Performance evaluation of a double drum dryer for potato flake production.

摘要

A double drum dryer working under atmospheric pressure was developed for water evaporation rate of 20 kg/h. Potato slurry of 12% solid concentration was dried to obtain potato flakes. Experiments were carried out at drum speed of 5 to 30 rpm, steam pressure 2 to 7 kg/cm2 gauge (saturation temperature 120-164 degrees C) and liquid level 5 to 10 cm at the nip of drums. The responses obtained were, moisture content of the potato flakes: 1.18-44.15% (db), dry matter output rate: 1.33-2.87 kg dry solid/h and L value of colour: 30.9-66.4. Steam pressure and drum speed were the most influencing parameters affecting all 3 responses. Optimum combination of operating variables for obtaining potato flakes of 8% (db) moisture content, high dry solid output rate and high L value of colour was: drum speed 19.6 rpm, steam pressure 4.3 kg/cm2 gauge (saturation temperature 145 degrees C) and liquid level at the drum nip 6.3 cm. At this combination of independent variables, residence time of the product on drum surface would be 2 s, final moisture content of product 8% (db), product output rate 2.4 kg dry solid/h and L value of colour 53.