Spray drying organic dyestuffs

Niro Atomizer spray dryers are used worldwide by all leading manufactures of organic dyestuffs in powder form. Handling and processing demands for dry dyestuffs have established spray drying as the preferred drying and particle formation process. Niro Atomizer technology and industrial drying experience guarantee the most suitable spray dryer design for each dyestuff application - a design that fulfills requirements of particle size, particle form, plant operational safety, pollution-free drying, and ease of cleaning between color changes.

The spray drying process

Spray drying is one of the most convenient industrial technologies for transforming liquid dyestuff formulations into powders if specific physical properties. The liquid is sprayed into hot air using either rotary (wheel) atomizers or nozzles. Drying takes place virtually instantaneously, dyestuff particles remain low in temperature, and even the most heat sensitive formulations can be handled.

Organic dyestuff applications Soluble Acid Basic Direct Azoic Diazo compounds Naphthols VAT Indanthrene Indigo Indigosol Microdisperse Reactive

Fluidized spray dryer Tall form spray dryer Air disperser/rotary atomizer arrangement on co-current spray dryer

System selection

Powder characteristics and operational requirements decide the choice.

Particle size requirements are met through correct choice of atomizer and drying chamber design. Fine to medium coarse powders (mean size up to 150 microns) are conveniently produced in co-current drying chambers, type SD, with rotary atomizers. Coarser, dustless powders are produced by nozzle atomizers in tall form designs, type TFD, or in fluidized spray dryers, type FSD, featuring rotary or nozzle atomizers.

Spray dryer with rotary atomizer (Type SD)   mean size: 80 micron

The fluidized spray dryer is a new mixed-flow design concept featuring a fluid bed integrated into the drying chamber base. Dustless powders of improved dispersion characteristics can be produced in a low energy consuming operation. Drying is accomplished at much lower powder temperatures, and dyestuffs have better color retention properties. The FSD design is a new invention from Niro Atomizer.

Tall form spray dryer with nozzle atomizer (Type TFD)   mean size: 200 micron

Stationary and vibrating fluid beds as separate attachments are used with rotary atomizer and tall form nozzle plant for post-drying, cooling and dedusting in two-stage processing.

Cleaning-in-place (CIP) systems, semi- or fully automatic, are available for all Niro Atomizer plant.

Fluidized spray dryer (Type FSD)   mean size: 300 micron

Operational safety and environmental protection

Many organic dyestuffs can form potentially explosive mixtures in air. To spray dry such products in complete safety, recycle systems operating in the self-inertizing mode are used if feeds are aqueous. Gas tight inert recycle systems are essential where feeds contain organic solvents. In cases where explosion/fire hazards are considered slight, conventional open cycle plants are selected, fitted with over-pressure venting systems and/or suppression devices to give complete safety.

Discharge of dyestuff particles to atmosphere with the air exhausted from an open cycle plant is prevented by critical selection of the cyclone/bag filter/scrubber combination. Air cleaning equipment is available to meet the strictest emission codes. Recycle systems provide an excellent alternative to open cycle drying, since the possibility for particulate emission is much reduced as air volumes vented to atmosphere are small.