A main-auxiliary combined low-concentration gas submerged combustion device and method

Abstract

The present invention discloses a main-auxiliary combined low-concentration gas submerged combustion device and method, which adopts a main burner and an auxiliary burner combined, wherein the auxiliary burner is in a gradually expanding frustum shape, and the change of the auxiliary burner diameter can effectively expand the combustion limit of the low-concentration gas. When the gas concentration is 3.6% to 8%, an adaptive combustion zone can be formed by adjusting the flow rate, so that the low-concentration gas can be fully burned and release heat; the auxiliary combustion generates high-temperature flue gas, which enters the main burner and then generates convection heat exchange in a heat storage body filling bed, and then directly utilizes the coal mine extraction gas without using additional high-grade fuels such as diesel and natural gas to preheat the main burner heat storage body filling bed, so as to realize direct heat storage combustion treatment of low-concentration gas without catalysis and countercurrent oxidation, avoid the fluctuation of the temperature field in the oxidation device and the thermal stress damage of the heat storage body in the traditional hot countercurrent oxidation cycle reversing mode, and improve the stability and safety of the device operation.

Description

Technical Field

[0001] The invention relates to a gas heat storage combustion device and method, in particular to a main-auxiliary combined low-concentration gas submerged combustion device and method, belonging to the technical field of coal mine energy conservation and emission reduction and gas utilization. Background Art

[0002] For the ultra-low concentration gas in coal mines with a methane volume concentration of less than 3% in the extraction and mine ventilation, it is necessary to mix with air to maintain the gas concentration below 1.2%, and use it through thermal countercurrent oxidation technology and catalytic countercurrent oxidation technology. This indirect utilization method is affected by concentration fluctuations and mixing costs, and has poor safety and stability and high operating costs. In addition, the methane volume concentration of coal mines is currently 3% to 8%. Whether it is mixed with air to reduce the methane volume concentration to 1.2% for countercurrent oxidation, or by mixing high-concentration gas to increase the methane volume concentration to more than 8% for combustion and power generation, there is a problem of high-quality and poor use of high-quality energy. If low-concentration gas is directly used as the main fuel to directly participate in the combustion and oxidation process, there is a technical problem of difficulty in activating and burning low-concentration methane (CH bond energy is as high as 434kJ / mol), which is the key to restricting the combustion and utilization of ultra-low concentration gas in coal mines and carbon emission reduction. Therefore, low-concentration methane with a volume concentration of 3% to 8% extracted from coal mines is usually discharged directly, resulting in a large amount of energy waste.

[0003] In view of the above phenomenon, the direct thermal storage combustion / oxidation utilization of low-concentration gas with a volume concentration of 3% to 8% of methane extracted from coal mines has become a technical bottleneck that needs to be solved urgently for coal mine gas carbon emission reduction. Up to now, the improvement of low-concentration gas combustion / oxidation technology is mainly through increasing the initial temperature of the intake air to induce ignition of the combustible mixed gas, or by increasing the initial pressure of the intake air to expand the flammability limit of the mixed gas. The thermal storage oxidation technology is based on the heat recovery transmission effect of solid porous media, transferring the combustion heat from the product to the reactant. It has the advantages of realizing enhanced preheating of the reactant, inducing a higher combustion reaction rate and an expandable low-concentration gas lean combustion limit. However, since the combustion of low-concentration gas is extremely sensitive to fluctuations in gas concentration, it has an important impact on ignition and subsequent combustion flame propagation. When the gas concentration fluctuates greatly, it is very easy to cause the reactor to overheat or extinguish, making it impossible for the burner to continuously and stably burn and utilize low-concentration gas.

[0004] Therefore, how to provide a new device and method to achieve direct heat storage combustion treatment of low-concentration gas without catalysis and countercurrent oxidation, and to continuously maintain stable combustion of low-concentration gas in the burner heat storage bed, thereby greatly improving the utilization efficiency of low-concentration gas in coal mines, is the research direction required by the present invention. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a main-auxiliary combined low-concentration gas submerged combustion device and method, in which the auxiliary burner generates high-temperature flue gas to preheat the main burner, and supplements heat to maintain the continuous and stable combustion of the low-concentration gas in the heat storage bed of the main burner, thereby realizing direct heat storage combustion treatment of the low-concentration gas without catalysis and countercurrent oxidation, greatly improving the utilization efficiency of low-concentration gas in coal mines.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a main-auxiliary combined low-concentration gas submerged combustion device, including a gas source and flow regulation system, a main burner, an auxiliary burner, a heat extraction chamber and a data collection and control system;

[0007] The main burner is provided with a plurality of combustion chambers and heat extraction chambers, each of which is provided with a heat storage body filling bed and a heat preservation layer, the heat preservation layer wraps the heat storage body filling bed to keep it warm; the heat storage body filling bed is used to perform submerged combustion on the low-concentration gas entering; the heat extraction chamber is provided with a heat exchange tube, the heat exchange tube is provided with a heat exchange liquid, the heat exchange liquid exchanges heat with the high-temperature gas in the heat extraction chamber to form a heated liquid flowing out of the heat extraction chamber; the plurality of combustion chambers and the heat extraction chambers are connected in series in sequence, and the heat extraction chamber is farthest from the air inlet of the main burner, so that the low-concentration gas entering the air inlet of the main burner passes through each combustion chamber in sequence and burns to generate high-temperature gas which enters the heat extraction chamber, and the high-temperature gas is discharged from the exhaust port of the main burner after heat exchange and cooling;

[0008] The number of the auxiliary burners is the same as that of the combustion chambers. The auxiliary burners are in the shape of a gradually expanding frustum, with the end with a smaller diameter being the low-concentration gas inlet end of the auxiliary burner, and the end with a larger diameter being the high-temperature flue gas outlet end of the auxiliary burner. The high-temperature flue gas outlet end of each auxiliary burner is respectively connected to the side of each combustion chamber for adaptive combustion of low-concentration gas, thereby forming a high-temperature flue gas preheating combustion chamber and providing heat supplement for the operation process of each combustion chamber;

[0009] The gas source and flow regulating system comprises a gas transport pipeline, a main input pipeline, a gas diverter and an auxiliary input pipeline; one end of the gas transport pipeline is connected to the gas source, and the other end is connected to the inlet of the gas diverter; one of the outlets of the gas diverter is connected to the air inlet of the main burner through the main input pipeline, and the other outlet of the gas diverter is connected to one end of the auxiliary input pipeline; a plurality of branch pipes are arranged at the other end of the auxiliary input pipeline, and each branch pipe is respectively connected to the low-concentration gas inlet end of each auxiliary burner; the gas diverter diverts the low-concentration gas passing through, and one part enters the main burner and the other part enters each auxiliary burner; a stop valve, a pressure sensor, a gas concentration sensor and a flame sensor are sequentially arranged on the gas transport pipeline according to the flow direction of the low-concentration gas; the stop valve is used to control the gas flow; The on-off of the transport pipeline; the pressure sensor and the gas concentration sensor are respectively used to monitor the air pressure and gas concentration in the gas transport pipeline; the flame sensor 1 is used to detect whether there is a flame at the location; the main input pipeline is provided with a double-control cut-off valve 1, a flow rate regulating valve 1 and a gas flow meter 1 in sequence according to the flow direction of the low-concentration gas, and the auxiliary input pipeline is provided with a double-control cut-off valve 2, a flow rate regulating valve 2 and a gas flow meter 2 in sequence according to the flow direction of the low-concentration gas, the double-control cut-off valve 1 and the double-control cut-off valve 2 are respectively used to control the on-off of the main input pipeline and the auxiliary input pipeline; the flow rate regulating valve 1 and the flow rate regulating valve 2 are respectively used to adjust the gas flow in the main input pipeline and the auxiliary input pipeline; the gas flow meter 1 and the gas flow meter 2 are respectively used to monitor the gas flow in the main input pipeline and the auxiliary input pipeline;

[0010] The data collection and control system is used to receive data fed back by the pressure sensor, gas concentration sensor, flame sensor 1, gas flowmeter 1 and gas flowmeter 2, and after analysis and processing, controls the opening and closing of the stop valve, double-control shut-off valve 1 and double-control shut-off valve 2, and the opening of flow rate regulating valve 1 and flow rate regulating valve 2.

[0011] Furthermore, the auxiliary burner is filled with 3-15 mm heat storage ceramic particles, and a silicon-molybdenum rod is arranged at the low-concentration gas inlet end to preheat the heat storage ceramic particles.

[0012] Furthermore, the heat storage body filling bed is made of ceramic particles, honeycomb ceramics or foam ceramics.

[0013] Furthermore, the gas transportation pipeline is also equipped with a wet compressor, a dehydrator, an automatic explosion suppression device and a water-seal fire-blocking explosion-relief device. The wet compressor is used to pressurize low-concentration gas, and the dehydrator is used to dehydrate the pressurized low-concentration gas; the automatic explosion suppression device and the water-seal fire-blocking explosion-relief device are used to prevent explosion and prevent flame spread, respectively. This can meet the gas transportation pressure requirements and is safer.

[0014] Furthermore, the main input pipeline and the auxiliary input pipeline are both equipped with flame arresters for blocking the backflow flame and high-temperature energy generated by the explosion of low-concentration gas in the main burner and the auxiliary burner; the heat exchange tube is a serpentine heat exchange tube, and the serpentine heat exchange tube is provided with fins.

[0015] Furthermore, a high-temperature resistant observation window is provided on the side of the combustion chamber for observing the combustion conditions inside the combustion chamber; a temperature sensor 1 and a flame sensor 2 are provided in the combustion chamber, and the temperature sensor 1 and the flame sensor 2 are connected to the data collection and control system for real-time transmission of flame position and temperature data, and analysis of the temperature field distribution and flame transmission conditions inside the main burner; a plurality of temperature sensors 2 are provided in the auxiliary burner for real-time monitoring of temperature data at different positions of the auxiliary burner.

[0016] Furthermore, the expansion angle of the auxiliary burner is 10° to 30°. The use of this angle range has more impact on the flameout limit. Increasing the expansion angle of the auxiliary burner can significantly improve the flameout limit of the burner, widen the stable combustion area, and help expand the stable combustion range of low-concentration gas. When the gas concentration fluctuates, the flame can automatically move up and down in the auxiliary burner to expand or reduce the flame surface area. This flame movement area is called the adaptive combustion zone. The gradually expanding frustum-shaped auxiliary burner can effectively prevent flashback or blowout caused by gas concentration fluctuations; wherein, the stable combustion range is a low-concentration gas stable combustion range constrained by the inlet gas concentration and the inlet gas flow rate. Compared with free flame combustion, the flame speed of premixed flame combustion in the pores of confined porous media is no longer a single value, but a range, with a minimum flame speed and a maximum flame speed. The minimum flame speed corresponds to the inlet gas speed at the lower limit of stable combustion, and the maximum flame speed is the inlet gas speed at the upper limit of stable combustion.

[0017] Furthermore, an adjustable air distribution plate is provided in the combustion chamber to change the flow direction of the high-temperature flue gas generated by the auxiliary burner and evenly preheat the heat storage body packed bed in the combustion chamber.

[0018] The working method of the main-auxiliary combined low-concentration gas submerged combustion device comprises the following specific steps:

[0019] Step 1: Inspection of combustion device: Inspect the entire submerged combustion device to ensure the integrity of the combustion system connection, the normal operation of the electric components and the normal circulation of each gas input pipeline; conduct a trial run of the flame sensor and temperature sensor, and turn on the flue gas analyzer for air calibration; introduce air to purge each combustion chamber of the main burner and the interior of the auxiliary burner to ensure that there is no residual mixed gas in the combustion space, and close the valves of each submerged combustion device after purging;

[0020] Step 2: Preheating the combustion device: First, turn on the silicon-molybdenum rod to preheat the heat storage body in the auxiliary burner. When the temperature rises to 650-800℃, the stop valve and wet compressor of the gas extraction transportation pipeline are opened, and the dual-control shut-off valve 2 and flow rate regulating valve 2 of the auxiliary input pipeline are opened to control the low-concentration gas to enter the auxiliary burner through the auxiliary input pipeline. Since the heat storage body in the auxiliary burner reaches the required temperature to form an adaptive combustion zone, the low-concentration gas entering at this time begins to burn in the adaptive combustion zone. After the gas is ignited, the flow rate regulating valve 2 is used to control the intake speed of the low-concentration gas to keep the low-concentration gas burning steadily in the adaptive combustion zone to form high-temperature flue gas. Then, the high-temperature flue gas enters each combustion chamber, and is discharged from the exhaust port of the main burner after convective heat exchange with the heat storage body filling bed, so as to achieve uniform heating of the heat storage body filling bed in each combustion chamber.

[0021] Step 3, main burner operation: wait for the minimum temperature of the heat storage body filling bed in each combustion chamber of the main burner to be preheated to 650-800℃, open the dual-control shut-off valve 1 and the flow rate regulating valve 1 of the main input pipeline, control the large flow of low-concentration gas to be input into the main burner through the main input pipeline, use the high-temperature electrode igniter installed at the air inlet of the main burner for ignition, transmit the flame position and temperature data in real time through the flame sensor and temperature sensor in the main burner, analyze the temperature field distribution and flame transmission of each combustion chamber in the main burner, and determine the combustion state of the low-concentration gas in the heat storage body filling bed of each combustion chamber by combining the observation window observation, then adjust the low-concentration gas inlet flow rate by the opening of the flow rate regulating valve 1, keep the low-concentration gas in the heat storage body filling bed of each combustion chamber to achieve stable submerged combustion, keep the auxiliary burner running to continuously provide high-temperature flue gas auxiliary heat during the operation of the main burner, supplement the heat to the heat storage body filling bed of each combustion chamber during the submerged combustion, and maintain the gas oxidation environment temperature in the main burner;

[0022] Step 4: Recycling of waste heat: Low-concentration gas continues to heat the heat storage bed during the exhaust of flue gas generated by immersed combustion in the heat storage bed of each combustion chamber, thereby ensuring heat replenishment in the main burner, allowing the low-concentration gas to self-sustain and stably burn. After entering the heat extraction chamber, the high-temperature flue gas exchanges heat with the heat exchange liquid in the heat exchange tube for cooling, and is discharged from the exhaust port of the main burner after heat exchange and cooling. At the same time, the heat exchange liquid exchanges heat with the high-temperature gas in the heat extraction chamber to form a heated liquid for subsequent utilization.

[0023] Furthermore, in step 2, the flow rate regulating valve 2 is used to control the low-concentration gas intake speed to keep the low-concentration gas burning stably in the adaptive combustion zone to form high-temperature flue gas, specifically:

[0024] The average preheating temperature of the heat storage body in the auxiliary burner The area-weighted average and volume-weighted average methods are used to simplify the calculation:

[0025] The auxiliary burner cross section is divided into four concentric annular areas from the inside to the outside. The temperature monitored by the temperature sensor 2 in the annular area approximately represents the regional temperature. The weighted average of the annular area temperature and the annular area area is calculated to obtain the average cross-sectional temperature. The calculation method is shown in formula (1); secondly, the average temperature of the regenerator preheating needs to be calculated again by weighted average calculation of the regional temperature and regional volume. The burner is divided into multiple areas according to the position of each temperature sensor in the axial direction of the auxiliary burner. The average cross-sectional temperature of the upper part of each area is taken as the temperature of each area. The average temperature of the regenerator preheating is The calculation method is shown in formula (2);

[0026]

[0027] Where: T ij is the temperature of the jth measuring point in the ith section of the gradually expanding burner.

[0028]

[0029] According to the above calculation formula, the average preheating temperature of the heat storage body in the real-time auxiliary burner is obtained. Thus, by adjusting the low-concentration gas intake speed, the average temperature of the heat storage body preheating Always at 650-800℃ to maintain the adaptive combustion zone.

[0030] Compared with the prior art, the present invention adopts a main-auxiliary combination method to carry out low-concentration gas submerged combustion, which has the following advantages:

[0031] (1) The present invention utilizes a main and auxiliary combined burner to coordinate thermal storage oxidation to treat low-concentration gas of 3.6% to 8% extracted from coal mines. Compared with a catalytic oxidation device, the present invention realizes direct thermal storage combustion treatment of low-concentration gas without the need for catalysis and countercurrent oxidation, thereby avoiding failure and replacement of the catalyst during use and reducing the operating cost of the gas utilization device.

[0032] (2) The auxiliary burner in the present invention is in the shape of a gradually expanding frustum. According to existing experimental results, the change in the diameter of the auxiliary burner can effectively expand the combustion limit of low-concentration gas. When the gas concentration is 3.6% to 8%, an adaptive combustion zone can be formed by adjusting the flow rate, so that the low-concentration gas can be fully burned and release heat. The high-temperature flue gas generated by the auxiliary combustion enters the main combustion chamber and generates convective heat exchange in the heat storage body filling bed, thereby directly utilizing the coal mine extraction gas without using additional high-grade fuels such as diesel and natural gas to preheat the main burner heat storage body filling bed.

[0033] (3) The present invention uses an auxiliary burner to provide auxiliary heat from high-temperature flue gas, supplements heat to the heat storage body filling bed in the low-concentration gas treatment process of the main burner, maintains the gas oxidation environment temperature in each combustion chamber, and enables the main burner to achieve continuous combustion treatment of large-flow low-concentration gas, realizes unidirectional direct current combustion of ultra-low-concentration gas extracted underground, avoids the fluctuation of the temperature field in the oxidation device under the traditional thermal countercurrent oxidation cycle reversing mode and the thermal stress damage of the heat storage body, and improves the stability and safety of the device operation.

[0034] (4) The present invention adopts a ceramic particle porous medium to form a heat storage body packing bed. This material can improve the shape of the flame surface, avoid the occurrence of unstable phenomena such as flame surface rupture, tilting and stratification due to irregular flame structure, further prevent the damage of the heat storage body packing bed caused by uneven heat distribution, and increase the service life of the burner; and the above-mentioned porous medium arranges multiple layers of ceramic particles of different particle sizes to form a stepped gradient structure, which can enhance the ability of the auxiliary burner to adapt to gas concentration and speed fluctuations; the axial porosity of the heat storage body packing bed changes continuously, thereby enhancing the ability of the main burner to adapt to gas concentration and speed fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of this embodiment;

[0036] Figure 2 is the distribution of stable combustion intervals of different auxiliary burners during the experiment of this embodiment, where α is the gradual expansion angle of the auxiliary burner, d p is the diameter of ceramic particles, (a) α = 10°, d p =5mm; (b) α = 10°, d p =10mm; (c) α = 10°, d p =15mm; (d)α=20°, d p =5mm; (e)α=20°, d p =10mm; (f)α=20°, d p =15mm; (g)α=30°, d p =5mm; (h)α=30°, d p =10mm; (i) α = 30°, d p =15mm;

[0037] Figure 3 The calculation area for the average temperature of the auxiliary burner cross section in this embodiment is divided;

[0038] Figure 4 This is the area division for calculating the average temperature of the auxiliary burner preheating zone in this embodiment.

[0039] In the figure: 1-gas transport pipeline; 2-stop valve; 3-wet compressor; 4-automatic explosion suppression device; 5-water seal fire retardant and explosion relief device; 6-dehydrator; 7-pressure sensor; 8-gas concentration sensor; 9-flame sensor 1; 10-gas diverter; 11-main input pipeline; 12-auxiliary input pipeline; 13-double control shut-off valve 1; 14-flow rate regulating valve 1; 15-gas flow meter 1; 16-flame arrester 1; 17-double control shut-off valve 2; 18-flow rate regulating valve 2; 19-gas flow meter 2; 20-flame arrester 2; 21-auxiliary burner; 22-thermal storage ceramic particles; 23-silicon molybdenum rod; 24-main burner; 25-thermal storage body packed bed; 26-insulation layer; 27-observation window; 28-heat extraction chamber; 29-heat exchange tube. DETAILED DESCRIPTION

[0040] The present invention will be further described below.

[0041] like Figure 1 As shown, a main-auxiliary combined low-concentration gas submerged combustion device includes a gas source and flow regulating system, a main burner 24, an auxiliary burner 21, a heat extraction chamber 28 and a data collection and control system;

[0042] The main burner 24 is provided with a plurality of combustion chambers and a heat extraction chamber 28, each of which is provided with a heat storage body filling bed 25 and a heat preservation layer 26, wherein the heat preservation layer 26 wraps the heat storage body filling bed 25 to keep the heat of the heat storage body filling bed 25 warm; the heat storage body filling bed 25 is used for immersion combustion of the low-concentration gas entering; a heat exchange tube 29 is provided in the heat extraction chamber 28, wherein a heat exchange liquid is provided in the heat exchange tube 29, and the heat exchange liquid exchanges heat with the high-temperature gas in the heat extraction chamber 28 to form a heated liquid flowing out of the heat extraction chamber 28; the plurality of combustion chambers and the heat extraction chamber 28 are connected in series in sequence, and the heat extraction chamber 28 is farthest from the air inlet of the main burner 24, so that the low-concentration gas entering the air inlet of the main burner passes through each combustion chamber in sequence and burns to generate high-temperature gas which enters the heat extraction chamber 28, and the high-temperature gas is discharged from the exhaust port of the main burner 24 after heat exchange and cooling; the heat storage body filling bed 25 is made of ceramic particles, honeycomb ceramics or foam ceramics.

[0043] The number of the auxiliary burners 21 is the same as that of the combustion chambers. The auxiliary burners 21 are in the shape of a gradually expanding truncated cone. The end with a smaller diameter is the low-concentration gas inlet end of the auxiliary burner 21, and the end with a larger diameter is the high-temperature flue gas outlet end of the auxiliary burner 21. The high-temperature flue gas outlet end of each auxiliary burner 21 is respectively connected to the side of each combustion chamber for adaptive combustion of low-concentration gas, thereby forming a high-temperature flue gas preheating combustion chamber and providing heat supplement for the operation process of each combustion chamber; the auxiliary burner 21 is filled with 3-15mm heat storage ceramic particles, and a silicon-molybdenum rod 23 is set at the low-concentration gas inlet end to preheat the heat storage ceramic particles. The gradual expansion angle of the auxiliary burner 21 is 10° to 30°. The use of this angle range has more influence on the flameout limit. Increasing the gradual expansion angle of the auxiliary burner 21 can significantly increase the burner flameout limit, widen the stable combustion area, and help expand the stable combustion range of low-concentration gas. When the gas concentration fluctuates, the flame can automatically move up and down in the auxiliary burner 21 to expand or reduce the flame surface area. This flame movement area is called the adaptive combustion zone. The gradually expanding frustum-shaped auxiliary burner 21 can effectively prevent flashback or blowout caused by gas concentration fluctuations; wherein, the stable combustion interval is a low-concentration gas stable combustion range constrained by the inlet gas concentration and the inlet gas flow rate. Compared with free flame combustion, the flame speed of the premixed flame combustion in the pores of the confined porous medium is no longer a single value, but a range, with a minimum flame speed and a maximum flame speed. The minimum flame speed corresponds to the inlet gas velocity at the lower limit of stable combustion, and the maximum flame speed is the inlet gas velocity at the upper limit of stable combustion. The stable combustion interval of the gradually expanding frustum-shaped auxiliary burner measured within the above-mentioned gradually expanding angle range is as follows Figure 2 shown.

[0044] The gas source and flow regulating system comprises a gas transport pipeline 1, a main input pipeline 11, a gas diverter 10 and an auxiliary input pipeline 12; one end of the gas transport pipeline 1 is connected to the gas source, and the other end is connected to the inlet of the gas diverter 10, and the gas source is a low-concentration gas with a gas concentration of 3.6% to 8%; one outlet of the gas diverter 10 is connected to the air inlet of the main burner through the main input pipeline 11, and the other outlet of the gas diverter 10 is connected to one end of the auxiliary input pipeline 12, and the other end of the auxiliary input pipeline 12 is provided with a plurality of branch pipes, each branch pipe is respectively connected to the low-concentration gas inlet end of each auxiliary burner 21, and the gas diverter 10 diverts the low-concentration gas passing through, so that one part enters the main burner 24 and the other part enters each auxiliary burner 21; a stop valve 2, a pressure sensor 7, a gas concentration sensor 8 and a flame sensor 9 are sequentially arranged on the gas transport pipeline 1 according to the flow direction of the low-concentration gas; the stop valve 2 is used to control The gas transport pipeline 1 is used to control the on-off of the gas transport pipeline 1; the pressure sensor 7 and the gas concentration sensor 8 are used to monitor the air pressure and gas concentration in the gas transport pipeline 1 respectively; the flame sensor 9 is used to detect whether there is a flame at the location; the main input pipeline 11 is provided with a double-control shut-off valve 13, a flow rate regulating valve 14 and a gas flow meter 15 in sequence according to the flow direction of the low-concentration gas, and the low-concentration gas auxiliary input pipeline 12 is provided with a double-control shut-off valve 2 17, a flow rate regulating valve 2 18 and a gas flow meter 2 19 in sequence according to the flow direction of the low-concentration gas, the double-control shut-off valve 13 and the double-control shut-off valve 2 17 are used to control the on-off of the main input pipeline 11 and the auxiliary input pipeline 12 respectively; the flow rate regulating valve 14 and the flow rate regulating valve 2 18 are used to adjust the gas flow in the main input pipeline 11 and the auxiliary input pipeline 12 respectively; the gas flow meter 15 and the gas flow meter 2 19 are used to monitor the gas flow in the main input pipeline 11 and the auxiliary input pipeline 12 respectively.

[0045] The data collection and control system is used to receive data fed back by the pressure sensor 7, the gas concentration sensor 8, the flame sensor 1 9, the gas flow meter 1 15 and the gas flow meter 2 19, and after analysis and processing, controls the opening and closing of the stop valve 2, the double-control cut-off valve 1 13 and the double-control cut-off valve 2 17, and the opening of the flow rate regulating valve 1 14 and the flow rate regulating valve 2 18.

[0046] As an improvement of the present invention, the gas transport pipeline 1 is also equipped with a wet compressor 3, a dehydrator 6, an automatic explosion suppression device 4 and a water-seal fire-blocking explosion-relief device 5. The wet compressor 3 is used to pressurize low-concentration gas, and the dehydrator 6 is used to dehydrate the pressurized low-concentration gas; the automatic explosion suppression device 4 and the water-seal fire-blocking explosion-relief device 5 are used to prevent explosion and prevent flame spread, respectively. This can meet the needs of gas transport pressure and is safer.

[0047] As another improvement of the present invention, the main input pipeline 11 and the auxiliary input pipeline 12 are respectively equipped with a flame arrester 16 and a flame arrester 20, which are used to block the backflow flame and high temperature energy generated by the explosion of low-concentration gas in the main burner 24 and the auxiliary burner 21; the heat exchange tube 29 is a serpentine heat exchange tube, and the serpentine heat exchange tube is provided with fins. The side of the combustion chamber is provided with a high-temperature resistant observation window 27 for observing the combustion situation inside the combustion chamber; the combustion chamber is provided with a temperature sensor 1 and a flame sensor 2, and the temperature sensor 1 and the flame sensor 2 are connected to the data collection and control system for real-time transmission of flame position and temperature data, and analysis of the temperature field distribution and flame transmission situation inside the main burner 24; the auxiliary burner 21 is provided with multiple temperature sensors 2 for real-time monitoring of temperature data at different positions of the auxiliary burner. The combustion chamber is provided with an adjustable air distribution plate for changing the flow direction of the high-temperature flue gas generated by the auxiliary burner 21 and uniformly preheating the heat storage body filling bed in the combustion chamber.

[0048] The working method of the main-auxiliary combined low-concentration gas submerged combustion device comprises the following specific steps:

[0049] Step 1, combustion device inspection: inspect the entire submerged combustion device to ensure the integrity of the combustion system connection, the normal operation of the electric components and the normal circulation of each gas input pipeline; conduct a trial run of the flame sensor and temperature sensor, and turn on the flue gas analyzer for air calibration; introduce air to purge each combustion chamber of the main burner and the interior of the auxiliary burner 21 to ensure that there is no residual mixed gas in the combustion space, and close the valves of each part of the submerged combustion device after purging;

[0050] Step 2: Preheating the combustion device: First, turn on the silicon-molybdenum rod 23 to preheat the heat storage body in the auxiliary burner 21. When the temperature rises to 650-800℃, the stop valve 2 and the wet compressor 3 of the gas extraction transport pipeline 1 are opened, and the double-control shut-off valve 2 and the flow rate regulating valve 2 of the auxiliary input pipeline 12 are opened to control the low-concentration gas to enter the auxiliary burner 21 through the auxiliary input pipeline 12. Since the heat storage body in the auxiliary burner 21 reaches the required temperature to form an adaptive combustion zone, the low-concentration gas entering at this time starts to burn in the adaptive combustion zone. After the gas is ignited, the flow rate regulating valve 2 18 is used to control the low-concentration gas intake speed to keep the low-concentration gas burning stably in the adaptive combustion zone to form high-temperature flue gas. Specifically:

[0051] The average preheating temperature of the heat storage body in the auxiliary burner The area weighted average and volume weighted average methods are used to simplify the calculation. The weighted average area is divided as follows: Figure 3 and Figure 4 As shown:

[0052] The cross section of the auxiliary burner 21 is divided into four concentric annular areas from the inside to the outside. Figure 3 As shown in the figure, the temperature monitored by the temperature sensor 2 in the annular area approximately represents the regional temperature. The weighted average of the annular area temperature and the annular area area is calculated, and the cross-sectional average temperature is The calculation method is shown in formula (1); secondly, the average temperature of the heat storage body preheating needs to be calculated again by weighted average of the regional temperature and regional volume, and the auxiliary burner 21 is divided into multiple areas according to the position of each temperature sensor in the axial direction of the auxiliary burner. Figure 4 As shown, the average cross-sectional temperature of each area is taken as the temperature of each area, and the average preheating temperature of the heat storage body is The calculation method is shown in formula (2);

[0053]

[0054] Where: T ij is the temperature of the jth measuring point in the ith section of the gradually expanding burner.

[0055]

[0056] According to the above calculation formula, the average preheating temperature of the heat storage body in the real-time auxiliary burner 21 is obtained. Thus, by adjusting the low-concentration gas intake speed, the average temperature of the heat storage body preheating Always at 650-800℃ to maintain the adaptive combustion zone;

[0057] Then the high-temperature flue gas enters each combustion chamber, and is discharged from the main burner exhaust port after convective heat exchange with the heat storage body packed bed 25, so as to evenly heat the heat storage body packed bed 25 in each combustion chamber;

[0058] In addition, the auxiliary burner preheating efficiency needs to be calculated to reflect the preheating capacity of the auxiliary burner heat storage area for gas, which is used to optimize the material, structure and porosity of different heat storage materials filling the auxiliary burner;

[0059] The auxiliary burner preheating efficiency η pre The calculation formula is as follows:

[0060]

[0061] Where: c g is the specific heat capacity of the mixed gas, is the mass flow rate of the mixed gas, is the average preheating temperature of the heat storage body, T ais the inlet gas temperature (273K), LHV is the lower heating value of CH4; according to the above formula, the heat storage body with the highest preheating efficiency is selected to fill the auxiliary burner.

[0062] Step 3, main burner operation: wait for the minimum temperature of the heat storage body packed bed 25 in each combustion chamber of the main burner 24 to be preheated to 650-800°C, open the double-control shut-off valve 13 and the flow rate regulating valve 14 of the main input pipeline 11, control the large flow rate of low-concentration gas to be input into the main burner 24 through the main input pipeline 11, use the high-temperature electrode igniter installed at the air inlet of the main burner for ignition, transmit the flame position and temperature data in real time through the flame sensor and temperature sensor in the main burner 24, analyze the temperature field distribution and fire of each combustion chamber in the main burner 24 The flame transmission condition is combined with the observation window 27 to determine the combustion state of the low-concentration gas in the heat storage body filling bed 25 of each combustion chamber, and then the low-concentration gas inlet flow rate is adjusted by the opening of the flow rate regulating valve 14 to maintain the low-concentration gas in the heat storage body filling bed 25 of each combustion chamber to achieve stable submerged combustion. During the operation of the main burner 24, the auxiliary burner 21 is kept running to continuously provide high-temperature flue gas auxiliary heat, and heat is supplemented to the heat storage body filling bed 25 of each combustion chamber during the submerged combustion process to maintain the gas oxidation environment temperature in the main burner 24;

[0063] Step 4: Recycling of waste heat: The low-concentration gas continues to heat the heat storage bed 25 during the exhaust of the flue gas generated by the submerged combustion in the heat storage bed of each combustion chamber, thereby ensuring the heat replenishment in the main burner 24, so that the low-concentration gas can self-sustain and stably burn. After entering the heat extraction chamber, the high-temperature flue gas exchanges heat with the heat exchange liquid in the heat exchange tube 29 for cooling, and is discharged from the exhaust port of the main burner after heat exchange and cooling. At the same time, the heat exchange liquid exchanges heat with the high-temperature gas in the heat extraction chamber 28 to form a heated liquid for subsequent utilization.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A main-auxiliary combined low-concentration gas submerged combustion device, characterized in that: It includes gas source and flow regulation system, main burner, auxiliary burner, heat extraction chamber and data collection control system; The main burner is provided with a plurality of combustion chambers and heat extraction chambers, each of which is provided with a heat storage body filling bed and a heat preservation layer, the heat preservation layer wraps the heat storage body filling bed to keep it warm; the heat storage body filling bed is used to perform submerged combustion on the low-concentration gas entering; the heat extraction chamber is provided with a heat exchange tube, the heat exchange tube is provided with a heat exchange liquid, the heat exchange liquid exchanges heat with the high-temperature gas in the heat extraction chamber to form a heated liquid flowing out of the heat extraction chamber; the plurality of combustion chambers and the heat extraction chambers are connected in series in sequence, and the heat extraction chamber is farthest from the air inlet of the main burner, so that the low-concentration gas entering the air inlet of the main burner passes through each combustion chamber in sequence and burns to generate high-temperature gas which enters the heat extraction chamber, and the high-temperature gas is discharged from the exhaust port of the main burner after heat exchange and cooling; The number of the auxiliary burners is the same as that of the combustion chambers. The auxiliary burners are in the shape of a gradually expanding frustum. The end with a smaller diameter is the low-concentration gas inlet end of the auxiliary burner, and the end with a larger diameter is the high-temperature flue gas outlet end of the auxiliary burner. The high-temperature flue gas outlet end of each auxiliary burner is respectively connected to the side of each combustion chamber for adaptive combustion of low-concentration gas, thereby forming a high-temperature flue gas preheating combustion chamber and providing heat supplement for the operation process of each combustion chamber; the auxiliary burner is filled with heat storage ceramic particles, and a silicon-molybdenum rod is arranged at the low-concentration gas inlet end for preheating the heat storage ceramic particles; A high temperature resistant observation window is provided on the side of the combustion chamber for observing the combustion conditions inside the combustion chamber; a temperature sensor 1 and a flame sensor 2 are provided in the combustion chamber, and the temperature sensor 1 and the flame sensor 2 are connected to the data collection and control system for real-time transmission of flame position and temperature data, and analysis of the temperature field distribution and flame transmission conditions inside the main burner; a plurality of temperature sensors 2 are provided in the auxiliary burner for real-time monitoring of temperature data at different positions of the auxiliary burner; The gas source and flow regulating system comprises a gas transport pipeline, a main input pipeline, a gas diverter and an auxiliary input pipeline; one end of the gas transport pipeline is connected to the gas source, and the other end is connected to the inlet of the gas diverter; one of the outlets of the gas diverter is connected to the air inlet of the main burner through the main input pipeline, and the other outlet of the gas diverter is connected to one end of the auxiliary input pipeline; a plurality of branch pipes are arranged at the other end of the auxiliary input pipeline, and each branch pipe is respectively connected to the low-concentration gas inlet end of each auxiliary burner; the gas diverter diverts the low-concentration gas passing through, and one part enters the main burner and the other part enters each auxiliary burner; a stop valve, a pressure sensor, a gas concentration sensor and a flame sensor are sequentially arranged on the gas transport pipeline according to the flow direction of the low-concentration gas; the stop valve is used to control the gas flow; The on-off of the transport pipeline; the pressure sensor and the gas concentration sensor are respectively used to monitor the air pressure and gas concentration in the gas transport pipeline; the flame sensor 1 is used to detect whether there is a flame at the location; the main input pipeline is provided with a double-control cut-off valve 1, a flow rate regulating valve 1 and a gas flow meter 1 in sequence according to the flow direction of the low-concentration gas, and the auxiliary input pipeline is provided with a double-control cut-off valve 2, a flow rate regulating valve 2 and a gas flow meter 2 in sequence according to the flow direction of the low-concentration gas, the double-control cut-off valve 1 and the double-control cut-off valve 2 are respectively used to control the on-off of the main input pipeline and the auxiliary input pipeline; the flow rate regulating valve 1 and the flow rate regulating valve 2 are respectively used to adjust the gas flow in the main input pipeline and the auxiliary input pipeline; the gas flow meter 1 and the gas flow meter 2 are respectively used to monitor the gas flow in the main input pipeline and the auxiliary input pipeline; The gas transport pipeline is also equipped with a wet compressor, a dehydrator, an automatic explosion suppression device and a water-seal fire-blocking explosion-relief device. The wet compressor is used to pressurize low-concentration gas, and the dehydrator is used to dehydrate the pressurized low-concentration gas; the automatic explosion suppression device and the water-seal fire-blocking explosion-relief device are used to prevent explosion and prevent flame spread respectively; The data collection and control system is used to receive data fed back by the pressure sensor, gas concentration sensor, flame sensor 1, gas flowmeter 1 and gas flowmeter 2, and after analysis and processing, controls the opening and closing of the stop valve, double-control shut-off valve 1 and double-control shut-off valve 2, and the opening of flow rate regulating valve 1 and flow rate regulating valve 2.

2. According to claim 1, the main-auxiliary combined low-concentration gas submerged combustion device is characterized in that: The auxiliary burner is filled with 3-15 mm heat storage ceramic particles.

3. The main-auxiliary combined low-concentration gas submerged combustion device according to claim 1 is characterized in that: The heat storage body filling bed is made of ceramic particles or honeycomb ceramics or foam ceramics.

4. The main-auxiliary combined low-concentration gas submerged combustion device according to claim 1 is characterized in that: The main input pipeline and the auxiliary input pipeline are both equipped with flame arresters for blocking the backflow flame and high-temperature energy generated by the explosion of low-concentration gas in the main burner and the auxiliary burner; the heat exchange tube is a serpentine heat exchange tube, and the serpentine heat exchange tube is provided with fins.

5. The main-auxiliary combined low-concentration gas submerged combustion device according to claim 1 is characterized in that: The expansion angle of the auxiliary burner is 10° to 30°.

6. The main-auxiliary combined low-concentration gas submerged combustion device according to claim 1 is characterized in that: An adjustable air distribution plate is arranged in the combustion chamber to change the flow direction of the high-temperature flue gas generated by the auxiliary burner and to evenly preheat the heat storage body packed bed in the combustion chamber.

7. A working method of the main-auxiliary combined low-concentration gas submerged combustion device according to any one of claims 1 to 6, characterized in that: The specific steps are: Step 1: Inspection of combustion device: Inspect the entire submerged combustion device to ensure the integrity of the combustion system connection, the normal operation of the electric components and the normal circulation of each gas input pipeline; conduct a trial run of the flame sensor and temperature sensor, and turn on the flue gas analyzer for air calibration; introduce air to purge each combustion chamber of the main burner and the interior of the auxiliary burner to ensure that there is no residual mixed gas in the combustion space, and close the valves of each submerged combustion device after purging; Step 2: Preheat the combustion device: First, turn on the silicon-molybdenum rod to preheat the heat storage body in the auxiliary burner. When the temperature rises to 650-800℃, the stop valve and wet compressor of the gas extraction transportation pipeline are opened, and the dual-control shut-off valve 2 and flow rate regulating valve 2 of the auxiliary input pipeline are opened to control the low-concentration gas to enter the auxiliary burner through the auxiliary input pipeline. Since the heat storage body in the auxiliary burner reaches the required temperature to form an adaptive combustion zone, the low-concentration gas entering at this time begins to burn in the adaptive combustion zone. After the gas is ignited, the flow rate regulating valve 2 is used to control the intake speed of the low-concentration gas to keep the low-concentration gas burning steadily in the adaptive combustion zone to form high-temperature flue gas. Then, the high-temperature flue gas enters each combustion chamber, and is discharged from the exhaust port of the main burner after convective heat exchange with the heat storage body filling bed, so as to achieve uniform heating of the heat storage body filling bed in each combustion chamber. Step 3, main burner operation: wait for the minimum temperature of the heat storage body filling bed in each combustion chamber of the main burner to be preheated to 650-800℃, open the double-control shut-off valve 1 and the flow rate regulating valve 1 of the main input pipeline, control the large flow of low-concentration gas to be input into the main burner through the main input pipeline, use the high-temperature electrode igniter installed at the air inlet of the main burner for ignition, transmit the flame position and temperature data in real time through the flame sensor and temperature sensor in the main burner, analyze the temperature field distribution and flame transmission of each combustion chamber in the main burner, and determine the combustion state of the low-concentration gas in the heat storage body filling bed of each combustion chamber by combining the observation window observation, then adjust the low-concentration gas inlet flow rate by the opening of the flow rate regulating valve 1, keep the low-concentration gas in the heat storage body filling bed of each combustion chamber to achieve stable submerged combustion, keep the auxiliary burner running to continuously provide high-temperature flue gas auxiliary heat during the operation of the main burner, supplement the heat to the heat storage body filling bed of each combustion chamber during the submerged combustion, and maintain the gas oxidation environment temperature in the main burner; Step 4: Recycling of waste heat: Low-concentration gas continues to heat the heat storage bed during the exhaust of flue gas generated by immersed combustion in the heat storage bed of each combustion chamber, thereby ensuring heat replenishment in the main burner, allowing the low-concentration gas to self-sustain and stably burn. After entering the heat extraction chamber, the high-temperature flue gas exchanges heat with the heat exchange liquid in the heat exchange tube for cooling, and is discharged from the exhaust port of the main burner after heat exchange and cooling. At the same time, the heat exchange liquid exchanges heat with the high-temperature gas in the heat extraction chamber to form a heated liquid for subsequent utilization.

8. The working method according to claim 7, characterized in that: In the step 2, the flow rate regulating valve 2 is used to control the low-concentration gas intake speed to keep the low-concentration gas burning stably in the adaptive combustion zone to form high-temperature flue gas, specifically: The average preheating temperature of the heat storage body in the auxiliary burner The area-weighted average and volume-weighted average methods are used to simplify the calculation: The auxiliary burner cross section is divided into four concentric annular areas from the inside to the outside. The temperature monitored by the temperature sensor 2 in the annular area represents the regional temperature. The weighted average of the annular area temperature and the annular area area is calculated to obtain the average cross-sectional temperature. The calculation method is shown in formula (1); secondly, the average temperature of the regenerator preheating needs to be calculated again by weighted average calculation of the regional temperature and regional volume. The burner is divided into multiple areas according to the axial position of each temperature sensor in the auxiliary burner, and the average cross-sectional temperature of the upper part of each area is taken as the average temperature of the upper cross-sectional area. As the temperature of each area, the average temperature of the heat storage body preheating The calculation method is shown in formula (2); Where: T ij is the temperature of the jth measuring point in the i-th section of the gradually expanding burner, j = 1, 2, 3, 4; According to the above calculation formula, the average preheating temperature of the heat storage body in the real-time auxiliary burner is obtained. Thus, by adjusting the low-concentration gas intake speed, the average temperature of the heat storage body preheating Always at 650-800℃ to maintain the adaptive combustion zone.

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