There are many classification methods for crucible kilns: according to the waste heat recovery method, they are divided into regenerative kilns and heat exchange kilns; according to heat sources, they are divided into electric heating kilns and flame kilns; according to the number of crucibles used, they are divided into single crucible kilns and multiple crucible kilns; According to the characteristics of the crucible, it is divided into an open crucible and a closed crucible; according to the flame flow direction, it is divided into an inverted flame kiln and a flat flame kiln; according to the shape of the heat exchanger, it is divided into a round furnace and a square furnace.
Classification of crucible kiln
The flame of the inverted-flame crucible kiln is injected from the center of the kiln bottom, and then discharged from the periphery of the kiln bottom. This type of kiln has a more uniform temperature distribution along the height of the crucible, and the molten glass is also more uniform. However, the bottom of the kiln and the bottom of the crucible are often at High temperature, easy to damage.
The flame of the flat-flame crucible kiln is sprayed from the top of the crucible and discharged from the bottom of the kiln. The temperature difference at the height of the crucible is large, which often makes manual forming operations difficult, so it is only used for products that require high-temperature melting and short forming time. For example, use the casting method to form optical glass products.
Most single crucible kilns use open crucibles to facilitate mechanical stirring and can be used for products with strict requirements for melting systems and high glass quality requirements. Most of them use electric heating elements (such as silicon carbide rods or silicon molybdenum rods) as heat sources to produce optical glass, filter glass and some special glasses.
Round furnace and square furnace refer to the shape of the heat exchanger. The shape of the heat exchanger is round, commonly known as round furnace, and the shape of square heat exchanger is commonly known as square furnace. The square furnace was developed from the round furnace. Compared with the round furnace, the square furnace has a larger heat exchange area and longer heat exchange time, and the preheated air temperature is higher, so the heat exchange effect is obvious. The square furnace is easy to build, the brick joints are tight, and the masonry is firm, which can reduce the thickness of the partition wall between air and flue gas, and further improve the heat exchange efficiency, so it is used more.
The regenerator multi-crucible kiln has a relatively large capacity, and generally has 8 to 14 closed crucibles. Its furnace temperature is high, the thermal efficiency is high, and it can use inferior coal. However, this kind of kiln requires all the crucibles to be charged, melted, cooled, and formed at the same time, and auxiliary equipment such as a gas generator must be added. The kiln structure is more complicated. There was a regenerative multi-crucible kiln in China in the early 1960s, but it was difficult to promote. Now only a few factories use this kiln to produce instrument glass and electric vacuum glass.
The heat exchange type multi-crucible kiln uses closed crucibles, which are widely used in the production of daily-use glass. The heat exchanger can be a metal heat exchanger or a ceramic heat exchanger. The metal heat exchanger has good airtightness and better heat transfer effect, but the material is required to be resistant to high temperature and corrosion. Although the airtightness of ceramic heat exchanger is not as good as that of metal heat exchanger, it has the characteristics of high temperature resistance and corrosion resistance. So it is widely used. At present, the ceramic heat exchangers mainly used in China include standard brick heat exchangers and cylindrical brick heat exchangers.
