Glasherstellung - Das Floatverfahren (Saint-Gobain)
Summary
TLDRThe script delves into the intricate process of glass manufacturing, highlighting its ubiquitous yet invisible nature in modern applications. Key ingredients like quartz sand, soda, and lime are crucial, with dolomite added for building and automotive glass. The float process is central, detailing the mixing, melting, and slow cooling stages. It emphasizes the float plant's role in producing high-quality, cost-effective glass, showcasing the importance of the float bath and the use of tin to create a smooth, planar glass surface. The script concludes by noting the adaptability of float glass for various applications, such as thermal insulation and soundproofing.
Takeaways
- 🏭 Glass is a material with a wide range of applications and is produced through an intricate process.
- 💠 The main raw materials for glass production are quartz sand, soda, and lime, with dolomite added for building and vehicle glass.
- 🔥 The raw materials are mixed and melted at temperatures between 800 to 900°C, with the melting process being observable only through special glasses.
- 🌡 The melting process involves three areas: melting of the mixture, refining at up to 1560°C, and cooling to around 1100°C.
- 💧 The float process is used for industrial glass production, where the glass is formed by flowing over a bed of molten tin.
- 🔄 The float process involves a non-visible transition area between the melting pot and the float bath, facilitated by a lip stone.
- 🌌 The principle of glass spreading evenly over the tin bath is similar to how two immiscible liquids like chloroform and glycerin form a smooth separation layer.
- 📏 The thickness of the glass is controlled by the speed at which the molten glass is drawn over the tin bath, managed by top rollers.
- 🌡️ The cooling process in the float bath is carefully controlled to prevent stress in the glass, with the temperature dropping from 1100°C to 600°C.
- 🛠️ The flat glass is then slowly cooled in a roller cooler to room temperature, ensuring a stress-free cooling process over a length of 160 meters.
- ♻️ Defective areas are identified and marked for automatic sorting out, and the glass is cut to size for transportation and potential recycling.
Q & A
What are the main raw materials used in glass manufacturing?
-The main raw materials for glass manufacturing are quartz sand, soda, and lime. For building and vehicle glass, dolomite is also added as an additional raw material.
What is the float process in glass manufacturing?
-The float process is an industrial method used to produce flat glass of a high quality standard. It involves floating molten glass on a bed of molten tin to create a flat, parallel surface.
Why is dolomite added to the raw materials for building and vehicle glass?
-Dolomite is added to the raw materials for building and vehicle glass to improve the chemical composition and physical properties of the final product.
What causes the brownish-red color of the glass mixture?
-The brownish-red color of the glass mixture is due to small amounts of iron oxide added to the raw materials.
How is the glass mixture melted and at what temperature?
-The glass mixture is melted in a melting furnace at temperatures between 800 and 900°C. The melting process begins when the quartz sand melts at around 1450°C.
What is the purpose of the three different areas in the melting furnace?
-The melting furnace has three areas: the first for melting the mixture, the second for refining at up to 1560°C to homogenize the glass melt and remove gas bubbles and streaks, and the third for cooling the melt to about 1100°C.
How does the float bath work in the glass manufacturing process?
-The float bath works by utilizing the different densities of tin and glass. The molten glass spreads evenly over the entire tin bath, floating on the surface due to the density difference.
Why is tin used in the float bath?
-Tin is used in the float bath because it remains liquid at 600°C and does not evaporate even at 1100°C, which is necessary for the glass to cool and solidify evenly.
How is the thickness of the glass controlled during the float process?
-The thickness of the glass is controlled by the speed at which the molten glass is drawn across the tin bath and managed with the help of top rollers.
What happens to the glass after it leaves the float bath?
-After leaving the float bath, the glass is slowly cooled in a roller cooler from 600°C to 200°C over a length of 160 meters to ensure stress-free cooling.
How is the quality of the glass checked after it is formed?
-The quality of the glass is checked for inclusions, bubbles, and streaks. Defective areas are marked and later automatically sorted out for potential recycling back into the melting process.
Outlines
🔍 The Complex Process of Glass Production
This paragraph delves into the intricate process of manufacturing glass, a material with a multitude of applications yet seemingly simple in appearance. The primary ingredients for glass production are quartz sand, soda, and lime, with dolomite added for building and automotive glass. The process involves five main steps: mixing the raw materials, melting the mixture, shaping the molten glass, slow cooling, and cutting. The industrial production of glass for construction and vehicles must meet high-quality standards while being cost-effective, a requirement met by the float process. The float plant is preceded by a batching house with storage for raw materials, ensuring quality. The materials are transported to mixers where the mixture is created, including recycled glass cullet from the float glass production, which contributes to the brownish color due to iron oxide additives. The mixture is then fed into a melting furnace, where approximately 700 tons of glass mass are melted per day in a continuous process at temperatures between 800 to 900°C. The melting process is observed through refractory glass, and gas burners provide the necessary heat. The melting furnace has three sections: melting, fining, and cooling, with the glass mass constantly moving due to temperature differences. The fining process at around 1560°C homogenizes the glass, removing gas bubbles and impurities, and the cooling section gradually reduces the temperature to prepare the glass for shaping.
🏭 The Float Glass Manufacturing Technique
The second paragraph explains the float glass manufacturing technique, which is used to create flat glass with a smooth and even surface. The process begins with the molten glass flowing over a 'Lippenstone' onto a bed of molten tin in a float bath, taking advantage of the different densities of tin and glass. This creates a smooth separation layer, similar to how two immiscible liquids like chloroform and glycerin form a distinct layer. The glass spreads evenly over the tin, and its thickness is controlled by the speed at which the glass is drawn across the tin and adjusted by top rollers. The hot tin, initially at 1100°C, ensures a flat underside of the viscous, glowing glass ribbon. The glass then cools down to around 600°C, with the temperature of the tin bath being stepped down and electric heaters on the glass surface ensuring an even temperature drop. The use of tin is crucial as it remains fluid at 600°C and does not evaporate even at 1100°C. The float process must occur in a protective gas atmosphere to prevent oxidation of the tin. By the end of the float bath, the glass ribbon is form-stable enough to be lifted from the tin bath, marking the completion of the forming process. The green glass ribbon is then guided into the roller coolers, where it is slowly and electronically controlled from 600° to 200°C over a 160-meter length to ensure stress-free cooling. The glass ribbon cools down to room temperature in the open roller track. Quality control checks for inclusions, bubbles, and streaks, marking defective areas for later automatic sorting. The glass is then cut to a transportable glass sheet size, with only these cut and sorted glass sheets being suitable for recycling back into the float plant. The outcome of the float process is flat glass with surfaces that are even and parallel, also referred to as mirror glass quality.
🌐 Applications and Further Processing of Float Glass
The final paragraph discusses the applications and further processing of float glass to meet modern demands for thermal insulation, solar protection, and sound insulation. Float glass serves as the starting product for a variety of applications and undergoes numerous additional processing steps to adapt to specific use cases. It is enhanced and transformed through various techniques to cater to the specialized needs of different industries, showcasing the versatility and importance of float glass in contemporary construction and automotive sectors.
Mindmap
Keywords
💡Glass
💡Raw materials
💡Float process
💡Melting
💡Homogenization
💡Annealing
💡Roller cooling
💡Quality control
💡Recycling
💡Tempering
💡Mirror quality
Highlights
Glass is a material with a wide range of applications, yet it is almost invisible at first glance.
The production of glass is a complex process despite its seemingly simple nature.
Key raw materials for glass production include quartz sand, soda, and lime.
Dolomite is also used as a raw material for building and vehicle glass.
The glass manufacturing process involves five main steps: mixing, melting, forming, annealing, and cutting.
The float process is used for the industrial production of building and vehicle glass, ensuring high quality and economic efficiency.
Raw materials are stored in silos and are mixed in a batching house before being sent to the mixers.
The red-brown color of the mixture is due to small amounts of iron oxide.
The melting process begins at around 700 tons of glass mass per day, requiring approximately 2000 tons of molten glass in the melting tank.
The melting process in the melting tank is observed through sight glasses and is fueled by gas burners.
Lime and soda act as fluxing agents in the mixture, reducing the melting point of the quartz sand.
The melting tank has three distinct areas: melting, fining, and cooling.
The glass melt is homogenized during the fining process, becoming free of gas bubbles and striations.
The glass melt flows onto a tin bath in the float process, where it takes advantage of the different densities of tin and glass.
The thickness of the glass is controlled by the speed at which the molten glass is drawn across the tin bath.
The glass is cooled in a controlled manner from 1100° C to 600° C in the float bath.
The float process must occur in a protective gas atmosphere to prevent oxidation of the tin.
The flat glass ribbon is already form-stable by the end of the float bath, ready to be lifted from the tin bath.
The glass ribbon is cooled slowly and electronically controlled in the roller coolers from 600° to 200° C.
Quality control checks for inclusions, bubbles, and striations, with defective areas marked for automatic sorting.
The glass is cut to a transportable size, with only sorted and defect-free glass suitable for recycling.
Float glass is the starting product for a variety of applications, adapted to specific uses through further processing steps.
The float process results in flat glass with even surfaces, also known as mirror glass quality.
Transcripts
Glas ein Werkstoff mit den
vielfältigsten
Anwendungen ein massives Material aber
trotzdem fast
unsichtbar auf den ersten Blick ein
scheinbar einfaches Produkt doch für die
Herstellung ist ein aufwendiges
Verfahren
notwendig die wichtigsten
Grundsubstanzen für die Glasherstellung
sind
Quarzsand
Soda und Kalk für Bau und Fahrzeugglas
setzt man als weiteren Rohstoff auch
Dolomit ein
fünf Schritte lassen aus den Rohstoffen
einen transparenten festen Werkstoff
entstehen zuerst werden die Rohstoffe
vermischt dann wird das Gemenge
geschmolzen
die zähflüssige Glasschmelze wird
geformt und anschließend langsam
abgekühlt schließlich erfolgt der
Zuschnitt die industrielle Herstellung
von Bau und Fahrzeugglas muss hohen
Qualitätsanforderungen genügen und
gleichzeitig wirtschaftlich sein diese
Bedingungen erfüllt das
Floatverfahren der floatanlage
vorgeschaltet ist das gemengehaus mit
den Vorratslagern für die Rohstoffe für
deren Qualität bürgen die Zulieferer
über transportwänder gelangen die
Rohstoffe zu den Mischern in denen das
Gemenge hergestellt
wird diesem Gemenge werden anschließend
noch Glasscherben aus der
flotglasproduktion
hinzugefügt die rotbraune Färbung des
Gemenges ist auf geringe Zugaben von
Eisenoxid zurückzuführen
einlegemaschinen schieben dann das
Gemenge in die Schmelzwanne das
Schmelzen der Rohstoffe
beginnt rund 700 Tonnen Glasmasse pro
Tag werden in einem kontinuierlichen
Prozess geschmolzen dafür müssen rund
2000 Tonnen flüssiges Glas in der Wanne
gehalten
werden bei 800 bis 900° Celsus setzt das
Schmelzen
ein der Schmelzprozess in der Wanne kann
nur durch Schaugläser beobachtet
werden meist gasbetriebene Brenner an
den Seitenwänden oberhalb der
Glasschmelze führen die erforderliche
Wärme
zu der Schmelzpunkt von Quarz liegt
eigentlich erst bei 1700° CS erst Kalk
und Soda im Gemenge reduzieren als
Flussmittel den Schmelzpunkt des
Quarzsandes die Schmelzwanne weist drei
Bereiche auf im ersten Bereich erfolgt
das Schmelzen des Gemenges
nach dem Schmelzen des Quarzsandes bei
Temperaturen von ca
1450° CS ist der Prozess beendet
aufgrund von Temperaturunterschieden ist
die flüssige glasmenge dabei ständig in
Bewegung im mittleren Bereich erfolgt
das läutern bei maximal
1560° CS beim Läutern homogenisiert die
Glasschmelze das heißt sie beruhigt sich
wird frei von gaseinschlüssen und
Schlieren
beim abstehen im letzten Bereich kühlt
die Schmelze langsam und gleichmäßig auf
ca 1100° Celsus ab
über den lippenstein fließt sie dann auf
flüssiges Zinn im sogenannten Floatbad
es folgt die Formgebung bei der aus der
Schmelze das flache Glas geformt
wird hier der nichtinsehbare gekapselte
Übergangsbereich zwischen Schmelzwanne
und flotbart mit dem lippenstein
im Floatbad macht man sich die
unterschiedlichen Dichten von Zinn und
Glas zu Nutze dieser Versuch mit
Chloroform und Glycerin macht das
Prinzip deutlich beide Flüssigkeiten
vermischen sich nicht es bildet sich
eine sehr glatte
Trennschicht genauso breitet sich die
Glasschmelze gleichmäßig über das
gesamte Zinnbad aus sie floet
die Dicke des Glases wird durch die
Geschwindigkeit mit der die Glasmasse
über das Zinnbad gezogen wird und mit
Hilfe der toproller gesteuert
das anfangs noch 1100° Celsus heiße Zinn
sorgt für eine Ebene Unterseite des
glühenden zähflüssigen
glasbandes bis zum Ende des flotbades
erfolgt dann eine Abkühlung auf etwa
600°
csus einerseits ist die Temperatur des
zinbades abgestuft andererseits sorgen
Elektroheizungen an der Oberseite des
glasb für eine gleichmäßige gesteuerte
Temperaturabnahme der erforderliche
Temperaturabfall innerhalb des flotbades
erklärt auch weshalb hier Zinn zur
Anwendung kommt nur zin ist bei 600°
Celsus flüssig und verdampft auch bei
1100° Celsus noch nicht
allerdings muss das floten in einer
Schutzgasatmosphäre erfolgen um das
oxidieren des Zins mit dem
Luftsauerstoff zu
verhindern am Ende des flootbades ist
das planparallele Glasband schon so
formstabil dass es vom Zinnbad abgehoben
werden kann damit ist die Formgebung
abgeschlossen
das grüne Glasband wird vom flüssigen
Zinn links im Bild in den anschließenden
rollenkühlofen
geführt hier kühlt man das Glas langsam
und elektronisch gesteuert von 600° auf
200° Celsus ab 160 m Bandlänge sind für
dieses spannungsfreie Abkühlen
notwendig im offenen rollengang kühlt
das Glasband dann auf Raumtemperatur ab
in der Qualitätssicherung wird das
Glasband auf Einschlüsse Blasen und
Schlieren
untersucht die schadhaften Stellen
werden gekennzeichnet und später
automatisch
aussortiert es folgt der Zuschnitt zu
einer transportfähigen Glastafel das
sogenannte Bandmaß
nur diese abgetrennten buchgläser und
aussortierten Glastafeln eignen sich zur
Zeit für das erneute Einschmelzen in der
flotanlage in der Entwicklung befinden
sich aber Verfahren mit denen man
zukünftig auch weiterverarbeitete
flachglasprodukte recyceln kann
das Ergebnis des flotverfahrens ist ein
Flachglas dessen Oberflächen eben und
planparallel sind man spricht auch von
spiegelglasqualität
aus dem rohstoffgemenge ist das
Ausgangsprodukt für eine Vielzahl von
Anwendungen
entstanden um heutigen Anforderungen im
Bereich Wärmedämmung Sonnenschutz oder
auch Schallschutz zu entsprechen wird
Floatglas in vielen weiteren
Verarbeitungsschritten jedem speziellen
Einsatzzweck angepasst es wird veredelt
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