FLOWING OUT OF AN INDUSTRIAL PLANT

The present invention relates to an apparatus and a process for recovering heat from a liquid flowing out of an industrial plant, in particular a discharge liquid previously used for chemical processing and/or treatments, such as dyeing and/or bleaching, by which it is possible to obtain an efficient heat exchange and to carry out a cleaning operation of the means adapted to the heat recovery in a very quick and effective manner.

Currently the machines in continuous use in an industrial textile plant for chemical processing such as washing, mercerizing, or rope bleaching and open-width bleaching, use water as the working liquid and, once the working liquid has finished being used, is still at a temperature sufficiently high that it can be used to heat the clean working liquid flowing into the industrial plant, and in particular in the machine that carries out such processing.

In the patent IT 1263729 a system is presented which allows to exchange heat between the outflowing slurry flow and the incoming liquid flow through a casing in which is placed a rotating shaft which carries a series of communicating discs. The clean liquid flows within the disc. Instead, the slurry flowing out of the machine or the industrial plant is circulated inside the casing in such a manner that the surface of the discs ensures a certain heat exchange between the incoming liquid and the slurry from which the heat recovering is desired.

The slurry flowing out of the machining presents therein residues such as cotton dust or chemicals having film-forming or aggregating properties, which may be deposited on the heat transfer surfaces, or close to them, thereby lowering the efficiency of heat exchange.

The system of the above patent does not lend itself to a quick cleaning, because the cleaning of the fouling inside the casing requires the dismantlement of the system. Moreover, this system facilitates the sedimentation of debris in the casing for the fact that the slurry is circulated around the discs whereby the speed relative to the walls of the casing is low and variable in direction. This aspect facilitates the sedimentation and accumulation of such debris.

Again, the shape of the discs can create structural problems due the high efforts that are created in particular on the peripheral area of the same, as a result of, in certain conditions, the generation of water hammer.

The object of the present invention is to provide an apparatus and a process for recovering heat from a polluted liquid flowing out of an industrial plant, in order to heat a clean liquid flowing into such a plant, which allows heat to be recovered with a higher heat exchange efficiency as compared to the systems currently known, and with fewer structural problems related to the pressure associated with the outflowing polluted and hotter liquid flow and/or with the incoming cleaner and colder liquid flow.

Another object of this invention is to provide an apparatus and a process for recovering heat from a polluted liquid flowing out of an industrial plant, in order to heat a clean liquid flowing into such a plant, which allows to perform the cleaning of the means for the circulation of the polluted liquid in a more quick and automatable manner than the systems currently known.

Further object of the present invention is to provide an apparatus and a process for recovering heat from a polluted liquid flowing out of an industrial plant, in order to heat a clean liquid flowing into such a plant, such that the exchange heat operation between polluted liquid and clean liquid is to be made in a such manner that the deposition of substances in the solid state on the surfaces of the means for the circulation of polluted liquid is less likely as compared to the systems currently known.

Such purposes are obtained by means of an apparatus and a process for recovering heat from a fluid flowing out of an industrial plant to heat a liquid flowing into such a plant, each comprising the technical characteristics exposed in one or more of the appended claims. The dependent claims correspond to different embodiments of the invention. Particularly, according to a first aspect, the present invention relates to apparatus for recovering heat from a liquid flowing out of an industrial plant, so as to heat a liquid flowing into this plant, comprising a delivery conduit for delivering a incoming liquid and that is suitable for being connected to the industrial plant system and at least one recovery conduit suitable for having the outflowing liquid flow through it, characterized in that the recovery conduit is disposed inside the delivery conduit and is operationally associated with at least one working machine so that the outflowing liquid passes through the recovery conduit at a pressure higher than the atmospheric pressure.

A possible embodiment of the present invention may comprise at least one of the following aspects.

Preferably, the recovery conduit comprises a plurality of recovery conduits disposed inside a delivery conduit.

Preferably, the delivery conduit and the recovery conduit comprise at least two flanked longitudinal sections and connection means between the two longitudinal sections.

Preferably, the apparatus comprises collection means, for example a collection tank, suitable for receiving the liquid outflowing from the industrial plant, and the working machine is operationally interposed between such collection means and the recovery conduit.

Preferably, the apparatus comprises an outlet hydraulic circuit connected to the recovery conduit and comprising a recovery conduit suitable for setting the recovery conduit and the collection means in communication, and a drainage conduit suitable for setting the recovery conduit in communication with a drain.

Preferably, the apparatus comprises one or more valves suitable for selectively setting the recovery conduit in communication with the recovery conduit or the drainage conduit. Preferably the apparatus comprises cleaning means disposed in communication with the recovery conduit for the introduction of the cleaning fluids in the recovery conduit, for example water, lactic acid and steam.

Preferably the cleaning means comprise input lines of the cleaning fluids disposed in communication with the collection means.

Preferably the apparatus comprises a control unit programmed to detect the state of operation of the industrial plant and activate the washing means when the industrial plant is inactive.

According to another aspect, the present invention relates to a procedure for recovering heat from a liquid flowing out of an industrial plant, so as to heat a liquid flowing into this plant. This method provides the introducing of the incoming liquid into a delivery conduit to be sent to the industrial plant, the introducing of the outflowing liquid in at least one recovery conduit disposed inside the delivery conduit and having said outflowing liquid through the recovery conduit at a pressure higher than the atmospheric pressure.

This process may have at least one of the following aspects.

Preferably it is provided the collecting of the liquid flowing out of the plant in collection means, for example a collection tank, before introducing it into the recovery conduit.

Preferably it is provided to perform at least one rinse cycle with a rinsing substance such as the water, preferably introduced into collection means arranged upstream of the recovery conduit. This rinsing substance is sent at a pressure higher than the atmospheric pressure to the recovery conduit. At the end of the rinsing step the substance rinsing is discharged through a drainage conduit.

Preferably it is provided to carry out at least one wash cycle for washing with a cleaning substance, for example lactic acid, preferentially introduced into the collection means disposed upstream of the recovery conduit, and which is sent to the recovery conduit at a higher pressure than the atmospheric pressure.

Preferably the wash cycle comprises at least one return step wherein the cleaning substance flowing out of the recovery conduit is sent back by means of a recovery conduit, to this recovery conduit, preferably passing through the collection means again.

Preferably the wash cycle comprises at least one step of heating the cleaning substance by means of the action of a gas, for example vapour introduced in collection means, so that this gas heats the cleaning substance.

The features of the present invention will be clarified from the following detailed description related to a preferred embodiment thereof provided by way of illustration, and not limitation, of the more general claimed concepts.

The following description refers to the accompanying drawings, in which - Figure 1 is a schematic view of an apparatus according to a preferred embodiment of the present invention;

- Figure 2 is a schematic sectional view of a detail of the plant of Fgure 1 along the line ll-ll and according to a first embodiment;

- Figure 3 is a schematic sectional view of a detail of the plant of Fgure 1 along the line ll-ll and according to a second embodiment;

- Figure 4 is a schematic view of a part of an embodiment of the present invention.

In Figure 1 , with I is shown an industrial plant used preferably in the textile field, and that uses a liquid as the working fluid, in particular water.

1 denotes a preferred embodiment of an apparatus according to the present invention for recovering heat from a fluid flowing out of the industrial plant I in order to heat a liquid flowing into the plant. The apparatus 1 comprises a delivery conduit 2 of the incoming liquid adapted to be connected to the industrial plant I, and at least one recovery conduit 3 adapted to be traversed by the outflowing liquid. "In" denotes an input flow in the delivery conduit 2 and "U" denotes a flow from the delivery conduit 2 disposed in fluid connection with the industrial plant I.

"In" denotes an input flow in the recovery conduit 3 coming from the industrial plant I.

The recovery conduit 3 is advantageously arranged inside the delivery conduit 2 and is operatively associated with at least a working machine 4 such as the outflowing liquid flows in the recovery conduit 3 with a pressure higher than the atmospheric pressure.

The delivery conduit 2 and the recovery conduit 3 comprise at least two flanked longitudinal sections S and connection means C between the at least two longitudinal sections S. In the example illustrated in Figure 1 three two by two, flanked longitudinal sections S have been provided, that are connected by connection means C.

In Figure 4, which shows one of the longitudinal sections S of the recovery 3 and delivery conduits 2, it can be noted that in this arrangement the connection means C from a section S to the another one of Figure 1 are, at each end of each section S, the one in communication with the delivery conduit 2 and the other one with the recovery conduit 3.

In Figure 3 is shown a cross-section of the delivery 2 and recovery conduits 3, in which it can be noted that the recovery conduit 3 may advantageously comprises a plurality of recovery conduits 3' arranged inside the delivery conduit 2, so as to further reduce more the amount of dirt contained in the outflowing liquid that is deposited on the walls of the recovery conduit 3. In Figure 2 is shown another possible configuration of the delivery 2 and recovery conduits 3, such that the latter comprises a single conduit 3 inside the delivery conduit 2, which results in a structural simplification of this portion of the apparatus 1 .

With reference to both the figures, the delivery conduit 2 is external to the recovery conduit whereby the incoming liquid occupies the space around the recovery conduit. The outflowing liquid occupies the space in the recovery conduit 3 which is preferably realized by means of one (or more) pipes defining at least an inner, cylindrical and smooth wall, i.e. devoid of protuberances or projections which would hinder the outflowing liquid flow. The apparatus 1 advantageously comprises collection means 5, for example a collection tank, suitable to receive the liquid flowing out of the industrial installation I. In this case the working machine 4 is operatively interposed between the collecting means 5 and recovery the conduit 3, to ensure that the outflowing liquid is sent under pressure to the recovery conduit 3.

According to the example illustrated in the figures, connection conduits 5', 5" may be provided that are interposed between the industrial plant and the recovery conduit 3 for transferring the outflowing liquid. In particular, the collection means 5 are preferably arranged along these connection conduits 5', 5".

Furthermore, along the connection conduit 5', interposed between the plant I and the collection means 5, there is a bypass conduit 5"' adapted to allow the exclusion of the passage inside the collection means 5, and then inside the recovery conduit 3, of the polluted fluid from the plant I.

In this way, in the case in which the fluid (polluted liquid) from the plant I must be discharged into the sewer or in another apparatus, the valve 12a, placed on the connection conduit 5', is closed, and the valve 12b, placed on the bypass conduit 5"', is open, in order to attain the above-mentioned exclusion of the flow into the collection means 5. In contrast, by closing the valve 12b of the bypass conduit 5" and by opening the valve 12a of the connection conduit 5' is allowed the passage of the fluid from the plant I towards the collection means 5.

In order to carry out the washing operations of the recovery conduit 3, cleaning means 6 can be advantageously present, that are disposed in communication with the recovery conduit 3 for the introduction of the cleaning fluids in the recovery conduit, preferably water and lactic acid.

The cleaning means 6 further comprise steam which is introduced into the recovery conduit (3) to heat said cleaning fluids.

These fluids allow to remove the residues and the fouling in contact with the surfaces of the recovery conduit 3.

To be able to perform an effective washing and possibly also a preliminary rinsing step, and/or a rinsing step after the actual washing, the cleaning means comprise input lines L for the cleaning fluids disposed in communication with the recovery conduit 3, preferably with the collection means 5. In particular, a first input line U is placed in communication with a reservoir 7 of a cleaning substance, preferably lactic acid, and has a metering pump V suitable for dispensing the acid according to predefined metered quantities according to the type of cleaning that must be implemented.

A second input line L" is placed in communication with a source of a rinsing substance, such as the water, and has a valve V" for the controlled delivery of such substance.

A third input line U" is placed in communication with a source of steam for heating, in particular for heating the cleaning substance.

The steam input line U" includes a system for managing the delivery of steam, provided with a valve V" for the controlled delivery of the steam inside the collection means 5 in order to maintain the temperature of the cleaning fluids within a pre-set value. In this way, a temperature sensor Tsi on the conduit 5" measures the temperature of the washing fluid and activates the delivery of steam in the event that this temperature should be raised to a pre-set value. Again, the third input line U" is preferably provided with a pressure reduction valve to delivery the steam inside the tank 5 at a pressure equal to or lower than 1 bar, thus avoiding excessive handling of the cleaning fluid (water and lactic acid) within the tank 5.

For the purpose of being able to quickly switch from the heat recovery step to the washing step, while maintaining a certain simplicity in the structural configuration of the apparatus 1 , an outlet hydraulic circuit 8 can be advantageously provided that is connected to the recovery conduit 3. The hydraulic conduct 8 comprises a recovery conduit 8a suitable for setting the recovery conduit 3 and the collection means 5 in communication, and a drainage conduit 8b suitable for setting the recovery conduit 3 in communication with a drain 9.

In order to also facilitate the automation of the washing operations, the apparatus 1 comprises one or more valves 10 suitable for selectively setting the recovery conduit 3 in communication with the recovery conduit 8a or the drainage conduit 8b. In particular there is provided a valve 10 on the recovery conduit 8a and a valve 10 on the drainage conduit 8b.

Again, the drainage conduit 8b presents, upstream of the respective valve 10, a siphon 13 adapted to prevent the complete emptying of fluids from the recovery conduit 3. Therefore, this siphon 13 ensures to avoid, even in a condition of non-use of the apparatus 1 , the emptying of the fluids from the conduit 3 while keeping the entire heat exchanger in a state of immersion.

Advantageously, the constant condition of immersion of the recovery conduit 3 prevents the formation of fouling on the internal surfaces of the recovery conduit 3 due to the presence of air and then to oxidation reactions of the pollutants present in the conduit 3 itself. Therefore, it is also maintained certain efficiency in the heat exchange of the recovery conduit 3 due precisely to the prevention of the surface structure of the conduit.

In use, the apparatus 1 allows to effectively recover the heat of a liquid flowing out of an industrial plant I. Even regardless of the aforementioned apparatus, a possible process for recovering heat from a fluid flowing out of an industrial plant to heat an incoming liquid in such a plant, according to the present invention, comprises:

introducing the incoming liquid into the delivery conduit to be sent to the industrial plant, introducing the outflowing liquid into the recovery conduit disposed inside of the delivery conduit and having said outflowing liquid flow through the recovery conduit at a pressure higher than the atmospheric pressure.

Before introducing it in the recovery conduit 3, it is preferable to collect the liquid flowing out of the installation, for example within the collection means 5.

In particular, it can be performed a wash cycle, which is carried out by means of a washing substance, preferably by lactic acid, preferably introduced into the collection means 5 disposed upstream of the recovery conduit 3, and sent to a pressure higher than the atmospheric pressure to the recovery conduit 3.

To this end, a control unit 1 1 can advantageously be present, that is programmed to detect the operating status of the industrial plant I and to activate the cleaning means 6 when the industrial plant I is inactive.

In accordance with a further embodiment, the cleaning means can also be activated during the operation of the industrial plant I by passing the fluid flowing out of the implant I through the bypass conduit 5"'. In this way, the outflowing fluid is discharged and is not conveyed in the apparatus 1 during the self-cleaning steps, thus guaranteeing the constant operation of the plant I.

Advantageously, a further step of activation of the cleaning means 6 is implemented by the control unit 1 1 by detecting a value of efficiency of the apparatus (1 ).

In accordance with this embodiment, the control means 1 1 are constituted by: a first temperature sensor Tsi placed in the connection conduit 5" in the input of the heat exchange zone; a second temperature sensor Tsu placed on the hydraulic conduit 8 upstream of the siphon 13; a third temperature sensor Tpi placed in the input flow In of the conduit 2 upstream of the heat exchange zone; and a fourth temperature sensor Tpu placed in the outflowing flow U of the delivery conduit 2 downstream of the heat exchange zone. Furthermore the control means 1 1 provide a flow meter Fs of the fluid placed in the connection conduit 5" in the input of the heat exchange zone, and a flow meter Fp of the fluid Tpi placed in the input flow In of the delivery conduit 2 upstream of the heat exchange zone.

In this way, by detecting temperatures and flow rates of the fluids it is possible to obtain the yield value h calculated by a management logic unit (which is not described in detail being of known type) with the following formula:

h = (Tpu - Tpi) x Fp

Tsi x Fs - Tpi x Fp

The yield value h calculated is then compared with a pre-set yield value indicating an operating condition of the apparatus 1 in which a cleaning action is required. Following this comparison, the logic unit provides for activating or not the above-mentioned cleaning means (6).

Advantageously, in this case the cleaning of the apparatus 3 is not only related to the mere operation or not of the plant I (and then only to the time spent in operation), but also to the measurement of the yield of the apparatus 1 and then to the apparatus's heat exchange capacity itself. In order to reduce the consumption of the cleaning substance, the wash cycle preferably comprises at least a return step in which the cleaning substance from the recovery conduit 3 is re-sent to the recovery conduit 3, preferably being collected in the collection means 5. In this way the cleaning substance recirculates several times within the recovery conduit 3, and ensures an efficient cleaning.

To increase its cleaning effect, the wash cycle can advantageously comprise a heating step for heating the cleaning substance, for example by introduction of a gas (steam) into the collection means 5 or directly into the recovery conduit 3.

To eliminate the polluted liquid that leaves the plant I before the actual washing, at least a rinse cycle with a rinsing substance (for example water) can advantageously performed, the rinsing substance being preferably introduced into the collection means 5 disposed upstream of the recovery conduit 3, sent under a pressure higher than the atmospheric pressure to the recovery conduit 3. The rinsing substance exiting from the recovery conduit 3 is subsequently discharged through the discharge conduit 8b.

The rinse cycle can advantageously be carried out to eliminate the remaining cleaning substance, even after the actual wash cycle, during which it recirculates the cleaning substance.

The above described process may represent a possible sequence using the apparatus 1 according to the present invention.