Defoaming device for papermaking pulp

Abstract

The defoaming device comprises a headbox, the headbox comprises a lip lower plate located at the bottom of a lip of the headbox and a lip upper plate located at the top of the lip, and a pulp flowing channel is formed between the lip lower plate and the lip upper plate; a through defoaming hole is formed in the lip upper plate; the upper surface of the lip lower plate is covered with a C12 or above higher fatty alcohol defoaming agent coating with the preset thickness; and a cooling device is arranged on the lower surface of the lip lower plate and is used for cooling the higher fatty alcohol defoaming agent. The upper surface of the lip lower plate is covered with a layer of C12 or above higher fatty alcohol defoaming agent with the preset thickness, tiny bubbles in slurry firstly make contact with the upper surface of the lip lower plate, and due to the existence of the defoaming agent coating, the small bubbles are rapidly combined into large bubbles, so that the bubbles in the lip lower plate are separated from the upper surface of the lip lower plate. And bubbles are discharged from the top end by utilizing the defoaming holes of the lip upper plate, so that the aim of simply and continuously defoaming is fulfilled on the premise of not influencing other structures of the headbox and not adding an additional defoaming agent.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and more particularly to a defoaming device for papermaking pulp. Background Art

[0002] In papermaking technology, the headbox is an essential key equipment, and its main function is to effectively disperse the fibers. The high-turbulence headbox can generate high-intensity micro-turbulence, which can effectively disperse the fibers, prevent fiber precipitation and re-flocculation, and effectively improve the strength of the paper sheet.

[0003] With the continuous advancement of papermaking technology, the process of special paper making is no longer limited to the preparation of pulp from traditional plant fibers. Inorganic fibers and synthetic resin fibers are also used. Various surfactants are added for pulp dispersion and homogenization, and high-speed shearing methods such as pulping and refining are used to form stably dispersed pulp. Due to the good adsorption and aggregation characteristics of surfactants, it is very easy to generate many tiny bubbles. These bubbles occupy a certain volume in the pulp, which will squeeze the space originally occupied by the pulp fibers, making the fibers easily adhere and agglomerate in the headbox, resulting in defects on the finished paper sheets and reduced quality.

[0004] At present, the defoaming method of paper pulp can change the local surface tension of the bubbles in the slurry through mechanical disturbance, vacuum, vibration, etc. The surface tension around the foam is almost unchanged, and the bubbles can be broken due to the traction and extension of the surface tension. Or a defoamer is directly added to the pulp slurry to destroy the double-layer stable structure of the bubbles and break the bubbles. For example, patent CN108071045 discloses a defoamer for papermaking, which is characterized by comprising higher fatty alcohols, higher fatty alcohol polyethers, fatty acid esters, silicone compositions, surfactants and deionized water.

[0005] These methods all have some disadvantages, such as complex mechanical structure, which may cause secondary bubbles to be generated even though the bubbles may be eliminated. Or the excessive amount of defoamer added may affect the multiple recycling of white water. Moreover, the defoamer may be kinetically unstable depending on the degree of reaction, and may easily lead to incomplete defoaming.

[0006] Therefore, how to provide a defoaming device for papermaking pulp with a simple structure and good defoaming effect has become a technical problem that urgently needs to be solved in the field. Summary of the invention

[0007] The object of the present invention is to provide a defoaming device for papermaking pulp which has a simple structure and good defoaming effect.

[0008] The present invention provides a defoaming device for papermaking pulp, comprising a flow box, wherein the flow box comprises a lip lower plate located at the bottom of the lip thereof and a lip upper plate located at the top of the lip, wherein a flow channel is formed between the lip lower plate and the lip upper plate; the lip upper plate is provided with through defoaming holes; a layer of a carbon twelve or higher higher fatty alcohol defoaming agent coating of a preset thickness is covered on the upper surface of the lip lower plate; a cooling device is provided on the lower surface of the lip lower plate, and the cooling device is used to cool the higher fatty alcohol defoaming agent.

[0009] Optionally, the higher fatty alcohol defoamer includes one or more of lauryl alcohol, tetradecanol, hexadecanol, stearyl alcohol, and eicosanol mixed in any proportion.

[0010] Optionally, the defoaming device further comprises a negative pressure component, which is arranged above the lip upper plate to create a negative pressure environment above the defoaming hole.

[0011] Optionally, a plurality of defoaming holes are evenly distributed on the lip upper plate, and the area of ​​the defoaming holes accounts for 5% to 18% of the area of ​​the entire lip upper plate.

[0012] Optionally, the negative pressure component includes a defoaming pipe and a vacuum pump, the defoaming pipe is located above the lip upper plate, and the vacuum pump is connected to the defoaming pipe.

[0013] Optionally, the lower surface of the lip upper plate is provided with a hydrophobic coating.

[0014] Optionally, the material of the hydrophobic coating includes one of silicone, polytetrafluoro emulsion, long-chain alkane, aromatic hydrocarbon, cycloalkane, polysiloxane, and paraffin, and the hydrophobic coating is sprayed on the lower surface of the lip upper plate.

[0015] Optionally, the cooling device includes a water chiller and a cooling jacket. The cooling jacket is arranged on the lower surface of the lip lower plate. The water chiller continuously replenishes cooling water into the cooling jacket and refluxes to form a cycle.

[0016] Optionally, a water chiller controls the water temperature of the cooling jacket to maintain at 5°C to 15°C.

[0017] Optionally, the inner surface roughness of the headbox is less than 1.6 μm.

[0018] According to the technical content disclosed in the present invention, the following beneficial effects are achieved:

[0019] The defoaming device for paper pulp provided by the present invention mainly acts on the lip of the headbox of the papermaking equipment, by covering the upper surface of the lower plate of the lip with a preset thickness of a high-grade fatty alcohol defoamer with carbon 12 or more, the high-grade fatty alcohol defoamer with carbon 12 or more is insoluble in water, and will not cause dissolution loss due to contact with the papermaking pulp; such defoamers have a high freezing point, and exist in a solid state at room temperature (20°C) or low temperature (<20°C), so setting a cooling device to cool the high-grade fatty alcohol defoamer can prevent the defoamer coating from dissolving due to excessive ambient temperature. The tiny bubbles in the slurry first contact the upper surface of the lower plate of the lip, and due to the presence of the defoamer coating, the small bubbles quickly merge into larger bubbles, quickly float up and use the defoamer holes of the upper plate of the lip to discharge the bubbles from the top, without affecting the rest of the headbox structure and without adding additional defoamers, to achieve the purpose of simple and continuous defoaming.

[0020] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0022] Figure 1 The present invention is a structural diagram of a defoaming device for paper pulp.

[0023] Figure 2 It is a structural diagram of the lip upper plate of the present invention.

[0024] Explanation of the reference numerals: 1. headbox; 10. slurry; 11. slurry inlet; 12. lip upper plate; 13. defoaming hole; 14. defoaming pipe; 15. vacuum pump; 16. lip lower plate; 17. cooling jacket; 18. chiller; 2. mesh drive roller; 21. mesh cloth; 3. dewatering box; 31. dewatering plate. DETAILED DESCRIPTION

[0025] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0026] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0027] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0028] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0029] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0030] The present invention mainly provides an efficient and simple defoaming device, which mainly acts on the lip of the headbox of papermaking equipment. By spraying a layer of defoaming agent on the upper surface of the lower plate 16 of the headbox lip, and using the defoaming holes and hydrophobic coating of the upper plate 12 of the lip to discharge bubbles from the top, the purpose of simple and continuous defoaming is achieved without affecting the other structures of the headbox and without adding additional defoaming agent.

[0031] See also Figure 1 The present invention discloses a defoaming device for papermaking pulp, comprising a headbox 1 and a mesh conveyor belt, wherein the mesh conveyor belt comprises a mesh driving roller 2 and a mesh 21, wherein the mesh driving roller 2 can rotate around its axis to drive the mesh 21 to move forward, and the forward direction is a direction gradually away from the headbox 1.

[0032] The headbox 1 is arranged on the material-incoming side of the mesh cloth conveyor belt, specifically, arranged above the front side of the mesh driving roller 2 .

[0033] A dehydration box 3 is arranged below the mesh cloth 21 of the upper layer, and a dehydration plate 31 is arranged on the top of the dehydration box 3 .

[0034] The flow box 1 includes a lip lower plate 16 located at the bottom of its lip and a lip upper plate 12 located at the top of the lip, and a flow channel is formed between the lip lower plate 16 and the lip upper plate 12; the lip upper plate 12 is provided with a through defoaming hole 13; a layer of a carbon twelve or higher higher fatty alcohol defoaming agent of a preset thickness is covered on the upper surface of the lip lower plate 16; a cooling device is provided on the lower surface of the lip lower plate 16, and the cooling device cools the higher fatty alcohol defoaming agent.

[0035] The papermaking slurry 10 enters the slurry flow channel from the slurry inlet of the slurry flow box 1, and the slurry 10 flows in the slurry flow channel toward the mesh conveyor belt; during the flow of the slurry 10, the slurry 10 reacts with the high-grade fatty alcohol defoamer with carbon 12 or above covering the surface of the lip lower plate 16, and the tiny bubbles in the slurry 10 first contact the upper surface of the lip lower plate 16. Due to the presence of the defoamer coating, the small bubbles quickly merge into larger bubbles, float up quickly, and are discharged from the defoaming holes 13 of the lip upper plate 12. It should be noted that in this embodiment, the defoamer is sprayed on the upper surface of the lip lower plate 16 by spraying.

[0036] The cooling device includes a chiller 18 and a cooling jacket 17. The cooling jacket 17 is arranged on the lower surface of the lip lower plate 16. The chiller 18 continuously replenishes cooling water into the cooling jacket 17 and refluxes to form a circulation. The chiller 18 controls the water temperature of the cooling jacket 17 to maintain 5°C to 15°C, ensuring that the defoamer sprayed on the upper surface of the lip lower plate 16 is in an insoluble state, ensuring that the higher fatty alcohol defoamer with carbon twelve or more will not melt, and is maintained in a solid form on the upper surface of the lip lower plate 16, so that only the surface portion of the higher fatty alcohol defoamer contacts and acts on the slurry 10. It can be seen that the key point of the present invention is to spray the defoaming agent on the upper surface of the lip lower plate 16. After the tiny bubbles in the slurry 10 come into contact with the lip lower plate 16, the stable double-layer stable system that has been formed is destroyed due to the change in surface tension, and the small bubbles gradually merge into large bubbles, further increasing the thermodynamic instability in the slurry system, producing a chain reaction, and the bubbles gradually become larger. Due to the buoyancy, the large bubbles will gradually float to the surface of the slurry and be quickly released through the defoaming holes.

[0037] The defoamer sprayed on the upper surface of the lip lower plate 16 is a high-grade fatty alcohol with carbon 12 or above, and the spraying thickness is 100-500μm. Including but not limited to: one or more of dodecanol, tetradecanol, hexadecanol, octadecanol, and eicosanol mixed in any proportion. This type of defoamer is insoluble in water and will not cause dissolution loss due to contact with papermaking pulp; this type of defoamer has a high freezing point and exists in solid form at room temperature (20°C) or low temperature (<20°C), and will not be carried away by the pulp due to melting. If there is no cooling water jacket, the defoamer coating will dissolve if the ambient temperature is too high.

[0038] Furthermore, a hydrophobic coating is provided on the lower surface of the lip upper plate 12. The material of the hydrophobic coating includes one of silicone, polytetrafluoro emulsion, long-chain alkane, aromatic hydrocarbon, cycloalkane, polysiloxane, and paraffin. The hydrophobic coating is sprayed on the lower surface of the lip upper plate 12 with a spraying thickness of 2-10 μm. After spraying, a dense hydrophobic layer is formed on the panel. A plurality of defoaming holes 13 are evenly distributed on the lip upper plate 12. The area of ​​the defoaming holes 13 accounts for 5% to 18% of the area of ​​the entire lip upper plate 12.

[0039] The defoaming device further includes a negative pressure component, which is disposed above the lip upper plate 12 to create a negative pressure environment above the defoaming hole 13. The negative pressure component includes a defoaming pipe 14 and a vacuum pump 15. The defoaming pipe 14 is located above the lip upper plate 12. The vacuum pump 15 is connected to the defoaming pipe 14. The vacuum pump 15 is used to evacuate the defoaming pipe 14 to form a slightly negative pressure state, with a pressure of -5 to -50Pa.

[0040] It can be seen that the lip upper plate 12 is provided with a plurality of defoaming holes 13, and a hydrophobic layer is sprayed on the lower surface of the lip upper plate 12. In this way, on the one hand, due to the good drainage of the lip upper plate 12, large floating bubbles are not easy to stay on its surface; on the other hand, a certain degree of micro-negative pressure can be applied through the defoaming tube 14, and the bubbles are discharged through the defoaming holes.

[0041] Furthermore, the inner surface roughness of the entire device including the headbox 1 is less than 1.6 μm.

[0042] Device pretreatment process:

[0043] First, remove the lower lip plate 16 of the headbox, heat the defoaming agent to the melting point to fully melt it, put it into an ultrasonic atomizer to spray the upper surface of the lower lip plate, then put it into a cold press to control the temperature at 10°C, and pressurize and solidify the upper surface to form a dense defoaming layer with a thickness of 200μm.

[0044] Then remove the headbox lip upper plate 12, put the hydrophobic agent into the ultrasonic atomization device to spray and dry the lower surface of the lip upper plate 12 to form a dense hydrophobic layer with a thickness of 6 μm.

[0045] The headbox is installed according to the designed structure. In addition, a cooling jacket 17 and a chiller 18 are arranged on the lip lower plate 16 , and a vacuum pump 15 is connected to the defoaming pipe 14 of the lip upper plate 12 .

[0046] Defoaming process:

[0047] Turn on the chiller 18 to make the water temperature of the cooling jacket 17 in the lip lower plate 16 10° C.; turn on the vacuum pump 15 to make the pressure of the defoaming tube 14 -25Pa.

[0048] The papermaking slurry is pumped into the headbox 1 through the slurry inlet 11. The tiny bubbles in the slurry 10 first contact the upper surface of the lip lower plate 16. Due to the presence of the defoaming agent coating, the small bubbles quickly merge into larger bubbles and float up quickly. When the bubbles contact the lower surface of the lip upper plate 12, due to the presence of the hydrophobic agent coating, the bubbles are difficult to stay on the lower plate surface and eventually move to the defoaming hole position. Driven by the micro-negative vacuum, the bubbles are discharged through the defoaming holes 13 to complete the defoaming process.

[0049] Papermaking process:

[0050] Since the bubbles in the slurry 10 have been completely discharged, the fibers in the pulp can be effectively and evenly dispersed, and the white water in the slurry 10 is filtered through the dewatering plate 31 to the dewatering box 3. The mesh roller 2 drives the mesh 21 to move forward, leaving the fibers on the mesh 21 to form a uniform paper sheet.

[0051] It should be noted that if the defoamer is directly added to the slurry 10, the excessive amount of defoamer added will affect the multiple recycling of white water; and the defoamer will be kinetically unstable with different reaction degrees, and the defoaming problem is prone to incomplete. Defoaming with a defoamer coating only requires breaking the stable thermodynamic state of the bubbles, and the direction-driven diversion is eliminated, which is more efficient and stable.

[0052] In summary, the defoaming device for paper pulp provided by the present invention is used to eliminate bubbles in paper pulp. Rapid elimination of bubbles is achieved by means of defoaming agent coating, hydrophobic agent coating, micro-negative pressure suction and the like. It has a simple structure and can achieve stable defoaming without adding complex mechanical equipment such as additional mechanical disturbance, ultrasonic vibration, centrifugal rotation, etc.; there is no need to add additional defoaming agent, and by breaking the original thermodynamically stable state of the slurry, small bubbles are gradually enlarged and driven by diversion to eliminate them in a certain direction; this defoaming structure is located at the lip of the headbox, which effectively avoids the generation of secondary bubbles, and can directly carry out dehydration and papermaking, and the paper sheets have good uniformity and no defects.

[0053] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A defoaming device for papermaking pulp, comprising a headbox, wherein the headbox comprises a lip lower plate located at the bottom of the lip and a lip upper plate located at the top of the lip, wherein a slurry flow channel is formed between the lip lower plate and the lip upper plate, and wherein: The upper plate of the lip is provided with through defoaming holes; A layer of carbon twelve or higher fatty alcohol defoamer with a preset thickness is covered on the upper surface of the lower lip plate; a cooling device is arranged on the lower surface of the lower lip plate to cool the higher fatty alcohol defoamer.

2. The defoaming device for papermaking pulp according to claim 1, characterized in that: The higher fatty alcohol defoamer includes one or more of lauryl alcohol, tetradecanol, hexadecanol, octadecyl alcohol and eicosanol mixed in any proportion.

3. The defoaming device for papermaking pulp according to claim 1 or 2, characterized in that: The defoaming device further comprises a negative pressure component, which is arranged above the lip upper plate to create a negative pressure environment above the defoaming hole.

4. The defoaming device for papermaking pulp according to claim 3, characterized in that: The lip upper plate is evenly distributed with a plurality of defoaming holes, and the area of ​​the defoaming holes accounts for 5% to 18% of the entire area of ​​the lip upper plate.

5. The defoaming device for paper pulp according to claim 3, characterized in that: The negative pressure component comprises a defoaming pipe and a vacuum pump. The defoaming pipe is located above the lip upper plate, and the vacuum pump is connected to the defoaming pipe.

6. The defoaming device for papermaking pulp according to claim 1 or 2, characterized in that: The lower surface of the lip upper plate is provided with a hydrophobic coating.

7. The defoaming device for paper pulp according to claim 6, characterized in that: The material of the hydrophobic coating includes one of silicone, polytetrafluoro emulsion, long-chain alkane, aromatic hydrocarbon, cycloalkane, polysiloxane and paraffin, and the hydrophobic coating is sprayed on the lower surface of the lip upper plate.

8. The defoaming device for papermaking pulp according to claim 1 or 2, characterized in that: The cooling device comprises a water chiller and a cooling jacket. The cooling jacket is arranged on the lower surface of the lip lower plate. The water chiller continuously replenishes cooling water into the cooling jacket and refluxes to form a cycle.

9. The defoaming device for papermaking pulp according to claim 8, characterized in that: The water chiller controls the water temperature of the cooling jacket to maintain at 5°C to 15°C.

10. The defoaming device for papermaking pulp according to claim 1 or 2, characterized in that: The inner surface roughness of the headbox is less than 1.6 μm.

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