Making a master and doctoral thesis was my best time during studying physics. It should be nice if again more students should perform research on cellular glass beyond the constraint of making profit. In this post, I mention three nice studies:
- Dr. Arjen Steiner made a study about the conversion of fly ash from a municipal solid waste incinerator into useful foamed glass. He did this work at the Technical University Eindhoven in the Netherlands. This student was responsible for the project in this previous post.
- Dr. Rudolf Trinkner studied the cell structure and calculated the mechanical stability of foamed glass and compared with experiments. The work was done at the Technical University Zurich, Switzerland.
- Dr. Selamet Kose made a nice work about the foaming mechanisms of glass with special attention for SiC as foaming agent. This work is very practical and contains cell gas composition measurements with a gas chromatograph. Also the relation of the cell structure with the thermal conductivity is calculated. This work is also done at the Technical University Zurich, Switzerland.
Especially the last thesis is important for the development of cellular glass, foamed from waste glass with alternative foaming agents.
BELGLAS would be pleased to help new PhD-students all over the world in their research on cellular glass.
I found a nice message in my mailbox. Indeed, Schaumglas Global Consulting managed to install a plant for the production of 300 000 m³ foamed glass gravel annually in Russia. Recycled glass can not be used in the regular glass industry if it contains all kind of contamination. In case there is a large request for foamed glass gravel, it is economic wise to use this waste glass without too much cleaning directly into foamed glass gravel.
Today, the further we go to the East, the larger is the growth of foamed glass, gravel and boards, while in West Europe, a foamed glass plant was recently closed. What should be the reason for this? More than 80 years ago, foamed glass was invented in Russia but that can’t be hardly the reason for this sudden growth and interest.
This patent application US20110302961 describes a continuous foaming method without cutting or sawing. Also in this case, continuous foaming on an endless belt is used but the glass/foaming agent powder is put in segments on the belt. In this way, the resulting foam is segmented. The individual blocks are lift up to a vertical position and introduced in a lehr. This lehr is essentially a hollow glass lehr. In this way, the total setup can be also much shorter than in the case of a horizontal lehr.
But the patent also gives a nice summary of the current state of the art. In my opinion, the foamed segments will not be flat and this process will generate a lot of waste due to extra cutting.
The idea to anneal vertically remains an important point due to the huge saving which can be generated by reducing the length of the lehr. But on the other hand, the ribbon width will be limited in that way because forced convection has also its practical limits.
If a suitable land can be found (length, flatness, ….), BELGLASCZ advises to work with radiation / natural convection cooling of a wide ribbon like developed by CNUD EFCO. All methods to work with a shorter lehr end up with more waste. It was suggested to use this waste for foamed glass gravel, but the added value of that product will always be much smaller than boards.
For every cellular glass plant, we have to choose between mold and continuous foaming on an endless belt. In case continuous foaming is chosen, we must decide where to saw the cellular glass ribbon. For float glass, cutting always happens on the cold end and this seems the obvious choice for cellular glass. Indeed, sawing the cellular glass after annealing seems to be the logic choice.
I was surprised to find a patent application US20130145796 where the ribbon is cut between the annealing (550°C) and the end of the structural relaxation point (450°C). The cutting can be transverse and longitudinal on the cellular glass ribbon. A saw, cutting wheel and knife are suggested.
But why cutting hot? Float glass people are familiar with the famous longitudinal flaw in the ribbon. Regular cutting will stop this flaw in time. Longitudinal cutting reduces the width of the ribbon and in that way, the area stress on the ribbon. In fact, larger temperature deviations are allowed in the lehr without inducing breakage. On the other hand, skilled lehr builder like CNUD-EFCO are able to work within very small temperature deviations.
But there is also an important other reason to work in this way. It allows to anneal the ribbon vertically, reducing enormously the length of the lehr. In this case, an hollow glass lehr is the obvious choice.
May 1, is the day we all think on the tragedy of this very skilled and friendly F1 driver Ayrton Senna. And that is probably the reason kinetic energy absorption crossed my mind in my previous post, although the idea was already published in a US2981317 patent about safety seats in 1961. In this post, I want to show my point with real numbers with a calculation in an Excel spreadsheet.
The following example could be tested. I assume a car at 300 km/h and a total weight of 1000 kg. I guess that this car hits a cellular glass wall and a cross section of 2 by 0.2 is really hitting the cellular glass wall. The used cellular glass has a compressive strength of 3 N/mm². The car will stop completely after crushing 3 m cellular glass and the deceleration will be about 250 g. A Head Injury Criterion (HIC) of 250 g should be the limit for concussions. An internal recoil of the brains will not be present because the cellular glass is entirely non-elastic, the kinetic energy is converted in breakage energy for the cellular glass.
Cellular glass, produced from only recycled glass (without remelting) by for example GLAPOR can be used for this application, costing less than 450 € for one running meter. The cellular glass is non combustible, can always be recycled and is water proof. Having an idea is always easy but only the F1 organization can bring it into real life. Bernie, please wake up.