The various substances used to prepare glass complexes are collectively referred to as glass raw materials.The main raw material refers to the raw material that introduces various oxides into the glass to form the main body of the glass structure, which determines the basic physical and chemical properties of the glass.The main raw materials are quartz sand, feldspar, limestone, dolomite, soda ash and so on.These raw materials are generally supplied in powder at present.(1) raw materials of silica the main raw materials of silica is silica sand (also known as quartz sand), which can be divided into natural silica sand and processed silica sand according to its existing state in nature.Due to the complexity of its formation process, the chemical composition of natural silica sand often fluctuates greatly, but its particle size distribution is relatively uniform.For the quality of natural silica sand, attention should be paid to control the chemical composition, the fluctuation of the composition and the refractory weight mineral. The chemical composition mainly controls the content of Fez 03, and is graded and used according to its quality.The quality grading of silica sand is listed in table 2-16.2) processing of silica sand processing of silica sand is quartz rock or sandstone raw ore by a certain process of processing and production of siliceous raw materials.Because the purity of quartzite or sandstone ore is generally higher, the impurity content is less and stable, the grade of silica sand produced by processing is higher and stable.However, from quartzite or sandstone ore to available silica sand with a certain grain size, it is difficult to control the grain size, so the cost is high.Silica sand is generally processed by wet method, with a certain moisture content.Silica sand is the most difficult material to melt.Particle size, particle size distribution and particle shape have important effects on mixing, melting and homogenization of composite.The decrease of particle size is beneficial to the melting of glass, but the finer the better.Silica sand powder will exist because of the cluster, granular gap exists in a large number of micro bubbles caused by melted difficulty, at the same time also the presence of silica sand powder can be premature and batch of material such as sodium, calcium, magnesium in reaction to generate primary melt density, viscosity, easy cause furnace material layer in the hierarchy, causing other refractory raw materials in the batch.The shape of sand grains is better with the angular shape, because the angular shape of the surface area is large, and the flux contact opportunities, in the process of mixing, transport is not easy to layer.The silica sand must be checked and accepted in the mining area. The moisture content of the silica sand must be controlled below 8% when the ore is produced, and below 5% when the sand is loaded in the workshop. The moisture fluctuation value is 0.4%.Table 2-17 shows the quality requirements of siliceous raw materials.(2) the content of A12 03 in ordinary bottle glass is generally 2.0% ~ 5.0%.High white material glass bottles of the A12 03 is mainly composed of alumina and aluminium hydroxide to catch, but lower the quality requirement of container glass and color glass, also can choose to use sodium feldspar, potassium feldspar, or calcium feldspar to draw in the use of feldspar spectacular A120 3 at the same time, the parts of the feldspar Naz O or K2 0 can replace part of the soda ash, is advantageous to the glass melting system.However, the content of iron in general feldspar is higher, Fe2 03 is less than 0.1% of very few, so can only be used for general bottle and can glass, and can not be used for higher grade bottle and can glass.Feldspar according to its different chemical composition can be divided into four kinds of potassium feldspar, sodium feldspar, calcium feldspar, barium feldspar.In nature, there are few individual deposits of the four feldspars, most of which are mixed with other minerals in different proportions.Table 2-18 lists the quality requirements for feldspar materials.(3) Na20, the raw material of sodium oxide, is a good flux for glass. Therefore, the content of Na20 in the chemical composition of glass bottles and cans is closely related to the melting conditions of glass, which is mostly in the range of 14% ~ 16% at present.Na2 0 in bottle glass is mainly introduced by soda ash.Soda ash is a kind of chemical raw material, its main component is Naz C03. Soda ash is divided into crystal soda (Na2 C03·10H20) and calcined soda (Naz C03). Most of the soda ash used in glass industry is calcined soda without crystal water made by ammonia alkali method.Calcined soda ash is a white powder, easily soluble in water, easy to absorb water in the air and deliquescence, caking, need to be stored in the dry warehouse.Soda ash is one of the most important factors affecting the cost of glass.Heavy alkali should be preferred for bottle glass.Compared with the light alkali, the heavy alkali has good looseness, hygroscopicity, less flying and layering tendency, which can improve the uniformity and melting speed of the compound.But too thick soda ash particles cannot effectively to cooperate with other refractory material in the material evenly help fusion effect, will result in uneven with the mixture of material itself, affect the quality of glass melting and clarification, therefore, appropriate particle size range of 0.22 ~ 0.42 mm. The place a long time of soda ash, often containing 5% ~ 8% water, when use should be timely determination of moisture.The volatilization of soda ash during glass melting is 0.5% ~ 3.2%.Calcined soda ash often contains a small amount of Nacl, because Cl is very active, the erosion of refractory is very serious.The amount of soda ash is large, and the accumulation of Cl in the glass solution has recently attracted the attention of the industry.(4) the role of potassium oxide (K20) in glass is similar to that of Na20. In the production of bottle and can glass, a small amount of K20 is used to replace a small part of Na20, which can increase the refractive index of glass and improve the gloss and transmittance of products.The chemical stability of two alkali oxides in glass is better than that of a single alkali oxide.In the ratio of the two, there is an optimal point, the phenomenon is.Mixed base effect.The effect of K2 0 on the thermal expansion coefficient of glass is greater than that of Na20.Therefore, when replacing part of Na20 with K20, the influence on thermal expansion coefficient of glass should be considered.K20 in bottle glass is generally introduced by calcining potassium carbonate. When potassium carbonate is melted in glass, the volatile loss of K20 is about 12% of its own mass.The quality requirements for potassium carbonate are: K2 C03 less than 96%, na2040.2%, KCI+K2 S04 43.5%, water insoluble < 0.3%, water -3%.The price of potash is higher than soda ash, because this, outside the bottle and can glass of special requirement, most bottle and can glass does not use potash to draw potassium oxide directly, take potassium oxide with feldspar instead.(5) introduction of calcium oxide raw material calcium oxide (Ca0) in the glass is the main role of stabilizer, that is, increase the chemical stability and mechanical strength of the glass, but when the content is too high, can make the glass crystallization tendency to increase, and easy to make the glass brittle.Cao content in ordinary bottle glass is 7% ~ 11%, generally not more than 12.5%.Cao in high temperature can reduce the viscosity of the glass, promote the melting and clarification of the glass but when the temperature drops, the viscosity increases very quickly, making the molding difficult, therefore, how much Cao content in the glass, in addition to considering the influence of Cao on the properties of the glass, also should consider the glass molding method and other factors.The glass with high Cao shape should be quickly into the annealing furnace, or the product is easy to burst.When melting sodium-calcium glass, it is better to approach 21 with Na0Ca0.The main raw materials used in jar glass are limestone, calcite and chalk.Limestone containing Fez 03 40.015% is used in the production of utensils and white materials. Limestone containing Fez 03 less than 0.04% is used in the production of colored glass. The water content of limestone should be controlled less than 1%.When the composition of glass requires the content of iron oxide to be very strict, it can be replaced by calcite, which is much purer than limestone, but also much more expensive.(6) the amount of magnesium oxide (Mgo) in the chemical composition of glass bottles and cans is generally less than 2%.When using partial Mgo to replace partial Cao, can increase the viscosity when vitreous liquid is high temperature, can make vitreous harden speed to become slow, makings sex to become long, improve vitreous form property and reduce its crystallization tendency, calcium, magnesium and 2 valence alkaline earth metal oxide can improve the chemical stability of vitreous, prevent product to fall in damp environment for a long time.Mildew.Phenomenon.Generally, the amount of replacement should be controlled below 3%, while the amount of replacement is greater than 3%, which will affect the glass melting and forming.Used to think that dolomite and limestone of fine particles to melt, but with the deepening of research on mechanism of high temperature glass batch, will found interloper dolomite particle adsorption around the large silica particles, prevent sand to participate in the reaction, while coarser limestone particles at the beginning of the silicate reaction not wetted by primary phase, the primary liquid can smoothly through the gaps between the big grain dolomite, limestone, silica sand for wetting surrounded, further increase the silicate reaction rate.However, in the later stage, the gases released by their rapid decomposition and melting are conducive to the clarification and homogenization of the glass liquid. It is found that when the particles of the two increase to 2.5mm, the melting and clarification properties of the glass are significantly improved, and when the particle size is greater than 3mm, the melting and clarification properties of the glass are significantly reduced.Therefore, the upper limit of dolomite and limestone particles should be controlled within a certain range.At present, the use of larger grain dolomite, limestone is a trend.In actual production, when calculating the glass formula, the dolomite is used to introduce Mgo, and the insufficient part of Cao is supplemented with limestone or calcite.If the glass composition does not contain Cao, the dolomite cannot be used to attract Mgo in the glass, should choose magnesium carbonate to attract Mg0. The quality requirements for dolomite are Mg0≥20%, Cao < 32%, Fe2O3 < 0.15%.(7) introduction of barium oxide raw material barium oxide (Bao) in the role of glass and Cao and Mgo is basically the same, but the glass containing barium and Cao containing glass, good luster, dense ‘degree is large, generally in the color bottle glass composition of 0.5% ~ 1% Bao in order to improve the gloss of the glass.Bao can accelerate the melting, clarification and prevention of glass crystallization, but when the dosage is too large, due to the occurrence of 2Ba0 1002 2Ba02 reaction, the glass clarification is difficult, and the crucible and refractory materials have a greater erosion.Natural barium sulfate (BaS04) known as barite, BaS04 contains a large amount of fluctuations, and the impurity content is also large, only used for the quality of glass requirements are not high.Industrial BaS04 is mainly used in fluorine opacities glass and imitation jade glass in bottle glass, making the glass produce a relatively weak opacities effect.But it happens when you use too much.Glass of water., to refractory materials, crucible, molding and product quality to bring a series of adverse effects.Bottle and can glass production, Bao is generally introduced by industrial barium carbonate.In addition, barium containing raw materials have a certain toxicity, in the batching operation should pay attention to protection.The quality requirements for industrial barium carbonate are Bac03 97%, Fe2 03 40.1% and acid insoluble 3%.
Post time: Apr-14-2020