Basic design methodology for a prilling tower

Abstract

A design methodology was developed for prilling towers based on simultaneous heat, mass, and momentum balances. Basic principles of the prilling process and related sub‐models were considered for production of relatively mono‐size prills. The method was employed in the design of a prilling tower for production of ammonium nitrate prills from a highly concentrated solution. A special showerhead spray, operating under laminar conditions in a Rayleigh jet break‐up regime, was designed to enhance production of mono‐size prills. Air was used at ambient conditions. The droplets leaving the showerhead fall through the air stream in a counter‐current fashion. Heat transfer from particles to air includes cooling in the fully liquid state, solidification, and cooling in the fully solid state. The Computational Fluid Dynamics (CFD) simulation revealed the formation of a quiescent zone around the nozzle discharge region, which had a significant effect on decreasing the secondary disintegration of the droplets, and hence narrowed down the size distribution towards the desired value. The size of the produced prills was larger than the predicted value due to the formation of ammonia bubbles inside the prills.

Decay of the melt stream during dispersion in granulation devices

“…The model of the jet decay is based on the solution of Navier-Stokes equations (11) - (12) z = A1r 2 z 2 + A2r + A3 (14) and transforming the equation (13), we obtain the value of the radial component of the jet velocity:…”

“…Given the fact that the pressure change in a jet in the radial direction is insignificant compared to the axial component, and by substituting (14) into (12) we get:…”

“…For example, ammonium nitrate granulators (dispersers), which are currently in operation, provide manufacturing of products with following granulometric composition in terms of mass fraction: 0.5 -1.5 % of granules < 1.0 mm in size, 90 -98 % of granules in the size range 2.0 -4.0 mm, where granules in the size range 2.0 -2.5 mm comprise 42 -71 % and granules in the size range 2.0 -3.0 mm comprise 85 -95 % [13,14]. Dispersion of melts producing more than 2 % of dust-forming particles of less than 1.0 mm as well as those over 3.5 mm in size, which can be also destructed making dust, leads to dust formation of nitrogenous fertilizers in air in the tower.…”

Reduction of Dust Emission by Monodisperse System Technology for Ammonium Nitrate Manufacturing

“…A comparative analysis of the experimental results and theoretical calculations of Equation (7) showed a discrepancy. Analysis of the results indicated that a jet was influenced by a set of perturbations, which were caused by uncontrolled outside noise and granulator construction [33], which were difficult to control. To obtain the analytical dependence of pressure changes in the jet, taking into account the noise, one needs to add a component, considering vibrations, which are caused by the external noise.…”

Spiralling liquid jets: verifiable mathematical framework, trajectories and peristaltic waves

“…Liquid jets spiralling out under the action of centrifugal forces are elements of many applications, including spinning disc atomization (Senuma et al 2000), drawing and spinning of polymers and glass (Pearson 1985), nanofibre formation (Mellado et al 2011), prilling (Saleh et al 2015) and some others. Theoretical research into the dynamics of curved and later spiralling liquid jets began with integral approaches (Entov & Yarin 1984;Tchavdarov et al 1993) and then moved on to a more detailed description, first, of nearly straight jets (Dewynne et al 1992;Cummings & Howell 1999) and then arbitrarily curved ones, including the effects of inertia and surface tension (Wallwork et al 2002), gravity (Decent et al 2002), viscosity with no gravity (Decent et al 2009), unsteadiness and arbitrary shape of the jet's trajectory, first, without surface tension0 (Panda et al 2008) and then with surface tension (Marheineke & Wegener 2009), propagation of waves (Pȃrȃu et al 2006), viscoelasticity (Alsharif et al 2015;Marheineke et al 2016), surfactants for Newtonian (Uddin et al 2008) and non-Newtonian fluids to mention but the main developments.…”