WO2006110972A1

WO2006110972A1 - Reusable sorbing coalescing and separating system

Info

Publication number: WO2006110972A1
Application number: PCT/CA2005/000585
Authority: WO
Inventors: Raymond Prud'homme; Serge Fraser; Marc Saad
Original assignee: Torr Canada Inc.
Priority date: 2005-04-18
Filing date: 2005-04-18
Publication date: 2006-10-26
Also published as: EP1874460A1; CA2606141A1

Abstract

A substantially self-cleaning reusable sorbing coalescing system facilitating the separation of a system containing at least two phases comprising: a) a non-aqueous phase and b) an aqueous phase. Optionally a third disperse particulate solid phase may also be present and separated out with the non-aqueous phase. The coalescing system comprises a combination of at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range. The non-aqueous phase and the third disperse particulate solid phase are recovered as one non-aqueous phase.

Description

REUSABLE SORBING COALESCING AND SEPARATING SYSTEM

FIELD OF THE INVENTION

The present invention relates to sorbing coalescing and separation technology.

BACKGROUND OF THE INVENTION

Inadvertent spillage of non-aqueous liquids causes both environmental, ecological and even toxicological problems for plant species, insects, wild life and even people. Examples of spilled liquids include oils and solvents, and a group of materials known as PCBs, which in addition to being pollutants are carcinogenic. Further, in many cases when the spilled liquid is a non-aqueous liquid which is not compatible with water, such as fuel oil and hydrocarbon solvents, in addition to the spilled liquid, aqueous emulsions are also often formed. Cleaning up methods including adsorption and coalescing steps are known, even for relatively difficult ones such as crude oil and toxic PCB's.

Patents in the prior art often involve a particulate material for adsorbing or coalescing a non-aqueous phase, typically crude oil or a derivative of it, such as gasoline, diesel fuel, lubricating oil, industrial fluid or bilge water. These patents utilise a wide range of adsorbents and/or coalescing and/or separating agents, not all of which are clearly defined. They include: polyethylene; polypropylene; polyisocyanurate; polyurethane; shreds of solids loaded polyurethane foam; silane cross linked polyolefin; polymethyl methacrylate; shredded fibreglass; wool; cork; styrofoam; polyester and/or cotton.

Kozlowski, in US 5,239,040 discloses particulate reusable polyurethane adsorbents capable of adsorbing many spilled liquids, and from which the adsorbed liquid can be removed by the simple process of centrifugation. The main limitation on the use of the particulate adsorbents of that invention is the properties of the liquid spilled. Any liquid which would destroy or dissolve a polyurethane polymer cannot be recovered using the product described by Kozlowski. The use of particulate reusable adsorbents, including polyurethane, capable of adsorbing spilled liquids, and from which the adsorbed liquid can be removed by the simple process of centrifugation is also described in the prior art. In other cases, particulate adsorbents are used in continuous separation processes, where the replacement of the coalescing system used in the process is performed after many hours of work.

Until quite recently it was considered that the chemical structure of the material used in the adsorbent or coalescing agent powder (units) determined the adsorptive, coalescing and separating characteristics of the adsorbent, coalescing and separating agent.

It has recently been found that media need to be developed for the specific use of supporting a constant flow across the media. Such a flow can have a flow rate ranging from 0 to 80 m/h. The media must support the resulting pressure drop without major deformation and, more important, without having any leaking that would allow that fluid to go around the media and avoiding the adsorbing, coalescing and desorbing process. If leaking occurs, the process efficiency is greatly reduced.

Coalescing media described in the prior art are not designed to support pressure drops and will undergo deformation and compacting when in contact with such a flow. The media reacts to the pressure drop that comes with the constant flow by rearranging itself by physically compacting and leaving more open space for the flow to pass through. As a result of this rearrangement the target fluid in the flow will leak from the media and will not have the desired contact with the coalescing media and the non-aqueous phase recovery performance will decrease.

In this invention it is shown that by adding a fiber to a coalescing media including a powder, the mechanical properties of the media are improved and the coalescing and separating properties are increased. Zimmerman et al in US 5,423,991 discloses a method of reclaiming petroleum from oil spills or slicks disposed on bodies of water wherein the first step includes preparing a mixture of polyurethane, a catalyst and a polyquatemary amine to form a powder mixture with powder particles having a positive charge which attracts petroleum and strongly bonds it to the petroleum particles.

Although a powder is used, there is no discussion of a combination with a fiber.

In US 5,129,923 Hunter et al teach a filter for coalescing droplets of atomized oil in an airstream, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer. The coalescing layer is fabricated or molded from an inorganic material. The coalescing layer is of borosilicate glass microfibres and is formed from layers of sheets wrapped one around the other, formed from a pleated sheet, made by moulding or vacuum forming. Here also, although microfibres are an option, the coalescing layer has only one component.

In EP 0292 204 Brown et al. teach a method of coalescence involving the use of a coalescer element consisting essentially of or comprising a sintered polymeric medium having a fine porous structure. Suitable polymers include thermoplastics or thermosetting resins. A filler is optionally present, the filler being a particulate material, comprising carbon, silica, silicon carbide or alumina, or a fibrous material, comprising glass or carbon. This invention uses a coalescing media presenting fine porous structure, but the polymers are sintered together, not mixed together.

In US 4,592,849 McMillen teaches a method for removing emulsified water from a produced crude oil stream by passing the crude oil stream containing emulsified water through a bed of a water-saturated hydrophilic coalescing medium selected from sand, crushed quartz, diatomaceous earth, porous silica and ground walnut shells. Although McMillen uses materials which could be in powder form, there is no indication that combinations of material are applied, nor is there any suggestion of the use of powders as a coalescer. Sjøblom et al. in WO 02/066137 teach a process for separation of oil, water and gas in a separator by breaking water-in-oil emulsions in a composition comprising a water, oil and optionally a gaseous phase, the composition containing inorganic or organic particulate solids. The organic particulate solids are constituted of nanosized asphaltene, metal organic acid, such as calcium naphthenate particles, or wax particles, such as heavy paraffin particles, or mixtures thereof. The inorganic particulate solids are constituted by clay, precipitated metal salt or scale particles such as calcium carbonate, barium sulphate, or mixtures thereof. This invention relies on the inorganic or organic characteristic of the composition rather than containing a powder and a fiber mixed together.

US 5,006,260 to Roques et al. teach a process for the separation of one phase dispersed in emulsion or in suspension in a continuous phase of a different density providing a coalescing enclosure having a filling formed of fibers or particles. Fibers are of a material selected from polypropylene, polyethylene, polyamide or polytetrafluoroethylene. The Roques et al. filling has a high coefficient of void and an inherent volume of particles or fibers of less than about 20% of the useable volume of said coalescing enclosure. The filling comprises a plurality of radial fibers connected to a central shaft extending along the axis of the chamber.

Ronan et al., US 5,965,015 teach an oil-separator system having a coalescing filter means comprising a glass fiber. Sprenger et al. in US 6,569,330 teach a filter coalescer cartridge for treating jet fuel including a first and a second layer of pleated fiberglass filter media. Although using fibers, both of these patents teach a filter having only one component. The same is true for Yves et al. in US 4,335,001 where a process for the continuous separation of a secondary emulsion of at least one dispersed phase by providing guide means is disclosed. The guide means comprises a packing of a particulate or porous material of high porosity and less density than a bed and being wettable by the dispersed phase wherein the material of the bed comprises glass fibers coated so as to be hydrophobic and the material of the guide means comprises metal fibers coated so as to be hydrophobic.

Veronneau et al. PCT/CA2004/000026 , describe a reusable sorbing coalescing agent facilitating the separation of a non-aqueous phase from an aqueous phase consisting of a ragged-edge particulate reusable material having substantially small uniform sized particulate units.

Other patents of the prior art use polyethylene, and describe comminuting a matrix material, typically a body of polymer foam, into small particles. However, no documents have described any coalescing medium or agent including a combination of material including fibers or powders.

Most of the inefficiencies of the medias of the prior art are caused by leaks.

According to this invention, combinations of two or more different components, at least one being a powder and one being a fiber, mixed at a predetermined volume and density ratio range, the components interacting and working together, increase the absorption-coalescing-desorption and separating capabilities of the coalescing media.

The structural stability of the media of this invention ensures that the material does not change in dimension and keeps its properties notwithstanding a certain pressure drop. In particular, it ensures that the emulsion does not tend to avoid the medium, and effectively go around it. A result of the diversion of the emulsion that otherwise occurs is that more stages need to be used to get the same effective performance.

Solid separation methods known in the art are mainly conventional filtration using bag filters, meshes or paper filters. Other methods use gravity as a separation factor and also centrifugation, such as in the hydrocyclone centrifugation. The higher the flow and/or the smaller the particle, the more difficult it is to separate the solids from a flow.

Gravity is not an efficient method of separation as its efficiency is very low, especially when the density of the particles is the same or a lower density than the aqueous emulsion.

When using conventional filtration other difficulties are presented. As an example, if a mesh is used for the separation, the size of the mesh grade will be very small causing the flow to reduce its speed as the mesh will largely obstruct the flow from passing through the mesh. Additionally, due to the small grade of the mesh, particles may easily plug the mesh. In order to avoid the difficulties described above, a lot of energy must be applied to, for example, control the flow and/or to clean-up the filter.

Hydrocyclone technology, although more efficient, still requires considerable energy to apply the same control as in conventional filtration. Furthermore, in the hydrocyclone method, separation will generally separate the solid particles or the non-aqueous phase but not both at the same time.

In addition to the drawbacks of the filtration methods described above, those methods do not support high pressure drops as, for example, to control the flow and/or to clean-up the filter.

SUMMARY OF THE INVENTION

The present invention seeks to provide a substantially self-cleaning reusable sorbing coalescing system facilitating the separation of a non-aqueous phase from an aqueous phase comprising a combination of at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range, wherein the proportion between the powder and the fiber vary from about 50%-50% to about 90%-10% powder-fiber, and wherein the combination of the powder and the fiber in the system contains from about 5% to about 50% free space.

The present invention also seeks to provide a substantially self-cleaning reusable sorbing coalescing system facilitating the separation of a system containing at least two phases comprising: a. a non-aqueous phase; b. an aqueous phase; and c. a third optionally disperse particulate solid phase wherein the coalescing system comprises a combination of at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range, and wherein the proportion between the powder and the fiber vary from about 50%-50% to about 90%-10% powder-fiber, and wherein the combination of the powder and the fiber in the system contains from about 5% to about 50% free space, and wherein the nonaqueous phase and the third disperse particulate solid phase are recovered as one non-aqueous phase.

The purpose of this invention is to increase the mechanical properties of the media, and to increase the absorption-coalescing-desorption capabilities of the media.

The coalescing media can be composed of raw materials other than polymers. The coalescing medium is intended to include application at high temperatures up to at least 250⁰C.

Any materials that are hydrophobic, oleophilic and that can be transformed to a powder or fiber can be used to manufacture the coalescing agent of this invention. In the combination, one or all components can be a polymer.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows a performance of the coalescing system operating with six stages, in terms of reduction of the oil concentration in the flow in comparison with the performance of a media comprising only powder. FIGURE 2 shows an average data on oil and solids particle concentration analysis throughout the coalescing system and at the inlet and outlet of the media.

DETAILED DESCRIPTION OF THE INVENTION

In a first embodiment, the present invention seeks to provide a substantially self- cleaning reusable sorbing coalescing system facilitating the separation of at least one non-aqueous phase from an aqueous phase comprising at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range.

In a second embodiment, the present invention seeks to provide substantially self-cleaning reusable sorbing coalescing system facilitating the separation of a system containing at least two phases comprising: a) a non-aqueous phase; b) an aqueous phase; and optional c) a third disperse particulate solid phase; wherein the coalescing system comprises a combination of at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range, and wherein the nonaqueous phase and the third disperse particulate solid phase are recovered as one non-aqueous phase.

By adding a fiber to a coalescing media including a powder the mechanical properties of the media do not change and the absorption-coalescing- desorption and separating capabilities of the coalescing system are increased. The selection of the fiber gives strength when mixed with the powder medium, and provides a three dimensional structure, which resists destruction or damage and permits the emulsion to continue to flow through the medium rather than around it. The combination of a fiber and a powder and its characteristics will increase the capabilities of the coalescing system.

First the fiber will give strength to the system, almost completely avoiding system deformation and compacting and consequently avoiding fluid leaking. The fiber will increase the mechanical properties of the system, which will increase the coalescing properties.

It is possible to select the proportion of powder/fiber to the different kinds and properties of flows to improve the coalescing ability of the system.

Where a third optionally disperse particulate solid phase is present in the emulsion, either in the aqueous phase or non-aqueous phase, it is possible to adjust such proportion in order to permit the capture of a very small droplet of the non-aqueous phase together with very small solid particles therein. The non-aqueous phase and the disperse particulate solid phase are recovered as one non-aqueous phase. The solid particles attach to the non-aqueous phase and can then be disposed of with the oil or can be subjected to further processing.

It is also possible to adjust such proportion to improve the ability of the system to avoid the solids present in the flow to clog the system and avoid congestion of the flow.

Adjustments are also possible to enable the system to work at high temperatures.

The two or more different components, at least one being a powder and one being a fiber, are mixed at a predetermined volume and density ratio range, the components interacting and working together to increase the absorption- coalescing-desorption separation capabilities of the coalescing system.

One or all of the components is preferably a polymer. However, the coalescing system can be composed of raw materials other than polymers. In fact any materials that are hydrophobic, oleophilic and that can be transformed to a powder or fiber can be used to manufacture the coalescing agent. The proportion between the powder and the fiber may vary from about 50%- 50% to 90%-10% powder-fiber. Although the proportion of powder-fiber may vary, preferably the system comprises an equal proportion between both or comprise more powder than fiber.

Additionally the combination of the powder and the fiber in the system may vary from about 5% to about 50% free space.

It is preferable that the powder component be the reusable sorbing coalescing agent as described in co-pending application PCT/CA2004/000026.

The terms "leak" and "leaking" in this application is described as fluid that can go through a channel, or an open space, that is large enough that oil droplets passing therethrough avoid contact of oil droplets with the media.

The term "reusable" for the purpose of this application refers first to a substantially self-cleaning material, dispensing with the need for any kind of interruption to perform a cleaning step and thus enabling a continuous usage until its recommended disposal, and second to material which suffers no significant degradation with successive use, thus dispensing with the need for a replacement each time it is used.

The term "absorption" for the purpose of this application refers to any process that causes one substance to penetrate the inside of another substance. In the case of a spill clean-up, the aqueous phase and the non-aqueous phase are absorbed into porous sorbent materials or into particulate material spaces.

The term "adsorption" for the purpose of this application refers to a process that causes one substance to be attracted to and stick to the surface of another substance, without actually penetrating its surface. The coalescing systems of this invention present high surface/volume ratios, substantially no shiny surface, affinity with oil, hydrophobic properties, porous, broken cells, small particles and fibrous edges. The media of this system is packed in a non-organized manner to force the fluid to continuously change direction when passing through the system.

Powders are not shiny and present excellent chemical properties.

Unfortunately, they can have less desirable mechanical characteristics, creating leaks when used alone or unaccompanied by a fiber.

Fibers are generally shiny and generally lack the desirable chemical properties to work in a coalescing system if used alone or unaccompanied by a powder.

Nevertheless, the presence of fibers in addition to suitable powders in the system of this invention provides the desirable mechanical characteristic for the system of improving its coalescing properties.

A coalescing media is a media placed in a constant flow and must have better characteristics than those of a static media. The coalescing systems of this invention keep their density over time without deforming under small pressure (up to 7 PSI). The components of systems also maintain an ability to force the fluid to go through them and not around them while coalescing.

In the coalescing system of the present invention, the powder mostly treats the non-aqueous phase and the fiber mostly provides mechanical support to the system. It has been observed that the fiber alone will not work properly. Use of the powder alone works well but not as well as is desired for a coalescing system and its efficiency degrades over time. In this invention it is proven that a mix of the two, a fiber and a powder provides an unexpectedly better result.

It is also possible to change the composition of the system or the characteristic of each of the components of the system to adapt the system to different types of targeting flows and to reach a predetermined target. Examples of changes that could be made to the system include those of a stiffer fibre to avoid deformation under higher pressure. As well, the powder size or powder concentration could be altered or reduced to allow solids to go trough. Still further the proportion of the components could be adjusted to better capture solid particles by attaching them to the non-aqueous phase that will be separated from the aqueous phase.

A fiber and a powder suitable for applications at high temperature could also be selected.

The coalescing action of the system provides for a flow rate ranging from a very low flow rate up to 80 cubic meter per hour per square meter across a bed area of particulate material of 1 square meter and results in a reduction of oil-in-water content ranging from 2000 ppm to less than 10ppm respectively. Reduction of oil-in-water content in flow rates outside this range is possible. The presently preferred flow rate is between 15 rr^/h/m² and 40 nr^/h/m². Within the optimum flow rate, the particulate sorbing coalescing agent's reduction rate can achieve high degreees of separation as can be seen in Figures 1 and 2.

In Figure 1 there is shown a graph of the performance of the coalescing system operating with six stages of the coalescing system in terms of reduction of the oil concentration in the flow. The Figure indicates an oil concentration reduction from 2226.84 ppm down to 0.23 ppm.

The system of the present invention, comprising a combination of at least two different particulate materials, one being a fiber and the other one being a powder shows much better performance of the compound with the performance of a media comprising only powder, as showed in Figure 1.

As can be seen in Figure 2, solid particle analysis at the inlet of the media showed average solids concentration of 1029 ppm with particle sizes varying between 3.36 μm and 58.12 μm in characteristic length. At the outlet the flow showed average solids concentration of 1 ppm. At the same time, the average oil concentration at the inlet and outlet of the media showed 754 ppm and 1.5 ppm respectively.

In the present invention, the particles are not simply being filtered out, as described in the known solid separate methods. Rather the particles are being redirected outside of the aqueous flow, together with the non-aqueous phase, for further separation from the non-aqueous phase if necessary or desired.

This mechanism has the advantage of separating very small solid particles or particles having the same or a lower density than of the aqueous emulsion.

Furthermore the system separates the non-aqueous phase and the solid particles from the non-aqueous phase particles simultaneously, without the use of additional equipment.

Contrary to the filtration methods of the prior art, the system of this invention supports high pressure drops and can be arranged to accept different types of emulsion flows.

These characteristics of the inventive coalescing system allow the separation of the non-aqueous phase and the solid particles to be performed at higher flow rates without plugging the media and without applying high energy to the system to control the separation conditions during the process.

Claims

Claims:

1. A substantially self-cleaning reusable sorbing coalescing system facilitating the separation of a non-aqueous phase from an aqueous phase comprising a combination of at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range,

wherein the proportion between the powder and the fiber vary from about 50%-50% to about 90%-10% powder-fiber, and

wherein the combination of the powder and the fiber in the system contains from about 5% to about 50% free space.

2. The coalescing system according to Claim 1 , wherein at least one of the particulate materials is a polymer.

3. The coalescing system according to Claim 1 , wherein the particulate material is an hydrophobic or oleophilic sorbing coalescing agent.

4. The coalescing system according to Claim 1 , wherein the composition of the system is constructed and arranged to accept different types of emulsion flows.

5. A substantially self-cleaning reusable sorbing coalescing system facilitating the separation of a system containing at least three phases comprising: a. a non-aqueous phase; b. an aqueous phase; and c. a third disperse particulate solid phase wherein the coalescing system comprises a combination of at least two different particulate materials, one being a fiber and the other one being a powder mixed at a predetermined volume and density ratio range, and

wherein the proportion between the powder and the fiber vary from about

50%-50% to about 90%-10% powder-fiber, and

wherein the combination of the powder and the fiber in the system contains from about 5% to about 50% free space, and

wherein the non-aqueous phase and the third disperse particulate solid phase are recovered as one non-aqueous phase.

6. The coalescing system according to Claim 5, wherein at least one of the particulate materials is a polymer.

7. The coalescing system according to Claim 5, wherein the particulate material is a hydrophobic or oleophilic sorbing coalescing agent.

8. The coalescing system according to Claim 5, wherein the composition of the system is constructed and arranged to accept different types of emulsion flows.

9. The coalescing system according to Claim 5, wherein the third disperse particulate solid phase is dispersed in the non-aqueous phase.

10. The coalescing system according to Claim 5, wherein the third disperse particulate solid phase is dispersed in the aqueous phase.

11. The coalescing system according to Claim 5, wherein the third disperse particulate solid phase is dispersed in both the non-aqueous phase and in the aqueous phase.

12. The coalescing system according to Claim 5, wherein the non-aqueous phase and the third disperse particulate solid phase are recovered as one nonaqueous phase through the coalescence and desorption of the non-aqueous phase.