Industrial silicon waste heat boiler system based on L-shaped arrangement and ash removal method

Abstract

The invention relates to the technical field of waste heat boilers. The invention discloses an industrial silicon waste heat boiler system based on L-shaped arrangement and an ash removal method of the industrial silicon waste heat boiler system, and belongs to the technical field of industrial waste heat recovery. According to the system, a natural circulation and forced circulation double-loop mixed circulation structure is adopted, and a natural circulation loop forms power by means of the vertical height difference larger than or equal to 15 m and is matched with a vertical descending section for radiation heat exchange; the forced circulation loop is provided with a variable-frequency forced circulation pump, and the flow can be dynamically adjusted to meet the convective heat exchange requirement of the horizontal section; and a high-temperature-resistant alloy steel baffle plate and a ceramic coating radiation heating surface are arranged in the vaporization settling chamber, so that dust pre-separation and flue gas cooling and temperature stabilization are realized. Differentiation schemes are designed for different section characteristics of the combined ash removal system. The waste heat recovery efficiency and the ash removal effect are improved, system operation energy consumption is reduced, abrasion of dust to equipment is reduced, and remarkable economic and environment-friendly benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of waste heat boiler technology, specifically to an industrial silicon waste heat boiler system based on an L-shaped arrangement and a ash removal method. Background Technology

[0002] As a basic industrial raw material, industrial silicon smelting generates a large amount of high-temperature flue gas with temperatures ranging from 500 to 1000°C. This flue gas contains abundant sensible heat and has extremely high waste heat recovery value. However, this type of flue gas has significant inherent defects, posing numerous technical challenges to waste heat recovery and severely restricting energy conservation, emission reduction, and green development in the industrial silicon smelting industry.

[0003] First, the flue gas contains extremely high levels of dust, such as SiO2, typically ≥30g / Nm³. This dust is highly adhesive, especially at temperatures >800℃, where its stickiness increases significantly, making it prone to rapid coking and ash buildup on the heating surfaces of the waste heat boiler. This not only drastically reduces the heat transfer efficiency of the heating surfaces, significantly diminishing the waste heat recovery effect, but can also cause blockages, affecting the stable operation of the boiler system and even requiring frequent shutdowns for cleaning, increasing maintenance costs.

[0004] Secondly, during industrial silicon smelting, the flue gas temperature fluctuates dramatically, typically exceeding ±50℃. This drastic temperature fluctuation causes concentrated thermal stress on the boiler's heating surfaces. Over time and repeated exposure to this stress can severely damage the heating surface structure, shorten the equipment's lifespan, and also affect the stability and safety of the waste heat recovery system, making continuous and efficient waste heat utilization difficult.

[0005] Furthermore, most existing industrial silicon waste heat boilers adopt a fully forced circulating water system, which relies on high-pressure water pumps to maintain water circulation. This system has an extremely high energy consumption ratio, exceeding 15% of the total system energy consumption, resulting in low overall energy efficiency of waste heat recovery, which is not in line with the current industry development trend of energy conservation and emission reduction.

[0006] Furthermore, traditional waste heat boilers employ a relatively simple ash removal method, failing to fully consider the differences in ash accumulation characteristics between the vertical and horizontal sections of the boiler. This single ash removal method cannot address the ash accumulation problems in different sections specifically, resulting in low ash removal efficiency, difficulty in ensuring the cleanliness of the heating surfaces, and further exacerbating the problems of decreased heat transfer efficiency and equipment wear.

[0007] In summary, the current field of industrial silicon waste heat recovery urgently needs a waste heat boiler technology solution that can adapt to the characteristics of flue gas with high temperature, high dust, and drastic temperature fluctuations, while taking into account low energy consumption, high ash removal efficiency, and long equipment life, in order to break through the existing technical bottlenecks and achieve efficient and stable recovery and utilization of waste heat from industrial silicon smelting flue gas. Summary of the Invention

[0008] The purpose of this invention is to address the core characteristics of industrial silicon smelting flue gas, such as high temperature, high dust, strong adhesion, and drastic temperature fluctuations, and to solve the technical pain points of traditional waste heat boilers, such as low heat transfer efficiency, short equipment life, poor ash removal effect, and high energy consumption, by providing a hybrid circulation industrial silicon waste heat boiler system based on an L-shaped arrangement.

[0009] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is: an industrial silicon waste heat boiler system based on an L-shaped arrangement, comprising a boiler body, a mixed circulating water system, and a combined ash removal system;

[0010] The boiler body includes a vaporization settling chamber, a vertical descending section, a turning flue, and a horizontal section connected sequentially along the flue gas flow direction; a flue gas inlet is provided on one side of the lower part of the vaporization settling chamber, and a flue gas outlet is provided at the end of the horizontal section away from the vertical descending section; a high-temperature superheater, a low-temperature superheater, a primary evaporator, and a secondary evaporator are arranged sequentially along the flue gas flow direction in the vertical descending section, and a tertiary evaporator and three sets of economizers are arranged sequentially along the flue gas flow direction in the horizontal section;

[0011] The mixed circulating water system includes a steam-water separator, a natural circulation loop, a forced circulation loop, and a water replenishment component;

[0012] The natural circulation loop is set in the vaporization settling chamber and vertical descending section of the boiler body. It forms a closed loop through the vaporization settling chamber, vertical descending section, primary evaporator, water-cooled walls and / or tube bundles of the secondary evaporator, as well as riser pipe, downcomer pipe and steam-water separator; the natural circulation power is formed by the density difference of the working fluid in the loop.

[0013] The forced circulation loop is set in the horizontal section of the boiler body, and forms a closed loop through the tube bundles of the three-stage evaporator and economizer, as well as the water supply pipe and return pipe. A forced circulation pump is installed on the water supply pipe; the forced circulation pump is used to generate forced circulation power.

[0014] The combined dust removal system includes a steel ball shot blasting dust removal device installed in the vertical descending section and a composite steel brush + compressed air linkage dust removal device installed in the horizontal section.

[0015] Preferably, the vertical height difference of the natural circulation loop is ≥15m; the forced circulation pump is a variable frequency pump, which can dynamically adjust the circulation flow rate according to the system load.

[0016] Preferably, the water replenishment component includes a water replenishment tank, a water replenishment pump, and a water replenishment valve. The water replenishment tank is connected to the water supply pipe of the forced circulation loop through the water replenishment pump and the water replenishment valve, and is used to replenish softened water to the mixed circulation water system to maintain the stability of the system water level.

[0017] Preferably, a baffle plate and a radiant heating surface are built into the vaporization settling chamber near the flue gas inlet;

[0018] The baffles are made of high-temperature resistant alloy steel, with a spacing of 200~300mm and an inclination angle of 30°~45°, and are used to separate dust particles with a diameter ≥50μm in flue gas.

[0019] The radiant heating surface is a finned tube structure connected to a natural circulation loop, with a high-temperature resistant ceramic coating sprayed on the surface to absorb the radiant heat of the flue gas, reducing the flue gas temperature from around 1000℃ at the flue gas inlet to 600~700℃, and reducing the flue gas temperature fluctuation range from ±50℃ to ≤±20℃.

[0020] Preferably, the steel ball shot peening and dust removal device includes a steel ball spreading mechanism disposed at the top of the vertical descending section, a steel ball storage bin disposed at the bottom of the vertical descending section, and a steel ball lifting mechanism for lifting the steel balls in the steel ball storage bin to the steel ball spreading mechanism.

[0021] Preferably, the combined cleaning system is also equipped with an intelligent control system. The intelligent control system is connected to the flue gas temperature sensor and the differential pressure sensor, and can dynamically adjust the cleaning frequency based on the real-time monitored flue gas temperature and the differential pressure signal of the heated surface.

[0022] Preferably, the turning flue is further provided with an inclined airflow guide plate group sloping towards the horizontal section. The airflow guide plate group can deflect and guide the flue gas in the vertical descending section to the horizontal section, and can collect and screen the steel balls and ash below the vertical descending section. The airflow guide plate group includes a grid plate in the upper layer and an ash-supporting steel plate in the lower layer. The grid plate and the ash-supporting steel plate form an ash-falling channel for ash to fall. The ash-falling channel gradually widens from top to bottom, and its lower end is connected to the ash hopper below the turning flue.

[0023] A gravity recovery chamber is provided in the turning flue corresponding to the lower end of the grating plate. The gravity recovery chamber is provided with a shot inlet for steel balls to fall into and a shot outlet for steel balls to exit. The shot inlet corresponds to the grating plate, and the shot outlet is connected to the steel ball storage chamber of the steel ball shot peening and dust removal device through a shot drop pipe. A recovery impeller is provided in the gravity recovery chamber to withstand the impact of steel balls and drive its rotation. A hammer wheel is provided in the turning flue on the back of the dust-collecting steel plate. The axles of the recovery impeller and the hammer wheel are connected by a transmission assembly.

[0024] Preferably, the lower part of the vertical descending section near the horizontal section is further provided with an inclined chute group for guiding steel balls and ash to the airflow guide plate group, the inclined chute group comprising two layers of staggered guide inclined chute.

[0025] Preferably, the axle of the hammering wheel is also connected to an auxiliary drive motor via an electromagnetic clutch.

[0026] This invention also discloses a dust removal method, comprising:

[0027] Vertical descending section dust removal:

[0028] S1.1 Start-up: When the intelligent control system detects that the dust removal conditions are met, it starts the steel ball lifting mechanism to transport the steel balls in the steel ball storage bin to the steel ball spreading mechanism at the top of the vertical descending section.

[0029] S1.2 Steel ball impact cleaning: The steel ball spreading mechanism evenly spreads steel balls, which fall along the heated surface in the vertical descending section and peel off the accumulated ash on the heated surface through impact.

[0030] S1.3 Material separation and guiding with hammering-assisted material discharge: The falling steel balls and stripped ash fall into the airflow guide plate group in the turning flue; the flue gas is deflected and guided to the horizontal section by the airflow guide plate group, and the ash passes through the gap of the grid plate under the action of gravity and enters the ash discharge channel between the grid plate and the ash support steel plate. The steel balls are guided down along the upper surface of the grid plate and enter the gravity recovery chamber.

[0031] S1.4 Ash and Slag Collection and Steel Ball Recovery: Ash and slag fall into the ash hopper for collection and discharge; steel balls entering the gravity recovery chamber are driven to rotate by the blades of the high-fluidity impact recovery impeller, and then flow back to the steel ball storage bin through the shot outlet and shot drop pipe of the gravity recovery chamber, realizing the recycling of steel balls; at the same time, the recovery impeller drives the hammer wheel to hammer the ash support steel plate, increasing the falling speed of the poorly fluid ash and slag on the ash support steel plate;

[0032] Horizontal section dust removal:

[0033] When the intelligent control system detects that the cleaning conditions are met and the flue gas temperature in the diversion duct drops to 350°C, it activates the composite steel brush cleaning device.

[0034] The beneficial effects of this invention are mainly reflected in:

[0035] 1. Highly efficient and stable circulating heat exchange

[0036] The natural circulation and forced circulation dual-loop systems work together. The natural circulation relies on a vertical height difference of ≥15m to form a reliable power source, which is suitable for the radiative heat exchange requirements of the vertical descending section. The forced circulation uses a variable frequency pump, which can dynamically adjust the flow rate according to the system load to meet the convective heat exchange requirements of the three-stage evaporator and economizer in the horizontal section. The dual-loop system improves the waste heat recovery efficiency and reduces the system's operating energy consumption.

[0037] 2. Excellent dust removal effect and low energy consumption

[0038] The combined dust removal system is designed with differentiated dust removal methods for different sections: the vertical descending section uses steel ball shot peening for dust removal, which efficiently removes ash from the heated surface through steel ball impact, and the steel balls can be recycled; during the dust removal process, the steel ball impact recovery impeller drives the hammer wheel to rotate, and uses the kinetic energy of the steel balls to achieve hammering to assist in material dropping, which can solve the problem of poor ash flowability without additional power and reduce the operating cost of the dust removal system; the horizontal section uses composite steel brush dust removal, which is suitable for the dust removal needs of the low temperature section and avoids the wear of the low temperature heated surface by steel ball shot peening.

[0039] 3. Excellent dust separation effect and high operational reliability.

[0040] The baffles in the vaporization settling chamber can separate dust particles with a diameter of ≥50μm from the flue gas. Combined with the ceramic coating on the radiant heating surface, it can reduce the flue gas temperature from around 1000℃ to 600~700℃ and control the temperature fluctuation range within ≤±20℃, reducing the thermal shock to the heating surface caused by sudden temperature changes. The airflow guide plate group realizes the efficient separation of flue gas, steel balls and ash. The structure design of the ash collection channel, which is wider at the top and narrower at the bottom, further improves the ash collection efficiency and reduces the risk of dust wear and blockage to subsequent equipment.

[0041] 4. The system operates intelligently and is highly adaptable.

[0042] The intelligent control system dynamically adjusts the cleaning frequency based on the flue gas temperature and the pressure difference signal of the heating surface. The cleaning of the horizontal section must meet the condition that the flue gas temperature in the turning flue drops to 350℃. This achieves precise control of the cleaning timing, avoids ineffective cleaning, ensures the heat exchange efficiency of the heating surface, and extends the service life of the heating surface and the cleaning device. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of the present invention;

[0044] Figure 2 This is a schematic diagram of a mixed circulating water system;

[0045] Figure 3 for Figure 1 The diagram shown is a structural schematic of a preferred embodiment of the structure.

[0046] Figure 4 for Figure 3 Enlarged view of section A in the middle;

[0047] Figure 5 A schematic diagram of the shaft connection structure for the recycling impeller and the hammer wheel;

[0048] Figure 6 For guiding the inclined groove in Figure 3 A schematic diagram of the installation structure from the right-middle view.

[0049] Figure label:

[0050] 1. Vaporization settling chamber; 2. Vertical descending section; 3. Diverting flue; 4. Horizontal section; 5. Flue gas inlet; 6. Flue gas outlet; 7. High-temperature superheater; 8. Low-temperature superheater; 9. Primary evaporator; 10. Secondary evaporator; 11. Tertiary evaporator; 12. Economizer; 13. Steam-water separator; 14. Ascending pipe; 15. Downcomer; 16. Water supply pipe; 17. Water return pipe; 18. Forced circulation pump; 19. Baffle plate; 20. Radiant heating surface; 21. Steel ball spreading mechanism; 22. Steel ball storage bin; 23. Steel ball lifting mechanism; 24. Airflow guide plate assembly; 25. Grating plate; 26. Ash support steel plate; 27. Gravity recovery chamber; 28. Shot inlet; 29. ​​Shot outlet; 30. Recovery impeller; 31. Hammering wheel; 32. Guide chute; 33. Electromagnetic clutch; 34. Auxiliary drive motor. Detailed Implementation

[0051] The following will be combined with the appendix Figure 1-6 This document provides a detailed description of the L-shaped industrial silicon waste heat boiler system and ash removal method of the present invention, including specific technical parameters, aiming to fully support the scope of protection of the claims and clarify the connection relationship, working principle and implementation details of each component.

[0052] I. Overall System Layout and Component Assembly

[0053] The boiler body of this invention adopts an L-shaped arrangement, with a vaporization settling chamber 1, a vertical descending section 2, a turning flue 3, and a horizontal section 4 connected in series along the flue gas flow direction. The overall structure is compact and adapted to the flow characteristics of industrial silicon smelting flue gas. The vaporization settling chamber 1 can be a cylindrical cavity structure with an inner diameter of 3.5m and a height of 8m. A flue gas inlet 5 is opened on one side of its lower part. The diameter of the flue gas inlet 5 is 1.2m, and it is connected to the flue gas discharge pipe of the industrial silicon smelting furnace through a flange seal to ensure that high-temperature flue gas does not leak into the system. The horizontal section 4 is a rectangular cross-section flue with dimensions of 2.5m × 2m. A flue gas outlet 6 is set at the left end away from the vertical descending section 2. A flue gas flow monitoring device is installed at the flue gas outlet 6 to provide real-time feedback on the system's flue gas processing capacity.

[0054] The vertical descending section 2 is a vertically arranged rectangular channel with a height of 25m. Along the flue gas flow direction, the high-temperature superheater 7, the low-temperature superheater 8, the first-stage evaporator 9, and the second-stage evaporator 10 are fixedly installed from top to bottom. Each heat-receiving surface adopts a staggered finned tube structure with a tube spacing of 150mm and a fin height of 30mm to increase the heat exchange area. In the horizontal section 4, the third-stage evaporator 11 and three sets of economizers 12 are arranged in sequence along the flue gas flow direction. The three sets of economizers 12 are set side by side, and the tube bundles of each set of economizers 12 are arranged in parallel to meet the convective heat exchange requirements of the horizontal section.

[0055] In the mixed circulating water system, the steam-water separator 13 can adopt a cyclone separation structure with a rated separation flow rate of 50t / h and a separation efficiency of ≥99.5%. It has a steam outlet at the top and is connected to the lower header of the water-cooled wall of the vaporization settling chamber 1 and the vertical descending section 2 through a downcomer 15 at the bottom. It is connected to the upper header of the water-cooled wall of the vertical descending section 2 and the outlet header of the first-stage evaporator 9 and the second-stage evaporator 10 through an upcomer 14 on the side, forming a natural circulation loop. The vertical height difference of this natural circulation loop is designed to be 18m, and theoretically not less than 15m. The circulation power is formed by the density difference of the working fluid after heating, with a vapor-liquid mixture density of about 700kg / m³ and an unheated working fluid density of about 950kg / m³. The circulation velocity is stable at 0.8m / s, without the need for additional power drive.

[0056] The water supply pipe 16 of the forced circulation loop is made of seamless steel pipe with a diameter of DN300. One end is connected to the lower water chamber of the steam-water separator 13, and the other end is connected to the inlet headers of the three-stage evaporator 11 and the three economizers 12 respectively. The return water pipe 17 has a diameter of DN350 and returns the outlet working fluid of the three-stage evaporator 11 and the economizer 12 to the steam-water separator 13 (which can be directly connected to the downcomer). The forced circulation pump 18 installed on the water supply pipe 16 is a variable frequency centrifugal pump with a rated head of 80m and a rated flow rate of 60t / h. It can adjust the frequency to 25-50Hz through the frequency converter according to the flue gas temperature and heating surface wall temperature of the horizontal section 4, dynamically match the circulation flow, and realize on-demand energy supply.

[0057] The forced circulation pipeline of the present invention can be directly replenished with water through the steam-water separator 13. In some cases, a water replenishment component can also be set up. The water replenishment component includes a water replenishment tank with a volume of 10m³, a water replenishment pump with a head of 50m, and an electric water replenishment valve. The water replenishment tank is connected to the softened water preparation system through a pipeline. The outlet pipeline of the water replenishment pump is connected to the water supply pipe 16 of the forced circulation loop through a tee. The water replenishment valve is linked with the system water level sensor. When the system water level is lower than 1 / 3 of the set value water level gauge scale, the water replenishment is automatically turned on. When the water level reaches 2 / 3 of the set value water level gauge scale, the water replenishment is turned off, maintaining the system water level fluctuation range ≤ ±50mm.

[0058] II. Structure and Operation of the Vaporization Settling Chamber

[0059] A baffle plate 19 and a radiant heating surface 20 are fixedly installed in the vaporization settling chamber 1 near the flue gas inlet 5. The baffle plate 19 is made of high-temperature resistant alloy steel 310S with a thickness of 10mm, a spacing of 250mm, and an inclination angle of 38°. Dust particles with a diameter ≥50μm impact the surface of the baffle plate 19 under the action of inertial force, and then slide down the plate surface to the ash hopper at the bottom of the vaporization settling chamber 1. The dust pre-separation efficiency is ≥85%.

[0060] The radiant heating surface 20 is a water-cooled wall structure. The inlet header of the radiant heating surface 20 is connected to the downcomer 15 of the natural circulation loop, and the outlet header is connected to the riser 14. By absorbing the radiant heat of the flue gas, the high-temperature flue gas of about 1000°C entering the vaporization settling chamber 1 is cooled to 650°C. At the same time, the heat is carried away by the flow of the working fluid in the natural circulation loop, so that the flue gas temperature fluctuation range is controlled within ±20°C, and thermal stress damage to the heating surface is avoided due to sudden temperature changes.

[0061] III. Structural and Assembly Details of the Modular Dust Removal System

[0062] The combined dust removal system includes a steel ball shot blasting dust removal device, a composite steel brush + compressed air linkage dust removal device, and an intelligent control system. The steel ball shot blasting dust removal device is adapted to the high temperature and strong adhesion dust accumulation characteristics of the vertical descending section 2, while the composite steel brush + compressed air linkage dust removal device is adapted to the low temperature and light dust accumulation requirements of the horizontal section 4.

[0063] The steel ball spreading mechanism 21 of the steel ball shot peening cleaning device is installed below the inspection hole at the top of the vertical descending section 2. It adopts a rotating spreading disc structure with a diameter of 500mm and a rotation speed of 60r / min. Driven by a motor, it evenly spreads steel balls across the entire cross-section of the vertical descending section 2. Alternatively, multiple fixed spreading discs can be used, as long as comprehensive coverage is ensured. The steel ball storage chamber 22 is located on the side of the bottom of the vertical descending section 2, with a volume of 5m³. It is equipped with a steel ball screening mesh with a mesh size of 3mm to filter out broken or non-compliant steel balls. The steel ball lifting mechanism 23 uses a bucket elevator with a lifting height of 28m and a lifting capacity of 10t / h. It transports the steel balls in the steel ball storage chamber 22 to the steel ball spreading mechanism 21, forming a circulation loop. The cleaning steel balls are made of GCr15 bearing steel with a particle size of 4mm, a hardness of HRC60-62, strong wear resistance, and a service life of ≥5000h.

[0064] As a key corner section in the L-shaped layout, the turning flue duct 3 is prone to vortices and stagnation zones in the flue gas flow. Therefore, an inclined chute assembly is installed on the lower part of the vertical descending section 2, near the horizontal section 4. The inclined chute assembly consists of two layers of staggered guide inclined chute 32, with multiple guide inclined chute 32s set in each layer as needed. The guide inclined chute 32 is made of 5mm thick stainless steel plate with an inclination angle of 40°. The lateral spacing between adjacent guide inclined chute 32s in the same layer is based on the lower layer's ability to completely catch the falling steel balls and ash. The guide inclined chute 32 not only accurately guides the falling steel balls and ash from the vertical descending section 2 to the center area of ​​the airflow guide plate assembly 24, but also, through its staggered arrangement, cuts and diverts the airflow at the L-corner, dividing the originally concentrated airflow into multiple uniform airflows, breaking the conditions for vortex formation, reducing airflow resistance, and allowing the flue gas to smoothly transition to the horizontal section 4, avoiding secondary dust adhesion caused by airflow stagnation.

[0065] The airflow guiding plate assembly 24 within the diversion flue 3 is the core component for achieving the integrated functions of "airflow guidance, material screening, and power conversion." Its tilt angle is 30-60°, smoothly transitioning with the flue wall to ensure that the flue gas flow resistance is ≤50Pa. The dual core functions of the airflow guiding plate assembly 24 are specifically manifested in two aspects: Firstly, through the precise design of the plate surface curvature and / or tilt angle, it forms a directional guiding force on the flue gas, guiding the high-temperature flue gas smoothly along a preset path to the horizontal section 4, avoiding heat exchange efficiency loss caused by airflow turbulence; secondly, relying on the double-layer structure of the upper grating plate 25 and the lower ash-supporting steel plate 26, it achieves efficient screening of steel balls and ash—the grating plate 25 uses stainless steel strip grating with a grating spacing adapted to the steel balls, allowing the highly fluid steel balls to slide along the surface with an accumulation angle ≤30°, while the ash passes through the grating gaps, completing the screening and separation.

[0066] Crucially, the screening process simultaneously achieves efficient power conversion: highly fluid steel balls slide along the grid plate 25 to the shot inlet 28 of the gravity recovery chamber 27, and under the action of gravity, they impact the blades of the recovery impeller 30, generating torque that drives the impeller to rotate at a speed of 30-50 r / min; the shaft of the recovery impeller 30 is rigidly connected to the hammering wheel 31 on the back of the ash-supporting steel plate 26 through a transmission assembly, thereby converting the kinetic energy of the steel balls into the hammering power of the hammering wheel 31, which periodically hammers the ash-supporting steel plate 26 that receives low-fluidity ash with a hammering force of 50-80N, effectively breaking the adhesion between the ash and the plate surface, promoting the rapid discharge and collection of ash, without the need for an additional power source, thus achieving cascade utilization of energy.

[0067] Meanwhile, constrained by the airflow guiding function of the airflow guide plate assembly 24, the ash-supporting steel plate 26 cannot be designed to be too short: if the length of the ash-supporting steel plate 26 is insufficient, it will cause the airflow guiding path to be interrupted, resulting in a sharp increase in flue gas flow resistance; while the usual design would result in a long ash and slag falling path, which would increase the risk of material accumulation for ash and slag with low fluidity. As for steel balls, their falling fluidity is relatively strong, so by diverting the flow and recovering the kinetic energy of the steel balls, the ash and slag on the ash-supporting steel plate 26 can be shaken, improving their falling fluidity. For this reason, the present invention provides a hammering wheel 31.

[0068] The hammering wheel 31 can adopt any structure capable of creating vibration on the ash-supporting steel plate 26. It can be an eccentric wheel structure with a wheel diameter of 150mm and an eccentricity of 20mm, hammering the ash-supporting steel plate 26 once per revolution. Alternatively, as shown in the figure, it can consist of a wheel body and multiple hammers mounted on the wheel body. Its wheel axle is connected to the auxiliary drive motor 34 via an electromagnetic clutch 33. The auxiliary drive motor 34 is a three-phase asynchronous motor with a rated power of 1.5kW and a rated speed of 1450r / min. When the steel ball circulation is insufficient, such as when the system is just started and the speed of the recovery impeller 30 is below 20r / min, the electromagnetic clutch 33 automatically engages, and the auxiliary drive motor 34 drives the hammering wheel 31 to rotate through a reducer with a reduction ratio of 30:1, ensuring the hammering effect on the ash-supporting steel plate 26 and preventing ash accumulation.

[0069] The width of the ash-falling channel formed between the grating plate 25 and the ash-supporting steel plate 26 gradually widens from 80mm at the upper end to 150mm at the lower end, preventing ash and slag from clogging the channel. The lower end of the ash-falling channel is connected to the ash hopper below the turning flue 3. A screw conveyor is installed at the bottom of the ash hopper to transport the collected ash and slag to the ash storage bin. The gravity recovery chamber 27 is installed in the side wall of the turning flue 3 at the lower end of the grating plate 25. Its shot inlet 28 is a strip-shaped structure with an opening width consistent with the width of the grating plate 25, ensuring that all steel balls fall in. The shot outlet 29 is connected to the steel ball storage bin 22 through the shot drop pipe, facilitating the downward sliding of steel balls by gravity. The recovery impeller 30 includes a shaft and blades evenly arranged on the shaft. The blades are made of wear-resistant cast iron, which is highly wear-resistant and can effectively transmit torque.

[0070] The intelligent control system uses a PLC controller as its core, and is connected to the flue gas temperature sensor 91 installed at the outlet of vaporization settling chamber 1, and the differential pressure sensors 92 at the inlet and outlet of the heating surfaces of the vertical descending section 2 and the horizontal section 4. The flue gas temperature sensor 91 has a measurement range of 0-1200℃ and an accuracy of ±1℃, while the differential pressure sensor 92 has a measurement range of 0-5kPa and an accuracy of ±0.01kPa. The PLC controller has a preset dust removal trigger condition: when the differential pressure on the heating surface of the vertical descending section 2 is ≥1.5kPa. When the pressure difference of Pa or flue gas temperature fluctuates by ≥±20℃, the steel ball shot peening cleaning device is activated; when the pressure difference of the heating surface of horizontal section 4 is ≥1.0kPa and the flue gas temperature of the turning flue 3 drops to 350℃, the composite steel brush cleaning device is activated. The composite steel brush cleaning device uses a motor-driven rotating steel brush. The steel brush material is high-temperature resistant nylon filament. The contact pressure with the heating surface is 20-30N, and the rotation speed is 80r / min. After the cleaning is completed, the pressure difference drops to 1 / 2 of the set value and it automatically stops, realizing intelligent and precise cleaning.

[0071] IV. Implementation process of dust removal method

[0072] Dust removal implementation of vertical descending section

[0073] S1.1 Start-up preparation: When the system is running, the intelligent control system collects the pressure difference and flue gas temperature signals of the heated surface of the vertical descending section 2 in real time. When the pressure difference is detected to be ≥1.5kPa, indicating that the ash accumulation thickness is ≥5mm, it is determined that the ash removal conditions are met and a start command is issued. The bucket elevator of the steel ball lifting mechanism 23 starts and uniformly lifts the qualified steel balls with a particle size of 5mm after screening in the steel ball storage bin 22 to the steel ball spreading mechanism 21 at the top of the vertical descending section 2. The steel ball conveying capacity is 2t / h.

[0074] S1.2 Steel ball impact cleaning: The rotating spreading disc of the steel ball spreading mechanism 21 rotates under the drive of the motor, spreading steel balls evenly to the entire cross section of the vertical descending section 2. Under the action of gravity, the steel balls fall along the heating surface tube wall of the high temperature superheater 7, low temperature superheater 8, primary evaporator 9 and secondary evaporator 10 at a falling speed of 3-5m / s. Through the impact pressure of the steel balls hitting the tube wall ≥2MPa, the adhering ash on the tube wall surface is peeled off, and the ash peeling rate is ≥90%.

[0075] S1.3 Material Separation and Guiding with Hammering Assisted Discharge: The falling steel balls and stripped ash are guided by the guide chute 32 of the inclined chute group at the bottom of the vertical descending section 2. While cutting and diverting the L-shaped airflow, the guide chute 32 precisely guides the material into the airflow guide plate group 24. The high-temperature flue gas (600-700℃) is deflected by the grid plate 25 of the airflow guide plate group 24 and flows smoothly to the horizontal section 4 under the guidance, with a flow resistance loss ≤30Pa. The ash passes through the grid plate 25 under gravity. The steel balls fall into the ash-falling channel between the grating plate 25 and the ash-supporting steel plate 26 through the gap, and are stably received by the ash-supporting steel plate 26 due to its sufficient length. The steel balls slide along the upper surface of the grating plate 25, fall into the gravity recovery chamber 27 through the shot inlet 28, and impact the blades of the recovery impeller 30. This drives the impeller to rotate and drives the hammer wheel 31 to hammer the ash-supporting steel plate 26 through the transmission component, causing the plate surface to vibrate and increasing the ash falling speed from 0.1m / s to 0.3m / s, thus promoting the downward discharge and collection of low-flowability ash.

[0076] S1.4 Ash and Slag Collection and Steel Ball Recovery: The ash and slag in the ash discharge channel slide downwards along the gradually widening channel and finally fall into the ash hopper below the turning flue 3. The screw conveyor in the ash hopper starts to transport the ash and slag to the plant's ash storage system for collection and discharge. The steel balls entering the gravity recovery chamber 27 slide down the inner wall of the chamber to the shot outlet 29 after hitting the blades. They then flow back to the steel ball storage bin 22 through the shot drop pipe. The steel ball recovery rate is ≥98%, achieving recycling. The entire process involves the secondary conversion of the steel ball's kinetic energy, eliminating the need for additional power to drive the hammering mechanism and reducing the energy consumption of the ash cleaning system.

[0077] Two-level section dust removal implementation

[0078] The intelligent control system monitors the pressure difference of the heating surface of horizontal section 4 and the flue gas temperature of the turning flue 3 in real time. When the pressure difference of the heating surface of horizontal section 4 is ≥1.0 kPa and the flue gas temperature in the turning flue 3 drops to 350℃, the dust viscosity in the flue gas is significantly reduced, and the steel brush cleaning effect is optimal. At this time, the composite steel brush cleaning device is started. The motor drives the rotating steel brush to rotate close to the tube bundle surface of the three-stage evaporator 11 and economizer 12. The accumulated dust is peeled off by the friction between the steel brush and the tube wall. During the cleaning process, the steel brush and the tube wall maintain a constant contact pressure to avoid wear on the tube wall. After the cleaning is completed, when the pressure difference of the heating surface of horizontal section 4 drops below 0.5 kPa, the intelligent control system issues a stop command, and the composite steel brush cleaning device stops operating.

[0079] V. System Operation Assurance and Adaptability Adjustment

[0080] In industrial silicon smelting flue gas treatment, this system is adaptable to operating conditions with flue gas temperatures of 500-1000℃ and dust concentrations of 20-50g / Nm³. Through pre-dust removal and temperature stabilization in the vaporization settling chamber 1, efficient heat exchange in the mixed circulating water system, and precise cleaning in the combined cleaning system, the system achieves a waste heat recovery efficiency of ≥85% and a boiler thermal efficiency of ≥88%. During system operation, the intelligent control system can automatically shorten the cleaning interval according to changes in flue gas parameters, such as increased dust concentration, to ensure stable system operation.

[0081] When encountering extreme conditions such as a sudden rise in flue gas temperature exceeding 1100℃, the ceramic coating of the radiant heating surface 20 can withstand short-term high-temperature impacts. At the same time, the working fluid circulation velocity of the natural circulation loop automatically increases, quickly carrying away heat. If the steel ball circulation system malfunctions, such as the steel ball lifting mechanism jamming, the auxiliary drive motor 34 drives the hammer wheel 31 to operate independently through the electromagnetic clutch 33, preventing ash and slag from accumulating and clogging on the ash-supporting steel plate 26, and ensuring the system's emergency operation capability.

[0082] This invention demonstrates the system's significant advantages in efficient heat exchange, precise dust removal, and low-consumption operation through the cutting effect of the guide chute on the L-shaped airflow and the three-in-one function of the airflow guide plate group of "airflow guidance-material screening-power conversion". It is suitable for waste heat recovery scenarios in the industrial silicon smelting industry.

Claims

1. An industrial silicon waste heat boiler system based on L-shaped arrangement, comprising a boiler body, a mixed circulating water system and a combined ash removal system. The boiler body comprises a vaporization settling chamber (1), a vertical descending section (2), a turning flue (3) and a horizontal section (4) connected in sequence along the flue gas flow direction; a flue gas inlet (5) is arranged on one side of the lower part of the vaporization settling chamber (1), and a flue gas outlet (6) is arranged at the end of the horizontal section (4) away from the vertical descending section (2); a high-temperature superheater (7), a low-temperature superheater (8), a first evaporator (9) and a second evaporator (10) are arranged in the vertical descending section (2) in sequence along the flue gas flow direction; a third evaporator (11) and three sets of coal economizers (12) are arranged in the horizontal section (4) in sequence along the flue gas flow direction. The mixed circulating water system comprises a steam-water separator (13), a natural circulation loop, a forced circulation loop and a water replenishment assembly. The natural circulation loop is arranged in the vaporization settling chamber (1) and the vertical descending section (2) of the boiler body, and forms a closed loop with the steam-water separator (13) through the water-cooled walls and / or tube bundles of the vaporization settling chamber (1), the vertical descending section (2), the first evaporator (9), the second evaporator (10), the riser (14) and the downcomer (15); the natural circulation power is formed by the density difference of the working medium in the loop. The forced circulation loop is arranged in the horizontal section (4) of the boiler body, and forms a closed loop with the tube bundles of the third evaporator (11) and the coal economizers (12), as well as the water supply pipe (16) and the return water pipe (17); the forced circulation pump (18) is arranged on the water supply pipe (16); the forced circulation power is generated by the forced circulation pump (18). The combined ash removal system comprises a steel ball shot blasting ash removal device arranged in the vertical descending section (2) and a composite steel brush + compressed air linkage ash removal device arranged in the horizontal section (4).

2. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 1, wherein: The vertical height difference of the loop of the natural circulation loop is greater than or equal to 15 m; the forced circulation pump (18) is a variable frequency pump, which can dynamically adjust the circulation flow according to the system load.

3. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 1, wherein: The water replenishment assembly comprises a water replenishment tank, a water replenishment pump and a water replenishment valve; the water replenishment tank is connected with the water supply pipe (16) of the forced circulation loop through the water replenishment pump and the water replenishment valve, and is used for supplementing softened water to the mixed circulating water system to maintain the stability of the water level of the system.

4. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 1, wherein: A baffle (19) and a radiation heating surface (20) are arranged in the vaporization settling chamber (1) near the flue gas inlet (5). The baffle (19) is made of high-temperature resistant alloy steel, and the interval is 200-300 mm and the inclination angle is 30-45°, which is used for separating the dust with a particle size greater than or equal to 50 μm in the flue gas; The radiation heating surface (20) is a finned tube structure connected to the natural circulation loop, and the surface is sprayed with a high-temperature resistant ceramic coating, which is used for absorbing the radiation heat of the flue gas, reducing the flue gas temperature from about 1000℃ at the flue gas inlet (5) to 600-700℃, and reducing the flue gas temperature fluctuation amplitude from ±50℃ to ≤±20℃.

5. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 1, wherein: The steel ball shot cleaning device comprises a steel ball sowing mechanism (21) arranged at the top of the vertical descending section (2), a steel ball storage bin (22) arranged at the bottom of the vertical descending section (2), and a steel ball lifting mechanism (23) for lifting the steel balls in the steel ball storage bin (22) to the steel ball sowing mechanism (21).

6. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 1, wherein: The combined cleaning system is also equipped with an intelligent control system, which is connected with the flue gas temperature sensor and the differential pressure sensor, and can dynamically adjust the cleaning frequency based on the real-time monitoring of the flue gas temperature and the differential pressure signal of the heating surface.

7. The L-type arrangement based industrial silicon waste heat boiler system as claimed in claim 5, wherein: The turning flue (3) is also provided with an inclined air flow guide plate group (24) inclined to the horizontal section (4), which can deflect the flue gas in the vertical descending section (2) to the horizontal section (4), and can collect and screen the steel balls and ash falling from the vertical descending section (2); the air flow guide plate group (24) comprises a grid plate (25) located at the upper layer and a ash holding steel plate (26) located at the lower layer, and a falling ash channel for the falling of ash is formed between the grid plate (25) and the ash holding steel plate (26), the falling ash channel gradually widens from top to bottom, and the lower end is communicated with the ash bucket below the turning flue (3); The turning flue (3) is also provided with an inclined air flow guide plate group (24) inclined to the horizontal section (4), which can deflect the flue gas in the vertical descending section (2) to the horizontal section (4), and can collect and screen the steel balls and ash falling from the vertical descending section (2); the air flow guide plate group (24) comprises a grid plate (25) located at the upper layer and a ash holding steel plate (26) located at the lower layer, and a falling ash channel for the falling of ash is formed between the grid plate (25) and the ash holding steel plate (26), the falling ash channel gradually widens from top to bottom, and the lower end is communicated with the ash bucket below the turning flue (3); 8. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 7, wherein: The vertical descending section (2) is also provided with a chute group on one side near the horizontal section (4) for guiding the steel balls and ash to the air flow guide plate group (24), and the chute group comprises two layers of staggered guide chutes (32).

9. The L-shaped arrangement based industrial silicon waste heat boiler system as claimed in claim 8, wherein: The shaft of the beating wheel (31) is also connected with an auxiliary driving motor (34) through an electromagnetic clutch (33).

10. The method for soot cleaning of an L-arrangement based industrial silicon waste heat boiler system according to any one of claims 7-9, characterized in that, It comprises: Vertical descending section (2) cleaning: S1.1, start: when the intelligent control system detects that the cleaning condition is met, start the steel ball lifting mechanism (23), and convey the steel balls in the steel ball storage bin (22) to the steel ball sowing mechanism (21) at the top of the vertical descending section (2); S1.2 steel ball impact cleaning: the steel ball sowing mechanism (21) uniformly spreads the steel balls, the steel balls fall along the heating surface in the vertical descending section (2), and the accumulated ash on the surface of the heating surface is stripped by impact action; S1.3 Material separation guide and beating auxiliary blanking: the falling steel balls and stripped ash fall into the air flow guide plate group (24) in the turning flue (3); the flue gas is guided to the horizontal section (4) through the air flow guide plate group (24), the ash is passed through the gap of the grid plate (25) under the action of gravity, enters the ash falling channel between the grid plate (25) and the ash holding steel plate (26), and the steel balls are guided to the lower row along the upper surface of the grid plate (25) and enter the gravity recovery cavity (27); S1.4 Ash collection and steel ball recovery: the ash falls into the ash bucket and is collected and discharged; The steel balls entering the gravity recovery cavity (27) are driven to rotate by the blades of the high-flow impact recovery impeller machine (30), then flow back to the steel ball storage bin (22) through the pellet outlet (29) and the pellet falling pipe of the gravity recovery cavity (27), realizing the recycling of the steel balls; at the same time, the recovery impeller machine (30) drives the beating wheel (31) to beat the ash holding steel plate (26), improving the falling speed of the ash with poor fluidity on the ash holding steel plate (26); Horizontal section (4) ash removal: When the intelligent control system detects that the ash removal condition is met and the flue gas temperature of the turning flue (3) is reduced to 350℃, the composite steel brush ash removal device is started.

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