Burners with adjustable spin

Control of the aforementioned problems requires an additional temperature sensor in each zone and a means for changing the mixing rate characteristic of the burner in response to the temperature measurements. Burners with adjustable spin (swirl) can be set to prevent much of the problem, especially if combined with a low-fire, forward-flow gas or air jet through the center of the burner. Such a jet is typically sized for 5% of maximum gas or air flow. 

If a long furnace is fired from one end, the cooling gases set up temperature differentials that affect the load heating rate. (See fig. 5.6.) Attaining a flat temperature profile along the length of a one-end-fired furnace requires burners with adjustable spin controlled by AT sensors. (See chap. 6.)... 

Another way to correct the hunting problem after a mill stoppage is to use burners with a controlled adjustable spin of the combustion products to keep two T-sensors, one close to the burner wall and one perhaps 10 to 15 ft (3 to 5 m) away, at the same temperature. At low-firing rates, this system may require a forward-firing gas lance to extend the heat flux to hold up the far thermocouple temperature. This lance can be turned on when the firing rate drops below a predetermined rate. The lance should be designed to pass 5 to 10% of the total fuel. Such a burner for controlling heat flux profile is now available. The same type of burner, with near and far T-sensors for control, is used to solve a crosswise temperature profile problem in cross-fired zones. (See sec. 3.8.5.)... 

Fig. 3.26. Batch fu rnace for good uniformity control, with top backwall fired by adjustable thermal profile burners and bottoms of sidewalls fired by hlgh-velodty burners multiple T-sensors on both sides. Flow lines show the sweeps of gases of the ATP burners spinning short mode flames, medium length flames, and long mode flames. (See also figs. 2.21,6.1, and 6.23.)...

---