Patent EA-000216-B1 (EA)
Title: Method for dewatering a sheet of cellulose material, using hot air, caused to flow therethrough by means of a high vacuum, device therefor
Inventor: MARCHAL PAUL
IPC: D21F5/18
Filed: 1996-03-20
Abstract: 1. A method for drying a sheet of cellulose material, particularly a sheet of wet paper having a dry grammage of 10-80 g/m<2> in dried condition and a starting dryness level of 8-30 % obtained, for example, after dewatering on a formation web wherein said sheet is supported on a permeable web and hot air is caused to flow therethroughat high speed by means of vacuum of 100-500 millibars generated underneath the web. 2. A method as claimed in Claim 1 wherein the temperature of dry air is 100-500 degree C. 3. A method as claimed in Claim 1 or 2, wherein the temperature of wet air is 50 90 degree C. 4. A method as claimed in Claim 1 wherein the air flow is circulated in a closed circuit and after passing through the sheet material the air is successfully: - directed into a receiving chamber with vacuum of 100-500 millibars; - further fed into air/water separator for water removal, said water being in a suspended condition; - subjected to compression, exceeding atmospheric; - heated to temperature 100-500 degree C; -fed to the surface of sheet material placed in traverse direction on the air permeable web. 5. A method as claimed in Claim 4 wherein part of compressed air is evacuated and corresponding quantity is fed into the circuit to maintain the temperature of wet air in the distribution chamber within 50-90 degree C. 6. A method as claimed in one of the preceding Claim s wherein at least another air flow flows therethrough the sheet material, said air flow disposed lower than the first air flow and its temperature is preferably lower. 7. A method as claimed in Claim 6 wherein both air flows are part of two different closed circuits, and each circuit comprises all steps according to Claim 4 and, at least the first circuit comprises the air/water separator 8. A method as claimed in one of the preceding Claims wherein the starting dryness level of a paper sheet being about 8-30% is raised to about 35-75%, preferably to about 35-50%, using the above said drying method and wherein the paper sheet is dried, using the cylinder of yankee type to obtain dryness level of about 95%. 9. A method as claimed in one of Claims 1-7 wherein the starting dryness level of a paper sheet being about 8-30% is raised to about 35-75%, by said drying method, while the web of "marqueuse" type is used as a conveyer web and wherein the paper sheet is dried, using the cylinder of yankee type to obtain dryness level of about 95%. 10. A method as claimed in one of Claims 1-7 wherein the starting dryness level of a paper sheet being about 8-30% is raised to about 20-45%, by said drying method, while the web of "marqueuse" type is used as a conveyer web and wherein the paper sheet is further dried on said linen, using at least one drying apparatus with penetrating air flow to obtain the dryness level of about 50-90% and, at last, using the cylinder of yankee type, connected to a wiper, to obtain the dryness level of about 95%. 11. A method as claimed in one of Claims 1-7 wherein the starting dryness level of a paper sheet being about 8-30% is raised to about 20-45%, by said drying method, while the web of "marqueuse" type is used as a conveyer web and wherein the paper sheet is further dried on said linen, using at least one drying apparatus with penetrating air flow to obtain the dryness level of about 95%. 12. A method as claimed in one of Claims 10 or 11, wherein at least part of air, fed into the distribution chamber, is drawn from said drying apparatus with penetrating air flow. 13. A method as claimed in one of Claims 8-10, wherein at least part of air, fed into the distribution chamber, is drawn from drying caps of said drying apparatus, having said cylinder of yankee type. 14. A method as claimed in one of the preceding Claims wherein water vapor in predetermined quantities is injected into hot air flow prior to its flowing through the sheet providing modulated vapor supply traverse the sheet to change the humidity of hot air flow before its passing through the sheet. 15. A method as claimed in one of Claims 7-14, wherein water vapor is injected into the first flow. 16. Device for dewatering a sheet of cellulose material as claimed in one of the preceding Claims wherein said device comprises: - mobile permeable web, on one side of which a sheet is supported to be dried; - chamber of air distribution with a channel of air input and an orifice for air supply to said side - a means for air heating, flowing into the channel of air input; - receiving chamber for air drawn from the distribution chamber, wherein the receiving chamber comprises, at least, one input aperture, disposed opposite the input air orifice of the distribution chamber; - a means for maintaining vacuum of 100-150 millibar in the receiving chamber. 17. Device as claimed in Claim 16, wherein said device comprises also: - air/water separator, connected with the receiving chamber; - air compressor, connected with separator; - a means of air heating, connected with the compressor; - a tube, connecting said heating means with said distribution chamber; - a means of air outlet, connected with the compressor; - a means of air input, connected with said heating means. 18. Device as claimed in Claim 17, wherein said device comprises gas turbine unit for the compressor driving and wherein the exhausted gas of said gas turbine unit is used for feeding said heating means. 19. Device as claimed in Claim 17, wherein said device comprises gas turbine unit for the compressor driving and wherein said heating means is a heat exchanger providing the input of said exhausted gas of said compressor from one side and from the other side the air flow from the compressor. 20. Device as claimed in one of Claims 16-19, wherein said device comprises at least two air circuits for dewatering and distribution chambers for successive zones, wherein, at least, the first circuit feeds the first zone, comprising said air/water separator. 21. Device as claimed in one of Claims 16-20, wherein said device comprises means of vapor input, disposed inside at least the first distribution chamber. 22. Device as claimed in Claim 21, wherein said distribution chamber is divided into a plurality of chambers, disposed traverse of the machine movement, wherein, at least, one of those chambers comprises a means of vapor input.