A qualitative risk assessment for ammonium nitrate facilities: correlating to historical data

The commercial fertiliser industry produces five primary chemicals which include phosphate, ammonia, urea, ammonium nitrate (AN), and nitric acid. The AN is widely used in agriculture but has been associated with numerous accidents due to inadequate post-accident investigations and management. A qualitative risk assessment is crucial for identifying and managing risks in such hazardous industries. This research demonstrates the application of a Process Hazard Analysis (PHA) method, specifically the Hazard and Operability Study (HAZOP), using Microsoft Excel. This research analyses AN manufacturing process facility located in the United States (US) as the US is a major global producer and consumer of AN and plays a significant role in the fertiliser and industrial explosives supply chain. The selected study nodes include raw material production unit, the product processing neutraliser, and AN storage unit. The key elements of the HAZOP study, including guide words, process parameters, causes, consequences, safeguards, risk ratings, and recommendations, were documented in Microsoft Excel. A total of eighteen deviations were identified, with the highest overall risk associated with the product processing neutraliser. In the manuscript, further discussion is focused primarily on the neutraliser, as it was identified as the highest risk. Historical accident data showed that the transportation unit had the highest accident frequency, alongside storage and manufacturing. The HAZOP methodology proved effective for identifying potential hazards and improving safety in AN facility. This approach allows the process safety management team to proactively address operational problems and enhance overall industry safety.