OCR Text |
Show (2) Relationship between Dioxins in the flue gas and CO (carbon aonoxide). Many reports have been Made as to the relationship between dioxins and CO, carbon monoxide, contained in the flue gas discharged fro. the furnace. Table. 2-1 shows part of the report contents incidentally, if No.2 figure of Table. 2-1 is superiMPosed with a average figure of dioxin (PCDO) measureMent results in NKK-V if> lund Waste-to-Energy Plant (double flue gas type). the average almost coincides with a line of extra-polation, confirming authenticity of these data. Re.aining CO in the flue gas can be supported by the existence of a zone of which therMal destruction effects are inferior in the cOMbustion gas flow in the furnace and the boiler. It is naturally considered that. as pyrolytic characteristics of dioxins are inferior to those of such CO, the level of dioxins formation is higher. (3) Relationship between dioxins in the flue gas and residence time. Results of experiment of the r e l~ t i o ns hip b~ tw ~e n residence time of flue gas in the combustion and the re-combus tion zones and dioxins destruction efficiency have been reported. Fig. 2-2 shows these results. According to this figure remaining dioxins are reduced to approxi. ately 1/100 after residence time of one second and to approximately 1/300 after two seconds. It is naturally supposed, however. that this dioxins destruction efficiency is incre~ se d greatly by combustion temperature on condition that oxygen 02 exceeds a certa i n I eve 1. 2-2) Dioxins control by combustion The following is a summary of the necessary conditions for dioxins control based on various data and information related with combustion conditions in a Waste-to-Energy Plant and dioxins formation, and our experience in the R&D and the practical applications of other air pollution control methods than for dioxins. IIU |