DEVICE AND METHOD FOR COALESCENCE SEPARATION

There are a device and a method for coalescence separation for a fluid having at least two phases at least partially immiscible with each other and having different specific density or gravity. The separation device has a plurality of sheets or trays that are spaced apart from one another to form passage channels that slow down and divert the flow favouring the coalescence separation.

FIELD OF THE DISCLOSURE

The present disclosure relates to a device and a method for coalescence separation for a fluid comprising at least two phases at least partially immiscible with each other and having different specific density or gravity.

DESCRIPTION OF THE RELATED ART

The problem of the separation of two partially immiscible phases present in a fluid has been known for years and several technologies have been developed to create devices and methods that can guarantee an effective separation between the two phases present in a fluid. The problem is felt in several technological sectors such as, for example, in the oil & gas or water management business where the presence of fluids containing water and hydrocarbons or oils in general is a focus of attention. During drilling operations for the extraction of hydrocarbons, the production of contaminated water is an unavoidable intrinsic phenomenon, which must therefore be resolved in order to ensure that the extracted waters are treated in accordance with current local regulations. Contaminated waters often contain hydrocarbons, gases, suspended solids, radionuclides and other harmful chemicals. The phenomenon of water production during the extraction of hydrocarbons is significant because, until a few years ago, it represented the largest volume of liquid produced during extraction operations, reaching up to three times the volume of the hydrocarbon extracted; today, through new drilling and extraction technologies, the volume of water produced has been reduced to about twice that of the extracted hydrocarbon. It is therefore clear that the treatment and purification of these large volumes of contaminated water is an important need to which various technologies have sought to respond. For offshore installations this need becomes imperative as the constraints on the weights and overall dimensions of water treatment plants are limited and the demand for compact, lightweight and efficient devices is ever more pressing.

In particular, for the removal of oils or hydrocarbons present in water, different water management and treatment strategies are currently available such as, for example, recycling and reinjection while other systems focus on discharge and disposal. For offshore plants, for example, the disposal of produced water at sea is the most common methodology; for the discharge of oily waters at sea, strict legislative parameters must be respected in order not to create negative impacts on the ecosystem, so systems for separating oil from water become fundamental both for their effectiveness and for their overall dimensions and weight.

The technological solutions available today for the removal of oils from contaminated waters or, more generally, for the separation of two phases having different specific density or gravity present in a fluid can be classified into three groups: separation by gravity (e.g. API skimmers, hydrocyclones and separators), separation by filtration (activated carbon filters, sand filters or oleophilic, hydrophilic or hydrophobic filters), coalescence separation (devices with interwoven meshes, corrugated plates or coalescing plates).

Separation by coalescence, which is also the method underlying the present disclosure, is normally carried out with very voluminous, often horizontally extending equipment, generally coupled to hydrocyclones or gravity systems. These devices are clearly unattractive for offshore applications or for upgrading existing plants in which there is not enough space for the installation of additional voluminous devices. Other solutions for coalescence rely on plates, metal nets or coalescing cartridges arranged in series or in parallel; these solutions fail to guarantee a constant flow of the fluid with evident impacts on the efficiency of the system that often does not meet the minimum separation requirements imposed by current regulations.

All devices known in the art require frequent maintenance and have a limited lifespan over time, resulting in higher operating costs for their operation.

SUMMARY OF THE DISCLOSURE

Object of the present disclosure is to realize a device that overcomes the drawbacks of the prior art, allowing the separation of two partially immiscible phases having different specific density or gravity in a more effective way than the systems known in the art, ensuring smaller overall dimensions of the device and greater versatility of use related to the compactness and lightness of the device.

According to the present disclosure, it is provided a coalescence separation device1for a fluid comprising at least two phases at least partially immiscible with each other and having different specific density or gravity, the device comprising:a hollow cylindrical body10provided, at one end, with an opening11defining the fluid inlet;a plurality of axial-symmetrical geometry coalescing sheets20with an axis A coinciding with that of the hollow cylindrical body, each of the coalescing sheets20comprising a circular central plane portion21provided with a through opening22and a frusto-conical peripheral portion23with a major base arranged towards the opening11of the cylindrical body and a minor base coinciding with the periphery of the central portion21;
the coalescing sheets20being arranged parallel to one another and spaced apart from one another to form passage channels40for the fluid, the circular central plane portion21of each coalescing sheet20being at least partially protruding with respect to the internal surface of the hollow cylindrical body10so as to intercept a portion of fluid flowing inside the hollow cylindrical body10and divert it radially inside the passage channels40towards the frusto-conical peripheral portions23, as described below.

The present disclosure also relates to a method for coalescence separation which diverts the fluid comprising at least partially immiscible phases from a longitudinal direction to radial directions with circumferentially distributed flow.

DETAILED DESCRIPTION OF THE DISCLOSURE

With reference toFIGS.1-4, the present disclosure relates to a coalescing separation device1comprising a plurality of axial-symmetrical geometry coalescing sheets20with symmetry axis A coinciding with that of a hollow cylindrical body10. The hollow cylindrical body10is provided, at one end, with an opening11defining the fluid inlet to the device1. Each coalescing sheet20comprises a circular central plane portion21provided with a through opening22and a frusto-conical peripheral portion23with a major base arranged towards the opening11of the cylindrical body. The sheets20are arranged parallel to one another and spaced apart from one another to form passage channels40for the fluid. Each central plane portion21at least partially protrudes with respect to the internal surface of the hollow cylindrical body10so as to intercept a portion of fluid flowing inside the hollow cylindrical body10conveying it towards the passage channels40.

The gist of the present disclosure lies in the fact that the portions of fluid intercepted in the hollow cylindrical body10by means of the central portions21are diverted so as to change the direction of the flow from parallel to the longitudinal axis of the cylindrical body to substantially radial with respect to the same axis. This diversion causes the fluid to move circumferentially away from the axis of the hollow cylindrical body10; following this first change in direction, the fluid portions undergo a further diversion due to the frusto-conical peripheral portions23. The variations in the direction of the flow induce accelerations on the immiscible phases contained therein and thus the forces dependent on the physical properties of the different phases, thus inducing a separation also due to inertial effects. In each passage channel40, a significant slowdown of the portion of fluid passing through it is also achieved since the annular-shaped circumferential passage sections that the fluid subsequently crosses in its radial path towards the outlet of the device1are gradually increasing in area. The combination of the inertial effect induced by the diversions imposed on the treated fluid through the passage channels40and the slowdown on the radial path of the fluid outlet maximise the effectiveness of the separation and coalescence of the immiscible phases included in the aforesaid fluid. Decreasing the velocity of the fluid increases its residence time, thereby increasing its separation efficiency. In addition, the slowdown of the fluid in the passage channels40reduces the risk of entrainment and entrapment of the separate phase (e.g., oil versus water) leading to a much higher overall fluid purification efficiency than that of the prior art systems. The velocity of the fluid at the inlet of each passage channel40is less than 1 m/s, preferably is less than 0.5 m/s; the velocity at the outlet of each channel is less than 0.1 m/s, preferably less than 0.05 m/s.

With reference toFIG.4, in a preferred embodiment of the separation device1with coalescing sheets20the area of the through opening22of the coalescing sheet closest to the opening11is the largest compared to the areas of the through openings22of the following coalescing sheets20which progressively decrease up to the coalescing sheet farthest from the opening11which is provided with a zero area opening. The progressive decrease of the areas of the through openings22along the longitudinal axis A of the hollow cylindrical body10introduces calibrated pressure losses that allow obtaining equal flow rates of diverted fluid at the inlet for each single passage channel40. In this way, each passage channel40receives at the inlet a portion of fluid with a flow rate at the inlet equal to that of the other passage channels40ensuring the same separation efficiency and operating constancy for all passage channels40. This configuration increases the total separation efficiency of the device1with coalescing sheets20.

In a further preferred embodiment of the disclosure of the separation device1with coalescing sheets20, the sheets20are arranged parallel to each other in an equidistant manner with a distance between 5 mm and 30 mm, said distance remaining constant along the passage channels40. The range of distance values identified allows a particularly effective operation of the device1with coalescing sheets. Longer distances between the sheets20have the effect of slowing down the fluid engaged in the passage channel formed by the aforesaid sheets; the slowing down of the fluid has a beneficial effect for the separation of the phases but, an excessively low velocity can compromise the transport of the coalescent phase droplets that would not be able to reach the outlet of the device1in order to be evacuated and collected.

With reference toFIGS.2and3, in a further preferred embodiment of the disclosure of the separation device1with coalescing sheets20, each frusto-conical peripheral portion23is provided on the major base circumference25with a curved axial-symmetrical profile50apt to favour the collecting of the coalescent phase of the fluid, the profile50being interrupted by at least one conduit51radially arranged and intended to evacuation of the coalescent phase accumulated along the profile50. The presence of the curved axial-symmetrical profile50ensures a zone of accumulation of the coalescent phase droplets that favours both further aggregation and channeled disposal.

In the case where the separation device1, as shown inFIG.9, is installed inside a pipe3and therefore the outlet of the fluid flow rate treated by the separation device1takes place inside said pipe, the distance60between the major base circumference25of the frusto-conical peripheral portions23and the internal surface of the pipe3is of particular importance. In fact, since the flow rate of fluid exiting from each passage channel40of the device1is added to the flow rates exiting from the previous passage channels40, there is a risk that the distance60, between the major base circumference25of the frusto-conical peripheral portion23and the internal surface of the pipe3, is not sufficient for configuring an area passage section such as not to create counterpressure to the discharge of the separation device1. To overcome this potential problem, in a further preferred embodiment of the separation device1with coalescing sheets20as previously described the diameter of the major base circumference25of the frusto-conical peripheral portion23of the coalescing sheet closest to the opening11is the largest compared to the major base circumferences25of the following frusto-conical peripheral portions23which progressively decrease up to the coalescing sheet farthest from the opening11. This configuration allows the progressive increase of the distance60between the major base circumference25of the frusto-conical peripheral portion23and the internal surface of the pipe3along the axis of the pipe3, which results in a progressive increase of the available passage area between the separation device1and the internal surface of the pipe3reducing the pressure drops of the fluid exiting the separation device1. This geometry with frusto-conical peripheral portions23which are tapered on the diameters of the major base circumferences25allows the discharge into a pipe3of the treated fluid flow rate without significant impacts on the separation efficiency.

With reference toFIG.5, the disclosure also relates to an alternative coalescence separation device2for a fluid comprising at least two phases at least partially immiscible with each other and having different specific density or gravity, the separation device2comprising a plurality of axial-symmetrical trays30concentrically arranged and generated by plane curves having a substantially elongated “J” shape and spaced apart from one another so as to form passage channels41between the trays themselves, the passage channels41forming concentric inlet mouths31having a circular crown section and intercepting the incoming flow of fluid, having a direction parallel to the symmetry axis of the axial-symmetrical trays30, and convey it towards exits with prevalently radial direction component of the flow of fluid. The separation device2is linked to the separation device1described above by the same inventive concept of diversion of the flow of the fluid to be treated from a direction prevalently parallel to the symmetry axis A to one with a radial flow direction component. The separation device2is therefore an alternative embodiment of the same disclosure.

The separation device2with axial-symmetrical trays30makes more efficient use of the inertial effect acting on the fluid thanks to the conformation of the passage channels41; the almost total inversion of the flow direction occurring in the central part of the elongated J-section channels drastically increases the inertial separation effect on the treated fluid. Furthermore, the redirection of the fluid in the various channels making it assume a direction with radial component at the exit allows a further slowdown of the fluid itself since the annular-shaped circumferential passage sections that the fluid subsequently crosses in its radial path towards the outlet of the device2are gradually increasing in area. The combination of the inertial effect induced by the diversions imposed on the treated fluid through the passage channels41and the slowdown on the radial path of the fluid outlet maximise the effectiveness of the separation and coalescence of the immiscible phases included in the aforesaid fluid. Decreasing the velocity of the fluid increases its residence time, thereby increasing its separation efficiency. In addition, the slowdown of the fluid in the passage channels41reduces the risk of entrainment and entrapment of the separate phase (e.g., oil versus water) leading to a much higher overall fluid purification efficiency than that of the prior art systems.

With reference toFIG.8, in a preferred embodiment of the separation device2with axial-symmetrical trays30as described above, each circular crown of each inlet mouth31is characterized by a difference between the major radius and the minor radius different from that of the other circular crowns so as to form passage sections that ensure a flow rate of fluid substantially constant in all the concentric inlet mouths31. In particular, the concentric mouth with a circular crown having a larger outer diameter will have a difference between the major radius and the minor radius that is smaller than the difference between the major radius and the minor radius of the other mouths, this difference progressively increasing according to the decrease of their major radius. As evident fromFIG.8, in a preferred embodiment of the separation device2as previously described, each passage channel41is characterized by having a longitudinal section in which the inlet distance Di between two adjoining axial-symmetrical trays30that define it at the inlet of the channel41is smaller than the exit distance Du of the same membranes at the outlet of the channel41, generating a diverging section which increases the passage area of the fluid passing through the channel41reducing the exit radial velocity thereof. The divergent course of the passage channel41introduces an additional element slowing down the fluid passing through the channel, maximising the process for coalescence separation.

With reference toFIGS.6and7, in a preferred embodiment of the separation device2with axial-symmetrical trays30as previously described each axial-symmetrical tray30is provided on the fluid exit edge with a curved axial-symmetrical profile53apt to favour the collecting of the coalescent phase of the fluid, the profile53being interrupted by at least one conduit54radially arranged and intended to evacuation of the coalescent phase accumulated along the curved axial-symmetrical profile53. The presence of the curved axial-symmetrical profile53allows coalescent phase droplets to be collected and conveyed to one or more conduits54for evacuation.

Preferably, the discharge conduits51for the separation device1with coalescing sheets20and54for the separation device2with axial-symmetrical trays30are arranged circumferentially with an angular distance of 45 degrees from one another to increase the evacuation capacity of the coalescent phase.

The present disclosure further relates to a method for coalescence separation of a fluid comprising at least two phases at least partially immiscible with each other and having different specific density or gravity, the method comprising the steps of:intercepting the fluid that moves in a longitudinally extending conduit by using a separation device1,2;diverting the fluid so as the longitudinal velocity thereof in the conduit at the inlet of the device1,2converts in radial velocity with respect to the same conduit at the outlet of the same separation device;slowing down the fluid between the inlet and the outlet of the device1,2by means of passage channels40,41with passage area increasing along the extent of the channels;separating the phases at least partially immiscible with each other and having different specific density or gravity.

The method according to the present disclosure, by redirecting the fluid through the passage channels that extend radially with respect to the incoming fluid flow, allows an important slowdown of the fluid itself facilitates coalescence separation.

The method for coalescence separation of the present disclosure, in a preferred configuration implements the step of intercepting the fluid by dividing the flow of the fluid at the inlet of the separation device1,2in equal flow rates in each passage channel40,41.

Dividing the total flow rate of the fluid to be treated in equivalent flow rates for each passage channel40,41of the separation device1,2maximises the separation efficiency. The materials of manufacture of the separation device1,2can be metallic materials, plastics or composite materials. The geometry of the separation devices1and2also lends itself to manufacture by 3D printing, ensuring ease of realization and reducing the difficulties of supply and shipping the devices to the field.

Two prototypes were built during the experimentation and research phase carried out for the separation devices1,2. Both the prototype of separation device1with coalescing sheets and the separation device2with axial-symmetrical “J” trays were dimensioned with a maximum diameter of 400 mm and a maximum height of 50 mm; 10 sheets or trays spaced 10 mm apart and 1 mm thick were provided. The separation devices1,2have been designed to be inserted into a pipe with a diameter of 500 mm. The treatment capacity of the separation devices1,2tested in the laboratory is 1000 barrels/day but their treatment capacity can be easily scaled up by adjusting the basic dimensioning parameters such as diameter, number of sheets/membranes and their spacing.

The separation device1,2of the present disclosure thus conceived is in any case susceptible to many modifications and variants, all falling within the same inventive concept; furthermore, all the details can be replaced by technically equivalent elements. In practice, the materials used can be of any type according to the technical requirements.

The protective scope of the disclosure is therefore defined by the appended claims.