UA72570C2 - Method of multi-step fine cleaning of fiber material in vortex conical cleaning devices - Google Patents

Abstract

A method for multi-step fine cleaning of fiber material in vortex conical cleaners is used in cellulose-paper industry. The method comprises of separation of condition fiber from the waste at the first stage of purification, with additional extraction of fiber from the waste at the following cleaning stages, at that the waste at each stage of cleaning is directed to the next cleaning stage with separation of the waste from the last stage, and the fiber extracted from the waste is returned to the first cleaning stage. At that, the fiber extracted at least at one stage, or the waste of at least one cleaning stage, or the mix of those is subjected to additional milling. This method increases the effectiveness of cleaning of the fiber material through prevention of blocking the vertex conical cleaning units and increase of the fiber material quality.

Description

The invention relates to the field of pulp and paper industry and can be used for the final fine cleaning of fibrous material from polluting inclusions in the process of its preparation for the production of paper products, as well as for the final fine cleaning of wood pulp from polluting inclusions.

The fibrous material obtained after dissolution of the fibrous semi-finished product, coarse and subsequent fine cleaning of various types of polluting inclusions larger than 2.0 mm and grinding is subjected to final fine cleaning.

For the final fine cleaning of fibrous materials (after the completion of the above-mentioned processes) from polluting inclusions crushed in the grinding process to point sizes with a density greater than that of the fiber, vortex conical cleaners (centricliners) are used.

All types of vortex conical cleaners have basically the same design and are a conical body with a conical chamber located inside it.

At the base of the conical body, a nozzle is tangentially mounted for the tangential supply of fibrous suspension into the chamber. In the center of the base of the conical body there is a nozzle for draining the suspension of purified fibrous material. At the top of the conical body there is a nozzle for removing cleaning waste from the chamber.

As a result of the tangential arrival of the mass, which is supplied under pressure, a rotational movement of the mass is created, during which heavier and larger particles are thrown to the periphery, then descend along the wall of the cone. In the center of the purifier, the speed of the flow increases so much that a flow of the opposite direction is formed. Under the influence of pressure, particles from one rotating layer pass into another, until the increasing centrifugal force balances the static pressure. At the same time, large particles move along with the mass flow and, having reached the walls of the housing, descend and are separated as cleaning waste. Conditioned (cleaned) fibers, having reached the lower part of the cone, fall into the central flow and together with it rise up and are discharged through the outlet nozzle. Smolyanitskyi B.3. Recycling of waste paper. M. Lesnaya promyishlennost, 1980., pp. 82-83|Y. In order to reduce the loss of fiber with waste, vortex conical cleaners are assembled in installations consisting of three or four stages of cleaning. In these installations, waste from the previous stage enters the next stage. Thanks to the multiple successive passes through the vortex conical waste cleaners, the loss of fiber with the waste is reduced to a minimum from the first stage of cleaning.

A known method of hydrocyclone processing of fibrous materials, protected by author. St. USSR M 589317, 02105/24, VO4S5/23, publ. 25.01.78.

The known method involves the main separation of fibrous material from waste at the first stage of purification with additional extraction of fiber from waste at subsequent stages of purification. At the same time, 50-8595 wastes after each stage of purification are directed into the waste stream of the previous stage of purification.

The fiber removed from the waste from the third stage after cleaning at the second stage is returned to the first stage of cleaning.

The amount of returned waste is determined by the level of contamination of the original product. Under the conditions of small clogging of the original product (0.1-0.790), this number is chosen close to 8595, with increasing clogging, this number is reduced accordingly.

The mentioned method allows to reduce fiber losses by 2.5-7.5 times. However, this method is advisable to use when cleaning fibrous materials with low clogging.

Cleaning fibrous materials with large clogging in this way, for example, waste paper, will lead to the accumulation of waste in the system. Since the long fiber is also removed with the waste, this leads to clogging of the exit holes of the vortex conical cleaners.

The closest to the proposed invention is the method of multi-stage fine cleaning of fibrous materials in vortex conical cleaners, given in the book "Equipment of pulp and paper production", vol. 1 "Equipment for the production of fiber semi-finished products" ed. V.A. Chichaeva, M., "Forest Industry", 1981, pp. 252-260.

According to this method, the initial fibrous mass enters the first stage of purification, after which the purified fibrous mass is directed into the technological flow, and the waste enters the second stage of purification. Together with the waste of the first stage of cleaning, a significant amount of high-quality fiber is removed, which is removed in the second stage cleaners. The waste of the second stage is directed to the third stage and after extraction from them the fibers are removed. The extracted fiber from the third stage enters the stream of the second stage and further to the first stage of purification.

During the operation of vortex conical cleaners, hydrodynamic flows characterized by high velocity gradients and large values of shear stress are formed inside them. The presence of these two hydrodynamic characteristics in the flow of a moving fibrous suspension determines the phenomenon of fractionation, that is, the phenomenon of the distribution of fibers in the working zones of each cleaner depending on their length with an increase in the length of the fibers in the direction from the center of the cleaner to its peripheral conical wall. This distribution of fibers inside each cleaner causes the output of shorter fibers through the outlet for cleaned fibrous material, and longer ones - through the outlet for waste, located at the top of the cone of the cleaner. The mentioned phenomenon causes a lower value of the mass fraction of fiber in a suspension of purified fibrous material than a similar indicator in a suspension at the entrance to a vortex conical cleaner, while the value of a mass fraction of fiber in a suspension of cleaning waste is higher than at the entrance to the cleaner.

In addition, the cleaning process in vortex conical cleaners according to the given method is accompanied by an increase in the value of the average fiber length index of both the cleaned material and the fibrous material in the cleaning waste from stage to stage in the direction from the first to the last. Moreover, in cleaning waste, the value of the average fiber length increases more rapidly than in the cleaned material. This phenomenon is determined by the fact that the long-fiber material removed at the second and subsequent stages of purification, returning to the entrances preceding each of the stages of purification, is in circulation between the stages of purification and is not removed from the system. In turn, the original fibrous material fed to the first stage of purification also adds its portion of long fibers, and thus in this system there is an accumulation of long fibers and the mass fraction of such fibers in the suspension increases. This phenomenon ultimately results in plugging of the cleaning waste outlets in vortex cone cleaners with long fiber plugs. The process of cleaning the fibrous material in the clogged vortex conical cleaners stops and the untreated fibrous material enters the openings for the exit of the cleaned material. Therefore, the efficiency of cleaning the fibrous material decreases.

To restore the normal operation of vortex conical cleaners with clogged holes, fibrous plugs are destroyed (manually) and removed. After a certain period of time, this phenomenon repeats itself. The time period between clogs of cleaners depends on the number of long fibers in the starting fiber material: the more there are, the more often the cleaners clog.

The task of the invention is to increase the efficiency of cleaning fibrous material by preventing clogging of vortex conical cleaners and thereby improving the quality of cleaning fibrous material.

To achieve the mentioned technical result in the proposed method of multi-stage fine cleaning of fibrous material in vortex conical cleaners, which includes separation of conditioned fiber from waste at the first stage of cleaning with additional removal of fiber from waste at subsequent stages of cleaning, in which the waste of each stage of cleaning is sent to the next stage cleaning with the removal of waste from the last stage, and the fiber removed from the waste is returned to the first stage of cleaning, according to the proposed invention, the fiber removed at at least one stage of cleaning and/or the waste of at least one stage of cleaning are additionally ground.

The proposed invention is illustrated by the diagrams presented in Fig. 1-3.

Figure 1 shows a schematic diagram of multi-stage fine cleaning of fibrous material in vortex conical cleaners with grinding of the extracted fiber from the second and third stages of cleaning.

Fig. 2 is a schematic diagram of multi-stage fine cleaning of fibrous material in vortex conical cleaners with grinding of first- and second-stage cleaning waste.

Fig. 3 is a schematic diagram of multi-stage fine cleaning of fibrous material in vortex conical cleaners with grinding of waste from the first stage of cleaning and extracted fiber from the third stage of cleaning.

The invention is illustrated by the following examples.

Example 1 (prototype). Paper pulp from waste paper with a mass fraction of fibers in suspension of 0.895 under a pressure of 280 kPa (2.8 kgf/cm-) is fed to the first stage of cleaning of the installation of vortex conical cleaners. The diameter of the vortex conical cleaners is 8 mm, the length is 800 mm.

Conditioned fiber from the first stage of cleaning is sent to the production of paper products, and the waste is collected in containers, diluted to a fiber mass fraction of 0.895, and then sent to the second stage of cleaning by vortex conical cleaners. The extracted fiber from the second stage of purification is fed to the first stage of purification, and the waste of the second stage is diluted to a fiber mass fraction of 0.895 and sent to the third stage of purification under a pressure of 280 kPa (2.8 kg/cm?). The third-stage cleaning waste is sent to the dump, and the extracted fiber is sent to the second stage of cleaning.

Determine the values of the indicators of the degree of grinding and the average fiber length of the original, cleaned (conditioned), extracted at the second and third stages of the cleaning of the fibrous material, as well as the fibrous material of the waste of the first and second stages of cleaning in the process of stable operation of the installation.

At the same time, in the process of stable operation of the installation of vortex conical cleaners, in the intervals between the blockages of the holes for the exit of cleaning waste, the value of the mass fraction of fibrous material in the suspension of cleaning waste of the first, second and third stages of cleaning is determined every 10 minutes.

Determine the number of blockages of the holes for the exit of cleaning waste in the cleaners within 5 hours.

Castings with a casting mass of 1m area are made from the conditioned and original fibrous material: god.

Clogging is determined according to GOST 14363.3-84 Cellulose and wood pulp. The method of determining weediness.

Cleaning efficiency is determined by the following formula:

E -10095-- 59. 10095,

St where: E - cleaning efficiency, 90;

So - the number of scraps with an area from 0.1 to 2.0 mm:2 per 1 m:? castings made from cleaned material.

St - the number of scraps with an area from 0.1 to 2.0 mm:? on 1m:2 casting made from the original fibrous material.

The results of the determinations are summarized in Table 1-2.

Example 2. The schematic diagram of multi-stage fine cleaning of fibrous material from polluting inclusions is shown in Fig. 1.

Paper pulp from waste paper is fed through pipeline 1 into fat pool 2. After dilution with water from pipeline C to a fiber mass fraction of 0.895, the resulting suspension from pool 2 is fed to the final thin cleaning to a three-stage installation of vortex conical cleaners b to the first cleaning stage 7 in the inlets of conical cleaners 8. The cleaned conditioned fibrous material from the conical cleaners 8 of the first cleaning stage 7 is fed to the production of paper products through the pipeline 9, and the cleaning waste is collected in the container 10 and after dilution with water to the value of the fiber mass fraction of 0.895, the obtained suspension is fed by the pump 11 under a pressure of 280 kPa (2.8 kgf/cm2) through the pipeline 12 for the extraction of the fiber to the second stage of cleaning 13 in the inlets of the cleaners 14. The extracted fiber from the second stage of cleaning 13 is removed to the pipeline 15, and the waste cleaning is collected in a container 16 and after dilution to the value of the mass fraction of fibers 0.896 I serve pump 17 and the pipeline 18 to the third stage of cleaning 19 in the inlets of the vortex conical cleaners 20. The cleaning waste is removed through the pipeline 21 to the dump, and the suspension of the removed fibrous material is fed under excess pressure through the pipeline 22 to the thickener 23.

A suspension of fibrous material removed at the second stage of purification is sent here through the pipeline 15 under excess pressure.

The fibrous suspension thickened to the value of the fiber mass fraction of 3.095 is sent to the fat pool 24 and further by means of the fat pump 25 through the pipeline 26 to the mill 27 for grinding. Thickening of the suspension of fibrous material before grinding is carried out to improve the quality of fiber grinding and save electricity for the grinding process.

The fibrous material ground in the mill 27 is sent to the fat pool 2 through the pipeline 28. After mixing these fibrous materials in the fat pool 2, the resulting mixture is sent to the cleaning in the vortex conical cleaners 6 to the first stage of cleaning 7 with the help of the pump 4 through the pipeline 5.

The design dimensions of conical cleaners correspond to the values given in example 1.

Example 3. Fine cleaning of fibrous material is carried out similarly to example 2, but only the fiber removed at the last (third) stage of cleaning is subjected to grinding. The fiber removed at the second stage of purification is sent to the first stage of purification.

Example 4. The schematic diagram of multi-stage fine cleaning is shown in Fig. 2.

Paper pulp from secondary fibrous material is fed through pipeline 1 into fat pool 2. After dilution with water from pipeline C to a fiber mass fraction of 0.895, the resulting suspension from pool 2 is fed by pump 4 and pipeline 5 under a pressure of 280 kPa (2.8 kgf/cm7) into the vortex conical installation cleaners 6 to the first stage of cleaning 7 into the inlets of the vortex conical cleaners 8. The purified conditioned fibrous material from the vortex conical cleaners 8 of the first stage of cleaning 7 is fed through pipeline 9 to the production of paper products, and the cleaning waste is ground in the mill 10, collected in containers 11 and after dilution with water to a mass fraction of fiber in suspension of 0.895 by a mass pump 12 under a pressure of 280 kPa (2.8 kgf/cm7) through a pipeline 13 is fed to extract the fiber to the second stage of cleaning 14 into the inlets of the vortex conical cleaners 15.

The fiber removed at the second stage of cleaning is sent to the pipeline 24, and the cleaning waste is ground in the mill 16, then collected in the container 17 and after dilution to a mass fraction of solid components in the suspension of 0.890o by the mass pump 18 and the pipeline 19 is fed to the third stage of cleaning 20 into the inlets vortex conical cleaners 21. The cleaning waste from the third stage is removed through pipeline 22 into the dump, and the suspension of the removed fibrous material under a pressure of 20 kPa (0.2 kgf/cm?) is directed through pipeline 23 into container 11, from where, after mixing with ground fibrous material, the waste of the first cleaning cleaning stage 7 and diluting the mixture to a fiber mass fraction of 0.895 is again submitted for cleaning to the second cleaning stage.

Example 5. Fine cleaning of fibrous material is carried out similarly to that given in example 4, but at the same time, only the waste of the second stage of cleaning is ground. Waste from the first stage of cleaning is fed to the second stage of cleaning without grinding.

Example 6. The schematic diagram of fine cleaning is shown in Fig. 3.

Paper mass from waste paper is fed through pipeline 1 to fat pool 2.

After diluting with water from pipeline C to the mass fraction of fibers 1.095, the resulting suspension from pool 2 is fed by pump 4 and pipeline 5 under a pressure of 320 kPa (3.2 kgf/cm?) to the installation of vortex conical cleaners 6 to the first stage of cleaning 7 to the inlets of cleaners 8.

Conditioned fibrous material from the first stage of cleaning 7 is fed through pipeline 9 to the production of paper products, and cleaning waste is fed into container 10, and from it to mill 11. The suspension of ground fibrous material is collected in container 12 and pump 13 under a pressure of 280 kPa (2, 8 kgf/cm7) is fed through pipeline 14 to extract fiber to the second stage of purification 15 in conical cleaners 16. The fiber extracted at the second stage of purification 15 is sent through pipeline 17 to the oil pan and pool 2. The waste of the second stage of purification is under a pressure at the outlet of the purifiers of 8 ZOkPa (0 ,Zkgfs/m2) are directed into the container 18 and after diluting with water to a mass fraction of solid components in the suspension of 1.095 by mass pump 19 and pipeline 20 under a pressure of 280kPa (2.8kgfs/cm2) are fed to the third stage of purification 21 into the inlets of purifiers 22.

The third-stage cleaning waste is removed to the dump through pipeline 23, and the suspension from the extracted fibrous under a pressure of ZO0kPa (0.Zkgfs/cm2) is discharged through pipeline 24 into container 10. From container 10, the suspension from the mixture of cleaning waste from the first stage of purification 7 and the fiber extracted at the third stage sent to mill 11, from where it is again submitted for cleaning to the second stage of cleaning.

Example 7 (prototype). Fine cleaning of fibrous material from contaminating inclusions in vortex conical cleaners is carried out similarly to example 1 by a known method, but chemical-mechanical wood pulp is used as fibrous material.

Example 8. Fine cleaning of fibrous material from polluting inclusions in vortex conical cleaners is carried out similarly to example 6, but chemical-mechanical wood pulp is used as fibrous material.

The results of determining the quality indicators of multi-stage fine cleaning of fibrous materials in the installation of vortex conical cleaners by known and proposed methods

Table 1 inn Bi Bo din Ma Pii ay as Nai 1 2 Z 4 5 b 7 8

The degree of sloppiness. "SR of the initial fibrous material to be cleaned 34 34 34 34 34 34 58 58 conditioned, cleaned at the first stage of cleaning fibrous material during stable operation of the installation (without clogging) 36 38 38 38 38 38 70 72 drawn, cleaned at the second stage of cleaning of fibrous material during stable operation of the installation (without clogging) 26 32 32 32 32 32 48 53 extracted, cleaned at the second stage of cleaning fibrous material during stable operation of the installation (without clogging) 0) 33 33 35 35 36 53 61 fibrous material of cleaning waste of the second stage of cleaning during stable operation of the installation (without clogging) 22 0) 29 0) 0) 31 38 52 of fibrous material removed at the third stage of cleaning during stable operation of the installation (without clogging) 25 32 31 35 35 33 40 54 of waste fibrous material cleaning of the third stage of cleaning during stable operation of the installation (without clogging) 19 25 25 27 25 25 29 44

Average fiber length, mm of the initial fibrous material to be cleaned 1.90 1.90 1.90 1.90 1.90 1.90 1.32 1.32 conditioned, cleaned at the first stage of cleaning fibrous material during 1.71 1.61 1.60 1.61 1.61 1.60 0.80 0.81 during stable operation of the installation (without clogging) of fibrous waste material of the first stage of cleaning during stable operation of the installation (without clogging) 2.33 1.94 1.95 1.94 1.95 1.93 1.51 1.36 of fibrous material removed at the second stage of cleaning during stable operation of the installation (without clogging) 2.19 1.77 1.78 1.92 1.93 1 .84 1.42 0.85 of fibrous material of second-stage cleaning waste during stable operation of the installation (without clogging) 2.65 2.01 2.03 2.00 2.02 1.94 1.80 1.40 removed on in the third stage of cleaning of fibrous material during stable operation of the installation (without clogging) 2.49 1.80 1.82 1.81 1.82 1.81 1.69 0.90 of fibrous material of cleaning waste in the third stage of cleaning during stable operation of the installation (without clogging) 2.89 2.07 2.08 2.07 2.07 2.08 1.91 1.45

The number of blockages of the cleaners of the installation of vortex conical cleaners, together, including: 11 (9) (9) (9) (9) (9) 7 (9) of the first stage of cleaning 5 (9) (9) (9) (9) (0) With (0) of the second degree of purification 4 (9) (9) (9) (9) (9) 2 (0) of the third degree of purification 2 (9) (9) (9) (9) (9) 2 (9)

Efficiency of cleaning of conditioned fibrous material in unstable mode of operation, 90 54 - - - - - 57 -

Cleaning efficiency of conditioned fibrous material in stable mode of operation, 95 80 80 80 80 80 80 81 81

Table 2

The results of determining the value of the mass fraction of fibrous materials in the suspension of cleaning waste of the first, second and third stages of cleaning work

Eoaso| tenet pnz probably | certain

The first stage of purification

Oh min (start 1.00 0.90 0.91 0.90 0.91 1.20 1.00 1.20 countdown) 10 min. 1.12 0.90 0.91 0.91 0.93 1.21 1.19 1.21 20 min. 1.26 0.91 0.90 0.91 0.92 1.19 1.32 1.20

Storage 1.32 0.90 0.91 0.90 0.92 1.21 1.44 1.21

The second stage of purification

Oh min (start 1.05 0.90 0.90 0.90 0.92 1.21 1.11 1.20 countdown) 10 min. 113 0.91 0.90 0.91 0.92 1.22 1.22 1.20 20 min. 130 0.91 0.91 0.90 0.93 1.22 1.39 1.20

Storage 1.35 0.91 0.91 0.91 0.92 1.22 1.45 1.20

The third stage of purification

Oh min (start 1.10 0.91 0.90 0.90 0.91 1.21 113 1.20 countdown) 10 min. 1.16 0.91 0.91 0.90 0.92 1.21 1.23 1.21 20 min. 1.35 0.91 0.91 0.89 0.92 1.22 1.38 1.21

REFERENCE 1.38 0.90 0.90 0.90 0.91 1.21 1.49 1.21

When comparing the values of the indicators of the degree of grinding and the average fiber length of the cleaned fibrous material and the fibrous material in the cleaning waste obtained at the first, second and third stages of cleaning in each of examples 1-8, given in Table 1, it can be seen that in all cases in the cleaned fibrous material material, the value of the degree of grinding is greater, and the value of the average fiber length is less than the value of similar indicators of the fiber material of cleaning waste.

When comparing the values of the indicators of the degree of grinding and the average fiber length of the cleaned fibrous material in each of the stages of purification and the values of similar indicators for fibrous materials of cleaning waste of the same stages of purification, it can be seen that the values of the degree of grinding of these fibrous materials decrease, and the values of the average length of the fiber increase in. direction from the first to the third degree of purification for all examples of implementation of fine purification.

However, in the case of the implementation of the process of fine cleaning of fibrous materials both from secondary fiber and from chemical-mechanical wood pulp from polluting inclusions in vortex conical cleaners according to the proposed method (examples 2-6 and 8, respectively), the manifestation of the above-mentioned regularities as a result of reducing the polydispersity of fibrous material by grinding long fibers is less rapid than in the case of the implementation of the cleaning process according to the known method (examples 1 and 7). The analysis of the data in Table 2 regarding the change in the values of the mass fraction of fibrous materials in the suspension of waste from the first, second and third stages of purification over time shows that during the implementation of the process of cleaning fibrous materials from secondary fibers and chemical-mechanical wood pulp by a known method (examples 1 and 7) there is an increase in the value of this indicator over time both in each stage and in the direction from the first to the third stage of purification. When implementing the cleaning process according to the proposed method (examples 2-6 and 8), no changes in the values of the fiber mass fraction indicator in the suspension of cleaning waste over time are observed either in individual stages or in the direction from the first stage to the third.

Based on the data in Tables 1 and 2 and the above-mentioned regularities of fine cleaning of fibrous materials from polluting inclusions in a multi-stage installation of vortex conical cleaners, it can be confirmed that this process is accompanied by the phenomenon of fractionation - the distribution of fibrous material depending on the degree of grinding and the average length of the fiber into mainly short-fiber and mainly long fiber fraction. The first of them is the cleaned fibrous material, and the second is separated together with polluting inclusions in the cleaning waste. In the process of cleaning fibrous materials from contaminating inclusions in vortex conical cleaners according to a known method, the phenomenon of fractionation causes the accumulation of long fibers and an increase in the mass fraction of fibers in the suspension of cleaning waste after a certain time, which leads to an increase in the viscosity of the fibrous suspension, an increase in the hydrodynamic forces of friction inside the liquid when exiting through the holes for cleaning waste, reducing its speed to zero. At this time, the fibrous mass is dehydrated and a fibrous plug is formed, which blocks the opening for the exit of waste.

The stability of the cleaning process is disturbed. At the same time, the paper pulp from the fibrous material to be cleaned is directed into the cleaned fibrous material.

Violation of cleaning stability according to example 1 leads to a decrease in cleaning efficiency from 8095 to 5495, and according to example 7 - from 8195 to 57905.

The implementation of fine cleaning according to the proposed method (examples 2-6 and 8), which involves reducing the polydispersity of fibrous material due to the grinding of long fibers, led to a significant weakening of the effect of fractionation in the cleaning process, which led to the prevention of the phenomenon of clogging of cleaners, ensuring the stability of the cleaning process and maintaining efficiency of cleaning fibrous material at the level of 8095 (examples 2-6) and 8195 (example 8).

Thus, the implementation of the process of fine cleaning of fibrous materials in vortex conical cleaners from polluting inclusions according to the proposed method, which ensures the stability of the cleaning process by preventing the phenomenon of clogging of the cleaners, increases the cleaning efficiency by 30-3395, which is an advantage in comparison with the known means.

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Claims (1)

A method of multi-stage fine cleaning of fibrous material in vortex conical cleaners, which includes separation of conditioned fiber from waste at the first stage of cleaning with additional removal of fiber from waste at subsequent stages of cleaning, according to which waste from each stage of cleaning is sent to the next stage of cleaning with removal of waste from the last stage, and the fiber removed from the waste is returned to the first stage of purification, which is characterized by the fact that the fiber removed at at least one stage of purification and/or the waste of at least one stage of purification are additionally ground.