Continuous reheat furnaces

K. S. Chapman, S. Ramadhyani, and R. Viskanta, Modeling and Parametric Studies of Heat Transfer in a Directly-Hred Continuous Reheating Furnace, Metal. Trans, 22B, pp. 513-534,1991. 

Honner, M., Vesely, Z., and Svantner, M. "Temperature and Heat Transfer Measurement in Continuous Reheating Furnaces." Scandinavian Journal of Metallurgy 32, no. 5 (2003) 225-32. 

Another problem with firing below the loads results from reducing the furnace crosssection in a continuous reheat furnace at about 50 to 60% of the furnace length... 

TABLE 6.5 Comparisons of heating curves for 6 in. (0.152 m) square steel blooms in a continuous reheat furnace, spacing = 1.6 1, with or without enhanced heating... 

Q9. Where should control T-sensors be located for shortest heat cycles with protection for the product in a continuous reheat furnace ... 

End view, continuous reheat furnace with enchanced heating. 

S.4. Continuous Reheat Furnaces. Continuous reheat furnaces may be rotary or linear. Either can be side fired or top fired. Top firing may be done with conventional type A, F, or G forward thmst flames (fig 6.2) in a sawtooth roof or with type E flat flames in a flat roof. End firing alone can be used only in small linear reheat furnaces, but it is sometimes used in combination with roof- or side-firing in all sizes. (See also sec. 3.8.5.) For donut rotary hearth furnaces, much detail is discussed in section 6.4.1. 

Oxy/fuel combustion has been used in many applications in the steel industry including both continuous and batch reheat furnaces, soaking pits, and ladle preheaters. Fuel savings of up to 60% have been reported.27 Typical fuel savings achieved by converting from air/fuel to oxy/fuel combustion are given in Table 1.4.28... 

Honner, Vesely, and Svantner [8] made temperature measurements in a continuous pusher-type metal reheating furnace using thermocouples imbedded in a billet used specifically as a "sensor". These were particularly challenging measurements, not only because of the harsh high temperature environment inside a reheat furnace, but also because the sensor billet was moving, which means the electrical wiring and battery-powered data acquisition system also moved through the furnace. 

Cameras monitor and record material flow processes in reheat furnaces, vacuum degassers, continuous casters, blastfurnaces, electric arc furnaces, continuous annealers, galvannealers, tunnel furnaces, and other operations. 

Fig. 4.18. Continuous steel reheat furnace, longitudinally fired in all five zones. Unless a recuperator will be above the furnace, flues at the far right bottom zone would be better than the up-flue shown (a) to minimize cold air inflow around the charge entrance and (6) for better circulation in the bottom right end of the furnace.

Fig. 4.19. Continuous steel reheat furnace, side tired from both sides, staggered, not opposed, in all top and bottom zones.

Hg. 5.10. Continuous steel pusher reheat furnace side fired with regenerative burners in the top and bottom heat and preheat zones, and root tired in the soak zone. Preheat zones often have been designed as unfired preheat zones, which are good for fuel economy. However, also firing the preheat zones with regenerative burners would add capacity while retaining high fuel efficiency. (For a discussion of controls for this furnace, see sec. 6.11.1.)... 

Fig. 5.27. Continuous steel reheat furnace with nine pairs of regenerative burners in three top control zones and four pairs in a bottom zone. The sweep of hot poc from side burners can alternately proceed all the way across the furnace width, avoiding the former uneven heating when opposed burners created a hot spot pileup of heat in the center when on high fire, and a cool stripe down the middle on low fire.

Q8. Why are adjustable thermal profile burners generally more efficient in continuous longitudinally fired reheat furnaces ... 

Refractory Heat Loss Sample Problem 8.1—Required Fuel Inputs. An added aspect of sample problem 8.1 (the same continuous walking beam steel reheat furnace) calculate the required gross heat input to each zone. (See worksheet tables 8.14 to 8.17.). 

Robert A. Shannon has more than 50 years experience with engineering work. He has been North American Mfg. Co. s authority on steel reheat furnaces, soaking pits, and forging furnaces. He continues private consulting relative to his extensive experience with steel reheat, pelletizing, forging, heat treating, catenary furnaces, and industrial boilers. 

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