Method of bleaching cellulose and other cellulosic and lignocellulosic fibrous materials and three-stage method of bleaching cellulosic and lignocellulosic materials

 

(57) Abstract:

The invention relates to the bleaching of cellulosic and lignocellulosic materials using hydrogen peroxide as a bleaching agent. The method includes short-term high-temperature phase at a pressure sufficient to prevent boiling, and a longer phase at atmospheric pressure and low temperature in order to have a reaction with a substantial part of the hydrogen peroxide remaining after a short phase. The method includes the following operations. Cellulose is injected at a concentration of 10 - 18% in the mixer, where it is heated to temperatures above 100oC, add sufficient sodium hydroxide to bring the pH of the pulp to 8.5. Then add a sufficient quantity of hydrogen peroxide, from about 0.5 to 5.0 percent by weight of cellulose, pass the pulp through the reaction column at a speed that provides the reaction time is in the specified column from 1 to 30 minutes Cellulose incubated in the reaction column at atmospheric pressure for reaction for 1 to 5 h until, until you spent a significant portion of the residual hydrogen peroxide. Perhaps predpochtitelney pH at least up to 9 between stages of bleaching. The technical result is the efficiency of pulp bleaching and reducing capital investment for a normal production capacity. 2 C. and 14 C.p. f-crystals, 9 Il., 7 table.

The invention relates to the bleaching of lignocellulosic material in the pulp and paper industry and, in particular, to a method of improving the performance characteristics of the pulp bleaching process using hydrogen peroxide. The process is particularly effective when used in combination with the sequence of operations developed for the production of pulp, bleach without the use of chlorine-containing compounds.

The need for removal of chlorine-containing compounds in bleaching pulp and reduce their negative impact on the environment has led to the formulation of the so-called "chlorine-free technologies. In the case of chlorine-containing compounds are excluded from the bleaching process, as a replacement for typically use hydrogen peroxide because it is believed that hydrogen peroxide does not have any harmful impact on the environment. Therefore, due to increased use of hydrogen peroxide, there is a need to develop more effectiveid hydrogen is a chemical bleaching agent, widely used in the bleaching of pulp obtained by mechanical, polymechanics, polychemicals ways, and return the pulp. It is also used in chemical pulp bleaching together with anyway.

Canadian Institute Pulp & Paper Research Institute of Canada (PAPRICAN) developed several new methods of bleaching wood pulp. Of particular interest is the high temperature peroxide system detected Lierbergott, as it allows to achieve the same brightness as traditional system of bleaching pulp of high density, but at medium density (10-14%). This is achieved by increasing the temperature of the pulp to about 85oC and decreasing pH, which is a contrast to conventional peroxide bleaching systems at high density. With faster reaction time in the reactor is reduced from hours to minutes (15-30 minutes), it does not require the use of silicate to stabilize the peroxide solution. The consumption of peroxide remains approximately the same as in conventional systems.

High temperature peroxide system, proposed in the application Bottan,G, operates at a temperature of 85-95oC within a very short period of time. Sinai and short residence time in the reactor at more than 100oC. it is Desirable to minimize the residence time of the pulp to reduce capital expenditures while maintaining the same brightness, which can be achieved with a large time consuming process.

Reactivation of residual peroxide was proposed Dominique Lachenal from the Centre Technique du Papier, Grenoble, France in bleaching wood pulp. This allows you to reactivate an unused (or residual) peroxide (after the first reaction column) by increasing the alkalinity of the pulp suspension. The problem is to eliminate expensive equipment for dehydration, usually used after bleaching columns to extract residual peroxide and return it to its place adding fresh peroxide (usually in the mixer in front of the column bleaching). This offer is great value compared with traditional two-stage peroxide whitening system, which requires the use of expensive equipment for dewatering between stages. In the first stage, the operation proceeds in a few hours in a regular column at 60oC before reactivation of residual peroxide. Then add caustic in proportion to the residual peroxide is wlosy, first of hydrogen peroxide used in systems of medium density, in which the pulp suspension from the previous stage obezvozhivani in the thickener or the washing apparatus to the content of 10-14%. The peroxide solution is usually added together with the alkali in re crusher (exit thickener or washing machine) or in front of the column average density in cellulose medium density or mixer.

When used as a separate stage for pulp bleaching traditional stage bleaching with hydrogen peroxide pulp medium density does not provide a sufficient increase whiteness and require more consumption of peroxide and an extremely long period of stay for just spending peroxide. To achieve more substantial delignification or white processing peroxide should be carried out in multiple columns.

Using the stages of bleaching peroxide at a density of more than 25% showed that it is possible to overcome many limitations of conventional technology using a peroxide bleaching of cellulose medium density. However, this method also has a drawback, which is that it requires installation of the equipment DL is consumed more energy than the system average density.

In the processing of cellulose is widely used acceleration stages oxidative extraction with the use of peroxide in addition to oxygen to reduce the amount of chlorine required in the first stage of pulp bleaching. In the traditional EIA process (oxidative extraction, enhanced peroxide) typically use countercurrent columns, requiring the use of oxygen gas and operating at 65-85oC.

Hydrogen peroxide is also used in the final stages of pulp bleaching to achieve high and stable white bleached pulp. The use of hydrogen peroxide for the bleaching of pulp temperatures are usually limited to less than 90oC, because it was believed that the peroxide will decompose, leading to inefficient use of a bleaching agent, reduced the strength of the pulp and economic disadvantage of the process.

Recently, the use of peroxide at high temperature and relatively long residence time was proposed as a means to obtain a cellulose ultra white when used at the end of the ordinary or of chlorine-free bleaching process. In suaniem of hydrogen peroxide under pressure during long-term exposure allow to increase the marginal value of whiteness compared with the value obtained using the traditional process, in which the bleaching is carried out at atmospheric pressure. It is desirable to minimize the required time under pressure to reduce investment in equipment. For example, in accordance with the known method, the temperature of more than 100oC for 1-3 h in laboratory conditions showed that these conditions are very effective in reducing the amount of time necessary for the process of pulp bleaching with peroxide. However, apparently, the known process is economically disadvantageous because of the investment when using a process requiring a stage for 1-3 hours supported pressure peroxide, high.

In accordance with the initial information about the cost of the known processes using conventional stage peroxide bleaching at atmospheric pressure and bleaching peroxide and oxygen at high pressure (CP), attachments necessary to use columns for aging of cellulose, can be calculated at one stage during the performance of approximately 850 tons/day:

a) a Column of hydrogen peroxide under pressure at time of stay

6 hours - $ 400 000

9 h $ 550 000

To achieve the same brightness level when using the traditional process of bleaching peroxide at atmospheric pressure it is necessary to maintain the residence time of more than 6 h in comparison with 1-3 hours, which is sufficient for the oxygen-peroxide systems under pressure. For example, you need to choose the size of the column in such a way as to achieve a residence time of 8-10 hours to achieve the same results that may be obtained for 2 h in an oxygen-peroxide system under pressure.

Given that only in North America is 350 bleaching enterprises, even if each plant will require only one system of peroxide bleaching, investment in the industry will be approximately $ 200-350 million. In order to meet the stringent requirements for the protection of the environment may need to install more than one stage peroxide bleaching on each woodworking factory, which will double the necessary investment. Thus, the main disadvantage of this method is a very significant investment required to implement known technologies.

This disadvantage is 9/16, 1991; EP 0208625 A1, D 21 C 9/16, 1987.

For example, in DE 1951709 A, D 21 C 9/16, 1974 describes a method of bleaching cellulose and other cellulosic and lignocellulosic fibrous materials with the use of peroxide and alkali. In the patent RU 2044809, D 21 C 9/153, 1989 describes a three-stage method of bleaching cellulosic and lignocellulosic materials, comprising the first stage of bleaching with alkaline hydrogen peroxide, the second stage of bleaching sonadoras gas and the third stage bleaching with hydrogen peroxide. However, in the known methods require expensive equipment.

The objective of the invention is the creation of a more effective method of bleaching pulp, which can reduce the capital investment for the normal production capacity.

This task is solved in that in the method of bleaching cellulose and other cellulosic and lignocellulosic fibrous materials with the use of peroxide and alkali regulate the consistency of the pulp so that it ranged from 8% to 18%, add alkali to increase the pH of the pulp above 9.5, add hydrogen peroxide to create residual peroxide after passing through the first reaction column, heat the pulp to a temperature above the 100oC when poderzhanoy the column at a speed providing a reaction time in the specified column less than 45 min, cooled pulp to a temperature below 100oC, add the lye to create the pH of the pulp above 9,0, soak the pulp in the reaction column at atmospheric pressure and conducting the reaction within 1-5 h until, until you spent a significant portion of the residual hydrogen peroxide, and unload the pulp for further processing.

Sufficient alkali to bring the pH of the pulp to a value in the range of from 9.5 to 11.5 may be added in the first addition of alkali.

Cellulose can pass through the reaction column at a speed that provides the reaction time is in the specified column from 5 to 20 minutes

The operation of adding hydrogen peroxide to create residual peroxide after passing through the first reaction column can include adding from 0.5% to 5.0% of hydrogen peroxide on the weight of cellulose oven drying.

Residual hydrogen peroxide can be re-activated by adding alkali in a quantity sufficient to achieve a pH of the pulp more than 9.5.

This task is solved by the fact that in the three-stage method of bleaching pulp and lignose the eskers so, so it ranged from 8% to 18%, and add alkali and hydrogen peroxide to achieve the pH of the pulp at least 9.5 and the content of hydrogen peroxide from 0.5% to 5.0% by weight of kiln dried pulp, heat the pulp to a temperature above the 100oC while maintaining sufficient pressure to prevent boiling of cellulose liquor, miss cellulose under pressure through the reaction column at a speed that provides the reaction time is in the specified column less than 45 min, cooled cellulose, unload the cooled pulp in a washing apparatus, in which a substantial part of the unspent bleaching chemicals and the dissolved material is removed from the pulp, and in which, if necessary, adjust the concentration of the cellulose to the preferred values for the stage of bleaching, in the second stage bleaching of pulp add a sufficient amount of acid or alkali to achieve preferable to chemical bleaching pH value of the pulp, serves the pulp in the mixer, in which there is a mixing of the pulp with the second bleaching reagent, unload the cellulose in the reaction vessel in which the cellulose was incubated for a time sufficient to Eudaemony part of the unspent bleaching reagents and dissolved organic material removed from the pulp, and which if necessary, adjust the concentration of the pulp to a value of from 8% to 18%, and spend the third stage of bleaching, which includes operations are identical to the operations listed for the first stage of bleaching with hydrogen peroxide after adjusting the concentration of the cellulose.

In the second stage of bleaching, you can add enough acid to achieve a pH of the pulp is less than 4, the operation of the feed pulp in the mixer may include adding in a suitable gas-carrier ozone, which are mixed with cellulose, cellulose can be unloaded from the mixer in the vessel for the reaction with ozone, in which the cellulose can withstand up to 10 minutes to absorb essentially all of the ozone, and unload the pulp from the vessel for the reaction with ozone in the wash apparatus in which a substantial part of the unspent bleaching reagents and dissolved organic material can be removed from the pulp, and in which optionally adjusting the concentration of the pulp to a value of from 8% to 18% for the third stage of processing.

The amount of ozone may be from 0.1% to 2.0% by weight of the cellulose oven drying.

Stage bleach which can range from 0.2% to 1.0% by weight of the cellulose oven drying.

The method may include more than one processing stage ozone in the absence of washing pulp between stages.

You can implement an additional stage of bleaching between the first processing peroxide and the second processing peroxide.

The concentration of the incoming pulp can be adjusted so that it was more than 20% of the discharged pulp can be dehydrating to the concentration of more than 20%, and the filtrate from the stage of dehydration, the next stage of bleaching, can be used to dilute the incoming pulp, thus disposing of a significant portion of the residual hydrogen peroxide.

The pulp discharged from the stage, you can stand in the reaction column for reaction for 30 min to 3 h until, until you spent a significant portion of the residual hydrogen peroxide.

For reactivation of residual hydrogen peroxide before ageing of cellulose in the reaction column, you can add the lye.

Cellulose can be cooled before keeping in the reaction column.

The above and other aspects of the present invention will be understood upon consideration of the subsequent detailed OPI the implementation of the present invention.

In Fig. 2 shows another preferred example of implementation of the present invention.

In Fig.3 shows another preferred example of implementation of the present invention.

In Fig. 4 shows another preferred example of implementation of this izobreteniya.

In Fig. 5 shows a diagram of the stage bleaching with another preferred example implementation of the present invention.

In Fig. 6 shows one preferred bleaching when using the present invention in combination with the existing technology of bleaching.

In Fig. 7 shows another preferred bleaching with the use of the present invention for disposal of residual peroxide in a conventional washing machine.

In Fig. 8 shows another preferred bleaching with the use of the present invention for disposal of residual peroxide in the press.

In Fig. 9 shows another preferred bleaching with the use of the present invention using a different method of disposal of residual peroxide in the press.

As can be seen in Fig. 1, the pulp out of the ordinary promino is of the cellulose and the alkali to increase the pH. Cellulose is heated and adjusted the pH to a value of more than 8.5, preferably of 9.5 to 10.5. The heated pulp with adjusted pH value is supplied from the mixer 100 through a pipe 20 to a conventional pump 200 to feed pulp density, which pumps the pulp through the pipe 30 into the mixer 300. In the mixer 300 serves the hydrogen peroxide solution through the pipe 35 in a quantity sufficient to achieve the desired whiteness at the end of the reaction. As in conventional systems, peroxide bleaching, can be added to compounds of magnesium to maintain the viscosity of the cellulose, as well as airing (e.g. SiO) or chelating agents (e.g. ethylenediaminetetraacetic acid (add) or diethylenetriaminepentaacetic acid (DTPC) together with the alkali solution through the pipe 15, the peroxide solution through the pipe 35 or separately through pipes 16 and/or 36. Since according to the present invention, the temperature of the pulp must be above the 100oC, and to pump the pulp at this temperature is not always convenient, the temperature of the pulp, for example, with 85-90oC up to more than 100oC is carried out by adding the pair to the area of the feed pulp from the pump 200 through the pipe 37 into the mixer 300.

The pulp is heated to the required timer which corresponds to the time of stay, required for reaction. According to the present invention, the ascending pipe is of such a size at which the time is 1-30 minutes, preferably 5-20 minutes, after which the pulp is discharged through a pipe 50 and the respective offloading device 500, such as a valve, and then through the pipe 60 to the next stage of washing and bleaching. Because the pulp is bleached at a temperature of more than 100oC, it may be desirable to lower this temperature to prevent "spillover" pulp, therefore, can be used for diluting the pulp with water or lye lower temperature, served on top of a rising pipe through the pipe 70. Expert it is clear that the present invention can be realized by using both ascending and descending, ascending/descending, or other configuration to achieve required for reaction time. Next, the specialist it is clear that for heating and cooling cellulose, respectively, before the reaction and after the use of auxiliary tools. These elements are listed in the description, not to limit the scope of the invention, and are intended to illustrate preferred example realisatie, identical is shown in Fig. 1, except for the descending column 600. According to the present invention, the ascending pipe is of such a size at which the time is 1-30 minutes, preferably 5-20 minutes, after which the pulp is discharged through a pipe 50 and the respective offloading device 500, such as a valve, and then through the pipe 60 in the normal column 600 bleaching, preferably in any pipe that is already installed at the factory and can now be used again instead of the operation of bleaching using chlorine. The pulp is kept in this column is optional for 1-5 h at the desired reaction temperature in order to react a substantial portion of the hydrogen peroxide introduced into the cellulose. After the pulp was bleached in the column 400 at a temperature of more than 100oC, it may be desirable to lower this temperature to prevent "spillover" of cellulose. In the present invention it is possible to cool the pulp before discharge from the ascending pipe, so that there was no "release" liquor together with cellulose. This example embodiment of the invention, it may be appropriate in some factories to limit potential emissions of steam and the dilution of the pulp through the pipe 70. For example, adding liquor at a temperature of 50-60oC in an amount of from 1.5 to 2.5 m3/tonne of pulp in a pulp having a concentration of 12% and processed in the ascending column at 110oC, will lead to cooling of the pulp to a temperature below 100oC and reducing its concentration to 10%, which will not impact significantly on the flow of the second reaction stage. Particularly desirable may be maintaining maximum at atmospheric pressure the temperature of the pulp.

In accordance with another preferred example of the invention shown in Fig. 3, the pulp is discharged through a pipe 60 to the column 600 and relieve pressure to atmospheric. Pulp entering the descending column has a maximum allowable temperature, for example 98-100oC, which promotes reaction with peroxide in the second stage. Next, reset the steam leaves through pipe 90 into the heat exchanger 700. The heat exchanger is used to pre-heat the washing water supplied in the washing machine, before stage bleaching with peroxide, which reduces the amount of steam required for submission at this stage through pipe 15 and 37. This increases the temperature of the wash bodyplendil in Fig. 3, is identical to the example in Fig. 2, with the exception of the point of discharge of the pulp from the rising of the reaction column 400. In this case, the cellulose after discharge is maintained for a substantial part of peroxide. The pulp is discharged through a pipe 50 into the corresponding mixing valve 500, where add additional pipe 55 alkali to raise the pH more than 8.5, preferably of 9.5 to 10.5 for the second reaction stage.

The pulp, after cooling by pressure relief discharged through the pipe 60 in the usual descending column 600 for carrying out the second stage reaction. Regular column downdraft shall be of such dimensions, in which a significant portion held peroxide reacts with the cellulose per stay 1-5 PM Bleached pulp discharged from the column 600 through a pipe 80 for the passage of the following operations.

The valve 500 is used to lower the pressure in the ascending pipe 400, with liquor and pulp are connected through it to the atmosphere. In front of this valve in the course of the stream is the place of supply of alkali, and turbulence, to confess valve, promotes mixing of alkali to cellulose. Presumably, the action of the valve is essentially equivalent to the installation of any mixer in this place.

In Fig. 5 shows a scheme of operations whitening according to the present invention. The pulp of the conventional washing machine or thickener 10 discharged through the pipe 11 to the mixer 20, which through a pipe or pipes 12 and 13 serves couples and/or bleaching reagents for heating the pulp to the desired reaction temperature and increasing pH for carrying out the first stage of bleaching. The heated pulp with adjusted pH is served through a pipe 21 to a conventional pump 30 for supplying the pulp in the mixer 40. Because cellulose is heated to a temperature above 100oC, usually for conclusa alkali peroxide, chelating agents and other features can be added through pipes 32 and 33 and mixed with the cellulose to obtain a homogeneous mass before discharge through the pipe 41 into the vessel 50 for carrying out the first reaction of the bleaching. The vessel 50 for the first reaction whitening has such a size at which the time is 1-30 minutes, preferably 5-20 minutes to achieve significant delignification and/or increase the whiteness before discharge through the pipe 51 into the offloading device 52. Preferably, but not necessary, to achieve the best efficiency of the process is to wash the pulp after the first surgery whitening, and if the washing machine is not under pressure, it is preferable to cool the pulp before unloading from the vessel for carrying out the first reaction of the bleaching. Liquor for cooling and dilution can be added to the vessel 50 for the first reaction whitening through a pipe 53. Perhaps, before pumping the pulp is advisable to dilute the filtrate is fed through the pipe 54, if the washing machine requires the use of cellulose of low concentration.

The pulp is washed in the washing device 60, and the washed pulp is discharged through the pipe 61 to the mixer 70. the about to perform at a high or moderate concentrations, however, preferably, if it is processing stage pulp average concentration, carried out with the concentration at the outlet of a conventional washing machine 10-14% to reduce the capital cost of the installation. As is known, it is necessary to carry out this stage at a pH less than 4 for best results, treatment with ozone. Thus, before conducting the treatment with ozone at the outlet of the vessel 50 for the first reaction stage can be added through pipe 53 acid, for example sulfuric acid, while the wash water in the washing apparatus 60 of the first stage of peroxide treatment serves on the tube 56 in the raw material is supplied through the pipe 62 to the pump 70, or in a separate mixer (not shown). The acidified pulp serves, is pumped by pump 70 through the pipe 71 to the mixer 80, which serves ozone through the pipe 72. The pulp discharged from the reaction vessel 90 for processing by ozone through the pipe 91 into the discharge device 92, which may consist of a valve, a variety of valves or mechanical devices to reduce the pressure of the reaction vessel for processing by ozone. The pulp is discharged through a pipe 93 to the device 220 for separating gas, where the gas is separated from the pulp and absorbed through the pipe 102 for processing and/or re-the hat to achieve the best efficiency of the process is to wash the pulp after treatment with ozone before the next operation of bleaching. Perhaps, before pumping the pulp is advisable to dilute the filtrate is fed through the pipe 54, if the washing machine requires the use of cellulose of low concentration. Cellulose serves on the tube 104 in the washing machine 120 and washed with water or filtrate is fed through the pipe 115.

Pulp washing apparatus 120 is discharged through the pipe 121 and fed into the mixer 130, which also serves couples and/or bleaching reagents pipes 122, 123 and 124 for heating the pulp to the desired reaction temperature and increase its pH to the required for the first peroxide treatment level. The pulp is heated to the desired reaction temperature and having a desired pH value, serves on the pipe 131 to the pump 140 to pump through the pipe 141 to the mixer 150. Because cellulose is heated to a temperature above 100oC, as a rule, for the final heat after the mixer is used pairs, usually supplied through a pipe 144. Additional chemicals, including alkali, peroxide, complexing agents and other features can be added through pipes 142 and 143, and mixed with the pulp before received the 160 for carrying out the second reaction whitening has such a size when the time is 1-30 minutes, preferably 5-20 minutes to achieve significant delignification and/or increase the whiteness before discharge through the pipe 161 in the offloading device 152. Preferably, but not necessary, to achieve the best efficiency of the process is to wash the pulp after the second surgery whitening, however it could be optional, if, in addition, carry out another operation whitening, for which no significant effect of the presence of residual peroxide and/or organic substances. If the washing machine is not under pressure, it is preferable to cool the pulp before unloading from the vessel for carrying out the first reaction of the bleaching. Cold liquor for cooling and dilution can be added to the vessel 160 for carrying out the second reaction whitening through a pipe 153. Perhaps, before pumping the pulp is advisable to dilute the filtrate is fed through the pipe 154, if the washing machine requires the use of cellulose of low concentration. The pulp is then washed in the washing machine 180 water or filtrate is fed through a pipe 156.

In Fig. 6 presents a schematic diagram of the whitening process of ispolzovat many factories now called DcEoDED. Existing bleaching process can be modified using the principles of the present invention with a large economic benefit. As shown in Fig. 6, almost all the existing equipment used in the modification process, and the necessary investments are made only in the acquisition of three mixers, three reaction vessels, ozone generator and various pipelines for connection of new equipment. In some cases, you may need to replace some of the materials in the existing columns for whitening, pipelines and other equipment.

In the example shown in Fig. 6, the current column chlorination, which is not used in the new bleaching process, can serve as additional storage or for any pre-processing before applying for a new bleach plant. The existing operation Eo can be used as a stage of chelation, which add ethylenediaminetetraacetic acid (edtc), diethylenetriaminepentaacetic acid (DTPC) and other chelating agents, when this operation is performed at controlled pH and temperature, preferably at a pH of 5-7 and 10-60o).

After washing in existing leaching apparatus Eo existing equipment for stage D1 can be used for carrying out the first operation whitening peroxide (P1) by feeding the pulp into a new mixer, suitable for the introduction of the peroxide, add a suitable reaction vessel and discharging into the existing column D1 in the implementation of the reactivation of residual peroxide according to the present invention or without him. The first stage peroxide bleaching is carried out at pH 8.5 to 12.5, when carrying out the first stage of the reaction at temperatures above 100oC, preferably 105-120oC, at the time of the reaction 1-30 minutes, preferably 5-20 minutes

After washing in existing leaching apparatus D1 for treatment with ozone using existing equipment for conducting E stage by feeding the pulp into a new mixer, suitable for feeding ozone, add a suitable reaction vessel and the gas separator and discharge into the existing column E. the processing Operation with ozone is carried out at a pH less than 4, preferably 2-4, and a temperature of 30 - 70oC, preferably less than 50oC, at the time of the reaction less than 10 minutes, preferably less than 5 minutes After washing them in which the equipment is designed for stage D2 by feeding the pulp into a new mixer, suitable for submission peroxide, add a suitable reaction vessel and discharging into the existing column D2 in the implementation of the reactivation of residual peroxide according to the present invention or without him. The second stage peroxide bleaching is carried out at pH 8.5 to 12.5, when carrying out the first stage of the reaction at temperatures above 100oC, preferably 105-120oC, at the time of the reaction 1-30 minutes, preferably 5-20 minutes

After washing in existing washing machine D2 pulp can be subjected to subsequent processing operations, but preferably cellulose will be a fully bleached pulp, which can be fed to the column for storing bleached pulp of high density.

Fig. 7 illustrates a preferred method of reuse of the effluent in the process QPZP. It should be noted that according to the present invention a substantial portion of the peroxide remains in the pulp after treatment with peroxide, for example usually the consumption of peroxide 2.5% on the weight of cellulose, however, the amount of peroxide used in the reaction generally is less than 1.5% by mass of cellulose. Since peroxide is relative to the stage and processing peroxide. This is carried out by recycling the filtrate from the washing operation after treatment with peroxide to the operation of washing before handling peroxide, as shown in Fig. For illustration the figure shows a typical flow scheme, for example, for each of the leaching apparatus, from which the discharged pulp density of 10%, the flow of filtrate is 9 kg of liquor/kg of pulp. The flow of wash water supplied to each of the washing apparatus when the dilution factor 2 typical installations whitening at the present time is 11 kg of solution/kg of pulp. According to the present invention filtrate recycle in countercurrent through the bleach plant, so that the residual peroxide is introduced into the pulp in the washing machine, and a significant portion of this residual peroxide is then dissipated to the machining stage peroxide. Desired flow peroxide for this operation is therefore reduced by the amount made from cellulose. The amount of residual peroxide, which is made from cellulose, is a function of the displacement efficiency (efficiency washing) washing machine. For example, if the displacement ratio of the leaching apparatus is 0.85, then about 60% of the residual peroxide is in the course of the treatment with peroxide. According to the invention the amount of bleaching chemicals used in the process, is significantly reduced by recirculation of the leachate, as shown in Fig. 7, in comparison with other possible schemes recirculation of the leachate.

Fig. 8 illustrates another preferred method of reuse of the effluent in the process QPZP, which may be preferred in case of construction of a new bleaching plant, without the use of existing equipment. In Fig. 8 depicts a process using presses, preferably brand Twin Roll Washing Press manufactured by Ingersoll-Rand Company, instead of the usual washing devices operating under vacuum or under pressure, or diffusers, working under vacuum or under pressure. A typical flow scheme of the filtrate are shown in Fig., on which each press out the pulp with a concentration of 33.3%, while for every kg of cellulose have 2 kg of the filtrate. The flow rate of washing water flowing in each of the washing apparatus when the dilution ratio is 2, the conventional today bleaching factories is 4 kg/kg of pulp. In this case, for washing the press use the filtrate in the same way as shown in Fig. 7. However, in addition CB cellulose, coming from pressure at a flow rate of 7 kg/kg of pulp. The number of extracted peroxide is similar to the number that are extracted with the use of the leaching apparatus operating under vacuum. The filtrate extracted in the press, is a function of the displacement coefficient (efficiency washing) press. If the displacement coefficient is 0,40, the number of extracted residual peroxide reaches about 60%. Attractive in the construction of the new factory is that the capital costs to match the cost of conventional washing apparatus operating under vacuum or under pressure. An additional advantage of this process is that it can include the stage of ozone bleaching of pulp high concentrations, at the same time as using presses as washing machines for bleaching with ozone comes cellulose medium density. This allows to reduce the number required for bleaching ozone and reduce the amount of energy consumed whitening installation.

As shown in Fig. 9, the pulp of the conventional washing machine or thickener discharged through the pipe 10 into the mixer 100, in which through a pipe 15 poda is llulose with adjusted pH value unloaded from the mixer 100 through the pipe 20 and serves to normal pump 30 for supplying pulp average concentration, which pumps the pulp through the pipe 30 into the mixer 300. In the mixer 300 through the tube 35 serves the hydrogen peroxide solution in a quantity sufficient to create a substantial balance at the end of the first reaction stage. As usual in systems of whitening peroxide in alkaline solution flowing through the pipe 15, it is possible to add compounds of magnesium to maintain the desired viscosity of the cellulose, as well as airing (for example, silicates and/or chelating agents such as EDTA or DTPA). The peroxide solution can be entered through the pipe 35 or separately through the pipe (or pipes) 16 and/or 36. Because cellulose according to the present invention is heated to a temperature above 100oC, and is currently pumping pulp at such high temperature is not carried out for the final heating of cellulose, for example, 85-90oC to temperatures above 100oC used pairs, usually supplied through the pipe 37 between the pump 200 and the mixer 300.

The heated pulp with adjusted pH pumped by the pump 40 in the ascending pipe 400, which has a size corresponding to the retention time required for the flow of the first reaction stage. According to the present invention, the ascending pipe is of such a size, acetelyne the amount of residual peroxide. The pulp is discharged through a pipe 50 into the corresponding pressing device 560, in which the concentration of the pulp increases from about 10% to about 25%. The filtrate is pumped back through the pipe 55 to the pipe 30 to extract a portion of the peroxide, the unspent at the first stage of the reaction.

The pulp discharged through the pipe 60 in the usual descending column of 600 on the second step of the reaction, which is carried out at high concentration (25-30%). Normal descending column has a size, which results in the expenditure of a substantial part of the residual peroxide, and the retention time is 1-5 hours. Bleached pulp is discharged from the column 600 through the pipe 80 and serves on the subsequent stage of the process.

Is depicted in Fig. 1-6 pumps and mixers, as well as handling devices are not shown in this figure, as well as the heat exchangers required to maintain the desired temperature at each stage of bleaching. The composition of each installation whitening, as shown by the engineering practice, includes heat exchange device.

Expert it is clear that the present invention can be used ascending, descending, ascending/descending, and any other structure shall be used as an additional means of heating and cooling of the pulp before the next reaction or after it. The specialist also it is clear that valve to maintain the pressure at the first retention time (rising pipe) can be located either to the mixer, and after it. See details serve to explain the invention and not as limiting its scope.

Specialist it is also clear that the use of chelating agents and sequestrants may be desirable or necessary to achieve the advantages of the present invention, however, the presence of these operations, the present invention also may not limit its scope. In the examples described processes QP, QPQP, QPQZP, QPZQP, PZQP and others. Specialists will also be clear that the acid treatment, in particular at very low pH, for example less than 3, can in some cases effectively replace the use of chelating agents in processes of this kind, or that the replacement of acid treatment chelating agents also relates to the field of the present invention.

The technology, called "PAPAROXIDE", can be used for processing cellulosic or lignocellulosic materials from wood of coniferous and deciduous breeds or different fibers of non-timber origin, vklua-fibrous mass. The advantages of using the present invention will become apparent from the following examples.

The first operation process PAPEROXIDE" is the reaction of the pulp with a peroxide at a pH of 8.5-12.5 and high temperature (more than 100oC) for a limited period of time of about 30 min, preferably 5-20 minutes it is Important that this stage is proceeded in the absence of metallic impurities in cellulose. The results of the first operation shown in the following example.

Example 1

A sample of Kraft pulp from coniferous wood with Kappa number, 27,2 was subjected to delignification oxidation (stage A) to the value of Kappa 1. This sample pulp was then treated with complexing agents using 0.6% of etc (stage X) approximately at the 50oC and holding time of 30 minutes and Then the sample was again subjected to delignification by the conventional methods of treatment with hydrogen peroxide (stage R) and ozone (Z) to achieve the Kappa number of 2.0 and white 77,9% ISO with a viscosity of 14.4 MPa under the following conditions and the costs of chemicals (PL. A).

The pulp was then treated with peroxide under pressure as in the known method, with the results obtained in comparison with the first stage of the new% the wide oxygen pressure of 75 lb/in2. When bleaching is used reagents (see table. 2 at the end of the description).

As can be seen from the table, in the first stage of the process proposed in the present invention, it is possible to achieve 85% white, oddly enough, without compromising viscosity and at a substantially lower consumption of peroxide, in a very small time in comparison with the known method, which requires about one hour or more. Although the example is a pressure of the pulp used gaseous oxygen, to conduct the first stage of the present invention does not necessarily use oxygen. This is shown in the following example.

Example 2.

A sample of Kraft pulp from coniferous wood with Kappa number, 27,2 was subjected to delignification oxidation (stage Q) to the value of Kappa 14. This sample pulp was then treated with complexing agents using 0.6% EDTA (stage Q) approximately at the 50oC and holding time of 30 minutes and Then the sample was again subjected to delignification by the conventional methods of treatment with hydrogen peroxide (stage R) and ozone (Z) to achieve the Kappa number 1,3 and white 81,8% ISO. Then the pulp was processed in the usual way peroxide at atmospheric pressure, and then penglase the present invention (see table. 3 at the end of the description).

In all cases, the pulp was treated at a concentration of 10%, was used reagents (see table. 4 at the end of the description).

As can be seen from the table, in the first stage of the process proposed in the present invention, it is possible to achieve results similar to the results obtained using known processes with a long exposure at atmospheric pressure and at a stage of processing peroxide and oxygen under pressure. In contrast to known methods, comparable results can be obtained without the use of oxygen in the first stage of the reaction. For a short high temperature first stage of the present invention described in example (with a retention time of 5 min), the vapor pressure of a suspension of cellulose 110oC was only 35 lbs/inch2in comparison with the known process, requiring the use of gaseous oxygen under high pressure. In accordance with these examples, and in accordance with the present invention can be obtained similar results when using known processes, but for a short time at high temperature stage, which dramatically reduces the investment in realizazzione rapid delignification and improving the whiteness in a relatively short period of time at temperatures of about 100-120oC and residence time in the small reaction column less than 30 min, and then discharging the pulp in a conventional column with a great time for about 1-5 h at atmospheric pressure, i.e. at less than 100oC without washing the pulp between the two stages. Use the subsequent aging at atmospheric pressure within the traditional 1-5 h leads to a further increase in the consumption of hydrogen peroxide, which is accompanied by a further improvement in whiteness. This allows the use of cellulose having a lower brightness than that indicated in the example.

Stage peroxide bleaching can be further improved by the simultaneous use of, on the one hand, high temperature and short residence time, and, on the other hand, the reactivation of residual peroxide after bleaching in the bleaching column. If you are reactivating peroxide, the peroxide solution is added in excess to provide considerable residual peroxide after completion of the first stage reaction, which is carried out at time 1-30 minutes, preferably 5-20 min, providing residual peroxide in the second stage of the reaction. This combination of operations is stuudio plant pulp bleaching and/or construction of new bleaching plants for pulp production waste-free (ECF) or chlorine-free (TCF) technology. The use of short high-temperature stage of processing peroxide with subsequent curing or without it and with the reactivation of residual peroxide or without it, in combination with traditional bleaching reagents allows low-cost to implement the construction of the plants whitening short time.

For example, using two short high-temperature stage peroxide bleaching using ozone, it is possible to obtain TCF pulp, high whiteness, for example above 80% ISO, delignification oxygen Kraft pulp softwood with an initial Kappa number of about 14. This scheme whitening allows the entire process of teeth whitening at the time of the pulp bleach plant less than 2 hours Thanks to the use of small reactors bleaching compared with traditional technology, this approach enables an unprecedented reduction in investment costs compared with all known schemes TCF pulp production. It shows the following example.

Example 3.

A sample of Kraft pulp from softwood with a Kappa number of 25.7 subjected to delignification oxidation (stage) until the value is 6% add (stage Q) approximately at the 50oC and holding time of 30 min, after which the spent bleaching pulp to achieve whiteness 85% ISO scheme P-Z-Q. According to the present invention in the first stage, tooth whitening peroxide for a short time (5-15 min) and at high temperature (107-110oC), but with additional conventional stage bleaching with ozone between the two stages of bleaching peroxide.

White bleached pulp is 82,3; 87,6 and 91,0 when the total time spent on the two stages of bleaching peroxide respectively 10, 20 and 25 minutes, it Should be noted that the number of Kappa bleached pulp is quite small, for example less than 3. Currently, there are a few plants for pulp bleaching, which receive the TCF pulp using only peroxide as the active bleaching agent, and these plants produce a bleached pulp having a high Kappa number, for example more than 5, which is undesirable, especially from the point of view of the deterioration of the white paper, obtained from such pulp. This combination of the first stage of the present invention with the conventional technology of bleaching with ozone has a significant advantage compared to conventional technology on quality paper, e the invention, as can be seen from table 5, it was simulated in the laboratory using gaseous oxygen to a pressure of the pulp during the bleaching. In practice when modeling whitening in laboratory conditions, the temperature of the pulp is maintained at a level above the 100oC. In accordance with the data of table 2, however, there is no need to apply gaseous oxygen, and it is also expected that he will not need in the industry to achieve the advantages of the present invention.

Modeling of this process involves the treatment with high concentrations of ozone for the convenience of the laboratory tests, i.e., about 40%, however, found that at moderate costs of ozone, for example less than 0.6% by mass of cellulose, essentially the same results were obtained when using the average concentration, i.e., about 10-14%. Therefore, the present invention is not limited to the use of ozone average concentration, in fact it is preferable to use ozone in moderate concentrations in order to use the existing equipment, and it, therefore, is the preferred option.

Specialist it is also clear that the scheme p is the acid treatment, can also be implemented using other chemicals, which are preferably in the acidic environment, i.e., at a pH of less than 7. Examples of other intermediate stages include, for example, processing peracetic acid, acid Caro, processing of various enzymes and a combination of these reagents.

Further, it should be noted that the processing of the specific cellulose may not be a need for both processing stages peroxide according to the first stage of the present invention, since you can use the traditional stage of processing peroxide in combination with one stage bleaching peroxide according to the first stage of the present invention, one or more intermediate processing. It is assumed that the holding of more than two processing stages peroxide intermediate treatments may also be an effective use of the present invention. The examples should not be viewed as limiting the scope of the present invention, but merely as an illustration of just one or two processing stages peroxide, although from an economic point of view it is preferable to limit the number of stages in order to minimize the required capitalista whitening installation, for example, existing columns extraction, treatment with hypochlorite or chlorine dioxide as a device for exposure after a short high-temperature stage bleaching peroxide according to the present invention, which allows to reduce the operating costs of the bleaching process in comparison with the previous example and requires minimal equipment in addition to the incumbent.

Example 4.

A sample of Kraft pulp from softwood with a Kappa number of 25.7 subjected to delignification oxidation (stage A) to the value of Kappa 13,6. This sample pulp was then treated with chelating agent using 0.6% of etc (stage Q) approximately at the 50oC and holding time of 30 min, after which the spent bleaching pulp to achieve whiteness 85% ISO scheme P1-Z-P2. According to the present invention whitening peroxide conducted for a short time (5-15 min) and at high temperature (107-110oC), but with the additional aging at atmospheric pressure after each short stage high-temperature processing, and in combination with traditional stage bleaching with ozone between the two stages of bleaching peroxide.

As can be seen from the table. 6 (the second processing according to the present invention allows to obtain results comparable with the results obtained by a known method with the use of extracts under pressure at each stage within 1-3 h with the introduction of the same amount of peroxide on the weight of cellulose. This is especially convenient because it allows you to reuse for the operation of the shutter operating whitening columns pulp and paper mills that requires minimal investment. As previously stated, for the installation vessel for holding under pressure within 1-3 h can be expensive, and it is assumed further that even if you want to build a new vessel for holding at atmospheric pressure within 1-5 h, a new vessel in combination with a vessel for a short (5-15 min) high temperature exposure will be more economically advantageous for the implementation of the new bleaching process than the holding of investments in known technology. According to the present invention the additional use of the ascending pipe for a short (5-20 min) exposure in combination with the use of the existing pulp and paper mill bleaching columns for additional exposure within 1-4 h will reduce the cost per stage factories in North America approximately $ 90 million. In comparison with known methods that will reduce costs 130-430 million dollars.

The data presented illustrate the conditions of some preferred implementations of the invention, but they are not intended to limit the scope of the invention. Specialist it is obvious that there are many ways to implement the present invention for achieving the benefits. To illustrate this, some examples, but not intended to limit its scope. Below is a list of sites of current or new installation whitening, which can be used is the process "PAPEROXIDE" proposed in the present invention.

1. On the site of delignification before the bleach plant.

2. For the final bleaching at the end of the installation Orbeliani.

3. To replace the current setup stage bleaching.

4. To modify the current stage to improve the performance or reduce the use of chlorine-containing compounds in bleach plant.

5. As a pre-treatment before the subsequent stage of bleaching.

6. On any of the above areas with ispolzovat with one or more intermediate processing operations.

1. The method of bleaching cellulose and other cellulosic and lignocellulosic fibrous materials with the use of peroxide and alkali, characterized in that it includes the steps of regulating the concentration of the cellulose so that it contains from 8 to 18% of fibrous materials, adding alkali to increase the pH of the pulp above 9.5, adding hydrogen peroxide to create residual peroxide after passing through the first reaction column, heating the pulp to a temperature above the 100oC while maintaining sufficient pressure to prevent boiling of cellulose liquor, passing the pulp through the reaction column at a speed that provides the reaction time in the specified column less than 45 min, the cooling of the pulp to a temperature below 100oC, addition of alkali to create the pH of the pulp above 9,0, keeping the pulp in the reaction column at atmospheric pressure and the reaction for 1 to 5 h until, until you spent a significant portion of the residual hydrogen peroxide, and discharging the pulp for further processing.

2. The method according to p. 1, characterized in that the add sufficient alkali to bring the pH of the pulp to a value in the interval is passed through the reaction column at a speed providing a reaction time in the specified column from 5 to 20 minutes

4. The method according to p. 1, characterized in that the operation of adding hydrogen peroxide to create residual peroxide after passing through the first reaction column comprises adding from 0.05 to 5.0% of hydrogen peroxide on the weight of cellulose oven drying.

5. The method according to p. 4, characterized in that the residual hydrogen peroxide reactivit by adding alkali in a quantity sufficient to achieve a pH of the pulp more than 9.5.

6. Three-stage method of bleaching cellulosic and lignocellulosic materials, comprising the first and third stages of pulp bleaching with hydrogen peroxide and the second stage of pulp bleaching other bleaching reagent, characterized in that the first stage of bleaching pulp with hydrogen peroxide includes the regulation of the concentration of the cellulose so that it ranged from 8 to 18%, adding alkali and hydrogen peroxide to achieve the pH of the pulp at least 9.5 and the content of hydrogen peroxide is from 0.5 to 5.0% by weight of kiln dried pulp to heat pulp to a temperature above the 100oC while maintaining sufficient pressure to prevent boiling of cellulose Ccii in the specified column less than 45 min, cooling cellulose, discharging the cooled pulp in a washing apparatus, in which a substantial part of the unspent bleaching chemicals and the dissolved material is removed from the pulp, and in which, if necessary, adjust the concentration of the cellulose to the preferred values for the stage of bleaching, the second stage of pulp bleaching involves adding a sufficient amount of acid or alkali to achieve preferable to chemical bleaching pH value of the pulp, the flow of pulp in the mixer in which the mixing of the pulp with the second bleaching reagent discharging pulp in the reaction vessel in which the cellulose was incubated for a time sufficient to trashdolls significant portion of the injected reagent, discharging the pulp in the washing apparatus in which a substantial part of the unspent bleaching reagents and dissolved organic material removed from the pulp, and in which, if necessary, adjust the concentration of the pulp to a value of from 8 to 18%, and the third stage bleaching includes the operations that are identical to the operations listed for the first stage of bleaching with hydrogen peroxide after regenia add enough acid to achieve a pH of the pulp is less than 4, during this operation the feed pulp in the mixer includes adding in a suitable gas-carrier ozone, which are mixed with cellulose, and unload the pulp from the mixer in the vessel for the reaction with ozone, in which the cellulose can withstand up to 10 minutes to absorb essentially all of the ozone, and unload the pulp from the vessel for the reaction with ozone in the wash apparatus in which a substantial part of the unspent bleaching reagents and dissolved organic material removed from the pulp, and in which, if necessary, adjust the concentration of the pulp to a value of from 8 to 18% for the third stage of processing.

8. The method according to p. 7, characterized in that the amount of ozone is from 0.1 to 2.0% by weight of the cellulose oven drying.

9. The method according to p. 7, characterized in that stage bleaching with ozone is carried out at concentrations of cellulose from 8 to 18%.

10. The method according to p. 9, characterized in that the amount of ozone is from 0.2 to 1.0% by weight of the cellulose oven drying.

11. The method according to p. 7, characterized in that it includes more than one processing stage ozone in the absence of washing pulp between stages.

12. Sposobem and second treatment peroxide.

13. The method according to p. 7, characterized in that regulate the concentration of the incoming pulp so that it was more than 20% of the discharged pulp is dewatered to a concentration of more than 20%, and the filtrate from the stage of dehydration, the next stage of bleaching, is used to dilute the incoming pulp, thus disposing of a significant portion of the residual hydrogen peroxide.

14. The method according to p. 13, characterized in that the pulp discharged from the stage, stand in the reaction column for reaction for 30 min to 3 h until, until you spent a significant portion of the residual hydrogen peroxide.

15. The method according to p. 14, characterized in that add the lye to the reactivation of residual hydrogen peroxide before ageing of cellulose in the reaction column.

16. The method according to p. 14, characterized in that the pulp is cooled before keeping in the reaction column.

 

Same patents:

The invention relates to the field of pulp and can be used to produce bleached pulp without molecular chlorine (ECF-cellulose)

The invention relates to a method of bleaching cellulose and can be used in the pulp and paper industry in the production of bleached fibrous semi-finished products

The invention relates to a process of bleaching cellulose and can be used in the production of fibrous materials for various purposes

The invention relates to the pulp and paper industry, specifically, to improvements in the method of bleaching hardwood sulphate pulp, allowing for increasing the selectivity of the delignification process to increase the degree of whiteness and pulp quality

The invention relates to the field of pulp and paper industry and can find application in the manufacture of bleached wood pulp from deciduous or coniferous wood chips for subsequent use in various compositions for the manufacture of paper and cardboard products

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

The invention relates to a method of manufacturing pulp without the use of chlorine chemicals, in particular for ozone bleaching of pulp

The invention relates to a reactor device and method for ozone bleaching of lignocellulosic pulp, and more particularly to a reactor that includes a rotating elements to move in the radial direction of the dispersed particles through the mass of ozonotherapy gas in corkboard mode flow

The invention relates to the pulp and paper industry and can be used in the production of bleached pulp by bleaching with ozone pre-treatment of unbleached pulp with oxygen in an alkaline medium

The invention relates to a method of bleaching cellulose ozonotherapy gaseous bleach and reactor apparatus and reactor for carrying out this method

The invention relates to a method for producing bleached pulp, and to a new and environmentally acceptable method for the delignification and bleaching of lignocellulosic pulp, which eliminates the need to use chlorine gas and it turns out the pulp with acceptable strength

The invention relates to a method of bleaching chemicals containing cellulose, and device for implementing the method

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

FIELD: chemical industry; food industry; pharmaceutical industry; perfume-cosmetic industry; construction materials industry.

SUBSTANCE: the invention presents the reactor-mixer used for treatment of the treatment of the caking viscous-fibrous materials and may be applied in chemical industry, food industry, pharmaceutical industry, perfume-cosmetic industry and in production of construction materials. The device contains a body and the bladed feed screws being in engagement with each other. The bladed feed screws are made with a controlled rate of rotation, the blades are removable and are the fragments of the screw surface with a step H from 0.5 up to 1,3 of the diameter, with the central angle φ from 90° up to 270°. The vanes on the shaft are mounted with a step Hl = H· φ / 360° with a shift of φ / 2, mainly in a direction of the screw line of the blades. A direction of the swirl of the screw lines of blades of adjacent feed screws is different and blades are mounted with an angular shift from 0 ° up to 180 °. The invention allows to exclude an excessive axial recycling of the mixture, to average duration of the particles presence in the reactor, to equalize the time of the particles contact with the heat exchange surface.

EFFECT: the invention allows to exclude an excessive axial recycling of the mixture, to average duration of the particles presence in the reactor, to equalize the time of the particles contact with the heat exchange surface.

3 cl, 1 dwg

Up!