CFD Diagnosis of the Cyclotol Manufacturing Plant: Product Quality and Process Operation

Abstract

The production of cyclotol, a military high explosive used in manufacture of aerial bombs, involves the multiphase mixing of molten TNT, RDX solid particles and water. Textural homogeneity of the final cyclotol mixture and near-zero water composition are critical requirements to minimize bomb-rejection rate and hence improved plant profitability. Although current data reveal significant statistical variation in product quality, detailed investigation of the complex mixing operation does not lend itself to physical experimentation due to the explosive nature of the process. This forestalls opportunities for improved process operation or re-design. To circumvent this constraint, a computational fluid dynamics (CFD) simulation of the industrial-scale process was carried out to understand how current mixing protocols impact on key in-tank profiles such as water draw-down, RDX particles suspension, turbulence kinetic energy, velocity magnitude, vector direction and water-entrainment. The analysis revealed that while the maximum impeller speed allowable to avoid water draw-down is 20 rpm, the minimum speed necessary to suspend the RDX particles for homogeneous mixing is 40 rpm. These opposing requirements are neither accommodated by the present mixing protocols nor achievable with the existing tank design. Even so, the 'mystery' of irrational cyclotol quality has been uncovered by a judicious use of CFD modeling and opened up the possibility of a revised tank design and optimal process operation for superior plant economics.