A vertical waste heat boiler with misaligned segmented layout for submerged arc furnace flue gas

Abstract

The present invention discloses a vertical waste heat boiler with staggered and segmented arrangement for the flue gas of an electric arc furnace, comprising an inlet flue, a bypass flue, a superheater, a high-temperature evaporator, a steel ball cleaning device, an ash hopper, a low-temperature evaporator, an economizer, a soot blower, a guide and regulating baffle, and a steel frame. The waste heat boiler is staggered in an upper and lower section. The first section is a bare tube heating surface that uses steel balls for soot cleaning; the second section is an H-shaped finned tube that is equipped with a soot blower such as compressed air or shock wave. The flue gas enters the first section from the inlet flue and exchanges heat with the superheater and the high-temperature evaporator, then enters the second section through the guide and regulating baffle, and is discharged after exchanging heat with the low-temperature evaporator and the economizer. When an abnormality occurs in the first section, the guide and regulating baffle are closed, and the flue gas temperature is lowered by cold air before it enters the second section directly from the bypass flue. The present invention improves the efficiency of waste heat utilization and achieves long-term safe operation.

Description

Technical Field

[0001] The invention belongs to the field of industrial flue gas waste heat utilization, and in particular relates to a staggered and segmented vertical waste heat boiler for submerged arc furnace flue gas. Background Art

[0002] Waste heat is a secondary heat energy source. It is the heat released after the conversion of primary energy and combustible materials. It is the remaining heat after the fuel combustion process is completed. Waste heat is generally categorized into seven types: high-temperature flue gas, high-temperature steam, hot slag, high-temperature heat recovery products (including intermediate products), heat from cooling media, combustible waste heat, and waste heat from chemical reactions and carbon residues. Common waste heat recovery methods include using waste heat boilers to produce hot water or steam, preheating air with flue gas, and treating high-temperature flue gas with fluid heat exchangers. The production process of submerged arc furnaces typically uses carbonaceous reducing agents, generating large amounts of flue gas containing components such as CO, CO₂, and H₂. This exhaust gas contains significant amounts of waste heat, accounting for approximately 50% of the total energy consumption of the submerged arc furnace. Therefore, utilizing advanced process technologies to recover and utilize the energy from submerged arc furnace flue gas is of great significance, as it can improve energy efficiency and reduce industrial production costs.

[0003] Waste heat from submerged arc furnaces is heat energy that cannot be effectively utilized during production or that cannot be rationally utilized during the heating process. Flue gas generated during the smelting process is currently the primary target for waste heat utilization. Waste heat power generation not only saves energy but also benefits the environment. Waste heat boilers are the most important equipment for waste heat power generation. They use the heat of the waste working fluid as a heat source or combustible material to produce steam for power generation.

[0004] The exhaust flue gas from submerged arc furnaces contains large quantities of fly ash particles. When the dust-laden airflow enters the waste heat boiler (HRSG), these particles can settle on the heating surfaces, causing serious damage. Ash has a very low thermal conductivity, which increases thermal resistance and reduces the heat transfer capacity of the heating surface. If the flue gas temperature in high-temperature areas rises, the particles tend to melt more easily, making them more likely to adhere to the walls, causing slagging and triggering a vicious cycle. Ash accumulation in low-temperature areas can also clog flow channels, increasing resistance, fan load, and power consumption. Severe slagging and ash accumulation can only force the boiler to operate at low load or even shut down for maintenance, resulting in reduced equipment utilization and inevitable economic losses.

[0005] Slagging can occur on the high-temperature heating surfaces of waste heat boilers (HRSGs). Flue gas temperatures in this area can reach over 600°C, causing ash particles to melt and deform, forming slagging on the walls. Slag forms on the front of the flue tubes and grows against the airflow. These slag blocks are tough and difficult to remove. Ash accumulation on low-temperature heating surfaces primarily consists of fly ash that impacts the heating surface. Fly ash forms solid particles below its freezing point. Submerged arc furnace flue gas contains a large number of fine fly ash particles, which have a strong adsorption capacity and can easily lead to severe ash accumulation on the low-temperature tube bundles, thus affecting the boiler's energy efficiency.

[0006] Purpose of the invention: The purpose of the present invention is to overcome the slagging and dust accumulation problems of existing industrial silicon waste heat boilers, and to provide a staggered and segmented vertical waste heat boiler for the flue gas of industrial silicon ore-fired furnaces. The boiler is arranged in two sections, and different heat exchange elements and cleaning methods are used in the two sections. While making full use of the waste heat of the flue gas, it can also effectively reduce the slagging and dust accumulation problems on the heating surface.

[0007] The present invention divides the waste heat boiler into two staggered sections. Compared to a purely vertical waste heat boiler, this staggered arrangement allows for the timely removal of slag and ash deposits from the high-temperature heating surface after cleaning. This significantly reduces ash accumulation on the various heating surfaces in the intermediate and low-temperature sections, improving heat transfer efficiency. Both sections of the waste heat boiler are arranged vertically, which is more effective than a horizontal arrangement in reducing ash accumulation and removing slag and ash from the boiler bottom. The first section of the boiler includes a superheater and a high-temperature evaporator, and its heating surface adopts a smooth tube. The surface of the smooth tube heating surface is not easy to slag, and even if slag is formed, it is easy to remove. Steel ball cleaning is selected as the cleaning method. Steel ball cleaning has the advantages of good cleaning effect, simple structure, low manufacturing, use and maintenance costs. A steel ball spreading device is arranged on the top of the first section of the boiler, and a steel ball collecting device is arranged at the bottom. During cleaning, steel balls are spread by the steel ball spreading device, and collide with the superheater and the high-temperature evaporator to knock down the slag blocks on the heating surface. The steel ball collecting device at the bottom collects the steel balls that fall into the ash hopper, and then the steel ball lifting device sends the steel balls back to the steel ball spreading device. Compared with the vertical waste heat boiler with straight upper and lower non-offset, the present invention has a short steel ball flow process, realizing short-process and low-energy steel ball cleaning; and the staggered arrangement also avoids the steel balls falling on the H-shaped fin tube bundle to cause dust accumulation and blockage of the flow channel, affecting long-term safe operation. The ash removed from the first-stage heating surface of the boiler falls into the ash hopper due to gravity and the centrifugal force of the boiler structure. Small fly ash particles are homogenized by the flue gas through diversion and regulating baffles before entering the second stage of the boiler. The second stage of the boiler, which includes a low-temperature evaporator and economizer, utilizes H-shaped finned tubes for its heating surfaces. These tubes are wear-resistant, have a turbulent flow field that prevents ash accumulation, have a large heating surface, provide excellent heat transfer performance, and exhibit low flow resistance. Due to the inherent characteristics of the H-shaped finned tubes and the fact that large ash particles in the flue gas have already been removed in the first stage of the boiler, the use of compressed air or shock wave sootblowers can remove the accumulated ash from the heating surfaces. In the event of an anomaly in the first stage of the boiler, the flue gas enters the second stage of the boiler through a bypass flue for waste heat utilization. Summary of the Invention

[0008] The present invention provides a staggered vertical afterheat boiler for the flue gas of an ore-heating furnace. The afterheat boiler is staggered and arranged vertically in two sections, wherein the flue gas flow direction is perpendicular to the ground; the first section of the afterheat boiler includes a superheater and a high-temperature evaporator; the heating surface of the first section of the afterheat boiler is a light tube, which is cleaned with steel balls, a steel ball spreading device is arranged on the top of the first section of the afterheat boiler, a steel ball collecting device and an ash hopper are arranged at the bottom, and a steel ball lifting device is arranged on the side; the second section of the afterheat boiler includes a low-temperature evaporator and an economizer; the afterheat boiler The heating surface of the second section of the boiler is an H-shaped finned tube, and a compressed air or shock wave soot blower is arranged; a flue gas diversion and adjustment baffle is arranged at the connection between the first section and the second section of the waste heat boiler, and the boiler shell wraps the first section and the second section of the waste heat boiler; a bypass flue is arranged on the outside of the inlet flue; multiple cold air emergency valves are respectively provided on the inlet flue, an outlet flue is provided at the tail end of the second section of the waste heat boiler, and a boiler drum is arranged for steam-water separation to form a complete water circulation loop; a steel frame is arranged to support the inlet flue of the entire waste heat boiler.

[0009] Preferably, the inlet flue is divided into a flue gas inlet and an air inlet; the inlet flue has multiple flue gas inlets. When the flue gas temperature is too high, the air inlet valve of the inlet flue is opened to allow the flue gas and air to mix before entering the first section of the waste heat boiler.

[0010] Preferably, the superheater and the high-temperature evaporator are composed of a number of parallel light tubes, the center lines of the light tube bundles are arranged horizontally and perpendicular to the flue gas flow direction, and gaps are provided between adjacent light tubes.

[0011] Preferably, the low-temperature evaporator and the economizer are composed of a plurality of H-shaped finned tubes arranged in parallel, and gaps are provided between adjacent H-shaped finned tubes.

[0012] Preferably, after the first section of the waste heat boiler recovers the waste heat of the flue gas, the flue gas is subjected to centrifugal force at the bottom of the first section of the waste heat boiler, and large ash particles are thrown into the ash hopper to achieve primary separation, thereby reducing ash accumulation and wear on the second section of the waste heat boiler. The remaining small ash particles enter the second section of the waste heat boiler after being homogenized by the flue gas through the diversion and adjustment baffle.

[0013] Preferably, the first section of the waste heat boiler adopts steel ball cleaning, a steel ball spreading device is arranged on the top, the removed ash falls into the ash hopper, a steel ball collecting device is arranged at the bottom to recover the cleaned steel balls, and a steel ball lifting device is arranged to send the steel balls back to the steel ball spreading device.

[0014] Preferably, a soot blower is arranged in the second section of the waste heat boiler to clean the low-temperature evaporator and the economizer, and the soot blowing method is compressed air method or shock wave method.

[0015] Preferably, when the first section of the high temperature zone of the waste heat boiler cannot operate normally, the flue gas diversion and adjustment damper are closed, and the flue gas enters the second section of the medium and low temperature zone of the waste heat boiler through the bypass flue.

[0016] Preferably, the superheater, high-temperature evaporator, low-temperature evaporator and economizer are all water-tube heat exchangers.

[0017] Preferably, the fin pitch of the H-shaped fin tubes used in the low-temperature evaporator and economizer is not less than 30 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The diagram shows the main cross-sectional structure of a vertical waste heat boiler with staggered segmented arrangement for the flue gas of a submerged arc furnace.

[0019] Figure 2 This is a schematic diagram of the main body of a vertical waste heat boiler with staggered segmented arrangement for the flue gas of a submerged arc furnace.

[0020] Figure 3 This is a schematic diagram of the heat exchange tube bundle structure of the superheater and high-temperature evaporator in the present invention.

[0021] Figure 4 This is a schematic diagram of the heat exchange tube bundle structure of the low-temperature heat exchanger and economizer of the present invention.

[0022] In the figure: 1-superheater; 2-high-temperature evaporator; 3-steel ball lifting device; 4-ash hopper; 5-steel ball collecting device; 6-diversion and adjustment baffle; 7-soot blower; 8-inlet flue; 9-bypass flue; 10-steel ball spreading device; 11-boiler drum; 12-boiler shell; 13-low-temperature evaporator; 14-economizer; 15-outlet flue; 16-steel frame. DETAILED DESCRIPTION

[0023] The present invention provides a staggered and segmented vertical waste heat boiler for treating flue gas from a submerged arc furnace. The working principle of the system will be further described below with reference to the accompanying drawings and specific implementation methods.

[0024] Figure 1The schematic diagram shows a vertical waste heat boiler with staggered, segmented layout for treating blast furnace flue gas. The waste heat boiler is characterized by a staggered, vertical layout consisting of two sections (flue gas flows perpendicular to the ground). The first section includes a superheater 1 and a high-temperature evaporator 2. Its heating surfaces are bare tubes and use steel ball cleaning. A steel ball spreading device 9 is located at the top of the first section, along with a steel ball collection device 5 and an ash hopper 4 at the bottom and a steel ball lifting device 3 on the side. The second section includes a low-temperature evaporator 13 and an economizer 14. Its heating surfaces are H-shaped finned tubes and a soot blower 7, such as a compressed air or shock wave blower, is located. A flue gas diversion and regulation baffle 6 is located at the junction of the two sections. The boiler shell 12 encloses the first and second sections. A bypass flue 9 is located outside the inlet flue 8, each equipped with multiple cold air emergency valves. An outlet flue 15 is located at the rear of the second section. A boiler drum 11 is located for steam-water separation, forming a complete water circulation loop. A steel frame 16 supports the entire boiler.

[0025] The inlet flue 8 is divided into a flue gas inlet and an air inlet. The inlet flue has multiple flue gas inlets. When the flue gas temperature is too high, the air inlet valve of the inlet flue 8 is opened, and the flue gas and air are mixed before entering the first section of the waste heat boiler.

[0026] The superheater 1 and the high-temperature evaporator 2 are composed of a number of parallel light tubes. The center line of the light tube bundle is arranged horizontally and perpendicular to the flue gas flow direction, and there is a gap between adjacent light tubes.

[0027] The low-temperature evaporator 13 and the economizer 14 are composed of a plurality of H-shaped finned tubes arranged in parallel, with gaps being provided between adjacent H-shaped finned tubes.

[0028] The boiler is arranged in a two-stage staggered manner. After the flue gas waste heat is recovered in the first stage of the boiler, the flue gas is subjected to centrifugal force at the bottom of the first stage of the boiler. Large ash particles are thrown into the ash hopper 4 for primary separation, reducing ash accumulation and wear on the second stage. The remaining small ash particles enter the second stage of the boiler after being homogenized by the diversion and adjustment baffle 6 with the flue gas.

[0029] The first section of the boiler uses steel balls for ash cleaning. A steel ball spreading device 10 is arranged on the top. The cleaned ash falls into the ash hopper 4. A steel ball collecting device 5 is arranged at the bottom to recover the cleaned steel balls. A steel ball lifting device 3 is arranged to send the steel balls back to the steel ball spreading device 10.

[0030] A soot blower 7 is arranged in the second section of the boiler to clean the low-temperature evaporator 13 and the economizer 14. The soot blowing method can be selected from various methods such as compressed air method or shock wave method.

[0031] Arrange the bypass flue 9. When the first section of the high temperature zone of the boiler cannot operate normally, close the flue gas diversion and adjustment damper 6, and the flue gas enters the second section of the medium and low temperature zone of the boiler through the bypass flue 9.

[0032] The superheater 1, the high-temperature evaporator 2, the low-temperature evaporator 13 and the economizer 14 are all water-tube heat exchangers.

[0033] The fin pitch of the H-type fin tubes used in the low-temperature evaporator 13 and the economizer 14 is not less than 30 mm.

[0034] Its working process is:

[0035] The flue gas temperature in a submerged arc furnace is approximately 500-600°C, but can also reach transient high temperatures exceeding 1000°C. To prevent these transient high temperatures from causing more severe slagging, the inlet flue 8 includes a flue gas inlet and an air inlet. The inlet flue has multiple flue gas inlets, and the air inlet is equipped with a switch valve. When the flue gas temperature is too high, the valve opens, allowing the flue gas and air to mix before entering the boiler. The flue gas enters the first section of the boiler from the inlet flue 8, passes through the superheater 1 and the high-temperature evaporator 2, and is then homogenized by the guide and regulating baffle 6 before entering the second section of the boiler. After sufficient heat exchange with the low-temperature evaporator 13 and economizer 14 in the second section of the boiler, the flue gas leaves the waste heat boiler through the flue gas outlet 15. The waste heat boiler of the present invention has a boiler drum 11 disposed between the outlet header of the high-temperature evaporator 2 and the inlet header of the superheater 1. The steam-water mixture discharged from the outlet header of the high-temperature evaporator 2 enters the boiler drum 11 for steam-water separation. The steam then enters the inlet header of the superheater 1, where it is heated to a certain superheat temperature and sent to the steam turbine for power generation or other processes. The large-diameter downcomer at the bottom of the boiler drum 11 introduces undersaturated water into the inlet headers of the high-temperature evaporator 2 and the low-temperature evaporator 13, respectively, forming a complete water circulation loop. The boiler feed water is deoxygenated and then sent to the inlet header of the economizer 14. After absorbing the waste heat of the flue gas, it is heated to a certain temperature and then sent from the inlet header of the economizer 14 to the boiler drum 11. A bypass flue 9 is arranged so that when the first section of the boiler cannot operate normally, the flue gas enters the second section of the boiler through the bypass flue 9. The first stage of the boiler's soot cleaning is performed using steel balls. During this cleaning process, steel balls are spread by a steel ball spreading device 10. These balls collide with the superheater 1 and high-temperature evaporator 2, knocking slag off the heated surfaces and dropping it into the ash hopper 4. Simultaneously, due to centrifugal force, large ash and ash particles in the flue gas are thrown into the ash hopper 4. A steel ball collecting device 5 at the bottom collects the steel balls that fall into the ash hopper 4, and a steel ball lifting device 3 is arranged to return the steel balls to the steel ball spreading device 10. A soot blower 7 is arranged in the second stage of the boiler. Various cleaning methods can be selected, such as compressed air or shock wave methods, to effectively remove accumulated ash from the low-temperature evaporator 13 and economizer 14.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

[0037] The present invention adopts staggered arrangement, segmented control of slagging and dust accumulation, and bypass emergency regulation, thereby improving waste heat utilization efficiency and achieving long-term safe operation.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. In response to the complex composition of waste gas generated during the industrial silicon production process, and the serious problems of slagging and ash accumulation on the heating surfaces of traditional waste heat boilers, the boiler is creatively divided into two vertical staggered sections, and different heat exchangers and cleaning methods are selected for the two sections. A staggered and segmented vertical waste heat boiler for the flue gas of submerged arc furnaces is proposed. Specifically, the superheater and high-temperature evaporator of the first section of the boiler use light tube heating surfaces to effectively reduce slagging, and the steel ball cleaning method can be used to remove slagging on the light tubes. In addition, the inlet flue includes a flue gas inlet and an air inlet. The inlet flue has multiple flue gas inlets, and a switch valve is set at the air inlet. When the flue gas temperature is too high, the valve is opened, and the flue gas and air are mixed before entering the boiler, preventing the flue gas from instantaneously becoming high temperature and also reducing the problem of boiler slagging. The low-temperature evaporator and economizer in the second section of the boiler use H-shaped finned tube heating surfaces with a pitch greater than 30mm. The self-cleaning advantages of the H-shaped finned tubes can reduce dust accumulation on the heating surface. Soot blowers are also deployed to clean the low-temperature evaporator and economizer. Cleaning methods include compressed air and shock waves, effectively removing accumulated dust from the low-temperature evaporator and economizer. In summary, the present invention can effectively prevent and control slagging and dust accumulation on the heating surfaces.

[0040] 2. Efficiently recover flue gas waste heat, achieving energy conservation and consumption reduction. Exhaust gas generated during industrial silicon production enters the first section of the boiler through the inlet flue, exchanges heat with the superheater and high-temperature evaporator, and then enters the second section of the boiler for a second heat exchange. The low-temperature evaporator and economizer in the second section of the boiler utilize H-shaped finned tubes, which reduces the number of pipes and increases the heat exchange area, facilitating optimal heat exchange between the flue gas and the working fluid, and fully recovering the flue gas waste heat.

[0041] 3. Improved unit operation stability and reliability. A bypass flue is installed. If the first section of the boiler fails to operate normally, the flue gas enters the second section through the bypass flue, ensuring continuous operation of the entire unit. During bypass operation, the first section of the boiler can be repaired.

Claims

1. A vertical waste heat boiler with staggered and segmented arrangement for the flue gas of submerged arc furnace, characterized in that: The waste heat boiler is arranged vertically in two sections with staggered positions, wherein the flue gas flow direction is perpendicular to the ground; the first section of the waste heat boiler comprises a superheater (1) and a high-temperature evaporator (2); the heating surface of the first section of the waste heat boiler is a bare tube, which is cleaned with steel balls, a steel ball spreading device (10) is arranged on the top of the first section of the waste heat boiler, a steel ball collecting device (5) and an ash hopper (4) are arranged on the bottom, and a steel ball lifting device (3) is arranged on the side; the second section of the waste heat boiler comprises a low-temperature evaporator (13) and an economizer (14); the heating surface of the second section of the waste heat boiler is an H-shaped finned tube , a compressed air or shock wave soot blower is arranged; a flue gas guide and regulating baffle (6) is arranged at the connection between the first section and the second section of the waste heat boiler, and the boiler shell (12) wraps the first section and the second section of the waste heat boiler; a bypass flue (9) is arranged outside the inlet flue (8); the inlet flue (8) is respectively provided with a plurality of cold air emergency valves, an outlet flue (15) is arranged at the tail of the second section of the waste heat boiler, and a boiler drum (11) is arranged for steam-water separation to form a complete water circulation loop; a steel frame (16) is arranged to support the inlet flue (8) of the entire waste heat boiler; The inlet flue (8) is divided into a flue gas inlet and an air inlet; the inlet flue (8) has multiple flue gas inlets. When the flue gas temperature is too high, the air inlet valve of the inlet flue (8) is opened to allow the flue gas and air to mix before entering the first section of the waste heat boiler; After the first section of the waste heat boiler recovers the waste heat of the flue gas, the flue gas is subjected to centrifugal force at the bottom of the first section of the waste heat boiler, and large ash particles are thrown into the ash hopper (4) to achieve primary separation, thereby reducing the accumulation of ash and wear on the second section of the waste heat boiler. The remaining small ash particles are homogenized along with the flue gas through the guide and regulating baffle (6) and then enter the second section of the waste heat boiler; The first section of the waste heat boiler adopts steel ball cleaning, a steel ball spreading device (10) is arranged on the top, the cleaned ash falls into the ash hopper (4), a steel ball collecting device (5) is arranged at the bottom to recover the cleaned steel balls, and a steel ball lifting device (3) is arranged to send the steel balls back to the steel ball spreading device (10); The second section of the waste heat boiler is provided with a soot blower (7) for cleaning the low-temperature evaporator (13) and the economizer (14), and the soot blowing method is a compressed air method or a shock wave method; When the first section of the high temperature zone of the waste heat boiler cannot operate normally, the flue gas diversion and regulating damper (6) is closed, and the flue gas enters the second section of the medium and low temperature zone of the waste heat boiler through the bypass flue (9).

2. The staggered and segmented vertical waste heat boiler for submerged arc furnace flue gas according to claim 1, characterized in that: The superheater (1) and the high-temperature evaporator (2) are composed of a plurality of parallel light tubes, the center lines of the light tube bundles are arranged horizontally and perpendicular to the flue gas flow direction, and gaps are provided between adjacent light tubes.

3. The staggered and segmented vertical waste heat boiler for submerged arc furnace flue gas according to claim 1, characterized in that: The low-temperature evaporator (13) and the economizer (14) are composed of a plurality of H-shaped finned tubes arranged in parallel, with gaps being provided between adjacent H-shaped finned tubes.

4. The staggered and segmented vertical waste heat boiler for submerged arc furnace flue gas according to claim 1, characterized in that: The superheater (1), high-temperature evaporator (2), low-temperature evaporator (13) and economizer (14) are all water-tube heat exchangers.

5. The staggered and segmented vertical waste heat boiler for submerged arc furnace flue gas according to claim 1, characterized in that: The fin pitch of the H-shaped finned tubes used in the low-temperature evaporator (13) and the economizer (14) is not less than 30 mm.

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