OPERATIONAL EXPERIENCE OF AN OXY-FUEL FIRED GLASS MELTER USING AN 

IMPROVED SILICA CROWN AND WIDE FLAME BURNERS 

Alonso Gonzalez R., Gmpo Pavisa, Naucalpan, MEX, Mexico 

Wladimir Sanniento-Darkin, Praxair, Inc., Tonawanda, NY, USA 

John T. Brown, GMIC, Corning, NY, USA 

Len Switzer, Praxair, Inc., Burr Ridge, lL, USA 

Euan Evenson, Praxair, Inc., Tonawanda, NY, USA 

Sho Kobayashi, Praxair, Inc., Danbury, CT, USA 

Cuauhtemoc Lagos, Praxair Mexico S. de R.L. de C.V., Mexico, D.F., Mexico 

ABSTRACT 

The implementation of oxy-fuel firing technology in glass furnaces has become a technically 

feasible solution for producing glass over the last 2 decades. However, challenges do still exist 

concerning refractmy corrosion and fumace life. It has been recognized that the high concentration of 

sodium species in an oxy-fuel fired furnace can lead to acce lerated corrosion of the furnace crown. In 

this paper, the details of an operational campaign for an oxy-fuel fired container glass furnace are 

presented and discussed. The furnace crown was constructed with a low lime silica brick (0.8% CaO) 

which was expected to offer superior cmTosion resistance to a conventional silica crown. The fumace 

also employed ultra low-momentum, Wide Flame bumers to help minimize volatilization from the 

melt surface. The experi ence from this furnace campaign indicates that the crown material and bumers 

both met performance expectations and should be considered as part of a robust operating solution for 

container glass manufacturers. 

INTRODUCTION 

The fundamental picture of a continuous glass melting operation has changed little in the past 

!50 years. Although the concept of an all refi·actmy, reverberatoty fumace with continual operation 

has not changed, great strides have been made in the materials of constmction, maintenance and 

operation of these systems. One operational change which has greatly changed the operation and 

environmental footprint of glass production is the use of industrially pure oxygen in place of air. The 

conversion of typical air-fired glass furnaces to oxy-fuel firing has led to reductions in specific energy 

requirements, reduced emissions of air pollutants, increased specific pull rates, simplified furnace 

construction, and improved operational consistency and glass quality. However, oxy-fuel technology 

has also forced glass makers to consider alternative materi als of constmction , creative constmction, 

operational changes and robust maintenance programs to address the challenges of using industrially 

pure oxygen. 

The primary goal in optimizing the design, operation and maintenance of an oxy-fuel fired 

glass furnace has been extending the life of superstructure refractories, particularly the fumace crown. 

Traditional air-fired furnaces utilize silica brick for crown construction due to its relatively low 

density, thetmal conductivity, corrosion characteristics, and moderate cost. However, silica crown 

bricks applied to oxy-fuel fumaces sometimes experience acce lerated corrosion, , vatying greatly with 

system design (e.g. burner choice and placement) and the operating conditions of the fumace (e.g. 

crown temperature). The mechanism of this accelerated conosion is based on the formation of an 

alkali containing silicate or calcium silicate slag which is highly dependent on the concentration of Na 

species in the Jilmace atmosphere [1-5). Water vapor in the atmosphere reacts with Na species to form 

NaOH, and the NaOH is present near the silica brick interface. The NaOH reacts with the silica and 

l'alcium in the brick to lower the equilibrium melting point, resulting in a Na20-Ca0-Si02 slag which 

slowly "dissolves" the brick. The corrosion process is highly dependent on the temperature, NaOH 

~oncentration in the vapor phase, water content, gas velocity and calcium content in the brick. 
Melter 

w that by maintaining sufficie?~ tem~cra~·e at 

volatilization, corrosion of hc~ .bnck ctown 

itmaoe under ox.y-fucl firing conditions [6). . 

:d furnaces bas been demonstrated, substailtlal 

ls of consfn~ction for the crown [7-8). ~ondcd 

na or fused cast AZS) show excel\cnl res.IStance 

nation. However, these refractory matenal ore (more . tecl infrastructure required) nd arc 

10 install. One tactic ro address the les than 

st advantages over other alternatives has been 

ijmize the CaO concentration. Tl.te presence ~fa 

l f a calcium illcale slag in whtch th~ ca~cmm 

il.g. The alkali results in further reduction m ~e 

:ausing the lag to nm. By redu~ing the CnO Ill 

~ in a larger, effective Ol>erntmg range (e.g. 

I to traditional silica [9J. 

materials for oxy-fuel fire~ glas~ . fumnces· 

critical role in fumace integnty. Jltca crown 

srruction practices to minimize joint~ Wld by the 

during the furnace campaign. Alkali vapo~ can 

e regime in which sing devel?ps. and to:ms 

age on the crown is critical to mamtam uffictent 

e also critical to reduce a species volatilization 

from the melt is 11 function of temper~t~re, gas 

.s burners should be designed and posiitoncd to 

,~ proper temperature disrribuLion throughout the 

:crnative materials, combustion technology and 

modem, oxy-fue·l fired container glass furnace. 

tonlic operation of a soda-lime glass fu~tac~ a 

I. [1 0] sugge ted a number oF goal or obJii:Cttvcs 

.y-fuel furnaces, and this li t can be expanded for 

•le I . While these goal: are mo tly .common ensc 

valuate tlJese hems during any maJor change to a 

Operational Experience of an Oxy-Fuel Fired Glass Melter 

Table 1. Objectives for proper design and operation of an oxy-fuel glass metter 

Design/Operating Consideration: Goal: 

Investment Cost Minimize refractorv costs relative to performance 

Life Expectancy Maintain or improve upon "tvoical" life comoared to air-fuel 

Materials Investigate alternative materials or improvements on available 

materials 

Construction and Heat-up Utilize quality materials, stay true to fabrication drawings, 

minimize possibility of joint expansions 

Operation Maintain proper temperatures and utilize correct tools to optimize 

energy and environmental footprint (e.g. electric boost and 

burners) 

Operating Cost Improve competitiveness by designing system to minimize 

operating cost 

Maintenance Observe system carefully throughout operation, identify issues 

early and proactively repair 

Burners and furnace layout Utilize burners, burner positioning and flue positioning to 

minimize volatilization and maximize heat transfer 

Grupo Pavisa in Naucalpan, Mexico, has worked to optimize these objectives on an oxy-fuel 

container furnace (Furnace 14) built in early 2000. This fumace was built to replace a smaller oxy-fuel 

glass melter. The furnace specifications are shown in Table 2. One of the major goals of this furnace 

design was to implement a potential improvement on typical silica crowns by utilizing a low lime silica 

brick which was specifically manufactured as a single production run for this furnace. The reduced 

CaO content (approximately 0.8%) was expected to reduce crown corrosion while maintaining a 

reasonable cost for the material and traditional silica crown construction practices. Table 3 shows a 

comparison of the basic properties of a conventional silica brick against the new, low-lime silica 

material used in Furnace 14. 

Table 2. Operating and design soecifications for Fumace 14 Grupo Pavisa) 

Parameter Value 

Glass: Soda-lime, flint 

Melter Area: 527 fiT (50 m") 

Aspect Ratio: 2.2 

Nominal Pull Rate: 165 tod (150 t/d) 

Electric Boost: 600kW 

Fuel: Natural Gas 

Oxidant: Oxygen- Onsite VPSA 

Nominal Cullet Ratio: 50% 

Average 2779 °F (1530 °C) 

Minimum 2712 op (1489 °C) 

Maximum 2835 °F (1557 °C) 

Ave. Specific Energy : 3.8 MM BTU/ston (952.2 kcal/kg) 

70th Conference on Glass Problems · 35 
Operational Experience of an Oxy-Fuel Fired Glass Melter 

. Burners: Wide Flame (6), opposed 

Crown Material: Low-Lime Silica (0.8% Ca.O) 

Average ofHHV of natural gas and electnc boost over furnace campaign 

T ablc3. ST 1 tea refractory_prQgcrtics 

Commercial Silica 

Low Flux Factor Low Lime Silica 

Bulk Densitv, kg/m' 1794 1875 

% ADoaront Porosity 23.0 t8.0 

Modulus of Rupture 

At2l°C,MPa 6.2 4.3 

Reheat Test at tsoo•c 

% Linear Change +0.2 +0.2 

Chemical Analysis 

Silica 95.9 98.4 

Alumina 0.2 0.2 

lro110xide 0.6 0.4 

Lime 3.0 0.8 

4/ka/ies Tr 0.1 

Others 0.2 0.1 

Silica Phases 

Ouartz <1 <1 

Crist + Trid. 75+ 75+ 

Amol·nhous N.D. N.D. 

The combustion system was also designed to minimize refractory con·osion. The furnace 

utilized six (6) Prax:air Wide Flame burners in an opposed arrangement. The burners were specifically 

designed to minimize gas momennuu near the melt surface while maintaining good heat transfer 

characteristics and low NOx emi. sions. With this combination of materials and combustion system, 

Grnpo Pavisa hoped to maintain prop~:r fumace life while optimizing operating costs. 

The early results (frrst 45 months) of operation of this furnace have been previously described 

and the construction details outlined [10]. For bu ine 's reasons, Grnpo Pavi a made the decision to 

end the furnace campaign and complete a cold repair in April 2009 aficr 9 years and 4 month of 

operation . . A summary of thi furnace campaign is pre cntcd below. 

RESULTS: EXPERIENCE DURING SERVICE LIFE 

FURNACE OPERATING SUMMARY 

Furnace 14 started operation in late January 2000 and concluded operation in April of 2009, 

making approximately 440,000 ton of glass during the campaign. Figure I illu trates the pull rate and 

cullet ratio of the furnace over a 110 month period leading up to the hutdO\Yll and sub equent cold 

repair. Over the ftrst 60 months of operation production gradually increased to the nominal capacity 

of ISO tid. ear the end of the campaign the pull mte exceeded the nominal capacity reaching a 

36 · 70th Conference on Glass Problems 

Operational Experience of an Oxy-Fuel Fired Glass Melter 

maximum of 162 t/d and production remained hi h until th ft 

furnace also varied significantly over the fu gl'fi . le rmace shutd~wn: The cullet ratio of the mace 1 e, mam y due to the avallabt!Jty of external cullet. 

180 ----- 100 

90 

140 80 

! 120 70 

E. 100 60 l ~ 0 

"' 0:: 80 ,..,..., 60 ~ :; 

" .P"' 2 a. 60 '""\/', I 40 :; 

u (I I 30 40 \I 

• 20 20 

10 

0 

0 20 40 60 80 100 

Months of Operation 

Figure I. Furnace 14 Pull Rate and Cullet Ratio versus Month of Operation 

Furnace operating conditions were ad· t d d · h . . the production lines and to res 0 ~us e unng t e campaign to satJsfY requirements from 

electric boost during times of]~:! ~ub:~~~~u~anables changes. This included a general increase in 

Figure 2 illu tratcs the energy input · ft 1 d . boost was used -omewhat sporadica~:; u:~o~~l ~~~:c~c boost over .the life of the fumaee. The electric 

~~~dthe L;;n~~~~~t ~~:a~~n~h: ~~~:c~~~o:~~n~ . watter t:;e e~:~;~~!:; :~s~~:~~~n c;:~:g ~~tfu~~~i~~ electrode area of the tank 10 avoid 1 ys em. ot work_ also had to be perforrned in the 

rate for the combustion system hal~~ b leaks and Juarrullee contmued operability. Thus, the firing 

temperatures (up to 2900 oF or 1595 •c). e mcrease to compensate which resulted in higher crown 

70th Conference on Glass Problems . 37 
Operational Experience of an Oxy-Fuel Fired Glass Melter 

40.0 

35.0 

~ 30.0 

~ 25.0 

:::;; 

!. 20.0 

~ [! 15.0 

~ 

... 10.0 

5.0 

20 40 8l) 

Months of Operation 

1-· •- Natural Gas --e- Electric Boost I 

Eloctrode 

Folluro 

100 

1000 

900 

BllO 

700 §' 

600 ;!. 

1 500 Ill 

u 

400 :; 

u 

300 w 

200 

100 

Figure 2. Flll1lace 14 Fuel Energy Input and Electric Boost versus Month of Operation 

Analysis of the energy efficiency of the furnace over time requires normalization to 

compensate for changes in pull rate, cullet ratio and electric boosting. 

Figure 3 illustrates the normalized specific energy consumption in MMBTU/short ton of glass and 

melting temperature versus the months of operation of the furnace. The normalization of the specific 

energy was based on a constant pull rate of !52 lid 50% of cutlet ratio and no electric boosting. It was 

also necessary to correct for an inc.remcnt observed in the glass temperatures at higher loads. After 

applying all COITection an increase of around 7% in the specific energy consumption over the course 

of the furnace life wa obsorved (or 0.77 %/y on linear bases). A careful review of the historic 

operating data of furnace 14 has revealed that most of the increment on the energy consumption is due 

to an increased amount of parasitic air leakages going into the furnace, which was calculated to be 

about 22% of the flue gas flow rate from the fuel and oxygen flow rates and the flue gas 02 

concentration. Parasitic air leakages are typically less than 5 tolO% of the flue gas flow rate for a new 

furnace or an old furnace with extensive sealing of open joints. If the specific energy consumption 

were corrected for the increment of parasitic air, the increase in the specific fuel consumption would be 

less than 1-2%, which would correspond to the furnace aging loss attributable to the increased wall 

heat losses. 

38 70th Conference on Glass Problems 

Operational Experience of an Oxy-Fuel Fired Glass Melter 

6.00 

5.50 

c 

~ iii 5.00 :::;; 

!. 

~ 4.50 l; 

c 

w 

u 

!E 4.00 u 

~ en 

3.50 

20 40 60 

Months 

80 100 

1,600 

1.550 

e 

~ 

1,500 1; 

~ E 

~ 

Figure 3. Furnace 14 Specific Energy Consumption and Melting Temperatures versus Month of Operatwn. 

LOW LIME SILICA CROWN RESULTS 

The plant expectations for using the low-lime silictt brick as crown material were to h crown that last a full · · 1 • • • ave a . . campa1gn wnt mmnnal detertoration and few to no hot repairs. Based on the 

opetratmg expderd1ence from lhe full furnace campaign, the performunce of the new refractory material me or excec e these ex pee tat' o B · k 1 d · · · · . . h 1 n · nc s towc mtntmum detenorahon after more than 9 years of operatiOn Wit oxy-fuel tiring. 

70th Conference on Glass Problems 39 
Operational Experience of an Oxy-Fuel Fired Glass Melter 

fl three different zones. Zon A wa Figure 4 illustrates three brick ample t~kcn from the crown ~om d Z ne C was ncar the gin 

in the vicinity of the batch charge area Zone B was near the ot spot a~ ~ . al brick height of Idischarge point. The dotted line near the top of the fi~ure r~presents It e on~~n f b vtWecn 1-1.3 

inches. Examining the men ured height of the remauung bnck rcven corroston o r. e\,liS level of 

inches (2.5-3.3 em) of material, or a matenal los:: rnte of about 2.7to 3.5 mm/yea 

material loss (or less) was consistently observed throughout the c1own. 

Original 

Brick Height 

Zone C- Zone A- Zone B- Hot Spot Glass Discharge Area 

Batch Charge Area d C 

Figure 4. Crown Brick Samples taken from 3 Zones: A- Batch Charging Areas, B- Hot Spot, an -

Glass Discharge Area. 

The temperature of the fumace crown was monitored throughout the campaign, and the profile · d · 1 U rate Figure 5 illustrate the average crown along the length of the furnace vane Will pu ·. II l As might be expected higher 

temperature prolile along the length of the furnace at varymg p~ ~les . e~dting condition Ul~ crown 

pull rates resulted. in higher crownC tcnhl?C:~~rc ld o~:~:: ~~C:H a?·orption itlto a caldium silicate 

temperature was htghcr than 1450 , w. 1c s . ou mm1 

slag (3]. 

1560 

(.) 1540 -1---------'+ 

1I 

1§ " 1520 -1-----77'-

"' c. 

~ 1500 +----~----------------------1 

1480 1---------------------

1460 -!---------·~·--· -··-- ·-- ~---- 0 _ _ 4...,5-0---1500 

0 50 100 150 200 250 300 350 

Distance from Back Wall, in 

-+--166 TP-0 - . .:-;-53TPD- M4TPD - --12s r~l 

. · f· tl Back Wall at Various Pull Figure 5. Average Crown Temperature as a Funcuon ofD1stance 10m le 

Rates 

40 70th Conference on Glass Problems 

Operational Experience of an Oxy-Fuel Fired Glass Melter 

Maintenance of the crown was not a major issue during the course of the campaign and no 

repairs were required associated with the performance of the low lime brick. The only problem 

reported with the crown was in the expansion joint zones. Fumace 14 had two expansion joint zones, 

one close to the charging end and the other close to the refining area. Immediately after the furnace 

startup, sealing problems were detected at the expansion joints. However, at that time, the magnitude 

of the fumace gas leakage was not considered impo1tant and the issue was not immediately corrected. 

After a period of operation, alkali vapors started to penetrate the joint, absorb into a slag layer 

attacking the crown and causing damage to tlle nearby bricks. Hot repairs had to be made in these areas 

to avoid losing parts of the superstructure. No additional hot work was required after making this 

repair. Figure 6 and Figure 7 show images of the crown after cooling the furnace at the end of the 

campaign. The images illustrate consistent wear throughout the crown, and no significant points of 

deterioration. 

The operations team at Grupo Pavisa felt that the furnace could have operated for at least 2 

additional years under these conditions. However, the decision to rebuild the furnace after only 9+ 

years of operation was primarily due to market conditions and a desire to modify the fumace to enable 

the production of different product lines. With the cmTent global economic downturn, this was an 

ideal time to take a fum ace outage. Also, the tank refractory contained higher levels of chrome than 

desired for color requirements of ce11ain product lines. Finally, the loss of electric boost resulted in an 

increase in furnace temperature due to increased gas firing, and the team felt it was important to restore 

electric boost capacity to properly balance furnace energy input. It should be noted, however, that 

even though a 40-50 oc increase in crown temperature occmTed upon loss of electrodes, no deleterious 

effects were observed on the crown or other pa11s of the superstmcture. 

Figme 6. Fumace 14 Crown During Demolition- View 1 

70th Conference on Glass Problems 41 
Operational Experience of an Oxy-Fuel Fired Glass Metter 

BURNER 

Grupo Pavisa fumace 14 i equipped with ix of Praxair's first gene~a ion Wide Fl~me mers 

installed in an oppo ed an·angement. The c burners were designed to be a unplc and flextble ptece of 

combustion equipment and Grupo Pavisa selected this bumer due to its unique attribute . The b~ rner generates a wide name pattern that covers up to 200% more of the glass surface than convenuonal 

oxy-fuel burners. In addition, the large, low velocity, luminous flame allows the bumer to transfer heat 

more efficiently and prevent hot pot on the glass surface. uffieicntly high burner e lcvauon together 

with low flame velocities and low momentum minimize alka li volatilization !Tom the gla melt 

resulting in less furnace upersiructure cotTosion, longer furnace life, and reduce? . p~culatc formation. Figure 8 shows a schematic of the first generation burner. In order to mtllltntze NOx 

formation, oxygen is staged through a eparate set of nozzles under the fuel nozzle . The burners were 

fired between 2.5 to 6.5 MMBtulhr (0. 75 to 1.9 MW). 

· .. 

~ 1 o~~ 

.. Jj ... .. ~101>fl . . $ 0 

HI [''~'JAJ 1: I ©•tt . ' . . 

Figure 8. Praxair's Wide Flame Burner First Generation (From left to right: back, top & side and front) 

A second generation of Wide Flame Burner was recently introd ce~ to fu rther rnprove burner 

performance and to minimize maintenance requirements. Th new gcnerauon burner :o~o~a es an 

evolution in Dilute Oxygen Combustion technology, includiJ1g deeply staged oxygen mJe~tlon and 

minimized gas ,,clocities near the burner face. The result is a robust and durable burner wtth all _tlte 

positive characteri tics of the previou gencmtion a well as the benefit of advanced flame dynamtcs. 

Figure 9 illustrates a schematic view of the second generation burner. 

42 · 70th Conference on Glass Problems 

Operational Experience of an Oxy-Fuel Fired Glass Melter 

Figure 9. Praxair's Wide Flame Burner (Second Generation) 

Grupo Pavisa tested two of the ne\ generation burners in position I (Right and Left) of its 

furnace 14 from July 2008 to th furnace shut down in April 2009. Total evaluation time wa 

appro imately 9 m011ths (37 weeks). During this time the burners were fired continuously at about 5 

M I.Btulhr (1.5 MW) without needing any maintenance. Figure 10 illustmtes the installed view 

outstde the furnace (left) and the burner in operation from the interior view of the fumacc L!U'ough a 

viewport (right). 

Figure 10. Wide Flame Burner Second Generation Prototype at Grupo Pavisa Furnace 14. 

The flame shape and heat transfer characteristics were consistent with the first generation 

design, making substitution a seamless process. Both burners were carefully inspected after the shut 

down. ~he re ul~s of the inspection revealed that the burners were in excellent condition wi.tll no ign 

of detenoratton m the burner blocks or other parts. These results indicate that the bumcrs hould be 

n~le to operate without mnintenance for a much longer period of time. Grupo Pavisa was very pleased 

\\'II? th . perfom1ance of the new burner design and plans to replace the ex isting burners with the new 

de 1g~ m the near furore. Anotl1er test of the next generation burner is cul1'entl y underway on a 

coma mer gla furnace at another site, with similar ob ervation ru1d re ults to date. . 

CONCLUSION 

In thi paper, the operational experience of an oxy-fuel container glass furnace has been 

~re ented i.ncluding i. ues around material elect.ion, construction practice, and operational practice . 

. he opc_rnu.ng ~a'."patgn of Furnace 14 at Grupo Pavisa demonstrates the potential for a new type of 

sthca bnck to hum crown corro ion. This low-lime silica brick contained relatively tow level ofCaO 

(-0.8%) while maintaining the general physical and thern1odynamic attributes of standard silica brick. 

Th: furna ce also untilized low-momentum Wide Flame burners to reduce volatilization off the melt 

whtle mai t · · d h " ' n ammg goo eat trans,er and emissions characteristics. Implementation of these new 

70th Conference on Glass Problems · 43 
(perience of an oxy-Fuel Fired Glass Melter 

minimal crown deterioration over the course of 

:ens (TNO) and Enrique Solorzano (PAVISA) 

~r. 

lmic Analysis of Silica Refractory Corrosion in 

ochemical Society. 148(2) 859, 200l. . . 

i corrosion of uperstructure refractory bncks m 

a/ Symposium on Glass Problem', eptember 4-

ms of alkali vapours with silica based refractory 

;msfer, Glass Technology, 46(6) 371, 2005. 

Jmeri~al modeling of alkali volatization in glass 

·ed furnace design.' Proceedings of the 4'" 

tsion & Proces lng of Glass, 1995, Wiirzburg, 

•lass melting technology - Experience, evolution 

~I Commission on Glass, September 21-25, 2003, 

d container glass furnace with silica crown- 14 

on Glass Problems, Ed. C. H. Drummond IlL 

3-11. 

:eadrick, R.E. Moore. J.G. Hemrick, and J.M,; 

1der oxyfuel environment." Proceeding of the 1 

tsion & Processing of Glas . July 27-3_1, 2003, 

-.P. Seward 10, H.A. Schaeffer. Westerville, OH: 

namic analysis of alumina refractory corrosion by 

lting furnaces," Journal of The E/ectrochemtcal 

and HE Wolfe "New silica refractory for lre, . . · Journal - A. T.I. V. Conference XV. Parma, Italy, 

M.A. Nelson. "A review of improved silica crown 

~ss melters." 641

h Conference on Glass Problems, 

merican Ceramic Society, 33-42, 2004. 

,nsional modeling of alkali volatilization/crown 

lnnual Meeting of the American Ceramic Soctety, 

Jnsiderations and modeling of the glass metter 

International Congress on Glass,Madrid, Spain, 

'Reduction of alkali volatilization and refractory 

•wtional Glass Journal - A.T.I. V. Conference XV. 

romise in service." The Glass Industry, 80(8), 23-

C'MON, LEVEL WITH ME 

Terry Berg 

Sr. Pr. Process Engineer 

CertainTeed Saint Gobain 

ABSTRACT 

There are many factors which affect glass level stability. Some of these include the type of charging 

system, the reliability and sensitivity of the level detector, the type of control logic loop and the 

stability of the process itself. This paper will only consider the various types glass level sensors and the 

pros and cons associated with each. A summary table is provided at the end. 

When it comes to sensing changes in glass level, there are many different methods available from 

which to choose. They can be broken down into two basic categories, i.e. contact and non-contact. The 

contact types are oscillating probes, static conductivity probes and bubble pressure tubes. The noncontact types include nuclear, pneumatic, laser and optical. They vary in cost of installation and 

operation, frequency and cost of maintenance and system requirements. Since the various processes 

and glass compositions used in the industry have different requirements, this paper will look at the 

advantages and drawbacks of several techniques with the aim of helping you with the selection 

process. This information was derived where ever possible from interviewing engineers who have 

hands-on experience with these pieces of equipment installed in their plants. YMMV! ( For nontexters, "Your mileage may vary") 

Oscillating Probes 

These are probably the most commonly used level sensing 

devices in use today and there are several different makes and 

installation methods. The one pictured here is installed directly 

into the forehearth through the breastwall. Some plants will have 

a separate alcove off to the side of the refiner or forehearth but 

the principle is the same. The oscillator moves a platinum-tipped 

probe down until contact with the glass is made. This completes 

an electric circuit telling the batch charger to speed up or slow 

down depending on the glass level and tells the oscillator to raise 

the probe to start another cycle. This process is very 

straightforward but not without its problems. 

The unit shown here has a ceramic tube having a 

platinum tip. During a recent upset, the temperature in this 

section of the forehearth went up 200°F and the tube began 

droop. The batch charger interpreted this as a high level reading 

and stopped charging. The level dropped a couple of inches 

before the effects were seen in the process downstream. 

Fortunately, this was corrected before the electrodes became exposed. The same unit in the sister plant 

has a water-cooled probe which has never drooped. 

If the temperature near the probe goes down and the glas becomes tncky, the probe will start to 

pull "stringers" or get a build up on it and again the batch charger will think the glass level i high and 

slow down or stop. To prevent this, the temperature in this zone hould be monitored closely and the 

probe should be visually inspected periodically to make sure th!ll no build up is ocomring. 

45 
70th Conference 

on Glass Problems 

A Collection of Papers Presented at the 

70th Conference on Glass Problems 

The Ohio State University, Columbus, Ohio 

October 11-12, 2009 

Edited by 

Charles H. Drummond, Ill 

The 

American 

Society~~ 

Ceramic A'~ 

~WILEY 

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ISBN 978-0-470-64415-7 (special edition) 

Printed in the United States of Ametica. 

10 9 8 7 6 5 4 3 2 I 

Contents 

Foreword 

Preface 

Acknowledgments 

GLASS MELTING 

Rapid Refining of Submerged Combustion Melter Product Glass 

David Rue, Walter Kunc, John Wagner, Bruno Purnode, and Aaron Huber 

Modeling the Quality of Glass Melting Processes . . . Adriaan Lankhorst, Andries Habraken, Mathi Rongen, Ph1l1p S1mons, and Ruud 

Beerkens 

Process Optimization of the Glass Forming Process by Advanced 

3D Forming Models 

Erik Muijsenberg 

Operational Experience of an Oxy-Fuel Fired Glass Melter Using an 

Improved Silica Crown and Wide Flame Burners . Alonso Gonzalez, Wladimir Sarmiento-Darkin, John T. Brown, Len Switzer, 

Euan Evenson, Sho Kobayashi, and Cuauhtemoc Lagos 

C'mon, Level with Me 

Terry Berg 

THE FUTURE OF THE GLASS INDUSTRY AND ENVIRONMENTAL 

REGULATIONS 

How Big is My Carbon Footprint? 

Todd J. Seifried, Christopher J. Hoyle, and Douglas H. Davis 

ix 

xi 

xlii 

3 

11 

21 

33 

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53 

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