Activated Carbon Chemical Strainer Knowledge Introduction
Chemical Strainer removes chemical gases in the air pollutants, in order to meet the micro-electronics, nuclear industry, pharmaceutical, chemical, environmental, laboratory animals, light industry and other industries needs.
With industrial development and urban growth, the concentration of harmful gases in the atmosphere increases; technological progress and living standards improve, people's demand for clean air has improved. And the demands for chemical strainers gradually increase.
The current chemical strainers are mostly activated carbon strainers
●Adsorption theory
activated carbon selectively adsorbs gases, rather than mechanical "strainering" impurity
There are a large number of microporous on activated carbon surface, most of which diameter is less than 500A (1A =10-10m). the total surface area of unit material microporous, referred as "specific surface area", which can up to 700 ~ 2300m2 / g
When related to adsorption, the harmful gases in the air are called "adsorbate", activated carbon is "adsorbent." As the gravitational forces between molecules, adsorption sticks to the porous hole inner surface. If accompanied with chemical reaction, said as chemical adsorption, or as physical adsorption.
At the same time of adsorbate is adsorbed by the adsorbent, there will be part of the adsorbate away from the adsorbent, called as "desorption." When in using, the adsorption capacity will continue to weaken, desorption increases to a certain extent, activated carbon is scrapped.
In some cases, heating or using water vapor suffocating will make the adsorbent away from adsorbate, make activated carbon regeneration.
●activated carbon material
activated carbon materials are devided into particle carbon, fiber carbon.
The traditional granular activated carbon with coal charcoal, wood charcoal, coconut shell charcoal, bone charcoal. Sometimes, the particles are made of carbon powder, stick in the other porous materials, reprocessing molding.
Activated carbon fiber is made from the organic fiber containing carbon. Its aperture is small (<50A), large adsorption capacity, fast adsorption, fast regeneration. Commonly used fiber substrates are phenolic aldehyde, plant fiber, polyacrylonitrile, pitch.
●Activated Carbon Adsorption
adsorption capacity—to certain gases, the maximum amount of unit activated carbon adsorption is referred as "absorption capacity." Different materials, or adsorbing different gases, the adsorption capacity is different.
Retention time ─ flow through the activated carbon layer time referred as "retention time." The longer the retention time, the more adequate absorption. In order to maintain sufficient retention time, carbon layer should be thick enough, strainering wind speed can not be too high.
Service life—new activated carbon adsorption efficiency is high, the efficiency constantly weakens when in the use, when the strainer downstream harmful substances concentration near the permitted extent, the strainer is scrapped. The time before scrap is the service life, also known as "penetration time."
Selective ─ generally speaking, large amount of molecular or high boiling point gas is easy to adsorb; adsorption of volatile organic gases are easier than the inorganic molecules’; chemisorption is stronger than physical adsorption selectivity. After activated carbon is impregnated Chemically, it increases a specific gas adsorption capacity.
●Selection of activated carbon strainers
The main factors that affect activated carbon strainer adsorption efficiency and service life are: the type and concentration of pollutants, air temperature, pressure, relative humidity, retention time.
When in the actual selection, you should based on the pollutant type, concentration and processing blowing rate conditions, determine the type of activated carbon and strainer form
By monitoring changes in pollutant concentrations before and after strainers, you can determine whether the activated carbon need to be replaced. However, there is no convenient and practical domestic monitoring tool, so users can only according to the specified cycle or experience to decide the activated carbon strainer service life.
In using process, activated carbon strainer resistance is unchanged, but the weight will increase and experienced professionals can determine the strainer life according to weight change.
Activated carbon strainer upstream and downstream should have a good dust strainer, its efficiency specifications shall not be less than F7. The upstream strainer prevents dust clogging activated carbon material; downstream strainer removes activated carbon own dust.
