Adsorption is one of the most widely used VOCs treatment technologies in the industry and is relatively mature. According to the process conditions, it can be divided into variable pressure adsorption, temperature adsorption, temperature-pressure adsorption and electricity adsorption, and the advantages and disadvantages of the adsorption method for different process conditions .
Absorption technology
Absorption method is the use of absorption liquid and organic waste gas to the principle of phase solubility to achieve the purpose of organic waste gas treatment.
Common absorbents can be divided into mineral oil (such as diesel, washing oil and other non-polar mineral oil), water composite absorbents (such as water - washing oil, water - surfactants - additives and other composite absorbents) and high boiling point organic solvents (such as DBO, DEHA, DEHP, etc.).
Absorption method has the advantages of mature treatment process, simple equipment, good absorption effect, etc., can deal with most of the volatile organic compounds, widely used in industrial fields. The absorption equipment commonly used in industrial production is packed absorption tower and spray absorption tower. As shown in Figure 1, the packed absorption tower has a large phase interface, which allows a wide range of adjustment of gas-liquid contact time and gas-liquid ratio, as well as high operational flexibility and low cost, with good pressure drop and separation efficiency.
Condensation technology
Condensation recovery method is the process of condensing and separating volatile organic compounds in the vapor state by changing the temperature or pressure of the system.
Condensation technology is generally applied to organic waste gas with high concentration and high boiling point, and is usually used in combination with absorption and adsorption methods.
Membrane Separation Technology
Membrane separation technology can be divided into 2 major categories: liquid separation and gaseous separation according to the state of the treated material. In gaseous membrane separation, for example, the organic waste gas is pressurized by a compressor and then enters a condensing system, after which the condensed liquid VOCs can be recycled or processed in the next step.
The membrane separation system selectively allows the uncondensed gas to pass through so that the VOCs are enriched, and the gas that cannot pass through the membrane can be directly discharged as purified gas, while the waste gas that passes through the membrane returns to the compressor to continue the cycle of treatment.
Compared with traditional VOCs treatment technology, membrane separation method has the advantages of high mass transfer efficiency, low energy consumption, small device size and simple operation. The key of this technology lies in the selection of membrane. The selection of membrane material should consider membrane stability, mechanical properties, hydrophobicity, economy, and high temperature resistance if the temperature of the treated waste gas is high