Safety Systems and Legal Requirements

Synopsis.

It was felt that the most useful way of covering this topic was to take a practical case which would be of fairly general. interest in the fertiliser industry. The paper therefore deals with safety aspects of the design and operation of Nitrigin Eirean’s (NET’s) new CAN/AN prilling plant.

With this type of process there are two aspects of safety to be considered:

a) General safety standards for dealing with corrosive or toxic fluids such as ammonia, nitric acid and ammonium nitrate and for the solids handling and bagging operations. The Paper seeks to highlight some of the more important and universally applicable conditions in this area.

b) Safety in process design to ensure that decomposition of ammonium nitrate does not occur, in particular that it does not occur in an enclosed space where an explosion could result.

NET have adopted what we would call a “common sense” approach to this problem. Certain combinations of temperature, pressure, residence time, pH, concentration or level of impurities are needed to produce decomposition. There is no virtue in spending money to eliminate one of these variables if the other variables needed to produce decomposition are absent anyway. What is necessary is that in normal operation, a number of these variables should have to change to produce a decomposition situation. Process and instrument design must therefore be such as to prevent this happening. Also the process operators must have adequate training to appreciate the significance of all changes in process variables.

The application of this philosophy to the design and operation of such items as the neutraliser, the concentrators and the 99.8 % AN pumps is discussed.

J F Killeen, Nitrigin Eirean Teoranta, Ireland.

14 Pages, 3 Figures, 1 Table.

Discussion 13 Pages.