NO346022B1

NO346022B1 - A method and a system for purifying a fluid

Info

Publication number: NO346022B1
Application number: NO20181290A
Authority: NO
Inventors: Finn Aarseth
Original assignee: Combipro As
Priority date: 2018-10-05
Filing date: 2018-10-05
Publication date: 2021-12-27
Also published as: EP3860739A1; WO2020070336A1; NO20181290A1

Description

Overview of the disclosure

The present disclosure constitutes a novel centrifugal purification method and system where improved performance is empowered by use of well-known physical phenomena such as electrostatic (ES) and/or electromagnetic (EM) fields.

By use of nano particles (MNP) with paramagnetic properties that are functionalized for bonding to targeted contamination dissolved in a fluid, the contamination can now be controlled by external applied electrostatic and magnetic fields induced by the MNP, and thus interact with the balance of centrifugal forced fluid flow for disposal.

MNP in general, but especially small targeted particles with specific weight close to the fluid and with no active centrifugal force, as well as other particles which do not interact with electrostatic purification, can thus be controlled by MNP and ES and/or EM interaction for movements in desired directions.

Oscillated interaction will stimulate a relative movement as a function of viscous thinning. By periodically halting or staggering said oscillation at peak amplitudes, small particles will remain in its new orbit and can thus systematically build an enhanced centrifugal forced separation.

Field

The present disclosure relates to a method and process for fluid purification where functionalized paramagnetic particles (MNP) bond to targeted contamination dissolved in a liquid or gaseous fluid, and thereafter being interacted by electromagnetic (EM) and or electrostatic (ES) fields forces that are directed with the centrifugal separator fluid flow for disposal.

The disclosure is addressed toward industrial purification in general and is typically suited for purification of fine graded particles or oil droplets found in produced water from oil and gas production. When the term “particle” is used the term encompasses droplets, as we refer to a particle being a small localized object to which can be ascribed

several physical or chemical properties such as volume, density or mass. Particle includes fusible and infusible particles and colloidal particles. A colloidal particle can be solid, liquid, or gaseous; as well as continuous or dispersed. The dispersed-phase particles have a diameter of between approximately 5 and 200 nanometres. Particle and droplet may be used interchangeably, depending on the context, but has the same definition, except that a droplet is not infusible.

Background

Demand for removal of small particles dissolved in fluid has increased the recent years, especially removal of small particles that may accumulate in large concentrations and may harm the environment and human health. Such pollution can be related to industrial waste, combustion gasses from household and cars, but also simple abrasion from car tires and asphalt roads.

Most particles generated in land-based environment will find their way to the sea, which over decades has been a silent litter for all kind of man-made rubbish. The oil and gas industry have in this respect been carefully watched for its pollution potential, but also their need to dispose and/or release large quantities of produced water to sea.

This challenge has been enhanced by governmental demand for an optimal recovery, , demanding the operators to exploit more than the first and most beneficial phase of the reservoir capacity. Such extended time related production profile involves normally an increasing amount of produced water, where mature fields may reach a higher water cut than 50%. First at this level where the cost for water handling equals the oil revenue, the well may be plugged, and the field abandoned.

Produced water may at some fields be reinjected in the reservoir and thus used to increase oil production, and some platforms may be forced to release their water to sea. Over the recent years most of the oil producing countries have enforced regulations to control the content and release of dissolved oil in such water (OiW). The limits are per today varying between 20 and 30 ppm among oil producing countries. In Norway, the authorities are planning to reduce the limit to 15 ppm for oil in water for new installations. Future oil installations in more sensitive artic areas like the Barents Sea might encounter requirements for lower limits.

Due to volume, weight and cost facilities for separating water from oil are normally not oversized and found to have a low normative capacity. Water is however not produced as a predictable flow and may appear in large amounts. For this reason, relaxed regulations are called for, allowing short periods with terms water for polluted water dumping higher than regulatory limits and/ or be allowed to dilute high-level oily water by clean sea water prior to release.

This is not a sustainable situation, and international societies requires the absolute maximum release to be lowered to the same level as for the marine industry, for instance oil in water of 15 ppm.

A major challenge with the art of cleaning and separation technology of today, is that the maximum economic efficiency of industrial cleaning efforts of large volumes to meat 30 ppm. has in practice been reached long time ago. This limit is controlled by a function of volume, (resilience-) time and related operational cost, which bottlenecks oil production.

New and more efficient separation and cleaning methods and process facilities are therefore urgently needed.

Description

The present disclosure relates to a method and process for fluid purification where functionalized paramagnetic particles (MNP) bond to targeted contamination dissolved in liquid or gaseous fluid, and subsequently interact with electromagnetic (EM) and/or electrostatic (ES) fields forces directed with the axis of a centrifugal separator forced flow for disposal.

Same or similar operational achievement can also be facilitated for cyclones, hydro cyclones, electro coalescers.

Such method of purification is particularly well suited for separation of oil from water and thus used as a base case for illustration and exemplification herein.

Contaminating particles are often associated with a solid material but can also be a sphere in form of a liquid droplet or a hybrid of both. Such droplets are well known by the oil and gas industry and they may appear as small fractions of Water in Oil (WiO) or Oil in Water (OiW) , to be removed prior to being dispatched to rivers and sea environment.

Three phase production of oil, gas and water, are normally processed to separate fractions prior to export. Said water will in most cases have residual contaminations in form of free oil or large oil drops, but also a large amount of small dispersed droplets and/ or emulsions with diameters less than 50 µm. Correspondingly, also the sales oil and gas for pipelined export may have an excessive water content, which can generate corrosion and hydrate blockages.

Natural gravity settling of oil and water droplets follows Stokes Law, but implies a timeconsuming effort and use of large tank spaces, not feasible to be used at many industrial plants. However, under favourable fluid properties, environmental conditions and by use of unlimited time, it is known that natural gravity may achieve purification in the nano scale. In this context it is also known that improved gravity settling-speed can be achieved by a multiple layer of aligned plating and fluid shaking. Further improvements can also be made by increased gravity and use of centrifugal separators, hydro cyclones and coalescers, that may also use ES and EM fields to interact with dissolved contamination.

Functional mechanism by ES interaction as used by electro coalescers, comprises use of narrow conduits where a high voltage DC field may induce an electrical charge in conductive water drops. Provided the oil has sufficient dielectric properties, the charge will be conserved and divide the water drop skin with positive and negative ends. Such dipolar state creates a force that will attempt to drive the droplet towards the higher gradient. Experience shows that small droplets fails sufficient charge and power to break loose for a steady movement in desired direction. Applying AC power may for some droplets introduce an oscillation movement which over time, may overcome the shear forces and provides a thinning effect that stimulates further movements. Such oscillation increases the probability of droplet collisions, which leads to small droplets merger and thus gives birth to larger ones, and thereby stimulate the subsequent gravity settling velocity.

Of obvious reasons ES interaction will not be possible for water drops dissolved in highly conductive oil. Electro coalescers and ES techniques can thus not be used for purification of oil in water (OiW) and/or water in oil (WiO).

For similar reasons, magnetic interactions of none chargeable particles that cannot be magnetized, is not possible.

Under steady favourable production conditions, it is known that electric coalescers may achieve oil purification down to some 0,5% water cut. At this stage the total remaining content of dissolved oil, emulations, sand and production-chemicals etc., must be considered for adequate purification prior to release to rivers or sea waters. Whereas some odd cases must be resolved by chemical treatment, use of hydro cyclones, centrifugal separators and filtering are frequently used.

Filtering technique is known to represent the best qualitative option and can remove OiW down to 1 ppm but is not feasible for use at large flow quantities of oil and solid particles. Hydro cyclones are however the simplest and the most frequent used tool currently employed for oil-water separation but is qualitatively limited and not capable to separate particles and oil droplets of size below 20 µm.

US patent 6,355,178 proposes in this context to use electrostatic, magnetic and other physical phenomena to enhance cyclone and hydro cyclones qualitative and quantitative performances. Unfortunately, obvious restraints to functionalize a variable flow of random and partly resistant content of purities could not easily be achieved.

Centrifugal separators are considered to be the qualitative better alternative for purifying oil from water but is often failing quantitative performances for inline operations. US patent 1,558,382 as well as its related successor US patent 5,352,343, disclose how to overcome said shortages by employment of ES and EM attraction features, but with the same shortcoming results as mention above for US patent 6,355,178.

The present disclosure concerns thus how a successful interaction between MNP and Electrostatic (ES) / or and Electromagnetic (EM) shall resolve this deficiency, independent of dissolved fluid and targeted particles initial properties.

The process by which individual particles aggregate into clotlike masses or precipitate into small lumps, is called “flocculation”. It occurs as a result of a chemical reaction between the clay particles and another substance, usually salt water. Flocculation is a process wherein colloids come out of suspension in the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution. In the flocculated system, there is no formation of a cake, since all the flocs are in the suspension.

It is known that centrifugal forces will increase and/ or decrease proportionally with the collective weight of MNP-bonded contamination. This disclosure will therefore show how to stimulate some flocculation of the bonded MNP oil-droplets, but also for a further and other purpose than previously addressed. Indeed, ES and EM field variations may well bring MNP and contented droplets to oscillate and collide to larger drops with enlarged MNP interaction. However, by control of said interacting oscillations they may systematically be halted or staggered at their maximum oscillating amplitude in the centrifugal flow direction, the particles with little or no centrifugal forces, will be left in a new orbit with a repeating incremented centrifugal radius and force.

ES and EF field strengths will vary by different frequencies of typically 1 to 5 kHz, for ex 0.1 to 15 kHz, preferably 0.5 to 10 kHz, most preferably 1 to 5 kHz

Use of ferrofluids are known from the early days of NASA rocket fuel development in 1946 and comprise ferromagnetic nano particles such as magnetite and hematite suspended in a colloidal fluid. Each particle is being coated with a surfactant to prevent flocculation. Not limited to but being the most frequent used surfactants comprise: oleic acid, tetramethylammonium hydroxide, citric acid, soy lecithin.

Later development of the nano technology has enabled many disciplines development of different new applications, including purification of contaminated fluid. Micro and nano sizes particles have been tailormade with coating and inherent properties for suspension in any fluid and functions, are nowadays commercially available via Internet and word wide postal delivery. Various published patents and pending applications do describe certain nanoparticle design, function and usage. Patent application WO 2008/055371 A2 teaches interaction of magnetic nanoparticles for separating a dispersed phase or dissolved material from a continuous phase for removal by an applied magnetic gradient field. Such method that relies in using mixing tanks, residence time (e.g. average time of residence in the reactor) and need a further process for reclaiming the waste, is not likely be feasible for industrial purification, especially not for inline service.

The present disclosure represents however, another approach for magnetic interaction, namely by addressing the MNP and its bonded oil, to collaborate with centrifugal forced flow and particle drag forces in direction towards its collective disposal. Coalescing as well as flocculation of such drops are welcomed for enhanced separation efficiency. Coalescence may be explained as merger of droplets (with or without particles), and flocullation is aggregation thanks to another chemical or particle. Thus, in this disclosure the related terms may be used interchangeably.

Similarly, US patent 8,636,906 B2 claims the rights to remove a target moiety from a liquid using magnetic nanoparticles by allowing said particles to establish moiety complexes, for thereafter using a magnetic field to segregate the nanoparticles from the fluid.

It is obvious that the above referred patents teach how to use gradient magnet field interaction to gather, isolate and to collect bulks of targeted particles from a solution.

The present disclosure does however address use of MNP interaction in a distinct different way as well as for another objective. Paramagnetic MNP and bonded oil droplets in produced water will here enter into a rotating centrifugal separator, which is equipped with a perpendicular directed magnetic field of adequate strength. The moving MNP and bonded oil will thus be subject to an interacting radial magnetic force with a vectoral direction towards its disposal.

This disclosure demonstrates how to exploit magnetic force action on a MNP to be superposed to ES forces acting in a preferred direction and thus enhance the separation effort.

It should be noted that the term paramagnetic nano particles is one representative of a large family of different materials such as: paramagnetic, diamagnetic, ferromagnetic, antiferromagnetic etc. Corresponding information used herein is however limited to paramagnetic in the sole attempt to exemplify purification of produced water from oil.

Notwithstanding usage of other materials, iron oxide nanoparticles Fe3O4 are preferred used due to its none toxic effects and no harm to the environment. In form of solid magnetite, it will have a specific weight of 5.200 kg/ m<3>.

Paramagnetic iron oxide generates a form of magnetism which occurs only in the presence of an externally applied magnetic field. Paramagnetic materials have a relative magnetic permeability of 1 or more. Paramagnets do not retain any magnetization in the absence of an externally applied magnetic field.

Notwithstanding other possible alternatives of MNP sizing, addressed use here in can range in diameter between about 1 nm and about 500 nm, and preferably 1 to 50 nm in cases where so-called superparamagnetic iron oxide nanoparticles (SPION) are being used.

Many patents and applications refer to the use of proprietary nanoparticles with dedicated properties as and performances. The present disclosure do however assume that relevant MNP particles are commercial available for all applications of interests. An example of such particles may be as outlined in publication (Society of Petroleum Engineers) SPE 181893 MS.

Centrifugal separators assume Newtonian fluids and particles with distinct differences in subject materials density/ specific weight, in such way that the heavier content seeks the outer radius, whereas the lighter fractions forms division borders between each pool of distinct density/ specific weight.

In order to resolve the challenge by separation of OiW where iron oxide MNP is heavier than oil and water, the following alternative groups of usage are proposed herein : Heavy solid functionalized Iron core oxide particles (Magnetite) ρ > 5 and Lightweight hollow core or Hybrid Particles (SPIONs embedded in shell) ρ < 1. Different usage demand a different functional approach in MNP usage, in such way that the heavy solid core iron oxide is being functionalized to absorb contaminating oil, whereas lightweight hollow spheres or light dense multi hollow polymer spheres, have a functionalized outer shell of embedded SPIONs.

As outlined above, interaction may be performed by use of the following physical phenomena: i) -Electro Magnetic Fields (EMF), ii) -Electro Static Fields (ESF), ii) -Concurrent and/ or discrete acting EMF and ESF.

Such interactions can be aimed towards MNP of different densities ρ > 1 and ρ < 1, but also in different combination of interacting fields and separation techniques for OiW, WiO and separation of oily MNP.

This disclosure shows how to enable use of MNP with different properties and mix of heavy and lightweight in order for a concurrent targeting of different substances.

Patent application US 2007/114181 A1 discloses methods for capturing, detecting, separating, isolating, and quantifying contaminants in a variety of starting materials including food products, clinical samples and environmental samples using magnetic nanoparticles. A fluid medium for mixing and collecting particles is confined to a small chamber and system first uses a rotating magnetic field to mix the material with magnetic particles to capture the target contaminants, and then afterwards a fixed magnetic field to separate and concentrate the captured target contaminants. Any non-collected particles are flushed away from the chamber with the fluid.

Patent application WO 2008/010687 A1 discloses methods of separation or purification of a specific protein using magnetic nanoparticles by means of a magnetic gradient field.

Patent application WO 2015/023573 A2 discloses a method of treating chemical compositions of a sample utilizing a magnetizable fluid in a magnetic field to manipulate the magnetizable fluids.

Patent application WO 2011/081531 A1 discloses a centrifugation apparatus using a combination of magnetic field and a two dimensional centrifugation for separation, mixing, moving, magnetic objects, washing etc. within a sample processing cartridge having multiple cavities

Brief Description of the Drawings

Prior art as well as the present disclosure with some examples of possible applications are, with reference to the accompanying drawings, described in the following, in which:

Fig.1A Prior art enhanced separation by use of electrostatic fields

Fig.1B Prior art enhanced separation by use of electromagnetic and electrostatic fields

Fig.2 Illustrates a falling particle subject for Stokes law for force balance

Fig.3 Illustrates how a centrifugal force has relation to other forces in other directions

Fig.4 Electrostatic force on a dipole

Fig.5 Principle example of dynamic interaction of magnetic fluxes, MNP and resulting force

Fig.6 Visualizes field and related forces Fc, Fs, Fm

Fig.7 Centrifugal separation of MNP adsorbed oil with ρ > 1

Fig.8A Process diagram with use of MNP – enhanced electrostatic coalescing and use of centrifugal separator for ρ >1

Fig.8B Diagram with divisions and pools at continuous 2 phase separation: MNP adsorbed oil – water

Fig.9 Principle arrangement for electromagnetic fields B and electrostatic fields Eo

Fig.10 Diagram with divisions and pools at continuous 4 phase separation: water - oil - oil with MNP – MNP with dense oil.

Fig.11 Centrifugal disk stack, with separate disks tightly predestined onto each other

Fig.12 A single disk which show radial bars that keep the distance to the next disk.

Some details of the drawings are further explained by:

Fig.1A Prior art (US1558382A) - Partial diagrammatic vertical longitudinal section of an electro-centrifugal separator. having a capillary action. Enhanced separation by use of electrostatic fields.

Fig.1B Prior art enhanced separation by use of electromagnetic and electrostatic fields. A HydroCyclone (1), constructed from non-magnetic material, and comprising a variable amplitude sound generator (2), a vibration generator (3) that can be electric, pneumatic or mechanical, and electro magnets (4). The electro magnets (4) are connected to a power source (5). A feeding device (6) feeds particle through a pump (7), and into the HydroCyclone (1). The pump (7) can be pneumatic or centrifugal. This results in an overflow (8) to other hydrocyclone stages, filter collectors or processing, and/ or an underflow (9) of fine particle collection and filtration.

Fig.2 Illustrates a falling particle subject for Stokes’ Law for force balance. Stokes’ Law defines the drag force appearance when sphere’s falls by a (constant) velocity in a liquid of known viscosity: Fd = 3πµVd, where Fd is the frictional force – known as Stokes' drag – acting on the interface between the fluid and the particle, µ is the liquid viscosity, V is the (terminal) velocity and d is the diameter of the sphere. By constant velocity forces must be in balance: Fd Fb = mg, where Fd is the sphere drag force, Fb is the buoyant force, me is the weight and g gravity the constant. Buoyant force: Fb = 1/6 pfgπd<3>, where pf is the liquid’s density. Sphere weight: mg= 1/6psgπd<3 >where ps is the sphere density. Stokes’ Law is valid by no turbulent flow with a Reynolds number Re = (pVd/µ)<0,2. Drag Forces can thus be detailed as: Fd = 1/6 (ps – pf) gπd<3>.

Fig.3 Illustrates how a centrifugal force has relation to other forces in other directions. Forces are Euler (E), Coriolis (C1), centrifugal (C2) and Velocity (V).

Fig.4 Electrostatic force on a dipole. Acting electrostatic force on Water in Oil (WiO) droplets. Dipolar attraction is the electrostatic attraction force between oppositely charged ends of water droplets (4a). Electrophoresis is the electrical attraction between the charged electrode and oppositely charged water droplets in a uniform electric field (4b).

Dielectrophoresis is the movement of polarized water droplets in a nonuniform electrostatic field with the movement toward the direction of convergence of the electrostatic field (4c). A charged aqueous drop moving in oil under the action of a uniform electric field may have the following charge: qie = [π<2>/6] 4πr<2>ξ1ξ0E0, where r is the drop radius, E0 is the electric field strength, ξ1 is the fluid dielectric constant, ξ0 is the permittivity of vacuum. The electrostatic induced force in (Fe) in (4c) is then given by: Fe =qieE0.

Fig.5 Principle example of dynamic interaction of magnetic fluxes, EMP and resulting force. An electric field may do work as well charge electric field that will follow the tangent of an electric field line. A force on a charged particle is orthogonal to the magnetic field. Forces are magnetic torque (1), magnetic moment (2), mechanical torque (3) and vorticity (4).

Fig.6 Visualizes field and related forces Fc, Fs, Fm. Magnetic nanoparticles shall be used to enhance use of Electrostatic and/ or Electromagnetic forces addressed to Water in Oil, Oil in Water and/ or other unwanted particles.

Fig.7 Centrifugal separation of magnetic nanoparticles (MNP) adsorbed oil with ρ > 1. Bowl drive (1), flow of dense MNP and oil (2), flow of clean water (3), flow of produced water and MNP (4).

Detailed Description

Purification of particles and fractions by gravity forces are divided in phases, where the settling velocity is dependent of degree of free sight on its way to the bottom. Gravity settling follows Stokes Law, defining certain fluid properties for particles that sink (or rise) with a constant velocity, namely that the difference in specific weight must be larger (or smaller) than the sum of particle buoyancy and hydraulic friction, also called drag force as illustrated in Fig.2.

Fig.3 describes how the centrifugal force actually can be decomposed in multiple virtual vectors, which interact with the objects in the gravity field. Although the centrifugal force drives the separations process, dissolved particles that are lifted out of its occasional residence and centrifugal orbit by means of EM and/ or ES forces, will be subject to interaction by Euler and Coriolis in the transition periods when EM and ES forces changes. It is thus disclosed how to utilize this phenomenon to enhance centrifugal purification efficiency.

The radial bars shown in Fig.12 prevents fluid to rotate in accordance with the Coriolis force, although this force forms the basis for hydrocyclones.

Particles and droplets dissolved in fluid can be polarized by interaction of external electrostatic fields and being attracted by a force toward the same field as illustrated in Fig.4.

Correspondingly is shown in Fig.5, how a magnetic field will interact a force on a para magnetic particle in motion. Although similar phenomena have been exploited over many years by the purification industry, significant shortcoming has been experienced as some particles resists said polarization. This has made said methods less relevant due to usability, capacity and efficiency. By projecting subject properties over to multiple different MNP that can provide a safe interaction by both ES and/ or EM and thus different targeted contamination, in order to provide a more universal, predictable and effective method and system for industrial purification.

Fig.6 illustrates how interaction of MNP- targets can be controlled by electrostatic and magnetic fields to collaborate with the even minor or initial non-existing centrifugal forced contamination. Centrifugal force acts equally on each point by establishing a fluid pressure differential over each particle or complex groups. Magnitude of such force is given by

, which obviously demands a certain difference in density.

Collaboration with MNP and interaction via EM and/ or ES forces aims alleviate this problem. By bonding MNP to subject particles and thereby adding common properties, it is foreseen that multiple MNP - droplets will add weight (or buoyancy) and volume as a time dependent function. However, a slight change may allow a certain elastic movement, that may well be generated by oscillation of the EM and ES fields and interacting forces.

It can thus easily enable a phenomenon known as thinning, which is tied to an initial movement of dissolved particles influence on the layer around the particles and lowers dynamic resistance. It is consequently an objective to utilize said forces in a coordinated act to achieve a maximum oscillation, and to systematically cut the EM and ES power at max amplitude in the flow direction. Subject particles will then remain in the new orbit with an enhanced centrifugal force, and thus reportingly have their separation velocity significantly increased.

Separation phases and how they divide at a steady state operation, is for the heavy 2-phase EMF separation case for MNP ρ > 1 represented in Fig.8. Oil droplets and/ or agglomerations of MNP saturated by absorbed oil, will be centrifuged as heavy particles in a cake clarification separating process. EMF interaction will further enhance the pool of dense oily MNP and water, establishing the following phase diversions: i) Outer separation phase will be a cake of compact oily MNP with some water, ii) Middle pool will consist of a water solution with dense oily MNP and iii) Inward pool will comprise clear water.

Centrifugal separators with vertical Disk stack operate at high speed gaining some 100.000 G, which are primarily applied for the clarification and separation of liquids with solid maximized to some 0,5 mm. The throughput capacities of separators range from 50 to 250,000 l / h. Its general design can easily be configured for purification of various contaminated fluid from oil and gas production such as drilling mud, brine, MEG, heavy oil produced water bilge water, hydraulic and lubrication oil etc. Magnitude of worldwide daily use of centrifugal separators has recently been calculated to a number of some 30 – 50.000 units only in the marine area (GEA Fachkolloquium 3 – 2018).

The 2-phase separator is shown in more details in Fig.7 where it appears that all oil related particles have been married with a satisfactory number of MNP. However, although a waste number has been bonded through a preceding mixing, the process will continue throughout the separation process. Separated MNP and oil will at this be washed and possible dried in an adequate centrifugal separator.

EM field arrangement, which may be arranged an outside coil as well as an ES power high voltage potential between rotor and stator of a centrifugal disk separator has been illustrated in Fig.9

EMF interaction is provided through a horizontal potential and field between the centrifugal separator stator and rotor. Voltage will typically be as for electro coalescers, 0 – 5 kV at 0 – 5 kHz. Magnetic fields will be provided through coil windings outside of the separator stator. Disk stack will preferable be made from materials with high magnetic permeability.

An arrangement will also be to fabricate the disk stack from paramagnetic material, which became magnetic from an outside generated flux source, but where each disk maintained the flux flow from top to bottom. The flux lines will this case be perpendicular to and from each surface, but the dynamics vis a vis the relative movement of the MNP needs further investments. A model is shown in Fig.12.

Lightweight 4- phase EMF and ESF separation and regeneration of MNP ρ < 1 is depictured in in Fig.10

produced water inlet will be to the separation zone/ pool 2 where water will be centrifuged as the heaviest fraction to the outer stratosphere and pool 1.

Possible light free oil will be expelled inwards to the stratospheric balance for oil in pool 3, and so will also the even lighter oily MNP, which has been propelled by EMF interacting forces from pool 1, be driven to its stratosphere of pool 4.

If EMF also effects the bonding efficiency between oil and MNP, it can be gradually lowered within pool 4, allowing centrifugal and flow forces action to depart some oil from the oily MNP. This will create a phase split between lean oily MNP in phase 4a and the even more lean and lighter oily MNP phase which will be packed in 4b.

When still in an Newtonian shape to flow, phase 4b pool can be subject for a continuous drainage of highly concentrated MNP, ready for washing and reuse.

It is obvious that any water appearance in the oily phase of pool 3 and 4 will be affected by ESF, and in way of relevant properties, will be subject for dielectrophoretic forces directed toward the water pool.

Fig.8A show a 3 – phase oil, Gas and water plant where water is processed through an electrical coalescer prior to entering a water treatment tank. It is obvious that electro coalescer with qualitative performance results of 0,3 % water cut, do have potential for improvements. In this context is foreseen that disclosed system and method can be applied for such improvement as outlined for interactive use of MNP and EM and ES fields.

This disclosure teaches how to combine use of functionalized MNP to enhance electro coalescing in such way that subject MNP retained in the water phase outlet can be promoted for further bonding in and a subsequent centrifugal separation process, prior to be separated and collect subject MNP for reuse, and disclose:

i. A method for purifying a fluid containing contaminants, comprising adding magnetic nanoparticles to the fluid for binding contaminants, and separating said magnetic nanoparticles bound to contaminants from said fluid through centrifugation enhanced by either an electromagnetic field or an electrostatic field or both. 

ii. The method in i) where the size of the magnetic nanoparticles is comprised between 1 and 500 nm, preferably between 1 and 50 nm 

iii. The method in i), where the frequencies of the electromagnetic and/or electrostatic field used to enhance centrifugal separation are in a range of 1 to 5 kHz

iv. The method  in i), where the magnetic nanoparticles have been functionalized v. The method in i), where the magnetic nanoparticles comprises paramagnetic nanoparticles

vi. The method  in iv),, where the magnetic nanoparticles have been coated, preferably with a surfactant to prevent flocculation

vii. The method  in i), where the fluid is a mixture of water and hydrocarbons in liquid and/or gas phase 

viii. The method  in i),, where the electromagnetic field used to enhance centrifugal separation is coaxial with the centrifugation rotation axis

ix. The method in i),, where the electrostatic field used to enhance centrifugal separation is orthogonal to the centrifugation rotation axis

x. A system for purifying a fluid containing contaminants, comprising means for mixing added magnetic nanoparticles with contaminants in the fluid, means for applying centrifugal forces to the fluid, means for applying a magnetic field or means for applying an electrostatic field or both to the fluid being centrifuged, and means for separating the nanoparticles bound to the contaminants from the rest of the fluid.

xi. A system as in in x) where the frequencies of the electromagnetic and/or electrostatic field used to enhance centrifugal separation are in a range of 1 to 5 kHz

xii. A system as in in x) where the electromagnetic and/or electrostatic field result from a voltage difference between the rotor and the stator, preferably 0 to 5 kV

xiii. A system as in in x) where the means for applying a centrifuge force is a centrifugal separator comprising a stack of disks

xiv. A system as in in xiii) where the disks are made either of a material of high magnetic permeability or of paramagnetic characteristics

Claims

1. A method for purifying a fluid containing contaminants, characterized in that the method comprising adding magnetic nanoparticles to the fluid for binding contaminants, and separating said magnetic nanoparticles bound to contaminants from said fluid through centrifugation enhanced by either an electromagnetic field or an electrostatic field or both.

2. The method according to claim 1 where the size of the magnetic nanoparticles is comprised between 1 and 500 nm, preferably between 1 and 50 nm.

3. The method according to claim 1, where the frequencies of the electromagnetic and/or electrostatic field used to enhance centrifugal separation are in a range of 1 to 5 kHz.

4. The method according to claim 1 where the magnetic nanoparticles have been functionalized.

5. The method according to claim 1 where the magnetic nanoparticles comprises paramagnetic nanoparticles.

6. The method according to claim 4, where the magnetic nanoparticles have been coated, preferably with a surfactant to prevent flocculation.

7. The method according to claim 1, where the fluid is a mixture of water and hydrocarbons in liquid and/or gas phase.

8. The method according to claim 1, where the electromagnetic field used to enhance centrifugal separation is coaxial with the centrifugation rotation axis.

9. The method according to claim 1, where the electrostatic field used to enhance centrifugal separation is orthogonal to the centrifugation rotation axis.

10. A system for purifying a fluid containing contaminants, comprising means for applying centrifugal forces to the fluid, means for applying a magnetic field or means for applying an electrostatic field or both to the fluid being centrifuged, characterized in that the system further comprises means for mixing added magnetic nanoparticles with contaminants in the fluid and means for separating the nanoparticles bound to the contaminants from the rest of the fluid.