OCR Text |
Show 2.3.3 Compacting of the burner 6 With the two stage combustion burner, a trend towards possible reduction of N O x is seen with the increase in distance between the center main gas injection outlet and the secondary air injection outlet, but this requires enlarging of burner tiles which contradicts the concept of this burner. Therefore, the burner nominal capacity is assumed first and then the burner tile dimensions permissible for the forge furnace to which the burner would be applied was decided. Next, the burner dimensions becomes relatively smaller when the burner capacity is increased. Therefore in the prototype test stage, the burner nominal capacity was decided by gradually increasing the combustion rating within a range of permissible pressure drop and N Ox values. Table 1. shows the burner capacity and burner tile dimensions finally decided. Table 1. Burner capacity and tile dimensions of PAX-R burner Model Burner nominal capacity Burner tile dimensions PAX-50N-R 580kW •400mm PAX-75N-R 830kW • 480mm PAX-120N-R 1400kW • 550mm PAX-180N-R 2100 kW • 750mm 2.3.4 Selection of a regenerator element A case for filling with regenerator element is attached below the above mentioned burner section structure. The case is filled with alumina balls which serve as a regenerator element. Alumina balls are more economical compared with honeycomb structures and such and also with a large heat capacity, changes in temperature of exhaust emitted by the regenerator is small even with some unbalancing of the air and exhaust flow rate. This is of an advantage in structuring a simple system for forge furnaces. 2.3.5 Changeover valve With forge furnaces, the number of regenerative burner units installed per furnace is relatively small, and therefore control of changeover timing may be simple but on the other hand, not much space is available for piping. Therefore, a 4-way-valve was selected as the most simple changeover valve. The exclusive 4-way-valve shown in Fig. 5 was developed for this purpose. Fig. 5 4-way valve for the PAX-R burner |