Cold blast cupola furnace

Figure 2.9 Schematic outline and miniature model of a (cold blast) cupola furnace [44, ETSU, 1993], [237, HUT, 2003]...

The data show that the average, the standard deviation and the range of values are similar for both cold blast and hot blast furnaces. The median value for hot blast is lower than for cold blast furnaces. This confirms the statement from [224, Helber, et al., 2000] that there is no statistical difference between dioxin emissions for hot and cold blast cupola furnaces. The high standard deviation shows that the data should be interpreted on a plant-by-plant basis rather than on an averaged basis. 

The thermal efficiency of the cold blast cupola furnace can be improved by the installation of a secondary row of tuyeres. These provide extra oxygen above the combustion zone, which induces the oxidation of the CO in the combustion gases, the CO being formed by the endothermic reduction of CO2 by C (coke). This technique liberates the latent heat of the combustion gases, thus improving the thermal efficiency of the cupola. 

The effect and use of the oxygas burner depends on the cupola concerned. In cold blast cupola furnaces, the technique is used to ensure easy restarts or to reduce the proportion of coke. In hot blast operation, the technique is used to increase the furnace capacity without modifying the melting bed. The replacement of part of the coke with CH4 results in a reduction in flue-gas voliune. This is used as a means of increasing the furnace capacity, without over-saturating the installed flue-gas cleaning system. 

Table 4.36 Operational data of cold blast cupola furnaces with a bag filter for dust abatement data taken from [43, Batz, 1996] and [202, TWG, 2002], [225, TWG, 2003]...

HBI has been successfully melted in cupolas (hot or cold blast), induction furnaces (coreless or channel), and electric arc furnaces. It can be a valuable charge material for ductile and malleable irons as well as steel. It is of particular value in making ductile iron castings because of its very low residual element content. 

Due to its batch character, the rotary furnace provides an equal flexibility as the coreless induction furnace in the cast iron foundry. The investment costs however are lower. A 5 tonne furnace costs EUR 500000 - 600000, of which 30 % are for the exhaust system and dedusting. The rotary furnace is also a good alternative for the small-scale cold blast cupola, due to its higher flexibility and lower environmental costs. Rotary furnaces are used for melting volumes of 2 to 20 tonnes, with production capacities of 1 to 6 tonnes per hour. 

CBC Cold blast cupola HBC hot blast cupola RF rotary furnace IF induction furnace EAF electric arc furnace ... 

Cupola furnaces In cupola furnaces, a massive surplus of chlorine is always present from coke. Enough carbon is present from coke too, but an additional input of carbon may be needed the event of caused by poor scrap qualities. Under specific operational conditions, the conditions for dioxin formation could occur. Since de novo synthesis mainly occurs during cooling of the flue-gas, this applies to both hot blast and cold blast cupolas. In Table 3.34, the result of a statistical analysis of all the measurement data from Table 3.33 for CBC and HBC is given. Whereas Table 3.33 presents average values per plant, for Table 3.34 individual measurements were used to perform an overall analysis. 

In this section, techniques concerning melting practices and furnace operation will be discussed. These techniques may apply either to cold or hot blast operation, or to both. Flue-gas related techniques, such as post combustion and flue-gas cleaning, are discussed in Section 4.5.2. That section also discusses the conversion of cold blast to hot blast cupola furnaces. 

On the basis of the stated criteria, the replacement of the eupola by induction or rotary furnaces may be eonsideied. The selection of induction or rotary furnaces is given priority over cold blast cupolas for small foundries casting a variety of products in several European countries (e g. Austria, Belgium (Flanders)). 

The replacement of a cold blast cupola by an induction or rotary furnace is applicable imder the criteria stated above and upon major refurbishment of the installation. 

Installing post combustion on cold blast cupolas can be combined with a full retrofit to hot blast operation. In general, this choice is based on operational considerations. The characteristics of hot blast and long campaign furnaces are discussed in Section 2.4.1. 

For economic reasons, the application of post combustion has mainly been related to hot blast cupolas. However, recently, a post combustion system for cold blast furnaces, without the complexity of a hot blast installation, has also been developed. This system is currently in operation in France. In-shaff post combustion therefore applies to both hot blast and cold blast cupola operation. 

UK Environment Agency (2002). "DRAFT Process Guidance Note Hot and cold blast cupolas and rotary furnaces", UK Environment Agency, 163. 

Calculation of the heat balance results in the stated heat transfer efficiencies. The cold blast cupola shows an efficiency of <30 %. The application of oxygen or secondary air increases the efficiency to 37 - 40 %. The hot blast cupola shows a further increased efficiency, providing the furnace wall is refractory lined. In liningless operation, the efficiency drops below 40 %, which may be somewhat compensated for by adding oxygen. The cokeless cupola with inductive superheating results in a very high efficiency, close to 60 %. 

CTIF induction furnace, hot blast, cold blast, cokeless cupola Neumann cokeless, hot blast, cold blast cupola Nodular base cast iron... 

To y, almost all European hot blast cupolas inject oxygen through the tuyeres. For cold blast furnaces, the use of oxygen enrichment can be considered as the standard technique. In this case, enrichment of the blast supply is usually applied. The oxygen level of the oxidising air mixture is usually between 22 and 25 % (i.e. an enrichment of 1 % to 4 %). 

Due to the absence of cokes (and CO), no latent heat is lost from the cokeless furnace system. Full heat recuperation from the flue-gas occurs in the shaft. In duplex configurations (for example in conjunction with an induction furnace), efficiencies in the range of 40 to 60 % may be obtained. Thermal efficiencies for coke fired cupolas vary between 25 % (cold blast) and 45 % (hot blast, long campaign). 

The technique may be applied on both cold blast and hot blast cupolas in both new and existing installations. The advantages drawn from the application (increased flexibility, economical benefit, reduced flue-gas volume, increased capacity) will depend on the specific melting conditions of the installation under consideration. The technique has been reported to cause difficulties for controlling the process and also increases the complication of the furnace shell required. 

Units Melting device Cold blast cnpola Hot blast cnpola Cokeless cnpola Indnction furnace Hot blast cupola Cokeless cupola Induction furnace... 

The history of iron and steelmaking has been substantially influenced by the availability of oxidants for the various metallurgical processes. Iron making in North America dates back to the 1600s. The process utilized charcoal and local iron ores in a blast furnace that looked more like a modem cupola into which cold air was blown, powered by a bellows. The primary product was cast iron (containing 2 to 4% carbon). Steel (0.1 to 0.8% carbon) could only be made by a very low quality, labor-intensive process known as puddling. 

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