The combustion of biomass - the impact of its types and combustion technologies on the emission of nitrogen oxide

Milica Mladenovic,Mirko Komatina,Milijana Paprika,Stevan Nemoda,Branislav Repic,Dragoljub Dakic,Aleksandar Eric

doi:10.2298/hemind150409033m

Abstract

Harmonization of environmental protection and the growing energy needs of modern society promote the biomass application as a replacement for fossil fuels and a viable option to mitigate the green house gas emissions. For domestic conditions this is particularly important as more than 60% of renewables belongs to biomass. Beside numerous benefits of using biomass for energy purposes, there are certain drawbacks, one of which is a possible high emission of NOx during the combustion of these fuels. The paper presents the results of the experiments with multiple biomass types (soybean straw, cornstalk, grain biomass, sunflower oil, glycerin and paper sludge), using different combustion technologies (fluidized bed and cigarette combustion), with emphasis on the emission of NOx in the exhaust gas. A presentation of the experimental installations is given, as well as an evaluation of the effects of the fuel composition, combustion regimes and technology on the NOx emissions. As the biomass combustion took place at temperatures low enough that thermal and prompt NOx can be neglected, the conclusion is the emissions of nitrogen oxides primarily depend on the biomass composition- it is increasing with the increase of the nitrogen content, and decreases with the increase of the char content which provides catalytic surface for NOx reduction by CO.

Highlights

Harmonization of environmental protection and the growing energy needs of modern society promote the biomass application as a replacement for fossil fuels and a viable option to mitigate the greenhouse gas emissions
NH3 tends to be oxidized to NO and N2 instead of N2O at temperatures of 800–900 °C [7], so N2O emission is not the subject of this paper. Another point of consideration with respect to nitrogen oxides (NOx) emissions during the biomass combustion is the catalytic effect of the char and ash on NOx formation and reduction [6]
After starting the installation by combustion of liquid gas and reaching temperatures of FB required for beginning of the examined fuel combustion, it is dosed with the increasing of operating FB temperature to the desired value

Summary

Introduction

Harmonization of environmental protection and the growing energy needs of modern society promote the biomass application as a replacement for fossil fuels and a viable option to mitigate the greenhouse gas emissions For domestic conditions this is important as more than 60% of renewables belongs to biomass. The two precursors (especially NH3) can serve as reducing agents for NO reduction, as follows: NH3 + O2 → NO + H2O + H NH3 + NO → N2 + H2O + H Quite a low N2O concentration was detected during large-scale biomass combustion [3,5] This phenomenon has been attributed to the N functional groups present in biomass fuels, mainly amino groups, which are usually form NH3 as the main N-product during pyrolysis [1,3,4,5,6]. NH3 tends to be oxidized to NO and N2 instead of N2O at temperatures of 800–900 °C [7], so N2O emission is not the subject of this paper. Another point of consideration with respect to NOx emissions during the biomass combustion is the catalytic effect of the char and ash on NOx formation and reduction [6]

Results

Discussion

Conclusion