Soaking pits

FIG, 5-22 Thermal perfo rmance of weU-stirred fiirnace chambers reduced efficiency as a function of reduced firing density D and reduced sink temperature Tj. (a) Radiant section, oil tube stills, cracking cods, (h) Domestic boiler combustion chambers, (c) Open-hearth furnaces, (d) Soaking pits. 

Tief-ofen, m. (Metal.) soaking pit. -punkt, m. low point, mimmum point. 

Weiche, /. softness aide, (pi.) groin siding, switch soaking vessel (Leather) soak pit, soak. 

Source From Energetics, Inc., Energy and Environmental Profile of the U.S. Iron and Steel Industry, DOE/EE-0229, U.S. Department of Energy, Washington, DC, 2000. a Includes soaking pits. 

Blast furnace gases, brick kilns, annealing furnaces, boilers, acid production, reactors, superheater tubes, nuclear pile instrumentation, soaking pits, glass tank flues. 

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... 

Fig. 3.10. Box furnace, in-and-out furnace, or soak pit with two rows of slabs.

In one-way, top-fired soaking pits, complications stem from large temperature differentials from burner wall to wall opposite the burner. With burners that produce straight ahead poc gas flow lines, the temperature differential in the space above the ingots can be 140 to 300 °F (78 to 167 °C),with the highest temperature near the wall opposite the burner. 

With this soaking pit control system, ingots are all heated alike in much shorter time, and with no greater temperature differential (AT) from top to bottom of the ingots than 40 °F (22 °C) with a hearth coverage of 35%. Greater density of hearth coverage increases the AT. 

Example (a) In a one-way, top-fired soaking pit without spin, control of its poc will have an end-to end temperature difference of about 175°F (97°C) at the time when the load is expected to be reliable, but with oxy-fuel firing and its lower mass circulation, the corresponding end-to-end temperature difference might be 400°F (222°C) or more. 

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