An external ring cavity pressure balanced gasifier and a pressure balancing method of the gasifier

Abstract

The application provides an external ring cavity pressure balance gasification furnace and a pressure balance method of the gasification furnace, and relates to the field of gasification furnaces.The external ring cavity pressure balance gasification furnace comprises a furnace body and an external pressure balance mechanism, the furnace body comprises a pressure-bearing shell, a hearth and a water-cooled wall, the inner wall of the water-cooled wall surrounds a waste pot cavity, the hearth is communicated with the waste pot cavity, a partition plate is arranged between the outer wall of the water-cooled wall and the pressure-bearing shell, the partition plate separates a ring cavity and a cooling cavity, a balance hole is arranged on the water-cooled wall, the external pressure balance mechanism comprises a first pressure balance pipe and a second pressure balance pipe which are communicated through a pressure balance valve, the first pressure balance pipe is connected with the ring cavity, the second pressure balance pipe is divided into an air guide pipe and a discharge pipe at the end far from the pressure balance valve, the air guide pipe is used for connecting the cooling cavity, and the discharge pipe is used for connecting downstream equipment.The external ring cavity pressure balance gasification furnace can realize pressure balance of the ring cavity and the waste pot cavity, can realize communication when the water-cooled wall bears abnormal internal pressure or external pressure, can reduce the pressure difference, and can avoid instability deformation of the water-cooled wall.

Description

Technical Field

[0001] This invention relates to the field of gasifiers, and more specifically, to an external annular cavity pressure-balanced gasifier and a pressure-balancing method for the gasifier. Background Technology

[0002] Waste boiler-type high-pressure gasifiers typically have a thick-walled outer shell, with an internal reaction space consisting of coiled or tubular water-cooled walls. The cavity between the water-cooled walls and the pressure-bearing outer shell is usually called the annular cavity. Generally, the outer thick-walled shell is the pressure-bearing component of the gasifier, while the water-cooled walls, acting as a confinement device for high-temperature gases, maintain a pressure balance between their internal and external components; that is, the water-cooled walls do not bear internal or external pressure. To ensure the pressure balance between the internal and external components of the water-cooled walls and to prevent the backflow of high-temperature gas and fine ash into the annular cavity, continuous purging of the annular cavity is required. Simultaneously, to reduce energy consumption, one or more balance holes with a cross-sectional area much smaller than the annular cavity are provided between the annular cavity and the water-cooled walls confining the inner cavity, allowing gas to continuously drain into the inner cavity. Because the pressure fluctuations during the start-up and shutdown of the gasification unit are large, especially when the internal cavity is venting under abnormal operating conditions, the pressure in the annular cavity will be higher than the pressure in the internal cavity due to the limited flow area of ​​the balance hole. This will cause the water-cooled wall to become a component that bears external pressure, which can easily cause the water-cooled wall to become unstable, deformed or torn, resulting in a major production accident caused by damage to the water-cooled wall. However, in order to avoid the untimely release of annular cavity pressure, the flow area of ​​the balance hole must be increased, which will further lead to a significant increase in the amount of purging gas and increase energy consumption. Summary of the Invention

[0003] The present invention includes, for example, providing an external annular cavity pressure balancing gasifier and a pressure balancing method for the gasifier.

[0004] The embodiments of the present invention can be implemented as follows:

[0005] In a first aspect, the present invention provides an external annular pressure-balanced gasifier, comprising a furnace body and an external pressure balancing mechanism. The furnace body includes a pressure-bearing outer shell, a furnace chamber, and a water-cooled wall. The inner wall of the water-cooled wall forms a waste pot cavity, and the furnace chamber communicates with the waste pot cavity. A partition is provided between the outer wall of the water-cooled wall and the pressure-bearing outer shell, dividing the space between the pressure-bearing outer shell and the water-cooled wall into an upper annular cavity and a lower cooling cavity. The water-cooled wall is provided with a balancing hole for communicating with the waste pot cavity and the annular cavity. The external pressure balancing mechanism includes a first pressure balancing pipe and a second pressure balancing pipe, which are connected by a bidirectional pressure balancing valve. The end of the first pressure balancing pipe away from the pressure balancing valve is used to connect to the annular cavity, and the end of the second pressure balancing pipe away from the pressure balancing valve is divided into an intake pipe and a discharge pipe. The intake pipe is used to connect to the cooling cavity, and the discharge pipe is used to connect to downstream equipment.

[0006] In an optional embodiment, the pressure balancing valve is activated when the pressure difference between the annular cavity and the waste pot cavity is 10-70 kPa.

[0007] In an optional embodiment, the number of the first pressure balancing tube and the second pressure balancing tube are 1-10 sets respectively.

[0008] In an optional embodiment, a first isolation shut-off valve is provided on the first pressure balancing pipe, and a second isolation shut-off valve is provided on the second pressure balancing pipe, with the pressure balancing valve located between the first isolation shut-off valve and the second isolation shut-off valve.

[0009] In an optional embodiment, the external pressure balancing mechanism further includes a protective air pipe, which includes a first purge branch pipe and a second purge branch pipe. The first purge branch pipe is connected to the first pressure balancing pipe on the side of the first isolation shut-off valve away from the pressure balancing valve, and the second purge branch pipe is connected to the second pressure balancing pipe on the side of the second isolation shut-off valve away from the pressure balancing valve.

[0010] In an optional embodiment, both the first purge branch pipe and the second purge branch pipe are provided with orifice plates for forming a uniform, stable and continuous purge gas.

[0011] In an optional embodiment, the external annular pressure-balanced gasifier further includes an annular protection pipe for introducing protective gas into the annular cavity. The annular protection pipe is connected to the annular cavity in a separate path, or the annular protection pipe is connected to the protective gas pipe and serves as a branch of the protective gas pipe to the side of the first pressure-balanced pipe near the pressure-bearing outer shell.

[0012] In an optional embodiment, the external annular pressure-balanced gasifier further includes a crude gas pipe for discharging crude gas. The crude gas pipe is connected to the cooling chamber in a separate line, or the gas inlet pipe and the outlet pipe are integrated into the crude gas pipe, which is connected to the second pressure-balanced pipe.

[0013] In an optional embodiment, a bypass valve assembly line for connecting the first pressure balancing pipe and the second pressure balancing pipe is further provided between the first pressure balancing pipe and the second pressure balancing pipe, and a bypass valve is provided on the bypass valve assembly line.

[0014] Secondly, the present invention provides a pressure balancing method for a gasifier, which is carried out using an external annular cavity pressure balancing gasifier as described in any of the foregoing embodiments.

[0015] The beneficial effects of the embodiments of the present invention include, for example:

[0016] This invention provides an external annular pressure-balanced gasifier. Through an externally mounted first pressure balancing pipe, pressure balancing valve, and second pressure balancing pipe, it achieves pressure balance between the annular cavity and the waste heat boiler cavity. This allows for connection when the water-cooled wall is subjected to abnormal internal or external pressure, reducing pressure differential and preventing instability and deformation of the water-cooled wall. Especially when the annular cavity pressure is lower than the waste heat boiler cavity pressure, the annular cavity can be replenished with cooled crude gas discharged from the cooling chamber. This helps reduce the amount of high-temperature gas entering the annular cavity through the balancing holes, preventing the water-cooled wall from being subjected to outward expansion pressure due to low annular cavity pressure, thus reducing losses. The pressure balancing valve in this embodiment allows for bidirectional flow, enabling timely pressure release or replenishment when the annular cavity pressure is higher or lower than the waste heat boiler cavity pressure. This prevents the pressure difference between the annular cavity and the waste heat boiler cavity from increasing, leading to instability and deformation of the water-cooled wall and damage to the equipment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the external annular pressure-balanced gasifier provided in the embodiments of this application.

[0019] Icons: 100 - External annular pressure-balanced gasifier; 110 - Pressure-bearing outer shell; 111 - Water-cooled wall; 112 - Waste boiler chamber; 113 - Baffle plate; 114 - Annular cavity; 115 - Cooling chamber; 116 - Balancing hole; 117 - Crude gas outlet pipe; 118 - Furnace chamber; 120 - First pressure balancing pipe; 121 - First isolation shut-off valve; 130 - Second pressure balancing pipe; 131 - Second isolation shut-off valve; 132 - Inlet gas pipe; 133 - Discharge pipe; 140 - Pressure balancing valve; 150 - Protective gas pipe; 151 - Annular cavity protective pipe; 152 - First purging branch pipe; 153 - Second purging branch pipe; 154 - Throttling orifice plate; 160 - Bypass valve group pipeline; 161 - Bypass valve. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and 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, and therefore should not be construed as a limitation of this invention.

[0024] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0025] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0026] Please refer to Figure 1 This embodiment provides an external annular pressure-balanced gasifier 100, which includes a furnace body and an external pressure balancing mechanism. The furnace body includes a pressure-bearing outer shell 110, a water-cooled wall 111, and a furnace chamber 118. The inner wall of the water-cooled wall 111 forms a waste pot cavity 112. The furnace chamber 118 is located above the waste pot cavity 112 and communicates with it. A partition 113 is provided between the outer wall of the water-cooled wall 111 and the pressure-bearing outer shell 110. The partition 113 divides the space between the pressure-bearing outer shell 110 and the water-cooled wall 111 into an upper annular cavity 114 and a lower cooling cavity 115. A balancing hole 116 is provided on the water-cooled wall 111. The balancing hole 116 can connect the waste pot cavity 112 and the annular cavity 114 to achieve pressure balance between the waste pot cavity 112 and the annular cavity 114. The pressure-bearing outer shell 110 is also provided with a crude gas outlet pipe 117 on the side wall corresponding to the cooling chamber 115. The high-temperature flue gas generated by the furnace 118 passes through the waste boiler chamber 112, and is then cooled by the water washing cooling chamber 115 before finally being discharged from the crude gas outlet pipe 117.

[0027] The main function of the waste boiler cavity 112 is to recover the sensible heat of high-temperature syngas and slag to improve energy utilization efficiency. The waste boiler cavity 112 is usually designed as a cylindrical structure formed by connecting pipes of several water-cooled walls 111 through fins. As a special pressure-bearing component, the pressure of the annular cavity 114 is slightly greater than the pressure inside the waste boiler cavity 112 during normal operation. However, during the start-up and shutdown of the gasifier or under certain abnormal operating conditions, due to the limited flow area of ​​the balance hole 116, the pressure difference between the annular cavity 114 and the waste boiler cavity 112 may increase or decrease instantaneously, causing the water-cooled walls 111 to be subjected to external or internal pressure. This makes the water-cooled walls 111 a component subjected to external pressure, which can easily cause instability, deformation or tearing of the water-cooled walls 111, resulting in a major production accident caused by damage to the water-cooled walls 111. However, to avoid untimely pressure release from the annular cavity 114, the flow area of ​​the balance hole 116 must be increased, which further leads to a significant increase in the amount of purging gas and increases energy consumption.

[0028] Therefore, in this embodiment, without increasing the flow area of ​​the balance hole 116, a dual adjustment is achieved by using an external balance adjustment mechanism in conjunction with the balance hole 116, which can effectively prevent pressure imbalance between the waste pot cavity 112 and the annular cavity 114.

[0029] Specifically, in this embodiment, the external balancing mechanism includes a first pressure balancing pipe 120 and a second pressure balancing pipe 130. The first pressure balancing pipe 120 and the second pressure balancing pipe 130 are connected by a bidirectional pressure balancing valve 140. The end of the first pressure balancing pipe 120 away from the pressure balancing valve 140 is used to connect to the annular cavity 114. The end of the second pressure balancing pipe 130 away from the pressure balancing valve 140 is divided into an air intake pipe 132 and an exhaust pipe 133. The air intake pipe 132 is used to connect to the cooling cavity 115, and the exhaust pipe 133 is used to connect to downstream equipment (e.g., a washing device) to achieve washing of the discharged gas.

[0030] In this embodiment, the second pressure balance pipe 130 can be directly connected to the cooling chamber 115 through the air intake pipe 132, or the second pressure balance pipe 130 can be connected to the crude gas outlet pipe 117. In this case, the air intake pipe 132 and the discharge pipe 133 can be integrated as the crude gas outlet pipe 117.

[0031] In this embodiment, a first pressure balancing pipe 120 and a second pressure balancing pipe 130 are respectively provided on the side walls of the pressure-bearing shell 110 corresponding to the annular cavity 114 and the cooling cavity 115. The first pressure balancing pipe 120 and the second pressure balancing pipe 130 are connected through a bidirectional flow pressure balancing valve 140, and the second pressure balancing pipe 130 is connected to the crude gas outlet pipe 117.

[0032] This embodiment achieves pressure regulation of the annular cavity 114 by setting up an external first pressure balancing pipe 120, a second pressure balancing pipe 130 and a pressure balancing valve 140, so as to realize timely release or replenishment of pressure in the annular cavity 114, and avoid the situation where the pressure difference between the annular cavity 114 and the waste pot cavity 112 increases, causing the water-cooled wall 111 to become unstable and deformed, and damaging the equipment.

[0033] Generally, the water-cooled wall 111 is designed to withstand an external pressure of no more than 40 kPa. When the gasifier pressure fluctuates or an emergency pressure is released, the pressure difference will increase. In this embodiment, the pressure balancing valve 140 is activated when the pressure difference between the annular cavity 114 and the waste pot cavity 112 is 10-70 kPa. Preferably, the pressure balancing valve 140 is activated when the pressure difference between the annular cavity 114 and the waste pot cavity 112 is 10-30 kPa. It can be activated before the pressure difference between the annular cavity 114 and the waste pot cavity 112 reaches 40 kPa, thereby achieving the adjustment of the pressure in the annular cavity 114 and the waste pot cavity 112.

[0034] Since the gasifier's diameter is approximately 1.4-2.2m, to ensure rapid pressure release or replenishment within the annular cavity 114, in this embodiment, the number of the first pressure balancing pipe 120 and the second pressure balancing pipe 130 are 1-10 sets respectively. Furthermore, in this embodiment, the diameters of the first pressure balancing pipe 120 and the second pressure balancing pipe 130 are larger than the diameter of the balancing hole 116, enabling pressure to be preferentially released or replenished from the first pressure balancing pipe 120 and the second pressure balancing pipe 130.

[0035] When the pressure in the annular cavity 114 is higher than the pressure in the waste pot cavity 112, the water-cooled wall 111 will bear inward pressure. If the pressure is too high, it will cause the water-cooled wall 111 to become unstable and deform, resulting in damage to the water-cooled wall 111. In this embodiment, when the pressure in the annular cavity 114 is higher than the pressure in the waste pot cavity 112, in addition to releasing some gas through the top balance hole 116, gas can also be released to the gasifier outlet pipeline through the first pressure balance pipe 120, the pressure balance valve 140, and the second pressure balance pipe 130. This can achieve rapid release of pressure in the annular cavity 114 and prevent the water-cooled wall 111 from becoming unstable and deformed due to the high pressure in the annular cavity 114.

[0036] When the pressure in the annular cavity 114 is low, the high-temperature gas from the waste boiler cavity 112 will enter the annular cavity 114 through the balance hole 116. Since the medium temperature in the waste boiler cavity 112 is high, it will cause serious damage to the pressure-bearing outer shell 110. At this time, the low pressure in the annular cavity 114 will generate negative pressure suction, which can bring the cooled crude gas in the crude gas outlet pipe 117 into the annular cavity 114 through the second pressure balance pipe 130, the pressure balance valve 140 and the first pressure balance pipe 120. This helps to reduce the amount of high-temperature gas entering the annular cavity 114 through the balance hole 116, and avoid the water-cooled wall 111 from being subjected to outward expansion pressure due to the low pressure in the annular cavity 114, thus reducing the loss.

[0037] Furthermore, in this embodiment, a first isolation shut-off valve 121 is provided on the first pressure balancing pipe 120, and a second isolation shut-off valve 131 is provided on the second pressure balancing pipe 130. A pressure balancing valve 140 is located between the first isolation shut-off valve 121 and the second isolation shut-off valve 131. Under normal operating conditions, both the first isolation shut-off valve 121 and the second isolation shut-off valve 131 are open. When there is an abnormality in the opening and closing of the pressure balancing valve 140, maintenance of the pressure balancing valve 140 can be achieved by closing the first isolation shut-off valve 121 and the second isolation shut-off valve 131.

[0038] Furthermore, to prevent pressure imbalance during the maintenance of the pressure balancing valve 140, in this embodiment, a bypass valve assembly line 160 is provided between the first pressure balancing pipe 120 and the second pressure balancing pipe 130 to connect them. A bypass valve 161 is installed on the bypass valve assembly line 160. Under normal operating conditions, the bypass valve 161 is normally closed, and is only briefly opened during the maintenance of the pressure balancing valve 140 to ensure that there is no pressure imbalance during the overall operation of the gasifier.

[0039] Furthermore, a protective air pipe 150 is also provided on the side wall of the pressure-bearing outer shell 110 corresponding to the annular cavity 114. The protective air pipe 150 can introduce protective gas into the annular cavity 114 and can also purge the pressure balancing valve 140 to prevent blockage of the pressure balancing valve 140. Specifically, the protective air pipe 150 includes an annular cavity protective pipe 151, a first purging branch pipe 152, and a second purging branch pipe 153. The annular cavity protective pipe 151 is connected to the side of the first pressure balancing pipe 120 near the pressure-bearing outer shell 110. The first purging branch pipe 152 is connected to the side of the first pressure balancing pipe 120 corresponding to the side of the first isolation shut-off valve 121 away from the pressure balancing valve 140. The second purging branch pipe 153 is connected to the second pressure balancing pipe 130 corresponding to the side of the second isolation shut-off valve 131 away from the pressure balancing valve 140. Both the first purging branch pipe 152 and the second purging branch pipe 153 are provided with orifice plates 154. The first purge branch pipe 152 and the second purge branch pipe 153 can continuously purge the pressure balancing valve 140, thereby ensuring that the pressure balancing valve 140 is not blocked.

[0040] It should be noted that in this embodiment, the annular cavity protection pipe 151 can be a separate line directly connected to the annular cavity 114, or it can be used as a branch pipe for the protection air pipe 150, thereby simplifying the pipeline.

[0041] According to the external annular pressure-balanced gasifier 100 provided in this embodiment, the working principle of the external annular pressure-balanced gasifier 100 is as follows:

[0042] When the pressure in the annular cavity 114 is higher than the pressure in the waste boiler cavity 112, some of the gas in the annular cavity 114 will be released through the top balance hole 116. At the same time, the gas will also be released to the gasifier outlet pipeline through the first pressure balance pipe 120, the pressure balance valve 140 and the second pressure balance pipe 130. This can achieve rapid discharge of the pressure in the annular cavity 114 and prevent the water-cooled wall 111 from being subjected to inward pressure due to the high pressure in the annular cavity 114, which could lead to instability and deformation.

[0043] When the pressure in the annular cavity 114 is lower than the pressure in the waste boiler cavity 112, the low pressure in the annular cavity 114 will generate negative pressure suction, which can allow the cooled crude gas in the crude gas outlet pipe 117 to enter the annular cavity 114 through the second pressure balance pipe 130, the pressure balance valve 140 and the first pressure balance pipe 120. At this time, it is beneficial to reduce the amount of high-temperature gas entering the annular cavity 114 from the balance hole 116, and avoid the water-cooled wall 111 from being subjected to outward expansion pressure due to the low pressure in the annular cavity 114, thus reducing the loss.

[0044] In this embodiment, the externally mounted first pressure balancing pipe 120, pressure balancing valve 140, and second pressure balancing pipe 130 achieve pressure balance between the annular cavity 114 and the waste pot cavity 112. This allows the water-cooled wall 111 to maintain connectivity when subjected to abnormal internal or external pressure, reducing the pressure difference and preventing instability and deformation of the water-cooled wall 111. The pressure balancing valve 140 in this embodiment allows for bidirectional flow, enabling timely release or replenishment of gas pressure in the annular cavity 114 when the pressure is higher or lower than the pressure in the waste pot cavity 112. This prevents the pressure difference between the annular cavity 114 and the waste pot cavity 112 from increasing, which could lead to instability and deformation of the water-cooled wall 111 and damage to the equipment. Furthermore, in this embodiment, the pressure balancing valve 140 is continuously purged through the first purge branch pipe 152 and the second purge branch pipe 153, effectively preventing blockage and ensuring its normal operation. Under normal operating conditions, both the first isolation shut-off valve 121 and the second isolation shut-off valve 131 are open. When there is an abnormality in the opening and closing of the pressure balancing valve 140, the pressure balancing valve 140 can be repaired by closing the first isolation shut-off valve 121 and the second isolation shut-off valve 131.

[0045] In addition, the present invention also provides a pressure balancing method for a gasifier, which is carried out using an external annular cavity pressure balancing gasifier 100 as described in any of the foregoing embodiments.

[0046] In summary, this embodiment of the invention provides an external annular pressure-balanced gasifier 100, which achieves pressure balance between the annular cavity 114 and the waste pot cavity 112 through an externally mounted first pressure balancing pipe 120, pressure balancing valve 140, and second pressure balancing pipe 130. This allows the water-cooled wall 111 to maintain connection when subjected to abnormal internal or external pressure, reducing the pressure difference and preventing instability and deformation of the water-cooled wall 111. In this embodiment, the pressure balancing valve 140 enables bidirectional flow, allowing for timely release or replenishment of gas pressure in the annular cavity 114 when the pressure in the annular cavity 114 is higher or lower than the pressure in the waste pot cavity 112. This prevents the water-cooled wall 111 from becoming unstable and deformed due to an increased pressure difference between the annular cavity 114 and the waste pot cavity 112, thus avoiding damage to the equipment.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An external annular pressure balanced gasifier, characterized by, The external ring cavity pressure balance gasification furnace comprises a furnace body and an external pressure balance mechanism, the furnace body comprises a pressure-bearing shell, a hearth and a water-cooled wall, an inner wall of the water-cooled wall surrounds a waste pot cavity, the hearth is communicated with the waste pot cavity, a partition plate is arranged between an outer wall of the water-cooled wall and the pressure-bearing shell, the partition plate divides a space between the pressure-bearing shell and the water-cooled wall into an upper ring cavity and a lower cooling cavity, a balance hole for communicating the waste pot cavity and the ring cavity is arranged on the water-cooled wall, the external pressure balance mechanism comprises a first pressure balance pipe and a second pressure balance pipe, the first pressure balance pipe and the second pressure balance pipe are communicated through a pressure balance valve capable of flowing in two directions, one end of the first pressure balance pipe away from the pressure balance valve is used for connecting the ring cavity, one end of the second pressure balance pipe away from the pressure balance valve is divided into an air guide pipe and a discharge pipe, the air guide pipe is used for connecting the cooling cavity, and the discharge pipe is used for connecting downstream equipment. A first isolation cut-off valve is arranged on the first pressure balance pipe, a second isolation cut-off valve is arranged on the second pressure balance pipe, and the pressure balance valve is located between the first isolation cut-off valve and the second isolation cut-off valve. The external pressure balance mechanism further comprises a protective gas pipe, the protective gas pipe comprises a first purging branch pipe and a second purging branch pipe, the first purging branch pipe is connected to the first pressure balance pipe on a side corresponding to the first isolation cut-off valve and away from the pressure balance valve, and the second purging branch pipe is connected to the second pressure balance pipe on a side corresponding to the second isolation cut-off valve and away from the pressure balance valve.

2. The external annular pressure balanced gasifier of claim 1, wherein, The pressure balance valve is started when the pressure difference between the ring cavity and the waste pot cavity is 10-70 kPa.

3. The external annular pressure balanced gasifier of claim 1, wherein, The number of the first pressure balance pipe and the second pressure balance pipe is 1-10 groups respectively.

4. The external annular pressure balanced gasifier of claim 1, wherein, The first purging branch pipe and the second purging branch pipe are both provided with a throttle orifice plate for forming uniform, stable and continuous purging gas.

5. The external annular pressure balanced gasifier of claim 1, wherein, The external ring cavity pressure balance gasification furnace further comprises a ring cavity protective pipe for introducing protective gas into the ring cavity, the ring cavity protective pipe is communicated with the ring cavity in a single way, or the ring cavity protective pipe is communicated with the protective gas pipe and connected to the first pressure balance pipe on a side close to the pressure-bearing shell as a branch thereof.

6. The external annular pressure balanced gasifier of claim 1, wherein, The external ring cavity pressure balance gasification furnace further comprises a raw coal gas pipe for discharging raw coal gas, the raw coal gas pipe is communicated with the cooling cavity in a single way, or the air guide pipe and the discharge pipe are integrated into the raw coal gas pipe, and the raw coal gas pipe is communicated with the second pressure balance pipe.

7. The external annular pressure balanced gasifier of claim 1, wherein, A bypass valve group pipeline for communicating the first pressure balance pipe and the second pressure balance pipe is further arranged between the first pressure balance pipe and the second pressure balance pipe, and a bypass valve is arranged on the bypass valve group pipeline.

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