Electric boosting

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 rate of flow in normal tank furnaces is of the order of meters per hour, with a maximum which can exceed lOmph at the surface. In front of the temperature maximum, the rate of surface flow in the longitudinal direction decreases by the elTect of natural convection, increasing again beyond the maximum. The maximum thus acts as a thermal barrier which may be made more effective and stabilized by gas bubbling or by electric boosting in particular with high-pull tanks (with a rapid throughput flow). 

FIG. 100. Container glass tank with electric boosting using six horizontal and four vertical electrodes (JV, Y, Z — connection of the source phases, / and 2 — independent heating circuits). 

The thermal efficiency of glass melting furnaces is relatively low, in particular that of pot furnaces. Values of 20—35% are reported for tank furnaces with classical heating (see below). Efforts to raise thermal efficiency led to experiments with shaft and rotary furnaces, with fluidized bed melting furnaces, etc. Only electric boosting and all electric glass furnaces have so far found wider practical application. 

Tank ovens have been improved further by supplementary electrical heating (electrical boosting) in the melting zone. The glass melt, due to its ionic conductivity, acts as the electrical resistance. Only molybdenum can be used as the... 

Electrical auxiliary healing (electrical boosting) in the melting zone improves the furnace heating ami reduces the evaporation losses... 

Reduced electricity costs by substituting combustion energy for electric boost energy ... 

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... 

Since substitution of top firing for electric boost also affects the temperature and flow patterns in the melt, CFD modeling can be used to evaluate changes in the flow and temperature patterns in the melt to assure no negative impact to product quality. 

Davies, R. M. "Heat Transfer Measurements on Electrically-Boosted Hames." 10th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, 755-66,1965. 

Advanced Expert Systems such as ESm have been used successfully for lumace control for two decades. Advantages include predictability as well as the chance to bias the energy balance to the cheaper media. In most geographical areas this means more fossil energy and less electrical boosting. This results in lower energy costs, and often less total energy consumption. 

In this car too, logical management of the two engines allows shifting from a merely electric powertrain with short interventions of the six cylinders to a traditional petrol propulsion with electric boosting during top acceleration. 

We have covered a quick review of the electric boosting and melting equipment and design from our prospective. There are certainly significantly more criteria for the choices of location, power requirements, and control. The particular application and customer desired benefits must be provided and closely studied to provide the most efficient and cost effective system. 

Furnace A" has been continuously operated since January 2012, also producing high quality, low iron, soda lime glass for tableware production, utilizing a carbon/sulfate fining system. Furnace A is a five (5) port cross-fired furnace, which is electrically boosted and utilizes one (1) burner per port, with independent flow control to each of these ports. The typical pull rates are between 160 and 230 US tpd. The cullet ratio is 18% to 28%. 

With batch preheat operation it might also be recommended to reduce application of electric boosting as much as possible. E-boost application might reduce CCb-emission on short term relevant to the facility only. Electric power generation produces about O I4m3/kWh (0,421 kg/kWh) CO2. A comparative analysis of the CO2- Emission for different operation conditions is given in the following table... 

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