GB2189161A - Separators - Google Patents

Abstract

A separator for removing hydrocarbon fuel from water, or solids or water from air, comprises a packing of hollow and perforate spheres 9 enclosed between mesh supports 12, 13. In Fig. 3 water flows inwards through the packing, and fuel therein is coalesced by contact with the oleophilic surfaces of the spheres and rises through quiescent zone 19 created by impervious plate 18. Fig. 5 (not shown) illustrates a separator for air, whose spheres are hydrophilic to coalesce water particles which drain out of the packing, assisted by the shaking of the spheres by the air flow. <IMAGE>

Description

SPECIFICATION Separators The invention relates to separators for removing a contaminant from a fluid particularly, though not exclusively, for use in removing pollutants from water being discharged from a tank, or for removing liquid or particulate matter from air.

Some types of ship are fitted with fuel systems wherein when the fuel tank is emptied of fuel it is refilled with water (a water-compensated fuel system). When these ships are refuelled, it is desirable for the water in the tanks to be discharged rapidly to enable refuelling to be carried out at a reasonable rate.

The water being discharged from a fuel tank will be contaminated with fuel and, in order to avoid pollution, it is necessary to remove as much of the contaminant as possible. International Law requires that the discharge of water into the sea contains less than 100 parts of oil per million parts of water when further than 12 miles from shore, 15 ppm between shore and 12 miles out and nil in special areas such as the Mediterranean. This applies equally to ships, such as tankers, discharging ballast water or tank washing water.

The same problem of removing contaminants from water arises when disposing of drainage water from petrol station forecourts and other areas where fuel and water mix and it is desirable or necessary to remove the contaminants from the water before it can be discharged.

There are several different methods of preventing fuel-polluted water from being discharged. The most basic is simply to let the water stand in a tank for a time to allow the fuel and water to separate into layers before pumping out the water layer. In a ship's water-compensated fuel system the contaminated water may be fed into one tank which is then left. This takes up space that could otherwise be used for fuel.

A coalescing type of separator is used in some instances. This uses a fine filter which filters out the fuel. This works adequately on ships out at sea but, as the filter also removes dirt and other solid matter, it becomes blocked if used where there is a lot of particulate matter in the water eg in harbours or rivers.

In large ships, a gravity type of separator, known as an oily water separator, can be installed. In a known arrangement this comprises a stack of a number of sheets of an oleophilic plastic which are shaped similar to egg trays with a hole in the top of each dimple. The sheets are separated from each other by a small gap and the oily water is passed through the stack. The shape of the sheets provides a flow geometry that encourages all the water to make repeated contacts with the oleophilic surface. The oleophilic surface encourages coagulation of the oil from the oily water and the flow holes allow the oil to migrate upwards such that the water discharged from low down from the separator has most of the contaminating fuel removed.

To provide the flow rate required in refuelling a ship, these separators have to be very large. An alternative is to have a smaller plant which stores the water on board the ship and then discharges it slowly over a couple of days. Both these systems thus take up a space that could otherwise be used for fuel.

The separating of a liquid, such as water, or particulate matter from an air flow is necessary in many situations, particularly in industry, where matter such as sawdust or blastgrit may have to be removed from an air flow, and in vehicle engine air filters. The prior art methods of filtering air include cloth, paper or fibre layer filters through which the air is passed, electrostatic filters, impingement filters, cyclone filters and settling chambers wherein particles are left to settle out of the air.

The object of the invention is to provide a system for separating contaminating matter from fluids, such as fuel from other liquids such as water, or liquid or particulate matter from air. It is a further object of the invention to provide such a separating system which is small and compact whilst still being capable of a rapid flow-through of fluid.

The invention provides a gravity type separator for separating contaminants from fluids, wherein the separator comprises: (a) a fluid inlet (b) a number of hollow spheres including holes through their surfaces contained within a cage; and (c) a fluid outlet.

Conveniently the cage is made of wire mesh or netting or a similar type of material.

Preferably the cage is constructed such that the spheres are contained between an inner cage wall and an outer cage wall. Preferably the fluid discharge outlet is enclosed by the inner cage wall.

Advantageously a strainer is included in the fluid discharge outlet to prevent any of the spheres passing through the outlet if the spheres should escape from the cage for any reason.

Advantageously the shape of the cage is such that the flow paths from outside the cage to the discharge outlet within the inner cage are all approximately the same length.

A separator according to the invention is advantageously used to separate non-miscible liquids. Advantageously the spheres included in such a separator are made from or coated with a material which is chemically attractive to a liquid which is to be separated from the other liquids in the mix. Conveniently in one form the separator is used to remove contam inants, such as fuel, from water. Preferably the spheres in such a separator are made of an oleophilic material, such as an oleophilic plastics material. Alternatively, the spheres may be made from some other material and coated with an oleophilic material.

Preferably, in the separator for separating non-miscible liquids, part of the upper surface of the outer cage wall is a solid plate, which causes the flow through the area beneath it to be lower than through the surrounding area, thus allowing the fuel or other contaminating liquid to coagulate further on the oleophilic surfaces and then to float upwards. Preferably the gross flow through the system is low enough to enable this to occur effectively.

Advantageously the cage is such that it can be built over existing pipes and frames within a tank. This can be done without appreciably altering the performance of the separator.

If the separator is used in a chain of tanks, it is preferably positioned in the final tank in the chain before the discharge outlet.

Conveniently the separator may be left in a tank permanently as it is simple to remove if, for example, the tank requires painting. The spheres can be removed using a dustbin type vacuum cleaner or by any other suitable means, including by hand. Alternatively the separator may be portable and be fitted in a tank when it is required.

Conveniently the separator can be adapted so that the fuel or other fluid collecting under the plate in the top of the cage can be collected if so desired such that the separator is used as an oil (or other fluid) collector.

Preferably the spheres may be used in a separator to remove a liquid from air or particulate matter such as sawdust or blastgrit from air. Advantageously the air outlet is at the top of such a separator and the air and contaminant pass through a cage containing the spheres such that the liquid or particulate matter collects in the areas of low flow within and between the spheres and falls downwards under gravity to a collector at the bottom of the separator. The number of spheres held within the cage is preferably such that the air flow agitates the spheres to help shake the liquid or particulate matter downwards.

If water is to be separated from the air flow, the spheres can advantageously be made of hydrophilic material.

Preferably the size of the spheres is such that the flow-through of fluid through the system is as rapid as required and the size of the system is as small as necessary. The diameter of the spheres is conveniently between 0.5cm and 2.5cm but may be larger or smaller if required. For ease of manufacture, the spheres are advantageously all of approximately the same diameter but the system will also work if the spheres are of varying diameters.

In order that the invention may be more fully understood, it will now be described, by way of example only, with reference to the attached drawings of which: Figure 1 shows a known gravity type oily water separator; Figures 2a and b show two different views of a hollow sphere as used in the invention; Figure 3 is a cross-sectional view of a separator for separating fuel from water according to the invention; Figure 4 shows a separator for separating fuel and water according to the invention built over a frame-work at the bottom of a tank; and Figure 5 shows a separator for separating liquid or particulate matter from air according to the invention.

Referring to Fig. 1, a gravity type oily water separator 1 consists of a number of sheets 2 of an oleophilic plastics material shaped similarly to egg-trays. The sheets are held within a framework (not shown) and are separated from each other by a small gap 3 and each dimple 4 in the sheet 2 has a hole 5 in its top. Oily water 6 flows into the separator 1 and as it passes through the flow geometry of the system causes the fluid 6 to make repeated contacts with the oleophilic surfaces of the sheets 2. The oil in the fluid 6 coagulates on the oleophilic surfaces and then migrates upwards through the holes 5 so that the fluid flowing out of the separator 1 is divided into oil 7 from the top of the separator and water 8 from low down on the separator.

Referring now to Figs. 2a and b, two views of the sphere 9, as used in the invention, are shown. The sphere 9 is hollow and has a number of holes 10 through its surface such that approximately half of the surface of the sphere 9 is holed.

Fig. 3 shows a gravity type of fuel and water separator according to the invention, in cross-section. The spheres 9 are contained within a cage 11, with an outer cage wall 12 and an inner cage wall 13, positioned on the bottom of a tank 14. Contaminated water 15 flows into the cage 11 and flows through the spheres 9. The spheres 9 provide a large surface area on which the oil or other contaminant is deposited and the random packing of the spheres ensures that the fluid 15 follows an undulating path between or through the spheres such that the flow strikes the oleophilic surface repeatedly. The occurrence of stagnant areas within or between the spheres allows the oil etc to coagulate and then migrate upwards. Once the contaminanted water 15 has passed though the cage 11, clean water 16 is drawn from the area within the inner cage wall 13 into a pipe 17 and away to the water discharge outlet (not shown).

A plate 18 is provided on the top of the outer cage wall 12 which has the effect of creating an area with a very low flow rate 19 beneath it This area of low flow 19 encourages the oil etc to coagulate further before floating upwards.

The construction of the cage 11 is simple and robust and can be tailored to fit any tank, while the weight and loss-of-space penalties are minimal.

Fig. 4 shows a fuel and water separator such as that shown in Fig. 3 in position over a framework within a tank. The cage 11 is positioned over the framework 20 on the tank bottom 14 such that the outer 12 and inner 13 (not visible) cage walls fit closely over the framework 20.

Fig. 5 shows a separator for removing a liquid or particulate matter from air. The contaminated air 21 is passed into a tank 22 where the air flow then passes through the spheres 9 held within the outer cage wall 12 and then out through the outlet 23 which is covered by the inner cage wall 13. The liquid or particulate matter collects in the areas of low flow between and within the spheres 9 and falls to the bottom of the tank 22 where it is collected in a container 24 from which it can easily be removed. The air flow through the spheres 9 keeps them agitated which helps to shake the liquid or particulate matter downwards.

A separator sysem using spheres of a material which is chemically attractive to a contaminant which is to be separated from a liquid mix, such as fuel from water, has many advantages over the prior art separator systems. The spheres present a relatively large surface area compared to their volume so a much smaller system can be used to remove contaminants from water than was previously possible without losing effectiveness or having to reduce the flow rate. When the spheres are contained within a cage, as described, the system is easily fitted into any tank or container where it is required. The weight and loss-of space penalties are minimal and the resistance to flow through the system does not significantly reduce the flow through rate from that when no separator is used.

Claims (18)

1. A gravity type separator for separating contaminants from fluids, wherein the separator comprises: (a) a fluid inlet; (b) a number of hollow spheres including holes through their surfaces contained within a cage; and (c) a fluid outlet.

2. A gravity type separator according to claim 1 wherein the cage is constructed such that the spheres are contained between an inner cage wall and an outer cage wall.

3. A gravity type separator according to claim 2 wherein the fluid discharge outlet is enclosed by the inner cage wall.

4. A gravity type separator according to any one preceding claim wherein a strainer is included in the fluid discharge outlet to prevent any of the spheres passing through the outlet if the spheres should escape from the cage for any reason.

5. A gravity type separator according to any one preceding claim wherein the shape of the cage is such that the flow paths from outside the cage to the discharge outlet within the inner cage are all approximately the same length.

6. A gravity type separator according to any one preceding claim, for use in separating non-miscible liquids, wherein the spheres are made from or coated with a material which is chemically attractive to a liquid which is to be separated from the other liquids in the mix.

7. A gravity type separator according to claim 6 for use in removing fuel from water, wherein the spheres are made of an oleophilic material.

8. A gravity type separator according to claim 7 wherein the oleophilic material is an oleophilic plastics material.

9. A gravity type separator according to claim 6 for use in removing fuel from water, wherein the spheres are coated with an oleophilic material.

10. A gravity type separator according to claim 6 wherein part of the upper surface of the outer cage wall is a solid plate, which causes the flow through the area beneath it to be lower than through the surrounding area, thus allowing the fuel or other contaminating liquid to coagulate further on the oleophilic surfaces and then to float upwards.

11. A gravity type separator according to claim 6 wherein the separator is adapted so that the fuel or other fluid collecting under the plate in the top of the cage can be collected.

12. A gravity type separator according to any one of claims 1 to 5, for use as a separator for removing a liquid or particulate matter from air.

13. A gravity type separator according to claim 12 wherein the air outlet is at the top of such a separator and the air and contaminant pass through a cage containing the spheres such that the liquid or particulate matter collects in the areas of low flow within and between the spheres and falls downwards under gravity to a collector at the bottom of the separator.

14. A gravity type separator according to claim 12 or claim 13 wherein the number of spheres held within the cage is such that the air flow agitates the spheres to help shake the liquid or particulate matter downwards.

15. A gravity type separator according to any one of claims 12 to 14, for separating water from air, wherein the spheres are made of a hydrophilic material.

16. A gravity type separator according to any one preceding claim wherein the size of the spheres is such that the flow-through of fluid through the system is as rapid as required and the size of the system is as small as necessary.

17. A gravity type separator according to any one preceding claim wherein the diameter of the spheres is between 0.5cm and 2.5cm.

18. A gravity type separator according to any one preceding claim wherein the spheres are all of approximately the same diameter.