Niro has supplied more than 450 industrial sized polymer drying plants, the first one in 1952, making an average of almost 10 plants a year. This record probably makes Niro the world's most experienced company in drying of polymers.

Many polymers need drying and Niro is familiar with all of those.

As to drying, the polymers can be divided into 2 main groups:

1. wet powders, where the particles are already formed; polymers like s-PVC, c-PVC, ABS, MBS, HDPE, PP, PAN, c-PE, POM, PVAl
2. emulsions and solutions, where the particles are formed during the drying process; polymers like e-PVC, EVA, UF, MF, PF, PMMA, PVAc, PVP, Acrylic Resins, Paraformaldehyde.

Today dry product rates already exceed 35 t/h for some of the wet powders and 5 t/h for some of the emulsions and solutions. Niro is able to supply single continuous-running drying units for these capacities.

For the wet powders the drying equipment is fluid bed dryers or flash dryers ? in some cases a combination of those. A special high-energy efficient fluid bed is the Niro CONTACT FLUIDIZERTM, where 80-85% of the evaporative energy is supplied from heating panels submerged in the fluidized product layer. The overall energy saving compared to other types of dryers, for instance for s-PVC drying, is 10-45% depending on the grade in question.

For emulsions and solutions the drying equipment is a Spray Dryer, often followed by fluid bed post drying or cooling.

When the polymers are water wet, which is the case for most of the polymers, open drying plants are often applied, meaning that ambient air is taken in, heated up, performing drying, cleaned of particles and sent back to the atmosphere.

When the polymers are solvent wet (for example hexane/pentane wet HDPE or PP), the concentration of oxygen has to be very low in order to avoid explosion/fire in the dryer. Consequently, Nitrogen is often used as drying gas. In order to save cost, the Nitrogen is reused in a closed loop: it is heated up, performing drying, cleaned of particles, the evaporated organic solvent is condensed and pumped away, after which the Nitrogen gas is recirculated to the inlet heater and used for drying once more.

For some products a dust explosion can be a potential risk during drying, for instance for ABS and PVAc. In these cases open plants in Pressure Shock Resistant execution combined with Explosion Relief Panels or Explosion Suppression systems can be supplied. Alternatively, low oxygen plants are applied, using Nitrogen as drying gas in a closed loop. A speciality is the Self-inertized plant, where the low oxygen content is achieved by a special direct-fired heater.

Some thermoplastic polymers can be sticky during the drying, for instance PVAc and UF-resins. In order to spray dry these, special precautions, such as Jet SweepPT and Air Broom, are often necessary to avoid product build-up in the dryer.

Stripping of VOCs (Volatile Organic Compounds) is a special form of heat treatment/drying, often performed in a specially designed Stripper Fluid Bed.

Here topics for studying could be: Which Dryer Type for which Polymer, Dryer Cleaning, Dust Emissions and VOC Emissions.