8/11/2019 Fosam Glass Paper http://slidepdf.com/reader/full/fosam-glass-paper 1/5 SPECIALTY CELLULAR GLASS PRODUCTS AND THEIR APPLICATIONS David Rostoker Pittsburgh Corning Corporation Pittsburgh Pennsylvania ABSTRACT Cellular glass products are composed of hermetically-sealed cells containing gases which exhibit no extracellular diffusion. As such, these products are impermeable to liquids and gases. FOAMGLAS® blocks have long been used as fireproof thermal insulation, especially in low temperature applications where conden sation and subsequent ice formation in insulation can cause significant reduction in insulating value. Recently, specialty compositions have been developed in the borosilicate and boroaluminosilicatefields which exhibit a high degree of resistance to corrosion by agressive chemicals as well. One product, s,old as TM PENN GU RD block by Pennwalt Corporation, is used as a liner for chimneys where acid corrosion had previously caused substantial maintenance problems. The product is also used as an insulative, acid-resistant liner in numerous chemical processes. A more refractory foam called FOAMSID®-12 insulation has been developed for use in extremely corrosive environments at elevated temperatures. One such field of application, the Alcoa Smelting Process, i n ~ o l v the use of molten salts which tend to impregnate materials which are porous to either salt vapors or to the liquid phase. Such impregnation of ordinary insulating materials causes a significant increase in ~ t transfer rates. FOAMSID®-12 blocks, with their unique properties of light weight, high strength, impermeability, and low thermal conductivity offer an opportunity for industrial energy conservation which did not previously exist. INTRODUCTION Cellular glass, long used in industrial and architectural applications as a thermal insulating m ~ t e r i is enjoying increased popularity in other applications where its total impermeability to the passage Of liquids and vapors leads to long service. Cellular glass, when properly manufactured, is exclusively glass of a single composition and consists of small, hermetically sealed cells which contain the gases formed at elevated temperatures which, at ambient, are at a pressure of about 0.3 atmosphere. FOAMGLAS® Insulation The product most people recognize as a cellular glass, FOAMGLAS® insulation, contains CO with small 2 amounts of CO, H and HS (the reason for the pungent smell when it is cut or broken). Knowing the high 2 2 activity of H one would expect that if anything could diffuse out of such a closed-cell system, it would 2 be H 2 . Nevertheless, FOAMGLAS® blocks taken from a hot job installed 25 years ago which had been eXP9sed to 450°F for most of its in-place life were found to have an H content of the cells essentially the same as 2 that measured for production ware 25 years ago. FOAMGLAS® insulation is used successfully in sub-ambient to cryogenic industrial pipe and vessel insula tion systems where its impermeability keeps it from being penetrated by moisture which,if present, could freeze. Water or ice adds substantially to the thermal conductivity of an insulation and even thoughure thane or polystyrene foams have lower thermal conductivities than FOAMGLAS® insulation, it doesn't take long for the moisture content to increase the k value of those permeable materials up to and in excess of that of the FOAMGLAS® ware which remains essentially constant. In addition, cellular glass is especially valuable where the stored material is a combustible liquid or gas because an all-glass insulation cannot soak up the combustibles and can never burn. Figure 1 depicts a laboratory experiment run by insulating a refrigerated pipe section held at -BOoF. The k factor was measured indirectly by means of a heat flow meter. Four years are required for the urethane 1021 ESL-IE-79-04-119 Proceedings from the First Industrial Energy Technology Conference Houston, TX, April 22-25, 1979
SPECIALTY CELLULAR GLASS PRODUCTS AND THEIR APPLICATIONS
David RostokerPi t t sbu rgh Corning Corporation
Pittsburgh Pennsylvania
ABSTRACT
Cel lu lar g lass products are composed of hermet ica l ly-sealed c e l l s conta in ing gases which exhibi t no
ex t r ace l lu l a r d i f fu s ion . As such, these products are impermeable t o l i qu ids and gases . FOAMGLAS® blocks
have long been used as f i r ep roo f thermal i n su la t ion , e spec i a l ly i n low temperature app l i ca t i ons where conden
sa t ion and subsequent i c e formation in insula t ion can cause s ign i f i can t reduct ion in i n su la t ing value .
Recently, spec i a l t y composit ions have been developed in the boros i l i ca t e and boroa luminos i l i ca t e f i e ld s
which exh ib i t a high degree of res is tance to corros ion by agress ive chemicals as well . One product , s,old asTM
PENN GU RD block by Pennwalt Corpora t ion , i s used as a l i n e r fo r chimneys where ac id corros ion had previous ly
caused substant ia l maintenance problems. The product i s also used as an i n su la t ive , ac id - re s i s t an t l i n e r in
numerous chemical processes .
A more r e f r ac to ry foam ca l l ed FOAMSID®-12 i n su la t ion has been developed fo r use in extremely corros ive
environments a t elevated temperatures. One such f i e l d of app l i ca t ion , the Alcoa Smelting Process , i n ~ o l v
the use o f molten s a l t s which tend to impregnate mater ia ls which are porous to e i t h e r s a l t vapors o r to the
l i qu id phase. Such impregnation of ordinary i n su la t ing mater ia ls causes a s ign i f i can t increase in ~ t
t r ans fe r r a t e s .
FOAMSID®-12 blocks , with t h e i r unique proper t ies of l i g h t weight , h igh s t r eng th , impermeabi l i ty, and low
thermal conduct iv i ty offe r an oppor tuni ty for i ndus t r i a l energy conservat ion which did not previous ly ex i s t .
INTRODUCTION
Cel lu l a r g las s , long used in i ndus t r i a l and a rch i t ec tu ra l app l i ca t i ons as a thermal i n su la t ing m ~ t e r i
i s enjoying increased popular i ty in other app l i ca t i ons where i t s t o t a l impermeabi l i ty to the passage Of
l iquids and vapors leads to long service . Ce l lu l a r g lass , when proper ly manufactured, i s exclus ively g lass
of a s ingle composit ion and cons i s t s of smal l , hermet ica l ly sea led c e l l s which conta in the gases formed a t
elevated t empera tures which, a t ambient, are a t a pressure of about 0.3 atmosphere.
FOAMGLAS® In su l a t i on
The product most people recognize as a c e l l u l a r g las s , FOAMGLAS® i n su la t ion , conta ins CO with small2amounts of CO, H and H S ( the reason for the pungent smell when i t i s cut or broken). Knowing t he high2 2ac t iv i ty of H one would expect t ha t i f anything could d i f fu se out of such a c losed -ce l l system, i t would2
be H2 . Nevertheless, FOAMGLAS® blocks taken from a hot job i n s t a l l e d 25 years ago which had been eXP9sed to
450°F for most of i t s in-place l i f e were found to have an H content of the c e l l s essen t i a l ly the same as2t ha t measured for product ion ware 25 years ago.
FOAMGLAS® i n su l a t i on i s used successful ly i n sub-ambient to cryogenic i n d u s t r i a l pipe and vesse l i n su la
t ion systems where i t s impermeabili ty keeps i t from being penetra ted by moisture which, i f present , could
f reeze . Water or ice adds subs t an t i a l l y to the thermal conduct iv i ty o f an i n su la t ion and even t houghure
thane or polystyrene foams have lower thermal conduc t iv i t i e s than FOAMGLAS® i n su la t ion , i t doesn ' t take long
for the moisture content to increase the k value o f those permeable mate r i a l s up t o and in excess o f t ha t of
the FOAMGLAS® ware which remains essen t i a l ly constant . In add i t i on , c e l l u l a r g la s s i s especia l ly valuable
where the s tored ma te r i a l i s a combustible l i qu id or gas because an a l l - g l a s s i n su la t ion cannot soak up the
combustibles and can never burn.
Figure 1 depic ts a labora tory experiment run by i n su la t ing a r e f r ige ra t ed pipe sect ion held a t -BOoF.
The k f ac to r was measured i nd i r ec t ly by means of a heat f low meter. Four years are required for the ure thane
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to equal the FO MGL S® i n su la t ion in conduct iv i ty in a temperature-control led dry environment of a labora tory.
On an actual job , ic ing condi t ions l i ke those depic ted in Fig. 2 have been known to occur in a l i t t l e over a
year despi te the vapor bar r i e r s ins t a l l ed over the i n su la t ion . This shows how FO MGL S® i n su la t ion i s the
only t ru ly impermeable and t he r e fo re constant i n su la t ing mater ia l avai lable commercially. One product can
not , however, sa t i s fy a l l needs. The purpose of t h i s paper i s to show how the wide ranging cha rac te r i s t i c s
of glass as a bas ic mater ia l can be used to c rea t e spec i a l ty c losed -ce l l g l a s s foams to be used for unique
energy saving appl ica t ions i n extremely hos t i l e environments. Severa l c e l l u l a r glasses were developed tomeet speci f ic se t s of environmental c r i t e r i a .
EFFECTIVE THERM L CONDUCTIVITY (-50 to +70Of Indoor Steady State Experiment
versusElapsed Time (days)
• • •
FO MGL S®In su l a t i on
500 1000 1500
Elapsed Time (days)
FIGURE 1
At t h i s point , a digress ion to descr ibe how g las s foams are made i s warranted. The process s t a r t s with
a glass tank from which a uniform and homogeneous melt of appropr ia te composit ion i s drawn which has s u f f i c
i en t dissolved gas , genera l ly S03' t o y i e ld oxygen in a high temperature redox r eac t ion . The cooled g las s
cu l l e t i s then o ~ i l l e d with a carbon reducing agent t o a very f ine p a r t i c l e s i ze . Homogeneity i s c r i t iCa l
This f ine powder i s put i n s ide a s t a in le s s s t e e l sui tcase which en te r s a furnace. The l i t t l e b i t of powder
ins ide the mold expands t o f i l l the rec tangular su i t ca se which i s then s t r ipped away for re-use while the
foam bun slowly cools in an annealing furnace. Since annealing r a t e var i e s d i rec t ly as desni ty and the
square of the th ickness and inverse ly, as the coe ff i c i en t of expansion, long annealing t ime i s necessary.
In the case of a low expansion body, higher dens i t i e s are f eas ib l e in economic th icknesses (four inches) .
FO MGL S® insula t ion has been used as a l i n e r for acid vessels or s tacks i n a few app l i ca t ions , but i t
has two weaknesses. F i r s t i t has a high coe ff i c i en t o f thermal expansion and thus tends t o f r ac tu re o r
thermal shock under rapid changes of temperature and, second, although i t i s s t rong and r i g i d i t i s not
strong enough for some pressur ized environments. In add i t i on , although i t s acid r e s i s t ance i s good, higher
r e s i s t ance i s desi rable .
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Proceedings from the First Industrial Energy Technology Conference Houston, TX, April 22-25, 1979
Accordingly, Pi t tsburgh Corning Corporation PCC) developed a boros i l i ca t e glass foam which would, l i k e
PYREX® ware, be able t o r e s i s t thermal shock due t o i t s low thermal expansion. The main l i m i t a t i o n ~ s t h a t
i t should be su i t ab l e for manufacture in our ex i s t i ng equipment when capaci ty was ava i l ab l e . This r ~ s t r
requi red a g la s s which could be foamed to 12 pcf a t about 1700 oF, the upper l i m i t for the s t a in le s s s t e e l
su i t ca se .
The r e su l t i ng product , termed FOAMSIL® 28 i n su la t ion , has grea t e r thermal shock r e s i s t a n c e f a r grea t e r
acid durab i l i t y, and higher s t r eng th than the r egu la r FOAMGLAS® i n su la t ion .
Since the PCC market ing s t r eng th i s pr imar i ly in the i n su la t ing f i e l d an exclus ive market ing arrange
ment was developed with t h e Pennwalt Corporation who provides marketing s t r eng th and experience i n t h e acid
corros ion r e s i s t a n t l i n e r market. Pennwalt offe r s t h i s acid r e s i s t a n t c e l l u l a r g la s s under t h e i r t r ~ d e m
PENNGUARD™ block.
To give you s o ~ idea of t he thermal shock r e s i s t ance o f t h i s mate r i a l , a s tandard , acceptable t e s t4 .t h a t has been developed i s t o bo i l two-inch cubes in 10 mole HCl for two hours , cool for two hours , then
plunge them d i r e c t l y i n to a 600°F oven. I f there i s no spa l l i ng , cracks , l o s s o f s t r eng th , or i m p e ~ e
detec ted a f t e r ten such cyc l e s , t he ware i s cons idered acceptable .
PENNGUARD blocks , and systems for t h e i r i n s t a l l a t i o n a re beginning to enjoy acceptance as s t ~ k
l i n e r s where acid s tack condi t ions cause corros ion of s t e e l yet the thermal environment i s too hot fo r
organic mater ia ls to survive . The blocks can be r ead i ly shaped to a wide var i e ty o f conf igu ra t ions a s can
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Proceedings from the First Industrial Energy Technology Conference Houston, TX, April 22-25, 1979
FOAMGLAS® insulat ion, and shaped blocks are much l e s s labor- in tensive to i n s t a l l t han ac id brick. I t seems
t ha t the marketplace i s ready for a l ightweight , insulat ing, corros ion- and shock-res is tant l i n e r and Penn
walt i s busy sat isfying t h a t opportunity.
FOAMSID® 12 Insula t ion
The excursion in to boros i l i ca t e glass foams was a tame venture compared to the next one t r i e d PCC
attempted to develop a closed c e l l i n su la t ion tha t could r e s i s t the at tack of fused chlor ide s a l t s a t around
1300 oF. In addi t ion to t h i s highly corrosive environment for such refractory use, the ma te r i a i has to be
impermeable to the s a l t s because fused s a l t s cause comparable l o s s in insulat ion effect iveness to tha t of ice
in cryogenic conditions. A fu r the r requirement for appl icat ions as an i n t e rna l insu la tion for an e lec t roly t i c vessel i s tha t t he insu la t ion be load bearing and r e s i s t creep a t the maximum use temperature.
In glass technology, to achieve t h i s set of t a rge t s t he g la s s had to have a s t r a in point a t l eas t equal
to the highest use temperature which required a high s i l i c a content. However, high s i l i c a content glasses
l ike fused s i l i c a are prone to dev i t r i f i ca t ion espec ia l ly in the presence of fused s a l t s Thus a composition
was designed that was a l l s i l i c a except f o r t h e small percentages of oxides tha t would s t ab i l i ze the s i l i c a
against dev i t r i f i ca t ion .
e f inal ly found a glass composition tha t would su i t the process needs but i t had to be melted in
platinum-rhodium crucibles a t 3300 oF, cooled, and beaten out o f t h e c r u ci b le because i t would not flow. Such
a technique was hardly sui table to volume production.
To solve t h i s problem, a glass- forming process was developed tha t was termed "foamelting" in which glass
forming and foaming are accomplished simultaneously in one opera t ion. The process i s r e l a t ive ly simple once
appropriate raw mate r i al s a r e selected. The d i f f i c u l t part i s the f i r ing . Nevertheless, we have produced
over 1,000 cubic feet of t h i s mater ia l in blocks as l a rge a s 1 9" x 15" x 2" and they have been in use for
severa l years . e c a l l th i s product FOAMSIL® 12 ce l lu la r glass .
Blocks of FOAMSIL® 12 insula t ion and FOAMSIL® 28 insulat ion are used by Alcoa in t h e i r Anderson County
Works near Pa les t ine , Texas, which i s the i n i t i a l i n s t a l l a t i o n of the Alcoa Smelting Process. (1 ,2 ,3)
Alcoa has used FOAMSIL® 12 i n su la t ion for t h e i r smel t ing process in a var i e ty of l i n ing app l i cat ions fo r
periods of over two years . So f a r, a l l of the t e s t s and a l l of the ins t a l l a t ions show tha t i t r e t a ins i t s
res is tance to fused s a l t corros ion or impregnation over the t e s t per iod and r e s i s t s creep under l o ad a s
required.
CONCLUSION
Table I shows the sa l i en t physica l proper t ies o f the th ree ce l lu la r glasses described in t h i s paper.
I t can be sa fe ly sa id t h a t c e l l u l a r g lass , as a unique closed c e l l insulat ion mater ia l can, by appropr ia te ly
varying t he g la s s composit ion, be adapted for use in a varie ty of hos t i l e environments and i s able to
exhibi t constant i n su la t ing and load-bearing charac te r i s t i c s .
REFERENCES
1. Jacobs, S. C. (1974) USP 3,785,941. Refractory for Production of Aluminum by Electrolysis of Aluminum
Chloride.
2. Haupin, W. E. (1973) USP 3,755,099. Light Metal Production.
3. Washburn, M. E. (1978) Sil icon Oxynitride Refractory Mater ia ls . Symposium on New Developments in
Ceramic Mater ia ls . AICLE.
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Proceedings from the First Industrial Energy Technology Conference Houston, TX, April 22-25, 1979
