Glass-ceramic production is fit for the future

At SCHOTT, another glass melting tank was put into operation for the production of glass ceramics: Christoph Fark/Executive Vice President of Advanced Optics, Herman Ditz/Member of the SCHOTT Board, Ralf Reschke, Dr. Thomas Westerhoff, Ludwig Dürsch and Christopher Klein (from left).

With a state-of-the-art melting tank for ZERODUR® glass-ceramic production, SCHOTT is now increasing its production capacities in Mainz to ensure customers reliable delivery

When a melting tank is put into operation in the glass industry, it is a special milestone. After planning and months of construction, the tank begins a journey that will last several years during which the melting unit, in order to be economically viable, must sustain full power and withstand great stress at high temperatures. The SCHOTT technology group has now “fired up” (as insiders call the official start of operation) a new glass melting tank for ZERODUR® glass-ceramic production at its Mainz site. “The second tank reserved exclusively for ZERODUR® glass-ceramic is designed to meet the material’s long-term high demand and to contribute to the success of customers. In addition, the investment in the Mainz site, our company’s center of glass-ceramic expertise, will secure jobs,” said Christoph Fark, Executive Vice President of Advanced Optics at SCHOTT.

During firing up, the burner lance of a mobile gas-air burner is directed into the completely empty tank interior and ignited. There is a special reason: “Before glass can be melted, the residual moisture of the special stone-on-stone refractory material must first be removed with a tempering device and the tank must be brought to an operating temperature of at least 1,000 degrees Celsius,” explains the responsible engineer and project manager Thomas Lifka. Only then can the actual glass melt begin in the new tank. The pre-mixed raw materials – in the case of ZERODUR®, mainly silicon, aluminum and lithium – are introduced into the pre-heated tank over a period of several days and brought to melting temperatures of more than 1,600 degrees Celsius using a combination of electric and fossil heating.

Tank production expert Lifka: “The tank is a so-called discontinuous tank, which means that it is completely filled and emptied at periodic intervals.” The molten glass takes a form according to a fixed casting plan, either round or rectangular depending on the final product. The new tank in Mainz is also designed for mirror substrates with a diameter of up to 4.25 meters. The two ZERODUR® mirror substrates for the secondary and tertiary mirrors of the Extremely Large Telescope, for which SCHOTT received the order from the European Southern Observatory (ESO) in mid-January, will be cast from this tank. (See also Press Release No. 007/2017 from Jan. 18, 2017).

What happens after casting? In order to produce glass-ceramics with the required properties, the so-called raw glass must be subjected to a temperature process in both cooling and ceramizing furnaces. At first, the temperature is slowly increased to such an extent that crystal nucleation begins. After a determined holding time creates the desired number of crystal nuclei, the temperature is further increased to the range of crystal growth. After setting the desired crystallite sizes, blocks are cooled again in a defined manner. The correct ratio of the temperature-increasing glass phase, about 30 percent, and the shrinking crystal phase of about 70 percent with the correct number and size of the crystallites, ensure the combination’s extremely low thermal expansion.

The ZERODUR® glass-ceramic developed by SCHOTT has been the standard material for mirror substrates in astronomical telescopes for almost 50 years, providing extremely high-resolution images from space due to its “practically” zero expansion property. In addition to astronomy, the extraordinary material is also a material of choice in other technical applications where extremely low thermal expansion and precision are critical, for example in IC/LCD lithography, aviation and measurement technology. In Mainz, around 100 employees are engaged in the production and sale of ZERODUR® glass-ceramic.

In the future, bigger DESERT power plants will be set up on Brazilian soil, and together with existing turnkey production systems, they intend to take up a large share of the products and assets this sector will possess locally. J.v.G. Thoma plans to build up a local network of sales agents that can extend a premium offering to neighbouring countries in South America. Eventually, the company hopes to be able to expand its customer base to clients in North America.

Hans Thoma, general manager from the Thoma-group, is eager to acquire a substantial market share in Brazil, a growing country with tremendous potential for solar energy output. Having complied with local official procedures (Inmetro, TÜV, Fraunhofer CSP) and cleared the way for future business collaboration, he expresses his hope that the solar industry will henceforth expand quickly.

”Being able to introduce Brazil to the infinite opportunities of a solar industry is a privilege for J.v.G. Thoma GmbH, and one that we are extremely grateful for. At the same time, this placed the ball squarely in our court, and the pressure to get the ball rolling quickly was high. Now that the lengthy initial formalities are out of the way, we can focus on making this project a success.“

The first DESERT solar module production in BRAZIL! Lets go ....
J.v.G. Thoma GmbH is delivering a DESERT turnkey production line to Brazil, the first of its kind and hopefully the first in many breakthroughs to leave the factory floor on their way to the largest country in South America. With a capacity of 30 MW, this is a small semi-automatic DESERT production line, but still a flagship in terms of DESERT solar module production and electricity generation in the country, now fully functional and ready to start with operation.

The machinery consists of DESERT production machines for high-efficiency DESERT solar modules built specifically for extreme hot climate, such as can be seen in deserts or in tropical areas. Made solely in Germany and built using the latest in DESERT and TROPIC module production, the systems inlcudes all cutting-edge technology.

Certified DESERT solar modules, DESERT containers, DESERT power plants and DESERT manufacturing machinery built using pioneering DESERT and TROPICS technology are now fully set up, and ready to perform. But powering on the machinery has been a long time coming. Up until recently, this advanced piece of equipment had been waiting for clearance at a port in Brazil. Now that the formalities have been dealt with, both J.v.G. Thoma and its customer in Brazil can get production under way.

J.v.G. Thoma GmbH is a company whose vision has always been to harness the infinite power of the sun and convert it into an inexhaustible supply of energy. But a vision such as this requires global reach, and this project has opened new doors. Brazil is not only a gateway to South American cooperation, but also the launchpad to international reach and expansion.

Following the delivery of this initial order, J.v.G. Thoma GmbH will be looking forward to an ongoing collaboration with the Brazilian company. From setup and initial training to setting the scene for a ramp up, J.v.G. Thoma will be there to provide expertise and assistance. Moreover, the company will be jointly responsible, along with the client, for the successful integration of the DESERT solar module factory.

In the future, bigger DESERT power plants will be set up on Brazilian soil, and together with existing turnkey production systems, they intend to take up a large share of the products and assets this sector will possess locally. J.v.G. Thoma plans to build up a local network of sales agents that can extend a premium offering to neighbouring countries in South America. Eventually, the company hopes to be able to expand its customer base to clients in North America.

Hans Thoma, general manager from the Thoma-group, is eager to acquire a substantial market share in Brazil, a growing country with tremendous potential for solar energy output. Having complied with local official procedures (Inmetro, TÜV, Fraunhofer CSP) and cleared the way for future business collaboration, he expresses his hope that the solar industry will henceforth expand quickly.

”Being able to introduce Brazil to the infinite opportunities of a solar industry is a privilege for J.v.G. Thoma GmbH, and one that we are extremely grateful for. At the same time, this placed the ball squarely in our court, and the pressure to get the ball rolling quickly was high. Now that the lengthy initial formalities are out of the way, we can focus on making this project a success.“

The first DESERT solar module production in BRAZIL! Let
Source: SCHOTT AG