OCR Text |
Show Figure 3 : Schematic of Compact Regenerative Burner System Heat Recovery Bv Load Recuperation An alternative method to reduce flue gas losses, is to use the heat to preheat the stock prior to being introduced into the furnace. A n extension to such a concept is the rapid heating furnace. Gas Fired Rapid Heating:- Some manufacturing processes involves the production of a very large number of the same basic component: the manufacturer of vehicle components is a good example. In these cases it m a y well be more appropriate not to use conventional, batch hearth type furnaces, but utilise the clean combustion properties of natural gas flames in rapid heating furnaces. In this design of furnace the hot combustion products can be both fired directly onto the stock as well as pass over their surface at high velocity: Figure 4. In each case very high levels of convective heat transfer are achieved culminating in high furnace efficiencies without the need for high temperature heat recovery systems, such as external regenerators, because of in-built load recuperation. In addition, the combination of superior temperature control and reduced billet residence times at the highest temperatures give very low metal loss. The furnaces can either be designed to part heat the billet or whole bar units. The rapid response of this design of furnace lends itself to being particularly adaptable for incorporation into automatic production lines. Moreover, the low thermal inertia within the furnace construction means very rapid startup from cold and there is no need to keep the furnace hot during production stoppages. Also, the load recuperation avoids the need for air preheating which keeps N O x levels at the same levels as conventional burners. This issue will be discussed more later in this paper. |