Dioxins are highly toxic substances and can be formed when waste is incinerated. There are, therefore, very strict requirements set for their low emissions. B&W Environmental, through our GMAB product line, offers ADIOX® technology, a dioxin removal solution which has been proven in more than 100 installations worldwide.
Typical applications
ADIOX can be applied in various processes, wherever emissions of dioxins need to be reduced. It is suitable for installation in wet scrubber systems or in other types of containers in a gas cleaning system and at thermal treatment plants for:
Installation options
ADIOX is produced and delivered in the form of tower packing and droplet separators, with all the conventional advantages these provide. They can be installed in scrubbers and also in dedicated dioxin removal absorbers where the gas is dry or saturated (semi-wet operation).
The material is installed in various applications including wet scrubbers, semi-wet (moisture saturated) absorbers, dry absorbers and droplet separators.
ADIOX is especially well suited for avoiding the so-called dioxin memory effect or where a multi-functional solution is required with integrated separation of HCl, SO2, HF, Hg and dioxins, in combination with substantial energy recovery through flue gas condensation. ADIOX is available in different sizes and types of tower packing such as knitted mesh droplet separators and lamella demisters. The material is supplied in bulk to end users for installation in existing scrubbers and as components in upgrades or new flue gas treatment plants.
ADIOX technology offers many advantages
Analysis package
We offer our customers an inspection program in which the material's dioxin content, surface and mechanical qualities are regularly analyzed (usually once annually). The purpose of this procedure is to ensure the installation is functioning well and that the material enjoys maximum economic use. The test results are presented in a report and following repeated analyses, an absorption history is presented for each stage.
SUCCESS STORIES
Gärstadverket , Linköping
WtE Flue Gas Treatment Plant Upgrade
This project included the upgrading of the flue gas treatment plant for incineration lines 1, 2 and 3 at Tekniska verken Gärstadverket waste-to-energy plant.
This was our first full scale installation of ADIOX in a dry dioxin removal application. The absorber is a fully static system filled with two beds of ADIOX tower packings. The use of ADIOX in a dry process provided the plant with efficient dioxin removal and a system in which hot spots (fire hazards) are avoided.
Filbornaverket, Helsingborg, Sweden
New 70 MW Waste-to-Energy Plant
In this 2012 application, B&W (formerly Götaverken Miljö AB) was contracted to supply a multi-stage scrubber system to be positioned after a semi-dry gas treatment system. The unit includes stacked scrubber sections for removal of ammonia and remaining acidid components as well as recovery of energy by flue gas condensation. An absorption heat pump system provides for optimal efficiency.
The scrubber, of tower packing type, includes packing material and droplet separators of ADIOX material for maximum dioxin removal and dioxin “memory effect” prevention.
Vestforbrænding, Copenhagen
Flue Gas Condensation Upgrade
Vestforbraending is one of the largest waste-to-energy plants in Denmark, producing 140,000 MWh of electricity and 440,000 MWh district heating. This upgrade project included installation of flue gas condensation and integrated absorption heat pumps.
Tower packings and droplet separators are made of ADIOX dioxin removal material. In the event of an upstream failure of the flue gas treatment, ADIOX will act as an additional police filter for dioxins. ADIOX does not cause the memory effects that ordinary plastic material, used in scrubber internals, bring about.
TECHNOLOGY
Dioxins in equilibrium between gas and polymer (left). Dioxins are absorbed in the polymer and bound to the carbon particles (ADIOX, right).
Dioxin molecules in the flue gas are first absorbed by the polymer, then they diffuse to carbon particles where they are bound powerfully to the surface. The polymer acts as a selective membrane that protects the carbon from substances that do not dissolve as well in polymers, such as water.
Dioxin Memory Effect
Dioxin is absorbed efficiently by various polymers such as polypropylene until equilibrium is reached, which means dioxin desorption can also take place. Typically, dioxins are absorbed during operational disruptions or start-ups when concentrations are high, to be released again during normal operations when concentrations are lower. Small temperature variations can also lead to absorption/desorption equilibrium displacements. This phenomenon is called the memory effect, and can lead to problems in staying under dioxin limits. ADIOX is often used to minimize the memory effect.
