Off-gas detection and treatment for green air-plasma process

• Published in: Green processing and synthesis 2022-10, Vol.11 (1), p.965-973
• Main Authors: Bai, Liuyang, Ouyang, Yuge, Wang, Hongbing, Wang, Min, Yuan, Fangli
• Format: Article
• Language: English
• Subjects: Absorption; Air temperature; Chemical activity; Emission standards; Gas analyzers; green process; High temperature; Materials processing; off-gas; Oxidants; Oxidizing agents; Oxygen content; Plasma; removal of NO; removal of nox; thermal plasma; Thermal plasmas; Waste treatment
• ISSN: 2191-9550; 2191-9542; 2191-9550
• DOI: 10.1515/gps-2022-0082

Thermal plasma is a promising technology widely used in materials processing and waste treatment due to its unique properties including high temperature, high energy density, high chemical activity, and high quench rate. Air-plasma is preferentially used because air is of low price as plasma gas. The content of NO in off-gas from air-plasma was determined using a gas analyzer, and a treatment unit was designed for the green air-plasma process. Results show that the concentration of NO in off-gas from air-plasma was 2,489 and 9,112 ppm when the plasma input power was 50 and 150 kW, respectively. O in the off-gas would act as an oxidant to promote NO absorption; thus, alkali absorption method was directly used for the treatment of the present off-gas from air-plasma. The absorption efficiency could be increased to 62.2% when additional O was provided into the off-gas to change its O content from 20% to 50%. The absorption rate was estimated based on the experimental data and a multistage absorption unit design, which could be reduced below 100 ppm and meet the emission standard. This article presents the feasibility of thermal plasma off-gas purification, so as to truly realize the green plasma process.