Slag composition

There are limits to the level of zinc in final slag, because as the oxygen potential is lowered to reduce more zinc, the tendency to reduce FeO and form iron is increased. At slag temperatures of 1350°C the presence of metallic iron can cause considerable difficulties in the tapping process. Generally zinc levels are not reduced much below six per cent in final slag for this reason. 

---

Additioaal components such as alumiaa [1344-28-1] are also added to obtaia more favorable thermodyaamics, and to obtain a slag having favorable properties. Many different feed and slag compositions exist, as do alternative reductants for ferrosiUcon. It is also theoretically possible to manufacture magnesium metal by the reduction of MgO with carbon. 

The path designated by A—B represents the change in the slag composition when siUcon having 0.6% Al and 0.2% Ca reacts to equiUbrium with oxygen ... 

One of the important differences between calciothermic and aluminothermic reduction of oxides concerns the interaction between the reduced metal and the reductant. Calcium does not form stable solid solutions or alloys with the reduced metals calcium contamination in the metal is, therefore, relatively small. Aluminum, on the other hand, readily forms solid solutions with the reduced metals, and the product generally contains appreciable quantities of residual aluminum. This is not a serious problem because in many cases either a certain aluminum content is desired in the reduced metal or the residual aluminum can be effectively removed in post-reduction purification operations. The extent of the contamination of a reduced metal with the reductant can be related to factors such as the reaction temperature, the standard free energy change associated with the reaction, and the slag composition. Let the following generalized reaction be considered ... 

Real MHD Channel Slag (Ki). Detailed TMS and KMS studies were made of vapor transport over a high liquidus temperature (a. 1700 K) potassium-enriched coal slag with initial composition as indicated in Table II. This slag sample was obtained by combustion of Illinois No. 6 coal with additional potassium added to the combustor [see ( )[. Note that this slag composition lies between those of the "Eastern" and "Western" coal-types. 

Although the data obtained in these studies have been valuable in interpreting the slagging phenomena observed in gasifier tests, a more fundamental objective of the current work is to develop correlations that can be used to predict a priori the viscosity behavior of low-rank-coal slags from a knowledge of the ash or slag composition. 

The compositions of the slags from these viscosity tests are listed in Table II. (The compositional data are normalized to 100% the median closure on raw analytical data was 94.2%.) Also included are several other parameters that traditionally have been employed to characterize coal-ash slags. It should be emphasized that, unless otherwise noted, all calculations discussed herein were based on slag composition data (as opposed to ash composition data). This was done primarily for two reasons ... 

Slag Viscosity/Composition Correlations. Several attempts have been made in the past to define the linear portion of the viscosity/ temperature curve based on the composition of the coal ash. In the mid-1960 s, workers at the British Coal Utilization Research Association (BCURA) developed. two such correlations based on work with British (bituminous) coals, now generally referred to as the Watt-Fereday (4) and S (3) correlations (6). Unfortunately, attempts to apply this correlation to low-rank coal slags, using either ash or slag composition data, have been generally unsuccessful. 

Slag Composition, Weight Percent Acid Silica AI2O3 Lignite Factor ... 

---