Boiler system for co-combustion of low-calorific-value fuel gas and high-calorific-value fuel gas

Abstract

The embodiment of the invention provides a boiler system for co-combustion of low-calorific-value fuel gas and high-calorific-value fuel gas, and relates to the technical field of combustion equipment, the boiler system comprises a boiler body, an ignition air pipeline, an ignition fuel gas pipeline, a main air pipeline, a low-calorific-value fuel gas pipeline, a high-calorific-value fuel gas pipeline and a control unit; a main combustor and an ignition combustor are arranged in a combustion chamber of the boiler body, the gas outlet ends of an ignition air pipeline and an ignition gas pipeline are communicated to the ignition combustor, and the gas outlet ends of the main air pipeline, a low-heat-value gas pipeline and a high-heat-value gas pipeline are communicated to the main combustor, so that low-heat-value gas and high-heat-value gas are mixed for combustion. The technical problem that low-heating-value fuel gas cannot be independently and stably combusted is solved. The low-heat-value gas pipeline and the high-heat-value gas pipeline are each provided with a flow adjusting valve, and the flame stability during combustion can be guaranteed through flow control.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion equipment, and particularly to a boiler system for co - burning low - calorific - value gas and high - calorific - value gas. Background Art

[0002] Low - calorific - value gas refers to fuel gas with a calorific value less than 6.28 MJ / m 3 . Common low - calorific - value gases in industry include blast furnace coke - oven gas, petrochemical smelting tail gas, landfill gas, and coal mine gas. Discharging a large amount of low - calorific - value gas into the air every year not only causes huge waste of resources but also leads to serious greenhouse effect problems.

[0003] Combustion purification is the most effective method for treating low - calorific - value gas. This method can not only effectively eliminate harmful substances in low - calorific - value gas but also extract the energy in low - calorific - value gas, achieving the purpose of improving the utilization rate of existing energy and protecting the environment. However, when low - calorific - value gas is burned alone as fuel gas, there is a phenomenon of unstable flame and it is easy to go out. Summary of the Invention

[0004] In view of this, the embodiments of the present invention provide a boiler system for co - burning low - calorific - value gas and high - calorific - value gas to solve the technical problem that the flame is unstable and easy to go out when low - calorific - value gas is burned alone.

[0005] A boiler system for co - burning low - calorific - value gas and high - calorific - value gas provided by the embodiments of the present invention includes: A boiler body, in which a main burner and an ignition burner are arranged in the combustion chamber of the boiler body; An ignition air pipeline, the intake end of the ignition air pipeline is connected to a blower, and the outlet end of the ignition air pipeline communicates with the ignition burner; An ignition gas pipeline, the intake end of the ignition gas pipeline communicates with a high - calorific - value gas supply source, and the outlet end of the ignition gas pipeline communicates with the ignition burner; A main air pipeline, the intake end of the main air pipeline is connected to the blower, and the outlet end of the main air pipeline communicates with the main burner; an air baffle with adjustable opening is arranged in the main air pipeline; A low - calorific - value gas pipeline, the intake end of the low - calorific - value gas pipeline communicates with a low - calorific - value gas supply source, and the outlet end of the low - calorific - value gas pipeline communicates with the main burner; a low - calorific - value gas flow regulating valve is arranged on the low - calorific - value gas pipeline; A high - calorific - value gas pipeline, the intake end of the high - calorific - value gas pipeline communicates with a high - calorific - value gas supply source, and the outlet end of the high - calorific - value gas pipeline communicates with the main burner; a high - calorific - value gas flow regulating valve is arranged on the high - calorific - value gas pipeline; A control unit, both the low calorific value gas flow regulating valve and the high calorific value gas flow regulating valve are electrically connected to the control unit; when the gas pressure of the low calorific value gas fails to reach the lower limit of the required pressure, the high calorific value fuel burns alone; when the gas pressure of the low calorific value gas reaches the lower limit of the required pressure, the low calorific value gas and the high calorific value gas burn together. An air cavity, a high calorific value gas cavity, a low calorific value gas cavity and a premixing cavity are separated in the main burner. Among them, the air cavity and the premixing cavity are both communicated with the main air pipeline, the high calorific value gas cavity is communicated with the high calorific value gas pipeline, and the low calorific value gas cavity is communicated with the low calorific value gas pipeline and is connected to the premixing cavity.

[0006] Optionally, along the gas flow direction of the low calorific value gas pipeline, a low calorific value gas pressure transmitter A, a low calorific value gas pressure switch A, a low calorific value gas pressure gauge, the low calorific value gas flow regulating valve, a low calorific value gas stop valve A, a low calorific value gas stop valve B, a low calorific value gas orifice plate, a low calorific value gas pressure switch B and a low calorific value gas ball valve are sequentially arranged; the low calorific value gas pressure transmitter A is electrically connected to the control unit.

[0007] Optionally, a low calorific value gas pressure transmitter B is connected between the inlet end and the outlet end of the low calorific value gas orifice plate, and the low calorific value gas pressure transmitter B is electrically connected to the control unit.

[0008] Optionally, along the gas flow direction of the high calorific value gas pipeline, a high calorific value gas pressure switch A, a high calorific value gas pressure gauge, a high calorific value gas pressure stabilizing valve, the high calorific value gas flow regulating valve, a high calorific value gas stop valve A, a high calorific value gas stop valve B, a high calorific value gas orifice plate, a high calorific value gas pressure switch B and a high calorific value gas ball valve are sequentially arranged.

[0009] Optionally, the inlet end of the ignition gas pipeline is communicated between the high calorific value gas pressure switch A and the high calorific value gas pressure gauge.

[0010] Optionally, along the gas flow direction of the ignition gas pipeline, an ignition gas stop valve A, an ignition gas pressure stabilizing valve, an ignition gas stop valve B, an ignition gas orifice plate and an ignition gas ball valve are sequentially arranged.

[0011] Optionally, an air ball valve and an air orifice plate are sequentially arranged along the air flow direction of the ignition air pipeline.

[0012] Optionally, a flue gas oxygen content transmitter is installed at the flue gas outlet of the boiler body; the air blower is provided with a frequency converter; both the flue gas oxygen content transmitter and the frequency converter are electrically connected to the control unit.

[0013] Optionally, the ignition burner is inserted into the air chamber. A through hole for the ignition burner to pass through and a plurality of air holes for air to pass through are provided at the bottom of the air chamber. The high calorific value gas chamber is sleeved outside the air chamber, and both the low calorific value gas chamber and the premixing chamber are sleeved outside the high calorific value gas chamber. The low calorific value gas chamber extends into the premixing chamber and is provided with a plurality of low calorific value gas holes communicating with the premixing chamber. A plurality of jet pipes communicating with the premixing chamber are arranged at intervals along the circumferential direction of the bottom of the premixing chamber. Corresponding to the circumferential direction of the outer wall of the high calorific value gas chamber, a plurality of high calorific value gas nozzles communicating with the high calorific value gas chamber are provided. The high calorific value gas nozzles are respectively inserted into the corresponding jet pipes, and a gap for the mixed gas to pass through is left between the two.

[0014] Optionally, a plurality of high calorific value gas holes are arranged at intervals along the circumferential direction of the inner wall of the high calorific value gas chamber, and the high calorific value gas holes are located on the air outlet side of the air holes.

[0015] The embodiments of the present invention have the following beneficial effects: 1. By mixing and burning the low calorific value gas and the high calorific value gas, the technical problem that the low calorific value gas cannot be stably burned alone is solved. 2. By controlling the flow rates of the two gases, the flame stability when the two gases burn simultaneously is ensured. 3. When there is low calorific value gas, the low calorific value gas and the high calorific value gas are mixed and burned; when there is no low calorific value gas, it can be automatically switched to the single combustion mode of the high calorific value gas, and the flame stability when the high calorific value gas burns alone is ensured through flow control. 4. The low calorific value gas is premixed with the combustion air and then burned, so that the low calorific value gas can be fully burned. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a schematic structural diagram of the system according to the embodiment of the present invention; Figure 2 It is a schematic diagram of the adjustment of the low calorific value gas flow rate and the high calorific value gas flow rate in the embodiment of the present invention; Figure 3 It is a schematic structural diagram of the main burner and the ignition burner in the embodiment of the present invention; The numbers in the figure represent: 1. Boiler body; 2. Ignition air pipeline; 3. Ignition gas pipeline; 4. Main air pipeline; 5. Low calorific value gas pipeline; 6. High calorific value gas pipeline; 7. Control unit; 8. Main burner; 9. Ignition burner; 10. Blower; 11. Air damper; 12. Low calorific value gas pressure transmitter A; 13. Low calorific value gas pressure switch A; 14. Low calorific value gas pressure gauge; 15. Low calorific value gas flow regulating valve; 16. Low calorific value gas stop valve A; 17. Low calorific value gas stop valve B; 18. Low calorific value gas orifice plate; 19. Low calorific value gas pressure switch B; 20. Low calorific value gas ball valve; 21. Low calorific value gas pressure transmitter B; 22. High calorific value gas pressure switch A; 23. High calorific value gas pressure gauge; 24. High calorific value gas pressure stabilizing valve; 25. High calorific value gas flow regulating valve; 26. High calorific value gas stop valve A; 27. High calorific value gas stop valve B; 28. High calorific value gas orifice plate; 29. High calorific value gas pressure switch B; 30. High calorific value gas ball valve; 31. Ignition gas stop valve A; 32. Ignition gas pressure stabilizing valve; 33. Ignition gas stop valve B; 34. Ignition gas orifice plate; 35. Ignition gas ball valve; 36. Air ball valve; 37. Air orifice plate; 38. Flue gas oxygen content transmitter; 39. Frequency converter; 40. Air cavity; 41. High calorific value gas cavity; 42. Low calorific value gas cavity; 43. Premixing cavity; 44. Air holes; 45. Low calorific value gas holes; 46. Jet pipe; 47. High calorific value gas nozzle; 48. High calorific value gas holes. Detailed implementation manners

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] Please refer to Figure 1 As shown in the figure, the embodiment of the present invention provides a boiler system for co - firing low calorific value gas and high calorific value gas, including a boiler body 1, an ignition air pipeline 2, an ignition gas pipeline 3, a main air pipeline 4, a low calorific value gas pipeline 5, a high calorific value gas pipeline 6 and a control unit 7. A main burner 8 and an ignition burner 9 are arranged in the combustion chamber of the boiler body 1.

[0020] The intake end of the ignition air pipeline 2 is connected with a blower 10, and the outlet end of the ignition air pipeline 2 communicates with the ignition burner 9, for providing ignition air for the ignition burner 9. The intake end of the ignition gas pipeline 3 communicates with a high calorific value gas (such as conventional gas like natural gas) supply source, and the outlet end of the ignition gas pipeline 3 communicates with the ignition burner 9, for providing ignition gas for the ignition burner 9.

[0021] The intake end of the main air pipeline 4 is also connected to the air blower 10, and the outlet end of the main air pipeline 4 communicates with the main burner 8 to supply combustion air for the main burner 8. An air baffle 11 with adjustable opening is provided in the main air pipeline 4, and the air flow in the main air pipeline 4 can be adjusted by adjusting the opening of the air baffle 11.

[0022] The intake end of the high calorific value gas pipeline 6 is communicated with the high calorific value gas supply source, and the outlet end of the high calorific value gas pipeline 6 communicates with the main burner 8 to supply combustion gas for the main burner 8. The intake end of the low calorific value gas pipeline 5 is communicated with the low calorific value gas supply source, and the outlet end of the low calorific value gas pipeline 5 also communicates with the main burner 8 to introduce low calorific value gas (such as biogas, by - product hydrogen, blast furnace gas and other by - product gases generated in the industrial production process) into the main burner 8 for combustion. Mixing the low calorific value gas and the high calorific value gas for combustion can solve the technical problem that the low calorific value gas cannot be stably combusted alone.

[0023] A low calorific value gas flow regulating valve 15 is provided on the low calorific value gas pipeline 5, and a high calorific value gas flow regulating valve 25 is provided on the high calorific value gas pipeline 6. Both the low calorific value gas flow regulating valve 15 and the high calorific value gas flow regulating valve 25 are electrically connected to the control unit 7 to automatically adjust the low calorific value gas flow and the high calorific value gas flow through the control unit 7 to ensure the flame stability during combustion.

[0024] Specifically, in the embodiment of the present invention, along the gas flow direction of the low calorific value gas pipeline 5, a low calorific value gas pressure transmitter A12, a low calorific value gas pressure switch A13, a low calorific value gas pressure gauge 14, a low calorific value gas flow regulating valve 15, a low calorific value gas stop valve A16, a low calorific value gas stop valve B17, a low calorific value gas orifice plate 18, a low calorific value gas pressure switch B19 and a low calorific value gas ball valve 20 are sequentially arranged. When the boiler is operating normally, when the gas pressure of the low calorific value gas (detected by the low calorific value gas pressure switch A13) reaches the lower limit of the required pressure, the low calorific value gas stop valve A16 and the low calorific value gas stop valve B17 open, and the low calorific value gas and the high calorific value gas burn together; when the gas pressure of the low calorific value gas (detected by the low calorific value gas pressure switch A13) is too small and fails to reach the lower limit of the required pressure, the low calorific value gas stop valve A16 and the low calorific value gas stop valve B17 close, and automatically switch to the single - fuel combustion mode of the high calorific value fuel burning alone. When the low calorific value gas pressure detected by the low calorific value gas pressure switch B19 is too high (i.e., reaches the upper limit of the required pressure), it will trigger the interlock protection program of the boiler system, causing the boiler to shut down automatically.

[0025] The low calorific value gas pressure transmitter A12 is electrically connected to the control unit 7. The control unit 7 can automatically calculate and adjust the opening degree of the low calorific value gas flow regulating valve 15 according to the pressure signal sent by the low calorific value gas pressure transmitter A12, as Figure 2 shown. At the same time, it automatically calculates and adjusts the opening degree of the high calorific value gas flow regulating valve 25 to adjust the supply ratio of the low calorific value gas and the high calorific value gas. Further, a low calorific value gas pressure transmitter B21 can be connected between the inlet end and the outlet end of the low calorific value gas orifice plate 18. The low calorific value gas pressure transmitter B21 is also electrically connected to the control unit 7 and can feedback the detected pressure signal to the control unit 7. The monitoring of the low calorific value gas pressure can also be realized through the low calorific value gas pressure transmitter B21.

[0026] Specifically, along the gas flow direction of the high calorific value gas pipeline 6 in the embodiment of the present invention, a high calorific value gas pressure switch A22, a high calorific value gas pressure gauge 23, a high calorific value gas pressure stabilizing valve 24, a high calorific value gas flow regulating valve 25, a high calorific value gas stop valve A26, a high calorific value gas stop valve B27, a high calorific value gas orifice plate 28, a high calorific value gas pressure switch B29 and a high calorific value gas ball valve 30 are sequentially arranged. Among them, the opening degree of the high calorific value gas flow regulating valve 25 is automatically calculated and adjusted by the control unit 7.

[0027] The inlet end of the ignition gas pipeline 3 can be directly connected between the high calorific value gas pressure switch A22 and the high calorific value gas pressure gauge 23. Specifically, along the gas flow direction of the ignition gas pipeline 3 in the embodiment of the present invention, an ignition gas stop valve A31, an ignition gas pressure stabilizing valve 32, an ignition gas stop valve B33, an ignition gas orifice plate 34 and an ignition gas ball valve 35 are sequentially arranged. Along the air flow direction of the ignition air pipeline 2, an air ball valve 36 and an air orifice plate 37 are sequentially arranged.

[0028] Further, a flue gas oxygen content transmitter 38 is installed at the flue gas outlet of the boiler body 1; a frequency converter 39 is provided on the forced draft fan 10; both the flue gas oxygen content transmitter 38 and the frequency converter 39 are electrically connected to the control unit 7. The flue gas oxygen content transmitter 38 can detect the oxygen content in the flue gas discharged from the boiler and feedback the detection result to the control unit 7; the control unit 7 then calculates the correction coefficient of the frequency converter 39 according to the oxygen content in the flue gas and adjusts the operating frequency of the forced draft fan 10 to achieve the best combustion effect.

[0029] Correspondingly, the embodiment of the present invention also provides a main burner 8 supporting the co-firing of low calorific value gas and high calorific value gas. As Figure 3As shown in the figure, the main burner 8 is divided into an air chamber 40, a high calorific value gas chamber 41, a low calorific value gas chamber 42 and a premixing chamber 43. Among them, both the air chamber 40 and the premixing chamber 43 are connected to the main air pipeline 4, the high calorific value gas chamber 41 is connected to the high calorific value gas pipeline 6, and the low calorific value gas chamber 42 is connected to the low calorific value gas pipeline 5.

[0030] The ignition burner 9 is inserted into the air chamber 40. A through hole for the ignition burner 9 to pass through and a plurality of air holes 44 for air to pass through are provided at the bottom of the air chamber 40 (the side facing the combustion chamber). The combustion air in the air chamber 40 can enter the combustion chamber of the boiler body 1 through the air holes 44.

[0031] The high calorific value gas chamber 41 is sleeved outside the air chamber 40, and both the low calorific value gas chamber 42 and the premixing chamber 43 are sleeved outside the high calorific value gas chamber 41. The low calorific value gas chamber 42 extends into the premixing chamber 43 and is provided with a plurality of low calorific value gas holes 45 communicating with the premixing chamber 43, so that the low calorific value gas in the low calorific value gas chamber 42 can enter the premixing chamber 43 through the low calorific value gas holes 45 and mix with the combustion air in the premixing chamber 43. A plurality of jet pipes 46 communicating with the premixing chamber 43 are arranged at intervals along the circumferential direction at the bottom of the premixing chamber 43 (the side facing the combustion chamber). The mixed gas in the premixing chamber 43 can enter the combustion chamber of the boiler body 1 through the jet pipes 46. Premixing the low calorific value gas with the combustion air before combustion can ensure the full combustion of the low calorific value gas.

[0032] A plurality of high calorific value gas nozzles 47 communicating with the high calorific value gas chamber 41 are correspondingly arranged along the circumferential direction on the outer wall of the high calorific value gas chamber 41. Each high calorific value gas nozzle 47 is respectively inserted into the corresponding jet pipe 46, and a gap for the mixed gas to pass through is left between them. The high calorific value gas in the high calorific value gas chamber 41 can enter the combustion chamber of the boiler body 1 through the high calorific value gas nozzles 47 and quickly mix with the mixed gas ejected from the jet pipes 46, which is convenient for combustion. Further, a plurality of high calorific value gas holes 48 can be arranged at intervals along the circumferential direction on the inner wall of the high calorific value gas chamber 41. The high calorific value gas holes 48 are located on the air outlet side of the air holes 44. The high calorific value gas ejected from the high calorific value gas holes 48 can mix with the combustion air ejected from the air holes 44 below the ignition burner 9, which is convenient for the ignition burner 9 to ignite and burn.

[0033] In this article, specific examples are used to illustrate the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the technical solutions and their core ideas of the present invention. Those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A boiler system for mixed combustion of low calorific value gas and high calorific value gas, characterized in that: include: A boiler body, wherein a main burner and an ignition burner are arranged in a combustion chamber of the boiler body; An ignition air pipeline, wherein an air inlet end of the ignition air pipeline is connected to a blower, and an air outlet end of the ignition air pipeline is connected to the ignition burner; An ignition gas pipeline, wherein the gas inlet end of the ignition gas pipeline is connected to a high calorific value gas supply source, and the gas outlet end of the ignition gas pipeline is connected to the ignition burner; A main air pipeline, wherein the air inlet end of the main air pipeline is connected to the blower, and the air outlet end of the main air pipeline is connected to the main burner; an air damper with an adjustable opening is provided in the main air pipeline; A low calorific value gas pipeline, wherein the gas inlet end of the low calorific value gas pipeline is connected to the low calorific value gas supply source, and the gas outlet end of the low calorific value gas pipeline is connected to the main burner; a low calorific value gas flow regulating valve is provided on the low calorific value gas pipeline; A high calorific value gas pipeline, wherein the gas inlet end of the high calorific value gas pipeline is connected to the high calorific value gas supply source, and the gas outlet end of the high calorific value gas pipeline is connected to the main burner; a high calorific value gas flow regulating valve is provided on the high calorific value gas pipeline; A control unit, the low calorific value gas flow regulating valve and the high calorific value gas flow regulating valve are both electrically connected to the control unit; when the gas pressure of the low calorific value gas does not reach the required lower pressure limit, the high calorific value fuel is burned alone; when the gas pressure of the low calorific value gas reaches the required lower pressure limit, the low calorific value gas and the high calorific value gas are burned together; The main burner is divided into an air chamber, a high calorific value gas chamber, a low calorific value gas chamber and a premixing chamber, wherein the air chamber and the premixing chamber are both connected to the main air pipeline, the high calorific value gas chamber is connected to the high calorific value gas pipeline, and the low calorific value gas chamber is connected to the low calorific value gas pipeline and is connected to the premixing chamber.

2. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 1, characterized in that: A low calorific value gas pressure transmitter A, a low calorific value gas pressure switch A, a low calorific value gas pressure gauge, the low calorific value gas flow regulating valve, a low calorific value gas stop valve A, a low calorific value gas stop valve B, a low calorific value gas throttling orifice plate, a low calorific value gas pressure switch B and a low calorific value gas ball valve are sequentially arranged along the gas flow direction of the low calorific value gas pipeline; the low calorific value gas pressure transmitter A is electrically connected to the control unit.

3. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 2, characterized in that: A low calorific value gas pressure transmitter B is connected between the gas inlet end and the gas outlet end of the low calorific value gas throttling orifice plate, and the low calorific value gas pressure transmitter B is electrically connected to the control unit.

4. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 1, characterized in that: The high calorific value gas pipeline is provided with a high calorific value gas pressure switch A, a high calorific value gas pressure gauge, a high calorific value gas pressure stabilizing valve, the high calorific value gas flow regulating valve, a high calorific value gas stop valve A, a high calorific value gas stop valve B, a high calorific value gas throttling orifice plate, a high calorific value gas pressure switch B and a high calorific value gas ball valve in sequence along the gas flow direction.

5. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 4, characterized in that: The air inlet end of the ignition gas pipeline is connected between the high calorific value gas pressure switch A and the high calorific value gas pressure gauge.

6. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 5, characterized in that: An ignition gas stop valve A, an ignition gas pressure-stabilizing valve, an ignition gas stop valve B, an ignition gas throttling orifice plate, and an ignition gas ball valve are sequentially arranged along the ignition gas pipeline in the direction of gas flow.

7. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 1, characterized in that: An air ball valve and an air throttling orifice plate are sequentially arranged on the ignition air pipeline along the air flow direction thereof.

8. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 1, characterized in that: The flue gas outlet of the boiler body is equipped with a flue gas oxygen content transmitter; the blower is provided with a frequency converter; the flue gas oxygen content transmitter and the frequency converter are both electrically connected to the control unit.

9. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to any one of claims 1 to 8, characterized in that: The ignition burner is inserted in the air cavity, and the bottom of the air cavity is provided with a through hole for the ignition burner to pass through and a plurality of air holes for air to pass through; the high calorific value gas cavity is sleeved on the outside of the air cavity, and the low calorific value gas cavity and the premixing cavity are both sleeved on the outside of the high calorific value gas cavity; the low calorific value gas cavity extends into the premixing cavity and is provided with a plurality of low calorific value gas holes connected with the premixing cavity; a plurality of injection pipes connected with the premixing cavity are arranged at intervals along the circumference of the bottom of the premixing cavity, and a plurality of high calorific value gas nozzles connected with the high calorific value gas cavity are correspondingly arranged along the circumference of the outer wall of the high calorific value gas cavity, and the high calorific value gas nozzles are respectively inserted into the corresponding injection pipes and a gap is left between the two for the mixed gas to pass through.

10. A boiler system for mixed combustion of low calorific value gas and high calorific value gas according to claim 9, characterized in that: The inner wall of the high calorific value gas cavity is provided with a plurality of high calorific value gas holes spaced apart along the circumference thereof, and the high calorific value gas holes are located at the gas outlet side of the air hole.

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