Modelowanie optymalnego spalania paliwa w kotłach przemysłowo-grzewczych

Celem opracowania modelu fizyko-matematycznego (MFM) było uzyskanie sposobu określenia przedziału, w którym oczekuje się optymalnych wskaźników sprawności i ekologiczności spalania paliwa w zakresie możliwych zmian następujących czynników wpływu: zużycia paliwa Bg, współczynnika nadmiaru powietrza w palenisku, zmiany współczynnika nadmiaru powietrza na skutek nieszczelności i, temperatury powietrza tp i paliwa tg, wartości opałowej paliwa Qn, stopnia zanieczyszczenia ekranowych powierzchni kotła, sprawności cieplnej konwekcyjnych powierzchni kotła.

Development of a physical and mathematical model (PMM) allows to define an interval of changes inside which optimum factors of fuel burning efficiency and ecological character can be expected. Such solution allows to reduce considerable the number of required boiler operation mode changes and measurements made. The fuel burning optimization assessment was performed, from the point of view of both efficiency and ecological character, basing on the energetic and ecological criteria developed by the authors. The primary values defining criteria are: reduced flue gas toxicity indicator Gsp and the boiler unit gross balance efficiency nbr. Therefore authors have undertaken the task to develop the furnace, convection tube banks and economizer heat exchange process model and analyse the factors having impact on the process. Therefore, the heating surface of the boiler unit was divided into measurement zones (Fig. 1) to develop the model. The heat exchange in particular sections was calculated by application of the heat balance equations and heat exchange theory. The physical and mathematical model of change of the parameters defining the energetic and ecological criteria values which allowing to reduce the number of experiments was developed with aid of the Microsoft Office Visual Basic software. The only factor controlled during combustion process, was flow of air. Fig. 2÷5 show impact of the temperature and natural gas calorific value, air temperature, screen surfaces and furnace pollution degree and air inflow along boiler's gas duct on the optimum values of factors determining the fuel combustion mode i.e. O2 and CO. Basing on the performed analyses it has been ascertained that change of value of no non-regulated factors has no significant impact on CO concentration. The developed PMM contributed to minimization of the operation period through reduction of the parameters change interval.