Environment-air constant flow automatic sampling system and sampling method thereof

Abstract

The invention discloses an environment-air constant flow automatic sampling system and a sampling method thereof. The system comprises a vacuum sampling tank, a buffer container and a switch valve, wherein the buffer container is respectively communicated with the vacuum sampling tank and the atmospheric environment through the switch valve; through the switching control of the switch valve, the buffer container is alternately communicated with the atmospheric environment and the vacuum sampling tank to reach the air pressure balance of the sample feeding gas. The invention also discloses a constant current environment air sampling method. The technical monopolization in foreign countries on the high-precision atmosphere constant current sampling device is broken; the atmospheric samplingflow rate control precision is controlled; the inertness of the integral gas flow path is ensured; the flexible flow rate control and regulation mode is realized; the common use industrial volume production devices and materials are used; consumable avoidance and easy maintenance are realized; the economic and efficient fully automatic environment air constant flow automatic sampling system is built; the contribution is made for national atmospheric environment monitoring and control.

Description

technical field [0001] The invention belongs to air sampling technology, in particular to an ambient air constant flow automatic sampling system and a sampling method thereof. Background technique [0002] Volatile organic compounds (VOCs) are important precursors of ozone pollution. In order to actively promote the monitoring system and capacity building of ambient air VOCs, find out the key types of VOCs that generate ozone, grasp the concentration level and change law, and carry out targeted ozone pollution prevention and control work. The country has formulated a work plan for ambient air VOCs monitoring, which clearly stipulates the sampling mode of ambient air: use pre-vacuumized Suma tanks, and collect continuously at a constant flow rate within a set period of time 8 times a day (3 hours each time) Atmospheric samples, one canister is sealed under negative pressure each time. In non-key areas and time periods, atmospheric samples are continuously collected every 24 ...

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Problems solved by technology

However, it has not become a mainstream sampling solution at present. The main disadvantage is that the electronic mass flow sensor itself cannot be made of inert materials, and the silanization coating process is not suitable for the surface treatment of the sensor, so the overall inertization degree of this solution cannot be compared with the mechanical constant. Compared with the flow device, there is potential damage to the analysis target of VOCs with high activity such as sulfide

At the same time, the proportional valve used in the flow controller inevitably uses an elastic sealing material, usually fluororubber, which is difficult to ensure that it will not release additional organic gas in a high vacuum environment, causing secondary damage to the gas production. Pollution

High-precision electronic mass flow controllers are also relatively expensive. In order to ensure reliability, an inert filter must be used to pre-filter the sampled gas, and the cost of consumables and maintenance is high.

In addition, the electronic mass flowmeter is sensitive to the temperature and humidity changes of the use environment and the measured gas, so the sampling flow accuracy control will be reduced under complex climatic conditions

The national sampling plan also requires that all sampling lines can be removed and cleaned to avoid cross-contamination between different sampling points. At this point, electronic mass flow controllers as part of the gas flow path obviously cannot meet the requirements.

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