Tank Heel Research Articles

Numerical Study on the Tank Heel Determination Using Smoothed Particle Hydrodynamics

Tank heel minimization is a significant issue in the design of LNG fuel tanks because it is associated with stable suction pump operation and thermal shock requirements during LNG bunkering. This study examined how the LNG tank heel is minimized, maintaining a suction pump fully submerged in LNG during dynamic vessel motion. The study assumed two LNG fuel tanks mounted on the forward deck of a 50,000 deadweight class oil product carrier. Information on the dimensions and shape of the LNG fuel tank was determined from Wartsila’s brochure, and the specifications of Vanzetti’s suction pump were referred to. The LNG fuel tank and LNG heel were modeled as rigid elements and hydrodynamically smoothed-particles, respectively. The number of particles could be determined by performing even keel analyzes by adding or subtracting particles until the target head was satisfied under the gravity load. To simulate the motion of the LNG fuel tank, the pitch and roll periods and amplitudes of the ship were calculated using the DNV classification rules. Visual observations of the dynamic flow during the pitch and roll motions with respect to the ship’s center of mass showed that the roll motion was more critical from the viewpoint of the LNG heel than the pitch motion. After performing the simulations for three cycles of roll and pitch motions, the suction pump submergence was reviewed in the last cycle. Under the conditions assumed in this study, a filling ratio of 15% was determined as the minimum LNG tank heel. Although the LNG heel has customarily been determined, the LNG heel needs to be determined through hydrodynamic analyses of each vessel because it depends on the shape of the fuel tank and the vessel motion characteristics.

Dealing with Multiple Tank Outflows and In-Line Blending in Continuous-Time Crude Oil Scheduling Problems

The crude oil scheduling problem has been focus of many studies in the past, which is justified by its importance in the oil industry. Optimizing crude oil blending is of paramount importance given that it can substantially impact the economic performance of a refinery. In this work, operational features of a real-world existing refinery are addressed. Only operations limited to the refinery battery are in scope such as splitting of parcels unloaded from a supplying pipeline segment, tank heels and capacities, brine settling time, multiquality tracking, crude distillation unit (CDU) straight-run products profile, multiple tank outputs, and multiple CDU inputs. Moreover, different policies as to the handling of the refinery tank farm are evaluated. The presented formulation is taking from the multioperation sequencing (MOS) proposed by Mouret, Grossmann, and Pestiaux ( Comput. Chem. Eng. 2011, 35, 1038−1063. DOI: 10.1016/j.compchemeng.2010.07.007). The novelty of the present work relies on how to accuratel...

Analysis of 36Cl in Savannah River Site radioactive waste

Radioactive waste cleanup and subsequent closure of waste storage tanks is currently underway at the Savannah River Site, prompting the need to characterize the residual contents (heels) of the tanks. Each tank heel has variable chemical constituents and radiological distributions that pose unique analyte characterization and quantification challenges. For example, similar target detection limits for each tank heel are often difficult to meet as a result of complex matrices and methods must be tailored to characterize each new tank heel to the level of detection required. Furthermore, continuous programmatic evaluations of allowable closed-tank radiological inventories result in steadily decreasing detection limit targets for many of the isotopes required for characterization. Some of the target isotopes required for characterization need to be quantified to levels approaching 10 orders of magnitude below the radioactive concentrations of interfering isotopes. One particularly troublesome target analyte is 36Cl. As a pure beta-emitting radionuclide, 36Cl (T1/2 = 3.01 × 105 ± 3,000 years) must be isolated from interfering beta-emitting radionuclides such as 90Sr, 90Y, 137Cs, 99Tc, and 14C, as well as actinides and lanthanides prior to quantification. Due to its half-life, the target detection limit for 36Cl is extremely low compared to the concentrations of other beta-emitting radionuclides typically present in residual tank solids. A method of analysis for 36Cl was developed which utilizes a combination of traced acid digestion of radioactive waste tank samples followed by aggressive decontamination of interfering beta-emitting radionuclides via repeated resin-strikes, distillation, precipitation as AgCl, and analysis by gas flow proportional counting for the 36Cl—containing precipitate. The separation is traced by neutron activation analysis of stable chloride imparted during the initial digestion, and results are corrected for the separation yield. Recent campaigns have successfully achieved interference-free AgCl precipitates and, ultimately, detection limits of 0.37 Bq/g from matrices containing ~1E7 Bq/g of other beta-emitting radionuclides.