OCR Text |
Show 5.3 Air, exhaust flow rate control for open furnaces 17 With the small type forge furnaces, operators successively put in and take out processing materials directly from the furnace or place part of an irregular shaped processing material in the furnace. With such furnaces, the door is left open or a large opening is provided and therefore exhaust suction flow rating control by internal furnace pressure of regenerative burner systems is difficult. Therefore a system was made practical as shown in Fig. 20 in which the exhaust flow rating is controlled by measuring the temperature of exhaust emitted by the regenerator element. In concrete terms, the temperature of exhaust emitted from the regenerator element depends on the temperature and flow rate of exhaust entering the regenerator element and therefore the furnace temperature and air flow rate are actually measured, calculated and a set point of exhaust temperature emitting from the regenerator element at that time is set and automatically inputted into the controller. When the flow rate of exhaust emitting from the regenerator element is throttled, the temperature drops and when the flow rate is increased, the temperature rises. Therefore, by controlling the valve provided in the exhaust line by this controller, the temperature of the exhaust emitting from the regenerator element can be controlled. By this method, the most effective air/exhaust flow rate ratio can be set over the entire temperature zone without relying on furnace pressure of open furnaces such as those mentioned above. At present, w e have applied this system with a rotary type regenerative R R X burner using a honeycomb regenerative element. Te: Exh.Temp. standard Tf: Furnace Temp, standard Qa : Air flow standard k : flow parameter Exhaust temperature measiirpri valiiA PV? Rotary type regenerative burner Furnace temperature measured ~~ " Value P v Y' TIC No.l Furnace temperature controller Fig. 20 Air, exhaust flow rate control for open furnaces |