FR3042683A1 - ECONOMIC FREEZING PROCESS FOR THE VALORISATION OF CERTAIN ANIMAL BY-PRODUCTS OF AQUACULTURE - Google Patents

Abstract

A method of raising fish, of the type implementing an oxygenation of or some of the rearing tanks, oxygenation carried out from oxygen stored on the site in liquid form (1), and where it is carried out the vaporization (2) of the liquid oxygen before it is injected into the basins, where the operations are also carried out (3) for freezing and / or maintaining the temperature of dead animals or remains of dead animals , characterized in that one proceeds to the recovery (4) of all or part of the frigories produced during said vaporization to provide all or part of the frigories necessary for said freezing operations or maintenance temperature.

Description

The present invention relates to the field of fish farming, and is particularly interested in a problem related to the fact that since a recent regulation, breeders must autonomously manage dead animals, not intended for sale.

Indeed, it can be recalled that following the end of the Public Separation Service (SPE), every farmer is obliged to have a rendering contract with a company approved for the treatment of dead fish, even if the mortality in the exploitation is low.

The only alternatives to rendering for Class C2 fish by-products are: 1 / Raccoons and raptor feeding areas. Approval concerning this use is issued to the person in charge of such structures. 2 / Composting and biogas production, provided that these by-products have been subjected to a hygienic treatment (type 70 ° C / 1h).

It is also recalled that the feeding of dogs and cats from shelters, kennels or others can only be done from animal by-products of category 3 (in the same way as slaughterhouse waste).

As in all animal production sectors, fish farmers produce animal by-products of category C2, within the meaning of the European Regulation n ° 1069/2009; that is to say, essentially, the fish or fish remains not recoverable in food and feed. These, estimated at more than 2 000 tonnes per year at the French national level, are currently eliminated from the farms by rendering companies. However, rendering, which was a public service until 2009, is now entirely the responsibility of the breeders, which represents a significant additional cost.

This extra cost is particularly inappropriate in fish farming at a time when farmers have to cope with considerable increases in many production costs (raw materials, energy, etc.). Also, for fish farming to remain a healthy, dynamic and competitive rural economy, fish farmers have found a recovery axis that requires freezing dead animals (or animal remains), and keeping these animals at a temperature close to - 18 ° C for long periods (to be defined according to the farms concerned).

To limit the costs of freezing and keeping cold, it is then necessary to be able to offer fish farmers an economical solution to make the cold necessary for this specific application.

It can be said that there are two types of conventional solutions for the production of frigories: a) The so-called "mechanical" cold, which requires substantial investments to produce the frigories (compressors, heat exchangers), and a high energy consumption . b) The so-called "cryogenic" cold, where the investment is lower but where the energy cost can be prohibitive for this type of operation.

One of the objectives of the present invention is then to propose a technical solution for producing the necessary frigories, which can overcome the drawbacks listed above.

As will be seen in more detail in the following, the great merit of the present invention is to have found that in this field of fish farming, a large number of operators use oxygen on the site, this for well-known reasons. Indeed, the high density of fish in the basins requires to bring oxygen into the water to compensate for its natural decline. The availability of oxygen in the water has a direct effect on the performance of the fish farm. The necessary oxygen is traditionally stored on the site in liquid form at a temperature close to -180 ° C. Also to inject the oxygen in the basins one proceeds to its vaporization, most often using atmospheric vaporizers.

These vaporizers allow the cryogenic liquid (L02) to change state and be used at temperatures close to room temperature, a clement temperature essential for fish.

And it is therefore the merit of the present invention to propose, for such installations using liquid oxygen (and it is a large part of the operators in this profession), to value the frigories produced in this type of system. vaporization, in order to contribute, in whole or in part, to the contribution of the frigories necessary for the freezing and / or keeping in cold of animals or remains of animals, dead, that produces such a site.

The present invention thus relates to a method for rearing fish, of the type implementing an oxygenation of the breeding pond or tanks (or some of the basins on the site considered), oxygenation carried out from oxygen stored on the site under liquid form, and where one proceeds to the vaporization of the liquid oxygen before its injection in the tank or basins, where one also carries out operations of freezing and / or maintenance in temperature of dead animals or dead animal remains, characterized in that one proceeds to the recovery of all or part of the frigories produced during said vaporization to provide all or part of the frigories necessary for said freezing operations or maintenance temperature.

It is clear from the above that in the majority of cases, the valuation will provide all the frigories necessary for freezing, but it may occur on some sites, for various reasons including technical, that this valuation does not provide some of the frigories necessary for freezing, the site may then be required to provide the other party by "conventional" means.

According to one of the embodiments of the invention, the frigories produced during said vaporization and thus their recovery are recovered in an exchanger, exchanger for example located on the breeding site in a refrigerating chamber where the so-called freezing operations or maintenance of temperature of dead animals or remains of dead animals are carried out, exchanger able to receive the following fluids and to carry out the following exchanges: the exchanger is able to admit in one of its piping circuits the oxygen to vaporize; - The heat exchanger is adapted to admit in it the air to be cooled (for example the air of the refrigerating chamber where are performed said freezing operations or maintenance temperature); - The exchanger performs a heat exchange between the liquid oxygen admitted and the air to be cooled and redirects the air thus cooled to said freezing operation or maintenance temperature.

As will be seen in more detail in the following, according to various embodiments of the present invention, the invention provides modes of regulating the valuation of these particularly advantageous frigories.

According to one of the embodiments of the invention, an "all-or-nothing" type of regulation is implemented, as illustrated in FIG. 1 appended hereto: - therefore, on the breeding site, there is a reservoir 1 d liquid oxygen (liquid oxygen used to oxygenate the water of basins or some of the basins); oxygen is injected into the tanks in gaseous form, the liquid oxygen therefore passes through a heater 2 before reaching the basins; according to the invention, the frigories produced during this vaporization are valorized to provide the necessary frigories (or at least part of the necessary frigories) for the operation of freezing or maintaining at low temperature (typically -18 ° C.) of the fish dead or remains of dead fish produced by the site, operation carried out in the refrigerating chamber 3.

In this context we have a set of two valves V1 and V2 and regulation, which uses a PID, acts on these two valves to allow two phases: -> Oxygen passes entirely into the refrigerating chamber 3 via the valve V1, or the oxygen passes entirely through the atmospheric heater 2 via the valve V2. -> If the temperature of the chamber 3 is higher than a given set temperature, the valve V1 is open and the V2 closed, the oxygen passes into the chamber 3, leaving its frigories in exchanging with the air (5) of the chamber (within the exchanger 4 which is there), before being directed to the heater 2 (as mentioned above, it is preferable to heat up the gas leaving the exchanger again) 4 before directing it to the fish). - If the temperature of the chamber 3 is lower than a given set temperature, the valve V1 is closed and the valve V2 is open, the oxygen does not pass into the chamber 3, it is directed into the heater 2 to be there vaporized before reaching the ponds. In any case, according to this regulation, the valves V1 and V2 can be closed at the same time.

According to another of the embodiments of the invention, an All or Little type of regulation is implemented, which will also be illustrated by FIG. 1, but where this figure is implemented by a different regulation, which allows 3 phases: -> the oxygen passes entirely in the chamber 3, or the oxygen passes entirely through the heater 2, or the oxygen passes in parallel in both the chamber 3 and the heater 2. -> if the temperature of the chamber 3 is significantly greater than a set temperature (for example at least 2 ° C), the valve V1 is open and the V2 is closed, all the oxygen passes into the chamber 3, it leaves its frigories by exchanging with the air of the chamber (within the exchanger 4 which is there), before being directed towards the heater 2. -> if the temperature is slightly higher than a temperature of setpoint (for example 0.5 ° C or less), the V1 valves and V2 are open. -> if the temperature of the chamber 3 is lower than a set temperature, the valve V1 is closed and the valve V2 is open, the oxygen does not pass into the chamber 3, it is directed into the heater 2 to be there vaporized before reaching the ponds. -> Under no circumstances, according to this regulation, the valves V1 and V2 can be closed at the same time.

According to another of the embodiments of the invention, a proportional type regulation is implemented, which will be illustrated by the appended FIG.

As can be seen, in this figure, the valves V1 and V2 above are replaced by a three-way valve 10.

According to a logic that is now well understood, this three-way valve orients the cryogen completely to the refrigerating chamber 3, or partly to this refrigerating chamber 3 (with a partition coefficient that may be variable according to need) or all the way to the heater 2.

In no case are the outputs of the three-way valve on chamber 3 and on heater side 2 are closed at the same time.

Let us illustrate the invention by the thermal calculation which follows. - 1 kg of liquid oxygen stored at 8 bar releases 300kJ when vaporized at 8 bar and -30 ° C. With a yield of 90%, 270 kJ are available per kg of oxygen. - A typical fish farm uses an average of 250 kg of oxygen per day, or about 10 kg / hour. - The vaporization of the oxygen used can therefore produce a power of 270x10 = 2700kJ / h is 750J / s is 750Watt. - To maintain at -20 ° C a refrigeration chamber of 2.5 x 2.5 x 3m with a coefficient K = 0.4 W m'2 K'1 and an outside temperature of 15 ° C, it requires a power of 0.4 x 42.5 m2 x 35K = 595W. - The introduction of about 20 kg of unfrozen fish per day and a safety reserve for the opening of the doors requires an additional power estimated at 150W. Thus, for a total need of 745W when the outside temperature is 15 ° C, the vaporization of oxygen (750W) will provide all the cold requirements of the freezing operation.

Claims (3)

claims 1. Process for rearing fish, of the type implementing an oxygenation of the or some of the rearing tanks, oxygenation carried out from oxygen stored on the site in liquid form (1), and where the procedure is carried out the vaporization (2) of the liquid oxygen before it is injected into the basins, where operations are also carried out (3) for freezing and / or maintaining the temperature of dead animals or animal remains dead, being characterized in that one proceeds to the recovery (4) of all or part of the frigories produced during said vaporization to provide all or part of the frigories necessary for said freezing operations or maintenance temperature. 2. Method for rearing fish according to claim 1, characterized in that the recovery of the frigories produced during said vaporization and thus their recovery, in a heat exchanger (4), for example exchanger located on the breeding site in a refrigerating chamber (3) where the so-called freezing operations or maintenance of temperature of dead animals or remains of dead animals are carried out, exchanger able to receive the following fluids and to carry out the exchanges following: - the exchanger is able to admit in one of its piping circuits oxygen (1) to vaporize; - The exchanger is adapted to admit into it the air (5) to cool, for example the air of the refrigerating chamber (3) where are performed said freezing operations or maintenance temperature; - The exchanger performs a heat exchange between the liquid oxygen admitted (1, V1) and the air (5) to cool and redirects the air thus cooled to said freezing operation or maintenance temperature. 3. Process for rearing fish according to claim 2, characterized in that said recovery of frigories is regulated according to one of the following modes: i) an "all-or-nothing" type of regulation is implemented where the oxygen is sent: - in full (V1) in a refrigerating chamber (3) where are performed said freezing operations or maintenance temperature, passing through said exchanger (4); or all (V2) in an atmospheric heater (2) performing said vaporization before reaching the basin or basins; - And where if the temperature in the refrigerating chamber (3) is greater than a given set temperature, it is ordered that the oxygen passes entirely into the chamber (3), leaving its frigories in exchanging with the air of the chamber before being directed towards said heater (2), whereas if the temperature in the refrigerating chamber (3) is lower than a set temperature, it is ordered that the oxygen passes entirely into said heater ( 2) to be vaporized before reaching the pool (s). j) implementing a "All or Little" type of regulation where the oxygen is sent: - in totality (V1) in a refrigerating chamber (3) where the so-called freezing or temperature maintenance operations are carried out, passing in said exchanger (4); or all (V2) in an atmospheric heater (2) performing said vaporization before reaching the basin or basins; - Or in parallel both in the refrigerating chamber (3) and in said heater (2); - And where if the temperature in the refrigerating chamber (3) is significantly greater than a given set temperature, it is ordered that the oxygen passes entirely in the chamber (3), leaving its frigories in exchanging with the air from the chamber before being directed towards said heater (2), whereas if the temperature in the refrigerating chamber (3) is slightly higher than a given set temperature, it is ordered that the oxygen passes in parallel with both in the refrigerating chamber (3) and in said heater (2), whereas if the temperature in the refrigerating chamber (3) is lower than a set temperature, it is ordered that the oxygen passes entirely in said heater (2) to be vaporized before reaching the pool (s). k) a "proportional" type regulation is implemented using a 3-way valve (10), where the oxygen is sent: - entirely in a refrigerating chamber (3) where the said operations are carried out freezing or maintaining temperature, passing through said exchanger (4); - Or entirely in an atmospheric heater (2) performing said vaporization before reaching the basin or basins; - or partly to the refrigerating chamber (3), with a partition coefficient that can be variable as required.