NO343579B1 - injection Mixer - Google Patents

Description

Field of the invention

The present invention relates to the injection into, mixing and conditioning of fluids flowing through a pipeline. The invention relates more particularly to a multifluid injection mixer, a mixer and an assembly including the multifluid injection mixer, applicable for a large number of mixing, injection and conditioning operations, especially in connection with the treatment of hydrocarbons and "in-line" reactor processes for the production of fine chemicals.

Background of the invention and prior art

The processing of fluids is a large technical area that finds applications in most industries. Processing of fluids flowing in a pipeline typically involves phase separation of the fluid contents and delivery of the separated constituents of a specified quality according to the subsequent application. For example, the flow from a hydrocarbon well is separated into oil, gas and water, the phases being processed and cleaned of contaminants until a specification is met. The processing will typically involve the injection of fluids, such as chemicals, solvents or extraction fluids, to improve the efficiency of the separation and processing equipment.

The most commonly injected fluids (additives) can be summarized as follows:

Scavengers/flushing/irreversible solvents (liquid to remove acidic components, such as H2S, mercury, mercaptans)

Corrosion inhibitors, hydrate inhibitors, scale inhibitors, wax inhibitors, drag reducers, desalination agents, de-emulsifiers, oil removers, defoamers,

Antifouling agents

Flocculating agents (improving the coalescence rate of the dispersed phase) Condensate/hydrocarbon (extraction fluids)

Gas (flotation or suppression of plug formation)

Water (desalination or control of the water fraction in a multiphase flow away from the critical value)

The respective additives are typically introduced into the flow in a line upstream of the treatment equipment, such as upstream of a separator. The flow can be any multiphase mixture of gas and one or more liquids, a single gas or a combination of gases, any liquid or mixture of miscible liquid components or immiscible components, such as hydrocarbon liquid and water. The flow can thus be, for example, an untreated well flow, produced water, treated oil water flow, treated gas flow, produced water contaminated with dispersed and dissolved hydrocarbon, treated water flow contaminated with hydrocarbon liquid, or water from which a gas component is to be removed (e.g. deoxygenation). The range of surface tension, viscosity, pressure and temperature can vary considerably, and additional types of fluids or additives are also relevant.

While the description above and below mainly concerns the processing of hydrocarbons, mixing of fluids is an essential unit operation in other parts of the process industry as well, such as the production of food (e.g. production of emulsions), pharmaceuticals, chemicals (reactive streams which may include activators or reagents), paper (refining/pulp treatment) and melts (alloys) and other processes. These processes generally include batch production or the use of large containers where the different fluids are mixed by means of stirrers. There is reason to assume that the use of line flow mixing instead of stirring in containers is attractive both because of investment, labor costs, production flexibility, safety and product quality.

The flow rate of the additives injected into the line is typically very small compared to the volumetric flow rate of, for example, a multiphase flow. The challenges of the addition are therefore associated with achieving a stable non-oscillating injection rate, securing axial mixing and simultaneously achieving homogeneous dispersion and distribution of the addition over the conductor cross-section of the relevant multiphase flow (radial mixing).

The resulting droplet size distribution for dispersed injected additive is affected by the mixer design, fluid properties and the applicable flow rates.

Injection pipes are the most common injection device for additives, but injection pipes do not provide effective distribution of the chemical into the multiphase flow. With the requirement to achieve a constant injection rate, downscaling of the additive's flow quantity is also limited. Nozzles normally provide better distribution than injection pipes for the injected fluid into the continuous phase. Disadvantages, however, are associated with limitations in the secondary break-up of droplets, narrow working areas for the additive flow rate (downscaling) and limited mechanical robustness.

Furthermore, scaling up to larger wire dimensions is questionable.

For the Sulzer mixer and similar static mixers, the additive is injected upstream of the mixer. The mixers are based on plates or screens arranged in series so that the multiphase flow is repeatedly exposed to shear forces to finally achieve an acceptable mixture of the injected fluid and the continuous fluid phase. This typically requires a significant pressure drop (equivalent to high energy consumption, limited capacity or production rate) and long installed mixing units. Such mixers typically provide a relatively uneven droplet distribution of the injected mixture for practical lengths of the static mixers, as only part of the addition is exposed to large shear forces on the surface of the screens or plates.

Single shot mixers such as throat devices or venturis expose the inflowing multiphase flow to a high shear zone achieved in a relatively short mixer. In the case of these mixers, the injected fluid is pre-injected upstream of the mixing device, the injected fluid being captured in the main volume of the continuous phase. The injected fluid is therefore generally not exposed to the part of the mixer where the shear forces are high, i.e. near the mixer wall. To compensate for this and ensure breakup of the injected fluid (as associated with the stretching of "fluid elements" in areas with high shear force; large fluid velocity gradient) the mixers must have a high pressure drop.

The Westfall Manufacturing Company of Bristol, Rhode Island, USA offers a static mixer adapted for placement in a conduit containing fluid flow, the static mixer including a circumferential flange extending radially inwardly from the inner conduit surface and further having at least a pair with opposing baffles extending from there at an angle in the direction of the fluid flow. The aforementioned static mixer is described in patent publication US 5,839,828, to which document reference is made here. Operation of the static mixer results in a combination of laminar and turbulent flow (column 1, lines 36-39). In addition, chemicals can be added through injection openings on the downstream side of the discs (claim 4, figures no. 10 and 7, column 3, lines 2133 and 59-62). In this device, the chemical is point-injected behind a plate, namely a guide disc, and not injected so that the chemical is homogeneously distributed in the continuous phase. There is no description of any sharp edge.

With the invention of the "ProPure" injection mixer designated C100, as described in patent EP 1294473 B1, the technology of mixing and injection was brought forward. The injection mixer C100 consists of a contact element shaped as a contracting or constricting tube (contraction line or section) through which a gas flows, and an injection element consisting of a liquid inlet designed to produce a ring of liquid around the inner circumference of the contraction line, a sharp edge at the end of the contraction line and a further line section downstream of the sharp edge. The downstream conduit section is preferably a spreading conduit to recover part of the pressure drop across the contraction section. In patent EP 1294473 B1 it is described how the injection mixer C100 can be used to distribute a liquid into a gas stream, for the absorption of a selected gas component from a gas stream by bringing the gas stream into contact with a liquid that includes a solvent or a reagent for the selected gas component, to separate H2S from natural gas, to selectively remove H2S from a natural gas rather than CO2, to simultaneously remove acidic gas components from a natural gas stream, for deoxygenation of water, for dehydration of natural gas, and how it is used in combination with existing columns for adaptation to an existing plant to withstand a change in feeding conditions. In addition, it is described how the injection mixer can be used as a mixer for renewed mixing of the phases in a fluid flow, without injecting chemicals. It is also described how several injection mixers can be combined in series or in parallel to inject several liquids, by injecting a chemical into each mixer (cf. claims 15, 16, figure no. 10a and 10b in EP 1294473 B1). Injection of several additive fluids in one injection mixer is not considered in EP 1294473 B1, presumably because injection of several additive fluids at the same time is considered inefficient. For example, injecting a gas together with a viscous liquid is considered inefficient because the additive fluids are not expected to mix homogeneously due to the large difference in fluid properties in terms of density, surface tension and viscosity. This combined with the current flow rate and resulting current pressure gradient across the injection line may act to cause oscillating injection flow rates for at least one of the injected additive fluids. Based on the teachings of EP 1294473 B1, the average person skilled in the art will only consider injection of a liquid into a gas stream, only one injection element will be considered and only a contact element shaped like a narrowing tube will be considered, as there are no indications of other embodiments or opportunities for improved technical effect.

Despite the advantageous properties of the C100 injection mixer, there is a need for technology that simplifies the injection of several chemicals or additives with one injection mixer, thus reducing the pressure drop and the number of injection mixers. There is also a need for improved technical effect in relation to the C100 injection mixer with regard to the mixing of additive fluid, especially with multifluid additive, deposition of the additive on the inner pipe wall, and also alternative constructions of an injection mixer which may prove to be advantageous for special applications, such as modification of existing equipment to improve the technical effect. A need exists for an injection mixer with a smooth, non-oscillating, minimized additive injection rate (axial mixing) and homogeneous dispersion and distribution of the chemical into the fluid phases (radial mixing) over a wide range of flow conditions, with a narrow range of droplets/ bubble sizes at low pressure drop and low deposition rate for the additive. A need also exists for a mixer to homogeneously mix fluids flowing in a line. A further need exists for an assembly of an injection mixer with additional equipment, particularly suitable for treatment of produced water, treatment of oil, desalination and flow assurance.

Relevant technology has been found described in the patent publications US 4,812,049 A, DE 25 08 665 A1, DE 29521 184 U1 and US 4,989,988 A1. None of the publications describe a multifluid injection mixer where the additive fluid is injected onto a deflecting contact element surface, in that the flowing fluid in the line drives the additive fluid onto and along the deflecting surface until said deflecting surface ends over a sharp edge, with a sharp angle, where the additive fluid releases and breaks up to filaments. No indication of improved technical effect with such features is indicated in the aforementioned publications.

Summary of the invention

The above-mentioned needs are met with the present invention by providing a multifluid injection mixer for injecting gas and/or liquid as an additive fluid to gas and/or liquid flowing through a line, and homogeneous mixing of the additive fluids and the line fluids, the multifluid injection mixer constituting a section of the wire.

The multifluid injection mixer according to claim 1 is characterized by the fact that it comprises:

at least one contact element with at least one contacting surface which faces and deflects a portion of the conduit fluid flow while forming a constriction of the conduit's internal cross-section, so that the conduit fluid flow is accelerated and fluid flowing near said surface is deflected to flow along the surface until the surface terminates over a sharp edge at the point of maximum constriction and flow rate,

at least one injection element arranged with a fluid connection to said surface of the contact element, so that additive fluid can be injected onto said surface and along said surface be carried along by the flowing conduit fluid over the sharp edge, but for a contact element designed as a narrowing pipe section it is arranged at least two injection elements, characterized in that the contact element is shaped as one or more inverse cones or inverse cone rings.

Preferably, the contact element is designed as an inverse cone arranged coaxially to the pipe axis, as this provides an advantageous technical effect, particularly with regard to the deposition of additive fluid on the inner pipe surface. An inverse cone-shaped contact element has the sharp edge at the base of the cone, i.e. the widest part of the cone. A contact element shaped like a cone section has the sharp edge at the narrow base of the cone, i.e. the narrow or truncated part of the cone.

Advantageously, the contact element comprises several cone sections, arranged across the cross-section of the pipe, for example side by side.

The contact element can advantageously comprise several inverse cones or inverse cone sections, arranged over the cross-section of the wire, for example side by side.

Advantageously, the contact element is shaped as one or more rings of inverse conical cross-section, which means at least one ring-shaped contact element where a cross-section along the radius is of an inverse cone shape with two deflecting surfaces. Furthermore, the contact element can comprise combinations of the above designs.

Preferably, there is arranged at least one passageway for conduit fluid along the interior of the pipe wall, which bypasses the contact element, resulting in conduit fluid flow along the interior pipe wall, which reduces deposition of the additives on the interior pipe wall.

The contact element is advantageously assembled from replaceable parts, which allows adaptation of the shape of the contact element to the prevailing conditions, preferably adaptable so that homogeneous mixing is achievable over the entire cross-section of the line at any relevant flow condition. Furthermore, the contact element advantageously includes a suspension with spring folding, so that increased line flow amount results in increased opening for additives and flow amount of additives, which thus provides a self-regulating injection rate of additives. The contact element and the injection element are advantageously integrated as one unit.

The injection element advantageously comprises a channel or openings for injection of additive fluid evenly over the deflecting surface of the contact element, upstream of the sharp edge, one injection element being advantageously arranged for each intended additive fluid, and injection elements for gases are advantageously arranged upstream of injection elements for liquids. Furthermore, the injection elements are advantageously adjustable with regard to openings and pressures for the flow amount of additive fluid of any type or mixtures of additive fluids.

Diverging pipe sections or elements are advantageously arranged downstream of the contact element, to provide a controlled volume of turbulence and an approximation of the pipe pressure and flow rate, by gradually bringing the flow cross-section back to the conduit cross-section. However, the technical effect is also advantageous when the multifluid injection mixer is connected directly to a downstream line or coupling. Accordingly, a diverging pipe or a similar element is not mandatory, which is surprising in light of patent application EP 1294473 B1.

With the expression that the multifluid injection mixer forms a section of the line, it is meant that the injection mixer is introduced as a section in the line or introduced at the beginning or end of the line, so that the line fluids flow through the injection mixer. The term homogeneous mixture in this context means close or intimate mixing, preferably over the overall cross-section of the line, with the additive fluids evenly distributed as small drops or bubbles of very small size, typically a size measured in micrometres. The term a sharp edge in this context means a release edge where the injected fluids leave the inner surface and break up into filaments. The filaments are then broken up into small drops or bubbles. The sharp edge will usually form an acute angle. The expression that the sharp edge is located at the point of maximum constriction and flow velocity means that the sharp edge is located at the downstream end and the most constricted end of the inner surface in relation to the direction of flow along the inner surface, and that the cross-section of the fluid flow immediately further downstream of the sharp edge is somewhat extended. A stagnant volume is thus formed on the underside of the scraped edge, as this stagnant volume is of significant importance for forming a section of intense turbulence which is considered to be of decisive importance for homogeneously mixing the additive fluids and the line fluids.

It is now surprisingly possible to inject more than one additive fluid of any type into a single injection mixer, with one or more injection elements, even if one additive fluid is a high viscosity liquid and another additive fluid is a gas. It is surprising that a technical effect can also be achieved with other forms of contact element than a narrowing line, and some embodiments provide a significantly improved technical effect while other embodiments provide the opportunity to modify existing equipment to improve the technical effect.

The contact element according to the invention is shaped as one or more inverse cones or inverse cone rings, which is considered to provide homogeneous mixing over the entire line cross-section, with the lowest flow rate of additive fluids, over the widest range of prevailing conditions and lowest deposition rate. The stagnant zones on the lee side of the sharp slip edges do not extend to the inner conduit wall for the entire conduit circumference, and they do not extend to the inner conduit wall at all, as this reduces the deposition rate. To achieve that, the contact element deflects the wire flow away from the inner wire wall over a maximum of a portion of the wire circumference.

One injection element is preferably arranged for each additive fluid, on each contact element, and injection elements for gases are preferably arranged upstream in relation to injection elements for liquids, which has proven to be effective. Miscible additive fluids can be injected through an injection element. Additive fluids that form the more stable film flow, usually the additives that have a higher viscosity, are generally injected closer to the sharp edge than the additive fluids that form the less stable filaments or films.

Drawings

The present invention is illustrated by means of drawings, of which:

Figure 1 is a section along the longitudinal axis of a multifluid injection mixer according to the present invention, more specifically an inverse conical ring mixer, Figure 2 is a view from the underside of the mixer according to Figure 1,

Figure 3 is a multifluid injection mixer according to the present invention, with seven cones (contact elements) and three passageways for fluid along the line wall (line fluid openings 10),

Figure 4 is a multifluid injection mixer according to the present invention, where the contact element is shaped as an inverse cone ring,

Figure 5 is an inverse conical ring mixer according to the present invention, which is sometimes referred to as a ring mixer, and

Figures 6 and 7 give results related to Example 5.

Detailed description

Reference is first made to Figure 1, which in a longitudinal section illustrates a multifluid injection mixer 7 according to the present invention, which injection mixer includes a contact element 2, 2a, 2b shaped as an inverse cone ring, that is, the cross section of the contact element, along the radius of the ring , is an inverse cone. The inlet pipe or line 1 carries fluid to be processed to the mixer. The contact element 2, designed as an inverse cone ring with inner 2b and outer 2a contact surfaces, continuously accelerates the fluids in the line towards a prescribed maximum speed and dynamic pressure. The diameter at the outlet of the contact surfaces is determined by the dynamic pressure/traction force required to tear up the injected fluids effectively at a sharp edge 4, 4a, 4b at the outlet. The injection elements 3a and 3b are used for injection of additive fluids to form a liquid/gas bubble film on the inner contact surfaces. The injection elements include a chamber or an annular channel from which injected fluids are directed to the contacting surfaces via a continuous channel. The diameter and length (depth) of the channel, both advantageously adjustable, are calculated from the liquid/gas fluid properties and the liquid/gas additive injection flow rates such that the pressure drop across the circular channel normally exceeds the difference in gravitational force across the circumference for a horizontally mounted mixer. At the downstream end of the contact element, the sharp edges 4a and 4b are located, one for each contact surface, preferably sharp edges with an angle less than 90º, designed so that the liquid/gas bubble film is accelerated by the draft acting from the fluids and torn into liquid/gas bubble filaments in the volume downstream instead of "seeping" at the pipe wall on the downstream side. An expanding element 5, designed as a diverging pipe, is arranged downstream of the contact element and the sharp edge, for deceleration down towards the normal flow velocity in the pipeline. The angle and length of the expanding element is particularly important for turbulence generation and permanent pressure drop across the injection mixer. The outlet pipe 6 leads the processed fluid mixture on. As illustrated in the figure by the size and distribution of small droplets/bubbles in the outlet pipe 6, small droplets and gas bubbles are broken up to extremely small sizes and distributed very evenly over the entire cross-section of the line. The size of the droplets/bubbles can be as small as a few microns.

The embodiment illustrated in Figure 1, having a design as an inverse cone ring, includes two contact surfaces, namely one on each side of the inverse cone, with one injection element for additive injection for each contact surface. The sharp edges are located at 4a and 4b respectively, designed as sharp edge rings. Figure 2 illustrates the multifluid injection mixer in Figure 1, but seen from below, that is from the downstream side. The sharp edges 4a and 4b are indicated. The design illustrated in figures 1 and 2 is very advantageous with regard to mixing and deposition, which means that the injected additive fluids are very evenly mixed in a long section downstream without deposition on the inner conduit surface.

Many alternative geometries are possible, of which a few preferred ones are illustrated. Figure 3 illustrates a multifluid injection mixer with 7 cone-section-shaped contact elements. Said injection mixer provides a large contact surface area and a long length of sharp edge, i.e. drop edge, relative to the cross-section of the pipe. Furthermore, there are three pipeline fluid bypass openings 10 arranged along the interior of the conduit wall, resulting in a "curtain" for conduit fluid along the conduit's inner wall, which lowers the deposition of additives on the inner conduit wall. Consequently, the technical effect is favorable.

Another embodiment can be seen in figure 4, which illustrates an inverse cone ring mixer, where the inverse cone is arranged coaxially with the axis of the pipeline. The volume for turbulence is located downstream and on the leeward side of the inverse cone, which means away from the inner pipe wall, resulting in a low deposition rate for the injected additive fluids.

Figure 5 illustrates an embodiment of the multifluid injection mixer according to the present invention, designated a ring mixer, which mixer is an embodiment of the inverse cone ring mixer illustrated in Figures 1 and 2, and provides a fairly similar technical effect. The deflection of the flow of conduit fluid increases near the sharp edge, which can be beneficial.

As a further explanation and with reference to Figure 1, the drop formation sequence can be divided into four steps of which A indicates that initially an annular film of the injected fluid is subjected to accelerating conduit fluid flow. At B, the particular sharp edge design favors the formation of filaments of the injected fluids into the continuous flow. At C, the filaments of the injected fluid are broken down into small droplets. The degradation is determined by the Weber number (We number) as calculated from the surface tension σ between the conducting fluid phase and the injected fluid, the characteristic filament dimension d, the relative velocity U and the density ρ of the continuous phase (ref. Krzeczkowski, 1980):

We = ρ ∙ U<2>∙ d/ σ

Decomposition corresponds to We > Wecr. For wind tunnel tests and droplet injection into the flow field, Wecrblitt is determined to be 8-10. At D, radial droplet mixing takes place, determined by the initial breakdown of the filament droplets and the local turbulence, as represented by the local Reynolds number of the conduit flow.

It is important to control the injection pressure and the injection rate so that additive fluids are injected on the internal contacting surfaces instead of in the line flow, and so that line fluids do not flow into the injection equipment.

Example 1 - Treatment of produced water

A compilation was used to reduce the content of oil in produced water. The injection mixer had an injection element designed as a cone section. The reblender was according to claim 2 of US 5971 604. Two additive fluids were injected, namely nitrogen gas upstream of a liquid flocculant. Nitrogen can be completely or partially replaced with natural gas. The line length was in the range of 0.1-30 m. The actual volumetric flow rates were generally as follows:

Produced water: Qw

Nitrogen gas: Qw∙ 10<-2>

Flocculant: Qw∙ 10<-5>

With equivalent flow rates, an equal or better performance can be achieved in terms of oil content in the downstream separated produced water, compared to an injection arrangement with two C100 injection mixers according to EP 1294473 B1 in series, at 50% of the pressure drop, or compared to an injection arrangement of flocculant injected into an injection pipe or nozzle upstream of a C100 injection mixer used for gas injection. The pressure drop was in the range 0.02-2 bar depending on the line flow conditions. The injected gas produced a flotation effect. The re-mixer maintained the flotation effect for the gas bubbles and the uniform distribution of the flocculant and gas bubbles over the overall cross-section of the line.

A distance downstream of the re-mixer, oil-water separation equipment is installed, such as a hydrocyclone, which has been shown to be effective in separating oil from water streams that contain gas bubbles and coalesced small oil droplets. The remixer can be regulated with respect to mixing action and can be operated so that the operation of downstream separation equipment becomes efficient, even with somewhat varying line flow rates, to the extent that variations can be compensated for by regulating the mixing action of the remixer. The re-mixer can be replaced by a mixer according to the invention or an injection mixer according to the invention or the C100 injection mixer as the injection mixers are operated without injection of additional chemicals, but simply by being operated as a mixer or alternatively with additional injection of additives. The arrangement according to the invention with the injection mixer and the re-mixer connected to each other via a line section, however, provides a hitherto unknown technical effect for the treatment of produced water. It is believed, without wishing to be bound by any theory, that the injection mixer assembly with gas injection followed by flocculant injection serves to change the velocity profile and wall shear to which the injected flocculant is subjected. The gas is immediately dispersed into bubbles and the flow rate of the multiphase flow is increased locally near the wall of the mixer's injection part. This serves to increase the velocity gradient and thereby also the shear stress applied to the injected flocculant. The result is that an effective homogeneous dispersion of the flocculant is formed. This is particularly important if the residence time for the flocculant before separation is limited.

Example 2 - Treatment of oil

This example relates to the use of the composition according to the invention for a method of treating oil. Traditional oil-water treatment is normally carried out in large horizontal vessels so that the small water droplets can fall out based on gravity. When treating heavy oil systems, it is normally necessary to use considerable amounts of de-emulsifying chemicals to effectively release water from oil to satisfy the required product specification of less than 0.5% BS&W (volume fraction "Basic Sediment and Water"). The demulsifier is a surface-active compound that competes with the natural surface-active agents in the oil to displace these from the oil-water interface. The interface film around the droplets can thus be broken up to facilitate droplet-droplet coalescence.

When using equipment according to known techniques, such as injection nozzles and pipes, it is very difficult to ensure that the demulsifier reaches the droplet surface which is dispersed in the continuous oil flow. Overdosing of chemical can thus become a problem - instead of destabilizing an emulsion, a new emulsion can be formed, which leads to a malfunction in the oil-water separator.

It is known that recycling produced water can improve separator performance due to the increase of critical water fraction and the possible phase inversion to a continuous water system. By using the double injection function of the injection mixer, the recycled produced water and the de-emulsifier can be injected upstream of the production separator. Immediately water together with demulsifier is injected and mixed homogeneously in the continuous phase, the re-mixer according to US 5971 604 is used to form a surface area for droplet-droplet coalescence. With careful re-mixing of the injected chemical, recycled water and the multiphase flow to be treated, the de-emulsifying chemical can reach the new droplet surface area and immediate and efficient water droplet coalescence can begin. Such an effective mixture of demulsifier and subsequent coalescence of small water droplets can reduce the water content of the oil by at least 35% compared to traditional systems. Alternatively, 20% less de-emulsifying chemical can be added to the process and still meet the specification of 0.5% BS&W.

Example 3 - Desalination

This example concerns the use of the assembly according to the invention in a method for desalination of crude oil. Crude oil often contains water, inorganic salts, suspended solids and water-soluble trace metals. As a first step in the refining process, to reduce corrosion, plugging and contamination of equipment and to prevent poisoning of the catalysts in process units, these contaminants must be removed by desalination, extensive admixture injection, including water, multiphase flow mixing and downstream separation.

The two most typical methods for crude oil desalination, based on chemicals and electrostatic separation, use hot water as an extraction agent. In chemical desalination, water and chemical surfactants (demulsifiers) are added to the crude oil, which is heated so that salts and other contaminants dissolve into the water or stick to the water, and are then directed into a tank where they settle to the bottom. Electrical desalination is the application of high voltage electrostatic charges to concentrate suspended small water droplets at the bottom of the settling tank. Practical process adaptation for desalination can also include the combination of these methods.

Equipment according to the state of the art for injection/mixing of injected water/demulsifier, can be the combination of injection pipe with downstream Sulzer mixer or throttle valve.

Application of the assembly according to the invention will ensure efficient and homogeneous distribution of hot water and demulsifier, so that the optimal surface area is formed so that the salt can be extracted from the oil into the injected water. It can be expected that the efficiency of the process will be improved both in terms of the amount of demulsifier required to achieve a specified quality, the pressure drop required for the process, and the volumetric handling capacity of the desalination process.

Example 4 - Flow protection

This example concerns the use of the assembly according to the invention in a method for flow protection. Flow protection includes all features that are important for maintaining the flow of oil & gas from the reservoir to the receiving facilities. Potential pipeline blockages can be related to hydrates, waxes, asphaltenes, coatings or sand.

The formation of hydrates is a major operational and safety problem that can occur unpredictably in subsea pipelines and wellhead facilities. Gas hydrates can potentially form in underwater pipelines unless the water content is removed to below the lowest dew point encountered. Typical precautions are pipeline insulation, heating and/or inhibiting agents. The traditional method of inhibiting hydrates is the injection of methanol or glycol into the pipeline. In this way, the line of hydrate formation is shifted towards lower temperatures for the current pressure level.

When using the assembly according to the invention, methanol together with an irreversibly reacting triazine chemical is injected into the pipeline to simultaneously remove highly corrosive H2S and prevent the formation of hydrates. The triazine-based chemical that forms more stable films or filaments is injected through the injection element closest to the sharp edge in the multi-injection mixer, while methanol or glycol is injected through the injection element furthest from the sharp edge. Thus, the velocity profile of the wire flow is also affected, so that the shear stress on the surface area towards the sharp edge is increased. The result is that a more efficient deformation of the filaments and the formation of secondary droplet breakup of triazine takes place, compared to no immediate injection of methanol upstream of the injection of triazine.

Example 5 - Comparisons with C100 according to EP 1294473 B1

It is surprising that the preferred embodiments of the multifluid injection mixers according to the present invention make use of the turbulence generated by the sharp drop edge to distribute and hold the small droplets in gas phase, and probably correspondingly for any conducting fluid phase, for a longer time than with C100. By changing the geometry that defines the contact element and the sharp edge, the turbulence will surprisingly help to keep the small droplets in the gas phase. The new geometries allow the gas to flow over the sharp edge, as well as the generation of a gas curtain between the wall and the sharp edges. This serves to reduce the deposition of small droplets compared to C100.

The following tables, shown in Figures 6 and 7, show some typical parameters where three embodiments of the present invention are compared with the C100 mixer.

Figure 6 shows the fraction of the total liquid flux (additive fluid) that flows with the gas phase (line fluid) at a position 40 cm after the injection point. The rest of the liquid flows as a liquid film on the wall of the pipeline. As can be seen from the table, significant improvements have been achieved with the present invention with respect to entrained fraction at the downstream position.

Figure 7 shows the pressure drop measured when the mixer was tested with air at 1 bar and a surface speed of 22 m/s. The figure also shows the G-factor, which characterizes the geometry from an aerodynamic point of view. It is advantageous to have G as low as possible, as this represents a potential for low permanent pressure drop across the mixing unit.

The multifluid injection mixer according to the present invention can in principle be used in any industry where mixing, injection and fluid treatment can be carried out in a pipe containing flowing fluids.

Claims (12)

Patent claims 1. Multifluid injection mixer (7) for injection of gas and/or liquid as additive fluid to gas and/or liquid flowing through a line (1), and homogeneous mixing of the additive fluids and line fluids, the multifluid injection mixer forming a section of the line, the multifluid injection mixer includes: at least one contact element (2, 2a, 2b) with at least one contacting surface facing and deflecting part of the line fluid flow while forming a narrowing of the line's internal cross-section, so that the line fluid flow is accelerated and fluid flowing near said surface is deflected to flow along the surface until the surface ends above a sharp edge (4, 4a, 4b) at the point of maximum constriction and flow velocity, at least one injection element (3, 3a, 3b) arranged with a fluid connection to said surface of the contact element, so that additive fluid can be injected onto said surface and along said surface be carried along by the flowing conduit fluid over the sharp edge, but for a contact element designed as a narrowing pipe section, at least two injection elements are arranged, characterized by the contact element is shaped as one or more inverse cones or inverse cone rings. 2. Multifluid injection mixer according to claim 1, characterized by the fact that the contact element comprises several cones, arranged over the cross-section of the wire. 3. Multifluid injection mixer according to claim 1, characterized by the fact that the contact element is designed as one or more inverse cone rings. 4. Multifluid injection mixer according to claim 1, characterized by the fact that the contact element comprises one inverse cone arranged coaxially to the line axis and at least one inverse cone ring. 5. Multifluid injection mixer according to claim 1, characterized in that at least one passageway for line fluid along the inner line wall, for circulation of the contact element, is arranged. 6. Multifluid injection mixer according to claim 1, characterized in that the injection element comprises a channel or openings for injection of additive fluid evenly over the contact surface of the contact element, upstream of the sharp edge. 7. Multifluid injection mixer according to claim 1, characterized by the fact that one injection element is arranged for each intended additive fluid. 8. Multifluid injection mixer according to claim 1, characterized by the fact that injection elements for gases are arranged upstream of injection elements for liquids. 9. Multifluid injection mixer according to claim 1, characterized in that the injection elements are adjustable with regard to openings and pressure for flow rate of additive fluid of any type or mixture of additive fluids. 10. Multifluid injection mixer according to claim 1, characterized by the fact that the contact element is composed of replaceable parts, which enables adaptation of the contact element's shape to the prevailing conditions. 11. Multifluid injection mixer according to claim 1, characterized by the fact that the contact element includes a suspension with a spring effect, so that an increased amount of flow in the line results in an increased opening for additive and the amount of flow of additive. 12. Multifluid injection mixer according to claim 1, characterized by the fact that the contact element and the injection element are integrated as one unit.