Research Of PCDD/Fs Inhibition From Waste Incinerator By S-N-containing Compounds

With the implementation of the new national standards of municipal solid waste (MSW) incineration pollution control, control low emission of Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from waste incineration is full of challenges. To research the whole process of PCDD/Fs emission from typical waste incinerator systematically, clarify the key inhibition mechanism of sulfur-based and nitrogen-based compounds, develop new kind of cheap and efficient inhibitors, as well as inhibition technology for industrial application, this paper carried out a series of experimental study, and made some practical guiding research results and conclusions, including:1) In the paper, we have researched the whole process of PCDD/Fs emission in the flue gas from typical waste incinerator systematically. PCDD/Fs concentration in the flue gas of the outlet of the furnace is 0.03-1.09 ng I-TEQ/Nm3, with an average concentration of 0.62 ng I-TEQ/Nm3,0.02-54.07 ng I-TEQ/Nm3 with an average concentration of 11.54 ng I-TEQ/Nm3 for the outlet of low-temperature super-heater,6.70-126.11 ng I-TEQ/Nm3 with an average concentration of 67.15 ng I-TEQ/Nm3 for the inlet of air pollution controlling devices (APCDs), and 0.08-2.17 ng I-TEQ/Nm3 with an average concentration of 0.93 ng I-TEQ/Nm3 for the outlet of filter bag house, PCDD/Fs emission during the incinerator is a process of increasing and decreasing, and the area from the outlet of low-temperature super-heater to the inlet of APCDs is the main area for PCDD/Fs formation during 250-450, as well as the main area for PCDD/Fs memory effect. Reduce times of stove-fire and start-stop during incinerator operation will help reduce PCDD/Fs memory effect.2) In this paper, we have comprehensively clarified the key inhibition mechanism of sulfur-based and nitrogen-based compounds, and explore a new efficient kind of S-N-containing inhibitor by the rule of economic, not-toxic, easy-to-use and high S and N molecules, including sludge drying pyrolysis gas (SDPG). S-N-containing inhibitor could reach a high suppression of more 99% during low-temperature experiment. The suppression efficiency of S-N-containing inhibitor depends on the type of nitrogen-base and (S+N)/C1 mole ratio, and a (S+N)/C1 mole ratio of 1.4-2.0 is an appropriate ratio.3) We have explored an inhibitor-recycling technology in a pilot-scale system (500 Nm3/h) in the bypass flue gas of a commercial waste incinerator. The pilot-scale system can realize a strong accumulation ability of S-N- atmosphere with doubling (S+N)/Cl mole ratio in the flue gas. After sulfur-amino inhibitor recycling, the suppression of PCDD/Fs reach more than 95% with decreasing the PCDD/Fs concentration to 0.08 ng I-TEO/Nm3, less than the new national standards of 0.1 ng I-TEQ/Nm3.4) We have explored a new inhibiting technology of inhibitor solution injection in the high-temperature furnace and inhibitor powder injection in the low-temperature furnace, and completed the industrial applications research in the full-scale incinerator (600-800 t/d). A suppression of PCDD/Fs reaches more than 85% and a synergistic suppression of NOx of 43% are reached after adding sulfur-amino inhibitor (0.1% of MSW). The new inhibiting technology shows no negative effects for conventional pollutants in the flue gas.