Transformation of inorganic matter in poultry litter during fluidised bed gasification

This work investigates the transformation, release and fate of inorganic matter during fluidised bed gasification of poultry litter and also poultry litter mixed with limestone as an additive. The poultry litter, the cyclone and bed ash were characterised by means of chemical fractionation analysis, as well as X-ray diffraction. Concurrently, the release of inorganic species during gasification of the feedstock was measured in separate laboratory experiments using molecular beam mass spectrometry. In addition, FactSage was used to predict the formation of gaseous species and the composition of solid residues from gasification under equilibrium conditions. On average, the cyclone ash accounts for 4.6 wt% and the bed ash 12.4 wt% of the total poultry litter fed into the reactor. All phosphorous (P) was present in the cyclone ash as stable phosphates, while potassium (K) in both cyclone and bed ash was mainly present as H2O leachable KCl, organically associated and stable phosphates and silicates. Furthermore, an assessment was made against the appropriate criteria, whether the ashes from gasification can be categorised as component materials for EU fertiliser products. •Bed and fly ash from poultry litter fluidised bed gasification were analysed.•Irrespective of process conditions P present in the cyclone and bed ash in the form of HCl leached phosphates.•(Ca5(PO4)3OH), KNaCa2(PO4)2 and (Ca3(PO4)2) were the P-containing crystalline compounds in cyclone ash.•Most of K in cyclone and bad ash present in water soluble form.•There was more S and Cl present in cyclone ash than in bed ash.