Refractory linings calculating

Primary air is usually defined by a percentage of the stoichiometric air calculated for the total amount of fuel. In the case of PF, it provides a transport air stream that can or can not be considered in the total amount of primary air. Since the very hot secondary air has to be entrained into the fuel-primary air jet, it can have an important impact on the fuel-oxidant macro-mixing. The flow patterns of the secondary stream are mainly determined by the design of cooler uptake and the kiln hood itself. The relationship between primary air jet momentum and secondary air velocity has a significant impact on the flame geometry as well as on the heat transfer to the material and refractory lining. 

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 %. 

Many furnace stacks are not only too tall but also too large. This may be because the steel shell of the stack often needs a protective refractory lining, which may be difficult to install in a small-diameter stack. Stack dimensions should be determined by calculation for each individual case. 

Calculate Skin Temperature for Refractory Lined Components... 

Ans. (b) (convection + radiation) = 4.426 W Gas Radiation and Convection to a Stack. A furnace discharges hot flue gas at 1000 K and 1 atm abs pressure containing 5% CO2 into a stack having an inside diameter of 0.50 m. The inside waOs of the refractory lining are at 900 K and the emissivity of the lining is 0.75. The convective heat-transfer coefficient of the gas has been estimated as 10 W/m K. Calculate the rate of heat transfer q A from the gas by radiation plus convection. 

Figure 8.9 Control volumes for bed heat transfer calculations (a) active layer (b) plug flow region and refractory lining.

Heat capacity values are required for nonstationary calculations of refractory linings and for the recalculation of thermal conductivity characteristics, obtained by stationary and nonstationary methods. 

Figure 23 Chondrite-normalized abundances of REEs in representative harzburgites from the Oman ophiolite (symbols—whole-rock analyses), compared with numerical experiments of partial melting performed with the Plate Model of Vemieres et al. (1997), after Godard et al. (2000) (reproduced by permission of Elsevier from Earth Planet. Set Lett. 2000, 180, 133-148). Top melting without (a) and with (b) melt infiltration. Model (a) simulates continuous melting (Langmuir et al., 1977 Johnson and Dick, 1992), whereas in model (b) the molten peridotites are percolated by a melt of fixed, N-MORB composition. Model (b) is, therefore, comparable to the open-system melting model of Ozawa and Shimizu (1995). The numbers indicate olivine proportions (in percent) in residual peridotites. Bolder lines indicate the REE patterns of the less refractory peridotites. In model (a), the most refractory peridotite (76% olivine) is produced after 21.1% melt extraction. In model (b), the ratio of infiltrated melt to peridotite increases with melting degree, from 0.02 to 0.19. Bottom modification of the calculated REE patterns residual peridotites due to the presence of equilibrium, trapped melt. Models (c) and (d) show the effect of trapped melt on the most refractory peridotites of models (a) and (b), respectively. Bolder lines indicate the composition of residual peridotites without trapped melt. Numbers indicate the proportion of trapped melt (in percent). Model parameters...

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