DE102011009792A1 - Method for cleaning contaminated fibers of waste paper, involves moving fibers to be cleaned with liquid, and bringing together solid-fluid mixture with air-liquid mixture - Google Patents

Abstract

The method involves moving the fibers to be cleaned with liquid, and bringing together a solid-fluid mixture is with an air-liquid mixture, where the combining of the air-liquid mixture with the solid-liquid mixture takes place with widely differing flow speeds. The dissolved contaminated particles settle on the air bubble from the air-liquid mixture. The mixture of a fractionation is subjected to separation of the fiber portion. An independent claim is also included for an arrangement for cleaning contaminated fibers.

Description

The invention relates to a method and an arrangement for cleaning fibers. Both may find application in physical processes intended to effect the separation of impurities from fibrous solid particles and in which the fibrous solid particles are in a liquid-solid mixture with liquids. This can be z. As in plants for waste or printing paper recycling be the case in which distributed in volumes of water pulp fibers are that it is to be cleaned of adhering ink particles.

The state of the art in the cleaning of used paper to be treated with cellulose fibers has a number of solutions which make use of the flooding of the fibers.

The essential step in processing recovered paper for reuse is to remove the printing inks as much as possible. In conventional flotation cleaning, the fibers of the waste paper are swelled by the use of alkaline substances, which makes it possible to detach the printing ink. Hydrophobic ink particles can be collected and floated from the suspension of fibers, fillers and inks by an in situ precipitated fatty acid salt. By means of this conventional process, comprising whipping the paper, sorting, flotation under alkaline conditions and, if appropriate, subsequent flotation, hydrophobic printing ink can usually be satisfactorily removed.

Water-soluble printing inks, such as flexographic printing inks and inkjet inks, which often contain hydrophilized very small color pigments by means of sulfonation, can not be removed satisfactorily by conventional flotation deinking. The high-quality raw material office paper becomes a problem because it is too dark even for graphic paper with the lowest white content, newsprint. The dissolved inks also pollute the water cycle. Although such water-soluble inks and hydrophilized color pigments can be separated by washing the waste paper - at the same time, however, the fillers are also removed, so that the yield of this cleaning process drops to values of less than 70%.

Solutions proposed in the patent literature are intended to improve these purification methods.

So z. B. in the German publication DE 11 2006 002 685 T5 proposed a device for performing a deinking process, which has a special diffuser in a flotation cell.

Also in the German Offenlegungsschrift 10 2009 006 033 A1 For example, a flotation process and a flotation apparatus for removing contaminants by means of gas bubbles from an aqueous pulp suspension in a flotation tank are described. The flotation tank has at least one of a stream of pulp suspension perfused mixing device for supplying at least one stream of gas and also has at least one derivative for the flotation foam formed with the impurities and at least one outlet for the purified pulp suspension.

In this case, a reliable and effective removal of contaminants should be made possible even at relatively high material densities, that in the flow channel several nozzles for supplying pulp suspension partial flows open.

Also in the publication DE 698 14014 T2 The invention relates to a process for deinking pulp which originates from the formation of a pulp of different grades of water with water, in which the pulp stream is traversed at least once by an air bubble stream. The process is characterized in that a counterflow of water is led into the air bubble stream for deinking, after these bubbles have flowed through the slurry and have loaded with ink particles, so that the water countercurrent flows through the particles entrained by these deinking bubbles, z. As fibers, sludge or fillers and continues with it.

The main disadvantage of these solutions is a high level of technical implementation of this deinking systems, the high manufacturing and assembly and maintenance costs entails, the quality of cleaning is still unsatisfactory, since experience has shown that only a degree of purification is achieved, the whiteness increase by three degrees equivalent.

From this disadvantage of the solutions of the prior art, the task arises to develop a method with which the desired cleaning of fibers from unwanted adhesions, for. B. ink particles u. Ä., Can be achieved with significantly reduced technical and economic effort. In addition, an arrangement is to be developed with which a method satisfying the aforementioned requirements can be realized. At the same time both inventions should allow a significantly improved degree of purification.

The object of the invention is achieved by a method which includes the method steps according to claim 1. Furthermore, the object of the invention with an arrangement is achieved, which is constructed according to the features of claim 8. The respective subclaims 2 to 7 contain advantageous embodiments of the method end.

The essence of the process invention is that the fibers to be cleaned, preferably ink-contaminated cellulose fibers, with liquid, preferably water, are added and merged as a solid-water mixture with an air-water mixture flowing. The confluence of the air-water mixture with the solid-water mixture takes place with greatly different flow velocities. Upon collision of the particles of the two mixture streams, a solution of the contaminants from the surfaces of the fibers takes place.

The coalescence process is carried out in such a way that at the same time a significant dilution of the water-solid mixture takes place and the dissolved impurity particles settle on the air bubbles from the air-water mixture.

According to the invention, the coalescence process can be carried out in several variants: it is possible to allow the mixtures to be brought together to flow together in countercurrent, in the same flow direction or at arbitrary angles.

The air-water mixture combined with the solid-water mixture is produced by one or more mixing systems from which the air-bubble-conveying air-water mixture exits through a high-velocity differential pressure acting in the systems.

The flow process described can proceed without further expenditure on equipment in piping of a cleaning system. Here, already mixture-dilution, fiber-impurity separation and binding of the impurity particles to air bubbles, without this separation process of the impurities required by the fibers of special process vessels.

In a subsequent process step, a separation of fiber content, contamination-loaded foam from the air bubbles and water is carried out.

Only to this separation of fiber content, polluted foam from the bubbles and water, the mixture is passed into a known fractionator, where the resulting on the surface foam, contaminated with contamination, is separated from the fibers.

The nature of the array invention is characterized by the layout scheme of a fiber cleaning plant which is limited to the presence of piping having one or more mixing systems disposed therein and one or more fractionators downstream of the piping.

The execution of the inventive method within a likewise inventive arrangement shows that it is surprisingly possible, waiving elaborate process apparatuses known arrangements, already exert the desired cleaning effect on contaminated fibers with the simple means simple in piping integrated mixing systems and simple downstream fractionators.

The invention will be explained in more detail with reference to an exemplary embodiment.

The accompanying drawing shows a schematic diagram of a plant for waste paper fiber cleaning according to the inventions.

According to the drawing, the plant for waste paper fiber cleaning of the embodiment, a filtrate container 1 , a fabric container 2 , a fractionator 3 , a foam breaker 4 , Mixed systems 5 as well as pumps 6 and 7 on.

The mentioned elements of the plant for waste paper fiber cleaning are with pipelines 11 to 17 connected as follows:
With piping 11 is over pump 6 a solid-water mixture with 4% solids content of fibers to be cleaned from the substance container 2 towards the fractionator 3 promoted. The fibers to be cleaned are contaminated with adhering on its surface contaminant particles in the form of ink particles.

The solid-water mixture is passed through the pipeline at a flow rate of 1560 l / min 11 transported, which has a diameter of 125 mm has. The flow rate at these parameters is 2.12, m / s.

With piping 12 is over pump 7 a filtrate-air mixture from the filtrate tank 1 also in the direction of the fractionator 3 promoted. The filtrate-air mixture is passed through the pipeline at a flow rate of 4685 l / min 12 transported, which has a cross section of 21 × 18 mm. The flow rate at these parameters is 14.62 m / s.

From pipeline 12 branches pipeline 15 and carries a portion of the filtrate through a mixing system 5 , In this, the filtrate stream is mixed with air bubbles, which are caused by the water flow within the mixing system 5 entrained by the injector effect air. The size and number of air bubbles are due to the flow rate and throughput of filtrate water through the mixing system 5 adjustable, so that depending on the conditions of the specific cleaning task, the optimal bubble size microbubbles up a filtrate-air mixture is available, which by piping 17 at the branch point 8th back into the pipeline 12 is mixed in.

From branch point 8th leads the pipeline 12 So a filtrate-air mixture with high flow velocity and a high number of small air bubbles possible. An advantageous implementation of the method according to the invention takes place at bubble sizes of about 0.5 mm or smaller.

At the branch point 9 are pipeline 11 and piping 12 merged and run together as a pipeline 13 to the fractionator 3 , pipeline 13 has a diameter of 200 mm in this embodiment.

At the branch point 9 meet the solid-water mixture with 4% consistency from pipeline 11 and the air-bearing filtrate-air mixture of piping 12 with very different flow rates each other. This air bubbles of the filtrate-air mixture collide with high kinetic energy on the contaminated fiber content of the solid-water mixture. Surprisingly, the contamination particles present on the fibers, z. As ink particles, separated from the fibers and attach to the surface of the air bubbles. This process is similar to the cleaning process of surfaces by high pressure water, known as "carhing".

In the union point 9 the piping 11 and 12 following pipeline 13 moves the now consisting of water, fiber content and impure air bubbles existing foamy mixture with a consistency of 1% fiber content, a flow rate of 6.250 l / min and a flow rate of 3.3 m / s to a fractionator 3 , Here, the now-cleaned fibers are separated from the contaminant-carrying foam.

This proportion of foam is via pipeline 14 to a foam breaker 4 passed through the pipeline 16 is fed with pure air-water mixture.

Decisive point of the cleaning method explained in the present embodiment is the meeting of the solid-water mixture with the contaminated fibers with the filtrate water-air mixture at high flow differential speed and the presence of a large number of fine air bubbles, which only causes the surprisingly occurring abrasive cleaning effect.

A particularly advantageous effect of the method occurs when the flow directions of the colliding mixtures differ greatly. The ideal case is given in the complete counterflow of the two mixtures.

In the embodiment shown, an exemplary arrangement has been described in an exemplary application of the method according to the invention. However, the invention includes all other arrangements with different process apparatuses in which a fiber cleaning is carried out by means of the method according to the invention.

The method according to the invention and the arrangement according to the invention can be used in all physical processes in which solid particles of adhering impurity particles are purified by separation and takeover of the impurity particles by means of air bubbles in an air-solid-liquid mixture.

With their application very large cost savings can be achieved in which can be dispensed with expensive process vessels in favor of the installation of technically inexpensive RV systems in transport pipes for air bubbles.

Preferably, the inventive method and the inventive arrangement for cleaning of printed waste paper can be used in paper production.

LIST OF REFERENCE NUMBERS

1

filtrate

2

fuel tank

3

fractionator

4

foam breaker

5

mixing system

6

pump

7

pump

8th

branching point

9

branching point

11

pipeline

12

pipeline

13

pipeline

14

pipeline

15

pipeline

16

pipeline

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 112006002685 T5 [0006]
• DE 102009006033 A1 [0007]
• DE 69814014 T2 [0009]

Claims (8)

Process for cleaning contaminated fibers, in which, in a first process step, the fibers to be cleaned are mixed with liquid and be combined in a second process step as a solid-liquid mixture with an air-liquid mixture, wherein the confluence of the air-liquid mixture with the solid-liquid mixture with greatly different flow rates and this process is performed so that at the same time a significant dilution of the solid-liquid mixture takes place and the dissolved impurity particles are on the air bubbles fix the air-liquid mixture, and in a third process step for the separation of fiber content, contaminated foam from the air bubbles and liquid resulting in the second process step mixture is subjected to fractionation, wherein the foam formed on the surface, contaminated with impurities, is separated from the cleaned fibers. A method according to claim 1, wherein the mixtures to be merged flow together in countercurrent or in the same flow direction or at arbitrary angles. The method of claim 1, wherein the solid-liquid mixture is present in an initial concentration of about 4% dry matter. The method of claim 1, wherein the solid-liquid mixture is diluted to a solids concentration of about 1% dry matter. The method of claim 1, wherein the air-liquid mixture at a flow rate of about 6 to 15 m / s against the solid-liquid mixture whose flow rate is about 2.0 m / s is performed. The method of claim 1, wherein the liquid in the respective mixtures is water. The method of claim 1 wherein the solid is the respective mixture of cellulosic fibers. Arrangement for the purification of contaminated fibers containing several pipelines ( 11 to 16 ) and at least one of the pipelines ( 11 to 13 ) downstream fractionator ( 3 ) for fractionation of fiber and impurity fractions of a foamed air-water-solid mixture, wherein in at least one pipeline region ( 15 and 17 ) a mixing system ( 5 ) is present for generating an air-liquid mixture of liquid and air bubbles.

Images