Multivariable Regression and Adaptive Neurofuzzy Inference System Predictions of Ash Fusion Temperatures Using Ash Chemical Composition of US Coals

In this study, the effects of ratios of dolomite, base/acid, silica, SiO2/Al2O3, and Fe2O3/CaO, base and acid oxides, and 11 oxides (SiO2, Al2O3, CaO, MgO, MnO, Na2O, K2O, Fe2O3, TiO2, P2O5, and SO3) on ash fusion temperatures for 1040 US coal samples from 12 states were evaluated using regression and adaptive neurofuzzy inference system (ANFIS) methods. Different combinations of independent variables were examined to predict ash fusion temperatures in the multivariable procedure. The combination of the “11 oxides + (Base/Acid) + Silica ratio” was the best predictor. Correlation coefficients ( ) of 0.891, 0.917, and 0.94 were achieved using nonlinear equations for the prediction of initial deformation temperature (IDT), softening temperature (ST), and fluid temperature (FT), respectively. The mentioned “best predictor” was used as input to the ANFIS system as well, and the correlation coefficients ( ) of the prediction were enhanced to 0.97, 0.98, and 0.99 for IDT, ST, and FT, respectively. The prediction precision that was achieved in this work exceeded that reported in previously published works. 1. Introduction Usually, coal quality for coal used for the generation of electricity refers to differences in heating value, grindability, sulfur content, and ash fusion characteristics. The potential for slagging on furnace walls is related to the ash composition and temperature. Ash fusibility is a factor that can be used to determine the performance of coals related to slagging [1]. ASTM Standard D1857, which specifies the experimental method for determining ash fusion temperatures (AFTs), is based on the gradual thermal deformation of a pyramid-shaped ash sample in either an oxidizing or reducing atmosphere. The test results can be reported for four temperatures: (1) the initial deformation temperature (IDT), which is the temperature at which the first rounding of the apex of the cone occurs and the pyramid begins to demonstrate evidence of deformation; (2) the softening temperature (ST) or fusion temperature (FT), which is the temperature at which the cone has fused and the height equals the width; (3) the hemispherical temperature (HT), which is the temperature at which the cone has fused into a hemispherical lump and the height is equal to half of the width at the base; and (4) the fluid temperature (FT), which is the temperature at which the fused mass has spread out in a nearly flat layer [2]. The temperature difference between the initial deformation temperature and the fluid temperature gives information on the type of deposit to be expected on