Recuperative catalytic oxidation (KNV, KOJ)
Recuperative catalytic oxidation is a simple and effective system for cleaning air from VOCs by burning on a catalyst bed at lower temperatures than thermal methods. The technology is ideal for medium to higher VOC concentrations in waste gas (in the order of grams per m³) and provides high emission removal efficiency.
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HOW DOES IT WORK?
The polluted air first passes through a heat exchanger, where it is preheated using the heat from the cleaned flue gases. It then enters a heating chamber with electric heating or a gas burner, which, if necessary, heats the gas to the operating temperature of the catalytic reaction (typically above 300 °C). The air then flows through a catalytic reactor filled with a layer of catalyst, where the VOC is oxidized to carbon dioxide and water. Since catalytic oxidation occurs at relatively low temperatures, it does not produce nitrogen oxides (NOx). The released reaction heat is transferred to the supplied polluted air in a built-in exchanger, thereby saving energy. This technology typically achieves a VOC removal efficiency of over 99%.
At a sufficient VOC concentration (approximately above 2 g TOC/m³), the process is autothermal, without the need for additional fuel, which further reduces operating costs.
Key benefits:
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High efficiency and clean operation: Removes >99% of VOCs from the air. Thanks to the low combustion temperature, secondary pollutants such as NOx are not produced.
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Energy saving: The integrated heat exchanger makes maximum use of the waste heat of the process. At higher VOC concentrations, the system operates autothermally, no external heat source is required.
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Low operating costs In the operating range above the autothermal limit (~2 g/m³ TOC), the unit has very low fuel consumption. The catalytic converter reduces the required combustion temperature and thus the heating costs.
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Robustness and safety: A simple design with a minimum of moving parts ensures reliability. Operating temperatures are lower than with thermal oxidation, which means less thermal stress on the equipment and higher safety.
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Reliability and safety of operation: RTO units are robust, long-lasting devices designed for continuous operation. Self-supporting ceramic fillings and high-quality insulation ensure safe operation without overheating the shell. The control system automatically switches modes and monitors temperatures to prevent fluctuations or incomplete oxidation.
Typical use:
Regenerative thermal VOC incinerators are suitable for medium VOC concentrations (typically ~1-5 g/m³) in combination with medium to very large air volumes. They are used across industries – in the chemical and petrochemical industries, pharmaceutical manufacturing, painting and printing (e.g. automotive paint shops, printers) and generally where diffuse solvent emissions occur. RTO is often the number one choice for paint shops and surface treatment lines (cars, steel structures, wood), where it removes VOCs from kilns and dryers. It is also used in the rubber and plastics industry, electronics manufacturing, oil refining, etc. Overall, RTO offers a balanced ratio between investment costs and low operating costs for a wide range of applications.
