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What is a catalytic process in gas treatment and purification?
The treatment of gases with catalytic processes is a key technique in industry for the control of pollutant emissions into the environment. Catalysts are used to accelerate chemical reactions that transform polluting gases into less harmful products.
Catalytic processes are based on the fact that, under specific conditions, certain chemicals can accelerate chemical reactions without being consumed in the process. These catalysts work by optimising the activation energy required for the reaction to occur, allowing reactions to take place at lower temperatures and under milder conditions.
The choice of which technology to use depends on many factors such as: pollutants (NOx, VOCs, SOx, CO…), operating conditions (temperature, pressure, pollutant concentration…), efficiency and costs (CAPEX, OPEX…).
The technologies available include catalytic reduction and oxidation. Each technology is optimal for treating different types of pollutants; in catalytic oxidation a catalyst is used for oxygen gain; in catalytic reduction the catalyst is used for oxygen loss.
Catalytic reduction is a technology widely used in gas treatment to reduce emissions of nitrogen oxides (NOx). This technology is based on the use of a catalyst, usually consisting of noble metals such as platinum or palladium, to facilitate the conversion of NOx into nitrogen (N2) and water (H2O) through a controlled chemical reaction.
For the catalytic reduction process and NOx treatment, there are two technologies used, selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR).
SNCR is simpler and less expensive than SCR, but is generally less efficient in NOx reduction. It requires better temperature control (850ºC – 1100ºC) in the injection zone of the reducing agent to optimise its effectiveness. It is often used in industrial applications where NOx reduction as stringent as that achieved with SCR technology is not required, or where system costs are an important consideration.
In a reactor, pollutant gases are passed through a catalyst bed, where the chemical reaction is initiated in the presence of oxygen and the catalyst, reducing the activation energy needed for oxidation to occur at lower temperatures. This allows contaminants to be converted into safer products at controlled temperatures and operating conditions. Common catalysts in catalytic oxidation include platinum, palladium and rhodium, which accelerate the chemical reaction without being consumed in the process, making them reusable and efficient.
The most common gaseous pollutants treated with this technology are volatile organic compounds (VOCs) and carbon monoxide (CO), which are transformed into less harmful products, such as carbon dioxide (CO2) and water (H2O), through a catalyst.
In summary, there are a multitude of catalytic processes for the reduction of pollutants, where the use of one or the other depends on multiple factors. Contact our specialist technicians for a personalised service.
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