Method and apparatus for drying products with a closed gas stream and a desiccant liquid

In a method of drying products comprising the steps of moving the product to be dried through a drying compartment;

• continuously circulating a drying gas stream in a closed cycle so as to cause it to pass the product to be dried;
• contacting the drying gas stream with a desiccant liquid to remove moisture from the gas;
• and regenerating the desiccant liquid by circulating at least a part of it through regenerating means which remove moisture therefrom;
• the improvement comprising producing at least one layer of the desiccant liquid and bringing about a continuous heat exchange between the desiccant liquid layer and the product to be dried by heating the desiccant liquid in the course of said regenerating and then contacting the desiccant liquid with said drying gas to cool the desiccant liquid and heat the drying gas to at least 40.degree. C. in the course of said contacting.

In an apparatus for drying products comprising at least one drying compartment for the product to be dried;

• at least one contacting device for contacting a drying gas stream with a desiccant liquid to remove moisture from the gas;
• gas conducting means for conducting the drying gas stream in a substantially closed path through said drying compartment and said contacting device;
• gas circulating means to cause the drying gas stream to circulate along said closed path;
• regenerating means for removing moisture from the desiccant liquid;
• and liquid circulating means for circulating at least part of the desiccant liquid through said regenerating means and said contacting device;
• the improvement in which said contacting device (43) includes means (13, 58) for producing at least one continuous layer (1, 41) of the desiccant liquid to be contacted with the drying gas stream;
• said contacting device (43) being located at the boundary of or within said drying compartment (25, 40) and said at least one continuous layer being disposed substantially perpendicularly to said path for conducting said drying gas stream in said drying compartment (25, 40).

In an apparatus for drying products comprising at least one drying compartment for the product to be dried;

• at least one contacting device for contacting a drying gas stream with a desiccant liquid to remove moisture from the gas;
• gas conducting means for conducting the drying gas stream in a substantially closed path through said drying compartment and said contacting device;
• gas circulating means to cause the drying gas stream to circulate along said closed path;
• regenerating means for removing moisture from the desiccant liquid;
• and liquid circulating means for circulating at least a part of the desiccant liquid through said regenerating means and said contacting device;
• the improvement comprising a basement (49), a shell-roof (65), and a false roof (54) provided with openings (47, 47A) for letting through the drying gas stream and located between said basement (49) and said shell-roof (65);
• said drying compartment (40) being located between said basement (49) and said false roof (54);
• said gas circulating means (66, 66') being placed between said false roof (54) and said shell-roof (65);
• said contacting device (43) comprising liquid film conducting elements (58A, 58B, 58C);
• said contacting device (43) being placed at said drying compartment (40) so that said liquid film conducting elements (58A, 58B, 58C) are arranged in at least one substantially vertical plane, said plane being substantially perpendicular to the direction of flow of the drying gas stream and extending between said basement (49) and said false roof (54).

In a method of drying products comprising the steps of moving the product to be dried through a drying compartment;

• continuously circulating a drying gas stream so as to cause it to pass the product to be dried;
• contacting the drying gas stream with a desiccant liquid to remove moisture from the gas;
• and regenerating the desiccant liquid by circulating at least a part of it through regenerating means which remove moisture therefrom;
• the improvement wherein said drying gas stream consists of at least two parallel partial gas streams;
• the product to be dried is moved acress said partial gas streams;
• and each of said partial gas streams is contacted with a desiccant liquid of different specific concentration and temperature;
• each of said partial gas streams being contacted with a more concentrated desiccant liquid than the desiccant liquid contacting the previous partial gas stream with respect to the direction of movement of the product to be dried;
• producing at least two separated groups of desiccant liquid films of different concentration;
• placing said groups of desiccant liquid films side by side in a way of said partial gas streams so that each of said partial gas streams is contacted with its own at least one group of desiccant liquid films;
• each of said groups of desiccant liquid films being provided with its own liquid circuit;
• the liquid circuit of the last group with respect to the direction of movement of the product to be dried being fed with the regenerated desiccant liquid coming from said regenerating means;
• the circuit of each preceding group being fed with the overflow of the circuit of the subsequent group;
• and the overflow of the circuit of the first group being conducted into said regenerating means.