Advantages of Atmospheric Pressure Plasma

2019-03-25

Generating plasma at atmospheric pressure is the most economical and efficient method. Typically, in order to maintain stable plasma generation, conventional systems must operate under low pressure. This requires vacuum chambers and vacuum pumps to maintain the low-pressure environment, which not only increases costs and decreases throughput per unit time but also results in high maintenance costs. For example, vacuum pumps are vulnerable to strong acids, strong alkalis, and particulates, making them easily damaged. Therefore, if stable plasma can be generated under atmospheric pressure, these vacuum devices are no longer necessary, simplifying equipment and greatly reducing operating and maintenance costs. Additionally, the workpieces are not limited by the size of the vacuum chamber, and the process can be operated continuously, significantly increasing throughput.
As shown in Figure 1, atmospheric plasma already has multiple industrial applications. See Table 1 for details. Among them, plasma jet systems and dielectric barrier discharge (DBD) systems have attracted much attention due to their non-thermal plasma characteristics and ease of integration into production lines.

Moreover, atmospheric plasma has the following advantages that make it highly promising for decomposing pollutants into non-toxic gases at room temperature in both gaseous and liquid-phase environments:
1. High removal efficiency: More reactive than traditional incineration or catalytic reaction methods, enabling originally slow reactions to proceed rapidly.
2. Low setup cost: The primary equipment is a high-frequency power supply, with no need for heating systems, making installation simple.
3. Energy saving: With low energy consumption and high efficiency. Plasma can be generated at low gas temperatures, and plasma chemical reactions occur near room temperature. Since there's no need to heat the gas, a significant amount of energy can be saved. Plasma energy efficiency is much higher than traditional chemical reactions because traditional or catalytic reactions rely on heating gas to increase molecular kinetic energy. After molecular collisions, only a small portion of kinetic energy is converted into potential energy to break molecular bonds. Thus, most of the added energy is spent on heating the gas, not on bond dissociation. However, plasma energy is applied directly to electrons, and the high-energy electrons break bonds very efficiently. The electron energy can be nearly 100% converted into the potential energy needed to break molecular bonds, without needing to increase molecular kinetic energy. Especially since gas has poor heat transfer efficiency, plasma's ability to break bonds at low temperatures greatly conserves energy.
4. Low operating costs and no secondary pollution: No need for chemical reagents like absorbents or adsorbents, nor catalysts or fuels, saving operational costs and avoiding secondary pollution.
5. Easy operation and maintenance: Plasma systems are simple and easy to operate, with no consumable parts in the reactor, thus requiring minimal maintenance.
6. Compact equipment: Plasma reactors are smaller than absorption towers, adsorption towers, or incinerators, saving space and making them ideal for improving air pollution in existing factories.
7. Can treat low-concentration pollutants: Capable of handling malodorous gases in the ppb to ppm range, comparable to adsorption methods and superior to absorption and incineration methods.
8. Short startup time: Unlike incinerators that require a warm-up period to reach high temperatures for decomposition, plasma reactors need no warm-up, thus avoiding energy waste in heating.

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