Biomass combustion-supporting sludge incineration boiler tail flue structure

Abstract

The utility model discloses a kind of tail flue structures of sludge incineration boiler of biomass combustion-supporting, solve after high-alkali metal content biomass fuel is burned, how to prevent liquid alkali metal compound easily adhere on high-temperature heating surface in tail flue, how to overcome the combination of fly ash in flue gas and dew drop on low-temperature heating surface causes blockage, with flue temperature, flue gas flow rate control, and strive to complete the design main line of dust removal in flue front section, with three-stage water-cooled front flue in series, realize the staged flow rate control of flue gas, and realize multistage dust removal of flue gas and the accommodation of CO in flue gas;The first two stages of three-stage high-temperature water-cooled flue are designed as water-cooled empty flue, the flue gas discharged in hearth passes through the first two stages of water-cooled empty flue, then flue temperature is reduced to below 600 degrees Celsius, and then make flue gas enter into third-stage high-temperature flue;After dust removal, substantially clean flue gas is discharged into U-shaped low-temperature flue, thereby solve the blockage problem of low-temperature heating surface.

Description

Technical Field

[0001] This utility model relates to a circulating fluidized bed boiler for sludge incineration, and particularly to the tail flue structure of a biomass-assisted sludge incineration boiler. Background Technology

[0002] Municipal sludge is a byproduct of urban sewage treatment. With the advancement of urbanization, the output of municipal sludge is increasing. How to safely and properly treat and dispose of municipal sludge, and truly realize the reduction, harmlessness and resource utilization of sludge, has become a major issue that needs to be addressed in the environmental field. Sludge incineration has a good volume reduction effect and can effectively decompose toxic and harmful organic matter in sludge. It is the most promising way to reduce, harmlessly and resourcefully utilize sludge. For the combustion treatment of sludge, circulating fluidized bed boiler technology for sludge incineration has emerged. The design furnace temperature of this type of boiler is generally around 900 degrees Celsius to adapt to the characteristics of sludge combustion. However, the existing technology has the following problems that need to be overcome: (1) Municipal Sludge has a high water content (absolute humidity of about 25%), and is characterized by high ash content and low and unstable calorific value. It is difficult to ignite during boiler combustion, especially the calorific value of continuously fed sludge fluctuates greatly, which seriously affects the stable operation of the boiler. The existing technology generally solves the problem of unstable calorific value by co-firing other fuels with stable calorific value. (2) Sludge has a high ash content, and a large amount of fly ash will be generated after combustion. The temperature of the working medium (cold water, ambient air) at the inlet end of the low-temperature economizer and air preheater is also low. When the flue gas with high humidity generated after sludge combustion passes through the outer wall of the inlet end of the low-temperature heating surface, a lot of dew will form. The dew will adsorb a large amount of dust particles in the flue gas. The large amount of fly ash generated after sludge combustion It will stick to the tube wall of the low-temperature heating surface and block the heating surface; (3) When the sludge is burned, a large amount of CO gas will be generated, and the flue gas velocity in the furnace is also relatively fast. A large amount of CO gas will enter the tail flue. How to treat the CO gas in the tail flue so as to achieve the standard of CO in the exhaust gas is also a problem that needs to be solved; (4) In the tail flue of a conventional circulating fluidized bed boiler, the high-temperature superheater / high-temperature reheater, low-temperature superheater / low-temperature reheater, economizer, and air preheater are generally arranged in sequence along the flue gas flow direction. The flue gas flow from the furnace and into the tail flue through the cyclone separator releases heat through the above-mentioned heating surfaces. The flue gas temperature gradually decreases from 850-900℃ to about 150℃ at the flue outlet; but when high-alkali fuel is used, the fuel Alkali metals in flue gas mainly enter the flue gas in the form of gaseous alkali metal compounds. When the flue gas temperature is between 650-800℃, the gaseous alkali metal compounds condense into liquid. At this time, if they encounter heating surfaces with high wall temperatures, such as superheaters and reheaters, the liquid alkali metal compounds will adhere to these heating surfaces, forming a complex and hard eutectic. This further adsorbs fly ash from the flue gas, causing severe fouling of the high-temperature heating surfaces, affecting heat exchange, and disrupting the normal flue gas flow path. Biomass fuel is a high-alkali fuel with a high proportion of alkali metal oxides in its fly ash. The fly ash has a low melting temperature and is prone to high-temperature slagging. If biomass fuel is used for combustion in sludge incineration boilers, flue gas with a high alkali metal content will be introduced into the flue gas, leading to the above situation.Therefore, the design and layout of the tail flue of a biomass-assisted sludge incineration boiler has become a problem faced by technicians in this field. Summary of the Invention

[0003] This utility model provides a tail flue structure for a biomass-assisted sludge incineration boiler, which solves the technical problems of how to prevent liquid alkali metal compounds from easily adhering to the high-temperature heating surface in the tail flue after using biomass fuel with high alkali metal content, how to overcome the blockage caused by fly ash in the flue gas combining with dew on the low-temperature heating surface, and how to achieve standard emission of high concentration CO in the flue gas.

[0004] This utility model solves the above technical problems through the following technical solution: The overall concept of this utility model is as follows: The flue gas entering the tail flue of the sludge incinerator using biomass fuel combustion has the following characteristics: (1) The gaseous alkali metal compounds in the flue gas at a temperature of 650-800℃ will condense into liquid and precipitate on the high-temperature heating surface, causing corrosion of the high-temperature heating surface; (2) The flue gas after sludge combustion has a high water content and is easy to form a large amount of dew on the low-temperature heating surface; the high-concentration fly ash produced after sludge combustion is easily adsorbed into the dew on the low-temperature heating surface, causing the low-temperature heating surface to be blocked; (3) A large amount of CO gas is produced when the sludge is burned in the furnace; This invention addresses the above three prominent characteristics of flue gas and, taking into account the three main lines of cooling, dust removal and CO consumption, develops the tail flue design of this invention; with the main lines of flue temperature and flue gas velocity control, and striving to complete dust removal in the front section of the flue, three water-cooled front flues connected in series are used to realize the flue gas The system employs graded flow velocity control to achieve multi-stage dust removal and CO elimination from the flue gas. The first two sections of the three-stage high-temperature water-cooled flue are designed as water-cooled air flues, where the flue gas temperature drops below 600 degrees Celsius after passing through these sections before entering the third stage of the high-temperature flue. The high-temperature heating surfaces are positioned in the third stage flue where the temperature has dropped below 600 degrees Celsius. By controlling the flue gas flow velocity, most of the dust is removed in the first three stages of the high-temperature water-cooled flue. The flue gas then enters a high-temperature metal cartridge dust collector, with the flow velocity controlled at 2-3 meters per second, achieving graded dust removal. Finally, the basically cleaned flue gas is discharged into a U-shaped low-temperature flue, where a low-temperature economizer and air preheater with low-temperature heat exchange surfaces are installed to solve the problem of blockage in the low-temperature heating surfaces.

[0005] A tail flue structure for a biomass-assisted sludge incineration boiler includes a circulating fluidized bed boiler furnace, a high-temperature adiabatic cyclone separator, and a tail flue. Sludge fuel and biomass-assisted fuel are incinerated in the circulating fluidized bed boiler furnace. The tail flue is a split-type design, consisting of a high-temperature section and a low-temperature section. A high-temperature metal cartridge dust collector is installed between the high-temperature and low-temperature sections. The high-temperature section consists of a first high-temperature vertically descending flue that is parallel to and sequentially connected end-to-end. It consists of a second high-temperature vertical upward flue and a third high-temperature vertical downward flue. The first, second, and third high-temperature vertical downward flues are all water-cooled film-wall flues. The first and second high-temperature vertical upward flues are empty flues with water-cooled film walls. A low-temperature superheater and a high-temperature economizer are installed in the third high-temperature vertical downward flue. The low-temperature section flue is a U-shaped steel plate flue, in which a low-temperature economizer and an air preheater are installed respectively.

[0006] A first ash remover is installed at the connection between the lower end of the first high-temperature vertical downward flue and the lower end of the second high-temperature vertical upward flue, and a second ash remover is installed at the bottom of the third high-temperature vertical downward flue.

[0007] The average temperature of the flue gas in the first high-temperature vertical downward flue is 800℃, and the flow velocity of the flue gas in the first high-temperature vertical downward flue is 7 m / s; the average temperature of the flue gas in the second high-temperature vertical upward flue is 650℃, and the flow velocity of the flue gas in the second high-temperature vertical downward flue is 7 m / s; the flue gas temperature at the upper inlet of the third high-temperature vertical downward flue is below 610℃, and the flow velocity of the flue gas in the third high-temperature vertical downward flue is 10 m / s; the flow velocity of the flue gas in the high-temperature metal cartridge dust collector is 2-3 m / s, and the heat dissipation temperature drop of the high-temperature metal cartridge dust collector is 20℃; the flue gas temperature at the inlet of the U-shaped steel plate flue is 380℃, and the flue gas temperature at the outlet of the U-shaped steel plate flue is 160℃; the flow velocity of the flue gas in the U-shaped steel plate flue is 7 m / s.

[0008] The sludge fuel has a moisture content of 40%-45% and is in the form of soil; the biomass combustion aid is a pellet fuel with a particle size of less than 10 cm.

[0009] This invention effectively prevents corrosion of the high-temperature heating surface at the tail end and slagging and blockage of the low-temperature heating surface. By setting up water-cooled flue gas ducts at both ends, the flue gas entering the high-temperature convection heating surface is reduced to below 650°C, cleverly avoiding the liquid precipitation of alkali metal elements in the high-temperature flue gas. Through the setting of a three-section high-temperature vertical flue gas duct and the control and variation of flue gas flow rate, effective preliminary dust removal of the flue gas is achieved. And through a high-temperature metal cartridge dust collector, basic purification of the flue gas is achieved, so that the large number of dew droplets formed on the low-temperature heating surface will not absorb dust particles in the flue gas, thus avoiding the blockage of the low-temperature heating surface. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0011] The present invention will now be described in detail with reference to the accompanying drawings: A tail flue structure for a biomass-assisted sludge incineration boiler includes a circulating fluidized bed boiler furnace 1, a high-temperature adiabatic cyclone separator 2, and a tail flue. Sludge fuel and biomass-assisted fuel are incinerated in the circulating fluidized bed boiler furnace 1. The tail flue is a split-type design, consisting of a high-temperature section and a low-temperature section. A high-temperature metal cartridge dust collector 3 is installed between the high-temperature and low-temperature sections. The high-temperature section consists of a first high-temperature vertically descending flue 4 and a second high-temperature section, which are arranged side-by-side and connected sequentially. The system consists of a vertical upward flue 5 and a third high-temperature vertical downward flue 6. The first high-temperature vertical downward flue 4, the second high-temperature vertical upward flue 5, and the third high-temperature vertical downward flue 6 are all water-cooled film-walled flues. The first high-temperature vertical downward flue 4 and the second high-temperature vertical upward flue 5 are empty flues with water-cooled film walls. A low-temperature superheater 7 and a high-temperature economizer 8 are installed in the third high-temperature vertical downward flue 6. The low-temperature section flue is a U-shaped steel plate flue 9, in which a low-temperature economizer 10 and an air preheater 11 are installed respectively.

[0012] A first ash remover 12 is installed at the connection between the lower end of the first high-temperature vertical downward flue 4 and the lower end of the second high-temperature vertical upward flue 5, and a second ash remover 13 is installed at the bottom of the third high-temperature vertical downward flue 6.

[0013] The average temperature of the flue gas in the first high-temperature vertical downward flue duct 4 is 800℃, and the flow velocity of the flue gas in the first high-temperature vertical downward flue duct 4 is 7 m / s; the average temperature of the flue gas in the second high-temperature vertical upward flue duct 5 is 650℃, and the flow velocity of the flue gas in the second high-temperature vertical downward flue duct 5 is 7 m / s; the flue gas temperature at the upper inlet of the third high-temperature vertical downward flue duct 6 is below 610℃, and the flow velocity of the flue gas in the third high-temperature vertical downward flue duct 7 is 10 m / s; the flow velocity of the flue gas in the high-temperature metal cartridge dust collector 3 is 2-3 m / s, and the heat dissipation temperature drop of the high-temperature metal cartridge dust collector 3 is 20℃; the flue gas temperature at the inlet of the U-shaped steel plate flue duct 9 is 380℃, and the flue gas temperature at the outlet of the U-shaped steel plate flue duct 9 is 160℃; the flow velocity of the flue gas in the U-shaped steel plate flue duct 9 is 7 m / s.

[0014] The sludge fuel has a moisture content of 40%-45% and is in the form of soil; the biomass combustion aid is a pellet fuel with a particle size of less than 10 cm. A method for arranging the tail flue of a biomass-assisted sludge incineration boiler includes a circulating fluidized bed boiler furnace 1, a high-temperature adiabatic cyclone separator 2, and a tail flue. Sludge fuel and biomass-assisted fuel are incinerated in the circulating fluidized bed boiler furnace 1. The flue gas temperature at the outlet of the high-temperature adiabatic cyclone separator 2 is 910°C. The tail flue is characterized by being arranged using the following method: The first step is to separate the tail flue into two independent sections: a high-temperature section flue and a low-temperature section flue. A high-temperature metal cartridge dust collector 3 is installed between the high-temperature section flue and the low-temperature section flue. The second step is to design the high-temperature section flue as a three-section high-temperature flue with a head-to-tail connection. That is, a first high-temperature vertical downward flue 4 is set at the outlet of the high-temperature adiabatic cyclone separator 2, a second high-temperature vertical upward flue 5 is connected to the bottom of the first high-temperature vertical downward flue 4, and a third high-temperature vertical downward flue 6 is connected to the top of the second high-temperature vertical upward flue 5. These three flue sections are connected head-to-tail and set up in parallel with each other. The third step is to design the first high-temperature vertical downward flue 4, the second high-temperature vertical upward flue 5, and the third high-temperature vertical downward flue 6 as water-cooled membrane wall flues. Fourth step: The first high-temperature vertical downward flue 4 and the second high-temperature vertical upward flue 5 are designed as empty flues with water-cooled wall panels; in the third high-temperature vertical downward flue 6, a low-temperature superheater 7 and a high-temperature economizer 8 are arranged in sequence from top to bottom. Step 5: Set the low-temperature section flue as a U-shaped steel plate flue 9, and install the low-temperature economizer 10 and the air preheater 11 in the U-shaped steel plate flue 9 respectively. Step 6: The bottom flue gas temperature of the first high-temperature vertical downward flue 4 is designed to be 700℃, and the flue gas velocity in the first high-temperature vertical downward flue 4 is designed to be 7 m / s; the top outlet flue gas temperature of the second high-temperature vertical upward flue 5 is designed to be 610℃, and the flue gas velocity in the second high-temperature vertical upward flue 5 is designed to be 7 m / s; the lower outlet temperature of the third high-temperature vertical downward flue 6 is designed to be 400℃, and the flue gas velocity in the third high-temperature vertical downward flue 6 is designed to be 10 m / s. Step 7: The flue gas velocity in the high-temperature metal cartridge dust collector 3 is designed to be 2-3 meters per second, and the heat dissipation temperature drop of the high-temperature metal cartridge dust collector 3 is designed to be 20℃. Step 8: The inlet flue gas temperature of the U-shaped steel plate flue 9 is designed to be 380℃, the outlet flue gas temperature of the U-shaped steel plate flue 9 is designed to be 160℃, and the flue gas velocity in the U-shaped steel plate flue 9 is designed to be 7 meters per second.

[0015] The first high-temperature vertical downward flue 4, the second high-temperature vertical upward flue 5, and the third high-temperature vertical downward flue 6 are all designed as fully suspended water-cooled membrane wall flue structures; the biomass combustion aid fuel is granular fuel with a calorific value of 3500 Kcal / kg; the combined calorific value of the sludge fuel and the biomass combustion aid fuel is 1200 Kcal / kg.

Claims

1. A tail flue structure for a biomass-assisted sludge incineration boiler, comprising a circulating fluidized bed boiler furnace (1), a high-temperature adiabatic cyclone separator (2), and a tail flue, wherein sludge fuel and biomass-assisted fuel are incinerated in the circulating fluidized bed boiler furnace (1); characterized in that, The tail flue is a split-type flue, that is, the tail flue is divided into a high-temperature section flue and a low-temperature section flue. A high-temperature metal cartridge dust collector (3) is installed between the high-temperature section flue and the low-temperature section flue. The high-temperature section flue is composed of a first high-temperature vertical downward flue (4), a second high-temperature vertical upward flue (5), and a third high-temperature vertical downward flue (6) that are parallel to each other and connected end to end. The first high-temperature vertical downward flue (4) and the second high-temperature vertical upward flue (5) and the third high-temperature vertical downward flue (6) are both water-cooled film wall flues. The first high-temperature vertical downward flue (4) and the second high-temperature vertical upward flue (5) are water-cooled film wall empty flues. A low-temperature superheater (7) and a high-temperature economizer (8) are installed in the third high-temperature vertical downward flue (6). The low-temperature section flue is a U-shaped steel plate flue (9). A low-temperature economizer (10) and an air preheater (11) are installed in the U-shaped steel plate flue (9).

2. The tail flue structure of a biomass-assisted sludge incineration boiler according to claim 1, characterized in that, A first ash remover (12) is provided at the connection between the lower end of the first high-temperature vertical downward flue (4) and the lower end of the second high-temperature vertical upward flue (5), and a second ash remover (13) is provided at the bottom of the third high-temperature vertical downward flue (6).

3. The tail flue structure of a biomass-assisted sludge incineration boiler according to claim 1 or 2, characterized in that, The average temperature of the flue gas in the first high-temperature vertical downward flue (4) is 800℃, and the flow velocity of the flue gas in the first high-temperature vertical downward flue (4) is 7 m / s; the average temperature of the flue gas in the second high-temperature vertical upward flue (5) is 650℃, and the flow velocity of the flue gas in the second high-temperature vertical upward flue (5) is 7 m / s; the flue gas temperature at the upper inlet of the third high-temperature vertical downward flue (6) is lower than 610℃, and the flow velocity of the flue gas in the third high-temperature vertical downward flue (6) is 10 m / s; the flow velocity of the flue gas in the high-temperature metal cartridge dust collector (3) is 2-3 m / s, and the heat dissipation temperature drop of the high-temperature metal cartridge dust collector (3) is 20℃; the flue gas temperature at the inlet of the U-shaped steel plate flue (9) is 380℃, and the flue gas temperature at the outlet of the U-shaped steel plate flue (9) is 160℃; the flow velocity of the flue gas in the U-shaped steel plate flue (9) is 7 m / s.

4. The tail flue structure of a biomass-assisted sludge incineration boiler according to claim 3, characterized in that, The sludge fuel has a moisture content of 40%-45% and is in the form of soil; the biomass combustion aid is a pellet fuel with a particle size of less than 10 cm.

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