A lime slaker, a lime slaker classifier screw comprising a helical flight, and a kit of replacement spare parts for a lime slaker classifier

Abstract

The disclosure relates to a lime slaker comprising a classifier screw (1) comprising a mounting bracket (2) for coupling the screw to a drive shaft (101) of a driving arrangement (102) configured to rotate the screw, wherein the screw comprises a shaftless helical flight (3) having a first end (4) configured to be directed toward the driving arrangement (102) when mounted, and a second end (5) configured to be directed away from the driving arrangement when mounted, and in that the mounting bracket (2) is rigidly fixed to an end turn (6) of the helical flight (3) at said first end (4). The disclosure further relates to a classifier screw (1) and a kit of replacement spare parts for a lime slaker classifier (100).

Description

[0001] A lime slaker classifier screw, a lime slaker and a kit of replacement spare parts for a lime slaker classifier

[0002] Technical field

[0003] The present disclosure relates to a lime slaker and a kit of replacement spare parts for a lime slaker classifier.

[0004] Background art

[0005] Lime slakers are designed to slake lime and separate grits and typically include a slaker tank in which milk of lime is formed under agitation, and a slaker classifier fluidly connected to the slaker tank. The purpose of the classifier is to allow grit and impurities to settle, and to separate the lime slurry from the grit and impurities to ensure that only the properly slaked lime, which is in a fine particle form, is used in subsequent processes. The classifier thus helps in maintaining quality and efficiency of the lime slaking process by removing grits in the form of unwanted larger particles and waste materials, by means of a grit conveyor extending along an inclined bottom of the classifier. The grit conveyor is typically a conveyor screw having flights mounted to a sturdy center shaft supported by bearings at its upper and lower ends. To avoid friction and take account for tolerances on the straightness of the screw, there is normally a small gap between the screw flights and the bottom of the classifier. The conveyor screw is a component that drives cost for the lime slaker and there is therefore a need of providing a more efficient solution for this.

[0006] Summary

[0007] The present invention relates to a lime slaker, comprising a slaker tank and a classifier, where the classifier comprises a settling tank and a lime slaker classifier screw, and aims in particular at providing a more effective and less complicated solution for the lime slaker classifier. In order to obtain this, an improved lime slaker classifier screw is provided, said screw comprising a mounting bracket for coupling the screw to a drive shaft of a driving arrangement configured to rotate the screw. The screw comprises a shaftless helical flight having a first end configured to be directed toward and attached to the driving arrangement when mounted, and a second end configured to be directed away from the driving arrangement when mounted. The mounting bracket is rigidly fixed to an end turn of the helical flight at said first end. By the provision of a shaftless helical flight attached at the upper end (first end) where the driving arrangement is located, the helical flight of the screw can be allowed to rest on a surface of the inclined bottom of the classifier when mounted. This means that no mounting is needed at the lower second end of the screw, and installation of the lime slaker classifier screw in the classifier is thereby facilitated.

[0008] The settling tank of the lime slaker has an inclined bottom surface sloping upward at an inclination angle of 15-35 degrees, which is at least partially comprised in the settling tank. A drive arrangement for the screw is arranged at an upper end of the inclined surface. The screw is mounted to a drive shaft of the drive arrangement, and the screw is arranged to rotatably rest on the inclined bottom surface. The classifier screw with the shaftless helical flight of the reduces cost since it is less complicated and since its low weight compared to a conveyor screw with a center shaft allows the helical flight to be attached at the upper end where the driving arrangement is located and to rest on a surface of the inclined bottom of the classifier when mounted and during operation. This means that no mounting is needed at the lower second end of the screw and installation of the lime slaker classifier screw in the classifier is thereby facilitated and results in a less complicated equipment. A replaceable lining may advantageously be arranged on the inclined bottom surface of the classifier, such that the helical flight of the classifier screw is arranged to rotatably rest on the replaceable lining, thus protecting the bottom of the classifier from wear. Conveyed materials, such as those present in the lime slaking process, are prone to forming hard scaling on the bottom surface lining, causing the screw to ride on the scaling instead of the lining surface and eventually causing the screw to rise. This may require the arrangement of a hindering device in the form of a steel plate or a steel profile, such as an angle bar, arranged along one, or preferably both, sides of the screw and suitably at an angle greater than an angle R, typically at least 90°, preferably approx. 114°.

[0009] The present invention further relates to a kit of replacement spare parts for a lime slaker classifier as described above, which kit comprises a lime slaker classifier screw and a classifier lining. The classifier screw and the classifier lining of the kit are designed to be used together to replace worn lime slaker classifier screw and classifier lining and restore functionality of the slime slaker classifier.

[0010] The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the disclosure. Hence, it is to be understood that the herein disclosed disclosure is not limited to the particular component parts of the device described or steps of the methods described since such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only and is not intended to be limiting.

[0011] Brief of the

[0012] The objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the detailed description and to the following illustrative and nonlimiting example embodiments of the present invention, when taken in conjunction with the accompanying drawings.

[0013] Figure 1 shows a perspective view of a lime slaker classifier screw of the lime slaker of the present invention;

[0014] Figure 2 shows a lime slaker of the present invention;

[0015] Figure 3 is a cross-sectional view of a lime slaker classifier of the present invention including a lime slaker classifier screw;

[0016] Figure 4a is a side view of a first end of the lime slaker classifier screw of the present invention;

[0017] Figure 4b is a side view of a first end of the lime slaker classifier screw of the present invention, seen from another angle than in Fig. 3a;

[0018] Figure 5a shows a cross-sectional of the helical flight of the lime slaker classifier screw according to an embodiment of the present invention;

[0019] Figure 5b shows a cross-sectional of the helical flight of the lime slaker classifier screw according to another embodiment of the present invention;

[0020] Figure 6 shows a perspective view of a second end of a lime slaker classifier and lime slaker classifier screw of the present invention;

[0021] Figure 7 shows the lime slaker classifier screw of the present invention seen from a first end thereof together with a replaceable lining.

[0022] Figure 8 illustrates a kit of replacement spare parts for a lime slaker classifier according to the present invention. Figure 9 shows a perspective view of a second end of a lime slaker classifier and lime slaker classifier screw of the present invention;

[0023] Figure 10 shows the lime slaker classifier screw of the present invention seen from a first end thereof together with a replaceable lining.

[0024] Detailed description

[0025] The present invention aims at providing a more effective and less complicated solution for the lime slaker classifier. The lime slaker classifier screw of the lime slaker of the present invention is configured to be mounted to a driving arrangement, e.g. a motor, at an upper end of an inclined bottom of a lime slaker classifier. The lime slaker classifier screw comprises a shaftless helical flight having a first end configured to be directed toward the driving arrangement when mounted, and a second end configured to be directed away from the driving arrangement when mounted. A mounting bracket is located at the first end of the helical flight for coupling the screw to a drive shaft of the driving arrangement configured to rotate the screw, and the mounting bracket is rigidly fixed to an end turn of the helical flight at the first end.

[0026] A shaftless helical flight is less complicated and has a low weight compared to a conveyor screw with a center shaft, thus reducing cost. Further, the screw is easy to install in a lime slaker classifier due to the provision of the shaftless helical flight that is attached to the driving arrangement at the upper end of the classifier, while the helical flight of the screw can be allowed to rest on a surface of the inclined bottom of the classifier when mounted, such that no mounting is needed at the lower second end of the screw. A helical flight without a central shaft can flex and adapt to the load more effectively, reducing the risk of the helical flight lifting from the classifier bottom due to uneven material distribution. It can also handle higher fill rates compared to shafted screws, which means they can move more material more efficiently and with less risk of backflow. Thereby, operational disruptions can be minimized and the need for maintenance be reduced. Further, a hindering device in the form of a steel plate or a steel profile, such as an angle bar, can be arranged along one or both sides of the screw. The hindering device can be attached to the side walls of the settling tank or at the top of the side walls of the trough, with a mounting part that is attached to the side wall and a protruding part that extends over the screw to prevent it from lifting.

[0027] The inclined bottom surface and / or the classifier lining is designed to be substantially rigid, whereas the shaftless helical flight is designed to be flexible. In operation, the flexible shaftless helical flight is allowed to rotatably rest on the substantially rigid surface, ensuring a grit transport with essentially no gap between the helical flight and the bottom surface. However, due to practical tolerances on the straightness of the helical flight, a maximum clearance of approximately 10 mm may occur between the helical flight and the lining or bottom surface at various points along the screw's length.

[0028] The helical flight may suitably have an outer edge surface at its periphery, which is advantageously essentially flat. The outer edge surface area is defined as the total surface area of the outer edge of the helical flight designed to contact the inclined bottom surface (L-w, where L is the axial length and w is the width of the outer edge surface). When the helical flight is allowed to rest on the bottom surface of the classifier during operation, a portion of the peripheral outer edge surface will be in contact with bottom surface. As the outer edge surface of the helical flight is contact with the bottom surface, it will be subjected to wear. This is acceptable because the cost of the lime slaker classifier screw is reasonably low and the installation of the screw in the classifier is relatively simple, as described above, such that the lime slaker classifier screw can be replaced when worn out. This may be done on a regular basis, such as every 18 months, suitably at the same time as performing regular maintenance of the slime slaker.

[0029] The contact pressure applied by the helical flight on the classifier bottom surface when mounted is a parameter that may influence wear of the helical flight. The helical flight of the classifier screw of the present invention preferably has a weight per outer edge surface area of 0.02-0.05 kg / cm2, more preferably 0.035-0.04 kg / cm2, resulting in a contact pressure that does not cause excessive wear of the helical flight and at the same time allowing the classifier screw to be mounted only at its upper end, such that there is no need for a mounting bearing at the lower end of the classifier.

[0030] The width of the outer edge surface may suitably be 20-50 mm, preferably 25-35 mm, more preferably 29-31 mm, thereby balancing stiffness with contact pressure and wear. A more narrow outer edge surface may cause higher contact pressure and wear, and a wider outer edge surface may be difficult and or more expensive to manufacture.

[0031] The pitch / diameter ratio of the helical flight may influence the efficiency of material transport and the torque required. Pitch is the distance a screw would move forward in one complete revolution. The helical flight of the present classifier screw preferably has a pitch / diameter ratio of 0.3-0.6, to obtain reliable and effective material transport and limited wear. A too high pitch / diameter ratio may cause ineffective material transport due to the larger pitch and straight angle of attack, while a too low pitch / diameter ratio may cause higher wear due to the need of higher rotation speed. The helical flight may suitably have a diameter of 250-1100 mm, preferably 350-570 mm, to achieve sufficient material transport without needing too much space and keeping the cost for the screw low.

[0032] In order to reduce the weight of the helical flight, while giving improved strength and stiffness, the helical flight may advantageously comprise a first portion located at an outer edge of the helical flight and a second portion located radially inward of the first portion, where the first portion has a first rectangular cross-section with a first thickness and a first height, and the second portion having a second rectangular cross-section with a second thickness and a second height, and wherein said second thickness is less than said first thickness, preferably 40-60% of said first thickness. The first portion may suitably have a first rectangular cross-section with a first thickness of 20-50 mm, preferably 25-35 mm, and a first height of 25-70 mm, preferably 55-65 mm, and the second portion may suitably have a second rectangular cross-section with a second thickness of 10-20 mm, preferably 12-18 mm, and a second height of 45-65 mm, preferably 50-60 mm. If desired, the helical flight may comprise a third portion located radially inward of said second portion, and having a third rectangular cross-section with a third thickness and a third height, and wherein said third thickness is greater than said second thickness, to give increased stiffness from an increased area moment of inertia without increasing the weight too much. The third portion may preferably have smaller thickness than the first portion and a smaller height than the second portion.

[0033] The shaftless helical flight of the present classifier screw advantageously has a length in the axial direction of 8-15 meters, to allow effective conveying of grit from the bottom of a lime slaker classifier.

[0034] As mentioned above, a shaftless helical flight can flex and adapt to load more effectively than a screw with a center shaft, such that the shaftless helical flight is less sensitive to impact and can withstand wobbling to some extent. This means that the shaftless screw can be made in parts because it is not critical that the shaftless helical flight is absolutely straight when mounted. The shaftless helical flight may thus be comprised of two or more shaftless helical flight parts, assembled into the shaftless helical flight. This allows the helical flight to be assembled on site in connection with installation of the classifier screw, and the classifier screw can thus be transported in a more compact package, which reduces transport cost. The mounting bracket by which the classifier screw is to be mounted to the drive arrangement comprises a disc portion fixed to an end turn of the helical flight at said first end, i.e. the upper end where the drive arrangement is. The disc portion is suitably positioned such that a main surface thereof is substantially perpendicular to an axial direction of the shaftless helical flight, and a wedge portion suitably positioned at the perimeter of the helical flight between the disc portion and a part of said end turn, said wedge portion having a narrow end and a wide end and preferably having a notch at the wide end. This will distribute load and reduce stress concentrations during operation of the classifier screw, thus reducing risk of fatigue failure. The notch allows the wedge portion to flex to some extent further distributing load away from welding joint. The disc portion may have a central opening therein, allowing a shaft of the drive arrangement to be centered more easily.

[0035] Alternatively, the mounting bracket could be comprised of a short hollow cylinder attached, suitably welded, to an inward edge of the helical flight at the two or three threads closest to the first (upper) end of the helical flight and including a flange that can be attached to the drive arrangement at an upper end of the cylinder. Another alternative for the mounting bracket could be comprised of a rectangular plate welded perpendicular to the short end of the last thread, with a shaft and a plate and a reinforcement plate, which in turn is bolted to a counter plate fixed by means of welding to the shaft directly or to one or more than one plates acting as reinforcement to the said counter plate and which in turn is welded to the shaft.

[0036] The helical flight of the classifier screw may suitably be made of carbon steel to reduce the cost of the screw. Carbon steel is generally cheaper than stainless steel that is traditionally used for classifier screws. The carbon steel used for the helical flight may preferably have a hardness of 140-190 HB. This may be softer than the material of the bottom surface of the classifier against which the helical flight is allowed to rest when mounted and in operation, which would mean that the helical flight wears more than the bottom surface, which is acceptable since it is not expensive or difficult to replace the classifier screw of the present invention. Details regarding the material of the helical flight is discussed further below in connection with the description of a lime slaker comprising the present classifier screw.

[0037] The lime slaker of the present invention comprises slaker tank and a classifier comprising a settling tank, which is fluidly connected to the slaker tank. In the slaker tank slaked lime is formed under agitation. Slaked lime is a suspension of fine particles of calcium hydroxide (Ca(OH)2) in water and is highly alkaline and can be used in various industrial applications, including water treatment, food processing, and as a neutralizing agent in wastewater treatment. Lime slakers may be used for example in the causticizing stage of a chemical recovery cycle within the kraft sulphate process of the pulp and paper industry. The slaking reaction which is exothermic result in an increase in temperature within the slaker. Following this, the second reaction, known as causticizing, occurs, producing sodium hydroxide and calcium carbonate. In these processes, particularly during slaking, larger particles known as grits are formed, which consist of various non-process elements. These unwanted particles are removed from the process by means of a settling tank comprising a conveyor screw collecting the particles, most of which tend to sink.

[0038] The settling tank of the classifier has an inclined bottom surface sloping upward and being at least partially comprised in the settling tank. A support post can be arranged under the inclined bottom surface to help carry the weight of the settling tank. The settling tank can have a V-shaped cross section with side walls narrowing down toward the screw and trough at the inclined bottom of the settling tank, to facilitate the movement of settled particles towards the center help and concentrate the settled grit at the lowest point, making it easier to remove and ensuring that heavier particles are efficiently collected and do not remain suspended in the slurry. A V-shaped tank is also compact, making it suitable for installations where space is limited. A discharge port may be arranged at the bottom of the classifier to allow emptying the settling tank in connection with maintenance.

[0039] A drive arrangement for the screw, e.g. a motor, is arranged at an upper end of the inclined bottom surface and the classifier screw is mounted to a drive shaft of the drive arrangement and is arranged to rotatably rest on the inclined surface. As discussed above, the shaftless helical flight of the classifier screw has a simple construction and low weight allowing it to be attached at its upper end and to rest on the inclined bottom of the classifier when mounted and during operation. This means that no mounting is needed at the lower second end of the screw and installation of the lime slaker classifier screw in the classifier is thereby facilitated and results in a less complicated and cost-efficient equipment. The grit transport obtained by the classifier screw is also improved because the helical flight is in contact with the inclined bottom surface with essentially no gap between the helical flight and the bottom surface. A discharge outlet for conveyed grit and impurities is suitably arranged at an upper end of the inclined bottom surface.

[0040] The inclined bottom surface in the lime slaker classifier helps heavier grit and impurities settle more efficiently. The settled grit can then be elevated by the classifier screw and discharged, ensuring a cleaner lime slurry. By aiding in the separation and removal of grit, the inclined surface helps reduce wear and tear on the equipment, leading to lower maintenance requirements. The inclination angle may be chosen based on the space available for the classifier and should preferably be kept at 35 degrees or less, to ensure good conveying efficiency, as by avoiding too much friction preventing grit particles from being conveyed by the screw. The inclined bottom surface of the classifier is suitably sloping upward at an inclination angle of 15-35 degrees, preferably 25-35 degrees, to balance space needed for the classifier with conveying efficiency.

[0041] As mentioned above, the pitch / diameter ratio of the helical flight may preferably be 0.3-0.6 to obtain reliable and effective material transport and limited wear. The choice of pitch / diameter ratio may advantageously also take the inclination angle of the inclined bottom surface into account. Based on a specified diameter of the helical flight and a specified inclination angle the pitch can preferably be determined by the following formula:

[0042] P = (1 - 1 / 30 ■ d) ■ a + 1.44 ■ d - 28 where P is pitch; d is helical flight diameter; a is inclination angle.

[0043] In practice, the actual pitch of the helical flight may suitably be 80-120% of the target pitch value (P) determined by the formula P=(l-l / 30 • d) • a +1.44 • d - 28, to ensure effective material transport while allowing for practical manufacturing tolerances and variations in operating conditions, i.e. 0.8 ‘P — P actual — 1.2 ’P .

[0044] Because the helical flight is shaftless and is allowed to rest on the inclined bottom surface of the classifier, the lower end of the helical flight need not be mounted to the classifier. It is thus preferred that the classifier screw is unattached to the classifier at the second end (lower end) of the helical flight. The elimination of the need to mount the screw at bottom of the classifier in turn eliminates the need of having an access port at the bottom end of the classifier, such that the classifier settling tank can be closed at the bottom. Thereby there will be no risk that the highly alkaline liquid held within the settling tank might leak, and risk of staff injury caused by leaking chemicals is thus reduced. Traditional classifier screws with center shaft cannot withstand wobbling and must be mounted at both ends and thus require an access port at the bottom of the classifier in order to enable mounting at the lower end, and there will therefore be a potential risk of staff injury due to leakage.

[0045] A replaceable lining may advantageously be arranged on the inclined bottom surface of the classifier, whereby the helical flight of the classifier screw is arranged to rotatably rest on the replaceable lining, and not directly on the bottom surface of the settling tank. Thereby, the replaceable lining wears instead of the bottom of settling tank, thus substantially increasing the classifier lifetime.

[0046] The replaceable classifier lining may suitably have the shape of an elongated classifier lining through having a bottom portion and side portions, where the bottom portion and side portions preferably form a U-shape, to improve feeding capacity. The replaceable classifier lining may suitably have a thickness of 8-15 mm, more preferably approximately 10 mm. The U-shape may preferably envelop the circumference of the helical flight up to at least 60 degrees on each side of a vertical line through the center of the helical flight. The phrase "up to at least 60 degrees on each side" means that the coverage extends at least 60 degrees to the left and 60 degrees to the right of this vertical line, such that the coverage spans 120 degrees around the circumference of the helical flight. Preferably, the classifier lining may envelop the circumference of the helical flight approximately 85-95 degrees, i.e. approximately half the circumference of the helical flight. The replaceable classifier lining may suitably have a cutout or opening in its bottom portion at the end configured to be positioned at the upper end of the screw and adapted to provide an opening corresponding to the grit discharge outlet of the classifier to allow passage of grit conveyed by the classifier screw. The replaceable classifier lining may further suitably have a cutout or opening in its bottom portion at the end configured to be positioned at the lower end of the screw and adapted to provide an opening corresponding to the discharge opening for emptying the settling tank in connection with maintenance.

[0047] As mentioned above, the helical flight of the screw may suitably be made of a steel that is softer than the material of the inclined bottom surface of the classifier. This may apply also when a replaceable lining is used, such that the classifier screw may wear faster that the replaceable lining. This may be advantageous since it is easier to replace the classifier scare than the replaceable lining. The replaceable lining may for example need to be replaced only every second time the classifier screw is replaced. Accordingly, the helical flight of the screw is suitably made of a first steel having a first hardness and the replaceable lining may be made of a second steel having a second hardness, said second hardness being greater than said first hardness. The details given here regarding the material of the classifier screw included in the lime slaker applies as well to the independent classifier screw described above. The first hardness (i.e. of the material of the helical flight) may preferably be below 250 HB, such as 140-190 HB, as determined according to Standard EN ISO 6506 (Brinell Hardness). The second hardness (i.e. of the material of the replaceable lining) may preferably be at least 300 HBW, more preferably 370 HBW - 700 HBW as determined according to Standard EN ISO 6506-1 (Brinell Hardness Wolfram). A suitable steel for the classifier screw may be a mild steel, such as a structural steel S355, and a suitable steel for the replaceable lining may be for example a abrasion resistant steel, e.g. a hardened and rolled steel, such as a Hardox®400 to Hardox®600 steel.

[0048] The present invention further relates to a kit of replacement spare parts for a lime slaker classifier as described above, which kit comprises a lime slaker classifier screw as described above, and a classifier lining. The classifier screw and the classifier lining of the kit are designed to be used together to replace a worn lime slaker classifier screw and classifier lining and restore functionality of the slime slaker classifier. The classifier lining may preferably be in the form of a classifier lining trough having a bottom portion and side portions, the bottom portion and side portions preferably form a U-shape, such that it fits well at the inclined bottom surface of the classifier. The classifier lining may be configured to fit into an existing through for a classifier screw, and act as a protective lining for the existing through. Alternatively, the classifier lining may be designed to function independently as a through for a classifier screw and act as a protective lining for the bottom surface of the classifier. The lime slaker classifier screw of the invention as well as the kit of replacement spare parts may also be used as a retrofit solution for a lime slaker classifier having a conventional lime slaker classifier screw, with or without protective lining installed in the existing lime slaker, such that when replacing a conventional lime slaker screw with a lime slaker classifier screw according to the present invention, a classifier lining can be installed at the same time and the lime slaker can thereby be converted to the new type of lime slaker having the lime slaker classifier screw and classifier lining according to the present invention.

[0049] Similarly, as has been mentioned above regarding the replaceable lining, the classifier lining of the kit of replacement spare parts may suitably have the shape of an elongated classifier lining through having a bottom portion and side portions, where the bottom portion and side portions preferably form a U-shape, to improve feeding capacity. The U-shape may preferably envelope circumference of the helical flight up to at least 60 degrees of a vertical line through the center of the helical flight, preferably approximately 85-95 degrees.

[0050] Further, as has been discussed above, the helical flight of the screw may suitably be made of a first steel having a first hardness and the replaceable lining may suitably be made of a second steel having a second hardness, where the second hardness is greater than said first hardness. All details regarding choice of material for the helical flight of the classifier screw and the replaceable classifier lining discussed above in relation to the classifier of the lime slaker apply also to the kit of replacement spare parts.

[0051] Description of example embodiments

[0052] The present invention will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person.

[0053] Figure 1 shows a lime slaker classifier screw 1 of the lime slaker of the present invention. Figure 2 illustrates a lime slaker classifier 100 in which the lime slaker classifier screw of the present invention is used and illustrates how the screw is mounted in the settling tank 103 classifier. The lime slaker classifier screw 1 comprises a mounting bracket 2 for coupling the screw to a drive shaft 101 of a driving arrangement 102 configured to rotate the screw. The screw 1 comprises a shaftless helical flight 3 having a first end 4 configured to be directed toward the driving arrangement 102 when mounted, and a second end 5 configured to be directed away from the driving arrangement when mounted. The helical flight 3 has an outer edge surface 7 at its periphery, said outer edge surface having a width (w) of 20-50 mm. The driving arrangement is arranged at the upper end of the classifier, and when mounted to the driving arrangement, the screw 1 is allowed to rotatably rest on the inclined bottom surface 104. The bottom surface may be sloping upward at an inclination angle (a) of 15-35 degrees.

[0054] The screw is preferably unattached to the classifier at the second end 5 of the helical flight. A discharge outlet 111 for conveyed grit and impurities is arranged at the upper end of the inclined bottom surface 104. A support pillar can be arranged under the inclined surface of the classifier.

[0055] Figure 3 shows a lime slaker 110 comprising slaker tank 120 and a classifier 100. and wherein the screw 1 is mounted to a drive shaft 101 of the drive arrangement 102, and wherein the screw is arranged to rotatably rest on the inclined surface 104.

[0056] The mounting bracket is shown in more detail in Figs. 4a-4b. The mounting bracket 2 is rigidly fixed to the helical flight 3 at the first end 4 of the screw 1. A disc portion 11 is fixed to the end turn 6 of the helical flight 3 at the first end 4 and being positioned such that a main surface 12 thereof is substantially perpendicular to an axial direction A of the shaftless helical flight 3, and a wedge portion 13 positioned at the perimeter of the helical flight between the disc portion 11 and a part of said end turn 6, said wedge portion 13 having a narrow end 14 and a wide end 15 and preferably having a notch 16 at the wide end 15.

[0057] Fig. 5a shows how the helical flight comprises a first portion 8 located at an outer edge of the helical flight, said first portion having a first rectangular cross-section with a first thickness tl and a first height hl, and a second portion 9 located radially inward of said first portion 8 and having a second rectangular cross-section with a second thickness t2 and a second height h2, and wherein said second thickness t2 is less than said first thickness tl, preferably 40-60% of said first thickness tl.

[0058] Fig. 5b shows a helical flight according to an alternative embodiment, wherein the helical flight in addition to a first portion 8 and a second portion 9 having height and thickness as in the helical flight of Fig. 5a, further comprises a third portion 10 located radially inward of said second portion 9, and having a third rectangular cross-section with a third thickness t3 and a third height h3, and wherein said third thickness t3 is greater than said second thickness t2.

[0059] Figure 6 shows the second (lower) end of the lime slaker classifier 100 and the lime slaker classifier screw 1 and illustrates V-shaped cross section of the settling tank 103 (Fig. 1) with side walls 116 narrowing down toward the classifier screw 1 and the trough 106 at the inclined bottom of the settling tank. Fig. 6 also shows the replaceable lining 105 having the shape of an elongated classifier lining through 106, arranged on the inclined surface of the classifier. As shown in Fig. 7, the bottom portion 107 and side portions 108 may form a U- shape. In the shown example, the lining envelopes the helical flight 3 approximately 85-95 degrees (angle B) of a vertical line (v) through the center of the helical flight.

[0060] Figure 8 shows a kit of replacement spare parts for a lime slaker classifier such as the one shown in Fig. 2. The kit comprises a lime slaker classifier screw 1 as described above and illustrated in Fig. 1 and a classifier lining 105 as described above. The classifier lining 105 is preferably in the form of a classifier lining trough 106 having a bottom portion 107 and side portions 108. The lime slaker classifier screw 1 and classifier lining 105 have the same characteristics as described above for the lime slaker classifier screw 1 and the classifier lining 105 and are designed to be used together to replace worn lime slaker classifier screw 1 and classifier lining 105 and restore functionality of the slime slaker classifier 100. An opening 112 is provided in the bottom portion 107 of the lining 105, at the upper end 4 of the screw, and is adapted to the grit discharge outlet 111 of the lime slaker classifier into which the lining is to be used.

[0061] Fig. 9 illustrates how an opening 113 is provided in the bottom portion 107 of the lining, at the lower end 5 of the screw, is adapted to provide an opening corresponding to the discharge opening 114 for emptying the settling tank in connection with maintenance.

[0062] Figs. 9 and 10 also shows hindering devices in the form of angle bars 115 are arranged on each side of the screw 1 to prevent the screw from lifting too far from the bottom of the trough 106. The angle bars 115 are attached to the side walls 116 of the settling tank with a mounting part 117 attached to the side walls 116 and a protruding part 118 extending over the screw 1 to prevent it from lifting.

[0063] The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.

Claims

CLAIMS1. A lime slaker (110) comprising a slaker tank (120) and a classifier (100), said classifier comprising a settling tank (103) and a lime slaker classifier screw (1), wherein an inclined bottom surface (104) sloping upward at an inclination angle (a) of 15-35 degrees, preferably 25-35 degrees, is at least partially comprised in the settling tank, and a drive arrangement (102) for the screw (1) is arranged at an upper end of said inclined surface (104) and wherein the screw (1) is mounted to a drive shaft (101) of the drive arrangement (102) configured to rotate the screw, and wherein the screw is arranged to rotatably rest on the inclined bottom surface (104), characterized in that the classifier screw (1) comprises a mounting bracket (2) for coupling the screw to a drive shaft (101); and a shaftless helical flight (3) having a first end (4) configured to be directed toward the driving arrangement (102) when mounted, and a second end (5) configured to be directed away from the driving arrangement when mounted, and in that the mounting bracket (2) is rigidly fixed to an end turn (6) of the helical flight (3) at said first end (4).

2. The lime slaker of claim 1, wherein the helical flight (3) has an outer edge surface (7) at its periphery, said outer edge surface having a width (w) of 20-50 mm, preferably 25-35 mm, more preferably 29-31 mm.

3. The lime slaker of any one of claims 1 - 2, wherein the helical flight (3) has a weight per outer edge surface area of 0.02-0.05 kg / cm2, preferably 0.035-0.04 kg / cm2.

4. The lime slaker of any one of claims 1 - 3, wherein the helical flight (3) has a diameter (d) of 250-1100 mm, preferably 350-570 mm.

5. The lime slaker of any one of claims 1 - 4, wherein the helical flight comprises a first portion (8) located at an outer edge of the helical flight, said first portion having a first rectangular cross-section with a first thickness (tl) and a first height (hl), and a second portion (9) located radially inward of said first portion (8) and having a second rectangular crosssection with a second thickness (t2) and a second height (h2), and wherein said second thickness (t2) is less than said first thickness (tl), preferably 40-60% of said first thickness (tl).

6. The lime slaker of claim 5, wherein the first portion (8) has a first rectangular crosssection with a first thickness (tl) of 20-50 mm, preferably 25-35 mm, and a first height (hl) of 25-70 mm, preferably 55-65 mm, and the second portion (9) has a second rectangular cross-section with a second thickness (t2) of 10-20 mm, preferably 12-18 mm, and a second height (h2) of 45-65 mm, preferably 50-60 mm.

7. The lime slaker of claim 5 or 6, wherein the helical flight comprises a third portion (10) located radially inward of said second portion (9), and having a third rectangular crosssection with a third thickness (t3) and a third height (h3), and wherein said third thickness (t3) is greater than said second thickness (t2).

8. The lime slaker of any one of claims 1 - 7, wherein the mounting bracket (2) comprises a disc portion (11) fixed to said end turn (6) of the helical flight (3) at said first end (4) and being positioned such that a main surface (12) thereof is substantially perpendicular to an axial direction (A) of the shaftless helical flight (3), and a wedge portion (13) positioned at the perimeter of the helical flight between the disc portion (11) and a part of said end turn (6), said wedge portion (13) having a narrow end (14) and a wide end (15) and preferably having a notch (16) at the wide end (15).

9. The lime slaker of any one of claims 1 - 8, wherein the helical flight (3) of the screw (1) is made of carbon steel, preferably having a hardness of 140-190 HB.

10. The lime slaker of any one of claims 1 - 9, wherein the screw is unattached to the classifier at the second end of the helical flight.

11. The lime slaker of claim any one of claims 1 - 10, wherein a replaceable lining (105) is arranged on said inclined surface (104) whereby the helical flight (3) is arranged to rotatably rest on the replaceable lining.

12. The lime slaker of any one of claims 1-11, wherein the replaceable classifier lining (105) has the shape of an elongated classifier lining through (106) having a bottom portion (107) and side portions (108), said bottom portion (107) and side portions (108) preferably forming a U-shape, and further preferably enveloping said helical flight (3) up to at least 60 degrees of a vertical line through the center of the helical flight, preferably approximately 85- 95 degrees.

13. The lime slaker of any one of claims 1-12, wherein the helical flight (3) of the screw (1) is made of a first steel having a first hardness and the replaceable lining (105) is made of a second steel having a second hardness, said second hardness being greater than said first hardness, said first hardness preferably being below 250 HB, e.g. 140-190 HB and said second hardness preferably being at least 300 HBW, preferably 370 HBW - 700 HBW.

14. A lime slaker classifier screw (1) comprising a mounting bracket (2) for coupling the screw to a drive shaft (101) of a driving arrangement (102) configured to rotate the screw, characterized in that the screw comprises a shaftless helical flight (3) having a first end (4) configured to be directed toward the driving arrangement (102) when mounted, and a second end (5) configured to be directed away from the driving arrangement when mounted, and in that the mounting bracket (2) is rigidly fixed to an end turn (6) of the helical flight (3) at said first end (4).

15. A kit of replacement spare parts for a lime slaker classifier (100) in a lime slaker according to any one of claims 1-18, said kit comprising: a lime slaker classifier screw (1) comprising a mounting bracket (2) for coupling the screw to a drive shaft (101) of a driving arrangement (102) configured to rotate the screw, and a shaftless helical flight (3) having a first end (4) configured to be directed toward the driving arrangement (102) when mounted, and a second end (5) configured to be directed away from the driving arrangement when mounted, and in that the mounting bracket (2) is rigidly fixed to an end turn (6) of the helical flight (3) at said first end (4); and a classifier lining (105), preferably being in the form of a classifier lining trough (106) having a bottom portion (107) and side portions (108), said bottom portion (107) and side portions (108) preferably forming a U-shape, and further preferably enveloping said helical flight (3) up to at least 60 degrees on each side of a vertical line through the center of the helical flight, preferably approximately 85-95 degrees; wherein the lime slaker classifier screw (1) and classifier lining (105) are designed to be used together to replace worn lime slaker classifier screw (1) and classifier lining (105) and restore functionality of the slime slaker classifier (100).

Images