Reducing Fuel Consumption for Liquid Cargo Heating Systems

Abstract

Cargo vessels carrying heavy liquid petroleum products, such as No. 6 fuel oil or asphalt, traditionally have an extensive heating system. This system consists of thousands of feet of 1,2 or 2-in. pipe arranged in the bottom of the cargo tanks through which a heat-transfer fluid is passed. A heater is used to raise the temperature of the heating fluid, which is forced through the coils. This maintains the cargo at a temperature suitable for off-loading by centrifugal cargo pumps. This heat source (heater) for the fluid is fuel fired usually with diesel oil. With the costs of fuel spiraling upward, an approach that would reduce fuel consumption should be attractive to the owner/operator of such a vessel. This paper presents the results of an analysis to determine potential savings in heating systems for No. 6 fuel oil cargos. Since positive-displacement pumps can handle much more viscous fluids than centrifugal pumps, they were studied for off-loading instead of using traditional vertical deep-well mixed-flow pumps. Two types of petroleum cargo vessels were analyzed, including an oceangoing 180 000-bbl Tank Vessel and a river tow consisting of eight tank barges with a combined capacity of 160 000 bbl. The analysis indicates that a significant reduction in fuel consumption could be realized with the new cargo pump type by reducing the size of the heaters. Additionally, the quantity of heating coils could be reduced. This would reduce construction costs and save substantial operating costs if incorporated into petroleum cargo vessel design