This study investigated the effects of different calcium hydroxide (Ca(OH)2) addition methods on the potential for hydrogen chloride (HQ formation in a simulated densified refuse-derived fuel (RDF-5) with single metal combustion system. These experiments were conducted at 850'C with the Ca(OH)2 spiked in the RDF-5 production or injection in the flue gas treatment system. The results indicated that the potential for HC1 formation was decreased significantly by Ca(OH)2 spiked in the RDF-5 production or injection in the flue gas treatment system. However, the Ca(OH)2 injection method in the flue gas for HC1 emission reduction was better than other method. According to the relationship between the HO emission and amount of Ca(OH)2 injected or spiked, it is interesting to find that when the Ca(OH)2 injected or spiked ranged from 0% to 5%, the potential for HC1 formation in the single metal combustion system decreases significantly with increasing Ca(OH)2 injected or spiked ratio. A corresponding increase in the amount of CaC12 Partitioned to the fly ash was observed. However, with the ratio of Ca(OH)2 higher than 5%, the amount of HC1 formation showed that no further significant variation occurred with increasing Ca(OH)2 spiked ratio. (c) 2008 Elsevier BN. All rights reserved.