FI117560B - Steaming - Google Patents

Abstract

The invention relates to a method of steaming lignocellulosic material to be pulped. The material is treated in a superheated steam atmosphere. The treatment can be used for loosening up the structure of fibre for mechanical pulping and/or for facilitating the absorption of delignifying chemicals into the fibre.

Description

117560 Steam treated

The present invention relates to a process for vapor-treating a lignocellulosic material to modify the structure of the material and / or to impregnate the delignification chemicals into the fibrous disease cellulosic matrix. In the method, the lignocellulose-lime matrial is roasted with steam prior to absorption of the dehydrogenation chemical solution. The term "lignocellulosic material" as used herein refers to any herbal material used as a raw material for cellulose cooking, such as wood, straw, hay plants, 10 bagasse, etc. The lignocellulosic material used in the process is conventionally delignified, for example, wood.

Torture, as used herein, refers to the torture of lignocellulosic material, which includes some degree of chemical and thermal delignification of the lig-15 cellulosic material. For chemicals, heat and illignification can be supplemented with mechanical torture to achieve the desired degree of fiberification.

The treatment of lignocellulosic material in a superheated vapor atom contained in the invention may also be applied to loosen the structure of the lignocellulosic material for mechanical torture. A similar procedure has been used in the prior art, e.g. In the so-called TMP defibration process, but under saturated steam conditions, if steam treatment is carried out using the listed vapor instead, the fiber material creates a situation in which the moisture inside it tends to vaporize and penetrate the fiber. The lignin contained in the fiber softens as a result of this treatment, and at the same time the internal structure of the fiber is opened and loosened, resulting in *! !! is helping to advance the coming mechanical months After treatment (unless it has been over-dried), there is a situation within the fiber where there is saturated vapor inside the fiber. If the fiber in this state is subjected to conditions where the steam * * k · «* · condenses, and still relatively quickly, this causes collapse in the fibrous structure, which further relaxes the structure. This substantially contributes to fiber consolidation in the subsequent mechanical defibration. Fiberization requires less energy, and harmful breakdowns are reduced.

Delignification chemicals are used herein to mean all chemicals commonly used for this purpose that are absorbed into lignocellulosic material and that solubilize or soften the lignin contained therein are performed at temperatures above ambient temperature. Examples include sulphate and sulphite cellulose solutions.

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Reactions of lignin in the fibrous material with solubilizing and / or plasticizing chemicals will take place in the desired manner only if the chemicals have been uniformly and thoroughly penetrated into the material to be lost. The absorption of chemicals is influenced by two mechanisms, penetration and diffusion. In natural penetration, the cooking chemical solution penetrates into the fibrous material through its capillary structure under the influence of capillary forces. The penetration event can be facilitated by providing a differential pressure across the capillary structure.

··: ** · The speed and proper performance of the penetration process is highly dependent on the air contained in the fibrous material, which should be removed before the material is treated with delignification chemicals. One method used is the steaming of the fibrous material by steaming. The air expands • ♦ • · I ”through warming and partially exits the pore spaces of the fibrous material. The processing steam * · * · contributes to the pore spaces of the fibrous material where it condenses through the condensation and vaporisation of the fibrous material.

• · · ··· • · · ♦ ♦ • · • *. In prior art roasting, saturated steam has been used. The vapor temperature limit has been kept at 120-126 iC, and at higher temperatures the hydrolysis of the dry materials has been considered to be adversely affected. Also lignin con- • * * * · · * *. 30 densification at higher temperatures has been identified as a problem.

• · 117560

The prior art addition of saturated steam material of ignocellulosic fibrous material n inevitably results in an increase in the moisture content of the fibrous material, since substantially all of the steam used in the roasting condenses on the fibrous material and penetrates its structures. Accordingly, the condensation energy of the vapor increases the temperature of the fiber material under the casing. On the other hand, the vapor condensing on the surface layers of the fibrous material prevents the escape of air.

According to the basic idea of the invention, roasting of lignocellulose-based fibrous material is carried out in a superheated vapor atmosphere, and 1 ignocellulosic material is held under substantially vapor treatment pressure until at least the impregnation step. The roasting treatment is preferably carried out by introducing superheated steam into contact with the fibrous material. Other forms of energy input, such as indirect heating, or an inert energy carrier (such as fluidizing material) are also possible which maintain a superheated steam atmosphere in the roasting process.

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When using superheated steam delivered to the fibrous material, the inlet and end temperatures of the vapor are determined by the material of the fibrous material being processed. The superheated steam of biomass has a strong effect on the fiber material being treated. On the one hand, the superheated steam binds water to the fiber material, and on the other hand causes the fiber material to rise in temperature. The water in the fibrous material evaporates, travels to the surface of the material ··· · 2 and exits with the superheated steam from the fiber material. At the same time, steam trapping water drives air in the fiber structure away from the fiber. An essential element is also that evaporative water most likely opens the capillary and pore structure of the fiber.

. For the implementation of the invention, it is essential that the fiber is kept in conditions where the fiber. this open space of capillaries and pores is maintained as far as possible by delig- • · · • '::: absorption of chemical substances. In this respect, the residual moisture content of the fiber material and the surrounding atmosphere are decisive.

• · • · · 30 · · · · 2 * 1 4; 117560

The fibrous material is in such a state that its structure has at least a vapor-like ice bump. Best if there is so much moisture and in a state that it • <: still tends to evaporate and penetrate out of the structure. This ensures that the pore structure remains open. On the other hand, the moisture evaporating in the fiber structure binds the heat, which prevents the fiber material temperature from rising so high that the adverse degradation and condensation reactions of the fiber material begin The time when the The state of the surrounding atmosphere, in turn, is determined by the pressure therein.

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When the roasted fibrous material having an open pore structure (containing vaporized moisture and at least at ambient temperature saturated vapor pressure) is contacted with the solution containing the delignification chemicals, the solution penetrates into the fibrous structure to replace the moisture removed therefrom. The penetration of the lys-15 film into the fibrous structure can be facilitated by providing a condition in which the moisture in the fibrous structure condenses, resulting in a corresponding vacuum between the pores of the fiber structure and the environment. This situation can be achieved, for example, by using a slightly colder delignilization process relative to the saturation state of the fiber structure.

M

: * · Chemical solution.

With this arrangement, it has been found that the delignification solutions are rapidly absorbed uniformly throughout the fiber material. The arrangement also allows the impregnated fiber material to be substantially at a delignification temperature after impregnation. Slow • 1 absorption and elevation of delignification temperature associated with fiber and de-. ·. Adverse reactions of lignification chemicals are thus eliminated.

In the application of lignocellulosic material with superheated steam, the contact time between the material and the vapor is substantially short, of course, depending on the partial composition of the material.

. *. ta. For example, a fine-grained wood raw material (classified with the attribute '' chew '').

• · · «» * *. 30 particle size (about 3-5 mm) is an appropriate residence time of the order of seconds. 4 * ··· «.

• * 5 117560

The roasting step of the invention can be carried out in a so-called. in a flash-type processing apparatus, wherein the finely divided lignocellulosic material is fed to a stream of superheated steam and separated from that stream after a suitable residence time. The apparatus is illustrated in the accompanying drawing, in which: 5

Figure 1 illustrates one embodiment of a roasting and soaking apparatus according to the invention, and

Figure 2 illustrates an apparatus for a similar purpose, a part of the impregnation apparatus as an alternative embodiment.

In the embodiments according to the drawings, the roasting apparatus has a steam flow cycle 1 with a superheater 2 (boiler), a rotary fan 4, a superheat roasting section 4 having feeders 5 where appropriate, a return cycle of the roasted lignocellulosic material 10.

·· • * .. In the embodiment of Figure 1, the roasted lignocellulosic material is shown as a cancer. *: 20 for delivery through outlet damper 8 to impregnation device 11, which is fed with a solution of deliquine chemical from tank 9. The impregnation device may be a structure known in the art. Inside, there is usually a gently sloping screw feeder that conveys the ligno ***** * ”· * cellulosic fibrous material upwardly through the impregnator. The absorption device usually maintains a level of delignification solution of about half. 25 length of the absorber. The absorption occurs at the bottom of the device and at the top * ♦ * !!! drainage of excess solution occurs. The excess solution may be introduced into the solution container 9, possibly under control of the chemical content.

Preferably, the outlet end of the impregnation device 11 also has an outlet closure 12 which allows the suction device 11 to maintain independently adjustable pressure. From the outlet barrier 12, the lignocellulosic fibrous material is fed to the actual delignification until step 6 117560 delignification reactions are performed to the desired degree of delignification. The delignification vessel 13 maintains a suitable pressure and a corresponding saturated vapor temperature where delignification reactions have been found to be most advantageous with respect to the fibrous material. The temperature can be maintained, for example, in a known manner by means of a fluid circulation with heating.

Alternatively, post-roasting impregnation may be performed by proceeding as shown in Figure 2. In this embodiment, the clamp 8 can act as an outlet barrier. Delignification · The solution containing chemicals may be fed into the fiber material via the press; 10, and squeeze excess solution out of the press. Thereafter, the impregnated fibrous material is conducted to a delignification vessel .13, where the fibrous material is maintained at a / οη de-ligation temperature in the ambient vapor phase. Alternatively, the temperature can be maintained by indirect heat transfer from steam 16. With this arrangement 15, the amount of process fluid is minimized.

From the container 13, the fiber material is led through the outlet closure 14 to any mechanical defibration, and further to the conventional washing and bleaching steps. The arrangements according to Figures 1 and 2 allow the use of different conditions at different stages of the process. For the overall flow of the process, it is preferable that the fiber material be maintained substantially pressurized throughout the process, which is the pressure of the saturated water vapor at the temperature used in the counter-delignification step. It is also possible to act as a variation of this operating model to reduce the pressure slightly when moving to the trumpet. 25 from absorption to absorption. and further on transition from absorption to delignification.

• · · ···. ···. Other pressures, and similar temperature conditions, are also possible with respect to the fiber material (material source per se, particle size, moisture content), the chemicals used, and the desired degree of delignification.

The moisture exiting from the lignocellulosic material 1 in contact with the superheated steam in the roasting cycle 4 is transported with the steam to a separating device 6, from which excess steam 117560 is removed through 7. This vapor has a high energy level and can be utilized in subsequent stages of the defibration process, for example heating of delignification chemicals, chemical cycle regeneration, bleaching, washing, etc. The control of the exhaust steam 7 can also be used to adjust the heat cycle 5 of the superheat cycle. gas space.

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Claims (7)

1. A method for impregnating a lignocellulosic material to be defibrated with delignification chemicals prior to a delignification step, in which process the lignocellulosic material is treated in a steam atmosphere and the delignification chemicals are similarly impregnated with the previously treated Ugnocellulosic material, in a superheated meadow atmosphere whose superheated condition is maintained throughout the treatment, and that the lignocellulosic material is substantially at least pressurized at the pressure of the meadow treatment until the impregnation step. Method according to claim 1, characterized in that the meadow treatment is carried out substantially at the pressure of the delignification step. 15 3. A method according to claim 2, characterized in that the impregnation of the delignification chemicals is carried out substantially at the pressure of the delignification step. 4. A method according to claim 1,2 or 3, characterized in that the delignification. the chemicals are impregnated in the meadow-treated lignocellulosic material substantially at a temperature of the delignification step. A process according to claim 1,2 or 3, characterized in that the delignification chemicals are impregnated in the meadow-treated lignocellulosic material at a temperature. in turn lower than the temperature of the delignification. 25 • «· 6. A method of defibrating a lignocellulosic material, characterized in that the fiber material is treated with an overheated meadow space for partial elongation of the moisture contained by the fiber and that the fiber material is substantially defibrated in delta tiles. · Stand by mechanical defibration. «30 • * · '' ϊ 7. A method of defibrating a lignocellulosic material, characterized in that 11 '. The fibrous material is treated in a superheated meadow space for partial elongation of the moisture contained in the fiber, that the fibrous material is cooled, and that it is substantially defibrated in this state by mechanical defibration. 5 ** · · · φ φ 1 1 1 1 1 1 · «« «· · t t« t t t t t · • Φ · • · · • 1 • Φ * · · «• · Φ • ·. ··· 1 • φ Φ Φ 1 • · • 1 · • Φ 1 • Φ · Φ · · * 1 ··· ·