Waste heat recovery system and method for converter flue gas

Abstract

The application discloses a converter flue gas waste heat recovery system and method, and belongs to the technical field of steel metallurgy. The system comprises a falling cloud bed, a hot material storage chamber, a moving bed and a material circulation loop. The flue gas in the falling cloud bed directly contacts and exchanges heat with the falling heat storage material particles, and the fire particle and the adhesive dust in the flue gas are captured by adhering to the surface of the particles. The high-temperature particles after heat exchange are temporarily stored in the hot material storage chamber, and then continuously enter the moving bed to directly exchange heat with the heating surface to generate steam. The cooled particles are sent back to the top of the falling cloud bed through the circulation loop. The application realizes continuous utilization of intermittent waste heat by replacing heat through the 'falling cloud bed + moving bed', and the heat of the flue gas is first transferred to the particles, and then transferred to the heating surface by the particles. The application integrally solves three technical problems of discontinuous steam, fire explosion hidden danger and adhesive corrosion of high-temperature dust on the heating surface caused by intermittent gas supply in the converter flue gas treatment, and has the advantages of high waste heat recovery rate, safe and stable operation and low maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and in particular to a waste heat recovery system and method for converter flue gas. Background Technology

[0002] During converter steelmaking, the carbon-oxygen reaction generates a large amount of high-temperature flue gas, with temperatures reaching 1550℃ to 1700℃ and a volume of approximately 200 Nm³ / ton of steel. This flue gas contains pollutants such as CO, CO2, and particulate matter (including ash and iron oxide). This flue gas carries significant latent and sensible heat; direct emission would not only pollute the atmosphere but also result in a substantial waste of thermal energy. Therefore, recovering waste heat from converter flue gas, reducing steelmaking energy consumption, and improving energy efficiency are of great importance.

[0003] However, due to the instability and process complexity of steelmaking converter flue gas, three major technical challenges arise for waste heat recovery and utilization: First, there's the issue of rapid heating and cooling, and intermittent gas supply. Converter blowing is an intermittent operation; high-temperature flue gas is generated during each heat of steel blowing, but no flue gas is produced during non-blowing periods. The temperature and flow rate of the flue gas fluctuate frequently and significantly with the blowing cycle. This intermittent gas supply characteristic makes it impossible for traditional waste heat recovery devices to operate stably, resulting in intermittent steam production that cannot meet continuous steam demand.

[0004] Secondly, there is the issue of explosion hazards. Throughout the converter steelmaking process, the air-flue gas-gas conversion occurs repeatedly during each heat's blowing cycle. Converter flue gas contains a large amount of combustible gases such as CO, and when mixed with oxygen-containing air or flue gas, explosive conditions can form at any time. In particular, the flue gas may carry unburned spark particles, which, if they enter the waste heat recovery equipment, can easily trigger an explosion.

[0005] Third, there is the problem of adhesion and corrosion on the heated surfaces. Converter dust contains alkaline substances such as quicklime (CaO). If wet treatment is used, the quicklime will be activated into hydrated lime when it comes into contact with water, and then react with CO2 in the flue gas to form calcium carbonate scale. Even if a dry process is used, high-temperature dust particles are prone to deposit and sinter on the surface of the heated surfaces, forming scale that is difficult to remove, which seriously affects the heat exchange efficiency and may even lead to the scrapping of the equipment.

[0006] Currently, converter flue gas treatment methods mainly include wet (OG) method, dry (LT) method, and the all-dry process developed in recent years. The OG and LT methods reduce the flue gas temperature from over 1500℃ to approximately 800℃ through vaporization cooling of the flue. However, subsequent cooling via water spraying not only wastes the sensible heat in the low-temperature section but also introduces a large amount of water vapor into the flue gas, reducing the quality of the recovered gas. While the all-dry process avoids water spraying for cooling, it still does not effectively solve the problem of discontinuous steam supply caused by intermittent gas supply, nor does it address the risks of adhesion corrosion on heated surfaces and the potential for spark explosions.

[0007] For example, existing technology discloses a converter flue gas waste heat recovery and dust removal system, which further recovers sensible heat by adding a waste heat boiler after the vaporization cooling flue, and achieves dry gas recovery by using a fully dry dust removal method. However, this system still uses the method of direct heat exchange between flue gas and the heating surface, which fails to solve the problem of steam fluctuation caused by intermittent flue gas supply, as well as the problem of adhesion and corrosion of the heating surface by high-temperature fine particles and the risk of spark explosion.

[0008] Therefore, there is an urgent need in this field for a new converter flue gas waste heat recovery system and method that can solve the above three major technical problems in an integrated manner. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a converter flue gas waste heat recovery system and method. Through the "falling cloud bed + moving bed" displacement heat exchange technology, it solves the three major technical problems that have long existed in converter flue gas treatment: intermittent gas supply, risk of spark explosion, and adhesion and corrosion of heating surfaces.

[0010] The present invention adopts the following technical solution: On one hand, the present invention provides a waste heat recovery system for converter flue gas, comprising: The cloud bed has its inlet connected to the flue gas outlet of the converter and contains falling heat storage material particles. The cloud bed is configured to allow the incoming flue gas to directly contact the falling heat storage material particles for heat exchange, and in this process, the spark particles and / or sticky dust in the flue gas are attached to the surface of the heat storage material particles and captured. A hot material storage chamber is located below the cloud bed to receive and temporarily store heat storage material particles that fall from the cloud bed, have absorbed the heat of the flue gas, and have captured spark particles and / or sticky dust. A moving bed is disposed below the hot material storage chamber to receive the heat-storing material particles discharged from the hot material storage chamber. The moving bed is provided with a heating surface for the working fluid to pass through. The moving bed is configured to allow the descending heat-storing material particles to directly contact the heating surface for heat exchange, so as to heat the working fluid and generate steam. And a material circulation loop, which sends the heat-exchange-cooled heat-storing material particles discharged from the moving bed back to the top of the cloud bed to form a cycle.

[0011] In addition to any of the possible implementations described above, a further implementation is provided, which includes a feed pool disposed at the top of the settling bed. The feed pool has an upper inlet and a lower outlet, and is configured such that: when converter flue gas is detected entering, its lower outlet is simultaneously opened, allowing the heat-storing material particles to fall into the settling bed for heat exchange; when no flue gas enters, its lower outlet is closed, stopping the feeding. This synchronous control mechanism, on the one hand, achieves matching between material supply and flue gas supply, avoiding ineffective circulation and heat waste; on the other hand, closing the feed port when there is no flue gas prevents air from entering the settling bed through the feed pool, avoiding the formation of an explosive mixture with residual gas, further improving system safety.

[0012] In addition to any of the possible implementations described above, a further implementation is provided in which the flue gas inlet of the cloud bed is located at its lower part, and the heat storage material particle inlet is located at its upper part, so that the incoming flue gas and the falling heat storage material particles form a countercurrent contact. The countercurrent contact can enhance the heat exchange efficiency between gas and solid, allowing the flue gas to fully contact the continuously falling low-temperature particles during its ascent, thereby achieving rapid heat transfer.

[0013] In addition to any of the possible implementations described above, a further implementation is provided in which the heating surface within the moving bed includes one or more of a superheater, an evaporator, and an economizer for continuously generating steam. Because the hot material storage chamber stores a large amount of high-temperature heat-storing material particles, even when the converter is not in the blowing period and no flue gas enters, the heating surface within the moving bed can still maintain stable steam production by relying on the continuously supplied high-temperature particles from the storage chamber.

[0014] In addition to any of the possible implementations described above, a further implementation is provided that includes an additional heat exchange chamber disposed between the flue gas outlet of the settling bed and the subsequent dust removal equipment. This additional heat exchange chamber is equipped with convective heating surfaces for further recovery of residual heat from the flue gas. After heat exchange in the settling bed, the flue gas temperature drops to approximately 500°C, and then enters the additional heat exchange chamber to exchange heat with convective heating surfaces (such as economizer section II or a low-temperature heater), further cooling to below 150°C, thereby fully recovering the sensible heat of the flue gas.

[0015] In addition to any of the possible implementations described above, a further implementation is provided, which further includes a membrane wall flue disposed between the converter and the settling bed. This membrane wall flue is enclosed by a membrane water-cooled wall and is used for preliminary heat exchange and cooling of the high-temperature flue gas produced by the converter. The high-temperature flue gas produced by the converter, exceeding 1500°C, first passes through the membrane wall flue, where it exchanges heat with the membrane water-cooled wall and is cooled to approximately 1000°C before entering the settling bed, thus avoiding significant alterations to the original flue structure.

[0016] On the other hand, the present invention also provides a method for waste heat recovery from converter flue gas, the method employing the above-described system, the method comprising: S1. The intermittent high-temperature flue gas produced by the converter first enters the cloud bed and directly contacts the heat storage material particles falling from the cloud bed for heat exchange, transferring the heat of the flue gas to the heat storage material particles. At the same time, the spark particles and / or sticky dust in the flue gas adhere to the surface of the heat storage material particles and are captured. S2. The heat storage material particles that have absorbed heat and captured spark particles and / or sticky dust fall into the heat material storage chamber for temporary storage, forming a heat buffer. S3. The heat storage material particles at the bottom of the hot material storage chamber continuously enter the moving bed, slowly move down in the moving bed, and directly contact the heating surface set in the moving bed to exchange heat, transferring heat to the working fluid in the heating surface to generate steam. S4. The heat-storing material particles that have cooled down after heat exchange are discharged from the bottom of the moving bed and sent back to the top of the cloud bed through the material circulation loop for recycling.

[0017] In addition to any of the possible implementations described above, another implementation is provided in which, in step S1, the flue gas and the heat storage material particles in the cloud bed adopt a counter-current contact heat exchange, that is, the flue gas enters from the bottom and exits from the top, and the heat storage material particles enter from the top and exit from the bottom.

[0018] In addition to any of the possible implementations described above, another implementation is provided, which further includes a residual heat recovery step: the flue gas discharged from the dust collection bed enters an auxiliary heat exchange chamber, exchanges heat with the convective heating surfaces arranged in the auxiliary heat exchange chamber, and after further releasing the residual heat, enters the subsequent dry dust removal equipment.

[0019] In addition to any of the possible implementations described above, another implementation is provided, which further includes dry dust removal and gas recovery steps: the cooled flue gas is dusted by a dry dust collector, the purified gas is stored in a gas holder, and the unqualified gas is discharged through a venting chimney.

[0020] The beneficial effects of this invention are as follows: 1. Integrated solution to three major technical challenges. This invention solves three long-standing technical challenges in converter flue gas waste heat recovery in the same system by using a collaborative architecture of "falling cloud bed + hot material storage chamber + moving bed", achieving unexpected technical results.

[0021] (1) Solution to the problem of intermittent gas supply: The present invention sets up a hot material storage chamber to temporarily store and buffer the high-temperature heat storage material particles transferred from the moving bed. During converter blowing, the moving bed continuously transfers the heat of the flue gas to the particles and stores them in the storage chamber; during non-converter blowing, the high-temperature particles stored in the storage chamber continue to be supplied to the moving bed. The heating surface in the moving bed can thus obtain a continuous and stable heat source, generating continuous steam for users. At the same time, the control mechanism that synchronizes the opening of the lower outlet of the feed pool with the entry of flue gas ensures precise matching between material supply and flue gas supply, further optimizing the operating efficiency under intermittent conditions.

[0022] (2) Solution to the problem of spark explosion: In this invention, after the flue gas enters the cloud bed, it comes into direct contact with the falling heat storage material particles. The high-temperature spark particles carried in the flue gas collide with and adhere to the surface of the relatively cool heat storage material particles during the movement, and fall with the particles to the heat material storage chamber, thereby effectively removing the spark particles before the flue gas enters the subsequent equipment (additional heat exchange chamber, dust collector, etc.). This capture process is a side effect of the heat exchange process, and there is no need to set up an additional independent spark capture device. The structure is simpler and the effect is more reliable.

[0023] (3) Solution to the problem of adhesion corrosion on the heated surface: Similarly, adhesive dust (such as quicklime particles) in the flue gas collides and adheres to the heat storage material particles in the cloud bed, and is removed as the particles fall, thus preventing these adhesive dust particles from entering the moving bed or additional heat exchange chamber and depositing on the heated surface. Compared with the existing technology where the flue gas directly washes the heated surface, the heated surface (inside the moving bed) of the present invention does not directly contact the flue gas, but achieves indirect heat exchange through the heat storage material particles as the heat medium, fundamentally solving the problem of adhesion corrosion on the heated surface.

[0024] 2. Innovative "Displacement" Heat Exchange Architecture. This invention replaces the traditional direct "flue gas-heating surface" heat exchange with a decoupled displacement between "flue gas-particle" heat exchange and "particle-heating surface" heat exchange. After the heat from the flue gas is absorbed by the heat storage material particles, the particles become the heat carrier, and the utilization of heat is no longer constrained by the intermittent supply of flue gas. This displacement design allows the waste heat recovery system to operate independently, continuously, and stably, greatly improving waste heat utilization and steam quality.

[0025] 3. The entirely dry process ensures high-quality coal gas. This invention introduces no moisture into the entire waste heat recovery process. Flue gas cooling is achieved entirely through gas-solid heat exchange. The dry coal gas entering the gas holder contains no additional water vapor, has a high calorific value, and is of good quality, allowing for direct reuse. Simultaneously, the dry dust removal process avoids wastewater treatment issues, resulting in significant environmental benefits.

[0026] 4. Multiple safety features. In addition to the ignition capture function, the feed tank of this invention adopts a synchronous control strategy of "opening when there is smoke and closing when there is no smoke" to effectively prevent air from entering the system and forming an explosive mixture; a coarse powder collection bin is set at the bottom of the bent flue, and a fine powder collection bin is set at the bottom of the dry dust collector to recover smoke and dust in stages and prevent dust accumulation from causing accidents.

[0027] 5. Cascaded heat utilization for high energy efficiency. This invention divides the waste heat of flue gas into multiple temperature ranges for cascaded recovery: the ultra-high temperature range (>1000℃) is recovered by a membrane wall flue; the high temperature range (500-1000℃) is transferred to heat storage particles via a cloud bed; and the medium-low temperature range (150-500℃) is recovered by the convective heating surface of an additional heat exchange chamber. The heat in each range is rationally utilized, maximizing the overall heat recovery rate. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the converter flue gas waste heat recovery system in Embodiment 1 of the present invention.

[0029] Figure 2 This is a flow chart of the working fluid in the boiler and heating surface in Embodiment 1 of the present invention.

[0030] The attached figures are labeled as follows: 1-Falling bed; 2-Moving bed; 3-Hot material storage chamber; 4-Heat storage material granules; 5-Feeding pool; 6-Distributor; 7-Transfer car; 8-Converter; 9-Membrane wall flue; 10-Outlet flue; 11-Additional heat exchange chamber; 12-Bent flue; 13-Coarse powder collection bin; 14-Dust collector; 15-Fine powder collection bin; 16-Main induced draft fan; 17-Gas cooler; 18-Gas holder; 19-Vent chimney. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0032] The accompanying drawings illustrate a layer structure according to an embodiment of the present invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0033] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Example 1

[0036] I. System Structure like Figure 1 As shown, this embodiment provides a converter flue gas waste heat recovery system, including a settling bed 1, a moving bed 2, a hot material storage chamber 3, heat storage material particles 4, a feed pool 5, a distributor 6, and a transfer car 7.

[0037] A membrane wall flue 9 is installed above the converter 8. The membrane wall flue 9 is surrounded by a membrane water-cooled wall and is used to initially cool the ultra-high temperature flue gas produced by the converter.

[0038] The converter flue gas (temperature >1500℃) generated by converter 8 first enters the membrane wall flue 9, where it exchanges heat with the membrane water-cooled wall, and the flue gas temperature drops to about 1000℃. After preliminary cooling, the flue gas enters the settling bed 1 through the horizontal flue.

[0039] The lower part of the heat storage bed 1 is provided with a flue gas inlet, and the upper part is provided with a heat storage material particle inlet. Heat storage material particles 4 fall inside the heat storage bed 1. A feed tank 5 is provided at the top of the heat storage bed 1, with an upper inlet and a lower outlet. A distributor 6 is provided below the feed tank 5 to evenly distribute the heat storage material particles falling from the feed tank onto the cross-section of the heat storage bed 1.

[0040] A hot material storage chamber 3 is located below the cloud bed 1, and a moving bed 2 is located below the hot material storage chamber 3. The cloud bed 1, the hot material storage chamber 3, and the moving bed 2 are connected sequentially from top to bottom.

[0041] The moving bed 2 has an internal heating surface for the working fluid (water / steam) to pass through, including a superheater, an evaporator, and an economizer section I. A transfer car 7 is located below the moving bed 2 to collect the cooled heat storage material particles discharged from the bottom of the moving bed 2.

[0042] The transfer vehicle 7 lifts and transfers the cooled heat storage material particles to the feed pool 5 at the top of the cloud bed 1, forming a material circulation loop.

[0043] The upper part of the flue gas bed 1 is provided with an outlet flue 10, through which the flue gas after heat exchange in the flue gas bed 1 is discharged and enters the auxiliary heat exchange chamber 11. The auxiliary heat exchange chamber 11 is equipped with convective heating surfaces, including economizer section II and low temperature heater.

[0044] The flue gas outlet of the auxiliary heat exchange chamber 11 is connected to a bent flue 12, and a coarse powder collection bin 13 is provided at the lower part of the bent flue 12. A dust collector 14 (a bag filter is used in this embodiment, but an electrostatic precipitator or other dry dust collection equipment can also be selected) is connected to the outlet end of the bent flue 12, and a fine powder collection bin 15 is provided at the lower part of the dust collector 14. A main induced draft fan 16 is provided at the rear of the dust collector 14, and the outlet of the main induced draft fan 16 is divided into two paths: one path connects to a gas holder 18 via a gas cooler 17, and the other path connects to a venting chimney 19.

[0045] II. Material Circulation and Flue Gas Flow (a) Circulation process of heat storage material particles The circulation process of the heat storage material particles 4 within the system is as follows: 1. The heat storage material particles 4 released from the lower outlet of the feed tank 5 are evenly dispersed by the distributor 6 and fall into the cloud bed 1. They come into countercurrent contact with the rising flue gas for heat exchange, and after absorbing the heat of the flue gas, they are heated to about 900-1000℃. At the same time, they capture spark particles and sticky dust in the flue gas. 2. High-temperature heat storage material particles fall into the hot material storage chamber 3 for temporary storage; 3. High-temperature particles are continuously supplied from the bottom of the hot material storage chamber 3 to the moving bed 2, and the particles move slowly downwards within the moving bed 2; 4. Inside the moving bed 2, the high-temperature particles are in direct contact with the heating surfaces (superheater, evaporator, economizer section I), transferring heat to the working fluid inside the heating surfaces, and the particle temperature drops to below 200℃. 5. The cooled particles are discharged from the bottom of the moving bed 2, collected by the transfer vehicle 7 and lifted and transferred to the feed pool 5 at the top of the cloud bed 1 to complete one cycle.

[0046] The coordination mechanism between the transfer car 7 and the feeding pool 5 is as follows: when the transfer car 7 loads material into the feeding pool 5, the upper inlet of the feeding pool 5 opens and the lower outlet closes; when material needs to be discharged into the settling bed 1, the upper inlet closes and the lower outlet opens. Specifically, the opening of the lower outlet of the feeding pool 5 is synchronized with the entry of converter flue gas: when flue gas is detected from the converter 8, the lower outlet of the feeding pool 5 opens, and the heat-storing material particles fall into the settling bed 1 for heat exchange; when no flue gas enters, the lower outlet closes, and material discharge stops. This control mechanism, on the one hand, achieves precise matching between material supply and flue gas supply, avoiding ineffective circulation and heat waste; on the other hand, closing the discharge port when there is no flue gas effectively prevents air from entering the settling bed 1 through the feeding pool 5, avoiding the formation of an explosive mixture with any remaining combustible gas in the system, thus improving system safety.

[0047] (II) Flue gas flow direction and flow The flow path of the converter flue gas is as follows: 1. The high-temperature flue gas (>1500℃) produced by converter 8 first enters the membrane wall flue 9, where it exchanges heat with the membrane water-cooled wall and is cooled to about 1000℃. 2. The flue gas enters the cloud bed 1 through the horizontal flue and enters from the bottom. It comes into countercurrent contact with the heat storage material particles 4 falling from the top for heat exchange. The flue gas temperature drops to about 500℃. At the same time, the spark particles and sticky dust in the flue gas are captured by the heat storage material particles. 3. The flue gas is discharged from the outlet flue 10 at the top of the cloud bed 1 and enters the auxiliary heat exchange chamber 11, where it exchanges heat with the convective heating surfaces such as the economizer section II and the low temperature heater, and the temperature drops to below 150℃. 4. After cooling, the flue gas enters the dust collector 14 through the bent flue 12. At the lower part of the bent flue 12, large-diameter dust particles settle into the coarse dust collection bin 13 under the action of gravity; inside the dust collector 14, fine dust particles are separated and enter the fine dust collection bin 15. 5. The clean flue gas after dust removal is drawn out by the main induced draft fan 16. The qualified gas is cooled to below 70°C by the gas cooler 17 and then enters the gas holder 18 for storage and standby. The unqualified gas is discharged through the venting chimney 19.

[0048] III. Soft Drink Process like Figure 2 As shown, the carbonated beverage flow (working fluid flow) of this system is as follows: The demineralized water first enters the deaerator for deoxygenation treatment. After being pressurized by the feedwater pump, it sequentially enters the economizer section I in the moving bed 2 and the economizer section II in the auxiliary heat exchange chamber 11 for preheating. Since the converter flue gas is supplied intermittently, intermittent heat exchange will occur in the economizer section II. Therefore, a flow distribution control valve is installed between the economizer sections I and II to regulate the flow rate of the working fluid entering the economizer section II and ensure stable system operation.

[0049] The cryogenic heater (located in the auxiliary heat exchange chamber 11) also uses a flow regulation and distribution control valve to regulate the flow of the working fluid entering it, and the demineralized water from the outlet of the cryogenic heater is incorporated into the deaerator.

[0050] The working fluid from the economizer outlet enters the steam drum. The steam-water mixture inside the steam drum is separated into water through downcomers and then into the evaporators in the membrane wall flue 9 and the moving bed 2.

[0051] Inside the membrane wall flue 9, the working fluid absorbs the waste heat from the high-temperature flue gas exiting the converter 8, and the resulting steam-water mixture returns to the steam drum. In the evaporator within the moving bed 2, the working fluid absorbs the heat transferred by the high-temperature heat storage material particles to generate a steam-water mixture, which returns to the steam drum through the riser pipe.

[0052] The saturated steam separated from the steam drum enters the superheater in the moving bed 2, where it absorbs the heat from the high-temperature heat storage material particles to generate qualified superheated steam for use by the user.

[0053] Because the hot material storage chamber 3 stores a large amount of high-temperature heat storage material particles, even during the non-blowing period of the converter and when no flue gas enters the cloud bed 1, the moving bed 2 can still maintain a stable steam output by relying on the high-temperature particles continuously supplied by the storage chamber, thus achieving a continuous supply of steam.

[0054] IV. Principles for Solving Three Major Technical Problems (I) The principle of solving the problem of intermittent gas supply This invention achieves decoupling of heat generation and heat utilization through a three-section architecture consisting of a "cloud bed + hot material storage chamber + moving bed".

[0055] Specifically, during converter blowing (when there is flue gas), the moving bed 1 rapidly transfers the heat from the flue gas to the heat storage material particles, and the high-temperature particles are stored in the hot material storage chamber 3. During non-converter blowing (when there is no flue gas), although there is no new heat source, the high-temperature particles stored in the hot material storage chamber 3 can continue to supply heat to the moving bed 2. The heating surfaces in the moving bed 2 can therefore obtain a continuous and uniform heat source, and the produced steam is continuous and stable, unaffected by the converter blowing cycle.

[0056] In addition, the synchronous control mechanism of the lower outlet of the feed tank 5 and the flue gas inlet ensures the precise matching of material supply and heat source supply, avoiding energy waste and mechanical loss caused by ineffective particle circulation when there is no flue gas.

[0057] (II) Principles for solving the problem of spark explosion Ignition particles (unburned high-temperature solid particles) carried in converter flue gas are a major contributing factor to explosions. Once these ignition particles enter flue gas containing combustible gases such as CO, they can easily ignite the gas mixture.

[0058] In this invention, after the flue gas enters the settling bed 1, it comes into direct contact with the falling heat storage material particles 4. The temperature of the heat storage material particles 4 is much lower than the temperature of the ignition particles in the flue gas (the heat storage material particles are cooled by circulation when they enter the settling bed, and their temperature is usually below 200°C). When the ignition particles collide with the falling heat storage material particles as they rise with the flue gas, due to the large temperature difference and sufficient contact area, the ignition particles quickly cool down and adhere to the surface of the heat storage material particles, falling with the particles into the hot material storage chamber 3.

[0059] Through this physical process of "collision-cooling-adhesion," the ignition particles are effectively removed before entering subsequent equipment (additional heat exchange chamber 11, dust collector 14, etc.). Since the ignition particles have been removed, even if the flue gas reaches the explosion conditions (appropriate CO / O2 concentration ratio) in subsequent processes, there is no ignition source to ignite it, thus significantly reducing the risk of explosion.

[0060] (III) Principles for solving the problem of adhesion and corrosion on heated surfaces Converter dust contains a large amount of alkaline substances such as quicklime (CaO). These substances are sticky and easily deposit on the surface of the heated surface at high temperatures, forming a hard scale layer that is difficult to remove.

[0061] In existing technologies, flue gas directly washes over the heating surface of waste heat boilers, and sticky dust gradually deposits and sinters on the surface of the heating surface, forming a dense scale layer, which leads to a decrease in heat exchange efficiency and even blockage of the flow channel.

[0062] This invention uses heat storage material particles as an intermediate medium to separate the heat exchange between "flue gas and particles" and "particles and heated surfaces". Adhesive dust collides with and adheres to the heat storage material particles in the settling bed 1, and is removed as the particles fall, so it basically does not enter the moving bed 2 to contact the heated surface.

[0063] During the circulation process, the friction between the heat storage material particles causes the dust layer attached to the surface to break and peel off, forming fine dust. This fine dust is then carried out of the dust collection bed by the rising flue gas flow and captured by the coarse dust collection bin 13 and the fine dust collection bin 15 in the bent flue duct 12 and dust collector 14, respectively.

[0064] Meanwhile, fine dust particles in the flue gas that are not captured by the particles are also carried by the airflow into the downstream dust removal equipment and collected. Through the multiple effects of "particle capture + friction stripping + airflow carrying + graded collection" mentioned above, the dust in the system is continuously discharged, maintaining the relative cleanliness of the heat storage material particles. The heating surfaces in the moving bed 2 are thus kept clean for a long time, eliminating the need for frequent dust removal and fundamentally solving the problem of adhesion and corrosion on the heating surfaces.

[0065] This invention can solve the three major technical problems of intermittent gas supply, spark explosion, and heat transfer surface corrosion in converter flue gas waste heat recovery in an integrated and effective manner, and has significant industrial application value and promotion prospects. Example 2

[0066] This embodiment is a simplification based on embodiment 1, removing the membrane wall flue 9 and directly sending the high-temperature flue gas produced by converter 8 into the cloud bed 1.

[0067] This embodiment is suitable for applications with relatively low flue gas temperatures or where the requirements for waste heat recovery depth are not high. It features a more compact structure, lower equipment investment, and is suitable for small to medium-sized converters or applications where steam quality requirements are not particularly stringent.

[0068] The remaining structure and working principle are the same as in Example 1, and will not be described again. Example 3

[0069] This embodiment, based on Embodiment 1, adds the option to select the material of the heat storage material particles 4. The heat storage material particles 4 can be one or a combination of alumina balls, steel shot, ceramic balls, or pebbles. Alternatively, materials such as sand, gravel, and slag can be used, which are readily available and inexpensive.

[0070] Different materials produce particles with varying thermal conductivity, wear resistance, and cost characteristics. For example, alumina balls have good thermal conductivity, strong wear resistance, and long cycle life, making them suitable for applications requiring high heat exchange efficiency and particle life; steel shot has high thermal conductivity and density, but poor oxidation resistance, making it suitable for non-oxidizing atmospheres; ceramic balls offer excellent overall performance at a moderate cost; and pebbles have the lowest cost but poor wear resistance, making them suitable for short-term or experimental projects.

[0071] Those skilled in the art can select appropriate particle materials based on actual working conditions (flue gas temperature, composition, particle circulation rate, etc.), and these variations all fall within the protection scope of this invention. Example 4

[0072] This embodiment describes the specific structure of the distributor 6 in detail, based on embodiment 1. The distributor 6 is a conical distributor or a perforated plate distributor, which is located at the top of the cloud bed 1 and below the lower outlet of the feed tank 5.

[0073] The function of the distributor 6 is to evenly distribute the falling heat storage material particles 4 onto the entire cross-section of the cloud bed 1, so as to avoid the particles falling in a concentrated manner below the feed inlet and forming a "through flow", and to ensure that the flue gas and particles can fully and evenly contact and exchange heat at each height layer of the cloud bed.

[0074] Conical distributors utilize the principle of particle dispersion by scattering in all directions after impacting the conical surface; perforated plate distributors guide particles to different areas of the bed through holes at different locations. Both structures effectively improve the uniformity of gas-solid contact and increase heat exchange efficiency.

[0075] Industrial applicability The converter flue gas waste heat recovery system and method provided by this invention can be widely applied to the converter steelmaking process in the iron and steel metallurgical industry, enabling fully dry waste heat recovery and gas purification of converter flue gas. This invention comprehensively solves three major technical challenges: intermittent gas supply, spark explosion, and adhesion corrosion of heating surfaces. It achieves continuous and stable steam production, high-quality dry gas recovery, and a significantly reduced frequency of heating surface maintenance, demonstrating outstanding technical advantages and promising market application prospects.

[0076] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this application; at the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0077] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0078] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0079] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0080] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A waste heat recovery system for converter flue gas, characterized in that, include: The cloud bed has its inlet connected to the flue gas outlet of the converter and contains falling heat storage material particles. The cloud bed is configured to allow the incoming flue gas to directly contact the falling heat storage material particles for heat exchange, and in this process, the spark particles and / or sticky dust in the flue gas are attached to the surface of the heat storage material particles and captured. A hot material storage chamber is located below the cloud bed to receive and temporarily store heat storage material particles that fall from the cloud bed, have absorbed the heat of the flue gas, and have captured spark particles and / or sticky dust. A moving bed is disposed below the hot material storage chamber to receive the heat-storing material particles discharged from the hot material storage chamber. The moving bed is provided with a heating surface inside. The moving bed is configured to allow the descending heat-storing material particles to directly contact the heating surface for heat exchange, so as to heat the working fluid and generate steam. And a material circulation loop, which sends the heat-exchange-cooled heat-storing material particles discharged from the moving bed back to the top of the cloud bed to form a cycle.

2. The waste heat recovery system for converter flue gas as described in claim 1, characterized in that, It also includes a feeding pool located at the top of the falling cloud bed. The feeding pool has an upper inlet and a lower outlet. The feeding pool is configured to: when converter flue gas is detected entering, simultaneously open its lower outlet to allow the heat storage material particles to fall into the falling cloud bed for heat exchange; when no flue gas enters, close its lower outlet and stop feeding.

3. The waste heat recovery system for converter flue gas as described in claim 1, characterized in that, The flue gas inlet of the cloud bed is located at its lower part, and the heat storage material particle inlet is located at its upper part, so that the incoming flue gas and the falling heat storage material particles form a countercurrent contact.

4. The waste heat recovery system for converter flue gas as described in claim 1, characterized in that, The heating surfaces provided inside the moving bed include one or more of a superheater, an evaporator, and an economizer, used to heat the working fluid and continuously generate steam.

5. The waste heat recovery system for converter flue gas as described in claim 1, characterized in that, It also includes an additional heat exchange chamber, which is located between the flue gas outlet of the cloud bed and the subsequent dust removal equipment. The additional heat exchange chamber is equipped with a convective heating surface for further recovery of residual heat from the flue gas.

6. The waste heat recovery system for converter flue gas as described in claim 1, characterized in that, It also includes a membrane wall flue, which is set between the converter and the settling bed. The membrane wall flue is surrounded by a membrane water-cooled wall and is used to perform preliminary heat exchange and cooling on the high-temperature flue gas produced by the converter.

7. A method for waste heat recovery from converter flue gas, characterized in that, The method employs the system as described in any one of claims 1-6, and the method includes: S1. The intermittent high-temperature flue gas produced by the converter first enters the cloud bed and directly contacts the heat storage material particles falling from the cloud bed for heat exchange, transferring the heat of the flue gas to the heat storage material particles. At the same time, the spark particles and / or sticky dust in the flue gas adhere to the surface of the heat storage material particles and are captured. S2. The heat storage material particles that have absorbed heat and captured spark particles and / or sticky dust fall into the heat material storage chamber for temporary storage, forming a heat buffer. S3. The heat storage material particles at the bottom of the hot material storage chamber continuously enter the moving bed, slowly move down in the moving bed, and directly contact the heating surface set in the moving bed to exchange heat, transferring heat to the working fluid in the heating surface to generate steam. S4. The heat-storing material particles that have cooled down after heat exchange are discharged from the bottom of the moving bed and sent back to the top of the cloud bed through the material circulation loop for recycling.

8. The waste heat recovery method for converter flue gas as described in claim 7, characterized in that, In step S1, the flue gas and the heat storage material particles in the cloud bed adopt counter-current contact heat exchange, that is, the flue gas enters from the bottom and exits from the top, while the heat storage material particles enter from the top and exit from the bottom.

9. The waste heat recovery method for converter flue gas as described in claim 7, characterized in that, It also includes a residual heat recovery step for flue gas: the flue gas discharged from the dust collection bed enters the auxiliary heat exchange chamber, exchanges heat with the convective heating surface arranged in the auxiliary heat exchange chamber, and further releases the residual heat before entering the subsequent dry dust removal equipment.

10. The waste heat recovery method for converter flue gas as described in claim 7, characterized in that, It also includes dry dust removal and gas recovery steps: the cooled flue gas is dusted by a dry dust collector, the purified gas is stored in a gas holder, and unqualified gas is discharged through a venting chimney.

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