The method of bleaching pulp lignocellulosics

 

(57) Abstract:

Usage: when whitening lignocellulose pulp. The inventive slurry process complexing agent at a pH of 3.5 to 11.0 and a temperature of 26 - 100oC. Delignification organic percolate or its salts at a temperature of 50 to 140oC and the consumption of organic percolate in relation to the total number of percolate and hydrogen peroxide added at stages of delignification and bleaching, less than 60% by weight of dry pulp. Washed at a pH of at least about 4.0. Then the pulp is bleached. 9 C.p. f-crystals, 9 PL.

The invention relates to the pulp & paper industry, and specifically, to a method of bleaching lignocellulosic pulp.

For a long time for bleaching wood mass used bleach, chlorine-free. In subsequent years, it has become largely accepted to use bleach that does not contain chlorine, such as hydrogen peroxide and ozone for pulp bleaching, even in the initial stages. To avoid degradation of the pulp and excessive consumption of bleach, consider it necessary to pre-process the pulp crazii includes, mainly, treatment with an acid and processing complexing agent or salts of alkaline earth metals, possibly in combination. In the pre-treatment in a strong acid is removed ions desirable and undesirable ions of metals from the original pulp. In the pre-treatment with a suitable complexing agent is removed, mainly ions of undesirable metals, while ions of the desired metals retain or re-enter.

Know the use of peroxomonosulfate acid before treatment with oxygen and/or peroxide [1] the Slurry can be pushed on the stages of the process, when remove organic impurities and impurities of heavy metals. In the examples the pulp thus treated in the presence of DTRA (diethylenetriaminepentaacetic acid) at a pH of 2.0 before processing peroxometallic acid and oxygen. Such flushing acidic solution removes those metal ions, mainly alkaline earth metals, which are necessary for effective subsequent peroxide-based whitening compounds or ozone.

There is also known a method of improving the effect of the Penta at a pH of 3.1 9 and a temperature of 26 100oC. as a peroxide-based compounds using hydrogen peroxide and a mixture thereof with oxygen.

The objective of this method is to obtain the slurry for the initial alkaline peroxide treatment.

The known method, when the pulp is treated sequentially in two stages, the first stage add peroxomonosulfate acid, i.e. an acid Caro (inorganic acid containing sulfur) [3] Upon treatment with acid Caro may contain complexing agent. In the second stage, the pulp is bleached with hydrogen peroxide. When percolate present along with a complexing agent, i.e., on the same stage of processing, the influence of the complexing agent is greatly reduced due to the decomposition of complexing agents in the presence of percolat. With increasing requirements for environmental protection there is an increasing need for such methods designerware and bleaching lignocellulosic pulp, which was completely absent chlorine. To produce fully bleached pulps with the same characteristics concentration with a moderate number of stages and with a moderate consumption of bleach, you must t the high delignification and/or whitening ability.

The closest analogue is the way of whitening lignocellulosic pulp with hydrogen peroxide, comprising processing the slurry complexing agent, the delignification inorganic percolate or its salts and washing of the pulp prior to bleaching [4]

The objective of the invention is to improve the quality of the pulp by improving its whiteness.

This task is solved in that in the method of bleaching lignocellulosic pulp with hydrogen peroxide, comprising processing the slurry complexing agent, the delignification and rinse the pulp prior to bleaching, according to the invention, when processing a complexing agent to maintain pH 3.5 to 11.0 and a temperature of 26 - 100oC, the delignification conduct organic percolate or its salts at a temperature of 50 140oC and the consumption of organic percolate in relation to the total number of percolate and hydrogen peroxide added at stages of delignification and bleaching, less than 60% by weight of dry pulp, and the washing of the pulp prior to bleaching is carried out at a pH of at least about 4.0.

This washing is carried out after processing complexing agent and before delignifying pulp.

Percolate is peracetic acid.

Bleaching with hydrogen peroxide is carried out in the presence of oxygen.

The complexing agent is an organic compound that contains nitrogen.

The pulp delignification at a temperature in the range of 50 120oC, preferably 50 to 80oC.

The number added during the processing of the pulp complexing agent is 0.1 to 1.8 kg per ton of dry pulp, calculated on 100% of the complexing agent.

Processing complexing agent is preceded by an oxygen treatment.

Delignification peracetic acid is carried out at a pH in the range of 5.5 to 9.

The proposed method includes whitening lignocellulose pulp peroxide-based compound, ozone or dithionite sodium, in which the pulp before bleaching first sequentially treated with complexing agent at a pH in the range of 3.5 to 11 and at a temperature in the range of 26 - 100oC and then designerour organic acid or its salts at a temperature in the range from 50 to 140oC, while the pulp before bleaching washed at a pH at least equal to about 4.

Receives the pulp after treatment complexing agent without adverse effects on the environment optimized by processing complexing agent for subsequent bleaching without chlorine. It is known that ions of alkaline earth metals, especially when they are in the original pulp, have a beneficial effect on the selectivity at bleaching and consumption of bleach, chlorine-free, for example, peroxide-based compounds and ozone.

The invention is percolate or a salt thereof include organic percolate or their salts. As organic percolate use aliphatic percolate, aromatic percolate or their salts. Suitable for use is peracetic acid or paranavitana acid. As the cation of the salt is eligible to use the sodium, because such salts are typically inexpensive and sodium naturally occurs in the chemical balance of the pulp mill. Preferred are peracetic acid or its salts, when they are advantageous from the point of view of production and use. In addition, peracetic acid is an organic corrosion activity. Incidentally, peracetic acid has limited corrosion activity. By the way, any wastewater containing products again what about the extract.

In accordance with this method peracetic acid can be obtained by reacting acetic acid and hydrogen peroxide, which gives, as is known, the equilibrium peracetic acid, by distillation equilibrium peracetic acid for the removal of hydrogen peroxide, acetic acid and sulfuric acid, or by reacting the anhydride of acetic acid and hydrogen peroxide directly on the stage of bleaching, which results known to the receiving of peracetic acid in situ.

Typical equilibrium peracetic acid contains about 42% peracetic acid and about 6% of hydrogen peroxide, i.e., the weight ratio of peracetic acid to hydrogen peroxide is about 7 to 1. When this method is used equilibrium peracetic acid, the weight ratio between peracetic acid and hydrogen peroxide may be in the range from 10:1 to 1:60, suitably from 7:1 to 1:15 and preferably from 2.8:1 to 1:2.

Added the number of percolate or her salt should be in the range of 1 to 100 kg per ton of dry pulp, calculated on 100% percolate or its salt. Fit is a number in the range 2 to 45 kg per ton of dry pulp, preferably in the range of 3 to 25 kg per tonne Shoji percolate or its salts at a pH in the range of 2.5 to 12.0. In preferred embodiments, when the delignification spend peracetic acid, pH suitably is in the range of 3 to 11, preferably in the range of 5.6 9. The delignification other percolate or their salts mentioned above, carried out within the pH ranges common to the respective brighteners, which are well known to specialists in this field.

Incidentally, in the pulp manganese ions have a particularly adverse effect on whitening bleach that does not contain chlorine, for example, alkaline peroxide compounds or ozone. Thus, as complexing agents are used, primarily, the compounds that form stable complexes with various manganese ions. Such suitable complexing agents are organic nitrogen compounds, mainly nitrogen-containing polycarboxylic acids containing nitrogen polyphosphonate acids and polyhydric alcohols containing nitrogen. Preferred nitrogen-containing polycarboxylic acids, are diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), with particularly preferred avseries nitrogen. As complexing agents can also be used in other connections, for example, polycarboxylic acids, are suitable oxalic acid, citric acid or tartaric acid, or phosphonic acid. Incidentally, in addition, as complexing agents can also be used such organic acids that are formed during processing of the pulp bleach, chlorine-free.

When processing complexing agents and remove traces of unwanted metals and saving at the same time desirable ions, alkaline earth metal is critical pH. A suitable pH range depends, among other things, on the type and number of traces of metal ions in the incoming pulp. However, in the proposed method the processing of complexing agent should be carried out at a pH in the range of 3.5 to 11, are eligible 3.5 to 10, preferably 4.5 to 9, particularly preferred is a pH in the range 5 to 7.

To remove traces of unwanted ions of metals important temperature processing complexing agent. With increasing temperature processing complexing agent, which gives an increase in the degree of whiteness of ituru increase from the 20oC to 90oC, the viscosity also increases significantly. Processing complexing agent is carried out at a temperature of 26 120oC, suitably 26 100oC, preferably 55 to 90oC.

The added amount of complexing agent depends on the type and number of traces of metal ions in the incoming pulp. This number also depends on the type of agent used, and the treatment conditions complexing agent, for example, temperature, time and pH. However, the added amount of complexing agent should be in the range of 0.1 to 10 kg per ton of dry pulp, calculated on 100% of the complexing agent. Suitably, this number is in the range of 0.3 to 5 kg per ton of dry pulp, and preferably in the range of 0.5 to 1.8 kg per ton of dry pulp, calculated on 100% of the complexing agent.

In preferred embodiments, when the delignification by percolate and processing complexing agent is carried out at pH values close to neutral, the need to regulate the pH is reduced to a minimum. As a result, for washing can also be used the spent liquors from the stages of bleaching and processing. This gives a small total volume of silent hill 2">

Whitening peroxide-based compound, ozone or dithionite sodium can be done in a possible sequence or together. Peroxide-based compound comprises an inorganic peroxide compounds such as hydrogen peroxide or peroxometallic acid (acid Caro). Preferably peroxide-based compound is hydrogen peroxide or a mixture of hydrogen peroxide and oxygen.

When the bleach use hydrogen peroxide, the pulp can be processed at a pH of 7 to 13, suitably at a pH of 8 to 12, and preferably at a pH of 9.5 to 11.5. The other whitening bleach, mentioned above, occurs in the ranges of pH, normal for the relevant substances that are well known to specialists in this field.

The claimed method can also include stage bleaching peroxide-based compound or ozone before delignification by percolate or its salts. The claimed process is carried out with the stage of washing before bleaching peroxide-based compound, ozone or dithionite sodium, while the washing is carried out at a pH of at least about 4. Washing effectively removes traces of complex ions of metals that have neblagopriyatnym way ions of manganese, but also, for example, copper ions and iron. Since the pH value at the stage of washing is at least about 4, ions, alkaline earth metal, mainly ions of magnesium and calcium, which have a beneficial effect on the subsequent bleaching reagent that does not contain chlorine, are retained in the pulp. the pH at the stage of washing suitably is in the range of 5 to 11, preferably in the range of 6 to 10.

Washing before bleaching peroxide-based compound, ozone or dithionite sodium suitably carried out after processing complexing agent and before the delignification percolate or its salts.

In this way effectively remove traces of complex metal ions, while the remaining acid or peroxide-based compound, if necessary, can be used at a later stage of bleaching. When rinsing should be particularly effective, can be a stage of rinsing after treatment complexing agent, and after delignification with percolate or its salts.

Wash liquid may be fresh water, possibly with the addition of a chemical reagent that regulates pH or waste water from one or several of the Sabbath. more precisely, the flushing fluid may consist of other species, treated wastewater, provided that it has a negligible content of undesirable ions of metals such as manganese, iron and copper.

Flushing relates to methods of substitution, more or less complete, the waste liquid suspension of pulp to reduce the content of dissolved trace metal ions. Ways of washing may lead to an increase in the concentration of the pulp, for example, by extraction or pressing, as well as reducing the concentration of the pulp, for example, by diluting the wash liquid. Rinsing also relates to combinations and sequences in which the concentration of the pulp alternately increases and decreases one or more times. In this way choose this method of washing which removes not only the dissolved organic matter, but also traces of metal ions released during the processing of the complexing reagent, while taking into account whether the method is suitable washing from the point of view of technology and economy.

The washing efficiency can be represented as the number of substituted liquid phase compared to the liquid phase, prisutstvie at each stage of leaching. Thus, dewatering the pulp suspension after processing stage from 10% to 25% concentration of the pulp gives the leaching efficiency of 66.7%

After a subsequent stage of leaching, in which the pulp is first diluted to 3% and then dewatered to 25% of the total washing efficiency reaches a 96.9% compared to soluble impurities. The washing efficiency in this way must be at least 75% of eligible in the range 92

100% Especially preferred is the leaching efficiency within 96 100%

By using the present invention, the conditions for bleaching without chlorine optimize in such a way that achieved a high degree of whiteness, reduce the Kappa number and viscosity increase using the minimum amount of bleach that does not contain chemicals, for example, stabilizers and protective equipment, when bleaching without chlorine.

The remaining bleaching chemicals, such as hydrogen peroxide and alkali, is used mainly directly on the stage of bleaching, percolate stage or another appropriate stage, in order to obtain the optimum combination of methods of technique and economy of production.

In the scope of the invention also includes and what is s, as listed above. This increase is suitably carried out with hydrogen peroxide or a mixture of hydrogen peroxide and oxygen.

Lignocellulosic pulp refers to pulp that contains fiber, which is separated by chemical or mechanical treatment, or secondary fiber. Fibers can be made of hard wood or soft wood. Pulp refers to pulp that is subjected to a sulphate cooking, sulphite cooking, soda cooking or cooking using organic solvent. Wood pulp refers to pulp obtained by treating wood chips in a disk refiner (refined wood pulp) or by grinding logs in the defibrator (shredded wood pulp). Lignocellulosic pulp also applies to the pulps obtained by modifications or combinations of the above processes or methods. These include pulp thermo-mechanical, chemical, mechanical or chemi-thermomechanical pulp.

Is suitable to lignocellulosic pulp consisted of chemically extracted pulp, preferably sulphate pulp. Particularly preferably, lignocellulosic pulp consisted of sulfate polyatom in the range of 30 to 80% and preferably in the range of 45 - 65%

The claimed method can be carried out, for example, immediately after receipt of the pulp. When the method is used to chemically boiled pulp, it is preferable delignification oxygen stage before processing complexing agent.

The claimed method can be applied to chemically boiled to a pulp with the initial Kappa number in the range of 2 to 100, suitably 5 to 60 and preferably 10 to 40. Then the Kappa number was measured according to the standard method SCAN-C1:77.

In the invented method, the processing of complexing agent should be carried out during the period of time from 1 min up to 960 min, suitably from 15 to 240 minutes and preferably from 35 to 120 minutes, the Concentration of the pulp during processing complexing agent may be from 1 mass% to 60% are eligible from 2.5% by mass to 40% by weight, preferably from 3.5 mass% to 25 mass%, and most preferably from 5.5 by weight to 25% by mass.

In the proposed method designerware percolate should be carried out at a temperature of 50 140oC and suitably 50 120oC. Preferably the pulp delignification at a temperature of 50 100oC, more preferably 50 to 90oC.

The temperature in diapam the period of time from 1 min up to 960 min, suitably from 10 min to 270 min, and preferably from 30 minutes to 150 minutes, the Concentration of the pulp when delegirovano percolate can be 1 to 70% by weight, suitably 3 to 50 by weight, preferably 8 to 35% by weight and most preferably 10 to 30 mass%.

When in use bleach or hydrogen peroxide to the slurry should be treated at a temperature of 30 to 140oC and adjusted 30 - 120oC. Preferably, the slurry is treated at a temperature of 30 100oC and more preferably 60 to 90oC and over a period of time from 5 min up to 960 min, suitably from 60 min to 420 min, preferably from 190 min to 360 min When the bleach use hydrogen peroxide, the concentration of the pulp can be 1 to 70% by weight, suitably 3 to 50% by weight, preferably 8 to 35% by weight and most preferably 10 to 30% by weight. Processing other bleaches, mentioned above, is carried out in common for respective agents ranges of temperature, time and concentration of the pulp, which are well known to specialists in this field.

In preferred embodiments, when in use bleach hydrogen peroxide, the amount of hydrogen peroxide added at the stage of bleaching, has normalized, and installed taking into account economic considerations. A suitable amount of hydrogen peroxide is in the range of 6 to 50 kg per ton of dry pulp, and preferably in the range of 13 to 40 kg per ton of dry pulp, calculated on 100% hydrogen peroxide.

In preferred embodiments, when in use bleach hydrogen peroxide, the share of percolate added at the stage of delignification stage and bleaching should be less than 60% by weight. The number of percolate re-calculated in terms of 100% hydrogen peroxide. With repeated recalculation of peracetic acid to hydrogen peroxide of 1 kg peracetic acid was equivalent to 0.45 kg of hydrogen peroxide.

In preferred embodiments, when the bleach used ozone, the amount of ozone may be in the range of 0.5 to 30 kg per ton of dry pulp, suitable 1 15 kg per ton of dry pulp, preferably 1.5 to 10 kg per ton of dry pulp, and most preferably 1.5 to 5 kg per ton of dry pulp.

After processing complexing agent, delignification by percolate and subsequent bleaching peroxide-based compound, ozone or dithionite sodium, the pulp can be used to directly on Isny in one or several stages. A suitable final bleaching is also realized by means of such brighteners, chlorine-free, listed above, possibly with intermediate stages of extraction, which can be enhanced by using peroxide and/or oxygen.

In this way eliminated the education and unloading Oh. Can also be used in the final bleaching chlorine bleach, for example, chlorine dioxide, and in addition, to get a very limited education and unloading Oh, since the content of lignin in the pulp is reduced considerably when implementing this method.

The invention and its advantages will be illustrated in more detail by the following examples, which are presented, however, with the intention to illustrate the invention but not to limit it.

Percentages and parts listed in the description, claims and examples, refer, respectively, to percent by weight and parts by weight unless specified otherwise. In addition, the pH values given in the description, claims and examples, refer to the pH at the end of each treatment, unless specified otherwise.

In the examples below, the Kappa number, viscosity and grade and hydrogen and peracetic acid were installed, respectively, by titration with sodium thiosulfate and potassium permanganate and sodium thiosulfate.

Example 1. Sulphate pulp of softwood lumber delignification oxygen and having a Kappa number of 16, whiteness 37,1% ISO and a viscosity of 1010 DM3/kg, were treated with EDTA (ethylenediaminetetraacetic acid) in accordance with the invention, designerware peracetic acid and bleached with hydrogen peroxide in order to illustrate the importance of pre-processing for properties of the pulp after the implementation of this method. The pulp was treated with 2 kg of EDTA per ton of dry pulp at a temperature of 90oC, treatment time 60 min, the concentration of the slurry of 10% by weight and at variable pH. The number of added peracetic acid amounted to 22.4 kg per ton of dry pulp, calculated on 100% of peracetic acid. When delegirovano peracetic acid pH was 5.5 to 5.9, temperature 70oC, the processing time of 60 min and the concentration of the slurry of 10% by weight. Then the pulp was bleached with hydrogen peroxide at a temperature of 90oC, the processing time of 240 min and the concentration of the slurry of 10% by weight. The addition of hydrogen peroxide was 25 kg per tonne of dry pulp, calculated on 100% hydrogen peroxide. pH 10.7 to 11.6. For and 6). For further comparison, the pulp is treated at a pH of about 2 in the absence of complexing agent (tests 7 and 8). After each stage the pulp was washed with deionized water at pH 6.0. The pulp is first obasogie to the concentration of the pulp 25% and then diluted to a concentration of pulp 3% by weight. After a few minutes the pulp of obasogie to the concentration of the pulp 25% by weight. The total washing efficiency was approximately 97% Results after bleaching with hydrogen peroxide is presented below in table.1.

From table. 1 shows that treatment of the pulp of soft wood complexing agent on a separate stage at elevated temperature and at a pH in the range of 3.5 11 leads to a significant decrease in Kappa number and a marked increase in the degree of whiteness, and high viscosity.

Example 2. Sulphate pulp of softwood lumber delegirovano oxygen used in example 1 was treated with EDTA, was designerware peracetic acid and bleached with hydrogen peroxide in order to illustrate the effect of leaching between the individual stages in the sequence. Conditions when processing complexing agent were as in example 1 except that the pH was equal to 5.7 (tested the ore 1. In test 1 the pulp is washed in accordance with example 1, after treatment with EDTA, and after designerware peracetic acid. For comparison, the pulp was treated with 2 kg of EDTA per ton of dry pulp at a pH of 7, a temperature of 25oC and the concentration of the pulp 8% by weight within 10 min (test 2). In test 2 the pulp of obasogie after processing complexing agent to the concentration of the pulp 25% by weight. In test 2, the flushing or dewatering after delignification peracetic acid are not available. The washing efficiency in test 1 was about 97% and in test 2, about 74%

Results after bleaching with hydrogen peroxide (H2O2) are presented in table. 2.

From table. 2 it follows that invented the processing of the pulp of soft wood complexing agent at a high temperature, followed by rinsing, gives a much greater reduction in Kappa number and a much larger increase in the degree of whiteness at low flow rates of hydrogen peroxide and essentially saved the concentration of the pulp than it does processing at room temperature, followed by dehydration.

Example 3. Sulphate pulp of softwood lumber delignification oxygen, is for to illustrate the effect of peracetic acid and separate stages in sequence in accordance with the invention. Conditions when processing complexing agent were as in example 1, except that added to 11.2 kg peracetic acid per ton of dry pulp.

Conditions whitening hydrogen peroxide were as in example 1. In test 1 the pulp was treated with EDTA, was delignification peracetic acid and bleached with hydrogen peroxide. In test 2 the pulp was delignification peracetic acid in the presence of EDTA, after which the pulp was bleached with hydrogen peroxide. When delignification in the presence of EDTA, in test 2 the pH was 5,1, temperature 90oC and the processing time is 1 o'clock In test 3 the pulp was treated with EDTA, after which it was delignification and bleached peracetic acid in the presence of hydrogen peroxide. When delignification and bleaching in test 3 temperature was 70oC when the processing time is 1 h, after which it was raised to 90oC and maintained for 4 hours at this pH was equal to 11.1. For comparison, the pulp was treated with EDTA and bleached with hydrogen peroxide (test 4). After each stage the pulp was washed in accordance with example 1. Results after otbelivanie, processed in accordance with the present invention in the individual stages, shows a significant decrease in the Kappa number and a significant increase in the degree of whiteness with a low consumption of hydrogen peroxide and essentially saved the concentration of the pulp.

Example 4. Sulphate pulp of softwood lumber delignification oxygen used in example 1 was treated with EDTA, was delignification peracetic acid and bleached with hydrogen peroxide in order to illustrate the effect of pH during leaching on the degree of whiteness of the pulp after the stage of bleaching. Conditions when processing complexing agent were as in example 1 except that the pH was 5,7. Conditions for delignification of peracetic acid were as in example 1 except that the pH was equal to 6.1. Conditions whitening hydrogen peroxide were as in example 1. After each stage the pulp is washed in accordance with example 1, except that the pH was changed when washing after handling complexing agent. Results after bleaching with hydrogen peroxide (H2O2) are presented in table.4.

From table. 4 it follows that the soft wood pulp treated in accordance with the present image is raisiny, delignification oxygen used in example 1 was treated with EDTA, was delignification peracetic acid and bleached with hydrogen peroxide in order to illustrate the influence of the weight ratio of peracetic acid and hydrogen peroxide in equilibrium peracetic acid and washing efficiency between delignification and bleaching.

Conditions when processing complexing agent were as in example 1 except that the pH was equal to 5.7. Conditions for delignification of peracetic acid were as in example 1 except that the pH was 5,2 6,3.

Conditions whitening hydrogen peroxide were as in example 1 except that the amount of added hydrogen peroxide was 30 kg per ton of dry pulp, calculated on 100% hydrogen peroxide. In tests 1-4 pulp was washed as in example 1, i.e., when washing efficiency of about 97% In test 5, the washing efficiency was about 67% In test 6 after delignification peracetic acid washing and dewatering was not. Results after bleaching with hydrogen peroxide (H2O2) are presented in table. 5.

From table.5 it follows that the processing of the pulp of soft wood with the acid, and after bleaching with hydrogen peroxide.

Example 6. Sulphate pulp of softwood lumber delignification oxygen, having a Kappa number, 16,5, whiteness 36,0% ISO and a viscosity of 1010 DM3/kg EDTA treated in accordance with the invention, delignification peracetic acid and bleached with hydrogen peroxide in order to illustrate the pH pre-treatment for the properties of the pulp after the implementation of this method.

Conditions when processing complexing agent were as in example 1 except that the pH was equal to 4,0 (test 1). Peracetic acid was equilibrium peracetic acid at a mass ratio of peracetic acid and hydrogen peroxide, is 4 1.

The number of added peracetic acid was 5 kg per ton of dry pulp, calculated on 100% of peracetic acid. Conditions when delegirovano peracetic acid were as in example 1 except that the addition of hydrogen peroxide was 35 kg per ton of dry pulp, calculated on 100% hydrogen peroxide and the pH was equal to 11.2 to 12.0. For comparison, the pulp was treated with 1 kg per ton of dry pulp under the conditions specified above, except that the pH was RA is under example 1. Results after bleaching with hydrogen peroxide is presented in the following table. 6.

From table.6 it follows that the processing of the pulp of soft wood complexing agent at a pH of at least 3,5 leads to the production of pulp with superior properties in comparison with the processing of complexing agent at a pH that is more acidic.

Example 7. Sulphate pulp of softwood lumber delignification oxygen used in example 6, was treated with EDTA, was delignification peracetic acid and bleached with hydrogen peroxide (tests 1 and 2) in order to illustrate the effect of processing time and temperature on the stage of delignification. Conditions when processing complexing agent were as in example 1 except that the pH was equal to 5.7. The number of added peracetic acid was 10 kg per ton of dry pulp, calculated on 100% of peracetic acid. When delignification peracetic acid pH was 6,0 6,5 temperature 110oC and the concentration of the slurry of 10% by weight, whereas the processing time was changed. Conditions whitening hydrogen peroxide were as in example 1 except that the pH was 11,0-11,1.

For comparison, the pulp delignification stage the pulp was washed in accordance with example 1. Results after delignification peracetic acid are presented in the following table.7.

From table.7 shows that the treatment of the pulp of soft wood peracetic acid at a temperature in the range from 50 to 140oC leads to the production of pulp with superior properties compared to processing at lower temperatures.

Example 8. Sulphate pulp of softwood lumber delignification oxygen, having a Kappa number, 10,3, whiteness of 41.7% ISO and a viscosity of 1000 DM3/kg, was treated with EDTA, was delignification two kinds of peracetic acid and bleached with hydrogen peroxide in order to illustrate the effect of peracetic acid of different compositions.

Conditions when processing complexing agent were as in example 1 except that the pH was equal to 5.5, and download EDTA amounted to 1.5 kg per ton of dry pulp.

However, peracetic acid represented equilibrium peracetic acid with the mass ratio of peracetic acid and hydrogen peroxide 4:1 (egeul), and the other subjected to distilled peracetic acid, essentially, not containing hydrogen peroxide and acetic acid (Dist). When both types of peracetic acid added number and peracetic acid were as in example 1, except that the pH was 6 to 7. Conditions whitening hydrogen peroxide were as in example 1 except that the addition of hydrogen peroxide was 35 kg per ton of dry pulp, calculated on 100% hydrogen peroxide, in tests 2 and 4 pH was equal to 11.5 and the temperature was equal to 110oC.

After each stage the pulp was washed in accordance with example 1. Results after bleaching with hydrogen peroxide is shown in table.8.

From table.8 it follows that the processing of the pulp of soft wood in accordance with the invention results after bleaching pulp with excellent properties in combination with a moderate consumption consistently used bleach.

Example 9. Sulphate pulp of softwood lumber delignification oxygen used in example 8, was treated with EDTA, was delignification peracetic acid and bleached with hydrogen peroxide in order to illustrate the influence of the total number of brighteners and their distribution between stages of delignification (stage 2) and bleaching (stage 3). Conditions when processing complexing agent were as in example 1 except that the pH was equal to 5.5, and download the EDTA costabissara, essentially, not containing hydrogen peroxide and acetic acid. The number of added peracetic acid was changed between 11 and 80 kg per ton of dry pulp, calculated on 100% of peracetic acid. Conditions for delignification of peracetic acid were as in example 1 except that the pH was approximately 6 and 7. The amount of added hydrogen peroxide was changed between 2 and 30 kg per ton of dry pulp, calculated on 100% hydrogen peroxide. Conditions for bleaching of hydrogen peroxide were as in example 1 except that the pH was equal to 11.5. The total amount of hydrogen peroxide was in trials 1-4 20 kg per ton of dry pulp, in trials 5-8 it was 40 kg per ton of dry pulp.

The share of peracetic acid (in recalculation on 100% hydrogen peroxide) at stage 2 is in the form of a percentage of the total number. After each stage the pulp was washed in accordance with example 1. Results after bleaching with hydrogen peroxide is presented below in table.9.

From table.9 it follows that after delignification and bleaching in accordance with the present invention receive the pulp with excellent properties.

1. The method of bleaching lignocellulosic pulp peroxide water is edusim bleaching, characterized in that the processing of the complexing agent to maintain pH 3.5 to 11.0 and a temperature of 26 100oWith, the delignification conduct organic percolate or its salts at a temperature of 50 140oWith and consumption of organic percolate in relation to the total number of percolate and hydrogen peroxide added at stages of delignification and bleaching, less than 60% by weight of dry pulp, and the washing of the pulp prior to bleaching is carried out at a pH of at least 4.

2. The method according to p. 1, characterized in that the washing is carried out after processing complexing agent and before the delignification percolate or its salts.

3. The method according to p. 1, characterized in that lignocellulosic pulp is a chemical boiled pulp.

4. The method according to p. 1, characterized in that percolate is a peracetic acid.

5. The method according to p. 1, characterized in that the bleaching with hydrogen peroxide is carried out in the presence of oxygen.

6. The method according to p. 1, characterized in that the complexing agent is an organic compound that contains nitrogen.

7. The method according to p. 1, characterized in that the pulp delignification the number added during the processing of the pulp complexing agent is 0.1 to 1.8 kg per 1 ton of dry pulp, calculated on 100% complexing agent.

9. The method according to p. 1, characterized in that the processing of the complexing agent is preceded by an oxygen treatment.

10. The method according to p. 1, characterized in that delignification peracetic acid is carried out at a pH of 5.5 to 9.

Priority points:

26.01.96 under item 1;

27.11.92 on PP. 2 6, 8 10;

26.05.95 under item 7.

 

Same patents:

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The invention relates to a method and apparatus of the ozone bleaching of paper pulp and device for its implementation

The invention relates to the pulp and paper industry, and is intended for the bleaching of sulphate pulp

The invention relates to the field of chemical processes of cooking and, in particular, to method pulping (for example, for the manufacture of paper products), in which the fibrous material is cooked at elevated temperature and pressure in the presence of chemical reagents, and then treated in a digester to separate the fibers from the binders present in the material, and for bleaching cellulose pulp

The invention relates to the pulp and paper industry

The invention relates to the pulp and paper industry, in particular to a method of bleaching cellulosic staple fiber without the use of chlorine with ozone according to the three-step method consisting of bleaching with oxygen in the presence of hydrogen peroxide (EOR-step), bleaching with ozone (Z-stage) and peroxide bleaching (P-step)

The invention relates to methods of producing bleached pulp of different purposes and can find application in the pulp and paper industry

The invention relates to the field of pulp and paper production and is intended for use in the production of bleached pulp

FIELD: cellulose production.

SUBSTANCE: invention relates to manufacture of cellulose from cotton lint after alkali pulping or from prehydrolyzed wood cellulose and can be utilized in paper-and-pulp industry or in manufacture of artificial fibers, films, and other cellulose materials. Pulped cotton lint or prehydrolyzed wood cellulose is bleached by sodium hypochlorite at modulus 1:20 to 1:30 and 20-30°C, washed, treated for 50-60 min with 1.0-1.5% sodium hydroxide solution at 80-90°C, and subjected to souring, after which desired product is recovered. More specifically, cotton lint after alkali pulping is bleached in two steps separated by washing. In the first step, bleaching is carried out for 0.5-2.0 h at active chlorine concentration 0.3-2.0 g/L and, in the seconds step, for 0.5-6.0 h with 1.0-6.0 g/L active chlorine concentration. Prehydrolyzed wood cellulose is leached in one step for 0.5-6.0 h with 0.3-6.0 g/L active chlorine concentration.

EFFECT: improved quality of product, reduced average degree of polymerization, and increased reactivity thereof.

2 tbl, 18 ex

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