GB2549556A - Improved seperator vanes and methods of manufacture thereof - Google Patents

Abstract

A vane (100) suitable for a separator, comprises a plastics substrate with a surface energy greater than 48 gs-2. The plastic substrate may be a polyvinyl chloride, polypropylene or a composite of plastics and mineral powder and may be subjected to flame treatment or to corona discharge treatment. A plurality of vanes can be combined to form a separator. Also disclosed is a separate invention directed to a method of making a vane for a separator (300, Fig 3) characterised by imparting additional oxygen to the surface of the vane by passing at least one side of the vane (100) over or through a flame or corona discharge. Forming a vane from plastic provides a vane that is light-weight (in comparison to metal separator vanes) and easy to install, while also being highly efficient at removing water from airflow.

Description

Improved Separator Vanes and Methods of Manufacture thereof Field of the Invention

This invention relates to separator and to vane therefor and methods of making vane for separators. Background A separator is used to remove water from air flowing past it, for example for air inlets for gas turbine generators and other air inlets on ships, oil rigs and other installations in wet or harsh conditions. A separator generally comprises an array of corrugated metal (commonly stainless steel or aluminium) vanes arranged side-by-side across the airflow. Moist air is directed to the surface of the vanes where liquid and vapour are separated. From here, it may drain down under gravity and be removed from the airflow, thus substantially decreasing the moisture content of the air. The process of removing moisture from the airflow is important, as moisture carries contaminants such as salt and dust. Accordingly, separator design has evolved to remove as much moisture as possible and to cope with the stresses and strains of extreme environmental conditions. This optimisation has meant that separators are exceedingly heavy, weighing up to as much as 1000kg or more.

Separators are to be distinguished from air filters which filter dust and other particles. A separator can be used in combination with an air filter. Compared to air filters, separators are expected to have significantly longer lifespans and should therefore be significantly more robust.

Aspects of the present invention provide cost-effective solutions to the problem of maximising the amount of moisture separated from the airflow.

Other features and advantages of exemplary embodiments of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings.

Summary of the Invention

According to a first aspect of the invention, a vane for a separator is provided, comprising a plastics substrate having a surface energy greater than 48 gs'2.

The substrate is preferably formed of rigid polyvinyl chloride or polypropylene. According to a preferred aspect, the substrate has been subjected to flame treatment.

As an alternative, the substrate has been subjected to corona discharge treatment and/or the plastics substrate is a composite of plastics and mineral powder. A plurality of vanes can be combined to form a separator.

According to another aspect of the invention, a method of making a vane separator is provided comprising: providing a vane of plastics material; and imparting additional oxygen to the surface of the vane by passing at least one side of the vane over or through a flame or corona discharge.

The surfaces of the vane are preferably cleaned to remove surface impurities prior to flame or corona discharge treatment, for example using isopropanol.

The method preferably further comprises cooling the vane and assembling a separator from a plurality of such vanes. Both the first and second sides of the vane are preferably passed over a flame or corona discharge at a pre-determined distance, pre-determined speed and a predetermined number of times. The pre-determined distance may be between 50mm and 60mm. The pre-determined speed may be between 0.2m/s and 0.4m/s. The pre-determined number of times is preferably between 1 and 3.

Preferred embodiments of these and other aspects will now be described by way of example only with reference to the drawings.

Brief Description of the Drawings

Figs, la and lb are a cross sectional view and a perspective view respectively of a single vane.

Fig. 2 is a perspective view of the process of treating a vane.

Fig. 3 is a perspective view of a separator.

Fig. 4 is a flow diagram of a method to improve a vane.

Description

The present invention relates to improved separators and a method for treating the vanes for the purpose of improved surface wetting for special purpose air quality equipment.

Figure la shows an extruded vane 100 viewed along its length. The vane 100 has three parts arranged at obtuse angles to each other so that they form two corrugations. Air flows from the first part, towards the third part. The three parts all have a side A and a side B.

The first part of the vane 100 may be an incident section 126. A first drain channel 120 may be formed on side B along the downstream edge of the incident section 126. The first drain channel 120 may have an open end which may face upstream.

The second part of the vane 100 may be a downstream section 128 and may be formed along the downstream edge of the incident section 126 at a first obtuse angle, so that they form a corrugation.

The first obtuse angle faces side A.

The third part of the vane 100 is optional. It comprises a tail section 130 which is formed along the downstream section 128 at a second obtuse angle, so that they form a second corrugation. The second obtuse angle may face side B, in a direction opposite to the first obtuse angle. The tail section 130 may be substantially parallel to the airflow. A second drain channel 121 may be formed on side A along the downstream edge of the downstream section 128. The second drain channel 121 may have an open end which may face upstream. An optional third drain channel 122 may be formed on side B along the downstream edge of the tail section 130. The third drain channel 122 may have an open end which may face upstream. The drain channels 120, 121, 122 are water separating drain channels.

With a plurality of such corrugated vanes 100 arranged side-by-side across the airflow, moist air is directed to the surface of the vanes where it may be separated. Due to the direction of the airflow, water is particularly collected in drain channels 120-122. From here, it may drain down under gravity and be removed from the airflow, thus substantially decreasing the moisture content of the air.

The tendency for water to coalesce on the vane sections may be increased by forming the vane from a substrate which has a surface energy closer to that of water, as will be described. This enables the water to have better adhesion to the surface of the substrate and hence run off more easily.

Table 1 provides the surface energies of various materials. Currently stainless steel and aluminium are commonly used to make vanes. The surface energy of water is 72.2gs"2. The inventors have identified that a vane is more effective when it comprises a material with a surface energy similar to that of water.

As shown in Table 1, PVC that is cleaned and then treated, according to the method detailed herein, has a surface energy that is much closer to water than un-treated PVC. This results in an optimized, light-weight, inexpensive separator vane.

Flame or corona discharge treatment of rigid polyvinyl chloride (PVC) or polypropylene (PP) increases the oxygen content of the substrate and raises its surface energy to be closer to that of water. This is also true for other plastics materials. Forming a vane from this light-weight plastic results in a vane that is light-weight (in comparison to metal separator vanes) and easy to install, while also being highly efficient at removing water from the airflow. These vanes may be manufactured by extrusion and subsequently treated in the manner described below.

Alternatively, the surface energy of the substrate can be raised closer to that of water (to 48gs"2 or more) by creating a composite material. This may be done by mixing a mineral, such as powdered calcium carbonate or talcum powder, into a plastics substrate.

Figure lb shows a sectional view of the vane of Figure la. The incident section 126 and drain channel 120 are shown with microgrooves 105 formed along the direction of drainage, across the direction of air flow. The microgrooves 105 are formed on the principal air facing surface (incident section 126 and drain channel 120 are the first surfaces upon which the airflow may be incident). The microgrooves 105 increase the surface area of the vane sections on which they are formed. Water coalescing on the grooves may drain down and be removed from the airflow in much the same way as for drain channels 120. Surprisingly, it has been found that using vanes as described herein, air/water separation can be better without such microgrooves.

Microgrooves 105 may be present on any or all of the vane surface sections.

Figure 2 shows a treatment apparatus to treat vanes. It comprises a conveyer 202 transporting vanes 200 and an elongated flame 204. The conveyer 202 may move at 0.2-0.4 ms'1, the elongated flame 204 may be a distance of 50-60 mm away from the vane 200 and the elongated flame 204 may have a width of 150-250 mm.

The elongated flame 204 may have a source of fuel gas 208 which may flow at 10-20 Lmin"1 and a source of air 210 for combustion which may have an elevated oxygen content and may flow at 250-270 Lmin'1. The fuel gas type of the flame may be natural gas.

The combustion may be substantially non-stoichiometric combustion due to the elevated oxygen content. For example, the ratio of air to gas may be in excess of 10:1 for natural gas or methane and in excess of 24:1 for propane.

The plasma height of the flame 206 may extend 200-300 mm below the fuel gas and air outlets and the power output of the flame may be 150-170 Watts. Alternatively, the elongated flame 204 may be a corona discharge that produces an equivalent effect.

In operation the conveyer 202 moves a vane 200 below the flame 204 at a pre-determined distance and speed, a pre-determined number of times. This is described in relation to Figure 4.

The aim of the flame or corona discharge treatment is to balance imparting sufficient oxygen into the surface of the vane without destroying it. Treating the substrate surface increases the oxygen content and raises the surface energy of the substrate. This enables liquid to have better adhesion to the surface of the substrate and hence run off more easily.

Figure 3 shows an assembled separator 300. A plurality of vanes 100 and a filter element are provided in the housing 306. The plurality of vanes 100 may comprise vanes in accordance with Figures la and lb. Moisture from incident airflow will coalesce on the surface of the vane particularly in drain channels 120-122. From here, the water will drain down due to gravity and flow out through a drain at the base of the housing 306. After moisture has been removed from the airflow by the plurality of vanes 100, the air passes through filter element, where dust particles and other impurities not removed by the vane section are extracted.

Figure 4 illustrates the process of flame or corona-discharge treating of the vanes. In step 400, the surface of an un-treated vane is optionally cleaned to remove surface impurities. This allows the flame or corona discharge to better access the substrate surface and makes the treatment activation more efficient. The surface may be cleaned with isopropanol. In step 402 at least one side of the vane 100 is passed over the flame or corona discharge 204 at a pre-determined distance and speed, a pre-determined number of times. If only one side is treated it should be the side with the principal air facing surface. As incident section 126 and drain channel 120 are the first surfaces upon which the airflow may be incident, it is preferable to treat these sections. However, one skilled in the art will recognise that the treatment may be present and useful on any of the vane surface sections.

In step 404, the vane is cooled and the separator 300 is assembled from a plurality of vanes 100, as described above with reference to Figure 3.

Performance can be measured by droplet efficiency. For example, a fog of know distribution can be measured upstream and downstream of the separator in a wind tunnel. Using a fog with particle size of 5 microns, travelling at 3 ms'1, more than 97% of the particles are stopped by a stainless steel vane. By comparison, untreated PVC has a poor performance and stops only 68.9% of particles. By treating the vane as described above, this performance can be increased by at least about 10%. Similarly, particles of 3-4 microns at 6m/s give separation of 91.2% if untreated, but can be as good as (or almost as good as) stainless steel (100%) if treated.

The above description has been given by way of example only. Modifications of detail can be made without departing from the scope of the invention.

Claims (14)

Claims

1. A vane (100) for a separator, the vane comprising a plastics substrate having a surface energy greater than 48 gs"2.

2. The vane of claim 1, wherein the substrate is rigid polyvinyl chloride or polypropylene.

3. The vane of claim 1, wherein the substrate has been subjected to flame treatment.

4. The vane of claim 1, wherein the substrate has been subjected to corona discharge treatment.

5. The vane of claim 1, wherein the plastics substrate is a composite of plastics and mineral powder.

6. The vane of claim 1, wherein a plurality of vanes are combined to form a separator.

7. A method of making a vane for a separator (300) comprising: providing a vane (100) of plastics material; and imparting additional oxygen to the surface of the vane by passing (302) at least one side of the vane (100) over or through a flame or corona discharge.

8. The method of claim 7, wherein the surfaces of the vane (100) are cleaned (300) to removed surface impurities prior to flame or corona discharge treatment.

9. The method of claim 8, wherein the surfaces are cleaned with isopropanol.

10. The method of claim 7, further comprising: cooling (306) the vane (100); and assembling (306) a separator (300) from a plurality of such vanes (100).

11. The method of claim 7, wherein first and second sides of the vane (100) are passed a predetermined number of times over or through a flame or corona discharge at a pre-determined distance and a pre-determined speed.

12. The method of claim 11, wherein the pre-determined distance is between 50mm and 60mm.

13. The method of claim 11, wherein the pre-determined speed is between 0.2m/s and 0.4m/s.

14. The method of claim 11, wherein the pre-determined number of times is between 1 and 3.