Simulation of Urea Prilling Process: An Industrial Case Study

Rahmanian, Nejat; Homayoonfard, Marjan; Alamdari, Abdolmohammad

doi:10.1080/00986445.2012.722147

Cited by 22 publications

(17 citation statements)

References 10 publications

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“…The simulation was verified against three urea prilling studies found in the limited available literature [29,39,42]. The granulation of urea is done in a system identical to the one proposed here: a tall tower with air flowing upward.…”

Section: Detailed Tower Modelling and Performance Summarymentioning

confidence: 94%

“…Mechanistically however the process is slightly different from the straightforward solidification of a salt. The liquid urea solution also contains water and biuret impurities which influences the solidification behaviour [29,42]. The model parameters were adjusted to the values for urea and air, as well as the tower parameters for each of the different investigations found in literature.…”

Section: Detailed Tower Modelling and Performance Summarymentioning

confidence: 99%

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A novel heat exchanger concept for latent heat thermal energy storage in solar power towers: Modelling and performance comparison

Badenhorst

2016

Solar Energy

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Highlights• Study introduces spray crystallization as phase change heat recovery option.• Can be directly incorporated into tower of central power tower designs.• Particle diameter found to be largest single influence of tower height.• Prilling feed system identified as critical for further investigation.• Best case result indicates a 20% reduction in plant capital cost is achievable. AbstractThis study presents an innovative new alternative for utilizing phase change materials as energy storage media in solar power towers. The solar power tower prilling or granulation concept combines the existing molten salt design with a prilling tower incorporated into the central receiver. In this way heat transfer limitations normally associated with these systems can be overcome since only very small particles (diameter 1-2 mm) are utilized. Three design cases were considered and a detailed model of the process was developed. The model demonstrates the design dependence on several key variables including particle diameter and the necessity of considering the system in conjunction with the steam generation cycle. Pinch considerations within this cycle and the tower itself determine the operational feasibility. It was found that the receiver design and prilling feed systems are crucial aspects which must be investigated further to refine the concept design and complete a full techno-economic assessment and optimization. The "best case scenario" resulted in a reduction of the circulating salt flow by one third compared to the base case. Preliminary indications are that this would result in a 20% reduction of the * Corresponding author. Tel: +27 12 420 4989. Fax: +27 12 420 2516. E-mail: carbon@up.ac.za 2 overall plant capital cost, but additional costs such as solids handling and a complex receiver design have to be taken into account.

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Section: Detailed Tower Modelling and Performance Summarymentioning

confidence: 94%

Section: Detailed Tower Modelling and Performance Summarymentioning

confidence: 99%

A novel heat exchanger concept for latent heat thermal energy storage in solar power towers: Modelling and performance comparison

Badenhorst

2016

Solar Energy

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“…The prilling method is based on the forced disintegration of the melt jets of fertilizer into droplets outflowing from a rotating perforated bucket or a static system of fixed orifices, such as a shower head spray system, into a countercurrent flow of air stream inside the prilling tower [6][7][8][9][10]. Thus, the process of droplets cooling takes place during the free fall inside the tower, which may be associated with their crystallization.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Abstract:Prilling is a common process in the fertilizer industry, where the fertilizer melt is converted to droplets that fall, cool down and solidify in a countercurrent flow of air in a prilling tower. A vibratory granulator was used to investigate liquid jet breakup into droplets. The breakup of liquid jets subjected to a forced perturbation was investigated in the Rayleigh regime, where a mechanical vibration was applied in order to achieve the production of monodispersed particles. Images of the jet trajectory, breakup, and the formed drops were captured using a high-speed camera. A mathematical model for the liquid outflow conditions based on a transient two-dimensional Navier-Stokes equation was developed and solved analytically, and the correlations between the process parameters of the vibrator and the jet pressure that characterize their disintegration mode were identified. The theoretical predications obtained from the correlations showed a good agreement with the experimental results. Results of the experiments were used to specify the values of the process parameters of the vibration system, and to test them in the production environment in a mode of monodispersed jet disintegration. The vibration frequency was found to have a profound effect on the production of monodispersed particles. The results of experiments in a commercially-sized plant showed that the granulator design based on this study provided prills with a narrower size range compared to the conventional granulators, which resulted in a substantial reduction in dust emission.

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“…Prilling has the advantage of being able to create ideal spherical particles with a narrow size distribution and minimal external specific surface area in one single step, scalable to basically any capacity range needed . The simplest method of producing uniform droplets is by discharging the molten or highly concentrated solution through an orifice nozzle, which is generally used in urea granular particle production . Gezerman and Corbacioglu reported that prilling tower height could affect the crystalline structure of ammonium nitrate prills.…”

Section: Introductionmentioning

confidence: 99%

Basic design methodology for a prilling tower

Saleh

Ahmed²,

Al-Mosuli

et al. 2015

Can J Chem Eng

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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.

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Simulation of Urea Prilling Process: An Industrial Case Study

Cited by 22 publications

References 10 publications

A novel heat exchanger concept for latent heat thermal energy storage in solar power towers: Modelling and performance comparison

A novel heat exchanger concept for latent heat thermal energy storage in solar power towers: Modelling and performance comparison

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

Basic design methodology for a prilling tower

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