Yin Chen1 , Chengliang Han, Peng Chen, Zong Chen, L Y Liu and T Du 1, *1 School of Metallurgy, Northeastern University, Shenyang, Liaoning Province, China
Abstract. Existing air purifiers are mostly indoor air circulation, and most of them cannot achieve indoor and outdoor air circulation and provide fresh air to room. At the same time, the current air purifier filter on the market after absorbing a large amount of dust and other pollutants, if not replaced in time, is likely to cause secondary pollution. In response to these problems, this paper carried out an exploratory research that can achieve indoor and outdoor air purification device. According to the clean air volume of HEPA filter, the pressure of fan and the cross-sectional area of filter are determined, meanwhile, the air resistance of indoor and outdoor circulating air purifier, the effect of air blower on air purification efficiency and filter CADR are discussed in detail. According to the filtering characteristics of single-layer filter, a kind of indoor and outdoor circulating air purifier-single-layer filter type air purifier was designed. Among the air purifier, the PLC control circuit is used to achieve single-layer filter air purifier filter automatically replace.
1 Introduction
In the winter of 2012, air pollution in China was so severe that one-third of the Chinese territory was covered by fog and haze, and the continuously hazy weather in most big cities lasted for more than 30 days [1]. At the beginning of 2016, haze appeared in many places in China. During the severe smog period, many highways were blocked; the aircraft were grounded; the school was closed; patients with respiratory diseases increased significantly, and the normal production and living and physical health of the local residents have been severely damaged. The main component of haze is PM2.5. Research shows exposure to particulate matter less than 2.5 mu;m in diameter (PM2.5) is associated with asthma and respiratory symptoms and etc [2].
It should be pointed out that the annual average concentration of PM2.5 standard set by the World Health Organization is less than 10 mu;g / m3, and the annual average concentration of 35 mu;g / m3 will greatly increase the incidence of haze and death. A recent Chinese case study concluded that the reduction in life expectancy of about 3 years may be expected from long-term exposure to an additional 100 mu;g/m3 of Total Suspended Particles (TSPs) [3]. The status quo of haze pollution in China has been extremely serious. The problem of haze pollution control has long been impeded.
There are several purification technologies in air purifiers such as HEPA(high efficiency particulate air filter), mineralization technology of ultra-light structure, negative ion technology, the photocatalyst technology, electrostatic dust collection, activated carbon adsorption technology and etc [4].
There are two main types of air purifiers on the market in China. The first air purifier usually uses the filter with activated carbon to adsorb the tiny particles. The working capacity of this kind of purifier is limited. The purifying efficiency of the harmful gas and the dust will gradually decrease with the use time until it is completely deactivated. At this moment, the pollutants will accumulate in the indoor and the filter net, which seriously threatens human health. In severe haze, the filter needs to be replaced every 0.5-3 months, and each time the cost of more than 100 RMB, greatly increased the cost of late maintenance. The second air purifier uses high-voltage electrostatic to capture dust particles, but electrostatic dust removal technology can only remove particulate pollutants, cannot remove harmful gas pollutants. In addition, electrostatic dust collection has discharge electrode in which a direct current is applied [5], and the relevant high-voltage electrostatic generator, such as the discharge needles, need regular cleaning. The process is difficult to operate, and easily damaged, expensive, especially high voltage electrostatic technology will produce a large number of harmful ozone. At present, two types of air purifiers on the market are the circulation of the original indoor air, the circulation of indoor and outdoor air cannot be achieved, and the fresh air cannot be provided to the room.
2 Methodology
This paper designs an air purifier that can purify the outdoor air to the room and fresh air is supplied to the room by filtering outdoor air. The air pressure in the room is greater than the outdoor air pressure so that the air in the room passes through the gaps to the outdoor one-way circulation and prevents outdoor air backflow from bringing atmospheric pollutants into the room. In addition, the current air purifier filter on the market cannot be automatically replaced. Once used for some time, the filter will accumulate large amounts of dust and other pollutants in the absorption. If not timely replacement, it will be likely to cause secondary pollution. Therefore, this paper designed a single-layer filter air purifier that can automatically replace the filter through the PLC. Compared to the folded filter, this single-layer filter design will greatly improve the filterrsquo;s life and the volume of dust of the same area. The price will be relatively decreased, while not causing secondary pollution of indoor air.
2.1. HEPA filter HEPA filter efficiency for the 0.3 micron fine particles can reach 99.7%. Its characteristic is the air can pass, but the tiny particles cannot pass. HEPA filter is the most effective smoke, dust, bacteria and other pollutants filter material. Therefore, this paper chose Spring CMI300 HEPA filter net as a filter material.
2.2. Differential pressure gauge The Testo510 (shown in Figure 1) is a device for measuring differential pressure. It is commonly used for measuring differential pressure (such as measuring filter net permeability) an
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