top square section (7) with a rectangular cross-section. The bottom surface of the top square section (7) is provided with a tapered outlet structure that tapers downwards.

2. The apparatus according to claim 1, characterized in that, The inlet section (1) is a rectangular cross-section flue with a cross-section width of 9.6±0.1m and a height of 5.5±0.1m. The inlet section (1) consists of two straight pipe sections with orthogonal axes and an inclined pipe section connecting the straight pipe sections. A flow rectifier grid is installed in the straight pipe section of the inlet section (1) near the square and round section (2).

3. The apparatus according to claim 2, characterized in that, The rectifier grid (11) consists of multiple parallel grid plates with a spacing of 0.2-0.3m between adjacent grid plates.

4. The apparatus according to claim 3, characterized in that, The flow equalization plate is installed inside the square section (2).

5. The apparatus according to claim 4, characterized in that, The Venturi segment (3) is a seven-channel parallel structure. Each Venturi channel is arranged in a rectangular array. Each Venturi channel includes a contraction segment, a throat segment, and an expansion segment. The contraction angle of the contraction segment is 18°-25°, the expansion angle of the expansion segment is 6°-10°, and the cross-sectional area of ​​the throat segment is 35%-45% of the inlet cross-sectional area of ​​the contraction segment.

6. The apparatus according to claim 5, characterized in that, The lower cross-sectional shape of the conical section (4) matches the outlet of the Venturi section (3), and the upper cross-sectional shape matches the straight pipe section (5). The cone angle of the conical section (4) is 55°-65°, and the height is 6-8m. The side wall of the conical section (6) is uniformly provided with 4-8 spray water nozzle interfaces and 2-4 lime particle feeding interfaces along the circumference. The spray water nozzle interfaces are located 0.8-1.5m below the lime particle feeding interfaces.

7. The apparatus according to claim 6, characterized in that, The straight pipe section (5) is a cylindrical body with a circular cross-section, an inner diameter of 10.8±0.1m, and a height of 11.35±0.1m.

8. The apparatus according to claim 7, characterized in that, The top square section (7) is a cuboid structure with two openings on the bottom surface. One opening on the bottom surface is connected to the second square section (6), and the other opening on the bottom surface is the tower outlet. The top of the top square section (7) has a step from the corresponding side of the second square section to the other side, which reduces the cross-sectional area. The far corner of the top square section (7) away from the second square section is replaced with a slope for drainage.

9. The apparatus according to claim 8, characterized in that, Wear-resistant bushings are installed at the throat of each channel in the Venturi section (3). The bushings are made of high-chromium cast iron or ceramic composite material and are 20-40mm thick.

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