Introduction to Air Purifier
Air purifier, also known as "air cleaner", air freshener, purifier, refers to the decoration pollution that can absorb, decompose or transform various air pollutants (generally including PM2.5, dust, pollen, odor, formaldehyde and the like), Bacteria, allergens, etc.), products that effectively improve air cleanliness are mainly divided into household, commercial, industrial, and building.
There are many different technologies and media in the air purifier so that it can provide clean and safe air to users. Commonly used air purification technologies are: adsorption technology, negative (positive) ion technology, catalytic technology, photocatalyst technology, superstructure photo mineralization technology, HEPA high-efficiency filtration technology, electrostatic dust collection technology, etc .; material technologies mainly include photocatalyst, activated carbon, Synthetic fiber, HEPA high-efficiency material, negative ion generator, etc. Existing air purifiers are mostly of composite type, that is, multiple purification technologies and material media are used at the same time.
Background
According to a WHO research report, among the 4.3 million people who died from kitchen air pollution worldwide in 2012, stroke accounted for 34%, and chronic obstructive pulmonary disease and ischemic heart disease accounted for 22% and 26%, respectively. Lung cancer accounts for about 6%.
In a research project on disease risk assessment in the famous British medical journal "The Lancet", kitchen air pollution (smoke) has been listed as the biggest health hazard after high blood pressure, smoking, and alcoholism. More people die each year from the continuous inhalation of smoke from kitchen fires than the total number of deaths from malaria, tuberculosis, and AIDS.
The study of Chinese farmers in the Journal of the National Cancer Society in the United States also confirmed the impact of kitchen air pollution on human health. Chinese and American scientists who participated in the study surveyed more than 20,000 farmers in Yunnan Province and found that farmers without stoves in their homes were nearly twice as likely to develop lung cancer as those with chimneys or ventilation equipment added to their homes. Researchers say that to the extent that it causes lung cancer, using a stove without ventilation is similar to smoking.
Air purifiers are also known as products that can absorb, decompose or transform various air pollutants (generally including decoration pollution such as PM2.5, dust, pollen, odor, formaldehyde, bacteria, allergens, etc.), and effectively improve air cleanliness. , Mainly used in household, commercial, industrial, building.
Main types
Judging from the working principle of the air purifier, there are three main types: passive, active, and active-passive hybrid.
According to the air purifier's removal technology for particulate matter in the air, there are mainly mechanical filter type, electrostatic electret filter type, high-voltage electrostatic dust collection, negative ion and plasma method.
Mechanical filtration
Generally, the following four methods are used to capture particles: direct interception, inertial collision, Brownian diffusion mechanism, screening effect, which has a good collection effect on fine particles but high wind resistance. In order to obtain high purification efficiency, the resistance of the filter screen is large, and the filter The network needs to be dense, which leads to a reduction in life, and it needs to be replaced regularly.
High voltage electrostatic dust collection
A dust collection method that uses a high-voltage electrostatic field to ionize gas to charge dust particles to the electrode. Although its wind resistance is small, it has a poor collecting effect on larger particles and fibers, which will cause discharge, and it is troublesome and time-consuming to clean, and it is easy to produce ozone. Form secondary pollution.
"High-voltage electrostatic dust collection" is a method that not only ensures air volume but also absorbs fine particles. This is the way in which particles are charged by applying a high voltage before passing through the filter core so that the particles are "easy to be adsorbed" on the filter core under the action of electricity.
The high-voltage dust collecting part originally applied a high voltage to the two electrodes, and when the two electrodes were discharged, the passing dust was charged. Most dust is originally neutral or weakly charged, so the filter element can only filter dust larger than the mesh. But narrowing the mesh of the filter element can cause a blockage. The high-voltage electrostatic dust collection method can make the dust charged. Under the action of electricity, it is adsorbed on the specially processed and permanently charged filter element. Therefore, even if the mesh of the filter element is too large (thick), the dust can be reliably captured.
Static electret filter
Relative mechanical filtration can only effectively remove particles above 10 microns, and when the particle size of the particles is divided into the range of 5 microns, 2 microns or even sub-micron, the efficient mechanical filtration system becomes more expensive, and Wind resistance will increase significantly. Filtered by electrostatic electret air filter materials, it can achieve high capture efficiency with low energy consumption, and at the same time has the advantages of electrostatic dust removal and low wind resistance, but it does not need to be connected to a voltage of tens of thousands of volts, so it will not produce ozone, and Its composition is made of polypropylene, which is convenient for disposal.
Electrostatic precipitator
It can filter dust, smoke, and bacteria smaller than cells to prevent diseases such as lung disease, lung cancer, and liver cancer. The most harmful to the human body in the air is dust less than 2.5 microns because it can penetrate cells and enter the blood. Ordinary purifiers use filter paper to filter dust in the air, which is very easy to block the filter holes. The dust not only has no sterilization effect but also easily causes secondary pollution.
Electrostatic sterilization
Using a high-voltage electrostatic field of about 600 volts can completely kill bacteria and viruses attached to the dust in an instant, preventing colds, infectious diseases, and other diseases. Its sterilization mechanism is to destroy the 4 polypeptide chains of bacterial capsid protein and damage RNA.
The relevant standards of the national "Air Purifier" define the air purifier as "a device that separates and removes one or more pollutants from the air. A device that has a certain ability to remove pollutants in the air. It mainly refers to the room The single air purifier used and the modular air purifier in the centralized air conditioning ventilation system.
According to purification requirements, air purifiers can be divided into:
(1) Purified type. If it is located in an area with moderate indoor humidity, or if the air quality requirements are not too high, then a pure air purifier can meet the demand.
(2) Humidification and purification type. If it is located in a drier area, the air conditioner is often turned on and the air conditioner is dehumidified to cause the indoor air to dry, or the air quality requirements are high, then the purchase of an air purifier with humidification and purification function will be the most suitable choice. LG Future Celebrity Air Purifier also has natural humidification technology, which uses scientific and technological means to realize the vaporization of water. The windmill or disc filter rotates to remove harmful substances in the tray and eliminate only ultra-fine and clean water molecules. Into the air.
(3) Intelligent. If you like automated operation, intelligent monitoring of air quality, or embody noble taste, or need to be more decent for gift-giving, then the purchase of an intelligent air purifier is the best choice.
(4) Vehicle-mounted type. If it is used for car air purification, it is necessary to specifically purify car odors, car formaldehyde, and other car interior pollution and can be specifically placed in the car air purifier, so the best choice is the car-type air purifier.
(5) Desktop-type. That is, it is placed on the desktop to purify the air within a certain range around the desktop and protect the health of people near the desktop. If you often sit in front of a computer, desk, or desk, but the indoor area is not small, or in a public place, it is not cost-effective and fashionable to buy a large air purifier by yourself. A type of air purifier is a better choice.
(6) Large and medium size. It is mainly suitable for large-scale indoor occasions, such as home halls, senior bank offices, senior administrative offices, important lecture halls and conference halls, high-end hotels, hospitals, beauty salons, kindergartens, etc.
(7) Central air-conditioning system type. It is mainly applicable to the case where a central air conditioner is installed, or a single room with a ceiling or multiple rooms are cleaned together.
Suitable
1. Applicable place:
1-Residences that have just been renovated or renovated.
2-There are residences for the elderly, children, pregnant women and newborns.
3-The residence of people with asthma, allergic rhinitis, and pollen allergy.
4-Residences for keeping pets and livestock.
5-Residential buildings that are more closed or affected by second-hand smoke.
6-Hotels, public places.
7-The residence of people who are willing to receive a high-quality life.
8-Hospitals to reduce infections and prevent the spread of diseases.
2. Applicable people:
1-Pregnant women: Pregnant women may experience general discomfort in the air-pollution room, appear dizziness, sweating, dryness of the tongue, chest tightness and vomiting, etc., which will adversely affect the development of the fetus. [3] The possibility of suffering from heart disease is three times that of children born to pregnant women who breathe fresh air.
2-Children: Children's bodies are developing, the immune system is relatively fragile, and they are vulnerable to indoor air pollution, resulting in decreased immunity, delayed body development, induced blood diseases, increased incidence of asthma in children, and greatly increased children's intelligence reduce.
3-Office people: an enviable occupation when working in a high-end office building. However, in an environment with poor air quality and constant temperature, it is easy to cause dizziness, chest tightness, fatigue, and mood swings. It affects work efficiency, causes various diseases, and can cause cancer in severe cases.
4-The elderly: The physical function of the elderly declines and they often suffer from various chronic diseases. Air pollution not only causes respiratory diseases such as bronchitis, pharyngitis, and pneumonia in the elderly. It can also induce hypertension, heart disease, cerebral hemorrhage, and other cardiovascular and vascular diseases.
5-Patients with respiratory diseases: Long-term life in polluted air will cause decreased respiratory function and worsen respiratory symptoms, especially rhinitis, chronic bronchitis, bronchial asthma, emphysema, and other diseases. By breathing pure air to achieve an auxiliary and radical therapeutic effect.
6-Driver: There is a lack of oxygen in the car, and the exhaust gas of the car is seriously polluted.
Application field
Air purifiers are used in the home, medical, and industrial fields. In the home field, stand-alone home air purifiers are the mainstream products in the market. The main function is to remove particulate matter in the air, including allergens, indoor PM2.5, etc. At the same time, it can also solve the air pollution problem of volatile organic compounds in indoor, underground spaces, and vehicles due to decoration or other reasons. Because the release of air pollutants in relatively closed spaces has the characteristics of persistence and uncertainty, the use of air purifiers to purify indoor air is one of the internationally recognized methods to improve indoor air quality.
Filter technology
HEPA filter
High-efficiency particulate air filter (HEPA) is one of the most popular technologies used in air purification. The standard HEPA filter can absorb 99.7% of suspended particles with a size of 0.3 microns (0.3 microns is the most difficult to filter size), but its wind resistance is relatively large, and it is generally rarely used in air purifiers. Actual air purifiers The manufacturer claims that HEPA is actually true HEPA. Its filtration efficiency is slightly lower than HEPA, and its wind resistance is relatively low. Whether it is real HEPA or publicized HEPA, it makes the intake air fresher and cleaner. The filter absorbs chemical fumes, bacteria, dust particles, and pollen. After being filtered by the air purifier, the air is free of these pollutants.
The advantage of HEPA filter is effective and safe, and it is the most important technology for removing particulate pollutants in the air, but the disadvantage is that it can only filter suspended particles and cannot remove harmful gases. The air purifier using HEPA should have a good airtight design, otherwise, the air will wrap around the filter and lose the filtering effect.
Electrostatic electret filter technology
Using non-woven fabric loaded with electrostatic electret to collect dust is an upgraded version of HEPA technology. The advantages are low wind resistance, high efficiency, high dust holding capacity, and the most important is safety. Represented by the “high-efficiency electrostatic air filter” on the market, a breakthrough static permanent filter is used to effectively block particulate contaminants larger than 0.1 microns in the air, such as dust, dander, pollen, bacteria, etc. Impedance ensures energy saving. In addition, the deep dust-holding design ensures a longer service life. As of 2013, it has been widely used in home and vehicle air conditioners (such as SAIC, Volkswagen, GM, and other well-known brand best-selling models) and some commercial construction areas (such as Bird's Nest, Beijing Hotel, Capital Airport Phase III).
Activated carbon filter
Air purification activated carbon is an internationally recognized high-efficiency adsorption material, which was used in gas masks as early as the "World War I". Activated carbon is widely used in the car or indoor air purification. Activated carbon is a porous carbon-containing substance, and its well-developed void structure makes it have a large surface area, so it is easy to make full contact with toxic and harmful gases in the air, and the strong adsorption force field around the activated carbon pore will immediately become toxic Gas molecules are sucked into the pores, so activated carbon has a very strong adsorption capacity is also the main technology to remove gaseous pollutants. Activated carbon adsorption technology is mainly divided into two categories: physical adsorption and chemical adsorption.
Physical adsorption is mainly for the adsorption of these macromolecular pollutants through the microporous structure of activated carbon itself for macromolecular organic gases (such as TVOCs such as benzene). Chemisorption is mainly aimed at some small-molecule gaseous pollutants such as (formaldehyde, hydrogen sulfide, nitrogen oxides, etc.), because small-molecule gas is easily desorbed again after being adsorbed to form secondary pollution, so chemical treatment of activated carbon is required The adsorbed gas reacts with chemical components to achieve the adsorption effect.
Dust collection technology
The principle of high-voltage electrostatic adsorption is used to remove particulate contaminants in the air, such as dust, soot, pollen, cigarette smell, and kitchen fumes. The disadvantage of this technology is that it is easy to produce ozone, and it is only effective for large particles such as particulate matter. The disadvantage is that you need to pay attention to the safety of electrical appliances (high voltage can sometimes reach tens of thousands of volts), it is difficult to clean, and it is easy to produce ozone. You must properly design the ozone emission to below the safe concentration.
Ozone can sterilize while killing some viral bacteria, it may also kill human white blood cells, which may cause cancer. Therefore, it is generally not used for household air purification products. The ozone factor is mainly used to sterilize and disinfect the air. Ozone is world-renowned and highly effective sterilization and detoxification oxidant, which can efficiently decompose various decoration pollutants and quickly kill various viruses and bacteria. It can meet the needs of just decoration and periodic special static treatment, but because of the strong oxidation effect of ozone, it will cause harm to people and accelerate the aging of the surface of the object. It needs to be reminded that this treatment method requires personnel to avoid, and the treatment is completed regularly for 30 minutes After the automatic reduction to oxygen, it is a green oxidative decomposition agent without any chemical residue.
Ultraviolet rays are sterilized and sterilized by ultraviolet lamps inside the machine, but they are also prone to generate too much ozone. To achieve an effective disinfection function, the certain exposure time must be ensured. The air purifier generally has a high wind speed, so the ultraviolet sterilization ability is limited, and the human body cannot receive ultraviolet radiation for a long time, and its seal must be tight.
Physical technology
The photocatalyst is a general term for a photo-semiconductor material with photocatalytic function represented by nanometer titanium dioxide. It is coated on the surface of the substrate and produces a catalytic degradation function under the action of light. It can degrade toxic and harmful gases in the air. The photocatalytic air purification device with ultraviolet light source has a purification efficiency of 3% (calculated based on the difference in pollutant concentration at the inlet and outlet of the device), and the best does not reach 5%. Therefore, its purification efficiency is very low, and relevant studies have shown that highly toxic intermediate products will be produced in the process of photocatalytic.
Anion and plasma method
It is caused by the particles in the air being charged and coalescing to form larger particles and settling, but the particles are not actually removed, but only adhere to the nearby surface, which is easy to cause dust again. High-pressure ion technology produces ozone and other by-products during the work process.
Biotechnology
Sesquiterpenoids are often present in volatile oils in the form of alcohols, ketones, lactones, etc. in plants, with a strong aroma and biological activity, which can effectively digest airborne particulate matter, bacteria, etc. Remove odors, increase air oxygen content, keep the air fresh, etc. The plant itself has a certain smell and stays in the air. Once the oxidation process is completed, the smell will quickly disappear. Unlike other plant essential oils that stayed for a long time. The active ingredient, small terpenoid molecules, simultaneously surround, oxidizes, decomposes, removes, or harms toxic substances such as aldehydes, benzene, and others, and increases the effective oxygen content in the air. Developed Asian countries, Singapore, Japan, Hong Kong, and Taiwan, have already taken the lead in using this technology to purify the air in cities, homes, and cars. With the increasing frequency of communication between Hong Kong, Macao, and Taiwan, this technology has also entered mainland China.
Resolution Technology
Ecco oxygen polymerization is a technology that specifically treats and decomposes air pollutants in the air, and cannot be used to treat solid pollutants.
Nanomaterials can be adjusted according to the characteristics of the pollutants to improve the system's ability to process specific pollutants.
After the nanomaterials adsorb the pollutants, they can use active oxygen to decompose the pollutants and continuously regenerate. This will not only greatly extend the life of the system, but also increase the capacity to process pollutants.
The decomposition process of pollutants by active oxygen in nanomaterials is much faster than that in air. With the addition of a catalyst to the nanomaterials, the rate of decomposition of pollutants by living oxygen is further increased.
It cannot deal with non-gaseous pollutants that are difficult to decompose, such as oil and dust. Nanopores in nanomaterials will be blocked by these substances and lose their ability to deal with pollutants.
Mineralization
This technology adopts the method of mineralization to make micro-nano structural materials, improve its adsorption capacity, improve its response to light, activate energy from ultraviolet light to visible light, promote carrier separation, reduce the probability of recombination, and degrade The efficiency of pollutants has increased by two orders of magnitude, and the mineralization rate has increased by 85%.
The national indoor environment and indoor environmental product quality supervision and inspection center have authorized the detection rate of mineralized formaldehyde to reach 87%. This technology successfully realized the loading of photocatalytic materials, and maintained the high activity of nano-powders, and quickly mineralized the organic pollutants in waste gas into CO2 and H2O.
Development Path
In 1823, John and Charles Dean invented a new type of smoke protection device that would allow firefighters to avoid smoke intrusion when extinguishing fires.
In 1854, a man named Johns Townhouse made new progress based on the invention of his predecessors: through several attempts, he learned that adding charcoal to the air filter can filter out harmful and toxic gases from the air.
During World War II, the US government began to conduct research on radioactive materials. They needed to develop a way to filter out all harmful particles to keep the air clean and allow scientists to breathe, so HEPA filters came into being.
In the 1950s and 1960s, HEPA filters were once very popular. HEPA is a filtration standard, that is, for 0.3-micron particles, it has a filtration efficiency of more than 99.97%, and it emphasizes the single filtration efficiency. In the air purifier, the wind resistance of the filter that meets the HEPA standard is too high to be applicable.
In the 1980s, the focus of air purification has shifted to air purification methods, such as home air purifiers. The filters in the past are very good at removing odor, toxic chemicals and toxic gases in the air, but they cannot remove mold spores, viruses or bacteria. The new air purifiers for homes and offices can not only clean the toxic gases in the air It can also purify the air and remove bacteria, viruses, dust, pollen, mold spores, etc. in the air.
Since the late 1990s, as the demand for sterilization and deodorization has increased, and "antibacterial fever" has been launched in the field of air purifiers. The air purifier also used the photocatalyst filter element in 1996 to improve the sterilization and deodorization performance.
After 2002, affected by the spread of SARS and the epidemic of new influenza, people's demand for anti-virus in air purifiers is increasing. Develop and equip air purifiers with "streaming energy" technology. The air purifier technique uses decomposing (oxidizing) filter elements to capture bacteria and viruses.
In 2008, in addition to countermeasures to remove harmful substances in the air, in order to meet the demand for eliminating room drying, the air purifier added a "humidification function".
As of 2013, most of the air purifiers on the market, especially the air purifiers below 10,000 yuan, cannot be called "HEPA" for their particulate filters.
Working Principle
The air purifier is mainly composed of motor, fan, air filter, and other systems. Its working principle is: the motor and fan in the machine circulate the indoor air, and the polluted air passes through the air filter in the machine to remove various pollutants. Or adsorption, some models of air purifiers will also be equipped with a negative ion generator at the air outlet (the high voltage in the negative ion generator generates DC negative high voltage during operation), which continuously ionizes the air, generates a large number of negative ions, and is sent out by the micro fan. Form negative ion airflow to achieve the purpose of cleaning and purifying the air.
Passive adsorption filter type purification principle (filter purification)
The main principle of the passive air purifier is: use the fan to draw air into the machine and filter the air through the built-in filter screen, which can mainly play the role of filtering dust, odor, toxic gas and killing some bacteria. The filter is mainly divided into particulate matter filters and organic matter filters. The particulate filter is divided into a coarse effect filter and fine particulate filter.
The quality of the fans and filters of these products determines the air purification effect. The placement of the machine and the indoor layout will also affect the purification effect.
Active purification principle (no filter type)
The fundamental difference between the principle of active air purifiers and the principle of passive air purification is that active air purifiers get rid of the limitations of fans and filters, rather than passively waiting for indoor air to be drawn into the purifier for filtration and purification. Rather, it effectively and actively releases purification and sterilization factors into the air. Through the characteristics of air diffusion, it reaches all corners of the room to purify the air without dead ends.
The technologies for purifying and sterilizing factors on the market mainly include silver ion technology, negative ion technology, low-temperature plasma technology, photocatalyst technology and net ion group ion technology. The biggest defect of this type of product is the problem of excessive ozone emission.
Double purification (active purification + passive purification)
This purifier is actually a combination of passive purification technology and active purification technology.
Purification effect
First, compare the efficiency of air purification. The air purifier of the passive adsorption purification mode mostly uses the fan + filter mode for air purification, and the wind uses the flow of air to inevitably have dead corners. Therefore, passive air purification can only produce certain purification around the air purifier. It takes a long time to filter all the indoor air, and it is difficult to produce an effect on the purification of the entire indoor environment.
Active air purification is to use the diffuse characteristics of air to purify factors to all corners for air purification, wherever the air can diffuse can produce a purification effect. Comparing the negative ion air purifier, it is found that after releasing negative ions into the air, the negative ions can take the initiative to attack, search for polluting particulate matter in the air, and condense it into a mass, and actively settle it. From this point alone, active air purification has obvious advantages.
The second is to compare the removal effects of small air pollutants. Among the air pollutants, the most harmful to people is fine particles with a diameter of less than 2.5 microns (that is, PM2.5, which is medically called particulate matter in the lungs).
After experimental research, it is found that for these fine particles such as PM2.5, the passive purification mode is powerless. Small particles such as PM2.5 can easily penetrate the filter, activated carbon and other substances, and re-enter the air to harm human health.
Compared with the negative ion air purifier for air purification based on the principle of active purification, it is found that the negative ion with small particle size in the air can not only easily remove the large particle particles in the air, but also for the air purifier diameter less than 0.01%, it is difficult The particles removed have a 100% sedimentation removal effect. The ecological-grade negative ion generation technology that imitates nature has come out. It is characterized by small particle size and high activity. With its excellent diffusion effect and health care effect, it can achieve a better air optimization effect.
Finally, a comparative analysis of the quality of air treatment. The study found that under the principle of passive air purification if the filter pore size can be small enough, the result of air treatment can only achieve the purpose of purification, that is, only "clean" air can be obtained; while the negative ion air purifier is different, not only can Effectively remove particulate pollutants in the air, decompose formaldehyde and other harmful gases, provide clean air to the indoor environment, and also provide the indoor environment with air negative ions that have a high effect on human health and wellness, so that the indoor air quality reaches "healthy air" standard.