Investigation and modeling of an explosion in a propane absorption
column
Journal of Loss Prevention in the Process Industries, 14 (4):
251--260 (July 2001)DOI: http://dx.doi.org/10.1016/S0950-4230(01)00003-1
Abstract
An explosion destroyed a propane absorption column during startup
following a turnaround. The immediate cause is obvious enough, since
plugs were left off of the feed compressor, and the suction valves
were left closed, so air was pumped into the system. Detailed modeling
of the system provided valuable insights, helped rule out alternative
theories for the event ignition, and provided confidence to justify
subsequent mitigation measures. An example is provided here of estimating
explosion energies by four complimentary methods: modeling fuel/air
concentration profiles in the system, column strength analysis, fragment
trajectory analysis, and window breakage analysis. The fuel/air concentration
profiles showed that the concentrations in the column were largely
too rich until the opening of a pressure control valve bled out part
of the fuel. The column strength analysis made use of measured shell
thickness and known steel properties to obtain an upper bound for
explosion pressures at the point of failure. As part of the fragment
analysis, we pieced together the column fragments. The characteristic
chevron pattern on the edge of the fragments point to the initiating
failure point 1/3 of the way from the top. This is consistent with
the predicted concentration profile inside the column giving a run-up
distance for the explosion. Fragment trajectory analysis indicated
explosion pressures and energies. Window breakage analysis made use
of a program calculating dynamic window strain. The reasonable convergence
of four alternative methods provides increased confidence in the
postulated accident scenario.