FI61533B - FOERFARANDE FOER REGLERING AV TILLFOERSELN AV REAKTIONSKEMIKALIER VID DELIGNIFIERING OCH / ELLER BLEKNING AV MASSA - Google Patents

Description

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JSa w (11) utläggningsskrift ΟΊ533 ^ (51) Kv.ik.3 / tnt.ci.3 D 21 C 7/12, 9/10 FINLAND — FINLAND pi) 7523U3 (22) HakamtiplWt - Ana6fcnlng * dag 19.08.75 ( 13) AlkupMvi — GHtighetadag 19.08.75 (41) Tullut JulklMkiJ - ilhrit offaodl, 0g yg ymtti. and registries (44) NlhtMWpweB * ku «M« .w * n ’

Patent- och registerstyrelean 7 Subject matter wi «* d oeh uti-ikrtfun piibiic« r »d ju.ua.ö ^ (32) (33) (31) PyH« ttr • tuojk.u.-e ^ w prior ** 05.09 .71 *

Sweden-Sweden (SE) 7 ^ 112 ^ -5 (71) Mo och Domsjö Aktiebolag, Pack, S-891 01 Örnsköldsvik 1, Sweden-Sweden (SE) (72) John Rickard Bergström, Örnsköldsvik, Bengt Göran Hultman, Domsjoverken,

Astrid T. P. Dalborg, Bonässund, Sweden-Sverige (SE) (71 *) Berggren Oy Ab (5 ^) Method for controlling the conduction of reaction chemicals during delignification and / or bleaching of pulp

The present invention relates to a process for controlling the conduction of reaction chemicals by removing lignin from a pulp and / or bleaching a pulp produced in the cellulose industry. In particular, the invention relates to control methods in which reaction chemicals are added to a pulp suspension containing chemical consuming substances and subjected to a treatment step in which all or part of the reaction chemicals are consumed and the chemical addition is controlled by passing in the reaction step

In most cases, the purpose of bleaching cellulose pulp is to remove those lignin residues which have not been dissolved in the first chemical treatment of the wood by sulphite, sulphate, oxygen gas or other dissolution methods. In addition to dissolving the lignin during bleaching, it is also intended to increase the whiteness of the pulp. This is accomplished in factory-scale pulp bleaching processes by stepwise treating chlorine type, chlorine dioxide, hypochlorite, sodium hydroxide with existing reaction chemicals, and more recently, oxygen gas.

The consumption of chemicals incurs high costs, which form a very important part of the processing costs due to the production of bleached cellulose pulp. The amount of bleaching chemical added at any stage of the bleaching also affects the quality of the final product. When bleaching cellulose pulp, it is therefore important that the right amounts of chemicals can be added. The difficulty in doing this is due to the fact that the lignin content and thus the Kemi-cabbage requirement in the treated pulp varies all the time. Additional difficulties are also caused by the long residence time of the pulp in the various bleaching stages.

Environmental protection measures also cause an increase in the load on the sieve and washing compartments, with contaminants and washing residues being followed by an increased amount of pulp in the bleaching plant instead of being discharged into the discharge line. Variations in the degree of washing and cooking result in significant variations in the mass flow into the bleaching plant, partly in the total lignin content and partly in the distribution of lignin dissolved in the liquid and bound to the cellulosic fibers. In addition to lignin, the liquid also contains other chemicals, e.g. incompletely washed cooking chemicals. The substances contained in the liquid also consume bleaching agents.

As a result, bleaching chemicals are added during the bleaching of the cellulosic pulp, which react partly with the bleach consumable substances dissolved in the liquid, partly with the lignin bound to the cellulose.

The methods used heretofore to control the addition of bleaching chemicals to the needs of the cellulosic pulp have mainly used one of the following options: a) The addition of bleaching chemicals to the pulp suspension to effect bleaching is modified based on the concentration of residual chemicals in the pulp suspension after bleaching. The determination of residual chemicals, e.g. active chlorine compounds dissolved in the bleach waste solution, has taken place manually and at specified intervals.

..., 61 5 3 3 3

Due to variations in the properties of the added pulp suspension and the long processing time, the addition of bleaching chemicals must be made somewhat too large to ensure a satisfactory bleaching operation, which has negative effects on the pulp property and unnecessarily high bleaching costs.

b) The addition of bleaching chemicals to the pulp suspension to effect bleaching is adjusted based on the concentration of waste chemicals in the pulp suspension shortly after bleaching is started, keeping the measured value, e.g. redox potential, polarographic analysis value or optically obtained signal, constant. The desired constant value can then also be corrected as required on the basis of manual residual chemical analyzes. This method provides a faster correction than that mentioned in a), but does not sufficiently take into account the variations in the properties of the added pulp suspension because the measurement result is disturbed by the fact that the reaction chemicals are consumed not only by the pulp but also by the liquid phase.

(c) The addition of bleaching chemicals to the pulp suspension to achieve bleaching has been adjusted on the basis of the target value adjustment according to (b) above, but this target value is modified as necessary based on the measured values of the residual chemical analysis after bleaching. This represents an improvement over the previously mentioned alternatives, but in addition to the fact that the sharks mentioned in b) are retained in certain parts, the long residence time in the bleaching stage means that changes in chemical dosage can only compensate for relatively slow variations.

As mentioned above, none of the mentioned methods compensates for the fact that the lignin content of the cellulose pulp alone does not affect the chemical consumption. The pulp suspension coming from the white-Simo cooking and sieve compartment also contains lignin in dissolved form, i. those washing losses that have not been recovered and led to the evaporator and incinerator. This lignin, together with inorganic impurities, also consumes bleaching chemicals such as chlorine.

The present invention eliminates said disadvantages. Accordingly, the present invention relates to a process for controlling the conduction of reaction chemicals during delignification and / or bleaching of pulp produced in the cellulose industry, adding reaction chemicals to a pulp suspension containing chemical consumables and passing them to a reaction step and on the basis of the reaction chemical concentrations measured after the reaction, which method is characterized by a combination of determining the reaction chemical requirement of the suspension liquid before the treatment step and determining the amount of uncommitted reaction chemicals after chemical addition, and using According to this method, it is essential that the concentration of the remaining non-wearing reaction chemicals is determined at some point after the reaction chemicals have been added, since their prescribed wear begins immediately. Sampling to obtain this measured value can thus take place immediately after this addition. It is also possible to carry out the sampling itself during the treatment step when the reactions have started in a considerable amount. Sampling can then be carried out at the beginning, during or at the end of the treatment step, in which case it is very convenient to carry out sampling at the beginning of the treatment step in order to obtain the correct values from the treatment step as quickly as possible and to adjust the chemical addition. In the event that the reaction chemicals are not completely consumed in the treatment step, it is also possible to perform sampling based on the concentration of residual uncharged reaction chemicals after the treatment step.

By "treatment step" is meant, according to the invention, e.g. bleaching treatment, in which bleaching chemicals are added to the pulp and are allowed to react with it during the same time as the bleaching chemicals. Another form of treatment to which the invention can be applied is the extraction step in bleaching the pulp, in which the pulp, after bleaching and washing with water, is treated with an alkaline solution to dissolve the lignin. In this case, according to the invention, a first sample is taken to determine the alkali requirement of the suspension liquid in the extraction process and a second sample after the alkali addition, and the measured values obtained are used to control the alkali addition.

Surprisingly, the process according to the invention makes it possible to carry out, by direct control, an almost complete smoothing of the variations in the lignin content of the treated pulp.

The process according to the invention is very suitable for use in the treatment of wood material which has been dissolved by chemical processes such as sulphite, sulphate, oxygen gas / alkali, bisulphite and soda processes, but can also be applied to pulps obtained by semi-chemical and mechanical or thermomechanical processes. methods. It is very suitable to apply the process according to the invention to chemically prepared pulps having a lignin content of about 100-5, suitably 40-9 and most preferably 35-10, the process preferably being applied in a preliminary bleaching step, which in addition to improving whiteness also provides continuous lignin removal. In the event that the invention is applied to semi-chemical, mechanical or thermomechanical masses, the so-called for the production of high yield pulps, the whitening improving reaction is predominant over the lignin removal reaction.

The process according to the invention can also be applied to treatment steps which are divided into several phases, e.g. a bleaching step, using different bleaching chemicals, e.g. chlorine and chlorine dioxide, to successive phases in the same treatment step without intermediate alkali extraction or washing. It is also possible to apply the present invention using several reaction chemicals simultaneously, e.g. using mixtures of chlorine and chlorine dioxide as bleach in the bleaching step.

The process according to the invention is described below in connection with a preliminary bleaching step in a pulp mill using chlorine as a reaction chemical, to which, however, the invention is not limited.

The cooking screen compartment becomes a pulp suspension 1 with a concentration of 2-3¾ (see Figure 1). The liquid in which the pulp is suspended is the water in which the cooking chemical residues and the dissolved wood are dissolved. In a special sampling device 2, a liquid sample is taken from the pulp suspension. The stream 3 of this sample is fed to an analyzer 4, where the consumption of chlorine in the liquid is determined. In bleaching step 5, the pulp suspension is mixed with the chlorine stream 6. After the addition of chlorine, the pulp suspension 7 mixed with chlorine is allowed to react for a certain time, after which it goes on to the next bleaching step. After a certain time after the addition of chlorine, the pulp suspension passes the sampling point 8, where the fiber-free liquid sample 9 is separated from the pulp. The sampling time may vary from a few seconds after mixing the chlorine to the blink of an eye at which the pulp suspension leaves the bleaching step. The sample stream 9 is fed to an analyzer 10, where the waste chlorine content of the liquid is determined. From the results obtained from analyzers 4 and 10, it is now possible to calculate the amount of chlorine consumed by the cellulose-bound lignin and the amount of chlorine consumed by the substances dissolved in the suspension liquid, respectively. This calculation is performed electrically in the calculation unit 13, to which the measurement results are conducted electrically via lines 11 and 12. Based on the calculation results, the control device 14 adjusts the chlorine stream 6 by the control device 14, which is fed to the bleaching stage 5. In addition to controlling the stages. By performing two analyzes, one before the addition of bleaching chemicals and the other during bleaching, the actual bleaching requirement of the pulp can be calculated before starting the bleaching step. Thus, an amount of lignin or a lump number analyzer is obtained which measures the entire mass flow leading to the bleaching step and, in addition, gives continuous measurement values, which is a great advantage over hand-made samples. Bleaching chemicals are dosed on the basis of the number of chunks or chlorine in the incoming pulp, which is a measure of lignin content, and this can be related to a given chemical consumption. The method according to the invention makes it possible for the lignin flow analysis to be carried out for the first time continuously, accurately and directly using the process flow to which the bleaching addition is to be adjusted. Another important advantage of the method according to the invention is that the analysis before the bleaching step provides information on how effective the recovery of the cooking liquor is. In addition, the bleaching chemical consumption of the chemical consuming substances dissolved in the suspension liquid can be corrected at exactly the right time because a sample for this analysis is taken before the bleaching chemicals are added to the pulp suspension.

The analysis of the bleaching chemical consumption of the suspension liquid can take place in several ways. One suitable way is to add a known amount and excess of bleaching chemical to a sample of the suspension liquid, e.g. in the form of chlorinated water, and then, after a certain reaction time, to determine the excess of the bleaching chemical using some known method, e.g. iodine titration, polarographic measurement, redox potential measurement, conductivity or pH, photometric measurement, color measurement or the like. However, it is very advantageous to allow the flow 3 to react with the excess bleach and to measure the amount of heat generated. The method is hereinafter referred to as calorimetric. In this calorimetric order, it is also possible to use reagents other than chlorinated water, e.g. alachloric acid, hypochlorite, chlorine dioxide or hydrogen peroxide. Despite the fact that the substances dissolved in the suspension liquid form a mixture with a large number of largely unknown substances, it has surprisingly been found that the heat evolution that takes place can be taken as a reproducible measure of the bleach consumption of the suspension liquid.

The analysis of the bleach content in the pulp suspension after the pulp suspension and the bleach have been mixed and the bleaching reaction has started can take place in several ways. Common methods include oxidation reduction potential measurement, polarographic measurement, conductivity measurement or pH measurement, manual or automatic iodine titrations to obtain the remaining active bleach concentration. It is desirable that the analysis be continuous and specific to the bleach to be analyzed. It has been found to be very advantageous to take a non-fibrous sample of the suspension liquid 9, which is allowed to react with a suitable reagent, and then to use the heat generated as a reproducible measure of the amount of bleach remaining. By appropriately selecting the reagent, the analysis can thus be carried out, for example, on sodium hydroxide, hypochlorite, chlorine, chlorine dioxide or hydrogen peroxide. Bleaching mixtures are used in certain bleaching processes, and e.g. chlorine and chlorine dioxide can be advantageously used in the mixture. By selecting a suitable reagent, it is possible to determine the amount of calorimetrically active chlorine or to determine chlorine and chlorine dioxide separately. Thus, according to the invention, it is possible to obtain information on how the concentration of bleaching chemical changes as the reaction progresses.

The invention is illustrated by the following embodiments, of which Example 1 shows an analytical method for determining the chlorine consumption of a suspension liquid, Example 2 shows the determination of residual chlorine content after a certain reaction time and Examples 3 show chlorine flow control 61533 dioxide. Example 5 shows the adjustment of the alkali addition to the alkaline extraction step of the bleaching series.

Example 1

Adjusting Chlorine Consumption in the Liquid Removed from the Pulp Suspension A large number of samples were taken from the liquid of the pulp suspension fed to the bleaching plant at regular intervals and over a longer period of time. Samples were taken from both sulfate and sulfite plants. Chlorine consumption of liquid samples was determined partly by titration, partly by calorimetry.

The titration analysis was performed as follows: 50 ml of the liquid sample was reacted with 10 ml of saturated chlorine solution, about 5 g / l Cl 2. After 5 minutes, excess potassium iodide was added, which was acidified to a pH of about 1. The iodine formed was titrated with sodium thiosulfate. The blank test was carried out in the same way but using 50 ml of distilled water instead of the sample. For calorimetric analysis, a stream of fiber-free sample was mixed with a stream of saturated chlorine solution. The reaction mixture was then introduced into a reaction coil and the heat of reaction generated in the coil was measured as one potential using a series of thermocouples connected in series. The potential obtained from the thermocouple gave, in a large range, a result parallel to the consumption of chlorine determined by titration. The relationship between the analytical values obtained by calorimetry and titration is shown in Figures 2a and b, where the calorimetrically measured potentials are shown on the y-axis and the corresponding chlorine consumption values obtained by titration on the x-axis. Figure 2a shows the sulphate process and Figure 2b the sulphite process. As can be seen from these figures, the dependence is parallel (coefficient of equivalence 0.995), as a result of which the values obtained calorimetrically can be used with great certainty to determine the chlorine consumption of the liquid.

Example 2 Waste chlorine analysis during bleaching of cellulose pulp

A large number of samples were taken from the bleaching plants in the sulphate plant after a certain time after the pulp suspension and chlorine were mixed together. The fiber-free liquid sample was analyzed partly calorimetrically, partly manually using iodometric titration. Iodometric titration was performed in a conventional manner by reacting the sample with an acidified potassium iodide solution. The liberated iodine was then titrated with sodium thiosulfate, after which the waste chlorine content was calculated. In the calorimetric analysis of the chlorine content, a series of calibration solutions were prepared by adding 0.01, 0.05, 0.10, 0.15 g / l Cl 2 to the liquid sample 9 according to Figure 1, from which all chlorine had been removed. Accurate determination of the chlorine content in these calibration solutions was obtained by iodometric titration. In the calorimetric calibration, the calibration solution stream was mixed with a reagent solution stream containing 0.2% potassium iodide and 0.2% sulfuric acid. In this case, the heat of reaction evolved was measured by means of a heating element in the form of a potential. For continued measurements, the calibration solutions were exchanged for a continuous flow of sample 9 as shown in Figure 1. Figure 3, in which the calorimetrically measured values at several sampling points are shown on the y-axis and the corresponding residual chlorine concentrations obtained by titration on the x-axis, shows the consistency of the calorimetrically measured values, in mV, and the residual chlorine content, measured in grams, in grams. It can be seen from this figure that a clear and mainly linear consistency was obtained between the calorimetric values and the manual titration values. Waste chlorine determinations can thus advantageously be carried out using a continuous calorimetric determination method.

Example 3

Adjusting the chlorine flow to the initial chlorine stage Experiments were performed using a suspension of unbleached pine sulphate pulp flowing into a sulphate mill bleaching plant at a rate of 12,000 l / min and a pulp consistency of 2.5% and a temperature of 20 ° C. The chlorine conduction control test for the preliminary chlorination step was performed as follows:

During the test period, chlorine was added using standard target value control. During the second test period, chlorine was added using the method of the invention. The number of pieces of the incoming pulp, the chlorine consumption of the incoming liquid, and the pulp consistency were determined using hand-taken samples during each test period. The amount of lignin remaining in the pulp after chlorination and alkaline extraction was further determined. Using conventional target value control by oxidation reduction measurement, the target value for the active chlorine content was kept constant at 0.1 ^ 5 g / l when measured after a reaction time of 75 seconds between 10 61533 chlorine and lignin. When performing the adjustment according to the invention, the target value was changed manually every 5 minutes using the following equation: TARGET VALUE (g äkt chlorine / 1 = 0.145 / J1 + 0.00300 (F_ - 12 x KF - 20,827 2 where KF is the consumption of chlorine in the incoming liquid material (g / 1) and FC1 is the actual chlorine flow (kg / min).

The values obtained are shown in Table 1 below.

Table 1 When using When using the inventive control according to the invention_ adjustment_

Consistency of the pulp entering the bleaching step,% 2.50 to 0.01 2.50 to 0.01

Number of pieces, unbleached mass 33.2 to 3.9 32.9 to 4.0

Chlorine consumption of the suspension liquid entering the bleaching stage, g / l 0.10 1 0.12 0.20 - 0.10

Number of pieces after chlorination and alkaline extraction 6.15 ~ 0.71 6.16 - 0.10

As can be seen from the table, the variations in kappa number (= lignin content) in the pulp flowing to the initial chlorination step were approximately of the same order of magnitude in both experimental series (-3.9 resp.

- 4.0). However, in the test series according to the invention, the consumption of chlorine in the suspension liquid entering the bleaching stage was twice as high as in the test series using the conventional target value control, which is typical of the variations normally found in pulp mills due to washing efficiency variations. The table shows that the scatter in the obtained kappa number using the conventional target value adjustment was approximately 7 times higher than in the method according to the invention (-0.71 vs. -0.10). As chlorine consumption can normally fluctuate so strongly that it can double, the inadequacy of conventional target value control becomes very clear and the variations in the lignin content of the chlorinated pulp become considerable. The method according to the invention, on the other hand, provides an almost complete smoothing of the changes in the number of pieces after the bleaching step.

n 61533

Example 4

Adjustment of chemical addition during serial bleaching using chlorine and chlorine dioxide__

The experiments were performed using a suspension of unbleached pine sulphate pulp flowing into the bleaching plant of the sulphate plant, which was passed at a rate of 18,000 l / min and a pulp consistency of 3%. An experiment in which the flow of chlorine dioxide and chlorine was adjusted to a preliminary bleaching step, which was a reaction step in which chlorine dioxide and then chlorine were added successively without washing or alkaline extraction, was performed as follows:

During the test period, chlorine dioxide was introduced into the first reaction step and chlorine into the second reaction step using conventional control. During the second test period, chlorine dioxide and chlorine were introduced in a corresponding manner using the control according to the invention. In the experiments, the icons of the incoming pulp suspension were analyzed and the chlorine consumption in the incoming liquid. The chlorine was added using standard target control, keeping the active chlorine content constant at 0.130 g active chlorine / l by measuring after a reaction time of 30 seconds. In carrying out the control according to the invention, chlorine dioxide was passed directly to the first reaction stage in direct proportion to the reaction step. , which corresponded to the addition of 11.1 kg of active chlorine per minute.The residual amount of chlorine dioxide was determined as active chlorine after a reaction time of 10 seconds. a between lignin. The chlorine addition was adjusted manually in accordance with the invention every five minutes using the following equation.

FC12 = 3.93 (Fclo2 - 18 C + 18 KP), where FC1 and are the chlorine and chlorine dioxide fluxes in kg active chlorine / min, C is the residual chlorine dioxide content as determined active chlorine after a reaction time of 10 seconds g / 1,,;!? '12 61 533 KF is the consumption of bleaching chemical in the incoming suspension liquid, · g active chlorine / l.

The method according to the invention was thus applied while measuring the need for active chlorine in the suspension liquid in a pulp suspension passed to a bleaching step comprising two successive treatment steps, the analysis result from the first treatment step being used to adjust the chemical addition to the next step. The first bleaching step was thus used as a lignin flow analyzer. The results obtained are shown in Table 2 below.

Table 2 In use When using the conventional control according to the invention

Consistency of the pulp entering the bleaching step,% 3.05 - 0.15 3.00 - 0.16

Unbleached pulp, number 31.3 - 3, li 32.1 1 3.6

Chlorine consumption (g akt chlorine / l) of the suspension liquid in the bleaching stage '0.13 - 0.08 0.16 - 0.09

Part number after chlorination and alkaline extraction 5.90 to 0.73 3.95 to 0.14

As can be seen from Table 2, variations in the obtained kappa number were obtained from -0.73 using the conventional control method, while variations in the kappa number according to the invention were as small as -0.14. The result shows that by applying the invention, the addition of chlorine in the second reaction stage of the bleaching stage can be changed according to the instantaneous need, which is not possible when using the conventional target value control, which utilizes the so-called the feedback control and the chemical addition are adjusted by keeping the residual chlorine content constant at the measuring point. Thus, direct control of the chemical addition to the second reaction step is provided, which results in a more efficient utilization of the added chemicals. Thus, chemical costs can also be reduced.

Example 5

Control of the addition of alkali to the alkaline extraction step in the bleaching series has been described, but by performing a correction for a higher mass flow accordingly. After the chlorine step, the mass was washed and extracted with alkali. The experiment of adjusting the alkali flow to the initial extraction step following the initial chlorination step was performed partly using the conventional method and partly according to the feed control according to the invention by the consumption of chlorine caused by substances dissolved in the liquid and by the flow of chlorine into the chlorination step.

During the test period, alkali was introduced into the alkali phase in a conventional manner. In this case, the alkali was then introduced into this step by control of the manually measured pH values. In order to achieve complete lignin dissolution, the pH after this step should exceed 10.5.1. However, during the experiment it was forced to maintain a higher pH (11.0) after the extraction step because the residence time in the extraction step was 60 min so that the pH never fell below 10.5 .

In the second test period, which immediately followed the previous one, alkali was added to this step by means of the invention. In this case, the consumption of chlorine caused by the substances dissolved in the liquid in the bleaching plant was determined. Further, the target value adjustment of the chlorine addition was performed in the preliminary chlorination step. The value obtained by subtracting the product of the mass flow and the chlorine consumption of the incoming liquid from the chlorine flow was used in the lignin value determination. The alkali flow was adjusted to the next alkaline extraction step by means of a feed control using the following equation.

Salary (t + 60) = FCl2 (t) * ° ^ 29 "KP (t) * 5> 0k in which formula

Salary ^ + = alkali flow in kg / min to the alkaline extraction step with a time shift of 60 min from chlorine addition to the chlorine step, (t) = chlorine flow to the initial chlorine step, kg / min, <KF (t) = chlorine consumption of the bleaching chemical in suspension, g chlorine / l.

Claims (6)

A method for controlling the conduction of reaction chemicals in delignification and / or bleaching of pulp in the pulp industry, comprising adding reaction chemicals to a pulp suspension containing chemical consumables and passing them to a treatment step in which all or part of the reaction chemicals are consumed and adjusted during or after the reaction. concentrations, characterized by a combination of determining the need for reaction chemicals in the suspension prior to the treatment step and determining the amount of residual unreacted reaction chemicals after the chemical addition, and utilizing the measured values to control the addition of reaction chemicals to the pulp suspension before and possibly after the treatment step. Process according to Claim 1, characterized in that the concentration of the remaining non-abrasive reaction chemicals is determined during the treatment step. Method according to Claims 1 to 2, characterized in that the treatment step is formed by a so-called lignin-removing white matter, i.e. such that the lignin content of the added pulp corresponds to a number of pieces in the range of about 100 to 5, suitably 40 to 9 », most preferably 35 to 10. A method according to claim 3, characterized in that the lignin removal bleaching step is divided into several steps and that the chemical consumption in the first step is used to determine the chemical need in the next step or steps. Process according to Claims 1 to 4, characterized in that the reaction chemical requirement of the suspension liquid and / or the determination of the concentration of the remaining unused reaction chemicals is carried out calorimetrically. - Patentkrav 1. For the purpose of regulating the use of reaction chemicals in the form of chemical and / or non-reactive chemical substances, the mass and suspension of chemical substances used in the manufacture of chemical reaction plants and chemical plants the reaction with the reaction mixture is carried out by means of a combination of chemical reaction agents, the reaction to which the reaction medium is used and the reaction to the chemical reaction process is carried out by means of the chemical reaction process. The reaction chemical is used as a pulp suspension and, if appropriate, after treatment. i