Low-concentration gas coupled biomass self-excited oscillation combustion system and combustion method

Abstract

The application discloses a low-concentration gas coupled biomass self-excited oscillation combustion system and combustion method, which comprises a pipe body combustor, a gas supply unit, a biomass supply unit and a secondary air supply unit, and contains an oxygen-deficient combustion zone and an oxygen-rich combustion zone; the gas supply unit and the biomass supply unit supply low-concentration gas and biomass fuel to the oxygen-deficient combustion zone respectively; the oxygen-deficient combustion zone is a heat source and forms a vibration source capable of generating a self-excited oscillation wave along the pipe length direction; the oxygen-deficient combustion zone and the oxygen-rich combustion zone are alternately switched between positive pressure and negative pressure states under the action of self-excited oscillation; under the state of negative pressure of the oxygen-deficient combustion zone, the heat of the oxygen-rich combustion zone flows back to the oxygen-deficient combustion zone to preheat the low-concentration gas and compensate the temperature of the oxygen-deficient combustion zone; the self-excited oscillation combustion principle is used to take biomass waste and low-concentration gas as fuel, and the two are synergistically coupled to combust, so that the low-concentration gas and the biomass waste are efficiently utilized.

Description

Technical Field

[0001] This invention belongs to the field of low-concentration gas combustion and utilization technology, and specifically relates to a low-concentration gas coupled biomass self-excited oscillation combustion system and combustion method. Background Technology

[0002] Biomass is the only carbon-based renewable resource that can serve as an alternative fuel to coal for power generation or heating. Unlike other energy resources, biomass is widely distributed and ubiquitous. Because biomass power generation can achieve zero carbon dioxide emissions throughout its entire life cycle, it has seen significant development in my country in recent years. Existing industrial biomass combustion equipment draws on traditional coal-fired technologies, including fluidized bed boilers and vibrating grate furnaces. However, biomass power generation units are often smaller in scale than coal-fired power plants, necessitating the development of new technologies suitable for biomass combustion.

[0003] Based on the above background, this invention patent provides a low-concentration gas coupled biomass self-excited oscillation combustion system for power generation and heating. This system is the first to utilize the self-excited oscillation combustion principle, using biomass waste and low-concentration gas (concentration 1%~10%) as fuel. Through the synergistic coupling combustion effect of the two, it can reduce the NOx emission concentration of biomass combustion while efficiently utilizing low-concentration gas and biomass waste. The heat generated by combustion is used for power generation and heating for domestic and industrial use. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a low-concentration gas coupled biomass self-excited oscillation combustion system and combustion method. It utilizes the self-excited oscillation combustion principle to use biomass waste and low-concentration gas as fuel. Through the synergistic coupling combustion effect of the two, it can efficiently utilize low-concentration gas and biomass.

[0005] Technical solution: To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A low-concentration gas-coupled biomass self-excited oscillation combustion system includes a tube burner, a gas supply unit, a biomass supply unit, and a secondary air supply unit. The tube burner contains an oxygen-deficient combustion zone and an oxygen-rich combustion zone distributed along the length of the tube. The gas supply unit and the biomass supply unit supply low-concentration gas and biomass fuel to the oxygen-deficient combustion zone, respectively. The oxygen-deficient combustion zone serves as a heat source and constitutes a vibration source capable of generating a self-excited oscillation wave along the length of the tube. The oxygen-rich combustion zone is located on the oscillation path of the self-excited oscillation wave, and the secondary air supply unit introduces oxygen-rich gas into the oxygen-rich combustion zone. The oxygen-deficient combustion zone and the oxygen-rich combustion zone alternate between positive and negative pressure states under the action of self-excited oscillation. When the oxygen-deficient combustion zone is under negative pressure, the heat from the oxygen-rich combustion zone flows back to the oxygen-deficient combustion zone to preheat the low-concentration gas and compensate for the temperature of the oxygen-deficient combustion zone.

[0007] Furthermore, the tube burner is a vertically arranged straight tube structure, and the oxygen-deficient combustion zone is located at 1 / 4 of the tube length from bottom to top of the tube burner.

[0008] Furthermore, the tube burner includes a gas inlet corresponding to the oxygen-deficient combustion zone, and an ignition device is provided in the oxygen-deficient combustion zone corresponding to the gas inlet.

[0009] Furthermore, the oxygen-deficient burner contains a porous medium corresponding to the gas inlet.

[0010] Furthermore, the porous medium is a metal foam ceramic.

[0011] Furthermore, the ignition device is located at the gas flow outlet of the porous medium.

[0012] Furthermore, the gas supply unit includes a gas delivery pipeline, on which a flame arrester, an explosion-proof fan, a gas flow meter, and a gas concentration meter are connected in series.

[0013] Furthermore, the tube burner is also equipped with a steam-water unit for absorbing heat. The steam-water unit includes a heat exchanger, a feed water pump, a feed water flow meter, and a steam delivery pipeline connected in series. The heat exchanger is located inside the tube burner cavity.

[0014] Furthermore, the inner cavity of the tube burner is provided with a biomass fuel grate for carrying biomass fuel corresponding to the oxygen-deficient combustion zone, and the biomass fuel grate includes several slag discharge ports.

[0015] A combustion method for a low-concentration gas-coupled biomass self-excited oscillation combustion system includes the following steps:

[0016] Step 1: Vertically arrange straight-tube burners and determine the location of the heat source that can form a self-excited oscillating combustion effect within the burner when a combustion heat source is present;

[0017] Step 2: Place the biomass fuel grate at the designated heat source location and supply biomass fuel. Ignite the introduced biomass fuel and gas, and the biomass fuel will burn.

[0018] Step 3: Introduce a low concentration of methane gas towards the biomass fuel accumulation area. The heat generated by biomass combustion preheats and aids the combustion of the low-concentration methane gas. Simultaneously with combustion:

[0019] Due to thermo-acoustic coupling, acoustic vibrations of the fundamental mode are excited inside the tube burner. The oxygen-deficient combustion zone generates self-excited oscillation waves along the tube length. Under the action of self-excited oscillation, the oxygen-deficient combustion zone and the oxygen-rich combustion zone alternate between positive and negative pressure states. When the oxygen-deficient combustion zone is under negative pressure, the heat from the oxygen-rich combustion zone flows back to the oxygen-deficient combustion zone to preheat the low-concentration methane gas and compensate for the temperature in the oxygen-deficient combustion zone, thus extending the lean combustion limit of the low-concentration methane.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0021] (1) The self-excited oscillation combustion device realizes the synchronous combustion of low-concentration gas and biomass, which solves the problem of difficult combustion of low-concentration gas (methane concentration 1~10%) and at the same time reduces the environmental pollution caused by gas emissions. Meanwhile, the self-excited oscillation wave generated by the thermo-acoustic coupling of the self-excited oscillation combustion device induces the pulsating combustion phenomenon, which can enhance the disturbance of the combustion process, improve the combustion efficiency, and expand the lean combustion limit. Through this method, the lean combustion limit of low-concentration gas coupled with biomass combustion can be reduced to a minimum of 1%.

[0022] (2) Methane in low-concentration gas is a reducing gas that can release CHi free radicals in the combustion zone to reduce NOx generated by biomass combustion, thereby reducing the NOx emission concentration from biomass combustion. Secondary air can ensure that unburned biomass and a small amount of gas are fully burned in an oxygen-rich atmosphere.

[0023] (3) Low-concentration gas is coupled with biomass for power generation and heating, realizing the synergistic utilization of low-concentration gas and biomass waste. It is clean, efficient, and reduces carbon emissions. It achieves significant environmental benefits while realizing the synergistic disposal and utilization of low-concentration gas and biomass waste. Attached Figure Description

[0024] Appendix Figure 1 This is a schematic diagram of the low-concentration gas-coupled biomass self-excited oscillation combustion system of the present invention.

[0025] Appendix Figure 2 This is a schematic diagram showing the location of the heat source and the pressure and velocity curves of self-excited oscillating combustion in this invention. Detailed Implementation

[0026] The invention will now be further described with reference to the accompanying drawings.

[0027] As attached Figure 1 As shown, a low-concentration gas-coupled biomass self-excited oscillation combustion system includes a tube burner, a gas supply unit, a biomass supply unit, and a secondary air supply unit. The combustion chamber inside the tube burner contains an oxygen-deficient combustion zone 110 and an oxygen-rich combustion zone 111 distributed along the length of the tube. The oxygen-deficient combustion zone and the oxygen-rich combustion zone represent the relative degree of oxygen concentration. Because the gas with a concentration between 1-10% has a high air content but a lower oxygen concentration than air, the secondary air supply unit introduces oxygen-rich gas towards the oxygen-rich combustion zone 111. The oxygen-rich gas is air. The secondary air can ensure that unburned biomass and a small amount of gas are fully combusted in the oxygen-rich atmosphere.

[0028] The gas supply unit and biomass supply unit respectively supply low-concentration gas and biomass fuel to the oxygen-deficient combustion zone 110. The oxygen-deficient combustion zone is the combustion zone for low-concentration gas and biomass fuel. The oxygen-deficient combustion zone 110 is a heat source and constitutes a vibration source capable of generating a self-excited oscillation wave along the pipe length direction. The oxygen-rich combustion zone 111 is located on the oscillation path of the self-excited oscillation wave 100. The oxygen-deficient combustion zone and the oxygen-rich combustion zone alternately switch between positive and negative pressure states under the action of self-excited oscillation. When the oxygen-deficient combustion zone is under negative pressure, the heat from the oxygen-rich combustion zone flows back to the oxygen-deficient combustion zone to preheat the low-concentration gas and compensate for the temperature of the oxygen-deficient combustion zone. The simultaneous combustion of low-concentration methane and biomass was achieved using a self-excited oscillation combustion device, solving the problem of difficult combustion of low-concentration methane (1-10%) and mitigating environmental pollution caused by methane emissions. Furthermore, the self-excited oscillation waves generated by the thermoacoustic coupling of the self-excited oscillation combustion device induce pulsating combustion, which can enhance combustion process disturbance, improve combustion efficiency, and extend the lean-burn limit. This method can reduce the lean-burn limit of low-concentration methane coupled with biomass combustion to a minimum of 1%.

[0029] The tube burner is a vertically arranged straight tube structure, and the generated flue gas is discharged upward. The oxygen-deficient combustion zone 110 is located at 1 / 4 of the tube length from bottom to top of the tube burner. The oxygen-deficient combustion zone 110 is the area where gas and biomass are burned, forming a heat source. That is, the heat source is located at 1 / 4 of the tube length from bottom to top of the tube burner.

[0030] The tube burner includes a gas inlet corresponding to the oxygen-deficient combustion zone 110. An ignition device 103 is provided in the oxygen-deficient combustion zone 110 corresponding to the gas inlet. The ignition device includes an ignition needle, which is an electric spark igniter installed at 1 / 4 of the tube length, i.e., at the inlet where low-concentration gas enters the combustion equipment.

[0031] The oxygen-deficient burner contains a porous medium 104 corresponding to the gas inlet. The porous medium 104 is a metal foam ceramic. The ignition device 103 is located at the gas flow outlet of the porous medium 104. Low-concentration gas is ignited at the outlet of the porous medium 104. The porous medium 104 has an explosion suppression function.

[0032] The tube burner 101 is a self-excited oscillating combustion device, which is a continuous straight pipe section. When the heat source is located at 1 / 4 of the pipe length, it can generate a thermoacoustic coupled self-excited oscillation wave 111, which can induce pulsating combustion, making the temperature of the combustion zone uniform and the combustion stable. The combustion zone of the self-excited oscillating combustion device includes a fuel-rich combustion zone 110 and an oxygen-rich combustion zone 111.

[0033] A heat insulation layer 102 is also wrapped around the outside of the tube burner. The heat insulation layer is wrapped around the outer wall of the combustion equipment to prevent the heat generated by combustion from being lost outward through the wall.

[0034] The inner cavity of the tube burner, corresponding to the oxygen-deficient combustion zone, is equipped with a biomass fuel grate 105 for supporting biomass fuel. The biomass fuel grate 105 includes several ash discharge ports 106, from which the ash produced by biomass combustion is discharged. By adjusting the position of the biomass grate 105 in the tube burner, the position of the heat source is adjusted, enabling acoustic-thermal coupling to occur within the tube combustion chamber during combustion, thereby forming a self-excited oscillating combustion effect.

[0035] A porous medium, often metal foam ceramic, is installed at the low-concentration methane inlet to effectively suppress methane explosions. The self-excited oscillating combustion effect occurs within the combustion chamber. When the heat source combustion occurs at 1 / 4 of the tube's length, acoustic vibration of the fundamental mode is excited within the tube due to acoustic-thermal coupling, resulting in the self-excited oscillating combustion effect. This effect promotes combustion disturbance and generates changes in positive and negative pressure within the combustion chamber. When negative pressure occurs, the high-temperature flue gas after combustion flows back to the low-concentration methane inlet, preheating the low-concentration methane gas and thus promoting combustion and extending the lean-burn limit of the low-concentration methane. The structure and principle of the oscillating tube are shown in the figure. The acoustic pressure and velocity distribution within the burner tube vary along the tube length, exhibiting a semi-wave standing wave distribution. The pressure amplitude is largest in the middle of the burner and smallest at both ends. The velocity distribution is exactly opposite to the pressure distribution, zero in the middle and largest at both ends, with opposite phases, as shown in the attached figure. Figure 2 As shown, Figure a is a schematic diagram of the structure of the tube burner and the location of the heat source; Figure b is a schematic diagram of the pressure curve, velocity curve and half-waveform curve of the self-excited oscillation wave in the combustion chamber.

[0036] Appendix Figure 2 The markings in the text are as follows: L—pipe length; d—pipe diameter; x—heat source location; p'—pressure; u'—velocity; λ—wavelength.

[0037] Low-concentration methane is difficult to burn and is within the explosive range. The oscillation frequency of self-excited combustion is generally 70Hz~120Hz, and the furnace pressure generally fluctuates between ±3000Pa. The low pressure fluctuation value is conducive to promoting combustion, but does not cause damage to the equipment.

[0038] Methane gas with a concentration between 1% and 10% has a high air content and low calorific value, making it difficult to achieve safe and efficient combustion using conventional methods and equipment. Especially for low-concentration methane gas (less than 4%), its calorific value is less than the heat carried away during combustion, making it difficult to meet its own combustion needs. Therefore, simply burning methane gas at this concentration presents challenges. This invention addresses this by adding a small amount of biomass to supplement the insufficient heat during combustion, thereby achieving effective utilization of this concentration of methane gas.

[0039] This invention couples self-excited oscillatory combustion with biomass combustion, effectively extending the lean combustion limit of low-concentration gas. The applicant's experiments show that this method can achieve combustion utilization of as low as 1% low-concentration gas. At 1% low-concentration gas combustion utilization, only 0.2 kg of conventional biomass (with a biomass calorific value of 3500 kcal / kg) needs to be added per cubic meter of low-concentration gas combustion. 3 / h): Biomass fuel (kg / h) = 5:1.

[0040] Gas concentration sensors 109 are installed on the combustion chamber of the tube in the oxygen-deficient combustion zone and the oxygen-rich combustion zone, respectively.

[0041] It also includes a dust removal unit located at the flue gas discharge end of the tube burner. The dust removal unit includes a dust collector bag 107 and an induced draft fan 108 for supplying or exhausting air to the dust collector bag 107. The high-temperature flue gas generated by combustion flows upward under the action of the induced draft fan 107, and after heat exchange through the steam-water system, it enters the bag filter dust collector 107 for dust removal. The purified flue gas is discharged by the induced draft fan.

[0042] The gas supply unit includes a gas delivery pipeline 201, on which a flame arrester 202, an explosion-proof fan 203, a gas flow meter 204, and a gas concentration meter 205 are connected in series. The gas delivery pipeline 201 is connected to a coal seam gas extraction device or a coal seam gas collection and storage device. The gas concentration meter 205 monitors the gas concentration in real time, and the gas flow meter 204 monitors and regulates the gas flow rate, which is then delivered to the burner by the explosion-proof fan. The flame arrester is installed in the gas delivery pipeline 201 to prevent gas backfire.

[0043] The biomass supply unit includes a screw feeder 301, a biomass hopper 302, and a frequency-controlled motor 303. The screw feeder 301 drives the blades, which are fixed to a central shaft, to compress the biomass, thus achieving the effect of conveying biomass. The rotational speed of the central shaft is adjusted and controlled by the frequency-controlled motor 303. The biomass hopper 302 is used to store biomass raw materials, ensuring a continuous and stable supply of biomass fuel.

[0044] The secondary air supply unit includes a fan 401 and a secondary air flow meter 402. The flow rate of the secondary air is monitored and regulated by the secondary air flow meter connected to the control system.

[0045] The tube burner is also equipped with a steam-water unit for absorbing heat. This unit includes a heat exchanger 501, a feed water pump 502, a feed water flow meter 503, and a steam delivery pipeline 504 connected in series. The heat exchanger 501 is located inside the tube burner. Water is pumped into the heat exchanger 501 by the feed water pump 502 to absorb heat from the high-temperature flue gas and heat it into saturated steam. This steam is then delivered to the application terminal 701 via the steam delivery pipeline 504 for power generation or heating.

[0046] The online monitoring and control system includes the use of sensors in the data acquisition module 601 to control the ignition needle 103 used for ignition, monitor and control the thermocouple 107 for testing the combustion zone temperature, monitor and control the gas flow meter 204 for regulating gas flow, monitor the gas concentration meter 205 for monitoring gas concentration, monitor and control the flow meter 402 for regulating secondary air flow, and monitor and control the water supply flow meter 503 of the steam-water system. The data collected in real time by the sensors in the data acquisition module 601 is transmitted to the control unit of the display and control terminal 602. The relevant data is displayed and judged by the software program, and adjustments are made automatically.

[0047] The terminal application system 701 can be a turbine, steam turbine, screw expander, etc., that uses steam to drive a generator to generate electricity, or it can be a residence, office building, factory, workshop, etc. that has the need for heating, hot water, etc.

[0048] The gas pressure in the gas delivery pipeline, the secondary air pressure in the secondary air system, and the steam pressure in the steam delivery pipeline are all monitored and controlled by corresponding pressure gauges. These pressure gauges can be adjusted manually or by data acquisition modules that collect data and adjust the pressure through the control system. Each delivery pipeline is equipped with a pressure reducing valve.

[0049] A combustion method for a low-concentration gas-coupled biomass self-excited oscillation combustion system includes the following steps:

[0050] Step 1: Vertically arrange straight-tube burners and determine the location of the heat source that can form a self-excited oscillating combustion effect within the burner when a combustion heat source is present;

[0051] Step 2: Place the biomass fuel grate at the designated heat source location and supply biomass fuel. Ignite the introduced biomass fuel and gas, and the biomass fuel will burn.

[0052] Step 3: Introduce a low concentration of methane gas towards the biomass fuel accumulation area. The heat generated by biomass combustion preheats and aids the combustion of the low-concentration methane gas. Simultaneously with combustion:

[0053] Due to thermo-acoustic coupling, acoustic vibrations of the fundamental mode are excited inside the tube burner. The oxygen-deficient combustion zone generates self-excited oscillation waves along the tube length. Under the action of self-excited oscillation, the oxygen-deficient combustion zone and the oxygen-rich combustion zone alternate between positive and negative pressure states. When the oxygen-deficient combustion zone is under negative pressure, the heat from the oxygen-rich combustion zone flows back to the oxygen-deficient combustion zone to preheat the low-concentration methane gas and compensate for the temperature in the oxygen-deficient combustion zone, thus extending the lean combustion limit of the low-concentration methane.

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-concentration gas coupled biomass self-excited oscillating combustion system, characterized in that: The pipe body combustor includes an oxygen-poor combustion zone (110) and an oxygen-rich combustion zone (111) arranged along the length direction of the pipe, a gas supply unit, a biomass supply unit, and a secondary air supply unit. The gas supply unit and the biomass supply unit supply low-concentration gas and biomass fuel to the oxygen-poor combustion zone (110) respectively. The oxygen-poor combustion zone (110) is a heat source and constitutes a vibration source capable of generating self-excited oscillation waves along the length direction of the pipe. The oxygen-rich combustion zone (111) is located on the oscillation path of the self-excited oscillation waves (100), and the secondary air supply unit introduces oxygen-rich gas to the oxygen-rich combustion zone (111). The oxygen-poor combustion zone and the oxygen-rich combustion zone are alternately switched between positive pressure and negative pressure states under the action of the self-excited oscillation. When the oxygen-poor combustion zone is in a negative pressure state, the heat of the oxygen-rich combustion zone flows back to the oxygen-poor combustion zone to preheat the low-concentration gas and compensate for the temperature of the oxygen-poor combustion zone. The pipe body combustor is a vertical straight pipe structure, and the oxygen-poor combustion zone (110) is located at 1 / 4 of the length of the pipe body combustor from the bottom to the top. The pipe body combustor includes a gas inlet corresponding to the oxygen-poor combustion zone (110), and an ignition device (103) is arranged corresponding to the gas inlet in the oxygen-poor combustion zone (110).

2. The low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 1, characterized in that: A porous medium (104) is arranged corresponding to the gas inlet in the oxygen-poor combustion zone.

3. The low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 2, characterized in that: The porous medium (104) is a metal foam ceramic.

4. The low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 2, characterized in that: The ignition device (103) is located at the gas outflow end of the porous medium (104).

5. The low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 1, characterized in that: The gas supply unit includes a gas delivery pipeline (201), and a flame arrestor (202), an explosion-proof fan (203), a gas flow meter (204), and a gas concentration meter (205) are sequentially connected in series on the gas delivery pipeline.

6. The low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 1, characterized in that: The pipe body combustor also has a steam-water unit for absorbing heat, which includes a heat exchanger (501), a feedwater pump (502), a feedwater flow meter (503), and a steam delivery pipeline (504) connected in series, and the heat exchanger (501) is arranged in the inner cavity of the pipe body combustor.

7. The low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 1, characterized in that: A biomass fuel grate (105) for carrying biomass fuel is arranged corresponding to the oxygen-poor combustion zone in the inner cavity of the pipe body combustor, and the biomass fuel grate (105) includes a plurality of slag discharge ports (106).

8. The combustion method of a low-concentration gas coupled biomass self-excited oscillation combustion system according to claim 1, characterized in that: The method includes the following steps: Step 1: vertically arrange a straight pipe type pipe body combustor and determine the heat source position in the pipe body combustor where the self-excited oscillation combustion effect can be formed when there is a combustion heat source; Step 2: place a biomass fuel grate at the determined heat source position to supply biomass fuel, ignite the introduced biomass fuel and gas, and burn the biomass fuel; Step 3: introduce low-concentration gas to the accumulation area of the biomass fuel, preheat and assist combustion of the low-concentration gas with the heat generated by the biomass combustion, and simultaneously: Due to the thermo-acoustic coupling effect, the acoustic vibration of the base mode is excited in the pipe, and the self-excited oscillation wave is generated along the pipe length in the lean oxygen combustion zone. The lean oxygen combustion zone and the rich oxygen combustion zone are alternately switched between the positive pressure state and the negative pressure state under the action of the self-excited oscillation. In the negative pressure state of the lean oxygen combustion zone, the heat of the rich oxygen combustion zone is backflowed to the lean oxygen combustion zone to preheat the low-concentration gas and compensate the temperature of the lean oxygen combustion zone, thereby expanding the lean combustion limit of the low-concentration gas.

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