hello Hugo
short list of most used commercially available software packages
HYDRAULICS : steady state Aspen Flare System analyser ( Flarenet) will both rate and design a new system for you .
Unisim Flare ( virtually the same, ), Aspen Plus, Chemcad Safety, VMG
dynamic Aspen Hysys and Unisim Design , VMG,
RaDIATION & Dispersion FLARESIM, Phast,
There are several other packages that do "bits" of the design /rating but the ones above are the most widely used in the industry
No doubt other users will add one or two i have missed out .
flarenuf