A swirling jet flameless oxidation device and method for low-concentration methane gas

Abstract

This invention relates to a swirling jet flameless oxidation device and method for low-concentration methane gas, comprising an oxidation chamber for achieving low-concentration methane gas oxidation, and an ignition system disposed within the oxidation chamber. A flame stabilizing plate is disposed at one end of the oxidation chamber, and a high-temperature flue gas outlet is opened at the other end. A swirling tube, which causes turbulence in the methane gas within the oxidation chamber, is inserted along the circumference of the flame stabilizing plate. A through-hole is disposed on the flame stabilizing plate, communicating with a main air inlet and a secondary air inlet. The total area of ​​the through-hole is smaller than the cross-sectional area of ​​the high-temperature flue gas outlet. By setting the swirling tube, the high-temperature flue gas is recirculated. Setting the total area of ​​the through-hole smaller than the cross-sectional area of ​​the high-temperature flue gas outlet ensures stable combustion of the methane gas. Furthermore, placing the swirling tube along the circumference of the flame stabilizing plate improves the methane oxidation effect.

Description

Technical Field

[0001] This invention belongs to the field of efficient coal mine gas control and utilization technology, and specifically relates to a swirling jet low-concentration gas flameless oxidation device and method. Background Technology

[0002] In order to reasonably solve the safety problem in mines, the gas drainage method is usually adopted to reduce the gas concentration in ventilation to a safe level of less than 1%.

[0003] Methane, the main component of coalbed methane, has a greenhouse effect equivalent to 24.6 times that of CO2 and a destructive power to the ozone layer equivalent to 7 times that of CO2. The large annual release of unusable low-concentration coalbed methane not only results in a severe waste of limited non-renewable resources but also exacerbates air pollution and the greenhouse effect. As a high-quality energy source, coalbed methane has a calorific value of approximately 35,000 kJ / Nm3, comparable to conventional natural gas, and can be used as fuel and chemical feedstock. However, because oxygen is a flammable additive, its introduction increases the explosion hazard of coalbed methane, posing significant challenges to its processing and transportation. Currently, the types, proportions, utilization rates, and main utilization methods of extracted coalbed methane are as follows: Medium-to-high concentration coalbed methane (CCH4>30%) accounts for approximately 6%, with a utilization rate exceeding 90%. Low-concentration coalbed methane accounts for approximately 94%, but its utilization rate is less than 35%. Because the low concentration of methane in low-concentration methane makes its utilization difficult, the main utilization methods are thermal regenerative oxidation and co-combustion power generation with high-concentration methane. These methods are also relatively inefficient, resulting in most of the low-concentration methane being directly discharged into the atmosphere, causing huge waste of resources and significant environmental damage.

[0004] Low-concentration methane gas, ranging from 4% to 10%, is extremely rare and near its explosive limit, making stable combustion and efficient utilization through conventional methods difficult. Therefore, it is typically released directly into the atmosphere, resulting in significant energy waste and severe environmental pollution. While current coal mine safety regulations stipulate that low-concentration methane gas below 30% cannot be directly combusted, this, despite supplementary explanations, limits the research, development, promotion, and application of low-concentration methane utilization technologies.

[0005] Therefore, the design of a flameless oxidation device and method for low-concentration methane using swirling jets, which achieves strong turbulence in the oxidation chamber through the swirling tubes in the oxidation device, thereby enabling the rapid oxidation of high-temperature flue gas and disrupting the methane deflagration energy wave within the explosion limit, and stabilizing the oxidation process, is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a swirling jet flameless oxidation device and method for low-concentration methane. The swirling tube in the oxidation device enables strong turbulence within the oxidation chamber, thereby achieving high-temperature flue gas recirculation and rapid oxidation of the methane. It also serves to disrupt the methane deflagration energy wave within the explosion limit and stabilize the oxidation process, thus achieving flameless oxidation of low-concentration methane.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A swirling jet flameless oxidation device for low-concentration methane includes an oxidation chamber for achieving low-concentration methane oxidation and an ignition system disposed within the oxidation chamber. A flame stabilizing plate is disposed at one end of the oxidation chamber, and a high-temperature flue gas outlet is opened at the other end. A swirling tube, capable of creating turbulence in the methane gas within the oxidation chamber, is inserted along the circumference of the flame stabilizing plate. Through holes are disposed on the circumference of the flame stabilizing plate, communicating with a main air inlet and a secondary air inlet. The total area of ​​the through holes is smaller than the cross-sectional area of ​​the high-temperature flue gas outlet.

[0009] Preferably, the swirl tube is connected to the secondary air inlet through an arc-shaped gas distribution pipe, and the distance between the outlet of the swirl tube and the cross-section of the flame stabilizer is 1 / 10 to 1 / 5 of the length of the oxidation chamber.

[0010] Preferably, the oxidation chamber has two or more irregular DC jet nozzles along the circumference of the flame stabilizer, and the DC jet nozzles are connected to the main air inlet.

[0011] Preferably, the cyclone tube is equipped with a device for adjusting the angle and flow rate of the gas jet.

[0012] Preferably, the system further includes an initial oxidation temperature monitoring system located inside the oxidation chamber near one end of the flame stabilizing plate, an oxidation body temperature monitoring system located near the middle of the oxidation chamber, and a flame monitoring system located inside the oxidation chamber.

[0013] Preferably, the outer periphery of the oxidation chamber is provided with a heat storage body and a heat insulation layer from the inside to the outside.

[0014] Preferably, the flame stabilizer has a gas inlet at its center, and the gas inlet has a switch at its end that can open and close the gas inlet. The gas inlet is connected to a gas pipe in the middle of the secondary air inlet.

[0015] Preferably, the total area of ​​the through holes is 1 / 3 to 1 / 2 of the cross-sectional area of ​​the high-temperature flue gas outlet.

[0016] This invention also discloses a swirling jet flameless oxidation method for low-concentration methane gas, using the swirling jet flameless oxidation device described above, comprising the following steps:

[0017] Gas enters the oxidation chamber through the main air inlet, the flame stabilizer, and the direct jet nozzle, and is ignited by the ignition system.

[0018] When the temperature of the oxidation chamber rises, gas is introduced through the secondary air inlet and injected into the oxidation chamber through the cyclone pipe, causing the gas to oxidize rapidly at high temperature.

[0019] Preferably, when the temperature of the oxidation chamber is below 600°C and the flue gas recirculation ratio is below 60%, gas with a volume concentration higher than 6% shall not enter the oxidation device through the DC jet nozzle.

[0020] The present invention achieves the following technical effects compared to the prior art:

[0021] By setting up a swirl tube, the gas introduced from the secondary air inlet can form turbulence in the oxidation chamber, enabling rapid gas oxidation and achieving high-temperature flue gas recirculation. This ensures flameless gas oxidation. Setting the total area of ​​the through-holes to be smaller than the cross-sectional area of ​​the high-temperature flue gas outlet ensures that the gas entering through the through-holes has a certain pressure, preventing turbulent gas from disturbing the gas burning through the through-holes and causing unstable flame at the flame stabilizer. This ensures stable gas combustion. In addition, setting the swirl tube around the circumference of the flame stabilizer allows gas to be injected through the swirl tube after ignition by passing through the flame stabilizer and reaching the set temperature. The gas introduced through the swirl tube is then sprayed out from the circumference of the flame stabilizer, increasing the contact area between the gas sprayed from the swirl tube and the burning gas sprayed from the flame stabilizer, allowing for instantaneous gas oxidation and improving the gas oxidation effect. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Appendix Figure 1 This is a schematic diagram of the overall structure of the swirling jet low-concentration gas flameless oxidation device and method disclosed in the embodiments of the present invention.

[0024] The components include: 1. Main air inlet; 2. Direct current jet nozzle; 3. Flame stabilizer; 4. Secondary air inlet; 41. Gas pipe; 5. Gas distribution pipe; 6. Swirl pipe; 7. Heat storage body; 8. Ignition system; 9. Initial oxidation temperature monitoring system; 10. Oxidation chamber; 11. Oxidation main body temperature monitoring system; 12. High-temperature flue gas outlet; and 13. Thermal insulation layer. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The purpose of this invention is to provide a swirling jet flameless oxidation device and method for low-concentration methane. The swirling tube 6 in the oxidation device can achieve strong turbulence in the oxidation chamber 10, thereby realizing the rapid oxidation of high-temperature flue gas and methane, and also destroying the energy wave of methane deflagration within the explosion limit and stabilizing the oxidation, thus achieving flameless oxidation of low-concentration methane.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] refer to Figure 1The swirling jet low-concentration gas flameless oxidation device disclosed in this embodiment of the invention includes at least an oxidation chamber 10 for achieving low-concentration gas oxidation. An ignition system 8 is installed inside the oxidation chamber 10. A flame stabilizer 3 is installed at one end of the oxidation chamber 10, and a high-temperature flue gas outlet 12 is opened at the other end. A swirling tube 6, which allows turbulence to form in the gas within the oxidation chamber 10, is installed along the circumference of the flame stabilizer 3 on the oxidation chamber 10. A through-hole is provided on the flame stabilizer 3, communicating with the main air inlet 1. The swirling tube 6 communicates with the secondary air inlet 4. The total area of ​​the through-hole is smaller than the cross-sectional area of ​​the high-temperature flue gas outlet 12. By installing the swirling tube 6, turbulence can be formed in the oxidation chamber 10 from the secondary air inlet 4, enabling rapid gas oxidation and achieving high-temperature flue gas recirculation. To ensure flameless oxidation of the gas, the total area of ​​the through holes is set to be smaller than the cross-sectional area of ​​the high-temperature flue gas outlet 12. This ensures that the gas entering through the through holes has a certain pressure, avoiding the formation of turbulent gas after passing through the swirl tube 6, which would disturb the gas burning through the through holes and cause instability of the flame root at the flame stabilizer 3. This ensures stable combustion of the gas. In addition, the swirl tube 6 is set in the circumference of the flame stabilizer 3. After ignition through the flame stabilizer 3 and the temperature reaches the set value, the gas is then injected through the swirl tube 6. That is, the gas introduced through the swirl tube 6 is sprayed out from the circumference of the flame stabilizer 3, which can increase the contact area between the gas sprayed from the swirl tube 6 and the burning gas sprayed from the flame stabilizer 3, so that the gas can be oxidized instantly, thereby improving the gas oxidation effect.

[0029] It should be noted that the axis of the flame stabilizer 3 coincides with the axis of the high-temperature flue gas outlet 12. The flame stabilizer 3 can be set as one or multiple. The oxidation chamber 10, the high-temperature flue gas outlet 12, the main air inlet 1, the secondary air inlet 4, etc. can be square or circular. The swirl tube 6 can be a pipe with a diameter that gradually decreases along the gas inlet direction, as long as it can achieve turbulence of gas inside the oxidation chamber 10.

[0030] The oxidation chamber 10 and the high-temperature flue gas outlet 12 adopt a variable diameter structure to enhance the high-temperature flue gas recirculation. Preferably, the cross-sections of the oxidation chamber 10 and the high-temperature flue gas outlet 12 can be abrupt or curved.

[0031] refer to Figure 1 In one implementation, a flow controller is installed in both the secondary air inlet 4 and the main air inlet 1 to control the gas flow rate. By installing the flow controller in the main air inlet 1 and the secondary air inlet 4, the air volume and pressure of the main air inlet 1 and the secondary air inlet 4 can be changed to the ratio of the dynamic pressure of the variable jet.

[0032] refer to Figure 1In one implementation, the swirl tube 6 is connected to the secondary air inlet 4 through an arc-shaped gas distribution pipe 5. The distance between the outlet of the swirl tube 6 and the end face of the flame stabilizer 3 is 1 / 10 to 1 / 5 of the length of the oxidation chamber 10. By setting the arc-shaped gas distribution pipe 5 between the secondary air inlet 4 and the swirl tube 6, the turbulence effect of the gas entering the oxidation chamber 10 can be further guaranteed. Furthermore, by setting the distance between the outlet of the swirl tube 6 and the flame stabilizer 3, a certain length can be ensured from the outlet of the swirl tube 6 to the high-temperature flue gas outlet 12, thereby improving the turbulence effect of the gas in the oxidation chamber 10.

[0033] refer to Figure 1 In one embodiment, two or more irregular direct current jet nozzles 2 are provided on the oxidation chamber 10 along the circumference of the flame stabilizing plate 3. The direct current jet nozzles 2 are connected to the main air inlet 1. By setting the direct current jet nozzles 2, the gas ejected from the direct current jet nozzles 2 can cross and collide with the gas ejected from the flame stabilizing plate 3, thereby slowing down the gas and ensuring that the gas is fully ignited in the oxidation chamber 10.

[0034] refer to Figure 1 As one implementation method, the swirl tube 6 is equipped with an adjustment device for changing the angle and flow rate of the gas jet, thereby changing the jet intensity and adjusting the entrainment and recirculation of the high-temperature flue gas in the oxidation chamber 10.

[0035] It should be noted that the regulating device can control the flow rate of the flow meter and the baffle that is hinged to the swirl tube 6 inside the swirl tube 6. The baffle is equipped with a lever to control the adjustment of the baffle angle. By moving the lever, the angle of the baffle can be adjusted, thereby adjusting the jet angle of the swirl tube 6.

[0036] refer to Figure 1 As one implementation, it also includes an initial oxidation temperature monitoring system 9 located inside the oxidation chamber 10 near one end of the flame stabilizer 3, and an oxidation body temperature monitoring system 11 located near the middle of the oxidation chamber 10. By setting the initial oxidation temperature monitoring system 9 and the oxidation body temperature monitoring system 11, the temperature at different locations inside the oxidation chamber 10 can be monitored, thereby providing signals for the opening and closing of the flow meter, and the opening and closing of the main air inlet 1 and the secondary air inlet 4.

[0037] It should be noted that the initial oxidation temperature monitoring system 9 can monitor flame signals, temperature signals, or both simultaneously. Flame signal monitoring can employ one or more of the following: ion probe, infrared, and ultraviolet. By monitoring the flame status within the oxidation system in real time, once an abnormal flame or flame extinguishing is detected, corresponding measures can be taken immediately, such as alarming, stopping gas supply, or activating fire extinguishing devices.

[0038] refer to Figure 1The oxidation chamber 10 is provided with a heat storage body 7 and a heat insulation layer 13 arranged sequentially from the inside to the outside. The heat storage body 7 is used to store heat in the oxidation chamber 10, and the heat insulation layer 13 can prevent heat loss.

[0039] refer to Figure 1 In one implementation, multiple through holes are provided and evenly distributed around the flame stabilizer 3. The distance between each through hole and the center of the flame stabilizer 3 is the same. The angle between the extension line of the through hole along the gas inlet direction and the extension line of the axis of the flame stabilizer 3 towards the oxidation chamber 10 is an acute angle. Setting the angle between the through hole and the axial direction of the flame stabilizer 3 to an acute angle can ensure that the gas entering from the through hole can cross and collide, thereby slowing down the gas and ensuring that the gas is fully ignited in the oxidation chamber 10.

[0040] refer to Figure 1 In one embodiment, a gas inlet is provided at the center of the flame stabilizer 3, and a switch is provided at the end of the gas inlet to realize the opening and closing of the gas inlet. The gas inlet is connected to the gas pipe 41 provided in the middle of the secondary air inlet 4. By connecting the gas inlet and the gas pipe 41, natural gas can be introduced through the secondary air inlet 4 and the gas inlet in sequence when there is no gas, and the main air inlet 1 is ventilated, so as to realize the dual use of gas and natural gas.

[0041] It should be noted that when natural gas is introduced, the gas inlet is in the open state, and when methane is introduced, the gas inlet is in the closed state. The inner diameter of the gas inlet is larger than the inner diameter of the through hole.

[0042] refer to Figure 1 In one embodiment, the total area of ​​the through holes is 1 / 3 to 1 / 2 of the cross-sectional area of ​​the high-temperature flue gas outlet 12.

[0043] refer to Figure 1 The present invention also discloses a swirling jet flameless oxidation method for low-concentration methane gas, which utilizes the swirling jet flameless oxidation device described above. The main steps are as follows:

[0044] Gas enters oxidation chamber 10 through main air inlet 1, through hole and direct injection port, and is ignited by ignition system 8;

[0045] After the initial oxidation temperature monitoring system 9 detects that the temperature of oxidation chamber 10 is higher than 600℃, the secondary air inlet 4 is opened to introduce gas. The gas is injected into oxidation chamber 10 through gas distribution pipe 5 and swirl pipe 6, and the gas is rapidly oxidized at high temperature.

[0046] The heat storage body 7 and the heat insulation layer 13 are used to store heat and reduce heat loss. The high-temperature flue gas is discharged through the high-temperature flue gas outlet 12 to provide a heat source for heat users.

[0047] To ensure safety, the initial oxidation temperature monitoring system 9 and the oxidation main body temperature monitoring system 11 are interlocked with the gas intake regulating device;

[0048] High-temperature flue gas is entrained by a strong swirling jet, allowing the gas to oxidize in a very short time. The gas concentration field and temperature field gradient within the oxidation chamber 10 are small, resulting in no obvious flame surface.

[0049] When the secondary air inlet 4 is filled with gas, the gas inlet is opened by a switch. The gas passes through the secondary air inlet 4, the gas pipe 41, and the gas inlet in sequence into the oxidation chamber 10. The through hole and the direct jet nozzle 2 are used to connect with the outside air to achieve combustion of the gas.

[0050] refer to Figure 1 As one implementation method, when the temperature of the oxidation chamber 10 is below 600°C and the flue gas recirculation ratio is below 60%, gas with a volume concentration higher than 6% shall not enter the oxidation device through the DC jet nozzle 2.

[0051] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0052] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A swirling jet flameless oxidation device for low-concentration methane gas, characterized in that, The device includes an oxidation chamber for achieving low-concentration gas oxidation, and an ignition system disposed within the oxidation chamber. One end of the oxidation chamber is provided with a flame stabilizing plate, and the other end of the oxidation chamber is provided with a high-temperature flue gas outlet. A swirl tube is provided on the oxidation chamber along the circumference of the flame stabilizing plate to create turbulence in the gas within the oxidation chamber. The flame stabilizing plate is provided with through holes, which are connected to the main air inlet, and the swirl tube is connected to the secondary air inlet. The total area of ​​the through holes is smaller than the cross-sectional area of ​​the high-temperature flue gas outlet. The swirling tube is connected to the secondary air inlet through an arc-shaped gas distribution pipe, and the distance between the outlet of the swirling tube and the flame stabilizing plate is 1 / 10 to 1 / 5 of the length of the oxidation chamber. The oxidation chamber has two or more irregular DC jet nozzles along the circumference of the flame stabilizer, and the DC jet nozzles are connected to the main air inlet.

2. The swirling jet low-concentration gas flameless oxidation device according to claim 1, characterized in that, The cyclone tube is equipped with an adjustment device to change the angle and flow rate of the gas jet.

3. The swirling jet low-concentration gas flameless oxidation device according to claim 1, characterized in that, It also includes an initial oxidation temperature monitoring system located inside the oxidation chamber near one end of the flame stabilizing plate, and an oxidation body temperature monitoring system located near the middle of the oxidation chamber.

4. The swirling jet low-concentration gas flameless oxidation device according to claim 1, characterized in that, The oxidation chamber is provided with a heat storage body and a heat insulation layer from the inside to the outside.

5. The swirling jet low-concentration gas flameless oxidation device according to claim 1, characterized in that, The flame stabilizer has a gas inlet at its center, and a switch is provided at the end of the gas inlet to open and close the gas inlet. The gas inlet is connected to a gas pipe located in the middle of the secondary air inlet.

6. The swirling jet low-concentration gas flameless oxidation device according to claim 1, characterized in that, The total area of ​​the through holes is 1 / 3 to 1 / 2 of the cross-sectional area of ​​the high-temperature flue gas outlet.

7. A swirling jet flameless oxidation method for low-concentration methane gas, using the swirling jet flameless oxidation device as described in any one of claims 1-6, characterized in that, Includes the following steps: Gas enters the oxidation chamber through the main air inlet, the flame stabilizer, and the direct jet nozzle, and is ignited by the ignition system. When the temperature of the oxidation chamber rises, gas is introduced through the secondary air inlet and injected into the oxidation chamber through the cyclone pipe, causing the gas to oxidize rapidly at high temperature.

8. The swirling jet low-concentration gas flameless oxidation method according to claim 7, characterized in that, When the temperature of the oxidation chamber is below 600°C and the flue gas recirculation ratio is below 60%, gas with a volume concentration higher than 6% shall not enter the oxidation device through the DC jet nozzle.

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