FI123597B - Method and apparatus for separating solids from slurry and use of the method and / or apparatus - Google Patents

Description

METHOD. AND EQUIPMENT FOR DETACHING SOLID FROM THE APPENDIX AND USING THE METHOD AND / OR EQUIPMENT

FIELD OF THE INVENTION

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The invention relates to a method for separating a solid from a slurry as defined in the preamble of claim 1. The invention further relates to apparatus as defined in the preamble of claim 9. The invention further relates to the use of a method and / or apparatus as defined in claim 17.

BACKGROUND OF THE INVENTION

15 Oil sand is a designation for bitumen that is bound to sand grains. Globally, the amount of oil in the oil sands is of the same order of magnitude as conventional petroleum. Widespread use of oil sands has only begun in the last couple of decades of the 20th century, as it is more difficult to exploit than conventional oil.

Bitumen has been formed from petroleum in such a way that petroleum has lost its lighter hydrocarbons and the heaviest part of the 25 is now partially degraded by bacteria. Bitumen is thus a partially degraded crude oil. The oil sand contains 1-20% bitumen.

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δ, The sand grains are surrounded by a water mantle containing various m S5 30 fine particles such as clay and other minerals. The bitumen film surrounding the water w envelope must be separated by sandy

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further processed, co σ>

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co § 35 The extraction and treatment of oil sands for the production of crude oil requires more energy and money than drilling a corresponding amount of oil from conventional sources.

2 As a result, large-scale exploitation of oil sands has not been profitable in the past, but with the rise in oil prices and technological advances, operations have become economically viable. Possibly in the future, as oil sources run out, the use of oil sands as the main source of crude oil will disappear. The environmental impact of refining oil sands is greater than that of conventional oil production.

10 This presentation focuses on the end of the oil sands refining process. finishing the finely divided sludge containing water, sand, clay and fine tailings as a suspension, so that the solids particles are separated as effectively as possible from the water. Large amounts of waste sludge are generated during the refining process. Traditionally, for example, in the oil sands regions of Canada, sludge has been led to large man-made ponds for clarification, however, the clarification is very slow and may take years. Today, efforts have been made to accelerate the separation of solids and water by flocculating sludge and separating solids and liquids with separators such as thickeners, centrifuges and filters. The solids can be used, for example, in earthworks and landscaping and recycled water can be recycled .

c \ j m S5 30 Known in the past for oil sands refining

cvj for example from US 4,224,433 and US

Er 5, 645, 714 Sludge Treatment Methods and Devices

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theists for separating the solid from the sludge, which

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oj contains suspension in liquid and fine solid particles of § 35. A liquid o cm flocculant is added to the slurry in an amount substantially less than the amount of slurry. The slurry and flocculant are mixed to form contact with the fine solids particles and the flocculant to bind the fine solids particles to the flocs. The flocculated slurry is then separated from the solid 5 and the liquid in a separate process step after the flocculation step. The flocculant, or Flok curing agent, is usually a long chain polymer which, when uniformly mixed with the slurry, electrochemically "glues" fine solids particles 10 together to form flocs large enough to be separated from the liquid by conventional separation techniques.

Known processes for mixing the flocculant with 15 slurries have employed a static mixer, several blade mixers in a row, or a drum mixer. The static mixer consists of a flow-through tube having a series of helical flow guides integral to its inner walls. The blade mixer comprises a rotatable blade rotor near the bottom of the mixing tank 20. In the blade blender, strong shear mixing produces a big swirl, but at the tip of the blade there is a large difference in speed and it causes too high turbulence with high energy intensity. It breaks the formed 25 flocs. The drum mixer is a rotatable drum with mixing blades attached to the inside of the wall. As the drum rotates, the blades mix and raise the pulp

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^ dropping it each round.

c \ j m S5 30 The problem with all these mixers is that, when mixed, the sludge is subjected to

Er shear forces that break the flocks already formed Q.

to smaller portions, impairing the efficiency of the post-mix separation step and undesirably leaving the liquid

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g 35 still fine solids. An attempt is made to improve the situation by increasing the amount of flocculant, which consumes a large amount of flocculant, which is detrimental because the 4 flocculants are very expensive. A further problem is that the separation step requires a larger sized separation plant than would be required if the flocs did not break during mixing. Further, the flow rate of the solids slurry to be treated is high in comparison with the flow rate of the flocculant to be mixed therewith, which makes it difficult to achieve uniform mixing by conventional mixing methods.

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PURPOSE OF THE INVENTION

The object of the invention is to eliminate the above disadvantages.

In particular, it is an object of the invention to provide a method and apparatus for providing a very gentle and flocculent-free mixture.

It is a further object of the present invention to provide a process and apparatus which allow the amount of flocculant required to be reduced and provide cost savings.

It is yet another object of the invention to provide a method and apparatus which allows the size of the apparatus required for the separation step after the flocculation step to be reduced and the separation to be accelerated, co δ

SUMMARY OF THE INVENTION

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S5 30 The method according to the invention is characterized by what is claimed in claim 1. Further, the apparatus according to the invention is characterized by Q.

what is claimed in claim 9. Still for the use of the method and apparatus according to the invention

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g 35 is characterized by what is set forth in claim 17.

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According to the invention, the flocculant is mixed with the slurry in a slurry rotor mixer at low agitation intensity by gently bringing the mixture into a vertical circulation flow in the cylindrical container 5 of the mixer, thereby generating smaller turbulent flows without substantially exerting shear forces on the mixture.

Similarly, according to the invention, the mixer included in the apparatus is a helical rotor mixer adapted to mix the flocculant slurry with low mixing intensity gently and essentially without applying shear forces to avoid flocculent cleavage.

The method and apparatus of the invention are particularly useful for separating solids from sludge in an oil sand refining process, wherein the slurry to be treated is a sludge containing fine solids from the oil sands refining process, wherein the fine solids are mainly sand and clay, jäännösbitumia.

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However, the invention is not limited to an oil-sand application, but is useful where

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£ in any separation of slurry solids and liquid in which the flocculant is mixed with slurry prior to separation

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9 to 30 teas.

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An advantage of the invention is that with a helical rotor mixer

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a very gentle and uniform mixing of the flocculant at low and uniform intensity with the slurry § 35 is achieved so that the mixture is subjected as much as possible to the low shear-breaking shear forces and the intense turbulence that they produce. The helical rotor mixer 6 provides a lot of slurry moving area, whereby the energy is evenly distributed in the mixture. The helical mixer does not have any tips that would produce strong turbulence and cleavage of the flocs. The helical rotor mixer can cover the entire volume of slurry, thereby ensuring that it rotates the slurry throughout the tank at every point. When using a helical rotor mixer flocculant, a smaller amount of 10 is required than with conventional mixers, whereby significant cost savings can be obtained. Further, the size of the separation device after the mixer can be reduced, which also results in significant cost savings.

In one embodiment of the method, the vertical vortex flow and the turbulent flows are formed by a helical rotor mixer having at least one helical rotor rotary rotor rotating with a helical element at a constant radius of rotation.

In one embodiment of the method, the flocculant is mixed with the slurry with a helical rotor mixer having a plurality of helical rotors. The larger the slurry-25 platform to be mixed and the larger the mixing tank, the more advantageous it is to use more coil rotors in the same tank. Only one coil rotor can be used in a small container, but if only one Large in S5 30 rotor is used in a large container, the peripheral speed of the rotor may become too high and floccular fragment turbulence may begin to form. In addition, you will come across strength-

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points. It is advantageous to increase the number of coil rotors-coxxj in order to keep the peripheral speeds low.

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§ 35 ° In one embodiment of the method, the flocculant is mixed with the slurry at a mixing intensity of from about 0.04 to 0.3 kW / m3, preferably up to 0.10 kW / m3.

In one embodiment of the method, a long chain anionic or cationic polymer such as polyacrylamide (PAM) and / or polyethyl oxide (PEO) is used as a flocculant.

In one embodiment of the process, a separate separation step after the flocculation step 10, wherein the solid and liquid are separated from the flocculated slurry, is provided by a thickener / clarifier, centrifuge or vacuum filtration.

In one embodiment of the method, the flocculant is mixed with the slurry at a volume flow rate of the order of 1:40.

In one embodiment of the apparatus, the helical rotor 20 mixer comprises a reservoir having an interior space limited laterally by a cylindrical side wall and a downwardly facing bottom; at least one helical rotor disposed indoors; a power unit for rotating the helical rotor, and a plurality of elongated vertical flow deflections extending from the sidewall to the central axis of the container.

In one embodiment of the apparatus, the helical rotor ^ comprises a vertical axis of rotation coupled to the power unit and a helical element attached to the axis of rotation by means of a beam spacing

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^ In one embodiment of the hardware, the helical member is

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§ 35 of circular cross section, such as pipe, no

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In one embodiment of the apparatus, the helical member has a non-circular cross-section, such as a flat rectangle.

5 In one embodiment of the apparatus, the helical rotor mixer includes a plurality of helical rotors.

In one embodiment of the apparatus, the helical rotor mixer comprises 2-8 helical rotors.

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In one embodiment of the apparatus, the rotary axes of the helical rotors are arranged radially relative to the vertical center axis of the container and at a constant distance from each other.

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LIST OF FIGURES

In the following, the invention will be described in detail by way of example with reference to the accompanying drawing, in which Figure 1 schematically illustrates a part of the process to which the invention relates, i.e. a mixer and a separator.

Figure 2 is a sectional view of an embodiment of a rotary rotor mixer according to the invention; Figure 3 is a sectional view III-III of Figure 2;

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Figures 4-6 show sections similar to Fig. 3

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c? 30 of the other three applications of the helical rotor mixer, c.

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DETAILED DESCRIPTION OF THE INVENTION

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Fig. 1 is a flow chart of a part of the process which runs g 35 for mixer 1 and subsequent separator O 0 CM 2.

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A slurry containing liquid and fine solid particles in suspension is introduced into mixer 1. The liquid flocculant is added to the slurry in an amount substantially less than the amount of slurry.

Mixer 1 mixes the slurry and the flocculant to form contact with the fine solids particles and the flocculant to bind the fine solids particles to the flocculants. From the mixer, the flocculated slurry is led to a separator 2 where the solid and liquid are separated from the 10 flocculated slurry.

The flocculant is mixed with the slurry, for example, by means of a helical rotor mixer 1 of Figure 2 at a low mixing intensity of, for example, 0.04 to 0.3 kW / m3, preferably up to 0.10 kW / m3, by gentle placing the mixture in the mixer cylindrical container while forming smaller turbulent microfluidic currents without substantially applying shear forces to the mixture to avoid flocculation. The vertical macrocirculation flow and turbulent microcurrents are formed by a helical rotor mixer-2.

2 and 3 illustrate an embodiment in which the rotary rotor mixer 1 comprises three pieces of double twin rotor 7. The rotor rotary mixer LT3 S5 30 1 includes a container 3 whose interior space 4 is delimited sideways by a cylindrical side wall 5 and an anvil facing bottom 6. which is

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shown in the interior 4 at a radius from the center of the container to the triangle as shown in Figure 3. The double-coil rotor 7 of the jacket 35 is driven by a power unit 8. Flow imperfections 9 project from the side wall 5 of the container 3 towards the central axis of the container. Each double helical rotor 10 comprises a vertical rotary axis 10 connected to a power unit 8 and two identical helical tubes 11 which are circular in cross-section and are fixed to the rotation shaft 10 by means of support arms 12 spaced symmetrically with each other.

Figures 4 to 6 illustrate still other possible mixers having different amounts of twin-screw spindle rotors 7. In Fig. 4, mixer 1 has only one centrally located twin-screw rotor 7. Fig. 5 mixer 1 has five twin-screw spindles 7 arranged in pentagonal symmetrically. The mixer 1 of Fig. 6 has eight double helical rotors 7 arranged in a pentagonal shape symmetrically about the vertical center axis of the container. The double helix rotors 7 may be any suitable number.

The examples above refer only exemplarily to a double helical rotor having two helical members. Depending on the application, the helical rotor may have only one helical member. Two coil members in one rotor make the root-25 torque structurally more robust and provide a more even distribution of mixing power compared to one coil member. In turn, the coil can be

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^ of non-circular cross-section.

^ It may be a spiral bent sheet, in which case S5 30 has a flat rectangle.

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The invention is not limited to the above embodiments only, but many variations are possible within the scope of the inventive idea set forth in Claim 35,

Claims (15)

A process for separating solids from waste sludge which arises in a refining process of oil sand and contains finely divided solids containing the water in suspension containing small amounts of residual bitumen and fine particles of solids which are mainly sand and clay, and in which process - liquid flocculant is added to the sludge in an amount substantially less than the amount of sludge, - the sludge and flocculant are mixed to form the fine solid particles and the flocculant to bond the fine particles 15. From the flocculated sludge, the solid and the liquid are separated from each other in a separate process stage after the flocculation stage, characterized in that the flocculant is gently mixed in the slurry with a spiral rotor mixer with a low mixing intensity by passing the mixture into a vertical macrocirculation flow in the mix the cylinder-shaped containers and at the same time, in the form of less turbulent micro-flows substantially without directing cutting forces towards the mixture to avoid splitting the flock. 25 Method according to claim 1, characterized in that the vertical spiral flow and the turbulent flows are formed with a spiral rotor mixer, in whose container ui) there is at least one helical rotor (helix rotor) provided with spiral means rotating a vertical axis of rotation at a standard radius. X DC CL CD 3. A process according to claim 1 or 2, characterized in that the flocculant is mixed in the sludge σ> g with a spiral rotor mixer comprising several spiral rotors. Process according to any of claims 1-3, characterized in that the flocculant is mixed in the sludge with a mixing intensity of the order of 0.04 - 0.3 kW / m3, preferably at most 0.10 kW / m3. 5 Process according to any of claims 1 to 4, characterized in that, as a curative agent, long-chain anionic or cationic polymer such as polyacrylamide (PAM) and / or polyethyloxide (PEO) is used. 10 Process according to any one of claims 1-5, characterized in that the separate separation stage after the flocculation stage, in which solid and liquid are separated from each other from the flocculated sludge, is accomplished with a thickening / sedimentation apparatus, a centrifuge or with vacuum filtration. Process according to any one of claims 1-6, characterized in that the flocculant is mixed in the slurry in a ratio of volume flows of the order of 1:40. 8. Plant for separating solids from waste sludge, which arises during a refining process of oil sand and contains finely divided solids containing the water in suspension containing small amounts of residual bitumen and fine particles of solids which are mainly sand and clay, and wherein the plant comprises m S5 - a mixer (1) for mixing flocculating agents to make contact between fine particles of solids and flocculants to bond the fine CL particles of solids - a separating device (2) arranged after the CD g mixer to separate solid and liquid, characterized in that the mixer (1) is a spiral rotor mixer adapted to gently mix the flocculant in the sludge with a low mixing intensity and substantially without directing cutting forces to avoid splitting the flock. Installation according to claim 8, characterized in that the spiral rotor mixer (1) comprises - a container (3), the inner space (4) of which is bounded on the side by a cylindrical side wall (5) and down-sealed by a bottom (6), - at least one spiral rotor (7) arranged in the inner space (4), - a force device (8) for rotating the spiral rotor (7), and - a plurality of elongated vertical flow barriers (9) pushing out of the side wall towards the center of the container. Installation according to claim 9, characterized in that the spiral rotor (7) comprises 20. a vertical axis of rotation (10) provided with the force device (8), and - one or two spiral members (11) which are clamped at the axis of rotation (10) with support arms (12) at a distance from the axis of rotation. 25 Installation according to claim 10, characterized in that the spiral means (11) has a circular cross-section. co δ 12. Installation according to claim 11, characterized in that the spiral member (11) has a non-circular cross-section, such as a flat rectangle. X cc CL Installation according to any of claims 8 - 12, characterized in that the spiral rotor mixer (1) CD § 35 comprises several spiral rotors (7). o c \ j Installation according to claim 13, characterized in that the spiral rotor mixer (1) comprises 2-8 spiral rotors (7). Installation according to claim 14, characterized in that the rotary axes (10) of the spiral rotors (7) are arranged radially in relation to the vertical center axis of the container (3). co δ c \ j i m o C \ l X cc CL CD O) CM CD O) O O CM