Basics - Industrial Burners (Nozzle and Premix)
Characteristics & Selection
Several burner characteristics come into play in making the proper selection for
an oven or furnace.
Burner firing capacity is usually the first characteristic to consider. No single
burner can cover the entire range of Btu inputs required by various industrial
processes, so burner types are built in families of different sizes. This permits
designers to choose the correct size for an application.
Getting a good
match between the burner's flame characteristics and the furnace or oven is the
fastest, most efficient heat transfer, providing good temperature uniformity.
Dimensions & Shape
The flame size and shape have to match the needs of the application.
Heat Release Concentration
The concentration of the heat released by the burner must match the characteristics
of the process.
temperature, lightly-loaded processes like bakery ovens need a relatively small
amount of heat distributed over a wide area. This calls for line burners, ribbon
burners and other designs that spread small flames over several feet of burner.
temperature, heavily-loaded applications, like metal melters and forging furnaces,
require a large amount of heat energy packed into a relatively small area. Burners
for these furnaces usually have compact, intense, fast-mixing flames.
Burner turndown is the maximum firing rate divided by its minimum firing rate.
It's an indication of the burner's flexibility in responding to variations in
heat requirements. The burner system turndown must match or exceed the heat requirement
turndown of the process.
One way to
stretch the turndown of a burner is to operate with excess air at certain firing
rates. In general, the larger the ratio flexibility of the burner, the greater
its turndown capability.
Burner exhaust emissions (NOx, carbon monoxide and unburned hydrocarbons) have
become a major consideration. In fact, in some areas, they are the
most important selection criteria. Regulations may require the use of special
low emission burners for a job, even though they may not be the first choice from
a heat application standpoint.
Burner flame velocity may be an important selection factor. High velocity burners
have become popular in recent years for certain applications requiring faster
heat transfer and good temperature uniformity.
Burner flame color isn't as important a factor as it used to be. In high temperature
applications (where most of the heat is transferred by radiation), many customers
believe a luminous yellow flame transfers heat faster and more uniformly.
blue flames are strongly preferred in applications like paint curing and food
processing because they indicate clean, soot-free combustion.