Thermal destruction is currently a widely used and researched method for treating organic waste gases, especially for low concentration organic waste gases. The thermal destruction of organic compounds can be divided into direct flame combustion and catalytic combustion. Direct flame combustion is a method of direct combustion of organic matter in an airflow and combustion of auxiliary fuels. In most cases, the concentration of organic matter is low enough to burn without auxiliary fuel. Direct flame combustion can achieve a heat treatment efficiency of 99% under appropriate temperature and retention time conditions.
Catalytic combustion is a method in which organic matter is heated in a gas stream and accelerated in chemical reactions (or efficiency degradation) under the action of a catalytic bed. The presence of a catalyst requires less retention time and lower temperature for organic matter during thermal degradation compared to direct combustion. Catalysts play an important role in catalytic combustion systems. The catalysts used for organic waste gas purification are mainly metals and metal salts, with metals including precious metals and non precious metals. The currently used metal catalysts are mainly Pt and Pd, which have mature technology and high catalytic activity. However, they are relatively expensive and when dealing with halogenated organic compounds containing elements such as N, S, and P, the organic compounds are prone to oxidation and other reactions, leading to catalyst deactivation. Non metallic catalysts include transition group elements such as cobalt and rare earths. In recent years, there has been a lot of research and development on catalysts both domestically and internationally, with a focus on non precious metal catalysts and many achievements. For example, catalysts made of V2O5+MOX (M: transition metal)+precious metals are used to treat methyl mercaptan waste gas, while Pt+Pd+Cu catalysts are used to treat nitrogen-containing organic alcohol waste gas.
Due to the frequent presence of impurities in organic waste gas, it is easy to cause catalyst poisoning, and the toxic substances that cause catalyst poisoning (inhibitors mainly include phosphorus, lead, bismuth arsenic, tin, mercury, ferrous ion zinc, halogens, etc.). The catalyst carrier plays a role in saving the catalyst, increasing the effective area of the catalyst, making the catalyst have a certain mechanical strength, reducing sintering, and improving catalytic activity and stability. The materials that can be used as carriers mainly include AL2O3 iron vanadium, asbestos, clay, activated carbon, metals, etc. The most commonly used are ceramic carriers, which are generally made into mesh, spherical, columnar, and peak nest shapes. In addition, in recent years, there have been many successful studies on zeolites such as zeolite. For catalytic combustion, the focus and hotspot of future research will still be to explore highly active catalysts and their supports, as well as catalytic oxidation mechanisms.