Prescriptions for Operating Flexibility

Prescriptions for operating flexibility despite delays and interruptions  

The previous improvements will make a continuous furnace flexible and profitable. The savings can be even more if done properly from the start. With industrial furnaces, it is usually true that Only the low bidder wins in a low-cost deal. (See chap. 8 for sample heating curves illustrating these points.) 

A continuous furnace may be heated so that the temperature of its zones is practically the same across the furnace. This temperature uniformity can be obtained by lengthwise firing in several zones (as illustrated by fig. 4.2), or by roof firing or side firing in several zones (as shown in fig. 4.3). In such furnaces, the heating capacity of a continuous furnace will equal or exceed the capacity of a same-size batch furnace. 

By eliminating the downtime for loading and unloading, continuous furnaces almost always can have better production capacity per unit time and per unit of hearth area than do batch furnaces. Of course, the cost of handling equipment to make possible the continuous loading and unloading raises the initial investment of continuous furnaces. 

Drawback 1 A reflective scale is generally formed when the preheat zone is held at temperatures at or above 2300 F (1260 C). The cause of the reflective scale is the normal softening of the scale above 2320 F (1271 C) and the lower conductivity of the surface. If a furnace has this problem, reducing the preheat zone temperatures and increasing the product discharge temperature will increase furnace productivity. 

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