An alternative method for invalid data in an online CO2 concentration monitoring system

Abstract

The application discloses a replacement method for invalid data of a CO2 concentration online monitoring system, and comprises the following steps: establishing an interpolation function fln(x) of CO2 concentration in different load intervals, calculating CO2 concentration data, calculating concentration coefficients f1, f2 and f3 of CO2 and CO2 under different loads, obtaining CO2 concentration data, determining whether CO2 concentration or CO2 concentration is used for replacing invalid data according to the relative error size of CO2 concentration and CO2 concentration. 2CEMS The application is mainly used in coal-fired power plants, coal-fired boilers and other systems taking coal as main fuel, and when data replacement is needed due to faults, maintenance, repair and the like of the CO2 concentration online monitoring system, whether CO2 concentration or CO2 concentration is used for replacement can be evaluated, the accuracy is high, and the method is simple and reasonable. 2负荷修正 2CEMS 2HJ75 2HJ75修正 2负荷修正 2HJ75修正 2负荷修正 2HJ75修正 2负荷修正 2HJ75修正 ​​​​​​​​​​

Description

Technical Field

[0001] This invention belongs to the field of carbon emission monitoring technology, specifically relating to a method for replacing invalid data in an online CO2 concentration monitoring system. Background Technology

[0002] Climate change caused by greenhouse gas emissions has drawn global attention. Major energy groups have already begun pilot monitoring of CO2 emissions from coal-fired power plants, and using online CO2 concentration monitoring systems to calculate carbon emissions is an inevitable trend. However, these systems can generate invalid data due to malfunctions, maintenance, and repairs. The accuracy of replacing this invalid data with scientifically sound data will affect the accuracy of total carbon emission calculations.

[0003] The current "HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources" provides a calculation method for estimating CO2 content using oxygen content. The calculation formula is as follows:

[0004] (1)

[0005] in, To produce the maximum amount of fuel combustion Volume percentage, in vol% The accuracy of oxygen monitoring, based on the standard oxygen content measured by the CEMS system, is constrained by various factors.

[0006] The "HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources" provides a method for estimating CO2 content using oxygen content. This method assumes that all the oxygen consumed by the unit combustion is combined into CO2, and then multiplies this by the maximum value for different types of coal to estimate the concentration. This method can provide the maximum boundary value for CO2 emissions.

[0007] The "HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources" stipulates that invalid data can be replaced by the maximum emission values ​​of the 180, 720 or 2160 effective hours before the last calibration, based on the CEMS out-of-control time.

[0008] However, CO2 emissions from coal-fired boilers are primarily determined by the carbon content of the fuel and the quality of fuel combustion. Therefore, CO2 emissions are highly correlated with the unit's fuel type, fuel consumption, and operating status. Under different loads, the total carbon emissions can vary by more than double. The methods specified in the "HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx, and Particulate Matter Emissions from Stationary Sources" cannot be directly applied to replace emissions during periods of CO2 concentration malfunction in the online monitoring system. Since the accuracy of total carbon emission measurement directly impacts the plant's final economic benefits, a scientific and reliable method is needed to replace invalid data from the online CO2 concentration monitoring system.

[0009] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0010] To address the technical problems existing in the prior art, the purpose of this invention is to provide a method for replacing invalid data in an online CO2 concentration monitoring system.

[0011] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows:

[0012] A method for replacing invalid data from an online CO2 concentration monitoring system includes the following steps:

[0013] Establish CO within different load ranges 2CEMS The concentration interpolation function is fln(x), where n is a positive integer and x is the loading value;

[0014] Calculate CO 2负荷修正 concentration;

[0015] Calculate CO under different loads 2CEMS and CO 2HJ75 The concentration coefficient f3 is then used to obtain CO. 2HJ75修正 Concentration data;

[0016] According to CO 2负荷修正 Concentration and CO 2HJ75修正 The relative error in concentration determines whether to use CO. 2负荷修正 Concentration, CO 2HJ75修正 Any one of the concentrations is a substitute for invalid CO2 concentration data.

[0017] In the method for replacing invalid data in the online CO2 concentration monitoring system provided by this invention, CO2 concentrations within different load ranges are established. 2CEMS The steps of the concentration interpolation function fln(x) include:

[0018] Under the current condition of similar coal type, the historical data of the calibrated online CO2 concentration monitoring system are first classified and organized to find data with similar or identical operating conditions under stable unit load over a certain period of time. Then, CO2 concentration is tested under two adjacent loads. 2CEMS Concentration, and then the interpolation function fln(x) is calculated:

[0019] fln(x)= Y1+(Yn-Y1) / (Xn-X1)*(x- X1)

[0020] Where Xn and X1 are two loads adjacent to the load value x, and Yn and Y1 are the CO2 emission concentrations under loads Xn and X1, respectively.

[0021] The condition for stable unit load is that the deviation from the load value x is no greater than 5MW.

[0022] The CO 2负荷修正 The formula for calculating concentration is:

[0023] CO 2负荷修正 = fln(x) / k

[0024] Where, k = xf 当前负荷 / xf 平均 xf 当前负荷 xf represents the hourly standard dry basis flue gas emission rate under current load. 平均 This represents the average hourly standard dry basis flue gas emission under the same historical load.

[0025] The formula for calculating the concentration coefficient f3 is as follows:

[0026] f3=CO 2CEMS / CO 2HJ75

[0027] Among them, CO 2CEMS and CO 2HJ75 The CO2 concentrations are measured by the calibrated online CO2 concentration monitoring system and estimated by the HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources, respectively. Different concentration coefficients f3 apply under different loads.

[0028] Furthermore, through the current load CO 2HJ75 Multiplying the concentration by the concentration coefficient f3 under the same load yields the CO concentration. 2HJ75修正 concentration.

[0029] The CO 2负荷修正 Concentration and CO 2HJ75修正 The formula for calculating the relative error E of concentration is:

[0030] E=abs(CO) 2负荷修正 -CO 2HJ75修正 ) / (CO 2负荷修正 +CO 2HJ75修正 )*100%

[0031] When the relative error E is no greater than 10%, use CO. 2负荷修正 Concentration and CO 2HJ75修正 Any alternative CO2 concentration data is invalid.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention discloses a method for replacing invalid data in an online CO2 concentration monitoring system, comprising the following steps: establishing CO2 concentration data within different load ranges. 2CEMS The concentration interpolation function is fln(x), where n is a positive integer and x is the loading value; CO2 is calculated. 2负荷修正 Concentration; Calculation of CO under different loads 2CEMS and CO 2HJ75 The concentration coefficient f3 is then used to obtain CO. 2HJ75修正 Concentration data; based on CO 2负荷修正 Concentration and CO 2HJ75修正 The relative error in concentration determines whether to use CO. 2负荷修正 Concentration, CO 2HJ75修正 This invention primarily applies to systems where coal is the main fuel, such as coal-fired power plants and boilers. When the online CO2 concentration monitoring system requires data replacement due to malfunction, maintenance, or repair, it can replace invalid CO2 concentration data by evaluating the CO2 concentration. 2负荷修正 Concentration and CO 2HJ75修正 The relative error of concentration determines whether to use CO. 2负荷修正 Concentration or CO 2HJ75修正 The method of using concentration substitution is accurate, simple, and reasonable. Detailed Implementation

[0034] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0035] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0036] A method for replacing invalid data from an online CO2 concentration monitoring system includes the following steps:

[0037] 1) Under the current conditions of similar coal types, the historical data of the calibrated CO2 concentration online monitoring system are first classified and organized. Data with similar operating conditions such as temperature, pressure, flow rate, and load in the past period are found. Data when the unit is running stably is used as data sample. The unit load is stable for at least 3 hours. The CO2 emission concentration in at least three stable load ranges of high, medium and low is obtained. When the load change is within ±5MW, it is considered to meet the conditions of stable or the same load.

[0038] 2) Record CO under different steady loads 2CEMS The concentration data were collected and categorized.

[0039] 3) Record CO under the same load conditions 2CEMS Comparison of CO concentration and hourly standard condition dry basis flue gas emission data to establish CO 2CEMS The data on concentration and standard dry basis flue gas emission were compared and categorized.

[0040] 4) For accumulated adjacent load segments, CO 2CEMS By performing linear interpolation or polynomial fitting on concentration data and load values, an approximate function is obtained for CO concentrations within different load ranges for the current coal type. 2CEMS The emission concentration is a function of fl1(x), fl2(x), fl3(x), fl4(x), ..., fln(x), where n is a positive integer and x is the load value. For example, when the CO2 emission concentrations are Y1 and Y2 at loads X1 and X2 respectively, fl1(x) can be obtained through linear interpolation.

[0041] fl1(x)=Y1+(Y2-Y1) / (X2-X1)*(X- X1) (2)

[0042] Where x represents the load point between X1 and X2, and so on. Alternatively, multiple load points and CO2 concentration data can be used to fit fln(x):

[0043] fln(x) = ax n + bx+c (3)

[0044] Where a, b, and c are fitting coefficients, and x is the current load value.

[0045] 5) For CO under the same cumulative load 2CEMS The concentration and hourly standard-condition dry-basis flue gas emission rate were averaged to establish a relationship between CO concentration and hourly standard-condition dry-basis flue gas emission rate xf. 2CEMSThe correction factor k for emission concentration is the average of the hourly standard dry basis flue gas emission rate under the current load and the hourly standard dry basis flue gas emission rate under the same historical load, xf. 平均 The ratio of the historical standard dry basis flue gas emission hourly average sample is not less than 3, that is:

[0046] k = xf 当前负荷 / xf 平均 (4)

[0047] When the CO2 concentration online monitoring system needs to replace data due to faults, maintenance, repairs, etc., the CO2 load concentration under the current load conditions can be obtained by using formula (2) or formula (3) based on the current load x.

[0048] Find the flue gas flow rate under the same load condition closest to the current load X, calculate k using formula (4), and then obtain the CO. 2负荷修正 Concentration data:

[0049] CO 2负荷修正 = fln(x) / k(5)

[0050] Establish CO under different load segments 2CEMS and CO 2HJ75 The concentration data were compared and divided to obtain the CO concentration under different loads. 2CEMS and CO 2HJ75 Concentration coefficient f3:

[0051] f3=CO 2CEMS / CO 2HJ75 (6)

[0052] Among them, CO 2CEMS and CO 2HJ75 The CO2 concentrations are measured by the calibrated online CO2 concentration monitoring system and estimated by the HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources, respectively. Different concentration coefficients f3 apply under different loads.

[0053] When invalid data replacement is required, it should be based on the CO under the current load. 2HJ75 Multiplying the concentration by the concentration coefficient f3 under the same load yields the estimated CO under the current load condition. 2HJ75修正 Concentration, i.e., CO 2HJ75修正 = CO 2HJ75 * f3, where the "Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources (HJ75-2017)" provides a calculation method for estimating CO2 concentration using oxygen content. The estimated CO2 concentration is denoted as CO. 2HJ75 .

[0054] CO 2负荷修正 Concentration and CO 2HJ75修正 The formula for calculating the relative error E of concentration is:

[0055] E=abs(CO) 2负荷修正 -CO 2HJ75修正 ) / (CO 2负荷修正 +CO 2HJ75修正 ) *100% (7)

[0056] CO 2负荷修正 Concentration and CO 2HJ75修正 When the relative error E of the concentration is no greater than 10%, the currently estimated CO2 substitution concentration data is considered reliable and can be used. 2负荷修正 Concentration and CO 2HJ75修正 Any of the concentrations can be used to replace invalid CO2 concentration data.

[0057] Example 1

[0058] A 320MW coal-fired power unit experienced a fault at 65% load (X=65%), and the fault handling time was 3 hours. In this case, the present invention is needed to scientifically replace the invalid data within 3 hours.

[0059] Over the past week, the target operating condition was one where the load remained stable at 60%. Load variations within ±5 MW were considered stable loads, with X1 = 60%. The average CO2 concentration measured by the online CO2 monitoring system was... 2CEMS Concentration of 240 g / m 3 Simultaneously, the system seeks a stable operating condition with a load of 70%, where the load variation is ±5MW, X2=70%, and the average CO2 concentration measured by the online CO2 monitoring system is [data missing]. 2CEMS Concentration of 250 g / m 3 The online CO2 concentration monitoring system references CN114487286A.

[0060] According to formula (2), fl1(65%) = Y1 + (Y2-Y1) / (X2-X1)*(X-X1) = 240 + (250-240) / (70%-60%)*(65%-60%) = 245g / m 3 .

[0061] Under the same load, changes in flue gas emission will also cause changes in CO2 concentration, so the result of fl1 (65%) needs to be corrected for flue gas emission.

[0062] Historical average standard condition dry basis flue gas emission rate xf at 65% load 平均 =800000m 3 / h, dry basis flue gas discharge rate xf under current load 当前负荷=802000m 3 / h, then k=802000 / 800000=1.0025; according to formula (5), CO 2负荷修正 = 245 / 1.0025 = 244.34 g / m³ 3 .

[0063] In this embodiment, the fuel type is bituminous coal, and the load is 60%. =18.55%, oxygen concentration is 7.57%, CO 2HJ75 =231g / m 3 Then f3 = CO 2CEMS / CO 2HJ75 =240 / 231=1.04; A fault occurred at a load of 65%, and the fault handling time is 3 hours. According to formula (1), with the current oxygen content at 7.35% and CO2 at 100%, the fault can be resolved in 3 hours. 2HJ75 =235g / m 3 At that time, CO 2HJ75修正 = CO 2HJ75 *f3=235*1.04=244.4g / m 3 ;

[0064] Therefore, the relative deviation E = abs(CO) obtained according to formula (7) is obtained. 2负荷修正 -CO 2HJ75修正 ) / (CO 2负荷修正 +CO 2HJ75修正 ) * 100% = abs(244.34-244.4) / (244.34+244.4) * 100% = 0.012%, which is less than 10%. According to the alternative method of the present invention, CO can be used. 2负荷修正 Concentration or CO 2HJ75修正 The concentration was used to replace invalid CO2 concentration data.

[0065] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0066] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for replacing invalid data in an online CO2 concentration monitoring system, characterized in that, Includes the following steps: Establish CO within different load ranges 2CEMS The concentration interpolation function is fln(x), where n is a positive integer and x is the loading value; Calculate CO 2负荷修正 concentration; Calculate CO under different loads 2CEMS and CO 2HJ75 The concentration coefficient f3 is then used to obtain CO. 2HJ75修正 Concentration data; According to CO 2负荷修正 Concentration and CO 2HJ75修正 The relative error in concentration determines whether to use CO. 2负荷修正 Concentration, CO 2HJ75修正 Any invalid concentration data that could be substituted for CO2; Establish CO within different load ranges 2CEMS The steps of the concentration interpolation function fln(x) include: Under the current condition of similar coal type, the historical data of the calibrated online CO2 concentration monitoring system are first classified and organized to find data with the same or similar operating conditions under stable unit load within the preset period. Then, CO2 concentration is tested under two adjacent loads. 2CEMS Concentration, and then the interpolation function fln(x) is calculated: fln(x)= Y1+(Yn-Y1) / (Xn-X1)*(x- X1); Where Xn and X1 are two loads adjacent to the load value x, and Yn and Y1 are the CO2 emission concentrations under loads Xn and X1, respectively; The condition for stable unit load is that the deviation from the load value x is no greater than 5MW; The CO 2负荷修正 The formula for calculating concentration is: WHAT 2负荷修正 = fln(x) / k; Where, k = xf 当前负荷 / xf 平均 xf 当前负荷 xf represents the hourly standard dry basis flue gas emission rate under current load. 平均 This represents the average hourly standard dry basis flue gas emission under the same historical load. The formula for calculating the concentration coefficient f3 is as follows: f3=CO 2CEMS / WHAT 2HJ75 ; Among them, CO 2CEMS and CO 2HJ75 The CO2 concentrations are measured by the calibrated online CO2 concentration monitoring system and estimated by the HJ75-2017 Technical Specification for Continuous Monitoring of SO2, NOx and Particulate Matter Emissions from Stationary Sources, respectively. Different concentration coefficients f3 exist under different loads. The CO 2负荷修正 Concentration and CO 2HJ75修正 The formula for calculating the relative error E of concentration is: E=abs(CO 2负荷修正 -WHAT 2HJ75修正 ) / (WHAT 2负荷修正 +CO 2HJ75修正 )*100%; When the relative error E is no greater than 10%, use CO. 2负荷修正 Concentration and CO 2HJ75修正 Any alternative CO2 concentration data is invalid.