CN1153241A - Process in association with pulp bleaching - Google Patents

Abstract

A process for chlorine-free bleaching of chemical pulp in association with the production thereof, where a suspension of the pulp preferably has a concentration exceeding 8% of cellulose-containing fiber material and where the pulp entering into a bleaching line is preferably fed continuously through at least one bleaching vessel in the bleaching line, is treated with at least one acid for adjusting the pH to a value below 7, and with a chelating agent, and is subsequently bleached in at least one stage to a brightness exceeding 75% ISO, preferably exceeding 80%, employed in a quantity exceeding 5 kg/BDMT. The bleaching of peroxide is happened in the bleaching vessel which has a higher temperature and pressure.

Description

The method of association with pulp bleaching

The present invention relates to a kind of chlorine-free bleaching method of the chemical pulp that combines with its production, wherein the paper pulp turbid liquid preferably has the fibrous material that denseness surpasses 8% cellulose, and the paper pulp that wherein enters the bleaching production line is preferred continuously by at least one bleaching cistern in the bleaching production line, with at least a acid for adjusting pH value to being lower than 7 and handle with a kind of chelating agent, and then at least one stage it is bleached brightness and surpass 75%ISO with the another kind of peroxide of hydrogen peroxide or a great deal of, preferably surpass 80%, the peroxide addition surpasses 5 kilograms/BDMT.

Requiring to carry out extensive studies from the environmental consideration of selling is that the bleaching purpose is used chlorine-containing compound with the elimination.Use current technology, be difficult to reach full bleaching the paper pulp that from the cork sulfate pulp, prepares with oxygen, hydrogen peroxide and ozone.

The peroxide bleaching method that many Lignox and Macrox type are arranged is wherein in conjunction with having used EDTA to handle and having added peroxide.These methods require minimum 4 hours of 90 ℃ of the reaction times, and, however, found when having carried out the successful bleaching of oxygen delignification softwood pulp, paper pulp has 12 card handkerchiefs and brightness has reached 77-79ISO, and nearly half used peroxide does not also obtain utilizing.The intent of the present invention is should reuse unemployed peroxide after adding fresh peroxide.As far as we know, this point does not also produce industrialized scale.In some cases, peroxide is got back to oxygen reactor, and the effort of any possible raising brightness has been left in the basket.

By disclosed Swedish patent application, 8503153-2 (Wagner-BiroAG) can learn a kind of method of using oxygen and/or ozone to remove the paper pulp lignin under the situation that rationally adds peroxide.In said method, under this reaction temperature and during the denseness of 2.5-4.5%, paper pulp is contacted with oxygen (may contain peroxide) and second stage is carried out under 10% denseness.The amount of used peroxide is 0-5 kilogram H ₂O ₂/ kilogram ptp.

In order to shorten the essential reaction time and/or to reduce residual peroxide to reach the optimum utilization of used hydrogen peroxide, the method that may produce immediately is elevated temperature and pressurization seemingly, and in fact this suggestion is included among the Swedish patent 8902058-0 (EKA Nobel AB) as a kind of possibility, has wherein described so-called Lignox method.Carried out the test of this direction, but failed, the result of each side is also more poor than what reached with pure normal pressure peroxide bleaching.Even existing people proposes that oxygen is nugatory in the bleaching of Lignox method.The use of pressure preferably uses the MC pump to reach, and the turbid liquid denseness of pumping surpasses 8% also preferably less than 18%.

It should be noted the test of having mentioned in patent and other document,, carry out with breadboard scale owing to understandable reason.If having obtained the poorer and peroxide bleaching of having reached a conclusion of (for example from 90 ℃ to 95 ℃) result that raises of sign temperature should preferably carry out in the temperature below 90 ℃.

The objective of the invention is to propose the method for the sort of type mentioned in a kind of the introduction, this method can provide effectively and bleaching more uniformly.

According to the present invention, be less than the flat myriametre of 4V by the peroxide bleaching that takes place under the temperature and pressure that in bleaching cistern, has raise and by the metal surface area that is exposed to bleaching cistern inside, here V represents a cubic metre volume, can reach this point, the every bit of said pressure in groove all surpass the steam pressure of liquid in the turbid liquid and wherein the cross-sectional area of bleaching cistern surpass 3,000 sides meter.

Surpass 3.0 * 10 according to the pressure in the further situation bleaching cistern of the present invention in the bottom of groove ⁵Handkerchief (3 crust), preferred 4.0 * 10 ⁵Handkerchief (4 crust) also more preferably surpasses 5.0 * 10 ⁵Handkerchief (5 crust), and the pressure at bleaching cistern top surpasses 1.0 * 10 ⁵Handkerchief (1 crust), preferred 1.2 * 10 ⁵Handkerchief (1.2 crust) and more preferably 1.5 * 10 ⁵Handkerchief (1.5 crust).

In addition, in laboratory bleaching, be to use plastic bag under the atmospheric pressure in 90 ℃-95 ℃ the water-bath in maximum temperature.Obviously, the pressurization program under an atmospheric pressure is carried out in acidproof autoclave.

The metal surface of the heat of autoclave surprisingly that occurs can the catalysis peroxide breakdown now.Be full of water and put into paper pulp and peroxide before with the autoclave that carries out the heat transmission between autoclave and plastic bag if put at the plastic bag of sealing, brightness, kappa value and viscosity all can improve and peroxide consumption reduces.

Using and do not using extra oxygen pressure (5.0 * 10 ⁵Handkerchief (5 crust)) tests respectively under the condition.Needn't adopt specific theory fully, it is contemplated that this being seemed possible approach is that the metal surface of autoclave heat is decomposed peroxide catalyzed.In order to study this point, described test below having carried out especially.These tests have confirmed that our imagination is correct.Because the amount of the metal surface of per unit volume interior exposed is the quadratic power minimizing with the volume increase of groove in the groove, our the problems referred to above of can reaching a conclusion are that the laboratory is distinctive, cross-sectional area (about 3 square metres are further reduced along with its influence of increase of cross-sectional area～D is inevitable) this influence when a special value that is bleaching cistern is conclusive.

Also occur surprisingly according to the present invention by use a kind of can anti-high pH value and Undec complexing agent can reach the further improvement of this method, high pH value is meant that pH reaches 11.

Knownly in present technical merit, added complexing agent in the Q stage, wash after as EDTA the paper pulp turbid liquid at first be for complexing be the transition elements that exists in the paper pulp turbid liquid in order to wash away then.Yet, will be retained in a certain amount of metal of EDTA complexing and to be brought to next stage in the turbid liquid.In addition, in may be in addition not being retained in the metal of EDTA complexing yet.

Because the used pH value of the not anti-bleaching stage of EDTA, the metal with the EDTA complexing under the pH value of it seems in next stage will be released.Because the metal ion that discharges and the metal ion of those complexings never decompose the peroxide of bleaching usefulness, so continuous technology is had adverse effect.

Therefore proved at Q after the stage, preferably added the high pH value of a certain amount of ability together and Undec complexing agent is an improvement that is to the inventive method with peroxide.This interpolation can be got rid of above-mentioned adverse effect.Preferred complexing agent is DTPA according to the present invention.

Further improvement of the present invention is an aerating oxygen in bleaching, and use amount is less than 5 kilograms/BDMT, preferably is less than 3 kilograms/BDMT and more preferably less than 1 kilogram/BDMT.Find that also available nitrogen replaces oxygen, peroxide consumption only has very little rising as a result.

Also finding does not have adverse effect because the pressure that adding oxygen or nitrogen cause can be adjusted by the pure hydrostatic pressure of the height generation of for example pumping mode or bleaching cistern self by use.

According to a further aspect in the invention, surpass 90 ℃ by temperature in the bleaching process, preferably equal or exceed 100 ℃, more preferably between 100 ℃-105 ℃, this method can be improved.

According to a further aspect in the invention, the amount by used peroxide surpasses 10 kilograms/BDMT and is less than 35 kilograms/BDMT, with the brightness that reaches above 85IS0 this method is improved.

According to a further aspect in the invention, surpass 3.0 * 10 by pressure ⁵Handkerchief (3 crust) is preferably in 0.5-1.5 * 10 ⁶Between the handkerchief (5-15 crust) and more preferably in 0.5-1.0 * 10 ⁶Between the handkerchief (5-10 crust) this method is improved.

According to a further aspect in the invention, do not allow too big scope by paper pulp in the bleaching process and contact with the metal surface, preferably the bleaching cistern inner surface is made with some polymeric material or ceramic material at least, and this method can improve.

According to a further aspect in the invention, by placing the Q stage to be less than 20 kilograms/BDMT before and by the brightness and the peroxide consumption amount that surpass 85 ISO that such dual stage process obtains Z stage or peracetic acid stage, this method can improve.

According to a further aspect in the invention, by not washing between the ZQ, and the preferred A stage at Z before the stage, this method can improve.

According to a further aspect in the invention, manganese content should be less than 5 gram/BDMT paper pulp in the paper pulp of peroxide stage, preferably is less than 1 gram/BDMT paper pulp, and more preferably less than 0.5 gram/BDMT paper pulp, and its content is identical with content in the final bleached paper pulp basically.

According to a further aspect in the invention, by at bleaching stage, before temperature is increased to finally that desired level is spontaneous and bleaches, before in pulp suspension, sneaking into peroxide, at first add pH value rising reagent being lower than under 90 ℃ the temperature, this method can improve.

According to a further aspect in the invention, added pH value rising reagent in the paper pulp turbid liquid before adding peroxide in the bleaching stage, initial pH value rising is not higher than 11.5 and preferably adjust the pH value between 10-11 and this method is improved.

According to a further aspect in the invention, participate in by have a kind of complexing agent at least in the peroxide bleaching stage, this complexing agent preferably and peroxide add together in the turbid liquid, this method can be improved.

According to a further aspect in the invention, can anti-fully pH value improve this method, the preferred DTPA of this complexing agent by at least a complexing agent up to 11.

According to a further aspect in the invention, by adding quantity, the complexing agent DTPA of preferred 1-2 kilogram DTPA/ADMT and this method is improved.

According to a further aspect in the invention, by with centrifugal pump, be that so-called MC pump obtains normal pressure this method is improved in bleaching cistern.

According to a further aspect in the invention, under the condition that does not have the gas phase existence in the bleaching cistern, carry out peroxide bleaching and this method is improved with the method for hydraulic pressure.

According to a further aspect in the invention, the diameter by bleaching cistern surpasses 3 meters, preferred 5 meters and more preferably 7 meters and this method is improved.

The following examples have illustrated the present invention and have confirmed wondrous and unexpected result.

To this test:

Together with following description, and consult accompanying drawing, here:

Fig. 1 represents according to the present invention in the process of bleaching respectively 5.0 * 10 ⁵Handkerchief (5 crust), 100 ℃ or 5.0 * 10 ⁵Handkerchief (5 crust), 110 ℃ 1,2,3 hour down, and 90 ℃, 0 handkerchief, 4 hours and 90 ℃, 5.0 * 10 ⁵Brightness (%ISO) and H under handkerchief (5 crust), 4 hours the situation ₂O ₂The wastage in bulk or weight (relation curve of kilogram/between ADMT).

Fig. 2 represents according to the present invention in the process of bleaching respectively 5.0 * 10 ⁵Handkerchief (5 crust), 100 ℃ or 5.0 * 10 ⁵Handkerchief (5 crust), 110 ℃ 1,2,3 hour down, and 90 ℃, 0 handkerchief, 4 hours and 90 ℃, 5.0 * 10 ⁵Brightness (%ISO) under handkerchief (5 crust), 4 hours the situation and the relation curve between the viscosity (cubic decimeter/kilogram).

Fig. 3 represents brightness in the bleaching process (%ISO) and H ₂O ₂(relation curve of kilogram/between ADMT), the P stage of wherein pressurizeing according to the present invention is inserted in the different bleaching sequences wastage in bulk or weight, and the pressure that ozone stage is in 50 ℃ and 6 kilograms or 4 kilograms down and contain the manganese of different amounts.

Fig. 4 represents the relation curve (test of same train) between brightness in the bleaching process (%ISO) and the viscosity (cubic decimeter/kilogram), P stage of wherein pressurizeing according to the present invention is inserted in the different bleaching sequences, and the pressure that ozone stage is in 50 ℃ and 6 kilograms or 4 kilograms down and contain the manganese of different amounts.

Fig. 5 represents that according to the present invention pressurization (PO) stage is at (QZ) the bleaching sequence after the stage and the brightness (%ISO) and the relation curve between the reaction time of the contrast sequence under 90 ℃ of atmospheric pressure.

Fig. 6 represents according to the present invention bleaching sequence and the brightness (%ISO) of the contrast sequence under 90 ℃ of atmospheric pressure and the relation curve between the viscosity (cubic decimeter/kilogram) among Fig. 5.

Fig. 7 represents according to the present invention bleaching sequence among Fig. 5 and brightness (%ISO) and the H in the contrast sequence under 90 ℃ of atmospheric pressure ₂O ₂Total flow (the relation curve of kilogram/between ADMT).

Fig. 8 represents to comprise according to the present invention the bleaching sequence in (PO) stage of pressurization and the brightness (%ISO) and the relation curve between the reaction time of the contrast sequence under 90 ℃ of atmospheric pressure.

Fig. 9 represents according to the present invention the relation curve between brightness (%ISO) viscosity (cubic decimeter/kilogram) of bleaching sequence in Fig. 8 and the contrast sequence under 90 ℃ of atmospheric pressure.

Figure 10 represents according to the present invention bleaching sequence in Fig. 8 and brightness (%ISO) and the H in the contrast sequence under 90 ℃ of atmospheric pressure ₂O ₂Wastage in bulk or weight (the relation curve of kilogram/between ADMT).

Figure 11 represents to include standard Q preliminary treatment or uses the brightness (%ISO) of the pretreated pressurization of DTPA (PO)-bleaching and the relation curve between the viscosity (cubic decimeter/kilogram) according to the present invention.This curve is represented the bleaching of cork.

Figure 12 represents to include standard Q preliminary treatment or uses the brightness (%ISO) of the pretreated pressurization of DTPA (PO)-bleaching and the relation curve between the viscosity (cubic decimeter/kilogram) according to the present invention.This curve is represented the bleaching of softwood kraft pulp.

Figure 13 represents that protective agent (as complexing agent) spends the brightness (%ISO) and the H of Q (the PO)-bleaching of lignin pulp to experiment ₂O ₂Wastage in bulk or weight (the curve of the influence of the kilogram/relation between ADMT) and the relation of viscosity (cubic decimeter/kilogram) and brightness (%ISO) thereof.

Figure 14 represents that protective agent (as complexing agent) spends the curve of the influence of the viscosity (cubic decimeter/kilogram) of Q (PO)-bleaching of lignin pulp and brightness (%ISO) relation to experiment.

Figure 15 represent pressurization (the PO)-bleaching of softwood pulp reaction time (hour) and the relation of brightness (%ISO) and the influence of pressure.

The O of oxygen delignification softwood pulp (pressurization P) bleaching

Since when autoclave when plastic bag on every side is full of water, heat transmission to the paper pulp turbid liquid has improved greatly, on the one hand for the influence of the difference that proves the paper pulp turbid liquid of bleaching with in bleaching cistern, directly contacting with the metal surface, on the other hand for the remote-effects of elevated temperature in the influence that proves working pressure and this procedure, the test below having carried out.

Kappa value is 12.1, denseness is 10%, viscosity is that 1020 cubic decimeters/kilogram paper pulp is under Q stage 70 ℃ temperature and original ph (H ₂SO ₄) be 4.7, final pH value equals to handle with EDTA under 5.0 the condition.The paper pulp of handling in this way will be 10% in denseness then, last 240 minutes and under 90 ℃ temperature through an EOP stage.This stage is at a, b, the normal pressure on c hurdle and 5.0 * 10 ⁵Carry out under normal pressure (oxygen atmospheric pressure) condition of handkerchief (5 crust).The results are shown in following table.

Table I

A b c d e f denseness, % 10 temperature, ℃ 90 times; Minute 240 average pressures, 10 ⁵Handkerchief ^{* * * * * * * * *}(excessive) 00055 5MgSO ₄, kilogram/BDMT 33333 3H ₂O ₂, kilogram/BDMT 35 35 35 35 35 35NaOH, kilogram/BDMT 25 25 25 25 25 25H ₂O ₂Consumption, 33.0 26.4 25.7 33.3 23.7 25.3 kilograms/BDMT final pH, 11.2 10.9 10.9 11.1 10.8 10.8 kappa values, 4.8 4.7 4.6 4.5 4.3 4.2 viscosity, 746 849 828 802 838 837 brightness of cubic decimeter/kilogram, %ISO 77.9 78.5 79.7 79.7 80.7 81.6 used amount of peroxides, kilogram/ADMT 33 33 33 33 33 33 peroxide consumption amounts, kilogram/ADMT 31 25 24 31 22 24 ^*In autoclave, directly contact with metal ^*Be sealed in and add autoclave in the plastic packets ^{* *}Be sealed in to join in the plastic packets and be equipped with in the autoclave of water to improving heat transmission

Not contacting between paper pulp turbid liquid and metal surface as can be seen from Table I directly influences H ₂O ₂The consumption and the latter also be subjected to influence to the supply of the heat of paper pulp turbid liquid, this point can be found out from the comparison between b hurdle and c hurdle.

Brightness has been improved two units and provided better choice and kappa value is descended from the application of the clearly visible oxygen pressure of Table I (5 crust), this point can be found out by relatively going up in the table c hurdle and f hurdle.

Raise 10 ℃ from 90 ℃ to the 100 ℃ slurry that approximately can make same amount of temperature is reached the identical required reaction time of final brightness and reduces by half.To with top test in the further test of identical paper pulp shown this point.In this case, all tests all use 5.0 * 10 ⁵The oxygen pressure of handkerchief (5 crust) carries out.In test parameters and the outcome record Table II below.Can prove Temperature Influence by f and the e among the II among the contrast I.

Table II

A b c d e f denseness, % 10 temperature, ℃ 100 times, minute 60 120 180 60 120 180 average pressures, 10 ⁵Handkerchief (excessive) 55555 5MgSO ₄, kilogram/BDMT 33333 3H ₂O ₂, kilogram/BDMT 25 25 25 35 35 35NaOH, kilogram/BDMT 24 24 24 25 25 25H ₂O ₂Consumption, 12.2 16.0 19.1 16.4 21.4 26.0 kilograms/BDMT final pH, 10.8 10.6 10.4 10.7 10.5 10.4 kappa values, 5.3 4.6 4.2 5.0 4.3 4.0 viscosity, 906 829 803 896 827 790 brightness of cubic decimeter/kilogram, % 73.8 79.6 81.4 76.9 81.3 83.1 used amount of peroxides, kilogram/ADMT 23 23 23 33 33 33 peroxide consumption amounts, kilogram/ADMT 11 15 18 15 20 24

Can find out also that from top Table II consumption with peroxide is reduced to 25 kilograms of ptp (2/3) from 35 and makes the desired reaction time of the brightness that reaches 81.4ISO be increased to 3 hours from 2 hours, promptly can save the consumption of peroxide by prolonging the reaction time.

E and c's is reduced to 25 kilograms of ptp (to 2/3) with the consumption of peroxide from 35 more as can be seen and makes the essential reaction time of brightness that reaches 81.4ISO be increased to 3 hours from 2 hours from Table II.

Contrast test under the different temperatures:

Table III

A b c d e denseness, % 10 temperature, ℃ 90 90 100 100 110 times, minute 240 average pressures, 10 ⁵Handkerchief (excessive) 0505 5MgSO ₄, kilogram/BDMT 3333 3H ₂O ₂, kilogram/BDMT 35 35 35 35 35NaOH, kilogram/BDMT 30 30 30 30 30H ₂O ₂Consumption, 33.0 31.1 34.8 34.9 34.9 kilograms/BDMT final pH, 11.4 11.3 11.1 11.3 10.0 kappa values, 4.6 4.4 4.4 3.5 3.9 viscosity, 707 733 660 685 675 brightness of cubic decimeter/kilogram, %ISO 77.4 81.4 76.4 80.6 80.8 used peroxide are put kilogram/ADMT 33 33 33 33 33 peroxide consumption amounts, and kilogram/ADMT 31 29 32 32 32

-in autoclave, directly contact with metal

The influence of-attention oxygen pressure

In addition, in order to prove that temperature combines the importance of generation at 0-10 with oxygen pressure ⁶Under the oxygen pressure of handkerchief (0-10 crust) identical paper pulp has been carried out further test.

From 110 ℃, 5.0 * 10 especially as can be seen of curve maps shown in Figure 1 ⁵The required reaction time is compared the essential reaction time was reduced to 1 hour from 4 hours when the Q under the condition of handkerchief (5 crust) (pressurization P)-sequence and condition of normal pressure and 90 ℃.In addition, essential peroxide consumption has reduced 25% and has promptly reduced to 18 kilograms of ptp.

Especially as can be seen merely use oxygen pressure to make brightness from～80 to～82 increase by 2 grades from curve map shown in Figure 2 at 90 ℃.

Find now, in case in the paper pulp descend P stage of might specially pressurizeing of peroxide content be divided into two stages, the first of this method takes place under for example atmospheric pressure and lower temperature 80-90 ℃ condition.And second portion takes place under the condition of 110-120 ℃ of use oxygen pressure.

The weight that Q before peroxide stage handles is known.If ozone combines with pressurization in the P stage, can use simple two sequence of stages to produce marketable paper pulp with full brightness (88-90ISO) and good strength character.Fig. 3 has set up the relation of hydrogen peroxide total flow and brightness (%ISO), and Fig. 4 has set up the relation of viscosity and brightness (%ISO).In these curve maps, can clearly be seen that the correlation between many not homotactic Mn content, brightness and peroxide consumption or the viscosity.This point can clearly find out from order ZQ, is that the Q stage that adds alkali (pH is 5-6) and do not insert flushing must be welcome concerning producing low manganese content and good result after the ozone sequence.

The weight of having found the existence of manganese is very crucial to peroxide consumption and pulp viscosity.Adding a gram manganese in the every BDMT paper pulp of our evidence makes peroxide consumption 2 kilograms/BDMT of increase and makes the SCAN viscosity (cubic decimeter/kilogram) of 10 to 20 units of pulp quality reduction must surpass 95%, preferred 99% in order to reach these low manganese content flushing degree.Preferably use one or more in the production line or be used in combination KAMYR Atmospheric Diffusion device, KAMYR pressurization diffuser or KAMYR washing press in bleaching.

Pressurization (PO) stage is compared with the routine techniques under the atmospheric pressure after the stage at (ZQ) had tangible advantage, from the curve map of Fig. 5, can observe the reaction time minimizing, the visible method of using peroxide and ozone pressurization to bleach has caused the obvious reduction of viscosity loss from the curve map of Fig. 6, promptly compare pulp viscosity and the higher brightness that has reached higher with reference test, and the curve map of Fig. 7 has proved that in order to reach the brightness of 88-89%ISO of the present invention, the consumption of comparing peroxide with the reference test that under atmospheric pressure carries out reduces by half.

Also contrast test (seeing Fig. 8,9 and 10) has been carried out in the bleaching under the bleaching of 105 ℃ pressurization-(PO) and 90 ℃ of paper pulp of the same race and atmospheric pressure with regard to oxygen delignification eucalyptus globule (Euc.globulus), bardwood pulp.Having kappa value and be 7.2 paper pulp will be 33 kilograms/ptp through the addition of an above-mentioned Q stage and peroxide.

Also carried out contrast test (seeing Figure 11) to show respectively with standard Q preliminary treatment and the DTPA preliminary treatment of influence use to(for) the viscosity of two kinds of different softwood pulp of pressurization (PO) stage bleaching.Can notice when identical viscosities respectively through reaching identical brightness in 3,4 hours.

Also carried out contrast test (seeing Figure 12) to show relation and the H of different (PO) stage combinations to (PO) stage viscosity and brightness ₂O ₂The influence of the relation of consumption and brightness.In first curve map, can notice and only add MgSO ₄Compare, add the consumption that DTPA has reduced peroxide.

Curve also represents to have used MgSO ₄In order to improve pulp quality, use Mg and Ca separately or in combination for known to the people who is skilled in technique.

Can notice in the curve below use as above be combined in identical brightness the time to the favourable influence of viscosity.

Also carried out contrast test (seeing Figure 13), the reaction time of pressurization (the PO)-bleaching of this test expression softwood pulp (hour) and brightness (%ISO) between relation and the influence of pressure.Yet, be surprisingly found out that and use identical condition 5.0 * 10 ⁵Handkerchief (5 crust) can reach ISO 79, and 10 ⁶Handkerchief (10 crust) reaches ISO 85.This also can express with following mode, and promptly ISO 84 is 10 ⁶During handkerchief (10 crust) about 1 hour and 5.0 * 10 ⁵During handkerchief (5 crust) about 5 hours.This can also followingly express, and the paper pulp that is obtained has similar characteristic with regard to intensity.

The utilization of the higher degree of the peroxide that the objective of the invention is to reach used and reach the high brightness of product simultaneously.Find that as us this point can be realized by many measures respectively.

The present invention is not limited to top described, but described feature can organically combine within the scope of the appended claims.

Claims (18)

1. the chlorine-free bleaching method of the chemical pulp that combines with its production, wherein the paper pulp turbid liquid preferably has the fibrous material that denseness surpasses 8% cellulose, the paper pulp of bleaching production line preferably continues to add by at least one bleaching cistern in the bleaching production line, with at least a acid for adjusting pH to being lower than 7 and use a kind of chelating agent to handle, and then the another kind of peroxide with hydrogen peroxide or a great deal of surpasses 75%ISO at least one stage bleaching to brightness, preferably surpass 80%, addition surpasses 5 kilograms/BDMT, the method is characterized in that raise surpass 100 ℃ of temperature and in bleaching cistern every pressure all surpass the vapour pressure of liquid in the turbid liquid and base pressure above 5.0 * 10 ⁵Realize peroxide bleaching under the condition of handkerchief (5 crust), and be that the metal surface area that is exposed to bleaching cistern inside is less than 4V square metre, V represents a cubic metre volume here.

2. according to the method for Patent right requirement 1, it is characterized in that the pressure at bleaching cistern top surpasses 10 ⁵Handkerchief (1 crust), preferred 1.2 * 10 ⁵Handkerchief (1.2 crust) and more preferably 1.5 * 10 ⁵Handkerchief (1.5 crust).

3. the method for any one that requires according to aforesaid right is characterized in that the oxygen addition is less than 5 kilograms/BDMT in the bleaching process, preferably is less than 3 kilograms/BDMT and more preferably less than 1 kilogram/BDMT.

4. the method for any one that requires according to aforesaid right is characterized in that in the bleaching process that temperature surpasses 100 ℃ and more preferably between 100 ℃-105 ℃.

5. the method for any one that requires according to aforesaid right, the consumption that it is characterized in that peroxide surpasses 10 kilograms/BDMT but is less than 35 kilograms/BDMT (to reach the brightness above 85ISO).

6. require the method for any one according to aforesaid right, it is characterized in that pressure surpasses 3.0 * 10 ⁵Handkerchief (3 crust) is preferably in 0.5-1.5 * 10 ⁶Between the handkerchief (5-15 crust) and more preferably in 0.5-1.5 * 10 ⁶Between the handkerchief (5-10 crust).

7. require the method for any one according to aforesaid right, it is characterized in that not allowing in the bleaching process paper pulp turbid liquid to have too on a large scale with the metal surface and contact, preferably the inner surface of bleaching cistern is made with some polymeric material or ceramic material at least.

8. require the method for any one according to aforesaid right, it is characterized in that Z stage or peracetic acid stage are less than 20 kilograms/BDMT at Q before the stage and by brightness and the peroxide consumption amount of using so two stage method to obtain to surpass 85 ISO.

9. according to the method for claim 7, it is characterized in that not washing between the ZQ, and the preferred A stage is at Z before the stage.

10. according to the method for claim 3, it is characterized in that bleaching stage temperature finally be elevated to desired level carry out spontaneous bleaching before, be lower than under 90 ℃ the temperature and before being mixed into peroxide and at first in paper pulp, adding pH value elevating agents.

11., it is characterized in that bleaching stage original ph rising when the paper pulp turbid liquid adds pH value elevating agents is different from 11.5, preferably rises to a value between the 10-11 according to the method for claim 9.

12. require any one method according to aforesaid right, it is characterized in that the peroxide bleaching stage has at least a kind of complexing agent to participate in, this complexing agent preferably adds in the turbid liquid together with peroxide.

13. require any one method according to aforesaid right, it is characterized in that having at least in the complexing agent a kind of be basically ability up to 11 pH value, the preferred DT-PA of this complexing agent.

14. require any one method according to aforesaid right, it is characterized in that the preferred 1-2 kilogram of the addition DTPA/ADMT of DTPA.

15. require any one method according to aforesaid right, it is characterized in that by using centrifugal pump, being that so-called MC pump obtains normal pressure in bleaching cistern.

16. require any one method according to aforesaid right, it is characterized in that in bleaching cistern, not having carrying out peroxide bleaching with the method for hydraulic pressure under the condition that gas phase exists.

17. require any one method according to aforesaid right, it is characterized in that the bleaching cistern diameter surpasses 3 meters, preferred 5 meters and more preferably 7 meters.

18. require the method for any one according to aforesaid right, it is characterized in that the paper pulp manganese content that is used for peroxide stage is less than 5 gram/BDMT paper pulp, preferably be less than 1 gram/BDMT paper pulp and more preferably less than 0.5 gram/BDMT paper pulp, its content is identical with content in the final bleached paper pulp basically.

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