Application of Geostatistical Methods to Describe Variation in Technological Parameters of Ash-Slags

Abstract

Spatial analyses were carried out to develop a 3D geostatistical model of the spatial variation in the technological parameters of an ash-slag heap connected with the operation of the power utilities located near Świecie (Toruń). Tank A filled with ash-slags was the subject of geostatistical studies. The spatial variation of organic carbon content C_org, ash content A_O, moisture content W and recoverability e’ (defined as the amount of carbon [kg] recovered from 1 ton of ash-slag), was analyzed. The variation of these parameters in the horizontal and vertical extents of the ash-slag heap was subjected to structural (variographic) analysis using the directional variogram function. The parameters of geostatistical models approximating the empirical variograms of content C_org., ash content A_O, moisture content W and recoverability e’ were the basis for the estimation. Averages Z* and corresponding standard estimation deviations σk were estimated for the particular depths of the tank using (3D) ordinary (block)
kriging.

The variation of the parameters clearly differs between the particular depth levels of the waste heap. Carbon content Corg. and recoverability e’ were found to vary greatly while the variation in ash content AO and moisture content W was respectively small and average. There is a spatial correlation between the values of the investigated parameters. The variation of content Corg., moisture content W and recoverability e’, shows a certain regularity within the waste heap tank. Maximum and minimum averages Z* (the upper limits) consistently decrease (a downward trend) with depth, in the interval of 1-10 m. The ranges of maximum averages Z* of content AO notably increase, reaching higher values in deeper ash-slag horizons.

Thanks to the application of the geostatistical methods to describe the parameters of the waste material (treated as an anthropogenic deposit) databases containing complete valuable input information for a project aimed at utilizing the deposited material were created.