Patent Application
20160038976
The present invention relates generally to stationary or vibrating screening devices. In particular, a screen cloth useful in stationary, rotating and/or vibrating screens for screening oversize objects in a material is provided which has a coating or liner comprising an elastomer, and a wear material, which protect the impact screen cloth against damage from the material to be screened.
Vibrating, rotating and/or stationary screens are used in the oil sand industry, in particular, in oil sand slurry preparation plants. Oil sand, such as is mined in the Fort McMurray region of Alberta, generally comprises water-wet sand grains held together by a matrix of viscous bitumen. It lends itself to liberation of the sand grains from the bitumen by mixing or slurrying the oil sand in water, allowing the bitumen to move to the aqueous phase.
As-mined or pre-crushed oil sand is generally mixed with warm or hot water to yield an oil sand slurry. The slurry is then conditioned in a hydrotransport pipeline and subsequently introduced into a large, open-topped, conical-bottomed, cylindrical vessel commonly termed a primary separation vessel (PSV) where the more buoyant aerated bitumen rises to the surface and forms a bitumen froth layer.
It may be desirable to remove the larger aggregates present in oil sand slurry prior to pipelining in order to avoid blockage or damage of downstream equipment, e.g., pump component wear. Thus, vibrating, rotating and/or stationary screens may be used at various points during slurry preparation to reject larger lumps of oil sand, rocks and other aggregates, which are large enough to block or damage downstream equipment, prior to pipeline conditioning. Screens may also be used to further screen oil sand tailings slurry prior to treating/disposing same.
However, oil sand slurry is extremely heavy and abrasive due to the large amount of sand, gravel and crushed rock contained therein. Further, in particular with primary vibrating screens, these screens are generally vibrating with an acceleration of approximately 4-5 g, so that all oil sand slurried material passes over and through the screen cloths of the vibrating screen. This results in the rapid spalling and eventual wearing through of the screen cloths of the vibrating screen (“hole-throughs”), which can lead to production interruption and an unplanned maintenance event.
Various types of screen cloths are currently used. Hard-faced screen cloths such as tungsten carbide overlays provide excellent resistance against abrasion wear, but often prematurely fail due to impact and fatigue damage. Elastomer-lined screen cloths exhibit improved wear performance due to their energy-dampening capability through elastic deformation; however, when the impact energy of oversize reject material is beyond the elastic capability of the elastomers, tearing or gouging occurs. Despite the availability of different types of screen cloths, poor wear capability and plugging remain persistent problems in screening.
Thus, it is desirable to have an improved screen cloth that can withstand the abrasiveness of oil sand slurry.
It was discovered that screen cloths of vibrating, rotating and/or stationary screening devices used to screen frozen lumps, rocks and the like from oil sand slurry were wearing through much quicker than desired due to the abrasive nature of the slurry. In particular, it was discovered that screen cloths of vibrating screening devices were suffering from localized wear phenomena resulting from the slurry flow distribution.
The current application is directed to an improved screen cloth and method of screening an oil sand slurry having oversize reject material using the improved screen cloth. It was surprisingly discovered that by using the screen cloth of the present invention, one or more of the following benefits may be realized:
(1) The screen cloth includes structural metal, a coating or liner comprising an elastomer coating or lining the structural metal, and a wear material at least partially embedded into the elastomer coating or liner. The wear material and elastomer together form a protective surface which can protect the structural metal from the abrasiveness of the oil sand slurry.
(2) The elastomer provides resistance against wear and corrosion.
(3) The wear material protects the elastomer from tearing or gouging at high impact and impingement areas.
(4) The elastomer coating or liner provides an energy dampening function, reducing the net energy imparted onto the wear material at least partially embedded into the elastomer coating or liner from the impact of oversize reject material and thereby reducing the risk of premature failure of the wear material.
Use of the present invention extends the running time of a vibrating, rotating and/or stationary screening device so that the operator does not have to shut down the screening device as frequently to replace the screen cloth.
Thus, broadly stated, in one aspect of the present invention, a screen cloth for use in a screening device for screening out oversize objects in a material flowing in a direction is provided, comprising:
In one aspect of the present invention, a screen for use in a vibrating, rotary or stationary screening device for screening oversize objects in a material is provided, comprising:
a plurality of screening rows positioned end to end between the feed end and the discharge end of the screen, each screening row comprising one or more of the above screen cloths.
In yet another aspect of the present invention, a method for screening an oil sand slurry having oversize reject material is provided, comprising:
Other features will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific embodiments, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the following figures. It is understood that the drawings provided herein are for illustration purposes only and are not necessarily drawn to scale.
a is a general schematic of a screen cloth comprising a metal plate coated or lined with a coating or liner comprising an elastomer.
b shows a side view of a portion of the screen cloth of
a is a schematic side view of a portion of the embodiment shown in
b is a schematic side view of a portion of an additional embodiment of a screen cloth of the present invention.
c is a schematic side view of a portion of an additional embodiment of a screen cloth of the present invention.
d is a schematic side view of a portion of an additional embodiment of a screen cloth of the present invention.
e is a schematic side view of a portion of an additional embodiment of a screen cloth of the present invention.
The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
The present invention relates generally to an improved screen cloth and method of screening an oil sand slurry having oversize reject material using the improved screen cloth.
a is a general schematic of a screen cloth having an elastomer coating. Screen cloth 10 is formed of a perforated plate 12 having a front edge (material or feed end) 14, a back edge (oversize exit end) 16, a first side edge 18, and a second side edge 20. Openings 22 in the perforated plate 12 are generally of a consistent size, wherein the size is dependent on the size of the oversize that one desires to screen out. In this embodiment, the openings 22 are rectangular. Screen cloth 10 further comprises an impact surface 34 (or top surface) and a bottom surface 36.
The perforated plate 12 can be made of a number of different materials, preferably, steel or any other suitable metal. In one embodiment, perforated plate 12 is constructed from a large piece of steel, which forms the perimeter of the screen cloth 10, and a regular pattern of openings 22 or holes are cut and/or punched (flame, plasma) therethrough to form the mesh of the perforated plate 12 which also comprises longitudinal ligaments 24 and transverse ligaments 26.
In
It can further be seen from
As can be seen in
It is understood that the elastomer coating can be coated onto the structural metal of the perforated plate by any means known in the art. Similarly, the elastomer liner can be deployed onto the structural metal of the perforated plate by any means known in the art. It is further understood that the application of the coating/liner is dependent on the coating/liner material. In some cases, the coating is poured as liquid, allowed to set and then cured in an oven. In other cases, liner is applied as layers or sheets of raw material and baked in an oven. In further cases, the coating is sprayed and cured. The wear material is typically positioned in the mold during or after placing the coating/liner. Special preparation of the wear material surface allows for strong bonding between the two different materials. In some cases, special mechanical anchors are used to position and secure the wear material.
It was surprisingly discovered that reinforcing the leading edges (relative to the flow of the material) of the portion of the transverse ligaments located in between the longitudinal ligaments by at least partially embedding a wear material into the elastomer coating or liner at the leading edge protected the elastomer coating or liner from wear and from potentially tearing or gouging due to the impact of oversize reject material. Further, the fact that at least part of the elastomer coating or liner may now be sandwiched between the structural metal and the wear material, provides an additional energy dampening function to the screen cloth.
As used herein, the term “wear material” means a material which is abrasion resistant. Wear material 234 may include, but is not limited to, chromium carbide, tungsten carbide (PTA or Technoginia products) or cast wear products (ceramic, Kencast™ (tungsten carbide chips suspended in an all-steel matrix) or sintered tungsten carbide).
As used herein, the term “elastomer” means a material which exhibits the property of elasticity, namely the ability to deform when a stress is applied and to recover its original form (i.e., length, volume, shape, etc.) spontaneously when the stress is removed. Elastomers typically have a low Young's modulus (i.e., the ratio of stress to strain, expressed in units of pressure), and a high yield strain (i.e., the strain at which a material begins to deform plastically). Suitable elastomers include, but are not limited to, synthetic or natural rubbers, polyurethane, other thermosetting elastomers, and thermoplastic elastomers.
Perforated plate 212 may be constructed from a large piece of steel, which forms the perimeter of the screen cloth 210. The openings 222 are cut and/or punched (flame, plasma) therethrough to form the mesh comprising longitudinal ligaments 224 and transverse ligaments 226. The longitudinal ligaments 224 are oriented substantially parallel to the direction of the material flow, extending essentially from the feed end 214 to the oversize exit end 216. The transverse ligaments 226 are oriented substantially perpendicular to the direction of the material flow, extending essentially from the first side edge 218 to the second side edge 220.
The perforated plate 212 has been coated with a coating comprising an elastomer, herein referred to as elastomer coating 230, either on the impact surface 234 only (or a portion thereof) or on both the impact surface 234 and the bottom surface 236. In this embodiment, leading edges 240 of the portions of the transverse ligaments 226 positioned in between the longitudinal ligaments 224 have been reinforced by embedding a wear material into the elastomer coating (or liner), as shown in
a is a schematic side view of an embodiment of a portion of a transverse ligament as shown in
In one embodiment, the elastomer coating 230 encapsulates the entire structural metal 228 forming the perforated plate 212 to provide resistance against wear and corrosion (
Wear material 242 is embedded into elastomer coating (or liner) 230 or a portion thereof, e.g., the leading edge 240 or portion of the leading edge 240 which is an area of high impact and impingement, to protect elastomer coating (or liner) 230 from tearing or gouging at the high impact and impingement areas 240 (
Wear material 242 in various forms and shapes may be used; for example, wear material 242 may be in the form of a rod, cylinder, sphere, tile, insert, segment, or combinations thereof.
In one embodiment, wear material 242 may be in the form of one piece or multiple pieces of tiles, covering at least the backside corner of the opening 222.
In one embodiment, wear material 242 may be in the form of one piece or multiple pieces of L- or C-shaped segments to cover at least the backside corner of the opening 222. It will be appreciated by those skilled in the art that the size and shape of the structural metal 228 forming the perforated plate 212, and the openings 222 may vary for example, to facilitate the passage of oversize reject material. In one embodiment, the openings 222 may tilt outwards from top or impact surface 234 to bottom surface 236 (
In one embodiment, the corner of the structural metal 228 facing the feed flow may be machined out, to have thicker elastomer layer between the structural metal 228 and the wear material 242 and thereby achieving higher energy dampening function (
In one embodiment, as shown in
The screen cloth 210 may be easily fabricated by molding or casting. Briefly, wear material 242 is temporarily affixed onto the mold. Elastomer coating (or liner) 230 is then filled into the annulus of the mold. Since the bonding between wear material 242 and elastomer coating (or liner) 230 is critical, wear material 242 may need to be surface prepared to ensure the proper surface profile or primer/adhesive may be required to provide suitable adhesion.
It is understood that multiple of these screen cloths 210 will be installed in a vibrating, rotating or stationary screening device's main cross members to form the screening deck (also referred to herein simply as the screen) of the vibrating or stationary screening device. Screen cloths 210 can be attached to the main cross members by means of bolts inserted through bolt holes. In one embodiment, the screen may include a feed end and a discharge end, and a plurality of screening rows positioned end to end between the feed end and the discharge end, with each screening row comprising one or more screen cloths 210 of the present invention.
The oil sand slurry having oversize reject material is screened by feeding the oil sand slurry onto the screen so that the slurry flows in the direction of the longitudinal ligaments and allows the oversize reject material to pass over the screen cloth 210. Since the wear material 242 and elastomer coating (or liner) 230 together form a protective surface, the screen cloth 210 can withstand the abrasiveness of the oil sand slurry and exhibits a considerably longer service life compared to those of prior art screen cloths.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.
| Number | Date | Country | |
|---|---|---|---|
| 62033238 | Aug 2014 | US |
