Removing micro-pollutants

European air regulations not only limit emissions of acid pollutants and dust, they also restrict micro-pollutants. These include dioxins, furans and volatile heavy metals: mercury, cadmium, etc.

Carbon-based sorbents, such as active carbon and lignite coke, are considered proven solutions for the adsorption of micro-pollutants and are widely used. However, these sorbents can combust or be ignited, which can cause serious damage to flue gas installations. Consequently, these products require special care regarding temperature, storage conditions and other factors.

This imposes constraints upon the user. A non-flammable, incombustible adsorbent would thus be an advantageous alternative to these carbon products, particularly for dry processes.

Research by the Lhoist R&D Center led to the development of a mineral substitute for carbon-based products: Sorbacal^® Micro 4099.

A non-flammable adsorbent, it removes micro-pollutants such as dioxins & furans. To determine the effectiveness of this product, tests were carried out for over a year at a Belgian incinerator for domestic and light-industrial waste. The tests compared four sorbents:

• activated carbon
• lignite coke
• Sorbacal^® Micro 4099
• a specific clay-based structure

Testing demonstrated that by using Sorbacal^® Micro 4099 sorbent the waste incineration plants could remove micro pollutants much more safely, and across a far wider range of treatment conditions. Sorbacal^® Micro 4099 sorbent offers major advantages:

• The 1.0 ng TEQ/Nm3 standard can be met with a dosage comparable to carbon compounds, and with less than 50% compared to the clay-based mixture.
• It is non-flammable, non-explosive and totally stable.
• It enables flue gas treatment residues to be easily stabilized.