Circulating fluidized bed boiler for blending combustion of gasified filter cake

Abstract

The invention relates to the field of solid waste resource utilization, in particular to a circulating fluidized bed boiler for blending combustion of gasification filter cakes. The circulating fluidized bed boiler is used for solving the problems that when an existing circulating fluidized bed boiler carries out blending combustion on filter cakes, a large amount of fine ash returns to a hearth, the bed temperature is overheated, the hearth is abraded, and dust removal and denitration burdens are large. The circulating fluidized bed boiler comprises a hearth, a separator and a return feeder, a smoke outlet of the hearth is communicated with an inlet of the separator, a feeding port of the return feeder is communicated with a discharging port of the separator, a return opening of the return feeder is communicated with the interior of the hearth, and a fine ash diversion opening for discharging fine ash is formed in the return feeder. And the fine ash diversion port is communicated to an ash storage tank through a pipeline. Thus, fine ash generated by gasifying the filter cake can be discharged from the fine ash diversion port of the return feeder, excessive fine ash caused by the fact that burnt-out fine ash enters the hearth again is avoided, unsmooth bed material fluidization, bed temperature exceeding and hearth abrasion are avoided, and reliability and stability of blending combustion are guaranteed on the whole.

Description

Technical Field

[0001] The present invention relates to the field of solid waste resource utilization, and particularly to a circulating fluidized bed boiler for co-firing gasification filter cake. Background Art

[0002] Circulating fluidized bed boilers are efficient and low-pollution clean combustion devices, which have been widely used in recent years, such as the circulating fluidized bed boilers equipped in the self-provided power plants of coal chemical enterprises. The core link of modern coal chemical industry (coal gasification, coal-to-oil, coal-to-olefins) is coal gasification. In the coal gasification process, after pulverized coal gasification and washing and filtering, gasification filter cake will be produced. The main components of the gasification filter cake include unreacted residual carbon (calorific value 2000 - 4000 kcal / kg), ash, a small amount of heavy metals (such as As, Pb, Cr) and sulfides. Although the calorific value of the gasification filter cake is low, it can still be used as a supplementary fuel. At this time, a circulating fluidized bed boiler can be used to co-fire it to achieve "using waste to supplement energy".

[0003] The circulating fluidized bed boiler includes a furnace, a separator and a return feeder. There is bed material arranged in the furnace. The bed material is mainly composed of coarse particles of 0.3 - 5 mm accounting for 85% - 90% (such as quartz sand, bottom slag), and is paired with 10% - 15% of fine ash of 0.1 - 0.3 mm, forming a particle size distribution of "coarse particle skeleton + fine particle filling" to balance the fluidization stability and heat transfer efficiency. When in use, the gasification filter cake is placed into the furnace through the feed port of the furnace. The gasification filter cake starts to burn when it encounters the high-temperature bed material in the furnace. The high-temperature flue gas carries the ash and other particles after the filter cake burns and leaves the furnace and enters the separator. The flue gas is discharged from the exhaust port of the separator. Part of the filter cake fly ash and other unburned particles fall downward into the return feeder and return to the furnace through the return feeder to form a cycle of materials. However, the filter cake has been ground by a coal mill, so a large amount of fine ash (ash particles with a particle size below 0.1 mm) is formed. The fine ash is not suitable as the bed material in the furnace. In the embodiments of the present application, a fine ash diversion port for discharging fine ash is arranged on the return feeder. In this way, the fine ash of the filter cake fly ash in the return feeder can be discharged from the fine ash diversion port, avoiding the fine ash from entering the furnace again and increasing the difficulty of controlling the bed temperature, reducing the wear of the heating surface and the burden of dust removal and denitrification, and ensuring the reliability and stability of co-firing as a whole. Summary of the Invention

[0004] The purpose of the present invention is to provide a circulating fluidized bed boiler for co-firing gasification filter cake to solve the problems that a large amount of fine ash in the filter cake fly ash in the existing circulating fluidized bed boiler will cause poor fluidization of the bed material, over-temperature of the bed temperature, and increased wear after returning to the furnace through the return feeder.

[0005] The circulating fluidized bed boiler for co-firing gasified filter cake according to the present invention includes a furnace, a separator, and a return feeder. The flue gas outlet of the furnace for discharging a large amount of fly ash is connected to the inlet of the separator. The feed inlet of the return feeder is connected to the discharge outlet of the separator. The return outlet of the return feeder is connected to the interior of the furnace. The return feeder is provided with a fine ash diversion port for discharging fine ash. The fine ash diversion port is connected to an ash storage tank through a pipeline.

[0006] Furthermore, a diversion valve is provided at the fine ash diversion port.

[0007] Furthermore, the fine ash diversion port is located on the upper part of the return feeder.

[0008] Furthermore, an ash discharge branch pipeline is provided on the pipeline connecting the feed inlet of the return feeder and the discharge outlet of the separator, and an ash discharge valve is provided on the ash discharge branch pipeline.

[0009] Furthermore, a slag cooling and screening device for cooling and screening slag is provided below the furnace, and a slag discharge pipe for discharging bed material slag to the slag cooling and screening device is provided at the bottom of the furnace bed.

[0010] Furthermore, the slag discharge cooling screening device is a slag cooler, and a fine slag discharge outlet is provided on the cylinder wall of the slag cooler. A fine slag filter screen is provided at the fine slag discharge outlet, and the discharge outlet of the slag cooler constitutes a coarse slag discharge outlet for discharging the coarse slag from the bed material.

[0011] Furthermore, the slag cooler is provided with a spiral channel for the bed material to move in a spiral motion within it.

[0012] Furthermore, the coarse slag outlet of the slag cooler is equipped with an automatic conveying device for transporting the bed material coarse slag into the furnace.

[0013] Furthermore, the automatic conveying device includes a bucket elevator, with an ash hopper provided on the side of the bucket elevator and the bucket elevator discharge port communicating with the ash hopper, and the ash hopper communicating with the furnace.

[0014] Furthermore, a screw conveyor is installed at the discharge port of the ash hopper and is connected to the furnace through the screw conveyor.

[0015] This invention proposes an improved technical solution to address the aforementioned technical problems. A fine ash distribution port is installed on the return feeder of a circulating fluidized bed boiler that co-fires gasified filter cake, allowing for the discharge of fine ash. This fine ash distribution port is connected to an ash storage tank via a pipeline. In this way, fine ash from the filter cake can be discharged from the fine ash distribution port, reducing the dust removal and denitrification burden on the furnace and improving operational economy. It also prevents a large amount of fine ash from entering the furnace and affecting the normal operation of the circulating fluidized bed boiler; furthermore, it prevents wear on the furnace heating surfaces caused by high-speed airflow, thus extending the service life of the circulating fluidized bed boiler. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a circulating fluidized bed boiler that co-fires gasified filter cake according to the present invention.

[0017] In the diagram: 1. Furnace; 101. Furnace feed inlet; 2. Separator; 201. Flue gas outlet; 3. Return feeder; 301. Fine ash diversion outlet; 4. Ash discharge branch pipeline; 5. Ash discharge valve; 6. Bed material; 7. Slag discharge pipe; 8. Slag cooler; 801. Fine ash discharge outlet; 802. Coarse ash discharge outlet; 9. Bucket elevator; 10. Screw conveyor; 11. Ash hopper. Detailed Implementation

[0018] This invention proposes an improved technical solution to address the aforementioned technical problems. The core concept of this invention is to provide a fine ash diversion port on the return feeder for fine ash discharge. In this way, fine ash in the filter cake fly ash can be discharged from the fine ash diversion port, reducing the dust removal and denitrification burden on the furnace and improving operational economy; it can prevent a large amount of fine ash from entering the furnace and affecting the normal operation of the circulating fluidized bed boiler; it can also prevent the furnace heating surfaces from being worn by fine ash under high-speed airflow, thus extending the service life of the circulating fluidized bed boiler.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: Based on the above inventive concept, the circulating fluidized bed boiler for co-firing gasified filter cake of the present invention includes, as follows: Figure 1The furnace 1 shown contains a bed of material 6. A furnace inlet 101 is located on the side of the furnace 1. During operation, the co-fired gasified filter cake is placed into the furnace 1 through the furnace inlet 101. The gasified filter cake ignites immediately upon contact with the high-temperature bed material 6 within the furnace 1. An air distribution plate and air cap are installed at the bottom of the furnace 1 to evenly distribute the primary air. The primary air is ejected from the bottom air cap, causing the bed material 6 to be in a state of vigorous fluidization. The ash from the burning filter cake and other unburned particles are carried upwards by the flue gas. A separator 2 is located on the side of the furnace 1, and the flue gas outlet of the furnace 1 is connected to the inlet of the separator 2. High-temperature flue gas, carrying a large amount of filter cake fly ash and other unburned particles, enters separator 2 through the flue gas outlet of furnace 1 and the inlet of separator 2. In this embodiment, separator 2 is a cyclone separator. The purified flue gas is discharged from the exhaust port 201 at the top of the cyclone separator. Other solid particles are thrown against the cylinder wall of the cyclone separator by the strong centrifugal force of the cyclone separator and slide down the cylinder wall. A return feeder 3 is provided at the bottom of the cyclone separator. The feed inlet of the return feeder 3 is connected to the discharge port of separator 2. The solid particles thrown against the cylinder wall of separator 2 slide down into the return feeder 3. The return port of the return feeder 3 is connected to furnace 1 through a return pipe. An air distribution plate and an air cap are also provided inside the return feeder 3. By adjusting the size of the return air sent from the air cap of the return feeder 3, the speed and flow rate of the returned material can be flexibly controlled.

[0020] The solid particles entering the return feeder 3 include filter cake fly ash, which is mainly fine ash (ash particles with a diameter of less than 0.1 mm). Fine ash is not suitable as bed material 6 in the furnace 1. Therefore, the present invention provides a fine ash diversion port 301 on the return feeder 3 for fine ash discharge. The fine ash diversion port 301 is connected to the ash storage tank through a pipeline. In this way, under the action of the return air, the fine ash that has been burned sufficiently and has reached the required carbon content is discharged through the fine ash diversion port 301, cooled, and then pneumatically conveyed to the ash storage tank. Other solid particles enter the furnace 1 along the return pipe. By setting a fine ash diversion port 301 on the return feeder 3, the fine ash in the filter cake fly ash in the return feeder 3 can be discharged from the fine ash diversion port 301, avoiding the fine ash from entering the furnace 1 and causing ash accumulation in the furnace 1, reducing the burden of dust removal and denitrification, and saving overall operating costs; it also avoids the difficulty of boiler operation caused by a large amount of fine ash returned by the return feeder 3; and it avoids the wear of the heating surface of the furnace 1 caused by the high-speed airflow, thus improving the service life of the circulating fluidized bed boiler. At the same time, the fine ash and alkali metals (such as potassium and sodium) in the gasified filter cake in the furnace are prone to form low-melting-point eutectic at high temperatures. Therefore, after the fine ash is discharged through the fine ash diversion port 301, it can also prevent the fine ash and alkali metals from depositing and coking in the furnace or heating surface, thus preventing blockage of the material circulation system.

[0021] A diversion valve is installed at the fine ash diversion port 301. In this way, the discharge volume of fine ash can be controlled by the diversion valve.

[0022] The fine ash separation port 301 is located at the upper part of the separator 2. For example... Figure 1 As shown, the fine ash diversion port 301 is located on the upper part of the front side of the separator 2, and its position is higher than that of the return pipe. Under the action of the return air, ash particles with low density and fine particle size will accumulate upwards. Therefore, the fine ash diversion port 301 located on the upper part of the return feeder 3 is more conducive to the separation of fine ash.

[0023] A discharge branch pipe 4 is installed on the pipeline connecting the feed inlet of the return feeder 3 and the discharge outlet of the separator 2. A discharge valve 5 is installed on the discharge branch pipe 4. When necessary, the discharge branch pipe 4 and the discharge valve 5 can be used to control the amount of solid particles entering the return feeder 3 through the separator 2, so as to adjust the amount of circulating material.

[0024] A slag cooling and screening device for cooling and screening slag is installed below the furnace chamber 1. A slag discharge pipe 7 is installed at the bottom of the bed material in the furnace chamber 1 to discharge the bed material slag to the slag cooling and screening device. Thus, the bed material slag can enter the slag cooling and screening device through the slag discharge pipe 7 for cooling and screening out fine and coarse bed material slag. Specifically, as... Figure 1 As shown, the slag cooling and screening device includes a slag cooler 8. A fine slag outlet 801 is located in the middle of the cylinder wall of the slag cooler 8, and a fine slag filter screen is installed at the fine slag outlet 801. The outlet of the slag cooler 8 forms a coarse slag outlet 802 for discharging the coarse slag from the bed material. To ensure sufficient screening and cooling of the bed material slag, a spiral channel is provided inside the slag cooler 8 to ensure that the coarse and fine slag from the bed material move along the spiral channel. When passing through the fine slag outlet 801, the smaller fine slag particles are screened out through the fine slag filter screen, while the larger coarse slag particles continue to move along the spiral channel and are eventually discharged from the coarse slag outlet 802. The cooled coarse slag from the bed material is collected and can be returned to the furnace 1 as bed material 6. This helps maintain the height of bed material 6 and facilitates temperature control of bed material 6, preventing overheating and coking.

[0025] An automatic conveying device is installed at the coarse slag discharge outlet 802 to transport the bed material coarse slag into the furnace 1. This facilitates the circulation of the bed material coarse slag. The automatic conveying device includes a bucket elevator 9, whose feed port is located below the coarse slag discharge outlet 802. Thus, the bed material coarse slag immediately falls into the bucket elevator 9 upon discharge, simplifying the transportation of the coarse slag. An ash hopper 11 is installed at the discharge port of the bucket elevator 9, and a screw conveyor 10 is installed below the ash hopper 11. The screw conveyor 10 connects the ash hopper 11 to the furnace 1. The bed material coarse slag is lifted to a high position by the bucket elevator 9 and falls into the screw conveyor 10 through the ash hopper 11. The screw conveyor 10 transports the bed material coarse slag into the furnace 1 by the rotation of its internal spiral blades. By installing the automatic conveying device, the efficiency of bed material coarse slag transportation is improved. Since the bucket elevator 9 and the screw conveyor 10 are existing technologies, their specific structures will not be described in detail here.

[0026] Regarding the location of the fine ash diversion port, the present invention also provides other embodiments. In one embodiment, the fine ash diversion port can be located in the middle of the return feeder; in another embodiment, the fine ash diversion port can also be located at the top of the return feeder, as long as it is ensured that the fine ash can be discharged from the fine ash diversion port.

[0027] Regarding the slag discharge cooling and screening device, the present invention also provides other embodiments. In one embodiment, the slag discharge cooling and screening device can be a drum-type slag cooler. A screen is provided on the drum body of the drum-type slag cooler. During the rotation of the drum body, the fine slag of the bed material with a smaller particle size can be screened out through the screen, while the coarse slag of the bed material with a larger particle size is retained in the drum-type slag cooler. In another embodiment, the slag discharge cooling and screening device can be a vibrating screening device. The vibrating screening device includes a screen box, on which a cooling structure is provided. A screen is provided in the middle of the screen box to divide the screen box into upper and lower layers. After the bed material slag falls into the screen, under the action of the overall vibration of the screen box, the fine slag of the bed material with a smaller particle size falls into the lower layer of the screen box through the screening of the screen, while the coarse slag of the bed material with a larger particle size remains in the upper layer of the screen box, thereby achieving the separation of the coarse slag and the fine slag of the bed material.

[0028] Regarding the transportation of bed material coarse slag, the present invention also provides other embodiments. In another embodiment, an automatic transportation device may not be set up, and the recovery of bed material coarse slag may be achieved by manual labor.

[0029] Regarding the automatic transport device, the present invention also provides other embodiments. In another embodiment, the automatic transport device can be a screw conveyor. The screw conveyor is inclined, and the feed inlet of the screw conveyor is located below the coarse slag discharge outlet of the slag cooler. The discharge outlet of the screw conveyor is connected to the furnace. In this way, the automatic transport of bed material coarse slag is efficiently realized.

[0030] Regarding the structure of the automatic transport device, the present invention also provides other embodiments. In another embodiment, an inclined downward pipe can be provided at the ash hopper outlet, and the pipe is connected to the inner cavity of the furnace so that the bed material coarse slag can fall into the furnace along the pipe by its own gravity.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A circulating fluidized bed boiler firing gasified filter cake, characterized in that: It comprises a furnace (1), a separator (2) and a return feeder (3), the flue gas outlet of the furnace (1) for discharging a large amount of fly ash is communicated with the inlet of the separator, the inlet of the return feeder (3) is communicated with the discharge port of the separator (2), the return port of the return feeder (3) is communicated with the inside of the furnace (1), the return feeder (3) is provided with a fine ash shunt port (301) for discharging fine ash, and the fine ash shunt port (301) is communicated to the ash storage tank through a pipeline.

2. A gas-spiked filter cake gasification circulating fluidized bed boiler according to claim 1, characterized in that: The shunt port valve is arranged at the fine ash shunt port (301).

3. A circulating fluidized bed boiler firing gasified filter cake according to claim 1 or 2, characterized in that: The fine ash shunt port (301) is arranged on the upper part of the return feeder (3).

4. A circulating fluidized bed boiler according to claim 1 or 2, characterized in that: The ash discharge branch pipeline (4) is arranged on the pipeline communicated between the inlet of the return feeder (3) and the discharge port of the separator (2), and the ash discharge valve (5) is arranged on the ash discharge branch pipeline (4).

5. A circulating fluidized bed boiler according to claim 1 or 2, characterized in that: The furnace (1) is provided below with a slag discharge cooling and screening device for cooling and screening the discharged slag, and the lower part of the bed material of the furnace (1) is provided with a slag discharge pipe (7) for discharging the bed material slag to the slag discharge cooling and screening device.

6. A gas-spiked filter cake gasification circulating fluidized bed boiler according to claim 5, characterized in that: The slag discharge cooling and screening device is a slag cooler (8), the fine slag discharge port (801) is arranged on the cylinder wall of the slag cooler, the fine slag filter screen is arranged at the fine slag discharge port (801), and the discharge port of the slag cooler (8) constitutes a coarse slag discharge port (802) for discharging the coarse slag of the bed material.

7. A gas-spiked filter cake gasification circulating fluidized bed boiler according to claim 6, characterized in that: The spiral channel is arranged in the slag cooler (8) for the spiral movement of the bed material slag.

8. The gas-spiked, filtered cake gasifying, circulating fluidized bed boiler according to claim 6, characterized in that: The automatic conveying device is arranged at the coarse slag discharge port (802) of the slag cooler (8) for conveying the coarse slag of the bed material into the furnace (1).

9. A gas-spiked filter cake gasification circulating fluidized bed boiler according to claim 8, characterized in that: The automatic conveying device comprises a bucket elevator (9), the side of the bucket elevator is provided with an ash bucket (11), the discharge port of the bucket elevator (9) is communicated with the ash bucket (11), and the ash bucket (11) is communicated with the inside of the furnace (1).

10. A gas-spiked filter cake gasification circulating fluidized bed boiler according to claim 9, characterized in that: The screw conveyor (10) is arranged at the discharge port of the ash bucket (11) and is communicated with the inside of the furnace (1) through the screw conveyor (10).

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