Initial deformation temperature

Ash Fusibility. A molded cone of ash is heated in a mildly reducing atmosphere and observed using an optical pyrometer during heating. The initial deformation temperature is reached when the cone tip becomes rounded the softening temperature is evidenced when the height of the cone is equal to twice its width the hemispherical temperature occurs when the cone becomes a hemispherical lump and the fluid temperature is reached when no lump remains (D1857) (18). 

Ash fusion temperatures, including the spread between initial deformation temperature and fluid temperature... 

Initial deformation temperature (IT) temperature at which the first rounding of the apex of the cone occurs... 

When determining the initial deformation temperature, shrinkage or warping of a cone is ignored if the tip remains sharp (Figure 7.5). 

Ash initial deformation temperature temperature at which coal begins to fuse and become soft. 

The three different type of boilers used in this study were found to exhibit different temperature profiles. The flame and boiler temperatures monitored in Boiler A, when measured, were observed to be well below the initial deformation temperature of the ash (see Table II). On the other hand, the flame temperatures encountered in the B and D boilers were above the initial deformation point of the ash, and in some cases above the temperature at which the ash becomes fluid. In addition, the temperatures monitored in... 

It can be seen from Table II that the fly ashes produced in the A boiler essentially form acidic leachates even though the major element composition of these fly ashes were comparable to the amounts found in the boiler C and boiler D fly ashes (see Table III). The Militant, Deep Hollow, Upshur and Badger fly ashes produced in this boiler encountered flame and boiler temperatures that are below even the initial deformation temperatures of the fly ash. Hence, the fusion reactions probably did not occur that might have led to formation of products that generate an alkaline leachate. 

The firing cycle of fired ware is comparatively long at temperatures of 1400 — — 1600°C, according to the content of secondary oxides. The ware is immediately provided with a protective coating by immersion in a tar bath. The usual materials of this type have a porosity of 15 to 20%, a compressive strength of 40 to 70 MPa, the initial deformation temperature (Tq.s) is 1710 to 1760 C their thermal shock resistance is satisfactory. 

The initial deformation temperature is a suitable characteristic for relative comparison of materials. However, it should not be interpreted as a temperature up to which a refractory can be utilized permanently. The temperature of long-term safe use depends on loading and temperature distribution. 

Sintered deposits form at the furnace exit at lower gas temperatures and in zones subject to rapid changes in direction. The deposit is composed of spheroidal particles, <40p, bound together by a molten substance. In those cases where substantial quantities of coarse pyrites are liberated from the pulverized coal, the spheroids are nearly pure FeaOa, as shown in Figure 11. The matrix contained silica, alumina, iron, and potassium, and has an initial deformation temperature of 1832°C, as determined by differential thermal analysis. The heavier pure iron spheroids deposit as a result of inertial impact. The mineral source of the molten phase is most likely illite. 

Initial Deformation Temperature (IDT). IDT was determined as the temperature at which a standard test bar (1.27 cm wide x 0.635 cm deep), centrally loaded on a 100 mm span, deflected an additional 0.25 mm under a load that gave a maximum (outer-layer) stress of 1.82 MPa, while being heated at a rate of 2 C/min. The operating procedure followed ASTM Method D648-72 for "Deflection Temperature of Plastics Under Flexural Load"... 

The initial deformation temperature (IDT) is the temperature at which the standard shape of ash just begins to show signs of deformation at its top as the temperature is raised. 

The initial deformation temperature corresponds to the temperature in an operating coal combustor at which the particles of ash passing through the furnace, have cooled so far that they have only a slight tendency to stick together and form a deposit slowly on heat transfer surfaces. When the ash... 

The implications for design are that the furnace exit gas temperature (that is the flue gas temperature leaving the radiant section) should be below the initial deformation temperature by about 50°C to avoid viscous flow sintering and potential slagging in the convection section. 

Sanyal and Cumming [1985] proposed an alternative method of determining the initial deformation temperature based on changes in the electrical resistivity of the ash as the temperature is raised. At a temperature where melting commences, ionic conduction markedly reduces ash resistivity. A plot of the log of resistivity against the reciprocal of the absolute temperature will show a discontinuity where melting commences. 

Gray and Moore [1974] proposed an empirical formula for the so-called Slagging Index (FS) considered to be a measure of the slagging propensity of the coal. It is based on the initial deformation temperature (IDT) and the hemisphere temperature HT. Jones [1978] demonstrated that the Slagging Index is a useful measure of slagging potential in boiler equipment. For lignitic ash the index is given by ... 

FT fluid lempeiatuce, HT hemisphetical temperature, IDT initial deformation temperature, IL Illinois, KY Kentucky, HDiNordt Dakota, PA Pertnsylvania, ST softening temperature, WV We t Virginia, WY Wyoming. 

Initial deformation temperature (IDT) or sintering temperature The first rounded edges occur and the initiation of stickiness (e.g., agglomeration in fluid bed). 

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