A validated flowsheeting tool for the study of industrial granulation processes

COTABARREN, IVANA; BERTIN, DIEGO; BUCALÁ, VERÓNICA; PIÑA, JULIANA

Sheffield

Workshop; 6th International Granulation Workshop; 2013

University of Sheffield

Nowadays, process simulators that accurately model real plant operation are commonly used for design, simulation, troubleshooting and optimization purposes [1,2]. Process modelling plays a key role in improving industry productivity, especially for large-scale plants with high energy consumption. Small process improvements often lead to great benefits in terms of overall plant performance [3]. However, most of the progress achieved in flowsheeting tools has been focused on fluid processes (i.e., the most traditional liquid/gas based industries). Indeed, the modelling of processes involving powders or granules is difficult because, among other reasons, they are distributed systems that have to be described by complicated mathematical functions. Consequently, the representation of solid processes is not a trivial task due to the complexity of the partial integro-differential equations associated to changes in particle properties distributions [1-3]. Within solids processes, granulation is one of the most important operations. In the fertilizers industry, it particularly provides products with high resistance to breakage and low tendency to caking and lump formation [4]. The operation of granulation circuits, which include not only particle size enlargement in the central granulator but also particle size classification in screens and particle size reduction in mills or crushers, is generally not simple and due to operational challenges the capacities are much less than the nominal ones with high recycle ratios that overload all process units [5,6]. Moreover, industrial circuits are usually operated by trial and error, being difficult to run the plants at steady state without frequent undesired shut-downs. In view of the above-mentioned difficulties, this work evaluates the capabilities of a complete dynamic simulator developed for a urea granulation circuit (based on fluidized-bed granulation) to analyze the process sensitivity against different disturbances and to study common operating problems. First, the circuit model is validated by comparing simulation results with experimental data from a high capacity plant. Based on a sensitivity analysis of the process variables, diverse strategies are explored aiming to solve typical operational challenges (i.e., too high granulation temperatures, undesired dust formation, units overload, plant capacity increase, product quality control,