An interesting and relatively simple process developed in three major steps: Slurry production, Spray Drying and Post Addition
Slurry is best described as suspension of solids inside a liquid. In our case, liquid is composed of water solution of active matter, produced by in-situ neutralization of Sulphonic Acid by Caustic Soda, combined with Sodium Silicate, and solids are composed of a combination of Sodium Sulphate, Sodium Carbonate, S.T.T.P., Zeolite.
All the ingredients of the formula are charged into the Reactor where they get properly blended. Sulphonic Acid gets neutralized by Caustic Soda. Finished material is transferred to a Maturator vessel where all the dry materials get properly hydrated.
This Slurry is then filtered twice: first by a magnetic filter to entrap eventual metal contaminates and then by a self-cleaning filter that filters out other contaminants and impurities.
Filtered material is sent to the Homogenizer Mixer that guarantees a proper granulometry. It also provides for a slight positive pressure that will help the High Pressure Pump. This is a piston plunger type pump capable of developing significant pressures necessary to convey the slurry to the top of the Spray Tower and disperse it into mist by means of appropriate nozzles.
Spray tower is in essence a steel tube of appropriate dimensions (quite big!) where the hot air that enters at the bottom of the tower (prepared by a separate section consisting of burner, oven and two air fans) bakes the droplets of detergent slurry sprayed on the top.
As they fall to the bottom of the tower, these droplets form perfect spherical shapes and heat up, causing the water inside to boil.
This steam forces the solids to the outside surface of the sphere and finally, as the internal pressure grows over the limit, breaks out of the sphere leaving it empty.
This shape is called “Hollow Head”.
These hollow beads are what the detergent powder is mostly composed of.
What we find at the bottom of the tower is called “base powder”.
Before its further use, it is cooled down and sieved to guarantee proper granulometry and homogeneity of the product.
Eventual lumps and off-specification material is recycled back into the slurry making.
Base powder is very seldom sold as a final product. Normally, commercial products have complex formulations that require a number of ingredients that cannot be sent to the tower.
This can be because of the heat sensitivity of the ingredient (enzymes would be de-activated) or due to the high losses that would occur (perfume would evaporate!).
These materials are added to the cold and sieved base powder in so called Post Addition.
This section consists of a continuous mixer where metered quantities of all ingredients are blended together and sent downstream for storage and packaging.