Dioxins and PP (polypropylene)

Memory Effect

Dioxins are easily absorbed from ue gases into plastic materials such as polypropylene (PP), which

is commonly used in wet ue gas cleaning systems. Inside the plastic material, the dioxin mole-

cules tend to migrate. Both the absorption and the migration processes are strongly temperature

dependent.

If the conditions change, and the dioxin concentration in the ue gas decreases, or if the tem-

perature raises by only a few degrees, dioxins in the plastic will migrate to the surface and be rele-

ased back into the ue gas. This increase in the dioxin content of ue gas is known as the “Memory

Effect”.

Facts about Dioxins

Full-scale operation

After substantial lab-scale development and testing, the new

What is commonly referred to as “dioxins”, or PCDD/F,

Adiox technology has been successfully veri ed in a full-scale

is a group of polychlorinated molecules called dioxins and

installation since September 2001. The application chosen is

furans.

wet ue gas cleaning after waste incineration. The material

is introduced as tower packing in scrubbers, preceded by an

The most toxic is “2,3,7,8-TCDD” (or 2,3,7,8-Tetra chlo-

electrostatic precipitator (for separating out particles) and a

rodibenzo-p-dioxin), to which the toxicity of other molecu-

quench (for a rapid cooling of the ue gas).

les in the group is often related. TEQ (Toxic EQuivalents)

The Adiox tower packing is developed for high perfor-

can be calculated by adding up the amounts of some spe-

mance dioxin separation, combined with the material pro-

ci ed dioxins and furans weighted with toxicity factors,

perties required for good function and lifetime of tower

where 2,3,7,8-TCDD equals 1. European regulations stipu-

packings.

late that emissions are less than 0.1 ng TEQ/Nm 3 . Dioxins

During 2002 other full-scale installations have been star-

are of a very stable nature and accumulate as they move up

ted up, applying the Adiox technology for reducing emissions

the food chain to humans. The high toxicity of dioxin is

of dioxin.

due to the fact that it can interact with the DNA molecule.

Since 1997 the World Health Organisation has recognised

2,3,7,8-TCDD as carcinogenic for humans.

Dioxins and the new Adiox

No re-emission

The Adiox process is based on the high af nity of dioxins to carbon - when in contact, the bond

between dioxins and carbon is very strong. By dispersing small particles of carbon in PP-plastics, a

material excellent for dioxin abatement is formed.

A dioxin molecule present in the ue gas is rst absorbed into the PP, where it migrates to a

carbon particle, on which it is very strongly adsorbed (connected to its surface). The plastic material

acts as a selective lter with a preference for molecules like dioxin.

Since the af nity for carbon is so high, there is no tendency for the dioxin molecules to be rele-

ased, even when the concentration in the ue gas decreases. Therefore, there is no Memory Effect!

The Adiox technology (patent pending) is related to the composition of the material (carbon- lled

PP). The form and shape of the material chosen for a speci c installation depends on where in the

process it is applied - and on the process conditions. A typical example is tower packing.

Advantages

Applications

Advantages of the Adiox technology

The Adiox technology can easily be introdu-

Since the Adiox material is applied in the

for dioxin abatement include:

ced in new or existing plants as tower pack-

form of normal components, the scrubber

ing in wet scrubber systems. By applying the

system can be designed to be multifunc-

• Memory Effect can be avoided

Adiox material in plastic components of the

tional, combining dioxin removal with e.g.

• Easily installed in scrubber systems

ue gas cleaning system, the Memory Effect

HCl-reduction and condensing for energy

can be avoided. By installing Adiox at the

recovery.

• Non complex systems

end of the cleaning system, it operates supp-

The Adiox technology can be applied

• Minimal maintenance

lementary to other dioxin abatement sys-

wherever emissions of dioxin need to be

tems. It will then be acting as a back-up

reduced. Obvious applications are in the

• High availability

system for problems such as leakage or coal-

ue gas cleaning system for incineration of:

• Ef cient also during start-up

dosing failure, and at installations expe-

conditions

• Household waste

riencing problems with the Memory Effect.

• Clean handling

Adiox can be used in combination with

• Industrial waste

other dioxin abatement systems for optimis-

• Safe disposal of dioxins

• Hazardous waste

ation of the system, and allowing reduction

• Applied as ordinary components

• Sludge

in continuous dosing of carbon. It can also

with additional function

be applied as unique dioxin lter. The solu-

The Adiox technology could also be applied

• Low cost for reducing emissions

tion chosen depends on the conditions of

in other processes where dioxins are present

of dioxins

the actual installation.

in the gas phase.

Forschungszentrum Karlsruhe

The Forschungszentrum Karlsruhe is one of the largest

non-commercial science and engineering research

institutions in Germany. It works on research and deve-

lopment problems of public interest, in the elds of

technology and environment.

The application-oriented activities of the Centre

comprise all stages of research, from basic ndings to

pre-product development. The Centre is regarded to be

internationally in the absolute forefront in the areas of

aerosol-, mercury- and dioxin research.

Götaverken Miljö AB

Based on dioxin research of the Forschungszentrum

Karlsruhe, the Swedish company Götaverken Miljö has

developed products and systems using the Adiox pro-

cess for reducing emissions of dioxins.

The cooperation with the Forschungszentrum Karls-

ruhe also includes the MercOx process, for reduction of

emissions of mercury. The MercOx process is based on

hydrogen peroxide being used in a scrubber system to

reduce emissions of mercury.

Götaverken Miljö offers both the Adiox and the

MercOx solutions to the international market.

Being an established engineering and contracting

company for systems within the elds of environment

and energy, Götaverken Miljö is an experienced supplier

of ue gas cleaning systems, large heat pump/chiller

systems and energy recovery systems.

For further information, please contact:

Address: Box 8876, SE-402 72 Gothenburg, Sweden

Phone: +46(0)31-50 19 60, Fax: +46(0)31-22 98 67

Homepage: www.gmab.se