Hearth of energy-saving steam boiler using biomass as fuel

Abstract

The invention belongs to the technical field of energy-saving steam boilers with biomass as fuel, and discloses a hearth of an energy-saving steam boiler with biomass as fuel, the hearth of the energy-saving steam boiler comprises a boiler shell and a plurality of layers of cylindrical membrane walls sleeved together, the top ends of water pipes in the membrane walls are communicated with an upper header, and the top ends of the water pipes in the membrane walls are communicated with a lower header. The bottom ends of the water pipes in the membrane wall are communicated with the lower collecting box; the top of the upper collecting box is communicated with the gas collecting bag through an overheating pipe; the plurality of layers of cylindrical membrane walls, the overheating pipe and the gas collecting bag are wrapped in the furnace shell; the vertical boiler has the beneficial effects that high-temperature fuel gas sequentially flows through the inner side surface and the outer side surface of the cylindrical membrane type wall, the membrane type wall is heated from the inner side and the outer side at the same time, the heating area of the membrane type wall is increased, the heat exchange efficiency is improved, and the technical problem of single-face heating of the membrane type wall in a vertical boiler in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy-saving steam boilers using biomass as fuel, and in particular relates to a furnace of an energy-saving steam boiler using biomass as fuel. Background Art

[0002] Chinese invention patent CN105465760A discloses a biomass steam generator, including a lower base, an upper body, a fire viewing hole, a refractory layer, a thermal insulation layer, a tertiary air duct, a smoke box, a soot blowing device, and an inspection hole; the lower base and the upper body are internally connected to form a furnace; at least three air ducts are formed in the steam generator, leading to the lower part of the lower base, the upper part of the lower base, and the upper part of the furnace respectively. The lower base is connected to a feed pipe and an air inlet pipe, and the lower base is provided with a grate; the at least three air ducts formed in the steam generator include a primary air duct, a secondary air duct, and a tertiary air duct; one end of the primary air duct is connected to the bottom of the grate, and one end of the secondary air duct is connected to the upper part of the grate; one end of the tertiary air duct is connected to the upper part of the furnace.

[0003] In its proposal, it is disclosed that the structure "the main body 11 adopts a multi-water tube structure, which is connected by the inner circle water tube 9 and the outer circle water tube 10 in the middle between the annular upper header 12 and the lower header 7. The inner circle water tube 9, the outer circle water tube 10 and the fins 20 are welded to form a membrane wall (fin tube) structure", "the inner circle water tube and the outer circle water tube are staggered, the flue gas flushes the water tube horizontally, and runs in an S shape horizontally in the convection flue, which is fully disturbed, the heat exchange efficiency is improved, and it is not easy to accumulate dust. The inner circle water tube, the outer circle water tube and the fins are welded to form a membrane wall (fin tube) structure, so that the convection flue does not leak air and the heat loss is small; the inner circle water tube can also be welded without fins, and a dense tube structure arranged tightly can be adopted; the outer circle water tube can also be welded without fins, and the outer circle water tube can be surrounded by an outer shell or a refractory layer to prevent smoke leakage; if necessary, the convection flue can be arranged with a multi-circle water tube design of more than 2 circles".

[0004] The biomass steam generator proposed in this patent has the advantages of safety, high efficiency, energy saving, environmental protection, compact overall structure, small footprint, quick installation, high degree of automation, simple operation and low operating cost.

[0005] However, it can be seen from the disclosed structure and the accompanying drawings that the complete membrane wall can only be heated on one side and the heat can only be absorbed from one side, which is not conducive to energy saving. Summary of the invention

[0006] The objective of the present invention is to solve the technical problem that in the prior art neutral energy-saving steam boiler using biomass as fuel, the membrane wall is heated on one side, which is not conducive to energy saving.

[0007] In order to achieve the above object, the present invention provides a furnace of an energy-saving steam boiler using biomass as fuel.

[0008] The specific technical solution adopted by the present invention is: A furnace of an energy-saving steam boiler using biomass as fuel, the furnace of the energy-saving steam boiler comprising a furnace shell and a plurality of layers of cylindrical membrane walls which are sleeved together, the top ends of water pipes in the membrane walls are connected to an upper header, and the bottom ends of water pipes in the membrane walls are connected to a lower header; the top of the upper header is connected to an air collecting bag through a superheating pipe; the furnace shell wraps the plurality of layers of cylindrical membrane walls, the superheating pipe and the air collecting bag in the furnace shell; The adjacent membrane walls form an intermediate flue for flue gas; the innermost membrane wall forms an inner flue; the outermost membrane wall and the furnace shell form an outer flue; the inner flue, several intermediate flues and the outer flue are connected alternately and sequentially through the top opening and the bottom opening; The furnace is provided with a combustion hole, which passes through the furnace shell and the membrane wall to send the burning biomass into the inner flue; a water inlet pipe is provided at the bottom of the membrane wall; and a smoke exhaust hole is provided at the furnace shell.

[0009] Furthermore, the plurality of layers of cylindrical membrane walls are preferably two, namely an inner membrane wall and an outer membrane wall.

[0010] Furthermore, the combustion hole is arranged at the top of the furnace, the inner flue is provided with a bottom opening, the outer flue is provided with a top opening, and the smoke exhaust hole is arranged at the bottom of the furnace shell.

[0011] Furthermore, the combustion hole is arranged at the bottom of the furnace, the inner flue is provided with a top opening, the outer flue is provided with a bottom opening, and the smoke exhaust hole is arranged at the top of the furnace shell.

[0012] Furthermore, a smoke guide plate is provided on the top opening and the bottom opening on the side where the smoke flows out.

[0013] Furthermore, the smoke guide plate is spiral-shaped.

[0014] Furthermore, metal wires are evenly distributed around the circumference of the inner flue, the middle flue and the outer flue, the metal wires are connected to the negative pole of the high-voltage power supply, the positive pole of the high-voltage power supply is grounded, the membrane wall and the furnace shell are grounded, and the dust is assisted by static electricity to move to and deposit on the membrane wall.

[0015] Furthermore, the channel cross-sectional areas of the inner flue, the middle flue and the outer flue decrease successively.

[0016] Furthermore, the angle between the superheater tube and the inner flue axis is A, 10°≤A≤80°.

[0017] Furthermore, the furnace shell is provided with a heat-insulating layer.

[0018] The positive effects of the present invention are: an intermediate flue for flue gas is formed between adjacent membrane walls; the innermost circle of membrane walls forms an inner flue; the outermost circle of membrane walls and the furnace shell form an outer flue; the inner flue, several intermediate flues and the outer flue are alternately connected in sequence through the top opening and the bottom opening, so that high-temperature combustion gas flows through the inner surface and the outer surface of the cylindrical membrane wall in sequence, and the membrane wall is heated from the inside and the outside at the same time, thereby increasing the heating area of ​​the membrane wall, improving the efficiency of heat exchange, and improving the technical problem of single-sided heating of the membrane wall in the existing neutral boiler; at the same time, due to the sudden contraction at the connection point of the inner flue, the intermediate flue and the outer flue, a low-speed zone is formed at the corners of the connection point, and dust particles are deposited, and the flow channel formed by the membrane wall is a cylindrical flow channel that is nested together and is smooth, so dust is not easy to deposit on the surface of the membrane wall, but slides down along the membrane wall into the bottom of the inner flue, the intermediate flue and the outer flue, which is convenient for dust collection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a three-dimensional structural schematic diagram of a furnace of an energy-saving steam boiler using biomass as fuel from a first viewing angle of the present invention; Figure 2 yes Figure 1 A schematic diagram of the three-dimensional structure of a furnace of an energy-saving steam boiler using biomass as fuel according to the present invention from a second viewing angle is shown in FIG. Figure 3 yes Figure 2 A schematic diagram of a half-section structure of a furnace of an energy-saving steam boiler using biomass as fuel according to the present invention is shown in FIG. Figure 4 yes Figure 3 A cross-sectional view of a furnace of an energy-saving steam boiler using biomass as fuel at a top opening or a bottom opening of the present invention is shown in FIG. Figure 5 This is a schematic diagram of the first type of flue gas flow structure of a furnace of an energy-saving steam boiler using biomass as fuel according to the present invention; Figure 6 The present invention is a schematic diagram of the second flue gas flow structure of the furnace of an energy-saving steam boiler using biomass as fuel.

[0020] Legend: 1—top opening of inner membrane wall, 101—bottom opening of inner membrane wall, 2—top edge of inner membrane wall rib, 201—bottom edge of rib, 202—smoke guide plate, 3—rib of inner membrane wall, 4—external flue, 5—middle flue, 6—inner flue, 7—bottom opening of outer membrane wall, 8—descaling pipe, 9—bottom of inner flue, 10—combustion hole, 1001—top combustion hole, 11—dust collection box, 12—water inlet pipe, 13—inner membrane wall, 1301—inner membrane wall water pipe, 14—outer membrane wall, 1401—outer membrane wall rib, 1402—outer membrane wall Wall water pipe, 1403—top edge of outer membrane wall rib plate, 1404—bottom edge of outer membrane wall rib plate, 15—lower interface of water level gauge, 16—upper header, 1601—lower header, 17—upper interface of water level gauge, 18—furnace shell, 19—top plate, 20—gas collecting bag, 21—top heating chamber, 22—top smoke exhaust hole, 2201—bottom smoke exhaust hole, 23—superheating pipe, 24—top opening of outer membrane wall. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments: In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0024] like Figures 1 to 6As shown, it is a structural diagram of the furnace of an energy-saving steam boiler using biomass as fuel provided by an embodiment of the present invention. The furnace of the energy-saving steam boiler includes a furnace shell 18 and a plurality of layers of cylindrical membrane walls which are sleeved together. The top ends of the water pipes in the membrane walls are all connected to the upper header 16, and the bottom ends of the water pipes in the membrane walls are all connected to the lower header 1601; the top of the upper header 16 is connected to the gas collecting bag 20 through the superheating pipe 23; the furnace shell 18 connects the plurality of layers of cylindrical membrane walls, the superheating pipe 23 and the collector The air bag 20 is wrapped in the furnace shell 18; the adjacent membrane walls form an intermediate flue 5 for flue gas; the innermost membrane wall forms an inner flue 6; the outermost membrane wall and the furnace shell form an outer flue 4; the inner flue 6, several intermediate flues 5 and the outer flue 4 are connected alternately in sequence through the top opening and the bottom opening; the furnace 18 is provided with a combustion hole 10, and the combustion hole 10 passes through the furnace shell 18 and the membrane wall to send the burning biomass into the inner flue; a water inlet pipe 12 is provided at the bottom of the membrane wall; and the furnace shell is provided with a smoke exhaust hole.

[0025] In the embodiment of the present invention, an intermediate flue for flue gas is formed between adjacent membrane walls; the innermost membrane wall forms an inner flue; the outermost membrane wall and the furnace shell form an outer flue; the inner flue, several intermediate flues and the outer flue are connected alternately and sequentially through the top opening and the bottom opening, so that the high-temperature combustion gas flows through the inner surface and the outer surface of the cylindrical membrane wall in turn, and the membrane wall is heated from the inside and the outside at the same time, which increases the heating area of ​​the membrane wall, improves the efficiency of heat exchange, and improves the technical problem of single-sided heating of the membrane wall in the prior art neutral boiler; at the same time, due to the sudden contraction at the connection between the inner flue, the intermediate flue and the outer flue, a low-speed zone is formed at the corners of the connection, and dust particles are deposited, and the flow channel formed by the membrane wall is a cylindrical flow channel that is fitted together and is smooth, so dust is not easy to deposit on the surface of the membrane wall, but slides down along the membrane wall into the bottom of the inner flue, the intermediate flue and the outer flue, which is convenient for dust collection.

[0026] In one embodiment of the present invention: A furnace of an energy-saving steam boiler using biomass as fuel, the furnace comprising a furnace shell 18 and a plurality of layers of cylindrical membrane walls sheathed together; Figure 5 or Figure 6 As shown, taking two layers of cylindrical membrane walls as an example, a cylindrical membrane wall with a smaller diameter is inserted into a cylindrical membrane wall with a larger diameter, thus forming a multi-layer membrane wall structure; the membrane wall is divided into an inner membrane wall 13 and an outer membrane wall 14; wherein the inner membrane wall 13 is formed by alternately connecting bracket-shaped inner membrane wall water pipes 1301 and inner membrane wall ribs 3 to form a closed cylindrical structure, and preferably, this connection method adopts welding; the outer membrane wall 14 is formed by alternately connecting bracket-shaped outer membrane wall water pipes 1402 and outer membrane wall ribs 1401 to form a closed cylindrical structure, and preferably, this connection method adopts welding.

[0027] The top ends of the water pipes in the membrane wall are connected to the upper header 16, and the bottom ends of the water pipes in the membrane wall are connected to the lower header 1601; a water inlet pipe 12 is provided at the bottom of the membrane wall through communication with the upper header 16 and the lower header 1601, so that water enters the membrane wall from the bottom, is heated to generate steam, and then enters the upper header 16.

[0028] The top of the upper header 16 is connected to the gas collecting bag 20 through the superheating pipe 23; the steam passes through the superheating pipe 23 and is dried before entering the gas collecting bag.

[0029] The furnace shell 18 wraps several layers of cylindrical membrane walls, superheating pipes 23 and gas collecting bags 20 in the furnace shell 18; in this way, after the steam is dried through the superheating pipes 23 and enters the gas collecting bag 20, it can still be heated by the flue gas, so that the superheated steam can be continuously dried and the temperature of the superheated steam can be guaranteed.

[0030] The adjacent membrane walls form an intermediate flue 5 for flue gas; the innermost membrane wall forms an inner flue 6; the outermost membrane wall and the furnace shell form an outer flue 4; the inner flue 6, several intermediate flues 5 and the outer flue 4 are connected alternately in sequence through the top opening and the bottom opening; taking the two-layer cylindrical membrane wall as an example, the high-temperature flue gas enters the intermediate flue 5 from the bottom or top after flowing through the inner flue 6, and then enters the outer flue 4 from the other end of the intermediate flue 5, thus traversing the inner and outer surfaces of all membrane walls, and realizing that the high-temperature combustion gas flows through the inner and outer surfaces of the cylindrical membrane wall in turn, heating the membrane wall from the inside and the outside at the same time, increasing the heating area of ​​the membrane wall, improving the efficiency of heat exchange, and improving the technical problem of single-sided heating of the membrane wall in the existing neutral boiler; the structural form of the mode with more than two layers is the same as the principle of two layers, and it is only necessary to connect more membrane walls in series in sequence on the outside of the second layer.

[0031] At the same time, the cross-sectional area of ​​the connection between the inner flue, the middle flue and the outer flue is smaller than the cross-sectional area inside the inner flue, the middle flue and the outer flue, so that there is a sudden contraction of the flue gas flow channel, and a low-speed zone of the flue gas is formed at the corners of the connection, and dust particles are deposited here. The flow channel formed by the membrane wall is a cylindrical flow channel that is fitted together and is smooth. Therefore, dust is not easy to deposit on the surface of the membrane wall, but slides down along the membrane wall into the bottom of the inner flue, the middle flue and the outer flue; and at the bottom of the inner flue, the middle flue and the outer flue, a dust collecting box is provided, and the bottom of the inner flue, the middle flue and the outer flue is an inclined surface or an arc surface, so that the deposited dust slides into the dust collecting box along the inclined surface or the arc surface, realizing automatic collection of dust.

[0032] Of course, in order to speed up the collection of dust, a vibrator can be arranged on the outside of the membrane wall to accelerate the dust to slide into the dust collection box along the membrane wall and the inclined surface or curved surface at the bottom of the membrane wall.

[0033] In addition, the furnace of an energy-saving steam boiler using biomass as fuel provided by the present invention can be applied to steam boilers using biomass as fuel, and can also be applied to steam boilers using oil or gas as fuel, and both require that the burning fuel be blown into the inner flue of the furnace from the combustion hole in the form of an airflow.

[0034] The furnace is provided with a combustion hole, which passes through the furnace shell and the membrane wall to send the burning biomass into the inner flue; a water inlet pipe is provided at the bottom of the membrane wall; and a smoke exhaust hole is provided at the furnace shell.

[0035] As a preferred embodiment of the present invention, Figure 4 As shown, a smoke guide plate 202 is provided at the top opening and the bottom opening on the side where the smoke flows out; specifically, a smoke guide plate 202 is provided at the top opening 1 of the inner membrane wall, or the bottom opening 101 of the inner membrane wall, or the bottom opening 7 of the outer membrane wall, or the top opening 24 of the outer membrane wall on the side where the smoke flows out; when the high-temperature smoke enters the inner flue from the combustion hole, since the smoke after combustion enters from the combustion hole 10 located on the side of the inner flue, the smoke is also subjected to the initial horizontal impact force in the process of rising or falling, so that the smoke rises or falls in a spiral in the inner flue; when the smoke passes through the smoke guide plate 2 02, a spiral airflow is further formed under the guidance of the smoke guide plate 202, and flows in the middle flue 5 or the outer flue 4. At this time, the dust in the smoke will move outward under the action of centrifugal force, and then deposit on the surface of the membrane wall. Since the surface of the membrane wall is smooth, and since the water pipe in the membrane wall is always replenished with new water from the water inlet pipe, the surface temperature of the membrane wall is always lower than the temperature of the smoke, that is, lower than the melting temperature of the dust in the smoke. Therefore, the dust can be deposited more easily, so that the dust slides downward along the membrane wall into the bottom 9 of the inner flue while being deposited, and then slides into the dust collection box 11.

[0036] Preferably, the smoke guide plate 202 is spiral-shaped, and a spiral smoke guide plate is more conducive to forming a spiral smoke airflow.

[0037] In this embodiment, two structural forms are provided for explanation of the flow of smoke: like Figure 5As shown, the combustion hole 10 is arranged at the top of the furnace, that is, the top combustion hole 1001, the inner flue 6 is provided with a bottom opening, that is, the inner membrane wall bottom opening 101, the outer flue 4 is provided with a top opening, that is, the outer membrane wall top opening 24, and the smoke exhaust hole is arranged at the bottom of the furnace shell 18, that is, the bottom smoke exhaust hole 2201; for the inner flue 6 is provided with a bottom opening, that is, the inner membrane wall bottom opening 101, this embodiment provides a structure for implementation, that is, a certain distance A is left between the bottom edge 201 of the inner membrane wall rib plate and the lower header 1601 , this distance A forms the bottom opening 101 of the inner membrane wall; a top opening is provided for the outer flue 4, that is, the top opening 24 of the outer membrane wall. In this embodiment, a certain distance B is left between the top edge 1403 of the outer membrane wall rib plate and the upper header 16, and this distance B forms the top opening 24 of the outer membrane wall; of course, the functions of distance A or distance B can also be achieved for other structural forms, such as the bottom edge 201 of the inner membrane wall rib plate is connected to the lower header 1601, but a through hole is provided at or near the connection to connect the inner flue 6 and the outer flue 4.

[0038] like Figure 6 As shown, the combustion hole 10 is arranged at the bottom of the furnace, the inner flue is provided with a top opening, i.e., the inner membrane wall top opening 1, the outer flue 4 is provided with a bottom opening, i.e., the outer membrane wall bottom opening 7, and the smoke exhaust hole is arranged at the top of the furnace shell 18, i.e., the top smoke exhaust hole 22; similarly, for the inner membrane wall top opening 1, this embodiment leaves a distance C between the top edge 2 of the inner membrane wall rib plate and the upper collecting box 16, and this distance C forms the inner membrane wall top opening 1; for the outer membrane wall bottom opening 7, this embodiment leaves a distance D between the bottom edge 1404 of the outer membrane wall rib plate and the lower collecting box 1601, and this distance D forms the outer membrane wall bottom opening 7.

[0039] As another preferred embodiment of the present invention, on the basis of the above embodiment, metal wires are evenly distributed on the circumference in the inner flue, the middle flue and the outer flue, the metal wires are connected to the negative pole of the high-voltage power supply, the positive pole of the high-voltage power supply is grounded, and the membrane wall and the furnace shell are grounded, so that the air in the flue gas is ionized, and the negative electrons are attached to the surface of the dust in the flue gas, driving the dust to move toward the membrane wall and the furnace shell, and the dust is assisted by static electricity to move to the membrane wall and deposit.

[0040] As another preferred embodiment of the present invention, on the basis of the above embodiment, the cross-sectional areas of the inner flue, the middle flue and the outer flue are reduced successively; the reason for such design is that the flow channel has a sudden expansion or contraction, which can form a low-speed zone locally, so that the flue gas has a lower flow velocity in this area and a longer residence time, and this area can absorb more heat.

[0041] As another preferred embodiment of the present invention, on the basis of the above embodiment, the angle between the superheater pipe and the inner flue axis is A, 10°≤A≤80°. At the same time, a top heating chamber 21 is formed between the furnace shell 18 and the top plate 19. The top heating chamber 21 is a flow channel for flue gas. The flue gas heats the superheater pipe 23 and the gas collecting bag 20 in the top heating chamber 21. At the same time, the heat absorbed by the top plate 19 is also radiated to the superheater pipe 23 and the gas collecting bag 20, further heating the superheater pipe 23 and the gas collecting bag 20.

[0042] As another preferred embodiment of the present invention, based on the above embodiment, the furnace shell is provided with a heat insulation layer.

[0043] Preferably, a descaling pipe 8 is provided at the bottom of the lower header 1601 .

[0044] Preferably, the top of the outer membrane wall 14 is connected to a lower interface 15 of the water level gauge, and the side of the air collecting bag 20 is connected to an upper interface 17 of the water level gauge, which is used to fix the water level gauge to facilitate observation of the water level.

[0045] The foregoing has broadly outlined some aspects and features of various embodiments, which should be construed as merely illustrative of various potential applications. Other beneficial results may be obtained by applying the disclosed information in different ways or by combining various aspects of the disclosed embodiments. Other aspects and a more comprehensive understanding may be obtained by reference to the detailed description of the exemplary embodiments in conjunction with the accompanying drawings, within the scope defined by the claims.

[0046] The above embodiments have been described in detail. Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, reductions, and substitutions made by relevant technicians within the essential scope of the present invention also fall within the protection scope of the present invention.

Claims

1. A furnace of an energy-saving steam boiler using biomass as fuel, characterized in that: The furnace of the energy-saving steam boiler comprises a furnace shell and several layers of cylindrical membrane walls which are sheathed together, the top ends of the water pipes in the membrane walls are connected to the upper header, and the bottom ends of the water pipes in the membrane walls are connected to the lower header; the top of the upper header is connected to the gas collecting bag through the superheating pipe; the furnace shell wraps the several layers of cylindrical membrane walls, the superheating pipe and the gas collecting bag in the furnace shell; The adjacent membrane walls form an intermediate flue for flue gas; the innermost membrane wall forms an inner flue; the outermost membrane wall and the furnace shell form an outer flue; the inner flue, several intermediate flues and the outer flue are connected alternately and sequentially through the top opening and the bottom opening; The furnace is provided with a combustion hole, which passes through the furnace shell and the membrane wall to send the burning biomass into the inner flue; a water inlet pipe is provided at the bottom of the membrane wall; and a smoke exhaust hole is provided at the furnace shell.

2. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 1, characterized in that: The plurality of layers of cylindrical membrane walls are preferably two, namely an inner membrane wall and an outer membrane wall.

3. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 2, characterized in that: The combustion hole is arranged at the top of the furnace, the inner flue is provided with a bottom opening, the outer flue is provided with a top opening, and the smoke exhaust hole is arranged at the bottom of the furnace shell.

4. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 3 is characterized in that: The combustion hole is arranged at the bottom of the furnace, the inner flue is provided with a top opening, the outer flue is provided with a bottom opening, and the smoke exhaust hole is arranged at the top of the furnace shell.

5. A furnace of an energy-saving steam boiler using biomass as fuel according to any one of claims 1 to 4, characterized in that: The top opening and the bottom opening are provided with smoke guide plates on the side where smoke flows out.

6. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 5, characterized in that: The smoke guide plate is spiral-shaped.

7. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 6, characterized in that: The inner flue, the middle flue and the outer flue are provided with metal wires evenly distributed on the circumference, the metal wires are connected to the negative pole of the high voltage power supply, the positive pole of the high voltage power supply is grounded, the membrane wall and the furnace shell are grounded, and the dust is assisted by static electricity to move to the membrane wall and deposit.

8. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 7, characterized in that: The channel cross-sectional areas of the inner flue, the middle flue and the outer flue decrease in sequence.

9. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 8, characterized in that: The included angle between the superheater tube and the inner flue axis is A, 10°≤A≤80°.

10. The furnace of an energy-saving steam boiler using biomass as fuel according to claim 9, characterized in that: The furnace shell is provided with a heat-insulating layer.

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