Understanding of halogen impacts in fluidized bed combustion

There is growing interest in cofiring coal with industrial wastes, some of which have an elevated halogen content. This study looks at the effects of adding halogens in a CFBC system.: Experimental work was carried out on a p ilot plant miniscale circulating FBC unit to which NaCl and I-2 were added during the combustion of a high-sulfur coke and a low-sulfur bituminous coa l at typical FBC temperatures. Further, the effects of limestone addition a nd cofiring with natural gas in conjunction with halogen addition were also investigated. Results showed that the halogen species inhibited CO and sup pressed NO reduction and N2O formation.:The distribution of halogen-contain ing products was predicted by the FACT thermodynamic database package for a wide range of combustion temperatures and other operating parameters. Resu lts indicated that fuel type and combustion conditions have a pronounced ef fect bn the amount of halogen or halide released. Dramatic changes in halog en products and their distribution were produced by changing the fuel from coal to petroleum coke, by adding limestone, and by cofiring with natural,g as. A CFBC NO/N2O model has been employed which is based on the general kin etic model and a single particle NO/N2O formation model.; The model uses th e semi-theoretical approach with some measured parameters as inputs. It is capable of describing the NO, N2O, and HCN concentration histories satisfac torily even in the case of iodine addition.