Forge furnace and heat treating with dual heat transfer systems: convection and radiation
The forge Furnace is a compact system constituted by two burners working in a cycle of minimum periods of 30 seconds with a global power of 28 kW on a LHV basis. The burners characterize because they possess heat regenerators accumulating heat from the combustion products transferring it to the air, preheating it before the combustion. The furnace is also equipped with a high emissivity silicon carbide radiant tube and a control system which activates or deactivates the burners during the selected commutation cycle among burners.
The solid to gas, gas to solid thermal regenerators, are heat exchangers consisting of a heat accumulating mass forming a refractory matrix through which the stray heat of combustion gases gains cold air which is later used for the combustion process.
To attain an optimum operation of the combustion system suitable control instruments were implemented to guarantee: a suitable quantity of combustion and ejection air, the fuel injection and the ignition for each cycle at a given time. The system possesses a safety protocol allowing the detection of combustion by means of flame detectors, in the absence of combustion; the system ceases the fuel supply. To control the process temperature, this system receives a signal from a thermocouple thus activating the electrovalves by opening or shutting them if temperature is lower or higher to that of set point, respectively.
The ejection system uses part of the air driven by the fan to evacuate combustion gases aiding in the overcoming of flow resistance produced by the regenerative pebble bed. Given the differences in the physical properties of currents, the magnitude of movement of the gas current is smaller compared to that of air. Pressured air is supplied through a convergent type nozzle generating a “Venturi” effect where critical speed levels are reached creating vacuum which drags smoke through the regenerative pebble bed evacuating it into the atmosphere.