GB2600925A

GB2600925A - A separator pad and a separator

Info

Publication number: GB2600925A
Application number: GB2017584.0A
Authority: GB
Inventors: Miller Jeremy; Kane Mitchell; Oliver David; Pearse Martin; Chu Brian
Original assignee: Spirax Sarco Ltd
Current assignee: Spirax Sarco Ltd
Priority date: 2020-11-06
Filing date: 2020-11-06
Publication date: 2022-05-18
Also published as: GB202017584D0

Abstract

A separator pad 12 for separating condensate droplets from a high pressure steam flow, comprising a hydrophilic mesh 42 comprising hydrophilic material, preferably PEEK, and a hydrophobic mesh 40 comprising hydrophobic material, preferably stainless steel. The hydrophobic and hydrophilic meshes may be intertwined to form a single bulk mesh or may form separate layers of the pad adjacent each other in a thickness direction. The pad 12 may be included in a separator 10 comprising a chamber 22 witha wet steam inlet 16, a dry steam outlet 18, and a condensate outlet 20. The pad 12 may bisect the chamber 22 between the wet steam inlet 16 and the dry steam outlet 18 so all steam flow passes through the separator pad 12. The separator pad 12 may discharge the condensate captured in the separator pad 12 through the condensate outlet 20.

Description

A SEPARATOR PAD AND A SEPARATOR

The present disclosure relates to a separator pad, a separator and an installation for separating condensate droplets from a high pressure wet steam flow. The present disclosure also relates to a method of separating condensate from a high pressure wet steam flow.

High pressure steam systems are frequently used in industrial applications. The high pressure steam can partially condense in pipework conveying the steam to provide wet steam. Wet steam may be undesirable for a number of reasons, including that it can damage components in the installation (such as turbines and the pipes themselves), and it has a higher rate of heat transfer than dry steam and therefore may be less thermally efficient to circulate.

According to a first aspect, there is provided a separator pad for separating condensate droplets from a high pressure steam flow, the separator pad comprising: a hydrophilic mesh comprising hydrophilic material; and a hydrophobic mesh comprising hydrophobic material.

The high pressure steam may be steam at a pressure of more than 7 Bar (700 kPa), for example it may be steam at a pressure of approximately 10 Bar (1000 kPa), which may be particularly suitable for use in the food and beverage industry. Some high pressure systems may be at a pressure of more than 10 Bar (1000 kPa), such as between 10 and 30 Bar (1000-3000 kPa), or more than 30 Bar (3000 kPa).

The hydrophobic mesh and the hydrophilic mesh may comprise a weave of hydrophobic and hydrophilic material respectively. The hydrophobic mesh and the hydrophilic mesh may comprise a porosity of between approximately 90-96%, preferably between approximately 92-94%.

The hydrophobic mesh and the hydrophilic mesh may be intertwined to form a single bulk mesh comprising hydrophobic material and hydrophilic material.

The bulk mesh may comprise interwoven hydrophilic and hydrophobic material.

The hydrophobic mesh and the hydrophilic mesh may each form separate layers of the pad which may be disposed adjacent to one another in a thickness direction of the pad.

The hydrophobic mesh may be sandwiched between two layers of hydrophilic mesh.

The hydrophobic material may be PEEK. The hydrophilic material may be stainless steel.

The hydrophobic material may have a water absorption coefficient of 0.1% or less. The hydrophilic material may have a water absorption coefficient of more than 0.1%.

The thickness of the pad may increases along one direction. The pad thickness may be increased by providing more alternating layers of hydrophilic mesh and hydrophobic mesh.

According to a second aspect, there is provided a separator for separating condensate droplets from a high pressure steam flow, the water separator comprising: a chamber comprising a wet steam inlet for receiving a high pressure steam flow, a dry steam outlet for discharging the high pressure steam flow, and a condensate outlet for discharging condensate; and a separator pad according to any preceding claim, the separator pad bisecting the chamber between the wet steam inlet and the dry steam outlet such that all steam flow which is discharged through the dry steam outlet in use passes through the separator pad, wherein the separator pad is configured to discharge condensate captured in the separator pad through the liquid water outlet.

The separator may comprise a baffle disposed in the chamber to isolate the condensate outlet from the high pressure steam flow in use by defining an isolated portion of the chamber which may be configured to collect condensate from the separator pad to discharge through the condensate outlet.

The hydrophobic mesh and the hydrophilic mesh may each form separate layers of the pad which are disposed adjacent to one another in a thickness direction of the pad. The hydrophobic mesh may be disposed towards a side of the chamber facing the dry steam outlet, and the hydrophilic mesh may be disposed towards a side of the chamber facing the wet steam inlet.

The inlet may comprise a flow distributor comprising an upstream end defining a first flow area, wherein the flow distributor is configured to deflect the steam flow from the upstream end such that the steam flow is distributed over a larger second flow area.

The flow distributor may be conical having an apex facing in an upstream direction, the conical flow distributor diverging radially outward from the apex in a downstream direction.

The thickness of the pad may increase in a direction towards the liquid water outlet.

According to a third aspect, there is provided a method of using a separator pad in accordance with the first aspect or a separator in accordance with the second aspect to separate condensate from high pressure steam.

According to a fourth aspect, there is provided an installation for separating condensate from a high pressure steam flow, the installation comprising a separator in accordance with the second aspect and a condensate discharge pipe, wherein the condensate outlet of the separator is connected to the condensate discharge pipe such that condensate captured in the separator pad flows to and discharges from the condensate outlet by gravity.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 schematically shows a cross sectional view of a steam installation having a separator with a first example separator pad; Figure 2 schematically shows an exploded cross-sectional view of the separator in Figure 1; and Figure 3 schematically shows an oblique view of a second example separator pad.

Figure 1 shows a steam installation 2 comprising a line 4 through which high pressure steam is circulated. In this example, the steam installation 2 is configured to circulate high pressure steam at a pressure of approximately 10 Bar (1000kPa). High pressure steam can be tapped from the line 4 through an outbound line 3 for use in systems, such as heating, and returned as condensate or wet steam to the line 4 through a condensate return line 5 once used. The steam installation 2 comprises a boiler 7 in the line 4 downstream of the condensate return line 5, which is configured to reheat the circulating steam (including the returned condensate or wet steam). During circulation of the steam in the line 4, condensate may build up due to heat transfer to atmosphere through pipes in the line 4.

The installation 2 comprises a separator 10 provided in the line 4 for separating condensate droplets from the high pressure steam flow in the line 4 to ensure that steam quality (i.e. dryness) is maintained. In some examples, a plurality of separators may be provided in the line intermittently to ensure steam quality is maintained. As explained above, condensate may form in the line 4 due to condensation of the high pressure steam in the line 4. The separator 10 comprises a container 14 defining a chamber 22 having a wet steam inlet 16 for receiving a high pressure steam flow, a dry steam outlet 18 for discharging the high pressure steam flow, and a condensate outlet 20 for discharging condensate which has been separated from the steam flow.

The condensate outlet 20 is connected to a condensate discharge pipe 30. The condensate discharge pipe 30 comprises a steam trap 32 to separate condensate from any steam which may have been discharged from the condensate outlet 20. The condensate may be passed to a boiler to reheat it, and may then be provided back to the line 4, or it may be used to recover heat by heat transfer to another fluid, and it may then be discharged from the installation 2.

The separator 10 comprises a baffle 24 which is disposed in the chamber 22 between the condensate outlet 20 and both the wet steam inlet 16 and the dry steam outlet 18. The baffle 24 is configured to isolate the condensate outlet 20 from the high pressure steam flow in use. The baffle 24 therefore separates the chamber 22 into an upper steam portion 22b, 22c and an isolated lower condensate collection portion 22a.

The separator 10 further comprises a separator pad 12. The separator pad 12 is received in the baffle 24 and bisects the upper steam portion of the chamber 22 to separate it into two portions; a steam inlet portion 22b which is open to the wet steam inlet 16, and a steam outlet portion 22c which is open to the dry steam outlet 18. The pad 12 therefore separates the wet steam inlet 16 from the dry steam outlet 18 such that in use, all steam flow which is discharged through the dry steam outlet 18 passes through the separator pad 12.

The separator pad 12 is configured to capture suspended condensate droplets from the high pressure steam flowing therethrough and to discharge the captured condensate to the condensate outlet 20 via the lower condensate collection portion 22a.

Separating the chamber 22 with the baffle 24 to form a lower condensate collection portion 22a provides better separation, as it allows the captured condensate to freely drain out of the separator pad 12 and fall into the lower condensate collection portion 22a, so that condensate does not clog up the separator pad 12 in use. Some variants of steam traps require a threshold amount of condensate to build up upstream of the steam trap in order to operate (for example some thermodynamic steam traps which rely on the condensate being at marginally lower temperature than the steam), and so the provision of the lower condensate collection portion permits this.

The separator pad 12 is seated in the baffle 24. As can be seen in Figure 2, which shows an exploded view of the separator 10, the baffle 24 comprises a recess for receiving the separator pad 12 and an opening in the base of the recess to allow captured condensate to drain from the separator pad 12 into the lower condensate collection portion 22a of the chamber 22, and to the condensate outlet 20.

In other examples, there may be no baffle and no lower condensate collection portion. In such examples, the separator pad may be embedded in a recess in the wall of the container such that it bisects the chamber to form the steam inlet portion and the steam outlet portion, or otherwise secured to bisect the chamber and communicate with a condensate discharge outlet The separator pad 12 in this example comprises a hydrophobic mesh layer 40 sandwiched between two hydrophilic mesh layers 42. The hydrophilic layers 42 are in contact with the hydrophobic layer 40. The hydrophobic mesh layer 40 comprises a weave of hydrophobic material and the hydrophilic mesh 42 comprises a weave of hydrophilic material. The hydrophobic mesh 40 and the hydrophilic mesh 42 have a porosity of approximately 93%. In some examples, the porosity of the meshes 40, 42 may be between 90-96%, for example between 92-94%. This high level of porosity ensures that the mesh is suitable and effective for use in a high pressure steam system -i.e. without an excessive pressure drop. In this example, the pressure drop over the separator pad 12 is 0.01 bar (1kPa) for a high pressure steam flow that approaches the separator 10 at 3 bar (300kPa), 154 degrees Celsius and 10m/s.

In this example, the hydrophobic material is PEEK, and the hydrophilic material is stainless steel. In some examples, the hydrophobic material may be any suitable material which has hydrophobic properties, such as having a water absorption coefficient of 0.1% or less. In other examples, the hydrophilic material may be any suitable material which has hydrophilic properties, such as a material having a water absorption coefficient of more than 0.1%. The water absorption coefficient is measured with the standard test described in ASTM C1794-15.

In some examples, the separator pad may comprise only two mesh layers: one hydrophobic mesh and one hydrophilic mesh disposed adjacent to one another in a thickness direction of the separator pad and in contact with one another. In such an example, the separator pad is disposed in the separator such that the hydrophobic mesh faces the dry steam outlet, and the hydrophilic mesh faces the wet steam inlet i.e. such that in use, the steam flow entering through the wet steam inlet impinges on the hydrophilic mesh before passing through the hydrophobic mesh.

The wet steam inlet 16 is configured to distribute the inlet steam flow, and comprises an upstream pipe section 46 defining a first flow area (i.e. the cross-sectional area through which the steam flows in use), and a distributor 48 disposed in the path of the flow and which is configured to deflect flow received from the upstream tube 46 to distribute the steam flow over a second flow area larger than the first flow area. The distributor 48 in this example is conical, comprising an apex facing an upstream direction (i.e. towards the upstream tube 46) and a curved surface gradually diverging radially outward from the apex in a downstream direction (i.e. towards the separator pad 12). In other words, the distributor 48 in this example is a curved cone.

In some examples, the distributor may be a straight cone, or any other diverging shape from the apex. In other examples, the distributor may simply be a curved inlet opening which deflects steam by the Coanda effect to distribute it over a larger area than the flow area of the upstream tube.

Distributing the steam flow ensures that the steam flow is spread over a larger area of the separator pad 12, such that the separator pad 12 can more efficiently and effectively remove condensate drops from the steam. In particular, it is thought that the performance of the separator pad 12 is likely to increase in proportion to the ratio of the area of the separator pad 12 upon which flow impinges relative to the mass flow rate of the steam.

In use, wet steam enters the separator 10 through the wet steam inlet 16 and passes through the pad 12 towards the dry steam outlet 18. The pad 12 captures condensate droplets which drain through the pad and out of the base of the pad to the condensate outlet 20. The applicant has found that this arrangement provides a separator with higher water separation efficiency than previously considered arrangements, without providing a significant resistance to the steam flow (i.e. with a relatively low pressure drop).

For example, the applicant has conducted tests on a separator 10 comprising the separator pad 12 in which wet steam at a dryness of approximately 85% and 95% was passed via the wet steam inlet 16 through the separator pad 12. The dryness of the steam was measured upstream and downstream of the separator pad 12. The tests were conducted at a pressure of 3 bar (300 kPa), and a steam velocity of 10m/s. The steam mass flow rate was 139kg/h and the steam was heated to a temperature of 153.7 degrees Celsius.

Results of the tests are shown below in table 1. It can be seen that the separator pad 12 successfully discharges drier steam than is received, with a separation efficiency of approximately 96%, and a pressure drop of only 1kPa from 300kPa EXpe rinient Dryness before separator pad 85.2% 95.0% arator pad 99.3% 99.8% Separation efficiency 96.1% 95.8% Pre ssure before separa tot 300kPa 300kPa Pressure after separator 299kPa 299kPa Table 1: Test results for dryness of steam before and after separator pad.

Without wishing to be bound by theory, it is thought that the condensate in a high pressure steam flow adheres to (e.g. coalesces on) the hydrophilic mesh 42, and that the adjacent hydrophobic mesh 40 repels the condensate to prevent the captured condensate from being carried through the separator pad 12 by the high pressure steam flow. It is thought that this repelling effect retains the condensate on the hydrophilic mesh 42 and simultaneously drives it to move along the hydrophilic mesh 42, therefore promoting the drainage of the captured condensate downward to the condensate water outlet 20.

It is thought that including a further layer of hydrophilic mesh 42 to sandwich the hydrophobic mesh 40 may capture any remaining condensate which would not otherwise be retained on the upstream hydrophilic mesh 42, to further improve the efficiency.

Figure 3 shows a second example separator pad 110 comprising a bulk mesh of intertwined woven hydrophilic material 112 and hydrophobic material 114. The hydrophilic material 112 and hydrophobic material 114 are interwoven to form the bulk mesh, and the thickness of the bulk mesh increases along one direction. In an example separator, the second example separator pad 110 is disposed in the separator such as described with reference to Figures 1 and 2, replacing the first example separator pad 12. In such an example, the thickest part of the bulk mesh is disposed on the baffle (i.e. the separator pad 110 is oriented so that the thickest part is at the bottom).

It is thought that having a separator pad 110 which is thicker towards the base than at the top provides more effective drainage of condensate from the separator pad 110 to the lower condensate collection portion 22a. The captured condensate must flow downward towards the lower condensate collection portion 22a, and as such, there will be more accumulated condensate lower down the separator pad 110 in use. Therefore, having a thicker mesh at the bottom will reduce clogging of the separator pad 110.

In some examples, a separator pad in accordance with the first example may increase in thickness along one direction in a similar manner to the second example separator pad. In such examples, the increasing thickness may be due to each layer increasing in thickness in one direction, or only the hydrophilic layers having increased thickness in one direction, or only the hydrophobic mesh having increased thickness, or by providing more alternating layers of hydrophilic mesh and hydrophobic mesh towards the base of the separator pad.

Claims

CLAIMS: 1. A separator pad for separating condensate droplets from a high pressure steam flow, the separator pad comprising: a hydrophilic mesh comprising hydrophilic material; and a hydrophobic mesh comprising hydrophobic material.
2. A separator pad according to claim 1, wherein the hydrophobic mesh and the hydrophilic mesh are intertwined to form a single bulk mesh comprising hydrophobic material and hydrophilic material.
3. A separator pad according to claim 1, wherein the hydrophobic mesh and the hydrophilic mesh each form separate layers of the pad which are disposed adjacent to one another in a thickness direction of the pad.
4. A separator pad according to claim 3, wherein the hydrophobic mesh is sandwiched between two layers of hydrophilic mesh.
5. A separator pad according to any preceding claim, wherein the hydrophobic material is PEEK.
6. A separator pad according to any preceding claim, wherein the hydrophilic material is stainless steel.
7. A separator pad according to any preceding claim, wherein the hydrophobic material has a water absorption coefficient of 0.1% or less.
8. A separator pad according to any preceding claim, wherein the hydrophilic material has a water absorption coefficient of more than 0.1%.
9. A separator pad according to any preceding claim, wherein the thickness of the pad increases along one direction.
10. A separator pad according to claim 9 when appendant to claim 3, wherein the pad thickness is increased by providing more alternating layers of hydrophilic mesh and hydrophobic mesh.
11. A separator for separating condensate droplets from a high pressure steam flow, the water separator comprising: a chamber comprising a wet steam inlet for receiving a high pressure steam flow, a dry steam outlet for discharging the high pressure steam flow, and a condensate outlet for discharging condensate; and a separator pad according to any preceding claim, the separator pad bisecting the chamber between the wet steam inlet and the dry steam outlet such that all steam flow which is discharged through the dry steam outlet in use passes through the separator pad, wherein the separator pad is configured to discharge condensate captured in the separator pad through the liquid water outlet.
12. A separator according to claim 11, comprising a baffle disposed in the chamber to isolate the condensate outlet from the high pressure steam flow in use by defining an isolated portion of the chamber which is configured to collect condensate from the separator pad to discharge through the condensate outlet.
13. A separator according to claim 11 or 12, wherein the hydrophobic mesh and the hydrophilic mesh each form separate layers of the pad which are disposed adjacent to one another in a thickness direction of the pad, and wherein the hydrophobic mesh is disposed towards a side of the chamber facing the dry steam outlet, and the hydrophilic mesh is disposed towards a side of the chamber facing the wet steam inlet.
14. A separator according to any of claims 11-13, wherein the inlet comprises a flow distributor comprising an upstream end defining a first flow area, wherein the flow distributor is configured to deflect the steam flow from the upstream end such that the steam flow is distributed over a larger second flow area.
15. A separator according to claim 14, wherein the flow distributor is conical having an apex facing in an upstream direction, the conical flow distributor diverging radially outward from the apex in a downstream direction.
16. A separator according to any of claims 11-15, wherein the thickness of the pad increases in a direction towards the liquid water outlet.
17. A method of using a separator pad according to any of claims 1-10 or a separator according to any of claims 11-16 to separate condensate from high pressure steam.
18. An installation for separating condensate from a high pressure steam flow, the installation comprising a separator according to any of claims 11-16 and a condensate discharge pipe, wherein the condensate outlet of the separator is connected to the condensate discharge pipe such that condensate captured in the separator pad flows to and discharges from the condensate outlet by gravity.