Gas burner

Propane burner used with forced air into a metal melting furnace.

Propane burner with bunsen flame.

Propane oxygen burner used for cutting through steel rails.

Flame of a Gas- and Oil dualburner.

A gas burner is a device to generate a flame to heat up products using a gaseous fuel such as acetylene, natural gas or propane. Some burners have an air inlet to mix the fuel gas with air to make a complete combustion. Acetylene is commonly used in combination with oxygen.

It has many applications such as soldering, brazing and welding, the latter using oxygen instead of air for getting a hotter flame which is required for melting steel. For laboratory uses a natural gas fired Bunsen burner is used. For melting metals with melting points of up to 1100 °C such as copper, silver and gold a propane burner with natural drag of air can be used.

Table 1: Flame temperatures of common gases and fuels

Gas / Fuels	Flame temperature
Propane in air	1980 °C
Butane in air	1970 °C
Wood in air (normally not reached in a wood stove)	1980 °C
Acetylene in air	2550 °C
Methane (natural gas) in air	1950 °C
Hydrogen in air	2111 °C
Propane with oxygen	2800 °C
Acetylene in oxygen	3100 °C +
Propane-butane mix with air	1970 °C ~
Coal in air	1900 °C (blast furnace)
Cyanogen (C2N2) in oxygen	4525 °C
Dicyanoacetylene (C4N2) in oxygen	4982 °C (highest flame temperature)

Info & Assuming:

• Adiabatic flame
• 20 degrees Celsius 1 bar atmosphere
• Complete combustion (no soot and more blue-like flame is the key) (Stoichiometric)
• Peak Temperature
• Speed of Combustion (has no effect on temp, but more energy released per second (as adiabatic) compared to normal flame)

• Spectral bands also affect colour of flame as of what part and elements of combustion
• Blackbody radiation (colour appearance only because of heat)

• Atmosphere - affects temperature of flame and colour due the atmospheric colour effect

Table 2: Explosive limits and ignition temperatures of common gases

	Explosive limits (lower & upper, in %)	Ignition temperatures
Natural gas	4.7 & 15	482-632 °C
Propane	2.15 & 9.6	493-604 °C
Butane	1.9 & 8.5	482-538 °C
Acetylene	2.5 & 81	305 °C
Hydrogen	4 & 75	500 °C
Ammonia	16 & 25	651 °C
Carbon monoxide	12.5 & 74	609 °C
Ethylene	3.4 & 10.8	490 °C

Note: Atmosphere is air at 20 degrees Celsius.

Table 3: Combustion values of common gases

Gas	Combustion value
	(Btu/ft³)	(MJ/m³)
Natural gas (methane)	950 to 1,150	35 to 43
Propane-butane mix	2,500 to 3,200	90 to 120
Propane	2,572	95.8
Butane	3,225	120.1

References

• Pocket Guide to fire and arson investigation, second edition, FM Global, Table 1,2 and 3