A few days ago, an oscillating balance monitor prototype passed the performance and reliability tests of the National Environmental Monitoring Station, completed the on-site certification assessment work of the China Environmental Protection Industry Association, and obtained the environmental product certification certificate.
This balance is not an ordinary balance. Its measurement accuracy reaches 0.01 micrograms. It is known as a balance that can be "weighed in space" and is a key equipment for monitoring PM2.5, PM10 and other airborne particles.
It not only filled the domestic gap, but also broke the foreign monopoly, and obtained 4 invention patent authorizations.
This oscillating balance monitor is another important result of 5 years of arduous research and development by Tianjin Tongyang Technology Development Co., Ltd. (hereinafter referred to as Tongyang Technology). The scientific research advantages of Tianjin University make products, become brands, go to the whole country, and go to the world.
Its monitoring technology in terms of gas characteristics and particle concentration has reached the international leading level.
The micro-oscillating balance method has more advantages in accuracy
With the continuous acceleration of industrial development and urbanization, air pollution continues to intensify, resulting in frequent occurrence of smog.
The main culprit causing the "smog blue" is airborne particulate matter. Its main components are fog, smoke and air dust. When the concentration reaches a certain level, it will cause a series of diseases in the human body, which is the main pollutant endangering human health.
The determination and analysis of the total suspended particulate matter content in the atmosphere is very important for the treatment of air pollution and the protection of human health. Accurately and comprehensively grasping the status of air particulate matter pollution and understanding its development and evolution are the basis for formulating air particulate matter prevention and control measures.
"Gravimetric method is currently the most accurate technology for measuring the concentration of ambient air particulate matter, but it needs to be completed in the laboratory." Fan Haichun, director of the Tongyang Technology R&D Center, introduced that at present, the technologies that can achieve rapid on-site monitoring of atmospheric particulate matter mainly include β-ray method, Micro-oscillating balance method and light scattering method.
Among them, the beta-ray method particle monitor and the oscillating balance method particle monitor are mainly used in the particle monitoring module of the domestic air station project.
The beta-ray method and the micro-oscillating balance method to measure the concentration of particulate matter are both called indirect "gravity methods."
"The beta-ray method uses the principle of beta-ray attenuation, and the mass concentration of particulate matter can be calculated by measuring the attenuation." Fan Haichun said, while the micro-oscillation balance method weighs the mass of particulate matter in the air by changing the oscillation frequency.
The two measurement methods have their own advantages and disadvantages, but with the continuous improvement of China's air quality monitoring standards, the requirements for particulate matter monitoring accuracy are becoming higher and higher.
If the accuracy of the monitoring instrument is not high, the value of PM10 and PM2.5 will be upside down. Especially when using the beta-ray particle monitor, the upside-down phenomenon between different parameters is very common.
Fan Haichun explained that particulate matter with a diameter less than or equal to 2.5 microns (PM2.5) is a subset with a diameter less than or equal to 10 microns (PM10). Under normal circumstances, the value of PM10 monitored should always be greater than PM2.5.
However, when the air quality is good, the value of PM10 monitored by the beta-ray method particulate matter monitor is often less than the value of PM2.5, resulting in inaccurate monitoring results.
It is understood that in the national standard method, the micro-oscillating balance method has advantages in measurement accuracy compared to the β-ray method, and its measurement accuracy and real-time performance are unmatched by traditional methods.
The U.S. Environmental Protection Agency's long-term observational experiment concluded that the micro-oscillating balance method is the closest technique to the gravimetric method among the current techniques for measuring the concentration of ambient air particles.
Core technology breaks through foreign monopoly
At present, PM2.5, PM10 and other particulate matter are the focus of environmental monitoring. There are more than 8,000 national standard air stations in China, and about 16,000 similar equipment are being used.
These devices will be updated every 5 to 8 years, and the average number of updates per year exceeds 2,000.
Corresponding to such a large demand, China's urban air quality automatic monitoring stations mainly rely on imported monitoring equipment, which are expensive, high maintenance costs, and limited in monitoring indicators, which are far from meeting the operational observation and scientific research of atmospheric particulate matter in China. Needs.
"The domestic oscillatory balance method monitor market has been monopolized by foreign companies for a long time, and there is only one company in the world that produces such instruments and equipment." Fan Haichun said that this situation occurs because the existing technology is difficult to bypass foreign patents. .
But if we want to produce our country's own oscillatory balance method monitor, we must make innovations and breakthroughs in basic research.
The core component of the oscillating balance method monitor is the oscillating balance method particle sensor, which is also the "stuck neck" technology of the research and development of the oscillating balance method monitor.
As the core sensor for measuring the concentration of particulate matter, it includes a resonant oscillator, a particulate matter collection membrane, drive and detection circuits.
To bypass the existing patents means that the "puzzle" of the core technology has to be broken up and recombined in a different way.
In 2016, Fan Haichun and the R&D team broke the R&D tasks into parts, and then made breakthroughs one by one.
The research on the material and structure of the vibrator in the mass sensor is the core of the core.
"The material and structure of the vibrator in foreign patents is a tapered tube made of quartz. We have to avoid this material and structure." In order to determine the vibrator material, Fan Haichun and his team used two or three years to select a variety of materials for pertinence. Testing and continuous improvement in combination with different shapes and sizes.
There are thousands of materials in nature. Finding suitable materials is like finding a needle in a haystack. After careful research and analysis, the R&D team narrowed the scope of screening to three, and finally established a special carbon fiber material.
"This material is made by adding other components to carbon fiber. Hundreds of experiments have been carried out just to study the composition ratio." Fan Haichun explained that because each material has different elastic coefficients, different elastic coefficients will lead to Because of the difference in shape, the materials need to be proportioned.
After determining the material, the researchers deduced the most matching vibrator structure to ensure the accuracy of the oscillating balance.
Due to the use of special carbon fiber materials, the vibrator in the oscillating balance developed by Tongyang Technology has a longer life and higher accuracy than the original foreign products under the same conditions.
"The quartz vibrators of foreign products need to be replaced once a year, and our carbon fiber vibrators can basically reach their lifetime. Therefore, the finished product can be greatly saved. Compared with foreign products, a single unit can save more than 50,000 yuan in cost." Fan Haichun said.
Innovative design makes the performance of domestic oscillating balance better
In order to improve the stability and accuracy of the oscillating balance monitoring instrument, the Fan Haichun team also innovatively carried out dynamic compensation system research and algorithm research.
"In addition to particulate matter, the collected atmospheric samples also contain a lot of water molecules. Especially in the humid environment in the south, the high content of water molecules will affect the accuracy of the final detection results." Fan Haichun said, so it is necessary to develop sampling dynamic dehumidification technology, Research on temperature and humidity compensation technology and precise collection of temperature, humidity and pressure.
When Fan Haichun’s team performed dehumidification and pretreatment of the sampled gas, they used spiral back-blowing gas selective permeation dehumidification drying technology and proton exchange membrane water molecule exchange technology to maximize the dehumidification efficiency, thereby reducing the impact of humidity on the measurement of particulate matter; temperature and humidity compensation technology The main purpose is to make subtle compensation for the impact of particulate matter on the measurement results under different temperatures and humidity, so that the measurement can achieve higher accuracy; the precision temperature, humidity and pressure collection technology includes multiple temperature, humidity, and pressure collections to ensure the accuracy of the measurement.
A set of "combined boxing" innovative technology needs to be matched with the corresponding algorithm.
Through the study of concentration algorithm, dynamic compensation algorithm, rapid precision control, linear compensation algorithm, a complete set of dynamic intelligent compensation system is formed, which can intelligently compensate for deviations caused by temperature, humidity, particulate matter composition, etc., so as to be more accurate Ground particulate matter concentration measurement.
As Tongyang Technology's oscillating balance monitor obtains the environmental protection certification, it will become the "Chinese core" of China's national standard air station. With the current demand in China, if all localized products are used, it will save hundreds of millions of dollars in cost.
Our reporter Chen Xi