PREDICTIONS OF THE SPECIATION OF ELEMENTS IN COAL ASH WITH THERMODYNAMIC EQUILIBRIUM CALCULATIONS FOR ADVANCED TECHNIQUES IN PF-COAL-FIRED POWER PLANTS CO-FIRING BIOMASS

摘要

Knowledge of speciation or chemical form of elements in flue gases and ashes of coal-fired power plants is vital for the understanding of processes and the prediction of operational, environmental and health effects. Slagging and fouling are influenced by the speciation of (macro) elements too. Deactivation of the DeNO{sub}X is also influenced by certain elements in combination with their speciation. Four example's are given, a) The capture of mercury depends very strongly on the speciation. b) The European Waste Catalogue (EWC) is another important example. Coal fly ash (CFA) from co-combustion has to be investigated on their toxicological properties by the presence and levels of the compounds (speciation of elements). E.G. carcinogenic compounds of As, Be, Cd, Co, Cr and Ni can be present in coal fly ash. c) Leaching of certain compounds of e.g. Cr and Se in CFA could be a problem if CFA is used in e.g. road construction, d) The personal exposure limits (PEL) of workers to CFA could be a problem by co-combustion of petroleum cokes for certain compounds of V. In Europe new technologies will be applied in pf-coal-fired boilers to enhance power plant efficiencies (Ultra Super Critical boilers or USC) and to reduce or overcome Commissions (high percentages of co-firing biomass and Oxyfuel). This paper presents research by means of thermodynamic equilibrium calculations on the speciation of (trace-) elements present in flue gases and ashes of pf-coal-fired power plants using high percentages (>10%) of co-firing of biomass and new techniques such as USC and Oxyfuel. Theoretical calculations will be verified with measurements as much as possible.