Process and system for preparing dry man-made cellulosic staple fibres

Abstract

The invention relates to a process for preparing man-made cellulosic staple fibres (4) for yarn spinning, the process comprising manufacturing man-made cellulosic staple fibres (4) from cellulosic raw material (2) in a manufacturing step (10, 100) providing a mass (6) of wet man-made cellulosic staple fibres (4) as a manufacturing output. The process comprises flash-drying the wet man-made cellulosic staple fibres (4) with heated drying gas flow into dry man-made cellulosic staple fibres (4) in a drying step (150).

Description

[0001]PROCESS^ AND^ SYSTEM^ FOR^ PREPARING^ DRY^ MAN-MADE^ CELLULOSIC^ STAPLE^FIBRES FIELD OF THE INVENTION The present invention relates to a process for preparing man-madecellulosic staple fibres and more particularly to a process according to preamble ofclaim 1. The present invention further relates to a system for preparing man-madecellulosic staple fibres and more particularly to a system according to preamble ofclaim 12. BACKGROUND OF THE INVENTION Man-made cellulosic staple fibres, or regenerated cellulosic staplefibres, such as viscose, cupro and Lyocell fibres, are made from natural cellulosethat is extracted from wood pulp. Man-made cellulosic staple fibres are used widelyfor example in textiles, nonwovens and hygiene products. Prior art process forproducing man-made cellulosic staple fibres is shown schematically in figure 1.Man-made cellulosic staple fibres are manufactured in a manufacturing process 10by dissolving cellulosic pulp 2 in a solvent, extruding the dissolved pulp into acontinuous filament by regeneration in a spin bath and cutting the filament intospecific lengths to form the man-made cellulosic staple fibres 4. The manufacturingprocess further comprises washing the man-made cellulosic staple fibres 4 to washout the chemicals needed in the manufacturing process 10. A wet mass of man-made cellulosic staple fibres is formed into a layer, or a web or a mat, 6, usuallycalled “a fleece”. Subsequently the layer of man-made cellulosic staple fibres isdried in a drying process. The drying may be preceded by squeezing of the layer toremove excess water. The drying of the man-made cellulosic staple fibres 4 is carried out inhot air conveyer dryers 14, 20, 21, 22 to achieve desired moisture content. Thelayer 6 of man-made cellulosic staple fibres 4 is conveyed on a wire conveyor 14.The layer 6 of man-made cellulosic staple fibres 4 travelling on the wire conveyor14 is subjected hot air flows 25 from air blowers 20, 21, 22. The hot air flows 25are blown from below towards the layer 6. The conveyor dryer comprises multiplesuccessive drying sections in which hot air flows 25 are blown towards the layer 6with the air blowers 20, 21, 22, respectively. For achieving efficient drying, the layer 6 of man-made cellulosic staplefibres 4 needs to have sufficient porosity to allow the hot air flows 25 penetratethrough the layer 6. The layer 6 of man-made cellulosic staple fibres 4 is usually upto 10 cm in thickness. During the conveyor drying the layer 6 of man-madecellulosic staple fibres 4 tends to compress due to air pressure caused by the hotair flows 25 from the air blowers 20, 21, 22. As the drying is carried out with hotair flows 25 blown against the layer 6, the drying occurs in an uneven manner inthe thickness direction of the layer 6 as the hot air contacts first the bottom of thelayer 6 and only then flows through upper parts of the layer 6. Furthermore, thecompressive effect of the hot air flows 25 blown towards the layer 6 increases theuneven drying as the more compact parts of the layer 6 tend to dry slower due todecreased flow-through of air. The uneven drying may cause also local over-dryingwhich deteriorates quality of the dry man-made cellulosic staple fibres or causesneed for moisture control of the dry man-made cellulosic staple fibres 4 after thedrying. Afluffer 26, 27, such as a spike roll, is needed between successive dryingsections of the conveyor dryer to break the layer 6 for reintroducing sufficientporosity to the layer 6 for restoring drying efficiency and decreasing unevendrying. The layer 6 of man-made cellulosic staple fibres 4 further needs to bebroken in a post-fluffer 28 after the last of the successive drying sections forproviding porous dry fibre mass of man-made cellulosic staple fibres 4. Dry fibremass of man-made cellulosic staple fibres 4 is further usually conveyed with a beltor wire conveyor 32 to post-processing 30. The post-processing comprisesmoisture control or re-moisturizing of the dry man-made cellulosic staple fibres 4for eliminating over-dried man-made cellulosic staple fibres and / or baling the dryman-made cellulosic staple fibres 4.BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide process and system forpreparing dry man-made cellulosic staple fibres so as to overcome or at leastalleviate the prior art disadvantages. The objects of the invention are achieved by a process for preparing dryman-made cellulosic staple fibres which is characterized by what is stated in theindependent claim 1. The objects of the invention are further achieved by a systemfor preparing dry man-made cellulosic staple fibres which is characterized by whatis stated in the independent claim 12. The objects of the invention are achieved bya use which is characterized by what is stated in the independent claim 19.The preferred embodiments of the invention are disclosed in the dependent claims. The present invention provides a process, system and use for preparingman-made cellulosic staple fibres which are suitable to be used in yarn spinning.The invention is based on the idea of providing a process for preparingdry man-made cellulosic staple fibres for yarn spinning, the process comprisesdrying wet man-made cellulosic staple fibres in a drying step. The processcomprises flash-drying the wet man-made cellulosic staple fibres with heateddrying gas flow into dry man-made cellulosic staple fibres in the drying step.Flash-drying is a drying method in which wet material is introduced into a heated drying gas flow which conveys the material through a drying reactor.The heated drying gas flow causes rapid evaporation of moisture from the wetmaterial during passing through the drying reactor. During the flash-drying the wet material dries and temperature of the drying gas decreases. In flash-drying the wet man-made cellulosic staple fibres are carried byheated drying gas through a flash-drying reactor. The heated drying gas provides efficient evaporation of moisture from the wet man-made cellulosic staple fibres during travel through the flash-drying reactor. The area of contact between the drying gas and the fibres is much higher than in conventional drying of fibres in a conveyor dyer. The drying gas may be for example air or the like gaseous medium suitable for flash-drying. The flash-drying prevents generation of compressed formations of theman-made cellulosic staple fibres and promotes disintegration of the man-madecellulosic staple fibres during the drying. This enhances even and uniform dryingof the man-made cellulosic staple fibres during the drying step.The flash-drying further prevents eliminates need for utilizing a flufferfor reintroducing sufficient porosity to the man-made cellulosic staple fibres forrestoring drying efficiency and decreasing uneven drying. Thus, the processbecomes simpler and more efficient. Furthermore, flash-drying of the wet man-made cellulosic staple fibres causes curling of the man-made cellulosic staple fibres. Curling is due to the fibre length and efficient drying. Curling means shortening of a fibre due to kinks, twists, and / or bendsformed in the fibre. In some embodiments, the process comprises manufacturing the man-made cellulosic staple fibres from cellulosic raw material in a manufacturing step, the manufacturing step providing a mass of wet man-made cellulosic staple fibresas a manufacturing output.The cellulosic raw material may be for example plant based cellulose fibre pulp, microbial cellulose or recycled cellulosic textile fibres. Manufacturing of the man-made cellulosic staple fibres comprisesutilizing semi-chemical methods that involve dissolution of cellulose. Themanufacturing of the man-made cellulosic staple fibres requires dissolving thecellulose after which it is regenerated. The man-made cellulosic staple fibres areregenerated in the manufacturing step by a wet spinning method or a dry-wet spinning method. Accordingly, the process provides specific manufacturing of the man- made cellulosic staple fibres. The manufacturing step further comprises forming a regeneratedcellulosic filament from the cellulosic raw material by the regeneration method andcutting the regenerated cellulosic filament into man-made cellulosic staple fibres. The cutting determines the length of the man-made cellulosic staple fibres. In the manufacturing and regeneration of the man-made cellulosicstaple fibres utilization of different chemicals is needed. These chemicals need tobe washed out from the man-made cellulosic staple fibres. Therefore, extensivewashing of the man-made cellulosic staple fibres is required for washing out thechemicals. Washing leaves the manufactured man-made cellulosic staple fibres wetand provides the mass of wet man-made cellulosic staple fibres. The mass of wetman-made cellulosic staple fibres is dried by the flash-drying.The manufacturing step comprises washing the man-made cellulosicstaple fibres and forming the mass of wet man-made cellulosic staple fibres.The manufacturing step further comprises the cutting of the filamentinto man-made cellulosic staple fibres.In some embodiments, the cut man-made cellulosic staple fibres havelength between 20 to 80 mm. Thus, the man-made cellulosic staple fibres are cut tolength between 20 to 80 mm. The length of at least 20 mm enables utilizing the man-made cellulosicstaple fibres in yarn spinning.In some other embodiments, the cut man-made cellulosic staple fibreshave length between 25 to 50 mm. Thus, the man-made cellulosic staple fibres arecut to length between 25 to 50 mm. The length between 25 to 50 mm is preferable for yarn spinning. In some further embodiments, the cut man-made cellulosic staple fibreshave length between 36 to 44 mm, or approximately 28 to 40 mm. Thus, the man- made cellulosic staple fibres are cut to length between 36 to 44 mm, or approximately 28 to 40 mm. This length corresponds cotton fibre length used in textiles. The man-made cellulosic staple fibres are solid fibres.In some embodiments, the drying step comprises drying the wet man-made cellulosic staple fibres to dry man-made cellulosic staple fibres havingmoisture content 2 to 20 weight-%.This moisture content enables storing and utilizing the man-madecellulosic staple fibres in yarn spinning.In some other embodiments, the drying step comprises drying the wetman-made cellulosic staple fibres to dry man-made cellulosic staple fibres havingmoisture content 10 to 15 weight-%, preferably 11 to 13 weight-%.These moisture contents are preferable for yarn spinning.In some embodiments, the process comprises forming the mass of wetman-made cellulosic staple fibres into porous bundles of wet man-made cellulosicstaple fibres in a pre-processing step prior to the flash-drying in the drying stepand flash-drying the porous bundles of wet man-made cellulosic staple fibres intodry man-made cellulosic staple fibres in the drying step.Forming the mass of wet man-made cellulosic staple fibres into porousbundles of wet man-made cellulosic staple fibres comprises dispersing ordisintegrating and defibrating the mass of wet man-made cellulosic staple fibressuch that porosity of the mass is increased. In some other embodiments, the manufacturing step comprisesproviding a layer of wet man-made cellulosic staple fibres as the mass, the processcomprises forming the layer of wet man-made cellulosic staple fibres into porousbundles of wet man-made cellulosic staple fibres in a pre-processing step prior tothe flash-drying in the drying step and flash-drying the porous bundles of wet man-made cellulosic staple fibres into dry man-made cellulosic staple fibres in thedrying step. The layer of wet man-made cellulosic staple fibres is in the form of aweb or a mat. Forming the mass of wet man-made cellulosic staple fibres into porousbundles of wet man-made cellulosic staple fibres comprises dispersing ordisintegrating the layer of wet man-made cellulosic staple fibres such that porosityis increased. Forming the mass of wet man-made cellulosic staple fibres into porousbundles of wet man-made cellulosic staple fibres is carried out such that the lengthof the man-made cellulosic staple fibres is maintained unchanged. The dispersing or disintegrating is carried out with a fluffer which isarranged to disperse or defibrate the mass or layer of wet man-made cellulosicstaple fibres into the porous bundles of wet man-made cellulosic staple fibres. Thefluffer may be for example spiked roller, spiked conveyer, disk fluffer, screw feeder or any combination thereof. Forming the mass or layer of wet man-made cellulosic staple fibres intothe porous bundles of wet man-made cellulosic staple fibres increases the porosityand effective surface area of the wet man-made cellulosic staple fibres. The increased porosity and effective surface area of the porous bundles of wet man-made cellulosic staple fibres enhances drying in the flash-drying and promoteseven or uniform drying of the wet man-made cellulosic staple fibres. Further, flash-drying promotes maintaining the porosity and disintegration of the porous bundles of wet man-made cellulosic staple fibres during the drying. In some embodiment, the process comprises adding one or more spinfinish chemicals to the mass or layer of wet man-made cellulosic staple fibresbefore the drying step or before the formation of the porous bundles of wet man-made cellulosic staple fibres. Spin finish chemicals are processing aids applied to the man-madecellulosic staple fibres for enhancing processability of the man-made cellulosicstaple fibres in the yarn spinning. The spin finish chemicals provide lubrication,anti-static properties and cohesion to the man-made cellulosic staple fibres. In some embodiments, the wet man-made cellulosic staple fibres provided to the flash-drying and the drying step have moisture content between 40 to 50 weight-%. Accordingly, the moisture content of the wet man-made cellulosicstaple fibres received in the flash-drying or in the drying step is between 40 to 50weight-%. In some embodiments, the process comprises pre-drying the mass orlayer of wet man-made cellulosic staple fibres provided from the manufacturingstep. The pre-drying is carried out before the drying step and the flash-drying or before the forming of the porous bundles of wet man-made cellulosic staple fibres. In some embodiment, the method comprises pre-drying the mass orlayer of wet man-made cellulosic staple fibres to moisture content between 40 to50 weight-% before the flash-drying or the drying step. In some embodiments, the pre-drying is carried out by press drying formechanically squeezing moisture out of the mass or layer of wet man-madecellulosic staple fibres. In some other embodiments, the pre-drying is carried out by directing a flow of heated drying gas towards the mass or layer of man-made cellulosic staple fibres. In some further embodiment, the pre-drying is carried out by pressdrying and by directing a flow of heated drying gas towards the mass or layer of man-made cellulosic staple fibres. In some embodiments, the process comprises conveying the porousbundles of wet man-made cellulosic staple fibres pneumatically with one or moregas flows through the drying step and / or pneumatically with one or more gas flows from the pre-processing step to the drying step and through the drying step. Accordingly, in some embodiments the wet man-made cellulosic staplefibres are conveyed through the drying step or the flash-drying with the heateddrying gas. In some embodiments the porous bundles of wet man-made cellulosicstaple fibres are conveyed to the drying step or to the flash-drying with a firstcarried gas flow. The porous bundles of wet man-made cellulosic staple fibres may also be conveyed to the drying step or to the flash-drying with the heated drying gas. Conveying the man-made cellulosic staple fibres pneumatically to thedrying step and / or through the drying step is efficient. In some embodiments, the drying step comprises drying the wet man-made cellulosic staple fibres in two or more successive flash-drying stages, thedrying step further comprises flash-drying the wet man-made cellulosic staplefibres with separate heated drying gas flows in the successive flash-drying stages.Accordingly, the wet man-made cellulosic staple fibres are exposed totwo or more successive flash-dying stages in the drying step. The processcomprises supplying a separate heated drying gas flow to each successive flash-dying stage. Each successive flash-drying stage comprises a separate flash-drying reactor. In the process wet man-made cellulosic staple fibres are conveyed fromone flash-drying stage to a successive flash-drying stage, preferably pneumatically.The two or more successive flash-drying stages enable detailed controlof drying and moisture content of the man-made cellulosic staple fibres during thedrying step. During the flash-drying moisture is released from the wet man-madecellulosic staple fibres to the heated drying gas causing the drying gas to cool andbecome damp. In some embodiments, the drying step comprises separating the man-made cellulosic staple fibres from damp drying gas after the flash-drying. Thisprevents the man-made cellulosic staple fibres being maintained in contact withthe damp drying gas. In some embodiments, the drying step comprises separating the man-made cellulosic staple fibres from damp drying gas after each flash-drying stage.This prevents the man-made cellulosic staple fibres being maintained in contactwith the damp drying gas and enables detailed control of drying and moisturecontent of the man-made cellulosic staple fibres during the drying step.Each successive flash-drying stage comprises a separate separator forseparating the man-made cellulosic staple fibres from the damp drying gas.In some embodiments, the process comprises conveying the dry man-made cellulosic staple fibres from the drying step pneumatically with a secondcarrier gas flow to post-processing. The process comprises supplying the second carrier gas flow forconveying the dry man-made cellulosic staple fibres from the drying steppneumatically to the post-processing. This is achieved due to the flash-drying which enables maintaining porosity and disintegration of the man-made cellulosicstaple fibres during the drying. Thus, the dry man-made cellulosic staple fibres aredischarged from the drying step in porous form. The pneumatic conveying is efficient. In some embodiments, conveying the dry man-made cellulosic staplefibres from the drying step to the post-processing comprises adjusting at least oneof temperature and humidity of the second carried gas for providing adjustedsecond carried gas, and conveying the dry man-made cellulosic staple fibres fromthe drying step to the post-processing pneumatically with the second adjustedcarrier gas flow. The process comprises adjusting the temperature or the humidity, or both, of the second carried gas and supplying the adjusted second carrier gas flowfor conveying the dry man-made cellulosic staple fibres from the drying steppneumatically to the post-processing. This enables adjusting the temperature ormoisture content, or both, of the dry man-made cellulosic staple fibres duringconveying from the drying step to the post-processing. Thus, the dry man-made cellulosic staple fibres may be cooled duringconveying from the drying step to the post-processing.Further, the moisture content of the dry man-made cellulosic staplefibres may be equalized and controlled in detail. The moisture content of the dryman-made cellulosic staple fibres may be controlled to be 2 to 20 weight-%, 10 to15 weight-%, or 11 to 13 weight-%.In some embodiments, the process comprises post-processing the dry man-made cellulosic staple fibres. In some embodiments, the post-processing comprises baling the dryman-made cellulosic staple fibres in a baler.The present invention is also based on an idea of providing a system forpreparing dry man-made cellulosic staple fibres for yarn spinning. The systemcomprises a manufacturing arrangement arranged to manufacture man-madecellulosic staple fibres from cellulosic raw material, the manufacturingarrangement being arranged to provide a mass of wet man-made cellulosic staplefibres as a manufacturing output. The system comprises a flash-dryer configuredto dry the wet man-made cellulosic staple fibres with heated drying gas flow intodry man-made cellulosic staple fibres. The flash-dryer comprises a flash-drying reactor through which the wetman-made cellulosic staple fibres are carried by the heated drying gas. The heateddrying gas provides efficient evaporation of moisture from the wet man-madecellulosic staple fibres during travel through the flash-drying reactor.The flash-dryer is arranged to carry out the above disclosed flash- drying. The flash-dryer usually comprises vertical flash-drying reactor in whichthe wet man-made cellulosic staple fibres are carried by the heated drying gas flowupwards. Accordingly, the flash-dryer provides a small footprint area in the facility. Furthermore, the closed flash-drying reactor enables placing the flash-dryer outdoors in the facility. These enable saving indoor spaces. The manufacturing arrangement of man-made cellulosic staple fibrescomprises equipment for dissolving cellulosic raw material by utilizing semi-chemical methods and regenerating the man-made cellulosic staple fibres by a wetspinning method or a dry-wet spinning. Accordingly, the manufacturing arrangement comprises specificequipment for manufacturing the man-made cellulosic staple fibres. The manufacturing arrangement comprises a regeneration unitcomprising dissolving equipment arranged to dissolve cellulosic raw material andregeneration equipment arranged to regenerate a cellulosic filament from thedissolved cellulosic raw material. The manufacturing arrangement further comprises cutting equipment arranged to cut the regenerated cellulosic filament into man-made cellulosic staple fibres. In some embodiments, the cutting equipment in arranged to cut man-made cellulosic staple fibres to length between 20 to 80 mm, or to length between25 to 50 mm. In some other embodiments, the cutting equipment is arranged to cutthe man-made cellulosic staple fibres to length between 36 to 44 mm, orapproximately between 38 to 40 mm. Some man-made cellulosic staple fibres comprise non-round cross- sectional shape, such as multilobal cross-section. Water retention in fibres with non-round cross-section is higher than in fibres with rounded cross-sections. Theflash-drying of man-made cellulosic staple fibres comprising non-round cross-sectional shape is especially advantageous due to the increased evaporation. The manufacturing arrangement further comprises fibre washingequipment arranged to wash out chemicals needed in manufacturing of the man-made cellulosic staple fibres. The man-made cellulosic staple fibres become wet inthe washing. Therefore, a mass of wet man-made cellulosic staple fibres is providedas a manufacturing output from the manufacturing arrangement. In some embodiments, the manufacturing arrangement is arranged tooutput the mass of wet man-made cellulosic staple fibres as a layer or mat of wetman-made cellulosic staple fibres. In some embodiments, the manufacturing arrangement is arranged tooutput the layer of wet man-made cellulosic staple fibres on a conveyor, such as awire or belt conveyor. In some embodiments, the system comprises a disintegrator provided upstream of the flash-dryer and arranged to disperse or disintegrate the mass orlayer of wet man-made cellulosic staple fibres into porous bundles of wet man-made cellulosic staple fibres and the flash-dryer is configured to dry the porousbundles of wet man-made cellulosic staple fibres with the heated drying gas flowinto the dry man-made cellulosic staple fibres. The disintegrator comprises one or more fluffers which are arranged todisperse or disintegrate and defibrate the mass or layer of wet man-made cellulosicstaple fibres into the porous bundles of wet man-made cellulosic staple fibres. Thefluffer may be for example spiked roller, spiked conveyer, disk fluffer, screw feeder or any combination thereof. Dispersing or disintegrating the mass of wet man-made cellulosic staplefibres into the porous bundles of wet man-made cellulosic staple fibres in thedisintegrator increases the porosity and effective surface area of the wet man-made cellulosic staple fibres which further enhances drying in the flash-drying andpromotes even or uniform drying of the wet man-made cellulosic staple fibres. The disintegrator is arranged to form the mass of wet man-madecellulosic staple fibres into the porous bundles of wet man-made cellulosic staple fibres such that the length of the man-made cellulosic staple fibres is maintained unchanged. In some embodiments, the flash-dryer comprises two or more successive flash-drying units. The successive flash-drying unit comprise separate drying gas sources arranged to provide separate heated drying gas flows to the two or more successive flash-drying units. Accordingly, the wet man-made cellulosic staple fibres are conveyedsuccessively through two or more successive flash-dying units. Each successive flash-drying unit comprises a separate flash-dryingreactor. Each successive unit comprises a separate drying gas source or drying gas supply device arranged to supply heated drying gas to the respective flash- drying reactor. The two or more flash-drying units are arranged successively anddirectly one after the other such that the wet man-made cellulosic staple fibres areconveyed from one flash-drying unit to a successive flash-drying unit.The two or more successive flash-drying units enable detailed controlof drying and moisture content of the man-made cellulosic staple fibres. In some embodiments, the flash-dryer comprises the flash-dryingreactor configured to dry the wet man-made cellulosic staple fibres with the heated drying gas flow, and a separator downstream of the flash-drying reactor. Theseparator is arranged to separate the man-made cellulosic staple fibres from dampdrying gas downstream of the flash-drying reactor.In some embodiments, the separator is a cyclone separator. Cycloneseparator provides good separation and is energy efficient.In some other embodiments, the separator is a filter separator in whicha filter is arranged to separate the man-made cellulosic staple fibres from the dampdrying gas. In the embodiments where the flash-dryer comprises two or moresuccessive flash-drying units, each of the two or more successive flash-dryer unitscomprise a flash-drying reactor configured to dry the wet man-made cellulosicstaple fibres with heated drying gas flow and a separator downstream of the flash-drying reactor. The separator being arranged to separate the man-made cellulosicstaple fibres from the damp drying gas.This prevents the damp drying gas from one flash-drying reactor fromentering the successive flash-drying reactor. Therefore, detailed control of dryingand moisture content of the man-made cellulosic staple fibres is achieved.In some embodiments, the system comprises a post-processing unit and a pneumatic post-processing conveyer arranged to convey the dry man-madecellulosic staple fibres from the flash-dryer pneumatically with carrier gas flow tothe post-processing unit. The pneumatic post-processing conveyer comprises a second carrier gas supply device arranged to supply second carrier gas for conveying the dry man-made cellulosic staple fibres from the flash-dryer to the post-processing unit viaconveyer channel. In some embodiments, the second carrier gas supply device is providedwith a temperature adjuster arranged to adjust temperature of the supplied secondcarrier gas, and / or with a humidity adjuster arranged to adjust the humidity of thesupplied second carried gas. This enables adjusting the temperature or moisturecontent, or both, of the dry man-made cellulosic staple fibres during conveyingfrom the drying step to the post-processing unit.In some embodiments, the system comprises the post-processing unitarranged to post-process the dry man-made cellulosic staple fibres. In some embodiments, the post-processing unit comprises a balerdevice arranged to bale the dry man-made cellulosic staple fibres into bales.The disclosed system is arranged to carry out the process disclosed above. The present invention is further based on an idea of use of flash-dryingwith heated drying gas flow for drying wet man-made cellulosic staple fibres,having length between 20 to 80 mm, preferably between 25 to 50 mm, into dryman-made cellulosic staple fibres. The present invention further comprises use offlash-drying with heated drying gas flow for drying the wet man-made cellulosicstaple fibres, having length between 36 to 44 mm, preferably between 38 to 40 mm,into dry man-made cellulosic staple fibres. The present invention provides a simple and efficient process andsystem for preparing dry man-made cellulosic staple fibres. Utilizing flash-drying enables eliminating disintegration of the mass of man-made cellulosic staple fibres between drying stages and after the drying. Furthermore, the dry man-madecellulosic staple fibres have improved quality due to even and uniform drying. Thedry man-made cellulosic staple fibres are further provided with curling whichenhances fibre properties for yarn spinning. BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in detail by means of specific embodimentswith reference to the enclosed drawings, in whichFigure 1 shows schematically a prior art process and system;Figures 2 to 5 disclose schematic flow charts of processes according tothe present invention; Figure 6 shows schematically one embodiment of the system accordingto the present invention; Figures 7 and 8 shows schematically different embodiments of thesystem having a dryer according to the present invention; andFigures 9 and 10 shows schematically different embodiments of asystem having a dryer with two flash-dryer units according to the presentinvention. DETAILED DESCRIPTION OF THE INVENTION Figures 2 to 5 disclose schematically different embodiments of a process for preparing dry man-made cellulosic staple fibres. The process comprises a manufacturing step 100 for manufacturing man-made cellulosic staple fibres. Manufacturing output from the manufacturing step 100 is a mass of wetman-made cellulosic staple fibres from cellulosic raw material.The manufacturing step 100 comprises dissolving the cellulosic rawmaterial, regeneration of a continuous cellulosic filament from the dissolvedcellulosic raw material, cutting the cellulosic filament into man-made cellulosicstaple fibres, and washing the man-made cellulosic staple fibres for removingchemicals used in the dissolving and regeneration.Washing the man-made cellulosic staple fibres causes wetting andprovides a mass of wet man-made cellulosic staple fibres.The cellulosic raw material is dissolved by utilizing semi-chemicalmethods that involve dissolution of the cellulosic raw material.Regeneration comprises regenerating the continuous cellulosic filament from the dissolved cellulosic raw material by a wet spinning method or a dry-wet spinning method. The manufacturing step 100 further comprises the cutting of thecontinuous cellulosic filament into the man-made cellulosic staple fibres. The cutting of the continuous cellulosic filament determines the lengthof the man-made cellulosic staple fibres manufactured in the manufacturing step100. The continuous cellulosic filament is cut into the man-made cellulosicstaple fibres having length between 20 to 80 mm, or preferably between 25 to 50mm. The length is determined such that the man-made cellulosic staple fibres aresuitable for yarn spinning. Then the man-made cellulosic staple fibres are subjected to the washingin which the chemicals utilized in the manufacturing step 100 are washed out and removed from the man-made cellulosic staple fibres. Washing leaves themanufactured man-made cellulosic staple fibres wet. Therefore, the manufacturingoutput from the manufacturing step is the mass of wet man-made cellulosic staple fibres. In step 110 the mass of wet man-made cellulosic staple fibres isprovided from the manufacturing step 100 for further processing. The wet man-made cellulosic staple fibres need to be dried beforeutilization. The mass of wet man-made cellulosic staple fibres is a dense mass.Dense mass is difficult to dry in an even and uniform manner and efficiently.Further, supplying the dense mass to subsequent drying is difficult. Therefore, the process comprises a forming step 130 in which the massof wet man-made cellulosic staple fibres is formed into porous bundles of wet man-made cellulosic staple fibres in a pre-processing step prior to the flash-drying inthe drying step and flash-drying the porous bundles of wet man-made cellulosicstaple fibres into the dry man-made cellulosic staple fibres in the drying step.Forming the mass of wet man-made cellulosic staple fibres into theporous bundles of wet man-made cellulosic staple fibres comprises fluffing themass of man-made cellulosic staple fibres such that the porous bundles of wet man-made cellulosic staple fibres are formed.Fluffing the mass of man-made cellulosic staple fibres comprises anycombination of shredding, breaking, dispersing, disintegrating or the like toincrease porosity of the mass of wet man-made cellulosic staple fibres in theforming step 130. The process comprises flash-drying the wet man-made cellulosicstaple fibres with heated drying gas flow into the dry man-made cellulosic staplefibres in a drying step 150.The porous bundles of wet man-made cellulosic staple fibres arereceived in the drying step 150. The porous bundles of the wet man-made cellulosicstaple fibres are flash-dried with the heated drying gas flow. In the flash-drying theporous bundles of wet man-made cellulosic staple fibres are carried by the heateddrying gas through a flash-drying reactor. The heated drying gas causes efficientevaporation of moisture from the porous bundles of wet man-made cellulosicstaple fibres during travel through the flash-drying reactor. At the same timeporosity of the man-made cellulosic staple fibres is maintained due to the flow ofthe heated drying gas. The drying output from the drying step 150 is the dry man-made cellulosic staple fibres. The wet man-made cellulosic staple fibres received in the drying step150 have moisture content between 40 to 50 weight-% before the drying. The dry man-made cellulosic staple fibres leaving the drying step 150have moisture content between 2 to 20 weight-%, or between 10 to 15 weight-%,or between 11 to 13 weight-%, after the drying. Accordingly, the wet man-madecellulosic staple fibres received in the drying step 150 are dried to the dry man-made cellulosic staple fibres having moisture content between 2 to 20 weight-%,between 10 to 15 weight-%, or between 11 to 13 weight-% in the drying step 150.The drying step 150 may comprise drying the wet man-made cellulosicstaple fibres in one or more successive, or in two or more successive, flash-dryingstages. Accordingly, the drying step 150 may comprise one or more successiveflash-drying stages. The wet man-made cellulosic staple fibres are driedsuccessively in the one or more successive flash-drying stages. The wet man-madecellulosic staple fibres are conveyed successive through the one or more flash-drying stages in the drying step 150. Each flash-drying stage comprises providing a separate heated dryinggas flow for drying the wet man-made cellulosic staple fibres. During the flash-drying moisture is released from the wet man-madecellulosic staple fibres to the heated drying gas causing the drying gas to cool andbecome damp. Each flash-drying stage comprises separating the man-madecellulosic staple fibres from damp drying gas after the flash-drying.Each successive flash-drying stage comprises a separate separator forseparating the man-made cellulosic staple fibres from the damp drying gas.In some embodiments, the process comprises conveying the dry man-made cellulosic staple fibres from the drying step pneumatically with a secondcarrier gas flow to post-processing. In some embodiments, the process comprises pre-drying the dry man-made cellulosic staple fibres before the drying step 150.The pre-drying may be carried out before the forming step 130 for pre- drying the mass of wet man-made cellulosic staple fibres. Alternatively, the pre- drying may be carried out between the forming step 130 and the drying step 150for pre-drying the porous bundles of wet man-made cellulosic staple fibres.In the pre-drying the wet man-made cellulosic staple fibres, or the massor the porous bundles, are pre-dried to the moisture content between 40 to 50weight-% in which the wet man-made cellulosic staple fibres are received in thedrying step 150. Figure 3 shows another embodiment of the process according to the present invention. In this embodiment, the manufacturing step 100, the forming step 130 and the drying step 150 are similar to the embodiment of figure 2. In the embodiment of figure 3 of the process, the mass of wet man-madecellulosic staple fibres manufactured in the manufacturing step 100 is provided asa layer or web or sleeve of wet man-made cellulosic staple fibres in step 110. Thislayer is often called “a fleece”. The layer of wet man-made cellulosic staple fibres has usually athickness between 5 to 15 cm. The layer of wet man-made cellulosic staple fibres may be provided ona conveyor, such as a wire or belt conveyer. The process comprises conveying the layer of wet man-made cellulosicstaple fibres in step 120 to the formation of the porous bundles of wet man-madecellulosic staple fibres. Conveying the layer in step 120 may be carried out with the conveyor. The forming step 130 comprises forming the layer of wet man-madecellulosic staple fibres into porous bundles of wet man-made cellulosic staplefibres. In some embodiments, the pre-drying of the wet man-made cellulosicstaple fibres is carried out in connection with or during the conveying of the layerof wet man-made cellulosic staple fibres to the formation step 130.The pre-drying comprises pre-drying the layer of wet man-made cellulosic staple fibres. In some embodiments, the pre-drying is carried out by directing a heated pre-drying gas flow towards or against the layer of wet man-made cellulosicstaple fibres from above or below the layer. The heated pre-drying gas flow may beprovided by a pre-drying gas blower. The pre-drying gas blower is arranged in connection the conveyor.The process further comprises a supplying step 140 in which the porousbundles of wet man-made cellulosic staple fibres are supplied to the drying step150 or to the flash-dryer. Forming the porous bundles of wet man-made cellulosic staple fibres inthe formation step 130 enables carrying out the supplying step 140 by pneumatically supplying the porous bundles of wet man-made cellulosic staplefibres to the drying step 150.The pneumatic supplying comprises providing a first carrier gas flowand conveying the porous bundles with the first carrier gas flow to the drying step 150. The first carrier gas flow may be provided with a first carried gas source or a first blower arranged to convey the porous bundles along supply channel to the drying step 150. Alternatively, the porous bundles are supplied to the drying step 150 or to the flash-dryer with the heated drying gas flow configured to dry the porousbundles of wet man-made cellulosic staple fibres in the flash-drying reactor. Theheated drying gas flow forms the first carrier gas flow.The wet man-made cellulosic staple fibres are further dried in thedrying step 150. Figure 4 shows another embodiment of the process according to the present invention. In this embodiment, the manufacturing step 100, the mass providing step 110, the forming step 130 and the drying step 150 are similar to the embodiment of figure 2. In this embodiment, the dry man-made cellulosic staple fibres dried inthe drying step 150 are further conveyed to post-processing in a conveying step160 and the dry man-made cellulosic staple fibres are further post-processed inthe post-processing step 170.The conveying step 160 comprises providing a carrier gas flow andconveying the dry man-made cellulosic staple fibres from the drying step 150pneumatically to the post-processing step 170.The pneumatic conveying comprises providing a second carrier gasflow and conveying the dry man-made cellulosic staple fibres with the secondcarrier gas flow to the post-processing step 170. The second carrier gas flow may be provided with a second carried gassource or a second blower arranged to convey the dry man-made cellulosic staplefibres conveying channel to the post-processing step 170.Conveying the dry man-made cellulosic staple fibres from the dryingstep 150 to the post-processing step 170 may comprise conditioning the dry man-made cellulosic staple fibres during the conveying. The conditioning comprisesadjusting at least one of temperature and humidity of the second carried gas forproviding adjusted second carried gas flow, and conveying the dry man-madecellulosic staple fibres from the drying step 150 to the post-processing step 170pneumatically with the second adjusted carrier gas flow. Temperature or moisturecontent, or both, of the dry man-made cellulosic staple fibres is adjusted orcontrolled during conveying from the drying step 150 to the post-processing step170 with the second carried gas flow.The post-processing step 170 may comprise baling of the dry man-made cellulosic staple fibres into bales of dry man-made cellulosic staple fibres.Figure 5 shows an embodiment of the process in which the previousembodiments of figures 2, 3 and 4 are combined into one embodiment. Thus, thesteps 100 to 170 are as disclosed in connection with figures 2 to 4. It should be noted, that the process according to the present inventioncomprises at least drying the wet man-made cellulosic staple fibres by utilizingflash-drying in drying step 150. The present invention also provides use of flash-drying for drying wet man-made cellulosic staple fibres. The process may also comprise the manufacturing step 100, providingthe mass of wet man-made cellulosic staple fibres in the step 110 and the formationstep 130. The conveying steps 120, 140 and 160 may be omitted or one or moreof them may be combined with the steps 100, 110, 130 and 150.Further, the post-processing step 170 may be omitted or combined with any of the steps 100, 110, 120, 130, 140, 160 and 150. Figure 6 shows schematically a system for preparing dry man-madecellulosic staple fibres according to the present invention.The manufacturing arrangement 10 arranged to manufacture man-made cellulosic staple fibres 4 from cellulosic raw material 2. The manufacturingarrangement 10 is configured to carry out the manufacturing step 100 of the process. The manufacturing arrangement 10 comprises a regeneration unit (notshown) comprising dissolving equipment (not shown) arranged to dissolvecellulosic raw material and regeneration equipment (not shown) arranged to regenerate the continuous cellulosic filament from the dissolved cellulosic rawmaterial. The manufacturing arrangement 10 further comprises cutting equipment(not shown) arranged to cut the continuous cellulosic filament into the man-madecellulosic staple fibres. The manufacturing arrangement 10 further comprises fibre washing equipment (not shown) arranged to wash out chemicals needed in manufacturing of the man-made cellulosic staple fibres. The manufacturing arrangement 10 is arranged to output the mass 6 ofwet man-made cellulosic staple fibres 4.In the embodiment of figure 6, the manufacturing arrangement 10 isarranged to output the mass 6 of wet man-made cellulosic staple fibres 4 on a layerconveyer 14 as a layer 6 of wet man-made cellulosic staple fibres 4.The layer conveyer 14 is a wire conveyer or a belt conveyer. The layer conveyer 14 is arranged to convey the layer or mass 6 of wetman-made cellulosic staple fibres 4 from the manufacturing arrangement 10 to adisintegrator 40. The layer conveyer 14 is configured to carry out the conveying step 120 of the process. The disintegrator 40 is configured to carry out the forming step 130 of the process.The disintegrator 40 is arranged to form, or disperse or disintegrate, themass or layer 6 of wet man-made cellulosic staple fibres 4 into the porous bundles8 of wet man-made cellulosic staple fibres 4.The disintegrator 40 comprises one or more fluffers which are arrangedto disperse or disintegrate the mass or layer 6 of wet man-made cellulosic staplefibres 4 into the porous bundles 8 of wet man-made cellulosic staple fibres 4. Thefluffer is a spiked roller, spiked conveyer, disk fluffer, screw feeder or the like, or any combination thereof. The disintegrator 40 is arranged to provide the porous bundles 8 of wetman-made cellulosic staple fibres 4 as a disintegration output.A pre-dryer 20 is provided in connection with the layer conveyer 14. The pre-dryer 20 is arranged to carry out the above disclosed pre-drying of themass or layer 6 of wet man-made cellulosic staple fibres 4.The pre-dryer 20 is arranged supply a heated pre-drying gas flowtowards or against the layer or mass 6 of wet man-made cellulosic staple fibres 4from below. The porous bundles 8 of wet man-made cellulosic staple fibres 4 aresupplied as input to a flash-dryer 50.Supplying of the porous bundles 8 of wet man-made cellulosic staplefibres 4 from the disintegrator 40 to the flash-drying is carried out according to thesupplying step 140 of the process.A pneumatic supply equipment is provided to generate a first carrier gas flow to a supply channel 42. The supply channel 42 is provided between the disintegrator 40 and the flash-dryer 50. The porous bundles 8 of wet man-madecellulosic staple fibres 4 are introduced to the supply channel 42 and the firstcarrier gas flow from a first carrier gas blower or source (not shown) is directed to the supply channel for conveying the porous bundles 8 of wet man-made cellulosicstaple fibres 4 to the flash-dryer 50.Alternatively, a mechanical conveyer may be used for supplying theporous bundles 8 of wet man-made cellulosic staple fibres 4 to the flash-dryer 50.In the flash-dryer 50 the wet man-made cellulosic staple fibres 4 areflash dried with heated drying gas flow. Output from the flash-dryer 50 is the drythe man-made cellulosic staple fibres 4.The flash-dryer 50 is configured to carry out the drying step 150 of the process. The dry man-made cellulosic staple fibres 4 are further conveyed from the flash-dryer 50 to a post-processing unit 98. Conveying of the dry man-made cellulosic staple fibres 4 from the flash-dryer 50 to the post-processing unit 98 is carried out according to the conveyingstep 160 of the process. Apneumatic discharge equipment is provided to generate a secondcarrier gas flow 104 to a discharge channel 92. The discharge channel 92 isprovided between the flash-dryer 50 and the post-processing unit 98. The dry man-made cellulosic staple fibres 4 are introduced to the discharge channel 92 and thesecond carrier gas flow 104 from a second carrier gas blower or source 102 isdirected to the discharge channel 92 for conveying the dry man-made cellulosicstaple fibres 4 to the post-processing unit 98.The second carrier gas blower or source 102 comprises a temperature controller (not shown) configured to adjust temperature of the supplied carrier gasflow 104, and / or a humidity controller (not shown) configured to adjust humidityof the carrier gas flow 104 supplied to the discharge channel 92.Alternatively, a mechanical conveyer may be used for conveying the dryman-made cellulosic staple fibres 4 to the post-processing unit 98.The post-processing unit 98 comprises a baling device arranged to balethe dry man-made cellulosic staple fibres 4 into bales of dry man-made cellulosicstaple fibres. The post-processing unit 98 may also comprise other devices for post- processing the dry man-made cellulosic staple fibres. Figure 7 shows schematically one embodiment of the flash-dryer 50.The porous bundles 8 of wet man-made cellulosic staple fibres 4 are supplied tothe flash-dryer 50 via the supply channel 42. The flash-dryer 50 comprises a drying gas source or a drying gas blower 60 configured to generate and supply a heated drying gas flow 62. The drying gas source 60 is connected to the supply channel 42 and arranged to supply the heated drying gas flow 62 into the supply channel 42. The flash-dryer 50 comprises a flash-drying reactor 70 having a flash-drying zone 75. The porous bundles 8 of wet man-made cellulosic staple fibres 4are supplied from the supply channel 42 together with the heated drying gas flow62 to the flash-drying reactor 70 and the flash-drying zone 75.The porous bundles 8 of wet man-made cellulosic staple fibres 4 andthe heated drying gas flow 62 are arranged to flow through the flash-drying zone 75. The heated drying gas is configured to dry the porous bundles 8 of wet man-made cellulosic staple fibres 4 during the flow through the flash-drying zone 75. The flow through the flash-drying reactor 70 and the flash drying zone 75 may be enhanced with a dryer blower 72 arranged upstream of the flash-drying zone 75. The dryer blower 72 may also be omitted and the heated drying gas flow62 may be used to carry the porous bundles of wet man-made cellulosic staplefibres 4 through the flash-drying zone 75.In the embodiment of figure 7, the flash-drying reactor 70 and the flash-drying zone 75 are provided as a vertical flash-drying column. The man-madecellulosic staple fibres 4 and the heated drying gas flow upwards in verticaldirection in the flash-drying reactor 70 and the flash-drying zone 75. The supply channel 42 is provided to the lower end of the flash-drying reactor 70 and the flash-drying zone 75. The flash-drying reactor 70 and the flash-drying zone 75 may also be provided as a horizontal or tilted structure. The heated drying gas receives moisture from the wet man-madecellulosic staple fibres 4 and cools during the flow through the flash-drying zone75 and becomes damp drying gas. The man-made cellulosic staple fibres 4 and thedamp drying gas exit the flash-drying reactor 70 and the flash-drying zone 75 to an outlet channel 76. The outlet channel 76 is provided to opposite end of the flash- drying reactor 70 and the flash-drying zone 75 in relation to the supply channel 42. The outlet channel 76 is provided to upper end of the flash-drying reactor 70 and the flash-drying zone 75. The flash-dryer 50 further comprises a separator 80 provideddownstream of the flash-drying reactor 70. The separator 80 is arranged toseparate the man-made cellulosic staple fibres 4 from the damp drying gas.The outlet channel 76 is arranged to extend between the flash-dryingreactor 70 and the separator 80. The man-made cellulosic staple fibres 4 and thedamp drying gas enter the separator 80 from the outlet channel 76.In the embodiment figure 7, the outlet channel 76 is provided as a gooseneck channel turning the flow from upwards direction to downwards. Thus,the man-made cellulosic staple fibres 4 and the damp drying gas enter theseparator 80 in downwards direction.The separator 80 may be any kind of separator device arranged toseparate the man-made cellulosic staple fibres 4 from the damp drying gas.The separator 80 comprises a drying gas outlet 84 via which the separated damp drying gas flow 65 is discharged from the separator 80 and from the flash-dryer 50.The discharge channel 92 is provided as fibre outlet to the separator 80.The separated man-made cellulosic staple fibres 4 exit the separator 80 via thedischarge channel 92. The separator 80 is provided as a vertical separator in which the outletchannel 76 is provided to the upper end or upper part of the separator 80 and thedischarge channel 92 is provided to the lower end or lower part of the separator 80. The second carrier gas blower or source 102 is provided in connectionthe discharge channel 92 for conveying the dry man-made cellulosic staple fibres 4to the post-processing unit 98, as disclosed in connection with the figure 6. The discharge channel 92 may be further provided with a dischargeblower 90 arranged between the flash-dryer 50 and the post-processing unit 98for enhancing flow of the dry man-made cellulosic staple fibres 4 to the post-processing unit 98. The discharge blower 90 may also be omitted and the secondcarrier gas flow 104 may be used to carry the dry man-made cellulosic staple fibres4 to the post-processing unit 98. Figure 8 shows an embodiment in which the separator 80 is provided as cyclone. The cyclone 80 is arranged to separate the man-made cellulosic staplefibres 4 from the damp drying gas.The outlet channel 76 is provided to the upper end or upper part of thecyclone 80. The damp drying gas and the man-made cellulosic staple fibres 4 enterthe cyclone from the upper end or upper part of the cyclone 80. The drying gas outlet 84 via which the separated damp drying gas flow65 is discharged from the cyclone 80 and from the flash-dryer 50 is provided to theupper end of the cyclone 80. The discharge channel 92 is provided to the lower end or lower part ofthe cyclone 80 and the dry man-made cellulosic staple fibres 4 are discharged fromthe lower end of the cyclone 80 to the discharge channel 92. In alternative embodiments, the separator 80 may comprise or be provided as a filter device instead of the cyclone. Figure 9 shows an embodiment in which the flash-dryer 50 comprisetwo flash-dryer units 51, 52 instead of only one in figures 7 and 8. The two flash- dryer units 51, 52 are arranged successively to each other such that the during theflash-drying the man-made cellulosic staple fibres 4 flow successively through thetwo flash-dryer units 51, 52. The two flash-dryer units 51, 52 are configured to carry out the flash- drying in two successive flash-drying stages according to the drying step 150 of the process. Both of the two flash-dryer units 51, 52 correspond the flash-dryer orflash-drying unit of figure 7. The porous bundles 8 of wet man-made cellulosic staple fibres 4 aresupplied to a first flash-dryer unit 51 via the supply channel 42. The first flash-dryer unit 51 comprises a first drying gas source or a first drying gas blower 60configured to generate and supply a first heated drying gas flow 62. The first drying gas source 60 is connected to the supply channel 42 and arranged to supply the first heated drying gas flow 62 into the supply channel 42. The first flash-dryer unit 51 comprises a first flash-drying reactor 71having a first flash-drying zone 95. The porous bundles 8 of wet man-madecellulosic staple fibres 4 are supplied from the supply channel 42 together with thefirst heated drying gas flow 62 to the first flash-drying reactor 71 and the first flash-drying zone 95. The porous bundles 8 of wet man-made cellulosic staple fibres 4 andthe first heated drying gas flow 62 are arranged to flow through the first flash- drying zone 95. The first heated drying gas is configured to dry the porous bundles8 of wet man-made cellulosic staple fibres 4 during the flow through the first flash-drying zone 95. The flow through the first flash-drying reactor 71 and the first flashdrying zone 95 may be enhanced with a first dryer blower 72 arranged upstreamof the first flash-drying zone 95. The first dryer blower 72 may also be omitted. The first heated drying gas receives moisture from the wet man-madecellulosic staple fibres 4 and cools during the flow through the first flash-dryingzone 95 and becomes first damp drying gas. The man-made cellulosic staple fibres4 and the first damp drying gas exit the first flash-drying reactor 71 and the firstflash-drying zone 95 to a first outlet channel 77.The first flash-dryer unit 51 further comprises a first separator 81provided downstream of the first flash-drying reactor 71. The first separator 81 isarranged to separate the man-made cellulosic staple fibres 4 from the first dampdrying gas. The first outlet channel 77 is arranged to extend between the first flash-drying reactor 71 and the first separator 81. The man-made cellulosic staple fibres4 and the first damp drying gas enter the first separator 81 from the first outletchannel 77.The first separator 81 may be any kind of separator device arranged toseparate the man-made cellulosic staple fibres 4 from the first damp drying gas.The first separator 81 comprises a first drying gas outlet 85 via whichthe first separated damp drying gas flow 66 is discharged from the first separator81 and from the first flash-dryer unit 51.A connection channel 83 is provided as a first fibre outlet to the firstseparator 81. The separated man-made cellulosic staple fibres 4 exit the firstseparator 81 via the connection channel 83.The man-made cellulosic staple fibres 4 are supplied to a second flash-dryer unit 52 via the connection channel 83. The connection channel 83 is arranged between the first flash-dryer unit 51 and the second flash-dryer unit 52. Theconnection channel 83 forms a supply channel to the second flash-dryer unit 52.Further, the connection channel 83 is arranged between the first separator 81 and a second flash-dryer reactor 73 of the second flash-dryer unit 52. The second flash-dryer unit 52 comprises a second drying gas source ora drying gas blower 63 configured to generate and supply a second heated dryinggas flow 64. The second drying gas source 63 is connected to the connectionchannel 83 and arranged to supply the second heated drying gas flow 64 into theconnection channel 84.The second flash-dryer unit 52 comprises a second flash-drying reactor73 having a second flash-drying zone 96. The wet man-made cellulosic staple fibres4 from the first flash-dryer unit 51 are supplied from the connection channel 83together with the second heated drying gas flow 64 to the second flash-dryingreactor 73 and the second flash-drying zone 96.The wet man-made cellulosic staple fibres 4 and the second heateddrying gas flow 64 are arranged to flow through the second flash-drying zone 96.The second heated drying gas is configured to dry wet man-made cellulosic staplefibres 4 during the flow through the second flash-drying zone 96.The flow through the second flash-drying reactor 73 and the secondflash drying zone 96 may be enhanced with a second dryer blower 74 arrangedupstream of the second flash-drying zone 96. The second dryer blower 74 may alsobe omitted. The second heated drying gas receives moisture from the wet man-made cellulosic staple fibres 4 and cools during the flow through the second flash-drying zone 96 and becomes second damp drying gas. The man-made cellulosicstaple fibres 4 and the second damp drying gas exit the second flash-drying reactor73 and the second flash-drying zone 96 to a second outlet channel 78.The second flash-dryer unit 52 further comprises a second separator 86provided downstream of the second flash-drying reactor 73. The second separator86 is arranged to separate the man-made cellulosic staple fibres 4 from the seconddamp drying gas. The second outlet channel 78 is arranged to extend between the secondflash-drying reactor 73 and the second separator 88. The man-made cellulosicstaple fibres 4 and the second damp drying gas enter the second separator 83 fromthe second outlet channel 78. The second separator 86 may be any kind of separator device arrangedto separate the man-made cellulosic staple fibres 4 from the second damp dryinggas. The second separator 86 comprises a second drying gas outlet 87 viawhich the second separated damp drying gas flow 67 is discharged from the secondseparator 86 and from the second flash-dryer unit 52.The second drying gas outlet 87 may be connected to the first drying gas blower 60 with a recycling channel 99 for supplying the second separated damp drying gas flow 67 to the first drying gas blower 60 and utilizing it as the firstheated drying gas flow 62 to the first flash-dryer reactor 51. The second separateddamp drying gas flow 67 may be heated and supplied to the supply channel 42 as the first heated drying gas flow 62. The dry man-made cellulosic staple fibres 4 are output of the secondflash-dryer unit 52 and the flash-dryer. The discharge channel 92 is connected to the lower end or lower part ofthe second separator 86 for discharging the dry man-made cellulosic staple fibres4 from the second flash-dryer unit 52 and the flash-dryer.Figure 10 shows an embodiment in which the flash-dryer comprises thefirst and second flash-dryer units 51, 52 and the first and second separators 81, 86are provided as cyclones.The first flash-dryer unit 51 comprises a first cyclone 81 as the first separator and the second flash-dryer unit 52 comprises a second cyclone 81 as the second separator. The flash-dryer and first and second flash-dryer units 51, 52 of figure 10 correspond embodiment of figure 9 with the first and second cyclones 81, 86 corresponding the cyclone of figure 8. It should be noted that the flash-dryer may also comprise more thantwo flash-dryer units 51, 52. The additional flash-dryer units are arrangedsuccessively in series in similar manner as the first and second flash-dryer units 51, 52. The invention has been described above with reference to the examples shown in the figures. However, the invention is in no way restricted to the aboveexamples but may vary within the scope of the claims.

Claims

CLAIMS 1. A process for preparing dry man-made cellulosic staple fibres (4) foryarn spinning, the process comprising drying wet man-made cellulosic staplefibres (4) in a drying step (150), c h a r a c t e r i z e d in that the processcomprises flash-drying the wet man-made cellulosic staple fibres (4) with heateddrying gas flow into dry man-made cellulosic staple fibres (4) in the drying step(150).

2. A process according to claim 1, c h a r a c t e r i z e d in that theprocess comprises manufacturing the man-made cellulosic staple fibres (4) fromcellulosic raw material (2) in a manufacturing step (100), the manufacturing step(100) providing a mass (6) of wet man-made cellulosic staple fibres (4) as amanufacturing output.

3. A process according to claim 2, c h a r a c t e r i z e d in that themanufacturing step (100) comprises forming a regenerated cellulosic filamentfrom the cellulosic raw material (2) by a regeneration method and cutting theregenerated cellulosic filament into the man-made cellulosic staple fibres (4).

4. A process according to any one of claims 1 to 3, c h a r a c t e r i z e din that the man-made cellulosic staple fibres (4) have length between 20 to 80 mm,preferably between 25 to 50 mm.

5. A process according to any one of claims 1 to 4, c h a r a c t e r i z e din that the drying step (150) comprises drying the wet man-made cellulosic staplefibres to dry man-made cellulosic staple fibres having moisture content 2 to 20weight-%, or preferably 10 to 15 weight-%.

6. A process according to any one of claims 1 to 5, c h a r a c t e r i z e din that: -the process comprises forming the mass (6) of wet man-madecellulosic staple fibres (4) into porous bundles (8) of wet man-made cellulosicstaple fibres (4) in a pre-processing step (130) prior to the flash-drying in thedrying step (150) and flash-drying the porous bundles of wet man-made cellulosicstaple fibres (4) into the dry man-made cellulosic staple fibres (4) in the dryingstep (150); or- the manufacturing step (100) comprises providing a layer (6) of wetman-made cellulosic staple fibres (4) as the mass, the process comprises formingthe layer (6) of wet man-made cellulosic staple fibres (4) into porous bundles (8)of wet man-made cellulosic staple fibres (4) in a pre-processing step (130) prior tothe flash-drying in the drying step (150) and flash-drying the porous bundles ofwet man-made cellulosic staple fibres (4) into the dry man-made cellulosic staplefibres (4) in the drying step (150).

7. A process according to claim 6, c h a r a c t e r i z e d in that theprocess comprises conveying the porous bundles (8) of wet man-made cellulosicstaple fibres (4) pneumatically with one or more gas flows (62, 64) through thedrying step (150) or pneumatically with one or more gas flows from the pre-processing step (130) to the drying step (150) and through the drying step (150).

8. A process according to any one of claims 1 to 7, c h a r a c t e r i z e din that the drying step (150) comprises drying the wet man-made cellulosic staplefibres (4) in two or more successive flash-drying stages, the drying step (150)further comprises flash-drying the wet man-made cellulosic staple fibres (4) withseparate heated drying gas flows in the successive flash-drying stages.

9. A process according to any one of claims 1 to 8, c h a r a c t e r i z e din that: -the drying step (150) comprises separating the man-made cellulosicstaple fibres (4) from damp drying gas after the flash-drying; or- the drying step (150) comprises separating the man-made cellulosicstaple fibres (4) from damp drying gas after each flash-drying stage.

10. A process according to any one of claims 1 to 9,c h a r a c t e r i z e d in that the process comprises conveying the dry man-madecellulosic staple fibres (4) from the drying step (150) pneumatically with a secondcarrier gas flow to post-processing (170).

11. A process according to claim 10, c h a r a c t e r i z e d in that theconveying the dry man-made cellulosic staple fibres (4) from the drying step (150)to the post-processing (170) comprises adjusting at least one of temperature andhumidity of the second carried gas for providing adjusted second carried gas, andconveying the dry man-made cellulosic staple fibres (4) from the drying step (150)to the post-processing (170) pneumatically with the second adjusted carrier gas flow.

12. A system for preparing dry man-made cellulosic staple fibres (4) foryarn spinning, the system comprises a manufacturing arrangement (10) arrangedto manufacture man-made cellulosic staple fibres (4) from cellulosic raw material(2), the manufacturing arrangement (10) being arranged to provide a mass (6) ofwet man-made cellulosic staple fibres (4) as a manufacturing output,c h a r a c t e r i z e d in that the system comprises a flash-dryer (50) configuredto dry the wet man-made cellulosic staple fibres (4) with heated drying gas flowinto dry man-made cellulosic staple fibres (4).

13. A system according to claim 12, c h a r a c t e r i z e d in that themanufacturing arrangement (10) comprises a regeneration unit arranged to forma cellulosic filament from the cellulosic raw material (2) and cutting equipmentarranged to cut the regenerated cellulosic filament into the man-made cellulosicstaple fibres (4) having length between 20 to 80 mm, preferably between 25 to 50mm.

14. A system according to claim 12 or 13, c h a r a c t e r i z e d in that:- the system comprises a disintegrator (40) provided upstream of theflash-dryer (50) and arranged to disintegrate the mass (6) of wet man-madecellulosic staple fibres (4) into porous bundles (8) of wet man-made cellulosicstaple fibres (4) and the flash-dryer (50) is configured to dry the porous bundles(8) of wet man-made cellulosic staple fibres (4) with the heated drying gas flowinto the dry man-made cellulosic staple fibres (4); or- the manufacturing arrangement (10) is arranged to provide a layer (6)of wet man-made cellulosic staple fibres (4) as the mass, the system comprises adisintegrator (40) provided upstream of the flash-dryer (50) and arranged todisintegrate the layer (6) of wet man-made cellulosic staple fibres (4) into porousbundles (8) of wet man-made cellulosic staple fibres (4) and the flash-dryer (50) isconfigured to dry the porous bundles (8) of wet man-made cellulosic staple fibres (4) with the heated drying gas flow into the dry man-made cellulosic staple fibres (4).

15. A system according to any one of claims 12 to 14,c h a r a c t e r i z e d in that the flash-dryer (50) comprises two or moresuccessive flash-drying units (51, 52), the successive flash-drying unit (51, 52)comprise separate drying gas sources (60, 63) arranged to provide a separateheated drying gas flows (62, 64) to the two or more successive flash-drying units(51, 52).

16. A system according to any one of claims 12 to 15,c h a r a c t e r i z e d in that:- the flash-dryer (50) comprises a flash-drying reactor (70) configuredto dry the wet man-made cellulosic staple fibres (4) with the heated drying gasflow, and a separator (80) downstream of the flash-drying reactor (70), theseparator (80) being arranged to separate the man-made cellulosic staple fibres(4) from damp drying gas; or- each of the two or more successive flash-dryer units (51, 52) comprisea flash-drying reactor (71, 73) configured to dry the wet man-made cellulosicstaple fibres (4) with the heated drying gas flow and a separator (81, 86)downstream of the flash-drying reactor (71, 73), the separator (81, 86) beingarranged to separate the man-made cellulosic staple fibres (4) from damp dryinggas.

17. A system according to any one of claims 12 to 16,c h a r a c t e r i z e d in that the system comprises a post-processing unit (98)and a pneumatic post-processing conveyer (90, 92, 102) arranged to convey thedry man-made cellulosic staple fibres (4) from the flash-dryer (50) pneumaticallywith carrier gas flow to the post-processing unit (98).

18. A system according to any one of claims 12 to 17,c h a r a c t e r i z e d in that the system is configured to carry out the processaccording to any one of claims 1 to 11.

19. Use of flash-drying with heated drying gas flow for drying wet man-made cellulosic staple fibres (4), having length between 20 to 80 mm, preferablybetween 25 to 50 mm, into dry man-made cellulosic staple fibres (4).

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