A reasonable operation system of the melting furnace is an important guarantee for extending the service life of the melting furnace and obtaining high-quality products. The operation of the melting furnace must be carried out strictly in accordance with the sequence stipulated in the process regulations.
01 Firing the Furnace
After the construction of the tank furnace is completed, it must be fired for an appropriate period of time before it can be put into production. The main purposes of firing the furnace are: to evenly remove the moisture in the refractory materials by heating the furnace body, small furnaces, regenerative chambers or heat exchange chambers, flues, and chimneys, so that the refractory materials reach a certain stable state, thereby enhancing their structural strength and extending their service life; to check whether the furnace body and its auxiliary equipment are functioning properly through “no-load operation”, and to make preparations for production to ensure safe operation; and to gradually heat the furnace body to a certain temperature to facilitate the official start of production.
02 Temperature Rise
During the firing process of the melting furnace, the temperature rise requirements are very strict. Besides controlling the thermal expansion of refractory materials and ensuring proper clearance between the furnace body and the steel structure, attention must also be paid to the expansion phenomenon caused by the crystal state changes of the refractory materials themselves. For instance, the expansion of silica bricks is extremely intense between 100-650℃; magnesia bricks expand most intensely above 1000℃; and fused cast AZS bricks expand gradually and smoothly above 800℃. Therefore, improper temperature control during the firing process can lead to cracks in the furnace body, affecting the service life of the melting furnace and the refractory materials. Thus, the temperature rise during firing must be strictly carried out in accordance with the regulations, and a strict temperature rise system should be established.
03 Charging
During the glass melting process, the charging method has a certain impact on the melting quality. Maintaining a dynamic balance between the charging amount and the discharging amount is the main measure to ensure the stability of the glass liquid level.
The charging machines used in the horse-shoe flame tank furnace include reciprocating, electromagnetic vibrating, wrapping, swinging, and spiral types. Regardless of the type of charging machine used, the most important thing is to control the thickness of the charge layer. If the charge layer is too thick, the cold air it brings into the melting pool will affect the melting temperature. The surface of the charge layer will absorb a large amount of radiant heat and act as an insulator, preventing the radiant heat from reaching the lower layers of the charge, resulting in un-melted quartz particles flowing into the working pool due to insufficient melting time, causing the formation of un-melted quartz particle stones. The charge layer near the glass liquid surface will absorb a large amount of heat, causing a sharp drop in the temperature of the melting pool. Therefore, a thick charge layer will have a series of impacts on the temperature system of the melting pool and the convection of the glass liquid. Thus, controlling the appropriate thickness of the charge layer is an important process regulation.
Another important factor affecting charging is the charging speed, which is directly related to the melting rate of the glass, the discharging amount, and the thickness of the charge layer. The charging speed should adhere to the principle of slow, thin layer, small amount, and frequent charging under the premise of maintaining a balanced discharging.
04 Discharging and Drainage
The function of the discharging hole is to allow the dirty glass liquid that has been cleaned at a low position to flow out from this hole during the first charging. Generally, it flows for 4 hours, then the hole is blocked with a conical plug, and then the charge is added to exceed the liquid level line. When conducting high-temperature and high-liquid-level cleaning, the hole is opened again. After the cleaning is completed, the hole is blocked again, and finally, the official charging begins.
The function of the drainage hole is to discharge the uneven glass at the bottom during normal production, thereby eliminating streaks and improving the quality of the products. There is a lead drainage tube in the drainage hole, with two sets of heated platinum wires inside. The discharging hole and the drainage hole are set at the bottom of the two corners near the bridge wall of the melting pool, the center of the cooling section bottom, and the bottom in front of the channel adjustment section. An overflow device is set at the end of the cooling section, which can remove the scum and dirty materials on the surface of the glass from this location.
05 Changing the Charge
Small and medium-sized tank furnaces often need to produce two or three colors of glass or different types of glass, which requires changing the charge. Therefore, when designing small and medium-sized tank furnaces, the issue of changing the charge should be considered, and simple charge-changing devices should be installed during the construction of the furnace.
When changing the charge, all the glass liquid in the tank furnace is first discharged, which is the same as the discharging process mentioned earlier. Then, the furnace is washed. It is best to wash the furnace with a full charge, so that the entire inner side of the tank can be cleaned thoroughly. However, this takes too long, so it is also possible to add only 300mm of glass liquid and then wash the furnace. However, this will result in the upper part of the pool wall not being cleaned thoroughly. Even if the residual glass on the upper part has a density not much different from the new glass, it cannot be well mixed and will form stripes. Therefore, it is necessary to find a way to remove it. During the material change, auxiliary burners should be added to the material channel to increase the temperature to ensure thorough cleaning. If the material channel is completely separated from the cooling section, no special treatment is required unless the glass type contains volatile components. For material channels that are connected to the flame space of the cooling section and contain volatile components in the glass, it is best to remove and replace them. If they are not replaced, the temperature should be raised to a higher level and maintained for a longer time, but even so, it is still difficult to clean thoroughly.
Post time: Jun-26-2025