Corrosion control for the pulp and paper industry

Increase operational reliability

Creating paper out of wood or pulp involves several complex processing steps in which the raw materials are chemically treated. This produces gases that have the potential to cause corrosive damage to the surrounding machinery and equipment. That is why they are classed as contaminant gases.

Pollutant gases in the pulp and paper industry

Pollutant gases	Process	Viledon ChemControl pellets
Hydrogen sulfide (H₂S)	Lignin removal (sulfite process) wastewater treatment	CCP 104, CCP 108, CCP 210, CCP 310, CCP 810
Mercaptans	Lignin removal (sulfite process)	CCP 104, CCP 108, CCP 210
Sulfur dioxide (SO₂)	Lignin removal (sulfite process)	CCP 104, CCP 108, CCP 210, CCP 310, CCP 810
Sulfur oxide	Bleaching of waste paper, bleaching of wood pulp	CCP 104, CCP 108, CCP 210, CCP 310
Chlorine (Cl₂)	Bleaching of pulp	CCP 310, CCP 510, CCP 610
Chlorine oxide (ClOₓ)	Bleaching of pulp	CCP 310, CCP 510, CCP 610
Ozone (O₃)	Bleaching of pulp	CCP 310, CCP 610

Key process steps in papermaking

Particularly at risk are sensitive areas such as electronic equipment, control rooms, process control systems and compressors. The negative effects of the corrosion of the copper and silver components of these devices include a loss of process efficiency, additional maintenance costs, expensive repairs and unplanned downtime.

We provide reliable protection against corrosion by contaminant gases that are released during the main process steps in papermaking.

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Lignin removal

You remove lignin from the raw materials. We remove contaminant gases from the air.

The technical removal of lignin is a key processing step during the manufacture of pulp. In chemical processes, the lignin needs to be dissolved from the lignocellulose and subsequently removed from the production process. Two methods have been established and are particularly important in pulp production: the sulphate and sulphite processes (see below). Depending on the procedure, various contaminant gases are released. Using different filtration media, we remove these from the air and prevent the corrosion of sensitive equipment.

Sulfate process

This alkaline process is currently dominant in pulp production and is used for both hardwood and softwood. The removal of lignin is caused by hydrogen sulfide ions (HS−) in a caustic medium. Within this process, both sodium hydroxide (NaOH) and sodium sulfide (Na₂S) are used, which in turn produce hydrogen sulfide (H₂S) and mercaptans. Once released, the H₂S causes corrosion and must be filtered out of the air.

Sulfite process

Comparatively rarely employed, this acidic method is used in the digestion of spruce, beech and eucalyptus. The removal of lignin is achieved by a sulfonation. Via sulfur dioxide, lignosulfonates are produced (salts of lignin). The flue gas containing sulfurdioxide (SO₂) represents a particular risk to machines and processes. We reliably remove this gas from the air using special media.

Bleaching

Bleaching protects paper against yellowing. Gas phase filtration protects equipment against corrosion.

Whether using wood pulp, pulp or waste paper: bleaching is an essential process step in paper production to remove unwanted stains. Because lignin is responsible for the yellowing of paper, it needs to be removed during the bleaching process. This ensures that the paper stays white. Bleaching is achieved via a technical process involving mainly chlorine bleach or a bleach with oxygen, chlorine dioxide, hydrogen peroxide or ozone. Depending on the chemical substances involved, this leads to the creation of various contaminant gases that need to be removed from the air.

Bleaching of wood pulp

Sodium sulfite (Na₂SO₃) is often used in the bleaching of wood pulps. This produces sulfur dioxide, which is responsible for the corrosion of nearby electronic devices.

Bleaching of pulp

Among other chemicals, chlorine (Cl₂), chlorine oxide (CLOₓ) and ozone (O₃) are used for the bleaching of pulp. Chlorine-free bleaching with ozone is more environmentally friendly, but leads also to the release of a corrosive and toxic gas.

Bleaching of waste paper

Dithionite is usually used in the bleaching of waste paper. This in turn releases sulfur gases that should be seen as the cause of corrosion.

Wastewater treatment

You ensure clean water. We ensure clean air.

At the end of the papermaking process comes the treatment of wastewater. This involves removing the polluting elements from the wastewater to restore its natural quality.

On the way from the dischargers to the sewage treatment plant, water purification is achieved through targeted chemical additives and biological processes. In the anaerobic environment, contaminant gases such as hydrogen sulfide (H₂S) are created.

This gas has the characteristic pungent odor of rotten eggs. Even more problematic than the smell, however, are the effects it has on humans and sensitive electronic components. Using special pellets and individual filtration concepts, we reliably remove hydrogen sulfide from the air.

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