JPH03227472A - Calculation of h-factor of continuous digester - Google Patents

Abstract

PURPOSE:To carry out an efficient operation by dividing a digester into plural stages from the top part to the bottom part and considering the difference of the reaction rate constant depending on weighting of H-factor to the respective reaction phases and on the difference in the activation energy based on the quality of a material. CONSTITUTION:A continuous digester is divided vertically into plural stages, (ST0, ST1,..., STn) from the top part to the bottom part and the boundary between penetration stage and digestion stage is estimated. For the respective stages, an H-factor is calculated while varying the value of activation energy making the standard value thereof the mean value and an estimated kappa-number is calculated so that a kappa-number dispersion correlation may be obtained. A point showing the highest value in the dispersion correlation is used as a parameter for H-factor calculation and the activation energy based on the quality of the pulp is calculated thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for calculating the H factor of a continuous digester used in a paper manufacturing plant for cooking wood chips. The present invention relates to an H-factor calculation method that is applied when calculating the H-factor using an off-line simulator.

<Traditional Branch Technique> In a paper manufacturing plant, the process of making pulp (fiber) from chips (wood chips) is called cooking.

To put it simply, the cooking mechanism is as follows: Chips are heated in a pot with an alkaline cooking liquor (mainly made of sodium hydroxide, called white liquor), the lignin in the chips is eluted, and only the fibers are removed. The goal is to carry out a delignification reaction that separates the .

An indicator of the efficient operation of such a continuous digester is the kappa number (KapPa value), a dimensionless number that indicates the degree of degunning of the mixture discharged from the digester. This largely depends on the temperature distribution function (this is called the H factor).

The H factor is generally expressed by equation (1) at a cooking scale of 7G.

H=/Kdt...(1) K=e
A-(B/T) K is the reaction rate constant, and for parameters A and B, Spruce (Sp
ruce) material, A=43.2°8=16.113
It is known that

Conventionally, such parameters have been used to manage the H factor in continuous digesters at operational sites in Japan.

<Problem to be solved by the invention> However, in this case, the reaction rate constant due to the weighting of the H factor by each reaction phase (infiltration stage, cooking stage, washing stage) in the digester and the difference in activation energy depending on the material. Because the difference is not taken into account,
This was a problem in operating the continuous digester efficiently.

The present invention has been made in view of these points, and
The purpose is to provide a method for calculating the H factor that can determine the optimal activation energy based on various materials at each stage in the kettle in pulp production equipment using a continuous digester. .

<Means for Solving the Problems> Fig. 1 is a flowchart showing the calculation method of the present invention.1 The method of the present invention consists of dividing the continuous digester from the top to the bottom into a plurality of stages in the vertical direction; , estimate where the boundary between the divided infiltration stage and digestion stage is, calculate the H factor by changing the value around the predetermined standard activation energy for each stage, and calculate the H factor obtained by calculating. An estimated kappa number is calculated using the factors, and this kappa number variance correlation is obtained, and the point having the highest value of this variance correlation is used as a parameter for H factor calculation.

<Example> Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic flowchart when the method of the present invention is implemented on a computer, and FIG. 3 is a conceptual diagram of the configuration of a continuous digester.

First, the inside of the continuous digester 1 is vertically divided into a plurality of stages from the top to the bottom. Here, it is assumed that the initial stages are divided into STO1 to STO5T15. This is based on the fact that in general continuous digesters, when designing a plant, stage 12 is conveniently set as the boundary between the initial (permeation) stage and the bulk (cooking) stage.

Here, in the washing stage, relatively low temperature washing water is injected into the upper and lower parts, so the cooking reaction is carried out at this stage.
It is assumed that you have already typed y. Therefore, we are focusing only on where the break between the infiltration stage and the digestion stage is.

Next, for the infiltration stage, cooking stage, and cleaning stage, various values are adapted and sequential calculations are performed for the activation energy of each stage, centering on the assumed reference energy value.

Since the activation energy depending on the material is unlikely to be the same at each stage, in the present invention, the assumed reference energy is approximately based on the following values at each stage.

Penetration stage = 40KJ/mol Digestion stage...150KJ/mol Washing stage =
120KJ/mo 1 Next, each infiltration stage is determined based on equation (1).

At the cooking stage and washing stage, the H factor is determined, and the calculated kappa number is determined using equation (2). Then, the correlation coefficients are compared and the activation energy at each stage is estimated.

Kappa value = A + B [I og (H factor) *
EaC] (2) Ea is alkaline concentration A conventional method is applied to find the parameters of constants A, B, and C in equation (2). In other words, the Kappa value can be predicted using the H factor by varying the parameters of the H factor obtained from equation (1) within a predetermined range (by adapting some values of ml and attempting the actual calculation). become.

FIG. 4 is a diagram showing the correlation coefficients calculated in this manner. In the example shown here, the separation between the infiltration stage and the cooking stage is determined by the number of the infiltration stage.

12 and the activation energy of the cleaning stage is 120 KJ/mol.

Activation energy at the penetration stage is 20KJ/mo
The activation energy that takes the maximum value of the correlation coefficient in the cooking zone is 95 KJ/m in this example.
It can be seen that o is around 1.

<Effects of the Invention> As explained in detail above, according to the method of the present invention, activation energy is determined based on the material of the pulp, and it is possible to improve the accuracy of the H factor and Kappa number. Furthermore, by finding the boundary between the washing zone and the cooking zone, it becomes possible to strictly control the H factor.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the calculation method of the present invention;
The figure is a schematic flowchart when the method of the present invention is realized on a computer, the third figure is a conceptual diagram of the structure of a continuous digester,
FIG. 4 is a diagram showing calculated correlation coefficients. Diagram

Claims (1)

[Claims] The continuous digester is vertically divided into a plurality of stages from the top to the bottom, and the boundary between the divided permeation stage and cooking stage is estimated, and a predetermined standard is set for each stage. Calculate the H factor by changing its value around the activation energy of A method for calculating an H factor for a continuous digester, characterized in that a point having the highest value is used as a parameter for H factor calculation.