Occupational and Process Safety in Ammonia Plants – Pitfalls to Avoid

OCI N.V. is a global fertiliser and methanol producer. OCI presently operates eleven ammonia plants forming the core of its fertiliser production. The size alone of the plants and the combustible and toxic nature of the chemicals involved in the ammonia production process, in combination with the harsh process conditions (temperature, pressures) in many equipment items, make ammonia production a challenging area when it comes to managing safety.

Safety has two aspects. It relates to a) occupational safety, also called workplace safety, that focusses on providing a safe working environment for the people in the plant and b) process safety that focusses on preventing loss of containment of hazardous substances or energy that could cause serious injuries or environmental damage within the site or outside its boundaries.

Typical occupational safety metrics that are used by OCI and many other industries are the Lost Time Injury Rate, and the Total Recordable Incidents Rate.

The first part of this paper describes some of the programs that are in place within OCI to improve occupational safety. This section also covers several occupational safety related topics:

• Health effects of ammonia exposure.

• First aid.

• Personal Protective Equipment.

• Hazards in the workplace.

The second part of this paper focusses on process safety. Many key process safety risks in ammonia plants are addressed, such as:

• Nickel carbonyl formation in the methanator catalyst.

• Formation of carbamate in the flare stack.

• Over speed of machinery.

• Formation of explosive mixtures.

• Accumulation of mercury at low temperature zone.

• Corrosion on copper containing material by ammonia.

• Presence of chlorine causing catalyst poisoning and stress corrosion cracking in stainless steel.

• Formation of explosive NH4NO2 compound in selective catalytic reactor de-NOx units.

• High temperature hydrogen attack.

• Ammonia tank stress corrosion cracking.

37 pages, 21 figures, 10 plates, 2 tables, 6 references