The invention relates to an SNCR (selective non-catalytic reduction) and SCR (
selective catalytic reduction) combined denitration method and an SNCR and SCR combined denitration device for
flue gas of a
coal-fired boiler. The SNCR and SCR combined denitration method includes adding reducing agents which are
ammonia-containing solution into a temperature window at the temperature
ranging from 800 DEG C to 1050 DEG C of a
hearth, enabling partial
ammonia to be subjected to SNCR reaction with
NOX in
flue gas and allowing rest escaping
ammonia to flow to a
flue with
flue gas to carry out heat exchange and cooling; and adding to replenish
reducing agent to a temperature zone at the temperature
ranging from 500 DEG C to 650 DEG C of the flue at an outlet of the boiler, dissolving ammonia, and enabling the ammonia to be subjected to SCR reaction with
NOX at the temperature
ranging from 300 DEG C to 420 DEG C in the presence of V2O5 and WO3 to remove the
NOX remained in the
flue gas. The V2O5 and the WO3 are active substances of catalysts, the
molar weight of NH3 in the total amount of the added ammonia-containing solution is 1.45-1.6 times of that of
NOx in the original
flue gas, the ammonia-containing solution containing the NH3 with the
molar weight of 1.1-1.2 times of that of the
NOx in the original flue gas is added into the temperature window at the temperature ranging from 800 DEG C to 1050 DEG C in the
hearth of the boiler, and the rest ammonia-containing solution is added into the temperature zone at the temperature ranging from 500 DEG C to 650 DEG C of the flue of the outlet of the boiler. By the method, the amount of the reducing agents added into an SNCR reaction section and the amount of escaping ammonia can be reduced, the total NH3 of the reducing agents added into the flue gas at the temperature ranging from 500 DEG C to 650 DEG C participates in the SCR reaction, the total consumption of the reducing agents is reduced, and the denitration efficiency is improved.