Unit Melter

Crystal glasses were traditionally melted in pot furnaces, but nowadays small continuous tank furnaces are used. Lead glasses are conveniently melted in Unit-Melter furnaces, lead-free glasses in all-electric furnaces with a daily output of several tons (cf. Fig. 102). Machine forming is being gradually introduced even for these types of glass. 

FIG. 99. Unit-Melter furnace (J) ports with indicated flame direction, (2) and (3) coupled ports. 

Unit melter. For large glass quantities up to a maximum of 1001 in continuous operation, short glass tanks (2 to 3 m wide, 10 to 12 m long) are used, which enable a rapid change from one glass type to another. 

Due to the very low energy efficiency and the use of individual burners, the air/fuel unit melters are very amenable to oxygen-enhanced combustion techniques, including supplemental oxy/fuel boosting, premixed oxygen enrichment, and full... 

Conversion to full oxy/fuel also provides an opportunity for production increase. The change in pull rate achieved with an oxy/fuel furnace, in comparison with an air/fuel furnace, varies depending on furnace type. Pull rate increases of up to 60% have been observed for unit melters. Cross-fired regenerative furnaces have seen increases as little as 10%. End-fired regenerative furnaces converted to oxy/fuel increase pull capacity by 20%. Recuperative melters typically achieve a 30% pull rate increase. 

Three types of furnace are in use regenerative, recuperative and unit melters. The last, while cheaper to install and easier to maintain, with shorter downtime on colour changes, is more expensive on fuel. Regenerative furnaces are in the majority. Several types of container glass are generally recognised ... 

For various reasons, including financial ones, the United States was slower than Japan and Europe to install continuous slab casters for the production of sheet. Electric melters cast billets continuously from about 1975 onward. Casting was done cmdely at first but the sophistication increased rapidly, culminating in the operation of a thin-slab caster at one of Nucor s plants. This opened up another avenue of attack on sheet markets, once the province of integrated mills. 

The ice crystals must be separated from the saline solution surrounding them, and washed with freshwater. This is accompHshed by a downward countercurrent flow of a small amount of freshwater through the ice slurry in the washer—melter unit. Keeping that unit at about 0°C limits the needed pressure rise by the compressor to only about 130—260 Pa, and an auxiUary refrigerator is often used to compensate for heat gains from the ambient and the compression. 

LOCAT units can be used for tail-gas clean-up from chemical or physical solvent processes. They can also be used directly as a gas sweetening unit by separating the absorber/oxidizer into two vessels. The regenerated solution is pumped to a high-pres.sure absorber to contact the gas. A light slurry of rich solution comes off the bottom of the absorber and flows to an atmospheric oxidizer tank where it is regenerated. A dense slurry is pumped off the base of the oxidizer to the melter and sulfur separator. 

Arc melter remediation technology derives from the steel industry. Today, half of all steel in the United States is produced in an arc melter. EPI DC arc melters are offered for commercial design, sale, and installation by Svedala Pyro Systems. 

According to researchers, arc melter systems can achieve higher temperatures than joule-heated vitrification units. Arc melter systems have a simphfied design compared to arc plasma systems, which require water to cool the metal electrodes. 

In the second plot, the energy required by the primary compressor is shown to be sensitive to the pressure in the evaporator-freezer and condenser-melter. Because both the evaporation and condensation are by direct contact of the refrigerant with water or ice, the opportunity exists for realistic achievement of a low over-all driving force. Experimentally, the evaporation has been found to occur so rapidly that a rate measurement has not been practical. The melting of the ice is more of a problem because the condensate film is a heat transfer barrier. However, the barrier is a fluid and not a stationary wall as in a distillation unit, wherein steam is condensed against water or boiling water. 

A commercial-scale field foaming unit and melter-mixers have been built and demonstrated. Both were designed to operate at field temperatures as low as —50°F chill factor, which is considered about the coldest practical temperature for carrying out construction work in the arctic. Operation of the overall Furcoat system is illustrated in the Appendix. 

Kinetics were determined using the laboratory pyrolysis unit with the melter/feed vessel temperature set at about 325°C and the pump temperature set at about 300°C. By varying the speed on the gear pump, residence times in the furnace were set. Residence times used ranged from 1 to 12 min, yielding a HDPE throughput of about 100 to 1200 g/h. 

In-can melting is the simplest choice as far as the melting device is concerned. No replacement or repair of a melter is necessary, and the potentially troublesome melt drain is avoided. On the other hand, the capacity of a canister is limited compared to a melter. Therefore parallel melting units are required with a complex technique to divert the feed from one canister to another. 

U.S. vitrification processes. In the United States [M2] development efforts are focused on two processes, a spray-calcine/in-can melting process and a ceramic melter process that may be... 

The bottom has a freezing unit and the top has a heating unit, or melter. Crystals are primarily formed at the bottom, but some are nucleated at the walls of the columns and are removed by the scraping conveyer. The column is operated with a reflux. 

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