Thin-layer treatment device

A method for producing a solution of cellulose with a solvent from a suspension of cellulose in the solvent and a volatile non-solvent, comprising:

• introducing the suspension into an inlet of a thin-film treatment apparatus;
• applying and distributing the suspension in a film-like form on a housing casing which is temperature-controlled by a heat exchanger, by sweeper elements rotating about a common axis in a process housing of the thin-film treatment apparatus;
• evaporating volatile non-solvent so that the cellulose is dissolved;
• and
• outputting the solution of cellulose from the thin-film treatment apparatus through an outlet;
• wherein at least a part of the sweeper elements cause the cellulose to be advanced in the direction of the outlet so that the discharge at the outlet is between 30 and 600 kg/h cellulose solution per m2 of the temperature-controlled surface of the housing casing, and
• wherein the specific area ratio of the rotor blades is below 10 m2s/m3,
• wherein the specific area ratio of the rotor blades results from a heat exchange area of an inner wall of the housing casing per the product of a rotor blade tip loading area and a blade tip speed,
• wherein the rotor blade tip loading area is the sum of tip areas of all rotor blades in a process zone of the thin-film treatment apparatus and a tip area is the area of a rotor blade which is opposite the inner surface of the housing casing.