Effect of colloidal particles associated with the liquid bridge in sticking during drying in superheated steam

Effect of colloidal particles associated with the liquid bridge in sticking during drying in superheated steam

It is important in the design of a drying system to evaluate the sticking behaviour of the materials being dried. A new approach to the sticking issue is applied in this study by carrying out a sticking test for the liquid associated with the materials under study. It was found that the liquid bridge is responsible for the initial sticking of the materials to the contact surfaces. The colloidal material in this liquid is eventually responsible of building a sticky solid bridge during drying. The glass transition temperature for the Brewers Spent Grain (BSG) particles and the colloidal solution expelled from these particles were tested using Differential Scanning Calorimetric (DSC). However, the chopped BSG particles showed no glass transition temperature; there were an appreciable number of particles stuck to the rotary drum dryer and the sample holders during drying. The colloidal
particles in the liquid bridge were filtered and concentrated through evaporation and then analysed by DSC where they showed a glass transition temperature at (-23) and (-33) oC. In addition, the associated liquid thus prepared showed a honey consistency and a sticky touch when concentrated.
These two properties are indications that this colloidal material may be responsible for sticking the BSG to the steel surfaces during drying.

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