Furnace performance

There have been a number of attempts to model the lead blast furnace, notably Lumsden (1971), MadeUn, Sanchez and Rist (1990), as well as descriptions of the prcxrss chemistry by Willis (1980) and Oldwright and Miller (1936). 

In simple terms, the furnace shaft may be divided into fom zones. 

The tuyere zone is from the hearth upwards to a point just above the tuyeres. This is the high temperature zone in which carbon is oxidised by the air blast to CO2 at temperatiires above 1500°C. 

Liquid phases pass down through this zone over the hot coke bed and into the slag bath. Passage of molten lead over the coke bed should counter any potential oxidation on passage through the flame region. 

The height of Zone 1 has been indicated by Madelin, Sanchez and Rist (1990) at 400 mm above the tuyere level, but is likely to vary significantly and this should only be taken as an order of magnitude guide. 

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Mass and energy balances are used to evaluate blast furnace performance. Many companies now use sophisticated computeri2ed data acquisition and analysis systems to automatically gather the required data for daily calculation of the mass and heat balances. Typical mass and heat balances are shown in Figure 4 and Table 5, respectively. 

The contents of the cmcible are tapped through a Roy tapper (8,9) iato external settlers for layer separatioa. The tapper removes blast furnace products as they are made, giving a more uniform blast-furnace performance. A typical buUion analy2es in wt %, 1.0—2.5 Cu, 0.6—0.8 Fe, 0.7—1.1 As,... 

The most effective phosphoms production technology uses a submerged arc furnace. The submerged arc furnace performs three functions chemical reactor, heat-exchanger, and gas—soHd filter, respectively, each of which requires a significant amount of preparation for the soHd furnace feed materials. 

The use of sensors for surveillance of industrial combustion processes is state of the art. Especially optical sensors detect the existence of a flame. With decreasing furnace performance the amount of installed sensors declines. In residential appliances there are nearly no sensors installed because the costs for both, sensors and actuators, have to be balanced with the technical profit. The efforts for setting up combustion controls are very ambitious but in many cases not successful. First a distinction has to be made between sealed boilers and those that are open towards the room in which they are installed. The resulting controls cannot be interchanged between these two groups of appliances. 

Heat-transfer view -of furnace performance [FURNACES, FUEL-FIRED] (Vol 12)... 

These studies can best be carried out in a generalized computational framework applicable over a wide range of feedstocks and capable of accurate predictions of furnace performance. 

Figure 5-23 has been used to correlate furnace performance data for a multitude of industrial furnaces and combustors. Typical operational domains for a variety of fuel-fired industrial furnaces are summarized in Table 5-7. The WSCC approach (or speckled furnace model) is a classic contribution to furnace design methodology which was first due to Hottel [op. cit.]. The WSCC model provides a simple furnace design template which leads to a host of more complex furnace models. These models include an obvious extension to a tanks-in-series model as well as multizone models utilizing empirical cold-flow velocity patterns. For more information on practical furnace design models, reference is made to Hottel and Sarofim (op. cit., Chap. 14). Qualitative aspects of process equipment have been treated in some detail elsewhere (Baukal, C. E., ed., The JohnZink Combustion Handbook, CRC Press, Boca Raton, Fla., 2001). 

The properties which determine heat transfer through a deposit layer of given thickness are thermal conductivity, emissivity, and absorptivity. These properties vary with deposit temperature, thermal history, and chemical composition. Parametric studies and calculations for existing boilers were carried out to show the sensitivity of overall furnace performance, local temperature, and heat flux distributions to these properties in large p.f. fired furnaces. The property values used cover the range of recent experimental studies. Calculations for actual boilers were carried out with a comprehensive 3-D Monte Carlo type heat transfer model. Some predictions are compared to full-scale boiler measurements. The calculations show that the effective conduction coefficient (k/As)eff of wall deposits strongly influences furnace exit temperatures. 

The technology is also applied to retrofit furnaces. The furnaces performances are optimized by using Technip s proprietary software SPYRO. Depending on the regulations various, options of NO abatement are incorporated. 

The MPF was designed to handle some residual agent heels, but more degraded agent gels and sludges may require modiflcations in operating parameters to maintain furnace performance. 

Whether preheated air is desirable to improve furnace performance. The temperature of furnace exit gases can increase considerably. 

Does the estimation of these feedstock-dependent parameters from bench scale data allow a good estimation of commercial furnace performance We believe so. Test runs were carefully made on a cotrmercial furnace at several severity levels. The same gas oil feed was then cracked in the bench unit under a wide variety of conditions. Th feedstock-dependent parameters that relate methane yield and K0 were then determined by plotting measured methane yield vs. a function of K0, as shown in Figure V,... 

Details of blast furnace performance and operation are covered in Chapter 5. 

Grant, R M and Cunningham, B C, 1971. The relationship between sintering practice and lead blast furnace performance at Port Pirie, paper A7 1-1 (The Minerals, Metals and Materials Society - American Institute of Mining, Metallurgical and Petroleum Engineers Warrendale). 

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