Regenerative furnaces

Fig. 13. Cross-fined regenerative furnace (a) end view (b) side ...

Development of molybdenum electrodes in the 1950s permitted the use of electrically assisted melting in regenerative furnaces (81). In the 1990s, approximately one-half of all regenerative tanks ate electrically boosted. Operating practice has shown that effective use of electricity near the back end of the furnace, where the batch is added, can reduce fossil fuel needs. This lowers surface temperature and reduces batch volatilisation. 

The Wulff process, which is in operation in Europe and South America with varying degrees of success, uses twin regenerative furnaces for cracking light petroleum fractions. The mixed gas product from the furnace is first combined with HC1, which reacts with the acetylene to form VCM. Ethylene then reacts with chlorine to form EDC. An EDC cracking process converts EDC to VCM and HC1, and HC1 is recycled to react with the acetylene in the mixed gas product. 

The first proposals for the employment of electrical heating in the production of phosphorus were made by Headman, Parker and Robinson.5 The simultaneous production of an alkali silicate by heating alkali phosphate, silica and carbon in a regenerative furnace was patented by Folie-Desjardins.6 In the Readman-Parker-Robinson process, as worked later, the phosphate, carbon and fluxes, previously heated to a high temperature, are introduced into the upper part of an electric furnace made of iron lined with refractory bricks and fitted with condensing pipes in its upper part. The gases pass through a series of copper condensers, the first of which contains hot water, the others cold water (or see p. 9). It has been found advisable to replace... 

These furnaces are good candidates for full oxy/fuel. Recuperative heat exchanger efficiencies are much lower than with regenerative furnaces, and therefore fuel savings can help to drive the conversion. Also, recuperative furnaces operate in a continuous and steady firing mode of operation similar to oxy/fuel furnaces. 

The Siemans furnace is the workhorse of the glass industry. Most flat glass and container glass are produced in this furnace type. Regenerative furnaces are also used in the production of TV products, tableware, lighting products, and sodium silicates. There are two common variants of the Siemans furnace the side-port regenerative melter, and the end-port regenerative melter. 

Side-port regenerative furnaces have ports located on the furnace side walls. Batch is charged into the furnace from the back wall. Figure 7.4 shows the layout of a... 

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. 

Proper use of oxygen enrichment can deliver many of the benefits of electric boost while decreasing melting cost. Typically, electric boost reduction is accomplished by either undershot enrichment or supplemental oxy/fuel burners. Undershot is more common on side-port regenerative furnaces, where installation of burners... 

Oxygen-based combustion delivers several control benefits that allow the operator to improve glass quality. Operators of regenerative furnaces are limited in tailoring the furnace profile by the flow patterns within the checkers. As noted previously, these flow patterns can change as the furnace ages. Oxy/fuel burners allow the... 

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