Caracterização e controle das emissões de óxidos de nitrogênio e material particulado em caldeiras para bagaço

Abstract

This work presents a characterization of the nitrogen oxides and particulate matter formation and emission, based in the literature, as well in measured date of Brazilian bagasse boilers, and in these cases, it evaluate the behavior of the emissions regarding the main operation parameters, like by example, the boiler load, loses by incomplete combustion and air excess coefficient. Also, based on the technical literature, it describes the empirical methodologies that were implemented in forms of calculation, and that permit evaluate different control systems for particulate matter (multiciclones, venturi scrubbers and the association of both) and for nitrogen oxides (selective non catalytic reduction), under the technical-economic view point, beyond models that predict the nitrogen oxides formation. Also it is presented a dispersion study of the nitrogen oxides for 800 m around of a sugar cane mill, considering different atmospheric stability conditions and for different boiler loads, in order to evaluate which the most unfavorable conditions of dispersion. Measured date of particles concentration in exhaust gas measured in the evaluated boilers present values in the range of 400 to 600 mg/Nm3, when are employed multiciclones, and 80 to 200 mg/Nm3, when are employed venturi scrubbers. Multiciclone associate to venturi scrubber is going to be better economic feasibility, presenting a smaller cost of control and guaranteeing the regulate concentration in the exit of 120 mg/Nm3. For the nitrogen oxides analysis it concluded that the values of emission are in the range of 100 to 200 mg/Nm3, it concluded that are inside the national standards established for the emission limit, and whose formation depending mainly of the air excess coefficient. However, when it is evaluated the dispersion of this pollutant, determined kinds of atmospheric stability do not guarantee the air quality standards. In that case must be adopted measures for the reduction, as by example, a reduction of 20% in the air excess, guarantee a reduction of 30% of NOx formation.