A particle sandblasting coating anti-coking device and method for high-alkali fuel boilers

Abstract

The present application relates to a kind of particle sand blasting coating anti-coking equipment and anti-coking method for high-alkali fuel boiler, above-mentioned anti-coking equipment includes: sand blasting coating system, coarse and fine particle separation system and material- waste heat recycling system;Sand blasting coating system is used to inject high melting point coating particles into high temperature zone of furnace, to be coated on the surface of semi-molten ash coke particles to form coating shell;Coarse and fine particle separation system is used to dissociate ash coke particles with coating shell, and respectively capture ash coke particles, coating particles, and is installed in tail flue;Material- waste heat recycling system is used to capture coating particles as material, and sensible heat of captured ash coke particles as heat source preheats flue gas containing coating particles, and is transported back to sand blasting coating system for use.The present application forms "coating-dissociation-circulation-waste heat utilization" closed loop process chain, and anti-coking effect, material economy and system energy efficiency are considered.

Description

Technical Field

[0001] This invention belongs to the field of clean and efficient utilization technology of high-alkali fuels, specifically relating to a particle sandblasting coating anti-scorching equipment and method for high-alkali fuel boilers, which is particularly suitable for boilers burning high-alkali coal and biomass fuels. Background Technology

[0002] Although high-alkali coal, represented by Zhundong coal, has huge reserves, the high alkaline content in the ash of coal-fired power units makes it easy to form a low-melting-point eutectic under the high-temperature reducing atmosphere in the furnace, resulting in a semi-molten, sticky surface on the ash particles. These fly ash particles with a high tendency to adhere are easily adhered to and deposited layer by layer when they impact water-cooled walls or high-temperature heating surfaces, sintering to form a dense coke layer. This leads to safety accidents such as reduced boiler thermal efficiency and overheating of heating surfaces causing tube rupture.

[0003] Existing coking prevention technologies are mainly divided into three categories: fuel blending, operational optimization, and post-coking removal. Among these, additive technology, represented by the co-firing of kaolin, uses a heterogeneous reaction with gaseous alkali metals at high temperatures to generate high-melting-point mineral phases to immobilize the alkali metals. However, this technology suffers from inherent bottlenecks such as capture efficiency being controlled by diffusion mass transfer, high consumption, and non-recoverability. Operational optimization methods are condition-dependent in their coking prevention effectiveness; post-coking removal cannot prevent the initial formation of coke.

[0004] Therefore, there is an urgent need to develop a new type of anti-coking equipment that can directly intervene in the surface adhesion characteristics of semi-molten ash coke particles, thereby blocking coking formation at the source. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a particle-based sandblasting coating anti-coking equipment and method for high-alkali fuel boilers. This invention breaks away from the traditional passive protection approach by actively injecting submicron-sized, high-melting-point coating particles into the high-temperature zone of the furnace. The surface adhesion between the coating particles and semi-molten coke particles causes the coating particles to form a coating layer on the surface of the coke particles, transforming the surface of the coke particles from sticky to elastic, thus preventing coking at its source. Simultaneously, a series separator dissociates the coating layer at low temperature and recovers the particles for recycling, balancing anti-coking effectiveness, material economy, and system energy efficiency.

[0006] The specific technical solution is as follows: The first aspect of the present invention is to provide a particle sandblasting and coating anti-coking equipment for a high-alkali fuel boiler, comprising: a sandblasting and coating system, a coarse and fine particle separation system, and a material-waste heat recycling system; The sandblasting coating system is used to spray high-melting-point coating particles into the high-temperature zone of the furnace to coat the surface of semi-molten ash and coke particles to form a coating shell. The coarse and fine particle separation system is used to dissociate ash and coke particles with a coating layer and collect the ash and coke particles and coated particles separately, which are then installed in the tail flue. The material-waste heat recycling system uses the coated particles obtained from the capture as material and the sensible heat of the ash and coke particles obtained from the capture as a heat source to preheat the flue gas containing the coated particles, and then transports it back to the sandblasting and coating system.

[0007] Furthermore, the sandblasting coating system includes a spraying unit, which consists of multiple layers of nozzles arranged in layers along the height of the furnace in the upper furnace, with each layer of nozzles arranged opposite each other.

[0008] Furthermore, the sandblasting coating system also includes a storage unit, a feeding unit, an air source unit, and a mixing unit; the storage unit is connected to the feeding unit, the feeding unit and the air source unit are respectively connected to the mixing unit, and the mixing unit is connected to the blasting unit.

[0009] Furthermore, the coarse and fine particle separation system consists of a primary separator and a secondary separator connected in series, with baffles inside the primary separator.

[0010] Furthermore, both the primary and secondary separators are cyclone separators, and the baffles are "tree branch" type baffles arranged along the height direction of the primary separator.

[0011] Furthermore, the material-waste heat recycling system includes a partition wall heat exchanger located below the discharge port of the primary separator. The primary side flow channel of the heat exchanger is connected to the discharge port of the primary separator, and the secondary side flow channel of the heat exchanger is connected to the discharge port of the secondary separator.

[0012] A second aspect of the present invention is to provide a method for preventing scorching, comprising: High-melting-point coated particles are injected into the rising flue gas in the high-temperature zone of the upper furnace, and the surface adhesion difference between semi-molten ash coke particles and solid fly ash is used to selectively coat the surface of ash coke particles. The ash and coke particles with the coating layer enter the tail flue with the flue gas and are cooled. Then, the ash and coke particles enter the first-stage separator and hit the baffle to undergo low-temperature brittle fracture. The separated ash and coke particles are discharged from the bottom of the first-stage separator, and the coated particles enter the second-stage separator with the airflow to be captured and recovered. The material-waste heat recycling system receives the coated particles recovered by the secondary separator and recovers the sensible heat carried by the ash and coke particles. The preheated coated particles are transported back to the sandblasting and coating system using flue gas as the carrier gas, realizing material recycling and cascade utilization of waste heat.

[0013] Furthermore, the melting point of the coated particles is greater than that of the ash coke particles.

[0014] Furthermore, the temperature in the high-temperature zone of the furnace is 850-1450℃.

[0015] Furthermore, the anti-scorching method is applied to high-alkali fuel boilers, which use fuels containing high-alkali coal or high-alkali biomass.

[0016] The beneficial effects of the above scheme are: In this invention, submicron-sized high-melting-point particles are injected into the high-temperature zone of the furnace. The difference in surface viscosity between semi-molten ash particles and solid fly ash is used to achieve selective coating. The coating target is directly applied to the semi-molten ash particles, which are the main body of coking growth, so that the surface of the ash particles changes from sticky to elastic, blocking coking from the source and fundamentally overcoming the defect of low capture efficiency of traditional additive technology.

[0017] This invention utilizes the "quenching effect" generated by the collision of low-temperature submicron high-melting-point particles with high-temperature materials to reduce the surface viscosity of the material. The coating layer maintains structural integrity under high-temperature heated surface collision conditions and dissociates in the low-temperature environment of the separator, achieving the dual function of "firm coating and controllable dissociation".

[0018] This invention forms a closed-loop process chain of "coating-dissociation-circulation-waste heat utilization". Submicron-sized high-melting-point particles can be recycled, and high-temperature flue gas waste heat can be recovered in stages, taking into account the anti-scorching effect, material economy and system energy efficiency.

[0019] This application is based on particle surface interface modification, which is non-selective for fuel type and applicable to a variety of fuels such as high-alkali coal, anthracite and biomass, and has good adaptability to operating conditions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the particle sandblasting coating anti-scorching equipment provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the sandblasting coating system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the coarse and fine particle separation system provided in an embodiment of the present invention; Figure 4 This is a technical roadmap of the anti-scorching method provided in an embodiment of the present invention.

[0021] In the attached diagram: 1. Storage unit; 2. Feeding unit; 3. Air source unit; 4. Mixing unit; 5. Conveying pipeline; 6. Injection unit; 7. Primary separator; 71. Baffle; 72. Discharge port; 8. Secondary separator; 81. Material leg; 9. Material-waste heat recycling subsystem. Detailed Implementation

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

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0025] like Figures 1 to 3 As shown, the particle sandblasting and coating anti-coking equipment provided in the embodiments of the present invention includes: a sandblasting and coating system, a coarse and fine particle separation system, and a material-waste heat recycling system 9; the sandblasting and coating system is used to spray high-melting-point coating particles into the high-temperature zone of the furnace to coat the surface of semi-molten ash and coke particles to form a coating shell layer; the coarse and fine particle separation system is used to dissociate the ash and coke particles with the coating shell layer and collect the ash and coke particles and the coating particles respectively, and install them in the tail flue; the material-waste heat recycling system 9 is used to use the collected coating particles as material and the sensible heat of the collected ash and coke particles as a heat source to preheat the flue gas containing the coating particles, and then transport it back to the sandblasting and coating system.

[0026] Specifically, such as Figure 1 , Figure 2 , Figure 4 As shown, the sandblasting coating system includes at least a spraying unit 6. The spraying unit 6 consists of multiple layers of nozzles arranged in layers along the height of the furnace in the upper furnace chamber. Each layer of nozzles is arranged opposite each other. This opposite arrangement allows the two jets to collide head-on at the center of the furnace, thereby extending the residence time of the coated particles in the high-temperature zone through strong turbulent pulsation, increasing the probability of collision between the particles and the molten coke. Furthermore, the surface adhesion between the coated particles and the semi-molten coke particles allows the coated particles to form a coating layer on the surface of the coke particles, transforming the surface of the coke particles from sticky to elastic, thus preventing coking at its source. It is understood that, to improve the above coating effect, this invention can select coating particles with a smaller particle size than the coke particles, such as submicron-sized coating particles, to coat the coke particles.

[0027] Specifically, such as Figure 2As shown, the sandblasting coating system may further include a storage unit 1, a feeding unit 2, an air source unit 3, and a mixing unit 4; the storage unit 1 is connected to the feeding unit 2, the feeding unit 2 and the air source unit 3 are respectively connected to the mixing unit 4, and the mixing unit 4 is connected to the blasting unit 6; the storage unit 1 may be a vertical conical bottom silo for storing submicron-sized coated particles, and the conical bottom structure can achieve continuous and uniform unloading by means of the powder's own weight, effectively avoiding powder bridging and material breakage; the feeding unit 2 is connected to the outlet of the storage unit 1 for controlling the feeding rate, preferably a powder metering feeder. It has an airtight structure to block the backflow of high-temperature flue gas in the furnace; the gas source unit 3 is preferably a blower or air compressor to provide a stable and continuous high-pressure ejector gas flow; the mixing unit 4 is preferably a solid-gas mixing ejector, which is connected to the feeding unit 2 and the gas source unit 3. When the high-pressure gas flow passes through the constriction throat, the flow velocity increases sharply and a negative pressure field is formed, which can continuously draw in a quantitative supply of particles and complete the uniform mixing of gas phase and solid phase in the diffusion section to form a stable dilute phase gas-solid two-phase flow; the injection unit 66 is connected to the mixing unit 4 through the conveying pipeline 5 to inject the gas-solid two-phase flow into the furnace.

[0028] Specifically, such as Figure 1 , Figure 3 , Figure 4As shown, the coarse and fine particle separation system consists of a primary separator 7 and a secondary separator 8 connected in series. The primary separator 7 has a baffle 71 inside. The primary separator 7 is preferably a cyclone separator, with its inlet connected to the flue gas outlet of the furnace. The primary separator 7 adopts a tangential volute inlet structure. Flue gas carrying ash and coke particles with a coating layer enters tangentially through the inlet, forming a high-speed rotating airflow. Subsequently, the particles in the airflow are thrown towards the inner wall of the separator under centrifugal force and spiral downwards along the wall. During this process, the particles repeatedly impact the baffle 71. The tangential shear stress generated by the inclined impact acts on the interface between the coating layer and the ash and coke particles, causing the coating layer to disintegrate. The disintegrated large-diameter ash and coke particles settle under gravity and are discharged through the discharge port 72. Submicron-sized high-melting-point coated particles, due to their small size and light weight, are resuspended by the rising airflow. The inlet of the secondary separator 8 is connected to the exhaust port of the primary separator 7. The secondary separator 8 is preferably a long conical cyclone separator, with its conical section length increased by 20%-30% compared to conventional cyclone separators. It is equipped with spiral guide vanes inside to extend the particle residence time and improve the collection efficiency of submicron-sized high-melting-point particles. After the sand-laden airflow enters the secondary separator 8 tangentially, it rotates at high speed. Under the action of centrifugal force, the submicron-sized high-melting-point particles migrate towards the wall and spiral down along the wall to the material leg 81. Then, they flow into the conveying pipeline 5 between the air source unit 3 and the mixing unit 4. Finally, the recovered particles are directly sent back to the nozzle to achieve recycling. In this invention, a rotary ash discharge valve and an airlock device can be further installed at the lower end of the material leg 81 to ensure continuous particle discharge and prevent external air from being sucked back into the separator and disrupting the internal flow field. To enhance the impact effect during the spiral descent of the particles, the baffle in this invention is preferably a "tree branch" structure, which utilizes the numerous branch structures in the baffle structure to increase the probability of impact. Furthermore, the baffle in this invention is made of wear-resistant alloy steel, with a tungsten carbide hard alloy layer welded to the surface, and wear-resistant liners that can be quickly replaced are provided in key parts.

[0029] Specifically, such as Figure 1 As shown, the material-waste heat recycling subsystem 9 includes a partition wall heat exchanger located below the discharge port of the primary separator 7. The primary side flow channel of the heat exchanger is connected to the discharge port of the primary separator 7, and the secondary side flow channel of the heat exchanger is used for the flow of flue gas containing submicron high-melting-point particles. Under the above structure, the sensible heat of the captured ash and coke particles is used as a heat source to preheat the flue gas, thereby raising the temperature of the flue gas. After being heated, the flue gas is transported and reused to the sandblasting and coating system under the action of the conveying carrier gas output from the gas source unit 3, forming a closed-loop process chain of "coating-dissociation-recycling-waste heat utilization". The submicron high-melting-point particles can be recycled, and the waste heat of the high-temperature flue gas is recovered in stages, taking into account the anti-coking effect, material economy and system energy efficiency.

[0030] The anti-scorching method using the above-mentioned device in this invention includes: High-melting-point coated particles (the melting point of the coated particles is greater than that of the ash coke particles, and they can preferably be high-melting-point materials such as kaolin or fly ash) are injected into the rising flue gas flow in the high-temperature zone (temperature of 850-1450℃) of the upper furnace. The difference in surface viscosity between the semi-molten ash coke particles and the solid fly ash is used to selectively coat the surface of the ash coke particles, so that the surface of the ash coke particles changes from sticky to elastic, thereby blocking the adhesion and growth of ash coke particles on the heated surface. The ash and coke particles with the coating layer enter the tail flue with the flue gas and are cooled to a low temperature. Then, the ash and coke particles enter the primary separator 7 and hit the baffle 71, causing low-temperature brittle fracture, which causes the coating layer to disintegrate. The disintegrated ash and coke particles are discharged from the bottom of the primary separator 7, and the coated particles enter the secondary separator 8 with the airflow to be captured and recovered. The material-waste heat recycling system 9 receives the coated particles recovered by the secondary separator 8, and at the same time recovers the sensible heat carried by the ash and coke particles. The coated particles are then transported back to the sandblasting and coating system by the carrier gas, realizing material recycling and cascade utilization of waste heat.

[0031] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A particle sandblasting and anti-scorching device for high-alkali fuel boilers, characterized in that, include: Sandblasting coating system, coarse and fine particle separation system and material-waste heat recycling system; The sandblasting and coating system is used to spray high-melting-point coating particles into the high-temperature zone of the furnace to coat the surface of semi-molten ash and coke particles to form a coating shell. The coarse and fine particle separation system is used to dissociate ash and coke particles with a coating layer, and to collect ash and coke particles and coated particles separately, which are then installed in the tail flue. The material-waste heat recycling system uses the coated particles obtained by the capture as material and the sensible heat of the ash coke particles obtained by the capture as a heat source to preheat the flue gas containing the coated particles, and then transports it back to the sandblasting and coating system.

2. The particle sandblasting and anti-scorching equipment for high-alkali fuel boilers according to claim 1, characterized in that, The sandblasting and coating system includes a spraying unit, which consists of multiple layers of nozzles arranged in layers along the height of the furnace in the upper furnace, with each layer of nozzles arranged opposite each other.

3. The particle sandblasting and anti-scorching equipment for high-alkali fuel boilers according to claim 2, characterized in that, The sandblasting coating system further includes a storage unit, a feeding unit, an air source unit, and a mixing unit; the storage unit is connected to the feeding unit, the feeding unit and the air source unit are respectively connected to the mixing unit, and the mixing unit is connected to the blasting unit.

4. The particle sandblasting and anti-scorching equipment for high-alkali fuel boilers according to claim 1, characterized in that, The coarse and fine particle separation system consists of a primary separator and a secondary separator connected in series, and the primary separator has baffles inside.

5. The particle sandblasting and anti-scorching equipment for high-alkali fuel boilers according to claim 4, characterized in that, Both the primary separator and the secondary separator are cyclone separators, and the baffle is a "tree branch" type baffle arranged along the height direction of the primary separator.

6. The particle sandblasting and anti-scorching equipment for high-alkali fuel boilers according to claim 4, characterized in that, The material-waste heat recycling system includes a partition wall heat exchanger located below the discharge port of the primary separator. The primary side flow channel of the heat exchanger is connected to the discharge port of the primary separator, and the secondary side flow channel of the heat exchanger is connected to the discharge port of the secondary separator.

7. A method for preventing scorching, characterized in that, The particulate sandblasting and anti-scorching equipment for high-alkali fuel boilers according to any one of claims 4-6 includes: High-melting-point coated particles are injected into the rising flue gas in the high-temperature zone of the upper furnace, and the coating particles are selectively coated onto the surface of the ash coke particles by utilizing the difference in surface adhesion between the semi-molten ash coke particles and the solid fly ash. The ash and coke particles with the coating layer enter the tail flue with the flue gas and are cooled. Then, the ash and coke particles enter the first-stage separator and hit the baffle to undergo low-temperature brittle fracture. The dissociated ash and coke particles are discharged from the bottom of the first-stage separator, and the coated particles enter the second-stage separator with the airflow to be captured and recovered. The material-waste heat recycling system receives the coated particles recovered by the secondary separator and recovers the sensible heat carried by the ash and coke particles. The preheated coated particles are transported back to the sandblasting and coating system using flue gas as the carrier gas, realizing material recycling and cascade utilization of waste heat.

8. The anti-scorching method according to claim 7, characterized in that, The coated particles are submicron-sized particles, and their melting point is greater than that of ash and coke particles.

9. The anti-scorching method according to claim 7, characterized in that, The temperature in the high-temperature zone of the furnace is 850-1450℃.

10. The anti-scorching method according to claim 8, characterized in that, The anti-scorching method is applied to a high-alkali fuel boiler, the fuel of which contains high-alkali coal or high-alkali biomass.

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