Evaluation method for drying capacity of paper machine drying system
By introducing the drying force index Dc12.5, the problem of uniformity in the evaluation of drying systems of different paper machines is solved, and unified evaluation and production optimization on different equipment is achieved.
Patent Information
- Application Number
- CN202510594563.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-09
- Publication Date
- 2025-08-12
AI Technical Summary
There is a lack of a unified method to evaluate the drying capacity of different paper machine drying systems, and the existing evaluation methods cannot be effectively compared on paper machines provided by different manufacturers.
By analyzing the relationship between the drying capacity of the paper machine, the basis weight and vehicle speed on the cylinder, the drying force index Dc was introduced, and Dc12.5 was set as the standard drying force index to evaluate the drying capacity of the paper machine drying system.
It provides a unified evaluation standard, which can evaluate drying capacity on the living paper machines of different equipment manufacturers, and guides production optimization and equipment procurement.
Smart Images
Figure CN120467950A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of household paper machines, and in particular relates to a method for evaluating the drying capacity of a paper machine drying system. Background Art
[0002] Paper machine drying capacity refers to the ability of the dryer section of a paper machine to effectively remove moisture from paper sheets. This capacity is influenced by a variety of factors, including the selection of drying equipment, the number and size of drying cylinders, steam pressure control, and drying system design. The drying system is a crucial component of the paper machine, primarily removing moisture from the paper sheets and, in the process, improving the strength and smoothness of the paper. The drying system's performance directly impacts the overall paper machine's production capacity and paper quality.
[0003] How do you evaluate the drying capacity of different paper machine drying systems? Traditionally, evaluations have mostly used steam consumption per ton of paper to determine a system's energy efficiency, or daily output to determine a paper machine's production capacity. However, there's been no unified method or approach for determining drying capacity across paper machines from different manufacturers. Summary of the Invention
[0004] The purpose of the present invention is to provide a method for evaluating the drying capacity of a paper machine drying system. The method analyzes the relationship between the drying capacity of a paper machine and the basis weight on the cylinder and the vehicle speed, and introduces a drying force index to evaluate the drying capacity of a paper machine drying system.
[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution: A method for evaluating the drying capacity of a paper machine drying system comprises the following steps: The first step is to start the machine on site and actually measure the paper machine to obtain known parameters, as follows: Paper machine drying cylinder upper basis weight r g , the unit is g / m2; the speed of the paper machine V, the unit is m / min; The second step is to set the drying force index Dc expression as: Dc=r g XV / 60, the unit is g paper / (s·m); By collecting real data on various parameters during the on-site paper machine production operation, the dryness conditions were set as follows: the dryness at the cylinder entrance was 39% and the dryness at the cylinder exit was 94%. Under the condition of a certain speed V, a relationship diagram between the basis weight on the cylinder and the drying force index was plotted. The maximum value of the drying force index Dc was statistically determined to be 250.0g paper / (s·m), at which the basis weight on the cylinder was 12.5g / m 2 of paper; According to the relationship between basis weight and drying force index, the basis weight on the cylinder is more than 12.5g / m2 When the paper is dried, the drying force index Dc no longer changes. Therefore, Dc12.5 is set as the standard drying force index of the paper machine and used as the standard for evaluating the drying capacity of the paper machine. The third step is to convert and correct the drying force index Dc expression in the second step. The expression is as follows: DcM=Dc12.5 X kw X ke in, Dc12.5=250.0g paper / (s·m); DcM is the drying force index of the basis weight M on the cylinder; kw is the paper dryness correction coefficient, kw = 0.957; ke is the comprehensive factor correction coefficient, ke is 0.75~0.95; Step 4: Verify the drying force index Dc expression in step 3 Different cylinder basis weights of the paper machine were selected and converted according to the measured moisture content of the paper sheets. The results calculated using the drying force index Dc expression were highly close to the field recorded data, thereby verifying that the drying force index Dc expression was correct, and ultimately determining to use Dc12.5 as the standard for evaluating the drying capacity of the paper machine.
[0006] As a preferred method, if the inlet and outlet dryness data are missing, the drying force index Dc is corrected using ke, and the ke value is taken as a conservative value towards the lower end. The drying force index Dc is expressed as: Dc12.5 X ke.
[0007] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The present invention analyzes the relationship between the drying capacity of the paper machine and the basis weight on the cylinder and the speed, and introduces the drying force index. The drying force index of the paper machine drying system increases with the increase of the basis weight on the cylinder, and when the basis weight on the cylinder is greater than or equal to 12.5g / m 2 When the drying force index reaches its maximum value, the paper with different in-and-out cylinder dryness and different cylinder basis weight is converted into Dc12.5, which is the standard drying force index. Dc12.5 is used as the standard to evaluate the drying capacity of different paper machine equipment, so that there can be a unified drying capacity evaluation or reference scale for different household paper machines from different equipment manufacturers. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 This is the distribution diagram of basis weight and drying force index on the cylinder; Figure 2 This is the relationship diagram between the base weight on the cylinder and the correction coefficient Ke. DETAILED DESCRIPTION
[0009] The technical solution of the present invention is further described in detail below with reference to the embodiments and drawings.
[0010] A method for evaluating the drying capacity of a paper machine drying system comprises the following steps: The first step is to start the machine on site and actually measure the paper machine to obtain known parameters, as follows: Paper machine drying cylinder upper basis weight r g , the unit is g / m2; the speed of the paper machine V, the unit is m / min; Table 1:
[0011] Table 1 shows the raw data collected from six paper machines at a paper mill. A total of 115 sets of data were collected. The main parameters of these six paper machines are: steel dryer cylinder diameter 3660 mm, paper width on the cylinder 2880 mm, paper width on the roll 2830 mm, dryer cylinder pressure 7.5 bar, hood air supply temperature 165°C (wet end) and 120°C (dry end), paper dryness entering the cylinder 39% and exiting the cylinder 94%. Calculations and statistics show that the minimum and maximum values of the basis weight on the cylinder are 8.710 and 15.375, respectively, in g / m². The corresponding drying force index distribution ranges from 200.0 to 250.0 g paper / (s·m). The second step is to set the drying force index Dc expression as: Dc=r g XV / 60, the unit is g paper / (s·m); By collecting the actual data of various parameters during the production and operation of the on-site paper machine, the dryness conditions are set as follows: the dryness of the cylinder is 39% and the dryness of the cylinder is 94%. Under the condition of a certain speed V, the relationship between the basis weight on the cylinder and the drying force index is plotted, as shown in the figure below. Figure 1 As shown, the maximum value of the drying force index Dc is obtained by statistics, which is 250.0g paper / (s·m), and the basis weight on the cylinder is 12.5g / m 2 of paper; from Figure 1 It can be seen that the maximum value of the drying force index appears at about 12.5g / m2 on the cylinder basis weight. When the cylinder basis weight increases, the drying force index basically does not change, which means that the cylinder basis weight is 12.5g / m2. 2 The maximum drying capacity of the drying system composed of the drying cylinder and the air hood can be exerted, and the corresponding drying force index is 250.0 g paper / (s·m); It should be noted that different equipment has differences in configuration and other factors, and the corresponding basis weight on the cylinder when the maximum drying force index appears should be slightly different; it may be slightly earlier or later, but it should be around 12.5g / m 2Under the current conditions, the maximum value of the drying force index appears at the corresponding cylinder weight of 12.5g / m 2 ; According to the relationship between basis weight and drying force index, the basis weight on the cylinder is more than 12.5g / m 2 When the paper is dried, the drying force index Dc no longer changes. Therefore, Dc12.5 is set as the standard drying force index of the paper machine and used as the standard for evaluating the drying capacity of the paper machine. The third step is to convert and correct the drying force index Dc expression in the second step. The expression is as follows: DcM=Dc12.5 X kw X ke in, Dc12.5=250.0g paper / (s·m); DcM is the drying force index of the basis weight M on the cylinder; kw is the paper dryness correction coefficient, kw = 0.957; ke is the comprehensive factor correction coefficient, ke is 0.75~0.95; The relationship between ke and the base weight on the cylinder is as follows: Figure 2 As shown, the solid line and dotted line in the figure represent the upper and lower limits of ke respectively; Step 4: Verify the drying force index Dc expression in step 3 Different cylinder basis weights of the paper machine were selected and converted according to the measured moisture content of the paper sheets. The results calculated using the drying force index Dc expression were highly close to the field recorded data, thereby verifying that the drying force index Dc expression was correct, and ultimately determining to use Dc12.5 as the standard for evaluating the drying capacity of the paper machine.
[0012] If the data of in-cylinder and out-cylinder dryness are missing, the drying force index Dc is corrected by ke, and the ke value is conservatively selected towards the lower end. The expression of the drying force index Dc is: Dc12.5 X ke.
[0013] In actual production, the factors that affect the drying capacity of paper machines are mainly: One is the change in dryness entering and leaving the cylinder. After passing through the pressure roller, the dryness of paper webs of different thicknesses entering the cylinder is different; the drying capacity of the system, that is, the drying force index is inversely proportional to the moisture content in the paper sheet. The higher the moisture content, the smaller the drying force index, and the smaller the moisture content, the greater the drying force index.
[0014] The second is the change in thickness of the paper web entering the cylinder. The greater the basis weight on the cylinder, the thicker the paper sheet, and the longer the drying time required, which directly leads to a decrease in vehicle speed. Without considering the unevenness of drying in the thickness direction of the paper web, the system drying capacity is linearly inversely proportional to the vehicle speed. The higher the vehicle speed, the smaller the drying force index, and vice versa. For paper with a small basis weight, the drying efficiency cannot be fully utilized, resulting in a waste of drying capacity. The thickness change will eventually affect the dryness of the paper web entering the cylinder after pressing.
[0015] The third is the influence of other factors. The drying system is a comprehensive system project. In addition to the operating status of the system itself and the status of the paper entering the cylinder, the factors that affect the drying capacity include the influence of environmental temperature and humidity, the steam pressure and temperature of the main pipeline, the stability of the pulp properties, and the subjectivity of the machine operator during operation.
[0016] In the present invention, taking into account the above three influencing factors, it is necessary to correct and convert the expression of the drying force index to: Dc12.5 X kw X ke; The following is a verification of the corrected and converted expressions: According to production technical requirements, the measured inlet dryness corresponding to Dc12.5 is 39% and outlet dryness is 94%. It is known that the drying force index at this time is Dc12.5 = 250.0 g paper / (s·m); When the measured Dc9.5 corresponds to a dryness of 38% when entering the cylinder, the dryness when leaving the cylinder is still 94%, where the 9.5 in Dc9.5 refers to the base weight on the cylinder; Dc9.5=Dc12.5 X kw X ke, kw is the paper dryness correction coefficient, kw = =0.957, the numerator represents the moisture content of the paper when the basis weight on the cylinder is 12.5, the denominator represents the moisture content of the paper when the basis weight on the cylinder is 9.5, ke is the comprehensive factor correction coefficient, which is 0.75-0.95.
[0017] Dc9.5 = Dc12.5 X kw X ke = 250.0 X 0.957 X 0.88 = 210.5 g paper / (s·m) This conversion result is highly close to the field recorded data.
[0018] When dryness data is lacking, only ke correction can be used, and the ke value should be conservatively selected towards the lower end. For example, calculation: Dc10.5=Dc12.5 X ke=250X0.85=212.5, which is close to the actual data.
[0019] When the base weight on the cylinder is greater than 12.5, its drying force index can be considered to be the same as Dc12.5.
[0020] Different paper machines, with the same basis weight on the cylinder, have varying degrees of press efficiency on the paper web, resulting in varying degrees of dryness upon entering the drying cylinder. Furthermore, each manufacturer's requirements and assessment of roll dryness also differ slightly. To establish a relatively uniform evaluation scale, we set "39% dryness upon entering the cylinder and 94% dryness upon exiting the cylinder" as the standard dryness conditions. The maximum drying force index achieved by a paper with a basis weight of 12.5 g / m² on the cylinder is designated as the "standard drying force index," denoted as Dc12.5b. This provides a unified standard for evaluating or referencing drying capacity across different tissue machines from different equipment manufacturers.
[0021] First of all, Dc12.5b obtained under standard dryness conditions can be used as one of the evaluation criteria for the drying capacity or performance of equipment when household paper manufacturers purchase paper machine equipment. The larger the Dc12.5b value, the better the drying power of the system, the higher the output per unit paper width, and the greater the competitiveness of the equipment.
[0022] The evaluation method of the present invention can also be used to guide the machine operator to determine the optimal operating speed for different cylinder weights. For example, when Dc12.5b is 250.0, after water content conversion and speed correction, Dc9.5 is equal to 210.5, and the calculated speed is 1329 m / min.
[0023] The machine operator can set this speed value as the operating speed, and then increase or decrease the speed according to the actual paper temperature on the roll or the measured dryness, so as to maximize the drying and production capacity of the paper machine.
[0024] At the same time, on the other hand, under the premise of meeting the quality and technical requirements of paper products, wrinkling can be reduced as much as possible to increase the basis weight on the cylinder and improve the comprehensive coefficient ke, thereby achieving higher production volume.
[0025] Third, it is easy to calculate the roll output. For example, when the roll paper width is 2830mm, the corresponding DC12.5=250; Its output on the roll = 250X2.83=707.5g / s, 707.5 X 3.6 is 2547kg / h corresponding to Dc9.5=210.5, The output on the roll = 215.2X2.83=595.7g / s, 595.7 X 3.6 is 2145kg / h.
[0026] It should be noted that the present invention analyzes the relationship between the drying capacity of the paper machine and the basis weight on the cylinder and the speed, and introduces the drying force index. The drying force index of the paper machine drying system increases with the increase of the basis weight on the cylinder, and when the basis weight on the cylinder is greater than or equal to 12.5g / m 2When the drying force index reaches its maximum value, the paper with different in-and-out cylinder dryness and different cylinder basis weight is converted into Dc12.5, which is the standard drying force index. Dc12.5 is used as the standard to evaluate the drying capacity of different paper machine equipment, so that there can be a unified drying capacity evaluation or reference scale for different household paper machines from different equipment manufacturers.
Claims
1. A method for evaluating the drying capacity of a paper machine drying system, characterized by: The steps include: The first step is to start the machine on site and actually measure the paper machine to obtain known parameters, as follows: Paper machine drying cylinder upper basis weight r g , the unit is g / m2; the speed of the paper machine V, the unit is m / min; The second step is to set the drying force index Dc expression as: Dc=r g XV / 60, the unit is g paper / (s·m); By collecting real data on various parameters during the on-site paper machine production operation, the dryness conditions were set as follows: the dryness at the cylinder entrance was 39% and the dryness at the cylinder exit was 94%. Under the condition of a certain speed V, a relationship diagram between the basis weight on the cylinder and the drying force index was plotted. The maximum value of the drying force index Dc was statistically determined to be 250.0g paper / (s·m), at which the basis weight on the cylinder was 12.5g / m 2 of paper; According to the relationship between basis weight and drying force index, the basis weight on the cylinder is more than 12.5g / m 2 When the paper is dried, the drying force index Dc no longer changes. Therefore, Dc12.5 is set as the standard drying force index of the paper machine and used as the standard for evaluating the drying capacity of the paper machine. The third step is to convert and correct the drying force index Dc expression in the second step. The expression is as follows: DcM=Dc12.5 X kw X ke in, Dc12.5=250.0g paper / (s·m); DcM is the drying force index of the basis weight M on the cylinder; kw is the paper dryness correction coefficient, kw = 0.957; ke is the comprehensive factor correction coefficient, ke is 0.75~0.95; Step 4: Verify the drying force index Dc expression in step 3 Different cylinder basis weights of the paper machine were selected and converted according to the measured moisture content of the paper sheets. The results calculated using the drying force index Dc expression were highly close to the field recorded data, thereby verifying that the drying force index Dc expression was correct, and ultimately determining to use Dc12.5 as the standard for evaluating the drying capacity of the paper machine.
2. The method for evaluating the drying capacity of a paper machine drying system according to claim 1, wherein: If the data of in-cylinder dryness and out-cylinder dryness are missing, the drying force index Dc is corrected by ke, and the ke value is taken as a conservative value. The expression of the drying force index Dc is: Dc12.5 X ke.