"PLANT FOR TREATING TEXTILES WITH AMMONIA, AND RELATIVE

SYSTEM TO RECOVER THE AMMONIA"

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FIELD OF THE INVENTION The present invention concerns a plant for treating textiles, knitwear or yarns with ammonia, advantageously in finishing operations, in order to carry out one or more treatments in at least a relative chamber in a desired sealed condition with respect to the external environment or with respect to one or more adjacent pre- or post- treatment chambers, which work at different pressures and atmospheres, in order to guarantee the compartmentation of the treatment chamber and to facilitate the recovery and re-use of the ammonia, reducing management costs and considerably simplifying the recovery plant

BACKGROUND OF THE INVENTION

It is widely known in the textile industry to subject a fabric, before making up, to various finishing treatments that have the function of giving the fabric desired characteristics that improve certain qualities, such as how pleasant the fabric is to the touch, good resistance to ageing and wear, good mechanical resistance and resistance to abrasion, good dermatological compatibility, greater resistance to creasing and others. Amongst the finishing treatments intended to obtain the characteristics mentioned above, a process has long been studied and applied industrially that uses liquid ammonia baths and subsequent removal of said ammonia from the fabric. In this process, a fabric is fed substantially continuously into a plant provided with one or more treatment and removal chambers, in which it is initially impregnated with liquid ammonia for a determinate period of

time; the ammonia is then made to react with the fibers of the fabric, and subsequently the fabric is made to transit in contact with heated cylinders, or in a bath of water, which remove the ammonia from the fabric. One of the main problems of known treatment systems is to guarantee that the treatment and removal chamber/chambers remains/remain airtight before, during and after the fabric treatment steps, above all in correspondence with the openings of the chambers through which the fabric continuously enters and exits, in order to prevent the ammonia fumes that have developed from leaking out from said chambers, contaminating the external environment and possibly causing harm to the operators involved. For this purpose it is known to provide an intermediate sealed chamber, interposed between a first treatment chamber and the external environment, in which the means to feed the fabric is placed in the external environment, and in which between the intermediate chamber and the treatment chamber four cylinders are provided, able to be disposed reciprocally near each other with desired pressure so as to define a sealed, or safety, compartment that guarantees a safe and complete separation of the two chambers.

Even though it allows a high level of sealing between the two chambers, this solution does not completely prevent small infiltrations of ammonia from passing from the treatment chamber to the intermediate chamber, and hence to the outside environment.

Furthermore, the ammonia that leaks into the environment in this way not only causes air pollution, with time, but also it cannot be recovered by the normal units that recover and introduce ammonia, thus entailing the need to frequently top up the ammonia.

One purpose of the present invention is to achieve a

plant for treating textiles with ammonia that will guarantee an excellent seal of the treatment chamber, substantially without the risk of possible ammonia leakages reaching the external environment. Another purpose of the present invention is to achieve a plant for treating textiles that allows to cyclically recover and re-introduce substantially all the ammonia used for the treatment that has not been consumed in the process. The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION The present invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes a plant for treating textiles with ammonia according to the present invention comprises:

- at least a chamber for treating with ammonia and removing said ammonia; and

- at least a first sealed chamber selectively able to be opened/closed by first sealing means, said first sealed chamber being used to separate in a sealed manner the treatment and removal chamber from the outside environment .

According to a characteristic feature of the present invention, a suction means is connected to at least the first sealed chamber, able to suck out from the latter a mixture of any air and fumes and/or ammonia fumes that have leaked through the first sealing means from the treatment

and removal chamber. The suction means is also associated with at least chemical/physical separation means into which said mixture is introduced, sucked from the first sealed chamber, and able to separate the ammonia from the other elements present in said mixture sucked in. In an advantageous form of embodiment, the chemical/physical separation means comprises at least a water tank where the mixture sucked in is made to bubble in order to obtain a solution of ammonia in water (ammonium hydroxide). In this way, an excellent seal of the treatment and removal chamber is guaranteed, since possible leakages of ammonia, substantially in their totality, are sucked in by the suction means, before they are able to reach the outside environment, and are sent to chemical/physical separation means.

Advantageously, the suction means is also associated with distillation means located downstream of the chemical/physical separation means, in order to obtain from the ammonia solution ( ammonium hydroxide ) a corresponding quantity of liquid anhydrous ammonia.

This liquid anhydrous ammonia is added to the rest of the ammonia normally recovered directly from the treatment and removal chamber, and can therefore be re-introduced into the same treatment and removal chamber, and play an active role in the treatment of the fabric. In this way substantially all the ammonia not used in the process is recovered, without leakages into the environment and reducing to a minimum the need for periodic refills.

A preferential form of embodiment of the present invention provides, respectively upstream and downstream of the treatment and removal chamber, a compartmentation chamber where the fabric enters and a compartmentation chamber where the fabric exits. Said entry and exit

compartmentation chambers, upstream and downstream of the treatment and removal chamber, can be selectively opened and closed in order to, respectively, load or unload the fabric to be treated or already treated. In this embodiment, the suction means is connected both to the first and also to the second sealed chamber, in order to suck in the leakages of ammonia both on entry to and exit from the treatment and removal chamber.

Said entry and exit compartmentation chambers are associated respectively with said first sealed chamber and with a second sealed chamber, which are disposed respectively at the entrance and exit of the treatment and removal chambers.

Said entry and exit compartmentation chambers can be selectively opened/closed by static sealing systems that guarantee an airtight closure thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein: - fig. 1 shows schematically a lateral view of a plant for treating textiles with ammonia according to the present invention; - fig. 2 shows an enlarged part of the textile treatment plant in fig. 1. DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

With reference to the attached drawings, number 10 indicates in its entirety a plant for the treatment with liquid ammonia (NH ₃ ) of a fabric 15 that has undergone previous preparation, finishing and possible dyeing steps.

The plant 10 comprises, in sequence, from left to right in fig. 1, in relation to the direction of movement of the

fabric 15, an entry compartmentation chamber 11, a chamber 12 for treatment in ammonia and removal thereof, and an exit compartmentation chamber 13. Furthermore, the plant 10 comprises a first sealed chamber 42 disposed between the entry compartmentation chamber 11 and the treatment and removal chamber 12, and a second sealed chamber 43 disposed between the treatment and removal chamber 12 and the exit compartmentation chamber 13.

As will be explained in detail later, the opening and/or closing of the first and second sealed chambers 42 and 43 are selectively defined by the reciprocal movement of relative sealing rollers 27 and 32.

The plant 10 also comprises a recovery and introduction unit 14 for the liquid ammonia, of a substantially known type, connected to the treatment and removal chamber 12, and a suction and recovery unit 16 for the leakages, connected both to the first sealed chamber 42 and to the second sealed chamber 43.

The plant 10 also comprises, in a substantially known manner, a depression unit 17 able to selectively create a vacuum inside the chambers 11, 12, 13, 42 and 43, and also, by means of a plurality of pipes, indicated with the reference numbers 54, 54a and 54b, possibly able to introduce into the chambers 11, 12 and 13 a determinate quantity of nitrogen gas at a determinate pressure, in order to render the treatment environment decontaminated and without atmosphere.

The depression unit 17 essentially comprises two vacuum pumps 21 and 22, able to be activated alternatively, in order to guarantee a vacuum in the chambers 11, 12, 13, 42 and 43, even in the case of a malfunction of one of the two.

The entry compartmentation chamber 11 comprises a lateral

opening 25 communicating with the outside, and an entry opening 26 made in correspondence with the treatment and removal chamber 12, to allow the fabric 15 entry to the latter. The possible airtight closure of the lateral opening 25 occurs by means of a respective sealing roller 28, only when the machine is stopped.

Four sealing rollers 27 are disposed in correspondence with the entry aperture 26, disposed in pairs horizontally and vertically with respect to each other, defining in this manner the first sealed chamber 42.

Indeed, as shown in fig. 1, the sealing rollers 27 selectively define the first sealed chamber 42 between chambers 11 and 12, and may be brought to an open or closed position, respectively in order to make the entry compartmentation chamber 11 communicate with the treatment and removal chamber 12 or to isolate it therefrom.

In this case, the sealing rollers 27 also have the function of contributing to the transport of the fabric 15 from the entry compartmentation chamber 11 to the treatment and removal chamber 12.

The exit compartmentation chamber 13 comprises an exit aperture 30 communicating with the treatment and removal chamber 12 and a lateral aperture 31 open towards the outside.

The possible airtight closure of the lateral aperture 31 is achieved by means of a respective sealing roller 29, only when the machine is stopped.

Four sealing rollers 32 are disposed upstream and downstream of the exit aperture 30.

In the same way as described for the sealed chamber 42, the sealing rollers 32 also selectively define the relative second sealed chamber 43 between chambers 12 and 13;

indeed, they can be moved in order to connect, or isolate, the exit compartmentation chamber 13 and the treatment and removal chamber 12, defining in this way the second sealed chamber 43. In this case, the sealing rollers 32 also have the function of contributing to the transport of the fabric 15 from the treatment and removal chamber 12 to the exit compartmentation chamber 13.

The suction and recovery of leakages unit 16 comprises a chemical/physical separation column 44 and a distillation column 45.

The chemical/physical separation column 44 is connected to the sealed chambers 42 and 43 by means of exit pipes 36, in turn mainly provided with respective exit flow meters 37, one for each sealed chamber 42 and 43, and with a ventilator 20, or blower, which generates a depression in the exit pipes 36, while the distillation column 45 is advantageously heated by means of a coil 48 and is connected to the chemical/physical separation column 44 by means of a delivery pipe 46 and a regulating pipe 47.

A pressurizing pump 49 and possibly a heat exchanger 53 are associated with the delivery pipe, while a pressure regulating valve 50 and possibly a heat exchanger 51 are associated with the regulating pipe 47. The suction and recovery unit for leakages 16 also provides two air inlet pipes 38 associated with each sealed chamber 42 and 43, and through which a desired quantity of air is introduced from the outside into the sealed chambers 42 and 43. Each entry pipe 38 is mainly provided with a flow meter 39 and a regulatory valve 40 for the flow of air.

In this way, each sealed chamber 42 and 43 is maintained at a slight depression, so that possible leakages of

ammonium gas coming from the treatment and removal chamber 12 are sucked in, guaranteeing a suction ratio that will maintain the desired efficiency of sealing and safety from the danger of explosions. Indeed, when the difference in flow measured by the two flow meters 37 and 39 shows that the suction ratio between ammonia leakages and air introduced differs from a given safety range, the regulation valve 40 is commanded to open or close, in order to bring said suction ratio within the determinate range.

According to a variant embodiment, not shown, the difference in pressure between the treatment and removal chamber 12 and the respective sealed chamber 42 or 43 is controlled by means of pressure probes or a differential pressure switch. In this embodiment, the flow of air into the sealed chambers 42 and 43 is regulated by modulating the suction of the ventilator/blower 20 by means of an inverter, of a substantially known type and not shown here.

For example, the differential pressure is advantageously maintained at a relative value of less than about 3000/5000 Pa.

Advantageously, the suction and recovery unit 16 of leakages is also connected to the entry and exit compartmentation chambers 11 and 13 by means of respective branches 36a and 36b of the exit pipe 36.

When the set security range is exceeded, the plant 10 is made to operate under emergency conditions, that is, the advance of the fabric 15 is stopped, the entry and exit compartmentation chambers 11 and 13 are closed by the action of the respective airtight sealing rollers 28 and 29, and the depression unit 17 is automatically activated, which creates a vacuum in the sealed chambers 42 and 43, therefore creating a double barrier against the leakage of

ammonia from the treatment and removal chamber 12.

The chemical/physical separation column 44 comprises a tank 52 at least partly filled with water, into which the respective exit pipes 36 end. In this way, the mixture of air/ammonia sucked in from the sealed chambers 42 and 43, and possibly from the entry compartmentation chamber 11 and exit compartmentation chamber 13, is introduced into the water and made to bubble, in order to create a reaction of the ammonia with the water (formation of ammonium hydrate), while the remaining gasses are discharged through the breather pipe 56 and sent to an abatement tower.

The ammonium hydrate formed in this way is sent, through the pressurizing pump 49, to the distillation column 45 where the distilled ammonia is sent, by means of the pipe 57, to the condenser (not shown) and then recovered in its liquid form.

The connection between the distillation column 45 and the chemical/physical separation column 44 guarantees, by means of the pressure regulation valve 50, that the specified pressure is maintained inside the distillation column 45, thus allowing the water in the system to be recycled.

The liquid ammonia recovered in this manner is sent to the recovery and introduction unit 14 through which it is then re-introduced into the treatment and removal chamber 12 during the step of treating the fabric 15.

The plant 10 according to the present invention described heretofore functions as follows.

First of all, a decontamination cycle is started, following the discharge of any possible condensations from the plant, in which, by means of the sealing rollers 28 and 29, the lateral openings 25 and 31 are closed and the sealed chambers 42 and 43 are opened, so that the loading chamber 11 and unloading chamber 13, the treatment and

removal chamber 12 and the sealed chambers 42 and 43 define a single internal compartment.

At this point one of the two vacuum pumps 21 or 22 of the depression unit 17 is activated, in order to generate a vacuum in said single internal compartment. The vacuum pump 21, or 22, is kept in operation until an absolute depression of about 60/80 Pa is reached for a determinate number of seconds.

When such condition is reached, a desired quantity of nitrogen is introduced into the single internal compartment by means of the pipe 54, alternating with a vacuum step for a determinate number of cycles, at the end of which the two sealing roller units 27 and 32 are reciprocally closed, in order to reciprocally separate the chambers 11, 12, 13, 42 and 43.

At this point, by means of the recovery and introduction unit 14, ammonia gas is introduced into the treatment and removal chamber 12, and contemporarily air is introduced into the entry and exit compartmentation chambers 11 and 13, by means of relative air introduction pipes indicated with reference numbers 55a and 55b.

The pressure in the entry and exit compartmentation chambers 11 and 13 must not exceed differences higher than about ± 10000 Pa with respect to the treatment and removal chamber 12.

In this step, the pressure inside the entry and exit compartmentation chambers 11 and 13 is managed by regulating the air introduced into said chambers 11 and 13, by means of respective regulation valves 40a and 40b. When a relative pressure equal to about 0 bar with a tolerance of ± 2000 Pa has been reached inside the treatment and removal chamber 12, the regulation valves 40 are opened in order to introduce a desired quantity of air

into the sealed chambers 42 and 43, until a depression of 0.1 bar is reached inside said chambers.

The ventilator/blower 20 is then started in order to carry out the suction of the mixture of introduced air/ammonia leakages from inside the sealed chambers 42 and 43. The pressure inside the sealed chambers 42 and 43 must in any case be lower than the pressure in the treatment and removal chamber 12, for example equal to about 3000 Pa.

This pressure inside the sealed chambers 42 and 43 is advantageously managed by the regulating the suction carried out by the ventilator/blower 20.

The lateral apertures 25 and 31 are then opened in order to allow, respectively, the loading and unloading of the fabric 15 from the plant 10, to begin an ordinary treatment cycle.

Before the ordinary working cycle begins, liquid anhydrous ammonia is introduced from the recovery and introduction unit 14, into a soaking tank 58 inside the treatment and removal chamber 12, and contemporarily a second ventilator/blower 20a is driven in order to recover the ammonia gas that forms during the ordinary treatment cycle in the treatment and removal chamber 12. The suction of the ammonia gas inside the treatment and removal chamber 12 is regulated by modulating the ventilator/blower 20a by means of an inverter, not shown, according to the pressure control inside the treatment and removal chamber 12.

In this step too, the flow meters 37 and 39 positioned before and after the sealed chambers 42 and 43 control the delivery of air introduced and the leakages, possibly setting off the alarm of the plant 10 when the flow of air/ammonia mixture exceeds the pre-set limits.

According to a variant, the control of the ammonia leakages can be carried out indirectly by controlling the

ammonia recovered by the distillation column 45.

At the end of the treatment of the fabric 15 the plant 10 undergoes a decontamination step, in which initially the liquid ammonia is rapidly discharged from the soaking tank 58. The discharge of the liquid ammonia may be carried out by means of a pump, not shown, and sent to the recovery and introduction unit 14.

In particular, the openings 25 and 31 are consequently closed by means of the respective sealing rollers 28 and 29, nitrogen is introduced into the entry and exit compartmentation chambers 11 and 13 through the nitrogen introduction pipes 54a and 54b, to allow a washout of the air with nitrogen, a vacuum of about 60/80 Pa is created in the sealed chambers 42 and 43, and then a vacuum is created both in the entry and exit compartmentation chambers 11 and 13 and in the treatment and removal chamber 12.

When such vacuum has been created, the sealed chambers 42 and 43 are opened, so that the entry and exit compartmentation chambers 11 and 13, the treatment and removal chamber 12 and the sealed chambers 42 and 43 define a single internal compartment, after which a desired quantity of nitrogen is introduced into the single internal compartment, alternated with a vacuum step for a determinate number of cycles. It is clear however that modifications and/or additions of parts or steps may be made to the plant 10 and method as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of plant for the treatment of textiles with ammonia, and relative recovery

system of the ammonia, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.