Glass melting fining

Used primarily to reduce the Fe202 to FeO to give the characteristic amber color, although the redox state of the glass melt also influences the fining... 

Day tank furnaces with melting tanks for 1 to 5 t glass are fired with gas or oil and are named after the work cycle length which for loading, melting, fining and discharge is 24 hours. 

The melt remains in the furnace for several days. A satisfactory yield during the subsequent drawing process requires that the fining of the glass melt be as good as possible i.e. very homogeneous and free from nonmolten raw materials and gas bubbles. This is achieved by air injection through one or more rows of platinum tubes at the... 

The fined glass melts can be converted into fibers by three processes by direct melting, marble melting and rod drawing. 

Many researchers have used fine wire thermocouples (T/Cs), with and without coatings. Costa et al. [77] used a bare 300 pm diameter wire uncoated Pt/Ptl3%Rh thermocouple to measure gas temperatures inside an industrial glass-melting furnace. Mital et al. [78] used three different diameter (76,125, and 200 pm) fine wire Type R thermocouples to measure the gas temperature inside porous ceramic radiant burners by extrapolating the measurements to zero diameter. 

Sample Preparation. Two methods were used to produce sodium silicate glass samples for this study. The primary method used conventional glass melting techniques to produce compositions ranging from 12 to 21 wt. % Na20. Batch ingredients, African sand, sodiiam carbonate, and sodium nitrate, were melted at 1600 C for six hours in platinum crucibles, poured into patties and fine ground into 1 1/2" diameter discs with thickness of one to four millimeters. These anhydrous discs were fully hydrated in a one cubic foot autoclave under saturated steam conditions and stored in controlled relative hiimidity desiccators at room temperature. 

Why is there an optimum size for the sand used in glass melting, i.e., what problems occur if the sand is (a) too coarse, or (b) too fine ... 

The experimental set up is also equipped with a high resolution CCD camera. Pictures of the batch/glass melt in the vitreous silica crucible are taken at regular intervals. These images can be used for, for example, detailed observation of the reactions taking place, onset of melting phase formation, measurement of foam amount, and determination of the fining onset... 

R. G. C. Fining of Glass Melts What we Know abtmiFining Processes Today. 

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