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

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 greenhouse 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 NO x 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 NO x 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 NO x emissions. As the biomass combustion took place at temperatures low enough that thermal and prompt NO x 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 NO x reduction by CO.

Experimental Characterization of Maize Cob and Stalk Based Pellets for Energy Use

“…By implication, the combustion reaction of sulphur will generate sulphates, which can liquefy in the walls of the heat exchanger and produce ashes. Thus, very low levels of sulphur in fuels are required [49]. Table 2 presents the ultimate analysis results of some selected biomass from García et al [16], however, it should be noted that Carbon, Nitrogen, and Oxygen are the major components in biomass fuel.…”

Eksperimentalna aparatura za simulaciju sagorevanja biomase i kontrolu azotnih oksida

“…Pri sagorevanju biomase oksidacija azota vezanog u gorivu je dominantan mehanizam formiranja NOx. Termički i promptni NOx je zanemarljiv zbog relativno niske temperature sagorevanja uslovljene niskom temperaturom topljenja pepela biomase [1][2][3][4][5][6][7][8].…”

“…Razlog tome je što ova biomasa sadrži visok procenat azota kao posledicu izraženog sadržaja proteina zbog čega je ona i značajna kao nutrient. Pored toga upotreba azotnih đubriva u poljoprivredi dodatno doprinosi povećanju ovog elementa u biomasi [1]. Zastupljenost azota u sastavu različitih tipova biomase dat je u tabeli 1. iz koje se vidi da je azot zastupljeniji u poljoprivrednoj biomasi u odnosu na drvnu.…”

“…1 dijagramima a i b, respektivno. Na prikazanim dijagramima se jasno vidi da su izmerene visoke koncentracije NO u odnosu na druge gasove, iako je organizacija sagorevanja dobra, što je indukovano malom emisijom ugljen monoksida, povoljnim temperaturama sagorevanja i povoljnim viškom vazduha [1,8].…”

“…Upravo ove navedene činjenice, kao i zastupljenost poljoprivredne biomase u ukupnom potencijalu biomase u Srbiji, bila je podsticaj da se detaljnije ispitaju mere denitrifikacije dimnih gasova pri sagorevanju poljoprivredne biomase. Kako pri sagorevanju biomase uticaj sadržaja azota u gorivu dominantno utiče na emisiju NOx [1], to primarne mere denitrifikacije -tehnike kontrole sagorevanja, same po sebi, često nisu dovoljne za zadovoljenje strogih granica emisije i/ili su neprimenljive u pos- Selektivna nekatalitička redukcija (SNCR) je redukcija NOx na azot, N 2 , u prisustvu kiseonika, O 2 , u reakcijama sa reagensima na amino-bazi, bilo amonijakom (NH 3 ) ili ureom (CO (NH 2 ) 2 ) na temperaturama od 800-1100°C (sl. 2), sa većom temperaturom potrebnom za ureu.…”