Experimental investigation of the NOx formation and control during the self-sustaining incineration process of N-containing VOCs (DIMETHYLFORMAMIDE)

An experimental investigation was conducted on N,N-dimethylformamide (DMF) pyrolysis at medium-temperature followed by extremely fuel-lean combustion. Furthermore, the NH₃-SNCR (Selective non-catalytic reduction) method was studied to control NOx produced in DMF oxidation. Jet-stirred reactors (JSRs) were used in experimental investigation, because the uniform gas-phase mixing state formed by high-speed turbulence in JSR makes the validation of detailed models easier. The major gaseous species produced by pyrolysis, oxidation, and SNCR, namely H₂, N₂, CO, CO₂, NOx, N₂O, HCN, and CxHy, are quantified because the mechanism of NOx reduction will be elaborated using these species. The results show that the main nitrogen-containing pyrolysis products are HCN and N₂, taking up 65% and 25% of DMF nitrogen, while carbon-containing pyrolysis products are mostly CO, CH₄ and HCN. The HCN concentration increases significantly by 42.13% as pyrolysis time increases from 1.5 to 7 s. In oxidation, HCN and N₂O concentration peaks are at 650 °C and 750 °C respectively, and NO concentration increases as temperature enhances when it is over 800 °C. A higher ratio of NO/N₂O concentration was shown in oxidation of the higher equivalence ratio. The de-NOx efficiency of NH₃-SNCR on oxidation flue gas peaked in range 825–875 °C, and as the NH₃/NO ratio increased to more than 2.5, NO removal rate tended to reach the maximum of about 50%. The N₂O removal rate rose significantly as temperature exceeded 900 °C in SNCR. The results shows the feasibility of NO emission control with DMF containing VOCs incineration in current industrial applications·NH₃-SNCR at 825–875 °C shows significant de-NOx effect, but not a proper solution to limit N₂O emission at the same time. This study could provide guidance for designing and optimizing the incinerator parameters and its de-NOx system, as well as provide validation data for future chemical kinetic model capable of predicting DMF combustion.