###### Abstract  
During coal combustion in boilers, light fly ash particles are carried away along with the hot flue gases and the heavier bottom ash particles fall to the bottom of the boiler. The fly ash particles stick on the convective heat transfer surfaces and the furnace wall, causing fouling and slagging deposition problems during the boiler operation. The fouling and slagging effect reduces the boiler's operational efficiency. This study was motivated by the decline in the operational efficiency of the installed boilers at Sasol synfuel operations in Secunda, Mpumalanga province in the Republic of South Africa. It was assumed that the drop in the boiler efficiency was caused by the coal ash deposition during the boiler operations. The rate of ash deposition and accumulation in the convective heat transfer tubes and furnace water walls during the boiler operation depends on the chemical composition of the coal ash produced during combustion. Coal fly and bottom ash samples were collected from the operational site for laboratory analysis to determine their chemical composition using induced coupled plasma optical emission spectroscopy, induced coupled plasma mass spectroscopy (ICP-OES, ICP-MS) and X-ray fluorescence (XRF) analytical methods. The major, minor and trace elements by mass (%) in the ash samples were obtained from the ICP-OES and ICP-MS, whereas the elemental composition in an oxidised atmosphere was obtained from the XRF analysis. The amount of unburnt coal particles within the ash samples was determined from the loss on ignition (LOI) test. The fouling and slagging prediction during Sasol boiler operation was evaluated using previously developed fouling and slagging indices as a guide using the analysed ash chemical composition results obtained in this study. It was concluded from the analysed results using the guided evaluated indices from the analysed coal ash chemistry that during the operations of Sasol boiler(s) there is a low to medium fouling prediction occurrence on the convective heat transfer tubes and a low slagging in the boiler furnace walls. ash analysis; fouling; slagging; boiler; combustion; chemical composition Article  
Failing and Slagging Investigation on Ash Derived from Sasol Coal Using ICP and XRF Analytical Techniques  
Soal Design  
transfer tube surface reduces the coal-fired boiler power plant's overall efficiency by 1% [5]. The study of monitoring ash deposition and soot accumulation during coal-fired boiler operation has become a more interesting, focused research area within the energy generating industry [6; 7; 8; 9]. Slagging and fouling are the major effects that reduces coal-fired boilers' steam output efficiency. Slagging occurs within the boiler region, where the heat exchange surfaces are directly exposed to the flame radiation area, such as the furnace water walls [10]. Slag particles or deposits are mostly molten and are in a liquid state [10]. The deposits or particles formed on heat exchange surfaces that are not directly exposed to the radiant flame area are referred to as fouling [10]. Fouling deposits are solidified particles that are loosely bound or partially sintered; hence, they can be easily cleaned off [10]. Slagging and fouling within the boiler undergo smooth transition; the extent to which the deposits lead to slagging or fouling is dependent on the coal type, mineral inorganic chemical composition, and the operating conditions of the boiler [11]. This study aims to address the problem of the decline in the steam output produced during the operation of the boilers installed at Sasol synfuel operations. This challenge seriously increased the company's maintenance cost and decrease its profitability. It was presumed that the decline in the boiler(s) operational efficiency was a result of the ash deposition in the boiler furnace water walls and the convective heat transferred surfaces. The severity of ash deposition and accumulation in the boiler heat transfer surfaces is assumed to depend on the chemical composition of the coal ash.