PTC:02-4

Methods for Design and Optimisation of Rotary Granulator, Dryer, Cooler and Kiln

This is a comprehensive report covering the complete process calculations of rotary granulator, dryer, cooler, kiln and other associated equipments especially employed in a fertilizer granulation plant.  The methods for simulation and design presented are equally useful for any other material other than fertilizers as well.  A typical granulation plant would employ a granulator, dryer, cooler, screens and recycle system, and dedusting cyclones for dryer and cooler air streams.  

The report consists of the following chapters:

1. Introduction.
2. Some basic concepts covering dry and wet bases, LMTD, psychrometric parameters, drying mechanisms, conversions factors and some useful basic data.
3. Solids residence time including its effect on solids hold-up and material filling.
4. Drive power for rotation including the influence of cake thickness, scale-up etc. for both co-current and counter-current operations, and the heat input due to power.
5. Granulator heat transfer covering water and steam injections, control logics, the influence of recycle on granulator performance etc.
6. Dryer heat transfer explaining the moisture evaporation process, overall mass and heat balances, surface and internal moisture evaporation rates for co- and counter-current flows, material CRH and its influence on evaporation and moisture re-absorption. Methods are presented for calculating outlet solids moisture content, outlet gas and solids temperatures, outlet air humidities and dew point, and fuel consumption.  The complete profiles of solids moisture content, gas and solids temperature within the dryer are predicted which give a great insight into dryer operation, material degradation, optimisation etc.
7. Cooler heat transfer giving an elegant and yet simple model for predicting the profiles of solids moisture content, gas and solids temperatures inside a counter-current cooler.
8. Kiln heat transfer with special focus on cement kiln circuit giving a model covering kiln, pre-heater and pre-calciner, grate cooler and fans.
9. Design aspects to establish optimum dryer diameter, length, rpm, slope, air speed etc. to achieve desired drying performance.
10. Carryover and collection of fines giving equations for dust entrainment rates, collection of entrained solids and design of overhead cyclones for the same.
11. Some industrial case studies illustrating the actual benefits derived by some plants using the various methods outlined in this report.  In this chapter, detailed predictions using our softwares GRAND and RDSIMUL illustrate the utility of the comprehensive mathematical model incorporating the various inter-connected equations presented in the previous chapters.
12. Conclusion.

The various mathematical calculational procedures are made easy to understand with the help of 39 worked-out examples and a few case studies.  These should be extremely useful to operating plants for achieving process optimisation, to designers for designing optimum equipments, and to engineers and plant operators as an effective learning/training aid.