Application of Fuel Additiwes to Reduce Corrosion and Stack Emissions in Saline Water Conwersion Corporation's Boilers

摘要

This paper deals with the burning of heavy residual fuel oil containing ~ 3.5 % sulfur and low vanadium (~ 40 ppm) under conditions prevalent in heating boilers to assess the use of fuel chemical additives on the formation of noxious and corrosive products of combustion.Saline Water Conversion Corporation's (SWCC's) boilers that are attached to the dual-purpose desalination/power plants in the Western Province of Saudi Arabia using heavy residual fuel oil are reported to have chronic corrosion problems causing unscheduled shutdown and frequent replacement of equipment resulting in high maintenance costs and loss of production besides creating environmental problems. The effectiveness of fuel chemical additives in controlling boiler internal corrosion and reducing the emission of hazardous gases was tested. Three magnesium-based compounds (A, B & E), one organic-based compound (C), and another hydrocarbon-based non-metallic (D) additive were selected based on the literature provided by the companies. Evaluation was carried out by online monitoring of flue gas parameters such as SO2, SO3, CO2 and NO_x, acid dew point, rates of acid build-up and quantitative determination of boiler soots. The effects of the additives on the boiler performance were also monitored by evaluating boiler load, efficiency, flue gas outlet temperature, opacity, fuel and steam flows. The boiler's internals were inspected before and after the testing of each additive.The results of the three MgO-based slurries tested were quite comparable. The organically based Mg-compound and the non-metallic additive showed lower efficiency in the cold end of the boiler. Though there was a slight decrease in the performance of the additives as the dose rates decreased, the optimum dose rates determined were 150-160 mg · kg~(-1) for chemical A, 200-250 mg · kg~(-1) for chemical B, 180-190 mg · kg~(-1) for chemical C, 500 mg · kg~(-1) for chemical D and 250 mg · kg~(-1) for chemical E to be effective. Based on the studies, chemical A was found to be the most effective and economical among the five chemicals tested.