METHOD FOR REDUCING EMISSIONS OF NITROGEN OXIDES AT OXYGEN AND FUEL COMBUSTION

摘要

1. A method of reducing nitrogen oxide emissions during oxygen fuel combustion, comprising supplying to the furnace (11) a boiler (10) with a circulating fluidized bed of at least one primary gas stream (15) and at least one secondary gas stream (16), where the primary gas (15) and secondary gas (16) are obtained by mixing oxygen and circulating fuel gas, characterized in that the oxygen content in the primary gas (15) is controlled so that a reduction zone (I) is formed at the bottom of the furnace (11), and the oxygen content in secondary gas (16) so that an oxidation zone (II) is formed above the reduction zone (I), and the oxygen content in the primary gas (15) and secondary gas (16) is controlled by changing the ratio of oxygen to the circulating flue gas in the aforementioned gas flows (15, 16) .2. The method according to claim 1, characterized in that two or more streams of secondary gas are fed into the furnace (11) at two or more different levels. The method according to claim 2, characterized in that the oxygen content in the secondary gas streams supplied at different levels is controlled so that the oxygen content is different from each other. The method according to claim 1, characterized in that the oxygen (24) and the circulating flue gas (25) are mixed using mixing means associated with the furnace (11), immediately before the primary gas (15) or secondary gas (16) is supplied to the furnace (11) .5. The method according to claim 1, characterized in that the oxygen (24) and the circulating flue gas (25) are mixed using mixing means (21, 22) immediately before the primary gas stream (15) or the secondary gas stream (16) is connected to firebox (11) .6. The method according to any one of claims 1 to 5, characterized in