At present, in order to solve the energy crisis and environmental pollution, countries have formulated policies aimed at promoting the development of renewable and clean energy.Driven by the new energy policies of various countries in the world, solar energy utilization products have become the main role in the green energy series.Photovoltaic glass is one of the important components of solar energy series products. It affects the absorption of visible light by solar energy series products and determines the conversion energy of photovoltaic modules.Therefore, the production of high quality and high light transmittance photovoltaic glass is of great significance for the utilization of solar energy.
1. Introduction to photovoltaic glass
Photovoltaic glass is also ultra-white glass, also known as low iron glass, colorless glass, high transparent glass, with high light transmittance and high transparency.The light transmittance of glass determines the quality of glass. The light transmittance of common float glass is 86%, while that of photovoltaic glass is more than 92%.
Quartz raw materials required for glass production include natural quartz sand, quartz sandstone, quartzite and vein quartz, etc., making the production of photovoltaic glass more difficult and requiring more quartz raw materials than ordinary glass.
2. Quality requirements and control of quartz sand for photovoltaic glass
In nature, it is rare to find quartz sand raw materials that can meet the needs of glass production without treatment, especially ultra-white glass.The quality requirements of photovoltaic glass for quartz sand are mainly reflected in three aspects: chemical composition, particle size, refractory minerals.
Chemical composition
The biggest difference between the chemical composition of photovoltaic glass and ordinary glass is the content of Fe2O3.The quality score of Fe2O3 is required to be no more than 1.50x 10-4.
The amount of iron oxide in quartz sand has a direct effect on the quality of solar glass.The content of iron oxide affects the absorption of visible light by glass, and it determines the conversion energy of photovoltaic modules, which is one of the key factors to measure whether it can be used as the principle of photovoltaic glass.
Iron-containing oxides stain the glass and reduce its light transmittance.Fe2O3 can make glass yellow.Fe O can make glass blue;They coexist to make the glass blue-green.
Iron oxide has a strong absorption effect on the heat radiation of glass melting, which can easily lead to the convection of glass liquid in the melting furnace and increase the difficulty of melting and clarification.
Particle size
The size of quartz sand particles affects the melting time of sand grains and the quality of glass products.Experimental results show that: thick particles are difficult to melt, and may even become scum, so that products appear on the wave bar or sand;Although the melting speed of sand particles with particle size < 0.1mm is fast, the premature formation of glass liquid will affect the conduction of heat and slow down the overall speed. In addition, the viscosity of ultra-fine particles will increase due to the electrostatic effect, and they are easy to form into a group, making it difficult to melt.
efractory minerals
Some refractory minerals in quartz sand, such as chromite, zirconium and other high melting point, stable chemical properties, even under high temperature conditions are difficult to be fused corrosion, so easy to form stones on the original glass plate.It has a great influence on the quality of the original glass and the later processing.The total amount of chromite and nickel-containing minerals shall not be more than 5ppm (in terms of Cr2O3), and the diameter of a single particle shall not be more than 0.25mm.For other refractory minerals, the diameter of a single particle shall not be greater than 0.25mm.
3. Quality control of quartz sand for photovoltaic glass
In the formation and growth of quartz, accompanied by a large number of impurity minerals, there is no raw quartz material that can meet the requirements of photovoltaic glass production without treatment.Therefore, the quality control of quartz sand for photovoltaic glass is mainly achieved through the purification of quartz sand.Physical and chemical methods are commonly used for the separation and purification of quartz sand.
Physical methods: water washing, magnetic separation, flotation, electrical separation, mechanical scrubbing, fractional desilting, microwave assisted, ultrasonic assisted.
Chemical methods: acid leaching, alkali leaching and microbial leaching.
Control method of iron content in quartz sand
There are various forms of iron-bearing substances in quartz sand, and each mineral processing and purification method of quartz sand can remove iron to a certain extent. Among them, fractional desliming is mainly to remove argillaceous iron, magnetic separation to remove iron-bearing substances in the ore, heavy separation to remove iron in the form of heavy minerals, and flotation to remove iron-bearing light silicate.It is necessary to remove iron from quartz sand for photovoltaic glass. In actual production, the purification process with the lowest cost and the simplest process should be selected based on the chemical composition of quartz sand.
Method for particle size control of quartz sand
The particle size control of quartz sand for photovoltaic glass can be realized by water separation and sorting and grading.The water concentration is mainly fine mineral particles less than 0.1mm;Coarse quartz sand particles are sorted by rolling screen and hindered settling machine.According to the requirement of grain size separation, the upper limit of feed grain size and the reasonable washing separation process can achieve the purpose of improving the yield of fine sand and product quality control of quartz sand.
Method for controlling refractory minerals in quartz sand
The control method of refractory minerals in quartz sand for photovoltaic glass is mainly realized by gravity separation.In the gravity concentration, the movement speed of the minerals with a large proportion tends to be lower in the trough and enter the tailings area.The minerals with small specific gravity move faster, tend to be outside the trough and enter the next process.It is worth noting that, in order to ensure the accuracy of re - election, re - election must be uniform feed.
The quality of quartz sand used in photovoltaic glass is effectively controlled mainly through the selection and purification of quartz sand.At present, China's glass industry to high value-added, specialized development, so that the selection of quartz sand purification also put forward higher requirements.The study on the selection and purification of quartz sand and the preparation of higher purity quartz sand are beneficial to the development of China's photovoltaic industry and in line with the national strategy of creating a "resource-conserving and environment-friendly" society
