Circulating fluidized bed boiler suitable for high-coking fuel

Abstract

The circulating fluidized bed boiler comprises a hearth, a feeding device, a material returning device, a secondary tuyere, an air distribution plate, a cyclone separator, a tail flue and a superheater, the hearth is divided into three areas including a preheating mixing area, a hearth combustion area and a hearth heat exchange area from bottom to top, refractory castable is laid in the hearth to form a heat insulation hearth, a superheater is arranged in a hearth heat exchange area on the upper portion in the hearth, and an evaporation water cooling screen is additionally arranged below the superheater in the hearth. According to the circulating fluidized bed boiler suitable for the high-coking fuel, the defects that a traditional circulating fluidized bed boiler is insufficient in combustion, prone to coking, uneven in hearth temperature distribution and the like when biomass fuel and garbage fuel are combusted are overcome, the combustion temperature and stability can be improved, coking is avoided, fluidization is more uniform, and the combustion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circulating fluidized bed boilers, and in particular to a circulating fluidized bed boiler suitable for high-coking fuel, which is applied to waste incineration and biomass power generation equipment. Background Art

[0002] With the rapid development of society, the world's demand for energy continues to increase, and fossil fuels can no longer meet this growing demand. Consequently, the development of renewable energy has become a global focus. Among these, biomass and waste fuel power generation technologies have been widely adopted. Due to the high moisture content, low calorific value, diverse shapes and sizes, and high levels of debris in biomass and waste fuels, conventional circulating fluidized bed boilers are prone to debris agglomeration, coking of air distribution plates, clogging of slag pipes, and large combustion fluctuations when burning these fuels. These factors lead to uneven bed temperature distribution, uneven fluidization, incomplete combustion, and uneven furnace temperature distribution. This can reduce boiler thermal efficiency, exceed pollutant emissions standards, and even cause emergency shutdowns.

[0003] The circulating fluidized bed boiler suitable for high-coking fuel of the present invention is one of the effective ways to solve the above-mentioned problems. The circulating fluidized bed boiler is designed for high-coking fuel, helps to improve the boiler's continuous operation stability, ensures boiler combustion safety, can effectively improve the boiler's economy, and has broad application prospects. Summary of the Invention

[0004] In order to overcome the shortcomings of traditional circulating fluidized bed boilers when burning biomass fuels and garbage fuels, such as incomplete combustion, easy coking, and uneven furnace temperature distribution, the present invention designs a circulating fluidized bed boiler suitable for high-coking fuels, which can increase the combustion temperature and stability, prevent coking, make fluidization more uniform, and improve combustion efficiency.

[0005] The present invention adopts the following technical solutions: A circulating fluidized bed boiler suitable for high-coking fuel includes a furnace, a feeding device, a return device, a secondary air inlet, an air distribution plate, a cyclone separator, a tail flue and a superheater. The furnace is divided into three areas, which are, from bottom to top, a preheating mixing area, a furnace combustion area and a furnace heat exchange area. Refractory castables are laid inside the furnace to form an insulated furnace. A superheater is arranged in the furnace heat exchange area above the furnace, and an evaporative water cooling screen is added below the superheater in the furnace.

[0006] Preferably, the feeding device is connected to the preheating mixing zone in the furnace.

[0007] Preferably, the bottom end of the cyclone separator is connected to the preheating mixing zone in the furnace through a return device.

[0008] Preferably, an air distribution plate is provided at the bottom end of the preheating mixing zone in the furnace and is connected to the primary air inlet.

[0009] Preferably, the secondary air inlet is connected to the furnace combustion zone in the furnace.

[0010] Preferably, the refractory castable is laid on the water-cooled walls around the lower furnace at the bends of the front and rear walls of the furnace combustion zone in the furnace.

[0011] Preferably, a multi-stage economizer is arranged in a row in the tail flue, and each row of economizers is connected to each other through a transverse flue.

[0012] Preferably, the tail flue is further provided with an air preheater, and the air preheater and the economizer are distributed separately and are connected at intervals through a transverse flue.

[0013] Preferably, a soot blowing device is provided in the tail flue corresponding to the economizer.

[0014] The beneficial effects of the present invention are: (1) The present invention can improve combustion efficiency and has a wide range of fuel adaptability. After the fuel enters the adiabatic combustion space of the furnace, due to the high heat capacity and high material concentration of the space, the fuel is instantly heated by the high-temperature flue gas and the material, and is preheated and dried. In addition, due to the characteristics of the fluidized bed boiler, the fuel is subjected to a strong mixing effect, so that the fuel can be stably and continuously burned in the combustion space. The invention can adapt to fluctuations in fuel characteristics, such as changes in calorific value, moisture, etc., so that the boiler has a high adaptability to such fuels with large changes in characteristics; (2) The present invention can effectively prevent the high coking fuel from sticking to the heating surface during the combustion process. The invention adopts a circulating fluidized bed boiler. There is a large amount of circulating material in the furnace. The temperature level in the furnace is relatively uniform, and the combustion effect is easy to control. At the same time, an evaporative water cooling screen is added below the superheater in the furnace to increase the heating area in the furnace to increase heat absorption, thereby reducing the flue gas temperature in the furnace and preventing the high coking fuel from melting due to excessive flue gas temperature and sticking to the heating surface. (3) The present invention can ensure that the temperature field along the entire cross section of the furnace is uniform; due to the characteristics of the circulating fluidized bed boiler, the invention takes into account the high coking property of the fuel and the temperature required for combustion. The water-cooled walls around the lower furnace at the bend of the front and rear walls of the furnace combustion zone are covered with refractory castables to reduce the heat absorption of the furnace and make the bed temperature of the entire combustion chamber 850-950℃, thereby ensuring that the temperature field along the entire cross section of the furnace is uniform; (4) The present invention can effectively prevent the adhesion of high-coking fuels on the heating surface; the present invention widens the transverse intercept of the economizer located in the tail flue while increasing the number of longitudinal rows, thereby ensuring the heating area while increasing the flue gas flow cross-sectional area, preventing the adhesion of fuels and bridging to form flue gas corridors. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is an enlarged view of the interior of the furnace of the present invention; In the figure: 1. Furnace, 2. Feeding device, 3. Return device, 4. Secondary air inlet, 5. Air distribution plate, 6. Cyclone separator, 7. Tail flue, 8. Superheater, 9. Economizer, 10. Air preheater, 11. Evaporative water cooling screen, 12. Soot blowing device, I. Preheating mixing zone, II. Furnace combustion zone, III. Furnace heat exchange zone. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: Figure 1 and Figure 2 As shown, a circulating fluidized bed boiler suitable for high-coking fuel includes a furnace 1, a feeding device 2, a return device 3, a secondary air inlet 4, an air distribution plate 5, a cyclone separator 6, a tail flue 7 and a superheater 8. The furnace is divided into three areas, which are: a preheating mixing area I, a furnace combustion area II and a furnace heat exchange area III from bottom to top. Refractory castables are laid inside the furnace to form an insulated furnace. A superheater is arranged in the furnace heat exchange area above the furnace, and an evaporative water cooling screen 11 is added below the superheater in the furnace.

[0017] The feeding device is connected to the preheating mixing zone in the furnace. The bottom end of the cyclone separator is connected to the preheating mixing zone in the furnace through the return device.

[0018] An air distribution plate is provided at the bottom of the preheating mixing zone in the furnace and is connected to the primary air inlet. The secondary air inlet is connected to the furnace combustion zone in the furnace.

[0019] Refractory castables are laid on the water-cooled walls around the lower furnace at the bend of the front and rear walls of the furnace combustion zone. Multi-stage economizers 9 are arranged in the tail flue, and each row of economizers is connected by a transverse flue.

[0020] The tail flue is also provided with an air preheater 10, which is arranged separately from the economizer and is connected to each other through a transverse flue. A soot blower 12 is provided in the tail flue at the location corresponding to the economizer.

[0021] During boiler operation, the primary hot air required for combustion enters through the primary air box located at the furnace bottom. It is fluidized by the air cap arranged on the air distribution plate 5 and serves as the boiler's fluidizing air. Secondary air, through the secondary air port 4, enters the furnace and participates in combustion. The primary and secondary air strongly disturb the fuel in the furnace, allowing it to quickly dry and mix, promoting complete combustion.

[0022] By adopting the present invention, by adjusting the primary air volume and the secondary air volume, the combustion can be precisely adjusted, the air distribution plate temperature is controlled within the range of 880°C to 900°C, the flue gas temperature at the outlet of the furnace combustion zone II is controlled within the range of 900°C to 1050°C, the flue gas temperature at the outlet of the furnace heat exchange zone III is controlled within the range of 800°C to 900°C, and the oxygen content is controlled within the range of 2.5% to 3.5%, thereby achieving the purpose of controlling combustion. For a circulating fluidized bed boiler burning a high-coking fuel, after the fuel enters the furnace, due to the large heat capacity and high temperature level in the furnace, the fuel is fully preheated, dried, and mixed, and can be completely burned. In addition, a water-cooled screen heating surface is added to the furnace, and the transverse intercept of the remaining heating surfaces is widened to ensure complete combustion of the fuel while preventing the fuel from coking.

[0023] By adopting the present invention, an evaporative water cooling screen 11 is added below the superheater 8 in the furnace 1 to increase the heating area in the furnace to increase heat absorption, thereby reducing the flue gas temperature in the furnace and preventing the high coking fuel from melting due to excessive flue gas temperature and sticking to the heating surface.

[0024] When the present invention is used, the fuel enters the waste heat mixing zone I from the feeding device 2 at the lower part of the front wall, the primary air enters the furnace from the air distribution plate 5 at the bottom of the furnace to fluidize the circulating material, the secondary air enters the furnace from the secondary air port 4, and then the fuel in the preheating mixing zone I, after preheating, drying and mixing, enters the furnace combustion zone II for combustion, the fine particles and circulating ash produced by the combustion rise with the flue gas, enter the furnace heat exchange zone III and exchange heat with the working medium in the superheater, and then the flue gas enters the cyclone separator 6, and the separated circulating ash returns to the furnace from the return device 3 at the lower part of the rear wall to continue the material circulation, and the flue gas enters the boiler tail flue 7 to exchange heat with the tail heating surface. Among them, the tail heating surfaces such as the superheater, economizer, and air preheater are arranged according to the design requirements to heat the working medium in the heating surface and reduce the exhaust gas temperature. The economizer 10 adopts a multi-stage split arrangement to supplement the preheating and evaporation heating surface to ensure the load capacity of the boiler.

[0025] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A circulating fluidized bed boiler suitable for high-coking fuel, comprising a furnace (1), a feeding device (2), a return device (3), a secondary air inlet (4), an air distribution plate (5), a cyclone separator (6), a tail flue (7) and a superheater (8), wherein: The furnace (1) is divided into three areas, which are: a preheating mixing area (I), a furnace combustion area (II) and a furnace heat exchange area (III) from bottom to top. Refractory castables are laid inside the furnace (1) to form an insulated furnace. A superheater (8) is arranged in the furnace heat exchange area (III) above the furnace (1). An evaporative water cooling screen (11) is added below the superheater (8) in the furnace (1).

2. A circulating fluidized bed boiler suitable for high coking fuel according to claim 1, characterized in that: The feeding device (2) is connected to the preheating mixing zone (I) in the furnace (1).

3. A circulating fluidized bed boiler suitable for high coking fuel according to claim 1, characterized in that: The bottom end of the cyclone separator (6) is connected to the preheating mixing zone (I) in the furnace (1) through the return device (3).

4. A circulating fluidized bed boiler suitable for high coking fuel according to claim 1, characterized in that: An air distribution plate is provided at the bottom end of the preheating mixing zone (I) in the furnace (1) and is connected to the primary air inlet.

5. A circulating fluidized bed boiler suitable for high coking fuel according to claim 1, characterized in that: The secondary air port (4) is connected to the furnace combustion zone (II) in the furnace (1).

6. A circulating fluidized bed boiler suitable for high coking fuel according to claim 1, characterized in that: The refractory castable is laid on the water-cooled wall around the lower part of the furnace at the bend of the front and rear walls of the furnace combustion zone (II) in the furnace (1).

7. A circulating fluidized bed boiler suitable for high coking fuel according to claim 1, characterized in that: The tail flue (7) is provided with multi-stage economizers (9) arranged in rows, and each row of economizers (9) is connected to each other via a transverse flue.

8. A circulating fluidized bed boiler suitable for high coking fuel according to claim 7, characterized in that: The tail flue (7) is further provided with an air preheater (10), and the air preheater (10) and the economizer (9) are distributed separately and are connected at intervals through a transverse flue.

9. A circulating fluidized bed boiler suitable for high coking fuel according to claim 7, characterized in that: A soot blowing device (12) is provided in the tail flue (7) at a position corresponding to the economizer.

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