Internship time: September 2007 1 1.
Internship location: Luoyang Glass Group Co., Ltd.
Instructor: Zhang Ying Ma Aiqiong.
Practical purpose: Through the visit to the glass factory, students can have a preliminary understanding of the production technology and main production equipment of float glass, and have a perceptual understanding of relevant professional theories, so as to pave the way for the study of professional courses in the future.
Company profile:
Shaanxi Blue Star Glass Co., Ltd. was formerly known as Shaanxi Glass Factory. Shaanxi Glass Factory is a large-scale state-owned second-class enterprise jointly invested by the central and local governments in the 1980s, and it is the only flat glass production enterprise in Shaanxi that integrates production and deep processing. The high-quality flat glass of 2mm, 3mm and 5mm produced by the nine-machine vertical wire drawing process has been widely used in industries such as architecture, mirror-making, instruments, handicrafts, etc., and sold well in 2/kloc-0 provinces, municipalities and autonomous regions in China, and exported to the Middle East. Introduce world-class deep processing equipment from Italy; All kinds of coating, mirror plating, edge grinding, spray carving, polishing and drilling are known as "fine products" in the decoration industry, which fills the gap in the northwest region and has an annual output value of 67 million yuan.
Now Shaanxi Glass Factory and Shandong Weihai Bluestar Group have cooperated and reorganized into Shaanxi Bluestar Glass Co., Ltd., which is located in the center of xianyang, Xi, with a very advantageous geographical position. The special railway line enters the national railway network, which is only 1 km away from the xianyang East exit of Shaanxi expressway network and 8 km away from Xi 'an Xianyang International Airport. The traffic is very convenient. Shaanxi Lanxing Glass Co., Ltd. is a company-owned enterprise with a brand-new mechanism and a brand-new system, in which Weihai Lanxing Glass Group is the main investor to participate in the restructuring of Shaanxi Glass Factory, and online coating glass and glass deep processing are the main industries. The existing fixed assets are 229 million yuan.
At present, the company has nine grooving vertical production lines, with an annual output of 6.5438+0.3 million weight boxes of flat glass. In recent years, the actual output has exceeded the production capacity, and glass deep processing products such as edging, painting, spray carving and mirror making have been developed one after another. The enterprise's nine-machine vertical drawing process was put into operation in May 2005, and the second float production line and one or two glass deep-processing production lines were put into operation at the end of 2005, with an annual output of 4.5 million weight boxes of float glass and 370,000 square meters of glass deep-processing products. Relying on the sunshine online painting technology with independent intellectual property rights, the market competitiveness of enterprises has been enhanced.
Float glass production line:
Flat glass produced by float method is called float glass. Float glass is a transparent and colorless flat glass, which is made of sea sand, seasonal sandstone powder, soda ash, dolomite and other raw materials. Melting in a furnace at high temperature, the molten glass continuously flows out of the furnace to float on the metal surface, spreads into a glass ribbon with uniform thickness, is polished by fire, cooled and hardened, separated from the molten metal, and then annealed and cut. The glass surface is particularly flat and smooth, with a very uniform thickness and little optical distortion. Float glass can be divided into three categories according to its appearance quality: excellent products, first-class products and qualified products. According to the thickness, it can be divided into seven types: 3, 4, 5, 6, 8, 10 and12 mm.
Float process is that molten glass continuously flows from melting kiln into molten metal tin bath protected by protective atmosphere. Due to the different densities of molten glass and molten tin, molten glass floats on the surface of molten tin. Due to the simultaneous action of gravity and liquid surface tension, molten glass is freely flattened on the surface of molten tin, thus becoming a molten glass ribbon with flat surface and uniform thickness, and moves to the back of tin bath under the action of external force. In the process of moving, it is polished, thinned, cooled and hardened by the flame from the top of the furnace, and then guided to the transition roller table. The rotation of the roller sends the glass ribbon into and out of the kiln, and after cooling, annealing and cutting, the flat glass product is formed.
Float glass has good thickness uniformity, purity and transparency. After smoothing the tin surface and flame polishing, the glass surface is smooth and tidy, with good parallelism and high optical performance. The decorative features of float glass are transparency, brightness and purity, bright indoor light and wide field of vision. Can be applied to building doors, windows, curtain walls, roofs, etc. It is the first choice for natural lighting of buildings and is applied to almost all buildings. It is the most used decorative glass in buildings, and it is also an important raw film in the glass deep processing industry. Its transparency and purity are even more ugly.
Compared with other molding methods, the production process of float glass has the following advantages:
1, which is suitable for manufacturing high-quality flat glass without ribs, uniform thickness, flat upper and lower surfaces and parallel to each other with high efficiency;
2, the scale of the production line is not limited by the molding method, and the energy consumption per unit product is low;
3, the utilization rate of finished products is high;
4. Easy scientific management, mechanization and automation, and high labor productivity;
5, the continuous operation cycle can be as long as several years, which is beneficial to stable production;
6. It can provide suitable conditions for online production of some new varieties, such as electro-floating reflective glass, coated glass during annealing, cold end surface treatment, etc.
Float glass production capacity accounts for more than 86% of china glass's total production capacity, and China has built the largest advanced float glass production line in Asia with a daily melting capacity of 900 tons.
Brief introduction of float glass production technology;
Raw material reserve: reasonably reserve the amount of raw materials for about 2 months.
Production silo: 1 ~ 5 days use silo.
Batching: adopt high-precision weighing system to weigh and mix broken glass, mix various raw materials and add a certain amount of clinker.
Feeding: put the qualified raw materials into the furnace and start heating, the maximum heating is 1600℃.
Combustion: the buyer can choose fuels: heavy oil, natural gas and gas to provide heat energy for the furnace to melt glass.
Melting: melting raw materials to make qualified glass liquid.
Stir: stir evenly to clarify the glass liquid.
Flowing into the tin bath: the molten glass controlled by the runner flows into the forming tin bath.
Preparation of shielding gas: H 2 and N 2 are used to protect high-temperature tin in tin bath from reacting with oxygen.
Forming and drawing: the molten glass is drawn into a glass plate in the tin bath by using edge drawing machine, electric heating and other equipment.
Glass annealing: eliminating the temperature stress generated when the glass plate is molded at 600℃ ~ 70℃.
Inspection: the glass plate is inspected and graded.
Cutting: cut the qualified glass plate into the size required by customers.
Packaging the original glass: tie the finished glass from the production line with equipment or manpower and put it into the packing box.
Main production processes:
(1) raw material preparation
First of all, the glass composition
The components of glass include silica, alumina, calcium oxide, magnesium oxide, sodium oxide and K2O.
Because some raw materials have their own special features, it is necessary to overcome them in each process in order to make glass that meets the requirements smoothly and reasonably. Because the melting point of SiO2 _ 2 is too high, which is about 17 10℃, it is necessary to add proper amount of CaO and K2O to reduce the melting point, and these two raw materials are expensive, which is easy to increase the production cost. Just add a proper amount of Al2O3 and other raw materials, all of which have their own intentions, and each raw material is added for a reason.
Second, the glass raw materials
Mainly: quartz sand, limestone, feldspar, soda ash, boric acid and so on.
Auxiliary raw materials: colorant metal oxide
Flux: fluorite CaF2
Clarifier: carbon
Third, batch preparation
1, powder bin
Upper part: cubic reinforced concrete structure
Lower part: pyramid steel plate structure
2. Transportation equipment
Intermittent: forklift crane
Continuous type: mechanical conveying: belt conveyor bucket elevator tube sliding.
Pneumatic conveying: pressure conveying type suction type.
3, weighing equipment:
Electronic scale: characterized by rapidity and accuracy.
Error value: decrement weighing method
Decreasing weighing method is the most suitable method to minimize the error after repeated modifications in specific operation practice.
(2) Melting of glass
The melting process of glass is a very complicated physical and chemical process. Generally, it can be divided into five stages: the formation of sinter, the formation of molten glass, the clarification of molten glass, the homogenization of molten glass and the cooling of molten glass.
Formation of sintered body: The batch with qualified quality is added into the glass furnace, and a series of physical and chemical reactions occur under the action of high temperature, forming an opaque sintered body. For ordinary soda-lime silicate cement, after this stage, the batch is transformed into a sintered body composed of silicate and residual timely particles.
Formation of molten glass: after further heating, the opaque sintered body dissolves the residual particles that are not completely melted in the batch, and the sintered body begins to melt and spread, and finally the opaque sintered body is transformed into transparent molten glass. But at this time, the glass liquid contains a lot of bubbles, and the composition of the glass liquid is very uneven.
Clarification of molten glass: Clarification of molten glass refers to the process of eliminating gas inclusions from molten glass. The calculation of gas production rate and glass output of glass batch shows that the amount of gas released during glass melting is about 15% ~ 20% of the batch mass.
Glass homogenization: The homogenization process is to eliminate the streaks and other chemical composition inhomogeneities in the glass melt, so as to obtain a glass melt with uniform chemical composition. Homogenization is a process of dissolution and diffusion of foreign bodies in glass liquid. Because the diffusion speed is obviously lower than the dissolution speed, the speed of homogenization process depends on the diffusion speed of heterogeneous body. The concentration difference between heterogeneous body and glass liquid composition is the source power for the dissolution and diffusion of heterogeneous body. The natural convection caused by the concentration difference of molten glass in different parts of the furnace also contributes to the diffusion of inhomogeneity. In addition, the forced convection of molten glass caused by auxiliary measures such as stirring and bubbling also promotes the dissolution and diffusion of foreign bodies.
Cooling of molten glass: In order to make the molten glass meet the viscosity requirements required for molding, the molten glass after high-temperature clarification and homogenization needs to be further cooled. The whole cooling process should be carried out smoothly to ensure the thermal uniformity of molten glass, prevent temperature fluctuation and avoid secondary bubbles.
It is difficult to completely separate the five stages of glass melting in actual production, and sometimes even happen at the same time.
(3) Forming of glass
The principle of glass float forming is that the glass liquid continuously flows in from the tank kiln and floats on the tin liquid under the protection of reducing atmosphere; Due to the comprehensive effect of interfacial tension and stress of each phase, the glass ribbon with uniform thickness, parallel upper and lower surfaces and fire polishing is unfolded, cooled and hardened, separated from tin liquid, and then annealed and cut to obtain float glass. The forming process of float products is carried out in tin bath.
When the gravity and surface tension of the molten glass on the tin surface reach equilibrium at high temperature (1050℃) without external force, the thickness of the glass ribbon has a fixed implant, which is about 6 ~ 7 mm Since the surface tension of the glass changes with the temperature of the molten glass, the equilibrium thickness also changes with the specific situation. In fact, this value is slightly smaller due to external longitudinal tension. In order to make the thickness of glass ribbon thinner or thicker than the equilibrium thickness, corresponding measures should be taken. For example, in the production of float glass, the mechanical edging method is adopted, that is, several transverse edging machines are placed on both sides of the glass ribbon in the middle section of the tin bath, which mainly plays the role of transverse edging, preventing the longitudinal tension of the annealing kiln roller from transferring to the glass ribbon in the high temperature area, so as to reduce its transverse shrinkage. When the drawing speed increases, the glass ribbon gradually becomes thinner and its width decreases. In the production of thick float glass, graphite edge guards are set on both sides of the high temperature area of the tin bath to prevent the glass liquid from thinning.
(4) Annealing of glass
In the process of glass formation, it has undergone drastic temperature changes and shape changes, thus leaving thermal stress in the glass. This thermal stress will reduce the strength and thermal stability of glass products. If it is directly cooled, it is likely to break itself during the cooling process or during the subsequent storage, transportation and use (commonly known as glass cold explosion). In order to eliminate the phenomenon of cold explosion, glass products must be annealed after molding. Annealing is to keep the temperature within a certain temperature range or slow down the temperature for a period of time to eliminate or reduce the thermal stress in the glass to an allowable value.
(5) cutting the glass plate
Glass is cut by direct cutting or scraping with a diamond cutter, and then external force is applied, so that the scar is cut by tensile stress. In the production of flat glass, overstress grinding wheel is used for on-line cutting; The further cutting of flat glass in deep processing is completed on a large automatic cutting machine.
Liquid such as kerosene, water or grinding fluid is often added in glass cutting, which can improve cutting efficiency and protect tools.
(6) packaging the original film:
The glass plate is moved from the workbench to the wooden glass box by the horizontal stacker.
2. Glass fiber production line
Glass fiber is an artificial inorganic fiber. First, it is melted into a glass state, and then it is stretched, blown or thrown into a very fine fibrous substance by external force. Its basic properties are: incombustible, non-corrosive, high temperature resistant, sound absorbing, heat insulating, small hygroscopicity, small elongation, good electrical insulation, light weight, high strength, good chemical stability, but fragile. Different glass compositions can be used to make it stand out in some aspects to meet the use requirements. Can be made into various shapes of yarn, cloth, belt, felt, plate, shell and other products; It can also be used as a reinforcing material to make composite products with various organic and inorganic materials; It can also be coated with organic matter to improve brittleness, flexibility, wear resistance and hand feeling. Because it has excellent characteristics that other fiber materials do not have, it is widely used. The industrial production of glass fiber didn't appear until 1930s. It is a new material and quickly resisted the war. There are thousands of products with more and more uses.
Glass fiber is the most typical continuous glass product, which is not only drawn continuously, but also has a simple circular cross section. Therefore, it is relatively easy to analyze and study its mechanism, and some achievements have been made, which has a leading role and reference significance for glass plates and glass rods. Continuous glass fiber forming belongs to the field of melt stretching; In fact, it also includes stimulating the stretch forming of polymer materials and other inorganic non-metallic materials. Since the late 1950s, a great deal of scientific research has been done on wire drawing mechanism in the world. Up to now, some research results are breakthrough, which can guide the production of the above materials and fibers. Fiber diameter and its change are the main morphological signs. Go ...
Reflections on practice;
Through this internship, I have a further understanding of the preparation of glass, especially the production process of float glass, which is very important for learning the relevant theories of inorganic nonmetallic materials.