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This guidance is one of several published by Fertilizers Europe in order to promote safety in the fertilizer industry. It replaces the previous one, which was issued by the industry associations IFA/APEA in 1985 (Ref. 1). It is much more detailed and takes into account the findings of the recent research work carried by TNO, a research organisation located in the Netherlands.

TNO, at the request of Fertilizers Europe, investigated the safety aspects of ammonium nitrate solutions at high temperatures and reported in 2003 (Ref. 2). The Fertilizers Europe steering group overseeing this work saw the opportunity as well as the necessity to follow up this project with the preparation of a more detailed guidance for the safe storage of hot ammonium nitrate solutions. This guidance seeks to translate the pertinent results of the Fertilizers Europe/TNO investigation into practical recommendations and also to encompass the results of intensive discussions within the steering group.

 

SCOPE AND PRINCIPLES

This guidance concerns the storage of hot ammonium nitrate solutions with a concentration in excess of 80% in fixed tanks. The recommendations are not intended for tanks used as process vessels in manufacturing plants. This guidance may also serve to determine the basic safety concept in performing safety studies and the design of storage tanks related to hot ammonium nitrate solutions.

This guidance is intended to apply to new installations but consideration must be given to adapting existing installations wherever reasonably practicable. It must also be borne in mind that not all recommendations may apply in every situation and retrofitting or modifying existing installations may not always be possible from a technical or practical point of view. In such cases appropriate safety studies should be carried out to establish that the existing situation is acceptable.

The guidance is not prescriptive in nature but provides a series of recommendations. It attempts to describe the relevant factors, their relative importance and various options available to specific situations.

This guidance addresses various safety related aspects of the storage of ammonium nitrate solutions, for example, location, design, construction, instrumentation, control systems and relief devices. It also briefly considers environmental aspects. In relation to safety it mainly covers: • Location and construction features

• Design features concerning, for example, heating coils and venting methods

• Safety equipment and first aid measures

• Normal process conditions (e.g. temperature, pH)

• Upset conditions (monitoring and prevention)

• Decomposition reactions (e.g. detection by changes in temperature, pH and concentrations of N2O, NOx etc.)

• Intervention techniques such as the addition of water and/or ammonia and dumping of the tank contents into a safe area.

Local site conditions need to be taken into account in considering all the aspects described in this guidance.

The guidance briefly describes the physical and chemical properties of AN, focusing on the potential hazards of hot AN solutions. It also covers the main regulations, which apply to the production and storage of hot ammonium nitrate solutions in the European Union. Readers are advised to refer to up-to-date regulations as there may have been changes since the publication of this guidance.