A system for preparing household paper and its papermaking method

Abstract

This invention discloses a papermaking system and method for producing household paper, comprising a short-fiber refining unit, a long-fiber refining unit, a papermaking unit for mixing short-fiber pulp from the short-fiber refining unit and long-fiber mixed pulp from the long-fiber refining unit to produce paper, and a waste paper recycling unit for recycling the papermaking unit. Utilizing the high-intensity beating of the long-fiber refining unit, waste paper and long-fiber pulp boards are fed into a long-fiber pulper for mixing and dispersing. The multi-stage refining units in series promote the fineness of waste paper pulp decomposition and pulverization, thoroughly solving the pulp spot problem in the recycling and processing of household paper waste paper. This avoids excessively thin paper, uneven pulping, and localized pulp spots, achieving a pulp spot qualification rate of over 99.8%. It improves the fineness of waste paper pulp pulverization and the uniformity of the pulp, while simplifying production equipment. The number of refining units can be selected based on the wet strength of the waste paper to meet the production needs of various paper products, reduce energy consumption and long-fiber usage, and lower equipment maintenance and consumable costs.

Description

Technical Field

[0001] This invention relates to a papermaking process, and more particularly to a system for preparing household paper and a papermaking method thereof. Background Technology

[0002] In the production process of household paper, such as Figure 1 The traditional waste paper recycling method involves sending waste paper to a pulper for crushing, followed by storage in a waste paper collection tank. The pulp is then centrifuged in a high-consistency pulp mill to remove slag before entering a high-frequency descaling machine to disperse the fibers. The dispersed pulp is then concentrated in a cylinder thickener to a concentration of 3%–5%, and finally stored in a waste paper storage tank. According to the production formula, the pulp in the storage tank is transported via pipelines to a mixing tank with long and short fiber pulps in a specific ratio. The pulp in the mixing tank then sequentially passes through a finishing mill, pre-papering tank, rinsing pump, pressure screen, dewatering unit, drying unit, and winding unit to complete the entire papermaking process. This waste paper recycling technology involves a long production process, high equipment failure rate, high maintenance costs, numerous electrical units, high power consumption, many process variables, difficult process control, and a high risk of pulp spotting. To address the problems of traditional waste paper handling methods, the industry has innovated a process that eliminates the four-stage steps of high-consistency pulp mill, high-frequency defroster, cylinder thickener, and waste paper storage tank. The pulp obtained from the pulverization process is sent from the waste paper collection tank to the short-fiber pulp line's pre-refining tank for mixing with the short-fiber pulp. The mixed pulp is then descaled to remove impurities and sent to a double cylinder thickener to increase the concentration to 18%–25% before entering the high-consistency refiner for beating. The beating pulp is then sent to the high-consistency post-refining tank, from which it can be sent to either the short-fiber storage tower or the long-fiber pre-refining tank for use in subsequent papermaking processes. This method simplifies the production process, reduces equipment failure rates and maintenance costs, reduces the number of electrical units, decreases power consumption, reduces process variables, and simplifies process control. However, after mixing and beating damaged pulp with short fiber high-consistency pulp, the resulting paper has poor thickness, uneven sizing, and is prone to local pulp spots. The beating energy consumption is high and the noise is loud. The grinding discs of high-consistency refiners are expensive, the consumable costs are high, the parts are numerous and complex, and the maintenance is difficult. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to solve the problems of low paper thickness and easy occurrence of pulp spots in recycled paper, while reducing production costs, and to provide a papermaking system for household paper; another purpose of this invention is to provide a papermaking method using the above-mentioned preparation system.

[0004] Technical Solution: The tissue paper preparation system of the present invention includes a short fiber pulping unit, a long fiber pulping unit, a papermaking unit, and a waste paper recycling unit for recycling the papermaking unit; the short fiber pulping unit includes a wet pulp storage tower, a pulper, a high-consistency tower, a short fiber intermediate tank, a short fiber pre-refining tank, a short fiber refiner, and a short fiber storage tower arranged in sequence; the long fiber pulping unit includes a long fiber feeding device, a second pulper, a long fiber pre-refining tank, a descaling device, a multi-stage refiner, and a long fiber storage tower arranged in sequence; the waste paper recycling unit includes a first pulper and a waste paper collection tank arranged in sequence, and the waste paper collection tank is connected to the long fiber pulping unit through the second pulper; the papermaking unit mixes the short fiber pulp from the short fiber pulping unit and the long fiber mixed pulp from the long fiber pulping unit to make paper.

[0005] Furthermore, the number of multi-stage refiners is set according to the wet strength of the paper loss, and the power of the refiners is set to 250-440 kW / h to promote the fineness of the decomposition and pulverization of the mixed pulp, and to avoid excessively thin paper, uneven sizing, and localized pulp spots. The number of refiners to be operated is selected under the premise of meeting process requirements to reduce energy consumption. A return pipe is provided between the multi-stage refiners and the long-fiber pre-refining tank to return the long-fiber mixed pulp and perform multiple deslagging and grinding processes. When one refining process cannot grind the paper loss to the process requirements, it can be transported to the pre-refining tank through the return pipe for further grinding to meet the process requirements, improve the pulp spot qualification rate, reduce the number of refiners required, and thus reduce production costs and equipment maintenance costs.

[0006] Furthermore, the waste paper recycling unit is used to collect the trimmed waste paper from the drying section and the waste paper generated during the initial winding and rewinding processes, so as to recycle as much waste paper as possible during the production process and put it back into production, thereby reducing the waste of raw materials.

[0007] The present invention also provides a papermaking method, comprising the following steps:

[0008] Step 1: The short fiber pulping unit provides short fiber pulp;

[0009] Step 2: The waste paper unit recycles and shreds the waste paper generated during the production process, and feeds it into the long fiber pulping unit through the shredder of the long fiber pulping machine in a certain proportion;

[0010] Step 3: The long fiber pulping unit provides long fiber mixed pulp;

[0011] Step 4: Short fiber pulp and long fiber mixed pulp are mixed in a certain proportion and fed into the papermaking unit to produce household paper.

[0012] Furthermore, in step 1, the freeness of the short fiber pulp is 300-380 ml, preferably 350 ml. The short fibers are refined to make them finer and more compact, thereby increasing the paper strength and reducing the amount of long fibers used.

[0013] Furthermore, in step 2, the waste pulp is diluted with concentrated white water to 2%–3%, and the wet strength of the finished paper is equal to the wet strength of the waste pulp. The mixing ratio of waste pulp to long-fiber pulp board is adjusted according to the wet strength of the waste pulp as a:b = 0.1–0.6:0.9–0.4, a+b = 1: the mixing ratio is reduced when the wet strength of the waste pulp is high, and increased when the wet strength of the waste pulp is low, thus controlling the disintegration pulp of the long-fiber mixed pulp formed by the mixing of waste pulp and long-fiber pulp board. The pulp concentration is 4%–6% and the free volume is 550–680 ml to ensure that the free volume of the long-fiber mixed pulp after refining is 250–400 ml. The high-intensity beating of the long-fiber refining unit is used to mix and disperse the waste pulp and long-fiber pulp board in the long-fiber pulper, which promotes the fineness of waste pulp decomposition and pulverization, completely solves the pulp point problem in the recycling and treatment of waste paper for household paper, improves the fineness of waste pulp pulverization and the uniformity of pulp, and simplifies the production equipment.

[0014] Furthermore, in step 4, the mixing ratio of short fiber pulp to long fiber mixed pulp is c:d = 0.9~0.6: 0.1~0.4, c+d = 1. After mixing, the short fiber pulp and long fiber mixed pulp are diluted with concentrated white water to 0.01%~0.02%. The reasonable mixing ratio, while ensuring the thickness, tensile strength, elongation and softness of the paper, increases the uniformity of the paper, avoids the occurrence of pulp spots, and further improves the yield and quality of the paper.

[0015] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: 1. Utilizing the high-intensity beating of the long-fiber refining unit, waste paper and long-fiber pulp boards are fed into the long-fiber pulper for mixing and pulping, promoting the fineness of waste paper decomposition and pulverization, completely solving the pulp spot problem in the recycling and treatment of waste paper for household paper, improving the fineness of waste paper pulp pulverization and the uniformity of pulp, while simplifying production equipment; 2. The series connection of multiple refining machines further promotes the fineness of waste paper pulp decomposition and pulverization after mixing, avoiding excessively thin paper products, uneven pulping, and local pulp spots, with a pulp spot qualification rate of over 99.8%; 3. The number of refining machines can be selected according to the wet strength of the waste paper to meet the production needs of various paper products, reduce energy consumption and long fiber usage, and reduce equipment maintenance costs and consumable costs. Attached Figure Description

[0016] Figure 1 A schematic diagram of the existing production process for household paper products;

[0017] Figure 2 This is a schematic diagram of the production process of the household paper of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0019] like Figure 2 The illustrated papermaking system includes a short fiber pulping unit 1, a long fiber pulping unit 2, a waste paper recycling unit 4, and a papermaking unit 3. The short fiber pulping unit includes a mixing and storage tower, a pulper, a high-consistency tower, a short fiber intermediate tank, a short fiber pre-refining tank, a short fiber refiner, and a short fiber storage tower arranged in sequence. The long fiber pulping unit includes a long fiber feeding device, a second pulper, a long fiber pre-refining tank, a descaling machine, a fourth-stage refiner, and a long fiber storage tower arranged in sequence. A reflux pipe is provided between the long fiber pre-refining tank and the fourth-stage refiner to return the long fiber mixed pulp for multiple descaling and refining processes. The waste paper recycling unit includes a first pulper and a waste paper collection tank arranged in sequence. The papermaking unit includes a pre-paper tank, a flushing pump, a pressure screen, a wire dewatering device, a drying device, and a winding device. The waste paper collection tank of the waste paper recycling unit is connected to the second pulper of the long fiber pulping unit. The pulp from the long fiber storage tower and the short fiber storage tower is fed into the pre-paper tank of the papermaking unit in a certain proportion for mixing and then passes through the flushing pump, pressure screen, wire dewatering device, drying device, and winding device to produce the finished product.

[0020] The power of each refiner is set to 250-440 kW / h. The number of refiners in operation is set according to the wet strength of the paper loss. While meeting the process requirements, the number of refiners in operation is reduced to lower energy consumption. When the fourth-stage refiner cannot meet the refining requirements after mixing the paper loss pulp and long fiber pulp board, it is transported to the front end of the fourth-stage refiner through the return pipe. The number of refiners in operation is selected according to the requirements for further refining to meet the process requirements.

[0021] Examples 1-18

[0022] The papermaking method using the above-described preparation system includes the following steps:

[0023] Step 1: The short fiber pulping unit provides short fiber pulp;

[0024] Step 2: The waste paper unit recycles the waste paper from the trimming of the drying section and the waste paper generated during the initial winding and rewinding processes. The waste paper is then pulverized into a certain concentration of waste paper pulp by the first pulper and sent to the waste paper collection tank for later use. The waste paper pulp and long fiber pulp board are fed into the second pulper in a certain proportion and then into the long fiber refining unit (the proportion is detailed in Table 1).

[0025] Step 3: The long fiber pulping unit provides long fiber mixed pulp;

[0026] Step 4: Short fiber pulp and long fiber mixed pulp are mixed in a certain proportion and fed into the pre-papermaking tank of the papermaking unit. The prepared pulp is diluted with concentrated white water to 0.01% to 0.02%, and then transported to the pressure screen for secondary screening by the pulp pump. The screened pulp enters the wire section dewatering device for dewatering and forming. The formed wet paper sheet is pressed and dried by the felt conveyor drying section to obtain tissue paper (the proportions are detailed in Table 1).

[0027] Table 1 Concentration and proportion of various slurries in Examples 1-18

[0028]

[0029] The physical properties of the paper products prepared in Examples 1-18 above were tested: basis weight, thickness, tensile strength (MDT) in the paper machine running direction, transverse tensile strength (CDT), elongation, wet strength and softness, as detailed in Table 2.

[0030] Table 2 Physical properties of finished paper from Examples 1-18

[0031]

[0032] The mixing ratio of waste paper and long-fiber pulp board is flexibly adjusted according to the wet strength of the waste paper: the mixing ratio of waste paper is reduced when the wet strength of the waste paper is high, and increased when the wet strength of the waste paper is low, to ensure the freeness of the long-fiber mixed pulp and to prepare paper products of different specifications in an appropriate ratio with short-fiber pulp. After the waste paper is recycled, it is fed into the long-fiber refining unit, and the proportion of long-fiber pulp is reduced while maintaining the quality indicators of the base paper. At the same time, the long-fiber refining unit is used for high-intensity beating, and the waste paper and long-fiber pulp board are fed into the long-fiber pulper for mixing and dispersing, which promotes the fineness of waste paper decomposition and pulverization, completely solves the pulp point problem in the recycling and treatment of waste paper for household paper, and the pulp point qualification rate reaches more than 99.8%, which improves the fineness of waste paper pulp pulverization and pulp uniformity, while simplifying production equipment, meeting the production needs of various paper products, saving electricity consumption, and reducing equipment maintenance costs and consumable costs.

[0033] The preparation system of the present invention can achieve multi-stage fine pulping of pulp, and is therefore also applicable to pulps or papermaking processes that require fine pulping, and is not limited to the long fiber and waste paper mixed pulping described in the present invention.

Claims

1. A system for preparing tissue paper, comprising a short-fiber pulping unit, a long-fiber pulping unit, a papermaking unit, and a waste paper recycling unit for recycling the papermaking unit; characterized in that, The short fiber refining unit includes a wet pulp storage tower, a pulp extruder, a high-consistency tower, a short fiber intermediate tank, a short fiber pre-grinding tank, a short fiber refiner, and a short fiber storage tower arranged in sequence. The long fiber refining unit includes a long fiber feeding device, a second pulper, a long fiber pre-grinding tank, a slag remover, a multi-stage refining machine, and a long fiber storage tower arranged in sequence. The waste paper recycling unit includes a first pulper and a waste paper collection tank arranged in sequence, and the waste paper collection tank is connected to the long fiber pulping unit through a second pulper; The papermaking unit mixes the short fiber pulp from the short fiber pulping unit and the long fiber mixed pulp from the long fiber pulping unit to make paper; The mixing ratio of waste pulp in the waste paper collection tank to long fiber pulp board in the long fiber pulping unit is a:b=0.1~0.6:0.9~0.4, a+b=1. The pulp concentration of the mixed pulp of waste pulp and long fiber pulp board after disintegration is 4%~6% and the freeness is 550~680ml.

2. The tissue paper preparation system according to claim 1, characterized in that, The number of multi-stage refiners is set according to the wet strength of the paper.

3. The tissue paper preparation system according to claim 2, characterized in that, The multi-stage pulper is connected to the long fiber pre-grinding tank by a return pipe for recirculating the long fiber mixed pulp and performing multiple slag removal and grinding processes.

4. The tissue paper preparation system according to claim 1, characterized in that, The waste paper recycling unit is used to collect waste paper from the trimming process in the drying section and waste paper generated during the initial and rewinding processes.

5. A papermaking method using the tissue paper preparation system as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: The short fiber pulping unit provides short fiber pulp; Step 2: The waste paper unit recycles and shreds the waste paper generated during the production process, and feeds it into the long fiber pulping unit through the shredder of the long fiber pulping machine in a certain proportion; Step 3: The long fiber pulping unit provides long fiber mixed pulp; Step 4: Short fiber pulp and long fiber mixed pulp are mixed in a certain proportion and fed into the papermaking unit to produce household paper.

6. The papermaking method according to claim 5, characterized in that, In step 1, the short fiber pulping unit provides short fiber pulp with a freeness of 300~380ml.

7. The papermaking method according to claim 5, characterized in that, In step 2, the pulp is diluted with concentrated white water to 2%~3%.

8. The papermaking method according to claim 5, characterized in that, The freeness of the long fiber mixed slurry provided by the long fiber pulping unit in step 3 is 250~400ml.

9. The papermaking method according to claim 5, characterized in that, In step 4, the mixing ratio of short fiber pulp to long fiber mixed pulp is c:d = 0.9~0.6: 0.1~0.4, c+d = 1.

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