Slag removal device and slag removal method for fluidized bed gasifier

Abstract

The present invention provides a slag discharge device (2) for a fluidized bed gasifier, wherein the slag discharge device (2) has a bottom slag inlet (a) and a bottom slag outlet, and the slag discharge device (2) is configured to gasify and cool the bottom slag (A). The present invention also provides a slag discharge method for a fluidized bed gasifier. The slag discharge device and slag discharge method for a fluidized bed gasifier according to the present invention can ensure smooth slag discharge of the fluidized bed gasifier, reduce safety hazards, save energy and reduce consumption, reduce the carbon content of the bottom slag, and improve the cold coal gas efficiency.

Description

Technical Field

[0001] The present invention relates to the field of gasification technology, and in particular to a slag removal device and method for a fluidized bed gasifier. Background Art

[0002] As an efficient and clean clean coal technology, gasification technology is the main way to convert solid primary energy such as coal into gaseous clean secondary energy. This technology is mainly used in chemical and metallurgical industries such as synthetic ammonia, synthetic methanol, hydrogen production, blast furnace reduction ironmaking, combined cycle power generation, and industrial and civil gas fields.

[0003] According to the movement state of solid fuel, modern gasification processes mainly include fixed bed gasification, entrained bed gasification and fluidized bed gasification. Fluidized bed gasification technology is one of the earliest industrialized gasification processes. The process is to blow a gasifying agent with a certain pressure from the bottom of the bed through the air distribution plate to lift the broken coal on the bed. When the gasifying agent rises, the coal particles move in a suspended state, rolling up and down, and fully contacting with the gasifying agent to undergo a gasification reaction. This type of technology includes traditional fluidized bed gasification technology and circulating fluidized bed gasification technology developed in recent years.

[0004] At present, fluidized bed gasification technology has been industrialized and has achieved good environmental, economic and social benefits. However, from the operation of existing fluidized bed gasifiers, there are the following problems:

[0005] (1) The slag discharge system has low operational flexibility and is prone to slagging during the slag discharge process, which affects the long-term stable operation of the gasifier;

[0006] (2) The slag removal method is mechanical. Once slag is formed, the blocking effect of slag on hot coal gas is destroyed, and hot coal gas is very likely to escape from the slag removal device, which poses a serious safety hazard.

[0007] (3) The system has high energy and water consumption, and fails to fully recover the sensible heat of hot slag (temperature greater than 900°C);

[0008] (4) The carbon content of the bottom ash is high, especially for coal with low reactivity, the carbon content of the bottom ash is ≥15%. Summary of the invention

[0009] The object of the present invention is to at least partially overcome the defects of the prior art and to provide a slag discharge device and a slag discharge method for a fluidized bed gasifier.

[0010] The present invention also aims to provide a slag discharge device and a slag discharge method for a fluidized bed gasifier, so as to solve the problem of slag formation during the slag discharge process, ensure smooth slag discharge of the fluidized bed gasifier, and reduce safety hazards.

[0011] The present invention also aims to provide a slag discharge device and a slag discharge method for a fluidized bed gasifier, which can reasonably utilize the sensible heat of the hot slag to achieve the purpose of energy saving and consumption reduction.

[0012] The present invention also aims to provide a slag discharge device and a slag discharge method for a fluidized bed gasifier, which can reduce the carbon content of the bottom slag and improve the cold gas efficiency.

[0013] To achieve the above purpose or one of the purposes, the technical solution of the present invention is as follows:

[0014] A slag discharge device for a fluidized bed gasifier, the slag discharge device having a bottom slag inlet and a bottom slag outlet, and the slag discharge device is configured to gasify and cool the bottom slag.

[0015] According to a preferred embodiment of the present invention, the slag discharge device comprises a slag falling pipe, a cooling cylinder and a slag discharge pipe, wherein the bottom slag inlet is arranged on the slag falling pipe for connecting with the gasifier, an end of the slag falling pipe opposite to the bottom slag inlet is connected to one end of the cooling cylinder, and the other end of the cooling cylinder is connected to the slag discharge pipe.

[0016] The cooling cylinder has an equivalent diameter greater than that of the slag dropping pipe and greater than that of the slag discharge pipe, and

[0017] The slag discharge device is provided with a gasifying agent inlet and a coolant inlet, which are used to respectively introduce the gasifying agent and the coolant into the slag discharge device.

[0018] According to a preferred embodiment of the present invention, the cooling cylinder has an upper involute section, a lower tapered section and a cylinder section between the upper involute section and the lower tapered section, wherein the equivalent diameter of the cylinder section is larger than the equivalent diameter of the slag dropping pipe and larger than the equivalent diameter of the slag discharge pipe.

[0019] According to a preferred embodiment of the present invention, the gasifying agent inlet is arranged on the slag dropping pipe.

[0020] According to a preferred embodiment of the present invention, the coolant inlet is arranged on the cooling cylinder, preferably, the coolant inlet is arranged on the upper involute section or the cylinder section.

[0021] According to a preferred embodiment of the present invention, the slag discharge device further comprises a sealing gas inlet for introducing sealing gas into the slag discharge device.

[0022] According to a preferred embodiment of the present invention, the sealing gas inlet comprises a first sealing gas inlet arranged on the slag discharge pipe.

[0023] According to a preferred embodiment of the present invention, the sealing gas inlet further comprises a second sealing gas inlet arranged on the lower tapered section of the cooling cylinder.

[0024] According to a preferred embodiment of the present invention, the slag discharge device further comprises a return gas outlet, and the return gas outlet is arranged on the cooling cylinder.

[0025] According to another aspect of the present invention, a slag removal method for a fluidized bed gasifier is provided. The slag removal method uses the slag removal device for a fluidized bed gasifier as described in any one of the aforementioned embodiments.

[0026] The slag discharge device and slag discharge method for a fluidized bed gasifier provided by the present invention have the following advantages over the prior art: (1) the problem of slag formation during slag discharge is solved, thereby ensuring smooth slag discharge in the fluidized bed gasifier and reducing potential safety hazards; (2) water and water vapor are used as gasifying agents or coolants, and water and water vapor are in direct contact with hot slag for heat exchange, which can effectively reduce the temperature of the hot slag. The water and water vapor can come from the condensed water of the coal gasification system, thereby realizing the rational use of the condensed water of the coal gasification system; (3) the sensible heat of the bottom ash is fully utilized to generate steam or overheat the steam, thereby improving the system efficiency; (4) the pressure in the slag discharge pipe is higher than the furnace bottom pressure, thereby effectively preventing the gasifying agent from being carried into the slag discharge pipe, thereby avoiding the problems of slag formation and gas blowby in the existing slag discharge method, thereby improving the operational flexibility of the gasifier slag discharge system and ensuring the long-term stable operation of the fluidized bed gasifier; (5) the steam reacts with the carbon in the bottom ash, thereby reducing the carbon content of the bottom ash to a certain extent, thereby improving the system carbon conversion rate and cold coal gas efficiency; (6) The temperature of hot slag can be reduced to below 100°C, thereby eliminating equipment such as slag coolers and saving investment and operation and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a general schematic diagram of a slag discharge device for a fluidized bed gasifier;

[0028] Figure 2 is a general schematic diagram of a slag discharge device for a fluidized bed gasifier according to an embodiment of the present invention; and

[0029] Figure 3 The figure is a general schematic diagram of a slag discharge device for a fluidized bed gasifier according to another embodiment of the present invention. DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements. In addition, in the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the disclosed embodiments. However, it is apparent that one or more embodiments may also be implemented without these specific details. In other cases, known structures and devices are embodied in a schematic manner to simplify the accompanying drawings.

[0031] In order to discharge the slag of the fluidized bed gasifier smoothly, the designer constructed a slag discharge device for the fluidized bed gasifier, such as Figure 1 As shown, in Figure 1 In the figure, the upper part is a gasifier. To simplify the attached figure, only the lower part of the gasifier is shown. Below the gasifier is a slag discharge device, which includes: a slag discharge pipe, a slag cooler and a conveyor. One end of the slag discharge pipe is connected to the slag outlet of the gasifier, and the other end of the slag discharge pipe is connected to the inlet of the slag cooler through a valve. The outlet of the slag cooler faces or is directed to the conveyor. The conveyor can be in the form of a slag conveyor belt. A cooling device is provided outside the slag discharge pipe to cool the slag passing through the slag discharge pipe. The cooling medium can be water. In this way, the hot slag discharged from the slag outlet of the gasifier is cooled by water cooling through the partition wall of the slag discharge pipe, and then cooled by the slag cooler, and finally transported to the slag bin via the slag conveyor belt. Judging from the operation of the slag discharge device, there are still some problems with the above slag discharge method:

[0032] (1) The slag discharge system has low operational flexibility and is prone to slagging during the slag discharge process, which affects the long-term stable operation of the gasifier;

[0033] (2) The slag removal method is mechanical. Once slag is formed, the blocking effect of slag on hot coal gas is destroyed, and hot coal gas is very likely to escape from the slag removal device, which poses a serious safety hazard.

[0034] (3) The system has high energy and water consumption, and fails to fully recover the sensible heat of hot slag (temperature greater than 900°C);

[0035] (4) The carbon content of the bottom ash is high, especially for coal with low reactivity, the carbon content of the bottom ash is ≥15%.

[0036] To this end, the designer further proposed a slag removal device for a fluidized bed gasifier and a slag removal method for a fluidized bed gasifier.

[0037] Figure 2 FIG. 1 is a general schematic diagram of a slag discharge device for a fluidized bed gasifier according to an embodiment of the present invention. Figure 2As shown, the fluidized bed gasification system includes a fluidized bed gasifier 1 and a slag discharge device 2, and the slag discharge device 2 is located below the gasifier 1 and connected to the gasifier 1. The slag discharge device 2 has a bottom slag inlet a and a bottom slag outlet, and the slag discharge device 2 is configured to gasify and cool the bottom slag A. Specifically, the slag discharge device 2 includes a slag drop pipe 21, a cooling cylinder 22, a slag discharge pipe 23 and an air locking device 24 connected in sequence, wherein the bottom slag inlet a is arranged on the slag drop pipe 21, and is used to be connected to the gasifier 1, and the end of the slag drop pipe 21 opposite to the bottom slag inlet a is connected to one end of the cooling cylinder 22, and the other end of the cooling cylinder 22 is connected to the slag discharge pipe 23. The air locking device 24 is arranged on the slag discharge pipe 23, and is used to control the slag discharge while preventing the gas from escaping from the slag discharge port. During operation, the air locking device 24 can seal the lower end of the slag discharge pipe 23, lock the gas, and prevent gas leakage.

[0038] The slag pipe 21, the cooling cylinder 22, and the slag discharge pipe 23 may be roughly cylindrical in shape, preferably a cylinder or a square cylinder. The diameter of the slag pipe 21 may be consistent with the diameter of the bottom slag outlet of the gasifier, and the cooling cylinder 22 has an equivalent diameter greater than that of the slag pipe 21 and greater than that of the slag discharge pipe 23. Here, the equivalent diameter refers to the diameter of a cylinder or the diameter of a cylinder that is equal to the hydraulic radius of a non-cylindrical object. Therefore, in the case of a non-circular or non-cylindrical object, the diameters mentioned in this article refer to equivalent diameters. Figure 2 As shown, the cooling cylinder 22 has an upper involute section, a lower tapered section and a cylinder section between the upper involute section and the lower tapered section, wherein the equivalent diameter of the cylinder section is larger than the equivalent diameter of the slag dropping pipe 21 and larger than the equivalent diameter of the slag discharge pipe 23 .

[0039] Among them, Figure 2 In the illustrated embodiment, the diameter of the slag pipe 21 is consistent with the diameter of the bottom ash outlet of the gasifier, but the present invention is not limited thereto. The diameter of the slag pipe may be 1-2 times the diameter of the bottom ash outlet of the gasifier, and the equivalent diameter of the cooling cylinder 22 (i.e., the equivalent diameter of the cylinder section) may be 1.5-5 times, preferably 3-4 times, the equivalent diameter of the slag pipe 21. In addition, the diameter of the slag discharge pipe 21 may be the same as or greater than the diameter of the slag discharge pipe 21. Specifically, the equivalent diameter of the slag discharge pipe 23 may be 1-3 times, preferably 1.2-2 times, the equivalent diameter of the slag discharge pipe 21. The structural dimensions of the slag discharge pipe 21, the cooling cylinder 22, and the slag discharge pipe 23 are functions of the coal ash content, the coal particle size, and the gasification temperature, and may be adjusted based on them.

[0040] exist Figure 2In the embodiment, since the gasified coal has a high basic ash content, a low gasification temperature, and a large amount of bottom ash, the equivalent diameter of the cross-section with the largest cross-sectional area of ​​the cooling cylinder 22 is set to 4 times the equivalent diameter of the gasifier bottom ash outlet or the slag discharge pipe 21, so that the bottom ash can be fully cooled in the cooling cylinder; the equivalent diameter of the slag discharge pipe 23 is 2 times the equivalent diameter of the slag discharge pipe 21, so as to ensure that the bottom ash reduced to below 100°C can be smoothly discharged from the slag discharge pipe.

[0041] The slag discharge device 2 is provided with a gasifying agent inlet b, a coolant inlet f, a sealing gas inlet d and a return gas outlet e. The gasifying agent inlet b and the coolant inlet f are respectively used to introduce the gasifying agent B and the coolant F into the slag discharge device 2, the sealing gas inlet d is used to introduce the sealing gas D into the slag discharge device 2, and the return gas outlet e is used to discharge the gas in the slag discharge device 2 and send them back to the furnace of the gasifier.

[0042] like Figure 2 As shown, the gasifying agent inlet b is arranged on the slag falling pipe 21, and the coolant inlet f is arranged on the cooling cylinder 22. However, the gasifying agent inlet b and the coolant inlet f are not limited to the positions, but preferably, the gasifying agent inlet b is arranged on the slag falling pipe 21 or at an upper position of the cooling cylinder 22, for example, on the upper involute section, so as to facilitate the gasifying agent to fully act. The coolant inlet f can be arranged on the upper involute section or the cylinder section to fully cool the bottom slag A during the falling process of the bottom slag A. Figure 2 In the illustrated embodiment, a return gas outlet e, a coolant inlet f and a sealing gas inlet d are provided on the cooling cylinder 22. The gasifying agent inlet b and the coolant inlet f may include a plurality of them respectively, preferably, the plurality of gasifying agent inlets b are evenly arranged along the circumferential direction, and the plurality of coolant inlets f are evenly arranged along the circumferential direction.

[0043] Preferably, the gasifier inlet b is constructed as a plurality of gasifier inlets b arranged in multiple rows, and the gasifier inlets b in any one gasifier inlet b are staggered with the gasifier inlets b in an adjacent row, and the coolant inlet f is constructed as a plurality of coolant inlets f arranged in multiple rows, and the coolant inlets f in any one row of coolant inlets f are staggered with the coolant inlets f in an adjacent row.

[0044] exist Figure 2In the embodiment, the sealing gas inlet d includes a first sealing gas inlet provided on the slag discharge pipe 23 and a second sealing gas inlet provided on the lower tapered section of the cooling cylinder 22. It should be noted that the second sealing gas inlet can be provided at other positions as long as it is located at the lower side of the coolant inlet f. There are multiple first sealing gas inlets and multiple second sealing gas inlets, respectively, and the multiple first sealing gas inlets are evenly arranged along the circumferential direction of the slag discharge pipe 23, and the multiple second sealing gas inlets are evenly arranged along the circumferential direction of the lower tapered section of the cooling cylinder 22. The sealing gas inlet d can also be constructed as an inlet ring continuous in the circumferential direction to facilitate uniform blowing of sealing gas.

[0045] The return gas outlet e can be arranged on the upper involute section of the cooling cylinder 22 to facilitate the discharge of the return gas E.

[0046] Further, the air lock device 24 can be constructed as a valve, and the valve is opened when the slag is discharged. Alternatively, the air lock device 24 includes an inlet, a first chamber, a second chamber, an intermediate chamber and an outlet, the intermediate chamber is between the first chamber and the second chamber, the inlet is arranged on the first chamber, the outlet is arranged on the second chamber, the first valve is arranged between the first chamber and the intermediate chamber, and the second valve is arranged between the intermediate chamber and the second chamber. During operation, the second valve can be closed and the first valve can be opened, so that the bottom slag discharged from the slag discharge pipe 23 directly enters the intermediate chamber through the inlet and the first chamber, and when the bottom slag in the intermediate chamber accumulates to a certain extent, the first valve is closed and the second valve is opened, so that the bottom slag can enter the second chamber and can be discharged from the outlet connected to the second chamber, and after the bottom slag in the intermediate chamber is emptied, the second valve is closed and the first valve is opened. In this way, gas leakage can be avoided.

[0047] Specifically, the gasifying agent can be water or water vapor. Preferably, the gasifying agent is steam generated by the waste heat boiler of the gasifier system and steam provided by other sections. The mass ratio of the gasifying agent to the bottom ash amount can be 0.02-0.3: 1. The coolant can be water or steam. Preferably, the coolant is condensed water generated by the gasifier system. The amount of coolant fed is a function of the bottom ash amount, the carbon content of the bottom ash, the temperature of the bottom ash, the temperature of the gasifying agent, and the amount of gasifying agent fed. Preferably, the mass ratio of the coolant to the bottom ash amount is 0.05-0.8: 1.

[0048] The sealing gas may be an inert gas such as CO2 or nitrogen, preferably, the sealing gas is nitrogen, and the mass ratio of nitrogen to bottom ash is 0.05-0.5:1.

[0049] Assuming that the pressure of the bottom ash outlet of the gasifier is P0, the pressure of the gasifying agent inlet is P1, the pressure of the coolant inlet is P2, and the pressure of the sealing gas inlet is P3, then P0<P1<P2<P3≤50kPa. In this way, it is conducive to gradually increase the pressure from the bottom ash outlet of the gasifier to the slag drop pipe to the cooling cylinder to the slag discharge pipe, effectively preventing the gasifying agent from being carried into the slag discharge pipe and avoiding gas blowby.

[0050] The following is combined with Figure 2 The working process of the slag discharge device for a fluidized bed gasifier according to the present invention is described in detail with reference to specific applications. First, the bottom ash A at 900°C from the gasifier 1 enters the slag discharge pipe 21 from the bottom ash inlet a, and the amount of bottom ash is 500kg / h. 60kg / h of condensed water generated by the gasifier system is introduced into the slag discharge pipe 21 to react with the carbon in the bottom ash for gasification, and at the same time, a cooling effect is generated on the bottom ash to generate 600°C slag with a low carbon content and reducing gas. The generated 600°C slag with a low carbon content enters the cooling cylinder 22, and 50kg / h of steam generated by the waste heat boiler is introduced into the cooling cylinder 22 to reduce the temperature of the bottom ash to 200°C, and the steam is heated at the same time. 80Nm 3 / kg of nitrogen as sealing gas is respectively introduced into the slag discharge device from the slag discharge pipe 23 and the lower part of the cooling cylinder 22, which plays a sealing role to prevent the coal gas from flowing downward. At the same time, the bottom slag temperature of 200°C from the cooling cylinder 22 is reduced to 80°C. The bottom slag reduced to below 80°C leaves the system after passing through the air lock device 24. The reducing gas generated in the slag discharge pipe 21, the steam heated in the cooling cylinder 22, and the nitrogen gas leave the slag discharge device through the return gas outlet e as the return gas, and return to the middle of the gasifier as the gasifier to participate in the reaction. In order to ensure smooth slag discharge, ensure that condensed water, water vapor and N2 can be introduced into the slag discharge device, and ensure that the return gas can return to the gasifier, the system pressure distribution is as follows: the pressure of the bottom slag outlet of the gasifier is P0, the pressure of the condensed water inlet is P1, the pressure of the water vapor inlet is P2, the pressure of the N2 inlet is P3, and P0<P1<P2<P3≤50kPa.

[0051] Figure 3 FIG. 1 is a schematic diagram of a slag discharge device for a fluidized bed gasifier according to another embodiment of the present invention. Figure 2 The embodiments shown are basically the same, and only the following description is made of Figure 2The difference between the embodiments shown in the figure lies in that: a sealed gas inlet d is only provided on the slag discharge pipe 23, and no sealed gas inlet d is provided on the cooling cylinder 22; the equivalent diameter of the cross section with the largest cross-sectional area of ​​the cooling cylinder 22 is 3 times the equivalent diameter of the gasification furnace bottom ash outlet or the slag dropping pipe 21, and the equivalent diameter of the slag discharge pipe 23 is 2 times the equivalent diameter of the slag dropping pipe 21. This is designed for gasification coal with low basic ash content, increased gasification temperature and reduced bottom ash amount.

[0052] The following is combined with Figure 3 The working process of the slag discharge device for a fluidized bed gasifier according to the present invention is described in detail with reference to specific applications. First, the bottom ash A at 1100°C from the gasifier 1 enters the slag discharge pipe 21 from the bottom ash inlet a. The amount of bottom ash is 300kg / h. 30kg / h of water vapor is introduced into the slag discharge pipe 21 to react with the carbon in the bottom ash for gasification, and at the same time, a cooling effect is generated on the bottom ash to generate 700°C slag with a low carbon content and reducing gas. The generated 700°C slag with a low carbon content enters the cooling cylinder 22. 40kg / h of cooling water is introduced into the cooling cylinder 22 to reduce the temperature of the bottom ash to 200°C. At the same time, the cooling water is heated to generate steam. 60Nm 3 / kg of CO2 is introduced into the system from the slag discharge pipe 23 as a sealing gas, which plays a sealing role to prevent coal gas from leaking down. At the same time, the bottom ash temperature of 200°C from the cooling cylinder 22 is reduced to 80°C. The bottom ash reduced to below 80°C leaves the system after passing through the air lock device 24. The reducing gas generated in the slag discharge pipe 21, the steam generated in the cooling cylinder 22, and the sealing gas (CO2) leave the slag discharge device as return gas through the return gas outlet e, and return to the middle of the gasifier as the gasifier to participate in the reaction. In order to ensure smooth slag discharge, ensure that steam, cooling water and sealing gas (CO2) can be introduced into the slag discharge device, and ensure that the return gas can return to the gasifier, the system pressure distribution is as follows: the pressure of the bottom ash outlet of the gasifier is P0, the pressure of the steam inlet is P1, the pressure of the cooling water inlet is P2, the pressure of the CO2 inlet is P3, and P0<P1<P2<P3≤50kPa.

[0053] According to another aspect of the present invention, a slag removal method for a fluidized bed gasifier is also provided, wherein the slag removal method uses the slag removal device for a fluidized bed gasifier as described in any one of the aforementioned embodiments. Specifically, the slag removal method for a fluidized bed gasifier may include the following steps:

[0054] S1: introducing a gasifying agent into the slag dropping pipe, so that the gasifying agent reacts with the carbon in the bottom slag at 1200°C-800°C from the gasifier, and at the same time produces a cooling effect on the bottom slag, generating bottom slag and flue gas with a low carbon content at 800°C-600°C;

[0055] S2: coolant is introduced into the cooling cylinder to reduce the temperature of the bottom slag from the slag falling pipe at 800°C-600°C to 300°C-200°C, and the coolant is heated at the same time;

[0056] S3: Introduce sealing gas into the slag discharge pipe to seal the bottom slag from the cooling cylinder at a temperature of 300°C to 200°C to below 100°C;

[0057] S4: The bottom slag, which is reduced to below 100°C, leaves the system after passing through the air lock device;

[0058] S5: The flue gas generated by the reaction of the gasifier and the bottom ash in the slag discharge pipe, the incompletely reacted gasifier, the gas phase coolant generated in the cooling cylinder, and the sealing gas are used as return gas and leave the slag discharge device through the return gas outlet.

[0059] The slag discharge device and slag discharge method for a fluidized bed gasifier provided by the present invention have the following advantages over the prior art: (1) the problem of slagging easily occurring during the slag discharge process is solved, thereby ensuring smooth slag discharge of the fluidized bed gasifier and reducing potential safety hazards; (2) water and water vapor can be used as gasifying agents or coolants, and the water and water vapor can come from the condensed water of the coal gasification system, thereby realizing the rational use of the condensed water of the coal gasification system; (3) the sensible heat of the bottom ash is fully utilized to generate steam or to superheat the steam, thereby improving the system efficiency; (4) the pressure in the slag discharge pipe is higher than the furnace bottom pressure, thereby effectively preventing the gasifying agent from being carried into the slag discharge pipe, thereby avoiding the problems of slagging easily occurring in the prior slag discharge method and gas blowby, thereby improving the operational flexibility of the slag discharge system of the gasifier and ensuring the long-term stable operation of the fluidized bed gasifier; (5) the steam reacts with the carbon in the bottom ash, thereby reducing the carbon content of the bottom ash to a certain extent, thereby improving the carbon conversion rate of the system and the cold coal gas efficiency; (6) the temperature of the hot slag can be reduced to below 100° C., thereby eliminating equipment such as a slag cooler and saving investment and operation and maintenance costs.

[0060] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of application of the present invention is defined by the appended claims and their equivalents.

[0061] List of reference numerals:

[0062] 1 Gasifier

[0063] 2 Slag discharge device

[0064] 21 Slag pipe

[0065] 22 Cooling cylinder

[0066] 23 Slag discharge pipe

[0067] 24 Air lock device

[0068] A Bottom slag

[0069] B Gasifier

[0070] C. Treated slag

[0071] D Sealing gas

[0072] E Return gas

[0073] F Coolant

[0074] a Bottom slag inlet

[0075] b Gasifying agent inlet

[0076] d Sealing gas inlet

[0077] e Return gas outlet

[0078] f Coolant inlet.

Claims

1. A slag discharge device (2) for a fluidized bed gasifier, the slag discharge device (2) having a bottom slag inlet (a) and a bottom slag outlet, characterized in that: The slag discharge device (2) is configured to gasify and cool the bottom slag (A); The slag discharge device (2) comprises a slag dropping pipe (21), a cooling cylinder (22) and a slag discharge pipe (23) which are connected in sequence; The slag discharge pipe (21) is provided with a gasifying agent inlet (b) for introducing a gasifying agent (B) into the slag discharge device (2); the cooling cylinder (22) is provided with a coolant inlet (f) for introducing a coolant (F) into the slag discharge device (2); the slag discharge pipe (23) or the cooling cylinder (22) is provided with a sealing gas inlet (d) for introducing a sealing gas (D) into the slag discharge device (2); Among them, P0<P1<P2<P3, so as to realize the pressure gradually increasing from the bottom ash outlet of the gasifier to the slag drop pipe (21) to the cooling cylinder (22) to the slag discharge pipe (23), P0 is the pressure of the bottom ash outlet of the gasifier, P1 is the pressure of the gasifying agent inlet, P2 is the pressure of the coolant inlet, and P3 is the pressure of the sealing gas inlet.

2. The slag discharge device (2) for a fluidized bed gasifier according to claim 1, characterized in that: The bottom ash inlet (a) is arranged on the slag dropping pipe (21) for connecting to the gasifier (1); the end of the slag dropping pipe (21) opposite to the bottom ash inlet (a) is connected to one end of a cooling cylinder (22); the other end of the cooling cylinder (22) is connected to a slag discharge pipe (23); the cooling cylinder (22) has an equivalent diameter greater than that of the slag dropping pipe (21) and greater than that of the slag discharge pipe (23).

3. The slag discharge device (2) for a fluidized bed gasifier according to claim 2, characterized in that: The cooling cylinder (22) comprises an upper involute section, a lower tapered section and a cylinder section between the upper involute section and the lower tapered section, wherein the equivalent diameter of the cylinder section is greater than the equivalent diameter of the slag dropping pipe (21) and greater than the equivalent diameter of the slag discharge pipe (23).

4. The slag discharge device (2) for a fluidized bed gasifier according to claim 2, characterized in that: The gasifying agent inlet (b) is arranged on the slag dropping pipe (21).

5. The slag discharge device (2) for a fluidized bed gasifier according to claim 3, characterized in that: The coolant inlet (f) is arranged on the cooling cylinder (22).

6. The slag discharge device (2) for a fluidized bed gasifier according to claim 5, characterized in that: The coolant inlet (f) is arranged on the upper involute section or the barrel section.

7. The slag discharge device (2) for a fluidized bed gasifier according to claim 1, characterized in that: The sealing gas inlet (d) comprises a first sealing gas inlet arranged on the slag discharge pipe (23).

8. The slag discharge device (2) for a fluidized bed gasifier according to claim 7, characterized in that: The sealing gas inlet (d) further comprises a second sealing gas inlet arranged on the lower tapered section of the cooling cylinder (22).

9. The slag discharge device (2) for a fluidized bed gasifier according to any one of claims 1 to 8, characterized in that: The slag discharge device (2) further comprises a return gas outlet (e), and the return gas outlet (e) is arranged on the cooling cylinder (22).

10. A slag removal method for a fluidized bed gasifier, characterized in that: The slag discharge method uses the slag discharge device (2) for a fluidized bed gasification furnace according to any one of claims 1 to 9.

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