WO2019151871A1

WO2019151871A1 - Separator for separating liquids

Info

Publication number: WO2019151871A1
Application number: PCT/NO2019/050016
Authority: WO
Inventors: Jan Inge Eielsen
Original assignee: Loss Prevention As
Priority date: 2018-02-05
Filing date: 2019-01-23
Publication date: 2019-08-08
Also published as: NO344226B1; NO20180184A1

Abstract

It is described a separator (1) for separating at least two liquids having different density, the separator (1) comprising: - an inlet (3) having a first cross sectional area; - a flow channel (4) in fluid communication with the inlet (3), the flow channel (4) having a second cross sectional area being larger than the first cross sectional area; - a separation chamber (5) in fluid communication with the flow channel (4), the separation chamber (5) having a third cross sectional area being larger than the second cross sectional area; - a first outlet (6) in fluid communication with the separation chamber (5) for drainage of the liquid having the lower density; and - a second outlet (7) in fluid communication with the separation chamber (5) for drainage of the liquid having the highest density, wherein the separator (1) further comprises a first weir (62) for overflow of the lower density liquid and a second weir (712) for overflow of the highest density fluid, the first weir (62) having a higher elevation relative to the second weir (712).

Description

SEPARATOR FOR SEPARATING LIQUIDS

This invention relates to a separator for separating at least two liquids having different density. More particularly, the invention relates to a separator for separating oil from water after an oil spill. The separator is arranged with several flow chambers to reduce the flow velocity of the liquids and create a laminar flow such that gravity results in the liquids sep arating. Even more particularly, the invention relates to a separator having an outlet for water arranged such that the centre of the water outlet is near a liquid level in the separa tor for reducing the hydrostatic pressure at said outlet. The separator further has an outlet for oil arranged such that the centre of the oil outlet is below the liquid level in the separa- tor for increasing the hydrostatic pressure at said outlet.

During or after an oil spill at sea the oil is often contained within an oil retention system. The oil, together with a considerable amount of water, is pumped up from the retention system to an intermediate storage, said storage often being tanks on a vessel. It is not uncommon that the ratio of water to oil is in the range 2:1 , or higher. Thus, the oil recu- peration efficiency is low as water take up much of the volume in the tanks.

It is known to have a separator onboard an oil response vessel for separating water and oil before storing the oil in the tanks and pumping the water back to sea. The vessels used for oil spill response are often multi-purpose vessels, and thus having a separator system onboard these vessels permanently is impractical and expensive. It is therefore a need for a separator system that quickly can be mobilized onboard an oil spill response vessel. It is further a need for a simple and robust separator system that can be operated by the crew onboard the vessel, and eliminate the need for dedicated operators.

Patent document US5149443 discloses a system for recovering oil from the ocean con trolled by a wave profile generating computer. In addition, the invention relates to a sys- tern for separating oil from water before sending the separated oil to storage tanks in a vessel. The separation system comprises a series of tanks incorporated into the structure of the vessel. The system further comprises comprehensive pipe works and sensoring equipment. The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow. The invention is defined by the independent patent claim. The dependent claims define advantageous embodiments of the invention.

More specifically, the invention relates to a separator for separating at least two liquids having different density, the separator comprising:

- an inlet having a first cross sectional area;

- a flow channel in fluid communication with the inlet, the flow channel having a second cross sectional area being larger than the first cross sectional area;

- a separation chamber in fluid communication with the flow channel, the separation chamber having a third cross sectional area being larger than the second cross sectional area;

- a first outlet in fluid communication with the separation chamber for drainage of the liquid having the lower density; and

- a second outlet in fluid communication with the separation chamber for drainage of the liquid having the highest density,

wherein the separator further comprises a first weir for overflow of the lower density liquid and a second weir for overflow of the highest density fluid, the first weir having a higher elevation relative to the second weir.

The invention solves the abovementioned challenges by providing a separator which is a single unit and easy to use. The size of the unit may be scaled depending on the available space where it is intended to be used. The separator can quickly be mobilized onboard a vessel as it only requires connection to a pumping system and hoses or pipes connected to the inlet, the first outlet and the second outlet before it is ready to use.

The flow channel may have a width substantially equal to an internal width of the separa tor for maximizing the cross-sectional area of the flow channel. The flow channel may be in fluid communication with the separation chamber via a vertical channel. A width of the separation chamber may be substantially equal to the internal width of the separator. In use, the liquids will flow from the inlet to the separation chamber via the flow channel and the vertical channel. After entering the separation chamber, the liquids will flow through the separation chamber and be drained out through the first outlet and the second outlet. The separation of the liquids may start in the flow channel as the flow velocity of the liq uids is considerably reduced compared to the flow velocity of the liquids through the inlet. The flow rate of the liquids through the inlet may be controlled to adjust the time it takes for a portion of the liquids to flow from the inlet to the first outlet or the second outlet. The longer time a portion of the liquids spend on flowing through the flow channel and the separation chamber, the better separation may be obtained. The cross-sectional areas have an increasing size relative to each other for reducing the flow velocity through the separator, and thus allow more time for separation.

The first weir may define a maximum liquid level in the separation chamber. A weir may be defined as a spillway. A first liquid column below the first weir may comprise a mix of the two liquids. The second weir may be arranged such that the liquids would have to flow via a lower portion of the separation chamber to reach the second weir. Thus, a second liquid column below the second weir may comprise substantially only the liquid having the highest density. This may result in a hydrostatic pressure formed by the second liquid col- umn being equal to a hydrostatic pressure formed by the first liquid column, even though the first liquid column is higher than the second liquid column. This allows the first weir to have a higher elevation relative to the second weir, and still liquid may drain over both weirs, and not only the weir having the lower elevation.

In one embodiment, the first outlet may be arranged at a lower elevation than the first weir and the second outlet may be arranged at a lower elevation than second weir. The first outlet may be positioned on a side of the first weir being opposite to the first liquid column. The second outlet may be positioned on a side of the second weir being opposite to the second liquid column. The first and second outlet may be positioned in the lower portion of the separator. This may create a column of the respective liquid above each respective outlet. The column of the respective liquid may form a hydrostatic pressure at the respec tive outlet which may improve drainage through the outlets.

The separator may in one embodiment comprise a plurality of partial partition walls ar ranged in the separation chamber. By partial it is meant a wall that does not cover the entire cross section of the separation chamber for allowing liquid to flow past the wall. At least one of the partial partition walls may be arranged substantially vertical. At least one of the partial partition walls may be arranged angularly relative to a vertical axis in a posi tion of use of the separator. When the separator is in use, the partial partition walls may slow the rate of liquid transfer in a longitudinal direction and/or a transverse direction of the separator if the separator is moving. Movement of the separator may for example oc cur if it is located on a ship floating on a sea.

The partial partition walls may improve separation of the liquids. During separation, drop lets of the liquid having the lower density may be trapped in the liquid having the highest density. The droplets may be trapped because they do not have sufficient buoyancy to float upwards in the highest density liquid. The droplets may attach to a surface of the partial partition walls. Adjacent droplets attached to the surface may merge and form a larger drop. At a certain size, the drop will get sufficient buoyancy to release from the sur face and float upwards in the highest density liquid, thus separating from said liquid. At least one of the partial partition walls may be configured to be heated. In one embodi ment, all the partial partition walls may be heated. Decreasing temperature may cause a viscosity of one liquid, or both liquids, to increase. The viscosity affects the flow properties of a liquid, and a high viscosity makes a liquid more resistant to flow. If a liquid tempera ture is low, or a surrounding air temperature is low, the liquids may flow poorly. Heating the partial partition walls may increase the temperature of the liquids and make the liquids less resistant to flow.

The separator may comprise an impulse brake arranged in the flow channel for distrib uting a flow of the liquids from the inlet over a width of the flow channel. The impulse brake may comprise of a plurality of guides. The guides may be arranged with different orientation for distributing the flow. The impulse brake may distribute the flow to reduce the flow velocity of the liquids.

The separator may in one embodiment comprise a pump for improving drainage of the separation chamber. For example, during tapping of the separator, it may be required to use a pump inside the separation chamber for draining the lower density liquid. In one embodiment, the separator may further comprise a removable end wall wherein the inlet, the first outlet, the second outlet, the first weir and the second weir are arranged on the removable end wall. The removable wall may give access to an inside of the separa tor for service and/or cleaning.

In one embodiment, the separator may be placed within a container. The container may be a standard 20-foot shipping container. Placing the separator inside a container simplify transport and handling of the separator. The container may be secured to a transport ve hicle or vessel using standard securing means, such as container twist locks. The con- tainer may be lifted using standard lifting means, such as a lifting spreader beam or a truck loading system.

In the following is described an example of a preferred embodiment illustrated in the ac companying drawings, wherein: Fig. 1 shows a cross section of a separator according to the embodiment of the invention;

Fig. 2a shows, in a smaller scale than figure 1 , an end view of the separator;

Fig. 2b shows, in a smaller scale than figure 2a, a cross section A-A of the separa tor in figure 2a; Fig. 2c shows, in the same scale as figure 2b, a cross section B-B of the separator in figure 2a;

Fig. 2d shows, in the same scale as figure 2b, a cross section C-C of the separator in figure 2a;

Fig. 3a shows, in a larger scale than figure 1 , an end wall of the separator from an inside of the separator;

Fig. 3b shows, in the same scale as figure 3a, a cross section D-D of the end wall in figure 3a;

Fig. 3c shows, in the same scale as figure 3a, a cross section E-E of the end wall in figure 3a; and Fig. 4 shows, in the same scale as figure 1 , a horizontal cross-section F-F of the separator in figure 2a.

The figures are depicted in a simplified manner, and details that are not relevant to illus trate what is new with the invention may have been excluded from the figures. The differ ent elements in the figures may necessarily not be shown in the correct scale in relation to each other. Equal reference numbers refer to equal or similar elements.

In what follows, the reference numeral 1 indicates a separator according to one embodi ment of the invention. The separator 1 comprises an inlet 3. The inlet 3 is shown to be in fluid communication with a flow channel 4 stretching from a first end portion 200 to a sec- ond end portion 201 of the separator 1. The flow channel 4 is in fluid communication with a separation chamber 5 stretching from the second end portion 201 to the first end portion 200 of the separator 1. The first end portion 200 of the separator 1 is shown with a first outlet 6 and a second outlet 7 (see figure 2c and 2d) for drainage of the liquids from the separation chamber 5. The separator 1 is configured for separating at least two liquids having different density, for example oil and water, wherein oil has a lower density than water. In what follows oil and water will be used to describe the at least two liquids. How ever, it should be understood that the at least two liquids may be any liquids having differ ent density. Figure 1 shows a cross section of the separator 1. The inlet 3 is configured to receive, in use, a mixture of oil and water. The mixture may come from a sea where there has been an oil spill. The mixture may be pumped from the sea to the separator via a hose (not shown) for separation of the oil and the water prior to collecting the separated oil in transport tanks (not shown), for example on a vessel (not shown). A flow velocity of the mixture may be high through the inlet 3, creating a turbulent flow of the mixture. The flow channel 4 forms a larger cross-sectional area (not shown) than the inlet 3 for reducing the flow velocity of the mixture. In the figures, a width of the flow channel 4 is equal to the internal width of the separator 1. As the flow velocity reaches a certain value, the flow may become laminar. The flow channel 4 is shown to be in fluid communication with the separation chamber 5 via a substantially vertical channel 8. The oil and water enter the separation chamber 5 through a chamber inlet 9 arranged in a substantially vertical centre of the separation chamber 5. The separation chamber 5 forms a larger cross-sectional area (not shown) than the cross-sectional area of the flow channel 4 to further reduce the flow velocity of the oil and water. The oil and the water will flow from the second end portion 201 towards the first end portion 200. During a period of time it takes for a particle in the oil or water to flow from the second end portion 201 to the first end portion 200, most of the oil may be separated from the water. At the first end portion 200 there will be a clear distinction be tween a bottom layer of water and an upper layer of oil (not shown). The separation chamber 5 is provided with a plurality of partial vertical partition walls 10 and a plurality of partial angular partition walls 1 1. In the figures the separation chamber 5 is shown to have eleven vertical partition walls 10 and twelve angular partition walls 1 1. The separation walls 10, 1 1 may aid in the separation of oil and water. Droplets of oil that are contained in the water and, because of their size, do not have sufficient buoyancy to separate from the water, may stick to a surface 101 of the separation walls 10,1 1. As more droplets stick to the surface 101 , the droplets may merge together and form a drop large enough to obtain the buoyancy required to float upwards and separate from the wa ter. The surface 101 of the partition walls 10, 1 1 may be heated. A viscosity of oil is depend ent on a temperature of the oil. The lower the oil temperature, the higher the viscosity of the oil becomes. The viscosity affects the flow properties of the oil. Higher viscosity makes the oil more resistant to flow. If the oil is mixed with seawater, the temperature may be come low, and thus the oil viscosity becomes high. In another scenario, an air tempera- ture may be low, which may cool the separator 1 , thus reducing the oil temperature and increasing the viscosity. Heating the surface 101 of the partition walls 10, 1 1 may heat the oil and lower its viscosity, making the oil flow easier.

Figure 2a shows an end view of the separator 1 . An end wall 20 may be removable and/or possible to open. The end wall 20 may for example be bolted, hinged or clamped to the first end portion 200 of the separator 1 . Removing/opening the end wall 20 enables ac cess to an interior 50 of the separator 1 , for example for cleaning, inspection or service.

Figure 2b shows a cross-section A-A of the separator 1 . The cross-section A-A cuts through a centre of the inlet 3. An arrow 30 shows a direction of flow through the inlet 3. Figure 2c shows a cross-section B-B of the separator 1 . The cross-section B-B cuts through a centre of the first outlet 6. The first outlet 6 is arranged in a lower portion 60 of an open-top duct 61. The duct 61 extends from a lower portion 51 of the separation chamber 5 to an upper portion 52 of the separation chamber 5. A first weir 62 defines an upper edge 62 of the duct 61 and defines a maximum liquid level in the separation cham ber 5. If the liquid level exceeds the first weir, liquid will flow over the weir 62 and to the first outlet 6. In use, most of the oil and water may be separated when arriving to the first end portion 200 of the separation chamber 5. Thus, the liquid having the lowest density, oil in this specific example, will float on top and spill over the weir 62 before being drained through the first outlet 6. A column of oil in the duct 61 may form a hydrostatic pressure at the first outlet 6, improving the drainage of oil through the first outlet 6. Figure 2d shows a cross-section C-C of the separator 1 . The cross-section C-C cuts through a centre of the second outlet 7. The second outlet 7 is arranged in a lower portion 72 of a double duct 71. A first duct 710 of the double duct 71 extends from the lower por tion 51 of the separation chamber 5 to the upper portion 52 of the separation chamber 5. A second weir 712 defines a maximum liquid level in the first duct 710. If the liquid level in the first duct 710 exceeds the level of the second weir 712, liquid will flow over the second weir 712 towards the second outlet 7. An elevation of the first weir 61 is higher relative to an elevation of the second weir 712. Figure 3a shows the end wall 20 from the inside 50 of the separation chamber 5. An angu lar wall 67, 68 is arranged to guide the oil and water towards the first outlet 6 and the sec ond outlet 7 respectively. Figure 3b shows a cross-section E-E of the end wall 20, through a centre of the first outlet 6. Arrows 1 1 indicate the flow path of the liquid having the lower density over the first weir 62, via the open-top duct 61 and through the first outlet 6. Figure 3c shows a cross-section D-D of the end wall 20, through a centre of the second outlet 7. Arrows 12 indicates the flow path of the liquid having the higher density through the first duct 710, over the second weir 712, towards the second outlet 7 via a second duct 71 1.

In use, a liquid column in the separation chamber 5 contain oil and water. As most of the liquid will be separated at the first end portion 200, oil will be floating on top of the water. Thus, mainly water may be present in the first duct 710. As the density of water is higher than the density of oil, a column of water will form a higher hydrostatic pressure than a column of oil and water having the same height as the water column. This is one of the main principles of the invention. To obtain an even hydrostatic pressure between the col- umn of mainly water in the first duct 710 and the column of oil and water in the separation chamber 5, the column in the separation chamber 5 must be higher than the column in the first duct 710. This enables the first weir 62 to be positioned at a higher elevation relative to the second weir 712, without water flowing over the second weir 712 and thus continu ously keeping the liquid level below the first weir 62. Figure 4 shows a horizontal cross-section F-F of the separator 1 , through the inlet 3 and the flow channel 4. An impulse brake 13 is arranged in the flow channel 4 to distribute the flow from the inlet 3 over the substantially whole width of the flow channel 4. The impulse brake 13 comprises a plurality of guides 130, in the figure shown with three guides 130, with different orientation. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodi ments without departing from the scope of the appended claims.

Claims

C l a i m s

1 . A separator (1 ) for separating at least two liquids having different density, the separator (1 ) comprising:

- an inlet (3) having a first cross sectional area;

- a flow channel (4) in fluid communication with the inlet (3), the flow channel (4) having a second cross sectional area being larger than the first cross sectional area;

- a separation chamber (5) in fluid communication with the flow channel (4), the separation chamber (5) having a third cross sectional area being larger than the second cross sectional area;

- a first outlet (6) in fluid communication with the separation chamber (5) for drainage of the liquid having the lower density; and

- a second outlet (7) in fluid communication with the separation chamber (5) for drainage of the liquid having the highest density,

c h a r a c t e r i s e d i n that a the separator (1 ) further comprises a first weir (62) for overflow of the lower density liquid and a second weir (712) for overflow of the highest density fluid, the first weir (62) having a higher elevation relative to the second weir (712).

2. The separator (1 ) according to claim 1 , wherein the first outlet (6) is arranged at a lower elevation than the first weir (62) and the second outlet (7) is arranged at a lower elevation than second weir (712).

3. The separator (1 ) according to claim 1 or 2, further comprising a plurality of par tial partition walls (10,1 1 ) arranged in the separation chamber (5).

4. The separator (1 ) according to any of the claims 1 -3, wherein at least one of the partial partition walls (10,1 1 ) is configured to be heated.

5. The separator (1 ) according to any of the preceding claims, further comprising a pump for improving drainage of the separation chamber (5).

6. The separator (1 ) according to any of the preceding claims, further comprising an impulse brake (13) arranged in the flow channel (4) for distributing a flow of the liquids from the inlet (3) over a width of the flow channel (4).

7. The separator (1 ) according to any of the preceding claims, further comprising a removable end wall (20) wherein the inlet (3), the first outlet (6), the second outlet (7), the first weir (62) and the second weir (712) are arranged on the removable end wall (20).

8. The separator (1 ) according to any of the preceding claims, wherein the separa tor (1 ) is placed within a container.