Six major factors affecting the glass melting process

[中玻璃网] First, the glass composition

The chemical composition of the glass has a decisive influence on the melting rate of the glass. Different compositions of glass have different melting rates of corresponding batch materials. In general, the higher the content of the high melting point component (SiO2, A12O3, etc.) in the glass, the slower the melting rate; the more the flux content in the batch, the faster the melting rate. That is to say, the higher the ratio of the alkali metal oxide and the alkaline earth metal oxide to the high melting point oxide in the glass composition, the faster the melting rate of the corresponding batch material.

Second, the nature of raw materials and ingredients

(1) Particle size of raw material The reaction rate of the glass forming process is proportional to the size of the reaction surface. The finer the raw material particles, the larger the reaction surface and the faster the reaction.

(2) It is necessary to add a certain amount of water to the batch material. The wet material is better than the dry material to reduce dust, prevent delamination, increase the melting speed and improve the uniformity of mixing.

(3) The gas rate of the batch material is accelerated by the melting of the glass, and the compound material is required to have a certain gas ratio. The gas escaping after the thermal decomposition has a stirring effect on the batch material and the glass liquid, and can promote the formation of the silicate. Homogenization of the glass. For soda lime glass, the gas ratio of the batch is 15% to 20%. If the gas rate is too large, bubbles are easily generated in the glass; the gas rate is too small, which is unfavorable for silicate formation and glass homogenization.

(4) Uniformity of batch materials The more uniform the mixture of materials, the more favorable for melting, the uniformity of the uniformity will directly affect the yield and quality of glass products. Generally, glass products require uniformity of the batch material to be greater than 95%.

(5) Influence of broken glass Adding a part of broken glass to the batch material can prevent delamination of the batch material and promote glass melting. However, the broken glass should be kept clean and harmful impurities should be removed. The composition of the broken glass is the same as that of the production glass. The dosage is generally controlled at 10%~30%. When using cullet for a long time, it is necessary to check the loss of basic oxides and the increase of silica in time. It is necessary to adjust and supplement in time to ensure the stability of the components. Too much cullet is not conducive to melting; too small a particle size will lengthen the time it takes for the melt to remove visible bubbles.

Third, the feeding method

The thickness of the layer of the batch material fed into the furnace has an important influence on its melting rate and furnace productivity. If the batching time is long and the material pile is large, the contact area between the material layer and the flame will be small, the melting process will be slowed down, and the surface compound will melt to form a film layer with low alkali content, which has a very high viscosity and a very high gas. Difficult to pass, brought difficulties to the clarification. The thin decomposition method can greatly accelerate the thermal decomposition process. In addition, due to the thin layer of the material, the surface temperature of the molten glass is high and the viscosity is small, which is favorable for the elimination of bubbles and improves the clarification speed.

Fourth, with the glass melting system

Mainly temperature system, stress system and atmosphere system.

The melting temperature determines the melting rate of the glass. The higher the temperature, the more intense the silicate formation reaction, the faster the quartz particles melt, and the faster the glass is formed. It can be seen that increasing the melting temperature is an effective measure to strengthen the melting of the glass and increase the production capacity of the melting furnace. However, when using high temperature melting, the temperature of the refractory and its life limit should be considered.

The pressure system of the melting furnace directly affects the temperature system, so the accuracy and stability of the pressure system play a certain role in guaranteeing the melting of the glass. Generally maintain a slight positive pressure or zero pressure.

The atmosphere in the kiln is divided into oxidizing, neutral and reducing atmospheres according to the nature of the kiln gas. The control of the atmosphere depends on the composition of the batch and glass and the specific process requirements.

Fifth, the application of accelerator

Accelerators are usually chemically active substances, generally do not change the composition and properties of the melt, but can reduce the surface tension and viscosity of the melt, increase the melt heat permeability, facilitate melt bubble elimination and chemical homogenization, and improve melt quality. . Therefore, accelerators are often also clarifying agents. Such substances mainly include sulfates, fluorides, and variable oxides.

6. Auxiliary electrofusion and agitation

In a furnace operation heated by fuel, a current is supplied to the molten glass to increase a part of the heat, so that the output can be increased without increasing the capacity of the furnace. This type of melting is called auxiliary electrofusion. Generally, they are respectively disposed in the melting portion, the feeding port and the working portion of the melting furnace. Mechanical agitation or bubbling in the furnace is an effective measure to increase the clarification speed and homogenization speed of the glass.

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