A biomass co-combustion system in the dense phase zone of a circulating fluidized bed boiler

Abstract

The present invention discloses a biomass blending and burning system in a dense phase zone of a circulating fluidized bed boiler. The system utilizes the oil gun hole on the original right wall bed as the furnace inlet for biomass fuel, delivers the biomass to the upper part of the boiler through a closed belt conveyor, and then utilizes a feed pipe to communicate with the furnace inlet through a vacuum generating device, so that the biomass is delivered to the furnace; and a sealing air is designed and arranged at the furnace inlet to prevent the high-temperature flue gas generated by the combustion in the furnace from flowing back; the system adopts a variety of technical means to effectively solve the problems of biomass blocking and flue gas flowing back, reduce the failure rate of the conveying system, improve the efficiency of the blending and burning in the furnace, and achieve the purpose of replacing coal; fully utilizes the vacuum generating device formed by the high-pressure fluidizing air with a high-pressure head and the venturi nozzle to form a negative pressure inside the feed pipe to generate siphoning, greatly improve the smoothness of the conveying, and reduce the overflow of smoke and dust, further reduce the impact on environmental protection, and make the biomass blending and burning safer and more efficient.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power generation, and in particular to a biomass blending combustion system in a dense phase zone of a circulating fluidized bed boiler. Background Art

[0002] Affected by the coal market, the cost of power generation in thermal power plants has increased significantly, and they are facing the challenge of increasing operating pressure. Biomass blending not only solves the problem of environmental pollution, but also solves the fuel problem of power plants. At present, there are two ways to blend biomass in large thermal power boilers: 1. The crushed biomass is blended with raw coal and sent to the furnace for blending through belt transportation. 2. The crushed biomass is sent to the furnace for blending through a long-distance pneumatic conveying pipeline. The disadvantages of these two solutions are:

[0003] Biomass has the characteristics of poor transport fluidity and uneven crushing. When mixed with raw coal and put into the furnace for combustion, it will lead to problems such as poor fuel entry into the furnace and transportation blockage. It will also be entangled on the rotating shaft of the rotating machinery, causing damage to the boiler fuel transportation system equipment, greatly reducing the stability and safety of boiler operation;

[0004] The method of entering from the top of the boiler and pneumatically conveying and burning over long distances requires a large amount of high-pressure gas to be transported from the ground fuel depot to the furnace inlet at the top of the furnace through a long-distance pipeline. This method enters from the top of the furnace (the distance from the furnace outlet), and there are problems such as short combustion distance, incomplete combustion, and low combustion efficiency. In addition, a large amount of air enters the furnace to increase the amount of oxygen involved in boiler combustion, resulting in high nitrogen oxide (atmospheric pollutant) generation values, resulting in excessive use of urea for reducing nitrogen oxide emissions and increased costs. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a biomass co-firing system in the dense phase zone of a circulating fluidized bed boiler, the purpose of which is to solve the above-mentioned technical problems.

[0006] In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical scheme: a circulating fluidized bed boiler dense phase zone biomass blending system, the system uses the oil gun hole on the original right wall bed as the inlet of biomass fuel, sends the biomass to the upper part of the boiler through a closed belt conveyor, and then uses a down pipe to connect with the inlet through a vacuum generating device to send the biomass into the furnace; and a sealing air is set at the inlet to prevent the high-temperature flue gas generated by the combustion in the furnace from flowing back.

[0007] Preferably, a feed hopper is arranged above the discharge pipe, and a pneumatic plug door 1, an expansion joint, and a pneumatic plug door 2 are installed on the body of the discharge pipe in sequence from top to bottom, and a number of disturbance air ducts are arranged on the discharge pipe; a furnace inlet pipe and a furnace inlet are arranged in sequence below the discharge pipe.

[0008] Preferably, a material blockage measuring point is installed at a distance close to the upper side of the expansion joint, and a safety interlock logic is set between the material blockage measuring point and the pneumatic plug door 1 and the pneumatic plug door 2. The interlock closes the pneumatic plug door 1 and the pneumatic plug door 2 in sequence, so that the material blockage can be discovered in time and effectively to prevent the blockage from further expanding.

[0009] Preferably, the boiler cold primary air is connected to the furnace inlet pipe near the furnace inlet on the side close to the water-cooled wall as the sealing air of the furnace inlet pipe;

[0010] The vacuum generating device includes: at the head of the furnace inlet pipe, a vacuum generating device is formed by using high-pressure fluidizing air with a higher pressure head through the venturi nozzle-shaped furnace inlet pipe, so that negative pressure is formed in the discharge pipe, generating a siphon effect, sucking the free-falling material in the discharge pipe into the furnace pipe and blowing it into the furnace.

[0011] Preferably, the feed hopper is fully sealed, a switchable observation window is installed on its surface, and a camera is installed inside the hopper for remote observation by the operator, so that the internal feeding situation can be observed in real time.

[0012] Preferably, a temperature sensor is installed at the second pneumatic gate, and the signal is connected to the temperature controller. The interlock closes the second pneumatic gate first and then the first pneumatic gate, thereby effectively preventing the high-temperature smoke from overflowing.

[0013] Preferably, since the furnace inlet pipe and the boiler body expand in the same direction, an expansion joint is installed on the upper part of the second pneumatic gate in order to protect the safety and smoothness of the biomass input.

[0014] Preferably, a furnace inlet pipe with a matching diameter is installed at the furnace inlet, and the furnace inlet pipe forms an angle of 45° with the horizontal; the bottom of the discharge pipe is connected to an inclined pipe, which is connected to the middle of the furnace inlet pipe, and the discharge pipe and the furnace inlet pipe maintain the same inclination angle for discharge.

[0015] Preferably, the furnace inlet pipe and the right water-cooled wall are sealed by a sealing box.

[0016] In summary, the present invention provides a biomass blending system in the dense phase zone of a circulating fluidized bed boiler. This patent uses a series of technologies to fully utilize the space of the original boiler equipment to install the furnace pipe mouth, thereby reducing the construction cost; this system uses a variety of technical means to effectively solve the problems of biomass blockage and flue gas backflow, reduce the failure rate of the transportation system, and improve the efficiency of blending into the furnace to achieve the purpose of replacing coal; this system uses pipeline transportation to effectively improve the biomass transportation efficiency, reduce the environmental risks caused by open-air transportation of biomass, and safely, environmentally friendly and efficiently dispose of biomass; using the advantages of pipeline transportation, fully utilizing the vacuum generating device formed by high-pressure fluidizing air with a high-pressure head and the Venturi nozzle, so that negative pressure is formed inside the discharge pipe to produce siphoning, greatly improving the smoothness of transportation, while reducing smoke and dust overflow, further reducing the impact on environmental protection, and making biomass blending safer and more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a biomass blending combustion system in a dense phase zone of a circulating fluidized bed boiler of the present invention;

[0018] In the figure: furnace inlet 1, discharge pipe 2, sealing air 3, feed hopper 4, pneumatic plug-in door 1 5, expansion joint 6, pneumatic plug-in door 2 7, disturbance air duct 11, furnace inlet pipe 12, boiler cold primary air 13, temperature sensor 14, inclined pipe 15, high-pressure fluidizing air 16, Venturi nozzle 17. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] like Figure 1 As shown: The present invention is a system that fully considers the issues of transportation, environmental protection, and combustion efficiency. The oil gun hole on the original right wall bed is 30 meters away from the furnace outlet as the inlet 1 for biomass fuel. The biomass is sent to the upper part of the boiler through a closed belt conveyor, and then sent into the furnace through a material discharge pipe 2 through a vacuum generating device;

[0021] The oil gun hole on the original right wall bed as the furnace inlet 1 has the advantages of long combustion distance and sufficient combustion, which can well solve the problem of excessive environmental data and large urea consumption caused by the biomass furnace top entering the furnace;

[0022] Two pneumatic gates are provided on the feeding pipe 2, and a certain number of disturbance air ducts 11 are provided on the feeding pipe 2. The disturbance air ducts 11 are preferably distributed on both sides of the feeding pipe 2 in the vertical direction and are distributed at intervals, which can effectively improve the smoothness of feeding and solve the problem of blockage of feeding of different types of biomass;

[0023] A material blocking measuring point is installed at a distance from the upper side of the expansion joint 6 and a safety interlocking logic is set for the pneumatic plug-in door 1 5 and the pneumatic plug-in door 2 7. The interlocking sequentially closes the pneumatic plug-in door 1 5 and the pneumatic plug-in door 2 7, which can timely and effectively detect the material blocking and prevent the further expansion of the material blocking;

[0024] On the side close to the water-cooled wall, the cold primary air 13 of the boiler is connected to the inlet furnace tube 12 as the sealing air 3 of the inlet furnace tube 12. The sealing air 3 seals the hot flue gas in the furnace, which can prevent the flue gas in the furnace from flowing back and ensure the safety of feeding. At the same time, it also has a certain cooling effect on the inlet furnace tube 12, reducing the stress between the tube wall and the water-cooled wall.

[0025] The vacuum generating device is configured as follows: at the head of the furnace inlet pipe 12, a vacuum generating device is formed by using a high-pressure fluidizing air 16 with a higher pressure head through the furnace inlet pipe 12 in the shape of a venturi nozzle 17, so that a negative pressure is formed in the discharge pipe 2, and a siphon effect is generated, so that the free-falling material in the discharge pipe 2 is sucked into the furnace pipe 12 and blown into the furnace, which greatly improves the smoothness of biomass entering the furnace, solves the problem of poor fluidity of biomass and difficulty in transporting, and at the same time, the high-pressure transporting air can further prevent the hot material in the furnace from flowing back;

[0026] Specifically, the crushed biomass enters the feed pipe 2 through the feeding port at the top of the furnace, and then falls into the furnace inlet pipe 12 driven by the gravity and negative pressure of the biomass itself, and is blown into the furnace by high-pressure conveying wind, thereby avoiding the biomass from being concentrated on the right side of the furnace to burn and cause local overheating.

[0027] In at least one embodiment, the feed hopper 4 is fully sealed to effectively control the environmental pollution caused by the smoke overflow and dust from the furnace. A switchable observation window is installed at a suitable position, and a camera for remote observation by the operator is installed inside the hopper to observe the internal feeding situation in real time.

[0028] At least in one embodiment, a temperature sensor is installed at a suitable position on the upper part of the pneumatic gate 2 7, and the signal is connected to the temperature controller, which is interlocked to close the gate 2 first and then the gate 1, effectively preventing the high-temperature smoke from overflowing;

[0029] At least in one embodiment, since the furnace inlet pipe 12 and the boiler body expand in the same direction, in order to protect the safety and smoothness of the biomass input, an expansion joint 6 is installed on the upper part of the pneumatic gate 2 7;

[0030] At least in one embodiment, the bottom of the feed pipe 2 is connected to an inclined pipe 15, which is connected to the middle of the furnace inlet pipe 12, and the feed pipe 2 and the furnace inlet pipe 12 are kept in the same direction of inclination angle to feed, so as to avoid back blowing of conveying wind;

[0031] Compared with the existing boiler biomass combustion method, the patent of this invention achieves the following technical improvements:

[0032] Make full use of the original space of the oil gun mouth on the right wall bed of the boiler as the biomass input port, install a furnace inlet pipe 12 with a matching diameter, and the furnace inlet pipe 12 forms an angle of 45° with the horizontal, which effectively improves the smoothness of biomass entering the furnace;

[0033] The furnace inlet pipe 12 and the right wall water-cooled wall are sealed by a sealing box, which effectively isolates heat loss, smoke leakage, and transfers the weight of the furnace inlet pipe 12, making the structure safer and more stable;

[0034] The feed pipe 2 is installed with pneumatic gate 1 5, expansion joint 6, and pneumatic gate 2 7 from top to bottom. A sealing wind 3 is designed at the end of the furnace inlet pipe 12, and the boiler cold primary air 13 is used as the sealing wind 3 to effectively prevent the high-temperature flue gas generated by the combustion in the furnace from flowing back. At the head of the furnace inlet pipe 12, cold primary air and high-pressure fluidizing air 16 with a high-pressure head are designed as high-pressure conveying air. After the high-speed flowing gas is ejected through the Venturi nozzle, a vacuum area is generated near the nozzle, and a negative pressure is formed inside the feed pipe 2 to suck the biomass into and send it into the furnace. Each air source is controlled by an electric regulating butterfly valve to control the valve opening. The size of the negative pressure of the feed pipe 2 is controlled according to the different back pressures of the furnace inlet 1 to ensure stable sealing under various working conditions in the furnace to prevent the hot material in the furnace from flowing back, such as Figure 1 As shown;

[0035] A temperature sensor is installed on the upper part of the pneumatic gate 2 7, and the signal is connected to the temperature controller. When the temperature exceeds the set value, the interlock closes the gate 2 first and then the gate 1, effectively preventing the high-temperature smoke from overflowing;

[0036] Install a material blocking measuring point at a suitable position near the upper side of the expansion joint 6 and set a safety interlock logic for the pneumatic plug-in door 1 5 and the pneumatic plug-in door 2 7. The interlock sequentially closes the pneumatic plug-in door 1 5 and the pneumatic plug-in door 2 7, which can effectively detect the material blocking in time and prevent the further expansion of the material blocking;

[0037] The biomass is conveyed by a belt to the feeding port at an elevation of 56 meters, enters the discharge pipe 2, and then falls into the furnace inlet pipe 12, and is sent into the furnace by high-pressure conveying wind, which avoids the biomass from being concentrated on the right side of the furnace and causing local overheating.

[0038] The embodiments of the present invention are only used to illustrate the present invention and do not constitute a limitation on the scope of the claims. Other substantially equivalent substitutes that can be thought of by those skilled in the art are all within the protection scope of the present invention.

Claims

1. A circulating fluidized bed boiler dense phase zone biomass co-firing system, characterized in that: The system uses the oil gun hole on the original right wall bed as the furnace inlet (1) for biomass fuel, delivers the biomass to the upper part of the boiler through a closed belt conveyor, and then uses a feed pipe (2) to communicate with the furnace inlet (1) through a vacuum generating device, so that the biomass is delivered into the furnace; A sealing air (3) is provided at the furnace inlet (1) to prevent the high-temperature flue gas generated by the combustion in the furnace from flowing back; A feed hopper (4) is arranged above the material discharge pipe (2); a pneumatic gate door 1 (5), an expansion joint (6), and a pneumatic gate door 2 (7) are sequentially installed on the body of the material discharge pipe (2) from top to bottom, and a plurality of disturbance air ducts (11) are arranged on the material discharge pipe (2); a furnace inlet pipe (12) and a furnace inlet (1) are sequentially arranged below the material discharge pipe (2); On the side close to the water-cooled wall, the furnace inlet pipe (12) is connected to the boiler cold primary air (13) near the furnace inlet (1) as the sealing air (3) of the furnace inlet pipe (12), the diameter of the furnace inlet (1) is matched with the diameter of the furnace inlet pipe (12), and the furnace inlet pipe (12) forms an angle of 45° with the horizontal; The bottom of the material discharge pipe (2) is connected to an inclined pipe (15), the inclined pipe (15) is connected to the middle of the furnace inlet pipe (12), and the material discharge pipe (2) and the furnace inlet pipe (12) maintain the same inclination angle for material discharge; At the head of the furnace inlet pipe (12), a vacuum generating device is formed by using a high-pressure fluidizing air (16) with a higher pressure head through the furnace inlet pipe (12) in the shape of a venturi nozzle (17), so that a negative pressure is formed in the discharge pipe (2), generating a siphon effect, and sucking the free-falling material in the discharge pipe (2) into the furnace pipe (12) and blowing it into the furnace.

2. The circulating fluidized bed boiler dense phase zone biomass co-firing system according to claim 1, characterized in that: A material blockage measuring point is installed at the portion of the feed pipe (2) located on the upper side of the expansion joint (6). A safety interlocking logic is set between the material blockage measuring point and the pneumatic plug-in door 1 (5) and the pneumatic plug-in door 2 (7). The interlocking sequentially closes the pneumatic plug-in door 1 (5) and the pneumatic plug-in door 2 (7), thereby timely and effectively discovering the material blockage and preventing the further expansion of the material blockage.

3. The circulating fluidized bed boiler dense phase zone biomass co-firing system according to claim 1, characterized in that: The feed hopper (4) is fully sealed, a switchable observation window is installed on its surface, and a camera for remote observation by operating personnel is installed inside the feed hopper (4), so that the internal feeding situation can be observed in real time.

4. The circulating fluidized bed boiler dense phase zone biomass co-firing system according to claim 1, characterized in that: A temperature sensor (14) is installed at the second pneumatic gate (7), and the signal is connected to the temperature controller. The interlock closes the second pneumatic gate (7) first and then the first pneumatic gate (5), effectively preventing the high-temperature smoke from overflowing.

5. The circulating fluidized bed boiler dense phase zone biomass co-firing system according to claim 1, characterized in that: Since the furnace inlet pipe (12) and the boiler body expand in the same direction, in order to protect the safety and smoothness of the biomass input, an expansion joint (6) is installed on the upper part of the second pneumatic gate (7).

6. The circulating fluidized bed boiler dense phase zone biomass co-firing system according to claim 1, characterized in that: The furnace inlet pipe (12) and the right water-cooled wall are sealed by a sealing box.

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