The throat lies between the melting zone and the cooling zone. It is where to install the cooling water drum and stirrers to eliminate the impact of cooling airflow on the glass molding.

Molten glass is not suitable for molding due to its low viscosity. It must be cooled to achieve desired viscosity. So, the cooling zone is set. The cooling zone has the same structure with the melting zone. It can also be divided into the superstructure and the lower tank. What is different is that the breast wall is lower than that of the melting zone and the tank is shallower than the melting tank. The cooling method is natural cooling, relying on the uniform heat dissipation from the glass liquid level to the sidewall and the bottom. 

 

The throat mainly consists of the low arch structure and suspend wall structure.
 

The previous low arch structure had no stirrer in the throat. The back gable arch of the melting zone, the throat arch and the front gable arch of the cooling zone have the same or similar span to rise ratio. with the increasing of the breast wall, some springer bricks are directly laid on the sidewall to reduce the space opening.  
 

The stirrer has two types: the vertical type and the horizontal type. The vertical stirrer is inserted from the reserved hole of the throat arch roof. It has no requirement on the height of the breast wall. The horizontal type is inserted from the breast walls. It is installed in pair. There is no need to reserve holes on the arch roof, but there are 300mm high and long enough holes reserved on the breast walls. So, the breast walls should be raised. This structure can create the conditions for removing large pipes from the end of the melting zone to the breast walls of the throat. 
 

Given the security consideration, the rise to span ratio of the low arch structure cannot be too small, so the space opening is bigger which affects the partition of the space. The use of the horizontal stirrers and the increasing of the height of breast walls make the partition effect worse. so, the suspend wall structure is developed. The rise to span ratio can be a little bigger to increase its security. The space is separated by the suspend wall. The suspend wall is generally built with silica bricks and sintered mullite bricks. The bricks are in H shape or 王 shape. Bricks are connected by biting and hanging. Both sides are clamped with steel plates. 
 

In addition to the two structures, there are also U-shaped suspend arch, double L-shaped arch and the flat suspend arch. Since those throat structures are complex and costly, they are mainly used in high-grade glass lines and rolled glass lines. 

 

The cooling zone is where to uniformly cool down molten glass liquid. 

 

The structure of the cooling zone is similar to that of the melting zone. It consists of the crown, springer, breast wall, sidewall and bottom as well as the corresponding steel structures. But the tank can be the same with the melting pool or a little shallower. The span is shorter than that of the melting zone. So it is simpler in the structure. However, refractories used can be different depending on the quality requirements. In high-grade glass furnaces, the sidewall and the bottom is built with α-β fused cast alumina blocks. Under the paving blocks there is a layer of α-β Al2O3 ramming mass. Its foaming index and its potential pollution are 0, so it has no pollution to glass liquid. The breast wall and crown are built with high quality silica bricks.