The advanced dual fluidized bed (DFB) steam gasification technology allows to generate medium- calorific product gas from various feedstock. Thereby, biogenic residues, municipal and industrial wastes e.g. sewage sludge or rejects from pulp and paper industry can be utilized. The varying fuel properties of these feedstocks pose a challenge not only to the DFB reactor system, but also demand improved gas cleaning of the generated product gas. The product gas can be used in a variety of synthesis processes like Fischer-Tropsch (FT) or methanation or conditioning processes like hydrogen production. This flexibility provides a promising use of biogenic feedstocks for the production of sustainable energy carriers. Over the last years, extensive research has been conducted and over 50 feedstocks were tested using a 100 kWth advanced DFB pilot plant at TU Wien. Based on the gained experience, a 1 MWth demonstration plant was designed, built and commissioned during the last two years. Investigating the feasibility of upscaling the advanced gasification technology with regards to product gas quality and operation performance is the focus of the current experimental campaigns. In order to validate and verify the data from these campaigns, a process flow simulation using the software IPSEpro is conducted to calculate mass and energy balances. This paper presents the results from these simulations and accompanying analytics to provide a comparison of different operating points for the feedstocks wood chips, forest residues, bark and plastic rejects. Different temperatures, fuel loads, steam-to-fuel ratios and circulation rates, determine these operating points. Input data for the simulation model consists of records from the plants distributed control system, feedstock and bed material analyses, online gas analytics, and analytical results of tar, dust, H2O, NH3, H2S, HCl, HF and HBr sampling. Key performance indicators for the demonstration plant include e.g. cold gas efficiency, water conversion, and product gas yield. Additionally, by the use of the simulation results, the fluidization regimes in the reactor system can be determined. In order to investigate long-term operation, scale-up considerations, minimizing the risk of technology development and finally create the basis for techno-economic evaluation of this technology in an industrial environment according to TRL 5, an upscale to a 1 MWth fuel input power demonstration plant was performed. Results from the simulation allow drawing meaningful comparisons between design parameters, derived from 100 kWth pilot plant operation and the up-scaled 1 MWth demonstration plant. This gives the opportunity to generate design values for industrial applications of advanced DFB gasification in the future. The results enable a contribution to sustainability and energy security.