Chromium(VI) in incineration ash from waste incineration plants

How chromates form in grate, boiler and filter ash, and why the dust leaves the furnace during overhauls

Decontamination on the incinerator grate in full protective equipment

Chromium(VI)-containing incineration ash is formed by the oxidation of chromium-containing waste components and of corrosion products from the alloys of the stainless steel grates. At high temperatures and with excess oxygen, Cr(III) compounds react with calcium, sodium or potassium compounds from the waste, among others, to form chromates. These mix with the grate, boiler and filter ash.

Even when the doors are opened briefly, and above all during overhauls, the ash and the chromium(VI) compounds it contains can spread in an uncontrolled way. Areas around the furnace become contaminated as well.

Work at the open furnace door

This dust is seen as nothing more than ash. In fact, it is an inhalation and skin hazard to people and the environment. It settles on clothing and under footwear and is carried away unintentionally, in some cases into the employees' private lives.

The chromate remediation team of Kavarmat® and the Chromate Experts have developed work procedures that prevent exposure outside the work area. The ash and combustion residues left contaminated with chromates in the furnace after shutdown are decontaminated and collected. Further work can then be carried out at lower risk.

KavarClean®Redox Powder is used to bind the dust in the furnace. The reducing solution is not stored ready to use. It is mixed with water immediately before application.

Decontamination in the scaffolded combustion chamber

This treatment chemically reduces chromium(VI) to chromium(III), and the treated contamination is then removed. It is a supporting occupational safety measure that reduces possible exposure. It does not replace the risk assessment or the protective measures that follow from it.

Removing contamination at the furnace door