A few days ago, Liaoning Province issued a letter seeking opinions on the local standard of the Liaoning Province "Determination of Low-Concentration Particulate Matter from Fixed Pollution Sources by the β-Ray Method" (Consultation Draft). Details are as follows:
In order to implement laws and regulations such as the "Environmental Protection Law of the People's Republic of China", "Air Pollution Prevention and Control Action Plan" and "Liaoning Province Air Pollution Prevention Regulations" and other laws and regulations, to prevent and control environmental pollution of exhaust particulate matter from fixed sources of pollution, and to protect human health, the Liaoning Ecological Environment Monitoring Center The local standard "Determination of low-concentration particulate matter from stationary sources of pollution β-ray method" has been prepared. At present, the preparation unit has completed the draft of the standard and a description of the preparation. According to the relevant regulations of local standards management in Liaoning Province, the public is now soliciting opinions. Please submit to the authoring unit in writing before January 22, 2020.
Contact: Zheng Peisheng, Liaoning Provincial Ecological Environment Monitoring Center
Mailing address: 30A-3, Shuangyuan Road, Dongling District, Shenyang City, Liaoning Province
1. "Determination of low-concentration particulate matter from fixed sources of pollution β-ray method" (draft for comments)
2. Standard preparation instructions
Standards Development Group
December 23, 2019
Determination of low-concentration particulate matter from stationary sources of pollution β-ray method
This standard specifies the β-ray method for the determination of low-concentration particulate matter in fixed sources of pollution.
This standard is applicable to the determination of low-concentration particulate matter (≤50 mg / m3) in the exhaust gas from a fixed pollution source. When the measurement result is greater than 50 mg / m3, it is expressed as "> 50 mg / m3".
When the sampling volume is 1 m3 (standard dry volume), the method detection limit is 0.1 mg / m3.
2 Normative references
The following documents are essential for the application of this document. For dated references, only the dated version applies to this document. For undated references, the latest version (including all amendments) applies to this document.
GB / T 16157 Determination of particulate matter and sampling of gaseous pollutants in exhaust from stationary pollution sources
HJ / T 48 Soot Sampler
HJ / T 397 Fixed source exhaust gas monitoring technical specifications
HJ 836 Determination of low-concentration particulate matter from stationary sources of exhaust gas by gravimetric method
3 terms and definitions
The terms and definitions defined in HJ 836 and the following apply to this standard.
A stream of electrons emitted during the nuclear decay of radioactive elements.
Note: β-ray source can use 147Pm, 14C or 85Kr.
A method of sampling particulate matter in a flue gas at a constant velocity and trapping the particulate matter on a filter medium located outside the flue gas.
4 Method principle
The particulate sampling tube with heating function is inserted into the flue through the sampling hole, and a certain amount of exhaust gas containing particulates is extracted by the principle of constant velocity sampling. The particulate is trapped on the filter membrane by means of filtering outside the flue. When β-rays pass through the filter, the energy is attenuated, and the mass of the particulate matter is calculated by measuring the amount of attenuation. β-ray attenuation and the mass of particles follow the following absorption laws:
N = N0e-km (1)
In the formula: N——the amount of β rays passing through the filter unit per unit time;
N0——the amount of beta rays emitted in a unit time;
k——unit mass absorption coefficient, cm2 / mg;
m——mass of particulate matter per unit area, mg / cm2.
The mass of particles was measured as follows:
Step 1: Determination of blank filter
N1 = N0 · e-km0 (2)
Step 2: Measurement of filter membrane after particulate matter retention
N2 = N0 · ek (m0 + Δm) (3)
Combining (2) and (3) gives:
N1 = N2 · ekΔm (4)
In the formula: N1——the amount of β-rays passing through the blank filter per unit time;
N2——the amount of β-rays that pass through the filter after the particulate matter is trapped;
m0——the mass of background particulate matter per unit area of blank filter membrane, mg / cm2;
△ m——the mass of particulate matter retained on the filter membrane per unit area, mg / cm2.
5 Reagents and materials
5.1 filter membrane
Filter membranes (including filter belts) such as glass fiber filters can be used. The filter membrane should have flat edges, uniform thickness, no burrs, no pollution, and no pinholes or any damage. The material of the filter membrane should not absorb or chemically react with gaseous compounds in the exhaust gas, and it should be thermally stable at the maximum sampling temperature; for standard particles with a diameter of 0.3 μm, the capture efficiency of the filter membrane should be> 99.5%. For standard particles of 0.6 μm, the capture efficiency of the filter should be> 99.9%.
5.2 Standard diaphragm
It is made of inert materials (such as polycarbonate) and should be stored away from light; check the membrane for damage before use.
6 Instruments and equipment
6.1 Measuring device for moisture content in exhaust gas
The moisture content measuring device in the exhaust gas should meet the requirements of the HJ 836 moisture content measuring device in the exhaust gas.
6.2 Device for measuring exhaust gas temperature, pressure and flow rate
The exhaust gas temperature measuring device shall meet the requirements of the exhaust gas temperature measuring device in GB / T 16157; the exhaust gas pressure and flow velocity measuring device shall meet the requirements of the exhaust gas pressure and flow velocity measuring device in GB / T 16157.
6.3 β-ray particle analyzer
6.3.1 Sampling device
The particulate sampling device is composed of a combined sampling tube, a cooling and drying system, a flow meter
and a suction pump unit, and a connecting pipeline. Except that the combined sampling tube is replaced by a filter membrane and a fixed device that filters outside the flue, and the filter tube and the filter tube sampling tube that are filtered in the flue, the rest of the sampling device shall meet the requirements of the sampling device in HJ / T 48.
The sampling tube shall be made of corrosion-resistant and heat-resistant materials, and shall have a heating function throughout. The heating temperature shall not exceed 110 ° C. The front end of the sampling tube should be bent, and the sampling nozzle and the sampling tube should be at an angle of 90 °. The surface of the front curved tube should be smooth to avoid sudden changes. The sampling nozzle shall meet the requirements of the sampling nozzle in HJ 836. To avoid the impact of static electricity on the sampling device, the sampling device should be equipped with a ground wire.
6.3.2 Analysis and measurement device
The analysis and measurement device is mainly composed of a 14C and other ray source, a beta ray detector, a filter transfer control device, and a filter heating device (the heating temperature should not exceed 110 ° C). The composition of different types of β-ray analysis and measurement devices can be different. This standard enumerates two types of schematic diagrams of sampling and analysis measurement devices for filtering particulate matter outside the flue. See Figure 1 and Figure 2 for details.
1-chimney wall; 2-sampling nozzle; 3-temperature measurement; 4-sampling tube; 5-pitot tube; 6- manometer
7-analytical measurement device; 8-filter belt; 9-filter belt pressing device; 10-β-ray source; 11-β-ray detector;
12- filter belt transmission control device; 13- dryer; 14- flowmeter; 15- suction pump
Figure 1 Schematic diagram of filter particulate sampling and analysis measurement device outside the flue (filter belt)
1-chimney wall; 2-sampling nozzle; 3-temperature measurement; 4-sampling tube; 5-pitot tube; 6-manometer;
7-analysis and measurement device; 8-membrane; 9-membrane pressing device; 10-β-ray source; 11-β-ray detector;
12-dryer; 13-flow meter; 14- suction pump
Figure 2 Schematic diagram of filtering and sampling device for filtering particulate matter outside the flue (filter membrane)
7 Sampling and determination
7.1 Sampling positions and sampling points
The setting of sampling positions and sampling points should comply with the relevant regulations in GB / T 16157, HJ / T 397, etc.
7.2 Sampling preparation
7.2.1 Check the filter membrane for damage or other abnormal conditions.
7.2.2 Calibrate the instantaneous flow rate and cumulative flow rate accuracy of the particulate sampling device in accordance with the flow accuracy requirements in HJ / T 48. For the combined sampling tube pitot tube coefficient, it should be calibrated once a year; when the shape of the pitot tube changes significantly, it should be maintained and calibrated or replaced in time.
7.2.3 Determine the site conditions, sampling points and sampling holes, sampling platform, working power, lighting and safety measures, etc. shall meet the monitoring requirements.
7.2.4 Prepare other instruments, protective equipment and original records required for monitoring.
000011.3 Sample collection and determination
7.3.1 According to the actual measured flue size on site, select the monitoring section according to 7.1 to determine the number of sampling points.
7.3.2 Record the basic situation on site and clean up the ash deposits at the sampling holes.
7.3.3 Check whether the sampling system is leaking. The leak detection shall meet the requirements of system on-site leak detection in GB / T 16157.
7.3.4 The instrument should be inspected with a standard diaphragm before testing. The error between the inspection result and the nominal value of the standard diaphragm should be within ± 5%.
7.3.5 Set the heating temperature of the sampling tube and filter heating device according to the operation requirements of the instrument manual.
7.3.6 After the heating temperature reaches the set value and is stable, measure the β-ray transmission of the blank filter membrane according to the operating instructions of the instrument manual.
7.3.7 Start sampling. Refer to the sampling steps in GB / T 16157 for the sampling steps, or use a microcomputer to perform parallel automatic sampling in accordance with the operation method of the instrument. Equal, relative error is less than 10%. The sampling process should ensure that the temperature of the sampling tube and the temperature of the membrane heating device are within the required range.
7.3.8 After the sampling is completed, measure the β-ray transmission of the filter after the particulate matter is trapped.
7.3.9 Obtain the amount of particulate matter retained on the filter membrane based on the attenuation of β-rays passing through the filter membrane before and after sampling, and combine this standard dry sampling volume to calculate the particulate matter concentration.
8 Results calculation and representation
8.1 Calculation of results
The particle concentration is calculated according to formula (6):
Where: ρ——particle concentration in dry flue gas under standard conditions, mg / m3;
m——mass of particles collected on the filter membrane, g;
Vnd——Dry gas production volume under standard conditions, L.
8.2 Results representation
The particle concentration calculation results are retained to one decimal place.
9 Precision and accuracy
Six verification laboratories measured the dust source concentrations of 3 mg / m3, 25 mg / m3, and 40 mg / m3 dust sources:
Relative standard deviations in the laboratory are: 6.0% to 11.2%, 3.0% to 7.4%, 4.1% to 7.0%;
The relative standard deviations among laboratories are: 1.1%, 1.6%, and 1.4%;
Repeatability limits are: 0.7 mg / m3, 3.3 mg / m3, 6.0 mg / m3;
Reproducibility limits were 0.6 mg / m3, 3.2 mg / m3, and 5.7 mg / m3, respectively.
Six verification laboratories measure the concentration of particulate matter in the flue gas emissions from typical sewage outlets such as the general outlet of a power plant, the outlet of a steel plant, and the outlet of a coking plant. The concentration of particulate matter in the flue gas from the total outlet of a power plant is 1.3 ~ 2.5 mg / m3, with an average value of 1.8mg / m3; m3; the concentration of particulate matter in the flue gas of a coking plant is 7.1 ~ 10.0 mg / m3, and the average particle concentration is 8.6 mg / m3.
The relative standard deviations in the laboratory are: 9.2% ~ 17.8%, 6.0% ~ 16.8%, 7.6% ~ 13.2%;
The relative standard deviations between laboratories were: 10.3%, 1.3%, and 3.6%;
Repeatability limits are: 0.8 mg / m3, 2.7 mg / m3, 2.5 mg / m3;
Reproducibility limits were 0.9 mg / m3, 2.5 mg / m3, and 2.4 mg / m3, respectively.
Six verification laboratories have determined the source of particulate matter at concentrations of 3 mg / m3, 25 mg / m3, and 40 mg / m3:
The relative errors are: -6.1% ~ -6.7%, -2.7% ~ 7.0%, 0.5% ~ 2.3%;
The final relative errors are: -0.7 ± 5.7%, 1.5 ± 3.3%, 1.5 ± 0.7%.
10 Quality Assurance and Quality Control
10.1 The quality assurance measures for on-site sampling shall meet the requirements of on-site sampling quality assurance measures in HJ / T 397.
10.2 As far as the site conditions allow, select a sampling nozzle with a large inlet diameter as much as possible.
10.3 When collecting samples, ensure that the weight gain of each sample is not less than 1 mg, or the standard dry sampling volume is not less than 1 m3.
10.4 It shall be ensured that all particulate matter trapped on the filter membrane after sampling is within the range of β-ray irradiation; the amount of energy attenuation of β-rays passing through the filter membrane before and after testing shall not exceed 75% of the total.
11 matters needing attention
11.1 The standard diaphragm should be inspected regularly. If dust is found on the surface of the diaphragm, the surface of the diaphragm should be cleaned with absolute ethanol; if the surface of the diaphragm is damaged or discolored, the standard diaphragm should be replaced in time.
11.2 The sampling tube shall be backflushed with clean gas periodically according to the frequency of use, no less than once a month.