1. Overview of Printing Waste Gas
The printing industry generates organic waste gas during printing, drying, and cleaning processes. This is mainly due to the use of printing inks, especially during the printing drying process, where evaporation produces a large amount of organic waste gas. Organic solvents account for 70%-80% of the total amount of organic ink. The main components of printing waste gas are benzene, toluene, xylene, acetone, butanone, lipids, ethers, and other organic waste gases, which not only affect the health of employees but also cause air pollution to the surrounding environment. Therefore, it is necessary to purify printing waste gas to meet emission standards.
2. Treatment Methods for Printing Waste Gas
Organic waste gas is the main air pollutant in printing. In China, there are many treatment methods for organic waste gas. The most common methods are activated carbon adsorption, low-temperature plasma, incineration, and UV photolysis. Next, Tian Haoyang will introduce the common treatment methods for printing waste gas.
(1) Activated Carbon Adsorption Method
The main principle of the adsorption method is to use porous solid adsorbents (activated carbon, silica gel, molecular sieves, etc.) to treat organic waste gas. In this way, harmful components can be fully adsorbed through chemical bond force or molecular gravity and adsorbed on the surface of the adsorbent, thereby achieving the purpose of purifying organic waste gas. Currently, the adsorption method is mainly used to purify large-volume, low-concentration (≤800mg/m3), particle-free, non-viscous, and low-concentration organic waste gas at room temperature.
Activated carbon has a high purification rate (activated carbon adsorption rate can reach more than 95%), is widely used, easy to operate, and requires low investment. After adsorption saturation, the activated carbon must be replaced with new activated carbon. The cost of replacing saturated activated carbon also requires finding professionals for hazardous waste treatment, and the operating cost is high.
(2) Low-Temperature Plasma Process
The low-temperature plasma method utilizes the characteristics of high chemical activity in plasma. The high-voltage discharge device will generate high-energy electrons and ions during the discharge process to separate oxygen molecules in the air. After the oxygen molecules absorb energy, they will generate free oxygen ions. The pollutants in the organic waste gas react with the free oxygen groups and are finally converted into CO2 and H2O, thereby achieving the purpose of purifying waste gas.
This method has the characteristics of wide applicability, high purification efficiency, and small equipment area, and is suitable for organic waste gas that is difficult to treat by other methods. However, due to the selection of high-voltage discharge devices, it is prone to explosions in enclosed spaces with high water content, dust content, and organic waste gas concentration, so it is limited.
(3) Incineration
In the incineration method, volatile organic compounds are completely incinerated and decomposed into CO2 and H2O only under high temperature and sufficient air conditions. The incineration method is suitable for various organic waste gases and can be divided into direct incineration, thermal incineration, and catalytic incineration.
High-concentration waste gas with an emission concentration greater than 5000mg/m3 generally uses direct incineration. VOC waste gas is incinerated as fuel. The incineration temperature is generally controlled at 1100℃, and the treatment efficiency can reach 95%~99%.
Thermal incineration is suitable for treating waste gas with a concentration of 1000-5000 mg/M~3. In thermal incineration, the concentration of VOCs in the waste gas is low, and other fuels or auxiliary gases are needed. The temperature required for thermal incineration is lower than that of direct incineration, about 540-820℃. However, if the VOCs waste gas contains s, N, and other elements, the direct discharge of the incinerated waste gas will cause secondary pollution.
After the organic waste gas is treated by thermal incineration or catalytic incineration, the purification rate is high, but the investment and operating costs are high. Due to the large number of emission points and small emission amounts, it is difficult to complete centralized collection. There are many sets of incinerators, which require a large amount of ground space. Thermal incineration is more suitable for 24 hours
The above information is provided by a waste gas treatment manufacturer
