A method for correcting the monitoring results of heating furnace flue gas emission pollutants in an oxygen-enriched combustion state

Abstract

The application discloses a correction method for monitoring results of flue gas emission pollutants in a heating furnace under an oxygen-enriched combustion state, and belongs to the technical field of flue gas pollutant monitoring. The application takes CO2 in flue gas as a reference object, and obtains a corresponding compensation correction coefficient by comparing the difference between a theoretical calculation value of CO2 content in flue gas under air combustion with an oxygen content of 21% and a measured value of CO2 in flue gas under an oxygen-enriched combustion state, so as to realize correction of the monitoring results of flue gas pollutants under the oxygen-enriched combustion state on the monitoring results of flue gas pollutants under corresponding air combustion. The application can effectively realize correction of the monitoring results of flue gas pollutants under the oxygen-enriched combustion state on the monitoring results of flue gas pollutants under corresponding air combustion, and is helpful to popularization and application of energy-saving and carbon-reducing technologies such as oxygen-enriched combustion.

Description

Technical Field

[0001] This invention relates to the field of flue gas pollutant monitoring technology, and in particular to a method for correcting the monitoring results of pollutant emissions from a heating furnace under oxygen-enriched combustion conditions. Background Technology

[0002] Currently, the state regulates the emissions of SO2 and NO from thermal equipment such as steel rolling heating furnaces. x Emission intensity limits have been established for pollutants such as particulate matter. Generally, the oxygen conversion method is used, which uses an air oxygen content of 21% as a baseline and calculates the emission level of flue gas at the same specified oxygen content to determine whether emissions meet standards. This method eliminates the interference of different air distribution volumes on monitoring results, ensuring standardized and consistent results.

[0003] With the requirements of the national "dual carbon" policy, oxy-fuel combustion technology has gradually been recognized and adopted by the industry due to its significant energy-saving and carbon-reduction effects. However, the oxygen content of the combustion air used in oxy-fuel combustion is greater than 21%. As a result, the oxygen conversion calculation based on the existing 21% oxygen content in the air yields a higher evaluation value than that obtained using air-assisted combustion technology, and may even lead to excessive emissions, directly affecting the promotion and application of oxy-fuel combustion technology. Summary of the Invention

[0004] 1. The technical problem that the invention aims to solve

[0005] In view of the problems existing in the prior art, the present invention provides a method for correcting the monitoring results of pollutants emitted from a heating furnace under oxy-fuel combustion conditions. This invention can effectively correct the monitoring results of pollutants emitted from flue gas under oxy-fuel combustion conditions for monitoring results under corresponding air-assisted combustion conditions, thus contributing to the promotion and application of energy-saving and carbon-reducing technologies such as oxy-fuel combustion.

[0006] 2. Technical Solution

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] The present invention discloses a method for correcting the monitoring results of pollutants emitted from a heating furnace under oxy-fuel combustion conditions. Using CO2 in the flue gas as a reference, the method compares the theoretically calculated CO2 content in the flue gas under oxy-fuel combustion with the measured CO2 content under oxy-fuel combustion conditions with the actual measured CO2 content under oxy-fuel combustion conditions. The method then obtains a corresponding compensation correction coefficient to correct the monitoring results of pollutants emitted from the flue gas under oxy-fuel combustion conditions for the corresponding monitoring results under oxy-fuel combustion.

[0009] Furthermore, the specific process for obtaining the correction coefficient is as follows:

[0010] (1) Under air-supported combustion conditions, obtain 1m3 The volumes of CO2, N2, and H2O in the combustion products of coal gas are calculated, and the volume percentage of CO2 in the dry flue gas is calculated accordingly.

[0011] (2) Under actual oxygen-enriched combustion conditions, the volume percentages of O2 and CO2 components in the flue gas are obtained through online monitoring, with O2 as the metric. 2富氧 CO 2富氧 express;

[0012] (3) Under air-supported combustion conditions, the percentage content of O2 and CO2 in flue gas is converted to the same oxygen content as under oxygen-enriched combustion conditions to obtain the CO2 conversion value. 1 express;

[0013] (4) The correction factor is the dry flue gas CO2 under the same reference oxygen and air-supported combustion conditions. 1 Content and CO content in dry flue gas under oxygen-enriched combustion conditions 2富氧 The ratio of content.

[0014] Furthermore, in step (1), under air-assisted combustion conditions, the volume percentage of dry gas components is first measured, and the volume percentage of wet gas components is calculated based on this volume percentage; based on the obtained volume percentage of wet gas components, the theoretical dry air volume L0g is calculated, and then the volume percentage of 1m³ is extrapolated. 3 The volume of CO2, N2, and H2O in the combustion products of coal gas is used to calculate the volume percentage of the wet flue gas components, thereby determining the volume percentage of CO2 in the dry flue gas.

[0015] Furthermore, in step (1), the measured dry gas components include H2, CH4, CO, and C. n H m CO2, O2, N2 and H2O.

[0016] Furthermore, in step (1), under the condition of obtaining the volume percentage of dry gas components, the volume percentage of wet gas components is converted using a temperature of 45°C and a water volume percentage of 9.45% in the gas under saturated conditions at this temperature as the standard.

[0017] Furthermore, in step (1), the formula for calculating the theoretical dry air volume is as follows:

[0018] Theoretical dry air quantity L0g = 0.0238 (H2) s +CO s )+0.0952*CH4 s +0.0476*3*CmHn s -0.0476*O2 s

[0019] In the formula, H2s CO s CH4 s 、CmHn s O2 s This indicates the volume percentage of the corresponding wet gas composition.

[0020] Furthermore, in step (1), 1m 3 The formulas for calculating the volumes of CO2, N2, and H2O in the combustion products of coal gas are as follows:

[0021] CO2=(CO s +2CmHn s +CO2 s +CH4 s ) / 100

[0022] N2=N2 s / 100+(100-21) / 100*L0g

[0023] H2O=((H2 s +2*(CmHn s +CH4 s )+H2O s ) / 100+gk*0.00124

[0024] In the formula, CO2 s CH4 s N2 s H2O s This indicates the volume percentage of the corresponding wet gas component, and gk indicates the moisture content of the dry air.

[0025] Furthermore, step (3) involves monitoring the oxygen volume percentage (O2) obtained in step (2) under oxygen-enriched combustion conditions online. 2富氧 It is used as a baseline oxygen value for conversion.

[0026] Furthermore, in step (3) CO2 1 The formula for calculating the content is based on the national standard GB28665-2012 "Emission Standard of Air Pollutants for Steel Rolling Industry".

[0027] Furthermore, a monitoring system is used to collect data for the correction process. The monitoring system includes a flue gas analyzer and a coal gas analyzer. The heating furnace is connected to the main flue gas pipe, which is connected to the chimney. A sampling port is set in the middle of the chimney, and the sampling port is connected to the flue gas analyzer via a flue gas sampling pipe. The heating furnace is connected to a coal gas branch pipe, and the coal gas sampling pipe takes samples from the coal gas branch pipe and is connected to the coal gas analyzer.

[0028] 3. Beneficial effects

[0029] Compared with existing known technologies, the technical solution provided by this invention has the following significant advantages:

[0030] This invention uses CO2 in flue gas as a reference. By comparing the theoretically calculated CO2 content in flue gas under air-assisted combustion (oxygen content of 21%) with the measured CO2 content in flue gas under oxy-fuel combustion, a corresponding compensation correction coefficient is obtained. This allows for the correction of flue gas pollutant monitoring results under oxy-fuel combustion to those under corresponding air-assisted combustion, which helps promote the application of energy-saving and carbon-reducing technologies such as oxy-fuel combustion. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the flue gas emission pollutant monitoring system of the heating furnace of the present invention.

[0032] Figure 2 This is a schematic diagram of the modified process of the present invention.

[0033] Explanation of the labels in the diagram:

[0034] 1. Heating furnace; 2. Burner; 3. Gas branch pipe; 4. Air branch pipe; 5. Flue gas main pipe; 6. Chimney; 7. Flue gas intake pipe; 8. Gas intake pipe. Detailed Implementation

[0035] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0036] This invention uses CO2 in flue gas as a reference and obtains the theoretical calculation value of CO2 content in flue gas under air-assisted combustion (oxygen content of 21%) through gas composition analysis. By comparing the difference between the measured value of CO2 in flue gas under oxygen-enriched combustion and the actual value, a corresponding compensation correction coefficient is obtained to correct the flue gas composition monitoring results under oxygen-enriched combustion and the flue gas composition monitoring results under air-assisted combustion.

[0037] Example 1

[0038] Combination Figure 1 This embodiment mainly consists of a heating furnace, a gas composition monitoring system, and an online flue gas monitoring system, forming a heating furnace flue gas emission pollutant monitoring system.

[0039] Heating furnace 1 mainly consists of a furnace body, an air / gas supply system, a combustion system (with several air / gas burners arranged inside the furnace chamber), and a flue gas exhaust system. The primary function of heating furnace 1 is to ensure complete combustion of the gas within it, heating the materials inside the furnace. The furnace temperature should be controlled between 800 and 1300°C, and the heating process should not affect the composition of the flue gas. Steel rolling furnaces and heat treatment furnaces are also examples of this type.

[0040] Coal gas is fed into burner 2 through gas branch pipe 3, and oxygen-enriched combustion air is fed into burner 2 through air branch pipe 4. The air and coal gas are mixed in proportion at burner 2 and then fed into heating furnace 1 for combustion to heat the material. The flue gas generated by the combustion of coal gas in the heating furnace is collected through flue gas main pipe 5 and sent to chimney 6 for exhaust. Chimney 6 uses the temperature difference (height) to generate suction to guide the flue gas out. An induced draft fan can be used instead.

[0041] The flue gas sampling pipe 7 takes samples from the sampling port in the middle of the chimney 6. The flue gas collected from the chimney 6 is transported to the flue gas analyzer. The flue gas sampling pipe 7 is made of corrosion-resistant materials such as stainless steel and polytetrafluoroethylene, and has electric heat tracing function. It meets the relevant CEMS analysis and sampling requirements and ensures that the composition of the flue gas does not change during the transportation process.

[0042] The flue gas analyzer detects flue gas components (NOx, SO2, O2, CO, CO2) in real time, employing an extraction-type, cold-drying sampling and analysis method. Specifically, flue gas is directly extracted online through an orifice, undergoes cooling purification, transportation, steam-water separation, cooling drying, extraction pressurization, desulfurization, dust removal, and flow stabilization before entering the flue gas analyzer for analysis. Technical requirements comply with relevant CEMS requirements. Technical performance: Repeatability error: Cv≤1%, Linearity error: ≤1%FS.

[0043] The gas sampling pipe 8 takes a sample from the gas branch pipe 3. The gas sampling pipe 8 is connected to the gas analyzer and delivers the gas collected from the gas branch pipe to the gas analyzer. The gas sampling pipe 8 is made of corrosion-resistant materials such as stainless steel and polytetrafluoroethylene.

[0044] The gas analyzer can detect gas components (O2, CO, H2, CH4, CO2, CnHm, N2) in real time or offline. Technical performance: repeatability error: Cv≤1%, linearity error: ≤1%FS.

[0045] The specific process for monitoring and correction is as follows:

[0046] (1) Calculation of flue gas composition under air-supported combustion conditions:

[0047] First, the composition of dry coal gas was measured, and the composition of wet coal gas was calculated according to GB / T 13338-2018 "Basic Rules for Determination and Calculation of Heat Balance of Industrial Furnaces". The compositions of dry and wet coal gas are shown in the table below:

[0048]

[0049] Note: The gas contains water (H2O). s The gas thermometer shows a gas temperature of 45℃. At this temperature, the gas contains 9.45% water by volume under saturation.

[0050] Based on the obtained wet gas composition, calculate the theoretical dry air volume under air-assisted combustion conditions:

[0051] Theoretical dry air quantity L0g = 0.0238 (H2) s +CO s )+0.0952*CH4 s +0.0476*3*CmHn s -0.0476*O2 s =2.02m 3

[0052] Because under conditions of excess air coefficient of 1 (O2 in flue gas is 0, and it also contains combustible substances), the main combustion products are CO2, N2, and H2O; therefore, 1m 3 The combustion products of coal gas are estimated as follows:

[0053] CO2=(CO s +2CmHn s +CO2 s +CH4 s ) / 100=(14.05+2*1.01+10.33+9.32) / 100=0.36m 3 ;

[0054] N2=N2 s / 100+(100-21) / 100*L0g=1.88m 3 ;

[0055] H2O=((H2 s +2*(CmHn s +CH4 s )+H2O s ) / 100+gk*0.00124=0.63m 3

[0056] Note: The moisture content (gk) of dry air is 21.83 g / Nm³. 3 The values ​​were calculated based on the hygrometer readings of 30.6°C for the dry bulb and 24.8°C for the wet bulb.

[0057] Based on the obtained 1m 3 The volumes of the combustion products CO2, N2, and H2O were calculated, along with the volume percentages of the wet and dry flue gas components. The results are shown in the table below.

[0058]

[0059] (2) Under actual oxygen-enriched combustion conditions, online monitoring obtained O 2富氧 CO 2富氧 Smoke composition:

[0060]

[0061] The conversion of O2 and CO2 flue gas composition under air-assisted combustion conditions to the same oxygen content as under oxygen-enriched combustion conditions:

[0062]

[0063] Note: According to GB28665-2012 "Emission Standard of Air Pollutants for Steel Rolling Industry", CO2 (converted value with a reference oxygen content of 9.28%) = (21 - 9.28 / 21) * 15.99 = 8.92

[0064] (3) Calculation of correction factor

[0065] The correction factor is the dry flue gas CO2 under the same reference oxygen conditions and air-assisted combustion conditions. 1 Content and CO content in dry flue gas under oxygen-enriched combustion conditions 2富氧 The ratio of content. The correction factor also reflects the following rules: ① Correction factor < 1 indicates oxygen-rich combustion; ② Correction factor > 1 indicates the oxygen content of the combustion air is less than 21%.

[0066] Correction factor = CO2 1 / CO 2富氧 =8.92 / 11.08 = 0.8054

[0067] (4) Practical application of correction factor

[0068] This correction method is applicable to SO2 and NO. x It is applicable to pollutants such as particulate matter.

[0069] Taking NOx as an example, the national standard GB28665-2012 stipulates that the NOx emission intensity limit under 8% reference oxygen is 200 mg / Nm³. 3 .

[0070] If CEMS shows a NOx equivalent of 220 mg / Nm³ under 8% standard oxygen conditions, then... 3 This constitutes excessive emissions.

[0071] When the correction factor is 0.8054, the corrected NOx equivalent value = 220 * 0.8054 = 177 mg / Nm³ 3 .

[0072] It can be seen that the NOx concentration under air-supported combustion conditions is 177 mg / Nm³. 3 Emissions meet standards; NOx is 220 mg / Nm³ after oxygen-enriched combustion. 3 Emissions exceeding standards were corrected to meet standards.

Claims

1. A method for correcting monitoring results of pollutant emissions from a heating furnace under oxygen-enriched combustion conditions, characterized in that: Using CO2 in flue gas as a reference, by comparing the theoretical calculation value of CO2 content in flue gas under air combustion with an oxygen content of 21% with the measured value of CO2 in flue gas under oxygen-enriched combustion, a corresponding compensation correction coefficient is obtained to correct the flue gas pollutant monitoring results under oxygen-enriched combustion under the corresponding air combustion. The specific process for obtaining the correction coefficient is as follows: (1) In the air combustion condition, 1m 3 The volume of CO2, N2, H2O in the coal gas combustion product, and the volume percentage of CO2 in the dry flue gas is calculated accordingly; (2) In the actual oxygen-enriched combustion condition, the volume percentage of O2 and CO2 in the flue gas is obtained on-line, and the O2 and CO2 contents are expressed as 2富氧 , CO 2富氧 ​ (3) Under the air combustion condition, the percentage content of O2 and CO2 flue gas components under the same oxygen content as that under the oxygen-enriched combustion condition is converted to obtain the CO2 conversion value, which is expressed by CO2 1 / (O2 + CO2) (4) The correction factor is the dry flue gas CO2 under the same reference oxygen and air-supported combustion conditions. 1 Content and CO content in dry flue gas under oxygen-enriched combustion conditions 2富氧 The ratio of content.

2. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 1, characterized in that: In step (1), under air-assisted combustion conditions, the volume percentage of dry gas components is first measured, and the volume percentage of wet gas components is calculated based on this volume percentage. Based on the obtained volume percentage of wet gas components, the theoretical dry air volume L0g is calculated, and then the volume percentage of 1m³ is extrapolated. 3 The volume of CO2, N2, and H2O in the combustion products of coal gas is used to calculate the volume percentage of the wet flue gas components, thereby determining the volume percentage of CO2 in the dry flue gas.

3. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 2, characterized in that: In step (1), the measured dry gas components include H2, CH4, CO, and C. n H m CO2, O2, N2 and H2O.

4. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 3, characterized in that: In step (1), under the condition of obtaining the volume percentage of dry gas components, the volume percentage of wet gas components is converted using the standard of 9.45% water content in the gas under saturated conditions at a temperature of 45℃.

5. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 4, characterized in that: In step (1), the formula for calculating the theoretical dry air volume is as follows: Theoretical dry air quantity L0g = 0.0238 (H2) s +CO s )+0.0952*CH4 s +0.0476*3*CmHn s -0.0476*O2 s In the formula, H2 s CO s CH4 s 、CmHn s O2 s This indicates the volume percentage of the corresponding wet gas composition.

6. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 5, characterized in that: In step (1), 1m 3 The formulas for calculating the volumes of CO2, N2, and H2O in the combustion products of coal gas are as follows: CO2=(CO s +2CmHn s +CO2 s +CH4 s ) / 100 N2=N2 s / 100+(100-21) / 100*L0g H2O=((H2 s +2*(CmHn s +CH4 s )+H2O s ) / 100+gk*0.00124 In the formula, CO2 s CH4 s N2 s H2O s This indicates the volume percentage of the corresponding wet gas component, and gk indicates the moisture content of the dry air.

7. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 6, characterized in that: Step (3) The oxygen volume percentage obtained from step (2) under oxygen-enriched combustion conditions is monitored online. 2富氧 It is used as a baseline oxygen value for conversion.

8. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 7, characterized in that: CO2 in step (3) 1 The formula for calculating the content is based on the national standard GB28665-2012 "Emission Standard of Air Pollutants for Steel Rolling Industry".

9. The method for correcting the monitoring results of pollutants emitted from a heating furnace under oxygen-enriched combustion conditions according to claim 8, characterized in that: A monitoring system is used to collect data for the correction process. The monitoring system includes a flue gas analyzer and a coal gas analyzer. The heating furnace (1) is connected to the flue gas main pipe (5), the flue gas main pipe (5) is connected to the chimney (6), and a sampling port is set in the middle of the chimney (6). The sampling port is connected to the flue gas analyzer via a flue gas sampling pipe (7). The heating furnace (1) is connected to a coal gas branch pipe (3), and a coal gas sampling pipe (8) takes samples from the coal gas branch pipe (3). The coal gas sampling pipe (8) is connected to the coal gas analyzer.

Images