Lennart Gustavsson

Modeling of chemical reactions in afterburning for the reduction of N2O

Afterburning involves burning a secondary fuel in the flue gases from a fluidized bed combustor to raise the temperature, and thereby decrease the emission of N2O. Tests in a 12-MW circulating fluidized bed boiler used the cyclone as an afterburning combustor. The results from these tests are analyzed by chemical kinetic calculations with homogeneous hydrocarbon and nitrogen chemistry. Furthermore, a study is made of the influence on the calculation of particles in the flue gases. The deviation between calculated and measured data is small at high temperatures, but increases at the lower temperatures investigated. The influence of particles is predicted to be small under conditions prevailing in the cyclone.

Methods for reducing the emission of nitrous oxide from fluidized bed combustion

Abstract - Two methods for the reduction of nitrous oxide emissions, afterbuming and reversed air staging, are investigated in a 12 MW circulating fluidized bed boiler. With afterburning the N2O emission can be reduced by 90% or more, using an amount of secondary fuel corresponding to 10% of the total energy input. With reversed air staging it is possible to reduce the emission of N2O to one fourth (25 ppm), without significantly affecting the other emissions. With reversed air staging no secondary air is used in the combustor and an air-ratio of about unity is maintained throughout the combustion chamber. Air for final combustion is added in the cyclone outlet.

Report: waste refinery in the municipality of Borås.

This paper briefly describes waste treatment trends in Sweden and describes an example of state-of-the-art treatment in a local integrated waste treatment system (Borås). The focus is on treatment of household waste, to illustrate what can be done to establish a sustainable waste treatment system with high recovery of materials and energy. The various processes have resulted in a low amount of landfilled household waste, and high proportions of recovered energy and materials. Heat, electricity, vehicle fuel and fertilizers, metals and construction materials are recovered from the local waste in Borås, with less than 4% of domestic waste being sent to landfill.