Ash properties from cynara cardunculus L. Gasification

The current study analyzes the fines produced from Cynara cardunculus L. air-gasification in a bubbling fluidized bed. The temperature is varied from 700 to 800ºC in an olivine bed, with an equivalence ratio of 0.2. Magnesite is also used 800ºC. Relatively high carbon content in the entrained fines is obtained for all experiments, showing a decreasing trend with temperature and being higher in the case of magnesite for the same temperature. The lower heating value (LHV) of the elutriated fines varies from 5.7 to 7.9 MJ/kg db, being also higher for magnesite at the same temperature (7.6 MJ/kg db vs 5.7 MJ/kg). These properties provide some interesting options for the reuse of fly ashes in the gasifier to convert the remaining carbon into gas, or use it as fuel in a combustor for heat generation. Al, Ca, K, Mg, Na, Si and, to a lesser extent, Fe, are the main elements found in the fines, while Cu, Cr, Ni, Se and Mn are the dominant minor elements. Around 75% of the metals in the ashes is captured in the first cyclone, with 5% deposited in the second cyclone and the remaining 20% in the hot filter. Metal recovery in the fly ash is mostly below 50% of the metals input from biomass.