Uncertainty analysis of emissions from the Statoil Mongstad oil refinery

In new European and national legislations, there is increased focus on the reporting of the emmissions related to greenhouse gases from process plants. This includes reporting and documentation of uncertainty in the reported emmissions, in addition to specific uncertainty limits depending on the type of emission and type of measurement regime.

In a process plant like the Statoil Mongstad oil raffinery, there may be a huge number of measurement points for mass flow. These measured mass flow rates have to be added in order to obtain the total emission for a given source. Typically, orifice plates are used at many of the measurement points. These orifice plate meters are ususally not equipped with individual densitometers. In stead, they are pressure and temperature corrected from a common upstream densitometer. This will give correllations between the individual flow meters.