WO2012107897A1

WO2012107897A1 - Plant and method for processing fluids

Info

Publication number: WO2012107897A1
Application number: PCT/IB2012/050594
Authority: WO
Inventors: Giuliano Cavaglia'; Daniele CRUDO; Valentina BOSCO
Original assignee: E-Pic S.R.L.
Priority date: 2011-02-10
Filing date: 2012-02-09
Publication date: 2012-08-16
Also published as: ITTO20110113A1; EP2673238A1; IT1404266B1; WO2012107897A4

Abstract

A plant (11) for processing fluids, comprising a saturator (13) and a cavitational element (15), said cavitational element (15) being located downstream the saturator (13) whereby said fluid to be processed passes through said saturator and said cavitational element in succession, and wherein the saturation gas is CO₂ or a gas mixture containing a high percentage of CO₂.

Description

PLANT AND METHOD FOR PROCESSING FLUIDS

DESCRIPTION

Technical field

The present invention relates to a plant and a method for processing or treating fluids.

More particularly, the invention relates to a plant and a method aimed at reducing the bacterial charge in fluids to be processed.

Prior Art

The presence of microorganisms and/or the increase of the microorganism content within a fluid often cause a degradation of the qualitative characteristics of the fluid itself, because of the formation of moulds, bacteria, yeasts and enzymes.

Because of such phenomena, a fluid can become a medium for the generation and growth of microorganisms, and, for this reason, it can be a vehicle for conveying pathologies and infections.

The protection of consumer's health, as well as of the nutraceutical and/or the applicative properties in general of the processed fluids is a very important aspect, falling within the wider field of the safety of all those fluids coming in contact with living beings.

It is therefore very often necessary to reduce the microorganism charge, especially the pathogen bacteria charge, in fluids, in order to meet the standards of both safety and quality, in order to keep the preservability of the fluid itself and/or to extend the so-called "shelf life" thereof.

At present, in order to eliminate or deactivate microorganisms such as viruses and bacteria contained in some fluids, in particular in liquids, high-temperature or high- pressure treatments are for instance performed.

Conventional high temperature treatments usually applied today in industry, such as for instance pasteurisation and sterilisation, are based upon the principle of the inactivation and/or destruction of some microorganisms as an effect of high temperatures.

High pressure treatments are another conventional practice industrially applied in order to destroy and/or inactivate microorganisms present in fluids. High pressure, actually, can first generate modifications at the level of the cell morphology and then determine a considerable increase in the permeabilisation of the cell membrane, which can lead to the microorganism's death.

Some scientific publications (Ferrentino, G., 2009, Microbial Stabilization of Liquid Food With Carbon Dioxide Under Pressure, Doctoral Thesis, University of Salerno), (Erkmen, O., 1997, Antimicrobial Effect of Pressurized Carbon Dioxide on Staphylococcus aureus in Broth and Milk, Lebensm.-Wiss. u.-Technol, 30, 826 - 829),

(Ferrentino, G., et al., 2008, Microbial inactivation and shelf life of apple juice treated with high pressure carbon dioxide, Journal of Biological Engineering 2009, 3:3) have proposed associating the high-pressure sterilisation technology with carbon dioxide injection, in order to improve destruction and/or inactivation of some microorganisms.

Microorganism inactivation and sterilisation techniques through the use of high density carbon dioxide, continuously fed to a device operating under high pressure conditions, are also disclosed in CN 201188863 and JP 2006-333835.

As known, water-based fluids, in contact with pressurised C0₂, generally become acidic, since the following reactions occur:

C0₂ (g) <→ C0₂ (1) (1.1)

C0₂ (1) + H₂0 <→ H₂C0₃ (1.2)

H₂C0₃ <→ H⁺ + HC0₃- (1.3)

HC0₃ - <→ H⁺ + C0₃ ² (1.4)

Formation and dissociation of H₂C0₃ releases H ions, promoting a lowering of pH in the bulk of the liquid being processed, thereby contributing to increase the permeability of the microorganisms' cells to C0₂ and hence making C0₂ penetration into the cells themselves easier.

Dissolved C0₂ can diffuse inside the cell membrane and accumulate in the lipophilic (phospholipidic) layer, due to the high affinity between C0₂ and cell plasma. C0₂ accumulation in the lipidic phase and the presence of HC0₃ ^" ions create a structural and functional alteration of the cell membrane itself.

The cell membrane is governed by an equilibrium, resulting also from a regulation of the internal pH (one of the mechanisms for such regulation is proton expulsion in response to a variation of pH between the inside and the outside of the cell itself). If too much dissolved C0₂ enters the cell cytoplasm, the cell is no longer capable of expelling protons to the outside, and internal pH starts decreasing. If said pH attains too low values, the cell vitality is seriously weakened. Many functional and structural aspects of the cell are strongly influenced by internal pH, especially the catalytic activity of the enzymes essential for regulating the processes and the metabolism of the cell. The presence of C0₂ and HC0₃ ^" alters the cell enzymatic function, responsible for the metabolic reactions, including carboxylation and decarboxylation reactions. Accumulation of C0₂ in cytoplasm promotes conversion of ions HC0₃ ^" in ions C0₃ ^2", responsible for intracellular precipitation of magnesium carbonate (MgC0₃) and calcium carbonate (CaC0₃), thereby altering the regular osmotic pressure of the cell.

C0₂, having a high solvent power, can extract the vital constituents from the cells or the cell membranes. In such a mechanism, pressurised C0₂ first penetrates into the cell, and then extracts the intracellular constituents thereof, such as phospholipids and hydrophobic compounds, thereby altering the membrane structure and the biologic balance of the system and promoting its inactivation.

More specifically, it is possible to summarise the bacterial inactivation mechanisms determined by the action of pressurised C0₂ through the following steps:

- solubilisation of pressurised C0₂ into the liquid to be processed;

- modification of the cell membrane;

- decrement of intracellular pH,

- inactivation of the main enzymes and inhibition of the cell metabolism due to a reduction of cytoplasm pH;

- inhibition due to the direct effect induced on the metabolism by CO₂ and HCO₃ ^" molecules;

- alteration of intracellular electrolytic equilibrium;

- removal of the vital constituents of cell membranes and cells.

Other commonly used disinfection techniques are chlorination, filtration and UV-ray treatment.

In general, the main disadvantages associated with the conventional processes are due to the high operation costs and energy consumptions, to plant and operation complications, to the high maintenance costs, to the considerable use of chemicals, to the impossibility, sometimes, of application to certain kinds of fluids, to the severe operating conditions and consequently to the criticalities related to the selection of the materials the plants are made of.

In order to overcome the disadvantages of the conventional techniques, processes and relevant plants have been developed in the past for the treatment of fluid currents, in particular in liquid state, through the use of cavitation inducing elements.

In order to induce the cavitation phenomenon in a fluid, it is necessary to generate an intense and locally concentrated critical event. The most used techniques are: optical cavitation, by using lasers; acoustic cavitation, thanks to the generation of ultrasounds; and hydrodynamic cavitation, which is defined as "static" in case of fluid flow through a stationary cavitational element, or "dynamic", in case the element causing cavitation is moving. In cavitational regimen, a state transition from liquid to gas takes place, resulting in the formation and implosion, within time periods of infinitesimal duration, of a highly unstable bubble cluster. Cavitation is often an unwanted phenomenon: in particular, in pumps, it creates operation problems associated with erosion of the metal parts. In other cases, cavitation is induced in order to promote generation, in the implosion volume and time, of pressure/temperature conditions preventing survival of bacteria, viruses, spores and microorganisms in general.

The need to identify process solutions for disinfecting and sterilising fluids, allowing reducing the operating costs and the carbon footprint, has justified development of these innovative techniques, which are used in combination with or in place of the conventional techniques. These innovative non-thermal methods allow performing treatment without altering the organoleptic properties of the product and denaturing same, and without inducing degradation of the attributes (physical, chemical, optical and mechanical characteristics).

Plants and relevant processes of the above kind are disclosed, for instance, in US 7,833,421 and RU 2 359 763. US 7,833,421 discloses a method of destroying microorganisms in a fluid by means of a device inducing cavitation or supercavitation. RU 2 359 763 discloses an element comprising several modules which, connected in series, create the ideal conditions for inducing cavitation of the fluid being treated. More specifically, the possible applications of such an element are disclosed: creating emulsions, suspensions, dispersions and disinfecting liquids.

The prior art, moreover, discloses cavitational apparatuses including one or more gas or vapour injection points, as described for instance in WO 2005/000453.

An apparatus for treating a fluid, comprising a cavitation unit, is disclosed for instance in WO 2005/108301.

The main limitation of the systems mentioned above is related to the partial elimination of the bacterial charge. For some applications, this entails an incomplete disinfection or sterilisation treatment.

It is a first object of the invention to provide a plant and a method for treating fluids, which does not suffer from the drawbacks of the prior art and which allows, in particular, obtaining a higher effect of elimination of the bacterial charge from the fluid being treated.

It is another object of the invention to provide a plant and a method for treating fluids, which allows preserving the qualitative properties of the fluids being treated.

It is a further object of the invention to provide a plant and a method of the above kind, which are cheaper than the known treatments. It is a further, but not the last object of the invention to provide a plant and a method of the above kind, which can be industrially performed at limited costs and which can be used for the treatment of strong fluid flows.

Description of the invention

The above and other objects are achieved by means of the plant and the method as claimed in the appended claims.

Advantageously, the plant and the method according to the present invention are suitable for treating fluids, more particularly liquids, containing different kinds of microorganisms. More in detail, the plant and the method according to the invention are suitable for treating fluids containing microorganisms such as the ones listed below by way of non-limiting and non-exhaustive example: Saccharomyces Cerevisiae, Escherichia Coli, Lactobacillus Plantarum, Lactobacillus Sakei, Zygosaccharomyces Bailii, Bacillus Coagulans, Clostridium sporogenes, Faecal Coliforms, Faecal Streptococci, Listeria Monocytogenes, Staphylococcus aureus, Bacillus cereus, Pseudomonas Aeruginosa, Yersinia Enterocolitica, Absidia Coerulea, Pseudomonas Fluorescens, Salmonella Typhimurium, Vibrio Cholerae, Shigella Flexneri, Legionella Pneumophila.

Advantageously, the combination of the treatment by gas or gas mixture saturation with the induction of the cavitation effect in the saturated fluid results in a stronger reduction of the microorganism content in a fluid with respect to what is hitherto known.

A particular embodiment of the invention is based on the discovery of a surprising effect resulting from the use of C0₂ in cavitational reactors. Actually, it has been experimentally ascertained that, contrary to what is known in the field, use of C0₂ in a cavitational reactor improves the effect of reduction of the bacterial charge in fluids to be treated. In fact, Parag R. Gogate in "Hydrodynamic Cavitation for Food and Water Processing. Food Bioprocess Techno 1. (2010)" and in "Application of cavitational reactors for water disinfection: current status and path forward. Journal of Environmental Management 85 (2007) 801-815", refers that favourable conditions for the operation of cavitational reactors are determined by the use of gases with high polytropic constant and low thermal conductivity, that is, monatomic gases, thus discouraging use of gases with triatomic molecules, such as C0₂, in cavitational reactors.

In a particular embodiment of the invention, the effects of bacterial charge reduction induced by the cavitation phenomenon are thus associated with those induced by carbon dioxide, whereby an advantageous emphasizing effect of the performance of the overall treatment occurs. Advantageously, according to a preferred embodiment of the invention, C0₂, or the mixture containing a high percentage of C0₂, are introduced into the saturator as the saturation gas or saturation gas mixture and, thanks to the subsequent cavitation step, they carry out more effectively their disinfecting effect.

Advantageously, cavitation is preferably assisted by a cavitation-inducing gas or gas mixture or vapour. Said cavitation-inducing gas or gas mixture or vapour aim in particular at promoting bubble formation, that is, at more effectively inducing the cavitation phenomenon and, in accordance with a first embodiment of the invention, they can advantageously contain C0₂ or a mixture containing a high percentage of C0₂. In other words, the gas or gas mixture or vapour is introduced in order to increase the cavitation nuclei and consequently to increase their volume, to the advantage of the performance of the cavitation phenomenon.

Advantageously, according to another embodiment of the invention, when the saturation gas or the saturation gas mixture introduced into the saturator is C0₂ or contains a high percentage of C0₂, the second gas or gas mixture or vapour aimed at inducing cavitation can comprise a gas different from C0₂, e.g. a monatomic gas, or a gas mixture wit low C0₂ content, or possibly vapour.

Advantageously, according to the invention, the fluid treatment is substantially a cold treatment, i.e. it occurs without an appreciable increase in the fluid temperature, so as to preserve the fluid properties.

Moreover, advantageously, the plant and the method according to the invention allow reducing energy consumption and fluid denaturation, thanks to the use of carbon dioxide as the process gas for the assisted cavitation.

Brief Description of the Figures

Some preferred embodiments of the invention will be described by way of non limiting examples with reference to the accompanying drawings, in which:

- Fig. 1 is a block diagram of a plant according to a preferred embodiment of the invention;

- Fig. 2 is a schematic sectional view of a detail of the cavitational element.

Description of a Preferred Embodiment

Referring to Fig. 1, the plant for treating fluids according to the invention, generally denoted by reference numeral 11, essentially comprises a saturator 13 and a cavitational element 15, located downstream saturator 13 in the flow direction of the fluid to be treated. Thus, according to the invention, the fluid to be treated successively passes through saturator 13 and cavitational element 15. Always according to the invention, moreover, saturator 13 and cavitational element 15 are located in succession immediately after each other, i.e. at a relatively short distance, e.g. 1 m, thereby optimising the synergic effect of saturation on the fluid treated in cavitational element 15.

Saturator 13 is an apparatus arranged to solubilise a gas or a gas mixture in the fluid to be treated and, for this reason, it is associated with a duct 17 for introducing said gas into saturator 13. Said duct arrives from a gas source such as, for instance, a reservoir or a delivery circuit (not shown).

According to a particular embodiment of the invention, preferably the gas fed to saturator 13 is C0₂ or a gas mixture containing a high percentage of C0₂, said percentage preferably exceeding 40%.

In a preferred embodiment of the invention, the C0₂ gas employed will have purity not lower than 90% and more preferably not lower than 99%.

Preferably, saturator 13 is a saturator comprising a casing 19, preferably cylindrical with vertical axis, and internally houses a bed 21 of filling material having a high specific surface. A material having the above characteristics is for instance the product commercialised under the name "Raschig Super Ring".

Preferably, material 21 is packed inside casing 19 and it occupies substantially the whole transversal section within said casing, so as to guarantee a high contact surface among the phases and therefore a high efficiency of substance transfer.

Preferably, moreover, the fluid to be processed is fed to saturator 13 from the top and exits from the bottom, so that the fluid current flows through the whole bed 21 of filling material.

Preferably, moreover, saturator 13 is fed with the gas or the gas mixture, preferably C0₂ or containing a high percentage of C0₂, in countercurrent, by means of a distributor 23 located within casing 19, below bed 21 of filling material, preferably, just below said bed 21.

Cavitational element 15 is an apparatus capable of inducing the cavitation phenomenon and, according to the invention, it preferably comprises a static hydrodynamic cavitational unit, which will be described in more detail hereinafter.

Always with reference to Fig. 1 , the plant according to the invention, in the preferred embodiment, includes a pump 25, of which the main purposes is feeding saturator 13 with the fluid to be treated, at the operating pressure of saturator 13, for instance in the range 1 to 15 bars. In the exemplary embodiment illustrated, pump 25 receives the fluid to be treated through a duct 27 coming, for instance, from a collecting reservoir or a delivery circuit (not shown). A duct 29, associated with the outlet of pump 25, conveys the fluid to be treated to saturator 13 and, preferably, as mentioned before, to the top 31 of said saturator 13. A duct 33, preferably associated with the base 35 of saturator 13, is provided for transferring the fluid flowing out from saturator 13 to cavitational element 15. According to the invention, said fluid flowing out from saturator 13 is saturated with gas or gas mixture, preferably C0₂ or containing a high percentage of C0₂, introduced into saturator 13 through duct 17. Moreover, a duct 37 will be provided for bringing excess gas or gas mixture out of saturator 13 and possibly recovering such excess gas or gas mixture.

In a particular embodiment of the invention, in order to further improve the efficiency of abatement of the microorganisms contained in the fluid to be treated, the fluid to be treated is recirculated through cavitational element 15. Said recirculation is obtained by means of a recirculation circuit 39, which intercepts part of the flow leaving cavitational element 15 through duct 65 and redistributes it to the inlet of said element 15, whereby the fluid to be processed passes several times through cavitational element 15.

Since the multiple passages of the fluid through cavitational element 15 cause a temperature increase in the fluid itself, it could be necessary, depending on the fluid to be treated and its characteristics demanded as a result of the treatment, to cool the fluid by means of a heat exchanger 41 arranged along duct 43 in recirculation circuit 39.

If the pressure at the outlet from saturator 13 is not sufficient to overcome the head losses the fluid undergoes when passing through cavitational element 15, or even if it is simply desired to increase the pressure of the fluid to be treated at the outlet from saturator 13, a pump 45 could be provided, for instance located in a branch 47 of duct 43, as in the illustrated example, or along main duct 43. Preferably, pump 45 will be a centrifugal pump avoiding pressure and flow rate pulsations.

According to a preferred embodiment of the invention, the pressure at the inlet of cavitational element 15 will be in the range 1 to 15 bars.

Event though the described example refers to an arrangement in which a single saturator 13 and a single cavitational element 15 are provided, yet, always according to the invention, a plant equipped with a plurality of saturators and/or cavitational elements, in both a parallel and a serial arrangement, could be provided.

According to the invention, the fluid having passed through saturator(s) 13 arrives at cavitational element(s) 15, where it undergoes a further treatment caused by the cavitation phenomenon. In general, the essential parameters for evaluating the yield of the cavitation phenomenon induced by using a static hydrodynamic cavitational unit are: the pressure of fluid feed to the cavitational apparatus, the physical-chemical properties of the fluid and the initial nucleation radius and the geometry of the constriction.

A parameter which takes into account all the above factors and is essential for predicting the cavitation regimen is the cavitation number, defined in the literature as:

1/2 p vo²

where p₂ is the pressure recovered downstream the cavitational element, p_v is the vapour pressure of the fluid, p the fluid density and vo the average fluid velocity in the constricted section of the cavitational element. Cavitation ideally occurs when the values of C_v are equal to or lower than 1. Velocity v₀, in cavitational regimen, attains values close to 20 - 45 m/s. From the instant the bubble has been generated, its implosion or a bubble volume oscillation can take place, which generate pressure waves whose intensity is variable depending on the geometry of the cavitational element and can attain values of the order of some hundred bars. The phenomenon is also accompanied by temperature oscillations such as to cause localised temperature increases, close to some thousand degrees Celsius. Generally, therefore, cavitation, induced by a static hydrodynamic cavitational unit, promotes the formation and the subsequent implosion of bubbles, thereby creating point conditions (of the time duration of the order of the microseconds) of very high temperature (i.e. 400 - 10,000 °K) and pressure (5 - 5,000 bar).

Under real conditions, the fluid to be treated can contain foreign bodies such as suspended solids or dissolved gases, which can favour the cavitation regimen also for values of the cavitation number a little higher than 1 (for instance 2 or 4).

Referring to Fig. 2, in a preferred embodiment of the invention, cavitational element 15 comprises a static hydrodynamic cavitational unit equipped with one or more Venturi tubes 51, each including a gas/vapour injection system 53 located upstream region 55 where the cavitation phenomenon occurs.

In the alternative to, or in combination with the at least one Venturi tube 51, cavitational element 15 may include one or more bored plates, each having at least one bore with such a geometry as to maximise the perimeter/flow area ratio. Preferably, said at least one bored plate will be arranged transversally to the flow of the fluid to be treated. Preferably, moreover, the bores will be located centrally of the plate, taking into account the velocity profile of a liquid flowing in turbulent regimen in a tube. The plate thickness can vary depending on the bore diameter and, preferably, it will be in the range 1 to 10 mm, even if the plate can have even greater thicknesses, for instance in the range 1 to 50 mm.

Preferably, Venturi tube 51 has, in the constricted section 57, a circular, elliptical, square or rectangular cross section (transversal to the liquid flow) and, taking into account the longitudinal section of Venturi tube 51, the geometry profile is preferably linear in the convergence region 59 and the divergence region 61, without points of discontinuity. The fluid is hence forced to pass in a region 59 with a convergence angle a preferably in the range 10° to 40°, then in the constricted section 57, and lastly in a region 61 with a divergence angle β preferably in the range 4° to 90°, and more preferably in the range 4° to 20°.

The kinetic energy of the fluid to be treated, in the proximity of the constricted section 57, increases to the expenses of the pressure energy, as described in the prior art by the Bernoulli equation. At the instant when, ideally, the pressure of the fluid passing through the Venturi tube 51 attains its vapour pressure, a phase transition from liquid to gas takes place in the fluid bulk, where bubbles are generated. Said bubbles are trailed by the fluid flow and implode due to the increasing pressure recovery downstream the constricted section 57. Cavitation region 55 is identified as the space within which the formation and subsequent implosion of the bubbles take place, i.e. the space where the fluid is in the cavitational regimen.

Advantageously, according to a preferred embodiment of the invention, the cavitation phenomenon induced in element 15 is emphasized by introducing a certain amount of gas or gas mixture into the fluid to be treated, in the immediate vicinity of and upstream the region where the cavitation phenomenon is induced, which region corresponds, in the illustrated example, to cavitation region 55 immediately downstream the constricted section 57. Advantageously, according to an embodiment of the invention, said gas is C0₂ or a mixture containing a high percentage of C0₂, preferably at least 40%.

When, according to a particular embodiment of the invention, the gas fed to saturator 13 is C0₂ or a gas mixture containing a high percentage of C0₂, the second gas or gas mixture introduced into cavitational element 15 in order to induce cavitation can possibly comprise also a gas different from C0₂, e.g. even a monatomic gas, or a gas mixture with a C0₂ percentage lower than 40%, or possibly even vapour. Indeed, the second gas or gas mixture for treating the fluid is aimed in particular at promoting bubble formation and hence at improving or emphasizing the cavitation phenomenon.

In a preferred embodiment of the invention, the gas or gas mixture are introduced into cavitational element 15 through a duct 63 associated with injection system 53.

A preferred embodiment of the treatment method according to the invention will be described hereinafter.

According to the invention, the fluid to be treated is subjected to a first saturation step and then to a second cavitation step.

According to a preferred embodiment of the invention, the saturation step takes place in a saturator, with the introduction of C0₂ or a mixture containing a high percentage of C0₂, preferably at least 40%>.

Always according to a preferred embodiment of the invention, the cavitation step takes place in a cavitational element, preferably a static hydrodynamic element.

Preferably, the cavitation step is assisted by introducing a second gas or a gas mixture or a vapour.

Always according to a preferred embodiment of the invention, the cavitation step takes place by introducing C0₂, or a mixture containing a high percentage of C0₂, preferably higher than 40%, into said cavitational element. As stated above, when the gas fed to saturator 13 is C0₂ or a gas mixture containing a high percentage of C0₂, said second gas or gas mixture introduced into cavitational element 15 in order to induce cavitation can possibly comprise also a gas different from C0₂, e.g. even a monatomic gas, or a gas mixture with a C0₂ percentage lower than 40%>, or possibly even vapour. Indeed, the second gas or gas mixture for treating the fluid is aimed in particular at promoting bubble formation and hence at improving or emphasizing the cavitation phenomenon.

According to the invention, the fluid to be treated is pumped to the saturator at a predetermined pressure, which is mainly a function of the gas amount which it is desired to dissolve in the liquid to be treated and of the efficiency of microorganism abatement which it is desired to achieve. Preferably, saturation is performed by means of carbon dioxide introduced at a pressure preferably higher than 1 atm and such as to guarantee the necessary desired amount of dissolved C0₂.

In a preferred embodiment of the invention, advantage is taken, besides of the cavitation effects, also of the presence of C0₂ dissolved in the previous step by means of saturation. Indeed cavitation, by creating zones with a strong pressure gradient, emphasizes solubilisation of pressurised C0₂ in the liquid to be treated and consequently promotes C0₂ penetration through the microbial cell membrane and hence promotes the subsequent inactivation steps.

Moreover, known chemical treatments (for instance based on Cl₂, H₂0₂, 0₃) may be advantageously employed in association with the described method, thanks to the fact that cavitation promotes penetration of the oxidising chemical agents through the microbial cell membrane thanks to the strong pressure gradient being generated. Moreover, cavitation may facilitate breaking up of microorganism clusters in solution and increase the efficiency of chemical disinfectants.

EXAMPLES

A case, representative of bacterial inactivation and identified as Example 1, has been defined by means of a plant equipped with the cavitational element only, from the point of view of the characteristics of the liquid current to be treated. The data listed below refer to such Example 1.

Example 1

Feed characteristics:

Feed Sea water + microorganisms Flow rate 1.3 1/s

Temperature 15 °C

Pressure 1 bar

Density 998 kg/m³

Microorganisms being investigated Zooplankton

Zooplankton concentration (with size > 50 um) ~ 100,000 microorganisms/m³

Product Characteristics:

Exiting current Sea water + microorganisms Temperature 15 °C

Pressure 3 bar

Density 998 kg/m³

Zooplankton concentration (with size > 50 μιη) ~ 25,000 microorganisms/m³

Characteristics of the cavitational element

Feed pressure 6 bar

Type Bored plate Bore number 1

Bore geometry Circular

Bore position Central

Bore diameter 17 mm

Tube diameter to bore diameter ratio 1.43

Plate thickness 2 mm

Gas/vapour assisted cavitation No

A second case, representative of combined bacterial inactivation "cavitation + C0₂" and identified as Example 2, has been defined from the point of view of the characteristics of the liquid current to be treated. The data listed below refer to such Example 2.

Example 2

Feed characteristics:

Feed Sea water + microorganisms

Flow rate 1.3 1/s

Temperature 15 °C

Pressure 1 bar

Density 998 kg/m³

Microorganisms being investigated Zooplankton

Zooplankton concentration (with size > 50 μιη) ~ 100,000 microorganisms/m³

Product characteristics:

Exiting current Sea water + microorganisms

Temperature 15 °C

Pressure 3 bar

Density 998 kg/m³

Zooplankton concentration (with size > 50 μιη) ~ 12,000 microorganisms/m³

Saturator characteristics:

Pressure of C0₂ saturation 6.2 bar

Head losses 30 mbar

Diameter 450 mm

Height 2500 mm

Filling Raschig Super Ring n° 03

Filling specific surface 315 m²/m³

Filling vacuum degree 0.96 Filling height 1400 mm

Characteristics of the cavitational element

Feed pressure 6 bar

Type Bored plate

Bore number 1

Bore geometry Circular

Bore position Central

Bore diameter 17 mm

Tube diameter to bore diameter ratio 1.43

Plate thickness 2 mm

Gas/vapour assisted cavitation Yes

Type of gas C0₂

Gas flow rate 0.06 1/s (@ 6 bar, 15 °C)

The abatement efficiency of Zooplankton with size greater than 50 μιη, computed as (Zooplankton concentration at the inlet - Zooplankton concentration at the outlet) / (Zooplankton concentration at the inlet) as resulting from Example 1, in the absence of saturation with C0₂ and in the absence of assisted cavitation, was 75%, whereas in Example 2 it increases to 88%, in the presence of saturation with C0₂ at 6.2 bar and in the presence of C0₂ assisted cavitation, the remaining operating conditions being unchanged.

A third case, representative of combined bacterial inactivation "cavitation + C0₂" (C0₂ for saturation only) and identified as Example 3, has been defined from the point of view of the characteristics of the liquid current to be treated. The data listed below refer to such Example 3.

Example 3

Feed characteristics:

Feed Milk + microorganisms

Flow rate 2 1/s

Temperature 15 °C

Pressure 1 bar

Density 1030 kg/m³

Microorganisms being investigated Clostridium sporogenes

Clostridium concentration ~ 5 log CFU/ml

Product characteristics: Exiting current Milk + microorganisms

Temperature 15 °C

Pressure 5 bar

Density 1030 kg/m³

Clostridium concentration (with size > 50 um) ~ 4.3 log CFU/ml

Saturator characteristics:

Pressure of C0₂ saturation 8.2 bar

Head losses 30 mbar

Diameter 450 mm

Height 2500 mm

Filling Raschig Super Ring n° 03

Filling specific surface 315 m²/m³

Filling vacuum degree 0.96

Filling height 1400 mm

Characteristics of the cavitational element

Feed pressure 8 bar

Type Bored plate

Bore number 1

Bore geometry Circular

Bore position Central

Bore diameter 17 mm

Tube diameter to bore diameter ratio 1.87

Plate thickness 2 mm

Gas/vapour assisted cavitation No

A fourth case, representative of combined bacterial inactivation "cavitation + C0₂" (C0₂ for both saturation and in the presence of assisted cavitation) and identified as Example 4, has been defined from the point of view of the characteristics of the liquid current to be treated. The data listed below refer to such Example 4.

Example 4:

Feed characteristics

Feed Milk + microorganisms

Flow rate 2 Vs

Temperature 15 °C Pressure 1 bar Density 1030 kg/m³

Microorganisms being investigated Clostridium sporogenes

Clostridium concentration ~ 5 log CFU/ml

Product characteristics:

Exiting current Milk + microorganisms

Temperature 15 °C

Pressure 5 bar

Density 1030 kg/m³

Clostridium concentration (with size > 50 um) - 3.95 log CFU/ml

Saturator characteristics:

Pressure of C0₂ saturation 8.2 bar

Head losses 30 mbar

Diameter 450 mm

Height 2500 mm

Filling Raschig Super Ring n° 03

Filling specific surface 315 m²/m³

Filling vacuum degree 0.96

Filling height 1400 mm

Characteristics of the cavitational element

Feed pressure 8 bar

Type Bored plate

Bore number 1

Bore geometry Circular

Bore position Central

Bore diameter 13 mm

Tube diameter to bore diameter ratio 1.87

Plate thickness 2 mm

Gas/vapour assisted cavitation Yes

Type of gas C0₂

Gas flow rate 0.06 1/s (@ 8 bar, 15 °C)

The abatement efficiency of Clostridium sporogenes, computed as (Clostridium sporogenes concentration at the inlet - Clostridium sporogenes concentration at the outlet) / (Clostridium sporogenes concentration at the inlet), as resulting from Example 3, in the presence of saturation with C0₂, is 80%, whereas in Example 4 it increases to 91%, in the presence of saturation with C0₂ and C0₂ assisted cavitation.

The plant and the method as described and illustrated can undergo several variants and modifications, lying within the same inventive principle.

Claims

Patent claims

1. A plant (11) for processing fluids, comprising a saturator (13) fed with a first saturation gas or a first saturation gas mixture and a cavitational element (15), said cavitational element (15) being located downstream the saturator (13) whereby said fluid to be processed passes through said saturator and said cavitational element in succession.

2. A plant according to claim 1, wherein said first gas is C0₂ or said first gas mixture contains a high percentage of C0₂.

3. A plant according to claim 1 or 2, wherein said cavitational element (15) is fed with a second gas or a second gas mixture and wherein said second gas is C0₂ or said second gas mixture contains a high percentage of C0₂.

4. A plant according to any of the preceding claims, wherein the saturator (13) comprises a casing (19) wherein a bed (21) of filling material having high specific surface is hosted packed inside the casing (19) so as to occupy substantially the whole transversal section within said casing, so as to guarantee a high contact surface among the phases and therefore a high efficiency of substance transfer.

5. A plant according to claim 4, wherein the casing (19) is a casing with vertical axis.

6. A plant according to claim 5, wherein the fluid to be processed is fed to the saturator (13) from the top and exits from the bottom, so that the fluid current flows through the whole bed (21) of filling material.

7. A plant according to any of claims 4 to 6, wherein the saturator (13) is fed with the saturation gas or gas mixture in countercurrent.

8. A plant according to claim 7, wherein the saturator (13) is fed in countercurrent by means of a distributor (23) located within the casing (19), below the bed (21) of filling material.

9. A plant according to any of the preceding claims, wherein the cavitational element (15) is capable of inducing the cavitation phenomenon in the fluid passing through it and comprises a static hydrodynamic cavitational unit.

10. A plant according to any of the preceding claims, wherein recirculation of the fluid to be processed is provided through the cavitational element (15), said recirculation being obtained by means of a recirculation circuit (39) which intercepts part of the flow exiting the cavitational element (15) and redistributes it to the entrance of said element (15), whereby the fluid to be processed passes several times through the cavitational element (15).

11. A method for fluid processing comprising a first step of saturating the fluid to be processed, said first step being obtained by means of a first saturation gas or a first saturation gas mixture, and a second step of processing the fluid which underwent said saturation step by inducing the cavitation phenomenon in said fluid.

12 Method according to claim 11, wherein said first gas is C0₂ or said first gas mixture contains a high percentage of C0₂.

13. Method according to claim 11 or 12, wherein said cavitation step is a step of cavitation assisted by a second gas or a second gas mixture and wherein said second gas is C0₂ or said second gas mixture contains a high percentage of C0₂.

14. Method according to any of claims 11 to 13, comprising the steps of:

- equipping the saturator (13) with a casing (19) wherein a bed (21) of filling material having high specific surface is hosted packed inside the casing (19) so as to occupy substantially the whole transversal section within said casing, so as to guarantee a high contact surface among the phases and therefore a high efficiency of substance transfer; and

- feeding the fluid to be processed to the saturator (13) from the top and making it flow out from the bottom, so that the fluid current flows through the whole bed (21) of filling material.

15. Method according to claim 14, wherein the saturator (13) is fed with the saturation gas or gas mixture in countercurrent.