Energy optimized steam blow box

Abstract

The invention relates to a steam application system (1) and a method for the efficient operation of the steam application system (1) for the efficient heating of a paper, cardboard or fibrous web (2) by means of steam condensation, comprising a steam blow box (3) which includes a plurality of application zones (4) which are connected to a steam line (9) by means of application valves (8), wherein the steam application system (1) includes a control device (6) which is configured to control the amount of steam applied to each application zone (4), wherein the application valves (8) include a device for detecting the valve position, and the steam line (9) includes a pressure measurement (7), and wherein the control device (6) is configured to calculate the amount of steam applied from the valve position and the measured value of the steam measurement (7).

Description

[0001] The invention relates to a steam application system for the efficient heating of a paper, cardboard, or fiber web by means of steam condensation, comprising a steam blow box that includes a plurality of application zones connected to a steam line by means of application valves. The invention further relates to a method for applying steam to a paper, cardboard, or fiber web by means of a steam application system.

[0002] Steam blowing chambers are known from the prior art for heating the paper web in paper production. WO 2021 20 92 32 A1 discloses a particularly compact steam blowing chamber in which steam quantity measurement and steam conditioning are already integrated. However, steam quantity measurement is always complex and prone to errors. In practice, steam blowing chambers are still not operated effectively to ensure that steam that does not condense on the paper web does not escape into the environment as mist. Finding the ideal operating point requires extensive manual trials, for which there is often insufficient time in practice due to variable boundary conditions.

[0003] Document DE 690 08 877 T2 shows a steam application system according to the preamble of claim 1.

[0004] The object of the invention is to provide an efficient steam application system to achieve efficient steaming of the paper web and to prevent steam from escaping unused into the environment and from condensing on the paper, cardboard, or fiber web. Furthermore, in an advantageous embodiment of the invention, steam quantity measurement can be dispensed with in order to obtain a particularly efficient and cost-effective steam application system by means of calculations, as well as to provide a method for operating this system efficiently. This should enable more efficient automatic control of the steam quantity.

[0005] The problem is solved according to the invention by an embodiment according to the independent claims. Further advantageous embodiments of the present invention are found in the dependent claims.

[0006] Furthermore, the object is solved according to the invention, wherein the steam application system comprises a control device which is configured to control the amount of steam applied to each application zone, wherein the application valves comprise a device for detecting the valve position, and the steam line comprises a pressure measurement, and wherein the control device is configured to calculate the amount applied from the valve position and the measured value of the pressure measurement.

[0007] To control the application quantity, it is necessary to determine the steam flow rate. Prior art methods employ flow measurements, which require a defined inlet and outlet length of a steam line. These flow measurements are particularly susceptible to errors, making precise and therefore efficient application quantity dosing difficult. This invention therefore eliminates the need for flow measurements on the steam line. Instead, the application valves include a measuring device for detecting and transmitting the exact valve position. This measuring device can be implemented using a displacement sensor or by calculating the position through the detection of a stepper motor's movements. For hydraulic or pneumatic valves, the valve position can also be determined by measuring the pressure of the control medium.To determine and control the application quantity for each application zone, a characteristic curve for the application valves is stored in the control system. This curve defines the application quantity as a function of the steam pressure in the steam supply line and the ambient pressure. Advantageously, the pressure measurement can also include a temperature measurement, allowing the temperature to be considered in the calculation of the application quantities (the pressure measurement is then temperature-compensated). The characteristic curve can also incorporate specific geometric information about the application chamber and achieve high accuracy for use in the steam blower box. The application valves are advantageously integrated into the steam blower box and are located between the steam line and the application zone.The application zones advantageously include a larger number of application nozzles or application openings, in particular between 10 and 200 application openings per application zone, through which the steam passes onto the paper, cardboard or fiber web.

[0008] A further advantage is a steam application system wherein the control device includes a speed value of the paper, cardboard or fiber web, and regulates the amount of steam applied in correlation with the speed value.

[0009] To calculate and control the application rate per unit area of ​​the paper, cardboard, or fiber web, a speed value is advantageous. The speed is either the production speed and / or the speed at which the paper, cardboard, or fiber web moves past the steam blowing box. This speed value is advantageously transmitted digitally from the machine control system to the control device.

[0010] A further advantage is a steam application system wherein the control device includes a grade value of the paper, cardboard or fiber web, and regulates the amount of steam applied in correlation with the grade value.

[0011] The grade value is advantageously transmitted digitally from the machine control and / or a production planning system to the control device. The grade value is a sum of various quality values ​​and / or production settings of the paper, board, or fiber web. It includes a basis weight value and / or values ​​relating to the material composition of the paper, board, or fiber web. Settings in a forming section and / or a press section of the machine used to produce the paper, board, or fiber web can also be optionally included in the grade value. The amount of steam to be applied can also be selected specifically for the grade and automatically adjusted accordingly by the control device.

[0012] A further advantage is a steam application system, wherein the steam application system comprises a measuring system, wherein the measuring system determines quality values ​​of the paper, cardboard or fiber web as profile values ​​across the machine transverse direction (CD) and transmits them to the control device, and wherein the control device regulates the application quantity in correlation with the profile values ​​for each application zone.

[0013] The quality values ​​of the paper, cardboard, or fiber web are measured as a profile across the web width. This is advantageously determined using a measuring frame and traversing sensors in a quality control system (QCS), which is part of the steam coating system. Control of the steam coating system via a control device and measured values ​​from the QCS is beneficial because the coating quantity can then be adjusted across the machine's cross-direction (CD), thus compensating for and / or improving the quality values. Fluctuations in the raw material and / or machine parameters can lead to varying quality values ​​across the width of the paper, cardboard, or fiber web. Targeted, increased heating with steam in specific coating zones can improve the quality values ​​in these areas, for example, by improving drying or dewatering.

[0014] A further advantage is a steam application system, wherein the steam application system comprises a measuring system, wherein the measuring system determines a moisture value and / or basis weight value of the paper, cardboard or fiber web as profile values ​​across the machine transverse direction (CD) and transmits it to the control device, wherein the control device regulates the application quantity in correlation with the profile values ​​for each application zone.

[0015] The steam application system can directly influence the moisture content of the paper, board, or fiber web, as the increased temperature from steam application enables improved dewatering and / or drying. Therefore, the moisture content is a beneficial input parameter for the steam application system's control device. The basis weight is also measured by the measuring system or QCS and advantageously transmitted to the control device, since the amount of steam applied has a different effect depending on the basis weight of the paper, board, or fiber web; the higher the basis weight, the greater the amount of steam that can be applied.

[0016] Furthermore, a steam application system is advantageous, wherein the steam application system includes a temperature sensor, wherein the control device is designed to regulate the application quantity in correlation with the measured value of the temperature sensor.

[0017] The temperature of the paper, cardboard, or fiber web, as well as the ambient temperature, directly influences the effectiveness of steam application. The higher the web temperature, the lower the condensation rate of the applied steam. Other process temperatures can also be advantageously considered in the control system, as they affect product quality or quality parameters. The temperature sensor can be a contact sensor, an infrared sensor, or an indirect measurement device that is transmitted to the control system, for example, from a process control system, via calculation or measurement.

[0018] A steam application system is also advantageous, wherein the steam line has a cross-sectional area of ​​100 - 3000 cm² over its length in the transverse direction of the machine (CD), in particular a cross-sectional area of ​​200 - 1000 cm².

[0019] Controlling the application zones via application valves is only possible if a uniform steam pressure is present at all application valves. A correspondingly large steam line is therefore advantageous. Only when the line has a sufficient cross-sectional area can an adequate steam supply be ensured across the entire web width in the machine transverse direction (CD) to all application valves. The steam line is particularly advantageously dimensioned when the cross-sectional area is between 250 and 1000 cm² and the length of the steam line is between 3 and 13 m.

[0020] A further advantageous method is a method for applying steam to a paper, cardboard or fibrous web by means of a steam application system comprising 10-200 application zones, wherein each application zone is connected to an application valve, characterized in that the following process steps are carried out: Determining the valve position for each application valve and transmitting the values ​​to a control device. Measuring the steam pressure in the steam line and transmitting the measured values ​​to a control device. Calculating the application quantity for each application zone in the control device using the aforementioned measured values. Regulating the application quantity for each application zone by adjusting the application valves.

[0021] The method for regulating the amount of steam applied to each application zone advantageously eliminates the need for additional steam flow measurements. This offers benefits in terms of both investment costs and control accuracy, as measurement errors associated with steam flow measurement are avoided. Instead of measuring the quantity and / or volume in the steam line, this method uses only a pressure value and a precisely determined valve position to determine and / or regulate the application quantity. Furthermore, pressure measurement in the steam line is necessary for control via valve position. This pressure measurement is advantageously located downstream of a steam flow control valve that regulates the amount of steam flowing into the steam line. The pressure measurement also advantageously includes a temperature measurement to enable temperature compensation of the pressure measurement.

[0022] Furthermore, a method is advantageous in which, in a further process step, temperature values, grade values ​​and / or speed values ​​are transmitted to the control device and taken into account for the control of the order quantity.

[0023] The transmission of temperature, grade, and / or speed values ​​is advantageously carried out from the control system of the machine used to produce the paper, cardboard, or fiber web. Typically, a distributed control system (DCS) is used, which transmits various measured values ​​to the control device of the steam application system via digital signal transmission. The measured values ​​are determined in the DCS from various sensors and / or calculations.

[0024] A further advantage is a method wherein the steam application system comprises a measuring system, wherein the measuring system transmits a profile value of a quality value of the paper, cardboard or fiber web to the control device, wherein the target variable for the control of the application quantity for each application zone is executed taking into account the profile value.

[0025] Irregularities can arise across the web width during the manufacturing process of paper, cardboard, or fiber webs. These are detected by a quality measurement and control system (QCS) and transmitted as profile information to the control device of the steam application system.

[0026] A further advantage is a method in which the quality values ​​include the moisture content and / or the basis weight of the paper, cardboard or fiber web.

[0027] From the profile values ​​determined in the QCS, the basis weight and moisture content of the paper, cardboard or fiber web are particularly important in order to efficiently control the amount of steam applied.

[0028] A further advantage is a method in which a condensation potential of the paper, cardboard or fiber web is calculated in the control device, whereby the condensation potential is taken into account for the control of the application quantity.

[0029] The amount of steam applied to the paper, cardboard, or fiber web, which condenses on the surface, depends on various factors. The moisture content, basis weight, and speed of the paper, cardboard, or fiber web are the most relevant quality parameters for condensation. Steam condensation heats the paper, cardboard, or fiber web, and the web exhibits a condensation potential that varies both temporally and locally. By taking this condensation potential into account, the optimal amount of steam applied to the paper, cardboard, or fiber web can always be calculated for changing production conditions. This amount is then applied to the paper, cardboard, or fiber web in the application zones of the steam application system. This prevents steam from escaping unused from the steam application system into the surrounding environment and causing mist.On the other hand, if the order quantity is too small, the beneficial heating cannot be sufficiently utilized if the condensation potential is not exploited.

[0030] The invention will be explained below with reference to a figure.

[0031] The Figure 1Figure 1 shows a schematic, non-scale isometric overview of a steam application system 1 for applying steam to a paper, cardboard, or fiber web 2. The steam application system 1 comprises a steam blower 3, a control system 6, a measuring system 5, and the lines for transporting steam, compressed air, and / or signals. The steam blower 3 is designed to apply varying amounts of steam to the paper, cardboard, or fiber web 2 by means of multiple application zones 4. The application zones are advantageously distributed across the paper, cardboard, or fiber web 2 in the transverse direction CD of the machine. Advantageously, the application zones 4 are between 5 and 50 cm wide (in CD). For a typical web width of 3 to 13 m, a steam blower 3 advantageously comprises between 10 and 300 application zones 4.A zone width of 4–40 cm and a number of 25–250 application zones in CD are particularly advantageous, as this allows for particularly precise control of the steam application quantity in CD. Each application zone 4 has a distribution chamber, advantageously with steam outlet openings or steam application nozzles. The distribution chamber of each application zone is connected to an application valve 8 and is supplied with steam from a common steam line 9. The steam line 9 is advantageously designed with a sufficiently large volume to provide the same pressure at all application zones. A steam line 9 with a cross-sectional area of ​​100 cm² to 1000 cm² after a steam flow control valve 10 is particularly advantageous. The steam blower box comprises the application zones 4, the application valves 8, the steam line 9, a steam flow control valve 10, and a pressure sensor 7 that measures the pressure in the steam line 9 after the steam flow control valve 10.The steam line 9 advantageously includes (not shown) further valves for draining condensate and / or heated chambers to reduce condensation in the steam blower box. The application valves 8 advantageously have a position sensor for the valve position, whereby the steam flow rate as a function of the valve position and the pressure differential before and after the application valve 8 can be represented by a characteristic curve. These characteristic curves are advantageously stored as data in the control device 6 for each application zone. The control device 6 advantageously includes a computer system, the technical devices for signal processing (IO interfaces, D / A / D converters), and corresponding converters for transmitting control signals to the application valves and achieving the corresponding adjustment there.The application valves 8 transmit their current valve position as input variables to the control device 6. Furthermore, data from a measuring system 5 are transmitted to the control device 6. The control system is also connected to the pressure measurement 7 from the steam supply, which is typically designed for a steam pressure in the range of 0–8 bar gauge pressure, and in particular for a range of 0–2 bar gauge pressure. The measuring system 5 is designed to record quality values ​​16 of the paper, cardboard, or fiber web 2 and is located in the manufacturing process downstream of the steam blowing box. The measuring system 5 is designed to perform a multitude of measurements of the quality values ​​16 across the web width in the transverse direction CD of the machine, so that a profile value 14 can be determined.The measuring system 5 is advantageously designed to determine quality values ​​16 for the moisture content, temperature, and / or basis weight of the paper, cardboard, or fiber web 2. Typically, further production sections are arranged between the steam blowing box 3 and the measuring system, such as (not shown) a press section, a drying section, and / or a size press. The control device 6 is designed to process the transmitted profile values ​​14 and output control signals to the application valves 8. Advantageously and optionally, further signals from the manufacturing process and / or the machine's environment are processed in the control device for the production of the paper, cardboard, or fiber web 2. The velocity value 12 is particularly advantageously used in the control device 6 to adjust the amount of steam applied.The velocity value correlates linearly with the amount of steam that can be condensed on the paper, cardboard, or fiber web 2. Similarly, a temperature value determined by a temperature sensor 15 can also influence condensation and be used accordingly in the control device 6. Particularly advantageously and optionally, the temperature of the paper, cardboard, or fiber web can be measured, and / or an ambient temperature and / or a process temperature. The condensation rate on the paper, cardboard, or fiber web 2 is lower the higher the temperature of the paper, cardboard, or fiber web 2. The control device 6 can also take differences in the paper, cardboard, or fiber web 2 into account in the control; in particular, information such as the grade value 13, which is a composite value of several quality values ​​16, can be used advantageously and optionally in the control. Reference symbol list

[0032] 1 Steam application system 2 Paper, cardboard or fiber web 3 Steam blow box 4 Application zones 5 Measuring system 6 Control device 7 Pressure measurement 8 Application valve 9 Steam line 10 Steam flow valve 11 Steam supply 12 Speed ​​value 13 Grade value 14 Profile value 15 Temperature sensor 16 Quality value CD Machine cross direction (Cross Direction) MD Machine direction (Machine Direction)

Claims

1. A steam application system (1) for the efficient heating of a paper, board or fibre web (2) by means of steam condensation, comprising a steam blow box (3), which comprises a plurality of application zones (4) connected to a steam line (9) by means of application valves (8), wherein the steam application system (1) comprises a control device (6) configured to regulate the amount of steam applied to each application zone (4), characterised in that the application valves (8) comprise means for detecting the valve position, and the steam line (9) comprises a pressure gauge (7), and wherein the control device (6) is arranged to calculate the application quantity from the valve position and the measured value of the pressure gauge (7).

2. Steam application system (1) according to claim 1, characterised in that the control device (6) comprises a speed value (12) of the paper, board or pulp web (2), and regulates the amount of steam applied in correlation with the speed value (12).

3. Steam application system (1) according to claim 1 or 2, characterised in that the control device (6) comprises a grade value (13) of the paper, board or pulp web (2), and controls the amount of steam applied in correlation with the grade value (13).

4. A steam application system (1) according to one of the preceding claims, characterised in that the steam application system (1) comprises a measuring system (5), wherein the measuring system (5) determines quality values of the paper, board or fibre web (2) as profile values (14) across the machine cross-direction (CD) and transmits them to the control device (6), wherein the control device (6) regulates the application quantity in correlation with the profile values (14) for each application zone (4).

5. A steam application system (1) according to one of the preceding claims, characterised in that the steam application system (1) comprises a measuring system (5), wherein the measuring system (5) determines a moisture value and / or basis weight value of the paper, board or fibre web (2) as profile values (14) across the machine cross-direction (CD) and transmits these to the control device (6), wherein the control device (6) regulates the application rate in correlation with the profile values (14) for each application zone (4).

6. Steam application system (1) according to one of the preceding claims, characterised in that the steam application system (1) comprises a temperature sensor (15), wherein the control device (6) is configured to control the application quantity in correlation with the measured value of the temperature sensor (15) .

7. A steam application system (1) according to any of the preceding claims, characterised in that the steam pipe (9) has a cross-sectional area of 100-3000 cm2 over its length in the machine cross-direction (CD), in particular a cross-sectional area of 100-1000 cm2.

8. A method for applying steam to a paper, board or fibre web (2), by means of a steam application system (1) according to one of the preceding claims, wherein the steam application system (1) comprises 10-250 application zones, and wherein each application zone (4) is connected to an application valve (8), characterised in that the following method steps are carried out: • measuring the valve position for each application valve (8) and transmitting the measured values to a control device (6) • Measuring (7) the steam pressure in the steam line (9) and transmitting the measured values to a control device (6) • Calculating the application quantity for each application zone (4) in the control device (6) using the aforementioned measured values • Regulation of the application quantity for each application zone (4) by adjusting the application valves (8).

9. A method according to claim 8, characterised in that, in a further method step, temperature values, grade values and / or speed values are transmitted to the control device (6) and are taken into account for the control of the application quantity.

10. A method according to claim 8 or 9, characterised in that the steam application system (1) comprises a measuring system (5), wherein the measuring system (5) transmits a profile value (14) of a quality value of the paper, board or fibre web to the control device, wherein the target value for controlling the application quantity for each application zone (4) is determined taking into account the profile value (14).

11. A method according to claim 10, characterised in that the quality values comprise the moisture content and / or the basis weight of the paper, board or fibre web (2).

12. A method according to any one of claims 8 to 11, characterised in that a condensation potential of the paper, board or fibre web (2) is calculated in the control device (6), wherein the condensation potential is taken into account in the control device (6) for controlling the amount of steam applied.

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