RECOVERING ENERGY FROM STOCK MOMENTUM

BACKGROUND

1. Technical Field

[0001] The present invention relates generally to recovering energy used during the fabrication of products from suspensions of suspended solids, such as paper products.

2. Description of Related Art

[0002] Paper, tissue, board, and other cellulose-based products are often fabricated from a suspension (e.g., of cellulose in water, hereinafter: stock). A headbox may inject stock between a loop of forming wire (e.g., a porous wire mesh or cloth) driven around a lead roll, and a loop of fabric (e.g., a felt or another forming wire), which is typically driven around a forming roll. Forces applied to the stock (e.g., via the headbox, the forming wire, the fabric, or the rolls) cause the water to pass through the forming wire to form a web of cellulose between the forming wire and fabric.

[0003] Large amounts of high-velocity water are ejected from the stock as it passes through the forming wire. Recovery of energy from this stock may improve the efficiency of papermaking. US patent no. 6,398,913 describes an arrangement and method for recovery of energy in a paper machine forming section, in which kinetic energy imparted to the stock is recovered via a turbine. However, such prior energy recovery apparatus may suffer from suboptimal energy recovery efficiency. Adaptability to different flow conditions and papermaking apparatus could improve the efficiency of papermaking.

[0004] FIG. 1 illustrates some challenges associated with implementing an energy recovery apparatus. A typical forming section of a papermaking machine has a forming wire loop 130 driven around a lead roll 120, a fabric loop 132 driven around a forming roll 110, and a headbox 101 configured to inject a stock 108 into a moving sandwich created by the forming wire and fabric loops.

[0005] As the machine operates, stock 108 is filtered by the forming wire 130, ejecting water through forming wire 130. A guide plate 150 guides this ejected water into a turbine 140, which is driven by the momentum of the water to generate electricity.

[0006] Several challenges with such an implementation may present themselves. In a first region 160 proximate to the lead and forming rolls, water may overshoot the guide plate. In a second region 170 proximate the turbine, water may miss the turbine and/or pass into the turbine at an inefficient angle. In such cases, the water's energy may not be harvested by the turbine. [0007] Over the guide plate in general (as illustrated in middle region 180) water may "bounce back" from the guide plate, hitting the forming roll. Such bounce back may degrade the paper product sandwiched between the fabric and forming wire.

[0008] Many designs that appear feasible "on paper" may not work as desired when actually implemented at full scale in the real world. Deformation due to gravity may displace a component, such that a desired position "on paper" is not the actual position of the component in the real world. Jet forces may deform a component. For example, a plate may have one shape before the impinging water jet is turned on, yet have a different shape when deformed by the water jet.

SUMMARY OF THE INVENTION

[0009] Kinetic energy imparted to stock during papermaking may be recovered using an apparatus for recovering energy comprising a turbine (e.g., a Banki turbine). As water is ejected through the forming wire, it may be guided to a turbine using a guide plate. The guide plate may have a shape comprising a curvature (of the surface that guides the ejected water) that efficiently captures water ejected through the forming wire and directs this water into the turbine while minimizing "bounce back" of water into the forming roll.

[0010] Various aspects provide for a guide plate for use in an apparatus for recovering energy from a forming section of a papermaking machine, an apparatus comprising such a guide plate, and/or a papermachine comprising such a guide plate.

[0011] A papermaking machine may comprise a forming wire loop driven around a lead roll, a fabric loop driven around a forming roll, and a headbox configured to inject a stock into a moving sandwich created by the forming wire and fabric or fabric loops. The apparatus may comprise a turbine coupled to a generator, a curved guide plate shaped to direct water ejected through the forming wire into the turbine.

[0012] The guide plate may have a shape comprising different curvatures. In some cases, guide plate may have a first portion having a first curvature, and a second portion having a second curvature (and may have a third portion having the second curvature). In some cases, the curvatures of the various portions are different (e.g., a second portion has a second curvature and third portion has a third curvature). In some embodiments, at least one of the second and third curvatures has a radius of curvature that is larger than that of the first portion. The second and third curvatures may be the same. In some cases, at least one of the second and third curvatures (or even both curvatures) is planar. The second and/or third curvature may be smaller than the first curvature.

[0013] A guide plate may have a curvature designed according to the geometrical layout of the forming section and expected process conditions to calculate (inter alia) one or more breakout angles. A breakout angle may be used to calculate a breakout vector, which may define expected directions in which water is ejected from the forming wire. A breakout vector may intersect the surface of the guide plate. An angle of incidence between the breakout vector may be defined by a tangent at this point of intersection and the breakout vector. The curvature of various parts of the guide plate may be chosen such that these angles of incidence meet certain criteria (e.g., are less than 25 degrees).

[0014] In some embodiments, a papermaking machine may comprise a forming section (e.g., a headbox, forming roll, lead rolls, forming wire, and fabric) and an apparatus to recover energy from stock injected by the headbox. Stock may be injected in a direction defined by one or more injection vectors 103 emanating from an opening of the headbox. One or more breakout angles may be used to define one or more breakout vectors, which may define expected directions in which filtered stock is ejected from the forming wire. The

papermaking machine may comprise an apparatus for recovering energy from the stock after ejection through the forming wire. The apparatus may comprise a turbine coupled to a generator, and a guide plate having a shape and orientation configured to direct water ejected through the forming wire into the turbine.

[0015] The shape (e.g., the curvature) and the orientation (e.g., with respect to the forming section) of the guide plate may fulfill a constraint such that fewer than 10%, preferably fewer than 5%, preferably fewer than 1%, preferably none of the incident angles between each breakout vector and the point on the guide plate at which that breakout vector intersects the guide plate exceeds 30 degrees, preferably 25 degrees, preferably 22 degrees, preferably 20 degrees, preferably 18 degrees, preferably 15 degrees, preferably 10 degrees.

[0016] Prior to actual use, a difference between an embodiment and another (e.g., prior art) device may not be apparent without the benefit of modern, computer aided design and modeling tools. Yet, while subtle, these differences are significant. A person of ordinary skill uses such tools extensively (typically exclusively) for design (e.g., using Solidworks, Pro-E, Catia, Autocad, and the like). Modeling and predictive tools are used frequently. The behavior of a design (and that of changes to the design) may be predicted using computer use modeling tools (e.g., the finite element method, FEM) that impart

representative loads to a structure and calculate the effect of these loads on the structure. Such models may predict the behavior of an apparatus during use, and by extension, distinguish between the behavior of different devices.

[0017] For large, expensive, complicated apparatus, particularly those undergoing complex reactions with the environment (e.g., a car crashing into a barrier) computer modeling may be the only way to identify a desired design prior to its manufacture and use (at which point, the ramifications of a poor design might be destructive). Various embodiments described herein require the use of computer-aided tools to compare them to other devices (in the prior art or afterwards). The use of such tools (e.g., CAD, FEM) is within the capabilities of a person of ordinary skill. Exemplary commercial packages include ANSYS, Abaqus, NASTRAN, COMSOL, and LS Dyna.

[0018] The present description claims the priority benefit and incorporates by reference Swedish patent application no. 1450812-1, filed July 1, 2014, entitled "Adjustable Device for Recovering Energy from Stock

Momentum," and Swedish patent application no. 1450823-8, filed July 2, 2014, entitled "Guide Plate Shape for Recovering Energy from Stock Momentum." The present description is related to, and incorporates by reference, PCT patent application no. , filed July 1, 2015, and entitled "Adjustable

Device for Recovering Energy from Stock Momentum."

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 illustrates an implementation of an energy recovery apparatus, according to the prior art.

[0020] FIG. 2 illustrates a forming section of a papermaking machine, according to some embodiments.

[0021] FIG. 3 illustrates an exemplary guide plate curvature, according to some embodiments.

[0022] FIG. 4 illustrates an exemplary constraint on curvature of a portion of a guide plate, according to some embodiments.

[0023] FIG. 5 illustrates an exemplary constraint on curvature of a portion of a guide plate, according to some embodiments.

[0024] FIG. 6 illustrates an exemplary constraint on curvature of a portion of a guide plate, according to some embodiments.

[0025] FIG. 7 illustrates a representative difference between two guide plate shapes, according to an embodiment.

[0026] FIGS. 8A and 8B are illustrations showing computer simulations of flow vectors (of impinging water) for forming sections and process conditions that are identical, except for the choice of guide plate shape, according to an embodiment. [0027] FIGS. 9A and 9B are "higher magnification" illustrations of the simulations shown in FIGS. 8A and 8B, respectively, .

[0028] FIGS. 10 A and 10B illustrate components of certain guide plates, according to some embodiments.

[0029] FIG. 11 illustrates a representative box section, according to some embodiments.

[0030] FIG. 12 illustrates a guide plate according to some

embodiments.

[0031] FIG. 13 illustrates a guide plate according to an embodiment, with several representative identification lines used to demarcate deformation during FEM simulations.

[0032] FIG. 14A illustrates the coordinate systems used to report the modeled behavior of the lines shown in FIG. 13, according to an embodiment.

[0033] FIG. 14B is a plot of modeled deformation (generated using ANSYS) of guide plate 1350, under both gravity loading and jet force loading (from velocity and volume of impinging water of an actual paper machine in actual operating conditions) according to an embodiment.

[0034] FIG. 15 illustrates a predicted deformation due to jet loading by impinging water, according to some embodiments. [0035] FIGS. 16 A and 16B illustrate modeled deformation of a guide plate, according to some embodiments, in this example using ANSYS.

DETAILED DESCRIPTION OF THE INVENTION

[0036] Systems and methods described herein may enable the recovery of energy during papermaking. Kinetic energy imparted to stock during papermaking may be recovered with a turbine coupled to a generator. As water is ejected through the forming wire, it may be guided to the turbine using a guide plate. The guide plate may have a specific shape that improves energy efficiency and the quality of the formed paper products

[0037] FIG. 2 illustrates a forming section of a papermaking machine, according to some embodiments. Exemplary papermaking machine 100 may include a headbox 101 configured to receive and inject stock 108. Headbox exit gap size 102 may vary among machines (e.g., between 2 and 30 mm, including 5- 25mm, including 6-18 mm, including 9-14 mm, including 12-13 mm) A position 106 of headbox 101 with respect to the lead and forming rolls (e.g., a distance from the headbox exit gap to the "sandwich" formed by the forming wire and fabric) and/or a headbox angle 104 may vary over different machines and/or process conditions.

[0038] A forming roll 110 may guide another forming wire and/or a forming fabric or felt, described herein as fabric 132. Some forming rolls have a diameter between 500 and 2500 mm, including between 700 and 2000 mm, including between 1000 and 1900 mm, including about 1200 to 1850 mm. A lead roll 120 may guide a forming wire 130.

[0039] Forming wire 130 and fabric 132 are typically disposed as loops, coming together to form a continuous "sandwich" of moving loops of forming wire 130 and fabric 132, into which headbox 101 injects stock 108. As the sandwich moves around forming roll 110, water is ejected from the sandwiched stock, leaving a cellulose web between the forming wire 130 and fabric 132. The sandwich may be separated at lead roll 122, after which the web of dewatered stock may be further processed.

[0040] Energy recovery apparatus 200 includes a turbine 140 coupled to a generator 160 and a guide plate 250. Guide plate 250 guides water (ejected through forming wire 130) into turbine 140, which drives generator 160 to generate electricity.

[0041] Guide plate 250 may have a shape comprising different curvatures. Guide plate 250 may have a first portion 260 having a first curvature, and a second portion 270 and/or 280 having a second curvature. In some cases, the curvatures of portions 260, 270, and 280 are different (e.g., portion 270 has a second curvature and portion 280 has a third curvature). In some embodiments, at least one of the second and third curvatures has a radius of curvature that is larger than that of the first portion, preferably wherein the at least one of the second and third curvatures is planar.

[0042] In exemplary FIG. 2, first portion 260 may be described as a "mid-portion" of guide plate 250. A second portion may comprise a leading portion 270 comprising a leading edge 154, located proximate to headbox 101. A second portion may comprise a terminal portion 280 including a terminal edge 153 and located proximate to turbine 140.

[0043] Different machines may have different geometric parameters, (e.g., diameters of forming roll, lead roll, and positions of these two rolls with respect to each other may vary). As such a guide plate shape, distance, and orientation with respect to the forming and lead rolls may typically be designed according to the layout of the forming section, optionally with expected process conditions. Appropriate curvatures for the various portions of guide plate 250 may be chosen using a model (e.g., a computer aided design) of the forming section comprising apparatus 200 (e.g., with shapes, curvatures, distances, and angles laid out in a CAD design). For example, the distance between the circumferences of lead roll 120 and forming roll 110 may be used to define a position of forming wire 130 as it travels from lead roll 120 to forming roll 110. Various headbox parameters (e.g., a headbox exit size 102, a headbox distance 106 from the forming wire/fabric sandwich, and headbox angle 104 may be used to identify one or more injection vectors 103. Injection vectors 103 may define an expected direction (or directions) in which stock 108 travels from headbox 101 to the sandwich created by the forming wire 130 and fabric 132 between lead roll 120 and forming roll 110.

[0044] Different papermaking machines may have different operating conditions (e.g., volume of stock/second, stock concentration, fiber type within the stock, % of recycled fiber % (e.g., % of de-inked recycled paper), fiber composition (e.g., birch, fir, spruce, pine), fiber length, fabric/wire velocity, angular velocities of various rolls, forming wire type, fabric type, and the like). Geometric data may be combined with values associated with these processing conditions to calculate breakout angles associated with the ejection of stock through the forming wire. These breakout angles may be used to define the expected angles of incidence of filtered stock (e.g., water, such as white water) impinging on the guide plate. The curvature of various parts of the guide plate may be chosen such that these angles of incidence meet certain criteria (e.g., are less than 30 degrees).

[0045] FIG. 3 illustrates an exemplary guide plate curvature, according to some embodiments. Expected process conditions may be combined with geometrical parameters to calculate expected injection vectors 103, which may be used to determine an expected set of breakout vectors 303. A breakout vector 303 may define a direction in which the filtered stock is ejected after having been filtered by the forming wire. Each breakout vector 303 may intersect guide plate 250 at a point on the guide plate, at which a tangent may be determined, resulting in an incident angle 310 for that breakout vector. Each incident angle 310 may define the angle at which a particular breakout vector 303 impinges on guide plate 250.

[0046] Breakout vectors 303 may be used to determine a shape and orientation (e.g., distance, angle) of guide plate 250. Various portions may be shaped to efficiently convert the impinging momentum of the filtered water to tangential momentum, carrying the water to the turbine with minimal frictional or turbulent losses. The shape and/or orientation of guide plate 250 may be designed such that, for a plurality of incident angles 310 resulting from the intersection of a plurality of breakout vectors 303 (over the surface of the guide plate), one or more constraints on the incident angles is fulfilled. Preferably, fewer than 10%, preferably fewer than 5%, preferably fewer than 1%, preferably no incident angles 310 between a breakout vector and the point on the guide plate at which the breakout vector intersects the guide plate exceeds 30 degrees, preferably 25 degrees, preferably 22 degrees, preferably 20 degrees, preferably 18 degrees, preferably 15 degrees, preferably 10 degrees. [0047] In exemplary FIG. 3, guide plate 250 has a first portion comprising a mid portion 260, a second portion comprising a leading portion 270, and a third portion comprising a terminal portion 280. Leading portion 270 may have a leading distance 272 from leading edge 154 to a boundary between the first (e.g., mid) and leading portions. Terminal portion 280 may have a terminal distance 282 from terminal edge 153 to a boundary between the first (e.g., mid) and terminal portions. Leading distance 272 may be the same or different than terminal distance 282. In some embodiments, leading distance 272 is smaller than terminal distance 282. Preferably, leading distance 272 may be greater than terminal distance 282.

[0048] The relationship between distances between the headbox outlet, lead roll and forming roll may be used to determine an appropriate guide plate shape. For a lead roll closer to the headbox, a leading distance 272 may be larger than for a similar configuration in which the lead roll is farther from the headbox. Leading distance 272 and/or terminal distance 282 may be between 0.05% and 10%, including between 0.1% and 8%, including between 1% and 7% of the forming roll diameter. For a forming roll having a diameter of 1500-1560 mm, leading distance 272 may be between 70 and 120 mm, including between 90 and 110 mm, and terminal distance 282 may be between 50 and 100 mm, including between 60 and 80mm. Leading edge 154 may be positioned approximately 30-50mm from the forming roll, and as close as possible (e.g., 12- 20mm) from the lead roll. Terminal edge 153 may be approximately 80-120 mm from the forming roll, including 90-110 mm from the forming roll.

[0049] In some embodiments, a first portion (e.g., a mid portion) has a radius of curvature larger than that of the forming roll (e.g., the radius of curvature of the first portion is 100%-120% of that of the forming roll, including 108% to 118%. The guide plate may include a second portion having a radius of curvature smaller than that of the forming roll (e.g., 70%-95%, including 75% to 90%). The second portion may comprise an interface between the first portion and another portion.

[0050] In some forming sections, breakout vectors 303 and

requirements of the guide plate may vary over the length of the guide plate. For example, leading portion 270 may be shaped to prevent "overspray" of filtered stock (e.g., passing above the guide plate in FIG. 3). Terminal portion 280 may be shaped to efficiently direct water into turbine 140.

[0051] FIG. 4 illustrates an exemplary constraint on curvature of a portion of a guide plate, according to some embodiments. At least a portion of the guide plate may be designed to capture filtered stock (e.g., white water) that is ejected through the forming wire before the forming wire contacts forming roll 110. FIG. 4 illustrates an exemplary leading portion 270. A breakout angle 400 between injection vector 103 and a breakout vector 403 may be used to determine an incident angle 410. Breakout angle 400 may be chosen according to a type of stock, stock concentration, fiber type, forming wire type, forming wire velocity, stock velocity, and the like. A breakout angle 400 may be chosen according to an angle of the forming wire (e.g., an angle between the forming wire (going from the lead to forming rolls). An angle between the forming wire and breakout vector 403 may be between 10 and 15 degrees, including between 12 and 14 degrees.

[0052] In some embodiments, a breakout angle (e.g., breakout angle 400) may be greater than 0 degrees, including 1-14 degrees, including 2-12 degrees, including greater than three degrees, between 3 and 9 degrees, including between 6 and 8 degrees. For some machines and/or stocks, a breakout angle may be between 4 and 16 degrees, including between 6 and 12 degrees, including between 8 and 10 degrees. The shape and orientation of guide plate 250 may be chosen such that incident angles 410 associated with various breakout vectors 403 do not exceed 30 degrees, preferably 25 degrees, preferably 22 degrees, preferably 20 degrees, preferably 18 degrees, preferably 15 degrees, preferably 10 degrees. In an exemplary embodiment, incident angles over a guide plate vary from about 14 degrees to about 20 degrees. [0053] FIG. 5 illustrates an exemplary constraint on curvature of a portion of a guide plate, according to some embodiments. FIG. 5 illustrates an exemplary mid portion 260, which may be associated with various points at which stock is ejected from the forming roll. A breakout angle 500 between a breakout vector 503 and a tangent 505 to the forming roll at the point at which breakout vector 503 is ejected from the forming roll may be greater than zero degrees, including 1-14 degrees, including 2-12 degrees, including greater than three degrees, between 3 and 9 degrees, including between 6 and 8 degrees. The shape and orientation of guide plate 250 may be chosen such that incident angles 510 associated with various breakout vectors 503 do not exceed 30 degrees, preferably 25 degrees, preferably 22 degrees, preferably 20 degrees, preferably 18 degrees, preferably 15 degrees, preferably 10 degrees. In an exemplary implementation, the incident angles vary from about 18 to about 24 degrees, including from about 20 to about 22 degrees.

[0054] FIG. 6 illustrates an exemplary constraint on curvature of a portion of a guide plate, according to some embodiments. FIG. 6 illustrates an exemplary terminal portion 280, which may be associated with various points at which stock is ejected from the forming roll. A breakout angle 500 between a breakout vector 503 and a tangent 505 to the forming roll at the point at which breakout vector 503 is ejected from the forming roll may be greater than zero degrees, including 1-14 degrees, including 2-12 degrees, including greater than three degrees, between 3 and 9 degrees, including between 6 and 8 degrees. The shape and orientation of guide plate 250 may be chosen such that incident angles 610 associated with various breakout vectors 503 do not exceed 30 degrees, preferably 25 degrees, preferably 22 degrees, preferably 20 degrees, preferably 18 degrees. In an exemplary embodiment, the incident angles vary from about 22 to 27 degrees.

[0055] In some embodiments, breakout angles may be substantially the same over the forming wire. In some cases, two or more breakout angles 300, 400, 500, 600 may differ. In some cases, a a plurality (even a continuity of many) breakout vectors is used to define a plurality of breakout angles, and the guide plate is shaped such that none of these angles exceeds a desired limit on breakout angle size. In some cases, a shape may be constrained to have a minimum breakout angle (e.g., 1, 3, 5 or even 10 degrees).

[0056] Typically, a breakout angle associated with a region in which filtered stock is ejected from the forming wire prior to the forming roll (e.g., angle 400) may be larger than (e.g., 1% larger, 2% larger, or even 5% larger) than a breakout angle associated with the ejection of stock when the forming wire is contacting the forming roll (e.g., angles 500, 600). In some embodiments, a first breakout angle 400 is between 4 and 18 degrees, including between 6 and 16 degrees, including between 8 and 14 degrees, and a second breakout angle 500, 600 is between 4 and 10 degrees, including between 5 and 9 degrees, including between 6 and 8 degrees.

[0057] Variation of these conditions and parameters may change the velocity, position, and/or shape of the water stream (or spray) ejected through forming wire 130. To accommodate differences in these characteristics, guide plate 250 may have a shaped that matches a combination of forming section dimensions and expected process conditions. Using a computer simulation (e.g., finite element modeling, FEM), according to a computer aided design (CAD) layout of the forming section, an expected set of injection vectors 103 may be identified. The points of impact of these vectors with the guide plate may be used to choose shape the guide plate to match the forming section and operating conditions. In some embodiments, a papermaking machine comprises a guide plate for which a first breakout vector 403 defines a direction in which filtered stock is ejected from the forming wire after having been filtered by the forming wire, and a first breakout angle 400 between the first breakout vector 403 and an injection vector 103. A second breakout vector 503 may define a direction in which filtered stock is ejected from a point on the forming roll, and a second breakout angle 500 between the second breakout vector 503 and a tangent 505 to the forming roll at a point on the forming roll from which the second breakout vector 503 is ejected. In some cases, a first set of breakout vectors is associated with a first portion of the guide plate, and a second set of breakout vectors is associated with a second portion of the guide plate.

[0058] Various embodiments may comprise a guide plate 250, an apparatus 200 including a guide plate 250, and/or a papermaking machine 100 comprising a guide plate 250 (e.g., as part of an apparatus 200). Some

embodiments may be identified by the guide plate itself (e.g., a guide plate having a plurality of curvatures). Some embodiments may be identified in concert with the apparatus and forming section of the papermaking machine (e.g., via experimentally determined and/or modeled breakout vectors, which may be used to calculate breakout angles).

[0059] It may be advantageous, or even necessary, to utilize modern computing tools to predict the performance of an apparatus during use, and the effect of a design change on performance change. Efficient energy harvesting may require an extremely precise guide plate shape and position, particularly with respect to the terminal edge of the guide plate. FEM simulation (e.g., using ANSYS) may incorporate loads due to gravity, the impinging water jet (of ejected stock) and the like to identify optimal shapes and positions. A design may be modeled, performance may be estimated, the design may be changed (ostensibly improved) and the changed design may be modeled to determine whether the design change improved performance. While such a process may seem "trial and error" based, it may be significantly accelerated by using criteria identified herein as "targets." For example, a constraint on impingement angle may be readily incorporated into a model, and this constraint may be used to rapidly design a guide plate (e.g., according to a particular forming section geometry) that meets this constraint.

[0060] EXAMPLE 1

[0061] FIG. 7 illustrates a representative difference between two guide plate shapes, according to an embodiment. FIG. 7 is a scale illustration. A first guide plate 710 may comprise a planar leading portion 270, and a second guide plate 720 may comprise a leading portion 270 having the same curvature as a center portion 260 of the guide plate. The incorporation of a planar leading portion 270 (in guide plate 710) results in a lower incident angle of impinging water, notwithstanding the guide plates having the same position of leading edge 154. Visually, such a change may appear small. For example, a distance 740 between the front faces of guide plates 710 and 720 might not exceed 7mm for a guide plate having a chord distance 730 of over 900 mm (e.g., below 3%, 2%, 1%, or even below 0.5%). However, while such a small change in shape may appear insignificant, it may have a significant effect on processing. [0062] FIGS. 8A and 8B are computer simulations of flow vectors (of impinging water) for forming sections and process conditions that are identical, except for the choice of guide plate shape, according to an embodiment. FIGS. 8A and 8B illustrate simulated water flow using dotted lines, in which breakout vectors represent water flow off the forming wire, after which the vectors contact the guide plate and "reflect" according to their incident angles. FIG. 8A illustrates expected flow vectors for an apparatus having guide plate 710 (FIG. 7). With guide plate 710, no flow vectors "bounce back" into forming roll 110. FIG. 8B illustrates expected flow vectors for an apparatus having guide plate 720 (FIG. 7). With guide plate 720, a portion of the flow vectors "bounce back" into forming roll 110, as shown in bounceback region 810.

[0063] FIGS. 9A and 9B are "higher magnification" illustrations of the simulations shown in FIGS. 8A and 8B, respectively. For guide plate 710, a finite distance 900 separates all flow vectors from the surface of forming roll 110 (none of the vectors bounce back into the forming roll). Such a configuration is expected to prevent ejected stock from bouncing back into the forming roll. FIG. 9B illustrates bounceback region 810, and shows how certain vectors (arriving at the leading portion of the guide plate) bounce back into the forming roll.

Bounceback of water into the forming roll may damage or deform the web of cellulose, which typically damages or degrades the subsequent paper product. [0064] FIGS. 10 A and 10B illustrate components of certain guide plates, according to some embodiments. Guide plate 1050 may comprise a back plate 1060. A back plate may cover and/or protect internal features of the guide plate. A back plate may provide a relatively smooth, "clean" surface that reduces the likelihood that unwanted material (e.g., mist, fiber) deposits on the back of the guide plate.

[0065] FIG. 10B illustrates several internal beams. The maintenance of a desired shape may require a combination of high stiffness and relatively low mass. High stiffness may increase resistance to deformation due to the

impinging water. Reduced mass may reduce gravitational loads (and the associated deformation caused by these loads). In some cases, it may be advantageous to implement one or more beams 1070, as shown with guide plate 1050'. Beams 1070 may increase the stiffness of the guide plate with relatively modest weight increases. Beams 1070 may be arranged in several directions (e.g., forming a structural "web" supporting the front face of the guide plate). Beams 1070 may be combined with back plate 1060. This combination may increase stiffness and/or reduce the deposition of unwanted material in the open regions between beams 1070.

[0066] Contact between the guide plate and moving turbine is generally undesirable. FEM simulations may be used to predict deformations, and these deformations may be minimized (with design) and/or accounted for (e.g., during installation). In some cases, it may be advantageous to incorporate a bushing (e.g., Teflon, Delrin, Duralon, and the like) that prevents inadvertent contact between the guide plate and turbine blades. In FIG. 10B, bushing mounts 1080 may be located at a portion of the guide plate (e.g., an outer edge) that, were contact with the turbine to occur, would locate this contact at a less-damaging point of the turbine (e.g., not on the blades). An exemplary bushing may be 10- 20 cm thick, including about 12-16 cm thick. A bushing may be connected to a box section and/or other structural feature "behind" the guiding surface of the guide plate.

[0067] FIG. 11 illustrates a representative box section, according to some embodiments. A guide plate may comprise one or more box sections, particularly hollow box sections, separating a front face of the guide plate form a back sheet of the guide plate. In FIG. 11, guide plate 1150 comprises box sections 1100, which may stiffen the guide plate in various directions. According to a desired size, shape, number of and distance between pivot point mounts, number of and distance between actuator mounts, the box section dimensions and sheet thicknesses (of metal) may be optimized (e.g., using FEM simulations). Optimization may comprise choosing dimensions that minimize gravity load (and its associated deformation) while still providing sufficient resistance to deformation due to the impinging water. Typical box dimensions (normal to the face of the guide plate) may be between 5mm and 300 mm, including between 10mm and 200mm, including between 20mm and 80mm, including between 30mm and 60mm. In exemplary guide plate 1150, box dimension 1110 is 40mm, and box dimensions 1120 and 1130 are 50mm.

[0068] FIG. 12 illustrates a guide plate according to some

embodiments. A guide plate may be fabricated using metal rolling techniques, which may suffice (e.g.,) for overall shape fabrication. Energy recovery optimization may require improved fabrication methods. Energy efficiency may be increased by finishing the surface of the guide plate to have an arithmetical mean roughness (Ra) that does not exceed 8 microns, particularly 3 microns, particularly 1 micron, particularly 0.5 microns, particularly 0.3 microns.

[0069] Energy recovery efficiency may be increased with the use of a terminal edge located as close as possible (e.g., closer than 3mm, or even 1 mm, or even closer than 0.6mm) to the turbine. However, the guide plate should generally not contact the turbine blades during operation. To reduce or eliminate manufacturing inaccuracies associated with rolling, a guide plate may include a machined surface. In FIG. 12, guide plate 1250 includes a machined terminal portion 1240 and a machined terminal edge 153. [0070] It may be advantageous to implement modern computer- implemented methods to design and model the behavior of various apparatus. By modeling expected loads and their effects, the guide plate may be designed to have a desired shape during operation that maximizes energy recovery.

[0071] FIG. 13 illustrates a guide plate according to an embodiment, with several representative identification lines used to demarcate deformation during FEM simulations. In this example, guide plate 1350 is a scale model. Line 1310 spans the guide plate across a cross-direction of the guide plate in leading portion 270. Lines 1320 and 1330 span the guide plate in a terminal portion 280. Lines 1310, 1320, and 1330 will be used to identify representative deformations in the following FEM simulations. A terminal portion may have a distance 282 that is between about 3 and 15 cm, including 4 and 10 cm, including between 6 and 9 cm.

[0072] EXAMPLE 2

[0073] FIG. 14A illustrates the coordinate systems used to report the modeled behavior of the lines shown in FIG. 13, according to an embodiment. In FIG. 14A, a finite element model (in this case, using ANSYS) was used for deformation modeling, according to some embodiments. FIG. 14A illustrates the coordinates used to represent deformation at line 1310 in leading portion 270 and lines 1320 and 1330 in terminal portion 280. In each portion, the relevant coordinate system comprises an x-direction that is tangent to the guide plate surface (with positive value pointing "downstream") and a y-direction that is orthogonal to the surface (of that portion). Because the surface is curved, the coordinate systems "change direction." Thus, a positive x-value for line 1310 represents deformation in a similar direction as a negative y-value (for lines 1320 and 1330). A positive y-value (for line 1310) represents a similar deformation as a positive x-value for lines 1320 and 1330. Guide plate 1350 utilizes box sections and a back sheet.

[0074] FIG. 14B is a plot of modeled deformation (generated using ANSYS) of guide plate 1350, under gravity loading and jet force (from velocity and volume of impinging water of an actual paper machine in actual operating conditions) according to an embodiment. The deformation/displacement of line 1310 does not exceed 2mm in the x-direction, or "away" from the forming roll. The deformation/displacement of line 1310 does not exceed 4mm in the negative- y direction (or "upward" in FIG. 14A. The deformation/displacement of lines 1320 and 1330 does not exceed 1.5mm in the negative-x direction (or "upward" on FIG. 14A). The deformation/displacement of lines 1320 and 1330 does not exceed 1.1mm in the negative-y direction (or "downstream" with respect to the machine direction). [0075] Deformation due to gravitational loads may be accommodated during installation. For example, a guide plate may be installed and aligned (i.e., under gravity load) with respect to the forming roll, lead roll, and turbine.

However, deformation due to jet forces requires starting and running the machine, which should not be undertaken without confidence that an apparatus will function as desired. FEM simulations may be used to determine a shape, size, and mounting configuration expected to result in a desired performance.

[0076] FIG. 15 illustrates a predicted deformation due to jet loading by impinging water, according to some embodiments. Efficiency may typically be increased by positioning the terminal edge of the guide plate very close (e.g., within a few mm, including within 2mm, including within 1mm) of the turbine. Such positioning requires confidence that, during operation, the guide plate and turbine will not contact each other inadvertently. FIG. 15 illustrates the effect of jet forces on guide plate shape and position, using lines 1310, 1320, and 1330 (FIG. 13) and the coordinate systems of FIG. 14A. The expected deformation of the terminal portion (represented by lines 1320 and 1330) does not exceed 0.12 mm in the x-direction ("downward" toward the turbine) and negative 0.15 mm in the y-direction ("downstream" toward the turbine). These values may be used to offset the terminal portion during installation. These values may also increase confidence that the shape of the guide plate will not change so much during operation (via jet forces) that performance may be hindered or the equipment may be damaged.

[0077] The lines show a "wavy" profile across the plate, associated with the position of the (two) mounting points. Increased box section thickness may be used to reduce this waviness. An increased number of mounting points (e.g., three, four, or even six mounting points) may also reduce this waviness. Comparing FIGS. 14B and 15, the importance of FEM simulations of guide plate shape become apparent. For the leading portion, gravity loads may be

appreciable. Without the jet, the leading portion may "sag" under its own weight, which could cause a portion of the jet to "pass above" the leading edge. However, jet contact with the leading portion may "lift" that portion, which could cause the leading edge to contact the lead roll. An optimal guide plate shape may capture impinging water without deforming into another component, and still maintain desired impingement angles to result in efficient energy transfer to the turbine.

[0078] For the terminal portion, the jet forces may result in significant deformation (as compared to gravity loading). In such a configuration, FEM simulations may be critical to predict an actual position of the terminal edge (with respect to the turbine) prior to starting the machine.

[0079] EXAMPLE 3 [0080] FIGS. 16 A and 16B illustrate modeled deformation of a guide plate, according to some embodiments, in this example using ANSYS. FIG. 16A illustrates the combination of jet loading and gravity loading, and illustrates a maximum deformation of the leading portion 270 (before and after the jet is turned on) of 4.31 mm. FIG. 16B illustrates deformation and displacement of the guide plate due to jet loading only, with the back plate removed to view the back side of the guiding surface per se (showing beams). FIG 16B compares the calculated deformation and displacement to an "unstressed" shape and position (which is shown as a "shadow" using exaggerated displacements in the illustration). Thus, the deformation and displacement is graphically exaggerated to facilitate viewing. The overall curvature of the guide plate may decrease slightly (the loaded guide plate is more "bowed") and the leading edge of the guide plate is moved "downstream" slightly. Additionally, the lateral bending "waviness" is shown. However, overall deformation does not exceed 0.54mm.

[0081] FEM methods may be used to design geometry (e.g., number and size of actuator and pivot connections), spacing between connections, box size and shape, metal thicknesses, and the like. This geometry may be modeled to predict an actual shape of the guide plate when loaded (during use). The actual shape may be compared with desired constraints (e.g., on impinging angles) to ensure that ejected water actually impinges at the desired angles. As a result, energy efficiency may be maximized, while probability of damage (e.g., due to inadvertent contact) may be minimized.

[0082] Embodiments need not incorporate all, or even a plurality of, features described herein. Various features described herein may be

implemented independently and/or in combination with each other. An explicit combination of features does not preclude the omission of any of these features from other embodiments.

[0083] The entirety of this description, including figures and abstract, is copyright protected, Valmet AB, Karlstad, Sweden.

[0084] The above description is illustrative and not restrictive. Many variations of the invention will become apparent to those of skill in the art upon review of this disclosure. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.