Principium Research Of SNCR DeNO_x Process

Coal is a main energy in China, but it brings a series of environment pollution problem including air pollution. Great achievements have been made in SO_x emission control, and NO_x emission control will be the next assignment. The Selective Non-Catalytic Reduction (SNCR) DeNO_x technique is comparative easy to be realized, and costs lower, so it is a suitable technique to be expanded in our power plant. However, the work on NO_x emission control started at a comparatively late date in China. More basic research of SNCR technique is still needed.In this thesis, the effect of several operation parameters on NH₃-SNCR process and the reaction mechanisms are studied by numerical simulation. First of all, a most suitable detailed reaction mechanism, which is named AC Mechanism, consisting 78 species and 522 elementary reactions, is selected by comparison of simulation and experimental results. The mechanism is then introduced to the simulation process. The results of simulation indicate that:Four parameters: temperature, initial mole ratio of NH₃ to NO (NSR), inlet NO concentration and flue gas oxygen concentration are studied. Temperature is the most important influential factor among them, for that NO_x emission meets with the standard for discharge only when the SNCR process is working in a narrow temperature window (1200K-1350K). The reason is that NO_x reduction during the SNCR process relays largely on the concentration of radicals, especially OH radical. Only under favorable temperature can proper quantities of OH be produced, who stimulates many branch reactions leading to NO_x reduction. NSR is the factor having a great influence on NO_x reduction but has no influence on temperature window. It should be sustained between 1.0-2.0 to achieve NO_x reduction as well as low NH₃ emission. For the same purpose, more NH₃ should be put in when inlet NO_x concentration raised, because the outlet NO_x concentration goes up with an elevated inlet NO_x concentration. At last, flue gas oxygen concentration does a little influence on NO_x reduction, indicates that the NH₃-SNCR process is very sensitive to NO reduction.Addictives like CH₄, C₂H₆, H₂, CO or H₂O₂ all can expend the SNCR temperature window effectively, having little influence on NO_x reduction. Adding different addictives generates different radicals which initiates element reactions that...