EP2831217A1

EP2831217A1 - A system for producing electricity from combustible vegetable oil self-produced by algae growth

Info

Publication number: EP2831217A1
Application number: EP13724384.6A
Authority: EP
Inventors: Andrea Andreucci; Luca SEBASTIANI
Original assignee: Romea Import - Export Srl
Current assignee: Romea Import - Export Srl
Priority date: 2012-03-30
Filing date: 2013-03-29
Publication date: 2015-02-04
Also published as: WO2013144915A1; ITFI20120067A1

Abstract

The system of the present invention is such as to exceed the limits of productivity and cost of the production of combustible oil from microalgae by means of a closed-loop, entirely modular system comprising regulation systems of the temperature and of the amount of light independently from the environment, fully installable inside existing industrial facilities, adapted to self-produce and the amount of light in a manner independent of the environment, CO2 and hot water, adapted to integrate the process created so as to produce energy at a constant flow, to perform an effective treatment of the waste and to manage the controlled release of O2, further adapted to be rapidly installed in sites without specific characteristics for example in the case of emergencies such as earthquakes and conflicts. The system of the present invention is further characterised by extremely low atmospheric emissions, for a use of limited amounts of water, net reduction of fertilisers with respect to common agricultural crops, production of oxygen and complete reuse of waste, which is also biodegradable.

Description

A SYSTEM FOR PRODUCING ELECTRICITY FROM COMBUSTIBLE VEGETABLE OIL SELF-PRODUCED BY ALGAE GROWTH.

Field of the invention

The invention of the present application relates to the alternative energy sector, in particular to the technical sector relating to the production of combustible obtained from vegetable oils. In the present invention, the fuel is produced starting from high lipid content microalgae grown in suitable systems.

Background of the invention

Combustible vegetable oil has been available on the market for years and is substantially a type of diesel with characteristics similar to that obtained by fractional distillation of petroleum, but with important distinctive features:

it is obtained from renewable vegetable or animal raw materials;

it does not contain aromatic compounds, namely highly carcinogenic benzene derivatives, except in minimal part; its sulphur content is about 100 times lower than the diesel obtained from fossil fuels;

it is completely biodegradable.

To date, combustible vegetable oil is industrially obtained from oil seeds with a high fat content. In particular, sunflower, colza, corn seeds and the seeds of other plants and, partially, recovered vegetable oils are used.

The high fat content is essential for the production of fuel as this is obtained by means of mechanical and chemical procedures intrinsic to this component, which in the seeds is oleic.

This is principally composed of mixtures of fatty acids, i.e. carbon compounds characterised by the presence of the =COOH group and by glycerol, i.e. an alcohol which is the basis of the production of glycerine.

In general, the glycerol is separated due precisely on account of its viscosity and tendency to deposit waxes, which are incompatible with the operation of an engine. The fatty acids are the combustible part, following a chemical transformation, as they contain numerous carbon atoms. Most of the animal and plant fatty acids have molecules comprising a number of carbon atoms ranging between 10 and 24. In order to achieve combustible vegetable oils, oleic acid and linoleic acid (C 18), both contained in oilseeds, are particularly important; acid molecules with a greater number of C atoms indeed worsen combustion and tend to generate unwanted deposits.

From a practical point of view, the combustible vegetable oil is substantially analogous to diesel obtained by fractional distillation of petroleum. Albeit having a slightly inferior yield, it also has a higher density therefore the actual consumption is equivalent as demonstrated by the fact that the calorific value is the same. In addition, the cetane rating, i.e. the parameter that evaluates the self-ignition capacity of a fuel to be used in a diesel cycle engine, is indeed better than "fossil" diesel therefore an engine powered by combustible vegetable oil is less noisy and more efficient.

The industrial production of combustible vegetable oil is also linked to the obligation for producers to place on the market petrol or diesel with a percentage of at least 4.5% biofuel. In Italy, for example, about 700,000 tons of combustible vegetable oil was produced in 2009.

The combustible vegetable oil currently produced from vegetable raw material involves the exploitation of large agricultural areas for the cultivation of oily plants; this has important consequences on both the cost of production and on social impact:

Reduction of the areas intended for the production of food.

In 2003 it was estimated that in order to produce about 5.5 million tonnes of combustible vegetable oil (not even 2% of EU requirements), 9.3 million hectares of soybean or sunflower oil cultivation were required i.e. about one and a half times the area used at that time in Europe for food crops

Another immediately comprehensible parameter is that the average weekly productivity is less than 20 I of combustible vegetable oil per hectare (about 1000 I/ hectare per year).

Soil and atmospheric emissions and energy consumption due to the production cycle, including agricultural machinery, fertilisers and pesticides.

Yield is dependant on climatic conditions.

- Need for fertilization and rotation of the land. For these reasons, research has also focused on the cultivation of organisms other than vegetable raw material, by directing the efforts thereof towards microalgae in particular.

Microalgae are organisms that live in salt or fresh water; they do not feed on other organisms, but essentially grow through the chlorophyll photosynthesis mechanism, i.e., they use the CO₂ contained in the water in the presence of light as nourishment, thus growing and releasing oxygen. In practice, the same mechanism as trees, but in water. Algae are thus autotrophic organisms.

The industrial cultivation of microalgae began in the 1980s since they are the food base of molluscs and fish species for aquaculture. Systems were then also developed for the production of food supplements for humans and animals or for the cosmetics and pharmaceutical industry. In particular, the Spirulina, Chlorella and Dunaliella microalgae were cultivated.

The major production sites are located in the tropical area, in southern California, in China, in India, in the Hawaiian islands due to climatic factors and to the temperature of the water, which is an essential parameter in the growth rate of the microalgae.

The typical structure of the microalgae cultivation system generally comprises suitable tanks or pools or specially created outdoor water channels (raceways). If produced in a closed environment, said cultivation systems cultivation generally use transparent tube bundles (PVC, for example) to allow the light to penetrate inside and start photosynthesis, with forced circulation of the fluid containing the microalgae.

Interest in the cultivation of certain types of microalgae is primarily due to the high yield of combustible vegetable oil, in a process wherein the alga in fact absorbs C0₂ for its own nourishment. The ecological balance thus appears promising since:

fossil fuels are not used; the source is renewable; growth occurs by removing C0₂ from the atmosphere;

- the culture does not remove land from agricultural crops;

production waste can be used as feed or fuel; the extraction process is analogous to that of the oleic seeds. On the other hand, the most critical aspects that have for now prevented the diffusion of the use of microalgae for the production of combustible vegetable oil are as follows:

the overall yield, limited by the low concentration of CO₂ in the atmosphere and thus by the slowness of the growth process, also on account of the the low availability of light. The latter is limited by the alternation of day / night, by the seasonality and by the low penetration in water on account of which only a few cm of surface water can be counted for the activation of photosynthesis.

The energy expenditure necessary for continuous agitation of the fluid, which is a fundamental parameter for the rapid growth of the alga.

The difficulty in collecting and separating the alga from the water.

The need to have water at a sufficient temperature (> 20 °C).

The risk of both physicochemical and biological contamination of the waters.

Notwithstanding the above-listed factors, performance expectations are, however, very high.

Currently, the microalgae can produce between 15 and 300 times more combustible vegetable oil per unit of cultivated surface area than for traditional cultures. In addition, the harvesting cycle is much more rapid and and about equal to a harvest every 10 days at most instead of two harvests a year as in traditional crops.

According to the results of research published in 2007, the production values of combustible vegetable oil from microalgae per unit of surface area area are up to 16 times greater than best terrestrial plant, the oil palm.

Another 2007 study forecasted market values for microalgae-derived products of USD1000/ton for cosmetics and foodstuff use, USD 600/ton for the production of combustible vegetable oil and USD 30/ton for production intended for absorption of CO₂ that is moreover integrated in the previous two.

To date, the possibility of using microalgae in an economically advantageous way for the production of combustible vegetable oil remains as yet unsatisfied.

Moreover, the first object of the present invention is to produce an integrated system that overcomes the problems that currently prevent, in fact, the large-scale use of microalgae for the production of combustible oil. These problems can be summarised in the following points: a) reduced productivity linked to the use of systems having a large surface area arranged outdoors;

b) need to have abundant water at a temperature of >20 °C;

c) availability of sufficient amounts of CO ₂;

d) need to agitate the liquid mass that houses the microalgae culture.

Brief description of the drawings

Figure 1 illustrates the block diagram of the system according to the present invention.

Summary of the invention

The present invention relates to the field of biofuel production systems, in particular the system according to the present invention produces combustible vegetable oil obtained by pressing microalgae grown in controlled environmental conditions in a closed system.

In a preferred embodiment, the invention according to the present patent application concerns a system for producing electricity from combustible vegetable oil that uses, as the growth environment of the microalgae, bags - referred to as containers or reactors - made of a suitable transparent material, preferably of transparent and partially permeable plastic materials that are adapted to being positioned inside suitable industrial facilities.

Alternatively, reactors made of transparent material, shaped like tube bundles, can be arranged.

The oil produced by pressing microalgae grown in the system according to the present invention is burned in motor alternators consisting of a diesel traction unit coupled to an alternator.

The exhaust gases are rich in CO₂, which, in a preferred embodiment of the present invention, is separated and in part allowed to flow within the bags in order to constitute the nourishment of the algae. The water in the engine cooling system is used, through a special separate system, to heat the culture water and keep it in the envisaged temperature range without contamination.

Lastly, suitable mechanical apparatuses allow the emptying of the bags by dripping.

The present invention is such as to overcome the technical problems of the prior art in that:

a') microalgae production takes place indoors in a controlled environment, b') There can be availability of abundant water at a temperature of > 20 °C, irrespective of the season and geographic location.

c') The availability of C0₂ is obtained from within the process itself, thus improving the system's overall ecological balance.

d') The liquid mass can be easily recirculated with the assistance of simple pumps. The system according to the present invention is thus substantially autonomous and allows significant amounts of microalga to be continuously produced in special industrial facilities without consumption of land and natural resources.

Detailed description of the invention

In reference to the accompanying figure 1 , the system of the present invention essentially comprises three separate modules that interacting with each other: i) An algae growing module A.

ii) An oil extraction and treatment module B.

iii) A thermoelectric energy production module C.

Said alga growing module A comprises:

A cultivation reactor 10 - possibly comprising a plurality of individual cultivation reactors - adapted to cultivate algae of an appropriate type for the production of combustible vegetable oil; control means of the amount and of the temperature of the water contained in said reactor 10; control means of the PH of the water contained in said reactor 10; control means of the amount of nutrients and/or fertilisers contained in the water contained in said reactor 10; control means of the amount of C02 dissolved in the water contained in said reactor 0; extraction and harvesting means of said algae from said reactor 10;

Said oil extraction and treatment module B comprises: Separation means of the algae harvested from undesired foreign material and impurities; drying means of said algae; extraction and collecting means of combustible oil from said algae; treatment means of the residual waste of said extraction of combustible oil from said algae;

Said thermoelectric energy production module C comprises:

An internal combustion engine of the diesel type compatible to be fed with combustible vegetable oil, preferably of the multi-fractionated type; an alternator associated to said internal combustion engine of the diesel type; feeding means of said internal combustion engine associated to said extraction and collecting means of the combustion oil from said algae; extraction and collecting means of CO2 from the exhaust fumes of said internal combustion engine, associated to said control means of the amount of C02 dissolved in the water contained in said reactor;

With reference to the accompanying figure 1 , in a preferred embodiment of the system according to the present invention, said control means of the amount and of the temperature of the water contained in said reactor 10 comprise a water tank 1 associated to a possible make-up cistern 2; a first hydraulic circuit comprising a first supply pump 3 of the water contained in said tank 1 - and in said possible make-up cistern 2 - toward a process cistern 6, a valve 5 and a heat exchanger 4; A second hydraulic circuit comprising said process cistern 6, a second recirculation pump 9 of the water contained in said process cistern 6, an agitator 7 and a heater 8 associated to the water contained in said process cistern 6;

Said algae growing module A further comprises illumination means 1 1 associated to said reactor 10 and adapted to irradiate the algae contained in said reactor; bleeding means 12 associated to said reactor 10 is to said process cistern 6; extraction means 12bis of the oxygen in excess from said reactor 10;

The main functions of said alga growing system A are the following: to promote the circulation of the algae culture fluid and controlled flow rate, to promote the passage of light in the fluid for the activation of photosynthesis, to eliminate the excess 0₂ which forms in the photosynthesis reaction inside said reactor and, lastly, to harvest the algal production. The above-mentioned steps are essential for the yield of the system, which, according to the present invention, is in this sense innovative in that it is entirely produced inside and with a substantially closed loop, while maintaining under complete control the physicochemical parameters involved.

The photosynthesis process takes place according to the chemical reaction:

6 C0₂ + 6 H₂0 = C₆Hi₂0₆ + 6 0₂ in the presence of light.

The starting substances are thus water and carbon dioxide and the substances obtained are glucose (which the organism of the microalgae accumulates, substantially in lipid form, as energy reserve) and oxygen to be released, as well as to prevent the presence of pressurised gas, also because an accumulation thereof would slow down the reaction.

To obtain a good yield during growth and, thus, during oil production, it is necessary to optimise the management of a number of fundamental physicochemical parameters that it is not always possible to carry out in traditional systems which consequently have a limited efficiency. This is why conventional systems are primarily for the production of feeds and supplements, which have a greater price per unit of weight on the market than combustible vegetable oil.

The fundamental parameters that determine the amount of biomass are: the lipid content of the microalga, the temperature of the culture water, the light and the agitation of the culture water.

The lipid content of the microalga is in reality a parameter that envisages an almost mandatory choice in that it is more convenient to cultivate microalgae having high lipid content.

The average composition of the so-called spirulina alga, the production of which is the aim of a preferred embodiment of the system according to the present invention, is as follows: 40% lipids, 25% cellulose, 20% proteins / lignin, 10% starch and 5% carbohydrates.

The percentage of lipids (fats) is directly proportional to the production of oil with an average yield factor of about 50% by weight.

The residual part does not constitute waste as it is commonly used, as previously mentioned, by the cosmetics and feed/food supplements industry. In addition, part of the residue can also be used as solid fuel. There are also parameters that also influence the growth rate of the alga and are thus fundamental in industrial production:

The temperature of the culture water is a fundamental physical parameter therefore it is extremely important to be able to maintain the value constant inside the system, something that is extremely difficult in outdoor systems, which, for this reason, are generally produced in the tropical area. The optimal temperature is between 15 °C and 35 °C; temperatures outside this range do not allow growth of the microalga if not in a very slow manner.

The light is the source of energy necessary for activation of the photosynthesis process, which in nature is, for all purposes, a reaction based on solar energy.

In the systems thus far produced on an industrial scale, the light comes directly from the sun. Even the tube bundle systems made of transparent PVC are generally located in open or closed facilities but always naturally irradiated.

In the laboratory special lamps with a suitable wavelength for reaction in the microalgae are also used; a wavelength which was experimented to be a range of specific wavelengths, in the visible field between red and blue.

The system according to the present invention optimises this parameter with the use of artificial light optimised on the necessary wavelength using low voltage LED that have various advantages in terms of duration, efficiency, controllability and energy saving or suitable fluorescent lamps, each having having wavelengths between 380 and 750 nanometres. The maximum peaks of the photosynthesis activity are at 430 and 662 nanometres but this is the apical point of the curve. The power demand is 150 W/m² at most.

Agitation of the culture water is the most important parameter for production efficiency since it: prevents the algae from settling on the bottom of the container on account of the weight; minimises reciprocal shading; maximises contact with the nutrients and the C0₂and, lastly, removes the oxygen produced in the reaction.

In addition to the strict control of the above-mentioned parameters, the harvesting of the algae produced, which must be simple and effective, is of the utmost importance. For such purposes, the system object of the invention has a layout and devices that optimise these needs in a contained environment and indoors by producing, inside a facility, a continuous and complete production, treatment and combustion process of combustible vegetable oil for producing electricity.

The algae growing system can be based on reactors of a known type, and preferably on vertical module reactors - of the so-called "bag" type - or single-hose or transparent tube bundle type, that is mechanically hung and supported, wherein the water is forcibly circulated by means of suitable pumps within labyrinth drop paths.

The circulation pumps are sized and appropriately made so as to prevent the physical or mechanical degradation of the microalgae.

The temperature of the culture water is maintained within the envisaged range thanks to a heat exchanger that directly or indirectly exploits the heat of the exhaust fumes to heat the water in a circulation.

The illumination is controlled by suitable lamps interposed between the reactors so as to allow the photosynthetic reaction even in the absence of natural light. To this end, the lamps are automatically controlled by a detection system and emit light in a specific wavelength range.

Agitation is guaranteed by the continuous flow generated by the circulation pumps and the specific shape of the flow channels.

Each individual module is connected to the others in a closed circuit and is made of transparent and gas "permeable" plastic material (e.g. PVC) so as to allow the release of the O₂ and of any excess C0₂. The reactor is resistant to chemical compounds, to UV rays, is non-toxic, is easy to work mechanically (in terms of sealing, perforating, welding) and is resistant to mechanical stresses and to heat. Examples of suitable reactors are bags made of transparent plastic material or PVC tubes as produced in some of the existing systems.

Harvesting of the algae takes place by gravity by tilting the bag and collecting the saturated fluid, then utilising mechanical filters with controlled porosity for the primary separation of the algal part from the water.

During the normal operation of the system according to the present invention, the nourishment that could possibly become necessary can be added to the fluid by suitable make-up cisterns inserted in the hydraulic system. The necessary C0₂ is blown directly into the system bleeding it from the exhaust fumes of the system for producing electricity (motor alternator). The necessary water is in a closed loop, and can thus be preventively checked in order to prevent the presence of microorganisms and chemical pollution that could reduce plant productivity and prevent the sale of the waste to the cosmetics and feedstuff industry. The system according to the present invention also has a draindown system for the envisaged full replacement of the water that must be envisaged on an established and regular basis to prevent pollution from slag and metabolites that accumulate during the microalgae growth phases.

In the system according to the present invention, the water is completely immune from chemical and biological contaminations, something which does not occur in the prior art systems that are located outdoors or that operated on an open loop basis.

The illumination is optimal and is guaranteed by suitable rows of LEDs or fluorescent lamps interposed between the parallel rows of bags in battery. The light inside of the bags is thus constant over the entire surface of the reactor thus maximising growth in any position of the alga.

The water in circulation is kept at the correct temperature by means of heat exchangers that use either the engine cooling water or the heat exchange with the exhaust fumes.

The system is additionally free of chemical agents and and presents no explosion or fire risk, thus it is economical to operate and can be kept running in a continuous loop with just oversight staff.

Again in reference to the accompanying figure 1 , inside said oil extraction and treatment system, said means for separating the harvested algae from undesired foreign materials and impurities comprise: a filtering device 13, adapted to perform a first filtering of the harvested algal material; a centrifuge separator 14 associated to said tank 1 and adapted to separate undesired impurities from said algae harvested from said reactor 10; furthermore, said extraction and collecting means of the combustible oil from said algae comprise apparatuses selected from the group comprising ultrasound sonicators 18 and drying 16 and pressing 17 apparatuses arranged in cascade. The filtering devices used can be advantageously of the mechanical type possibly associated to filters with controlled porosity (about 2-120 μηη). The remaining part of filtering process can be reinserted into the reactor for growth.

The extraction steps of the oil at this point of the process are as follows: drying, oil extraction and possible treatment of the waste.

Drying becomes necessary as in this step the algae contain an average of 80% water. It is thus necessary to dehydrate the algae, which takes place rapidly by oven drying.

The extraction is carried out in mechanical systems and allows separation of the oleic part from the residue which, when treated, is intended for the industry as a base for the production of feed or cosmetics. Hence the importance of using uncontaminated water in algal production.

Oil extraction can take place with several methods that are selected from the group comprising pressing, enzyme treatment, extraction by means of chemical solvents and ultrasound sonication.

In a further preferred embodiment of the present invention, extraction is carried out by sonication, which is a method that not only allows extraction of the oleic part, but the simultaneous separation from glycerol, which, as previously mentioned, must not be part of the fuel.

This process is achieved in an industrial sonicator and avoids pressing; In practice, the presence of the ultrasounds and of the reagent in the mixture allow rapid separation of the glycerol, which is therefore an exclusive by-product of this step and is stored and sold to the cosmetic industry.

The oil thus produced is, if necessary, subjected to a further filtering by means of suitable filtering means of the raw oil 19 and is ready to be used as fuel by a diesel cycle engine - for example the diesel engine of said thermoelectric energy production system - with characteristics similar to the diesel obtained from petroleum. Lastly, the treatment of waste envisages that the waste be collected as dry residue and treated so as to promote the subsequent use thereof, as a fuel for example.

Again in reference to the accompanying figure 1 , in a preferred embodiment of the system according to the present invention, said thermoelectric energy production system comprises an internal combustion engine 20 of the diesel type compatible to be fed with combustible vegetable oil; an alternator 21 associated to said internal combustion engine; feeding means of said internal combustion engine 20 associated to said extraction and collecting means B of the combustion oil from said algae; extraction and collecting means of CO₂ 22 from the exhaust fumes of said internal combustion engine 20 associated to said control means of the amount of CO₂ dissolved in the water contained in said reactor 10 and adapted to channel the C0₂ collected in said process cistern 6 so as to feed the chlorophyll synthesis carried out by the algae contained in said reactor 10.

The system according to the present invention can operate correctly even with external sources of C0₂, if located in sites where said C0₂ is already available. Furthermore, advantageously, the heat produced by said engine 20 of the diesel type can be employed to heat a fluid 23 that is sent to said exchanger 4 of said first hydraulic circuit so as to carry out a preheating of the water sent to said process cistern 6.

Claims

1. System for producing electricity from vegetable fuel oil comprising: an algae growing module (A) comprising a c reactor (10), adapted to cultivate algae of appropriate type for producing vegetable fuel oil, means for controlling the amount and the temperature of the water contained in said reactor (10), means for controlling the pH of the water contained in said reactor (10), means for adding nutrients and/or fertilisers to the water contained in said reactor (10) and means for controlling the amount of said nutrients and/or fertilisers, means for controlling the amount of C0₂ dissolved in the water contained in said reactor (10), means for extracting and harvesting said algae from said reactor (10); an extraction and treatment module (B) of fuel oil from said algae comprising means for separating the harvested algae from undesired foreign materials and impurities; drying means of said algae; extraction and collecting means of the fuel oil from said algae; a thermoelectric energy production module (C);

2. System according to claim 1 , wherein the extraction and treatment module (B) of fuel oil from said algae further comprises treatment means of the residual waste of said fuel oil extraction from said algae.

3. System according to claims 1 - 2, wherein said means for controlling the amount and temperature of the water contained in said reactor (10) comprise a water tank (1 ); a first hydraulic circuit comprising a first delivery pump (3) of the water contained in said tank (1 ) towards a process cistern (6), a valve (5) and a heat exchanger (4); a second hydraulic circuit comprising said process cistern (6), a second pump (9) for recirculating the water contained in said process cistern (6), an agitator (7) and a heater (8) adapted to move and heat the water contained in said process cistern (6).

4. System according to claims 1 - 3, wherein said water tank (1 ) is associated to a make-up cistern (2)

5. System according to claims 1 - 4, wherein said algae growing module (A) further comprises illumination means (11 ) associated to said reactor (10) and adapted to irradiate the algae contained in said reactor;

6. System according to claims 1 - 5, wherein said algae growing module (A) further comprises bleed-off means (12) associated to said reactor (10) and to said process cistern (6) and extraction means (12bis) of the excess oxygen from said reactor (10)

7. System according to claims 1 - 6, wherein said means for separating the harvested algae from undesired foreign materials and impurities, comprise: a filtering device (13) adapted to carry out a first filtering of the harvested algal material; a centrifugal separator (14) associated to said tank (1 ) and adapted to separate undesired impurities from said algae harvested from said reactor (10).

8. System according to claims 1 - 7, wherein said extraction and collecting means (B) of the fuel oil from said algae comprise apparatuses selected from the group comprising: ultrasound sonicators (18), driers (16) and pressers (17).

9. System according to claims 1 - 8, wherein said extraction and collecting means (B) of the fuel oil from said algae comprise chemical treatment means of said harvested algae, selected from the group comprising enzyme treatments and chemical solvent treatments.

10. System according to claims 1 - 9, wherein said extraction and collecting means (B) of the fuel oil from said algae further comprise appropriate crude oil filtering means (19).

11. System according to claims 1 - 10, wherein said thermoelectric energy production module (C) comprises an internal combustion engine (20) of the diesel type compatible with being powered by vegetable fuel oil; an alternator (21 ) associated to said internal combustion engine; power means of said internal combustion engine (20) associated to said extraction and collecting means (B) of the combustion oil from said algae; extraction and collecting means of CO2 (22) from the exhaust fumes of the said internal combustion engine (20), associated to said control means of the quantity of C0₂ dissolved in the water contained in said reactor (10).

12. System according to claim 11 , wherein said internal combustion engine (20) of the diesel type is further adapted to heat an appropriate fluid (23), which is sent to said exchanger (4) of said first hydraulic circuit so as to carry out a first preheating of the water sent to said process cistern (6).