Vliv OEC metod na emise NOx, rozložení teplot ve spalovací komoře a rozložení tepelných toků do stěny spalovací komory

The influence of oxygen-enhanced combustion methods on NOx emissions, in-flame temperatures and heat flux distribution

článek ve sborníku ve WoS nebo Scopus

en

The aim of the present study was to experimentally investigate and compare the characteristics of three various oxygen-enhanced combustion (OEC) methods including premix enrichment (further denoted as PE), air-oxy/fuel combustion (further denoted as AO) and oxygen lancing (further denoted as OL). The combustion tests were carried out with the experimental two-gas-staged burner at the large-scale burners testing facility. As for the PE method, the oxygen was injected into the incoming combustion air stream through the diffuser inserted in the air supply duct, while in the AO and OL methods the oxygen was injected directly into the flame through the oxygen nozzle heads placed at different positions depending on used OEC method. The total oxygen concentration in the incoming air was varied from 21 % to 38 %. All combustion tests were carried out at the burner thermal input of 750 kW for two combustion regimes – one-staged and two-staged fuel combustion. The target oxygen concentration in dry flue gas was kept around 3 % by volume. The characteristics of OEC methods such as the concentration of nitrogen oxides and carbon monoxide in flue gas, flue gas temperature, heat flux to the combustion chamber wall, in-flame temperatures distribution in the horizontal symmetry plane of the combustion chamber, and the stability of flame were investigated. NOx emission increased more than 40 times and by 20 times for the PE method if one-staged and two-staged combustion regime was used, respectively. Significantly better results were obtained during the tests of both AO and OL method, especially when the fuel was staged. Then the NOx emission was below 150 mg/mN3 at all oxygen flow rates. The radiative heat transfer was enhanced as the oxygen concentration was increased for all OEC methods. The available heat at 38 % O2 was higher by 20 % compared with that at 21 % O2. Flue gas temperature decreased with increasing oxygen concentration affected both by decreasing N2 concentration in the oxidant and by increasing radiant heat flux at the same time. Increasing oxygen concentration also led to higher temperature gradient near the burner tile in the horizontal symmetry plane of the combustion chamber.

Cílem práce bylo experimentálně vyšetřit vlastnosti dvou metod spalování s vyšším obsahem kyslíku (zkráceně OEC). Jmenovitě se jednalo o metodu přimíchávání kyslíku přímo do proudu spalovacího vzduchu a metodu nástřiku kyslíku přímo do spalovacího prostoru. Spalovací zkoušky byly provedeny s konvenčním experimentálním nízkoemisním hořákem s dvoustupňovým přívodem paliva. Celková koncentrace kyslíku se měnila v rozmězí 21 % a 38 %. Zkoušky byly provedeny při konstantním výkonu hořáku 750 kW pro dva spalovací režimy – jednostupňový a dvoustupňový přívod paliva. Koncentrace kyslíku v suchých spalinách byla udržována kolem hodnoty 3 %. Cílem zkoušek bylo vyhodnotit vliv koncentrace kyslíku, metody OEC a stupňovitého přívodu paliva na celou řadu parametrů spalování. Tyto parametry zahrnovaly emise oxidů dusíku, teplotu spalin, rozložení tepelných toků do stěny spalovací komory a rozložení teplot v horizontální rovině symetrie spalovací komory.

The aim of the present study was to experimentally investigate and compare the characteristics of three various oxygen-enhanced combustion (OEC) methods including premix enrichment (further denoted as PE), air-oxy/fuel combustion (further denoted as AO) and oxygen lancing (further denoted as OL). The combustion tests were carried out with the experimental two-gas-staged burner at the large-scale burners testing facility. As for the PE method, the oxygen was injected into the incoming combustion air stream through the diffuser inserted in the air supply duct, while in the AO and OL methods the oxygen was injected directly into the flame through the oxygen nozzle heads placed at different positions depending on used OEC method. The total oxygen concentration in the incoming air was varied from 21 % to 38 %. All combustion tests were carried out at the burner thermal input of 750 kW for two combustion regimes – one-staged and two-staged fuel combustion. The target oxygen concentration in dry flue gas was kept around 3 % by volume. The characteristics of OEC methods such as the concentration of nitrogen oxides and carbon monoxide in flue gas, flue gas temperature, heat flux to the combustion chamber wall, in-flame temperatures distribution in the horizontal symmetry plane of the combustion chamber, and the stability of flame were investigated. NOx emission increased more than 40 times and by 20 times for the PE method if one-staged and two-staged combustion regime was used, respectively. Significantly better results were obtained during the tests of both AO and OL method, especially when the fuel was staged. Then the NOx emission was below 150 mg/mN3 at all oxygen flow rates. The radiative heat transfer was enhanced as the oxygen concentration was increased for all OEC methods. The available heat at 38 % O2 was higher by 20 % compared with that at 21 % O2. Flue gas temperature decreased with increasing oxygen concentration affected both by decreasing N2 concentration in the oxidant and by increasing radiant heat flux at the same time. Increasing oxygen concentration also led to higher temperature gradient near the burner tile in the horizontal symmetry plane of the combustion chamber.

Spalování s obohaceným spalovacím vzduchem, stupňovitý přívod paliva, oxidy dusíku, tepelný tok, teploty v plameni

Oxygen-enhanced combustion, fuel-staged combustion, nitrogen oxides, heat flux, in-flame temperatures

2015

07.04.2015

Porto

978-972-99309-7-3

NEUVEDENO

Proceedings of the 10th European Conference on Industrial Furnaces and Boilers

1–11

11