PT103473B - CONTINUOUS CORK TREATMENT PROCESS FOR DISINFECTION AND REMOVAL OF VOLATILE ORGANIC COMPOUNDS - Google Patents

Abstract

The present invention relates to the continuous process applicable to the generality of cork products, and which permits the removal of almost entirely volatile organic compounds responsible for oils and / or the transmission of flavor. The process is carried out in two stages, in a unit, or a disinfection machine, consisting of a blower (3), a blower manifold (5), an overheater (7) and a blower (8), and injectors (11).

Description

DESCRIPTION

Continuous Cork Treatment Process for Disinfection and Removal of Volatile Organic Compounds The present invention is in the area of Chemical Engineering.

GLOSSARY

cov Volatile Organic Compounds COOKING Primary treatment carried out on cork, for immersion in water at temperatures between 95 and 120 ° C PRODUCTS CORK Granules, discs, stoppers WITHOUT Abbreviation for Scaning Electron Microscope Scanning electron microscope HPLC High-pressure liquid chromatography TCA Trichloroanisole PIETEC Pressure Induceed Exchange by Thermal Extraction Conducted Continuosly Description of I invent

The present invention concerns a new continuous process for the treatment of cork products, using specific equipment designed for the almost total removal of volatile organic compounds responsible for odors and / or flavor transmission.

This process is applicable to most cork products relevant for sealing such as discs, granules, stoppers,

sections of baton and others, ensuring the respective

deodorization.

Cork is made up of dead cells, and therefore much drier than the corresponding feloderm cells. The drying that occurs after the death of the cells occurs gradually in such a way that the cell membranes remain cohesive, giving rise to films consisting predominantly of cellulose and suberin, which has a macromolecular structure with remarkable similarities with lignin.

After drying, the cork cells therefore remain reasonably liquid-tight, observing closed cell contents above 95% when measured with the aid of a helium pycnometer.

This typology leads to very low values of the diffusion of molecules such as TCA, terpenes and even water molecules (in the vapor state).

It is well known that cork has a tendency to adsorb volatile organic compounds to the surface and, in particular, compounds that can subsequently transmit undesirable odor and / or flavors to wine, namely 2, 4, 6 trichloroanisole of biogenic origin.

One of the most important and traditional applications of cork is as a stopper, either as a natural cork stopper or as a champagne stopper, but in any case to preserve wine or other drinks where the original flavor cannot be contaminated.

Unfortunately, a wide range of volatile organic compounds occurs in cork which, it has been proven, give flavor and / or odor capable of altering or overlapping the natural flavor and / or odor of the product to be preserved.

The following types of contaminants can be mentioned, but not exhaustively:

• 2, 4, 6 trichloroanisole and other polychloroanisols • Terpenes and their derivatives (eg: methyl isoborneol) • Phenols and their derivatives (eg: Guaiacol) • Unsaturated alcohols and ketones (eg: l-octen-3-ol and octen-3-one)

Of all these contaminants, many of them of biogenic origin, trichloroanisole, 2, 4, 6, which is commonly called TCA, is particularly important because it can be detected by smell, even at very low levels.

Systematic tests carried out with panels of tasters consistently showed by statistical treatment that it was possible for trained tasters to detect the presence of levels of the order of 2 nanograms / liter, and even for random panels the detection at the level of 5 nanograms per liter is confirmed.

It is recognized that contamination with TCA and other compounds that cause off-aromas has in many cases (if not all) biological origin.

It is also reasonably proven that biological contamination can originate in the field, in the live tree, but much more often in temporary storage piles (sometimes more than a year).

It is also reasonably proven that slow drying after cooking often leads to the flowering of fungal colonies, some of which have ACT as a product of the respective catabolism.

the relative weight of the chlorine atoms in the TCA molecule is greater than 50% whereas in the earth's crust the current mass fractions of chlorine atoms do not exceed 2% (about 2.2% in sea water).

TCA biosynthesis is therefore a chlorine atom concentrating process with a concentration effect greater than 25 times.

Fungi and other microorganisms with this ability to concentrate halogen atoms are called halophils, with 17 different species identified where the analysis of metabolites allows to identify the presence of TCA and other polychlorinated aromatic compounds.

The texture of the cork, with starlings, vapotranspiration microchannels and cells whose walls were broken during the drying process or by mechanical actions allows the fixation of some colonies of fungi in depth (the largest of 5 mm of external surface).

The removal of TCA and other off-flavors generated in depth is a specific object of the present invention.

The superficial TCA is very easy to remove and if contaminated corks are kept in a well-ventilated area, the concentration of TCA on the surface is reduced from week to week.

SEM observation of highly contaminated cork cuts allows identification of aggregates with a typical typology of fungal colonies. The preferred location is at the interior vertices of the cell walls, extending mainly to the faces that show fracture or rupture.

Completely covered cell walls are observed and the frequency with which cell walls occur with a wall fracture obstructed by the colonies seems to indicate that the colonies to retain moisture and delay drying cause obstruction of the holes in the cells in which they were installed.

The greater permeability of dry cell walls to oxygen and carbon dioxide molecules than water molecules results from the predominantly aliphatic waxy layer that constitutes a very effective barrier preventing the passage of water molecule aggregates.

The preparation of pervaporation membranes using solvents that were present in columns filled with cork dust (dissolving waxes and soluble oligomers) leads to significant increases in selectivity and an increase in the hydrophobic character of the membrane.

It is thus expected, although not yet proven, that colonies in cells where occlusion has already occurred will survive for some time, metabolizing compounds present in cell walls.

The metal coating under high vacuum prior to SEM observation removes, with high probability, all the TCA in addition to, of course, many other volatile compounds. In these circumstances it was not possible for SEM to identify the intracellular sites of deposition of the TCA, but it is admitted that it is partly deposited inside cells meanwhile closed due to obstruction according to the mechanism previously described.

The removal of TCA and other compounds responsible for occluded offaromas in closed cells is a specific object of the present invention.

State of the art

The stopper producing industries have been testing and using a wide range of methodologies to try to minimize the occurrence of stoppers with TCA and / or other compounds that transmit flavor and / or odor (VOC).

These methodologies can be grouped as follows:

• Prevention of formation of TCA and VOC • Prevention of migration of TCA and VOC (films, barriers) • Treatments for removal of TCA and VOC

Of these 3 types of methodologies, the third type is relevant for the analysis of this invention, that is, the treatments for the removal of TCA and other volatile organic compounds (VOCs).

Oxidative Treatment Processes

The washing of corks and other cork products such as discs, with solutions containing hydrogen peroxide (hydrogen peroxide) has been practiced for more than twenty years, and more recently processes have been exhaustively tested using solutions containing ozone.

These processes allow a superficial bleaching of the cork and a reduction in the content of adherent microorganisms (potentially metabolic TCA producers), but for practical contact times they are not effective in reducing TCA that is already present in the stoppers.

In view of the type of results that these processes achieve, it seems more appropriate to fit them in the so-called preventive processes.

Supercritical Extraction Process with C0 ₂

The processes described in patents in this context basically consist of a supercritical extraction with CCy.

The available experimental data show that the process is effective on a laboratory scale, managing to remove not only TCA but also other compounds responsible for transmitting odor and / or taste.

The implementation of the process on an industrial scale is inevitably costly due to the range of pressures at which it is necessary to operate.

This process is completely different from what is the subject of the present invention.

Steam entrainment processes

Process described in WO 2004/014436 A1 is a continuous process that uses a stream of steam with which it is intended to drag the TCA.

contact of a stream saturated with steam with cork at a temperature close to the environment, inexorably leads to the formation of condensate on the surface of the cork.

Due to surface tension and capillarity phenomena, the liquid film formed is impregnated in the pores forming meniscuses close to the surface.

In this as in many other situations the laws of physics are unavoidable and the diffusion of TCA that is found inside the pores becomes very difficult due to the presence of liquid from the occlusion (Fick's Laws).

The process still shows some effectiveness but is fundamentally different from what is the subject of the present invention.

In the present invention, cork products undergo preheating to equalize the temperature in order to avoid the harmful formation of said liquid film, in addition to a series of other differences regarding the equipment and operating mode.

Therefore, several processes have been developed in the last decades to treat cork products.

The cork processing industry, which has carried out many tests with all these processes, generally recognizes the limited efficacy to treat both batches with a high degree of contamination (above 8%) or batches with a low degree of contamination (below 2% ).

In the case of lots with medium contamination (between 2 percent and 8 percent), almost all methods show some effectiveness, but after treatment, the analyzes generally lead to values between 1 percent and three percent residual, mainly for deep contaminated corks and this range of values is not considered satisfactory by most of the Corticeira Industry, nor by the respective customers.

This generalized inefficiency of the previous processes and residual values not negligible, should result in part of the contamination in depth and the occlusive contamination, therefore these contaminations are more difficult to remove specific object of the present invention.

New Process Development

In the experimental development of the process, very contaminated coarse granules (5 + 7 mm) were used.

The tests in vertical column with fluidization by air and by mixing air with water vapor and ethanol vapor proved to be effective for removing the superficial TCA, but not the TCA present in depth.

The minimum fluidization speeds are relatively low due to the low specific gravity of the cork.

Even when operating at speeds only slightly lower than pneumatic transport, it is not possible to achieve great efficiency in mass transfer (comparative tests of drying cork)

This behavior can be interpreted based on the relatively low gas phase velocities, which lead to significant thicknesses of the laminar boundary layer, in which, of course, a concentration gradient is established.

In addition, the micro-roughness of the surface is of a very special type, consisting mainly of partially destroyed cells, with multiple cavities in which the gas phase is virtually stationary (absence of convection).

This set of tests made it possible to conclude the need to operate with a transported bed and with gas velocities higher than those used in fluidized beds.

Examples

1. In a pilot installation with rotary shaker and cylindrical glass chamber with external heating tape, small batches obtained by sectioning highly contaminated granules were treated (equivalent contamination corresponding to 11%)

NUMBER TEST TEMPERATURE RESIDENCE TIME RESIDUAL PRESSURE REDUCTION CONTENT TCA 17 100 ° C 30 min 0.01 Bar 2.4% 18 110 ° C 30 min 0.01 Bar 3.2% 19 120 ° C 30 min 0.01 Bar 4.8% 20 ¹ 110 ° C 1 hour 0.01 Bar 6.1% 21 120 ° C 1 hour 0.01 Bar 8.9% 22 110 ° C 30 min 0.001 Bar 64% 23 120 ° C 30 min 0.001 Bar 85% 24 110 ° C 1 hour 0.001 Bar 73% 25 120 ° C 1 hour 0.001 Bar 96% 26 120 ° C 2 hours 0.001 Bar 98%

This set of tests made it possible to verify the importance of the low residual pressure inside the treatment chamber.

Example 2

Superheated steam treatment tests

This set of tests was carried out in an assembly that is represented schematically and very contaminated coarse granules obtained by grinding stoppers (11%) were used.

Each granulate sample removed from the chamber was immediately placed in a sealed glass bottle until analysis was performed.

Results

APPROXIMATE GAS COMPOSITION IN THE CHAMBER TEMPERATURE IN THE CAMERA CONTENT REDUCTION TCA Only Air 110 ° C 3.6% Only Air 120 ° C 7.9% Steam + Air (50/50) 110 ° C 5.8% Steam + Air (50/50) 120 ° C 18.3% Overheated Air Only 170 ° C * 47%

* Cork with visible thermal degradation

Figure 2 describes the assembly scheme used for tests with superheated steam.

Example 3

Removal of occluded or deep-seated TCA

Knowing that part of the TCA is occluded in dry cork cells, comparative tests of different methods leading to cell opening were carried out.

In these tests, extra uncontaminated cork cubes, with dimensions of approximately 1 x 1 x 1 cm, were used, and the initial and final contents of open cells were determined with the aid of a helium pycnometer.

Method Apparent increase in open cell content Comments Mechanical compression in 3 faces (successive) 8.2% WITHOUT Many, “walls in harmony ”but few burst Immersion in solution methanolic KOH 12 &% (24 h) 2.7% Very attacked surface Sudden application of vacuum 0.0001 Bar (5 min.) 12.4% Macroscopic appearance not changed. Observable by SEM some apparently open operculums due to the sudden pressure variation Ultrasound (30 min.) 1.3% Not very effective Mechanical compression on 3 sides followed by sudden application of vacuum (5 min.) 26.3% WITHOUT Some broken walls in harmony

This set of tests was for comparative purposes only and the objective of preliminarily estimating the degree of effectiveness of the different processes.

The energies, intensities, times and temperatures were regulated manually and in such a way as not to cause permanent macroscopic deformation in the cork cubes used, since the process described in the present invention is applicable to cork products such as corks and discs.

CONCLUSION

None of the elementary methods tested led to high increases in open cell content.

The combination of mechanical compression followed by sudden application of reduced pressure seems to be the most effective, however leading to an increase in open cell content below the desired level.

This set of tests was repeated at a temperature close to 100 “centigrade but the results obtained were very mixed. In the case of immersion in methanolic solution, it was necessary to use a PARR reactor and significant destruction of the cube cube was observed.

In the remaining tests, the apparent increase in open cell content was always lower than that observed at room temperature, which seems to be interpreted by an additional flexibility of the cell walls due to the temperature.

Description of the Process The process which is the object of the present invention allows the continuous vapor phase extraction of TCA and other volatile organic compounds.

The equipment used for the execution of the process is shown in Fig. 1 and basically consists of two treatment chambers operating similar to worm conveyors.

The cork to be treated is heated by a substantially dry gas stream, and only subsequently is contacted by an extraction gas stream.

average residence time of the products within each of the chambers is adjustable by two distinct processes:

1. By varying the speed of rotation of the conveyor shaft

2. By adjusting the lower tolerance, that is, making several the distance between the helical edge of the screw and the concave bottom face of the tubular layer, (change in transport efficiency).

The process consists of two elementary steps:

Cork to be treated

Compression

Continuous

Treatment under transport

initial compression step is ensured by knurled rollers with spacing between adjustable shafts and both motorized.

Treatment under transport is then done in unit, or disinfection machine, constit ui by a fan (3j, one purg collector · ador (5), a superheater (/) and one cooler (8), and injectors (L 1), according to figure 1.

Description of Figures:

Figure 1 - Disinfection machine

1- I ^the internship

2- 2nd stage

3- fan

4- exhaustion

5- trap trap

6- hot water

7- superheater

8- cooler

9- compressed air

10- steam

11- injectors

Figure 2 - Assembly diagram used for tests with superheated steam,

12- Compressed air

13- Steam

14- Thermal oil

15- Glass wool

16- Granulated

17- Glass wool

Lisbon, April 27, 2006

Claims (13)

Claims 1. Cork treatment process for disinfection and removal of volatile organic compounds, namely disarmatisation and disinfection, reducing the levels of precursors and aroma compounds such as Trichlorophenol, Tetrachlorophenol, Pentachlorophenol, and corresponding brominated compounds, as well as brominated precursors some aromas generically referred to as molds, characterized by being made up of two elementary steps, compression and treatment under transport and inducing vaporization of the constituents of the off-aromas in a transported moving bed, under a controlled atmosphere, allowing for the continuous release in the vapor phase of TCA and other volatile organic compounds. 2. Process according to the first claim, characterized in that the initial compression step is ensured by knurled rollers with adjustable spacing between shafts, both motorized. 3. Process according to the first claim, characterized in that the transport is provided by a helical conveyor equipped with an electric or pneumatic motor. Process according to the first claim, characterized in that the controlled atmosphere in the treatment chamber consists of air, and water vapor, with successive pressure variations being carried out. Process according to the first claim, characterized in that the supply includes a mechanical pressurization system. Process according to the first claim, characterized by an injection pressure of the gas mixture of 0.9 to 1.5 bar, preferably from 1 to 1.1 bar. Process according to the first claim, characterized by a total contact time of more than 70 minutes and less than 120 minutes. 8. Process according to the first claim, characterized in that the treatment chambers are eccentric with motors independent of the respective conveyors Process according to the preceding claims, characterized in that the chambers with a hemi-cylindrical bottom have a diameter greater than 600 mm and less than 2000 mm, and a length per section greater than 5000 mm. Process according to the preceding claims, characterized in that the injection of gas mixture is carried out in at least 18 holes in each treatment chamber. Process according to the preceding claims, characterized in that the mixture of hot gases injected in the first chamber causes the temperature of the cork to rise from room temperature to at least 105 ° C. 12. Process according to the mixture injected in the second chamber promotes a profile of t and m e r to progressive t u r e s according to the claims for gas mixtures overheated with disinfection fluid and de-stemming. the preceding claims, characterized in that the upper parallelepiped is contained in the lower and have the respective axes in the same plane, which constitutes the plane of symmetry of the two chambers. Process according to the preceding claim, characterized in that it uses a disinfection machine consisting of a fan (3), a trap trap (5), a superheater (7) and a cooler (8), and injectors (11).