Explosions of Syngas/CO₂ Mixtures in Oxygen-Enriched Air

Abstract

Most of the scientific works on syngas combustion deal with dry air as oxidizer, whereas very few studies have been carried out on syngas combustion in oxygen-enriched air (i.e., oxy-combustion). In this work, the explosion behavior (peak pressure and burning velocity) for H 2 /CO/O 2 /N 2 /CO 2 mixtures has been evaluated experimentally and numerically, for different H 2 /CO ratios, fuel (H 2 +CO) concentrations with respect to O 2 , molar percentages of CO 2 , and for values of the oxygen-enrichment factor, E (= O 2 /O 2 +N 2 ), ranging from 0.21 (i.e., air) to 1 (i.e., pure oxygen). The Sandia PREMIX module of the CHEMKIN package, coupled to the detailed Davis reaction scheme, was used to calculate the unstretched laminar burning velocity. Results have shown a good agreement with the experimental data. Through ad hoc simulations, the role of CO 2 has been also evaluated. Furthermore, the ranges of validity of the additivity rule for the burning velocity have been identified. All tests show the typical trend of pressure time history of explosions occurring in a closed combustion chamber. However, some compositions show anomalous impulses that could not be explained by classical theory for deflagration/detonation. Explanation for this behavior is based on results of previous works by the same authors on combustion-induced Rapid Phase Transition (c-RPT).

Theoretical analysis of anomalous explosion behavior for H 2 /CO/O 2 /N 2 and CH 4 /O 2 /N 2 /CO 2 mixtures in the light of combustion-induced rapid phase transition

“…More recently, we have found a similar behavior during closed vessel explosion tests for CH 4 /O 2 /N 2 /CO 2 [13e15] and H 2 /CO/O 2 /N 2 /CO 2 [8,16] mixtures. In particular, a transition has been observed e with increasing oxygen content e from deflagration to an anomalous regime characterized by oscillations and over-adiabatic peaks in pressure time histories.…”

Effects of oxygen enriched combustion on pollution and performance characteristics of a diesel engine

“…A number of analytical and experimental studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] have demonstrated the benefits of using oxygen enriched combustion in diesel engines. The results of all these investigation show a considerable decrease in unburned hydrocarbon, carbon monoxide emissions and smoke while oxides of nitrogen emissions increased pro-rata with the oxygen added.…”

“…Song et al [16] compared the combustion and emission characteristics of oxygenated fuel and raw oxygen added into the intake air and found that the combustion characteristics of hydrocarbon fuel enhanced by supplying extra oxygen as it increases the flame velocity, flame temperature, lean flammability limit, flame stability, and available energy. Salzano et al [14] and Cammarota et al [4] report that, increase in flame velocity and flame temperature can lead to a flame propagation which is not deflagration but it is combustion induced rapid phase transition. An increased laminar burning velocity due to oxygen enrichment leads to increase in maximum pressure and rate of pressure rise as explained by Di Benedetto et al [7].…”

Experimental Study of the Laminar Flame Speeds of the CH4/H2/CO/CO2/N2 Mixture and Kinetic Simulation in Oxygen-Enriched Air Condition

“…They found that the increase of O 2 content promoted the laminar propagation velocity and expanded the flammable range of CH 4 . Salzano et al 11 and Xu et al 12 studied the explosive characteristics of syngas and hydrous bioethanol in oxygen-enriched air conditions. Results show that the rising oxygen fraction promoted the deflagration index and explosive pressure.…”