We report on an experimental investigation of oxy-fuel combustion carried out in a co-axial, horizontally-fired swirl-stabilized burner. Retrofitting possibilities and flame extinction have been investigated with methane or liquefied petroleum gas (LPG) as fuel and mixtures of oxygen (O 2)-carbondioxide (CO 2) or air as oxidant. Temperature profile measurements show that a higher oxygen concentration of around 33-34% by volume in the oxidizer is needed in oxy-fuel combustion to get temperature profiles similar to those for normal air combustion. Oxy-fuel flames have been found to be stable even for O 2 concentrations less than 30% by volume, though at reduced peak flame temperatures. The results of extinction studies with CO 2 or nitrogen (N 2) dilution indicate that CO 2-diluted flames are more prone to extinction by dilution than N 2-diluted flames. The former get extinguished at an oxygen concentration of 21% by volume whereas the latter can be sustained at oxygen concentrations down to 15% by volume. © 2011 Elsevier Ltd. All rights reserved.

Sreenivas Jayanti

Department Of Chemical Engineering

AIR COMBUSTION

Co-axial

EFFECT OF SWIRL

Experimental investigations

Experimental studies

FLAME EXTINCTION

FLAME TEMPERATURES

OXY-FUEL BURNERS

OXY-FUELS

Oxyfuel combustion

Oxygen concentrations

Temperature profiles

Carbon dioxide

combustion

Fuels

Light extinction

Liquefied petroleum gas

Methane

Oxygen

Retrofitting

Temperature control

temperature measurement

Flame research

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Fuel

Oxy-fuel combustion is one of the technologies which enable the economic and efficient carbondioxide (CO 2) removal. In the present paper, a new variant to the oxy-coal combustion in a pulverized coal burner is proposed in which CO 2-enriched flue gas is used to moderate the flame temperature in conventional oxy-fuel combustion. In this method, a flue gas conditioner is used to remove most of the moisture from the flue gas which results in CO 2 enrichment. This gas is recycled back to the furnace to be mixed with pure oxygen from an air separation unit to provide a CO 2-rich environment in which the hydrocarbon fuel is burnt. Thermodynamic analysis on a lignite coal-fired power plant shows that, for the same peak flame temperature, the flue gas is significantly richer in CO 2 (by up to 80.5% by mass) at the boiler exit. Compared to the conventional exhaust gas recycling, the proposed method is simpler in the sense that one hot-gas particulate cleaning system is eliminated. The volumetric flow rate of the flue gas through the boiler is also reduced. Both these factors make it attractive for high ash coals where particulate cleaning and erosion-related problems are of major concern. Thermodynamic exergy analysis shows that the optimized CO 2-enriched flue gas recycled power plant performs better than retrofitted flue gas recycled system. © 2008 Elsevier Ltd. All rights reserved.

Optimized enriched CO 2 recycle oxy-fuel combustion for high ash coals

A numerical study of oxy-fuel combustion has been carried out in the pressure range of 0.1-3 MPa with methane as the fuel and carbondioxide-diluted oxygen with trace amount of nitrogen (termed here as c_air) as the oxidant. The flame structure and NO generation rate have been calculated using the flamelet model with the detailed GRI 3.0 mechanism for two oxygen concentrations of 23.3% and 20% by weight in the oxidant at a strain rate of 40 s-1 (corresponding to a scalar dissipation rate of 1 s-1). It is observed that, for the reference case of 23.3 wt.% of oxygen, as the pressure increases, the peak temperature of the flame increases rapidly up to a pressure of 0.5 MPa, and more gradually at higher pressures. The concentrations of important intermediate radicals such as CH3, H and OH decrease considerably with increasing pressure while NO concentration follows the same trend as the temperature. Reducing the oxygen concentration to 20% by weight leads to an order of magnitude reduction in NO concentration. Also, for pressures greater than 0.3 MPa, the NO concentration decreases with increasing pressure in spite of the increasing peak flame temperatures. This can be attributed to the increasing domination of recombination reactions leading to less availability of the intermediate radicals H and OH which are necessary for the formation of NO by the thermal route. It is concluded that a stable, low NOx oxy-fuel flame can be obtained at high pressures at slightly increased dilution of oxygen. © 2008 Elsevier Ltd. All rights reserved.

Journal	Fuel
ISSN	00162361
Open Access	No