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DESCRIPTION

This invention relates to a device and a method for making emulsions of water in pure heavy fuel oil (HFO).

Heavy fuel oil (HFO) is a mixture of hydrocarbons obtainable as an end waste product of petroleum distillation processes. In particular, in the context of this invention, the intention is to identify mainly those residual products of petroleum processing which are commonly used as marine fuel or fuel for large thermoelectric power plants. In the former context, the heavy fuel oil is also referred to as marine sludge.

However, to more accurately identify them, it may be considered that the heavy fuel oils for which this invention is intended are those having viscosity of between 24° Engler and 50° Engler if measured at 50°C.

As already indicated, this invention in any case applies both to these pure residual products and to their mixtures.

In general the residue available after petroleum processing depends on the technical structure of the plants of the refineries in which it is produced. For example, in refineries without conversion plants the residue used is that from atmospheric distillation, whilst in more complex refineries the residue may be of various types, for example, from vacuum distillation.

Regarding the classification of fuel oils, at present in the sector there are many different ones based on various regulations in force.

For example, based on the sulphur content, fluid heavy fuel oil (HFO) may be defined as:

- LS, with sulphur content < 1 % by weight; and

- ULS, with sulphur content < 0.3% by weight;

whilst dense heavy fuel oil may be defined as:

- HS, with sulphur content < 3% by weight; - LS, with sulphur content < 1 % by weight; and

- ULS, with sulphur content < 0.3% by weight.

Since it is a waste product of practically any petroleum processing, enormous quantities of heavy fuel oil (HFO) are produced around the world each year. Although it is theoretically a waste product, since heavy fuel oil (HFO) as such still has excellent calorific value, it is now widely used as a fuel. At present, in particular, as already indicated, heavy fuel oil (HFO) is mainly used for marine propulsion, especially for large ships.

Therefore, it shall be understood that this invention is aimed mainly at a marine fuel which is heavy fuel oil (HFO)-based.

The main problem linked to the use of heavy fuel oil (HFO), even more than the combustion of any other hydrocarbon, is however the possible resulting pollution.

The combustion of hydrocarbons in general, and of heavy fuel oils in particular, in fact produces significant emissions of NOx and of CO and of PM (particulate matter).

With regard to this, it should be noticed for example that many states ban the use of marine sludge as a fuel when ships are less than a predetermined safe distance from the coast. In fact, the fumes deriving from the combustion of marine sludge are highly polluting. That makes it necessary for ships to have a second fuel available (usually diesel oil) to be used close to the coast, with a consequent significant disadvantage in economic terms, given that the cost of diesel oil is considerably higher than that of marine sludge. Alternatively, it would be possible to use SCR filters, but their extremely high cost has so far discouraged people from using them.

Moreover, for years now it has been known that to attempt to overcome the pollution produced by burning hydrocarbons it is possible to feed burners not with a pure hydrocarbon, but rather with a hydrocarbon in which water in emulsion has been inserted.

In fact, this technology allows not just a reduction in polluting residues of combustion, but also an increase in fuel efficiency and therefore a reduction in greenhouse gas emissions.

The main mechanism through which the water of the burning emulsion carries out its beneficial action is practically instantaneous evaporation, manifesting as proper micro-explosions of the droplets of water in emulsion. Since the water droplets are incorporated in larger drops of hydrocarbon previously atomised in a combustion chamber, their evaporation causes further atomisation of the individual drops of hydrocarbon (secondary atomisation). Therefore, following this secondary atomisation a large number of extremely small fuel particles is obtained, with a considerable increase in the surface area in contact with the air supporting combustion.

In the combustion of emulsions if the phenomenon of micro-explosions is substantial, that is to say, if most of the drops from primary atomisation are involved in secondary atomisation, there is a significant change in the shape and structure of the flame due to the reduction in the reaction time necessary for combustion (thanks to the fact that the drops to be burned are smaller). Moreover, in this way, the risk of unburnt particles is also reduced. As already indicated, the use of emulsions with water in the hydrocarbons sector has been known for many years. In particular, emulsions of water and diesel are known and used. In contrast, the use of emulsions of water and heavy fuel oil (HFO) is not currently known, since it has not yet been possible to define solutions which allow sufficiently homogeneous and stable emulsions to be obtained.

Therefore, definition of such solutions, and of a device and a method for making such emulsions, is very desirable. In fact, the possible benefits of use of emulsified heavy fuel oil (HFO) would include:

- increased combustion efficiency due to the reduced rate of unburnt particles, thanks to the lower burn-out times as a result of the small diameters of the drops of heavy fuel oil (HFO) obtainable thanks to secondary atomisation; - lower solid particulate matter emissions, again as a result of improved combustion caused by secondary atomisation; and

- the possibility of reducing excess air supporting combustion, which in contrast is essential in the combustion of only heavy fuel oil (HFO) in order to achieve acceptable combustion efficiency.

Thanks to the reduction in excess air, the following are achieved:

- improved combustion efficiency thanks to the reduction in the combustion temperature and therefore in the heat dispersed into the environment with the fumes;

- a noticeable reduction in the production of SO3 (up to 80%) due to the lower concentration of O2 in the fumes, as well as a reduction in NOx.

Furthermore, the combustion of emulsified heavy fuel oil (HFO) compared with combustion of pure heavy fuel oil (HFO) allows a reduction both in dirtying of surfaces and in corrosive phenomena. In fact, first, thanks to the improved combustion efficiency the heavy fuel oil (HFO) burns completely, resulting in a reduced deposit of unburnt particles on surfaces. Second, thanks to the use of less excess air, there is a fall in the amount of V2O5 which can form in favour of vanadium oxides with a lower oxidation number which are less prone to adhere to surfaces. Moreover, thanks to the fact that the emulsions of water in heavy fuel oil (HFO) produce shorter flames, any molten ashes, before striking the wall of the pipes, have more time to cool to a state in which their surface is firm or in any case is no longer able to adhere to the surfaces with which it comes into contact. Moreover, the shorter flame reduces or eliminates the risk that the flame may make contact with the surfaces of the pipes, and consequently there is a reduction both in the formation of hard corrosive salts in the high temperature zones, and in localised overheating of the pipes. Finally, the reduced presence of oxygen and the consequent reduction in SO3 causes less formation of H2SO4, and therefore a reduced corrosive effect.

The direct practical consequence of these benefits are: - reduced need for routine and extraordinary maintenance and consequent greater plant operating availability;

- possibility of reducing or eliminating installation and operating costs relating to systems for reducing NOx and solid particulate matter;

- improved performance of electrostatic filters (or other dust removal systems), or reduction-elimination of their installation and operating costs;

- complete elimination of pre-flame additives and drastic reduction of MgO based treatment;

- possibility of easier re-use of the marine fuel which seeps from the engines and is collected together with water in the bilge below.

Therefore, it seems obvious how the use of emulsions of water in heavy fuel oil (HFO) is absolutely desirable.

As is known, in general an emulsion is a mixture of two immiscible fluids, in which one of the two is present in the form of more or less large drops within the other. The fluid in dispersed drops is defined the dispersed phase, whilst the other is the continuous phase. Since the emulsion substantially adopts the chemical - physical properties of the continuous phase, in the context of hydrocarbons in general and of heavy fuel oils in particular, we refer only to those emulsions in which the continuous phase is the hydrocarbon (also called the oily phase) since they have the properties of the hydrocarbon and not of the water.

The main problem of all emulsions is that by their very nature they tend to be unstable. In fact, over time, the two phases tend to separate into the stable states of the dispersed and continuous phases.

According to the prior art, in an attempt to keep an emulsion with oily phase stable as time passes, surfactants are normally used, which are added to the water. In fact, the presence of surfactants in the droplets of water tends to reduce the interface tension between the water and the fuel oil, substantially preventing the droplets of water from aggregating and coalescing. However, even this solution has proved ineffective where homogenisation of the emulsion was not adequate and where the size of the drops of emulsifying water is not reduced enough.

Second, in order to guarantee constant performance in the combustion chamber, the emulsion must uniformly involve all of the individual drops of fuel which are atomised in the combustion chamber. In contrast, with the current technologies, the drops of water which are successfully incorporated in the fuel oil may be relatively too big to guarantee sufficient uniformity of combustion. In fact, both drops of fuel without water (which therefore have all of the problems of fuel oil which is not in an emulsion) and drops of water without fuel oil can enter the combustion chamber.

Moreover, as already indicated, the insufficient uniformity of the emulsion tends to also cause reduced stability of the emulsion itself as time passes. In this context the technical purpose which forms the basis of this invention is to provide a device and a method for making emulsions of water in heavy fuel oil which overcomes the above-mentioned disadvantages.

In particular, the technical purpose of this invention is to provide a device and a method for making emulsions of water in pure heavy fuel oil or in a mixture containing mainly fuel oil, which allow the obtainment of emulsions which are more homogeneous, with drops of water that are on average smaller, and consequently which are more stable than those obtainable with the current technologies.

The technical purpose and the aims indicated are substantially fulfilled by a device and a method for making emulsions of water in heavy fuel oil in accordance with what is described in the appended claims.

Further features and the advantages of this invention are more apparent in the detailed description, with reference to the accompanying drawings which illustrate several preferred, non-limiting embodiments of a device and a method for making emulsions of water in heavy fuel oil, in which:

- Figure 1 is a schematic axial section of a device for making emulsions of water in heavy fuel made in accordance with this invention; - Figure 2 is a schematic front view from the left of the device of Figure 1 ;

- Figure 3 is a schematic view of a first plant for making emulsions of water in heavy fuel oil comprising a device made in accordance with this invention and which can advantageously be used for making the emulsion not on board the ship; and

- Figure 4 is a schematic view of a second plant for making emulsions of water in heavy fuel oil comprising a device made in accordance with this invention and which can advantageously be used for making the emulsion on board the ship.

With reference to the accompanying drawings the numeral 1 denotes in its entirety a device for making emulsions of water in heavy fuel oil according to this invention.

As shown in Figure 1 , the device 1 for making emulsions of water in heavy fuel oil according to this invention comprises first a containment body 2 inside which at least an emulsion chamber 3 is made, and which comprises an inlet 4 and an outlet 5. The inlet 4 and the outlet 5 are both in fluid communication with the emulsion chamber 3.

In use, the inlet 4 is fed with a pressurised liquid mixture of water and heavy fuel oil (pure or in a mixture) and the outlet 5 supplies an emulsion of water in heavy fuel oil obtained following emulsification of the liquid mixture in the emulsion chamber 3. In this way, during continuous operation of the device 1 , inside the emulsion chamber 3 a liquid flow from the inlet 4 to the outlet 5 is created.

Advantageously, in the preferred embodiment the containment body 2 comprises overall a tubular shape which is elongate along a main axis of extension. The containment body 2 may also be constituted either of a single piece or of multiple parts connected to each other (three in the embodiment illustrated in Figure 1 , as described in more detail below). The ends of the containment body 2 form the inlet 4 and the outlet 5. Advantageously, the main axis of extension is horizontal. In the embodiment illustrated, the containment body 2 is in particular constituted of three parts: a tubular central part 6, a first end part 7 axially inserted in the central part 6 and forming the inlet 4, and a second end part 8 axially inserted in the central part 6 from the side opposite to the first end part 7, and forming the outlet 5. Advantageously, the first end part 7 and the second end part 8 are screwed into the central part 6.

According to an innovative aspect of this invention, the emulsion chamber 3 comprises a central zone 9, first liquid flow breaking means 10 positioned between the inlet 4 and the central zone 9, and second liquid flow breaking means 11 positioned between the central zone 9 and the outlet 5.

According to the preferred embodiment of the present invention, the central zone 9, which extends from first liquid flow breaking means 10 to second liquid flow breaking means 11 , is also delimited by a cylindrical wall that has a surface parallel to the main axis of extension.

Advantageously, in the preferred embodiment in which the emulsion chamber 3 is elongate along the main axis of extension, the first liquid flow breaking means 10 comprise a pierced barrier 12 positioned transversally to the main axis of extension (with holes advantageously having a diameter of between 0.5 mm and 0.75 mm). Advantageously, the pierced barrier 12 is constituted by a wall substantially perpendicular to the main axis of extension and relative holes extend substantially parallel to the main axis of extension and are distributed on the whole wall. The second liquid flow breaking means 11 instead comprise a tubular element 13 extending along the main axis of extension inside the emulsion chamber 3, comprising a blind first end 14 facing towards the inlet 4 and an open second end 15 in fluid communication with the outlet 5, and which also comprises a plurality of through holes 16 (advantageously having a diameter of between 0.2 mm and 0.5 mm), made through its lateral wall 17 (advantageously radial and distributed on it). However, in the preferred embodiment, the through holes are distributed only in the upper part of the tubular element 13; in particular, in the embodiment shown in the figures the through holes 16 are distributed along three rows one of which is placed on the top of the tubular element 13 (in this case radial through holes 16 are vertical), and the other two are opposite and placed at a horizontal plane passing through the main axis of extension (in this case radial through holes 16 are horizontal).

Moreover, in the embodiment illustrated, the central zone 9 of the emulsion chamber 3 is formed by the central part 6, the first liquid flow breaking means 10 are formed by the first end part 7, whilst the second liquid flow breaking means 11 are separate and are connected to the second end part 8.

According to a further innovative aspect of this invention, the device 1 comprises a plurality of magnets 18 distributed around the emulsion chamber 3 for creating a magnetic field inside the emulsion chamber 3. In the preferred embodiment they are permanent magnets 18, preferably constituted of lanthanum bars. Moreover, advantageously, the magnetic field is created with an average intensity of between 600,000 kA/m and 1 ,300,000 kA/m.

Moreover, advantageously, the magnets 18 are evenly distributed around the emulsion chamber 3 as shown in Figures 1 and 2. Even more preferably, the individual magnets 18 are relatively short, and overall are divided into a plurality of groups which are distributed and spaced along the main axis of extension. As illustrated in Figure 2, which shows a single group of magnets 18, the magnets 18 of each group are also distributed around the main axis of extension.

According to the preferred embodiment, the magnets 18 are arranged in such a way that they all have the same absolute orientation of the respective magnetic poles. In particular they are all positioned with a first pole facing towards the inlet 4 and a second pole facing towards the outlet 5, that is to say, with their magnetic axis parallel to the main axis of extension.

Moreover, according to the embodiment, it may be the case either that the magnets 18 are distributed around the main axis of extension in a single layer, as shown in Figure 2, or that they are distributed in multiple superposed and concentric layers.

In the preferred embodiment, the device 1 also comprises heating means 19 associated with the containment body 2 for in use keeping the mixture of water and heavy fuel oil at a preset temperature. Advantageously, similarly to the situation in all of the plants for the treatment of fuel oil in the liquid state, the heating means 19 may be constituted of electric heating elements coupled to the containment body 2, and the temperature of the heavy fuel oil may be kept at around 60°C.

Advantageously, the containment body 2 and/or the first liquid flow breaking means 10 and/or the second liquid flow breaking means 11 are made of a steel having the following magnetic properties:

magnetic coercive field (He) maximum 200 A/m;

- magnetic residual induction (Br) of between 0.35 and 0.80 Tesla;

saturation magnetic induction (Bs) 1 .6 Tesla; and

relative magnetic permeability (μ _Γ ) of between 1000 and 2000.

Moreover, advantageously, the containment body 2 and/or the first liquid flow breaking means 10 and/or the second liquid flow breaking means 11 are made of a steel comprising, as a percentage of the total weight, in addition to iron, at least the following components within the ranges indicated:

carbon from 0.005 to 0.020 %;

silicon from 0.50 to 1 .35 %;

manganese from 0.30 to 1 .25 %;

- chromium from 15 to 18 %;

molybdenum from 0.70 to 1 .10 %

phosphorus from 0.02 to 0.04 %;

sulphur from 0.20 to 0.30 %; and

nickel from 0.80 to 1 .00 %.

Preferably, while they are being made, the containment body 2 and/or the first liquid flow breaking means 10 and/or the second liquid flow breaking means 11 are subjected to an annealing thermal treatment comprising the steps of:

heating in a time interval of between two and a half hours and three hours to a treatment temperature of between 605°C and 830°C; preferably the treatment temperature is between 710°C and 730°C and advantageously it is equal to 720°C;

keeping at the treatment temperature for a time interval of between two hours and six hours;

- cooling to a temperature of between 490°C and 510°C with a cooling speed of between 50°C/h and 200°C/h;

cooling in a time interval of between one and a half hours and two and a half hours, preferably two hours, to a temperature of 300°C; and

cooling in a time interval of between half an hour and one hour to a temperature below 100°C.

Advantageously, the thermal treatment is carried out in an inert or reducing atmosphere.

Moreover, preferably, the heating steps and the cooling step are carried out in a radiant tube chamber, the second cooling step in an oven, the third cooling step in a water-jacketed chamber.

That distinctive thermal treatment allows special magnetic properties (coercive field, hysteresis curve and magnetic permeability) to be obtained which are not possessed by ferritic stainless steels annealed in "standard" conditions. In particular, if applied to a steel having the composition indicated above, said thermal treatment allows the magnetic properties described above to be obtained.

It should be noticed that protection may also extend to the annealing thermal treatment method in itself for some components of the device 1 described above.

Obviously the subject matter of this invention also includes plants 20 for making emulsions of water in heavy fuel oil (again pure or in a mixture) which comprise the device 1 described above.

In particular, Figures 3 and 4 show two different plants 20 designed for different applications. In fact, the plant 20 of Figure 3 was designed for initial production of the emulsion and so can advantageously be installed on harbour quays so that it can create the emulsion which will then be fed to the tanks of the ships. In contrast, the plant 20 of Figure 4 was designed to allow its installation directly on board a ship. In fact, in ships powered using heavy fuel oil, during operation the ship engines, which are structurally robust but relatively simple so as to guarantee reliability, allow part of the fuel to leak out, which comes out and falls into the collection bilges located below the engines. The fuel is then removed from the bilges by washing with water so that it can be recovered. Moreover, at present, before being able to re-use that fuel, it must be left to decant so as to separate it from the washing water. In contrast, thanks to the plant 20 of Figure 4, after simple filtering, recovered fuel and washing water can be directly run into a collecting tank, if necessary together with heavy fuel oil that has not yet been used. All of this is then fed to the device 1 according to this invention, which also allows the washing water present to be emulsified in the heavy fuel oil.

The first type of plant 20 (Figure 3) advantageously comprises an upstream tank 21 for in use containing a heavy fuel oil to be emulsified (pure or in a mixture), and a downstream tank 22 for in use containing the emulsion of water in heavy fuel oil. At least a main pipe 23 extends from the upstream tank 21 to the downstream tank 22 and along it at least one device 1 made in accordance with this invention is mounted. Moreover, at least a main pump 24 is mounted along the main pipe 23 upstream of the device 1 , and at least a secondary pipe 25 is connected to the main pipe 23 upstream of the main pump 24. Finally, there are water feed means 26 connected to the secondary pipe 25 for in use injecting water through it into the main pipe 23. Advantageously, the main pump 24 can generate in the liquid flow sent towards the device 1 a pressure of at least 35 bar, advantageously of 38-40 bar.

Upstream of the connection of the secondary pipe 25 to the main pipe 23, the plant 20 may also comprise a filter 27 for removing impurities from the heavy fuel oil, a secondary pump 28 mounted upstream of the filter 27, and at least one water content measuring device 29 associated with the main pipe 23. In the latter case, the plant 20 may also advantageously comprise a control unit (not illustrated) connected at least to the water feed means 26 and to the water content measuring device 29, for regulating operation of the water feed means 26 depending on how much is measured by the water content measuring device 29.

The water feed means 26 preferably comprise a metering pump 30 mounted along the secondary pipe 25.

The whole plant 20 may be equipped with heating means 19 mounted for example inside a jacket 31 for containing/insulating the various parts. More particularly, it comprises heating means 19 for heating at least the upstream tank 21 , the downstream tank 22 and the main pipe 23 for in use keeping the heavy fuel oil at a preset temperature.

The plant 20 of Figures 4 is similar to that of Figure 3, the only difference being the absence of the secondary pipe 25, the water feed means 26, the water content measuring device 29 and the control unit connected to the water feed means 26 and to the water content measuring device 29. Moreover, in this case, in use both the fuel oil and the emulsion water are simultaneously present in the upstream tank 21 . As indicated, to conclude, the subject matter of this patent application also includes a method for making emulsions of water in heavy fuel oil which can be implemented thanks to the device 1 and the plants 20 described above.

In general, the method comprises the operating steps of:

forming a liquid mixture of water in heavy fuel oil;

making the pressurised liquid mixture flow through an emulsion chamber 3, creating a whirling motion in it; and

at least during mixture flowing, maintaining a magnetic field in the emulsion chamber 3.

In more detail, the magnetic field is advantageously a constant magnetic field, and the liquid mixture feeding pressure is preferably at least 35 bar. Moreover, preferably, the magnetic field is created with an average intensity of between 800,000 kA/m and 900,000 kA/m.

Moreover, advantageously, on one hand the liquid flow is broken into a plurality of micro-flows both at mixture infeed into the emulsion chamber 3, and at outfeed, and on the other hand the emulsion chamber 3 output pressure is reduced (by the second liquid flow breaking means 11 in the embodiment illustrated) to a pressure that is less than 3 bar, preferably equal to 2 bar.

Finally, it should be noticed that the invention described above may be implemented without adding any emulsifying additive at least up to a water content equal, by weight, to 15% of the total. Above that threshold it is, in contrast, preferable to add an additive to the emulsion. That addition may be made by mixing with either the heavy fuel oil or with the water.

This invention brings important advantages.

In fact, thanks to this invention it was possible to define a device and a method which allow emulsions to be made that are more homogeneous than those currently obtainable, and that have drops of water which are on average smaller, and consequently greater stability over time than those obtainable with current technologies.

Therefore, thanks to this invention it is possible to obtain a fuel based on heavy fuel oil emulsified with water, which after combustion is significantly less polluting than is currently the case.

Finally, it should be noticed that this invention is relatively easy to produce and that even the cost linked to implementing the invention is not very high. The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted with other technically equivalent elements and the materials used, as well as the shapes and dimensions of the various components, may vary according to requirements.