Combustion device of multi-fuel heating furnace with extremely low heat value

Abstract

The invention discloses a combustion device of a multi-fuel heating furnace with an extremely low calorific value. Key links include a high-calorific-value fuel gas shunting module, an inner-layer rotational flow assembly-divergent nozzle-spherical nozzle structure and an acceleration section-outer-layer rotational flow assembly structure of an outer-layer channel. The high-calorific-value fuel gas distribution module adjusts the calorific value of premixed fuel gas in the outer layer channel, and it is guaranteed that the calorific value reaches the burner design value after different low-calorific-value fuel gas is mixed with high-calorific-value fuel gas A stable high-temperature heat source is provided for the combustion device through the structure of the inner-layer rotational flow assembly, the divergent nozzle and the spherical nozzle, and stable operation of the combustor is guaranteed. The accelerating section-outer layer rotational flow assembly structure ensures that premixed fuel gas and air are fully mixed, so that the low-heating-value fuel gas is quickly and stably combusted. Stable combustion of the gas with the extremely low heat value can be achieved, the fuel adaptability is good, and the operation cost of an enterprise can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heating furnace combustion device, in particular to a kind of extremely low heat value multi-fuel heating furnace combustion device. BACKGROUND

[0002] Chemical heating furnace uses gas fuel combustion to provide heat, in order to reduce enterprise operating cost, fuel is generally by-product gas generated in chemical production. Chemical by-product gas is influenced by raw material and process, and the flammable component and heat value fluctuate greatly. For extremely low heat value chemical by-product gas (flammable component is less than 5%), it cannot be directly combusted, and needs to be mixed with a certain proportion of high heat value by-product gas. Although the heat value of fuel gas is increased, there are still problems such as unstable combustion and poor adaptability in the combustion process. In order to improve the stability of combustion, the extremely low heat value chemical by-product gas needs to be mixed with a large proportion of high heat value by-product gas, that is, a large amount of high heat value high-quality fuel gas is additionally provided, thereby increasing the operating cost of the enterprise. This is mainly because many chemical by-product gases can still be used as other chemical production raw materials. SUMMARY

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present application is to provide an extremely low heat value multi-fuel heating furnace combustion device, which can realize stable combustion of extremely low heat value fuel gas and has good fuel adaptability, and can effectively reduce the operating cost of the enterprise.

[0004] The extremely low heat value multi-fuel heating furnace combustion device according to an embodiment of the present application comprises:

[0005] The layer pipe assembly comprises an inner layer pipe, a middle layer pipe, an outer layer pipe and a lateral shunt pipe. The inner layer pipe, the middle layer pipe and the outer layer pipe are arranged in sequence from inside to outside. The inner side of the inner layer pipe is a central passage. A middle layer passage is formed between the middle layer pipe and the inner layer pipe. An outer layer passage is formed between the outer layer pipe and the middle layer pipe. The inlet end of the central passage, the inlet end of the middle layer passage and the inlet end of the outer layer passage are located at one end of the layer pipe assembly and are respectively used for introducing high heat value fuel gas, air and extremely low heat value fuel gas. The lateral shunt pipe is connected between the inner layer pipe and the middle layer pipe, and is used for shunting a part of the high heat value fuel gas in the central passage to the outer layer passage to pre-mix with the extremely low heat value fuel gas in the outer layer passage. The outer layer passage has an acceleration section, and the acceleration section is located downstream of the connection between the lateral shunt pipe and the middle layer pipe.

[0006] An air splitter is provided, with one end inserted into the outlet end of the middle layer channel and the other end extending out of the outlet end of the middle layer channel; an inner air outlet is formed between the air splitter and the inner layer tube; an outer air outlet is formed between the air splitter and the middle layer tube, extending to the inner side of the middle layer channel and located downstream of the acceleration section; an annular nozzle is formed between the air splitter and the outer layer tube, and the inner side of the other end of the air splitter includes a gradually expanding nozzle communicating with the inner air outlet, the end face of the gradually expanding nozzle being flush with the end face of the annular nozzle;

[0007] A spherical nozzle, which is connected to the outlet end of the central channel and located in the gradually expanding nozzle;

[0008] An inner swirl assembly is disposed in the inner air outlet;

[0009] An outer swirl assembly is disposed between the air splitter and the outer tube, and is located downstream of the outer air outlet.

[0010] The working principle of the ultra-low calorific value multi-fuel heating furnace combustion device in this embodiment of the invention is as follows: high calorific value fuel gas, air, and ultra-low calorific value fuel gas are respectively introduced into the central channel, the middle channel, and the outer channel from the inlet end of the central channel, the inlet end of the middle channel, and the inlet end of the outer channel. A portion of the high calorific value fuel gas in the central channel enters the outer channel through a lateral diverter, where it is premixed with the ultra-low calorific value fuel gas to form premixed fuel gas. The other portion of the high calorific value fuel gas flows along the central channel to the spherical nozzle and is ejected from the spherical nozzle into the gradually expanding nozzle. The air in the middle channel is divided into two parts by an air divider; one part is outer layer air, which exits through the outer layer air outlet. The air flows into the high-speed negative pressure zone of the outer channel, while the other part of the air is the inner layer air. It is injected into the expanding nozzle through the inner layer air outlet and under the action of the inner layer swirling component. It mixes with the high-calorific-value gas swirling from the spherical nozzle and then burns, causing the flame to rotate and spray outward. This ignites the premixed gas and air mixture sprayed from the annular nozzle and forms a swirling negative pressure zone in the center of the expanding nozzle, which entrains high-temperature flue gas and improves combustion stability. The premixed gas in the outer channel is accelerated through the acceleration section and then premixed with the air flowing into the outer channel from the outer layer air outlet. Under the action of the outer layer swirling component, it is sprayed out of the annular nozzle and ignited by the rotating flame sprayed outward at the expanding nozzle, so that the premixed gas can burn fully and stably.

[0011] The key link of the very low heat value multi-fuel heating furnace combustion device is that the high heat value gas shunt module, the inner layer cyclone assembly-gradual expansion nozzle-spherical nozzle structure and the outer layer channel acceleration section-outer layer cyclone assembly structure. The high heat value gas shunt module adjusts the heat value of the outer layer channel premixed gas, and ensures that the heat value of the low heat value gas mixed with the high heat value gas reaches the design value of the burner. The inner layer cyclone assembly-gradual expansion nozzle-spherical nozzle structure provides a stable high temperature heat source for the combustion device, and ensures stable operation of the burner. The acceleration section-outer layer cyclone assembly structure ensures sufficient mixing of the premixed gas and air, so that the low heat value gas is quickly and stably combusted.

[0012] The advantage of the very low heat value multi-fuel heating furnace combustion device is that it can realize efficient combustion of different very low heat value gases, while reducing the amount of high heat value high-quality gas, thereby reducing the operating cost of enterprises. The center adopts the inner layer cyclone assembly-gradual expansion nozzle-spherical nozzle combined design, which not only provides a high temperature heat source for the outer ring gas, but also realizes stable combustion. The outer layer adopts the acceleration section-outer layer cyclone assembly structure, which realizes the cyclone premixing of the premixed gas and air, can realize the rapid and sufficient combustion of the premixed gas, shorten the combustion time, and improve the fuel burnout rate. By adjusting the high heat value gas shunt module, the high heat value gas shunt ratio is changed, the heat value of the premixed gas in the outer layer channel is changed, and the fuel adaptability of the combustion device is improved.

[0013] In some embodiments, the heat value of the premixed gas after the very low heat value gas and the high heat value gas in the outer layer channel are premixed is not less than 1500kJ / Nm 3 .

[0014] In some embodiments, the gas speed after the premixed gas in the outer layer channel is mixed with air is not less than 40m / s.

[0015] In some embodiments, the inner layer pipe comprises a first straight pipe section and an adjustable throttling pipe section, the inlet end of the lateral shunt pipe is connected with the first straight pipe section, and the adjustable throttling pipe section is connected between the first straight pipe section and the spherical nozzle.

[0016] In some embodiments, the adjustable throttling pipe section comprises a converging pipe section, a second straight pipe section and a gradual expansion pipe section connected in sequence, the converging pipe section is connected with the first straight pipe section, the throat flow area of the converging pipe section is adjusted by replacing a throttling plate, the inner diameter and outer diameter of the second straight pipe section are smaller than the inner diameter and outer diameter of the first straight pipe section, and the outlet end of the gradual expansion pipe section is connected with the spherical nozzle.

[0017] In some embodiments, the lateral shunt pipe has a plurality of inlet ends which are uniformly distributed on the first straight pipe section, and a plurality of outlet ends which are uniformly distributed on the middle layer pipe.

[0018] In some embodiments, the middle layer tube includes a third straight tube section and an acceleration tube section located downstream of the third straight tube section. The acceleration tube section includes a gradually expanding outer circumferential surface, and the acceleration section is formed between the gradually expanding outer circumferential surface and the outer layer tube.

[0019] In some embodiments, the annular nozzle includes an axially connected straight ring portion and a tapered ring portion, the straight ring portion being located between the outlet end of the outer air layer outlet and the tapered ring portion.

[0020] In some embodiments, the inner swirl assembly includes a plurality of inner swirl blades, which are circumferentially distributed; the outer swirl assembly includes a plurality of outer swirl blades, which are circumferentially distributed.

[0021] In some embodiments, a flame monitoring module is also included, which is installed in the outer channel to monitor whether there is a flame at the diffuser nozzle and the annular nozzle.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0024] Figure 1 This is a cross-sectional schematic diagram of the combustion device of the ultra-low calorific value multi-fuel heating furnace according to an embodiment of the present invention;

[0025] Figure 2 for Figure 1 Enlarged diagram of point A in the middle.

[0026] Figure label:

[0027] Inner tube 1; First straight tube section 11; Adjustable throttling tube section 12; Scaling tube section 121; Second straight tube section 122; Diverging tube section 123; Middle tube 2; Third straight tube section 21; Acceleration tube section 22; Diverging outer circumference 221; Outer tube 3; Lateral diverter tube 4; Air splitter 5; Diverging nozzle 501; Spherical nozzle 6; Inner swirl assembly 7; Outer swirl assembly 8; Flame monitoring module 9; Ignition gun 10; Central channel 100; Middle channel 200; Inner air outlet 201; Outer air outlet 202; Outer channel 300; Acceleration section 301; Annular nozzle 302; Straight ring section 3021; ​​Diverging ring section 3022. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] The following is combined with Figures 1 to 2 This invention describes an ultra-low calorific value multi-fuel heating furnace combustion device according to an embodiment of the present invention.

[0030] like Figure 1 and Figure 2 As shown, the ultra-low calorific value multi-fuel heating furnace combustion device according to an embodiment of the present invention includes a tube assembly, an air distributor 5, a spherical nozzle 6, an inner swirl assembly 7, and an outer swirl assembly 8.

[0031] Specifically, the layered pipe assembly includes an inner layer pipe 1, a middle layer pipe 2, an outer layer pipe 3, and a lateral branch pipe 4. The inner layer pipe 1, middle layer pipe 2, and outer layer pipe 3 are arranged sequentially from the inside to the outside. The inner side of the inner layer pipe 1 forms a central channel 100, the middle layer pipe 2 and the inner layer pipe 1 form a middle channel 200, and the outer layer pipe 3 and the middle layer pipe 2 form an outer channel 300. The inlet ends of the central channel 100, the middle channel 200, and the outer channel 300 are all located at one end of the layered pipe assembly and are used to introduce high-calorific-value gas, air, and very low-calorific-value gas, respectively, so that the high-calorific-value gas, air, and very low-calorific-value gas are transported to the other end of the layered pipe assembly through the central channel 100, the middle channel 200, and the outer channel 300, respectively. A lateral diversion pipe 4 is connected between the inner layer pipe 1 and the middle layer pipe 2. The inlet end of the lateral diversion pipe 4 is welded to the inner layer pipe 1, and the outlet end of the lateral diversion pipe 4 is welded to the middle layer pipe 2. The lateral diversion pipe 4 is used to divert a portion of the high-calorific-value gas in the central channel 100 to the outer layer channel 300 for premixing with the extremely low-calorific-value gas in the outer layer channel 300. In other words, the inner layer pipe 1 and the lateral diversion pipe 4 constitute a high-calorific-value gas diversion module. The high-calorific-value gas enters the inner layer pipe 1 (i.e., the central channel 100) from the inlet end of the central channel 100. When it reaches the inlet end of the lateral diversion pipe 4, a portion of the high-calorific-value gas is premixed with the gas. The high-calorific-value gas flows through the lateral diversion pipe 4 into the outer channel 300, where it is fully premixed with the very low-calorific-value gas in the outer channel 300 to form premixed gas, which flows to the outlet of the outer channel 300. Another portion of the high-calorific-value gas continues to flow along the central channel 100 to its outlet. The outer channel 300 has an acceleration section 301 located downstream of the connection between the lateral diversion pipe 4 and the middle pipe 2. This acceleration section 301 accelerates the premixed gas, generating a high-speed negative pressure at its downstream end, i.e., the outlet of the outer channel 300, thus entraining air. Furthermore, it should be noted that by adjusting the high-calorific-value gas diversion module, changing the high-calorific-value gas diversion ratio, and altering the calorific value of the premixed gas in the outer channel 300, the fuel adaptability of the combustion device can be improved.

[0032] An air splitter 5 is disposed at the other end of the layer tube assembly. One end of the air splitter 5 is inserted into the outlet end of the middle layer channel 200, and the other end of the air splitter 5 extends out of the outlet end of the middle layer channel 200. An inner layer air outlet 201 is formed between the air splitter 5 and the inner layer tube 1; an outer layer air outlet 202 is formed between the air splitter 5 and the middle layer tube 2, and the outer layer air outlet 202 extends to the inner side of the middle layer channel 200 and is located downstream of the acceleration section 301; an annular nozzle 302 is formed between the air splitter 5 and the outer layer tube 3, and the inner side of the other end of the air splitter 5 includes a gradually expanding nozzle 501 communicating with the inner layer air outlet 201, and the end face of the gradually expanding nozzle 501 is flush with the end face of the annular nozzle 302. Understandably, by setting up the air splitter 5, the outlet of the middle layer channel 200 is divided into an outer air outlet 202 and an inner air outlet 201. Thus, air enters the middle layer channel 200 from its inlet end. Upon reaching one end of the air splitter 5, a portion of the air passes through the outer air outlet 202 into the outer layer channel 300 and mixes with the premixed fuel gas accelerated by the acceleration section 301. Because the outlet end of the outer air outlet 202 is located in the high-speed negative pressure zone downstream of the acceleration section 301, it can entrain air. The premixed fuel gas and air can then be ejected at high speed from the annular nozzle 302. The other portion of the air rapidly enters the diffuser nozzle 501 through the inner air outlet 201. It should be noted that adjusting the diameter of one end of the air splitter 5 can change the air distribution ratio between the inner air at the inner air outlet 201 and the air at the outer air outlet 202.

[0033] The spherical nozzle 6 is connected to the outlet end of the central channel 100 and is located in the gradually expanding nozzle 501, which can form a negative pressure zone in the center.

[0034] The inner swirl assembly 7 is installed in the inner air outlet 201. By installing the inner swirl assembly 7, the air swirls and mixes thoroughly with the high-calorific-value combustion gas ejected from the spherical nozzle 6, forming a swirling negative pressure zone at the center of the gradually expanding nozzle 501, which entrains high-temperature flue gas and improves combustion stability.

[0035] The outer swirl assembly 8 is disposed between the air splitter 5 and the outer tube 3, and is located downstream of the outer air outlet 202. By setting the outer swirl assembly 8, the premixed gas can be premixed with the air swirl, which can achieve rapid and complete combustion of the premixed gas, shorten the combustion time, and improve the combustion rate of the mixed fuel.

[0036] The working principle of the ultra-low calorific value multi-fuel heating furnace combustion device in this embodiment of the invention is as follows: high calorific value fuel gas, air, and ultra-low calorific value fuel gas are respectively introduced into the central channel 100, the middle channel 200, and the outer channel 300 from the inlet end of the central channel 100, the inlet end of the middle channel 200, and the inlet end of the outer channel 300. A portion of the high calorific value fuel gas in the central channel 100 enters the outer channel 300 through the lateral diversion pipe 4, where it is premixed with the ultra-low calorific value fuel gas to form premixed fuel gas. The other portion of the high calorific value fuel gas flows along the central channel 100 to the spherical nozzle 6 and is ejected from the spherical nozzle 6 into the gradually expanding nozzle 501. The air in the middle channel 200 is divided into two parts by the air splitter 5; one part is outer layer air, which exits through the outer layer air outlet. The air flows from outlet 202 to the high-speed negative pressure zone of the outer channel 300, while the other part of the air is inner layer air. It is injected into the expanding nozzle 501 through the inner air outlet 201 and under the action of the inner swirl component 7. It mixes with the high-calorific-value gas swirling from the spherical nozzle 6 and then burns, causing the flame to rotate and spray outward. This ignites the mixture of premixed gas and air sprayed from the annular nozzle 302 and forms a swirling negative pressure zone in the center of the expanding nozzle 501, which entrains high-temperature flue gas and improves combustion stability. The premixed gas in the outer channel 300 is accelerated by the acceleration section 301 and then premixed with the air flowing into the outer channel 300 from the outer air outlet 202. Under the action of the outer swirl component 8, it is swirled out of the annular nozzle 302 and ignited by the rotating flame sprayed outward at the expanding nozzle 501, so that the premixed gas burns fully and stably.

[0037] The key components of the ultra-low calorific value multi-fuel heating furnace combustion device in this invention embodiment are: a high calorific value gas diversion module, an inner swirl assembly 7-gradiently expanding nozzle 501-spherical nozzle 6 structure, and an acceleration section 301-outer swirl assembly 8 structure in the outer channel 300. The high calorific value gas diversion module adjusts the calorific value of the premixed gas in the outer channel 300, ensuring that the calorific value of the gas after mixing different low calorific value gases with high calorific value gases reaches the burner's design value. The inner swirl assembly 7-gradiently expanding nozzle 501-spherical nozzle 6 structure provides a stable high-temperature heat source for the combustion device, ensuring stable burner operation. The acceleration section 301-outer swirl assembly 8 structure ensures thorough mixing of the premixed gas and air, enabling rapid and stable combustion of the low calorific value gas.

[0038] The advantages of the ultra-low calorific value multi-fuel heating furnace combustion device of this invention are: it can achieve efficient combustion of different ultra-low calorific value gases, while reducing the amount of high calorific value high-quality gas used, thus lowering the operating costs of enterprises. The central design employs an inner swirl assembly 7, a gradually expanding nozzle 501, and a spherical nozzle 6, which not only provides a high-temperature heat source for the outer ring gas but also achieves stable combustion. The outer layer adopts an acceleration section 301 and an outer swirl assembly 8 structure to achieve premixed gas and air swirl premixing, enabling rapid and complete combustion of the premixed gas, shortening combustion time, and improving fuel burnout rate. By adjusting the high calorific value gas diversion module, the high calorific value gas diversion ratio is changed, altering the calorific value of the premixed gas within the outer channel 300, thereby improving the fuel adaptability of the combustion device.

[0039] In some implementations, the calorific value of the premixed gas after premixing the extremely low calorific value gas and the high calorific value gas in the outer channel 300 is not less than 1500 kJ / Nm³. 3 This satisfies the design requirements for the complete combustion of premixed gas in the ultra-low calorific value multi-fuel heating furnace combustion device of this embodiment, thereby improving the fuel adaptability of the combustion device.

[0040] In some embodiments, the gas velocity after the premixed gas and air are mixed in the outer channel 300 is not less than 40 m / s, thereby ensuring negative pressure in the downstream end region of the acceleration section 301 and ejecting air.

[0041] In some embodiments, the inner tube 1 includes a first straight pipe section 11 and an adjustable throttling pipe section 12. The inlet end of the lateral branch pipe 4 is connected to the first straight pipe section 11, and the adjustable throttling pipe section 12 is connected between the first straight pipe section 11 and the spherical nozzle 6. The distribution ratio and flow rate of high-calorific-value gas in the inner tube 1 can be adjusted through the adjustable throttling pipe section 12.

[0042] In some embodiments, the adjustable throttling section 12 includes a scaling section 121, a second straight section 122, and a diverging section 123 connected in sequence. The scaling section 121 is connected to the first straight section 11. The throat flow area of ​​the scaling section 121 is adjusted by replacing the throttling plate. The inner and outer diameters of the second straight section 122 are smaller than those of the first straight section 11. The outlet end of the diverging section 123 is connected to the spherical nozzle 6. The scaling section 121 is used to adjust the distribution ratio and flow rate of high-calorific-value gas. The diverging section 123 is used to adapt to the spherical nozzle 6 and to adapt to the diverging nozzle 501, ensuring that the distance between the root of the diverging section 123 and the sidewall of the diverging nozzle 501, i.e., the radial dimension of the outlet end of the air inner layer outlet 201, is appropriate. For example, it gradually decreases towards the outlet direction, or it remains consistent with the radial dimension of the inlet end of the air inner layer outlet 201.

[0043] In some embodiments, there are multiple lateral diversion pipes 4, with the inlet ends of the multiple lateral diversion pipes 4 evenly distributed on the first straight pipe section 11, and the outlet ends of the multiple lateral diversion pipes 4 evenly distributed on the middle layer pipe 2. This facilitates the uniform mixing of high-calorific-value gas and very low-calorific-value gas.

[0044] In some implementations, the middle layer pipe 2 includes a third straight pipe section 21 and an acceleration pipe section 22 located downstream of the third straight pipe section 21. The acceleration pipe section 22 includes a gradually expanding outer peripheral surface 221, and an acceleration section 301 is formed between the gradually expanding outer peripheral surface 221 and the outer layer pipe 3. This acceleration section is used to accelerate and increase the flow rate of the premixed gas.

[0045] In some embodiments, the annular nozzle 302 includes an axially connected straight ring portion 3021 and a tapered ring portion 3022. The straight ring portion 3021 is located between the outlet end of the outer air outlet 202 and the tapered ring portion 3022. The tapered ring portion 3022 can increase the injection velocity of the premixed gas-air mixture.

[0046] In some embodiments, the inner swirl assembly 7 includes a plurality of inner swirl blades, which are circumferentially evenly distributed to allow the inner air to be swirled and ejected in a better manner; the outer swirl assembly 8 includes a plurality of outer swirl blades, which are circumferentially evenly distributed to allow the mixture of premixed gas and air to be swirled and ejected in a better manner.

[0047] In some embodiments, a flame monitoring module 9 is also included. The flame monitoring module 9 is installed in the outer channel 300 through a sleeve and is used to monitor whether there is a flame at the diffuser nozzle 501 and the annular nozzle 302.

[0048] In some embodiments, an ignition gun 10 is also included, which is disposed in the middle channel 200 and is used to ignite the high-calorific-value gas in the gradually expanding nozzle 501.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An extremely low-heat-value multi-fuel heating furnace combustion device, characterized by, The application relates to a high-efficiency premixing burner. The burner comprises a layer pipe assembly, an air shunt, a spherical nozzle, an inner-layer cyclone assembly and an outer-layer cyclone assembly. The layer pipe assembly comprises an inner layer pipe, a middle layer pipe and an outer layer pipe. The inner layer pipe, the middle layer pipe and the outer layer pipe are arranged in sequence from inside to outside. The inner side of the inner layer pipe is a central passage. The middle layer pipe and the inner layer pipe form a middle layer passage.

2. The extremely low-heat-value multi-fuel furnace combustion device according to claim 1, characterized by The heat value of the premixed gas after premixing of the extremely low heat value gas and the high heat value gas in the outer layer channel is not less than 1500 kJ / Nm 3 .

3. The extremely low-heat-value multi-fuel furnace combustion device according to claim 2, characterized by The outer layer pipe and the middle layer pipe form an outer layer passage.

4. The extremely low-heat-value multi-fuel furnace combustion device according to claim 1, characterized by The inlet end of the central passage, the inlet end of the middle layer passage and the inlet end of the outer layer passage are located at one end of the layer pipe assembly and are respectively used for passing in high-calorific-value gas, air and extremely low-calorific-value gas.

5. The extremely low-heat-value multi-fuel furnace combustion device according to claim 4, characterized by The side shunt pipe is connected between the inner layer pipe and the middle layer pipe and is used for shunting a part of the high-calorific-value gas in the central passage to the outer layer passage to premix with the extremely low-calorific-value gas in the outer layer passage.

6. The extremely low-heat-value multi-fuel furnace combustion device according to claim 4, characterized by The outer layer passage has an acceleration section which is located downstream of the connection between the side shunt pipe and the middle layer pipe.

7. The extremely low-heat-value multi-fuel furnace combustion device according to claim 4, characterized by The air shunt is inserted into the outlet end of the middle layer passage at one end and extends out of the outlet end of the middle layer passage at the other end. The air shunt and the inner layer pipe form an air inner layer outlet. The air shunt and the middle layer pipe form an air outer layer outlet which extends to the inner side of the middle layer passage and is located downstream of the acceleration section. The air shunt and the outer layer pipe form an annular jet. The other end of the air shunt comprises a diverging jet which communicates with the air inner layer outlet. The diverging jet of the other end of the air shunt is flush with the end face of the annular jet. The spherical nozzle is connected with the outlet end of the central passage and is located in the diverging jet. The inner-layer cyclone assembly is arranged in the air inner layer outlet. The outer-layer cyclone assembly is arranged between the air shunt and the outer layer pipe and is located downstream of the air outer layer outlet. The gas velocity of the premixed gas and air mixture in the outer layer passage is not less than 40 m / s. The inner layer pipe comprises a first straight pipe section and an adjustable throttling pipe section. The inlet end of the side shunt pipe is connected with the first straight pipe section. The adjustable throttling pipe section is connected between the first straight pipe section and the spherical nozzle. The adjustable throttling pipe section comprises a converging-diverging pipe section, a second straight pipe section and a diverging pipe section which are connected in sequence. The converging-diverging pipe section is connected with the first straight pipe section. The throat flow area of the converging-diverging pipe section is adjusted by replacing a throttling plate. The inner diameter and outer diameter of the second straight pipe section are smaller than those of the first straight pipe section. The outlet end of the diverging pipe section is connected with the spherical nozzle. The side shunt pipe has a plurality of inlet ends which are arranged on the first straight pipe section. The side shunt pipe has a plurality of outlet ends which are arranged on the middle layer pipe. The middle layer pipe comprises a third straight pipe section and an acceleration pipe section which is located downstream of the third straight pipe section. The acceleration pipe section comprises a diverging outer peripheral surface which forms the acceleration section together with the outer layer pipe.

8. The extremely low-heat-value multi-fuel furnace combustion device according to claim 7, characterized by The annular nozzle comprises an axially connected straight ring part and a tapered ring part, and the straight ring part is located between the outlet end of the air outer layer outlet and the tapered ring part.

9. The extremely low-heat-value multi-fuel furnace combustion apparatus according to any one of claims 1 to 7, characterized by The inner layer swirl assembly comprises a plurality of inner layer swirl vanes, and the plurality of inner layer swirl vanes are circumferentially distributed; the outer layer swirl assembly comprises a plurality of outer layer swirl vanes, and the plurality of outer layer swirl vanes are circumferentially distributed.

10. The extremely low-heat-value multi-fuel furnace combustion apparatus according to any one of claims 1 to 7, characterized by A flame monitoring module is further included, which is installed in the outer layer channel and used for monitoring whether there is flame at the divergent nozzle and the annular nozzle.

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