System and method capable of stabilizing negative pressure of combustion chamber and accurately measuring flue gas components

Abstract

The invention provides a method capable of stabilizing the negative pressure of a combustion chamber and accurately measuring smoke components, which comprises the following steps that: a system controller obtains a signal of smoke flow Qy generated by combustion in a hearth of the combustion chamber; a mixed integer quadratic programming algorithm is adopted to obtain a vacuum pump combination scheme with the lowest vibration amplitude and each vacuum pump operation scheme in the combination scheme according to the principle that the smoke flow distribution step length is 10% of Qy; the system controller controls the multistage vacuum pumps according to the obtained vacuum pump combination scheme with the lowest vibration amplitude and the vacuum pump operation scheme, so that the hearth pressure is regulated and controlled to the target pressure to stabilize the negative pressure of the combustion chamber; the vacuum pumps extract smoke generated by combustion in the combustion chamber hearth and then send the smoke to the smoke analyzer for component analysis, and the smoke analyzer is arranged on the smoke component measuring port. The invention further provides a system based on the method. According to the invention, by optimizing the combination and operation scheme of the vacuum pump, the influence of vibration and non-uniform exhaust rate on flame form and pollutant generation is weakened, and the flue gas components are accurately measured.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel combustion under high altitude conditions, and specifically to a system and method capable of stabilizing the negative pressure in the combustion chamber and accurately measuring the components of flue gas. Background Art

[0002] With the improvement of the industrial level in high altitude areas, the number of boilers has increased sharply. However, energy efficiency tests show that the low air pressure and oxygen mass concentration in high altitude areas have led to problems such as a general decline in thermal efficiency, an increase in pollutant emissions, and a decrease in stability in existing gas boilers, methanol boilers, and coal-fired boilers. The combustion flame morphology and pollutant generation characteristics of combustible gases, liquids, and solids under negative pressure conditions need to be studied urgently. This helps to guide the design of burners and furnace structures suitable for high altitude areas.

[0003] In order to study the combustion characteristics and pollutant formation characteristics of gases, liquids, and solids under negative pressure conditions, a negative pressure environment required for experiments needs to be obtained. Currently, there are two methods to obtain negative pressure conditions: (1) Build the same experimental platform in different altitude areas. For example, a patent with the publication number CN116293621A discloses an experimental device for variable air pressure combustion and heat transfer characteristics, and uses a freight vehicle to transport the experimental device to different high altitude areas for experiments. However, this method is time-consuming and laborious, has poor repeatability, and is limited by the temperature and infrastructure of the experimental site. (2) Simulate the plateau negative pressure combustion environment. This method uses a vacuum pump to extract the flue gas generated by combustion in a limited space to reduce the furnace pressure to the target negative pressure. For example, a patent with the publication number CN116928660A discloses a negative pressure traveling grate furnace simulating the plateau environment and its use method, and a vacuum pump is arranged at the furnace outlet to continuously extract flue gas to create a negative pressure environment inside the furnace. However, the experimental conditions covered by a single vacuum pump are few, and the load rate of the vacuum pump is less than 30% in some conditions. The unstable pumping rate and large vibration amplitude may affect the flame morphology and pollutant generation characteristics. In addition, the commonly used flue gas analyzer can only work normally under the negative pressure conditions of a sampling flow rate of 0.6Lmin -1 ~3.5Lmin -1 and a vacuum degree of 0 kPa to 20 kPa. The published related patents arrange flue gas measurement holes on the side of the furnace, and the sampling flow rate and working pressure of the flue gas analyzer cannot reach the rated conditions, which will lead to inaccurate measurement of flue gas components.

[0004] In view of this, it is necessary to improve the stability of the system and the accuracy of component measurement by optimizing the vacuum pump combination scheme, the vacuum pump operation scheme, and the position of the flue gas measurement port. Based on the above methods, the present invention proposes a system and method capable of stabilizing the negative pressure in the combustion chamber and accurately measuring the components of flue gas. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the object of the present invention is a system and method capable of stabilizing the negative pressure in the combustion chamber and accurately measuring the flue gas components. By optimizing the vacuum pump combination and operation scheme, the influence of vibration and uneven pumping rate on the flame morphology and pollutant generation is minimized, and the position of the flue gas measurement port is reasonably arranged to achieve accurate measurement of the flue gas components in a wide negative pressure range (0 kPa to 101 kPa), that is, within one atmospheric pressure range.

[0006] To solve the above technical problems, the first implementation solution given by the present invention is to provide a method for stabilizing the negative pressure in the combustion chamber and accurately measuring the flue gas components, including the following steps:

[0007] The flue gas generated by combustion in the furnace of the combustion chamber is sent out from the tail of the furnace, and after filtration, the flue gas flow rate measured by the flue gas flow meter is Q y ; After the system controller obtains the flue gas flow signal measured by the flue gas flow meter, it uses the mixed integer quadratic programming algorithm to obtain the vacuum pump combination scheme with the lowest vibration amplitude and the operation schemes of each vacuum pump in this combination scheme based on the principle that the allocated flue gas flow step is 10% of Q y

[0008] The system controller controls the multi-stage vacuum pump according to the obtained vacuum pump combination scheme with the lowest vibration amplitude and the vacuum pump operation scheme to adjust the furnace pressure to the target pressure for stabilizing the negative pressure in the combustion chamber;

[0009] The flue gas generated by combustion in the furnace of the combustion chamber is pumped by each vacuum pump and then sent to the flue gas analyzer for component analysis. The flue gas analyzer is set at the flue gas component measurement port behind each vacuum pump so that the flue gas analyzer can be used within one atmospheric pressure.

[0010] Preferably, the method for determining the vacuum pump combination scheme with the lowest vibration amplitude is as follows:

[0011] The system controller 22 obtains the flow signal of the flue gas flow Q y , and then allocates the flue gas flow Q1 to the first vacuum pump according to the principle that the step is 10% of Q y . When Q1 is greater than the rated pumping flow rate of the vacuum pump under the target negative pressure, re-allocate the flue gas flow to the first vacuum pump according to the principle that the step is 10% of 10% of Q y until the flue gas flow allocated to the first vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure; if the flue gas flow Q1 allocated to the first vacuum pump is less than the rated pumping flow rate of this vacuum pump under the target negative pressure, then continue to allocate the flue gas flow Q2 to the second vacuum pump according to the principle that the step is 10% of Q y . When Q2 is greater than the rated pumping flow rate of the vacuum pump under the target negative pressure, re-allocate the flue gas flow according to the principle that the step is 10% of Q y10% of 10% is used to allocate the flue gas flow to the second vacuum pump until the flue gas flow allocated to the second vacuum pump is less than the rated pumping flow of the vacuum pump under the target negative pressure; if the flue gas flow Q2 allocated to the second vacuum pump is less than the rated pumping flow of this vacuum pump under the target negative pressure, then continue with a step size of Q y 10% is used to allocate the flue gas flow Q3 to the third vacuum pump, and the flow is allocated to each stage of the vacuum pump in this way. Finally, the system controller 22 calculates the vibration amplitudes of all the exhaustively obtained schemes of the vacuum pumps and obtains the vacuum pump combination scheme with the lowest vibration amplitude.

[0012] Preferably, when using the mixed integer quadratic programming algorithm to obtain the operating schemes of each vacuum pump in the vacuum pump combination scheme with the lowest vibration amplitude:

[0013] When the load rate of a certain vacuum pump in a certain operating scheme is less than 30%, it is discarded; when the number of equipment with the same rated pumping flow in the vacuum pumps is n, when the load rate of a certain equipment is lower than (1 - 1 / n), directly turn off this equipment; when the vibration amplitudes of multiple operating schemes are the same, preferentially select the operating scheme with a small total rated pumping flow of one or more vacuum pumps.

[0014] Using the mixed integer quadratic programming algorithm to obtain the vacuum pump combination scheme with the lowest vibration amplitude and the operating schemes of each vacuum pump in this combination scheme is based on the quadratic function relationship between the load rate and the vibration amplitude of the vacuum pump and the quadratic function relationship between the furnace negative pressure and the pumping rate;

[0015] Among them, the relationship between the furnace negative pressure and the pumping rate is:

[0016] S p = 0.34381P + 0.00205P 2 + 15.48851

[0017] Among them, S p —Pumping rate / L·min -1 , P—Furnace pressure / kPa.

[0018] The relationship between the load rate and the vibration amplitude of the vacuum pump is as follows:

[0019] According to the operating empirical formula of the pump, when the load rate is greater than 30%, the formula for the load rate and the rotational speed is:

[0020]

[0021] Among them, P1—Actual power / W, P0—Rated power / W, P1 / P0—Load rate of the vacuum pump, n0—Rated rotational speed / r·min -1 , n1—Actual rotational speed / r·min -1 .

[0022] The formula for the amplitude and rotational speed of the pump is as follows:

[0023]

[0024] where A is the vibration amplitude of the pump / mm, f is the operating frequency of the pump / Hz, g is the acceleration due to gravity / m·s -2 , v is the linear velocity at the maximum radius of rotation / m·s -1 , and l is the maximum radius of rotation of the pump / mm.

[0025] Substitute the formula for the amplitude and rotational speed of the pump into the relationship between the load rate and vibration amplitude of the vacuum pump to obtain the relationship between the load rate and vibration amplitude of the vacuum pump. The relationship between the load rate and vibration amplitude of the vacuum pump is as follows:

[0026]

[0027] where P1 is the actual power of the vacuum pump / W, P0 is the rated power of the vacuum pump / W, P1 / P0 is the load rate of the vacuum pump, n0 is the rated rotational speed of the vacuum pump / r·min -1 , A is the vibration amplitude of the vacuum pump / mm, g is the acceleration due to gravity / m·s -2 , l is the maximum radius of rotation of the vacuum pump / mm, C is the quadratic term coefficient. Since there is no quadratic term of the amplitude A in the original formula, C is taken as 0 here.

[0028] Preferably, the flue gas flowmeter selects a high-temperature resistant flowmeter, and the temperature is -25°C to 200°C.

[0029] The first implementation solution provided by the present invention is to provide a system used for a method that can stably maintain the negative pressure in the combustion chamber and accurately measure the flue gas components, including:

[0030] A flue gas flowmeter, which is arranged on the pipeline. The inlet of this pipeline is connected to the tail gas extraction port of the furnace, and the outlet of this pipeline is respectively connected to multiple input branch pipes;

[0031] At least one first-stage vacuum pump and at least one second-stage vacuum pump. The inlets of each vacuum pump are respectively connected in parallel through pipelines to the first input branch pipe, and the outlets of each vacuum pump are respectively connected through pipelines to the first output branch pipe;

[0032] At least one third-stage vacuum pump and at least one fourth-stage vacuum pump. The inlets of each vacuum pump are respectively connected in parallel through pipelines to the second input branch pipe, and the outlets of each vacuum pump are respectively connected through pipelines to the second output branch pipe;

[0033] The primary expansion vacuum pump and the secondary expansion vacuum pump, the inlets of each expansion vacuum pump are respectively connected in parallel to the third input branch pipe through pipelines, and the outlets of each expansion vacuum pump are respectively connected to the third output branch pipe through pipelines; the three output branch pipes are connected to the output pipe, and the output pipe is respectively connected to the flue gas component measurement port and the flue gas discharge port through a tee joint;

[0034] The pressure measuring gauge is arranged at the pressure measurement port of the system and is used to measure the furnace pressure;

[0035] The flue gas analyzer is arranged at the flue gas component measurement port after each vacuum pump and is used to analyze the flue gas components;

[0036] The system controller, the signal inlet ends of which are respectively connected to the flue gas flowmeter, the pressure measuring gauge and the flue gas analyzer, and the signal outlet ends of which are respectively connected to at least one primary vacuum pump, at least one secondary vacuum pump, at least one tertiary vacuum pump, at least one quaternary vacuum pump, the primary expansion vacuum pump and the secondary expansion vacuum pump. The system controller compares the 10% of the measured flue gas flow signal Q y with the capacities of at least one primary vacuum pump, at least one secondary vacuum pump, at least one tertiary vacuum pump, at least one quaternary vacuum pump, the primary expansion vacuum pump and the secondary expansion vacuum pump one by one, so as to select the number of each vacuum pump connected in parallel to the system, so as to reduce the combustion chamber furnace pressure to the target pressure when the vibration amplitude of each vacuum pump is the lowest.

[0037] Preferably, a buffer tank is further arranged between the flue gas flowmeter and the tail gas extraction port of the furnace. The inlet of the buffer tank is connected to the tail gas extraction port of the furnace, and the outlet of the buffer tank is connected to the flue gas flowmeter through a pipeline. The buffer tank is used to stabilize the pressure of the furnace combustion environment.

[0038] Preferably, discoloring silica gel and a filter membrane are arranged at the bottom inside the buffer tank, and the discoloring silica gel and the filter membrane are used to filter moisture and particulate matter in the flue gas.

[0039] Preferably, at least one primary vacuum pump, at least one secondary vacuum pump, at least one tertiary vacuum pump, at least one quaternary vacuum pump, the primary expansion vacuum pump and the secondary expansion vacuum pump are all adjustable-speed oil-free diaphragm vacuum pumps.

[0040] Preferably, valves are arranged on both the input branch pipe and the output branch pipe connected to the primary expansion vacuum pump and the secondary expansion vacuum pump.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. In the method given by the present invention, by measuring the flue gas flow Q with the flue gas flowmeter y , with the flue gas flow distribution step length of Q yObtain the number of parallel vacuum pumps for access based on the principle of 10% of [specific value] to minimize the vibration amplitude of each vacuum pump. Use the mixed integer quadratic programming algorithm to optimize the vacuum pump combination and the vacuum pump operation plan with the minimum vibration amplitude of the system as the goal, and obtain the optimal combination plan and operation plan of multiple vacuum pumps under the lowest vacuum pump vibration amplitude. This optimal combination plan and operation plan can minimize the impact of vibration and uneven pumping rate on the flame shape and pollutant generation. Thus, it solves the problem of the impact on the flame shape and pollutant generation characteristics caused by the unstable pumping rate and large vibration amplitude due to the small number of experimental conditions covered by a single vacuum pump in the prior art and the load rate of the vacuum pump being less than 30% in some conditions. At the same time, the flue gas analyzer is set at the flue gas component measurement port behind each vacuum pump to achieve accurate measurement of flue gas components within a wide negative pressure range.

[0043] 2. The system given by the present invention can create stable negative pressure combustion conditions in the combustion chamber. At the same time, under the stable negative pressure combustion conditions of the combustion chamber, accurate measurement of flue gas components within a wide negative pressure range can be achieved through the flue gas analyzer located at the flue gas component measurement port behind each vacuum pump. The system and method can be used to carry out research on the combustion characteristics of solid, liquid, and gas fuels under low-pressure conditions. It can reduce the cost of field tests on the plateau and provide guidance for the efficient and clean operation of equipment such as coal-fired boilers, methanol boilers, and gas boilers in plateau areas. Brief Description of the Drawings

[0044] Figure 1 It is a system diagram that can stabilize the negative pressure in the combustion chamber and accurately measure flue gas components.

[0045] Figure 2 It is a comparison image of premixed flames in plateau field experiments and simulated low-pressure experiments; among them, (a) is the plateau field experiment, and (b) is the experiment under simulated low-pressure conditions.

[0046] Figure 3 It is a comparison diagram of the axial temperature of premixed flames in plateau field experiments and simulated low-pressure experiments; among them, (a) is the excess air coefficient of 1.2 in the plateau field experiment, (b) is the excess air coefficient of 1.3 in the plateau field experiment, (c) is the excess air coefficient of 1.2 in the experiment under simulated low-pressure conditions, and (d) is the excess air coefficient of 1.3 in the experiment under simulated low-pressure conditions.

[0047] Figure 4 It is a comparison diagram of CO and NOx of premixed flames in plateau field experiments and simulated low-pressure experiments; among them, (a) is the CO generation characteristics of plateau field experiments and experiments under simulated low-pressure conditions, (b) is the NOx generation characteristics of plateau field experiments, and (c) is the NOx generation characteristics of experiments under simulated low-pressure conditions.

[0048] Description of the Reference Numerals:

[0049] 1. Exhaust gas extraction port at the tail of the furnace; 2. Buffer tank; 3. Flue gas flowmeter; 4. First-stage vacuum pump; 5. Second-stage vacuum pump; 6. Third-stage vacuum pump; 7. Fourth-stage vacuum pump; 8. First-stage expansion vacuum pump; 9. Second-stage expansion vacuum pump; 10. Flue gas component measurement port; 11. Flue gas discharge port; 12. First-stage speed governor; 13. Second-stage speed governor; 14. Third-stage speed governor; 15. Fourth-stage speed governor; 16. First-stage valve of expansion vacuum pump; 17. Second-stage valve of expansion vacuum pump; 18. Third-stage valve of expansion vacuum pump; 19. Fourth-stage valve of expansion vacuum pump; 20. Pressure measurement port; 21. Pressure measuring gauge; 22. System controller. Detailed implementation manners

[0050] In order to make the above objects, features, and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] The inventor found that existing systems mostly use vacuum pumps to create a negative pressure environment in the combustion chamber. However, both too low or too high loads of the vacuum pumps will lead to a higher vibration amplitude and gas extraction instability, and existing flue gas analysis can only work properly under negative pressure conditions with a vacuum degree of 0 - 20 kPa. Although the existing systems and their usage methods solve the problem of the existing systems for creating a negative pressure environment in the combustion chamber, they do not reasonably weaken the influence of the vibration and gas extraction rate of the vacuum pumps on fuel combustion, and cannot solve the problem of accurately measuring flue gas components under lower negative pressure conditions.

[0052] In view of this, the present invention provides a system and method that can stabilize the negative pressure in the combustion chamber and accurately measure flue gas components. By optimizing the combination of vacuum pumps and the operation plan, the influence of vibration and uneven gas extraction rate on the flame morphology and pollutant generation is minimized, and the position of the flue gas measurement port is reasonably arranged to achieve accurate measurement of flue gas components in a wide negative pressure range (0 - 101 kPa).

[0053] A method and system provided by the present invention that can stabilize the negative pressure in the combustion chamber and accurately measure flue gas components can be applied to the research on the combustion characteristics of gaseous, liquid, and solid fuels under negative pressure conditions.

[0054] As Figures 1 to 4 shown, the present invention provides a method for stabilizing the negative pressure in the combustion chamber and accurately measuring flue gas components, including the following steps:

[0055] The flue gas generated by combustion in the combustion chamber of the furnace is sent out from the tail of the furnace, and after filtration, the flue gas flow measured by the flue gas flowmeter 3 is Qy ; After the system controller 22 obtains the flue gas flow signal measured by the flue gas flowmeter 3, it uses the mixed integer quadratic programming algorithm to obtain the vacuum pump combination scheme with the lowest vibration amplitude and the operation schemes of each vacuum pump in this combination scheme with the principle that the allocated flue gas flow step is 10% of Q y ;

[0056] The system controller 22 controls the multi-stage vacuum pump according to the obtained vacuum pump combination scheme with the lowest vibration amplitude and the vacuum pump operation scheme to regulate the furnace pressure to the target pressure for stabilizing the negative pressure in the combustion chamber;

[0057] The flue gas generated by combustion in the combustion chamber furnace is sent to the flue gas analyzer for component analysis after being extracted by each vacuum pump. The flue gas analyzer is arranged at the flue gas component measurement port 10 behind each vacuum pump so that the flue gas analyzer can be used within one atmospheric pressure.

[0058] The flue gas analyzers commonly used in the prior art can only work normally under the negative pressure conditions with a sampling flow rate of 0.6 L / min -1 ~3.5 L / min -1 and a vacuum degree of 0 kPa to 20 kPa. The relevant patents that have been published arrange flue gas measurement holes on the side of the furnace. The sampling flow rate and working pressure of the flue gas analyzer cannot reach the rated working conditions, which will lead to inaccurate measurement of flue gas components.

[0059] The reason for the allocated flue gas flow step being 10% of Q y is that when the allocated flue gas flow step is less than 10% of Q y , the calculation amount increases. When the allocated flue gas flow step is greater than 10% of Q y , although the calculation amount decreases, the optimization is rougher and inaccurate. Therefore, considering the calculation amount and the accuracy of the calculation, the allocated flue gas flow step is determined to be 10% of Q y .

[0060] In the present invention, the flue gas generated by combustion in the combustion chamber furnace is sent to the flue gas analyzer for component analysis after being extracted by each vacuum pump. Since the pressure behind the vacuum pump is basically the standard atmospheric pressure, the normal working pressure of the flue gas analyzer can be satisfied, and accurate measurement of flue gas components can be realized.

[0061] Specifically, the determination method for the vacuum pump combination scheme with the lowest vibration amplitude is as follows:

[0062] The system controller 22 obtains the flow signal of the flue gas flow Q y , and then allocates the flue gas flow Q1 to the first vacuum pump according to the principle that the step is 10% of Q y . When Q1 is greater than the rated pumping flow rate of the vacuum pump under the target negative pressure, re-allocate the flue gas flow according to the step of Q y10% of 10% is allocated to the first vacuum pump until the gas flow rate allocated to the first vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure; if the gas flow rate Q1 allocated to the first vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure, then continue with a step size of Q y 10% is allocated to the second vacuum pump as the gas flow rate Q2. When Q2 is greater than the rated pumping flow rate of the vacuum pump under the target negative pressure, re - allocate with a step size of Q y 10% of 10% is allocated to the second vacuum pump until the gas flow rate allocated to the second vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure; if the gas flow rate Q2 allocated to the second vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure, then continue with a step size of Q y 10% is allocated to the third vacuum pump as the gas flow rate Q3. Allocate the flow rate to each stage of the vacuum pump in this way. Finally, the system controller 22 calculates the vibration amplitude of all the exhaustively obtained vacuum pump combinations and obtains the vacuum pump combination plan with the lowest vibration amplitude.

[0063] Specifically, the optimization space provided by the multi - stage vacuum pump can be used to adjust the pump speed and load during variable - condition experiments to minimize the system vibration amplitude and ensure the stability of the pumping rate. However, this will cause a relatively long calculation time for the optimization algorithm. To simplify the algorithm running time and improve the system sensitivity, when using the mixed - integer quadratic programming algorithm to obtain the operating plans of each vacuum pump in the vacuum pump combination plan with the lowest vibration amplitude:

[0064] When the load rate of a certain vacuum pump in a certain operating plan is less than 30%, it is discarded; when the number of devices with the same rated pumping flow rate in the vacuum pumps is n, and the load rate of a certain device is lower than (1 - 1 / n), directly turn off this device; when the vibration amplitudes of multiple operating plans are the same, preferentially select the operating plan with a smaller total rated pumping flow rate of one or more vacuum pumps.

[0065] Specifically, the use of the mixed - integer quadratic programming algorithm to obtain the vacuum pump combination plan with the lowest vibration amplitude and the operating plans of each vacuum pump in this combination plan is based on the quadratic function relationship between the load rate and vibration amplitude of the vacuum pump and the quadratic function relationship between the furnace negative pressure and the pumping rate;

[0066] The relationship between the furnace negative pressure and the pumping rate is:

[0067] S p = 0.34381P + 0.00205P 2 + 15.48851

[0068] where, S p — pumping rate / L·min -1 , P— furnace pressure / kPa.

[0069] The relationship between the load rate and the vibration amplitude of the vacuum pump is as follows:

[0070] (1) According to the operating empirical formula of the pump, when the load rate is greater than 30%, the formula for the load rate and the rotational speed is:

[0071]

[0072] where P1—the actual power / W, P0—the rated power / W, n0—the rated rotational speed / r·min -1 , n1—the actual rotational speed / r·min -1 .

[0073] (2) The formula for the amplitude of the pump and the rotational speed is:

[0074]

[0075] where A—the vibration amplitude of the pump / mm, f—the operating frequency of the pump / Hz, g—the acceleration due to gravity / m·s -2 , v—the linear velocity at the maximum radius of rotation / m·s -1 , l—the maximum radius of rotation of the pump / mm.

[0076] (3) Substitute the formula for the amplitude of the pump and the rotational speed into the relationship between the load rate and the vibration amplitude of the vacuum pump to obtain the relationship between the load rate and the vibration amplitude of the vacuum pump. The relationship between the load rate and the vibration amplitude of the vacuum pump is as follows:

[0077]

[0078] where P1—the actual power of the vacuum pump / W, P0—the rated power of the vacuum pump / W, P1 / P0—the load rate of the vacuum pump, n0—the rated rotational speed of the vacuum pump / r·min -1 , A—the vibration amplitude of the vacuum pump / mm, g—the acceleration due to gravity / m·s -2 , l—the maximum radius of rotation of the vacuum pump / mm, C—the quadratic coefficient. Since there is no quadratic term of the amplitude A in the original formula, C is taken as 0 here.

[0079] Specifically, the flue gas analyzer is set at the flue gas component measurement port 10 behind each vacuum pump so that the flue gas analyzer can be used within one atmospheric pressure.

[0080] Specifically, the flue gas flowmeter 3 selects a high-temperature resistant flowmeter with a temperature range of -25°C to 200°C.

[0081] As Figure 1 shown, a system used in a method for stabilizing the negative pressure in the combustion chamber and accurately measuring the flue gas components includes:

[0082] A flue gas flowmeter 3 is installed on a pipeline. The inlet of this pipeline is connected to the tail gas extraction port 1 of the furnace, and the outlet of this pipeline is respectively connected to multiple input branch pipes.

[0083] At least one primary vacuum pump 4 and at least one secondary vacuum pump 5. The inlets of each vacuum pump are respectively connected in parallel to the first input branch pipe through pipelines, and the outlets of each vacuum pump are respectively connected to the first output branch pipe through pipelines; each primary vacuum pump 4 is connected to a primary speed regulator 12, and each secondary vacuum pump 5 is connected to a secondary speed regulator 13.

[0084] At least one tertiary vacuum pump 6 and at least one quaternary vacuum pump 7. The inlets of each vacuum pump are respectively connected in parallel to the second input branch pipe through pipelines, and the outlets of each vacuum pump are respectively connected to the second output branch pipe through pipelines; each tertiary vacuum pump 6 is connected to a tertiary speed regulator 14, and each quaternary vacuum pump 7 is connected to a quaternary speed regulator 15.

[0085] A primary expansion vacuum pump 8 and a secondary expansion vacuum pump 9. The inlets of each expansion vacuum pump are respectively connected in parallel to the third input branch pipe through pipelines, and the outlets of each expansion vacuum pump are respectively connected to the third output branch pipe through pipelines; the three output branch pipes are connected to an output pipe, and the output pipe is respectively connected to a flue gas component measurement port 10 and a flue gas discharge port 11 through a tee; an expansion vacuum pump primary valve 16 is provided on the pipeline connecting the input branch pipe to the primary expansion vacuum pump 8, an expansion vacuum pump secondary valve 17 is provided on the pipeline connecting the input branch pipe to the secondary expansion vacuum pump 9, an expansion vacuum pump tertiary valve 18 is provided on the pipeline of the output branch pipe connected to the primary expansion vacuum pump 8, and an expansion vacuum pump quaternary valve 19 is provided on the pipeline of the output branch pipe connected to the secondary expansion vacuum pump 9.

[0086] A pressure gauge 21 is installed on the pressure measurement port 20 of the system for measuring the furnace pressure.

[0087] A flue gas analyzer is installed on the flue gas component measurement port 10 after each vacuum pump for analyzing the flue gas components;

[0088] A system controller 22. Its signal inlet ends are respectively connected to the flue gas flowmeter 3, the pressure gauge 20, and the flue gas analyzer, and its signal outlet ends are respectively connected to at least one primary vacuum pump 4, at least one secondary vacuum pump 5, at least one tertiary vacuum pump 6, at least one quaternary vacuum pump 7, the primary expansion vacuum pump 8, and the secondary expansion vacuum pump 9. The system controller 22 compares the measured flue gas flow signals one by one according to the flue gas flow signal Q y10% of that and the capacities of at least one primary vacuum pump 4, at least one secondary vacuum pump 5, at least one tertiary vacuum pump 6, at least one quaternary vacuum pump 7, a primary expansion vacuum pump 8 and a secondary expansion vacuum pump 9, so as to select the number of each vacuum pump connected in parallel to the system, so as to reduce the combustion chamber furnace pressure to the target pressure when the vibration amplitude of each vacuum pump is the lowest.

[0089] Specifically, a buffer tank 2 is further provided between the flue gas flowmeter 3 and the tail gas extraction port 1 of the furnace. The buffer tank 2 is connected to the flue gas flowmeter 3 and the tail gas extraction port 1 of the furnace through pipelines, and the buffer tank 2 is used to stabilize the pressure of the furnace combustion environment.

[0090] Specifically, discolored silica gel and a filter membrane are provided at the bottom inside the buffer tank 2. The discolored silica gel and the filter membrane are used to filter moisture and particulate matter in the flue gas, and the particulate matter includes carbon black.

[0091] Specifically, at least one primary vacuum pump 4, at least one secondary vacuum pump 5, at least one tertiary vacuum pump 6, at least one quaternary vacuum pump 7, a primary expansion vacuum pump 8 and a secondary expansion vacuum pump 9 are all adjustable-speed oil-free diaphragm vacuum pumps, which can effectively avoid the pollution of the flue gas components by the machine oil. Moreover, the primary expansion vacuum pump 8 and the secondary expansion vacuum pump 9 can be detachably replaced with adjustable-speed oil-free diaphragm vacuum pumps with different capacities and powers.

[0092] Specifically, valves are provided on both the input branch pipe and the output branch pipe connected to the primary expansion vacuum pump 8 and the secondary expansion vacuum pump 9. The valves are respectively a primary expansion vacuum pump valve 16, a secondary expansion vacuum pump valve 17, a tertiary expansion vacuum pump valve 18, and a quaternary expansion vacuum pump valve 19.

[0093] When the flue gas flow rate is 0L to 30L, the methods and systems given above that can stabilize the combustion chamber negative pressure and accurately measure the flue gas components are all applicable.

[0094] Embodiment

[0095] According to the system diagram (the system diagram is as Figure 1 shown) and method given by the present invention, a simulation low-pressure condition gas combustion test bench was independently designed and built. The rated pumping rates of the primary vacuum pump 4, the secondary vacuum pump 5, the tertiary vacuum pump 6 and the quaternary vacuum pump 7 are 5Lmin -1 , 10Lmin -1 , 15Lmin -1 and 20Lmin -1Field experiments were carried out on the plateau to verify the feasibility of the above system and its usage method. Table 1 shows the experimental conditions of the field experiment on the plateau and the gas combustion test bench for simulating low-pressure conditions built according to the present invention; Table 2 shows the vacuum pump combinations and operation schemes optimized by the MIQP algorithm in the embodiments. And the influence laws of air pressure on the combustion flame morphology and flue gas components of methane gas were obtained ( Figure 2 , Figure 3 and Figure 4 ).

[0096] Table 1 shows the experimental conditions

[0097]

[0098] Table 2 shows the vacuum pump combinations and operation schemes optimized by the MIQP algorithm

[0099]

[0100]

[0101] Figure 2 are the flame morphologies of the field experiment on the plateau and the simulation experiment. Among them, Figure 2 in (a) is the field experiment on the plateau, Figure 2 in (b) is the experiment under simulated low-pressure conditions. For the internal flame height, consistent results were obtained from the field experiment on the plateau and the experiment under simulated low-pressure conditions. When the excess air coefficient is 1.2 and 1.3, the internal flame height increases with the decrease of pressure. In particular, when the excess air coefficient is 1.2 in the field experiment on the plateau, there is a faint pale yellow flame around the internal flame. This is because the air-fuel mixture will trigger a primary combustion reaction in the internal flame zone, and some unburned compositions will trigger a secondary combustion reaction in the external flame zone. This is different from the experiment under simulated low-pressure conditions, mainly because the wall temperature in the field experiment on the plateau is 423.15K, while the wall temperature under simulated low-pressure conditions is 393.15K. The higher temperature increases the combustion reaction rate, resulting in complete combustion of the air-fuel mixture during primary combustion.

[0102] Figure 3 is the comparison chart of the pre-mixed flame axis temperature between the field experiment on the plateau and the simulated low-pressure test. Among them, Figure 3 in (a) is the excess air coefficient of 1.2 in the field experiment on the plateau, Figure 3 in (b) is the excess air coefficient of 1.3 in the field experiment on the plateau, Figure 3 in (c) is the excess air coefficient of 1.2 in the experiment under simulated low-pressure conditions, Figure 3 in (d) is the excess air coefficient of 1.3 in the experiment under simulated low-pressure conditions. The flame zone temperatures of both methods decrease with the decrease of pressure, while the flue gas temperature above the furnace increases with the decrease of pressure. Figure 4For the comparison chart of premixed flame CO and NO in plateau field experiments and simulated low-pressure tests x Among them Figure 4 (a) shows the CO generation characteristics of plateau field experiments and experiments under simulated low-pressure conditions Figure 4 (b) shows the NOx generation characteristics of plateau field experiments Figure 4 (c) shows the NOx generation characteristics of experiments under simulated low-pressure conditions. When the excess air coefficient is 1.2, the CO generated by both methods increases with the decrease of pressure. When the excess air coefficient is 1.3, the CO generated in the plateau field experiment increases with the decrease of air pressure. However, the CO generation in the experiment under simulated low-pressure conditions is 0. Due to the higher temperature in the simulation experiment, the generation of CO is much lower than that in the field experiment. The NO generated by both methods decreases with the decrease of pressure. Generally speaking, the flame morphology, temperature distribution and NO generation characteristics of the two methods are consistent. Therefore, the system and its use method proposed in the present invention, which can stabilize the negative pressure condition of the combustion chamber and accurately measure the flue gas components in a wide range of negative pressures, can be used to study the flame morphology and pollutant generation characteristics under negative pressure conditions

[0103] The most significant feature of the implementation of the present invention is to optimize the vacuum pump combination scheme and the vacuum pump operation scheme by using the MIQP (Mixed Integer Quadratic Programming) algorithm, effectively improving the stability of the system and minimizing the influence of the instability of the vacuum pump vibration and pumping rate on the measurement of flame morphology and flue gas components. The flue gas measurement holes are reasonably arranged, and all commercially available flue gas analyzers can be adapted to this experimental device. The present invention provides effective guidance for the development of experiments under simulated low-pressure conditions in plain areas

[0104] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications

Claims

1. A method for stabilizing the negative pressure in a combustion chamber and accurately measuring the components of flue gas, characterized in that, It includes the following steps: The flue gas generated by combustion in the combustion chamber furnace is sent out from the tail of the furnace, and the flue gas flow rate measured by the flue gas flowmeter (3) after filtration is Q y ; after the system controller (22) obtains the flue gas flow rate signal measured by the flue gas flowmeter (3), the mixed integer quadratic programming algorithm is adopted with the principle that the flue gas flow rate distribution step is 10% of Q y to obtain the vacuum pump combination scheme with the lowest vibration amplitude and the operation schemes of each vacuum pump in this combination scheme; The system controller (22) controls the multi-stage vacuum pump according to the obtained vacuum pump combination scheme with the lowest vibration amplitude and the vacuum pump operation scheme to regulate the furnace pressure to the target pressure for stabilizing the negative pressure in the combustion chamber; The flue gas generated by combustion in the furnace of the combustion chamber is sent to the flue gas analyzer for component analysis after being extracted by each vacuum pump, and the flue gas analyzer is arranged at the flue gas component measurement port (10) behind each vacuum pump.

2. The method for stably maintaining the negative pressure in the combustion chamber and accurately measuring the flue gas components according to claim 1, wherein The method for determining the vacuum pump combination scheme with the lowest vibration amplitude is as follows: The system controller (22) obtains the flow signal of the flue gas flow rate Q y and then allocates the flue gas flow rate Q1 to the first vacuum pump according to the principle that the step is 10% of Q y . When Q1 is greater than the rated pumping flow rate of the vacuum pump under the target negative pressure, the flue gas flow rate is re-allocated to the first vacuum pump according to the principle that the step is 10% of 10% of Q y until the flue gas flow rate allocated to the first vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure; If the flue gas flow rate Q1 allocated by the first vacuum pump is less than the rated pumping flow rate of this vacuum pump under the target negative pressure, then continue to allocate the flue gas flow rate Q2 to the second vacuum pump at a step size of 10% of Q y When Q2 is greater than the rated pumping flow rate of the vacuum pump under the target negative pressure, re-allocate the flue gas flow rate to the second vacuum pump at a step size of 10% of 10% of Q y until the flue gas flow rate allocated to the second vacuum pump is less than the rated pumping flow rate of the vacuum pump under the target negative pressure; if the flue gas flow rate Q2 allocated to the second vacuum pump is less than the rated pumping flow rate of this vacuum pump under the target negative pressure, then continue to allocate the flue gas flow rate Q3 to the third vacuum pump at a step size of 10% of Q y Allocate the flue gas flow rate to each stage of vacuum pump in turn according to this method. Finally, the system controller (22) calculates the vibration amplitude of all the vacuum pump combinations obtained by exhaustive enumeration and obtains the vacuum pump combination scheme with the lowest vibration amplitude.

3. A method for stabilizing the negative pressure in a combustion chamber and accurately measuring the components of flue gas according to claim 1, characterized in that, When obtaining the operation schemes of each vacuum pump in the vacuum pump combination scheme with the lowest vibration amplitude by using the mixed integer quadratic programming algorithm: When the load rate of a certain vacuum pump in a certain operation scheme is less than 30%, it is discarded; when the number of devices with the same rated extraction flow rate in the vacuum pumps is n, when the load rate of a certain device is lower than (1 - 1 / n), this device is directly turned off; when the vibration amplitudes of multiple operation schemes are the same, the operation scheme with a smaller total rated extraction flow rate of one or more vacuum pumps is preferably selected.

4. A method for stabilizing the negative pressure in a combustion chamber and accurately measuring the flue gas components according to claim 1, characterized in that The mixed integer quadratic programming algorithm is used to obtain the vacuum pump combination scheme with the lowest vibration amplitude and the operation schemes of each vacuum pump in this combination scheme based on the quadratic function relationship between the load rate and the vibration amplitude of the vacuum pump and the quadratic function relationship between the furnace negative pressure and the extraction rate; Among them, the relationship between the furnace negative pressure and the extraction rate is: S p = 0.34381P + 0.00205P 2 + 15.48851 Among them, S p —Pumping rate / L·min -1 , P—Furnace pressure / kPa; The relationship between the load rate and the vibration amplitude of the vacuum pump is as follows: Among them, P1—the actual power of the vacuum pump / W, P0—the rated power of the vacuum pump / W, P1 / P0—the load rate of the vacuum pump, n0—the rated speed of the vacuum pump / r·min -1 , A—the vibration amplitude of the vacuum pump / mm, g—the acceleration of gravity / m·s -2 , l—the maximum rotation radius of the vacuum pump / mm, C—the quadratic coefficient.

5. A method for stabilizing the negative pressure in a combustion chamber and accurately measuring the components of flue gas according to claim 1, characterized in that, The temperature resistance range of the flue gas flowmeter (3) is -25°C to 200°C.

6. A system capable of stabilizing the negative pressure in the combustion chamber and accurately measuring the flue gas components according to claim 1, characterized in that, It includes: Each vacuum pump includes at least one primary vacuum pump (4), at least one secondary vacuum pump (5), at least one tertiary vacuum pump (6), at least one quaternary vacuum pump (7), a primary expansion vacuum pump (8) and a secondary expansion vacuum pump (9); The flue gas flowmeter (3) is arranged on the pipeline, the inlet of the pipeline is connected to the tail gas extraction port (1) of the furnace, and the outlet of the pipeline is respectively connected to multiple input branch pipes; At least one primary vacuum pump (4) and at least one secondary vacuum pump (5), the inlets of each vacuum pump are respectively connected in parallel to the first input branch pipe through pipelines, and the outlets of each vacuum pump are respectively connected to the first output branch pipe through pipelines; At least one tertiary vacuum pump (6) and at least one quaternary vacuum pump (7), the inlets of each vacuum pump are respectively connected in parallel to the second input branch pipe through pipelines, and the outlets of each vacuum pump are respectively connected to the second output branch pipe through pipelines; The primary expansion vacuum pump (8) and the secondary expansion vacuum pump (9), the inlets of each expansion vacuum pump are respectively connected in parallel to the third input branch pipe through pipelines, and the outlets of each expansion vacuum pump are respectively connected to the third output branch pipe through pipelines; the three output branch pipes are connected to the output pipe, and the output pipe is respectively connected to the flue gas component measurement port (10) and the flue gas discharge port (11) through a tee; The pressure measuring gauge (21) is arranged at the pressure measurement port (20) of the system for measuring the furnace pressure; The flue gas analyzer is arranged at the flue gas component measurement port (10) behind each vacuum pump for analyzing the flue gas components; A system controller (22), whose signal input ends are respectively connected to a flue gas flowmeter (3), a pressure measuring gauge (20) and a flue gas analyzer, and whose signal output ends are respectively connected to at least one first-stage vacuum pump (4), at least one second-stage vacuum pump (5), at least one third-stage vacuum pump (6), at least one fourth-stage vacuum pump (7), a first-stage expansion vacuum pump (8) and a second-stage expansion vacuum pump (9). The system controller (22) compares, one by one, 10% of the measured flue gas flow signal Q y with the capacities of at least one first-stage vacuum pump (4), at least one second-stage vacuum pump (5), at least one third-stage vacuum pump (6), at least one fourth-stage vacuum pump (7), a first-stage expansion vacuum pump (8) and a second-stage expansion vacuum pump (9), so as to select the number of each vacuum pump connected in parallel to the system, so as to reduce the combustion chamber furnace pressure to the target pressure when the vibration amplitude of each vacuum pump is the lowest.

7. A system for stably maintaining the negative pressure in a combustion chamber and accurately measuring the components of flue gas according to claim 6, characterized in that, A buffer tank (2) is further provided between the flue gas flowmeter (3) and the tail gas extraction port (1) of the furnace. The inlet of the buffer tank (2) is connected to the tail gas extraction port (1) of the furnace, and the inlet of the buffer tank (2) is connected to the flue gas flowmeter (3) through a pipeline.

8. A system for stably maintaining the negative pressure in a combustion chamber and accurately measuring the components of flue gas according to claim 7, characterized in that, Discolored silica gel and a filter membrane are provided at the bottom inside the buffer tank (2), and the discolored silica gel and the filter membrane are used for filtering moisture and particulate matter in the flue gas.

9. A system for stably maintaining the negative pressure in a combustion chamber and accurately measuring the components of flue gas according to claim 6, wherein At least one primary vacuum pump (4), at least one secondary vacuum pump (5), at least one tertiary vacuum pump (6), at least one quaternary vacuum pump (7), a primary expansion vacuum pump (8), and a secondary expansion vacuum pump (9) are all adjustable-speed oil-free diaphragm vacuum pumps.

10. A system for stabilizing the negative pressure in the combustion chamber and accurately measuring the flue gas components according to claim 9, characterized in that, Valves are provided on both the input branch pipe and the output branch pipe connected to the primary expansion vacuum pump (8) and the secondary expansion vacuum pump (9).

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