Dynamic simulation of the BP Texas City refinery accident

The paper investigates the causes and simulates the dynamics of the events that led to the catastrophic explosion on March 23, 2005 at the British Petroleum (BP) refinery in Texas City (USA) where 15 people died and 180 were injured.

The paper follows the timeline of the accident, investigates the premises that characterized its phenomenology, and performs a critical analysis to fill the gaps that can be found in the scientific literature concerning the accident. In particular, a commercial dynamic process simulator (UNISIM) was adopted and integrated with ad hoc models to explain the column flooding and overfilling, the opening of the relief valves, and the flow of a two-phase mixture into the pipe connected to the blowdown system. The main findings are: (1) that the mass balance and the liquid thermal expansion cannot explain the complete flooding and overflow of the isomerization column; (2) the vapor cap used to explain the column overflow is unrealistic in our opinion; (3) the overflow can be explained by the partial vaporization of the feed stream after 1:00 PM and the consequent dispersion of vapor bubbles into the liquid holdup above the feed tray. In particular, tray holes smaller than 8 mm could cause the overflow; (4) there is a significant change in the thermodynamic conditions of the mixture emitted by the column head (temperature, pressure, vapor/liquid fractions) along the 270 m pipeline that connects the relief valves to the blowdown system; (5) the HEM model, together with the initial conditions we applied cannot explain the blowdown drum filling and release, therefore further studies are necessary.