Slags corrosion

Refractory flaws can also be caused by the frequency of temperature cycling, the rate of temperature drop, and the amount of temperature drop, which can lead to thermal shock or structural flaws from thermal expansion differences. Where monolithic linings are used, anchors attach the refractory material to the shell. Those anchors can experience failure from mechanical stresses, metal fatigue, or corrosion, leading to gaps between the refractory shell and the lining. Any gap impacts heat transfer and can initiate other types of refractory failure, such as slag corrosion because of heat buildup at those sites. 

The flame imprinted characteristics of pulverized coal ash relevant to boiler slagging, corrosion and erosion have been discussed previously (1,2). Silicate minerals constitute between 60 and 90 per cent of ash in most coals and boiler deposits are largely made up from the silicious impurity constituents. This work sets out first to examine the mode of occurrence of the silicate mineral species in coal followed by a characterization assessment of the flame vitrified and sodium enriched silicate ash particles. The ash sintering studies are limited to investigations of the role of sodium in initiating and sustaining the bond forming reactions to the formation of boiler deposits. 

Essentially a Brookfield Rheolog was used to replace head in the rotating cylinder slag corrosion apparatus lag/refractory corrosion studies at Argonne National (ANL) (J ). Appropriate seals and ceramic structural permit maintenance of the desired low oxygen activity measuring chamber. The viscosity measuring bob was a... 

F. Raask, "Flame Imprinted Characteristics of Ash Relevant to Boiler Slagging Corrosion and Erosion," presented at the 1981 Joint Power Generation Conference, ASME Paper No. 81-JPGC-Fu-l. 

Eisa MMY, Fuel Additives to Combat Vanadic Slag Corrosion in Power-Generating Systems, M.Sc. Thesis, Baghdad University, Baghdad, Iraq, 2000. 

Mineral matter in coal is one of the most important sources of problems in coal combustion, including fouling, slagging, corrosion, among others. Mineral matter transformation and slag formation are specific properties of coal that provide more information on the suitability for coal combustion or gasification. 

Liquid slag corrosion of cyclone boilers Fossil 120 1.02... 

Most investigators have found that slag corrosion rates increase linearly with the percentage of apparent porosity within the refractory. This is usually true within a limited range of apparent porosity—for example, in the range 12-16% apparent porosity— but it is not necessarily true at high apparent porosities (>20%). 

A key concept of this principle is that the temperature gradient affects the extent of phenomena seen in slag corrosion. In a very steep temperature gradient, very little penetration of slag is seen, with corrosion reactions more or less restricted to the immediate slag and refractory interface. Mobility of fresh slag (reactant) to... 

There are a few cases of thick-wall designs where the refractory is so resistant to slag corrosion that corrosion reactions are restricted to the hot face region. Usually, these involve fusion cast refractories employed in furnaces that remain hot during their service life (minimal thermal cycling from hot to cold). 

Slag corrosion by liquids occurs whenever a threshold temperature is exceeded, which is usually when melting occurs between the refractory and the slag. Corrosion results in solution of refractory constituents in the liquid phase, result-... 

AI2O3 range in most standards Common terminology Phases General performance in the absence of slag corrosion or alkali attack conditions... 

Finally, the spinel phase formed at the hot face also tends to impede the infiltration of liquid slags into the brick s microstructure, which reduces the impact of slag corrosion. 

Alumina-rich, stoichiometric, and MgO-rich spinels are all used by the refractories industry, and their stoichiometry affects sinterabdity, physical properties such as mechanical strength, and chemical properties such as slag corrosion resistance of spinel-containing refractories (see Section VI). 

Figure 20 Al203-Mg0 castables show better slag corrosion resistance than AI2O3-spinel castables. (From Ref. 57.)...

Due to their excellent properties such as high refractoriness, mechanical strength, thermal shock resistance, and slag corrosion resistance, and environmentally... 

Sarpoolaky H, Zhang S, Argent BB, Lee WE. Influence of grain phase on slag corrosion of low-cement castable refractories. J Am Ceram Soc 2001 84(2) 426-434. 

Vezza TF, Richter T, Landy RA. Slag corrosion mechanism of cement-free AI2O3-MgO castables. Proc. Unified Inti. Tech. Conf. on Refractories, New Orleans, 23-32 (ACerS, Westerville, USA 1997). 

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