CN115162052A

CN115162052A - High-flatness gray paperboard and preparation method thereof

Info

Publication number: CN115162052A
Application number: CN202210884774.XA
Authority: CN
Inventors: 张永春; 朱琦; 周志强; 金华; 陈祥发; 陈光军; 周志璠; 刘儒; 王成甫
Original assignee: Liansheng Paper Industry Longhai Co ltd
Current assignee: Liansheng Paper Industry Longhai Co ltd
Priority date: 2022-07-26
Filing date: 2022-07-26
Publication date: 2022-10-11
Anticipated expiration: 2042-07-26
Also published as: CN115162052B

Abstract

The invention relates to a preparation method of high-flatness gray board paper, which comprises the steps of preparing pulp, pulping, preparing the pulp, dehydrating and forming in a net part, squeezing in a squeezing part and drying in a drying part. Different from the prior art, the technical scheme provides the preparation method of the high-flatness gray board paper which is simple, feasible and low in cost by adopting the recovered sludge and pulp residues, and can save energy and reduce consumption at the same time.

Description

High-flatness gray paperboard and preparation method thereof

Technical Field

The invention relates to the technical field of papermaking, in particular to high-flatness gray board paper and a preparation method thereof.

Background

The grey board is an industrial thick board. The single ash has a main ration of 280g/m ² 、300g/m ² 、350g/m ² 、400g/m ² 、450g/m ² 、500g/m ² 、550g/m ² The most important indexes are quantification, thickness and paper surface flatness, and the quantification, the uniform thickness and the strict control of deviation range are required to meet the requirement that the finished product package printing specification and the size of a customer are consistent. In addition, the hanging surface layer has uniform hue, good paper surface flatness, good paper surface fineness, no warpage and no delamination, and is also an important quality standard of the gray board. At present, in the paper industry, sizing is generally carried out on the paper surface to improve the paper surface flatness, but a large amount of steam and starch adhesive are required in the process. Granted patent number ZL201610614831.7 production method of a high-ash and high-thickness gray board paper adopts microbial cultivation on wood chip pulp, so that the surface chemical property and the pore structure of the wood chip pulp are modified, the chemical adsorption performance and the physical adsorption performance of a wood chip pulp adsorbent are improved, and the surface flatness of the gray board paper is effectively improved. However, the economy of microorganism culture and the time cost are high, and how to reduce the time and the economic cost is a problem facing and urgently needing to be solved by a grey board production enterprise.

Disclosure of Invention

In view of the above problems, the present application provides a method for preparing a high-flatness grey board with simple and easy operation and low cost by recycling sludge and pulp residue, comprising the following steps:

preparing slurry:

using domestic waste OCC as a raw material, and after pulping OCC linear disintegration, high-concentration slag removal, coarse screening and low-concentration slag removal, screening the obtained product into short fibers and long fibers; after fine screening and multi-disc concentration, disc grinding is carried out on the long fibers to obtain OCC long fiber pulp; carrying out light deslagging and multi-disc concentration on the short fibers to obtain OCC short fiber pulp;

using national waste secondary white as a raw material, and obtaining secondary white pulp through crushing, cleaning, coarse screening, high-concentration slag removal, fine screening, heavy slag removal, concentration and thermal dispersion;

using wood chips of brush wood and wood flakes as raw materials, preparing wood chip pulp mixture through feeding, wood chip hot grinding, pulp refining, screening and concentrating,

using papermaking pulp as a raw material, and obtaining recycled pulp through disc grinding, low-concentration deslagging, fine screening, concentration and disc grinding;

slurry preparation:

0-5% of damaged paper pulp, 60-70% of OCC long fiber pulp, 30-40% of wood chip pulp mixture and 0-3% of recycled sludge are used as surface layer pulp of the gray board paper;

25-30% of wood chip pulp mixture, 10-15% of OCC long fiber pulp, 30-35% of recycled slag pulp, 10-15% of cushion pulp, 5-10% of recycled broke pulp and 8-12% of recycled sludge are used as first core pulp of the gray board paper;

25-30% of wood chip pulp mixture, 10-15% of OCC long fiber pulp, 30-35% of recycled slag pulp, 10-15% of cushion layer pulp, 5-10% of broke recycled pulp and 8-12% of recycled sludge are used as second core layer pulp of the grey board paper;

60% of the secondary white pulp and 40% of OCC short fiber pulp are used as the bottom pulp of the grey board paper;

manufacturing paper:

the pulp is made into paper through the processes of net dewatering and forming, lining core and bottom compounding, pressing and dewatering, drying and drying.

Be different from prior art, above-mentioned technical scheme provides one kind and adopts recovery mud and thick liquids sediment, and the tiny fiber that adopts recovery mud and thick liquids sediment fills the clearance on thick liquids layer, through the multichannel squeezes for the paper web is levelled and evener more, obtains high roughness grey board.

In some embodiments, the concentration of the OCC long fiber pulp is between 4.0 and 6.0% with a degree of beating between 18 and 28 ° SR.

In some embodiments, the concentration of the OCC fluff pulp is between 4.0 and 7.0% with a degree of beating between 18 and 33 ° SR.

In some embodiments, the concentration of the repulping is 4.0 to 5.0% with a degree of beating 35 to 40 ° SR.

In some embodiments, the concentration of the grey board bottom layer slurry is 3.0 to 6.0% with a degree of kowtowing of 40 to 60 ° SR.

In some embodiments, the feeding ratio of the refined slices to the wood chips of the brush wood is 75-85: 15-25 percent, and the refined pieces are wood pieces with the water content of 40-50 percent.

In some embodiments, the pulp is obtained by multi-disc concentration of papermaking tailings.

In some embodiments, the press section pressing step comprises a vacuum pressing procedure of-65 kpa to-70 kpa.

The application also provides the high-flatness gray board which is prepared by adopting any one of the methods.

In some embodiments, the high-flatness gray board is 280-550 g/m in basis weight ² The A2-level high-flatness gray board of (1).

The above description of the present invention is only an overview of the technical solutions of the present application, and in order to make the technical solutions of the present application more clearly understood by those skilled in the art, the present invention may be further implemented according to the content of the text of the specification, and in order to make the above objects, other objects, features, and advantages of the present application more easily understood, the following description is given with reference to the detailed embodiments of the present application.

Detailed Description

In order to explain technical contents, structural features, and objects and effects of the technical means in detail, the following detailed description is given with reference to specific embodiments.

In order to explain in detail possible application scenarios, technical principles, practical embodiments, and the like, the following detailed description is given with reference to specific embodiments. The embodiments described herein are merely for more clearly illustrating the technical solutions of the present application, and therefore, the embodiments are only used as examples, and the scope of the present application is not limited thereby.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or related to other embodiments specifically defined. In principle, in the present application, the technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution as long as there is no technical contradiction or conflict.

Unless defined otherwise, technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the use of relational terms herein is intended to describe specific embodiments only and is not intended to limit the present application.

In the description of the present application, the term "and/or" is a expression for describing a logical relationship between objects, meaning that three relationships may exist, for example a and/or B, meaning: there are three cases of A, B, and both A and B. In addition, the character "/" herein generally indicates that the former and latter associated objects are in a logical relationship of "or".

In this application, terms such as "first" and "second" are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

Without further limitation, in this application, the use of the phrases "comprising," "including," "having," or other similar expressions, is intended to cover a non-exclusive inclusion, and these expressions do not exclude the presence of additional elements in a process, method, or article that includes the elements, such that a process, method, or article that includes a list of elements may include not only those elements defined, but other elements not expressly listed, or may include other elements inherent to such process, method, or article.

As is understood in the examination of the guidelines, the terms "greater than", "less than", "more than" and the like in this application are to be understood as excluding the number; the expressions "above", "below", "within" and the like are understood to include the present numbers. In addition, in the description of the embodiments of the present application, "a plurality" means two or more (including two), and expressions related to "a plurality" similar thereto are also understood, for example, "a plurality of groups", "a plurality of times", and the like, unless specifically defined otherwise.

The beating degree (beating degree) is referred to herein as beating degree. After the reaction slurry passes through a pulping machine, the fibers are cut off, split, swollen, hydrated and the like, and the effect of pulping is achieved. Pulping is to treat the fibers in the paper pulp by using a mechanical action method of grinding sheet and insection, so that the fibers are fluffed, properly cut and broomed; more importantly, the fibers absorb water and swell during pulping, so that the fibers have higher elasticity and plasticity, and meet the production requirements of a paper machine, and the produced paper can reach the expected quality index. Freeness represents the drainage performance of the pulp. The water quantity discharged from a side pipe of a Shore freeness instrument by using 2 g of absolute dry pulp, diluting the absolute dry pulp to 1000 ml and passing through an 80-mesh net at the temperature of 20 ℃ is the measured result. The beating degree is an index representing the property of the paper stock, and according to the beating degree of the paper stock, the future water filtration speed of the paper stock on a copper wire of a paper machine can be mastered, and the mechanical strength, tightness, manageability and the like of the paper produced in the future can be summarized and predicted, so that the mastering of the beating degree of the paper stock is an important technical control method in production.

The OCC-Old Corrugated Container described in this application is waste boxboard.

The waste paper is a general name of waste paper, and comprises small flowers, large flowers, book page paper and other various waste papers.

The branch wood chips refer to wood chips cut by branches except trunks and trunks of trees, and the materials can not be cut into solid wood boards generally for use due to diameter grade and structure and are used as raw materials of artificial boards such as medium-density fiberboards, shaving boards and the like.

The application the retrieval and utilization mud be to waste paper manufacturing paper's in-process production mud carry out a series of processing such as filter-pressing, fermentation deodorization, white water reconcentration after, let it have the activity, better absorption is on the fibre, a mud in the waste paper stock of recycling again.

The recycled pulp of the broke and the cushion layer is a semi-intermediate product generated in papermaking, and is reused in pulp preparation after being recycled and pulped. Wherein, the broke refers to wet broke and dry broke generated in the production process of the pulp on the wire. The wet broke refers to the net part edge cutting paper of the paper machine; the dry broke paper comprises the rewinding trimming paper of the parent roll, the residual roll bottom paper of the parent roll, the waste paper generated by paper breaking and the rewinding paper of unqualified products. And (4) re-pulping the wet broke and the dry broke to obtain the broke recycled pulp for recycling the pulp for the core layer and the bottom layer. The cushion recycled pulp is the recycled pulp obtained by processing redundant white water generated in the paper machine manufacturing process by using a white water recycling multi-disc machine. The concrete treatment process of the cushion recycling pulp comprises the following steps: adding partial OCC pulp (usually OCC long-fiber pulp to improve water filtering performance) into white water to form cushion filter cake on a multi-disc fan blade, removing water through the filter cake under the action of vacuum generated by a vacuum water leg of a white water recovery multi-disc machine, intercepting most of fine fibers in the white water by the filter cake to obtain recovery, and stripping the filter cake by using stripping spray water to obtain pulp, namely cushion recovery pulp.

The application provides a simple, easy and low-cost preparation method of high-flatness gray board paper by recycling sludge and pulp residues, which comprises the following steps:

preparing slurry:

using national waste Secondary white as a raw material, and obtaining secondary white pulp through crushing, cleaning, coarse screening, high-concentration deslagging, fine screening, heavy deslagging, concentration and thermal dispersion;

using brush wood chips and wood flakes as raw materials, and preparing a wood chip pulp mixture through feeding, wood chip hot grinding, pulp refining, screening and concentrating;

slurry preparation:

0-5% of damaged paper pulp, 60-70% of OCC long fiber pulp, 30-40% of wood chip pulp mixture and 0-3% of recycled sludge are used as surface layer pulp of the grey board paper;

25-30% of wood chip pulp mixture, 10-15% of OCC long fiber pulp, 30-35% of recycled residue pulp, 10-15% of cushion layer pulp, 5-10% of broke recycled pulp and 8-12% of recycled sludge are used as second core layer pulp of the grey board paper;

manufacturing paper:

In some embodiments, the concentration of the OCC fluff pulp is between 4.0 and 6.0% with a degree of kogation between 18 and 28 ° SR.

In some embodiments, the concentration of the OCC fluff pulp is between 4.0 and 7.0% with a degree of kogation between 18 and 33 ° SR.

In some embodiments, the concentration of the repulping is 4.0 to 5.0% with a degree of kowtowing of 35 to 40 ° SR.

In some embodiments, the feeding ratio of the refined slices to the wood chips of the brushwood is 75-85: 15-25 percent, and the refined pieces are wood chips with the water content of 40-50 percent and have the size of 50mm multiplied by 25mm multiplied by 6mm.

In some embodiments, the recycled residue slurry is obtained by multi-disc concentration of papermaking tailings.

The application also provides the high-flatness gray board with the quantitative weight of 280-550 g/m ² The A2-grade high-flatness gray board prepared by any one of the methods.

Examples

In order to further clarify the explanation and explanation of the technical solutions of the present application, the following non-limiting examples are also provided for reference.

In this embodiment, the paper machine parameters are as follows: width of the paper machine, width of the web: 6450mm, lip width: 6200mm, take-up width: 6020mm, maximum clear paper width: 5880mm; paper machine speed: the design vehicle speed is 400m/min, the balance vehicle speed is 600m/min, and the working vehicle speed is Max 350m/min. The paper machine parameters are set as follows:

approach flow part of paper machine

1. The liquid level of the surface-substrate mixing tank is set to be 50-60 percent, and the outlet concentration of the mixing pump is set to be 3.0-3.8 percent

2. The liquid level of the core mixing pool is set to be 50-60 percent, the outlet concentration of the mixing pump is set to be 3.8-4.0 percent

3. Surface layer screen front screen

A first-stage pressure screen: slurry feeding concentration: 0.5-1.0% of maximum working pressure 500kPa, pressure difference less than 50kPa, and slag discharge rate 8%

4. Core 1 layer screen

The pulp inlet concentration of the first-section screen is 1.05-2.0%, the maximum working pressure is 500kPa, the pressure difference is less than 50kPa, and the slag discharge rate is 8%; the pulp inlet concentration of the two-stage pressure screen is 0.6-0.85%, the maximum working pressure is 500kPa, the differential pressure is less than 50kPa, and the slag discharge rate is 10%; the slurry inlet concentration of the three-section pressure screen is 0.6-0.85%, the maximum working pressure is 250kPa, the pressure difference is less than 50kPa, and the slag discharge rate is 13%

5. Core 2-layer screen

The pulp inlet concentration of the first-section screen is 1.05-2.0%, the maximum working pressure is 500kPa, the pressure difference is less than 50kPa, and the slag discharge rate is 8%

6. Bottom layer screen front screen

The pulp inlet concentration of a screen in front of a first section of net: 1.1-1.3% of maximum working pressure 500kPa, pressure difference less than 50kPa, and slag discharge rate 8%

The concentration of the slurry entering the front screen of the surface layer and the bottom layer two-section net is 0.9 to 1.1 percent, the maximum working pressure is 500kPa, the pressure difference is less than 50kPa, and the slag discharge rate is 10 percent

7. Core layer dilution water screening:

the concentration of white water is 0.2-0.45%, the maximum working pressure is 500kPa, the pressure difference is less than 50kPa, the slag discharge rate is 10%, the proportion of dilution water is 12-15%

8. White water multi-disc recovery machine: the diameter of the disk is 5200mm, and the rotating speed is 0.8rpm; the concentration of the cushion layer slurry is 3.5-4.0%, and the proportion of the cushion layer slurry is set as follows: 0.25-0.35, multi-disc inlet concentration: 0.6 to 1.2 percent.

A pressing part: the second pressing of the pressing part adopts vacuum pressing of-65 to-70 kpa, the third pressing is large rolling with blind holes, the fourth pressing and the fifth pressing are large-roller-diameter pressing, the smooth pressing is two large rolling, and the semi-dry pressing is first pressing with coarse cotton cloth, so that the flatness of a paper surface is increased. And the last calendering is calendering by a calender.

Wherein, smooth pressure and press polish with two smooth roll-in, other way are pressed and are had the coarse cotton cloth on the roller, coarse cotton cloth operating tension: 3.5-4 KN/m.

Press section working pressure setting (gauge pressure)

Drying section

1. Dryer parameters

After-press dryness of 47-49 percent, half-dry press dryness of 75-80 percent, paper winder dryness of 92 percent, drying cylinder diameter of 1830mm, number of semi-dry pre-press drying cylinders pcs61, number of half-dry post-press drying cylinders pcs14 and maximum steam pressure of 5bar

2. Dryer steam

CylNo.	1-2 cylinders	3-5 cylinder	6-11 cylinder	2 groups of	Group 3
						Steam kpa	8	15	20	35～50	65～90
Differential pressure kpa		15	15	20	25
						CylNo.	4 to 5 groups of lower rows	4 to 5 groups of upper rows	Semi-dry pressing	6 groups of lower rows	6 groups of upper rows
Steam kpa	120～280	120～280	200	150～500	150～500
						Differential pressure kpa	25	25	25	35	35

In this embodiment, OCC slurry: and (2) secondary white pulp: recycling the slurry: recycling sludge: wood chip slurry mix = 9.

Example 1: OCC slurry preparation

OCC slurry flow path: using domestic waste OCC as a raw material, and performing crushing, slag removal, drum screening, high-concentration desander desanding, 2-stage coarse screening, slag removal by a flotation slag remover, impurity separation by an impurity separator and low-concentration deslagging by a pulping OCC line, and then separating short fibers and long fibers by a screening grade;

carrying out light deslagging and multi-disc concentration on the short fibers by a light deslagging device to obtain OCC short fiber pulp; the concentration of the obtained OCC fluff pulp is 4.0-7.0%, and the beating degree is 18-33 DEG SR.

Carrying out disc grinding after the long fibers are subjected to three-section fine screening (bar gap is 0.25 mm) and multi-disc concentration to obtain OCC long fiber pulp; the concentration of the OCC long fiber pulp is 4.0-6.0%, and the beating degree is 18-28 DEG SR.

Wherein:

the 2-stage coarse screening comprises:

primary coarse screening: screen gap F =0.6mm, pulp inlet concentration is 2.0-3.0%, and fine pulp concentration: 2.0% -3.0%, minimum slurry inlet pressure 207kPa, differential pressure: 34 to 50kPa, the pressure of dilution water is 300 to 350kPa, and the slag discharge rate is 30 percent.

And (3) a two-stage coarse screen with 1.6mm screen holes, 2.0-3.0% of pulp inlet concentration and good pulp concentration: 1.5-2.0 percent, the minimum slurry inlet pressure is 207kPa, the pressure difference is 34-50 kPa, the pressure of dilution water is 300-350 kPa, and the slag discharge rate is 30 percent.

Slag removal by a flotation slag remover: 5.0mm sieve mesh, inlet pressure of 1.8-2.2% inlet pressure of 240kPa, pressure drop of 40-80 kPa, good pulp concentration of 1.70-2.0%, light slag concentration of 2.0-2.5%, slag discharge concentration of 1.8-2.51% and slag discharge rate of 30%.

The impurity separator is used for separating impurities: sieve pore diameter is 3.0mm, pulp inlet concentration is 1.0-1.7%, spray water pressure is 500-600 kPa, pulp recovery concentration is 0.3-0.7%, and rotor-sieve plate gap is 2.0-2.5 mm.

The five-section low-concentration heavy slag removal comprises the following steps:

one-stage low-concentration: the pressure drop is 138kPa, the pulp inlet concentration is 0.8-1.5%, the good pulp concentration is 0.8-1.2%, the slag discharging concentration is 2.0-2.5%, the pressure drop is 110-130 kPa, the slag discharging pressure is 10-50 kPa, and the slag discharging rate is 15-25%;

second-stage low-concentration: the pressure drop is 138kPa, the pulp inlet concentration is 0.7-1.2%, the good pulp concentration is 0.8-1.0%, the slag discharging concentration is 2.0-3.0%, the pressure drop is 110-130 kPa, the slag discharging pressure is 10-50 kPa, and the slag discharging rate is 20-28%;

three-stage low concentration: the pressure drop is 138kPa, the concentration of the good pulp is 0.4-0.8% with the pulp inlet concentration of 0.5-0.9%, the concentration of the slag discharge is 2.0-3.0%, the pressure drop is 110-130 kPa, the slag discharge pressure is 10-50 kPa, and the slag discharge rate is 20-28%;

four-stage low-concentration: the pressure drop is 138kPa, the pulp inlet concentration is 0.5-0.9%, the good pulp concentration is 0.4-0.8%, the slag discharge concentration is 2.0-3.0%, the pressure drop is 110-130 kPa, the slag discharge pressure is 10-50 kPa, and the slag discharge rate is 20-28%;

five-stage low-concentration: the pressure drop is 138kPa, the pulp inlet concentration is 0.5-0.9%, the good pulp concentration is 0.4-0.8%, the slag discharging concentration is 2.0-3.0%, the pressure drop is 110-130 kPa, the slag discharging pressure is 10-50 kPa, and the slag discharging rate is 20-28%.

A classifying screen section: the set proportion is short fiber: long fiber =55:45

And (3) grading and screening: the inlet pressure with the width of 0.20mm of the screen slot is more than or equal to 207kPa differential pressure 10-70 kPa, the pulp inlet concentration is 1.8-2.2%, the stock concentration is 1.2-1.6%, the tail pulp concentration is 2.2-3.0%, the dilution water pressure is 300kPa, and the sealing water pressure is 400kPa.

Example 2: preparation of Erbai pulp

The method comprises the following steps of (1) carrying out pulping by a high-concentration hydrapulper, cleaning by an intermittent cleaning machine, roughly screening by a cylindrical screen, removing high-concentration slag, finely screening by three sections, removing heavy slag, concentrating by a disc concentrator and thermally dispersing by a disc thermal disperser to obtain the waste lime pulp; the concentration of the secondary white pulp is 4.0-5.0%, and the beating degree is 35-40 DEG SR.

The specific parameters are as follows:

sieve plate phi 6mm of cylindrical sieve

The high-concentration slag separator is of a two-section type: a section of high-concentration fine pulp capability 286.3td, the pulp inlet concentration is 3.09 percent, the pulp inlet pressure is 0.2 to 0.5MPa, and the slag discharge rate is 20 percent; second stage high concentration, good pulp ability: 56.3td, the slurry inlet concentration is 2.55 percent, the slurry inlet pressure is 0.2-0.5 MPa, and the slag discharge rate is 20 percent.

Three-stage fine screening: bar sewing: 0.15mm/0.15mm/0.15mm, the pulp inlet concentration is 2.85 percent, the pulp inlet pressure is 0.15-0.3MPa, the first-stage accepted pulp concentration is 2.5 percent, the second-stage accepted pulp concentration is 2.0 percent, the third-stage accepted pulp concentration is 1.5 percent, and the slag discharge concentration is 1.0 percent.

Example 3: preparation of wood chip pulp mixture

The method comprises the following steps of taking brush wood chips and wood flakes as raw materials, and preparing a wood chip pulp mixture through feeding, wood chip hot grinding, pulp refining, screening and concentrating, wherein the wood chip pulp mixture specifically comprises the following steps:

conveying wood chips: conveying 20% of brush wood chips and 80% of eucalyptus wood concentrate with water content of 40-50% from a bin to a swing screen through a double-screw conveyor and a belt conveyor;

crushing and impurity removal: screening wood chips by a swing screen to remove barks and large wood blocks, crushing the screened wood chips by a drum-type re-crusher, and conveying the crushed wood chips to a wood chip cooking system by a bucket elevator and a belt conveyor;

steam cooking: steaming the wood chips with high pressure steam, increasing the moisture of the wood, and softening the wood chips again;

wood chip hot grinding: after being cooked in the cooking bin, the wood chips are fed into a defibrator through a feeding screw, and the defibrator grinds the wood chips into single fibers;

thermal grinding slurry dilution: the concentration of the wood chip pulp mixture after the hot grinding is adjusted by a dilution screw and sent to a latency pool;

hot grinding pulp and latency elimination: after the wood chip pulp is subjected to latency elimination, fine pulp is carried out by a concentration-adjusting disc-feeding mill;

disc milling and fine sizing: using a double-disc mill to carry out fine sizing on the hot milled pulp, cutting and dissociating fibers so as to meet the requirement of pulp forming;

fine screening: and diluting and thickening the pulp at the outlet of the double disc mill, and feeding the pulp to a sawdust pulp fine screen for screening to obtain the sawdust pulp.

Example 4 preparation of recycled pulp residue

wherein the low-concentration slag remover is of a three-section type and has the following parameters:

number of items/segment	One section is 10 pieces	Two segments are 8	Three segments are 3
				Import concentration (%)	1.2	0.86	0.65
Pulp inlet pressure (kpa)	200～500	200～500	200～500
				Outlet pressure (kpa)	100	75	75
Pressure difference (kpa)	220	145	125
				Slag discharge rate (%)	25～30	25～30	25～30

The fine screen is of a two-stage type:

first-stage fine screening: bar sewing: 0.27mm, slurry feed concentration: 1.09 percent, the pulp inlet pressure is 0.15 to 0.3MPa, and the slag discharge rate is 24 to 28 percent;

two-stage fine screening: rod gap 0.27mm, slurry inlet concentration: 1.08 percent, the slurry inlet pressure is 0.15 to 0.3MPa, and the slag discharge rate is 24 to 28 percent

EXAMPLE 5 preparation of a Grey Board

manufacturing paper:

the pulp is made into high-flatness gray board paper after the dehydration and forming of a net part, the compounding of a lining core bottom, the pressing and dehydration of a pressing part and the drying of a drying part.

Manufacturing paper:

The process uses the recycled sludge, the pulp residue and the wood chip pulp to replace part of OCC waste paper pulp per ton of paper, so that the waste paper cost is saved by 63 yuan, and the production cost is saved by 1008 ten thousand yuan based on 16 ten thousand tons of annual output.

Finally, it should be noted that, although the above embodiments have been described in the text of the specification of the present application, the scope of the patent protection of the present application is not limited thereby. All technical solutions which are generated by replacing or modifying the equivalent structure or the equivalent flow according to the content described in the specification of the present application based on the substantial idea of the present application, and which directly or indirectly implement the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of the present application.

Claims

1. The preparation method of the high-flatness gray board is characterized by comprising the following steps of:

preparing slurry:

using papermaking pulp residue as a raw material, and obtaining recycled pulp residue through disc grinding, low-concentration residue removal, fine screening, concentration and disc grinding;

slurry preparation:

manufacturing paper:

the pulp is made into paper after dehydration forming of a net part, lining core bottom compounding, pressing dehydration of a pressing part and drying of a drying part.

2. The method according to claim 1, wherein the concentration of the OCC long fiber pulp is 4.0-6.0%, and the beating degree is 18-28 ° SR.

3. The method according to claim 1, wherein the concentration of the OCC fluff pulp is 4.0 to 7.0%, and the beating degree is 18 to 33 ° SR.

4. The method according to claim 1, wherein the concentration of the repulping is 4.0-5.0% and the degree of beating is 35-40 ° SR.

5. The method of claim 1, wherein the concentration of the bottom layer pulp of the gray board is 3.0 to 6.0% and the beating degree is 40 to 60 ° SR.

6. The preparation method according to claim 1, wherein the feeding ratio of the wood chips of the fine slices to the brush wood is 75-85: 15 to 25 percent, and the refined pieces are wood chips with the water content of 40 to 50 percent.

7. The preparation method according to claim 1, wherein the recycled residue slurry is obtained by multi-disc concentration of papermaking tailings.

8. The method as claimed in claim 1, wherein the press section pressing step includes a vacuum pressing process of-65 kpa to-70 kpa.

9. A high-flatness gray board, characterized in that it is prepared by the method of any one of claims 1-8.

10. The high flatness gray board of claim 9, wherein said high flatness gray board basis weight is 280-550 g/m ² 。