GRAND is an integrated software for fertilizer granulation plant simulation which includes a comprehensive module RDSIMUL for rotary dryer simulation.  It considers the influence of all the practical parameters like solids feed rate, temperature and particle size, gas flow rate and temperature, material critical relative humidity (CRH), critical moisture content (to account for surface and internal moisture evaporation), fuel type, water and steam injection etc. and even such usually neglected (but important) parameters like gas leakages (false air) into the system, entrainment of dust from the dryer and cooler and their subsequent capture in overhead cyclones.

RDSIMUL predicts the overall heat and mass balances and reports the important parameters at various stages and additionally predicts the following :

The integrated system GRAND predicts other important parameters pertaining to granulator, cooler and recycle system as well.   Specifically, the various moisture contents and temperatures, water and steam addition rates in granulator, heat balances for granulator and cooler etc. are predicted.   The important input parameters that affect the performance are the solids and gas flow rates, feed particle size, material CRH vs. T relationship, equipment dimensions, slope, rpm etc.  If one set of operating data is available, the software can be "tuned" for the particular plant and the resultant customised software would accurately predict for all other combinations of operating conditions.   A technical report entitled "Methods for Design and Optimisation of Rotary Granulator, Dryer and Cooler in Fertilizer Granulation Plants" has also been published which outlines the complete mathematical model with several worked-out examples, and the same is included as part of the software supply.

RDSIMUL is especially useful for designing optimum rotary dryers for any specific application.  It is possible to study before-hand the effect of changing equipment dimensions like diameter and length, and design conditions like rpm and slope on performance, thereby facilitating the optimum design choice.  Further, the software is extremely useful to offer after-sales technical support for troubleshooting and getting the maximum from the equipment supplied.  By showing the predictive strength of RDSIMUL to prospective equipment buyers, it can be used also as an effective sales tool.  The software can also be bundled along with the equipment supply which will be greatly appreciated by the buyer as the same would enable continuous optimal running of the plant.

The various methods and calculational procedures employed in GRAND and RDSIMUL are presented in our technical report No.PTC:02-4.

Both GRAND and RDSIMUL are completely menu-driven and user-friendly and come with detailed documentation.

Three sets of rotary dryer simulations using RDSIMUL are given below.  Although detailed predictions are obtained in tabular formats, we give below only the salient features of the profiles of solids moisture content, temperatures of gases, solids and dew-point, and relative humidity along the dryer length.  Further, the overall granulation plant flowsheet, directly obtained from the software, is also shown.    It can be seen from Figs. 4.2 and 8.2 that the solids reach a maximum temperature inside the dryer at around a length of 13 m.  In this case, the last  2.5 m of the dryer actually performs the function of a cooler, and the dryer could therefore have been that much shorter in length.  While Figs. 4.1- 4.4 refer to the case of a plant operating in an extremely cold country during summer, Figs. 8.1- 8.4 refer to the same plant operating during winter.  Figs. 13.1- 13.8 refer to another plant operating in a relatively warm country.  The software as such has been put to use for a variety of materials and operating environments.  The tabular result of the software is extremely comprehensive and can be furnished for a typical case upon special request. 

The air balance of a rotary dryer for one case is shown in Figs. 13.4-13.6.  While Fig. 13.4 shows the various contributions to air flow in three different units, Fig. 13.5 shows the same for two sets of units, namely Nm³/h and kg/h.  Fig. 13.6 represents the same in pie-graph.  The heat balance is similarly shown graphically for the above case in Figs. 13.7 and 13.8.  While both heat input and output are shown side by side in Fig. 13.7, the distribution of heat in the various output terms is shown in Fig. 13.8 in an alternate pie-graph.  Several combination of graphical analysis are possible using the integrated graphics system in GRAND and only a few are shown here for illustration.  For a comprehensive and complete understanding of the operation of a rotary dryer and a granulation plant, the use of GRAND is indispensable.  Its use at the design stage is still higher and simply can not be over-stated.