JPH07100915B2 - A device that continuously measures the moisture content of paper - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of continuously calculating the water content of paper at the entrance of a dryer, which is one of the most important control items in the operation control of a paper machine, during operation.

[0002]

2. Description of the Related Art FIG. 1 is a schematic view of a multi-cylinder dryer in a paper machine. Use steam as a source of energy for drying. In order to use this steam efficiently as shown in the figure, several dryer cylinders are used as the same steam pressure group to share a common steam header, and all dryer cylinders are divided into several groups (Fig. 1 is an example of 4 groups). It is common to configure a rage system. Then, the moisture content of the paper at the final dryer outlet can be measured by a measuring device (for example, B / M meter) that scans in the paper width direction. Similarly, the moisture content of the paper at the dryer entrance can also be measured by a measuring device (for example, B / M meter) that scans in the paper width direction, and is manufactured and sold by a measuring instrument maker.

However, in the vicinity of the entrance of the dryer, the measuring apparatus is not always in a condition where the environmental conditions are satisfied, and in particular, recently, a measuring sensor is mounted as the paper machine becomes faster and wider. In reality, the installation conditions for the head scanning frame are becoming more and more severe. For example, in order to prevent paper breakage at the press exit due to speedup, the space between the press part (dehydration device) and the dryer entrance part is very narrow, and there is a paper machine without a frame installation space. Also, the radiant heat of the dryer is high, and since it is a dehydration unit, the humidity is extremely high, and it is not an environment where electronic equipment can be installed. Even if it can be installed, its maintainability is extremely poor, and it is very difficult to maintain the reliability of the moisture content measuring device at a high level for a long period of time, and the moisture content of the paper at the dryer inlet is measured continuously and stably. It is desired to provide a method.

[0004]

In particular, as the speed and width of paper machines have become wider and the quality requirements for paper have become more stringent, the moisture content of the paper at the dryer entrance has to be known in order to precisely control the drying conditions in the dryer. The need is higher than ever. However, while the environmental conditions under which the measuring instruments are installed are getting worse, it is not possible to effectively deal with this problem. The present invention provides a way to effectively solve this problem. The present invention will be described below.

[0005]

As means for solving the above problems, the present invention comprises means for detecting the basis weight and moisture of paper at the dryer outlet, and means for detecting the traveling speed of paper at the dryer outlet. And a means for detecting the vapor pressure of the dryer. Further, using the preset overall heat transfer coefficient of the dryer, the evaporative water content of the dryer is obtained from the paper traveling speed at the dryer outlet, the basis weight, the water content and the steam pressure of the dryer, and the evaporative water content is calculated as the evaporative water content. The present invention provides an apparatus for continuously measuring the moisture content of the paper at the dryer inlet in a paper machine, which is provided with a computing device for summing the moisture content of the paper and computing the moisture content of the paper at the dryer inlet.

As described above, the present invention utilizes the data on the basis weight and moisture of the paper at the dryer outlet and the data on the speed of the paper. Further, the vaporized water content of the dryer is obtained from this data and the vapor pressure of the dryer. This is a device that can continuously grasp the moisture content at the dryer inlet by adding the moisture content of the paper at the dryer outlet to the amount. According to the present invention, a device (for example, a B / M meter) that scans the width of the paper at the dryer inlet to measure the moisture content is eliminated, and the moisture content of the paper at the dryer inlet is determined in cooperation with the information at the dryer outlet. It can be measured properly. Therefore, it solves the problem that it becomes difficult to secure a space for scanning by installing a moisture content measuring device at the entrance of the dryer, and the heat, humidity, paper dust, etc. of the dryer become disturbance factors and the reliability of the measurement is improved. It also eliminates the problem of damage to the dryer, and since it does not require installation of any device at the dryer inlet, maintenance work can be eliminated and the system can be streamlined.
Laborsaving, reliability improvement, and cost reduction can be achieved at the same time.

[Example] Method of calculating moisture content 1. Heat transfer and overall heat transfer coefficient (U) When considering the heat transfer rate or heat change rate, this is generally expressed as dQ / dΘ (Q is the heat quantity, Θ is time),
It is considered that this is proportional to the propulsive force ΔF and is proportional to the area orthogonal to the direction of movement, that is, the contact (direct and indirect) area A, and the proportional constant K is called the heat transfer coefficient, instead of the rate of change itself. It is a commonly used method to pay attention to these coefficients. That is,

[0006]

[Equation 1] Equation 1 is called a velocity equation.

When ΔF reaches the equilibrium state,
ΔF becomes zero. dQ / dΘ is the speed of movement because it is the amount of heat that changes or moves per unit time, but the differential form shows that the speed also changes as ΔF gradually decreases. This is also applicable to the case, and dQ / dΘ = Q / Θ may be set as long as the steady state, that is, Q does not change with time. In this case, ΔF also does not change with time. Equation 1 is, so to speak, a definitional expression of K. For convenience, the value of K defined in this way is obtained in such a way that the relationship with various factors in each case can be applied to the general case as much as possible, and this value is used. Then, it tries to obtain A which represents the size of the apparatus.

As described above, originally, the heat transfer coefficient is a coefficient used for determining the size of the apparatus, and the overall heat transfer coefficient described later is also used for the same purpose. However,
The actual value of K is not limited to the case where the moving speed shows a constant value regardless of the driving force. It depends on the experimental value because the moving speed is not always directly proportional to the first power of the propulsive force depending on the passing object (for example, paper, dryer cylinder, etc.). Now, Fig. 2 is a cross-sectional view of the dryer part in which the paper comes into contact with the dryer cylinder and is dried, and is in a thermal equilibrium state. This figure shows the t4 from the high temperature steam through the condensation steam drain, the dryer cylinder and the paper to the t4 Shows the temperature distribution when the calorific value q is flowing in the following steam per unit time, and this has been confirmed experimentally.

Inside the dryer cylinder, heat is transferred to the dryer cylinder, so that the steam loses latent heat of vaporization and becomes a condensation drain, so that a rim is formed on the inner surface of the rotating dryer by the action of the circular force, and the steam and its condensation drain are formed. It can be considered that the boundary temperature t1 of is equal to the saturation temperature of the steam. A temperature drop (t1-t2) occurs in the condensate drain.

On the other hand, the outside of the dryer cylinder comes into contact with the paper, and the moisture in the paper absorbs the heat of vaporization due to the amount of heat supplied through the dryer cylinder and is vaporized to become water vapor and move to the atmosphere.
When heat is taken inside the paper, a temperature drop (t3-t4) occurs, and when the temperature of the boundary between the paper and water vapor reaches equilibrium at temperature t4 when the water vapor pressure of the paper and the water vapor partial pressure of the atmosphere become equal. You can regard it. Here, regarding the heat transfer in the dryer cylinder of FIG. 2, Expression 1 is expressed as follows.

[0011]

[Equation 2] (H1, h2, h3 are heat transfer coefficients of heat transfer in each layer.) Or

[0012]

[Equation 3] Since the sum of the condensed vapor drain inside the dryer cylinder, the wall thickness of the dryer cylinder and the paper thickness is sufficiently smaller than the radius of the dryer, the area perpendicular to the direction of heat transfer

[0013]

[Equation 4] Substituting equation 4 into equation 3,

[0014]

[Equation 5] On the other hand, since it is difficult to actually calculate t2 and t3 in the formula 2, t1 and t4 which can be relatively easily known.
Equation 1 can be written as follows, where is the driving force.

[0015]

[Equation 6] As is clear from the formulas 5 and 6, the following formula is established.

[0016]

[Equation 7] Here, it has been experimentally revealed that h1 is most affected by the thickness of the drain rim of the condensed vapor,
If the state of drainage of the condensed vapor drain does not change with time, it can be treated as an almost constant value, and the drainage of the condensed vapor drain of the dryer cylinder can be handled during normal continuous operation in the actual paper machine operation. The state does not change over time,
h1 may be considered to be approximately constant.

H2 is determined by the thermal conductivity of the material of the dryer cylinder body and the thickness in the heat transfer direction, not by the operating state of the paper machine, but by the shape and material of the dryer. h3 is the type and physical properties of the raw materials (such as pulp) that make up the paper, and the mechanical structure of the paper (how the fibers are arranged, etc.)
In actual operation, if the brand of paper to be made is decided, the operating conditions (blending conditions of raw materials, operating conditions, etc.)
Is decided and becomes a constant value. That is, unless the drying conditions are significantly changed, the overall heat transfer coefficient (U) can be treated as a constant value determined by the raw materials of paper and operating conditions. 2. Heat balance in the dryer In the drying process, the temperature of the water inside the paper rises due to the heat supplied from the outside, absorbs the latent heat of vaporization (H) at that temperature, and finds the amount of heat absorbed. Only vaporize. When the vaporized water vapor pressure becomes higher than the atmospheric water vapor partial pressure, the water vapor diffuses into the atmosphere. This phenomenon is referred to as drying, and is continued as long as external heat is supplied and until the paper is drained.

Latent heat of vaporization (H) is a thermodynamic property value that is a function of temperature, and its value is generally known from a vapor table.
Therefore, when the water that evaporates is supplied continuously (for example, the paper is continuously passed through the dryer in the paper machine, that is, the paper is manufactured in the so-called paper machine), the amount of heat supplied from the steam is observed. The amount of vapor is dried by the amount of the amount of vapor, and the amount of vapor and the amount of evaporated water in the dryer reach a thermal equilibrium state. In FIG. 2, assuming that the amount of evaporated water (w) evaporates from the paper and is in an equilibrium state, the amount of heat of evaporation (qw) is proportional to the amount of evaporated water (w), and the proportional constant is equal to the latent heat of evaporation (H), It is expressed by the following formula.

[0019]

[Equation 8] However, in the general dryer, not all the heat quantity of the steam supplied to the dryer is used for the evaporation of the water, but the heat transfer from the dryer to other than the paper is also occurring at the same time. This heat dissipation (heat that does not contribute to paper drying)
Is treated as a heat loss amount (qr), there is a difference between the heat amount (q) supplied from the steam and flowing in the direction of the paper and the evaporation heat amount (qw) and the heat loss amount (qr) for moving the steam to the atmosphere. From the law of energy immortality

[0020]

[Equation 9] Holds. As is clear from the equations 6, 8 and 9, the following equation is established.

[0021]

[Equation 10] This equation 10 is generally called a heat balance equation in a dryer.

To calculate the overall heat transfer coefficient (U), the equation 10 is modified.

[0023]

[Equation 11] Or if qr = 0

[0024]

[Equation 12] Becomes Since t4, t1 and W can be measured,
Substitute the data into and calculate U. This overall heat transfer coefficient (U) is originally used when investigating the efficiency of existing dryers and the degree of paper drying, and reflecting the results in the design of dryer equipment.

3. Heat balance in an actual paper machine So far, the basic heat balance of a single dryer cylinder has been explained. Next, the heat balance in an actual paper machine will be explained.

Each variable used before the description is defined as follows. The "i-th" described in the definition means the i-th number counted from the entrance of the dryer device in which the entire dryer is divided into n (referred to as n group). Similarly, "j-th" means that the dryer cylinder in one group is counted as j-th from the entrance of the group in the paper flow direction.

Since the characteristic of the present invention is that the overall heat transfer coefficient (U) is known (treated as a constant value determined only by the type of raw material of paper and the operating conditions of the paper machine), the overall heat transfer coefficient (U U) must be decided.

Since the water content is calculated with this total heat transfer coefficient (U) being a constant value, the total heat transfer coefficient (actually measured U value) under the same operating conditions as when the target water content is calculated. , And use this value as a known value. Actually, several measured U values are obtained, and the average value is used as a known overall heat transfer coefficient (U). Next, a method of calculating the actually measured U value will be described. Here, it is assumed that the dryer is divided into n groups so that the calculation formula can be applied to a general paper machine, and the calculation order will be described.
Figure 3 shows a paper with moisture content (Me%) at a certain passing speed (SPD)
While passing through the dryer, the amount of evaporated water (W) is evaporated by the supply of heat (q) from the steam, and the moisture content (Mo%) and basis weight (BW) at the dryer outlet become paper. It is the figure which has gone out of the system continuously. Qr in the figure represents the amount of heat loss.

(3.1) Calculation of solid content of paper (BDW) Since the basis weight (BW) and moisture content (Mo) at the dryer outlet can be known by a measuring instrument, the absolute dry basis weight (BD) is It can be calculated from the formula.

[0030]

[Equation 13] Here, BD is referred to as absolute dry basis weight in terms of solid content weight per unit area. Therefore, the weight of solid content per 1 m of paper width (BD
W) is

[0031]

[Equation 14] hr) is a conversion factor for matching units. (3.2) Evaporated Moisture Content of Paper (W) The moisture content (Mo%) at the dryer outlet can be known by a measuring instrument as well as the basis weight, but the paper is sampled at the dryer inlet. Method based on JIS (method to actually determine the moisture content by drying the paper and weighing it)
There is no choice but to ask in. If this moisture content is set to Me (%),

[0032]

[Equation 15]

[0033]

[Equation 16] Since it is equal to the difference with the water content (BD ・ Mwo),

[0034]

[Equation 17] Therefore, by substituting the equation 14, it can be rewritten as the following equation.

[0035]

[Equation 18] (3.3) Calculation of latent heat of vaporization (H) of paper Since the vaporization temperature of paper is not exactly the same temperature in all dryer cylinders, the latent heat of vaporization of water, which is a function of temperature, is the inlet of the dryer. From exit to exit is not necessarily the same. However, the rate of water evaporation is 30
It is known that there is little change up to about 10% (drying during this period is called constant rate drying), and there is little change in evaporation temperature. Therefore, since 70% or more of the dryer cylinder enters this section, and the constant rate drying period does not change much when the brand of paper to be dried is determined in actual operation, the evaporation temperature of the paper is practically set to the dryer cylinder. The average latent heat of vaporization (H) of the paper is assumed to be equal to the average temperature of the entire paper and is equal to the latent heat of vaporization of water at that average temperature. (3.4) Calculation of heat quantity (q) supplied from steam In a multi-cylinder dryer of a paper machine, several steam cylinders are used as a common steam pressure group, and steam pressure is gradually increased from the inlet of the dryer. A common use is to raise and dry. Therefore, the heat value of the supplied steam will naturally differ depending on the steam temperature for each group. Therefore, if the i-th supplied heat value is qi, then the heat quantity of the supplied steam (q) for the entire dryer (if it is divided into n groups). Is the following formula.

[0036]

[Formula 19] Applying Equation 6 to each group,

[0037]

[Equation 20] Can be written. Substituting this equation into Equation 19,

[0038]

[Equation 21] Becomes

Here, the dry area Ai is a value obtained by integrating the contact area of the dryer cylinders in contact with the paper by the number of cylinders (mi) in the i group, but the area where the paper actually contacts the dryer is Since it is not the entire circumference of the cylinder, it is assumed here that it is the entire circumference in order to simplify the calculation. Under this assumption, the overall heat transfer coefficient is calculated to be smaller than the true value, but since the overall heat transfer coefficient is used as a constant in the process of calculating the moisture content, it is necessary to combine it with the measured moisture content (explained later). Therefore, the surplus of the dry area is corrected, and there is no problem in calculating the water content. Therefore, the paper width of the i-th group is 1 m
The dry area per unit (Ai) is calculated by the following formula.

[0040]

[Equation 22] Here, Ki, j represents the drying efficiency of the j-th dryer cylinder in the i-th group, and the ratio of the dryer cylinder that dries the paper is set as a reference value of 1.0 according to the usage of the dryer cylinder. . The fact that the drying area multiplied by the drying efficiency (Ki, j) is newly replaced by (Ai) does not contribute to the drying of the paper depending on the dryer tube in the group (for example, the valve of the steam inlet is fully closed). To avoid complicating the calculation formula when there is a cylinder that operates in a state) or a cylinder that contributes only partly (for example, there is a canvas between the contact surface of the paper and the dryer cylinder = single canvas) This is the action taken. Further, in general, most of the dryer cylinders have the same diameter except for a special case (for example, only the first dryer cylinder at the entrance of the dryer may be slightly reduced in diameter due to mechanical restrictions). Therefore, if the diameter is set to (D), then D = Di. Therefore, Equation 22 can be written as follows.

[0041]

[Equation 23] Substituting this into Equation 21,

[0042]

[Equation 24] Then, as described in section (3.3), the evaporation temperature of the paper can be regarded as the same temperature through all the dryers. Therefore, if the evaporation temperature (tpi) of the paper is replaced by (tp), Equation 24 becomes ,

[0043]

[Equation 25] Becomes Next is the calculation of the saturation temperature (ti) of steam.
It is possible to measure the saturation temperature directly, but in an actual paper machine, it is most economical to calculate assuming that the saturation temperature of steam in the dryer is equal to the saturation temperature of steam pressure in the steam header. , And practical. Although various formulas are widely used in this calculation formula, the following approximate formula is used as an example in the present invention.

[0044]

[Equation 26] This saturation temperature is used in Equation 25. (3.5) Calculation of heat balance and "measured U value"

[0045]

[Equation 27] When Equations 25 and 27 are applied to the basic equation 9 of the heat balance, q = qw + Qr. Here, Qr is the heat loss of the entire dryer. Substituting equations 25 and 27 into this equation,

[0046]

[Equation 28] Becomes Ui in Equation 28 (overall heat transfer coefficient of the i-th group) is actually slightly different depending on the group. This is because the overall heat transfer coefficient has a property of slightly changing depending on the temperature of the paper. However, since the amount of change is negligible compared to the previously assumed conditions, it is assumed that the overall heat transfer coefficient of each group is equal to its average, and is newly defined as (U). Although the overall heat transfer coefficient is slightly different from the true value due to this assumption, the overall heat transfer coefficient is used as a constant in the process of calculating the moisture content, so at the stage of combining with the measured moisture content (explained later). The difference from the true value of U will be corrected, and no problem will occur in the moisture content calculation. Therefore, Equation 28 can be written as follows.

[0047]

[Equation 29] Converting this expression to the expression for U,

[0048]

[Equation 30] And when Qr = 0,

[0049]

[Equation 31] Becomes This formula is the "measured U value" of an actual paper machine.
Is a specific general formula for obtaining.

In order to make (Qr) as small as possible, in an actual dryer device, a hood is installed outside the dryer cylinder to recover heat and improve efficiency.
In the actual operation, if the brand of paper to be made is determined, the operating conditions of the hood (exhaust humidity, exhaust temperature, etc. of each damper, etc.) are determined, and the amount of heat loss is determined by the operating conditions of the hood. Can be treated as a value. Here, the meaning of the overall heat transfer coefficient (U) differs depending on whether the heat loss is assumed to be zero or not. If it is assumed to be zero, the effect of heat loss is reflected in the value of the overall heat transfer coefficient (U), but if not, it is limited to that of the dryer cylinder only. In other words, in the former case, the quality of the hood is also taken into consideration, so it is the “total heat transfer coefficient (U) including the efficiency of the hood”, and the latter is the “between the dryer tube and the paper. Limited overall heat transfer coefficient (U) ". Whether Equation 30 or 31 is used here is only a matter of selecting whether or not to include Qr in the equation for calculating the water content. That is, in Equation 30, U
If you obtain, you can add Qr to the formula that gives the moisture content,
If it asks by Numerical formula 31, it will suffice if Qr is not entered.

Since it has nothing to do with the calculation result of the moisture content, it is better to simplify the calculation formula as much as possible within the range where practically no problem occurs. Since the embodiment uses Expression 31, Expression 31 will be used for the following description.

(3.6) Calculation of Moisture Content of Paper at Dryer Inlet Using "Actually Measured U Value" Up to now, a concrete procedure for calculating "actually measured U value" using measured data under a certain operating condition I have described various methods.
Next, an explanation will be given of a method of calculating the moisture content, in which the average value of the U values (actually, a large number of actually measured U values are obtained and the average is taken) is treated as a known overall heat transfer coefficient based on the operating conditions. . First, the known overall heat transfer coefficient is set as UAVG. Further, in order to facilitate understanding of the calculation, if the moisture content of the paper at the dryer inlet to be obtained is set to X [%] and the moisture content at that time is set to Xwe, Mwe in Equation 27 can be replaced with Xwe. ,

[0053]

[Equation 32] And substituting this into Equation 27,

[0054]

[Expression 33] Using q = qw (assuming Qr = 0),

[0055]

[Equation 34] Then, when converted to the formula for obtaining Xwe from Formula 34,

[0056]

[Equation 35] Becomes On the other hand, the amount of evaporated water (BDW) is

[0057]

[Equation 36] Therefore, the equation for calculating the moisture content (X) from Xwe can be modified by replacing Mwe with Xwe and Me with X in Equation 15,

[0058]

[Equation 37] Becomes

Equations 36, 37 and 38 are concrete calculation formulas of the present invention for obtaining the moisture content, and the numerical values used in this formula are summarized below. It becomes (3.7) "Moisture content calculated by calculation""Absolute dry water content"
Adjustment to (calibration) Since various assumptions are made in order to simplify the calculation, there is an error between the calculated water content (hereinafter referred to as the calculated water content) and the true value. The operation of reducing this error and matching the calculated water content to the true value is calibration. This work is performed in the same way as the calibration of other instruments. First, the actual paper at the entrance of the dryer is sampled, and the moisture content (hereinafter referred to as absolutely dry moisture content) is measured by a method based on the JIS method. Of course, the calculated moisture content is also obtained when sampling. Actually, it is impossible to know the true value of the water content at the inlet, so it is a common method to substitute the absolute dry water content as the true value for convenience. Make adjustments.
Therefore, plot the data on a graph with the calculated moisture content on the Y-axis and the absolute dry moisture content on the X-axis (Fig. 4), and take the correlation between the X-axis and the Y-axis so that this correlation is 1: 1. , UAVG (measured U value) is adjusted. As a result of this work, the assumptions that have been set variously for the sake of calculation have resulted in UAV
Since it is included in G and corrected, the smaller the difference between various assumptions and the actual, the smaller the true value and the error. If there is a large difference in operating conditions so that the error cannot be ignored, there is no problem in practice if another UAVG value (a value that allows the error to be within the allowable range) is set and used. .

[0060]

[Embodiments and Calculation Examples of the Present Invention] Equations 35 to 35 in an actual paper machine
A calculation example when 37 is applied is shown below. In the embodiment, FIG.
The drying apparatus and the operating conditions as described above were used, and it is assumed here that the “measured U value” has already been measured and known.

(1) Calculation conditions The operation data and constants of the drainage system during operation are as follows. Table 1 shows the number of dryer tubes in each group and the operating steam pressure. (2) Calculation of Moisture Content Table 2 shows the results of calculation by applying the calculation conditions of the previous section to the equation 35. Therefore, from Equation 36, And from Equation 16, Therefore, from Equation 35, From Equation 37, the moisture content of the paper at the dryer inlet is calculated as Thus, the moisture content of the paper at the dryer inlet is 55.9%.

A control system for a recent large-sized paper machine is a distributed computer control system A as shown in FIG.
In most cases, the basis weight moisture control system B is introduced. Data is transmitted and received by communication between the two systems. In the present invention, as described in detail above, a program for continuously calculating the moisture content at the dryer inlet is input in advance to the distributed computer control system A and placed. Data relating to the basis weight, moisture and running speed of the paper at the dryer outlet are loaded from the basis weight moisture control system B into the computing unit of the computer system A, and at the same time, the vapor pressure data of the dryer is loaded into the computing unit and the dryer outlet From the data and the steam pressure data detected from the dryer, use the preset overall heat transfer coefficient of the dryer to determine the amount of water evaporated in the dryer, and then use this amount of water evaporated to determine the amount of paper moisture at the dryer outlet. Therefore, the moisture content of the paper at the dryer entrance can be calculated easily and continuously.
The calculation result is the same as when the online moisture meter is installed.
It can be displayed on the CRT, marked in the table, and used for control. C in the figure is the grammage / moisture sensor of the system B installed on the dryer outlet side. As a means for detecting the speed of the paper at the dryer outlet, a known method of detecting from the drive motor M of the paper take-up reel is adopted. Similarly, FIG.
The means for detecting the vapor pressure data of the dryer shown in (1) can also use the existing detection device.

[0063]

By carrying out the present invention, the average moisture content of the paper at the dryer inlet can be continuously obtained online without installing a moisture measuring device at the dryer inlet, and the effect is very large. For example, it can be used to grasp the dehydration status of a press blanket (an endless blanket that runs with paper as an auxiliary tool used in the dehydration section) and to control the optimal time for blanket replacement, that is, to control the drying conditions and achieve great results. be able to. That is, as in the conventional example, a device for scanning by installing a B / M meter at the dryer inlet is omitted, and the prediction is made from the data of the basis weight, moisture and speed of the paper at the dryer outlet and the steam pressure data of the dryer. By using the set overall heat transfer coefficient of the dryer, the moisture content of the paper at the dryer inlet can be taken in easily and continuously, and this can be effectively used for the operation management of the paper machine. Since the B / M meter can be installed at the entrance of the dryer and the scanning device can be eliminated,
It is possible to remove the disturbance factors such as dryer temperature, humidity, and paper dust accompanying the installation of this device to measure the moisture content with high reliability, and to eliminate the maintenance management accompanying the installation of the device. The space for installing the device can be omitted, and rationalization of the device and cost reduction can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a typical multi-cylinder dryer used in a paper machine.

FIG. 2 is a cross-sectional view of a dryer portion in which the paper comes into contact with a dryer cylinder and is dried, and is in a thermal equilibrium state.
FIG. 3 is a diagram showing a temperature distribution when a heat quantity q is flowing in a unit time from a high-temperature steam of 1 to a steam of t4 through a condensing steam drain, a dryer cylinder, and a paper sheet.

FIG. 3 shows a paper having a moisture content (Me%) at a certain passing speed (SP
Heat quantity (q) from steam while passing through the dryer device in D).
FIG. 3 is a diagram in which the amount of evaporated water (W) is evaporated by the supply of the water and the paper having the water content (Mo%) and the basis weight (BW) is continuously discharged from the system at the dryer outlet.

[Figure 4] Absolute dry moisture content on the X-axis, calculated moisture content on the Y-axis, and fitting of the absolutely dry moisture content of the calculated moisture content (calibration)
It is a graph showing.

FIG. 5 is a diagram showing grouping of dryers to which the present invention is actually applied and operation data thereof.

FIG. 6 is a schematic diagram of a system configuration when the present invention is implemented.

[Table 1]

[Table 2]

Claims (1)

[Claims] 1. A means for detecting the basis weight and moisture of the paper at the dryer outlet, a means for detecting the traveling speed of the paper at the dryer outlet, and a means for detecting the vapor pressure of the dryer, further comprising: Using the overall heat transfer coefficient of the dryer set for the dryer, the amount of evaporated water in the dryer is calculated from the paper running speed at the dryer outlet, basis weight, moisture and steam pressure of the dryer. An apparatus for continuously measuring the moisture content of the paper at the dryer inlet in a paper machine, which is equipped with a computing device for summing the moisture and computing the moisture content of the paper at the dryer inlet.