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How much do you know about particulate matter measurement in stationary pollution source monitoring?
At present, in the monitoring of domestic fixed pollution sources, there are mainly three methods for measuring low-concentration particulate matter, namely, the gravimetric method, the micro-oscillation balance method, and the β-ray method. Principles and uses are different, we
Particulate matter is one of the main pollutants controlled in China, and it is a pollution factor that must be measured in most stationary pollution sources monitoring. Solid and liquid particulate matter in a gas. The generation of particulate matter is divided into natural and man-made
With the increasingly strict environmental management and the continuous improvement of environmental pollution control technology, especially the national air pollution source monitoring has been fully launched. In response to the "two lows and one high" situation of low particulate matter concentration, low temperature, and high humidity in the pipeline after desulfurization, the Ministry of Environmental Protection issued and implemented the "Measurement Method for Low Concentration Particulate Matter in Fixed Pollution Sources." Methods for monitoring and analyzing particulate matter include "," and ".
Hebei Province and other provinces and cities have released standards for portable particulate matter monitoring methods "Determination of β-ray method for particulate matter from fixed sources of pollution", and the Shandong Provincial Department of Ecology and Environment has also formulated local environmental standards.
The beta-ray absorption method has been widely used in ambient air. The technology has become more and more mature.
The principles and comparison of the gravimetric method, micro-oscillation balance method and β-ray method are introduced below.
1 weight method
At present, in the field of pollution source monitoring, the measurement of atmospheric particulates in China mainly uses the gravimetric method. .
The sampling environment and sampling frequency of ambient air monitoring shall be implemented as required.
Oscillatory balance
The micro method uses an oscillating hollow conical tube in the mass sensor, and a replaceable filter is installed at its oscillating end. The oscillation frequency depends on the characteristics of the conical tube and its quality. When the sampling airflow passes through the filter and particulate matter is deposited on the filter, the change in the quality of the filter causes a change in the oscillation frequency. Calculate the mass of the particulate matter deposited on the filter by changing the oscillation frequency, and then calculate the mass concentration of the particulate matter mark during this period based on the flow rate, ambient temperature and air pressure.
Micro-Vibration Balanced Particle Monitor
FDMS) micro-oscillation balance monitor body. The main component of a micro-oscillation balance sensor for measuring the mass of a sample in a host is a hollow cone with one end fixed and the other end equipped with a filter. In the special-shaped tube, the sample gas flows through the filter membrane, and the particulate matter is collected on the filter membrane. During operation, the hollow conical tube is in a state of reciprocating oscillation. Its oscillating frequency will change as the mass of particulate matter collected on the filter changes. The instrument will accurately measure the change in frequency to obtain the mass of collected particulate matter, and then calculate the sample concentration based on the volume of the collected sample.
3 Be / β rays
Ta-ray method is a very important method in the monitoring of pollution sources. Use the Beta attenuation principle. Ambient air is sucked into the sampling tube by the sampling pump and discharged through the filter membrane, and particulate matter is deposited on the filter membrane. When β-rays pass through the filter with the deposited particulate matter, the energy of the beta rays decays, and the concentration of the particulate matter can be calculated by measuring the amount of attenuation.
35%. After the sample enters the main body of the instrument, the particulate matter is collected on a filter membrane that can be replaced automatically. The β-ray source and the β-ray detector are arranged on both sides of the filter membrane of the instrument. As the sample was collected, more and more particles were collected on the filter, and the mass of the particles increased. At this time, the intensity of the beta ray detected by the beta ray detector will be weakened accordingly.
Because the output signal of the Beta-ray detector can directly reflect the mass change of the particulate matter, the instrument analyzes the particulate matter value of the Beta-ray detector and combines the sample volume collected during the same period to finally obtain the particles. Concentration during sampling. Equipped with a membrane dynamic measurement system, the instrument can accurately measure the particles volatilized during this process, which can effectively compensate * the final report data, which is close to the true value.