Method for evaluating direct combustion of low-concentration gas

Abstract

The invention discloses a low-concentration gas direct combustion evaluation method, and relates to the technical field of gas combustion evaluation, and the method comprises the following steps: obtaining components and gas concentration of low-concentration gas; the components comprise CH4 and O2; determining air supply of the low-concentration gas combustion system according to the gas concentration; calculating the standard emission concentration of the atmospheric pollutants according to the air supply and the actually measured emission concentration of the atmospheric pollutants; the actually measured atmospheric pollutant emission concentration is the sum of the concentration of each component in the flue gas; the atmospheric pollutant standard emission concentration is the low-concentration gas direct combustion pollutant emission concentration; according to the atmospheric pollutant standard emission concentration, generating an evaluation index; the evaluation indexes comprise a NOx evaluation index, a particulate matter evaluation index and a burnout degree evaluation index. According to the method, the evaluation precision and accuracy can be improved, and a technical basis is provided for low-concentration gas direct combustion and utilization pollutant emission concentration detection and combustion effect evaluation.

Description

Technical Field

[0001] The invention relates to the technical field of gas combustion evaluation, and in particular to a method for evaluating direct combustion of low-concentration gas. Background Art

[0002] Coal mine gas utilization technology is divided into four concentration ranges according to methane concentration: >30%, 9% to 30%, 3% to 9%, and <3% for cascade utilization. When the methane concentration is between 9% and 30%, it is within the explosion limit of methane. There are great safety hazards in the transportation and utilization of gas. Generally, it is directly discharged after being diluted to less than 5%. When the concentration is between 3% and 9%, it is also within the explosion range. At present, some unconventional combustion technologies are mainly used to try to improve its utilization rate, including porous media combustion, pulsating combustion, catalytic combustion, etc.; methane with a concentration of <3% is usually utilized by relatively mature thermal oxidation technology (0.75% to 3%) and air-deficient oxidation technology (<0.75%), which requires additional energy.

[0003] The amount of coal mine gas extracted, utilized, and utilized are all on the rise, but the overall utilization rate is relatively low. This is mainly because when the CH4 concentration is too low (especially when the CH4 concentration is 3% to 9%), it cannot be ignited or maintain flame combustion. In addition, the gas flow and concentration fluctuate greatly. At the same time, it contains substances such as coal dust, sulfides, and moisture, which are difficult to be stably processed by conventional combustion technology. Its utilization rate is only 1%, and it can usually only be directly discharged. On the one hand, it brings about a serious greenhouse effect, and on the other hand, it also causes a large amount of high-quality energy to be wasted. The development of efficient, safe, stable, and clean low-concentration gas utilization technology is of great significance to alleviating energy and environmental problems.

[0004] Academician Yuan Liang pointed out that the development and utilization of coal mine gas at all concentrations, especially the utilization of gas with a concentration of 9% to 30%, is a major issue in improving the clean and efficient utilization of coal resources. The key scientific and technological issues that need to be tackled urgently include: basic theory of efficient development and utilization of coal mine gas, theoretical process technology of coal mine gas and coal chemical industry, graded and classified development and utilization technology of coal mine gas, low-concentration gas thermal storage oxidation and air-deficient oxidation technology, etc. According to statistics from relevant departments, the amount of methane discharged into the atmosphere by air-deficient gas in China each year is equivalent to the annual gas transmission volume of the West-East Gas Transmission Project, and the greenhouse gas effect generated is about 200 million tons of carbon dioxide equivalent. Although the concentration of wind-exhaust gas is extremely low, the total amount is extremely large. The methane it contains accounts for about 81% of the total methane in my country's coal mine gas, and the annual emission is 15 billion m3. 3 At present, mixing the exhaust air with high-concentration gas to form low-concentration gas that can be directly burned as fuel is an effective means to solve the exhaust air gas emission.

[0005] Low-concentration coal mine gas is mainly composed of gas (CH 4) and air. When the methane ratio reaches 9.5%, the oxygen content in the air can meet the CH 4 The stoichiometric requirements of combustion. When the methane ratio is further reduced, the oxygen content in the mixed gas can meet the oxygen required for the complete combustion of methane. At present, low-concentration gas combustion technologies include porous medium catalytic combustion, pulse combustion, etc. Different air distribution methods and air volumes are required for different gas contents. For combustion products, especially pollutant emissions, when converted according to the oxygen content of flue gas, it is necessary to make appropriate conversions based on whether air oxygen is added. Therefore, the baseline oxygen of flue gas used in low-concentration gas combustion cannot be set according to a certain fixed value. At the same time, there is a lack of evaluation standards for the combustion effect of the burner. Therefore, it is necessary to formulate technical specifications for the detection of pollutant emissions from low-concentration gas combustion to provide a technical basis for the detection of pollutant emission concentrations and the evaluation of combustion effects for direct combustion of low-concentration gas. Summary of the invention

[0006] The purpose of the present invention is to provide a method for evaluating the direct combustion of low-concentration gas, which can improve the precision and accuracy of the evaluation and provide a technical basis for the detection of pollutant emission concentration and the evaluation of combustion effect of the direct combustion of low-concentration gas.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a method for evaluating direct combustion of low-concentration gas, the method comprising:

[0009] Obtain the composition and concentration of low-concentration gas; the composition includes CH 4 and O 2 .

[0010] According to the gas concentration, air supply for the low-concentration gas combustion system is determined.

[0011] The baseline emission concentration of atmospheric pollutants is calculated based on the air supply and the measured emission concentration of atmospheric pollutants; the measured emission concentration of atmospheric pollutants is the sum of the concentrations of various components in the flue gas; the baseline emission concentration of atmospheric pollutants is the emission concentration of pollutants from direct combustion of low-concentration gas.

[0012] According to the atmospheric pollutant baseline emission concentration, an evaluation index is generated; the evaluation index includes: NO x Evaluation index, particulate matter evaluation index and burnout evaluation index.

[0013] Optionally, determining the air supply of the low-concentration gas combustion system according to the gas concentration specifically includes:

[0014] When CH 4When Vol%≥8%, increase the air supply to the low-concentration gas combustion system.

[0015] When 6% ≤ CH 4 When Vol% is less than 8%, it is determined manually whether to increase the air supply to the low-concentration gas combustion system.

[0016] When CH 4 When Vol%<6%, the air supply to the low-concentration gas combustion system will not be increased.

[0017] Optionally, the calculation formula for the baseline emission concentration of atmospheric pollutants is:

[0018]

[0019] Among them, C 基 is the baseline emission concentration of air pollutants, mg / m 3 ; C 实 is the measured atmospheric pollutant emission concentration, mg / m3; φ 基 is the reference oxygen content of dry flue gas, %; φ 实 is the measured oxygen content of dry flue gas, %.

[0020] Optionally, based on the baseline emission concentration of air pollutants, an evaluation index is generated, specifically including:

[0021] Obtain NO in flue gas x The content concentration and the content concentration of the combustible gas component; the combustible gas includes CH 4 and CO.

[0022] According to the NO x The concentration of NO x Evaluation indicators and particulate matter evaluation indicators.

[0023] A burnout evaluation index is generated according to the content concentration of the combustible gas component.

[0024] Optionally, the low-concentration gas combustion system comprises:

[0025] Low-concentration gas detector is used to detect the composition and concentration of low-concentration gas.

[0026] Gas mixer, used to mix low concentration gas and air.

[0027] Flame arrester, used to prevent the spread of flame.

[0028] Low-concentration gas burner is used to burn low-concentration gas.

[0029] The combustion chamber is used to match the low-concentration gas burner and adjust the furnace size according to the combustion characteristics of the low-concentration gas burner; the combustion characteristics include: output thermal power, volumetric heat intensity, burner flame diameter and flame length.

[0030] Smoke composition detector, used to detect smoke components.

[0031] The first flow detection device is used to detect the flow of low-concentration gas.

[0032] The first pressure detection transposition is used to detect the pressure of low-concentration gas.

[0033] The first temperature detection device is used to detect the temperature of the low-concentration gas.

[0034] The second flow detection device is used to detect the flow of air.

[0035] The second pressure detection transposition is used to detect the pressure of the air.

[0036] The second temperature detection device is used to detect the temperature of the air.

[0037] Optionally, the low-concentration gas direct combustion evaluation method further includes:

[0038] The pipeline Reynolds number is used to determine whether the pipeline flow is in a turbulent state and obtain a judgment result.

[0039] If the judgment result is yes, the pipeline Reynolds number is greater than 2200.

[0040] If the judgment result is no, the pipeline Reynolds number is less than or equal to 2200.

[0041] Optionally, the calculation formula of the pipeline Reynolds number is:

[0042]

[0043] Where Re is the pipeline Reynolds number, ρ is the gas density, kg / m 3 ; ν is the gas velocity, m / s; D is the hydraulic diameter of the pipe, m; μ is the gas viscosity, Pa.s.

[0044] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0045] The present invention provides a method for evaluating direct combustion of low-concentration gas, by obtaining the composition and gas concentration of low-concentration gas; determining the air supply of the low-concentration gas combustion system according to the gas concentration; calculating the atmospheric pollutant baseline emission concentration according to the air supply and the measured atmospheric pollutant emission concentration; and then generating an evaluation index according to the atmospheric pollutant baseline emission concentration. The present invention can improve the precision and accuracy of the evaluation, realize dynamic air supply through online measurement of gas concentration and flue gas composition, ensure the repeatability of combustion, and improve the reliability of pollutant emission calculation through the determination of oxygen baseline concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 This is an application environment diagram of a low-concentration gas direct combustion evaluation method in one embodiment of the present invention.

[0048] Figure 2 A schematic flow chart of a method for evaluating direct combustion of low-concentration gas provided in one embodiment of the present invention.

[0049] Figure 3 A schematic structural diagram of a low-concentration gas combustion system provided in one embodiment of the present invention.

[0050] Figure 4 A schematic diagram of low-concentration gas measurement point requirements provided by an embodiment of the present invention.

[0051] Reference numerals:

[0052] 1- low concentration gas detector; 2- gas mixer; 3- flame arrester; 4- low concentration gas burner; 5- combustion chamber; 6- smoke composition detector. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] The low-concentration gas direct combustion evaluation method provided by the embodiment of the present invention can be applied to Figure 1 In the application environment shown in FIG. 1 , the terminal 102 communicates with the server 104 via a network. The data storage system can store data that the server 104 needs to process. The data storage system can be set up separately, integrated on the server 104, or placed on the cloud or other servers. The terminal 102 can send the obtained low-concentration gas composition and gas concentration to the server 104, and the composition includes CH 4 and O 2 ; After receiving the composition and gas concentration of the low-concentration gas, the server 104 determines the air supply of the low-concentration gas combustion system according to the composition and gas concentration of the low-concentration gas; calculates the baseline emission concentration of atmospheric pollutants according to the air supply and the measured atmospheric pollutant emission concentration; the measured atmospheric pollutant emission concentration is the sum of the concentrations of each component in the flue gas; the atmospheric pollutant baseline emission concentration is the pollutant emission concentration of the direct combustion of the low-concentration gas; generates evaluation indicators according to the atmospheric pollutant baseline emission concentration; the evaluation indicators include: NO x Evaluation index, particulate matter evaluation index and burnout evaluation index. The server 104 can feed back the obtained evaluation index to the terminal 102. In addition, in some embodiments, the low-concentration gas direct combustion evaluation method can also be implemented by the server 104 or the terminal 102 alone, such as the terminal 102 can directly perform combustion evaluation on the composition and gas concentration of the low-concentration gas, or the server 104 can obtain the composition and gas concentration of the low-concentration gas from the data storage system, and perform combustion evaluation on the composition and gas concentration of the low-concentration gas.

[0056] The terminal 102 may be, but is not limited to, various desktop computers, laptop computers, smart phones, and tablet computers. The server 104 may be implemented as an independent server or a server cluster consisting of multiple servers, or may be a cloud server.

[0057] In an exemplary embodiment, Figure 2 As shown, a method for evaluating direct combustion of low-concentration gas is provided. The method is executed by a computer device, and can be executed by a computer device such as a terminal or a server alone, or by a terminal and a server together. In an embodiment of the present invention, the method is applied to Figure 1 The server 104 in the example is used as an example to illustrate the method, which includes the following steps S1 to S4. Among them:

[0058] S1: Obtain the composition and concentration of low-concentration gas; the composition includes CH 4 and O 2 .

[0059] S2: Determine the air supply of the low-concentration gas combustion system according to the gas concentration.

[0060] S3: Calculate the baseline emission concentration of atmospheric pollutants based on the air supply and the measured emission concentration of atmospheric pollutants; the measured emission concentration of atmospheric pollutants is the sum of the concentrations of various components in the flue gas; the baseline emission concentration of atmospheric pollutants is the emission concentration of pollutants from direct combustion of low-concentration gas.

[0061] S4: Generate evaluation indicators based on the baseline emission concentration of atmospheric pollutants; the evaluation indicators include: NO x Evaluation index, particulate matter evaluation index and burnout evaluation index.

[0062] The implementation of the above-mentioned steps S1 to S4 can improve the precision and accuracy of the evaluation, realize dynamic air supply through online measurement of gas concentration and flue gas composition, ensure the repeatability of combustion, and improve the reliability of pollutant emission calculation by determining the oxygen baseline concentration.

[0063] like Figure 3 As shown, the low-concentration gas combustion system includes:

[0064] The low-concentration gas detector 1 is used to detect the composition and concentration of low-concentration gas.

[0065] The gas mixer 2 is used for mixing low-concentration gas and air.

[0066] The flame arrester 3 is used to prevent the spread of flame.

[0067] The low-concentration gas burner 4 is used for burning low-concentration gas.

[0068] The combustion chamber 5 is used to match the low-concentration gas burner and adjust the size of the furnace according to the combustion characteristics of the low-concentration gas burner; the combustion characteristics include: output heat power, volume heat intensity (load), burner flame diameter and flame length. It is ensured that there is no open flame at the combustion chamber outlet. The furnace volume heat load value range is generally 300-1000kW / m 3 A flame observation window is set at the combustion chamber outlet.

[0069] The smoke component detector 6 is used to detect the smoke components.

[0070] The first flow detection device is used to detect the flow of low-concentration gas.

[0071] The first pressure detection transposition is used to detect the pressure of low-concentration gas.

[0072] The first temperature detection device is used to detect the temperature of the low-concentration gas.

[0073] The second flow detection device is used to detect the flow of air.

[0074] The second pressure detection transposition is used to detect the pressure of the air.

[0075] The second temperature detection device is used to detect the temperature of the air.

[0076] The first flow detection device, the first pressure detection device and the first temperature detection device are respectively connected to Figure 3 The second flow detection device, the second pressure detection device and the second temperature detection device are respectively connected to the low concentration gas L, P and T correspondingly; Figure 3 In the middle, L, P and T correspond to those connected to the air.

[0077] As an optional implementation, when performing low-concentration gas component detection, CH 4 and O 2 It is a required option. The detection of other gas components shall be determined according to the on-site conditions.

[0078] When measuring flue gas components, NO x , particulate matter, SO 2 (Not subject to assessment), CH 4 ,CO,CO 2 , O 2 It is a required option. The detection of other gas components shall be determined according to the on-site conditions.

[0079] In another exemplary embodiment of the present invention, the low-concentration gas combustion system should determine whether to increase air supply as needed according to the fluctuation of gas concentration, that is, in step S2, specifically including:

[0080] S21: When CH 4 When Vol%≥8%, increase the air supply to the low-concentration gas combustion system.

[0081] S22: When 6% ≤ CH 4 When Vol% is less than 8%, it is determined manually whether to increase the air supply to the low-concentration gas combustion system.

[0082] S23: When CH 4 When Vol%<6%, the air supply to the low-concentration gas combustion system will not be increased.

[0083] During the evaluation process, CH 4The volume content fluctuation should not be greater than ±2%, and the low-concentration gas concentration range should be between 3% and 9%.

[0084] Pollutant emissions from direct combustion of low-concentration gas should be converted based on whether combustion air is added. For details, see formula (1).

[0085]

[0086] Among them, C 基 is the baseline emission concentration of air pollutants, mg / m3; C 实 is the measured atmospheric pollutant emission concentration, mg / m3; φ 基 is the reference oxygen content of dry flue gas, %; φ 实 is the measured oxygen content of dry flue gas, %. The reference oxygen content of dry flue gas is selected according to Table 1.

[0087] Table 1 Dry flue gas reference oxygen content

[0088] Serial number Low concentration gas methane content (Vol%) <![CDATA[Reference oxygen content φ 基 / %]]> 1 Vol≥8 3 2 6≤Vol<8 5 3 Vol<6 Based on the measured oxygen content in the flue gas

[0089] Measuring points should be set for pipeline flow, temperature and pressure. For detailed arrangement, see Figure 3 and Figure 4 .

[0090] a) The front end of the flow measurement point should have a horizontal pipe length of at least 5D, and the distance between the front and rear straight pipe sections required by the flow meter should be met.

[0091] b) The distance between the three measuring points of flow, temperature and pressure shall not exceed 0.15D. The accuracy requirements are shown in Table 2.

[0092] c) Install the flow meter correctly according to the flow meter type. The insertion direction of the insertion flow meter is perpendicular to the air flow direction, and the insertion depth is 1 / 2 of the inner diameter of the pipe.

[0093] d) The insertion depth of the temperature measuring point should be close to the center of the pipeline to avoid direct contact with the wall; the pressure and temperature measuring points can be staggered, and the pressure gauge should be installed vertically on the horizontal plane.

[0094] Table 2 Accuracy requirements

[0095] Serial number Test items Allowable error 1 Gas flow ±0.5％ 2 Gas pressure ±10Pa 3 Gas temperature ±1℃ 4 <![CDATA[O 2 , CH 4 Content]]> ±0.2％ 5 Other test gas content ±0.5％

[0096] The insertion depth of the sampling point for low-concentration gas component detection should be greater than 0.3D, and the CH 4 and O 2 Take real-time measurements.

[0097] In another exemplary embodiment of the present invention, when calculating the theoretical flue gas volume, the following steps are included:

[0098] A1: Assuming that the low-concentration gas is completely burned, the reaction equation is shown in equation (2). The gas volume flow rate is converted into the standard state (273.15K, 1atm) flow rate. The flue gas volume flow rate should be equal to the sum of the low-concentration gas flow rate and the air flow rate. The relative error between the actual measured flue gas standard state flow rate and the low-concentration gas standard state flow rate and the air standard state flow rate should not be greater than ±1%.

[0099] CH 4 +2O 2 =CO 2 +H 2 O (2);

[0100] The pipeline flow should be in a turbulent state, that is, the pipeline Reynolds number Re>2200. That is, the low-concentration gas direct combustion evaluation method also includes:

[0101] S5: Use the pipeline Reynolds number to determine whether the pipeline flow is in a turbulent state and obtain a determination result.

[0102] S6: If the judgment result is yes, the pipeline Reynolds number is greater than 2200.

[0103] S7: If the judgment result is no, the pipeline Reynolds number is less than or equal to 2200.

[0104] The calculation formula of the pipeline Reynolds number is:

[0105]

[0106] Where Re is the pipeline Reynolds number, ρ is the gas density, kg / m 3 ; ν is the gas velocity, m / s; D is the hydraulic diameter of the pipe, m; μ is the gas viscosity, Pa.s.

[0107] A2: Low concentration gas composition is CH 4 , O 2 and N 2 The density and viscosity of low-concentration gas can be estimated by equations (4) and (5).

[0108]

[0109] Among them, ρ ws is the density of low concentration gas; O 2 Volume fraction; CH 4 Volume fraction; N 2 Volume fraction; P is the pressure value measured inside the tube, Pa; T is the temperature value measured inside the tube, K.

[0110]

[0111] Among them, φij is the molecular ratio coefficient; m is the empirical coefficient; M is the molecular weight; η 0 is the gas viscosity at 273.15K, Pa.s; T is the temperature, K; T 0 =273.15K; n is the total number of components; i is the i-th component. η 0 and m are shown in Table 3.

[0112] Table 3 η of the detected gas 0 and m value

[0113] Serial number substance <![CDATA[η 0 ×10 6 kg.s.m -2 ]]> m 1 <![CDATA[N 2 ]]> 1.70 0.68 2 <![CDATA[O 2 ]]> 1.98 0.693 3 <![CDATA[CH 4 ]]> 1.06 0.76 4 <![CDATA[CO 2 ]]> 1.43 0.82 5 <![CDATA[H 2 The]]> 0.84 1.20

[0114] A3: The smoke composition is based on CH 4 After the reaction is complete, the air contains only O 2 and N 2 , ignoring the impurities in the low-concentration gas and the water vapor brought in from the air, the flue gas density and viscosity are estimated as shown in equations (8) and (5).

[0115]

[0116]

[0117] in, O in low concentration gas 2 Volume fraction; O in the air 2 volume fraction, 0.21; CH in low concentration gas 4 Volume fraction; N in low concentration gas 2 Volume fraction; N in the air 2 Volume fraction, 0.79; V ws is the low concentration gas flow rate, Nm3 / h; V a is the air flow rate, Nm 3 / h; For CO 2 Volume fraction; H 2 O volume fraction.

[0118] In another exemplary embodiment of the present invention, in step S4, specifically including:

[0119] S41: Obtain NO in flue gas separately x The content concentration and the content concentration of the combustible gas component; the combustible gas includes CH 4 and CO.

[0120] S42: According to the NOx The concentration of NO x Evaluation indicators and particulate matter evaluation indicators.

[0121] S43: Generate a burnout evaluation index according to the content concentration of the combustible gas component.

[0122] In this embodiment, the burner is evaluated based on the pollutant composition and combustible gas composition at the flue outlet. The stable operation time is not less than 20 minutes, the sampling time is not less than 10 minutes, the sampling frequency is not less than 1 minute / time, and the average value within 10 minutes is taken as the evaluation basis. x The evaluation indexes are shown in Table 4, the particulate matter evaluation indexes are shown in Table 5, and the burnout evaluation indexes are shown in Table 6.

[0123] Table 4 NO x Generate indicator evaluation

[0124] Serial number <![CDATA[Flue gas NO x Content mg / m3]]> grade 1 ≤50 1 2 ≤100 2 3 ≤200 3 4 ＞200 4

[0125] Table 5 Evaluation of particle generation index

[0126]

[0127]

[0128] Table 6 Burnout index evaluation

[0129] Serial number <![CDATA[Flue gas CH 4 + CO content mg / m 3 > grade 1 ≤50 1 2 ≤100 2 3 ≤200 3 4 ＞200 4

[0130] The present invention can improve the precision and accuracy of evaluation, realize dynamic air supply through online measurement of gas concentration and flue gas composition, ensure the repeatability of combustion, and improve the reliability of pollutant emission calculation through determination of oxygen reference concentration. The accuracy of Re number calculation is determined by calculating viscosity, ensuring that each parameter is obtained under turbulent state.

[0131] The present invention also provides an application scenario, which applies the above-mentioned low-concentration gas direct combustion evaluation method. Specifically: the low-concentration gas direct combustion evaluation method provided in this embodiment can be applied in the low-concentration gas direct combustion scenario. The low-concentration gas direct combustion scenario includes: low-concentration gas composition and gas concentration acquisition link, air supply link, atmospheric pollutant baseline emission concentration calculation link and evaluation link; according to the acquired gas concentration, the air supply of the low-concentration gas combustion system is determined; and then according to the air supply and the measured atmospheric pollutant emission concentration, the atmospheric pollutant baseline emission concentration can be calculated; finally, according to the atmospheric pollutant baseline emission concentration, the evaluation index can be generated; the evaluation index includes: NO x Evaluation index, particulate matter evaluation index and burnout evaluation index.

[0132] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for evaluating direct combustion of low-concentration gas, characterized in that: The low-concentration gas direct combustion evaluation method comprises: Obtaining the composition and gas concentration of low-concentration gas; the composition includes CH4 and O2; Determining air supply for a low-concentration gas combustion system according to the gas concentration; Calculate the atmospheric pollutant baseline emission concentration based on the air supply and the measured atmospheric pollutant emission concentration; the measured atmospheric pollutant emission concentration is the sum of the concentrations of various components in the flue gas; the atmospheric pollutant baseline emission concentration is the emission concentration of pollutants from direct combustion of low-concentration gas; According to the atmospheric pollutant baseline emission concentration, an evaluation index is generated; the evaluation index includes: NO x Evaluation index, particulate matter evaluation index and burnout evaluation index.

2. The low-concentration gas direct combustion evaluation method according to claim 1, characterized in that: According to the gas concentration, the air supply of the low-concentration gas combustion system is determined, specifically including: When CH4Vol%≥8%, increase the air supply to the low-concentration gas combustion system; When 6%≤CH4Vol%<8%, it is determined manually whether to increase the air supply of the low-concentration gas combustion system; When CH4Vol%<6%, the air supply to the low-concentration gas combustion system will not be increased.

3. The low-concentration gas direct combustion evaluation method according to claim 1, characterized in that: The calculation formula for the baseline emission concentration of air pollutants is: Among them, C 基 is the baseline emission concentration of air pollutants, mg / m 3 ; C 实 is the measured atmospheric pollutant emission concentration, mg / m3; φ 基 is the reference oxygen content of dry flue gas, %; φ 实 is the measured oxygen content of dry flue gas, %.

4. The low-concentration gas direct combustion evaluation method according to claim 1, characterized in that: According to the baseline emission concentration of air pollutants, evaluation indicators are generated, including: Obtain NO in flue gas x The content concentration and the content concentration of the combustible gas components; the combustible gas includes CH4 and CO; According to the NO x The concentration of NO x Evaluation index and particle evaluation index; A burnout evaluation index is generated according to the content concentration of the combustible gas component.

5. The low-concentration gas direct combustion evaluation method according to claim 1, characterized in that: The low-concentration gas combustion system comprises: Low-concentration gas detector, used to detect the composition and concentration of low-concentration gas; Gas mixer, used to mix low-concentration gas and air; Flame arrester, used to prevent the spread of flame; Low-concentration gas burner, used for burning low-concentration gas; A combustion chamber, used to match the low-concentration gas burner, and to adjust the size of the furnace according to the combustion characteristics of the low-concentration gas burner; the combustion characteristics include: output heat power, volume heat intensity, burner flame diameter and flame length; Smoke composition detector, used to detect smoke components; The first flow detection device is used to detect the flow of low-concentration gas; The first pressure detection transposition is used to detect the pressure of low-concentration gas; A first temperature detection device, used to detect the temperature of low-concentration gas; A second flow detection device, used for detecting the flow rate of air; The second pressure detection transposition is used to detect the pressure of the air; The second temperature detection device is used to detect the temperature of the air.

6. The low-concentration gas direct combustion evaluation method according to claim 1, characterized in that: The low-concentration gas direct combustion evaluation method also includes: The pipeline Reynolds number is used to determine whether the pipeline flow is in a turbulent state and obtain a judgment result; If the judgment result is yes, the pipeline Reynolds number is greater than 2200; If the judgment result is no, the pipeline Reynolds number is less than or equal to 2200.

7. The low-concentration gas direct combustion evaluation method according to claim 6, characterized in that: The calculation formula of the pipeline Reynolds number is: Where Re is the pipeline Reynolds number, ρ is the gas density, kg / m 3 ; ν is the gas velocity, m / s; D is the hydraulic diameter of the pipe, m; μ is the gas viscosity, Pa.s.

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