Impact of high temperature Muffle furnace There are many factors that directly affect the operational efficiency of high-temperature furnaces and muffle furnaces.
The impact of the furnace design and structure of high-temperature furnaces and muffle furnaces on the operational efficiency of electric furnaces.
1. High-temperature furnace and Muffle furnace Furnace designs are trending toward larger scale, multi-stage configurations, and greater levels of mechanization and automation. To enhance heat supply and boost production, large-scale heating furnaces with five, six, or even eight heating zones have emerged; as a result, the preheating zone, with its elevated temperature, has effectively become a new heating stage. The arrangement of burners has also undergone significant changes, such as the adoption of co-current and counter-current burners for both top and bottom heating. In uniform-heating forging furnaces, flat-flame burners are now commonly installed at the furnace roof, and some furnace designs have evolved to feature a fully flat-roofed configuration throughout the entire length, with all burners mounted on the roof. To provide more flexible control over furnace temperature profiles and hearth pressure distribution, side-mounted burners are arranged along the entire furnace length, transforming the furnace into a straight-through type with a single heating stage. Moreover, the specific productivity of these furnaces has increased dramatically, from the previous range of 300–400 kg/(m²·h) to 1 ton/(m²·h), with individual furnaces capable of producing over 350 tons per hour.
The degree of mechanization in furnaces has steadily increased, with rolling mills evolving from the traditional pusher-type continuous heating furnaces to a variety of step-type furnaces, roller-hearth furnaces, loop furnaces, and chain-type heating furnaces. Certain special-shaped billets that were previously heated in chamber furnaces are now processed in loop furnaces, resulting in a substantial increase in production efficiency.
High-temperature furnace and Muffle furnace Automation is the direction of development. By implementing automated thermal control, a series of thermal parameters—such as furnace temperature and furnace pressure—can be accurately and promptly monitored and effectively controlled, thereby enabling precise adherence to the desired heating schedule and boosting furnace productivity. The use of electronic computers allows for fully computer-controlled operations across the entire furnace process, from charge positioning and temperature control in each zone of the furnace, to fuel–air flow regulation, automatic furnace-pressure control, and even the timing and sequence of steel discharge. This enables optimal control of furnace conditions, resulting in highly uniform steel temperatures and minimal temperature differentials at the time of discharge.
2. The dimensions of high-temperature furnaces and muffle furnaces are continuously increasing.
Expand the furnace chamber to increase the charging capacity. With the furnace foundation remaining unchanged, this can be achieved by modifying the furnace shell to enlarge the chamber and accommodate a larger charge. For example, in the 1950s, China’s initial rolling mills constructed a number of center-burner, heat-exchanger-type soaking furnaces. However, because the central burners occupied a large portion of the furnace hearth and due to other shortcomings, most of these furnaces were subsequently retrofitted into top-corner-burner or top-single-side-burner soaking furnaces, thereby increasing the hearth area available for charging and boosting furnace productivity by 10%–20%.
Improve the furnace design and dimensions to make them more rational. Some furnaces adopt a generic design for both shape and size, without considering specific operating conditions; as a result, factors such as fuel type and billet dimensions may deviate significantly from the design specifications. In some cases, the furnace chamber is too high, leading to low metal surface temperatures, while in others the furnace roof is too low, resulting in a thin gas layer and reduced heat transfer through the furnace walls. Both of these conditions are detrimental to heat exchange. Therefore, the furnace design and dimensions should be refined based on practical experience to accelerate heat delivery to the billets, thereby enhancing furnace productivity.
Reduce heat loss from the furnace. Heat lost through furnace wall conduction and carried away by cooling water accounts for one-quarter to one-third of the furnace’s thermal load, resulting in both energy waste and a reduction in furnace temperature, which in turn affects the heating of the steel charge. Minimizing these losses can increase furnace output.
Insulating the water pipes at the bottom of the heating furnace is an important measure for conserving resources and increasing furnace output. Because the water pipes are in direct contact with the billets, a portion of the heat carried away by the cooling water constitutes useful heat; moreover, black marks form at the interface between the billets and the water pipes, necessitating longer soaking times to eliminate these marks—both of which adversely affect furnace productivity. Applying refractory plastic lining to the water pipes can, by itself, boost furnace productivity by 15%–20%. Recently, dry‑cooled sliding‑roll heating furnaces have also been developed, further enhancing furnace output. For example, when a small two‑stage water‑cooled heating furnace was converted to a dry‑cooled sliding‑roll heating furnace, the specific production rate increased from an average of less than 500 kg/(m²·h) to 700 kg/(m²·h), representing an increase of more than 30% in output.