METHOD FOR DETERMINING FUGITIVE EMISSION FACTOR (EF) AND LEAKAGE RATE OF COMBUSTION SOURCE

Abstract

A method for determining a fugitive emission factor (EF) and a leakage rate of a combustion source. For a combustion source capable of performing stack emission and fugitive emission, an organized EF, a fugitive EF, and a leakage rate of fugitive emission are respectively obtained through calculation based on material balance. The method solves the problem that it is impossible to collect a total amount of smoke and to quantify its volume in a field test and the problem that a conventional carbon mass balance (CMB) method cannot distinguish organized leakage from fugitive leakage. The method can be used not only for determining gas leaked from residential indoor stoves using coal, biomass, etc., but also for determining fugitive emissions from other sources, such as the amount of gas leaked to the surrounding environment through the body of a brick kiln in a brick and tile factory.

Claims

1. A method for determining a fugitive emission factor (EF) and a leakage rate of a combustion source, comprising: 1) performing an emission test by weighing an amount of fuel for a combustion test; combusting the amount of fuel, monitoring concentrations of pollutants and concentrations of various carbon-based species in smoke at a stack emission port and a leakage position during the combustion process, measuring a cross-sectional area of the stack emission port and a smoke flow velocity in the combustion process; and, after the combustion ends, recording emission time, weighing the mass of remaining fuel, and collecting all ash; 2) measuring the dry weight of the ash, the water content of the fuel, the carbon content of the fuel, the carbon content of the ash, and the average concentration of carbon species and pollutants at the stack emission port and the leakage position during an emission period; 3) (a) calculating the total mass Q.sub.emission of carbon emission as
Q.sub.emission=Q.sub.fuel−Q.sub.ash=M.sub.fuel×C.sub.%,fuel−M.sub.ash×C.sub.%,ash wherein Q.sub.fuel and Q.sub.ash are mass of carbon in the fuel used for combustion and the ash respectively, M.sub.fuel and M.sub.ash are dry weights of the fuel used for combustion and the ash respectively C.sub.%,fuel and C.sub.%,ash are carbon contents of the fuel and the ash respectively, and the dry weight M.sub.fuel of the fuel used for combustion is calculated according to the water content of the fuel; (b) calculating the mass Q.sub.chimney of organized carbon emission as
Q.sub.chimney=C.sub.C-species-C,chimney×V.sub.chimney wherein V.sub.chimney is the volume of organized smoke emission and is calculated by multiplying the cross-sectional area S.sub.chimney with a stack emission port by the smoke flow velocity v and emission time t; C.sub.C-species-C, chimney is the mass concentration of total carbon in organized smoke emission; (c) calculating the mass Q.sub.fugitive of fugitive carbon emission as
Q.sub.fugitive=Q.sub.emission−Q.sub.chimney; (d) calculating the equivalent volume V.sub.fugitive of fugitive smoke emission as
V.sub.fugitive=Q.sub.fugitive/C.sub.C-species-C,fugitive wherein C.sub.C-species-C, fugitive is the mass concentration of total carbon in fugitive smoke emission; (e) calculating an organized EF and a fugitive EF as
EF.sub.chimney, x=V.sub.chimney×C.sub.chimney,x/M.sub.fuel and
EF.sub.fugitive, x=V.sub.fugitive×C.sub.fugitive,x/M.sub.fuel wherein EF.sub.chimney, x and EF.sub.fugitive, x are the organized EF and the fugitive EF of any pollutant x respectively, and C.sub.chimney,x and C.sub.fugitive,x are mass concentrations of any pollutant x from stack emission and fugitive emission respectively; and (f) calculating a leakage rate as
F=EF.sub.fugitive,x/(EF.sub.fugitive,x+EF.sub.chimney,x) wherein F is a proportion of the leakage amount of any pollutant x in the total emission.

2. The method according to claim 1, wherein the mass concentration of carbon in the carbon-based species is obtained by conversion as
C.sub.C-species-C=C.sub.C-species×MWc/V; wherein C.sub.C-species-C is the mass concentration of carbon in a carbon-based species, C.sub.C-species is the mass concentration of a carbon-based species, MWc is the molar mass of carbon and V is the molar volume of gas.

3. The method according to claim 2, wherein the main carbon-based species in smoke comprise CO.sub.2, CO, CH.sub.4, and particulate matter (PM).

4. The method according to claim 1, wherein the fuel is dried and the mass of the fuel is weighed before and after drying to measure the water content of the filet.

5. The method according to claim 4, wherein elements of the dried fuel and the ash are analyzed to measure the carbon content of the fuel on a dry basis and the carbon content of the ash on a dry basis.

6. The method according to claim 1, wherein in the velocity of smoke at a stack emission port is measured in real time by an anemometer specially designed for measuring high-temperature gas.

7. The method according to claim 1, wherein the leakage position is a fuel feeding position close to a fuel source,

8. The method according to claim 1, wherein the emission test covers the whole combustion process and the concentration of pollutants and the concentration of carbon-based species are recorded in real time, and further comprising processing the data to calculate average concentrations of pollutants and carbon-based species in the whole combustion process.

Description

DETAILED DESCRIPTION

[0033] The present invention provides a method for measuring leakage emission of pollutants from solid fuel combustion in an indoor stove, which will be described in detail by taking a leakage emission test of stoves with chimneys in a rural area of Nanchong, Sichuan Province in July 2019 as an example. The method included the following steps.

1. Emission Test

[0034] (1) About 1.5 kg of each of biomass fuels (firewood, straw, bamboo, etc.) used by local farmers daily was weighed, and local farmers were asked to burn the biomass fuels in the stoves with chimneys, in this case, branches were used as an example.

[0035] (2) Measurement of the gas concentration/collection of PM: emission was collected by two similar emission measuring devices. Sampling probes were placed near a chimney outlet and a fuel feeding position close to a stove. According to the concentrations of pollutants at the two positions and the measurement range of an instrument, the emission was diluted with clean air, and the target pollutants such as CO/CO.sub.2/CH.sub.4 and NO/NO.sub.2/SO.sub.2 were measured online. PM.sub.2.5 was collected using filters. The flow rate of each pump in the sampling process was recorded in real time to calculate a dilution ratio of chimney emission. The sampling time was recorded to calculate the sampling volume. This particular sampling duration was 21.2 minutes in total. Before each test, a gas sensor was subjected to zero-point and span calibration in the laboratory and the gas sensor in the field was subjected to null testing. Background concentration of pollutants was measured and the average value was subtracted from the combustion emission calculation.

[0036] (3) Measurement of the exhaust gas velocity at a chimney opening: real-time velocity of the smoke was measured by an anemometer specially designed for measuring high-temperature gas. The gas velocity was calculated by the anemometer by using a constant temperature method, and the gas velocity, temperature, and relative humidity were recorded automatically. Before on-site use, the anemometer was calibrated by a standard turbine flowmeter. An anemometer inlet was placed near a chimney outlet at the same position as an emission-sampling probe. The emission sampling covers the whole combustion process. The cross-sectional area S.sub.chimney of the chimney was 0.0241 m.sup.2. The smoke flow velocity v at the chimney opening was 1.61 m/s. Therefore, the volume of smoke from chimney emission is V.sub.chimney=S.sub.chimney×v×t=0.0241 m.sup.2×1.61 m/s×21.2×60=49.39 m.sup.3=49,390 L.

[0037] (4) Remaining fuel was weighed, and all ash was collected.

2. Sample Analysis

[0038] (1) The fuel was dried by an oven, and the water content of the fuel was measured to be 9.5%; all the collected ash was dried by the oven, and the dry weight M.sub.ash of the ash was measured to be 140 g by an electronic balance.

[0039] (2) Elements of the fuel and the ash were analyzed, The carbon content of fuel on a dry basis was measured to be 45.1%. The carbon content of ash on a dry basis was 73.5%.

[0040] (3) A sampling membrane was weighed before and after sampling, and the difference was the mass of collected PM.

[0041] (4) An instrument directly measured concentrations of CO.sub.2, CO, and CH.sub.4 during the emission test period. The average concentration (C.sub.C-species) (it should be noted that the unit in measurement by the instrument was generally ppm, so it needed to be divided by 10.sup.6 to be expressed as the result of g/L) was measured during the whole sampling period. The mass concentrations C.sub.CO2-C, C.sub.CO-C and C.sub.CH4-C of carbon in these carbon-based species were further calculated. The carbon content C.sub.PM-C in PM was measured by using a photothermal method (such as an OC/EC analysis meter).

[0042] The total carbon mass concentrations C.sub.C-species-C, chimney and C.sub.C-species-C, fugitive in organized (chimney) emission and fugitive (leakage) emission were obtained by summing the measured concentrations of carbon-based species in chimney smoke and leakage smoke, respectively.

[0043] Since the mass concentration of carbon in PM is much lower than that of other pollutants, C.sub.PM-C can be ignored. In this measurement, the concentrations of CO.sub.2, CO, and CH.sub.4 were 6.39×10.sup.3 g/L, 2.15×10.sup.−4 g/L, and 4.30×10.sup.−4 g/L, respectively. MWc was 12 g/mol, and the molar volume of gas was 22.4 L/mol. Therefore,

[00001]$\begin{array}{c}{C}_{C\text{-}\mathrm{species}\text{-}C,\mathrm{chimney}}=\left(C_{\mathrm{CO}2}+C_{\mathrm{CO}}+C_{\mathrm{CO}4}+C_{\mathrm{PM}}\right)\mathrm{chimney}\times \mathrm{MWc}/V\\ =\begin{array}{c}\left(C_{\mathrm{CO}2}+C_{\mathrm{CO}}+C_{\mathrm{CH}4}\right)\mathrm{chimney}\times \\ 12g\text{/}\mathrm{mol}/22.4L\text{/}\mathrm{mol}\end{array}\\ =\begin{array}{c}(6.39\times {10}^{\text{-}3}+2.15\times {10}^{\text{-}4}+\\ 4.30\times {10}^{\text{-}4})\times 12g\text{/}\mathrm{mol}/22.4L\text{/}\mathrm{mol}\end{array}\\ =3.77\times {10}^{\text{-}3}g\text{/}L\end{array}$

The results show that 0.00377 g of carbon was contained in each her of gas emitted through the chimney.

[0044] In the same way, the concentrations of CO.sub.2, CO, and CH.sub.4 measured by the instrument were 2380 ppm, 68.7 ppm, and 25.9 ppm respectively; namely 2.38×10.sup.−3 g/L, 6.87×10.sup.−5 g/L, and 2.59×10.sup.−5 g/L.

C.sub.C-species-C,fugitive=(2.38×10.sup.−3+6.87×10.sup.−5+2.59×10.sup.−5)×12 g/mol/22.4 L/mol=0.00133 g/L

On average, 0.00133 g carbon was contained in each liter of leaked smoke.

[0045] 3. Calculation of a Leakage EF and a Leakage Rate

[0046] (1) The dry weight M.sub.fuel of fuel was calculated according to the water content: the dry weight of fuel was 1.15 kg×(1-9.5%)=1.04 kg according to the mass of burned fuel, which was 1.15 kg.

[0047] (2) Calculation of the total mass of carbon emission:

Q.sub.emission=Q.sub.fuel−Q.sub.ash=M.sub.fuel×C.sub.%,fuel−M.sub.ash×C.sub.%,ash=1040 g×45.1%−140 g×73.5%=366 g.

[0048] (3) Calculation of the mass of carbon in chimney emission:

Q.sub.chimney=3.77×10.sup.−3 g/L×49390 L=186 g.

[0049] (4) Calculation of the mass of carbon in leakage emission:

Q.sub.fugitive=Q.sub.emission−Q.sub.chimney=366 g−186 g=180 g.

The leaked carbon was equal to the total carbon emission minus the carbon emission through the chimney opening.

[0050] (5) Calculation of the equivalent volume of leaked smoke:

V.sub.fugitive=Q.sub.fugitive/C.sub.C-species-C,fugitive=180 g/0.00133 g/L=1.36×10.sup.5 L=136 m.sup.3.

[0051] (6) Calculation of an organized (chimney opening) EF of a pollutant x. The organized EF of any pollutant x emitted through the chimney opening, such as SO.sub.2 (MW=64 g/mol), was calculated. The concentration of SO.sub.2 from chimney emission measured by an instrument was 2.97 ppm and the molar volume of standard gas was 22.4 L/mol, then SO.sub.2 in the chimney was converted into the mass concentration as follows: C.sub.chimney, SO2=2.97 ppm/10.sup.6×64 g/mol/22.4 L/mol=8.49×10.sup.−6 g/L. According to the calculation in the previous step, the volume of gas from chimney emission was 49,390 L and the fuel consumption was 1.04 kg. Therefore, the organized (chimney) EF of SO.sub.2 is: EF.sub.chimney, SO2=C.sub.chimney,SO2×V.sub.chimney/M.sub.fuel=8.49×10.sup.−6 g/L×49390 L/1.04 kg=0.40 g/kg.

[0052] (7) Calculation of a fugitive EF of a pollutant x. The concentration of SO.sub.2 in the leaked smoke was measured to be 0.385 ppm, and was converted into the mass concentration as follows: C.sub.fugitive,SO2=0.385 ppm/10.sup.6×64 g/mol/22.4 L/mol=1.10×10.sup.−6 g/L. According to the calculation in the previous step, the volume of leaked smoke was 135,900 L and the dry weight of fuel was 1.04 kg. The fugitive leakage EF of SO.sub.2 is EF.sub.fugitive, SO2=C.sub.fugitive,SO2×V.sub.fugitive/M.sub.fuel=1.10×10.sup.−6 g/L×136000 L/1.04 kg=0.14 g/kg.

[0053] (8) Calculation of a leakage rate Fx of any pollutant x. The leakage rate was equal to the leakage EF divided by the total EF (a leakage EF+a chimney EF). For example, the calculation for SO.sub.2 is: F.sub.SO2=EF.sub.fugitive,SO2/(EF.sub.fugitive,SO2+EF.sub.chimney,SO2)=0.14/(0.14+0.40)×100%=26%.