DOUBLE SIDED MIXER

Abstract: A double sided mixer promotes efficient and effective chemical bleaching of pulp. In the case of oxygen bleaching, mixing of gas by the transverse motion of rotors (78, 81) through the pulp occurs throughout the mixer (10). A double sided mixer has more rotors per unit volume, and low energy and material requirements.

Description: DOUBLE SIDED MIXER BACKGROUND OF THE INVENTION There are many mixers used with wood pulp. One is described in U.S. Patent 4,303,470. A mixer manufactured by Kamyr is described in "State of the Art Chlorine Dioxide Mixer Installed at Weyerhaeuser," Pulp & Paper, June 1984, pp. 119-121. A mixer is the subject of U.S. Patent 4,435,085. We are aware of mixers manufactured by Rauma-Repola of Finland and IMPCO of U.S.A. Advertisements describing the Rauma-Repola mixer are included with this patent application. SUMMARY OF THE INVENTION The Rauma mixer has an asymetrical flow and has long pins agitating the pulp. However, better mixing is provided by a symetrical flow. Further, less power is required when pins are better utilized. The instant invention has a design in which pins are placed on both sides of a rotating plate to obtain greater mixing per unit power and to cause the pulp to exit on the back side of the rotating plate in order to provide uniform and symetrical flow of the pulp through the mixer. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of the mixer. Figure 2 is a back plan view of the mixer with a portion cut away along line 2-2 of Figure 1. Figures 3 and 4 are isometric views of the rotors, Figure 3 showing a double sided rotor and Figure 4 showing a single sided rotor. Figure 5 is a front plan view of the mixer with a portion cut away along line 3-3 of Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figures 1-5, the mixer 10 has a housing 15 and a rotating member 70. The housing 15 has an inlet pipe 20, a body 30 and a back plate 55 with outlet pipes 57. The inlet 20 is a cylindrical pipe 21 having a collar or flange 22 on its outer end. There are bolt holes 23 in the outer flange 22 for fastening the inlet to a pipe. There is a lining 24 on the cylindrical pipe 21 and an outer lining 25 on the outer face of flange 22 and a lining 26 on the inner edge of the cylinder 21. The linings 24, 25 and 26 are continuous and are composed of SYGEF, a trade name for a highly crystalline organic-fluoride polymer, to resist corrosion. The cylinder 21 is attached to the body 30. The body has a front plate 31 and side walls 32 forming a bowl. Anti-rotation vanes 33 are spaced around the inner periphery of the side walls 32. Each of the anti-rotation vanes 33 has a central relief 34 to accommodate the rotating member 70. The baffles prevent the rotation of the pulp slurry while it is being mixed by the rotating member. The body members are also lined. There is a lining 35 on the inner face of the front plate 31, a lining 36 on the inner face of the side wall 32 and a lining 37 on the edge of side wall 32. Stators are located on the front plate. There is a cincture of outer stators 38 and a cincture of inner stators 43 surrounding the inlet 20 mounted on the front plate 31. The outer stators 38 have outer heads 39 and attachment threads 40. The stators 38 are threaded into inserts 41 in the front plate 31. The inserts 41 have threads 42 into which the threads 40 of stator 38 are threaded. The inner stators 43 have outer heads 44 and threads 45 and again are inserted into inserts 46 in the front plate 31 which have threads 47. The gas passage 48 extends through the stator 43 for the introduction of gases and liquids into the mixer. An additional gas passage 100 extends through the shaft 84 and the rotating member 70 to a midpoint on the neutral axis of the rotor 81. The body 30 is attached to the back plate 55 by bolts -49 and nuts 50. The back plate 55 also has a lining 56 and a pair of outlets 57 fastened to it. The outlets 57 are preferably elbows. The elbows are shown as being short, but they may extend upwardly above the upper edge of back plate 55. A mechanical seal 58 surrounds the shaft 84 and is sealed to the back plate 55 with an O-ring 59 to prevent pulp fiber from exiting the housing 15. The rotating member 70 has a circular main frame 71 driven by a shaft 84 connected to a motor 101. The shaft 84 narrows to a square stem 89 that supports and translates torque to a brace 90, a back cone 76, a rotor disk 72 and two laminae 74. The brace 90, back cone 76 and rotor disk are attached to the stem 89 by a washer 87 and nut 88 secured to the stem 89 by a stud 86. A front cap 75 is attached to the laminae 74 by welding to form the front cone 73. Thus, the circular main frame 71 has a front cone 73, a rotor disk 72 and a back cone 76 braced against the stem 89 by a brace 90. There is a lining 77 on the back cone 76, a lining 91 on the brace 90 and a lining 85 on the shaft 84. The linings 77, 91 and 85 are continuous and are also composed of SYGEF. The rotor disk 72 has a cincture of outer double sided rotors 78 and cincture of inner single sided rotors 81. The inner single sided rotors 81 have a base 82 and an extension 83. The base 82 inserts into the front side of the rotor disk 72 for attachment of the inner rotor to the rotor disk. The inner single sided rotors 81 are placed on the rotor disk 72 to extend between the outer stators 38 and the inner stators 43. The outer double sided rotors 78 have a base 79 and two extensions 80. The base 79 inserts into either side of the rotor disk 72 for attachment of the inner rotor to the rotor disk. The outer double sided rotors 78 are placed on the rotor disk 72 to extend from the front side of the rotor disk to lie between the outer stators 38 and the anti-rotation vanes 33. The rotors 78 also extend from the back side of the rotor disk to lie adjacent to the anti-rotation vanes 33 on the pulp outlet side of the mixer 10. Wood pulp having a consistency of 1-18% on a dry basis enters the double sided mixer through the inlet pipe 20. The pulp is evenly distributed to the periphery of the mixer by the front cone 73. As the pulp passes to the periphery of the mixer it transversely passes cinctures of rotors and stators where mixing of pulp with fluids, such as gases and liquids, occurs. The effectiveness of mixing is determined by swept area as shown in U.S. Patent 4,303,470. For example, an increase in swept area is obtained by an increase in the length of rotors, travel of rotors and rotation of the rotating member 70. The passage of pulp transverse to the rotors is maintained by anti-rotation vanes 33. The anti-rotation vanes enable the pulp to move radially across the rotating member to obtain maximum swept area per rotor length, travel and rotation speed. After passing axially by the anti-rotation vanes, the pulp transversely passes more rotors and moves radially towards the mixer axis and completes its movement around the rotating member. The pulp is guided towards outlet pipes 57 by a back cone 76 and discharged.

Claims: CLAIMS 1. An apparatus for mixing fluids and chemicals with a wood pulp having a consistency of 1-18% comprising, a housing, a pulp inlet attached to said housing, a circular disk within said housing having a front and back face wherein said front face is opposite said pulp inlet, means for rotating said circular disk, rotors attached to said front face of said circular disk having an axis extending perpendicular to the directon of rotation, rotors attached to said back face of said circular disk having an axis extending perpendicular to the direction of rotation, and a pair of juxtaposed pulp outlets attached to said housing, said pulp outlets positioned opposite said back face of said circular disk and adjacent to said rotating means, whereby said pulp enters said housing through said pulp inlet, passes transverse to said front face rotors wherein said front face rotors are rotating, travels around said circular disk, passes transverse to said back face rotors wherein said back face rotors are rotating, and leaves said housing through said pulp outlets. 2. A mixer as claimed in claim 1 wherein anti-rotation vanes are attached to said housing. 3. A mixer as claimed in claim 1 wherein stators are attached to said housing opposite said front face of said circular disk certain of said stators having means for fluid and chemical addition. 4. A mixer as claimed in claim 3 wherein said stators and said rotors are cincturally located. 5. A mixer as claimed in claim 1 wherein certain of said rotors have means for fluid and chemical addition.

Inventors: BENTVELZEN JOSEPH MARIA, JORDAN MARVIN FRANKLIN, MEREDITH MICHAEL DEAN, BENTVELZEN, JOSEPH, MARIA, JORDAN, MARVIN, FRANKLIN, MEREDITH, MICHAEL, DEAN
Applicants: WEYERHAEUSER CO, WEYERHAEUSER COMPANY
Application year: 1986
Main classification: B01F15
IPC codes: B01F5, B01F7, D21C9