Biomass gasification produces a wide range of species, from permanent gases to condensable hydrocarbons, with different composition and boiling points. This complicates the mass balance of the system, as multiple techniques are needed to quantify the various components of the produced raw gas. In this study, a high-temperature reactor for thermal conversion of raw gas at 1700 degrees C was developed to generate a gas stream that consisted primarily of CO, CO2, H-2, and H2O. The reactor was experimentally evaluated and subsequently used for measurements of the raw gas from the Chalmers 2-4-MW dual fluidized bed gasifier. The gas stream that exits the reactor is analyzed to obtain the total elemental flows of C, H, O, and N, which facilitate determinations of the fuel conversion and oxygen transport in a dual fluidized bed reactor. The proposed system was operated in parallel with a gas-cleaning system, to determine the yield of condensable species, including tar and GC-undetectable species. A simplified approach is proposed for quantifying the average energy content of the condensable species, thereby allowing the wet raw gas efficiency and lower heating value (LHV) to be calculated.