A combination of laboratory prescreening tests and longer trials on a 2MW industrial chaingrate stoker have been used to investigate the effectiveness of fuel additives at alleviating alkali bonded fouling. In addition, the effect of copper oxychloride on slagging was assessed using a 150kW pilot scale pulverised fuel combustor. The studies indicated that additive performance was generally combustion regime specific. Magnesium oxide or hydroxide based additives were found to increase the level of available sodium, resulting in increased quantities and strength of fouling deposits in stokers. Kaolinite proved the most potentially beneficial antifoulant, reducing the available sodium levels and producing a corresponding reduction in deposition. Addition of copper oxychloride to an iron rich coal resulted in a change in the distribution of spinel phases in slag deposits collected.