Among the methods to reduce tar emission, the partial oxidation (POX) of biomass gasification tars has been studied both experimentally at a pilot-scale and numerically. The gasification producer gas ...was obtained at a temperature of 800°C in an air-blown fluidized bed with an equivalent ratio (ER) of 0.25. For the POX unit, two secondary ER values were selected: 0.05 and 0.10, with the option of pre-heating air or not. Multiple advanced analytical methods were employed to provide a detailed composition of the producer gas, tars and acid gases. The POX unit demonstrated the ability to reduce tar levels by 60 to 90% depending on the secondary ER (from 6.5 to 2.4 and 0.72 gtars/Nm3, excluding benzene). The lighter tars were almost completely eliminated. The permanent gases were barely modified while the light hydrocarbons (except C2H2) and benzene were significantly reduced. Consequently, there was a slight decrease in the lower heating value. These results were compared to an isothermal plug flow reactor model, which utilized a detailed radical kinetic scheme constructed from various sources to account for all the species measured during the experiments as well as soot mass yield. The model provided relatively accurate predictions of the hydrocarbon species variations, even though it did not consider the mixing between air and syngas at the inlet of the POX unit.
All-inorganic cesium lead iodide (CsPbI3) perovskite has improved thermal stability over the organic–inorganic hybrid perovskites and a suitable bandgap for optoelectronic and photovoltaic ...applications, but it is thermodynamically unstable at room temperature and has multiple structural polymorphs. Here, we show that the use of long-chain ammonium additives during thin film deposition as surface capping ligands results in the stabilization of metastable bulk CsPbI3 perovskite phases without alloying mixed cations or anions into the perovskite lattice. Moreover, two different metastable CsPbI3 perovskite polymorphs in the cubic (α-CsPbI3) and the much less common orthorhombic (β-CsPbI3) structures can be directly synthesized in a one-step spin coating film deposition by using oleylammonium or phenylethylammonium additives, respectively, and both phases are stable at room temperature for months. Time-resolved photoluminescence and photoluminescence quenching experiments show that the photoexcited species in the stabilized orthorhombic CsPbI3 thin film are mainly free carriers under solar illumination with a carrier lifetime of ∼50 ns and carrier diffusion length on the order of ∼100 nm, which implies efficient carrier transport within the film despite the presence of surface ligands. Our results provide a new chemical strategy to synthesize metastable all-inorganic CsPbI3 perovskites, which, together with the good photophysical properties, will open them up for applications in photovoltaic and other optoelectronic devices.
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