Christer Haugland, Modeling and Control of fertilizer granulation process

Modeling and Control of Fertilizer Granulation Process Christer Haugland Supervisors: Sigurd Skogestad Vidar Alstad (YaraTechnology Center) Christer Haugland, Modeling and Control of fertilizer granulation process

Outline • Fertilizer and granulation • Processdescription • Modeling • New crushermodel • Control • Re-tunedrecyclemassflowcontroller • Addedparticlesizecontroller

Fertilizer • A major product in the world’s chemical industry • Keep up with the increasing food demand in the world • One important process step in making fertilizer is granulation.

Granulation • Granulation consist of solidifying fertilizer melt into small granules which can be used in the agriculture. • Solid granule particles are about 3 mm in diameter.

Process description • Feed: • Slurry melt • Atomizing air • Spherodizer: • Drying • Granulation • Screen • Separation • basedonsize • Crusher • Crushoversize • particles

Spherodizer

Recycle mass flow controller • Split range controller

Modeling • Basedonworkdone by Yara in MATLAB • Extendedwithnewcrushermodel Old crusher model New crusher model

Control • Re-tuningofrecyclemassflowcontroller • Basedonopen loop stepresponse in model

Re-tuning of recycle mass flow controller • Two modelapproximations: • First order plusdelay: • Pure delay:

Re-tuning of recycle mass flow controller • Gainvariations in split range controllervalves. k2 = -670 k1 = -295

Re-tuning of recycle mass flow controller • Process gain variations in MV’s: • Gain scheduling control (one controller for each MV) • Changing the split in the split range controller (usually set at 50%) Gain scheduling:

Re-tuning of recycle mass flow controller • Comparing the two with a ”trial and error” approach:

Re-tuning of recycle mass flow controller • First order plusdelaymodel: Not a goodapproximation! SIMC rules:

Re-tuning of recycle mass flow controller • Comparing the two model approximations: Pure delay best!

Particle size control • Added another PI controller to control particle sizes in granulator loop. Vibration in screen as MV, D50 out of granulator as CV. • But the MV saturated!!

Particle size control • Recycle mass flow controller

Thank you!

Christer Haugland, Modeling and Control of fertilizer granulation process

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