A fly ash recycling system for a carbon-in-pulp bed

Abstract

The application discloses a fly ash recycling system of carbon-containing fluidized bed and belongs to the technical field of gasification furnace ignition systems. The application comprises a fluidized bed boiler and a coal powder bin. The fluidized bed boiler comprises a secondary air reaction zone in the middle and a fly ash pre-combustion zone at the bottom. Fly ash in the coal powder bin is input into the fly ash pre-combustion zone, and the fly ash pre-combustion zone is an oxygen-rich area. Secondary air is introduced into the secondary air reaction zone. A high-temperature gas-solid mixture formed after the fly ash is combusted and reacted in the fly ash pre-combustion zone is introduced into the secondary air reaction zone to generate secondary reaction. In view of the problems in the prior art, the application provides a fly ash recycling system of carbon-containing fluidized bed. By adopting a cascade combustion technology and a two-stage reaction zone, the recycling efficiency of the fluidized bed fly ash with low activity is greatly improved, the system can maintain self-sustaining combustion without additional fuel, energy consumption is greatly reduced, and production benefit is improved.

Description

Technical Field

[0001] This invention relates to the field of fluidized bed technology, and more specifically, to a fly ash recycling system for a carbon-containing fluidized bed. Background Technology

[0002] In the current industrial system, coal is generally utilized in two ways: one is to generate heat through coal combustion, which is then used for other purposes after heat exchange; the other is to produce coal gas through coal gasification, which is then used as fuel or chemical synthesis gas.

[0003] During coal gas production, a gasification reaction occurs, generating fluidized bed fly ash with high carbon content and low volatile matter. The carbon in this fly ash cannot be fully utilized, and treating it as solid waste would result in resource waste and environmental pollution. Therefore, the treatment and reuse of this type of low-activity fluidized bed fly ash has become an urgent technical challenge for the industry.

[0004] A search revealed that technologies for the treatment and reuse of fluidized bed fly ash are already publicly available in the industry. For example, Chinese patent application number 2016210946955 discloses a carbon-containing fluidized bed fly ash combustion system. This system includes: a combustion device, a combustion-supporting device for providing an adjustable and continuous ignition source to the combustion device, an air supply device for providing combustion-supporting air to the combustion device, a heat recovery device, and a flue gas treatment device. The input end of the combustion device is connected to the combustion-supporting device and the air supply device, respectively, and the output end of the combustion device is connected to the input end of the heat recovery device. The output end of the heat recovery device is connected to the flue gas treatment device. The heat recovery device is used to collect the heat generated during the combustion of carbon-containing fly ash in the combustion device. However, this system requires a combustion-supporting device to provide an adjustable and continuous ignition source and uses other fuels simultaneously during the fluidized bed fly ash treatment process, thus failing to achieve the goal of environmentally friendly treatment of fluidized bed fly ash. Summary of the Invention

[0005] 1. The technical problem that the invention aims to solve

[0006] To address the problems existing in the prior art, this invention aims to provide a fly ash reuse system for a carbon-containing fluidized bed. By adopting a cascade combustion technology and a two-stage reaction zone, the reuse efficiency of low-activity fluidized bed fly ash is greatly improved. Moreover, the system can maintain self-sustaining combustion without additional fuel, which greatly reduces energy consumption and improves production efficiency.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0009] The present invention discloses a fly ash reuse system in a carbon-containing fluidized bed, comprising a fluidized bed boiler and a pulverized coal silo. The fluidized bed boiler includes a secondary air reaction zone in the middle and a fly ash pre-combustion zone at the bottom. Fly ash in the pulverized coal silo is fed into the fly ash pre-combustion zone, which is an oxygen-rich area. Secondary air is introduced into the secondary air reaction zone, wherein the high-temperature gas-solid mixture formed after the fly ash undergoes combustion reaction in the fly ash pre-combustion zone enters the secondary air reaction zone to undergo a secondary reaction.

[0010] As a further improvement of the present invention, the solids in the high-temperature gas-solid mixture after the secondary reaction are discharged from the bottom of the fluidized bed boiler in the form of slag, and the flue gas in the high-temperature gas-solid mixture after the secondary reaction is discharged from the top of the fluidized bed boiler. The discharged flue gas is discharged into the atmosphere after flue gas treatment, and a small amount of fly ash in the flue gas is sent to the outside for use.

[0011] As a further improvement of the present invention, the reaction temperature in the fly ash pre-combustion zone is 1200℃~1350℃; the reaction temperature in the secondary air reaction zone is 900℃~950℃.

[0012] As a further improvement of the present invention, the fly ash in the pulverized coal silo is fed into the fly ash pre-combustion zone through the fly ash conveying pipe at the bottom, and the oxygen in the fly ash pre-combustion zone is supplied through the oxygen supply pipe.

[0013] As a further improvement of the present invention, an igniter is also provided on the fly ash pre-combustion zone, and the igniter is connected to the natural gas pipeline and the ignition fan.

[0014] As a further improvement of the present invention, the secondary air in the secondary air reaction zone is supplied through a secondary air duct, and a secondary air fan is provided on the secondary air duct.

[0015] As a further improvement of the present invention, the flue gas discharged from the top of the fluidized bed boiler is successively treated by the denitrification unit, the bag filter and the desulfurization tower before being discharged into the atmosphere, and a small amount of fly ash in the flue gas is sent to the outside for use by the bag filter.

[0016] As a further improvement of the present invention, the upper part of the fluidized bed boiler is provided with a heat utilization zone. After the boiler feedwater enters the fluidized bed boiler, it reacts with the hot flue gas generated in the fly ash pre-combustion zone to generate high-temperature steam. The pressure of the high-temperature steam is 1.6 MPa to 9.9 MPa.

[0017] As a further improvement of the present invention, a boiler feedwater pipe is provided on the top of the fluidized bed boiler, and an economizer feedwater pipe is provided on the economizer.

[0018] As a further improvement of the present invention, a coal powder feeding pipe is provided at the top of the coal powder silo, and a coal powder feeder is provided at the bottom of the coal powder silo.

[0019] 3. Beneficial effects

[0020] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0021] (1) The present invention provides a fly ash reuse system for a carbon-containing fluidized bed boiler. The fluidized bed boiler employs staged combustion technology. An oxygen-enriched fly ash pre-combustion zone is set in the lower part of the fluidized bed boiler. Through oxygen enrichment and reaction with fly ash, the reaction temperature is increased, and the fly ash activity is greatly increased, causing the fluidized bed fly ash to heat up rapidly. During this stage, a large amount of carbon in the fluidized bed fly ash is reacted to form a high-temperature gas-solid mixture. A secondary air reaction zone is set in the middle of the fluidized bed boiler. The high-temperature gas-solid mixture undergoes a secondary reaction in the secondary air reaction zone, increasing the flue gas volume and causing the temperature of the gas-solid mixture to decrease uniformly.

[0022] (2) The carbon-containing fluidized bed fly ash reuse system of the present invention, through the use of cascade combustion technology and the combination of two-stage reaction zones, greatly improves the reuse efficiency of low-activity fluidized bed fly ash, and can maintain self-sustaining combustion of the system without additional fuel, which greatly reduces energy consumption and improves production efficiency. At the same time, the use of pneumatic conveying as the main conveying process prevents ash leakage during the operation of the system, which greatly improves the on-site working environment.

[0023] (3) The present invention provides a carbon-containing fluidized bed fly ash recycling system. Since the fluidized bed fly ash is coal ash after a primary reaction, its activity is very low and it is difficult to burn. In order to enable it to burn fully, the reaction temperature is increased to improve the reactivity of the fly ash. Therefore, an oxygen-enriched fly ash pre-combustion zone needs to be set up at the bottom of the boiler and the temperature is raised to 1200℃~1350℃. At this time, the reaction temperature has reached above the melting point of the fly ash, and the fly ash is in a molten state. However, when the temperature rises to 1200℃~1350℃, coking will occur in the furnace. Therefore, it is necessary to increase the quenching and reaction effect of the secondary air reaction zone through the organization of the flow field. The main function of the secondary air reaction zone is, on the one hand, to further react the secondary air with the unreacted fly ash again, with a reaction temperature of 900~950℃, so as to improve the carbon conversion rate in the fly ash. On the other hand, since excessive secondary air will produce a quenching effect on the high-temperature flue gas, it will play a cooling role, so that the high-temperature molten slag will turn back into solid slag and prevent coking. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a fly ash recycling system with a carbon-containing fluidized bed according to the present invention.

[0025] Explanation of the labels in the diagram:

[0026] 100. Pulverized coal silo; 101. Pulverized coal conveying pipeline; 110. Pulverized coal feeder; 111. Fly ash conveying pipeline; 120. Pulverized coal conveying fan; 130. Dust collector; 131. Compressed air pipeline;

[0027] 200. Fluidized bed boiler; 201. Oxygen supply pipeline; 202. Secondary air pipeline; 203. Boiler feedwater pipeline; 204. Secondary air fan; 210. Secondary air reaction zone; 220. Fly ash pre-combustion zone; 230. Denitrification unit; 240. Economizer; 241. Economizer feedwater pipeline; 250. Ignition device; 251. Ignition fan; 260. Natural gas pipeline;

[0028] 300. Baghouse dust collector; 400. Desulfurization tower; 500. Chimney. Detailed Implementation

[0029] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0030] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] The present invention will be further described below with reference to embodiments.

[0032] To address the problems existing in the prior art, this invention aims to provide a fly ash recycling system containing a carbon fluidized bed. Example 1

[0033] like Figure 1As shown, this embodiment of a carbon-containing fluidized bed fly ash recycling system includes a fluidized bed boiler 200 and a pulverized coal silo 100. The fluidized bed boiler 200 includes a secondary air reaction zone 210 in the middle and a fly ash pre-combustion zone 220 at the bottom. Fly ash in the pulverized coal silo 100 is input into the fly ash pre-combustion zone 220, which is an oxygen-rich area. Secondary air is introduced into the secondary air reaction zone 210. Specifically, in this embodiment, the fly ash in the pulverized coal silo 100 is input into the fly ash pre-combustion zone 220 through a fly ash conveying pipe 111 at the bottom, and oxygen in the fly ash pre-combustion zone 220 is supplied through an oxygen supply pipe 201, making the secondary air reaction zone 210 an oxygen-rich environment. The secondary air in the secondary air reaction zone 210 is supplied through a secondary air pipe 202, and a secondary air fan 204 is installed on the secondary air pipe 202. The high-temperature gas-solid mixture formed after the fly ash undergoes combustion in the fly ash pre-combustion zone 220 enters the secondary air reaction zone 210 for secondary reaction. In this embodiment, the fluidized bed boiler 200 employs staged combustion technology. An oxygen-enriched fly ash pre-combustion zone 220 is located at the bottom of the boiler. Through oxygen enrichment and reaction with the fly ash, the reactivity of the fluidized bed fly ash is enhanced, and the fly ash temperature rises rapidly. During this stage, a large amount of carbon in the fly ash is reacted, forming a high-temperature gas-solid mixture. A secondary air reaction zone 210 is located in the middle of the boiler 200. The high-temperature gas-solid mixture undergoes secondary reaction in the secondary air reaction zone 210, increasing the flue gas volume and decreasing the temperature of the gas-solid mixture.

[0034] In this process, the solids in the high-temperature gas-solid mixture after the secondary reaction collide and adhere to the furnace wall in the secondary air reaction zone 210, forming large slag particles. These slag particles are discharged from the bottom of the fluidized bed boiler 200 as slag. The flue gas from the high-temperature gas-solid mixture after the secondary reaction is discharged from the top of the fluidized bed boiler 200. After flue gas treatment, the discharged flue gas is released into the atmosphere, and a small amount of fly ash in the flue gas is sent for external use. In this embodiment, the use of cascade combustion technology and the combination of two-stage reaction zones greatly improves the reuse efficiency of low-activity fluidized bed fly ash. Furthermore, the system can maintain self-sustaining combustion without additional fuel, significantly reducing energy consumption and improving production efficiency. Simultaneously, the use of pneumatic conveying as the main conveying process prevents ash leakage during system operation, greatly improving the on-site working environment.

[0035] In this embodiment, the reaction temperature in the fly ash pre-combustion zone 220 is 1200℃~1350℃; the reaction temperature in the secondary air reaction zone 210 is 900℃~950℃. Specifically, in this embodiment, the reaction temperature in the fly ash pre-combustion zone 220 is 1200℃; the reaction temperature in the secondary air reaction zone 210 is 900℃. Since fluidized bed fly ash is coal ash after a primary reaction, its activity is very low and it is difficult to burn. To ensure complete combustion, the reaction temperature is increased to enhance the fly ash's reactivity. Therefore, an oxygen-enriched fly ash pre-combustion zone 220 needs to be set up at the bottom of the boiler, and the temperature is raised to 1200℃~1350℃. At this point, the reaction temperature has reached above the melting point of the fly ash, and the fly ash is in a molten state. However, when the temperature rises to 1200℃~1350℃, coking will occur inside the furnace. Therefore, it is necessary to increase the quenching and reaction effect of the secondary air reaction zone 210 by organizing the flow field. The main function of the secondary air reaction zone 210 is to further react the secondary air with the unreacted fly ash at a reaction temperature of 900~950℃ to improve the carbon conversion rate in the fly ash. In addition, the excessive secondary air will have a quenching effect on the high-temperature flue gas, which will cool it down and turn the high-temperature molten slag back into solid slag, preventing coking.

[0036] In this embodiment, an igniter 250 is also installed on the fly ash pre-combustion zone 220. The igniter 250 is connected to a natural gas pipeline 260 and an ignition fan 251. The natural gas pipeline 260 provides ignition fuel gas for boiler startup. After successful ignition, fly ash and pure oxygen are sequentially introduced into the boiler, generating high temperatures above the fly ash pre-combustion zone 220. A large amount of carbon in the fly ash is reacted, and combustion can continue without further fuel, significantly saving energy consumption. In this embodiment, a pulverized coal silo 100 has a pulverized coal feeding pipe 101 at its upper part and a pulverizer 110 at its bottom. The pulverized coal silo 100 is a circular storage silo with a dust collector 130 installed on its upper part. The dust collector 130 has a compressed air pipeline 131 for purifying the exhaust gas. The lower part of the pulverized coal silo 100 is a hyperbolic cone to ensure smooth material feeding. Under normal operating conditions, fluidized bed fly ash generated from coal gasification or other processes is conveyed to the pulverized coal silo 100 via pneumatic conveying. The feed rate is adjusted by the rotational speed of the pulverizer 110. The fluidized bed fly ash falling from the pulverizer 110 is then conveyed by the Roots blower 120 through the fly ash conveying pipeline 111 to the fly ash pre-combustion zone 220 at the bottom of the fluidized bed boiler 200 for combustion treatment.

[0037] In this embodiment, the flue gas discharged from the top of the fluidized bed boiler 200 is sequentially treated by the denitrification unit 230, the bag filter 300, and the desulfurization tower 400 before being discharged into the chimney 500 and then into the atmosphere, ensuring that the discharged exhaust gas meets national standards. A small amount of fly ash in the flue gas is sent to the outside via the bag filter 300 for use in cement rotary kilns. The top of the fluidized bed boiler 200 is equipped with a boiler feedwater pipe 203, and the economizer 240 is equipped with an economizer feedwater pipe 241. The upper part of the fluidized bed boiler 200 has a heat utilization zone. After the boiler feedwater enters the fluidized bed boiler 200, it reacts with the hot flue gas generated in the fly ash pre-combustion zone 220 to produce high-temperature steam. The pressure of the high-temperature steam is 1.6 MPa to 9.9 MPa; specifically, in this embodiment, the pressure of the high-temperature steam is 1.6 MPa. The calorific value of fluidized bed fly ash used as raw material needs to be between 3500 and 6000 kcal / kg. Due to its high carbon content, if fluidized bed fly ash is treated as solid waste using conventional methods, it will not only pollute the environment but also cause significant economic losses.

[0038] Example 2

[0039] The fly ash reuse system with a carbon-containing fluidized bed in this embodiment has a structure that is basically the same as that in Example 1. The difference is that the reaction temperature in the fly ash pre-combustion zone 220 in this embodiment is 1350°C, and the reaction temperature in the secondary air reaction zone 210 is 950°C.

[0040] In this embodiment, after the boiler feedwater enters the fluidized bed boiler 200, it reacts with the hot flue gas generated in the secondary air reaction zone 210 to produce high-temperature steam. The pressure of the high-temperature steam is 4.9 MPa.

[0041] Example 3

[0042] The fly ash reuse system with a carbon-containing fluidized bed in this embodiment has a structure that is basically the same as that in Example 1. The difference is that the reaction temperature in the fly ash pre-combustion zone 220 in this embodiment is 1300℃; and the reaction temperature in the secondary air reaction zone 210 is 920℃.

[0043] In this embodiment, after the boiler feedwater enters the fluidized bed boiler 200, it reacts with the hot flue gas generated in the secondary air reaction zone 210 to produce high-temperature steam. The pressure of the high-temperature steam is 9.9 MPa.

[0044] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A fly ash recycling system containing a carbon-fluidized bed, characterized in that: The system includes a fluidized bed boiler (200) and a pulverized coal silo (100). The fluidized bed boiler (200) includes a secondary air reaction zone (210) in the middle and a fly ash pre-combustion zone (220) at the bottom. Fly ash in the pulverized coal silo (100) is fed into the fly ash pre-combustion zone (220), and the fly ash pre-combustion zone (220) is an oxygen-rich area. Secondary air is introduced into the secondary air reaction zone (210), where a high-temperature gas-solid mixture formed after the fly ash is burned in the fly ash pre-combustion zone (220) enters the secondary air reaction zone (210) to undergo a secondary reaction. The solids in the high-temperature gas-solid mixture after the secondary reaction are discharged from the bottom of the fluidized bed boiler (200) in the form of slag. The flue gas in the high-temperature gas-solid mixture after the secondary reaction is discharged from the top of the fluidized bed boiler (200). The discharged flue gas is discharged into the atmosphere after flue gas treatment, and a small amount of fly ash in the flue gas is sent to the outside for use. The reaction temperature in the fly ash pre-combustion zone (220) is 1200℃~1350℃; the reaction temperature in the secondary air reaction zone (210) is 900℃~950℃.

2. The fly ash reuse system with a carbon-containing fluidized bed according to claim 1, characterized in that: The fly ash in the pulverized coal silo (100) is fed into the fly ash pre-combustion zone (220) through the fly ash conveying pipe (111) at the bottom, and the oxygen in the fly ash pre-combustion zone (220) is supplied through the oxygen supply pipe (201).

3. The fly ash reuse system with a carbon-containing fluidized bed according to claim 2, characterized in that: An igniter (250) is also provided on the fly ash pre-combustion zone (220), and the igniter (250) is connected to the natural gas pipeline (260) and the ignition fan (251).

4. The fly ash reuse system with a carbon-containing fluidized bed according to claim 3, characterized in that: The secondary air in the secondary air reaction zone (210) is supplied through the secondary air duct (202), and the secondary air duct (202) is equipped with a secondary air fan (204).

5. A fly ash recycling system with a carbon-containing fluidized bed according to claim 4, characterized in that: The flue gas discharged from the top of the fluidized bed boiler (200) is successively treated by the denitrification unit (230), the bag filter (300) and the desulfurization tower (400) before being discharged into the atmosphere. A small amount of fly ash in the flue gas is sent to the outside for use through the bag filter (300).

6. A fly ash recycling system with a carbon-containing fluidized bed according to any one of claims 1-5, characterized in that: The fluidized bed boiler (200) has a heat utilization zone at the top. After the boiler feedwater enters the fluidized bed boiler (200), it reacts with the hot flue gas generated in the fly ash pre-combustion zone (220) to generate high-temperature steam. The pressure of the high-temperature steam is 1.6 MPa to 9.9 MPa.

7. A fly ash recycling system with a carbon-containing fluidized bed according to claim 6, characterized in that: The top of the fluidized bed boiler (200) is provided with a boiler feed water pipe (203), and the economizer (240) of the fluidized bed boiler (200) is provided with an economizer feed water pipe (241).

8. A fly ash recycling system with a carbon-containing fluidized bed according to claim 1, characterized in that: The upper part of the pulverized coal silo (100) is provided with a pulverized coal feeding pipe (101), and the bottom of the pulverized coal silo (100) is provided with a pulverized coal feeder (110).

Images