Estimation of solids circulation rate and char transfer rate from gasifier to combustor in a dual fluidized-bed pilot plant for biomass steam gasification

•A novel mass and energy balance method was developed to estimate solids flow rate.•This method also provides the char transfer rate from the gasifier to the combustor.•Gasifier heat loss obtained from two independent techniques matched well.•Estimated solids flow rates compared well with rates measured by another technique.•No other technique can determine char transfer rate from a gasifier to a combustor.