Thermal Design and Numerical Analysis of Transportable Bitumen Storage Tank for Improved Liquefied Bitumen Supply

Asphalt plant manufactures the hot black mix required for road construction. Bitumen is used as a binding agent that binds the aggregates (stones) together. Liquid bitumen ranging between 150 to 160 degrees C is sprayed on aggregates in a twin shaft mixer having mixer pads mounted on both shafts rotating in opposite direction with respect to each other (inward direction). Hence, asphalt plant needs the supply of hot and liquid bitumen, which is stored in storage tanks and is used as and when required. In this paper, the thermal design and simulation-based numerical analysis of 42,000 and 50,000 L capacity of transportable bitumen storage tank are presented. Usually, bitumen in the storage tank is heated by a thermal fluid called Therminol, having an inlet temperature of 180 degrees C, flows through tube bank present inside the storage tank. Therminol is heated by the fire-tube boiler. Thus, an effective heat exchanging system in the bitumen storage tank is crucial. In the existing storage tank, the solid bitumen rocks need 12 h of heating to obtain liquid bitumen ranging between 150 to 160 degrees C. Here, computational fluid dynamics (CFD)-based simulations are carried out to design the effective heat transferring system. Various flow conditions of Therminol, as well as different tube bank configuration, are been simulated and presented. The CFD analysis shows that with proper and modified distribution of tube bank inside the storage vessel helps to improve the heat transfer by a factor 2-3 and hence is capable to liquefy bitumen within 6 h.