WO1989007170A1 - Process and equipment for pretreatment of cellulosic raw material - Google Patents
Process and equipment for pretreatment of cellulosic raw material Download PDFInfo
- Publication number
- WO1989007170A1 WO1989007170A1 PCT/FI1989/000017 FI8900017W WO8907170A1 WO 1989007170 A1 WO1989007170 A1 WO 1989007170A1 FI 8900017 W FI8900017 W FI 8900017W WO 8907170 A1 WO8907170 A1 WO 8907170A1
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- solution
- raw
- penetration
- tank
- chips
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C1/00—Pretreatment of the finely-divided materials before digesting
- D21C1/10—Physical methods for facilitating impregnation
Definitions
- the present invention concerns a process and an eguip- ment for pretreatment of chip-formed wood or other cellu- ' losic raw-material by impregnation.
- the invention is in particular concerned with the penetration of the fibrous cell system, taking place as the first step in the impreg ⁇ nation.
- As the penetration solution it is possible to use a solution of chemicals or water.
- the object of the impregnation of the wood chips is to provide a desired amount of solution as uniformly distributed in the fiber walls in the chips.
- the detaching of the fibers while they remain as intact as possible and of suitable quality or the dissolution of lignin and of other encrust materials in a later stage of the process is promoted.
- the factors affecting the impregnation are indefinite and difficult to control, which may result, e.g., in an overdosage of time and chemicals when attempts are made to guarantee an acceptable final result.
- the penetration begins primarily from the cut faces of a chip, from which the solution penetrates into the fiber cavities. Owing to the counter-pressure caused by the air present in the cavities, the penetration slows down and stops soon. Almost the only factor that is men ⁇ tioned as a factor that promotes the penetration is an in ⁇ crease in the difference in pressure between the solution and the air present in the fiber cavities by reducing the component pressure of the air or by increasing the pres ⁇ sure of the liquid.
- diffusion is very slow. In diffusion the ions are transferred into the fiber walls in the solution because of differences in the concentra ⁇ tions of chemicals. The diffusion proceeds along liquid connections formed by the water which has penetrated into the fibrous cell system or which was present in said cell system.
- Raising of the temperature of the penetration solution promotes the mobility of the ions.
- the chemical concentration of the penetration solution has a decisive significance for the progress of the diffusion into the interior parts of the chips, because the diffu ⁇ sion is always retarded when the moisture contained in the chips dilutes the solution and when its chemical content is reduced as chemicals are absorbed into the cell walls.
- the amount and the coverage of the penetration have a highly essential importance for the initiation and progress of the diffusion as well as for the sufficiency and uniformity of the dosage of chemicals in the fiber walls, which is the ultimate goal.
- the amount of air contained in the cell systems in chips be reduced by means of vacuum produced mechanically or by means of steaming. However, only steaming is employed in the industry.
- the publication SE 135,529 deals with a continuous pro ⁇ cess and with equipment for impregnation of the chips with liquid.
- the impregnation takes place so that chips are fed continuously into the top portion of a tower, where it enters into a vacuum.
- the lower end of the tower, whose top end is closed, is placed in water, so that the chip column sinks in the tower slowly downwards and is submerged in the water, being impregnated at the same time.
- Thereat the pressure of the water surrounding the chips becomes gradually higher, until it reaches the atmospheric pressure as the chips are discharged out of the tower.
- the pressure of the air present in the fiber cell system is the same as the pressure of the surrounding water, whereby no penetration dependent on pressure gradient takes place.
- the start ⁇ ing material is first predried to about 18 %, and air is removed from it almost completely at an absolute pressure lower than 100 mmHg (about 0.13 bar) and at a temperature of 85 to 90°C. If a higher temperature is used, according to the patent, the vacuum-treatment pressure can be in ⁇ creased up to an absolute pressure of 200 mmHg (about 0.26 bar) .
- the changes in the density of the wood material are, as a rule, confined to the range of ⁇ 5...10 %, because attempts are made to use the same species of wood and to avoid the parts that are most difficult to impregnate, such as the resinous heart- wood of conifer trees.
- the moisture content of the chips varies within very wide limits.
- the chips arriving in the fiber production can normally contain water at a level of 30 to 120 % of the dry matter of the chips.
- the defibration is successful best when the chips are filled with water.
- the desired dosage of chemicals must be provided throughout the chips as uniformly diffused. Thereat, the quantity and the chemicals content of the solution to be penetrated into the fiber cell system free from water have an essen ⁇ tial effect on the diffusion.
- the first step is vacuum treatment
- the second step is penetration with a solution of chemicals or with water whose temperature is lower than its boiling point at the vacuum used.
- the vacuum treat ⁇ ment is carried out without substantial preceding moisten ⁇ ing of the raw-material.
- moistening means steaming, washing, or any other, conventional aqueous treatment.
- the penetration is carried out rapidly after the vacu ⁇ um treatment at the atmospheric or a higher solution pressure so that the fiber cavities in the raw-material do not have time to be closed substantially before the penetration. The more rapidly the penetration is carried out, the better.
- the vacuum-treated raw-material is sub ⁇ jected to solution pressure, e.g., within about 5 min., best, e.g., in 1 min., most appropriately in 0.5 min. from the vacuum treatment.
- the passing of the penetration solution into contact with the raw-material is started preferably while the vacuum is still effective. Optimally, the vacuum is maintained during the whole of the passing of solution. After the desired quantity of solution has been brought into contact with the raw-material, a pressure impact may be applied to the solution additionally.
- the vacuum that is used is, e.g., 0.1 to 0.5 bar, op ⁇ timally 0.2 to 0.4 bar.
- the temperature of the penetration solution is, e.g., 35 to 85°C, optimally 45 to 75°C.
- the concentration of chemicals in the penetration solution is advantageously regulated in accordance with the moisture or with the moisture and the density of the raw-material or in accordance with the quantity of the solution to be penetrated.
- the penetration solution is passed to among the raw-material in the same vessel in which the vacuum treatment was carried out, whereinafter the raw-material is transferred into a reception tank of a higher pressure, where the penetration is completed.
- a common processing vessel may be, for example, a rotor that revolves in a housing and that it open at least at one end.
- the necessary connecting ducts are fitted on the circumference of the rotor housing.
- the transfer duct When separate vessels are used for vacuum treatment and for penetration, between them it is possible to employ a transfer duct whose final end forms a barometric lock between the vessels.
- the transfer duct is preferably extended by a perforated penetration duct.
- the final end of the transfer duct is appropriately pro ⁇ vided with equipment for the removal of contaminations.
- the perforation duct it is appropriately possible to place an equipment for the removal of unpenetrated raw-material. Penetration liquid can be fed into the transfer duct, in particular into its initial end.
- the raw-material can also be passed into the vacuum- treatment tank through a feed-transfer duct passing through the penetration tank so that the initial end of the feed- transfer duct forms a barometric lock between the penetration tank and the vacuum-treatment tank. In such a case, the raw-material must, of course, pass through this lock so that it is substantially not moistened.
- the chips are pretreated in accordance with the inven ⁇ tion without a moistening substantial from the practical point of view.
- the walls of the cut-off fibers at the cut-off ends of the chips in particular those of their parts that contain hemicellulose, viz., absorb water very rapidly and, when they become swollen, contract or block the open cell cavities.
- vacuum-treated chips should preferably also be surrounded with solution as rapidly as possible. If the chips, however, end up in contact with water before the pretreatment in accordance with the invention, this contact time should, depending on the circumstances, be at the maximum about 1 min. , preferably, however, at the maximum about 20 to 30 or 5 to 15 seconds.
- the best penetration is not achieved by means of maximum vacuum, but by making use of the temperature of the pene ⁇ tration liquid, which said temperature is, depending on the wood species, 35 to 85°C.
- the magnitude of the vacuum pressure is determined so that vaporization of the liquid is still avoided.
- the necessary vacuum can be produced by means of normal equipment commonly used in the industry at a reasonable cost.
- the vacuum is advantage ⁇ ously 0.2 to 0.3 bar, and the temperature of the water solution 55 to 70°C.
- the amount of the solution that is penetrated is changed in the same proportion, but the total quantity of pene ⁇ trated solution and water contained in the chips remain at the same level, i.e. said penetration procedure permits equal filling of the cell system independently from the moisture content of the chips.
- the amount and uniformity of penetration are well reproducible in the process.
- the altered solids amount is measured in the form of a corresponding altera- tion in the penetration solution.
- the concentration of the solution of chemicals has a minor effect, which is insignificant under the conditions concerned.
- FIG. 4 illustrates a vacuum penetration solution in accordance with an advantageous embodiment of the invention
- FIG. 5 illustrates a vacuum penetration solution in accordance with another advantageous embodiment
- FIG. 6 illustrates a further vacuum penetration solution in accordance with an advantageous embodi ⁇ ment
- FIG. 7 and 8 illustrate the steps of operation of a continuous vacuum penetration device.
- the broken line 1 illustrates the proportion of the sinking chips during vacuum penetration when the chips are treated with NSSC-solution.
- the broken line 2 illustrates the proportion of the sinking chips when the chips are treated with NaHS ⁇ 3-solution. It is noticed that a treat ⁇ ment for one minute with NSSC-solution already reduces the amount of the sinking proportion by 24 %, and a treatment for three minutes by about 45 %. The corresponding reduc- tions in the case of treatment with NaHS ⁇ 3 ⁇ solution were about 30 % and about 70 %. In the test a procedure was used wherein the penetration was performed with a cooking liquor subjected to the atmospheric pressure and wherein the filling of the solution was started while the vacuum pressure that had prevailed was still effective.
- Fig. 1 An explanation of the phenomenon of Fig. 1 is that an aqueous solution has a remarkably rapid effect on the walls and surface properties of capillary cell cavities, whereby, at the cut faces of the chips, the cell systems and in particular the capillaries in summer wood are con ⁇ tracted relatively speaking most rapidly.. In this way, the amount of solution that is penetrated, i.e. the pro ⁇ portion of the chips that are sunk into the solution, is lowered rapidly as the soaking time is increased.
- Fig. 2 illustrates the effect of the temperature of the solution on the penetration with different treatment times.
- the left vertical axis represents the amount of the chips that sink into the solution as a percentage of the entire quanity of chips treated
- the horizontal axis represents the temperature of the solution as °C
- the right vertical axis represents the duration of treatment as minutes.
- the raw-material consisted of pine chips of a moisture content of 20 %, which said chips were treated with a 5-% NaHS ⁇ 3 ⁇ solution. It is seen that when the temperature of the solution rises from 20° to 50°C, the amount of the chips that sink into the solution (broken line 3) also increases significantly. Likewise, it is seen that a further raising of the temperature does not have a major effect on the result.
- the treatment time (straight line 4) was shortened in the tests, in spite of which the proportion of sinking chips remained invariable and even became somewhat higher. It comes out from the results unambiguously that the lower limit of the economical operating temperature of the solu ⁇ tion is somewhere around 35 to 40°C, whereas, according to the experiments, it is not so useful to heat the mate- rial to very high temperatures, because the penetration is not improved essentially. By means of heating, it is, however, possible to intensify the penetration decisively.
- Fig. 3 it is seen how the water content of the chips affects the amount of solution that is penetrated.
- the horizontal axis represents the water content of the chips, and the vertical axis represents the amount of penetrated solution and the amount of chips that sink into the solution, all as a percentage of the dry matter of the chips.
- the concentration of the solution of chemicals was 5 % and the temperature 65°C.
- the broken lines 1 to 3 illustrate the penetrations of pine chips 1. with sulphate solution, 2. with NSSC-solu ⁇ tion, and 3. with NaHS ⁇ 3-solution, as well as the broken line 4 illustrates birch chips treated with NSSC-solution. From the broken lines 1 to 3, it comes out that solutions essentially different from each other are penetrated approximately in the same way irrespective of the moisture content of the chips.
- the penetration of a solu- tion of chemicals is determined in an almost linear way by the amount of water contained in the chips. This comes out best from an examination, at the various test points, of the joint effects of the changes in the water contained as moisture in the chips and in the amount of water con ⁇ tained in the solution that penetrated into the chips.
- the total water quantity was within the range of 164 to 177 %, and in the birch chips within the range of 143 to 145 %, respectively.
- the scattering from the average value was with pine chips ⁇ 4 % and with birch , chips ⁇ 1 %.
- the proportion of sinking chips which was determined by means of a follow-up of the penetration level, was with pine chips 88 to 89 % and with birch chips 100 %, irres ⁇ pective of the moisture of the chips (broken lines 5 & 6).
- density is understood as meaning the nominal density of the wood species as fully dry.
- the density of the wood material proper is the same, 1.32 to 1.35, the higher density of birch, which is on the average one quarter higher than the density of pine, means a corres ⁇ pondingly smaller space of fiber cavities, which is also manifested in a corresponding change in the penetrated quantities of NSSC-solution shown in Fig. 3.
- a characteristic feature of conifer wood is dependence of the density on the differences between spring wood and summer wood.
- the walls of summer-wood fibers are remark ⁇ ably thicker and the diameters of the cell cavity capil- laries are only a fraction of the corresponding dimensions of spring-wood fibers. It has been noticed that the cap ⁇ illary action has a significant part in the penetration.
- the lifting force of the solution in a capillary is in ⁇ versely proportional to the second power of the radius of the capillary, the capillary filling of the fiber cell system starts strongest and most rapidly in the portion of summer wood, provided that a sufficient amount of solu ⁇ tion is available in the fiber cavities. It is apparent that the solution pressure formed removes remaining air, and the summer-wood fibers are filled first.
- Birch has no corresponding differences in the struc ⁇ tures of the cell systems of summer wood and spring wood. In the tests, this came out clearly in a better level and speed of penetration of birch as compared with pine chips. Occasional structural differences in wood, such as knots and inclusions caused by resin, have no major sig ⁇ nificance quantitatively, ⁇ npenetrated portions in cell systems are, in a way, taken into account in a way similar to the cell-wall material, i.e. they have the same effect as an increasing density has.
- the vacuum penetration device 10 that is shown sche- matically in Fig. 4 consists of a penetration tank 11, into which the chips are introduced through the feed open ⁇ ing 12, to which either a globe valve 13 used for the feed of chips or a chamber feeder or a high-pressure feeder can be connected. At the lower end of the tank 11 , there is an outlet opening 14 for the material, and therein a globe valve 15. Vacuum pressure is produced into the tank 11 by means of a connecting duct 16, which is, by means of a valve 17, connected either directly with a vacuum pump or with an intermediate vacuum tank, which, is provided so as to accelerate the removal of air.
- the tank 11 is further provided with a connecting duct 18, through which the penetration solution can be passed into the tank 11 by means of a valve 19, e.g., from a pressure accumulator.
- a valve 19 e.g., from a pressure accumulator.
- the equipment in accordance with Fig. 4 is used so that the tank 11 is filled through the feed opening 12, whereupon the valve 13 is closed and the valve 17 is opened and air is sucked out of the chips present in the tank 11.
- the vacuum pressure is allowed to sink to a value at which the penetration solution to be fed in the next step does not yet start vaporizing. In the filling, the vacuum pressure is settled, depending on the species of wood and on the arrangement of equipment, in 0.5 to 5 minutes, whereupon the valve 17 is closed and the valve 19 is opened, said latter valve letting the penetration solution into the tank as rapidly as possible.
- valve 17 It is also possible to keep the valve 17 open and to allow the vacuum pressure to act in a way intensifying the pene ⁇ tration during the filling of the solution. In the tests it has been noticed that such a filling is penetrated rapidly and uniformly in a few minutes.
- the equipment 20 shown schematically in Fig. 5 is intended for penetration of, e.g., birch chips and of other hardwood chips of corresponding cell systems which takes place as a continuous flow treatment.
- the penetra ⁇ tion part consists of an arc-shaped transfer duct 21 , which extends in its upper part as a vacuum chamber 22.
- the lower ends of the transfer duct which act as baromet- ric vacuum locks, are arranged in the tank 23 for the cooking liquor.
- the level of the liquor is kept constant, and, owing to the vacuum pressure produced in the vacuum chamber 22, the cooking liquor rises in the ends of the transfer duct 21 placed in the soaking basin 23 to the height h corresponding to the vacuum pressure and forms vacuum locks.
- the chips are fed by means of a screw con ⁇ veyor 24, at which the surrounding tube 25 is perforated in order that the air surrounding the chips should be able to escape before the chips are transferred onto the end- less conveyor in the transfer duct 21. From the rising part of the conveyor 21, the chips are discharged onto the screw conveyor 26 in the vacuum chamber 22. By adjusting the transfer speed of the conveyor 26, the chips can be given the desired time of stay in the vacuum chamber 22, from which the endless conveyor 21 again transfers the chips down into the cooking-liquor basin 23. At the turn 27 of the conveyor 21 , it is advantageous to provide sepa ⁇ ration of sand etc. corresponding contaminations from the chips.
- the portion of the chips that sinks into the solution is discharged out of the transfer duct 21 onto the bottom of the basin 23 so as to be shifted further to the process.
- the portion that does not sink into the solution consisting mainly of bark- covered, knotty, etc. poorly penetrated chips, is removed from the surface of the basin 23. By crushing this chip portion further, usable raw-material can be recovered from it.
- the equip- ment described above is simpler than the solution of Fig. 4 with its numerous valves. Moreover, the cost of produc ⁇ ing the vacuum is lower in this case, because most of the air carried along with the chips is already separated in the screw feeder 24 and does not enter into the vacuum system. Actually the only drawback of the equipment in accordance with this embodiment of the invention is the fact that the chips must already be in contact with the cooking liquor before the vacuum treatment, in the screw feeder 24 and in the lower end of the transfer duct 21.
- the chips are taken alternatingly from two intermediate tanks 41 , which can be subjected to vacuum pressure, into a vacuum chamber 42, from which a spiral feeder 43 feeds the chips sub ⁇ jected to vacuum pressure into a conveyor 45, which acts at the same time as a barometric vacuum lock between the vacuum chamber and the chip-reception tank 46.
- the con- struction of the conveyor 45 is such that it pulls the chips rapidly from the vacuum into the pressurized basin space. Sand, which is heavier than the chips, and other contaminations are separated at the point 47.
- the time of stay of the chips is regulated so as to com ⁇ plete the penetration.
- the portion of the chips that does not sink into the solution can be se ⁇ parated, e.g., for crushing..
- the penetrated chips are transferred into the process by means of the conveyor 50.
- the surface level of the solu ⁇ tion is kept invariable.
- the solution is fed at the level of the surface formed by the effect of the vacu ⁇ um at the barometric lock to the point 51, i.e.
- the equipment described above is suitable for continu ⁇ ous penetration of chips, in particular when a certain uniform dosage of chemicals is aimed at. If penetration with water is concerned, the varying requirement of water is taken care of by control of the water level in the reception tank.
- FIGs 7 and 8 are schematical illustrations of two operating positions of a vacuum penetration device, whose principle of operation is the same as in the device shown in Fig. 4 but in which the chip treatment space is a revolving rotor.
- Fig. 7 illustrates the starting situation, in which any transfer solution that remained in the rotor 60 after the preceding processing batch has been removed through the duct 61 and in which the chips are filled through the filling opening 62 while the punched plate placed at the other end of the rotor is in the position S.
- the chips are first acted upon by vacuum through the duct 63.
- the penetration solution or water is introduced through the duct 64, and after the filling, either immediately or after a certain incubation time, the treated chips are transferred, by means of a solution taken from the recep ⁇ tion tank through the duct 65, through the duct 66 into said reception tank.
- the reception tank it is advan ⁇ tageous, even though not necessary, to maintain a liquid pressure of a few bars.
- the further treatment of the chips can also be carried out by using the barometric vacuum lock of the equipment em ⁇ bodiments illustrated in Figs. 5 and 6. If penetration with water is concerned, the duct 64 is not needed.
- the arrangement of equipment described above is suit ⁇ able, e.g., for the treatment of chips for production of refiner mechanical fibers with water, to which said water it is advantageously possible, if necessary, to dissolve chemicals which improve the control of pH, the yield of fiber, or the colour.
- the penetration space must be made relatively small out of constructional reasons.
- advantages that are obtained are short and rapid vacuum-treatment or solution-filling times and thereby good handling capacity. Rapid and in ⁇ tensive pressure variations on removal of air and on pen ⁇ etration of solution into its place promote opening of the ring pores between the fibers, which improves the level and the speed of penetration.
- the process of the invention provides the possibility to adjust the dosage of chemicals in the chips, determined in relation to the dry matter, to the desired level by adjusting the concentration of chemicals in the solution to be penetrated.
- the apparatuses used for said purposes are suitable.
- the storage circulation time of chips is normally some weeks. Thereat, extreme conditions of water contents are equalized, and the variations in moisture content in the chips coming to use occur as wave-like variations. Since the density of the wood material in the fiber walls is, with all of the wood species that are concerned, practi ⁇ cally the same, 1.32 to 1.35, with some simplification, it is possible to start from the assumption that a flow or batch of chips that represents the same species of wood and the same density and that has been treated at a stand ⁇ ardized volume always contains the same weight quantity of dry matter of wood per unit of volume. Thereat, it can also be considered that the total volume of the cell cavities and pores remains at the same level.
- a measurement apparatus for constant monitoring of the water content and the weight of chips, e.g., a measurement apparatus is suitable wherein the water content is determined by means of neu ⁇ tron radiation and the weight by means of gamma radiation.
- the chip flow must be of invariable volume or the measurements must be carried out in a measurement space, in which case the filling density of the chips can be made invariable more readily.
- Variations in the densi ⁇ ty of the chips are normally of an order of a few per cent so that in most cases it is enough to make corrections to the density only after a certain limit has been surpassed or when the wood species or quality is changed remarkably. In the embodiments of equipment described, rapid and pre ⁇ cise treatment of a continuous flow of chips is possible.
- Said mode of opera ⁇ tion is advantageous in particular when high-yield pulps are produced by means of penetration devices of the type illustrated in Figs. 7 and 8. It is possible to make use of the measurement results obtained from the changes in the quantity of penetrable solution, which said changes are caused by variations in the water content and density of the chips. Thereat the solution volume of the solution penetrable in a flow or batch of chips to be treated is used in the control of the chemical content of the penetration solution for the next chip batch as a guide for the solution volume in which the desired chemical dosage must be contained.
- the error pro- 9 by the delay in this procedure has no significance in practice, because in the chip stores, which are changed relatively slowly, the greatest local differences in moisture content are equalized, and in the chips taken to production the moisture level can be characterized as varying in wave form in stead of abrupt moisture differ ⁇ ences.
- the process can be accomplished by means of simple embodiments of equipment, and therein the control of the regulation of the chemical concentrations in the solution is obtained from measurement of the factually penetrable cavity volume in the chip quality that is being treated at each particular time.
- the chemical concentration of the solution is regulated by means of dosage devices in a separate solu- tion mixer by means of a control obtained from changes in -the quantity of penetrable solution, which said changes are caused by the water content, density, and local blocks in the chips.
- the chemical content of the solution to be penetrated required in each particular case is obtained, e.g., by mixing concentrated chemical solution and chemi ⁇ cal solution obtained from a later stage in the process or waste liquor or waste water in a proportion that yields the desired chemical concentration.
- the concentration of the concentrated solution is adjusted close to the satura- tion point of the chemical concerned at the treatment temperature used in each particular case.
- connecting ducts are required, besides for intake of said solution components, also for passing the solution mixture into the penetration space and for recirculation of the chip transfer solution.
- the chip transfer solution is taken from the reception tank preferably out of the cylinder surrounding the ex ⁇ tended and perforated discharge pipe for the chips, where ⁇ at the concentration of the transfer solution is the same or, having been used in the preceding penetration, almost the same. It is also advantageous to use the transfer solution for the preparation of the solution to be pene ⁇ trated when, with an increasing water content in the chips, the chemical concentration must be increased.
- the penetrated chips are surrounded by a warm solution, whose chemical concentration corres- ponds to the average level of the solution concentrations of the preceding penetration batches, and the diffusion of the chemical ions into the walls of the chip cell sys ⁇ tems filled with solution can start immediately.
- the ob ⁇ jective of the impregnation, a desired chemical dosage adequately and uniformly diffused in the wood material, is achieved in a fraction of the time that is usually re ⁇ quired in practical impregnation when the major part of the chemicals must be obtained from a solution placed outside the chip particle by means of diffusion.
- Intensified penetration reduces the formation of knotter pulp. Further, the amount and quality of knotter pulp can be affected, as was described above, by treating the partly unpenetrated chips, which do not sink into the solution, separately. The separation can be carried out advantageously in the chip reception tank.
- the incom ⁇ pletely penetrated portion of the chips, to be removed from the top portion of the tank, is preferably reduced to splinters and, after a separate prolonged solution treatment, returned to the process or, in a repeated sepa ⁇ ration, the knotty or any other poorly defibrizable part of the raw-material is removed.
- a controlled and very rapid balanced impregnation of the chips improves the pro ⁇ duct quality indirectly and provides economies of raw- material and energy.
- the time taken by the process cycle is shortened essentially. In this way, for example, the capacity of existing digesting plants can be improved advantageously.
- the procedure is suitable for use in alkaline and neu ⁇ tral digesting processes. It is in particular suitable for the production of high-yield and chemi-mechanical pulps, whereat attempts are made to obtain a high yield and a good fiber quality by means of a little dosage of chemicals and short-time heating, possibly carried out in a steam phase. Further, the use of this process is advantageous in impregnation objects wherein little quan- titles of chemicals must be distributed uniformly in the raw-material.
- the objective may be, for example, stabi ⁇ lization of hemicellulose and the use of catalysts or bleaching chemicals.
- the chips In mechanical production of fibers, the chips may be penetrated with hot water, to which small amounts of chemicals may have been added.
- the procedure increases the possibilities of using a wood or chip qual ⁇ ity inferior to the customary quality, e.g. dried-up sawmill chips in TMP-, CTMP- and CMP-processes.
- the pretreatment of raw-material in accordance with the invention can, with the arrangements described above, be used in impregnation of a porous cellulosic raw-material, e.g., in the produc ⁇ tion of boards or when the raw-material is modified chem ⁇ ically, e.g. in converting wood to sugar, or in general in utilization of the constituents of wood.
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Abstract
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Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19893990074 DE3990074T1 (en) | 1988-02-08 | 1989-01-30 | METHOD AND DEVICE FOR PRE-TREATING CELLULAR RAW MATERIAL |
DE3990074A DE3990074C2 (en) | 1988-02-08 | 1989-01-30 | Process for the pretreatment of cellulose raw material |
AT902389A AT396128B (en) | 1988-02-08 | 1989-08-10 | Process and apparatus for the pre-treatment of pulp raw material |
SE9002601A SE507694C2 (en) | 1988-02-08 | 1990-08-08 | Process and apparatus for pre-treating chips using vacuum treatment |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI880560 | 1988-02-08 | ||
FI880560A FI80083C (en) | 1988-02-08 | 1988-02-08 | Method and apparatus for pre-treating cellulosic feedstock |
Publications (1)
Publication Number | Publication Date |
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WO1989007170A1 true WO1989007170A1 (en) | 1989-08-10 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/FI1989/000017 WO1989007170A1 (en) | 1988-02-08 | 1989-01-30 | Process and equipment for pretreatment of cellulosic raw material |
Country Status (6)
Country | Link |
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CA (1) | CA1322827C (en) |
DE (1) | DE3990074C2 (en) |
FI (1) | FI80083C (en) |
FR (1) | FR2650604B1 (en) |
SE (1) | SE507694C2 (en) |
WO (1) | WO1989007170A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2650604A1 (en) * | 1988-02-08 | 1991-02-08 | Osmo Aho | PROCESS AND EQUIPMENT FOR THE PRETREATMENT OF RAW CELLULOSIC MATERIAL |
WO1992013990A1 (en) * | 1991-02-06 | 1992-08-20 | Antti Aho | Method for controlling a defibration process |
WO1995009267A1 (en) * | 1993-09-29 | 1995-04-06 | Antti Aho | Pretreatment of chips |
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US3076501A (en) * | 1956-11-08 | 1963-02-05 | Escher Wyss Ag | Apparatus for treating fibrous materials in the production of cellulose or semi-cellulose |
DE1070013B (en) * | 1957-07-10 | 1959-11-26 | Escher Wyss G.m.b.H., Ravensburg | Method and device for the treatment of fibrous substances in the production of cellulose or semi-cellulose |
US3215587A (en) * | 1963-01-21 | 1965-11-02 | Lummus Co | Continuous process and apparatus for delignification of cellulosic material |
US3347741A (en) * | 1964-01-13 | 1967-10-17 | Crane Co | Feeder for solid materials |
US3446701A (en) * | 1967-12-28 | 1969-05-27 | Us Agriculture | Apparatus for impregnating and chemically converting cellulose-containing materials |
FI80083C (en) * | 1988-02-08 | 1990-04-10 | Antti Aho | Method and apparatus for pre-treating cellulosic feedstock |
-
1988
- 1988-02-08 FI FI880560A patent/FI80083C/en not_active IP Right Cessation
-
1989
- 1989-01-30 WO PCT/FI1989/000017 patent/WO1989007170A1/en active Application Filing
- 1989-01-30 DE DE3990074A patent/DE3990074C2/en not_active Expired - Fee Related
- 1989-02-07 CA CA 590344 patent/CA1322827C/en not_active Expired - Fee Related
- 1989-08-04 FR FR8910541A patent/FR2650604B1/en not_active Expired - Fee Related
-
1990
- 1990-08-08 SE SE9002601A patent/SE507694C2/en not_active IP Right Cessation
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2650604A1 (en) * | 1988-02-08 | 1991-02-08 | Osmo Aho | PROCESS AND EQUIPMENT FOR THE PRETREATMENT OF RAW CELLULOSIC MATERIAL |
WO1992013990A1 (en) * | 1991-02-06 | 1992-08-20 | Antti Aho | Method for controlling a defibration process |
WO1995009267A1 (en) * | 1993-09-29 | 1995-04-06 | Antti Aho | Pretreatment of chips |
Also Published As
Publication number | Publication date |
---|---|
SE507694C2 (en) | 1998-07-06 |
FI880560A0 (en) | 1988-02-08 |
CA1322827C (en) | 1993-10-12 |
SE9002601L (en) | 1990-08-08 |
FR2650604A1 (en) | 1991-02-08 |
FI80083B (en) | 1989-12-29 |
FR2650604B1 (en) | 1995-02-10 |
FI80083C (en) | 1990-04-10 |
FI880560A (en) | 1989-08-09 |
SE9002601D0 (en) | 1990-08-08 |
DE3990074C2 (en) | 2000-03-16 |
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