WO2020070336A1

WO2020070336A1 - A method for purifying a liquid with magnetic and centrifugal forces

Info

Publication number: WO2020070336A1
Application number: PCT/EP2019/077121
Authority: WO
Inventors: Finn Aarseth
Original assignee: Combipro As
Priority date: 2018-10-05
Filing date: 2019-10-07
Publication date: 2020-04-09
Also published as: EP3860739A1; NO20181290A1; NO346022B1

Abstract

The present disclosure pertains to a method for separating contaminants from a fluid, said method comprising the steps of: a) adding nanoparticles to a fluid comprising contaminants whereby said nanoparticles and said contaminants combine to form combined particles thus providing a fluid comprising combined particles, b) subjecting said fluid comprising combined particles to (i) a centrifuged forced flow, and (ii) a Lorentz force and/or an electrostatic force, wherein said (i) centrifuged forced flow and said (ii) Lorentz force and/or electrostatic force are arranged to allow for tuning a combined total force on said combined particles to provide - one or more separation zones wherein said combined particles are concentrated, and - one or more further separation zones wherein the fluid is depleted of said combined particles.

Description

A METHOD FOR PURIFYING A LIQUID WITH MAGNETIC AND CENTRIFUGAL FORCES

TECHNICAL FIELD

The present disclosure relates to a method, i.e. a 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 addresses industrial purification in general and 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 2000 nanometres (nm). 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.

US patent 6,355,178 proposes to use electrostatic, magnetic and other physical phenomena to enhance cyclone and hydro cyclones qualitative and quantitative performances. However, 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 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.

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 § collecting them by use of a magnetic gradient field. Such method that demands use of 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.

W02005/079995 A1 teaches separation by use magnetic particles and centrifugal forces by magnetization of a rotating matrix. Magnetic fluid with bonded contamination is here being circulated through a magnetized steel matrix. Particles with satisfactory

susceptibility will thus be attracted to and bind onto the matrix surface. Growth of the deposit will thereafter be slung out by centrifugal forces and mixed with a circulating fluid for Newtonian flow. The longitudinal magnetic field B is directed perpendicular onto the horizontal matrix in order to achieve a maximum magnetization of its ferrite steel materials.

Similarly, US patent 8,636,906 B2 teaches the removal of a target moiety from a liquid using magnetic nanoparticles by allowing said particles to establish moiety complexes, for thereafter using a magnetic field to collect the nanoparticles from the fluid.

More efficient separation and cleaning methods and process facilities are therefore urgently needed. The present disclosure teaches how the interaction between MNP and Electrostatic (ES) and/or Electromagnetic (EM) field, independent of the initial properties of the dissolved fluid and targeted particles, resolves problems of the prior art. SUMMARY

The present disclosure relates to a method, i.e. a 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.

It is an object of the present disclosure to allow for separation of contaminants from a fluid. This object is wholly or partially achieved by a method according to appended claim 1. Embodiments are set forth in the appended dependent claims and in the following description and example.

The disclosure is also applicable to cyclones, hydro cyclones, as well as compact flotation cyclones and similar centrifugal constructions and 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.

However, there are many areas of industry where purification is needed for other fluids and contaminants. Examples comprise:

- oil and gas industry - produced water, grey and wastewater, combustion gas and scrubber fluid, production and drilling fluids, refinery process fluid

- ships and marine activities - combustion gas and scrubber fluid, scrubber fluid from tanks and cargo holds

- aviation airports - glycol-water and peril uorinated compounds, runway overwater drain

- gasoline and car washing stations - drainage overwater, machine washing water drain

- mining and rare metal grain refining - reclaim and extraction of valuable content or purities from grained minerals

- metal processing industry - air and water residues from the steel and

aluminium production

- earth, soil and recycled waste - removal of harmful content from granulated compost soil

- food processing - removal of harmful and / or reclaim of valuable content nutritious such as soya oil - co₂ catch - co₂ recycle from various fluid

- tap and bottle water beverage industry - micro plastic

- drinking water - excessive content of impurities and harmful minerals

- desalination of saltwater

- municipal wastewater - reclaim of valuable content and / or removal of harmful content before release

- polluted snow melting - motor vehicle pollution deposits

- road overwater cleaning plants - motor vehicle pollution deposits, asphaltene road deposits

- nuclear/ chemical polluted sea / river water - prohibited release of contaminated fluid upon accidents

- national emergency and environmental preparedness - contaminated fluid environment mobile combat resources

It will be appreciated that the method of the present disclosure may be used in the above- mentioned examples. In particular, the method of the present disclosure may be used in the oil and gas industry such as the off shore oil and gas industry, to treat process water and/or petroleum. For instance, the method of the present disclosure may be used in treating process water including oil, such as oil droplets, to separate and/or remove the oil from the process water. Additionally or alternatively, the method of the present disclosure may be used in treating petroleum including water, such as water droplets, to separate and/or remove the water from the petroleum.

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 mm. 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 time- consuming 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.

ES interaction is less suitable 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). Nor is it possible to have magnetic interactions for none chargeable particles that cannot be magnetized.

Under steady favourable production conditions, it is known that electric coalescers may achieve oil purification of WiO down to some 0,5% water cut. At this stage the total remaining content such as dissolved oil, emulations, sand and production-chemicals 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 mm.

The process by which individual particles aggregate into clot-like 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 floe 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 floes 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 may vary by different frequencies for example from 100 Hz 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: amine, 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. The present disclosure represents however, another approach for magnetic interaction, namely by addressing the MNP and its bonded oil, to collaborate with centrifuged forced flow, also called 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 floculation is aggregation thanks to another chemical or particle. Thus, in this disclosure the related terms may be used interchangeably. The prior art teaches how to use gradient magnet field interaction to attract, isolate and to collect bulks of targeted particles from a solution.

The present disclosure teaches the use of MNP interaction in a distinct different way from prior art. Paramagnetic MNP and bonded oil droplets dispersed in produced water enters into a rotating centrifugal separator, which is equipped with a perpendicular directed magnetic field for interaction. The moving MNP and bonded oil will thus be subject to an interacting radial Lorentz force with a vectoral direction towards its disposal.

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

The term paramagnetic nano particles is one representative of a large family of different materials comprising paramagnetic, diamagnetic, ferromagnetic and antiferromagnetic materials. The present disclosure is exemplified by paramagnetic nano particles in demonstrating 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/ m³. 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.

Examples of such particles are in the publication from the 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) p > 5 and Lightweight hollow core or Hybrid Particles (SPIONs embedded in shell) p < 1. Different usage demands 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: i) -Electro Magnetic Fields (EMF), ii) -Electro Static Fields (ESF), iii) -Concurrent and / or discrete acting EMF and ESF.

Such interactions can be aimed towards MNP of different densities p > 1 and p < 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.

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

Fig.8 shows a top view of three separating zones comprising the combined particles and the fluid described herein.

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

Fig.10 shows a top view of five separating zones comprising the combined particles and the fluid described herein.

Fig. 1 1 shows the results of an experiment

DETAILED DESCRIPTION

Some details of the drawings are further explained by:

Fig.lA 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.1 B 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 = 3pmVd, where Fd is the frictional force - known as Stokes' drag - acting on the interface between the fluid and the particle, m 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, mg is the weight and g gravity the constant. Buoyant force: Fb = 1/6 pfgpd³, where pf is the liquid’s density. Sphere weight: mg= 1/6psgpd³ where ps is the sphere density. Stokes’ Law is valid by no turbulent flow with a Reynolds number Re = (pVd/m)<0,2. Drag Forces can thus be detailed as: Fd = 1/6 (ps - pf) gpd³.

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). The centrifugal force is 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 forces in the transition periods when EM and ES forces changes. It is thus disclosed how to utilize this phenomenon to enhance centrifugal purification efficiency.

During a three- dimensional interaction the resulting vectors will be taken into account as taught by the Lorentz force F = q (E + v x B) where q is the charge of the particle, E is the electric field and v x B is the vector cross product between the velocity of the particle and the magnetic field: A positively charged particle will be accelerated in the same linear orientation as the E field, but will curve perpendicularly to both the instantaneous velocity vector v and the B field.

The term qE is called the electric force, while the term qv× B is called the magnetic force. In the present disclosure , the term "Lorentz force" will refer to the expression for the total force.

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: where r is the drop

radius, E₀ is the electric field strength, x-i is the fluid dielectric constant, x₀ 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). The Lorentz force F acts on a charged particle (of charge q) in motion (instantaneous velocity v). The E field and B field vary in space and time.

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 p > 1.

Bowl drive (1 ), flow of dense MNP and oil (2), flow of clean water (3), flow of produced water and MNP (4).

Figure 8 shows a top view of three separating zones resulting from the method described herein comprising the combined particles and the fluid described herein. The separating zone 1 may comprise or consist of purified water such as process water from which oil has been partially or wholly removed. The separating zone 2 may comprise or consist of dense oily water and MNPs, e.g. water containing oil and combined particles as described herein. The separating zone 3 may comprise or consist of caked oily MNP, e.g. combined particles comprising oil and nanoparticles as described herein. It will be appreciated that the size of the zones and/or the concentration of the combined particles in the zones may be tuned, i.e. adjusted, by varying the (i) centrifugal force, and (ii) the Lorentz force and/or the electrostatic force using the method described herein. Figure 8 shows the result of a multiphase separation of water, oil and gas. The mixture of fluids is usually separated into its phases downstream the wellhead manifold, through a two -stage process comprising two gravity separator tanks followed by an electrostatic coalescing separator. Subject produced water is then led to the water treatment tank for further processing. As a functional example is proposed to add an appropriate amount of MNP into the oily water separated by the 2’nd stage separator for thereafter being led to the electro coalescer. The oily water is here forced though narrow channels with high velocity, where water is being subject for electrostatic dipole building as outlined for Figure 4a, band c. Electro coalesced separation of water and oil is more rapid and predictable to use than gravity settling, especially in order to meet separation to minimum sales requirement of less than 0,5 % WiO. Traditional separation by electrophoresis is however foreseen to achieve a significantly enhancement by use of hydrophilic functionalized MNP bond the oil. Further enhancement is foreseen by appliance of a magnetic field for interaction by Lorentz force.

Figure 10 shows shows a top view of three separating zones comprising the combined particles and the fluid described herein. Separating zone 1 may comprise or consist of combined particles and oil, e.g. MNPs as described herein together with oil, such as 20 wt% oil based on the total weight of this separating zone. Separating zone 2 may comprise or consist of combined particles as described herein and oil, e.g. MNPs as described herein and oil. Separating zone 3 may comprise or consist of combined particles as described herein, e.g. oil particles combined with nanoparticles as described herein. The combined particles of the separating zone 3 may be dense oily MNPs.

Separating zone 4 may comprise or consist of combined particles as described herein and water such as process water from the oil and gas industry. The combined particles of separating zone 4 may be MNPs as described herein. The separating zone 5 may comprise or consist of water such as Clear water, e.g. substantially pure water (i.e. water free from nanoparticles and/or combined particles as described herein). It will be appreciated that the size of the zones and/or the concentration of the combined particles in the zones may be tuned, i.e. adjusted, by varying the (i) centrifuged forced flow, and (ii) the Lorentz force and/or the electrostatic force using the method described herein. It will be appreciated that the size of the zones and/or the concentration of the combined particles in the zones may be tuned, i.e. adjusted, by varying the (i) centrifuged forced flow, and (ii) the Lorentz force and/or the electrostatic force using the method described herein.

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.

Radial bars such as radial bars present in a centrifuge may be used to prevent fluid to rotate in accordance with the Coriolis force, although this force forms the basis for hydrocyclones as well as Compact Flotation Cyclones and similar centrifugal

constructions.

Particles and droplets dissolved in fluid can be polarized by interaction of external electrostatic fields and thus being attracted by a force toward the same field as illustrated in Fig.4. Quite differently Fig. 5 shows how a magnetic field B will interact a charged magnetic particle (MNP) in motion, namely by Lorentz force. Although similar phenomena have been exploited over many years by the purification industry, significant shortcoming has been experienced as some particles resists charging and ignore said polarization.

This has made said methods less relevant due to usability, capacity and efficiency. By bonding multiple MNP to targeted droplets, common properties in form of weight and charge will provide a safe interaction by both ES and / or EM and the independent of the type of contamination. This provides a more universal, predictable and effective method and system for industrial purification.

Fig.6 illustrates how 3- dimensional interaction of MNP- targets can be controlled by electrostatic and magnetic fields to collaborate with the even minor or initial non-existing centrifuged 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 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, 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.

This enables 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. Particles lifted out of its resilient position, will due to the viscous adherence that held in the first place, hinder their return Subject particles will then remain in the new orbit with an enhanced centrifugal force, and thus reportingly have their separation velocity significantly increased for each oscillating step.

Separation phases and how they divide at a steady state operation, is for the heavy 2- phase EMF separation case for MNP p > 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 I / 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, or by means of inside permanent magnets. Disk stack will preferable be made from none-magnetic materials with high magnetic permeability. An arrangement will also be to locate fixed magnetize above and below the rotating disk bowl, that are forming an adequate field through the bowl.

The flux lines will this case be vertical to the separator disc stack and the relative movement of the MNP.

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

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.

When initiating the method of the disclosure, a choice of MNP is made, suitable for the fluid and contaminant. Based on their characteristics, an initial number of rotations per minute is chosen, as well as strength and frequency of the fields. T ogether with fluid viscosity, temperature and pressure, the process is tuned by adjusting these parameters until the desired level of purification is reached. In the initial stages of the separation the centrifugal forces will be present, but at later stages in the separation the Lorentz force can be the dominating or only force that affects the particles. Produced water from the coalescer is thereafter led to the water treatment tank where further amount of MNP is mixed and bonded to the residue oil content before entering the pipework leading to a centrifugal separator for an enhanced ES/EM processing enabled by MNPs.

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 inter alia the following aspects.

Further aspects

Further aspect 1.

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.

Further aspect 2

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

Further aspect 3

The method according to further aspect 1 or 2, wherein the frequencies of the

electromagnetic and/or electrostatic field used to enhance centrifugal separation are in a range of 1 to 5 kHz.

Further aspect 4

The method according to any one of the preceding aspects, wherein the magnetic nanoparticles have been functionalized.

Further aspect 5

The method according to any one of the preceding aspects, wherein the magnetic nanoparticles comprises paramagnetic nanoparticles Further aspect 6

The method according to any one of the preceding aspects, wherein the magnetic nanoparticles have been coated, preferably with a surfactant to prevent flocculation

Further aspect 7

The method according to any one of the preceding aspects, wherein the fluid is a mixture of water and hydrocarbons in liquid and/or gas phase

Further aspect 8

The method according to any one of the preceding aspects,

wherein the electromagnetic field used to enhance centrifugal separation is coaxial with the centrifugation rotation axis

Further aspect 9

The method according to any one of the preceding aspects, wherein the electrostatic field used to enhance centrifugal separation is orthogonal to the centrifugation rotation axis

Further aspect 10

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. Further aspect 1 1

A system according to further aspect 10, wherein the frequencies of the

electromagnetic and/or electrostatic field used to enhance centrifugal separation are in a range of 1 to 5 kHz

Further aspect 12

A system according to further aspect 10 or 11 , wherein the electromagnetic and/or electrostatic field result from a voltage difference between the rotor and the stator, preferably 0 to 5 kV

Further aspect 13

A system according to any one of further aspects 10-12, wherein the means for applying a centrifuge force is a centrifugal separator comprising a stack of disks Further aspect 14

A system according to any one of further aspects 10-13, wherein the disks are made either of a material of high magnetic permeability or of paramagnetic characteristics.

The present disclosure also provides the following items. Items

Item 1

A method for separating contaminants from a fluid, said method comprising the steps of: a) adding nanoparticles to a fluid comprising contaminants whereby said nanoparticles and said contaminants combine to form combined particles thus providing a fluid comprising combined particles,

b) subjecting said fluid comprising combined particles to

(i) a centrifugal force, and

(ii) a Lorentz force and/or an electrostatic force,

wherein said (i) centrifugal force and said (ii) Lorentz force and/or electrostatic force are arranged to allow for tuning a combined total force on said combined particles to provide

- one or more separation zones wherein said combined particles are concentrated, and

- one or more further separation zones wherein the fluid is depleted of said combined particles. Item I bis

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow, and

(ii) a Lorentz force and/or an electrostatic force,

wherein said (i) centrifuged forced flow and said (ii) Lorentz force and/or electrostatic force are arranged to allow for tuning a combined total force on said combined particles to provide

- one or more further separation zones wherein the fluid is depleted of said combined particles. Item 2

A method according to item 1 , wherein step b) is:

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow, and

(ii) a Lorentz force and optionally an electrostatic force,

wherein said (i) centrifuged forced flow and said (ii) Lorentz force and optionally electrostatic force are arranged to allow for tuning a combined total force on said combined particles to provide

- one or more separation zones wherein said combined particles are concentrated, and - one or more further separation zones wherein the fluid is depleted of said combined particles.

Item 3

A method according to item 1 , wherein step b) is:

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow, and

(ii) an electrostatic force and optionally a Lorentz force,

- one or more further separation zones wherein the fluid is depleted of said combined particles. Item 4

A method according to any one of the preceding items, wherein said Lorentz force and said electrostatic force are aligned.

Item 5

A method according to any one of the preceding items, wherein the centrifuged forced flow is caused by one or more of: Euler force, Coriolis force, centrifugal force, velocity.

Item 6

A method according to any one of the preceding items, wherein the Lorentz force and/or the electrostatic force is/are alternating. Item 7

A method according to any one of the preceding items, wherein the centrifuged forced flow and the Lorentz force are arranged to combine to provide a maximum combined total force in the direction of the Lorentz force.

Item 8

A method according to any one of items 1-6, wherein the centrifuged forced flow and the Lorentz force are arranged to combine to provide a maximum combined total force in the opposite direction of the Lorentz force.

Item 9

A method according to any one of the preceding items, wherein said combined particles move in the direction of the Lorentz force.

Item 10

A method according to any one of items 1-8, wherein said combined particles move in the opposite direction of the Lorentz force. Item 1 1

A method according to any one of the preceding items, wherein the combined particles are comprised within one zone or two or more zones.

Item 12

A method according to item 1 1 , wherein the concentration of the combined particles in the two or more zones is different.

Item 13

A method according to any one of the preceding items, wherein the fluid is depleted of said combined particles and comprised within one zone or two or more zones.

Item 14

A method according to item 13, wherein the purity of the fluid in the two or more further zones is different. Item 15

A method according to any one of the preceding items, wherein said Lorentz force and/or said electrostatic force is/are varied to change the number of zones and/or concentration of combined particles in said zones.

Item 16

A method according to any one of the preceding items, wherein said Lorentz force and/or said electrostatic force is/are varied to change the number of further zones and/or fluid purity in said further zones.

Item 17

A method according to any one of the preceding items, further comprising a step of separating the one or more zones and/or the one or more further zones from each other. Item 18

A method according to any one of the preceding items further comprising a step of removing said combined particles from said fluid.

Item 19

A method according to any one of the preceding items further comprising a step of collecting said zones and/or said further zones.

Item 20

A method according to any one of the preceding items further comprising a step of separating the combined particles into contaminants and nanoparticles.

Item 21

A method according to item 20, further comprising reusing said nanoparticles. Item 22

A method according to any one of the preceding items, wherein the fluid is oil, gas and/or water. A method according to any one of the preceding items, wherein the fluid is an oil well production fluid such as petroleum, gas and/or produced water.

Item 24

A method according to any one of the preceding items, wherein the fluid is oil or petroleum.

Item 25

A method according to any one of items 1-23, wherein the fluid is water or produced water.

Item 26

A method according to any one of the preceding items, wherein the contaminant is a solid, a liquid or a combination thereof.

Item 27

A method according to any one of the preceding items, wherein the contaminant comprises water.

Item 28

A method according to any one of the preceding items, wherein the contaminant comprises oil or petroleum.

Item 29

A method according to any one of the preceding items, wherein the contaminant and/or said combined particles is/are dispersed in said fluid.

Item 30

A method according to any one of the preceding items, wherein the contaminant has a largest dimension from 500 nm to 5000 nm.

Item 31

A method according to any one of the preceding items, wherein the nanoparticles have a largest dimension from 1 to 500 nm, such as from 1 to 50 nm. Item 32

A method according to any one of the preceding items, wherein the nanoparticles are composite nanoparticles with a coating. Item 33

A method according to any one of the preceding items, wherein the nanoparticles comprise a coating such as a coating preventing flocculation.

Item 34

A method according to any one of the preceding items, wherein the nanoparticles are functionalized for bonding to the contaminant.

Item 35

A method according to any one of the preceding items, wherein the nanoparticles are one of more of the following, paramagnetic nanoparticles, diamagnetic nanoparticles, ferromagnetic nanoparticles, antiferromagnetic nanoparticles.

Item 36

A method according to any one of the preceding items, wherein the nanoparticles are one or more of: paramagnetic nanoparticles, hydrophobic nanoparticles, iron oxide nanoparticles.

Item 37

A method according to any one of the preceding items, wherein the nanoparticles comprise or consist of oxide nanoparticles.

Item 38

A method according to any one of the preceding items, wherein the Lorentz force and/or the electrostatic force has/have a frequency from 1 to 5 kHz.

Item 39

A method according to any one of the preceding items, wherein the centrifuged forced flow is generated around a centrifugal rotation axis and the electrostatic force is orthogonal to said centrifugation rotation axis. Item 40

A method according to any one of the preceding items, wherein said method comprises reducing the amount of contaminants in said fluid by 80% or less. Item 41

A method according to any one of the preceding items, wherein said method comprises lowering of the concentration of said contaminants in said fluid to 10 ppm or less, such as to 5 ppm or less. Item 42

A method according to item 41 , wherein said lowering comprises lowering of the concentration of said contaminants in said fluid from 30 ppm or more to 10 ppm or less, such as to 5 ppm or less. It will be appreciated that the nanoparticles of the present disclosure and the combined particles of the present disclosure are susceptible to being affected by one or more of the following: a Lorentz force, a magnetic field, an electric filed such as an electrostatic field, an electrostatic force. It follows that the combined particles disclosed herein are susceptible to being affected by one or more of the aforementioned fields or forces. The nanoparticles described herein such as the nanoparticles mentioned in the claims and in the items may be the MNPs described herein. When a fluid comprising combined particles as described herein is subjected to (i) a centrifuged forced flow, and (ii) a Lorentz force and/or an electrostatic force, the combined particles will move and be concentrated into separation zones while the fluid moves into further separating zones where the fluid is depleted of said combined particles.

EXAMPLE

An example of how the present disclosure enables an industrial separation methodology better than prior art, is most evident shown by removal of small sized particles. These are typically found as a harmful residue content of produced water in sizes of 50 μm and bellow.

Tables 1 and 2 depictures the metrics of respective an oildrop of diameter 0.65 μm and a magnetic nano particle (MNP) of diameter 61.5 nm. Provided that the oildrop outer surface can be 100 % covered by bonded MNPs, a coverage factor fc = 1 can be defined. For corresponding less coverages such as for fc = 0.01 ; 0.1 and 0.5, achieved properties and related individual magnetic charges can then easily be propositioned.

Figure 11 shows plots for where subject magnetic interaction and related gravity have been combined to achieve a resulting separation velocity measured in meter pro second (m/s). As apparent plot i) addresses a gradient magnetic field in Tesla (T) as a function of the distance to the magnetic source. As shown from plot ii), Terminal velocity is being reached for the oildrop with fc 0.01 at 10e-6 m/s. This correspond approximately to the limit of related centrifugal separation effort. At the same gravity and magnetic flux level, plot iii) shows that the same particle with a coverage fc = 0.5, will reach a velocity of 10e-4 m/s.

This indicates a qualitative improvement of 100 times above todays gravity separation limit for small sized particles, but also that subject magnetic interaction aids a significant quantitative improvement already at very low magnetic levels of 0.01 to 0.1T.

Although subject example is being addressed towards oil globules manipulated by bonded MNPs, it should be evident that subject methodology and separation technique will be applicable for any industrial separation of MNP that are dispersed in a colloidal Newtonian fluid.

Table 1 : Droplet parameters and values

Table 2: MNP parameters and values

Claims

1. A method for separating contaminants from a fluid, said method comprising the steps of:

a) adding nanoparticles to a fluid comprising contaminants whereby said nanoparticles and said contaminants combine to form combined particles thus providing a fluid comprising combined particles,

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow , and

(ii) a Lorentz force and/or an electrostatic force,

- one or more further separation zones wherein the fluid is depleted of said combined particles.

2. A method according to claim 1 , wherein step b) is:

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow, and

(ii) a Lorentz force and optionally an electrostatic force,

3. A method according to claim 1 , wherein step b) is:

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow, and

(ii) an electrostatic force and optionally a Lorentz force,

4. A method according to any one of the preceding claims, wherein said Lorentz force and said electrostatic force are aligned.

5. A method according to any one of the preceding claims, wherein the centrifuged forced flow is caused by one or more of: Euler force, Coriolis force, centrifugal force, velocity.

6. A method according to any one of the preceding claims, wherein the Lorentz force and/or the electrostatic force is/are alternating.

7. A method according to any one of the preceding claims, wherein the centrifuged forced flow and the Lorenz force are arranged to combine to provide a maximum combined total force in the direction of the Lorentz force.

8. A method according to any one of claims 1-6, wherein the centrifuged forced flow and the Lorenz force are arranged to combine to provide a maximum combined total force in the opposite direction of the Lorentz force.

9. A method according to any one of the preceding claims, wherein said combined particles move in the direction of the Lorentz force.

10. A method according to any one of claims 1 -8, wherein said combined particles move in the opposite direction of the Lorentz force.

1 1. A method according to any one of the preceding claims, wherein the combined particles are comprised within one zone or two or more zones.

12. A method according to claim 1 1 , wherein the concentration of the combined particles in the two or more zones is different.

13. A method according to any one of the preceding claims, wherein the fluid is

depleted of said combined particles and comprised within one zone or two or more zones.

14. A method according to claim 13, wherein the purity of the fluid in the two or more further zones is different.

15. A method according to any one of the preceding claims, wherein said Lorentz force and/or said electrostatic force is/are varied to change the number of zones and/or concentration of combined particles in said zones.

16. A method according to any one of the preceding claims, wherein said Lorentz force and/or said electrostatic force is/are varied to change the number of further zones and/or fluid purity in said further zones.

17. A method according to any one of the preceding claims, further comprising a step of separating the one or more zones and/or the one or more further zones from each other.

18. A method according to any one of the preceding claims further comprising a step of removing said combined particles from said fluid.

19. A method according to any one of the preceding claims further comprising a step of collecting said zones and/or said further zones.

20. A method according to any one of the preceding claims further comprising a step of separating the combined particles into contaminants and nanoparticles.

21. A method according to claim 20, further comprising reusing said nanoparticles.

22. A method according to any one of the preceding claims, wherein the fluid is oil, gas and/or water.

23. A method according to any one of the preceding claims, wherein the fluid is an oil well production fluid such as petroleum, gas and/or produced water.

24. A method according to any one of the preceding claims, wherein the fluid is oil or petroleum.

25. A method according to any one of claims 1-23, wherein the fluid is water or

produced water.

26. A method according to any one of the preceding claims, wherein the contaminant is a solid, a liquid or a combination thereof.

27. A method according to any one of the preceding claims, wherein the contaminant comprises water.

28. A method according to any one of the preceding claims, wherein the contaminant comprises oil or petroleum.

29. A method according to any one of the preceding claims, wherein the contaminant and/or said combined particles is/are dispersed in said fluid.

30. A method according to any one of the preceding claims, wherein the contaminant has a largest dimension from 500 nm to 5000 nm.

31. A method according to any one of the preceding claims, wherein the nanoparticles have a largest dimension from 1 to 500 nm, such as from 1 to 50 nm.

32. A method according to any one of the preceding claims, wherein the nanoparticles are composite nanoparticles with a coating.

33. A method according to any one of the preceding claims, wherein the nanoparticles comprise a coating such as a coating preventing flocculation.

34. A method according to any one of the preceding claims, wherein the nanoparticles are functionalized for bonding to the contaminant.

35. A method according to any one of the preceding claims, wherein the nanoparticles are one of more of the following, paramagnetic nanoparticles, diamagnetic nanoparticles, ferromagnetic nanoparticles, antiferromagnetic nanoparticles.

36. A method according to any one of the preceding claims, wherein the nanoparticles are one or more of: paramagnetic nanoparticles, hydrophobic nanoparticles, iron oxide nanoparticles.

37. A method according to any one of the preceding claims, wherein the nanoparticles comprise or consist of oxide nanoparticles.

38. A method according to any one of the preceding claims, wherein the Lorentz force and/or the electrostatic force has/have a frequency from 1 to 5 kHz.

39. A method according to any one of the preceding claims, wherein the centrifuged forced flow is generated around a centrifugal rotation axis and the electrostatic force is orthogonal to said centrifugation rotation axis.

40. A method according to any one of the preceding claims, wherein said method comprises reducing the amount of contaminants in said fluid by 80% or less.

41. A method according to any one of the preceding claims, wherein said method comprises lowering of the concentration of said contaminants in said fluid to 10 ppm or less, such as to 5 ppm or less.

42. A method according to claim 41 , wherein said lowering comprises lowering of the concentration of said contaminants in said fluid from 30 ppm or more to 10 ppm or less, such as to 5 ppm or less.

43. A method for separating contaminants from a fluid, said method comprising the steps of:

b) subjecting said fluid comprising combined particles to

(i) a centrifuged forced flow, and

(ii) a Lorentz force and/or an electrostatic force,

- one or more further separation zones wherein the fluid is depleted of said combined particles

c) subjecting said fluid comprising combined particles to said Lorentz force to allow for a final or initial separation of the particles.