Low-concentration gas utilization pretreatment system and safety control method thereof

Abstract

The application discloses a low-concentration gas utilization pretreatment system and a safety control method thereof, wherein a multistage explosion resistance and suppression device of a gas extraction and transportation system is used for extinguishing a flame and resisting and suppressing explosion in the pretreatment system; a gas dehydration and preheating device is used for dehydrating and purifying and preheating gas flowing therethrough; electric regulating valves one and two are respectively used for controlling the on-off of a gas extraction and transportation pipeline and an air transportation pipeline; a mixer of a mixed air intake system is used for mixing gas and air and then transporting the mixed gas to a gas utilization device; and a control module of a concentration dynamic monitoring and regulation system analyzes concentration data and then adjusts the opening degrees of the electric regulating valves one and two, so that the gas concentration of output gas of the mixed air intake system is kept stable. The application can effectively improve the preheating efficiency of a combustion system air intake, keep the methane concentration of the air intake from fluctuating greatly and has a good explosion resistance and suppression effect, and finally ensures that low-concentration gas is safely, stably and efficiently utilized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low-concentration gas utilization, in particular to a low-concentration gas utilization pretreatment system and a safety control method thereof. BACKGROUND

[0002] In the field of comprehensive utilization of coal mine gas, the utilization technology of low-concentration gas (i.e. gas concentration of 3% to 8%) is an important way to realize clean energy conversion, but its pretreatment link has long been faced with multiple technical bottlenecks. The existing technical system has significant defects in safety, energy efficiency and system integration, which seriously restricts the process of large-scale application. First, the traditional explosion-proof system has the hidden danger of insufficient intrinsic safety: although the metal mesh fire barrier can block the propagation of high-frequency flame, the inhibition efficiency of low-frequency detonation wave is low, and the detonation superposition effect is easy to form in the complex working conditions underground. At the same time, the existing explosion-proof device is an independent operating unit, which lacks a multi-stage interlocking mechanism, and cannot achieve rapid isolation when a local explosion occurs, which can easily cause secondary disasters. Second, the energy efficiency and processing accuracy of the dehydration process cannot meet the needs of low-concentration gas utilization equipment, and the low-concentration gas treated by the freezing dehydration process will have a significant temperature drop to below -10℃ after completing deep dehumidification, resulting in the need for additional heat energy consumption to compensate for the temperature drop loss in the preheating link, which in turn reduces the combustion utilization efficiency. The inherent contradiction between the traditional dehydration process and the combustion utilization system in terms of thermal efficiency needs to be solved through thermal cycle optimization or waste heat recovery mechanism. In addition, the dynamic response capability of the concentration control system is lagging, and the conventional method cannot respond and adjust in time when facing a ±20% concentration fluctuation of the extraction system, which will directly lead to over-temperature or flameout in the utilization system.

[0003] In view of the above technical difficulties, it is necessary to build a new pretreatment system and its safety control method, which can effectively improve the preheating efficiency of the combustion system intake air, and keep the methane concentration of the intake air fluctuation small, and also has good explosion-proof and explosion-suppression effect, ultimately ensuring the safe, stable and efficient utilization of low-concentration gas. SUMMARY

[0004] In view of the problems existing in the prior art, the application provides a low-concentration gas utilization pretreatment system and a safety control method thereof, which can effectively improve the preheating efficiency of the combustion system intake air, and keep the methane concentration of the intake air fluctuation small, and also has good explosion-proof and explosion-suppression effect, ultimately ensuring the safe, stable and efficient utilization of low-concentration gas.

[0005] To achieve the above purpose, the technical scheme adopted by the application is: a low-concentration gas utilization pretreatment system, comprising an extracted gas conveying system, an air conveying system, a mixed intake air system and a concentration dynamic monitoring and control system.

[0006] The gas extraction and transportation system comprises a multi-stage explosion resistance and suppression device, a gas dehydration and preheating device and an electric regulating valve one arranged in the gas extraction and transportation pipeline, the multi-stage explosion resistance and suppression device is used for extinguishing fire and resisting and suppressing explosion in the gas extraction and transportation pipeline; the gas dehydration and preheating device is used for dehydrating and purifying the gas flowing through the gas and preheating the gas to a required temperature before the gas is transported to the air mixing system; and the electric regulating valve one is used for controlling the on-off of the gas extraction and transportation pipeline.

[0007] The air transportation system comprises an air injection fan and an electric regulating valve two arranged in the air transportation pipeline, the air injection fan is used for injecting air into the air transportation pipeline and transporting the air to the air mixing system; and the electric regulating valve two is used for controlling the on-off of the air transportation pipeline.

[0008] The air mixing system comprises a mixer arranged in the air mixing pipeline, which is used for mixing the gas and air transported to the mixer and then transporting the mixed gas to the gas utilization equipment.

[0009] The concentration dynamic monitoring and control system comprises a control module, a concentration meter one and a concentration meter two, the concentration meter one is arranged in the gas extraction and transportation pipeline and is used for monitoring the concentration of the gas flowing through the pipeline, the concentration meter two is arranged in the air mixing pipeline and is used for monitoring the concentration of the gas flowing through the pipeline; and the control module is used for acquiring the concentration data fed back by the concentration meter one and the concentration meter two, analyzing the concentration data and adjusting the opening degree of the electric regulating valve one and the electric regulating valve two, so that the concentration of the gas output by the air mixing system is kept stable.

[0010] Further, the multi-stage explosion resistance and suppression device comprises, in sequence according to the gas flow direction, an explosion isolation device, a self-control water seal fire resistance and explosion relief device, an overpressure wet type diffusion valve, a powder explosion suppression device and a flame sensor arranged in the gas extraction and transportation pipeline, the explosion isolation device is used for isolating gas explosion; the self-control water seal fire resistance and explosion relief device realizes dynamic explosion shock wave relief and flame front isolation by adjusting the water seal pressure and water level; the overpressure wet type diffusion valve is used for low-concentration gas safe relief and flame propagation physical isolation when the pipeline is overpressure; the powder explosion suppression device cooperates with the flame sensor to spray dry powder to form an inertization isolation barrier when the flame sensor detects the presence of flame.

[0011] Further, the gas dehydration and preheating device comprises, in sequence according to the gas flow direction, a filter, a cyclone dehydration device, a refrigeration dehydration device, a heat flow driving device and a heat energy compensation device arranged in the gas extraction and transportation pipeline, the filter is used for trapping impurities and removing water; the cyclone dehydration device and the refrigeration dehydration device cooperate to gradiently dehydrate and purify the gas flowing through the gas; the heat flow driving device has a core component of a plate heat exchanger, which is used for preheating low-temperature gas, recycling the waste heat of the refrigeration dehydration device and dynamically compensating the heat energy of the dehydrated gas through the heat energy compensation device and preheating the gas.

[0012] Further, the gas extraction pipeline is sequentially provided with a pressure stabilizing device one, a pressure gauge one, a flow meter one, a shut-off valve one and a one-way valve one in the direction of gas flow, the air pipeline is sequentially provided with a pressure stabilizing device two, a pressure gauge two, a flow meter two and a one-way valve two in the direction of air flow, and the mixed air pipeline is sequentially provided with a pressure gauge three, a flow meter three, a shut-off valve three and a one-way valve three in the direction of gas flow; the pressure stabilizing device one and the pressure stabilizing device two are respectively used to control the gas extraction and the air gas pressure to be stable in a set value range, and cooperate with the pressure gauges one to three to realize pressure monitoring and control of each pipeline; the flow meter one, the flow meter two and the flow meter three are respectively used to monitor the gas flow in the pipeline; the shut-off valve one and the shut-off valve two are respectively used to control the on-off of the pipeline; and the one-way valve one, the one-way valve two and the one-way valve three are used to keep the gas in the pipeline to flow in one direction and prevent the gas from flowing back.

[0013] Further, the multi-stage explosion suppression and inhibition device further comprises a blast explosion suppression device one arranged in the gas extraction pipeline and a blast explosion suppression device two and a heat backflow prevention device arranged in the mixed air pipeline, the blast explosion suppression device one and the blast explosion suppression device two are used to block the propagation of the blast and deflagration generated by the gas utilization equipment to the gas extraction pipeline and the mixed air pipeline, and the heat backflow prevention device is used to prevent the heat of the gas utilization equipment from flowing back.

[0014] Further, the measurement accuracy of the ultrasonic liquid level meter in the self-control water seal fire blocking and explosion relief device is ±0.5mm, the liquid level adjustment range of the servo motor driving the water pump is 0~10mm / min, and the rupture pressure of the explosion relief diaphragm is set to 80KPa±5%.

[0015] Further, the powder spraying explosion suppression device uses ABC dry powder stored in a pressure tank, which is sprayed in a high-pressure spraying mode by a high-speed electromagnetic valve to form a powder cloud, interfere with the flame chain reaction, improve the reaction inertness, and has ms-level response capability.

[0016] Further, the tangential inlet flow velocity of the cyclone dehydration device is 15~20m / s.

[0017] The control method of the above-mentioned low-concentration gas utilization pretreatment system comprises the following steps:

[0018] Step one, real-time monitoring of the gas concentration and flow rate of the gas in the gas extraction pipeline and the mixed air pipeline, and the flow rate of the gas in the air pipeline;

[0019] Step two, according to the target gas concentration value required by the gas utilization equipment, the control module automatically adjusts the opening degree of the electric regulating valve one and the electric regulating valve two by using the data fed back in step one and through a PID control algorithm, so that the mixed gas concentration in the mixed air pipeline is always maintained in a preset range;

[0020] Step three, when the gas utilization equipment flame or high temperature backflow to the pretreatment system, the multi-stage explosion suppression device keeps the safety of the pretreatment system through the multi-stage explosion suppression way;

[0021] Step four, all monitoring data are uploaded to the control module in real time to realize data recording.

[0022] Further, the step two is specifically:

[0023] Let the extraction gas flow in the extraction gas conveying pipeline controlled by the electric regulating valve one be Q m , the air flow in the air conveying pipeline controlled by the electric regulating valve two be Q g , the extraction gas concentration measured by the concentration meter one be C m , the total flow after mixing be Q mix , the mixed gas concentration measured by the concentration meter two be C mix , the required rated flow after mixing be Q t , the required rated flow concentration after mixing be C t , wherein,

[0024] (1)

[0025] (2)

[0026] When C m fluctuates, Q m and Q g are calculated in real time,

[0027] (3)

[0028] (4)

[0029] The control module uses the PID control algorithm to control the opening degree of the electric regulating valve one and the electric regulating valve two according to the formula calculation:

[0030] (5)

[0031] Wherein, k m , k g are the flow coefficients of the extraction gas conveying pipeline and the air conveying pipeline, under the premise that the control target concentration is C t , the input error e1 uses the PID control algorithm to output the opening degree u m of the electric regulating valve one, and u m ∈[0, 100],

[0032] (6)

[0033] (7)

[0034] Under the premise of controlling the target flow as Q t The input error e2 uses the PID control algorithm to output the electric regulating valve two opening degree u g , and the limitation u g ∈[0, 100],

[0035] (8)

[0036] (9)

[0037] Wherein, K p is a proportional term, K i is an integral term, and K d is a differential term, according to the output result control module, the opening degree of the electric regulating valve one and the electric regulating valve two is automatically adjusted, so that the mixed gas concentration in the mixed gas pipeline is always maintained in the preset range.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] 1. Since the extraction gas concentration will continue to fluctuate, in order to ensure the stability of the mixed gas concentration, the present application introduces a concentration control strategy based on the PID algorithm, and through the joint double-path flow and concentration feedback adjustment mechanism, the control precision of the mixed gas concentration finally output by the system reaches ±0.5% (i.e. the mixed gas concentration is always maintained within the set target value ±0.5%), and the stability and response speed are significantly better than those of the traditional artificial / single valve control mode, thereby ensuring the stable use of low-concentration gas by the gas utilization equipment.

[0040] 2. The multi-stage explosion suppression and explosion prevention and backfire prevention module of the present application constructs a multi-level joint protection of "mechanical explosion-proof - water seal explosion relief - powder explosion suppression - explosion-proof - backfire prevention", has millisecond-level response capability, and can effectively interrupt the explosion propagation path of the gas through the multi-level way, improve the overall impact resistance and operation safety level of the pretreatment system, and significantly enhance the safety redundancy compared with the traditional single explosion-proof structure.

[0041] 3. The present application adopts a gradient dehydration process combining cyclone pre-dehydration and deep freezing dehydration, which can effectively ensure the dehydration and purification of the extracted gas, and combines the heat flow driving device and the heat energy compensation device to realize the heat recovery and reuse in the freezing dehydration process, construct an energy closed loop path, effectively reduce the system heat loss, improve the temperature of the gas after freezing dehydration, and the energy saving effect is remarkable, which can effectively save energy and also continuously maintain the preheating effect of the treated gas. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is the overall structure schematic diagram of the present application.

[0043] In the figure: 1 - explosion-proof device; 2 - self-control water seal fire blocking and explosion relief device; 3 - overpressure wet type diffusion valve; 4 - filter; 5 - powder spraying explosion suppression device; 6 - flame sensor; 7 - cyclone dehydration device; 8 - refrigeration dehydration device; 9 - heat flow driving device; 10 - heat energy compensation device; 11 - pressure stabilizing device I; 12 - pressure gauge I; 13 - flow meter I; 14 - concentration gauge I; 15 - electric regulating valve I; 16 - shut-off valve I; 17 - one-way valve I; 18 - explosion blocking and detonation device I; 19 - air injection fan; 20 - pressure stabilizing device II; 21 - pressure gauge II; 22 - flow meter II; 23 - electric regulating valve II; 24 - one-way valve II; 25 - mixer; 26 - pressure gauge III; 27 - flow meter III; 28 - concentration gauge II; 29 - shut-off valve II; 30 - one-way valve III; 31 - explosion blocking and detonation device II; 32 - heat backflow prevention device. DETAILED DESCRIPTION

[0044] The application will be further described below.

[0045] As Figure 1 shown, a low-concentration gas utilization pretreatment system includes a gas extraction and conveying system, an air conveying system, a gas-air mixing system, and a concentration dynamic monitoring and control system.

[0046] The gas extraction conveying system comprises a multi-stage explosion resistance and suppression device, a gas dehydration and preheating device and an electric regulating valve one arranged in the gas extraction conveying pipeline, the multi-stage explosion resistance and suppression device is used for extinguishing fire and resisting and suppressing explosion in the gas extraction conveying pipeline, the gas dehydration and preheating device is used for dehydrating and purifying the gas flowing through the gas dehydration and preheating device and preheating the gas to a required temperature and then conveying the gas to the mixed air intake system, and the electric regulating valve one 15 is used for controlling the on-off of the gas extraction conveying pipeline; the multi-stage explosion resistance and suppression device comprises, in sequence along the gas flow direction, an explosion-proof device 1, a self-control water seal fire resistance and explosion relief device 2, an overpressure wet type diffusion valve 3, a powder injection explosion suppression device 5 and a flame sensor 6 arranged in the gas extraction conveying pipeline, the explosion-proof device 1 is used for isolating gas explosion, the self-control water seal fire resistance and explosion relief device 2 realizes dynamic explosion shock wave relief and flame front isolation by regulating water seal pressure and water level, the overpressure wet type diffusion valve 3 is used for low-concentration gas safe relief and flame propagation physical isolation when the pipeline is overpressure, the powder injection explosion suppression device 5 and the flame sensor 6 are cooperated to spray dry powder to form an inertization isolation barrier when the flame sensor 6 detects the flame at the position, the gas dehydration and preheating device comprises, in sequence along the gas flow direction, a filter 4, a cyclone dehydration device 7, a refrigeration dehydration device 8, a hot flow driving device 9 and a heat energy compensation device 10 arranged in the gas extraction conveying pipeline, the filter 4 is used for trapping impurities and water, the cyclone dehydration device 7 and the refrigeration dehydration device 8 are cooperated to gradiently dehydrate and purify the gas flowing through the cyclone dehydration device 7 and the refrigeration dehydration device 8, and the hot flow driving device 9 is used for preheating low-temperature gas by using a plate heat exchanger as a core component, recycling waste heat of the refrigeration dehydration device 8 and dynamically compensating heat energy of the dehydrated gas by the heat energy compensation device 10 and preheating the gas.

[0047] The air conveying system comprises an air injection fan 19 and an electric regulating valve two 23 arranged in the air conveying pipeline, the air injection fan 19 is used for injecting air into the air conveying pipeline and conveying the air to the mixed air intake system, and the electric regulating valve two 23 is used for controlling the on-off of the air conveying pipeline.

[0048] The mixed air intake system comprises a mixer 25 arranged in the mixed air intake pipeline, which is used for mixing the gas and the air conveyed to the mixer 25 and then conveying the mixed gas to the gas utilization equipment.

[0049] The gas extraction pipeline is sequentially provided with a pressure stabilizing device 11, a pressure gauge 12, a flow meter 13, a shut-off valve 16 and a one-way valve 17 in the gas flow direction, the air pipeline is sequentially provided with a pressure stabilizing device 20, a pressure gauge 21, a flow meter 22 and a one-way valve 24 in the air flow direction, and the mixed air pipeline is sequentially provided with a pressure gauge 26, a flow meter 27, a shut-off valve 29 and a one-way valve 30 in the gas flow direction; the pressure stabilizing device 11 and the pressure stabilizing device 20 are respectively used for controlling the gas extraction and the air gas pressure to be stable in a set value range, and the pressure gauges 12 to 26 are used for realizing pressure monitoring and control of each pipeline; the flow meter 13, the flow meter 22 and the flow meter 27 are respectively used for monitoring the gas flow in the pipeline; the shut-off valve 16 and the shut-off valve 29 are respectively used for controlling the on-off of the pipeline; and the one-way valves 17, 24 and 30 are used for keeping the gas in the pipeline to flow in one direction and preventing the gas from flowing back.

[0050] The concentration dynamic monitoring and control system comprises a control module, a concentration meter 14 and a concentration meter 28; the concentration meter 14 is arranged on the gas extraction pipeline and is used for monitoring the gas concentration flowing through the pipeline; the concentration meter 28 is arranged on the mixed air pipeline and is used for monitoring the gas concentration flowing through the pipeline; the control module is used for acquiring and analyzing the concentration data fed back by the concentration meter 14 and the concentration meter 28, adjusting the opening degree of the electric regulating valve 15 and the electric regulating valve 23, so that the gas concentration of the mixed air system output is kept stable.

[0051] As an improvement of the present application, the multi-stage explosion suppression and inhibition device further comprises a blast suppression device 18 arranged on the gas extraction pipeline, and a blast suppression device 31 and a heat backflow prevention device 32 arranged on the mixed air pipeline; the blast suppression device 18 and the blast suppression device 31 are used for blocking the propagation of the blast and deflagration generated by the gas utilization equipment to the gas extraction pipeline and the mixed air pipeline; and the heat backflow prevention device 32 is used for preventing the heat backflow of the gas utilization equipment; thus, a multi-level combined protection of mechanical explosion isolation, water seal explosion relief, powder explosion suppression, blast suppression and backfire prevention can be formed.

[0052] As another improvement of the present application, the measurement accuracy of the ultrasonic liquid level meter in the self-control type water seal fire barrier explosion relief device 2 is ±0.5mm, the liquid level adjustment range of the servo motor driving the water pump is 0~10mm / min, and the rupture pressure of the explosion relief diaphragm is set to 80KPa±5%. The powder explosion suppression device 5 adopts ABC dry powder stored in a pressure tank, which is sprayed in a high-pressure jetting mode to form a powder cloud, interfere with the flame chain reaction, improve the reaction inertness, and has ms-level response capability. The tangential inlet flow velocity of the cyclone dehydration device 7 is 15~20m / s.

[0053] In addition, each key node (such as a concentration meter, a pressure gauge, a flame sensor, a powder spraying device, and a shut-off valve) in the above-mentioned pretreatment system has an interlocking relationship, and any abnormality of any node will trigger the overall shutdown protection process, including explosion signal interlocking, overpressure interlocking, temperature abnormality interlocking, etc.

[0054] The control method of the above-mentioned low-concentration gas pretreatment system comprises the following steps:

[0055] Step one, real-time monitoring of the gas concentration and flow rate of the extracted gas in the extracted gas conveying pipeline and the mixed gas pipeline, and the flow rate of the gas in the air conveying pipeline.

[0056] Step two, according to the target value of the gas concentration required by the gas utilization equipment, the control module uses the data fed back in step one and automatically adjusts the opening degree of the electric regulating valve one 15 and the electric regulating valve two 23 through the PID control algorithm, so that the mixed gas concentration in the mixed gas pipeline is always maintained within the preset range, specifically:

[0057] Let the flow rate of the extracted gas in the extracted gas conveying pipeline controlled by the electric regulating valve one 15 be Q m , the flow rate of the air in the air conveying pipeline controlled by the electric regulating valve two 23 be Q g , the concentration of the extracted gas measured by the concentration meter one 14 be C m , the total flow rate after mixing be Q mix , the concentration of the mixed gas measured by the concentration meter two 28 be C mix , the required rated flow rate after mixing be Q t , and the required rated flow concentration after mixing be C t , wherein,

[0058] (1)

[0059] (2)

[0060] When C m fluctuates, Q m and Q g are calculated in real time,

[0061] (3)

[0062] (4)

[0063] The control module uses the PID control algorithm to control the opening degree of the electric regulating valve one 15 and the electric regulating valve two 23 according to the calculation results of the formula:

[0064] (5)

[0065] wherein, km k g The flow coefficients for the gas extraction pipeline and the air extraction pipeline are determined when the target concentration is C. t Under the premise that the input error e1 is used, the PID control algorithm is used to output the opening u of the electric regulating valve -15. m , limit u m ∈[0, 100],

[0066] (6)

[0067] (7)

[0068] With the target flow rate controlled as Q t Under the premise that the input error e2 is used, the PID control algorithm is used to output the opening degree u of the electric regulating valve 23. g , limit u g ∈[0, 100],

[0069] (8)

[0070] (9)

[0071] Among them, K p K is the proportional term. i K is the integral term. d As the differential term, the control module automatically adjusts the opening of electric regulating valve 15 and electric regulating valve 23 according to the output result, so that the concentration of mixed gas in the mixed air intake pipeline is always maintained within the range of the set target value ±0.5%.

[0072] Step 3: When the flame or high temperature of the gas utilization equipment flows back to the pretreatment system, the multi-stage explosion-proof and explosion-suppressing device maintains the safety of the pretreatment system through multi-stage explosion-proof and explosion-suppressing methods.

[0073] Step 4: All monitoring data is uploaded to the control module in real time to achieve data recording.

[0074] 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 utilization pretreatment system characterized by, The system comprises a gas extraction and conveying system, an air conveying system, an air mixing system and a concentration dynamic monitoring and control system. The gas extraction and conveying system comprises a multi-stage explosion-resistant and explosion-suppressing device, a gas dehydration and preheating device and an electric regulating valve one, which are arranged in the gas extraction and conveying pipeline in sequence. The air conveying system comprises an air injection fan and an electric regulating valve two, which are arranged in the air conveying pipeline in sequence. The air mixing system comprises a mixer, which is arranged in the air mixing pipeline. The concentration dynamic monitoring and control system comprises a control module, a concentration meter one and a concentration meter two.

2. The low concentration gas utilization pretreatment system according to claim 1, wherein, The gas dehydration and preheating device comprises a filter, a cyclone dehydration device, a refrigeration dehydration device, a heat flow driving device and a heat energy compensation device, which are arranged in the gas extraction and conveying pipeline in sequence. The filter is used for trapping impurities and removing water. The cyclone dehydration device and the refrigeration dehydration device are used for gradient dehydration and purification of the gas. The heat flow driving device is used for preheating low-temperature gas. The heat energy compensation device is used for dynamic compensation of heat energy of the dehydrated gas.

3. The low concentration gas utilizing pretreatment system according to claim 1, wherein The gas extraction pipeline is sequentially provided with a pressure stabilizing device one, a pressure gauge one, a flow meter one, a shut-off valve one and a one-way valve one in the gas flow direction, the air pipeline is sequentially provided with a pressure stabilizing device two, a pressure gauge two, a flow meter two and a one-way valve two in the air flow direction, and the mixed air pipeline is sequentially provided with a pressure gauge three, a flow meter three, a shut-off valve three and a one-way valve three in the gas flow direction; the pressure stabilizing device one and the pressure stabilizing device two are respectively used for controlling the gas extraction and the air gas pressure to be stable in a set value range, and cooperating with the pressure gauge one to the pressure gauge three to realize pressure monitoring and control of each pipeline; the flow meter one, the flow meter two and the flow meter three are respectively used for monitoring the gas flow in the pipeline; the shut-off valve one and the shut-off valve two are respectively used for controlling the on-off of the pipeline; and the one-way valve one, the one-way valve two and the one-way valve three are used for keeping the one-way flow of the gas in the pipeline.

4. The low concentration gas utilizing pretreatment system according to claim 1, wherein The multi-stage explosion resistance and suppression device further comprises an explosion resistance and suppression device one arranged in the gas extraction pipeline, and an explosion resistance and suppression device two and a heat backflow prevention device arranged in the mixed air pipeline, the explosion resistance and suppression device one and the explosion resistance and suppression device two are used for blocking the propagation of the explosion and deflagration generated by the gas utilization equipment to the gas extraction pipeline and the mixed air pipeline, and the heat backflow prevention device is used for preventing the heat backflow of the gas utilization equipment.

5. The low concentration gas utilizing pretreatment system according to claim 1, wherein The measurement accuracy of the ultrasonic level meter in the self-control water seal fire resistance and explosion relief device is ±0.5mm, the liquid level adjustment range of the servo motor driving water pump is 0~10mm / min, and the rupture pressure of the explosion relief diaphragm is set to 80KPa±5%.

6. The low concentration gas utilizing pretreatment system according to claim 1, wherein The powder spraying explosion resistance device adopts the ABC dry powder stored in the pressure tank, which is sprayed in a high-pressure spraying mode to form a powder cloud, interfere with the flame chain reaction, improve the reaction inertness, and has ms-level response capability.

7. The low concentration gas utilizing pretreatment system according to claim 2, wherein The tangential inlet flow velocity of the cyclone dehydration device is 15~20m / s.

8. A control method of a pretreatment system for low-concentration gas according to any one of claims 1 to 7, characterized by, The method comprises the following steps: Step one, real-time monitoring of the gas concentration and flow of the gas in the gas extraction pipeline and the mixed air pipeline, and the flow of the gas in the air pipeline; Step two, according to the target value of the gas concentration required by the gas utilization equipment, the control module automatically adjusts the opening degree of the electric regulating valve one and the electric regulating valve two by using the data fed back in step one and through a PID control algorithm, so that the mixed gas concentration in the mixed air pipeline is always maintained in a preset range; Step three, when the flame or high temperature of the gas utilization equipment backflows to the pretreatment system, the multi-stage explosion resistance and suppression device maintains the safety of the pretreatment system through multi-stage explosion resistance and suppression; Step four, all monitoring data are uploaded to the control module in real time to realize data recording.

9. The control method according to claim 8, characterized by, The step two is specifically: Let the flow of the extracted gas in the extracted gas conveying pipeline controlled by the electric regulating valve one be Q m , the flow of the air in the air conveying pipeline controlled by the electric regulating valve two be Q g , the concentration of the extracted gas measured by the concentration meter one be C m , the total flow after mixing be Q mix , the concentration of the mixed gas measured by the concentration meter two be C mix , the required flow after mixing be Q t , the required flow concentration after mixing be C t , wherein, （1） （2） When C m Q is calculated in real time m and Q g , （3） （4） The control module adopts a PID control algorithm, and the opening degree of the electric regulating valve one and the electric regulating valve two is controlled according to the formula calculation: （5） Wherein, k m , k g are the flow coefficients of the gas extraction pipeline and the air pipeline, and under the premise that the control target concentration is C t , the input error e1 uses the PID control algorithm to output the opening degree u m of the electric regulating valve 1 m , and the limitation u m ∈[0, 100]. （6） （7） Under the condition of control target flow Q t The input error e2 uses the PID control algorithm to output the electric regulating valve two opening degree u g , limit u g ∈[0, 100]; （8） （9） wherein K p is a proportional term, K i is an integral term, and K d is a derivative term. The output result control module automatically adjusts the opening of the electric regulating valve 1 and the electric regulating valve 2 according to the output result, so that the mixed gas concentration in the mixed gas intake pipeline is always maintained within the preset range.

Images