EP0133897B1 - Method and apparatus for drying textile materials in rope form - Google Patents

Description

The present invention relates to a method for pre-drying or drying textile webs or knitted fabrics in strand form, as well as a device which is suitable for this and works according to the jet principle and which also ensures the feed of the fiber material through the system.

From the published European patent applications EP-A 0014919 and EP-A 0078022 it is known to subject textile fabric strands in jet piece dyeing systems to a wet finishing, in particular for dyeing. In this process, the textile material combined into a strand and passed past the nozzles is either circulated using the treatment liquor circulating in the same direction via the nozzle system, or the locomotion is carried out by means of a gas stream or steam-air directed from the nozzles under excess pressure onto the fiber material Mix. The main feature of this working technique is therefore that the goods are conveyed through the unit repeatedly in the closed, continuous form through the kinetic energy imparted by the nozzle jet during tangential application. Although gas and liquid flow can be alternated or combined in accordance with the process control for the drive of the strand during the different treatment stages, which allows a seamless transition from one dyeing step to another without a standstill and under isothermal conditions, it was previously relied on for the drying of the wet-treated textile material in this way interrupting the spraying and thus the operation and, after removing the goods from the dyeing jet, performing the drying operation on a separate system of the usual type.

In the apparatus area, the drying of the textile goods after the wet finishing is an essential process step. Basically, drying facilities are to be aimed at, with which the goods can be dried in the same presentation form in which the wet finishing was carried out.

For example, DE-OS 3 046 292 describes a process for drying textile material in web form, according to which the moist goods are guided within a boiler that is sealed from the outside atmosphere during the continuous passage through a plurality of pipe section sections arranged one behind the other and in the broad form of the action of one in the longitudinal direction thereon is exposed to a pressurized steam-air mixture. In addition, for special purposes there is the possibility of discontinuous drying of sheet-like piece goods with batch loading of the dryer, for which so-called tumblers, i.e. Rotating drums are considered, in which the dry material is whirled around without tension and without pressure and the desired effect is achieved due to the intensive mechanical movement.

On the other hand, if the material to be dried is anchored on a material carrier, there are various drying systems available, such as flow-through dryers or chamber dryers, which also differ in the type of heat supply to the textile material and the elimination of moisture. A rapid and at the same time intensive drying is usually made possible when, for example, when treating yarn that is wound on packages or is similarly compactly attached, a stream of warm air penetrates the material pack radially.

The effectiveness of such discontinuous drying can be supported by carrying out the process under the influence of reduced pressure. The advantage of the vacuum, to increase the evaporation rate by reducing the boiling temperature, can only be used to a limited extent in through-flow dryers in which the air is constantly sucked through the textile material, since an intensive exposure of the winding body to heat from the inflowing warm air due to the Vacuum present lower density cannot be achieved. According to the technology described in DE-AS 1 902306 and DE-AS 1 927651, the evacuation phase is therefore separated from the heating phase.

In the case of the through-flow dryer, however, the use of superatmospheric pressure conditions can also be used. Since in this embodiment - in contrast to drying under normal pressure - the drying air circulates in a closed system, the heat contained in the exhaust air from the drying zone is not lost, which is noticeable in a higher heat input to the winding former with the same blower output. As a result of the greater amount of heat in the air flow before entering the dry material, a higher degree of moisture in the exhaust air is achieved with the pressure dryer. This is advantageously used for yarn packages in the process according to DE-OS 2616280.

In both vacuum drying and pressure drying, the respective measures can take place in the same vessel as the wet finishing.

The object of the present invention is now to develop a drying technology which is tailored specifically to the needs of devices which work according to the jet principle, so that the wet finishing together with the subsequent dewatering can be carried out in one train without the goods flow having to be interrupted and the time and thermal energy losses that have occurred due to the inevitable change of the system can be avoided or the quality of the goods treated in this way does not result as a result of the additional loading operation.

Experience in the field of steam-operated nozzle systems in accordance with the European patent applications EP-A 0014919 and EP-A 0078022 mentioned at the outset has shown that there is a good spread of goods, and indicated that, due to the high exit velocity, such a nozzle jet is located in an under The pressurized cycle of the moist goods tears out enough water, which is why this flow concept can be used to dry or partially dry the textile goods strand.

The present invention thus relates to a discontinuous process for the partial or complete drying of strands of textile fabrics or knitted fabrics circulating in jet piece dyeing systems in endless form following a wet treatment operation for textile finishing using the pull-out technique, the feed for the transport of the fiber material within the closed system takes place via the actuation of the nozzle system, characterized in that immediately after the wet refinement and after draining the treatment liquid from this previous processing step, evaporation drainage of the same to a certain residual moisture content is carried out in the course of the movement of the wet-refined wet strand of goods which has now been taken over and maintained by a gas stream when meeting and subsequent flow around with the circulated in the same apparatus arrangement via an associated separate circuit n drive gas, preferably steam-air mixture, which has been compressed and heated to a predetermined overpressure, which increases the density, the flow rate and the kinetic energy of the transport gas, which now also functions as a drying medium, in accordance with the pressure increase and the heat supply in the overall system, that the adhering material moisture is torn from the textile material or evaporated and thus removed in the flowing gas, then cooling of the gas resulting from the previous measure as exhaust air after the absorption of moisture due to the previous measure and with the extracted moisture from the resulting oversaturated again in a dry-saturated state simultaneous re-condensation of the moisture extracted from the textile material and separation of the same from the cycle of the gaseous drying agent.

In the foreground of the advantages that can be achieved by the novel method of working is the fact that after wet finishing in the same machine unit, predrying or drying of the bleached and / or dyed and / or finished fabric strand can then be carried out immediately afterwards. According to the invention, no independent pressure dryer is required, but it is sufficient to provide an existing jet dyeing machine with a few additional devices. Additional machine units are therefore unnecessary. The fact that the refined material remains in the previously used apparatus can save an enormous amount of time. Retrofitting is no longer necessary. Because drying takes place in a closed jet dyeing machine, there is also a much more favorable energy balance, especially since the heat of vaporization to be evaporated for the material moisture to be evaporated can be recovered as the heat of condensation of the water separated from the exhaust air in the circuit, with not insignificant amounts of such condensate.

But also with regard to the textile technological properties there are some not insignificant improvements when using the method according to the invention. Taking into account the fact that the strand of goods is moved quickly during drying, the fiber relaxes, which results in a very favorable grip and fullness of the material. In this way, softening agents such as plasticizers, fillers and the like can be saved under certain circumstances. A particular advantage of the invention is that the goods are laid with each circulation so that no folds can form. The idea of the invention on which the claimed method is based is based on the fact that the gaseous drive means providing the goods advance is also exploited to a certain extent as a pressure dryer for the purpose of dewatering. In such a function, the drying medium controlled in air recirculation mode - as in the case of pure goods transport - is guided tangentially to the direction of travel with simultaneous flow around the strand-like textile material, with the drying process as such - depending on the air speed and the type of moisture binding to the substrate - both mechanical drainage Turbulence and separation as well as thermal measures for the evaporation of the material moisture include.

The heat required to heat the textile material running in the form of a strand is preferably taken from a steam-air mixture. This desiccant flows in a closed system in the circuit, which is started by the power of a blower and is compressed by the same to the back pressure caused by the air volume. The delivery head, ie the total pressure difference that the compressor has to overcome, corresponds to the sum of all resistances for an intended gas volume when flowing through the circulation system including the goods. Since the present invention relates to evaporation drying, the steam-air mixture - except for the application of kineti sher energy via the compressor work - to achieve the desired drying speed, thermal energy is supplied via an air heater. This is built into the circuit on the pressure side of the compressor. The heat is given off to the continuously moving textile goods mainly within the nozzle section and the downstream transport section, on which the goods are accompanied by the gaseous heating medium. Adequate contact between the drying air and the strand of goods is ensured by the fact that the material to be dried, which is not specially laid out, is a quasi-open surface with corresponding free spaces. A more extensive penetration of the strand-like article with the drying air is then further promoted by a certain loosening of the packing density of the goods after passage of the nozzle in the course of the subsequent path through the drying zone. Inside the textile, moisture is transported to the outer areas initially due to capillary forces and in the further drying stage via vapor diffusion, as there is a difference in moisture and temperature from the surface at this point. The impulse for the forward movement of the textile material, ie the circulation of goods, which is caused by the gas flow, is used in the claimed process for the thermal drying process. The representation of the thermodynamic conditions for the drying agent within the nozzle and the state changes on the way to the suction port of the compressor can be represented in a moist air diagram.

As already mentioned above, according to the invention, after the wet finishing in the same machine unit, the strand-like fiber material is dried immediately afterwards. However, it is also quite conceivable that - after partial dewatering carried out in the manner described - the goods are passed into a separate dryer with several compartments to be shut off with the aid of the compressor connected to the nozzle dyeing machine.

The drying process according to the present invention proceeds as follows:

In order to bring the material that has been subjected to a wet finishing to a desired residual moisture content - it does not matter whether partial drainage or predrying or full drying is provided - the unit loaded with the moist textile goods is closed against the liquor cycle and the compressor is switched on. A predetermined overpressure then arises in the overall system. The density, the flow velocity and the kinetic energy of the steam-air mixture increase. The latter is then able to tear the water adhering to the textile material in the form of very fine droplets.

The moisture transferred into the gas space and absorbed by the gas stream is then removed from the circulating line of goods in this way and the moist air mixture formed on this occasion is removed from the treatment zone at the end of the common transport route and measures for drying are carried out. The recooling required to separate the moisture from the oversaturated exhaust air takes place in an air cooler to the recooling temperature specified by the respective drying process. The moisture which condenses when the temperature falls below the dew point coalesces in the downstream water separator, whereupon the gaseous medium thus dried is again fed to the circuit, compressed and heated and brought to action again on the moist strand material.

It is currently common in the textile industry to sell a product, e.g. refined after dyeing, not completely dewatered. A certain amount of residual moisture is often even desirable. According to the method, it is now easily possible to control the drying in the nozzle dyeing unit in such a way that the goods are conditioned at the same time, which applies to all types of fabric. Such a project can be realized by dewatering the line of goods within the closed dyeing jet to an equilibrium state of the material moisture, which corresponds to the conditioning moisture after removal from the system and cooling of the textile goods, or by lowering the line of goods within the closed dyeing jet the conditioning moisture of the same is dewatered and then the textile is conditioned by increasing the relative humidity of the drying air. The last-mentioned principle of humidification by means of conditioned air of a certain temperature and a certain moisture content is used on a similar basis in the case of DE-OS 2052440 for the conditioning of yarn spools made of hygroscopic fiber to compensate. the different degrees of moisture between the inner and outer layers of the coil winding.

A device suitable for carrying out the claimed method, to which the present invention also relates, consists of a conventional jet dyeing system (A) with a liquor circuit (B) for the hydraulic drive of textile fabric strands (W) in endless form by means of a treatment liquid Actuation of a built-in nozzle system (D), which is connected to a separate circuit (E) guided via the same nozzle arrangement (D) for a gas flow that may support or advance the product feed and includes a limited distance from the nozzle arrangement (D) along which the goods line (W) in the absence of liquid transport and out of service set circuit (B) is exposed to the influence of the kinetic energy of the drive gas, and is characterized in that in the gas circuit (E) - arranged in the order given - a blower (1) for compressing the gaseous medium and additional means for subsequent heating (2 ) of the same, following the aerodynamically effective contact section for the drive gas for the transport of goods together with the circulating textile material, means for recooling (3) the resulting gas stream including moisture removal from it, and means for separating (4) the resulting condensate are.

• A = Jet-Färbemaschine (Druckbehälter) aus Antriebsteil (Haspel), Transportdüse und Warenspeicherraum samt Abfluss (nicht mit Ziffern versehen)
• B = Zirkulationssystem für die Flotte, bestehend aus Umwälzpumpe, Wärmeaustauscher für Heizung und Kühlung mit nachgeordneter Drosselvorrichtung zur Regulierung der Flottenströmung (nicht mit Ziffern versehen)
• C = Ansatz- sowie Vorratsgefäss für Behandlungsflüssigkeiten mit nachgeordneter Dosierpumpe und Absperrventil (nicht mit Ziffern versehen)
• D = Düsensektion, die wahlweise hydraulischen oder aerodynamischen Vorschub des Warenstranges erlaubt
• E = separater Gaskreislauf, der bei Betrieb unter vorgegebenem Überdruck steht
• P = Pumpen zur Beschickung des Kreislaufs B mit Flotte bzw. zur Aufrechterhaltung von deren Umwälzung
• W = Behandlungsgut/Warenstrang
  • 1 = Gebläse (Verdichter)
  • 2 = Lufterhitzer
  • 3 = Luftkühler (Kondensator)
  • 4 = Abscheider für Feuchtigkeit aus der Umluft
  • 5 = Absperrklappen
  • 6 = Druckluftanschluss (Gasanschluss)
  • 7 = Dampfanschluss
  • 8 = Injektionsdüse für Wasser (evtl. Zumischung von Ausrüstungsprodukten)
  • 9 = Feuchtekondensatablass

An exemplary embodiment of a jet dyeing machine used according to the invention is shown schematically in cross section in the drawing of FIG. 1 given below. The reference symbols used are identical to the numbers used for this purpose in the text and have the following meaning:

• A = Jet dyeing machine (pressure vessel) consisting of drive part (reel), transport nozzle and goods storage space including drain (not numbered)
• B = circulation system for the fleet, consisting of a circulation pump, heat exchanger for heating and cooling with a downstream throttle device for regulating the fleet flow (not numbered)
• C = preparation and storage vessel for treatment liquids with downstream metering pump and shut-off valve (not numbered)
• D = nozzle section, which allows hydraulic or aerodynamic feed of the product line
• E = separate gas circuit, which is operated under specified overpressure
• P = pumps for charging circuit B with liquor or for maintaining its circulation
• W = material to be treated / strand of goods
  • 1 = blower (compressor)
  • 2 = air heater
  • 3 = air cooler (condenser)
  • 4 = separator for moisture from the circulating air
  • 5 = butterfly valves
  • 6 = compressed air connection (gas connection)
  • 7 = steam connection
  • 8 = injection nozzle for water (possibly adding equipment products)
  • 9 = moisture condensate drain

In Fig. 1, the parts of the jet dyeing machine designated by the letters A, B and C largely correspond to the prototype of such a device as is described in detail in US Pat. No. 3,949,575.

The principle of operation of the claimed device can be explained as follows:

After a wet refinement under the action of the hydraulically effective circulation system B (with the circulation pump P started and the shut-off valves 5 closed) with the treatment liquor fed from the storage container C (containing the finishing agent) and after the goods storage space has been emptied from the largely extracted liquid medium the two shut-off valves 5 for the circulation of the gaseous drying agent are opened and the blower 1 is switched on for drying or partial dewatering of the fabric strand W circulating in the jet dyeing machine A in unchanged loading form as before. By introducing compressed air from a compressed air source (not shown further) via the connection 6 for the first filling of the orbit connected to one another via a line, now consisting of the dyeing jet A now serving as a drying vessel, the air cooler 3, the water separator 4, the blower 1 and the air heater 2 E For the cycle of the gaseous drying agent, there is an intended overpressure for the flowing driving air of, for example, approx. 2.5 bar in the overall system. The density of the gas volume thus increases, as a result of which the total pressure difference prevailing at the blower 1 increases and thus also the air weight flowing per second. The flow velocity also increases and the kinetic energy of the aerodynamically active gas increases accordingly. The surface moisture is detached from the textile material and, as it were, eliminated as a mist in the form of the finest water droplets from the gas stream acting as a vehicle from the goods strand. The intensity of this drying section corresponds to that of mechanical dewatering, as can be achieved in a centrifuge, but the goods are dried without wrinkling.

In order to provide thermal energy for the drying of the moving strand W and in this way to support the swirling effect of the air flow to remove moisture, the gaseous drying agent compressed in the fan 1 to the back pressure caused by the amount of air in the downstream air heater 2 is set to a predetermined value Drying temperature warmed up and the moisture in the goods gradually evaporated under the influence of the heat contained in the drying air. According to the method, a heated steam-air mixture can preferably be used instead of air as the operating gas for the desiccant circuit by supplying steam via the connection 7.

At the end of the common contact path of the gaseous drying agent with the circulating strand W, the steam-air mixture which is laden with moisture and emerges from the drying vessel A (dyeing jet) is cooled to the intended recooling temperature during passage through an air cooler 3, whereupon in a downstream separator 4 The supersaturated water content contained in the exhaust air is below Condensation is separated and is removed through the drain 9. The almost water-free drying air leaving the water separator 4 or the dry-saturated steam-air mixture is then sucked in and compressed again with the aid of the blower 1 and, after subsequent warming up in the air heater 2, again in the drying vessel A to act on the goods W. - and passed through.

For the conditioning of the textile goods, the specified state values of the moist air mixture in the machine system are controlled and the injection nozzle 8 atomizes a specified amount of water per unit of time for a certain period of time in the circuit. This will expediently happen when the desired degree of drying is reached.

To illustrate the thermodynamic conditions of the drying method according to the invention, a simplified graphical representation of the drying process for a specific drying section is shown in FIG. 2 in an H, x diagram of humid air with flat rectangular coordinates:

Within the transport nozzle of the jet dyeing machine, the steam-air mixture in the circulating air with the status L1 hits the damp goods. For the entry in the coordinate network, the state L1 can be characterized by the values heat content H, steam or moisture content x and temperature. The drying air then flows in contact with the goods to be dried from the nozzle via a common transport path and the goods store to the exit point from the drying vessel. The state L1 of the drying air changes approximately on a straight line, the direction of which can be plotted over the marginal scale AH / Ax, taking into account the good temperature for the steady state. The condition L2 of the drying air reflects the conditions at the outlet of the goods store, depending on the drying process. Due to the cooling of the drying air to state L2 which occurs when the strand is acted on, the moisture in the drying air is simultaneously taken up together with a corresponding heat transfer to the textile goods, on the occasion of the dewatering of the goods brought about during this treatment phase. In the recooling of the drying air, which is now loaded with moisture, in the air cooler after separation of the strand material accompanied up to that point, no change in the moisture content of the outflowing air is registered until the dew point line y = 1 (saturation line) is reached in state point L3. Only in the course of the global reduction in the recooling temperature does the release of the supersaturated water content contained in the gaseous drying agent then occur, which is shown as a change in direction of the drying process in the sense of a shift in the condition point for the drying air to the left along the saturation line to state L4. This then leads to a reduction in the moisture content of the drying air under condensation by the amount _X3 -x ₄ kg of moisture per kg of dry air. This moisture content is separated from the drying air in the separator 4 and discharged from the machine.

The state L4 of the drying air characterizes its condition at the intake port of the blower 1, the drying air being heated to the state L5 by the amount of the compression work in the course of the subsequent compression with the moisture content unchanged. The subsequent section of the route from state L5 to state L1 then provides information about the amount of heat given off by the supply of heat from the air heater 2 to the drying air. When the steam-air mixture is heated from the saturation state in point L4 to the initial state of the circuit in point L1, the moisture content x = remains constant, so that there is a perpendicular course of the change in state.

The state L2 in the diagram explained above generally corresponds to the result of the interaction of the influences of two amounts of moist air, namely formed from the amount that flows into the nozzle from the compressor and the amount that is sucked into the nozzle with the goods.

Claims (5)

1. A batchwise process for partially or completely drying endless ropes of woven or knitted textiles circulating in jet-piece-dyeing machines immediately after a wet-treatment for finishing the textile using the exhaust method and advancing the fiber material within the fully autonomous machine by actuating the jet system, which comprises, immediately after the wet-finishing and after discharging the treatment liquid from this preceding treatment operation, evaporatively dewatering down to a certain residual moisture content the wet-finished moist rope, now kept moving forward by a gas stream, on meeting, and being surrounded by the drive gas which is separately circulated in a separate circulation system within and connected to the same apparatus and has been compressed to a predetermined superatmospheric pressure and heated, as a result of which, in conformity with the pressure increase and the heat supply in the overall system, the density, the flow velocity and the kinetic energy of the transport gas, which now also functions as the drying medium, increase in such a way that the textile material is stripped of the adhering moisture, which vaporizes and is thus carried away in the gas flow, subsequently cooling the gas, which, after the moisture uptake on account of the previous measure, results as the off- gas and as laden with the stripped moisture, from the resulting supersaturated state back into a dry-saturated state with simultaneous recondensation of the moisture stripped from the textile material and separation thereof from the circulation of the gaseous drying agent.

2. The process as claimed in claim 1, wherein the drying agent used is a compressed steam-air mixture which contributes the thermal energy required for evaporating the moisture.

3. The process as claimed in claim 1 or 2, wherein the rope is dewatered within the sealed dyeing jet down to an equilibrium state of the moisture content of the goods which corresponds to the conditioning moisture level of the textile material after it has been removed from the unit and cooled down.

4. The process as claimed in claim 1 or 2, wherein the rope is dewatered within the sealed dyeing jet to below the conditioning moisture level thereof and the textile material is then conditioned by increasing the relative moisture content of the drying air.

5. An apparatus for carrying out the process as claimed in claims 1 to 4, comprising a conventionally designed jet-dyeing machine (A) comprising a liquor circulation system (B) for the hydraulic propulsion of tectile ropes (W) in endless form by means of a treatment liquid by actuation of a built-in jet system (D) which is connected to a separate circulation system (E), passed via the same jet arrangement (D), for a gas stream which is optionally supporting of, or solely responsible for, the rope transport, and from jet arrangement (D) onward includes a limited transport section along which the rope (W), in the absence of liquid transport agent and deactivated circulation system (B), is subject to the influence of the kinetic energy of the drive gas, wherein there are present in the gas circulation system (E) - arranged in the stated order - a blower (1) for compressing the gaseous medium and additional means for subsequently heating it up (2), and, following the contact section, which is aerodynamically active on the rope transport, for the drive gas together with the circulating textile material, means for recooling (3) the resulting gas stream in addition to removing moisture therefrom, and means for separating off (4) the resulting condensate.

Images