Measurement of Premix Gas.
To produce the desired flame in a glass forehearth or when making fiberglass (glass fiber) insulation, an air/fuel pre-mixer is used. The pre-mixer combines compressed natural gas or propane with air and this mixture is then piped to the process burners At the burner, a fuelrich or fuel-lean flame is produced depending on the air/ fuel ratio selected. In many combustion applications, an oxygen analyzer
measures the excess oxygen (fuel-lean) or excess fuel (fuel-rich) directly in the flue gas. In this application however, the flue gas cannot easily be reached or may not provide an accurate measurement due to air leakage. A pre-mix gas analyzer must therefore be used.
Glass Fiber Manufacturing
Similarly, precise combustion control is needed to manufacture glass fiber insulation products of the correct quality. The final stage of the glass fiber process uses a high velocity flame to melt coarse glass strands and draw them out into extremely fine fibers. By controlling the air/fuel mixture, the tensile strength, density, weight, and “R” factor of the insulation are controlled. Depending on the end product, the flame is kept slightly fuel-rich or slightly fuel-lean.
Container Glass Forehearths
In the manufacture of bottles and other glass containers, open flame burners are used to control the atmosphere of the molten glass in the forehearth. Depending on the end product and desired process conditions, a slightly rich or a slightly lean combustion fuel mixture is needed in the different zones in the forehearth. Maintaining the correct air/fuel mixture both ensures the quality of the end product and also protects manufacturing equipment such as gobbing stirs.