The HORN DUALFLAME AC gas burner is installed as an underport burner in cross fired or end fired regenerative furnaces. Its design enables the furnace operator to adjust the flame formation smoothly within a wide range – from short and sharp to long and soft – by using two separate gas nozzles in one burner. The gas quantity flow in each nozzle can be controlled automatically by additional gas control valves in the burner gas supply stations. Thus the flame can be adjusted to achieve optimum results in terms of flame length, energy and NOx emission.
As is the case with the DUALFLAME MC burner, the AC burner works with two nozzles, an inner and an outer nozzle. The position of the inner nozzle can be controlled by a hand wheel at the rear of the burner in the same way as the DUALFLAME MC. Thus the flame can be shaped from soft and wide to sharp and strong.
The DUALFLAME AC (= Advanced Control) burner, however, works with an automatic control of the gas quantity towards the inner and outer nozzle. Therefore gas control valves for each nozzle are installed in the utility equipment in front of the burner. This enables the furnace operator to adjust the flame length automatically in the control room without manual adjustment directly at the burner under the hot burner port.
Apart from the automatic adjustment of the burner after a load change and/or a change in the gas quantity, the ratio of the gas flow between the inner nozzle and the outer nozzle is maintained exactly constant even when the total gas quantity changes. Furthermore, all burners can be regulated identically without variations since the gas quantity for the inner and outer nozzle is measured. This results in absolutely identical firing conditions in each firing period for both the left and the right burner ports.
Another advantage of the DUALFLAME AC burner is the laminar gas flow in the inner nozzle which, unlike the DUALFLAME MC burner, is not equipped with openings. Therefore the laminar outflow of the gas at the nozzle head is guaranteed and will prevent NOx formation.
Normally the gas quantity in the interior nozzle is adjusted by moving the outside nozzle valve when total gas quantity is constant:
- outside nozzle valve is closed in order to increase gas quantity in the inner nozzle
- outside nozzle valve is opened in order to decrease gas quantity in the inner nozzle.
The valve for the inside nozzle must always be fully opened. The adjustable gas velocity can vary e.g. between values of < 20 m/s and >200 m/s depending on gas admission pressure, gas consumption, gas distribution to each nozzle and the size of the nozzles.