Thread Content
I. Working Principle of the Flat Flame Burner The flat flame burner (FFB) is typically used on the roof of reheating furnaces. The burner is designed to spread the flame thinly over the roof surface. Since the flow rate of combustion gases along the burner axis is negligible, the temperature of the refractory furnace roof rises due to the substantial heat transfer from the flame to the roof. In this way, the fire-resistant roof becomes the main radiation surface. The burners at the front wall of the heating furnace typically have longer flames, while the burners at the side walls of the heating furnace have shorter, variable flames. The burners on the front wall of the heating furnace are usually axial-flow type and require extensive adjustment. Along the length of the furnace, the flow of combustion gases inside the furnace is smooth. They are large-capacity burners that limit the length of each zone along the length of the furnace. When the steel charge in the reheating furnace has a large, flat surface that may be parallel to the furnace roof, and the heating temperature of the steel charge is above 900 degrees Celsius, it is considered appropriate and advantageous to use flat-flame burners. Due to these burners, indirectly directed radiant heat transfer occurs. The heat generated by fuel combustion is transferred to the steel not only directly from the flame but also through the refractory materials on the furnace roof. The temperature of the intake air is preheated using heat exchange technology before combustion in the furnace. The exhaust gas flows through a burner equipped with a combustor, and the heat exchanger is installed inside the combustor. The heat in the exhaust gas is exchanged with the intake air before flowing out of the burner. Waste gas flows through the area surrounding the outside of the burner, while heat is exchanged inside the burner. One burner is in combustion mode, while the second burner is in exhaust mode. The burner burns as hot air from combustion blows past it. The second burner receives the hot exhaust gases from the furnace into its ceramic balls, in order to retain the heat within the burner. The exhaust gas is released only after passing through heat. After half a minute to one minute, the second burner switches to ignition mode, while the previous burner begins to receive hot exhaust gases. The ignition and receiving modes of the burner alternate and operate continuously until heating of the furnace is stopped. A higher preheated air temperature makes the combustion process very efficient. The burners on the sidewalls require a narrow adjustment range. These burners also have a large capacity, and there are limitations in terms of the width of the furnace. Since the direction of the burner is perpendicular to the length direction of the furnace, the flow of the combustion gases tends to drift. Since there is no nose portion in these burners, they do not complicate the structure of the furnace. The burner exhibits good uniformity along the length direction of the furnace. At this point, burners are needed to achieve uniform heating. In a reheating furnace equipped with long-flame burners, since most of the heating of the steel charge occurs through convection, the recirculation of combustion products essentially contributes to the heating rate and temperature uniformity. The long-flame burner generates high-speed gases, which carry and recirculate the combustion gases to ensure uniform temperature inside the furnace while using less excess air. Similar products include coal-based cooking fume generators and hot air stoves; you can check the details on their respective pages. II. Operating characteristics of the flat-flame burner 1. The temperature distribution in the FFB furnace and the steel feed is more uniform. Satisfactory temperature control in each area is achieved, thereby enabling the necessary furnace output. The faster heating rate caused by FFB reduces the time that the steel charge is exposed to high temperatures. Therefore, **it reduces the occurrence of surface oxidation or phenomena such as decarburization and coarse grain structure in steel. 2. The burner nose complicates the structure of the furnace. In these burners, heating is uniform along the width direction of the furnace, but the temperature tends to drop at the nose portion along the length direction of the furnace head. Except around the burners in lower positions where the temperature is lower, machinability is generally good when using flat-flame burners. 3. Flames that usually do not emit light are characterized by high temperatures and a relatively low emissivity, corresponding to the selective radiation of carbon dioxide and water vapor. Since the flame has no effect on the steel, the FFB heating furnace is called an indirect heating furnace. 4. After the furnace’s output is reduced by 100% to 50%, a significant reduction of up to 40% in fuel consumption can be achieved. The intense mixing of gaseous fuel and combustion air ensures rapid and complete combustion of the mixture at low excess air levels. 5. The structure of the flat-flame burner is similar to that of a radiant heat exchange tube, which heats the intake air to a higher temperature (about 750 degrees Celsius) by recovering heat from the exhaust gas and transferring it to the intake air. Therefore, heat exchange in the burner can improve combustion efficiency and save approximately 25% to 30% on fuel costs.