The slag deposited layer is one of the important factors to ensure a high-performance and reliable performance of the refractory furnace. A slag deposition layer directly affects the quality of the product, its service life, the operational safety and economical of the furnace, as well as the capital and operating costs associated with the necessary slag removal operations. This article will discuss the importance of the slag deposited layer in protecting the refractory furnace, and the methods for ensuring a stable slag deposited layer.
The Slag Deposition Layer (SDL) is a layer of material which is produced by the reaction between the slag, air, and other ingredients, such as refractory materials, in the refractory lining of the furnace. The SDL is usually composed of calcium and magnesium sulfates, calcium and magnesium oxides and carbonates, as well as other compounds. The SDL forms a highly resistant barrier between the hot refractory lining and the slag, protecting the refractory from attack by the slag.
The SDL protects the refractory furnace from thermal shock, which can cause cracking and failure of the refractory. Thermal shock occurs when the refractory is exposed to sudden changes in temperature, such as during start-up or shut-down operations. The SDL helps to maintain a steady temperature in the refractory, reducing the temperature difference between the inner and outer walls of the furnace, and thus minimising the risk of thermal shock damage.
The SDL also insulates the refractory from the direct heat of the slag, preventing the refractory from overheating and quickly deteriorating. The SDL can also act as a heat sink, dispersing the heat generated in the furnace in a more efficient manner. This reduces the risk of hot spots forming, which can lead to accelerated refractory deterioration as well as thermal stress on the furnace structure.
It is important to ensure a stable SDL in order to protect the refractory from attack by the slag and maintain a safe and efficient furnace operation. The first step in establishing a stable SDL is to ensure that the refractory lining is free from cracks and holes. A layer of slag covering any cracks and holes, such as those caused by wear or settling, can help protect the refractory from the slag.
It is also important to use a suitable refractory material for the furnace lining, as some materials are more prone to attack by the slag than others. For example, magnesite refractory is more resistant to attack by the slag than dolomite refractory. It is also important to ensure that the furnace is not operated at an excessively high temperature, as this can lead to an accelerated rate of refractory deterioration.
The slag can be prevented from attacking the refractory by introducing additives such as graphite or aluminium to the slag, or by installing baffles in the furnace to prevent the slag from directly contacting the refractory. In some cases, additional refractory material may be placed between the slag and the refractory, thereby forming an additional layer of protection.
Finally, regular maintenance of the furnace, including regular cleaning and slag removal, can help to keep the slag deposition layer stable and protect the refractory from attack.
In conclusion, a slag deposited layer is essential for protecting the refractory furnace from thermal shock, excessive heat and attack by the slag. Careful consideration should be given to the selection of a suitable refractory material, and regular maintenance should be undertaken to ensure a stable and protective SDL.
