GB2104791A

GB2104791A - Liquid separator

Info

Publication number: GB2104791A
Application number: GB08126664A
Authority: GB
Inventors: A W Toms
Original assignee: STETFIELD Ltd
Current assignee: STETFIELD Ltd
Priority date: 1981-09-03
Filing date: 1981-09-03
Publication date: 1983-03-16
Also published as: GB2104791B

Abstract

A suspension of oil and water is introduced at (22) to a liquid separator, including a porous bed defined between a top grill (25), an entry grill (26), and an exit grill (15). The water flows largely horizontally through the bed to exit grill (15) for collection over a weir (18) whose level is above the top grill (25) but below a weir (32) for collection of the oil. Oil separates partly in upstream settling space (21), to flow over weir (24), and partly coalesces in the bed and rises through grill (25) to weir (32). Grill (26) excludes solids from the bed, but the bed may be reverse-flow cleaned automatically if it clogs. The bed comprises packed hollow particles. <IMAGE>

Description

SPECIFICATION Liquid separator This invention relates to a liquid separator for example for separating oil from water or other coolant, although it is generally applicable to the separation of any two immiscible liquids, one of which is denser than the other.

It is already known to provide a porous bed into which the mixture is introduced because in such a bed the lighter liquids tends to rise and heavier liquid tends to fall faster than would normally be the case under gravity in a free chamber.

An object of the invention is to provide an improved liquid separator and according to the present invention, a liquid separator includes a porous bed, an inlet for introducing a mixture of liquids to the lower portion of the porous bed, and an outlet for removal of the denser liquid, which denser liquid can flow from the inlet to the outlet substantially horizontally.

In the past where a porous bed has been used for separating water from oil, the water has always been caused to flow with a substantial downward vertical component, but it has been discovered that if in accordance with the present invention, the water is able to flow substantially horizontally through the lower portion of the bed, the separation is even more efficient because the water provides less resistance to the upward flow of oil in the porous bed.

Preferably there is a grill at the entrance to the porous bed to prevent any solids in the incoming mixture from entering the bed.

Also it is advantageous if the mixture can flow horizontally before entering the porous bed through a chamber having space within which some oil can separate upwardly before the bed is encountered. Preferably the lighter liquid is able to rise to a height above the top of the porous bed.

In a preferred form of the invention, the particles forming the porous bed are constrained by solid walls, and by grills, there being a grill at the top preventing the escape of the porous particles but allowing the lighter liquid to enter its collecting space, and then there may be a weir or other means for defining a water level over which water can be collected, which is above the top of the porous bed but below the level of a weir or the equivalent over which oil is collected at the top of the collecting chamber.

There may be an arrangement responsive to the hydrostatic pressure at the entry to the porous bed for automatically causing reverse flow of water through the bed if the bed begins to be choked with collected solids as detected by a rise in the hydrostatic pressure at the entry. The device could comprise a water chamber having an entry level with the entry to the porous bed, and a level switch arranged to operate to initiate a cleaning cycle in response to the level rising above the initial level.

The invention may be carried into practice in various ways, and one embodiment will now be described by way of example, with reference to the accompanying drawings, in which FIGURE 1 is a diagrammatic perspective view of an oil/water separator; and FIGURE 2 is a sectional elevation of the separator of FIGURE 1 which is useful in illustrating the method of operation.

The separator comprises a tank which has a central main separating region 11 defined between vertical walls 12 and 13, entry of oil/water mixture being below the lower edge 14 of the wall 12, an exit of water from the main chamber being downwards through a grill 15 and then horizontally as shown by an arrow 16 into a water chamber 17 from which water is collected over the top edge 18 of a weir.

Oil/water mixture enters a first chamber 21 at 22 and in that chamber some oil will be at the top of the mixture, and can be collected by a collectinc device 23, entry to which is over edges 24 which are higher than the level of the weir 18.

The main chamber 11 contains two grills 25 and 26 which, in combination with the grill 15, the lower part of the wall 13, a wall 27 below the grill 26, a wall 28 parallel with the wall 27, and the side walls of the chamber, defines a space for a porous bed which consists of a number of hollow particles of the same, or different sizes packed fairly tightly together. One form of the particles is that of closed-end cylindrical shells but they could also be spherical for example. In the part of the central chamber 11 outside the porous bed is a second collecting device 31 for oil, and the edge 32 over which oil enters the device 31 is lower than the edge 24, but higher than the weir 18.

It will be seen from FIGURE 2 that oil/water mixture passing under the edge 14 in the wall 12, travels across a space in which some oil can rise to the top of the mixture before entering the porous bed through the vertical grill 26, and the general flow of water through the porous bed from the grill 26 is horizontal.

It is known that when two immiscible liquids of different specific gravities flow through such a porous bed, the action by which they would normally separate under gravity is much accelerated, and it has been discovered that if the general direction of flow through the bed is horizontal, then the separation of the lighter liquid by vertical upward movement is even more accelerated. Thus, oil separates from the water generally as indicated at 34 in FIGURE 2, and leaves the top of the porous bed through the grill 25. The water level is determined by the edge of the weir 18 and above that pure oil collects, and can be taken off over the edge of the collecting device 32 which is above that of the weir 18.

Water flows downwards through the grill 1 5 and then into the water chamber 17.

If there are any solids present in the incoming mixture, they do not enter the porous bed because of the protecting grill 26, but rise with the oil.

It will be seen that the top of the porous bed as defined by the grill 25 is below the oil/water interface as defined by the weir 18, and that helps to avoid the entrainment of solids in the porous bed.

A water column 41 is positioned in the space between the wall 12, and the grill 26 with an entry 42 at a level about a third of the height up that space. There is a chamber 43 at the top of the column containing a level switch 44 which when closed initiates a sequence of valve and pump operations for causing reverse flow of water through the porous bed for a preset time.

At starting when there is no clogging in the porous bed, the dynamic loss of pressure head through the bed is small compared with the static heads, so that the level in the chamber 43 is the same as that in the water discharge column over the weir 18. If however the bed becomes blocked then the dynamic head across the bed increases and the head in the column 41 increases, until the level switch operates to cause automatic back flushing to clean out the solids. There will be no normal flow through this column so that it will retain only the initial charge of water and will not be affected by oil content.

For handling a large rate of mixture flow, there could be a number of similar cells mounted side by side with the inflow being shared between them through a distributing channel.

Claims

1. A liquid Separator including a porous bed, an inlet for introducing liquids to be separated to the porous bed, and an outlet for removal of the denser liquid, and means causing the denser liquid to flow from the inlet to the outlet with a substantial horizontal component.

2. A separator as claimed in Claim 1 in which the liquids are arranged to be introduced into the lower portion of the porous bed.

3. A separator as claimed in either or the preceding Claims, including a filter at the entrance to the porous bed.

4. A separator as claimed in any of the preceding Claims including a chamber upstream of the entrance to the porous bed, within which the less dense liquid can separate upwardly before the bed is encountered.

5. A separator as claimed in Claim 4, in which the chamber has a weir over which the less dense liquid can escape, which weir is above the top of the porous bed.

6. A separator as claimed in any of the preceding Claims, in which the porous bed comprises particles which are constrained by solid walls and by grills, there being a grill at the top preventing the escape of the particles but allowing the less dense liquid to enter a collecting space.

7. A separator as claimed in Claim 6, including a weir above the top of the porous bed over which the denser liquid can be collected, which weir is above the top of the porous bed.

8. A separator as claimed in Claim 7, including a weir at the top of the collecting chamber for the less dense liquid, which weir is above the level of the weir for the denser liquid.

9. A separator as claimed in any of the preceding Claims, in which the porous bed consists of a number of hollow particles packed fairly tightly together.

10. A separator as claimed in any of the preceding Claims, including means responsive to the hydrostatic pressure at the entry to the porous bed for automatically causing reverse flow of the denser fluid through the bed if the bed begins to be chocked with collected solids as detected by a rise in the hydrostatic pressure.

11. A separator as claimed in Claim 10, in which the responsive means comprise a liquid chamber having an entry level with the entry to the porous bed, and a level switch arranged to operate to initiate a cleaning cycle in reponse to the level rising above the initial level.

12. A separator for liquids constructed and arranged substantially as herein specifically described, with reference to the accompanying drawings.