Aluminum Melting Furnace

Common aluminum melting furnace types are generally two types, rectangular and garden-shaped structural. Correct structure design for aluminum melting furnaces can improve the furnace heat transfer effect significantly, improve melting capacity, and reduce energy consumption. It can achieve the effect of reducing consumption, reducing burning, improving product quality, reducing labor intensity, improving working conditions, and improving production efficiency, suitable for intermittent operations.

The refractory lining is the heart of an aluminum melting furnace. It is the most important factor in furnace design after the "workability" of the furnace (that is, factors such as access for charging, cleaning, and repair). Not only does the refractory lining need to contain molten aluminum, but it also needs to withstand mechanical abuse and provide for minimum thermal wall losses.

Two areas of metal contact (the hearth and lower sidewall) suffer the most mechanical abuse and metal penetration. In the hearth, metal penetration can cause the hearth to heave up and away from the furnace bottom as a result of metal creeping into joints and cracks until it finally works its way under the top course of brick or a hot face lining.

When designing a refractory lining, its dry-out time (or curing time in the case of plastic refractory) should be considered based on the heat available. That is, can the burner system be used, or are external burners required? Even if the burners are capable of drying out the furnace, some well melters will need external burners in the well, especially if the well is lined with plastic. If the dry-out is not done correctly, plastic linings could sheet off some of the material or slip. With castable, the material could explode if heated too quickly.

Cross-sectional view of an aluminum well melter

In designing a brick lining for an aluminum melting furnace, all walls should have a header course at the hot face, and the thickness should be suitable & safe.

All walls, wall corners, wall-to-wall connections, and arches should be bonded closely. When installing a brick lining, the walls should be level, straight, and plumb, with minimum mortar joint thickness, and tapped in place using a leather mallet for a molten metal-tight wall. For very tall brick walls, an anchor brick should be spaced in the upper walls so the wall will not bow in and collapse into the furnace. The brick lining of a well melter should have a Rowlock course to cap off the well so molten metal will not destroy the backup lining.

Brick arches should be adapted. Thick and bonded. Also, the skew and backup of the arch are very important. If an arch is close to a wall, the soft block (crushable) should be eliminated and a hard cast should be installed to back up the skew so the arch will not collapse.

The design of the division wall between the main chamber and the well is very important because it is a "hot wall" that is hot on both sides. Wall thickness should be thick enough on the lower wall. The furnace steel casing should allow for the larger expansion of this wall.

For plastic linings, it is necessary to pay close attention to the wall anchor spacing and shelf brackets to support the uncured plastic. During plastic lining installation, ramming should be done parallel to the hot face, and the blocks broken into smaller slabs, which should be bonded with each course. Anchors should be tapped in place so there are no voids around them. After ramming is complete, the hot face should be trimmed to the refractory anchor face, but the surface should not be smoothed out. As with brick linings, the design of plastic linings must take into account the expansion of the lining.

A low-cement lining should be anchored to the casing only in the upper walls using a stainless steel stud projecting from the block back-up surface and a stainless steel "V" anchor welded to the stud. The placement of the cast should be done with a very large mixer for a more consistent pour. The wall-to-floor connections will be different than a brick or plastic lining to form a staggered joint.

A monolith roof should be supported using refractory anchors. Also, the roof should have control joints to control the cracking of the roof during the cool-down of the furnace. The roof-to-wall closure is very important and should be designed so the wall will be able to rise and not destroy the roof.

The first consideration is how the door is operated and then what type of refractory lining to use. The most common door operators are electric motors gearboxes and air cylinders. The location of the operators should be such as to keep them away from the heat of the furnace when the door is opened. To withstand mechanical abuse, a lightweight, high-temperature cast should be used indoors to save weight, and "V" anchors should be spaced closer than in walls. Fiber linings are being selected for this application in some instances to save weight. However, the amount of mechanical abuse that lining must withstand should be considered before selecting fiber linings for doors. In a direct-charged melter, mechanical abuse on a fiber door usually is a result of the scrap falling on the door or molten aluminum splashing on it.