Papermaking wood pulp and preparation process thereof

Abstract

The invention relates to papermaking wood pulp and a preparation process thereof. According to the process, high temperature is kept in the latency step of wood pulp production, so that separation of resin and fibers is facilitated, a micromolecule form easy to combine is kept, and the micromolecule is combined with the added papermaking sludge; the papermaking sludge and the resin in the pulp are fully combined and eliminated in the subsequent heavy slag removal step, so that the content of the resin in the wood pulp and subsequent flocculation are reduced, the generation of resin adhesive particles in the finished pulp is reduced, and the influence of formed impurity points on paper is reduced.

Description

Technical Field

[0001] The invention relates to the field of papermaking, and in particular to a papermaking wood pulp and a preparation process thereof. Background Art

[0002] In the papermaking wood pulp line, the raw material of papermaking wood pulp is wood chips. However, some wood materials, such as eucalyptus, contain a lot of resin particles. After the wood chips are broken by the system, the resin particles in the fiber flow into the pulp, which is easy to cause impurities in the paper machine and affect the quality of the paper. Due to the problem of resin particles, the pressure screen is also prone to flocculation of resin clumps, making the screen frame easy to scale and the pressure screen easy to self-wash, affecting the output. At the same time, the amount of wood pulp added to the paper machine is also limited due to its high resin content.

[0003] At present, in order to solve the problem of resin particles, resin glue control agents are generally used. The resin glue control agents are added into the slurry for intervention. However, the price of resin glue control agent is 20,000 yuan per barrel / ton, and the cost of resin control is high.

[0004] Papermaking sludge is produced after papermaking wastewater in the papermaking industry is treated by treatment facilities. Papermaking sludge is a biological solid waste and needs to be disposed of in sanitary landfills, which not only wastes land resources but also causes secondary pollution. Summary of the invention

[0005] In view of the above problems, the present application provides a process for preparing papermaking wood pulp, which uses papermaking sludge to solve the problem of resin particle flocculation, reduces costs, and improves the production efficiency of papermaking wood pulp.

[0006] The first aspect of the present application provides a process for preparing papermaking wood pulp, the process comprising the following steps:

[0007] Pre-treatment: Clean and dehydrate wood slices with a moisture content of more than 40%;

[0008] Steaming: Send the pre-treated wood slices into the steaming chamber for steaming at a temperature of 90-95°C for 20-30 minutes.

[0009] First extrusion impregnation: the steamed wood slices are sent to the first double-screw extrusion impregnation machine for the first extrusion impregnation, and the impregnation liquid is a 3% sodium hydroxide solution;

[0010] First stay reaction: put the output of the first double screw extrusion impregnation machine into the first reaction chamber at a temperature of 85-95°C and stay for 20-30 minutes for reaction;

[0011] Secondary extrusion impregnation: the output of the first stay reaction is sent to the second double-screw extrusion impregnation machine, and the impregnation liquid is added for secondary extrusion impregnation;

[0012] First grinding and refining: the output of the second double-screw extrusion impregnation machine is subjected to first grinding and refining to obtain first grinding pulp;

[0013] Secondary retention reaction: the first mixed pulp after the first disc grinding is put into the second reaction chamber to stay for 20 to 30 minutes for reaction;

[0014] Secondary disc refining: the output of the secondary retention reaction is subjected to secondary disc refining, and the pulping temperature is ≥90°C to obtain secondary disc refining pulp;

[0015] De-latency: dilute the secondary disc pulp with hot water to obtain a diluted pulp; add papermaking sludge to the diluted pulp, stir and mix at 65-75°C for 20-30 minutes;

[0016] Pulping: The mixed pulp after latent removal is subjected to heavy slag removal, pressure screen screening, and multi-disc concentration to obtain the papermaking wood pulp.

[0017] Different from the prior art, the high temperature is maintained in the de-latching step of wood pulp production, which is beneficial to the separation of resin and fiber, maintaining the small molecular form that is easy to combine with the added paper sludge; stirring and mixing at 65-75°C for 20-30 minutes, the paper sludge is fully combined with the resin in the slurry, and eliminated in the subsequent heavy slag removal step, thereby reducing the resin content in the wood pulp, as well as the subsequent flocculation, reducing the generation of resin glue particles in the pulp, and reducing the impact of the formation of impurity points on paper.

[0018] Furthermore, in the delatency step, the temperature of the hot water is 45-65°C.

[0019] Furthermore, in the delatency step, the concentration of the diluted slurry is 4-6%, and the temperature of the diluted slurry is ≥ 70°C.

[0020] Furthermore, in the delatching step, the concentration of the papermaking sludge is 1.0-6.0% and the temperature is 30-60°C.

[0021] Furthermore, in the de-latency step, the amount of papermaking sludge added is 5-15% of the absolute dry weight of the secondary disc pulp.

[0022] Furthermore, in the delatching step, the amount of papermaking sludge added is 10-20% of the mass of the wood chips.

[0023] Furthermore, in the de-substrate step, the papermaking sludge includes flotation sludge, deinking sludge, and sewage secondary sedimentation tank sludge.

[0024] Furthermore, the wood is eucalyptus wood.

[0025] Furthermore, in the pulping step, the screen opening of the pressure screen is 1.5-1.7 mm, and the screening concentration is 1.2-1.8%.

[0026] The second aspect of the present application also provides a papermaking pulp, which is prepared by any process described in the first aspect of the present application.

[0027] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the written contents of the specification, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the specific implementation mode and drawings of the present application are explained below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and shall not be considered as limitations of the present application.

[0029] In the drawings of the specification:

[0030] Figure 1 It is a schematic diagram of the preparation process of papermaking wood pulp. DETAILED DESCRIPTION

[0031] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0032] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0033] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0034] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0035] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0036] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0037] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0038] The recycled sludge described in the present application is a kind of sludge generated in the papermaking process that has been subjected to a series of treatments such as filtration pressing, fermentation deodorization, and white water concentration adjustment to make it active and better adsorbed on fibers, and then recycled into the pulp.

[0039] The heavy slag removal described in this application utilizes the eddy current centrifugal principle to remove heavy impurities in the slurry. The slurry enters the conical separation body from the slurry inlet along the tangential direction under a certain pressure, forming a high-speed eddy current motion. The eddy current axially close to the separation tube wall is directed to the end of the cone, and the heavy impurities in the slurry are thrown to the wall of the device and discharged from the lower end slag discharge nozzle. At the same time, the good slurry gathers toward the center of the separation tube to form the main slurry flow, which is sent out from the upper good slurry port to enter the next process. This design allows impurities with a higher specific gravity to be separated under the action of centrifugal force and gravity, while pulp fibers with a lower specific gravity are discharged from the upper part and enter other processing steps. The heavy slag remover is suitable for various slurry purification systems, and can effectively remove heavy impurities such as sand, iron filings, fibers, and some light impurities, ensuring the quality of the slurry and the efficiency of subsequent treatment. In this application, papermaking sludge particles are heavy impurities, and papermaking sludge particles can adsorb resin in the slurry and are removed in the heavy slag removal step.

[0040] In this embodiment, heavy slag removal adopts five stages, and the process parameters are:

[0041] The first stage of low concentration: pressure 138kpa, feed concentration 0.8-1.5%, good pulp concentration 0.8-1.2%, slag concentration 2.0-2.5%, pressure drop 110-130kPa, slag pressure 10-50kPa, slag rate 15-25%; the second stage of low concentration: pressure 138kpa, feed concentration 0.7-1.2%, good pulp concentration 0.8-1.0%, slag concentration 2.0-3.0%, pressure drop 110-130kPa, slag pressure 10-50kPa, slag rate 20-28%; the third stage of low concentration: pressure 138kpa, feed concentration 0.5-0.9%, good pulp concentration 0.4-0.8%, slag concentration 2 .0~3.0%, pressure drop 110~130kPa, slag discharge pressure 10~50kPa, slag discharge rate 20~28%; four-stage low concentration: pressure 138kPa, inlet pulp concentration 0.5~0.9%, good pulp concentration 0.4~0.8%, slag discharge concentration 2.0~3.0%, pressure drop 110~130kPa, slag discharge pressure 10~50kPa, slag discharge rate 20~28%; five-stage low concentration: pressure 138kPa, inlet pulp concentration 0.5~0.9%, good pulp concentration 0.4~0.8%, slag discharge concentration 2.0~3.0%, pressure drop 110~130kPa, slag discharge pressure 10~50kPa, slag discharge rate 20~28%. In this embodiment, the screen gap of the pressure screen is 1.5~1.7mm, and the screening concentration is 1.2~1.8%.

[0042] The first aspect of the present application provides a process for preparing papermaking wood pulp, the process comprising the following steps:

[0043] Pre-treatment: Clean and dehydrate wood slices with a moisture content of more than 40%;

[0044] Steaming: The pre-treated wood slices are sent to the steaming chamber for steaming at a temperature of 90-95°C for 20-30 minutes. The high temperature softens the wood fibers for easy separation. Steaming can also remove air from the slices, allowing the subsequent impregnation liquid to better penetrate and diffuse in the fibers, which is beneficial to the subsequent removal of the resin.

[0045] First extrusion impregnation: the steamed wood slices are sent to the first double-screw extrusion impregnation machine for the first extrusion impregnation, and the impregnation liquid is a 3% sodium hydroxide solution;

[0046] First stay reaction: put the output of the first double screw extrusion impregnation machine into the first reaction chamber at a temperature of 85-95°C and stay for 20-30 minutes for reaction;

[0047] Secondary extrusion impregnation: the output of the first stay reaction is sent to the second double-screw extrusion impregnation machine, and the impregnation liquid is added for secondary extrusion impregnation;

[0048] First grinding and refining: the output of the second double-screw extrusion impregnation machine is subjected to first grinding and refining to obtain first grinding pulp;

[0049] Secondary retention reaction: the first mixed pulp after the first disc grinding is put into the second reaction chamber to stay for 20 to 30 minutes for reaction;

[0050] Secondary disc refining: the output of the secondary retention reaction is subjected to secondary disc refining, and the pulping temperature is ≥90°C to obtain secondary disc refining pulp;

[0051] De-latency: dilute the secondary disc pulp with hot water to obtain a diluted pulp; add papermaking sludge to the diluted pulp, stir and mix at 65-75°C for 20-30 minutes;

[0052] Pulping: The mixed pulp after latent removal is subjected to heavy slag removal, pressure screen screening, and multi-disc concentration to obtain the papermaking wood pulp.

[0053] Different from the prior art, the high temperature is maintained in the de-latching step of wood pulp production, which is beneficial to the separation of resin and fiber, maintaining the small molecular form that is easy to combine with the added paper sludge; stirring and mixing at 65-75°C for 20-30 minutes, the paper sludge is fully combined with the resin in the slurry, and eliminated in the subsequent heavy slag removal step, thereby reducing the resin content in the wood pulp, as well as the subsequent flocculation, reducing the generation of resin glue particles in the pulp, and reducing the impact of the formation of impurity points on paper.

[0054] Furthermore, in the delatency step, the temperature of the hot water is 45-65°C.

[0055] Furthermore, in the delatency step, the concentration of the diluted slurry is 4-6%, and the temperature of the diluted slurry is ≥ 70°C.

[0056] Furthermore, in the delatching step, the concentration of the papermaking sludge is 1.0-6.0% and the temperature is 30-60°C.

[0057] Furthermore, in the de-latency step, the amount of papermaking sludge added is 5-15% of the absolute dry weight of the secondary disc pulp.

[0058] Furthermore, in the delatching step, the amount of papermaking sludge added is 10-20% of the mass of the wood chips.

[0059] Furthermore, in the de-substrate step, the papermaking sludge includes flotation sludge, deinking sludge, and sewage secondary sedimentation tank sludge.

[0060] Furthermore, the wood is eucalyptus wood.

[0061] Furthermore, in the pulping step, the screen opening of the pressure screen is 1.5-1.7 mm, and the screening concentration is 1.2-1.8%.

[0062] The second aspect of the present application also provides a papermaking pulp, which is prepared by any process described in the first aspect of the present application.

[0063] Example 1

[0064] Pre-treatment: Slice the eucalyptus wood with a moisture content of more than 40%, remove impurities, clean and dehydrate;

[0065] Steaming: The pre-treated wood slices are sent to the steaming chamber for steaming at a temperature of 90-95°C for 20-30 minutes. The high temperature softens the wood fibers for easy separation. Steaming can also remove air from the slices, allowing the subsequent impregnation liquid to better penetrate and diffuse in the fibers, which is beneficial to the subsequent removal of the resin.

[0066] First extrusion impregnation: the steamed wood slices are sent to the first double-screw extrusion impregnation machine for the first extrusion impregnation, and the impregnation liquid is a 3% sodium hydroxide solution;

[0067] First stay reaction: put the output of the first double screw extrusion impregnation machine into the first reaction chamber at a temperature of 85-95°C and stay for 20-30 minutes for reaction;

[0068] Secondary extrusion impregnation: the output of the first stay reaction is sent to the second double-screw extrusion impregnation machine, and the impregnation liquid is added for secondary extrusion impregnation;

[0069] First disk refining: the output of the second double screw extrusion impregnation machine is subjected to first disk refining, and the pulping concentration is 24-30% to obtain the first disk refining pulp;

[0070] Secondary retention reaction: the first mixed pulp after the first disc grinding is put into the second reaction chamber to stay for 20 to 30 minutes for reaction;

[0071] Secondary disc refining: The output of the secondary retention reaction is subjected to secondary disc refining, with a refining concentration of 24-30% and a pulping temperature of 90°C to obtain secondary disc refined pulp;

[0072] De-latching: dilute the secondary disk pulp with 60°C hot water to obtain a diluted pulp; the concentration of the diluted pulp is 5%, and the temperature of the diluted pulp is 80°C; add papermaking sludge with a concentration of 3.0% and a temperature of 50°C to the diluted pulp, and stir and mix at 70°C for 20 to 30 minutes; the amount of papermaking sludge added is 10% of the absolute dry weight of the secondary disk pulp;

[0073] Pulping: The mixed pulp after latent removal is subjected to heavy slag removal, pressure screen screening (the screen opening of the pressure screen is 1.5-1.7 mm, and the screening concentration is 1.2-1.8%), and multi-disc concentration to obtain the papermaking eucalyptus pulp.

[0074] Example 2

[0075] Pre-treatment: Slice the eucalyptus wood with a moisture content of more than 40%, remove impurities, clean and dehydrate;

[0076] Steaming: The pre-treated wood slices are sent to the steaming chamber for steaming at a temperature of 90-95°C for 20-30 minutes. The high temperature softens the wood fibers for easy separation. Steaming can also remove air from the slices, allowing the subsequent impregnation liquid to better penetrate and diffuse in the fibers, which is beneficial to the subsequent removal of the resin.

[0077] First extrusion impregnation: the steamed wood slices are sent to the first double-screw extrusion impregnation machine for the first extrusion impregnation, and the impregnation liquid is a 3% sodium hydroxide solution;

[0078] First stay reaction: put the output of the first double screw extrusion impregnation machine into the first reaction chamber at a temperature of 85-95°C and stay for 20-30 minutes for reaction;

[0079] Secondary extrusion impregnation: the output of the first stay reaction is sent to the second double-screw extrusion impregnation machine, and the impregnation liquid is added for secondary extrusion impregnation;

[0080] First disk refining: the output of the second double screw extrusion impregnation machine is subjected to first disk refining, and the pulping concentration is 24-30% to obtain the first disk refining pulp;

[0081] Secondary retention reaction: the first mixed pulp after the first disc grinding is put into the second reaction chamber to stay for 20 to 30 minutes for reaction;

[0082] Secondary disc refining: The output of the secondary retention reaction is subjected to secondary disc refining, with a pulping concentration of 24-30% and a pulping temperature of 95°C to obtain secondary disc refined pulp;

[0083] De-latching: dilute the secondary disk pulp with 50°C hot water to obtain a diluted pulp; the concentration of the diluted pulp is 4% and the temperature of the diluted pulp is 70°C; add papermaking sludge with a concentration of 2.0% and a temperature of 40°C to the diluted pulp, and stir and mix at 65°C for 20 to 30 minutes; the amount of papermaking sludge added is 12% of the absolute dry weight of the secondary disk pulp;

[0084] Pulping: The mixed pulp after latent removal is subjected to heavy slag removal, pressure screen screening (the screen opening of the pressure screen is 1.5-1.7 mm, and the screening concentration is 1.2-1.8%), and multi-disc concentration to obtain the papermaking eucalyptus pulp.

[0085] Example 3

[0086] Pre-treatment: Slice the eucalyptus wood with a moisture content of more than 40%, remove impurities, clean and dehydrate;

[0087] Steaming: The pre-treated wood slices are sent to the steaming chamber for steaming at a temperature of 90-95°C for 20-30 minutes. The high temperature softens the wood fibers for easy separation. Steaming can also remove air from the slices, allowing the subsequent impregnation liquid to better penetrate and diffuse in the fibers, which is beneficial to the subsequent removal of the resin.

[0088] First extrusion impregnation: the steamed wood slices are sent to the first double-screw extrusion impregnation machine for the first extrusion impregnation, and the impregnation liquid is a 3% sodium hydroxide solution;

[0089] First stay reaction: put the output of the first double screw extrusion impregnation machine into the first reaction chamber at a temperature of 85-95°C and stay for 20-30 minutes for reaction;

[0090] Secondary extrusion impregnation: the output of the first stay reaction is sent to the second double-screw extrusion impregnation machine, and the impregnation liquid is added for secondary extrusion impregnation;

[0091] First disk refining: the output of the second double screw extrusion impregnation machine is subjected to first disk refining, and the pulping concentration is 24-30% to obtain the first disk refining pulp;

[0092] Secondary retention reaction: the first mixed pulp after the first disc grinding is put into the second reaction chamber to stay for 20 to 30 minutes for reaction;

[0093] Secondary disc refining: The output of the secondary retention reaction is subjected to secondary disc refining, with a pulping concentration of 24-30% and a pulping temperature of 100°C to obtain secondary disc refined pulp;

[0094] De-latching: dilute the secondary disk pulp with 45°C hot water to obtain a diluted pulp; the concentration of the diluted pulp is 6%, and the temperature of the diluted pulp is 80°C; add papermaking sludge with a concentration of 6.0% and a temperature of 60°C to the diluted pulp, and stir and mix at 75°C for 20 to 30 minutes; the amount of papermaking sludge added is 5% of the absolute dry weight of the secondary disk pulp;

[0095] Pulping: The mixed pulp after latent removal is subjected to heavy slag removal, pressure screen screening (the screen opening of the pressure screen is 1.5-1.7 mm, and the screening concentration is 1.2-1.8%), and multi-disc concentration to obtain the papermaking eucalyptus pulp.

[0096] After the technical solution of this application was put into use by our company, 342.5 tons of sludge were recycled every month, and resin glue control agent was no longer used, which reduced production costs. At the same time, due to the reduction of resin glue flocculation, no glue clumps formed by resin glue were seen on the screen frame of the pressure screen, which prevented the scaling of the screen frame. The pressure screen does not scale, the pressure screen throughput increases, the screen does not self-clean, and the overall production capacity is improved.

[0097] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A process for preparing wood pulp for papermaking, characterized in that: The process comprises the following steps: Pre-treatment: Clean and dehydrate wood slices with a moisture content of more than 40%; Steaming: Send the pre-treated wood slices into the steaming chamber for steaming at a temperature of 90-95°C for 20-30 minutes. First extrusion impregnation: the steamed wood slices are sent to the first double-screw extrusion impregnation machine for the first extrusion impregnation, and the impregnation liquid is sodium hydroxide solution; First stay reaction: put the output of the first double screw extrusion impregnation machine into the first reaction chamber at a temperature of 85-95°C and stay for 20-30 minutes for reaction; Secondary extrusion impregnation: the output of the first stay reaction is sent to the second double-screw extrusion impregnation machine for secondary extrusion impregnation, and the impregnation liquid is sodium hydroxide solution; First grinding and refining: the output of the second double-screw extrusion impregnation machine is subjected to first grinding and refining to obtain first grinding pulp; Secondary retention reaction: the first mixed pulp after the first disc grinding is put into the second reaction chamber to stay for 20 to 30 minutes for reaction; Secondary disc refining: the output of the secondary retention reaction is subjected to secondary disc refining, and the pulping temperature is ≥90°C to obtain secondary disc refining pulp; De-latency: dilute the secondary disc pulp with hot water to obtain a diluted pulp; add papermaking sludge to the diluted pulp, stir and mix at 65-75°C for 20-30 minutes; Pulping: The mixed pulp after latent removal is subjected to heavy slag removal, pressure screen screening, and multi-disc concentration to obtain the papermaking wood pulp.

2. The process according to claim 1, characterized in that In the delatency step, the temperature of the hot water is 45-65°C.

3. The process according to claim 1, characterized in that In the delatency step, the concentration of the diluted slurry is 4-6%, and the temperature of the diluted slurry is ≥ 70°C.

4. The process according to claim 1, characterized in that In the delatching step, the concentration of the papermaking sludge is 1.0-6.0% and the temperature is 30-60°C.

5. The process according to claim 1, characterized in that In the de-latency step, the amount of papermaking sludge added is 5-15% of the absolute dry weight of the secondary disk pulp.

6. The process according to claim 1, characterized in that In the delatching step, the amount of papermaking sludge added is 10-20% of the mass of the wood chips.

7. The preparation process according to claim 1, characterized in that: In the de-latching step, the papermaking sludge includes flotation sludge, deinking sludge, and sewage secondary sedimentation tank sludge.

8. The process according to claim 1, characterized in that The wood is eucalyptus wood.

9. The process according to claim 1, characterized in that In the slurrying step, the screen gap of the pressure screen is 1.5-1.7 mm, and the screening concentration is 1.2-1.8%.

10. A papermaking wood pulp, characterized in that: The papermaking wood pulp is prepared by the process described in any one of claims 1-9.

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