Exhaust air purification chemical industry

In the chemical industry, products are manufactured for various industrial sectors. Production takes place either in discontinuous or continuous operation. Depending on the product, emissions such as formaldehyde, aromatic compounds, aliphatic amines or heterocyclic nitrogen compounds can be generated during the reaction phase, either by the input materials themselves or by the reaction products.

Organic problem substances enter the exhaust air via extraction systems and can be measured there as VOCs and odors in the exhaust air. As total carbon content, they can lie above the TA Luft guide values.

The UV/ozone technique can be used in particular to degrade polar organic mono-compounds or complex mixtures of different organic compounds. The oxidative degradation of the organic compounds is based on a radical reaction cascade. The combined technology of plasma and UV/ozone can also be used to degrade non-polar organic compounds, such as long-chain ester compounds. The radical process is first initiated with the plasma in the first stage, which supports the subsequent UV/ozone process and significantly increases its effectiveness. As an additional module, a water diffuser is used between the plasma technology and the UV/ozone technology to optimize reactivity in the downstream UV/ozone unit. Tests show that VOC contents above 1g/m³ can thus also be degraded.

The basis for the use of these technologies is knowledge of the exhaust air constituents, their content in the exhaust air, and the physical parameters of relative humidity and exhaust air temperature. With this knowledge, energetically highly efficient exhaust air purification systems, the effectiveness of which ensures that the limits set by the TA Luft are not exceeded, can be set up and operated.

This arrangement is clearly superior to conventional processes:

• Activated carbon filters, scrubbers: High costs due to activated carbon replacement.
• Biofilter systems: High space requirement, high maintenance and high investment costs; Low efficiency with aromatics such as benzene and phenol
• Incinerators: High investment costs and high operating costs, catalysts are expensive and wear out quickly, autothermal operation only possible for Cges > 2000mg/m³; catalyst poisoning for S-containing VOCs.

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• The advantages
• The limit values of the TA Luft are complied with
• Low investment costs compared to incineration plants
• Low operating costs
• Low maintenance requirements
• Low space requirement