Circulating fluidized bed boiler for pure combustion of high-alkali and high-chlorine fuel

Abstract

The utility model discloses a circulating fluidized bed boiler for pure combustion of high-alkali and high-chlorine fuel, which relates to the technical field of circulating fluidized bed boilers and comprises a hearth, a cyclone separator, a material returning device, an external bed, a cooling flue and a tail flue. An ash outlet of the cyclone separator is communicated with an ash inlet of the material returning device circulation, an ash outlet of the material returning device circulation is divided into two parts, one part is directly connected with the hearth, the other part is connected with the external bed and then is connected with the hearth, and a high-temperature heating surface is arranged in the external bed; a flue gas outlet of the cyclone separator is communicated with the cooling flue; and the cooling flue is communicated with the tail flue. According to the utility model, the high-temperature heating surface is arranged in the external bed, so that the high-temperature heating surface is prevented from being in direct contact with high-chlorine flue gas, and meanwhile, the fluidizing air in the external bed adopts high-pressure fluidizing air or low-temperature flue gas which is dechlorinated and dedusted at a boiler outlet, so that the problem of corrosion of the high-temperature heating surface caused by the fluidizing air is avoided; and large-size coke blocks can be conveniently discharged.

Description

Technical Field

[0001] This utility model relates to the field of circulating fluidized bed boiler technology, and more specifically to the field of circulating fluidized bed boiler technology that burns only high-alkali and high-chlorine fuel. Background Technology

[0002] Existing patents disclose the following technologies:

[0003] Patent CN212108372U proposes a multi-stage separation circulating fluidized bed boiler that burns pure high-alkali and high-chlorine coal. Through a multi-stage water-cooled U-shaped separator in the furnace, particulate matter in the flue gas is separated efficiently and sodium salt compound steam in the flue gas is condensed and precipitated, reducing fouling and slagging on the heating surface.

[0004] Patent CN212108373U proposes a circulating fluidized bed boiler that burns only high-alkali and high-chlorine coal. It uses a three-flow mode water-cooled wall and a large-pitch bare tube thick-walled buried tube to reduce the flue gas temperature to below 550℃, and precipitates sodium compound vapor in the flue gas on the bare tube thick-walled buried tube and water-cooled wall, thus solving the problem of fouling and slagging on the heating surface.

[0005] The aforementioned patents solved the fouling and slagging problems using a special structure, but did not propose effective measures for the problem of high-chlorine corrosion. This patent proposes a circulating fluidized bed boiler that burns only high-alkali and high-chlorine fuel, completely solving the fouling and corrosion problems caused by burning only high-alkali and high-chlorine fuel. Utility Model Content

[0006] The purpose of this utility model is to solve the technical problem of fouling and corrosion caused by burning high-alkali and high-chlorine fuels in existing circulating fluidized bed boilers. This utility model provides a circulating fluidized bed boiler that burns high-alkali and high-chlorine fuels.

[0007] To achieve the above objectives, this utility model specifically adopts the following technical solution:

[0008] This utility model provides a circulating fluidized bed boiler that burns pure high-alkali and high-chlorine fuel, including a furnace, a cyclone separator, a return feeder, an external bed, a cooling flue, and a tail flue. The flue gas outlet of the furnace is connected to the flue gas inlet of the cyclone separator, and the ash outlet of the cyclone separator is connected to the ash inlet of the return feeder. The circulating ash outlet of the return feeder is divided into two: one path is directly connected to the furnace, and the other path is connected to the external bed and then to the furnace. The external bed has a high-temperature heating surface arranged inside. In the external bed, the circulating ash and the high-temperature heating surface adopt a fluidized heat exchange method. The fluidizing medium is high-pressure fluidizing air or low-temperature flue gas from the boiler outlet after dechlorination and dust removal. The flue gas outlet of the cyclone separator is connected to the cooling flue, and the cooling flue is connected to the tail flue.

[0009] In one embodiment, the cooling flue includes the parallel downward flue and upward flue, with ash hoppers provided at the bottom of both the upward and downward flues, and a cooler with a large-pitch water-cooled auger provided below the ash hoppers.

[0010] In one embodiment, a water-cooled screen is installed inside the furnace, and the downward flue is either an empty flue or has a water-cooled screen heating surface. The water-cooled screen in the downward flue is arranged parallel to the flue gas inlet.

[0011] In one embodiment, the high flue gas temperature zone heating surface from above the dense phase zone of the furnace to the inlet of the water-cooled tube bundle is coated using a spraying process.

[0012] Specifically, in order to further reduce the corrosion of other heated surfaces by chlorine in the flue gas, castable refractory is laid in the dense phase zone of the lower part of the furnace, and a spraying process is used on the heated surfaces in the high flue gas temperature zone from above the dense phase zone of the furnace to the inlet of the water-cooled tube bundle.

[0013] In one embodiment, ash hoppers are provided at the bottom of both the upward and downward flue, and a cooler with a large-pitch water-cooled auger is provided below the ash hoppers.

[0014] Specifically, the above is the solution, which discharges the settled ash and large coke chunks falling from the front flue while ensuring a sealed environment.

[0015] In one embodiment, the external bed outlet is connected to the furnace, and the external bed inlet is connected to another outlet of the return feeder via a pipe equipped with a cone valve.

[0016] In one embodiment, the cooling flue includes an ash hopper at the bottom, a downward flue, and an upward flue. The bottom of the downward flue is connected to the bottom of the upward flue. The flue gas outlet of the cyclone separator is connected to the top of the downward flue, and the upward flue is connected to the tail flue.

[0017] In one embodiment, the downflow flue is an empty flue; the upflow flue is provided with a water-cooled tube bundle, a medium-temperature heating surface and a low-temperature heating surface arranged sequentially along the flue gas direction.

[0018] In one embodiment, a hydraulic soot blowing device is provided in the downflow flue.

[0019] Specifically, the downflow flue is equipped with a hydraulic soot blowing device, which can periodically clean the fouling layer on the downflow flue and ensure its heat exchange capacity. In addition to reducing the flue gas temperature, the downflow flue can also take advantage of the easy fouling characteristics of high-temperature flue gas to adsorb and reduce alkali metals and chlorine elements in the flue gas, forming an easy-to-clean fouling layer on the pipe wall.

[0020] In one embodiment, a high-temperature economizer, an SCR device, a low-temperature economizer, and an air preheater are arranged along the flue gas direction in the tail flue.

[0021] In one embodiment, castable refractory is laid in the dense phase zone at the bottom of the furnace.

[0022] In addition, the low-temperature heating surface, the medium-temperature heating surface, and the high-temperature heating surface can be superheaters or reheaters; the downflow flue and the upflow flue can be water-cooled or steam-cooled structures; and the water-cooled tube bundle can be set up or removed as needed.

[0023] Working principle:

[0024] Dust-laden flue gas at the furnace outlet is separated by a cyclone separator, with the majority of the ash being transferred to a return feeder. The ash outlet of the return feeder is divided into two parts. One part exchanges heat with the high-temperature heating surfaces in an external bed before returning to the furnace. The amount of ash entering the external bed is controlled by a conical valve. The other part of the ash is directly sent back to the furnace. The high-temperature heating surfaces are arranged in an external bed, avoiding direct contact with chlorine-containing flue gas and reducing the risk of chlorine corrosion of the high-temperature heating surfaces by the flue gas.

[0025] In the external bed, circulating ash and high-temperature heating surfaces utilize fluidized bed heat exchange. The fluidizing medium can be high-pressure fluidizing air or low-temperature flue gas from the boiler outlet after dechlorination and dust removal, thus avoiding chlorine corrosion of the external bed heating surfaces caused by fluidizing air. To further reduce the corrosion of other heating surfaces by chlorine in the flue gas, castable refractory is laid in the dense phase zone of the lower furnace, while the high-temperature flue gas heating surfaces from above the dense phase zone of the furnace to the inlet of the water-cooled tube bundle are coated using a spraying process.

[0026] After dust removal by the cyclone separator, the flue gas undergoes heat exchange in the downflow flue and then enters the upflow flue at a bend. The downflow flue does not contain serpentine tube heating surfaces; however, water-cooled screens can be added as needed, arranged horizontally with the flue gas inlet. In the upflow flue, water-cooled tube bundles, medium-temperature heating surfaces, and low-temperature heating surfaces are arranged sequentially along the flue gas direction. After passing through the downflow flue and water-cooled tube bundles, the flue gas temperature is reduced to below 650℃. An ash hopper is located at the bottom between the downflow and upflow flues. The flue gas, after heat exchange in the upflow flue, enters the tail flue, and then passes through a high-temperature economizer, an SCR device, a low-temperature economizer, and an air preheater before being discharged.

[0027] In addition, the large-pitch water-cooled auger's ash cooler facilitates the discharge of large-sized coke blocks.

[0028] The beneficial effects of this utility model are as follows:

[0029] 1. This utility model arranges the high-temperature heating surface in an external bed, avoiding direct contact between the high-temperature heating surface and the high-chlorine flue gas. At the same time, the fluidizing air in the external bed is high-pressure fluidizing air or low-temperature flue gas after dechlorination and dust removal from the boiler outlet, avoiding corrosion problems of the high-temperature heating surface caused by fluidizing air.

[0030] 2. Ash hoppers are installed below the downflow and upflow flues, and large-pitch water-cooled auger ash coolers are installed below the ash hoppers to discharge settled ash and large coke blocks falling from the front flue while ensuring a tight seal.

[0031] 3. By utilizing a large amount of circulating material in the furnace to flush the surface and laying refractory in the dense phase zone at the bottom of the furnace, and using a spraying process in the high flue temperature zone between the upper part of the dense phase zone and the water-cooled tube bundle, the problem of corrosion of the heated surface by high-temperature flue gas is solved.

[0032] 4. The downflow flue is an empty flue, without any serpentine tube convection heating surface. A water-cooled screen can be installed as needed. The water-cooled screen is arranged horizontally with the flue gas inlet, which effectively reduces the flue gas temperature at the separator outlet by more than 100°C. The flue gas temperature is further reduced to below 650°C by the water-cooled tube bundle, so that the tail heating surface avoids the fouling sensitive temperature range and solves the problem of fouling of the tail heating surface. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of this utility model;

[0035] Attached reference numerals: 1-furnace, 2-cyclone separator, 3-return feeder, 4-external bed, 5-downward flue, 6-upward flue, 7-water-cooled tube bundle, 8-medium-temperature heating surface, 9-low-temperature heating surface, 10-tail flue, 11-high-temperature economizer, 12-SCR device, 13-low-temperature economizer, 14-air preheater, 15-water-cooled screen, 16-high-temperature heating surface, 17-hydraulic soot blowing device, 18-ash hopper, 19-ash cooler, 20-cone valve. Detailed Implementation

[0036] To make the technical problems, technical solutions, and technical effects of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the 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.

[0038] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] In the description of the embodiments of this utility model, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the utility model product is usually placed when in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a circulating fluidized bed boiler that burns pure high-alkali and high-chlorine fuel, including a furnace 1, a cyclone separator 2, a return feeder 3, an external bed 4, a cooling flue, and a tail flue 10. The flue gas outlet of the furnace 1 is connected to the flue gas inlet of the cyclone separator 2, and the ash outlet of the cyclone separator 2 is connected to the ash inlet of the return feeder 3. The circulating ash outlet of the return feeder 3 is divided into two parts: one is directly connected to the furnace 1, and the other is connected to the external bed 4 and then connected to the furnace 1. The external bed 4 is equipped with a high-temperature heating surface 16. In the external bed 4, the circulating ash and the high-temperature heating surface 16 adopt a fluidized heat exchange method. The fluidizing medium is high-pressure fluidizing air or low-temperature flue gas from the boiler outlet after dechlorination and dust removal. The flue gas outlet of the cyclone separator 2 is connected to the cooling flue, and the cooling flue is connected to the tail flue 10.

[0042] Example 2

[0043] like Figure 1As shown, this embodiment provides a circulating fluidized bed boiler that burns pure high-alkali and high-chlorine fuel, including a furnace 1, a cyclone separator 2, a return feeder 3, an external bed 4, a cooling flue, and a tail flue 10. The flue gas outlet of the furnace 1 is connected to the flue gas inlet of the cyclone separator 2, and the ash outlet of the cyclone separator 2 is connected to the ash inlet of the return feeder 3. The circulating ash outlet of the return feeder 3 is divided into two parts: one is directly connected to the furnace 1, and the other is connected to the external bed 4 and then connected to the furnace 1. The external bed 4 is equipped with a high-temperature heating surface 16. In the external bed 4, the circulating ash and the high-temperature heating surface 16 adopt a fluidized heat exchange method. The fluidizing medium is high-pressure fluidizing air or low-temperature flue gas from the boiler outlet after dechlorination and dust removal. The flue gas outlet of the cyclone separator 2 is connected to the cooling flue, and the cooling flue is connected to the tail flue 10.

[0044] The outlet of the external bed 4 is connected to the furnace 1, and the inlet of the external bed 4 is connected to another outlet of the return feeder 3 through a pipe, on which a cone valve 20 is installed.

[0045] The cooling flue includes an ash hopper 18 at the bottom, a downflow flue 5, and an upflow flue 6. The bottom of the downflow flue 5 is connected to the bottom of the upflow flue 6. The outlet of the cyclone separator 2 is connected to the top of the downflow flue 5. The upflow flue 6 is connected to the tail flue 10.

[0046] Downward flue 5 is an empty flue; in upward flue 6, water-cooled tube bundle 7, medium-temperature heating surface 8 and low-temperature heating surface 9 are arranged sequentially along the flue gas direction.

[0047] A hydraulic soot blowing device 17 is installed in the downflow flue 5.

[0048] Specifically, the downflow flue 5 is equipped with a hydraulic soot blowing device 17, which can periodically clean the fouling layer on the downflow flue 5 to ensure the heat exchange capacity of the downflow flue 5. In addition to reducing the flue gas temperature, the downflow flue 5 can also take advantage of the easy fouling characteristics of high-temperature flue gas to adsorb and reduce alkali metals and chlorine elements in the flue gas, forming an easy-to-clean fouling layer on the pipe wall.

[0049] Example 3

[0050] This embodiment is a further optimization based on embodiment 2, specifically:

[0051] The tail flue 10 is equipped with a high-temperature economizer 11, an SCR device 12, a low-temperature economizer 13, and an air preheater 14 arranged along the flue gas direction.

[0052] The furnace 1 is equipped with a water-cooled screen 15. The downflow flue 5 is either an empty flue or has a water-cooled screen 15 as its heating surface. The water-cooled screen 15 in the downflow flue 5 is arranged parallel to the flue gas inlet.

[0053] Castable refractory is laid in the dense phase zone at the bottom of furnace 1.

[0054] The high flue gas temperature zone heating surface from the dense phase zone of furnace 1 to the inlet of water-cooled tube bundle 7 is coated with a spraying process.

[0055] Specifically, in order to further reduce the corrosion of other heated surfaces by chlorine in the flue gas, castable refractory is laid in the lower dense phase zone of furnace 1, and a spraying process is used on the heated surfaces in the high flue gas temperature zone from above the dense phase zone of furnace 1 to the inlet of water-cooled tube bundle 7.

[0056] Example 4

[0057] This embodiment is a further optimization based on embodiment 3, specifically:

[0058] Both the upper flue 6 and the lower flue 5 are equipped with ash hoppers 18 at the bottom, and a cooler 19 with a large-pitch water-cooled auger is installed below the ash hoppers 18.

[0059] Specifically, the above is the solution, which discharges the settled ash and large coke chunks falling from the front flue while ensuring a sealed environment.

[0060] In addition, the low-temperature heating surface 9, the medium-temperature heating surface 8, and the high-temperature heating surface 16 can be superheaters or reheaters; the downflow flue 5 and the upflow flue 6 can be water-cooled or steam-cooled structures; the water-cooled tube bundle 7 can be set up or removed as needed.

[0061] Working principle:

[0062] The dust-laden flue gas exiting furnace 1 is separated by cyclone separator 2, with the majority of the ash being separated into the return feeder 3. The ash outlet of the return feeder 3 is divided into two parts. One part exchanges heat with the high-temperature heating surface 16 in the external bed 4 and then returns to furnace 1. The amount of ash entering the external bed 4 is controlled by a conical valve 20. The other part of the ash is directly sent back to furnace 1. The high-temperature heating surface 16 is arranged in the external bed 4, avoiding direct contact with the chlorine-containing flue gas and reducing the risk of chlorine corrosion of the high-temperature heating surface 16 by the flue gas.

[0063] In the external bed 4, the circulating ash and the high-temperature heating surface 16 adopt a fluidized bed heat exchange method. The fluidizing medium can be high-pressure fluidizing air or low-temperature flue gas from the boiler outlet after dechlorination and dust removal, so as to avoid the chlorine corrosion problem of the external bed 4 heating surface caused by fluidizing air. In order to further reduce the corrosion of other heating surfaces by chlorine in the flue gas, castable refractory is laid in the dense phase zone of the lower part of the furnace 1, and the heating surface in the high flue gas temperature zone from the dense phase zone of the furnace 1 to the inlet of the water-cooled tube bundle 7 adopts a spray coating process.

[0064] After dust removal by the cyclone separator 2, the flue gas undergoes heat exchange in the downflow flue 5 and then enters the upflow flue 6 at a bend. The downflow flue 5 does not contain serpentine tube heating surfaces; however, a water-cooled screen 15 can be added as needed, positioned horizontally with the flue gas inlet. In the upflow flue 6, water-cooled tube bundles 7, medium-temperature heating surfaces 8, and low-temperature heating surfaces 9 are arranged sequentially along the flue gas direction. After passing through the downflow flue 5 and water-cooled tube bundles 7, the flue gas temperature is reduced to below 650℃. An ash hopper 18 is located at the lower part between the downflow flue 5 and the upflow flue 6. The flue gas, after heat exchange in the upflow flue 6, enters the tail flue 10, and then passes through the high-temperature economizer 11, the SCR device 12, the low-temperature economizer 13, and the air preheater 14 before being discharged.

Claims

1. A circulating fluidized bed boiler for clean combustion of high-alkali high-chlorine fuel, characterized in that, It comprises a hearth (1), a cyclone (2), a material return device (3), an external bed (4), a cooling flue and a tail flue (10), the flue gas outlet of the hearth (1) is communicated with the flue gas inlet of the cyclone (2), the ash outlet of the cyclone (2) is communicated with the ash inlet of the material return device (3), the circulating ash outlet of the material return device (3) is bifurcated, one branch is directly communicated with the hearth (1), and the other branch is communicated with the external bed (4) and then communicated with the hearth (1), the high-temperature heating surface (16) is arranged in the external bed (4), the circulating ash and the high-temperature heating surface (16) adopt fluidization heat exchange mode in the external bed (4), and the fluidization medium is high-pressure fluidization air or low-temperature flue gas after dechlorination and dust removal of the boiler outlet; the flue gas outlet of the cyclone (2) is communicated with the cooling flue, and the cooling flue is communicated with the tail flue (10).

2. A pure combustion high-alkali high-chlorine fuel circulating fluidized bed boiler according to claim 1, characterized in that, The high-temperature heating surface in the high-temperature area from the area above the dense phase zone of the hearth (1) to the inlet of the water-cooled tube bundle (7) adopts a spraying process.

3. A pure combustion high-alkali high-chlorine fuel circulating fluidized bed boiler according to claim 2, characterized in that, The outlet of the external bed (4) is communicated with the hearth (1), and the inlet of the external bed (4) is communicated with the other outlet of the material return device (3) through a pipeline, and a conical valve (20) is arranged on the pipeline.

4. A pure combustion high-alkali high-chlorine fuel circulating fluidized bed boiler according to claim 3, characterized in that, The bottom of the cooling flue is provided with an ash bucket (18), a downward flue (5) arranged in the cooling flue and an upward flue (6) arranged in the cooling flue, the bottom of the downward flue (5) is communicated with the bottom of the upward flue (6), the air outlet of the cyclone (2) is communicated with the top of the downward flue (5), and the upward flue (6) is communicated with the tail flue (10).

5. A pure combustion high-alkali high-chlorine fuel circulating fluidized bed boiler according to claim 4, characterized in that, A cold ash bucket (19) with a large-pitch water-cooled auger is arranged below the ash bucket (18).

6. A pure combustion high-alkali high-chloride fuel circulating fluidized bed boiler according to claim 4, characterized in that, The hearth (1) is provided with a water-cooled screen (15) inside, the downward flue (5) is an empty flue or is provided with a water-cooled screen (15) heating surface, and the water-cooled screen (15) in the downward flue (5) is arranged in parallel with the flue gas inlet.

7. A pure combustion high-alkali high-chloride fuel circulating fluidized bed boiler according to claim 4, characterized in that, The downward flue (5) is an empty flue, and the upward flue (6) is sequentially provided with a water-cooled tube bundle (7), a medium-temperature heating surface (8) and a low-temperature heating surface (9) along the flue gas direction.

8. A pure combustion high-alkali high-chlorine fuel circulating fluidized bed boiler according to claim 7, characterized in that, The downward flue (5) is provided with a hydraulic ash blowing device (17).

9. A pure combustion high-alkali high-chloride fuel circulating fluidized bed boiler according to claim 7, characterized in that, The tail flue (10) is provided with a high-temperature economizer (11), an SCR device (12), a low-temperature economizer (13) and an air preheater (14) along the flue gas direction.

10. A pure combustion high-alkali high-chloride fuel circulating fluidized bed boiler according to claim 1, characterized in that, Castable is laid in the lower dense phase zone of the hearth (1).

Images