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| The principle and classification of atmospheric samplers | |
| 2021-06-01 | |
| The principle and classification of atmospheric samplers can be divided into gas samplers and particulate matter samplers according to the collection objects; environmental samplers, indoor samplers and pollution source samplers can be divided according to the place of use. In addition, there are special-purpose atmospheric samplers, such as samplers that collect gas and particulate matter at the same time. The gas sampler is generally composed of three parts: collector, flow meter and pumping power system. Collectors: Generally, there are the following types: ¢Ù Absorption tubes: bubble absorption tubes and porous glass absorption tubes, mainly used to absorb gaseous or vaporous pollutants, the latter can also collect mist aerosols, such as sprayed pesticide emulsions. The impact absorption tube is mainly used to collect smoke and particles. ¢ÚFilter material sampling clip: used to collect smoke, dust and particulate matter. The filter materials are useful inorganic materials, such as glass fiber membranes, quartz filter membranes, and organic materials, such as acetic acid or nitrate fiber membranes, fluororesin membranes, polytetrafluoroethylene membranes and nylon membranes. Recently, the most commonly used organic filter membrane is nuclear-strike into a certain size of pore size, also known as nuclear pore filter. ¢ÛSolid particle sampling tube: The tube can be filled with silica gel, ceramic fragments or other solid particles to collect gaseous or misty pollutants. ¢Ü Gas sampling tubes, syringes, and vacuum bottles are used to collect a small amount of gaseous pollutants. The collectors that collect samples in the flue generally use probes to extend into the flue, and the structure is slightly different from the above-mentioned sampling clip, but their effects are similar. Flowmeter: generally use orifice or rotameter to measure air flow. It can also be equipped with automatic flow control components to ensure the stability of the air flow during the sampling period. Pumping power system: actually a vacuum pumping system. Usually electric vacuum pumps, scraper pumps, membrane pumps, electromagnetic pumps or other air pumps are used. The electric vacuum pump has a large pumping capacity and can be configured on a large flow sampler. The scraper pump, membrane pump, and electromagnetic pump have a small suction volume, but are lighter in weight and easy to carry. They can be configured on a small flow sampler. General particulate matter sampler: collect particulate matter within a certain size range. This kind of sampler is divided into a large-flow sampler (generally, the pumping rate is 1.1 to 1.7 meters per minute) and a small-flow sampler (the pumping rate is less than 20 liters per minute) according to the amount of suction. The particle size collected by the large flow sampler can be as large as 40-60 microns, and the sampling is greatly affected by the wind speed and direction. |
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