Glass Melting Technology

1 Glass MeltingTechnologyPerfect Solutions for the Glass Industry2 Air Preheatingpage 5 Regenerative End-fired Furnacespage 6 Regenerative Cross-fired Furnacespage 7 Recuperative Air Preheating page 8 Recuperative End-fired Furnaces page 10 Recuperative Side-fired Furnaces page 11 LoNOx Melter page 12 FlexMelter page 13 Boro-Oxy-Melter page 14 VSM All-electric Furnacepage 15 Barrier Wall SDR SORG Deep Refiner Refining Bankpage 16 Booster page 17 Bubbler CONTI-DRAIN page 18 Cullet Preheating NOxReduction page 19 Individual Burner Controlpage 20 Oxy-Fuel Heatingpage 21 Batch Charging Technologypage 22 SORG Furnaces for Special Glassespage 243 customers benefit fromthis success, which is foundedon technical competence, flexi-bility, reliability and, above all, anenormous wealth of experience.

2 SORG are able to supply manydifferent types and sizes of fur-nace for the widest range ofproduction and site Glass furnaces with a meltingcapacity of 700 t/24 h or moreare an integral part of the pro-gramme, as is the smallest opalglass furnace for lighting ware,with a capacity of 1 t/24 only soda-lime Glass , butalso lead-free crystal, full leadcrystal, opal and borosilicateglasses of differing compositionsand water Glass are melted inSORG articlesproduced on our installationscover almost the completerange of glassware commonlyproduced tableware, lightingware, tubing, insulators, fibres,pellets, flat Glass , rolled plate ,water Glass and, of course, alltypes of has long been renownedfor furnace development. Thisprogramme has led to significantimprovements in conventionalfurnace Technology and to thedevelopment of completely newfurnace brochure contains informationabout conventional furnaces,such as regenerative end-firedfurnaces, and also innovativeconcepts and various supple-mentary systems all suppliedby SORG.

3 At Home in the World of Glass the validity of this statementis demonstrated by over 250 SORG designed furnaces inoperation in more than 60countries throughout Air PreheatingThe regenerators, which forman intermediate storage medi-um, consist of two chambers,each of which is filled with anetwork of refractories, referredto as the packing. The wastegases from the furnace are pas-sed through one of the cham-bers, and the refractories in thechamber are heated up. Thecombustion air enters the furnacethrough the other a certain period of time theflows of air and waste gases arereversed. The combustion air nowflows through the hot chamberand is heated by heat transferfrom the refractories, whilst thewaste gases pass through theother chamber and heat therefractories in this chamber chambers are nor-mally vertical constructions inwhich the waste gases passdownwards, whilst the com-bustion air travels upwards.

4 Onmost furnaces single pass rege-nerators are used where thegases flow in one directionthrough one chamber. However,where there is insufficient cellardepth available for the installationof the necessary packing volumemultiple-pass regenerators canbe used. There are various forms of rege-nerator packing, but only two arenow widely used. Both designsutilise specially shaped blocks,cross-shapes for the cruciformsystem, and square sectiontube shapes for the chimneyblock system. Regenerative furnaces can bedivided into two basic types onthe basis of the location of theburner and the flame path: end-fired furnaces cross-fired furnaces5 Advantages High preheat temperaturesof up to approx. 1350 C possible Excellent energy con-sumption modern fossil-fired furnacesthe heat contained in the wastegases leaving the furnace isused to preheat the combustionair, in order to produce higherflame temperatures and im-prove efficiency.

5 The air pre-heating system most commonlyused is the regenerator chimney blockpacking during constructionEnergy savings dependency onpreheated air temperature506070403020100200 400 600 800 1000 1200 1400 Energy saving %Combustion air temperature CAir factor = gas temperature 1600 C1500 C1400 C1200 C1000 C800 C600 C2000 Flame temperature C1000 Combustion air temperature factorCorrelation between flame andpreheated air temperatureEnd-fired Regenerative FurnacesThe raw materials enter the fur-nace through one or two dog-houses installed on the furnacesides, immediately next to therear wall. Very large furnaces of this typehave a Melting area of approxi-mately 150 m2, whilst small unitsof approximately 20 m2are alsoin operation. This type of furnace has twoburner ports, located side byside in the furnace rear wall, andthe regenerators are situatedbehind the furnace.

6 Each port isequipped with 2 4 burners,depending on the size of flame travels forwards fromthe burner port, turns through180 and exits through the secondburner port. This creates a flameand waste gas path in the shapeof a horizontal U . As a resultthe combustion gases in thefurnace have a relatively longresidence time, which producesgood energy Very flexible furnace type Lower construction coststhan with cross-fired furnaces Lower energy consumptionthan a cross-fired applications Glass type: Soda-lime glassTypical products: containers rolled plateMelting capacities: 20 450 t/24 h100 m2regenerative end-fired furnacefor containersCross-fired Regenerative FurnacesThe burner ports are situatedalong the furnace side walls,normally covering almost thecomplete length. The number of ports depends onthe size of the furnace and usuallylies within the range 3 5.

7 Eachport is provided with 2 4 burners,according to the furnace size. The flame travels from one sideof the furnace to the other andthe waste gases are exhaustedexactly opposite the entry burnerport. The maximum flame lengthavailable is therefore determinedby the furnace two regenerator chambersare located on the sides of thefurnace and, in most cases, theyare almost as long as the this type of furnace theregenerator chamber suppliesseveral burner ports. Theair/gas ratio of the individualburner ports can only be con-trolled accurately if the regene-rator chambers are split intosub-chambers to accommodatethe number of burner can also be built for Melting capacities > 500 t/24 single doghouse is situatedon the furnace rear wall and thebatch is usually charged overalmost the complete tank a result of the greater numberof ports and larger regeneratorchambers, the heat loss area isgreater than with comparableend-fired furnaces.

8 Furnaces ofthis type smaller than approxi-mately 70 m2are used only rarely. Typical applications Glass type: Soda-lime glassTypical products: containers float Glass rolled plateMelting capacities: 200 800+ t/24 h Recuperatively preheated com-bustion air provides stable heatingwithout the flame/waste gas pathreversal that is necessary withregenerative systems. However,there is the disadvantage thatthe air preheat temperatures arelower than with recuperative furnaces forglass Melting utilise steel recu-perators. These are alwaysinstalled vertically, whereby thewaste gas flows either upwardsor downwards. Two basic types of steel recuperator are used: double shell recuperator tube cage recuperator8 Advantages stable flame path without reversal lower investment than regenerators with part load energy consumption increases more slowly than with regenerative of energy consumptionof a regenerative and a recuperativefurnace at part loadIn the Glass industry recup-erators are used to preheatcombustion air.

9 The hot wastegases and the cold combustionair pass throughparallel butseparate channels and heattransfer takes place throughthe intermediate wall. Recuperative Air PreheatingRecuperative Air PreheatingDouble shell recuperatorThis type of recuperator consistsof two concentric high tempera-ture resistant steel tubes of similardiameter, so that a narrow annularslit is formed between the twotubes. The hot waste gasespass through the inner tube,whilst the combustion air passesthrough the annular slit. The airmay be passed in the samebasic direction as the wastegases (parallel flow) or in theopposite direction (counterflow).Single modules of this type canbe used alone, or they can beplaced one after another to forma complete unit. 9 tube cage recuperatorIn a tube cage recuperator thecombustion air is led through alarge number of individual smalldiameter steel tubes arranged ina ring around the inner circum-ference of a large diameter outertube, through which the wastegases flow.

10 The outer tube is madeof steel, lined with refractorymaterial. The small diameter air tubes aresuspended from the top andsealed with refractory materialat the bottom in such a waythat the tubes are free to expand. This type of recuperator cangive air preheat temperatures ofup to 750 C. They are usuallyinstalled on larger furnaces. A double shell recuperator maybe added downstream of thetube cage unit to form a com-plete aggregate. Conventional recuperative fur-naces can be divided into twotypes on the basis of the locati-on of the burner and the flamepath: end-fired furnaces side-fired furnacesTube cage recuperatorDouble shell recuperators arecapable of giving a typical airpreheat temperature within therange 450 650 C. The majorityof these units are used for smallfurnaces up to a Melting capacityof approximately 50 t/24 h. End-fired Recuperative FurnacesThere are several installationarrangements for burners andthe recuperator in end-firedrecuperative furnaces, but oneparticular method has proved tobe the most beneficial.