ENERGY EFFICIENT TRANSPORT OF POOR FLOWING PRECIPITATED CALCIUM CARBONATE FOR SEALANT PRODUCTION

Gericke has delivered a material handling system for the storage, batching and pneumatic transport of various types of calcium carbonate powders to several mixers. For the production of adhesives and sealants different types of calcium carbonate powders have to be delivered in the correct amounts to the mixers. In addition to ground calcium carbonate powder that can be characterised with mostly free flowing properties, also precipitated calcium carbonate powder have to be handled. Due to the sub-micron particles of the precipitated calcium carbonate these powders are very challenging to handle as they are very cohesive and exhibit poor flowing performance.

Extensive trials were initially performed with various types of calcium carbonate powders in the Gericke test centre to evaluate the best pneumatic conveying conditions allowing an energy efficient and safe transport of the powders over 70 – 130m of conveying distance with minimal residues. As a result, the Gericke PulseFlow® PTA dense phase pneumatic conveying system achieved the lowest gas flow consumption per weight of transported product. This in turn also means the lowest energy requirement.

With the Gericke PulseFlow® PTA dense phase pneumatic conveying system a pressure vessel is used for transporting the powders as slowly moving product plugs powered by air velocities in the range of 4 –12 m/s. This in contrast to lean phase pneumatic conveying systems which operate with air velocities usually much above 20 m/s.

Due to the cohesive character of the precipitated calcium carbonate a special fluidising discharge system was used to maintain a steady discharge of the pressure vessel. The fluidising discharge system prevents the formation of rat holing and funneling effects in the vessel, which would reduce the conveying capacity and ultimately lead to failures in conveying and complete discharging of the loaded powder.

In the real plant the various calcium carbonate powder were fed according to the recipe into a weighed pressure vessel. Once the correct filling was reached the pneumatic transport started with conveying the powder to the dedicated destination above various mixers. Before stopping the conveying system and switching over to the next mixer the pipeline was purged to remove residues in the conveying pipe.