A circulating fluidized bed boiler for burning papermaking solid waste

Abstract

The utility model belongs to the technical field of boiler, concretely relates to a kind of circulating fluidized bed boiler of combustion papermaking solid waste, including hearth, water-cooled air chamber, under-bed ignition device, vapor cooling separator, return device, connecting flue I, water-cooled flue, connecting flue II, shaft flue, boiler drum, downcomer, communicating pipe, steam collecting header, primary hot air duct, secondary hot air duct, water-cooled flue includes front water-cooled flue, rear water-cooled flue, water-cooled flue turning chamber, overcome the deficiency of prior art, solve the air distribution plate slag pipe easy to block, the convection superheater tube is caused by corrosion and causes the problem of high CO emission caused by the fixed device of high-temperature zone convection heating surface easy to erode and fall off, tail convection heating surface tube easy to block and circulating fluidized bed boiler solid waste burning.

Description

Technical Field

[0001] This utility model belongs to the field of boiler technology, specifically relating to a circulating fluidized bed boiler that burns solid waste from papermaking. Background Technology

[0002] With the rapid development of my country's economy, the amount of solid waste generated has increased year by year, causing serious environmental pollution. Traditional solid waste treatment methods suffer from problems such as low efficiency, high energy consumption, and large land area requirements. Circulating fluidized bed (CFB) boilers, a new generation of coal-fired boilers developed in the 1980s, are characterized by high efficiency and low pollution. In a CFB boiler, hot air blows fuel of a certain size into the furnace, where it continuously boils, tumbles, and agitates. A large amount of material is carried to the upper part of the furnace by the flue gas. Ash blown out of the furnace is separated by a high-efficiency separator at the furnace outlet and then returned to the lower part of the furnace by a return material device for repeated combustion. The gas-solid mixing within the fluidized bed is intense, resulting in high heat and mass transfer rates. Newly added fuel is immediately surrounded by the hot bed material in the furnace, providing excellent heating and ignition conditions. The CFB has a large heat capacity and good material mixing, making it highly adaptable to various fuels, including low-quality fuels. Therefore, CFB boilers are one of the most suitable furnace types for incinerating complex, low-calorific-value, high-moisture paper residue solid waste.

[0003] Although existing circulating fluidized bed boilers for incinerating solid waste have made significant improvements over coal-fired boilers based on the fuel characteristics of solid waste, they still have many problems: 1. The air distribution plate and ash discharge pipe are prone to clogging; 2. The convection superheater tubes are prone to corrosion, causing tube rupture; 3. The fixing devices of the high-temperature zone convection heating surface are prone to corrosion and detachment; 4. The tail convection heating surface tubes are prone to clogging; 5. The high CO emissions caused by the burning of solid waste in circulating fluidized bed boilers, etc. Utility Model Content

[0004] The purpose of this utility model is to provide a circulating fluidized bed boiler that burns solid waste from papermaking, which overcomes the shortcomings of the prior art and solves the problems of easy clogging of the air distribution plate slag discharge pipe, tube bursting caused by corrosion of the flow heat exchanger tubes, easy corrosion and detachment of the fixed device of the high-temperature zone convection heating surface, easy clogging of the tail convection heating surface tubes, and high CO emissions caused by the combustion of solid waste in the circulating fluidized bed boiler.

[0005] To solve the above problems, the technical solution adopted by this utility model is as follows: A circulating fluidized bed boiler for burning papermaking solid waste includes a furnace, a water-cooled air chamber, an under-bed ignition device, a steam-cooled separator, a return material device, connecting flue I, a water-cooled flue, connecting flue II, a vertical flue, a boiler drum, downcomers, connecting pipes, a steam collector, a primary hot air duct, and a secondary hot air duct. The water-cooled flue includes a front water-cooled flue, a rear water-cooled flue, and a water-cooled flue turning chamber. The lower part of the furnace is connected to the water-cooled air chamber, and the under-bed ignition device is connected to the rear of the water-cooled air chamber. The upper outlet of the furnace is connected to the steam-cooled separator. The steam-cooled separator is connected to a return material device below it. The return material device is connected to the lower part of the furnace through the return material return device. The water-cooled flue is connected to the steam-cooled separator through connecting flue I. The water-cooled flue is divided into front and rear parts. The front water-cooled flue and the rear water-cooled flue are connected through the water-cooled flue turning chamber. The vertical flue and the rear water-cooled flue are connected through connecting flue II. The boiler drum is arranged at the top of the furnace. The boiler drum forms a natural circulation loop with the furnace and the water-cooled flue through the downcomer and connecting pipe. The steam collector is arranged at the top of the water-cooled flue.

[0006] Furthermore, an air distribution plate is arranged at the bottom of the furnace, and an air cap and slag discharge pipe are arranged on the air distribution plate. Coal feed pipe, feed pipe and secondary air nozzle are arranged in the lower part of the furnace. Auxiliary burners are arranged on the side wall in the middle of the furnace, and screen-type superheaters are arranged in the upper part of the furnace.

[0007] Furthermore, a water-cooled screen is arranged in the front water-cooled flue, and a medium-temperature superheater and a low-temperature superheater are arranged sequentially from bottom to top in the rear water-cooled flue. The medium-temperature superheater and the low-temperature superheater are suspended from the top plate by water-cooled hanging pipes.

[0008] Furthermore, the economizer and air preheater are arranged from top to bottom in the vertical flue, and the flue outlet is arranged with a flue outlet.

[0009] Furthermore, the air distribution plate adopts a variable pitch and variable resistance wind cap and pipe arrangement, the air distribution plate adopts multi-point, large-diameter slag discharge, and the slag discharge pipe is set as a rectangle.

[0010] Furthermore, a slag discharge port is set at the bottom of the furnace, close to the paper waste feed port, and an air cannon is installed on the slag discharge pipe at the bottom of the furnace for unblocking. Except for a portion of the furnace outlet area, the entire fire-facing surface of the furnace is covered with silicon carbide castable.

[0011] Furthermore, a water-cooled screen is installed inside the front water-cooled flue.

[0012] Furthermore, for the screen-type superheater, the exposed tubes are made of SA-213M TP347H material with better corrosion resistance, while the rest is covered with silicon carbide castable. The high-temperature section of the medium-temperature superheater tubes is made of SA-213MTP347H material with better corrosion resistance.

[0013] Furthermore, the heating surface tubes of the intermediate-temperature superheater and low-temperature superheater in the rear water-cooled flue are suspended in the form of water-cooled hanging tubes, while the front water-cooled flue is a descending vertical flue. The intermediate-temperature superheater, low-temperature superheater, economizer, and air preheater are all arranged in parallel with bare tubes. The intermediate-temperature superheater, low-temperature superheater, economizer, and air preheater adopt an enlarged transverse pitch.

[0014] Furthermore, a flue gas recirculation device is installed at the primary air inlet of the under-bed ignition device to reduce nitrogen oxide emissions.

[0015] Compared with the prior art, this utility model has the following advantages: The air distribution plate adopts a variable pitch, variable resistance air cap and pipe arrangement, dividing the air distribution plate into four areas to ensure good bed fluidization. The slag discharge port of the air distribution plate is a large rectangular diameter and close to the paper residue feed port for convenient bottom slag discharge. The slag discharge pipe is equipped with an air cannon for unblocking, making it less prone to clogging. This effectively solves the problem of easy clogging of the air distribution plate slag discharge pipe.

[0016] A water-cooled flue is installed, and a water-cooled screen is arranged inside the front water-cooled flue to control the inlet flue temperature of the medium-temperature superheater to be below 600℃. The medium-temperature superheater tubes are made of SA-213M TP347H material, which can effectively solve the problem of tube rupture caused by corrosion in the convective superheater tubes.

[0017] The heating surface tubes of the medium-temperature and low-temperature superheaters in the rear water-cooled flue are suspended by water-cooled hanging tubes, which can avoid the problem of the fixing device of the heating surface in the high-temperature corrosion zone falling off due to corrosion.

[0018] The convection superheater, economizer, and air preheater all adopt a bare tube arrangement with increased lateral spacing. By selecting a reasonable flue gas velocity, the heat transfer surface tubes are less prone to ash accumulation, which can solve the problem of easy blockage of the tail convection heat transfer surface tubes.

[0019] 5. The large cross-section, low flow rate furnace structure, the use of steam-cooled separators, and the reasonable arrangement of water-cooled flues all increase the material residence time, which is conducive to improving the material combustion rate, reducing fly ash combustibles, and reducing CO generation. This can effectively solve the problem of high CO emissions caused by the combustion of solid waste in circulating fluidized bed boilers. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a circulating fluidized bed boiler that burns solid waste from papermaking.

[0021] Figure 2 This is a schematic diagram of a partial structure of the furnace.

[0022] Figure 3 This is a partial structural diagram of the water-cooled flue and the vertical flue. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example

[0024] like Figure 1 As shown, the circulating fluidized bed boiler for burning papermaking solid waste according to this utility model includes a furnace 1, a water-cooled air chamber 2, an under-bed ignition device 3, a steam-cooled separator 4, a return material device 5, a connecting flue I 6, a water-cooled flue 7, a connecting flue II 8, a vertical flue 9, a boiler drum 10, a downcomer 11, a connecting pipe 12, a steam collector 13, a primary hot air duct 14, and a secondary hot air duct 15. The water-cooled flue 7 includes a front water-cooled flue 71, a rear water-cooled flue 72, and a water-cooled flue turning chamber 73. The lower part of the furnace 1 is connected to the water-cooled air chamber 2, and the under-bed ignition device 3 is connected to the rear of the water-cooled air chamber 2. The upper outlet of the furnace 1 is connected to... The steam-cooled separator 4 is connected to the steam-cooled separator 4. The return material device 5 is connected to the lower part of the furnace 1 through the return material return tube 51. The water-cooled flue 7 is connected to the steam-cooled separator 4 through the connecting flue I 6. The water-cooled flue 7 is divided into front and rear parts. The front water-cooled flue 71 and the rear water-cooled flue 72 are connected through the water-cooled flue turning chamber 73. The vertical flue 9 and the rear water-cooled flue 72 are connected through the connecting flue II 8. The boiler drum 10 is arranged at the top of the furnace 1. The boiler drum 10 forms a natural circulation loop with the furnace 1 and the water-cooled flue 7 through the downcomer 11 and the connecting pipe 12. The steam collector 13 is arranged at the top of the water-cooled flue 7.

[0025] like Figure 2 As shown, an air distribution plate 101 is arranged at the bottom of the furnace 1, and an air cap and slag discharge pipe 111 are arranged on the air distribution plate 101. A coal feeding pipe 102, a feed pipe 103, and a secondary air nozzle 104 are arranged in the lower part of the furnace 1. An auxiliary burner 106 is arranged on the middle side wall of the furnace 1, and a screen-type superheater 105 is arranged in the upper part of the furnace 1.

[0026] like Figure 3 As shown, a water-cooled screen 711 is arranged in the front water-cooled flue 71, and a medium-temperature superheater 721 and a low-temperature superheater 722 are arranged sequentially from bottom to top in the rear water-cooled flue 72. The medium-temperature superheater 721 and the low-temperature superheater 722 are suspended on the top plate by water-cooled hanging pipes 723.

[0027] like Figure 3 As shown, the economizer 91 and the air preheater 92 are arranged from top to bottom in the vertical flue 9, and the flue outlet 93 is arranged at the outlet of the vertical flue 9. Example

[0028] The preferred air distribution plate 101 adopts a variable pitch and variable resistance air cap and pipe arrangement. According to the distribution law of the particle size of the bed material, the air volume of each area on the entire air distribution plate is distributed, and the corresponding air caps and pipes are arranged to divide the air distribution plate into four areas, so that the bed fluidization state is good.

[0029] Preferably, the air distribution plate 101 adopts multi-point, large-diameter slag discharge, and the slag discharge pipe 111 is set as rectangular to facilitate the discharge of bottom slag such as long metal objects, glass, and metal iron and aluminum that are easily melted and stuck together.

[0030] Preferably, the slag discharge port at the bottom of the furnace 1 is located near the paper scrap feed port, so that the non-combustible material can be rolled to the vicinity of the slag discharge port by gravity and fall directly into the slag discharge port.

[0031] Preferably, an air cannon is installed at the bottom of the slag discharge pipe of furnace 1 for unblocking.

[0032] Preferably, except for a portion of the area at the furnace outlet, the entire fire-facing surface of the furnace 1 is covered with silicon carbide castable to reduce the corrosion of the heating surface by flue gas.

[0033] Preferably, a water-cooled screen 711 is arranged inside the front water-cooled flue 71. By controlling the heat absorption area of ​​the water-cooled screen 711, the flue gas outlet temperature of the front water-cooled flue 71 can be controlled below 600℃, thereby reducing the inlet flue gas temperature of the intermediate temperature superheater 721 and mitigating the corrosion of the intermediate temperature superheater 721 tube.

[0034] Preferably, the exposed tubes of the screen-type superheater 15 are made of SA-213M TP347H material with better corrosion resistance, while the rest are covered with silicon carbide castable to reduce the corrosion of the heating surface by flue gas.

[0035] Preferably, the high-temperature section of the 721 medium-temperature superheater tube is made of SA-213M TP347H, which has better corrosion resistance, to ensure the stability and reliability of the product in high-temperature environments.

[0036] Preferably, the heating surface tubes of the medium-temperature superheater 721 and low-temperature superheater 722 in the rear water-cooled flue 72 are suspended by water-cooled hanging pipes 723 to prevent the heating surface supports in the high-temperature corrosion zone from falling off due to corrosion.

[0037] Preferably, the front water-cooled flue 71 is a descending vertical flue. The easily sticky substances produced after combustion settle in the ash hopper at the bottom of the descending flue, preventing them from entering the superheater and forming sticky substances that could cause the flue to become blocked.

[0038] Preferably, the medium-temperature superheater 721, the low-temperature superheater 722, the economizer 91, and the air preheater 92 are all arranged in a smooth tube configuration, which makes it less prone to dust accumulation.

[0039] Preferably, the medium-temperature superheater 721, the low-temperature superheater 722, the economizer 91, and the air preheater 92 adopt an increased transverse pitch to increase the clearance between the tubes and prevent ash accumulation and blockage.

[0040] Preferably, the medium-temperature superheater 721, low-temperature superheater 722, economizer 91, and air preheater 92 are selected with reasonable flue gas velocities to ensure the self-cleaning and ash-carrying capacity of the flue gas, while also taking into account the wear of the heating surfaces.

[0041] Preferably, the furnace chamber 1 adopts an enlarged cross-section and low flow rate structure to increase the residence time of materials in the furnace chamber 1, which is beneficial to improving the material burnout rate.

[0042] Preferably, the steam-cooled separator 4 extends the number of cycles of fine particulate circulating ash, increases the residence time of unburned carbon in the combustion system, and reduces the combustibles in fly ash.

[0043] Preferably, the water-cooled flue 7 extends the residence time of flue gas, increases the combustion rate of combustibles in the flue gas, and effectively reduces the generation of CO.

[0044] Preferably, an auxiliary burner 16 is arranged in a suitable position in the furnace 1 to stabilize combustion and control the emission of harmful gases (dioxins). When the amount of solid waste is insufficient or the feed is blocked, the auxiliary burner is started to ensure a furnace temperature of 850°C.

[0045] Preferably, a flue gas recirculation device is installed at the primary air inlet of the under-bed ignition device 3 to reduce nitrogen oxide emissions.

[0046] Steam-water system: Boiler feedwater enters economizer 91, is heated by flue gas, and then enters water-cooled hanging pipe 723, and then enters boiler drum 10. Boiler water in boiler drum 10 enters the water-cooled wall of furnace 1 and the water-cooled wall of water-cooled flue 7 through downcomer 11. Boiler water in the water-cooled wall of furnace 1 and the water-cooled wall of water-cooled flue 7 are heated by flue gas and become steam-water mixture, which enters boiler drum 10 through connecting pipe 12. In boiler drum 10, a two-stage steam-water separation device separates the steam-water mixture into saturated steam and saturated boiler water. Boiler water enters downcomer 11 for the next round of natural steam-water circulation. Saturated steam passes sequentially through steam-cooled separator 4, low-temperature superheater 722, medium-temperature superheater 721, and screen-type superheater 105. After passing through two stages of water spray de-heating, the superheated steam that reaches the rated parameters of the boiler is introduced into steam collector 13 through connecting pipe and output from the boiler to the steam turbine.

[0047] Flue gas system: Paper waste solid waste is fed into the lower combustion chamber of furnace 1 from the furnace front feed pipe 103 by the furnace front secondary feeding system. After combustion, the generated high-temperature flue gas heats the water-cooled wall of furnace 1, the screen-type superheater 15, the steam-cooled separator 4, the front water-cooled flue 71, the water-cooled screen 711, the rear water-cooled flue 72, the medium-temperature superheater 721, the low-temperature superheater 722, the water-cooled hanging pipe 723, the economizer 91, and the air preheater 92. After cooling, the flue gas is discharged from the boiler through the outlet flue 93.

[0048] Return material circulation system: After fuel combustion, the high-concentration flue gas produced undergoes efficient separation in the steam-cooled separator 4. Fine particles enter the rear heating surface with the flue gas, while larger particles are separated and sent back to the furnace 1 via the return material device 5 and return material leg 51 for continued heat transfer. This process is repeated to form a material circulation. The under-bed ignition device 3 uses light diesel oil and is used during boiler ignition. The slag after fuel combustion is discharged from the boiler through the slag discharge pipe 111.

[0049] Air supply system: The air required for boiler combustion is supplied by primary and secondary air fans respectively. The air delivered by the primary air fan is heated by the air preheater 93 and then sent to the side of the under-bed ignition device 3 through the primary hot air duct 14, introduced into the under-bed water-cooled air chamber 2, and enters the combustion chamber through the air cap on the water-cooled air distribution plate 101; the air delivered by the secondary air fan is heated by the air preheater 93 and then sent to the furnace annular air box through the secondary hot air duct 15, and injected into the furnace through the secondary air nozzles 104 distributed on the front and rear walls of the furnace 1 to supplement air and enhance turbulence and mixing. Fuel and air are mixed and burned in a fluidized state in the furnace and exchange heat with the heating surfaces.

[0050] Recirculation system: A flue gas recirculation fan is installed near the boiler induced draft fan. The inlet of the recirculation fan is connected to the outlet of the induced draft fan; the outlet is connected to the primary air inlet of the under-bed ignition device 3. When the boiler is started from a cold state, the flue gas recirculation fan is started. Since the oxygen content at the outlet of the induced draft fan is relatively low, the flue gas from the recirculation fan (the flue gas volume is adjusted by the damper on the pipeline) is mixed with the primary air, which reduces the oxygen content of the air entering the furnace. This can effectively reduce the NOx emission concentration while ensuring normal bed fluidization.

[0051] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A circulating fluidized bed boiler for burning papermaking solid waste, characterized in that: The system includes a furnace, a water-cooled air chamber, an under-bed ignition device, a steam-cooled separator, a return material device, connecting flue I, a water-cooled flue, connecting flue II, a vertical shaft flue, a boiler drum, a downcomer, a connecting pipe, a steam collector, a primary hot air duct, and a secondary hot air duct. The water-cooled flue includes a front water-cooled flue, a rear water-cooled flue, and a water-cooled flue turning chamber. The lower part of the furnace is connected to the water-cooled air chamber, and the under-bed ignition device is connected behind the water-cooled air chamber. The upper outlet of the furnace is connected to the steam-cooled separator, and the return material device is connected below the steam-cooled separator. The return material device is connected to the lower part of the furnace via a return material feeder. The water-cooled flue and the steam-cooled separator are connected via connecting flue I. The water-cooled flue is divided into front and rear parts, with the front and rear water-cooled flues connected by a water-cooling system. The flue is connected to the turning chamber. The vertical flue and the rear water-cooled flue are connected through connecting flue II. The boiler drum is arranged at the top of the furnace. The boiler drum forms a natural circulation loop with the furnace and the water-cooled flue through downcomer pipes and connecting pipes. The steam collector is arranged at the top of the water-cooled flue. The bottom of the furnace is equipped with an air distribution plate. The air distribution plate is equipped with an air cap and a slag discharge pipe. The lower part of the furnace is equipped with a coal feed pipe, a material feed pipe, and a secondary air nozzle. The middle side wall of the furnace is equipped with an auxiliary burner. The upper part of the furnace is equipped with a screen-type superheater. A water-cooled screen is arranged in the front water-cooled flue. The medium-temperature superheater and the low-temperature superheater are arranged sequentially from bottom to top in the rear water-cooled flue. The medium-temperature superheater and the low-temperature superheater are suspended from the top plate by water-cooled hanging pipes.

2. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: The vertical flue is equipped with an economizer and an air preheater arranged from top to bottom, and the flue outlet is provided with a flue outlet.

3. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: The air distribution plate adopts a variable pitch and variable resistance wind cap and pipe arrangement. The air distribution plate adopts multi-point, large-diameter slag discharge, and the slag discharge pipe is set as a rectangle.

4. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: The furnace bottom slag discharge port is located near the paper waste feed port. The furnace bottom slag discharge pipe is equipped with an air cannon for unblocking. Except for a portion of the furnace outlet area, the entire fire-facing surface of the furnace is covered with silicon carbide castable.

5. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: A water-cooled screen is arranged inside the front water-cooled flue.

6. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: The exposed tubes of the screen-type superheater are made of SA-213M TP347H material, which has better corrosion resistance, while the rest are covered with silicon carbide castable. The high-temperature section of the medium-temperature superheater tubes is made of SA-213M TP347H material, which has better corrosion resistance.

7. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: The heating surface tubes of the intermediate-temperature superheater and low-temperature superheater in the rear water-cooled flue are suspended in the form of water-cooled hanging tubes. The front water-cooled flue is a descending vertical flue. The intermediate-temperature superheater, low-temperature superheater, economizer, and air preheater are all arranged in a row with bare tubes. The intermediate-temperature superheater, low-temperature superheater, economizer, and air preheater adopt an enlarged lateral pitch.

8. A circulating fluidized bed boiler for burning papermaking solid waste according to claim 1, characterized in that: A flue gas recirculation device is installed at the primary air inlet of the under-bed ignition device to reduce nitrogen oxide emissions.

Images