FI80083C - Method and apparatus for pre-treating cellulosic feedstock - Google Patents

Description

1 80083

Method and apparatus for pretreating a cellulosic feedstock

The present invention relates to a method and apparatus for pre-treating lump wood or other cellulosic feedstock by impregnation. In particular, the invention relates to the penetration of a fiber cell as a first step of impregnation. A chemical solution or water can be used as the penetration solution.

In pulp fiber production technology, the purpose of impregnating wood chips is to make the desired amount of solution evenly distributed on the fiber walls of the chips. This promotes the separation of the fiber as intact and of suitable quality as possible or the dissolution of lignin and other inlay substances at a later stage in the process.

15 For example, in the manufacture of pulp fiber used in paper production, pre-treatment of wood chips usually involves washing, steaming, treatment with a chemical solution or water, and slow progressive adequate leveling of the chemicals in the fiber walls. Pretreatment can take a third or even more of the total cooking cycle time. Factors affecting impregnation are vague and difficult to control, which can lead to overdose of time and chemicals when trying to ensure an acceptable outcome.

The professional literature describes the interaction of two physical factors of impregnation, penetration and diffusion, which begins immediately after the solution comes into contact with the chips.

Penetration begins primarily at the cutting surfaces of the chip, from which the solution penetrates the fibrous cavities. Due to the back pressure caused by the air in the cavities 30, the penetration slows down and stops quickly. Almost the only factor promoting penetration is the increase in the pressure difference between the solution and the air in the fibrous cavities by lowering the partial pressure of the air or increasing the pressure of the liquid.

35 Diffusion is very slow compared to penetration.

In it, ions are transferred to the fiber walls in solution due to differences in the concentration of chemicals. Diffusion proceeds along 2,80033 liquid connections formed by the water penetrated into and contained in the hakeso lock. Raising the temperature of the penetration solution promotes ion mobility. However, its chemical content is crucial for the propagation of diffusion into the interior of the chips, as the diffusion slows down as the wood moisture 5 dilutes the solution and its chemical content decreases as the chemicals are absorbed into the cell walls.

The amount and extent of penetration is thus very essential for the onset and progression of diffusion and for the ultimate goal of adequacy and uniformity of chemical-10 uptake in the fiber walls.

In fiber production, impregnation and especially its uniformity is influenced by standardizing the processing conditions and the chip size. The vaguely variable air and water content of the wood, which varies widely over a wide range, make it most difficult to adequately and controlledly impregnate the chips.

Light tree species may have nearly three-quarters and even heavy tree species about half the volume of space formed by cellular rolls and pores. The cavity of the surface wood is filled with water and almost airless after the felling of the wood. When peeled and especially as wood chips, the drying of the wood accelerates. The water first evaporates from the cell cavities in the so-called to the saturation point of the wood grain, to a humidity of 25-30%, leaving the remaining water exclusively in the fiber walls. During storage, the moisture content of the chips can usually reach a level of about 30%. Thus, the cavity of the chips to be taken into production may be completely full of air. Usually, however, it is filled with air and water in very different proportions.

It has been proposed to reduce the amount of air in the chip cell mechanically or by using a vacuum obtained by evaporation. However, only steaming is used in industry. Evaporation removes the air around the chips, and at the same time the part of the air corresponding to the increase in the temperature of the chips is discharged from the cell. The chips are best transferred from steaming to cold water or solution, whereby a vacuum corresponding to the cooling of the air space in the chipping cavity is introduced into the cavity. The wood chips must be steamed at a relatively low temperature and for a short time to avoid damage to the paint, etc., as a result of which the wood chips

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The air temperature rise of 3,80033 con can be at best 90 ° C at best. In this case, the air pressure in the cell corresponding to the decrease in the temperature of the chips drops to 0.8 bar, i.e. the air volume can be reduced by at most one-fifth, calculated from the water-free cavity air volume at +25 ° C and normal pressure. Due to the structure of the wooden cell, the intensification of penetration remains below said fifth.

Steam impregnation is a simple but not sufficient and controlled method if good and uniform penetration of hak-10 is desired. For example, it has been shown that as a result of impregnation with the cooking solution in different parts of the chip, the chemical-potassium concentrations varied over a wide range and that a considerably long diffusion time with preheating is required before the inner parts have the concentration required for chemical reactions.

The use of a vacuum to remove air has been described e.g. in Finnish patent publications 11987, 25505 and 30091.

In the pulp production method according to FI 11987, air is sucked in from the raw material to be treated, after which the airless material is treated with a liquid.

FI 25505 deals with a continuous method and apparatus for impregnating wood chips with a liquid. Impregnation takes place by continuously feeding the chips to the top of the tower, where it is vacuumed. The lower end of the Tor-25, which is closed at its upper end, is in the water so that the chip column sinks slowly downwards in the tower, sinking into the water and saturating at the same time. In this case, the pressure of the water surrounding the chips gradually rises until it reaches atmospheric pressure as the chips unload out of the tower. When the chip sinks into the water, the pressure of the air in the fibrous cell 30 is the same as in the surrounding water, so that no pressure gradient-dependent penetration occurs. However, the effect of rapidly evolving factors that slow down penetration begins immediately.

In the process of FI 30091, the starting material is first pre-dried to about 18% and deaerated almost completely at an absolute pressure of less than 100 mmHg (about 0.13 atm) and a temperature of 85-90 ° C. If a higher temperature is used, according to the publication, the vacuum treatment pressure can be increased * 80083 up to an absolute pressure of 200 mmHg (approx. 0.26 atm).

In the methods referred to, the impregnation takes place almost exclusively by diffusion. Penetration can only be utilized only partially and occasionally.

Compared to very large variations in air and water content of wood chips, changes in wood density are generally limited to + 5-10%, as the aim is to use the same wood species and to avoid the most difficult to impregnate parts, such as the resinous heartwood of conifers.

The moisture content of the chips varies within very wide limits. The chips entering the fiber production can normally contain 120-30% water from the dry matter of the chips. In mechanical production methods, defibering is best achieved when the chips are filled with water. In chemical methods, the desired chemical dosage must be obtained through the chips in a uniformly diffused manner. In this case, the amount and chemical concentration of the solution to be penetrated into the water cell free of water has a significant effect on the diffusion.

In the method now invented, a two-step pretreatment is performed. The first step is vacuum treatment and the second step is penetration with a chemical solution or water having a temperature lower than its boiling point in the vacuum used. The vacuum treatment is performed without prior substantial wetting of the raw material. Humidification as used herein means steaming, washing, or other conventional aqueous treatment.

Penetration is carried out rapidly after vacuum treatment at atmospheric pressure or higher so that the fibrous cavities of the raw material do not have time to close substantially before penetration. The faster the penetration is performed, the better. Depending on the conditions and the species of wood, the emptied raw material is subjected to solution pressure within, for example, about 5 minutes, preferably, for example, 1 minute, most preferably within 0.5 minutes of vacuum treatment.

The introduction of the penetration solution into the raw material is started while the vacuum is still active. It is best to maintain a vacuum throughout management. Once the desired amount of solution has been obtained in connection with the raw material, a further pressure shock can be applied to the solution.

The vacuum used is, for example, 0.1-0.5 bar, preferably 0.2-0.4 bar. The temperature of the penetration solution is then, for example, 35-85 ° C, preferably 45-75 ° C.

It is preferable to adjust the chemical content of the penetration solution according to the moisture of the raw material, or the moisture and density, or the amount of the penetrating solution.

According to one embodiment, the penetration solution is passed to the raw material in the same vessel where the vacuum treatment has been performed, after which the raw material is transferred to a higher-pressure receiving tank where the penetration is completed.

After penetration, it is preferable to separate the portion of the slurry from the raw material into the solution.

The apparatus according to the invention has a common vacuum treatment and penetration tank or they are separate.

For example, the common handling tank may be a rotor rotating in the housing, open at least at one end. The required 20 connections are fitted to the circumference of the rotor housing.

When separate vacuum treatment and penetration tanks are used, a transport channel can be used between them, the end of which forms a barometric barrier between the tanks. The extension of the transport channel is then preferably a perforated penetration channel. At the end of the transport channel there is suitably a dirt removal device. At the end of the perforation channel, on the other hand, a non-penetrating raw material removal device can be suitably placed. The penetrating liquid can be fed into the transport channel, in particular its initial end.

The raw material can also be led to the vacuum treatment tank along the feed conveying channel passing through the penetration tank, so that the beginning of the feed conveying channel forms a barometric barrier between the penetration tank and the vacuum treatment tank 35. In this case, the raw material must, of course, pass through this barrier so that it is not substantially wetted.

The chips are pretreated according to the invention without prior practical wetting. Namely, the walls of the chopped fibers at the cutting ends of the chips, in particular their hemicellulose-containing parts, absorb water very rapidly and, when swollen, constrict or clog open cell cavities. For this reason, it is also advantageous to surround the solution with the solution as quickly as possible when penetrating the vacuum-treated chip. However, if the chips come into contact with water before the pretreatment according to the invention, the contact time should not exceed about 5 minutes, preferably up to about 1 minute, preferably up to 20-30 or 10-15 s, depending on the conditions. Hardwood tolerates longer wetting times than softwood.

The chips are preferably vacuum treated under a relatively weak vacuum. The required vacuum can be produced with normal industrial common equipment at a reasonable cost.

According to the method of the present invention, the best penetration is not achieved with the highest possible vacuum, but by utilizing the temperature of the penetration liquid, which is 35-85 ° C, depending on the type of wood. The magnitude of the vacuum is determined in such a way that evaporation of the liquid is still avoided.

For example, conifers preferably have a vacuum of 0.2-0.3 bar and an aqueous solution temperature of 55-70 ° C.

With the chip quality and its moisture remaining the same, the amount and uniformity of penetration are very reproducible in the method.

As the water content of the chips changes, the amount of the penetrating solution changes in the same proportion, but the total amount of the penetrating solution and the water contained in the chips remains at the same level, i.e. the penetration procedure allows for the same level of filling of the chip independent of the chips.

As the density of the wood varies, the amount of changed solids becomes measured by the corresponding change in the penetration solution.

The nature and pH of the chemical solution have no significant effect on penetration.

35 The concentration of the chemical solution has a small effect which is insignificant in the circumstances in question.

If necessary, even high concentrations of chemicals are possible because of the temperatures at which the chemicals can be used

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7 80083 solubilities are good.

In the following, the method and apparatus according to the invention will be explained in more detail with reference to the accompanying figures, in which Figure 5 shows the effect of pre-vacuum chemical solution or water treatment on the amount of chips sinking into solution, Figure 2 shows the dependence of penetration on solution or water temperature. the effect of moisture and density of the chips on the amount of penetrating solution and the level of penetration, Fig. 4 shows a vacuum penetration solution according to a preferred embodiment of the invention, Fig. 5 shows a vacuum penetration solution according to another preferred embodiment; and 8 show the operating steps of a continuous vacuum netting device.

Factory-made chips were used in the experiments performed.

In order to determine the uniformity of the penetration and its level, the determination of the proportion of chips sinking into solution or water proved to be a sufficiently accurate procedure.

Figure 1 shows how much a negative effect on the penetrability of the broth has on the broth treatment before the vacuum treatment. The vertical axis shows the percentage of chips that have sunk into the solution as a percentage of the total amount of chips treated, and the horizontal axis shows the exposure time of the solution in minutes. Pine chips with a moisture content of 21% were used in the experiment. The temperature of the treatment solution was 65 ° C and the concentration was 5%.

The dashed line 1 shows the amount of chip 35 that sinks during vacuum penetration when the chip is treated with NSSC solution. Dashed line 2 shows the amount of sinking chips when treating the chips with NaHSC> 3 solution. It is noted that already one minute of treatment with NSSC solution reduces the amount of sinking part by 24% β 80033 and three minutes of treatment by about 45%. The corresponding reductions with NaHSO 3 solution were about 30% and about 70%. The experiment used a method in which the penetration was performed with a cooking solution under normal atmospheric pressure and the solution filling was started under the influence of the prevailing vacuum.

The explanation for the phenomenon of Figure 1 is that the aqueous solution has a remarkably fast effect on the walls and surface properties of the capillary cell cavities, whereby on the cutting surfaces of the chips the cell and especially the summer wood capillaries shrink relatively fast. The amount of solution that penetrates in this way, i.e. the proportion of chips that sink into the solution, decreases rapidly as the soaking time increases.

Figure 2 shows the effect of solution temperature on penetration at different treatment times. The left vertical axis shows the amount of chips that have settled into the solution as a percentage of the total amount of chips treated, the horizontal axis the solution temperature in ° C and the right vertical axis the processing time in minutes. The raw material in the experiment was pine chips with a moisture content of 20%, which was treated with 5% NaHSO 3 solution. It can be seen that as the temperature of the solution rises from 20 ° C to 50 ° C, the amount of chips sinking into the solution (dashed line 3) also increases significantly. It is also seen that raising the temperature no longer has a significant effect on the end result. Simultaneously with the solution temperature of nos-25 ton, the processing time was shortened in the experiments (straight line 4), nevertheless, the amount of sinking chips remained constant and even slightly increased. The results clearly show that somewhere around 35-40 ° C there is a lower economic operating temperature limit for the solution, while experiments show that there is little benefit in heating the material to very high temperatures because the penetration is not substantially improved. However, heating has the potential to decisively increase penetration.

Figure 3 shows how the water content of the chips affects the amount of penetrable solution. The horizontal axis shows the water content of the chips and the vertical axis shows the amount of solution penetrated and the chips sunk into the solution as a percentage of the dry matter of the chips. The test series contained

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9 80083 content 5% and temperature 65 ° C. Dashed lines 1-3 show the penetration of pine chips with 1. sulphate, 2. NSSC and 3. NaHSO3 solution and the dashed line with 4 birch chips treated with NSSC solution. Dashed lines 1-3 show that substantially different solutions penetrate approximately the same regardless of the moisture content of the chips.

With the same chip quality, the penetration of the chemical solution is determined almost directly by the amount of water contained in the chips. This is best seen by looking at the combined effect of changes in the moisture content of the chips and the amount of water contained in the solution penetrated into it at different test-10 points. The total amount of water in pine chips was in the range 164-177% and in birch chips 143-145%, respectively. The standard deviation from the mean was + 4% for pine chips and 15 + 1% for birch chips.

The proportion of sinking chips determined as monitoring of the penetration level was 88-89% for pine chips and 100% for birch chips, regardless of the moisture content of the chips (dashed lines 5 and 6).

The following example illustrates the role of wood chip moisture in the penetration of chemical solution penet-20. The almost dry pine chips with 10% moisture penetrated the NSSC solution at 560 kg per m3 of chips with a water content of 33 kg. Correspondingly, at 75% humidity, 325 kg penetrated and 250 kg / m3 of water was generated from the humidity. At the said test points, the total amount of water after penetration in the dry chips was 590 and in the wet 575 kg / m3 chips, although in the former test point the solution penetrated 72% more.

The clear difference in the level of penetration of pine and birch chips shown in Figure 3 is mainly due to the different density of the chips, which is on average 0.4 for pine and 0.5 for birch. Here, density refers to the nominal density of a tree species when completely dry, in which case the factors are the actual wood material and the volume of the fiber cavities larger than its volume.

35 Since the density of the actual wood material is the same as 1.32-1.35 for the wood species normally used for fiber production, the average density of birch on average is a quarter higher than that of pine, which is also reflected in the corresponding amounts of penetrated NSSC solutions in Figure 3.

In a comparative experiment with the quality of pine chips and NSSC solution in Figure 3, the impregnation was studied by evaporation.

5 After a steaming time of five minutes, the dry chips were best absorbed initially rapidly and in a total of two hours by about four-fifths of the volume of solution which penetrated under vacuum in five minutes. The level of penetration, especially in the dry chips after evaporation, was 10-10, only a fraction of the amount submerged in vacuum penetration sank into the solution. The chemical solution apparently enriched in the surface portions of the chips diluted with steam condensed water.

On the other hand, in the same wood species, the changes in the amount of wood in the cell walls and at the same time in the density become measured as changes in the amount of penetrating solution as well as above as the water content of the chips varies.

Overall, the variation in density compared to changes in water content is so small that, in practice, it is sufficient to take into account the combined effect of water content and density on most 20 chips.

Conifers are characterized by a density dependence of the difference between the spring and summer trees. The walls of summer wood fibers are considerably thicker and the diameter of the cellular cavity capillaries is only a fraction of the corresponding dimensions of spring wood fibers. Capillary forces have been found to play a significant role in penetration. When the lifting force of the solution in the capillary is inversely proportional to the square of the radius of the capillary, the capillary filling of the fibrous cell begins at the strongest and fastest in the summer tree-30 portion, provided that sufficient solution is available in the fibrous cavities. Apparently the resulting solution pressure removes the remaining air and the summer wood fibers fill first. This is important for the onset of diffusion and the leveling of chemicals in the thick-walled fibers of summer wood. The mentioned assumption is supported by e.g. the effect of promoting the penetration of the vacuum maintained during solution filling observed in the experiments.

Birch does not have the structure of summer and spring tree cells

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n 80083 corresponding differences. In the experiments, this was clearly manifested as a better level and rate of penetration of birch pine chips.

Occasionally occurring structural differences in wood, such as twigs and resin-induced inclusions, have no quantifiable significance. The non-penetrated cellular parts are in a way taken into account as a cell wall material, i.e. it has the same effect as increasing density.

When the moisture content of the chips is less than 30%, in which case the water is in the fiber walls and its pores, the freezing of the chips during the cold season is not likely to be essential for penetration. In wetter chips, especially if the water is in superficial moisture, clogging of the fiber capillaries makes it difficult to penetrate even after the ice has melted.

The vacuum penetration device 10 schematically shown in Fig. 4 consists of a penetration tank 11, into which the chips are introduced from a feed opening 12, to which either a ball valve 13 used for chip supply or a tray or high pressure feeder can be connected. At the lower end of the tank 11 there is a material outlet 14, and in it 20 a ball valve 15. A vacuum 16 is created in the tank 11 by means of a valve 16 connected either directly to the vacuum pump or to a vacuum intermediate tank arranged to accelerate deaeration. A further 18 is arranged in the container 11, from which a penetration solution, for example from a pressure accumulator, can be introduced into the container 11 by means of a valve 19.

The apparatus according to Figure 4 is operated in such a way that the tank 11 is filled through the supply opening 12, after which the valve 13 is closed and the valve 17 is opened and air is sucked in from the chips in the tank 11. The vacuum is allowed to drop to 30, at which point the penetration solution fed in the next step does not yet begin to evaporate. Depending on the type of wood and the equipment arrangements, the vacuum is equalized in the filling in 0.5-5 minutes, after which the valve 17 is closed and the valve 19 is opened, which discharges the penetration solution into the tank 35 as quickly as possible. It is also possible to keep the valve 17 open and to allow the vacuum to act on the penetration more efficiently during the solution filling. Experiments have shown that such a filling penetrates rapidly and evenly in a few minutes.

If it is desired to increase the equipment capacity, it is possible to discharge the filling into an overpressure-pressurized receiving tank, where the penetration is completed and the diffusion of chemicals can be started by raising the temperature.

The apparatus 20 schematically shown in Fig. 5 is intended for the penetration of, for example, birch and other hardwood chips of similar cellular size, carried out as a continuous anchovy treatment. The penetration section is formed by an arcuate conveying channel 21 which expands from the top to a vacuum chamber 22. The lower ends of the conveying channel, which act as a barometric vacuum seal, are arranged in the broth tank 23. The solution level is kept constant. at the ends to a height h corresponding to the vacuum, forming a vacuum seal. The chips are fed by a screw conveyor 24, the surrounding pipe 25 of which is perforated, so that the air surrounding the chips can escape before the chips pass to the endless conveyor 20 of the conveying channel 21. For the ascending portion of the conveyor 21, the chips are discharged to the screw conveyor 26 of the vacuum chamber 22. Adjusting the conveying speed of the conveyor 26 provides the desired residence time in the vacuum chamber 22, from which the endless conveyor 21 the difference between the chips and the chips. At the turning point 28, the chip part sinking into solution at the bottom of the basin 23 is discharged from the conveyor channel 21 for further transfer to the process. The part of the solution which does not sink into the solution, which is mainly the shell cover, twigs or the like raised the penetrated chips, is removed from the surface of the basin 23. By further crushing this chip portion, a usable raw material can be obtained from it.

The apparatus described above is simpler in structure and operation than the solution of Figure 4 with its many valves. In addition, the cost of producing the vacuum is lower in this case, since most of the air entrained in the chips is already separated in the screw feeder 24 and does not enter the vacuum system. Actually, the only weakness of the invention

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The device according to this embodiment has the fact that the chips have to be in contact with the cooking solution even before the vacuum treatment in the screw feeder 24 and at the lower end of the conveying channel 21. However, it has been found that when properly dimensioned, the carrier proportions within the liquid are so short that the soak time of the chips is 10-15 seconds. It is not yet of great importance in the treatment of wood chips made of easily penetrable wood. The wetting of the chips is further reduced by the air surrounding the chips discharged in the feeder 24 and by the vacuum 10, which starts to act immediately from the lower end of the conveyor 21.

In the device application shown in Fig. 6, the principal disadvantage mentioned in the device of Fig. 5 has been eliminated. The chips are taken from two empty intermediate tanks 41 alternately 15 to a vacuum chamber 42, from where a helical conveyor 43 feeds the empty chips to a conveyor 45, which at the same time acts as a barometric vacuum seal between the vacuum chamber and the chip receiving tank 46. The conveyor 45 is designed to rapidly pull the chips from the vacuum to the pressurized pool-20 space. Point 47 distinguishes between sand and other impurities heavier than wood chips. An adjustable speed transport coil 48 adjusts the chip delay to complete penetration. At 49, the part of the chips which does not sink into the solution can be separated, for example, for grinding. The Kul-25 jet 50 transfers the penetrated chips to the process. In the receiving basin 46, the height of the surface of the solution is kept constant. When a certain chemical dosage is penetrated into the chips, the solution is fed into the barometric barrier to the level of the vacuum surface 51 at 30, i.e. the height difference h between the solution surfaces corresponds to the vacuum in the vacuum chamber 43. Chip or plate valves or shut-off valves as well as 53 conventional shut-off devices for evacuation.

In Fig. 6, the device parts 41, 52 and 53 can be considered as replaceable, for example, in the penetration of birch chips with a plug-screw press, which feeds the chips into the vacuum space 42.

The apparatus described above is suitable for the continuous washing of wood chips, in particular with a view to achieving a certain even chemical-potassium dosage. In the case of water penetration, the need for variable water is handled by the adjustment of the water level in the receiving tank.

Figures 7 and 8 show diagrammatically two operating stations of a vacuum penetration device, the operating principle of which is the same as that of the device shown in Figure 4, but the processing mode of the chips is a rotating rotor.

Fig. 7 shows an initial situation in which the transfer solution left in the rotor 60 from the previous treatment batch is removed through 61 and the chips are filled through the filling opening 62 with the perforated plate at one end of the rotor in position S. In Fig. 8 the rotor screen plate S is first vacuumed through 63. The solution or water of Penetroin-15 is conveyed on line 64 and, after filling, either immediately or after a certain period of action, the treated chips are transferred from the receiving tank with the solution to be taken in line 65 to one of said receiving tanks. The receiving tank has the advantage, although not necessary, of maintaining a fluid pressure of a few bar. Instead of the receiving tank, the further processing of the chips can also be performed using the barometric vacuum barrier of the device applications of Figures 5 and 6. In the case of water penetration, compound 64 is not required.

The apparatus arrangement described above is suitable, for example, for treating wood chips for the production of pulp fiber with water, in which, if necessary, chemicals can be advantageously dissolved to improve pH adjustment or fiber yield or color.

In said rotor-equipped devices, the penet-30 space must be made relatively small for structural reasons. On the other hand, the advantages are short and fast vacuum or solution filling times and thus good permeation capacity. Rapid and strong pressure fluctuations as air escapes and the solution penetrates in its place promote the opening of the ring pores between the fibers, which improves the level and rate of penetration.

The method according to the invention makes it possible, if necessary, to adjust the chemical level defined in the chips per dry matter.

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is 80083 Dosage of cabbage to the desired level by adjusting the Kemi-potassium content of the solution to be penetrated. In this case, some examples of the necessary measuring and auxiliary equipment suitable for use in connection with all the mentioned vacuum penetration equipment applications are given below to illustrate the requirements for the applications.

For the measurement of the water content and density of the chips, as well as for the transfer and conversion of the measurement results for the control of the chemical content of the solution to be penetrated, the equipment used for purposes.

The turnaround time during storage is normally a few weeks. In this case, the extreme water content conditions level off and the variation in humidity in the wood chips to be used occurs as wavy changes. Since the density of the wood-15 material in the fiber walls is practically the same for all wood species in question 1.32-1.35, it can be simply assumed that a chip stream or batch treated with a constant volume and filling density, representing the same wood species and density, always contains the same weight. -20 amounts of wood dry matter per unit volume. In this case, the total volume of the cell cavities and pores can also be considered to remain at the same level. It follows that the difference in weight between the measured dry matter of the chips and its standard dry matter, which also includes changes in the density of the wood, can be taken as the sum of the water and the non-average density of the wood chips, minus the total volume of cell cavities. the free cavity volume, i.e. the volume of solution in which the desired dose of chemical must be dissolved.

The chemical content lfc (%) of the solution to be penetrated under the conditions is determined on the basis of the desired chemical dosage b (% of dry matter) and the combined effect of water content and density a (% of dry matter) of the chips of the formula 35-100 * b, where the value of factor n is. a factor derived from the density of the wood. Based on experience, factor n can include device-specific or the desired safety factor caused by the desired safety factor. For example, softwood at a density of 0.4 has a value of factor n without corrections of 176 and birch at a density of 0.6 at 93, respectively. It is essential in the formula that the amount of chips or the filling density have no effect on the result.

For continuous monitoring of the water content and weight of wood chips, a measuring device is suitable, for example, in which the water content is determined by means of neutron radiation and weight by means of gamma radiation. If continuous monitoring of the density variation of the chips is necessary, the chip flow in the measuring area of the conveyor belt must be constant in volume or the measurements must be performed in the measuring space, whereby the filling frequency of the chips can be easily standardized. Changes in the density of wood chips are normally in the order of a few per cent, so in most cases it is sufficient 15 that the density be corrected only after a certain limit has been exceeded or when there is a significant change in the species or quality of the wood. In the described device applications, fast and accurate processing of the continuous chip flow is possible.

A considerably simpler but in many cases 20 device application with sufficient accuracy is obtained when only the weight variation of the chips in the standardized volume and filling frequency is determined from the chips, either continuously or batchwise. Frozen chips do not cause a measurement error in this, as in the device application described above, but the difficulty of handling the chips in both the measurement and penetration phases would be best avoided by thawing the chips and partial drying of the surface moisture. This is done, for example, with a stream of warm air or, most simply, by allowing the chips to dry in a warehouse protected from rain. When there is a significant change in the type or quality of wood, a corresponding correction is made to the control factor. Said mode of operation is advantageous especially when producing high-yield pulps with penetration devices of the type shown in Figures 7 and 8.

35 Measurement results obtained from changes in the water content of the chips and the amount of penetrating solution caused by density variations can be utilized. In this case, the solution volume of the penetrating solution of the chip stream or batch to be treated is used

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17 80083 in the control of the chemical concentration of the penetration solution of the next batch of chips as a guide for the volume of solution in which the desired chemical dosage must be included. In doing so, the error due to the delay is practically irrelevant, because in the 5 rather slowly changing wood chip stocks the largest local moisture differences level off and in the wood chips taken into production the moisture level can be described as fluctuating wavy instead of steep moisture differences. The method is feasible with simple device applications, and in it the control of the adjustment of the potassium content of the solution is obtained from the measurement of the actually penetrating cavity volume of the chip quality to be processed in each case.

In the device applications described above as examples, the control of the changes in the water content, density and amount of penetrating solution caused by the localized blockages 15 controls the chemical content of the solution in a separate solution mixer by means of dosing devices. The chemical concentration of the solution to be penetrated in each case is obtained, for example, by mixing the concentrated chemical solution and the chemical solution or waste solution obtained from a later stage of the process or wastewater in a ratio producing the desired chemical concentration. The concentration of the concentrated solution is adjusted close to the saturation state of the chemical at the current treatment temperature.

25 High chemical concentrations are required as the water content of the chips increases to reduce the "free" fiber cavity space, which has the advantage of improving the solubility of the chemicals due to higher penetration temperatures. favorable starting position.

For example, dosing pumps can be used to control and transfer the amount of solutions.

Connections are required to the mixer, except for the intake of said solution components, to lead the solution mixture into the penetration space and to recycle the chip transfer solution.

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The chip transfer solution is preferably taken from the receiving tank from the cylinder surrounding the elongated and perforated discharge tube of the penetrated chip, the transfer solution having the same concentration or, when used in the previous penetration, almost the same level. It is also advantageous to use the transfer solution for the preparation of a penetrable solution when the chemical content has to be increased as the water content of the chips increases. If necessary, dilution into solution mixtures can be used, for example, in washing waters and waste solutions, taking into account their thermal and chemical content and the advantages of recycling in the process. The penetrated chips are surrounded in the receiving tank by a warm solution having a chemical concentration corresponding to the average concentration of the solutions in the penetration batches performed above, and the diffusion of chemical ions immediately enters the walls of the chip cell filled with the solution. The goal of impregnation, the desired chemical dosage sufficiently and evenly diffused into the wood, is achieved in a fraction of the time generally required for practical impregnation, when the majority of the chemicals must be obtained from the solution on the outside of the chip by diffusion.

Enhanced penetration reduces branching. Furthermore, the quantity and quality of the branching pulp can be influenced, as described above, by treating the non-sinking, partially non-penetrating chips separately. The separation can preferably be performed in a chip receiving tank. The incompletely penetrated part of the chips to be removed from the top of the tank is best reduced to a sliver and returned to the process after a separate extended solution treatment, or in a repeated separation 30 oxams or the like non-fibrous part of the raw material is removed.

The separation of mechanical impurities before the first stage vacuum treatment by washing with water cannot be carried out in the process according to the invention. In the treatment steps themselves, however, the chips are subjected to mixing and pressure fluctuations in the solution, which effectively removes the impurities attached to the chips. If the requirements for the purity of the chips are not feasible in said treatment, the normal cleaning treatment is carried out in connection with the further transfer of the chips ii 80083.

With the method and device applications described above, a sufficient solution filling can be quickly and controlledly penetrated into the chips through the chips. Its chemical content 5 can be adjusted, if desired, by the combined effect of the moisture and, if necessary, the density of the chips, so that the chemical dosage in the chips, calculated on its dry matter, remains practically at the same desired level. In this case, a favorable initial situation has been created for the completion of the uniform and complete impregnation of the chips, i.e. for the slow diffusion of chemical ions: the highest possible chemical concentration and temperature of the solution and a short distance to the reaction targets. Controlled very fast even impregnation of the chips indirectly improves the quality of the product and saves raw materials and energy. At the same time, the turnaround time of the process is substantially reduced. In this way, for example, the capacity of old cookers can be advantageously improved.

The procedure is suitable for use in time and neutral cooking methods. It is particularly suitable for the production of high-yield and chemimechanical pulps, in which case a high yield and a good fiber quality are achieved with low chemical dosage and short heating, possibly in the vapor phase. It is further preferred to use the method in impregnation sites where small amounts of chemical must be evenly distributed over the raw material. The purpose may be, for example, the stabilization of hemicellulose and the use of catalysts or bleaching chemicals. In mechanical fiber production, the chips can be penetrated with hot water to which small amounts of chemical may have been added. The procedure increases the possibilities of using wood or wood chips of a lower quality than usual, for example dried sawdust in the TMP, CTMP and CMP methods.

In addition to fiber production, the raw material pretreatment according to the invention can be used with the above arrangements for impregnating porous cellulosic raw material, for example in board production, or for chemical transformation of the raw material, for example in sugaring or generally utilizing wood ingredients.

The above are some preferred examples of the many modifications which fall within the scope of the invention and which are limited only by the appended claims.

2i 80083

A method for pretreating a cellulosic lump-like raw material in two steps, wherein in the first step 5 air is removed from the raw material by vacuum treatment and in the second step the raw material is contacted with a solution, characterized in that the vacuum treatment is carried out without substantial wetting of the raw material. , washing or other conventional aqueous treatment, that the solution is a penetroin-10 solution, which is a chemical solution or water and has a temperature below the boiling point of the solution under vacuum, and that the solution is allowed to penetrate the raw material rapidly after vacuum treatment, such as 5 min, preferably 1 min, preferably within 0.5 min of vacuum treatment, under a pressure of 15 atmospheres or higher.

Method according to Claim 1, characterized in that the penetration solution is introduced into the raw material while the vacuum is still acting and that, at the end of the conduction, the solution is best subjected to a pressure shock.

Process according to Claim 1 or 2, characterized in that the vacuum used is 0.1 to 0.5 bar, preferably 0.2 to 0.4 bar, and that an aqueous solution or water is penetrated into the raw material. the temperature is 35-85 ° C, preferably 45-75 ° C.

Method according to one of Claims 1 to 3. Characterized in that a chemical solution is penetrated into the raw material and that the chemical content of the solution is adjusted according to the moisture of the raw material, or moisture and density, or the amount of penetrable solution, preferably of formula 30 = According to 100 * bn - a, where lk is the chemical concentration, a is the combined effect of moisture and density, 35 b is the chemical dosage and n is the correction factor.

Method according to one of Claims 1 to 4, characterized in that the penetration solution is introduced into the feedstock 22 80 083 in the same vessel in which the vacuum treatment has been carried out, after which the feedstock is transferred to a receiving tank at atmospheric or higher pressure and the penetration is completed. , and that preferably the raw material is transferred from the vacuum treatment vessel to the receiving tank by means of a solution taken from the receiving tank.

Process according to one of Claims 1 to 5, characterized in that the penetration solution is prepared from a saturated or nearly saturated concentrated chemical solution and a chemical solution obtained from the further processing of the raw material or from washing or other waste water.

7. An apparatus for pretreating a cellulosic lump-like raw material in two steps, the apparatus comprising a processing tank having a raw material supply port, a raw material outlet, one for removing air from the processing tank, and a treatment solution supply port for subjecting the treatment solution to a vacuum-treated raw material. that the treatment tank is a substantially non-wettable raw material handling tank 20 (11/60), wherein the treatment solution supply port is a penetration solution supply port (18/64) for rapidly introducing the penetration solution into the tank under atmospheric or higher pressure and wherein the raw material outlet (14) 66) is best connected to a receiving tank having an air-25 circumferential pressure or higher.

Apparatus according to claim 7, characterized in that the apparatus has a rotor housing to which the raw material supply opening (62), the deaeration connection (63), the penetration solution supply opening (64) and the raw material outlet opening (66) 30 are connected and the treatment tank is rotatable in the housing, a rotor (60) open at least at one end, wherein the raw material transfer solution is also best associated with the rotor tube; feed opening (65).

9. An apparatus for pretreating a cellulosic lump-like raw material in two steps, wherein the apparatus; the equipment comprises a first stage vacuum treatment tank with a raw material inlet, a raw material outlet, and one for removing air from the vacuum treatment tank, and

II

23 80083 a separate second stage treatment tank for bringing the raw material and the treatment solution into contact with each other, the tank having a raw material supply opening, a treatment solution supply opening and a raw material outlet, characterized in that the vacuum treatment tank is substantially non-wetting raw. a vacuum treatment tank for the substance (22/43), that the second stage treatment tank is a penetration tank (23/46) with an atmospheric pressure or higher and which penetration tank is best separated from the vacuum treatment tank by a barometric closure (21/45).

Apparatus according to claim 9, characterized in that it has a feeder (24) for feeding the raw material to the penetration tank (23), a conveying channel (21) for rapidly conveying the raw material from the penetrating tank 15 to the vacuum treatment tank (22) and back into the tank. and the end end forms barometric brackets between the penetration tank and the vacuum treatment tank.

Claims (10)

24 80083 A process for pre-treating a two-stage cellulosic bite-shaped raw material, wherein in the first stage, the process is removed from the frame material by means of vacuum treatment and in the second stage the material is contacted with a solution, characterized in that the vacuum treatment is carried out without any substantial wetting of the frame material, such as displacement, washing or other traditional aqueous treatment, that the solution is a penetration solution which is a chemical solution or water and whose temperature is lower than the boiling point of the solution in the vacuum used, and penetrate into the frame material rapidly after the vacuum treatment, such as within 5 minutes, preferably 1 minute. and most preferably 0.5 min. after the vacuum treatment, under atmospheric pressure or higher. Method according to claim 1, characterized in that the input of the penetration solution into the frame material is started while the vacuum is still operating, and that at the end of the feed, a pressure shock is most preferably directed at the solution. Process according to Claim 1 or 2, characterized in that the vacuum used is 0.1-0.5 bar, preferably 0.2-0.4 bar, and that an aqueous solution or water of the temperature is penetrated in the frame material. -85 ° C, preferably 45-75 ° C. Process according to any of claims 1-3, characterized in that a chemical solution is penetrated into the raw material and the chemical content of the solution is regulated according to the moisture of the raw material, or moisture and density, or according to the amount of solution. which is penetrated, according to the formula 1. = ~~ - ~, in which formula 1 1 is the chemical content, a is the combined effect of the moisture and density, b is the chemical dosage, and n is a factor formed by the correction factors. Process according to any of claims 1-4, characterized in that the penetration solution is introduced into the raw material in the same vessel as the vacuum treatment is carried out, whereafter the raw material is moved to the receiving container, in which atmospheric pressure or higher escapes and where the penetration is completed. and that the raw material is suitably moved from the vacuum treatment vessel to the receiving vessel by means of the solution taken from the receiving vessel. Process according to any of claims 1 to 5, characterized in that the penetration solution is made of a saturated or almost saturated strong chemical solution and a chemical solution obtained from the after-treatment of the raw material or from the wash water or some other wastewater. A plant for pre-treating a two-stage cellulosic bite-shaped raw material, comprising a treatment container with an inlet opening for the raw material, an outlet opening for the raw material, a duct for removing air from the treatment container and an inlet opening for treatment processing the solution in contact with the vacuum treated raw material, characterized in that the treatment container is the treatment container (11/60) for the substantially non-humid raw material, in which the inlet opening for the treatment solution consists of the penetration solution (18/64) of the penetration solution. the penetration solution rapidly enters the container under atmospheric pressure or higher pressure, and in which the outlet opening (14/66) of the raw material is suitably joined with the receiving container, in which it erases atmospheric pressure or higher pressure. Installation according to claim 7, characterized in that it comprises a rotor housing, to which the feed material inlet opening (62), the air removal duct (63), the penetration solution inlet opening (64) and the raw material outlet opening (66) are connected, and that the treatment container is a rotor (60) rotating in the housing which is an open edible tone at one end, the rotor housing suitably also comprising an inlet opening (65) for the raw material transport solution. A plant for pretreating a two-stage cellulosic bite-shaped raw material, comprising a first stage vacuum treatment container, with a feed opening for the raw material, an outlet opening for the raw material, and a channel for removing air from the vacuum treatment container, a separate treatment container for the second stage for contacting the raw material and the treatment solution, which container comprises an inlet opening for the raw material, an inlet opening for the treatment solution and an outlet opening for the raw material, characterized in that the vacuum treatment container 22 is a vacuum treatment container (22). / 43) for substantially non-humid raw material, that the processing vessel for the second stage is a penetration container (23/46) under atmospheric or higher pressure and which penetrating container is readily separated from vacuum treatment -ling container by means of a barometric IAs (21/45). An installation according to claim 9, characterized in that it comprises a feeder (24) for feeding raw material to the penetration container (23), a transport channel (21) for rapid transport of raw material from the penetration container to the vacuum treatment. The return container (22) and thence back to the penetration vessel and whose input and output ends of the transport channel constitute a barometric load between the penetration vessel and the vacuum treatment vessel. i i