DE19930161A1 - Separation of mixtures of plastics, comprises feeding with separating medium into stirred container, pumping product to separator, heavy fraction from bottom and light fraction from top being fed to separate dewatering systems - Google Patents

Abstract

Separation of mixtures of plastics, comprises feeding with separating medium into stirred container, pumping product to separator, heavy fraction from bottom and light fraction from top being fed to separate dewatering systems. Separation of mixtures of plastics of different densities comprises feeding the optionally washed and powdered mixture while adding separating medium into a cyclone (1) and then into a container (2) fitted with a stirrer (3) so that separating medium with a constant content of mixture is produced. The product is fed via a controllable pump (5) from the conical lower section of the container (2) to a separator which is filled with separating medium. This is made up of an outer cylindrical central section (7), inner conical sections (11, 12, 13, 15) and outer conical sections (8, 9). The upper inner cone (13) and the upper outer cone (8) have an outlet (18) connected to a feeder pipe (17) fitted with a control valve (23). Separating medium can be removed from the lower quarter of the upper inner cone (8) via outlets (14). The separated heavy fraction is removed from the outer lower cone (11) via a controllable pump (20) which feeds it to a dewatering system (24). The light fraction is allowed to flow freely out of the upper outlet (18) via a feed pipe (19) to second, higher dewatering system (24). Separating medium from the dewatering systems is fed to a recycling tank (25) and from there back into the cyclone in accordance with the degree of filling of the stirred container (2) as indicated by a detector (4) in the container.

Description

The process is characterized by the following stages:
Stir the comminuted plastic mixture into a separation medium by using a stirring container, draw off and pump in the homogeneous mixture by using a controllable pump into a separation container completely flooded with the separation medium with the necessary internals for a trouble-free and successful separation purely according to the density difference, determined by the density the particles to the separation medium and discharge with increasing flow of the separated fractions by pumping down the heavy fraction flowing down from the separation container with a controllable pump onto a dewatering unit and free discharge of the light fraction flowing upwards, with a supportive flow increase through defined addition of separation medium an outlet gutter and entry into a drainage unit.

a) State of the art

The prior art has made numerous attempts to use plastics as mixtures of substances separate for recycling purposes.

DE 28 27 335 A1 describes a funnel-shaped separating device with a central one Agitator and separation of plastic particles heated up to 200 ° C. The agitator causes a turbulent flow against settling plates in the middle part of the funnel. The Heating the separation medium leads to a change in the specific weight.

This proposal can only lead to an imperfect degree of separation from multilayered Guide plastic objects.

DD 256049 A3 describes a process for processing "plastic waste". This one too Prior art uses a funnel-shaped separating device with baffles in the upper part of the task of the material to be separated. The short separation distance with turbulent vortexes only allow an incomplete separation of a light from a heavy fraction. The separated product with low purity can only be used for products can be used with low quality requirements. A recyclate made of pure plastic with Defined physical and technical data for an addition cannot be made.

FR 2573340 describes a method for processing plastic material Separation of paper with an intensive stirrer. There are supposed to be plastic particles in one cylindrical tube with a narrowing below the inlet tube by generation a zone with reduced flow velocity into a light, floating and into a heavy, sinking fraction can be separated.

In another constructive training, the broad tops should be on top of each other separating funnels. This should be brought about by the fact that the Separation space has parallel, vertical partitions, which are also tubular Represent dividing surfaces. On the circular dividing line of the two funnels should be a Form a small volume of a calming zone. However, this zone becomes horizontal Direction flows through the incoming and outgoing separation medium.

This device only allows the separation of plastics due to their chemical composition have larger differences in their specific weight. However, there is only an insufficient degree of separation and no single product. The throughput capacity in this device is also low, since the formation of a turbulent one Flow on the parallel plates must be reduced.  

EP 0557816 A2 describes a process with a plant for separating plastics. There are two cones with the tips to form a defined space opposite to achieve a decrease in flow rate. The separation in Fractions are said to be in two interconnected, adjoining cylindrical rooms respectively. These factions are supposed to emerge from the conical spaces that follow. The advantages of this process are due to the constructive training that is needed Blockage in the cone parts leads, restricted. So the area of application is only for granulate-like plastics and also here with a small difference in density Separation medium with the risk of clogging possible. Mixed plastics with a high proportion of Plastic films can only be produced under high production system failure to process.

This disadvantage is eliminated by the method of the invention.

DE 197 50 983 A1 describes a method similar to EP 0557816 A2. Only will Construction of the cones facing each other with parallel tips and supplemented with calming plates on the discharge. The disadvantages of EP 0557816 A2 are not eliminated. By decreasing the flow velocity in the space the On the contrary, the two opposite cones with the guide plates form Danger of blockage of the room due to stuck pieces of film (12-15 calming plates!) Or by sliding parts along the guide plates the resulting frictional force.

This danger also exists in a special way when the parts float up or down the conical upper and lower discharge segments of the separation container, as here one supporting flow velocity of the separation medium is very small and too slow increases linearly. The described solution of the lower discharge with one in height adjustable hose, which has to be raised to the height of the upper discharge, is at Material with a significantly higher density than the separation medium can lead to constipation.

The use of a propeller rotor with adjustable blades as a stirrer in the stirrer tank leads to material and material mixtures with low bulk density (e.g. film) Failure of the stir bar and thus the formation of a homogeneous mixture with the Separation medium disturbed. If mixed plastic is separated, the proportion of cork and EPS (or other foams) very high. Stirring in these materials is only conditional possible and undesirable foreign material when PE is achieved as a separate material.

These disadvantages are eliminated by the method of the invention.

b) beneficial effect

The method of the invention claims a separating plant in a calculable geometric Execution that the performance and effectiveness of the separation effect user-specific requirements by explaining all dependent influencing factors Defined separation exclusively according to the density of the materials in relation to the density of the separation medium used. Another special meaning is in the successful and trouble-free discharge of the separated materials within one Separation container, without the use of other mechanical devices and aids.

The method according to the invention enables the economically significant problem solve the mixed plastic or household waste after a Comminution and, if necessary, after prewashing into compatible mixtures or to separate pure plastics that define themselves in approximately the same density. This process works with high economic efficiency, low use of resources and manpower to enable recycling from plastic waste.  

c) Explanation of advantageous designs

Fig. 1 demonstrates as a scheme the constructive implementation of the arrangement according to the invention.

The comminuted, possibly pre-washed plastic mixture is flushed into the stirring tank ( 2 ) via a cyclone or inlet channel ( 1 ) with the addition of a separating medium ( 27 ).

The stir-in container ( 2 ) was previously filled with separating medium ( 27 ) via the feed line with control valve ( 23 ) using its level measuring device ( 4 ). The fill level is set to approximately the same height as the height of the upper discharge opening of the separating container ( 18 ). The separation tank ( 6 ) is completely flooded with separation medium and this is done via the separation medium inflow ( 17 ) with control valve ( 23 ).

The stirrer with stirring plate ( 3 ) creates a homogeneous mixture. This mixture is withdrawn from the stirred tank ( 2 ) via the continuous pump ( 5 ) and reaches the separating device ( 10 ) via the inflow pipe ( 16 ). The flow rate of the flow pump ( 5 ) is infinitely variable.

The separating device ( 10 ) consists of two circular cones ( 11 , 12 ) facing each other, one of the cones ( 11 ) constituting a circular truncated cone due to the inflow pipe ( 16 ) ending in it.

The inflowing mixture is diverted into a horizontal flow which is evenly distributed from the center of the separating device ( 10 ). Due to the square cross-section of the flow cross-section, the flow velocity decreases inversely proportional. Thus, the resulting force acting on the particles changes in the same ratio both in their acting direction and in their size. The particles separate increasingly rapidly, the further the flow through the separation space ( 28 ), formed by the cones facing each other, away from the center. This separation takes place solely on the basis of the acting upward or downward force, caused by the difference in density of the particles in relation to the separation medium used. Floating particles, as particles with the same density as the separation medium, separate purely at random.

The separation must be completed when leaving the separation space, since here the flow of the separation medium is divided into a lower flow, generated by the delivery volume of the lower discharge pump ( 20 ) and a resulting upper flow.

When passing through the lower and upper circular ring cross sections, formed by the radius of the circular cone and the radius of the cylindrical outer segment ( 7 ) of the separating container ( 6 ) surrounding the separating device ( 10 ), the flow rate of the separating medium is increased and to the same extent the separated fractions accelerated in their upward and downward movements. Structurally, this is brought about by an upper outer segment ( 8 ) and an upper inner discharge cone ( 13 ) of the separating container and a lower outer segment ( 9 ) and a lower inner discharge cone ( 15 ) of the separating container. For the additional promotion of this flow rate, separation medium can enter this buoyancy and driven space ( 29 , 39 ) regardless of the flow rate of the flow pump ( 5 ). This takes place via a separating medium inflow into the upper inner cone of the separating container ( 17 ) and / or into the lower inner cone of the separating container ( 31 ), regulated in quantity by the control valve ( 23 ). The separation medium pumped in here emerges in the lower quarter via outlet openings ( 14 ).

The fractions, which become increasingly concentrated downwards and upwards, are discharged as a heavy fraction via the lower discharge pump ( 20 ) with the separation medium and fed directly to a dewatering unit ( 24 ) and lifted as a light fraction through the separation medium via the upper outlet opening ( 18 ) and also runs via a discharge channel ( 19 ) to a drainage unit ( 24 ).

The separation medium separated from the fractions is passed into a circulation container ( 25 ) and in turn fed to the process via the circulation pump. Only the amount of separation medium carried away by the heavy and light fraction will be added to the circulatory system.

The heavy and light fraction obtained in this way can be further dried or further Separation according to the same structure described using a separation medium different density and / or further processing as a valuable material.

Fig. 2 describes the same functional relationship as described in Fig. 1, with the change that the flow pump is dispensed with and the stirred tank ( 2 ) via the inflow pipe ( 16 ) directly connected to the separator ( 10 ) in the separation container ( 6 ) is.

Instead of an open upper outlet opening ( 14 ), an upper discharge pump ( 21 ) is placed directly on an upper opening, the delivery rate of which is infinitely variable.

By working together the lower and upper discharge pump ( 20 , 21 ), a negative pressure is generated in the separation container ( 6 ) and this suction pulls the homogeneous mixture from the stirring container ( 2 ) via the inflow pipe ( 16 ) into the separation device ( 10 ).

Separable mixtures of plastics can be assigned to the following consumables:

By combining the described system in a row and using separation media different specific density is the almost sorted separation of the individual Plastics from the input mixture possible.

Terms

Fractions = separated substances from the material mixture, which are also present as a mixture, with a density greater or less than the density of the separation medium
Homogeneous mixture A mixture of material and separation medium with a uniform concentration
Separation medium liquid, with a density that is selected so that the desired separation is possible via a density difference
Particles, particles of individual material bodies from the material mixture
PE parts made of polyethylene

Figures to explain the invention

Fig. 1 shows a schematic representation of the separation system

Fig. 2 shows a schematic representation of the separation system in an alternative embodiment

It means the numbers in the figures

1

Cyclone or inlet channel with flushing

2nd

Stirring container

3rd

Stirrer with stirring plate

4th

Level measuring device

5

Flow pump

6

Separation container

7

Cylindrical outer segment of the separation container

8th

Upper outer cone of the separation container

9

Lower outer cone of the separation container

10th

Separator

11

Lower cone of the separator

12th

Upper cone of the separator

13

Upper inner discharge cone of the separation container

14

Outlet openings

15

Lower inner discharge cone of the separation container

16

Inflow pipe into the separator

17th

Separation medium inflow into the upper inner cone of the separation container

18th

Upper outlet opening

19th

Discharge channel

20th

Lower discharge pump

21

Upper discharge pump

22

Gate valve

23

Control valve

24th

Drainage unit

25th

Circular sound container

26

Circulation pump

27

Separation medium inflow

28

Separation room

29

Buoyancy space

30th

Output room

31

Separation medium inflow into the lower inner cone of the separation container

Claims (12)

1. Process for the separation of plastic mixtures of different densities in fractions, which are characterized by the upper and lower density difference of the individual particles to the liquid separation and transport medium used and the acting upward and downward force on the particles in the liquid separation and transport medium, characterized by following process stages:

• a) Introducing the possibly to be separated, pre-washed and crushed plastic mixture with the addition of a separation medium and thus flushing ( 1 ) into the stirring tank ( 2 ), which is kept at a constant filling level with the separation medium, and this separation medium with the flushed-in plastic mixture by a stirrer is stirred with a stirring plate ( 3 ) to a homogeneous mixture, which is drawn off from the conical lower part of the stirring container ( 2 ) by a continuous pump ( 5 ) with a controllable delivery rate.
• b) Introducing the mixture into a separation container ( 6 ) completely flooded with separation medium, which consists of a separation device ( 10 ) located in the center and the cylindrical segment of the separation container ( 7 ) that encloses the separation device ( 10 ), as well as the lower, inner and outer and upper, inner and outer container cone ( 15 , 11 , 13 , 12 ) and the respective inner cone ( 13 , 15 ) form a structural unit with the separator ( 10 ) and the inner upper container cone ( 13 ) from above in the middle the outlet opening ( 18 ) of the outer container cone ( 8 ) is provided with an inflow of separating medium ( 17 ), the amount of which is regulated by a valve ( 23 ), and this separating medium in the lower quarter of the upper inner container cone ( 13 ) via outlet openings ( 14 ) can emerge.
• c) withdrawing the separated heavy fraction from the lower outer container cone ( 11 ) by means of a pump ( 20 ) which can be regulated in the delivery quantity and forwarding this heavy fraction to a dewatering unit ( 24 ).
• d) Free discharge of the separated light fraction through the upper outlet opening ( 18 ) in the upper outer container cone ( 8 ) and free flow via an outlet channel ( 19 ) into a dewatering unit ( 24 ).
• e) The separating medium obtained by the dewatering units ( 24 ) is fed to a circulation container ( 25 ) and from there the material ( 27 , 23 ) is flushed into the stirring container ( 2 ) or depending on the level measuring device ( 4 ) in the stirring container ( 2 ) directly into the stirred tank ( 27 , 23 ) and only the amount of separation medium is replaced and fed to the circulatory system, which is carried away by the dewatered heavy and light fraction.

2. The method according to claim 1, characterized in that the water level in the stirred tank ( 2 ) is set equal to the height of the upper outlet opening ( 18 ) of the separating tank ( 6 ) and thus ensures that this, interrupted by the flow pump ( 5 ), connecting inflow pipe ( 16 ) from the lower cone of the stirring container ( 2 ) into the center of the separation device ( 10 ), which is arranged in the center of the separation container ( 6 ), has no pressure differences and to promote the homogeneous mixture from the stirring container ( 2 ) in a flow pump ( 5 ) is used in the separation container, the flow rate of which is infinitely variable by changing the speed. 3. The method according to claim 1, characterized in that the separating device consists of two cones ( 11 , 12 ), which face each other with the tips and the tip of the lower cone ( 11 ) is interrupted by the vertically ending from the inlet pipe ( 16 ), which comes from the stirred tank ( 2 ) via the flow pump ( 5 ) and the two cones ( 11 , 12 ) have the same geometric dimensions and the cone angle and cone radius are formed such that the flow of the mixture of plastic and separation medium is square, measured from the center of the cones facing each other in the horizontal direction, decreases and the buoyancy or downforce of the plastic mixture, which results from the difference in density to the separation medium, becomes greater than the flow force deflected horizontally by the two cones ( 11 , 12 ) and thus sets a clear density difference separation of the plastic mixture in the separation medium, which is determined by the resultant resulting force vector in direction and size, which acts on the respective particles. 4. The method according to claim 1, characterized in that the cone angle of the two opposing cones ( 11 , 12 ) of the separating device ( 10 ) is formed such that the material sliding along the conical surfaces ( 11 , 12 ) thereon by the resulting Frictional force is not prevented from moving and is expediently less than 120 °, but is still so large that a successful separation takes place according to the density difference in the volume of the separating device ( 28 ), which is formed by the center of the two cones ( 11 , 12 ) in the horizontal direction to the outlet, formed by the imaginary cylindrical surface, formed by the cone radius and the distance between the two radii. 5. The method according to claim 3, characterized in that the exit surface, formed by the imaginary cylindrical surface of the opposing cone ( 11 , 12 ) of the separating device ( 10 ), formed by the cone radius and the distance between the two radii, as a mathematical product from the circumference of a cone and the vertical distance to the cone opposite and the resulting discharge velocity of the separation medium, formed as a mathematical quotient of the flow rate from the stirring container ( 2 ) into the separation container ( 6 ) and this area, is less than 10 mm / s and the pump capacity of the controllable flow pump ( 5 ) between the stirring tank ( 2 ) and the separating tank ( 6 ) is still so great that there is no oversaturation, characterized by the breakdown of the stirring vortex in the stirring tank ( 2 ), of the material that has washed into the stirring tank during the stirring with the stirrer with stirring plate ( 3 ) comes. 6. The method according to claim 3 and 4, characterized in that the outer cylindrical container segment surrounding the separating device ( 7 ) has a height corresponding to the height of the two cones ( 11 , 12 ) of the separating device ( 10 ) facing each other and is formed by a radius , which is approximately equal to the mathematical result, is calculated from the root of the sum of the product from twice the distance between the two cones of the separating device facing each other with the radius of the cone and the square of the radius of the cone. 7. The method according to claim 1 to 5, characterized in that the cylindrical conical separating container segment ( 7 ) adjoining upper conical container ( 8 ) is limited by its volume formed by an inner conical body ( 13 ), which in turn directly on the upper cone ( 12 ) of the separator ( 10 ) is seated and the surface cross-section which decreases upwards produces a uniform increase in the flow rate of the separation medium and thus also the separated light fraction and the height of both cone bodies ( 8 , 13 ) is approximately the same size and this height is so great is that the resulting cone angle of the outer container cone ( 8 ) is as large as practically possible, but is not greater than 60 °. 8. The method according to claim 7, characterized in that in the inner upper conical body ( 13 ) is pumped from above separation medium, the amount of which is adjustable ( 17 , 23 ) and this separation medium in the lower quarter through outlet openings ( 14 ) from the conical body ( 13 ) emerges and the exit flow rate of the separation medium from these openings, formed from the mathematical quotient of the amount of separation medium pumped in and the sum of all individual exit surfaces, is significantly lower than the flow rate of the upward separation medium mixed with the separated light fraction. 9. The method according to claim 1 to 6, characterized in that the lower conical container ( 9 ) adjoining the cylindrical central separating segment ( 7 ) is limited by the volume formed, by an inner conical body ( 15 ) which in turn is directly on the lower one Cone ( 11 ) of the separation device ( 10 ) is seated and the surface cross-section, which decreases downwards, produces a uniform increase in the flow rate of the separation medium and thus also the separated heavy fraction and the height of both cone bodies ( 9 , 15 ) is approximately the same size and this height is large that the resulting cone angle of the outer container cone ( 9 ) is as large as practically possible, but not greater than 60 ° and the flow rate results from the variable delivery rate of the lower discharge pump ( 20 ), which at the end of the lower conical Body ( 9 ) is connected and the lower sw re fraction with separation medium feeds a drainage unit ( 24 ). 10. The method according to claim 1 to 9, characterized in that all the inner surfaces, formed by the inner surfaces of the central cylindrical separator container segment ( 7 ) and the conical separator container segments ( 8 , 9 ) adjoining the top and bottom, and the outer surfaces of the opposing cones ( 11 , 12 ) with the upper and lower conical bodies ( 13 , 15 ) has no sharp edges or protrusions and all connection points are rounded and smoothed and the upper outlet opening ( 18 ) with its circular outlet edge is circularly beaded and polished. 11. The method according to claim 1 to 10, characterized in that in another embodiment, the continuous pump ( 5 ), which conveys the stirred homogeneous mixture from the stirred tank ( 2 ) into the separation tank ( 6 ), replaced by a direct pipe connection ( 16 ) and an upper discharge pump ( 21 ) with adjustable delivery capacity is connected to the upper outlet opening ( 18 ) of the separation container ( 6 ), which, in cooperation with the adjustable lower discharge pump ( 20 ) via the negative pressure in the separation container ( 6 ), the homogeneous Aspirated mixture from the stirred tank ( 2 ) and otherwise no further changes are necessary. 12. The method according to claim 1 to 11, characterized in that the separating medium obtained via the dewatering units ( 24 ) is brought together in a circulation container ( 25 ) and from this directly into the stirring container ( 2 ) via the feed line ( 27-23 ), regulated is fed via the fill level measuring device ( 4 ) of the stirring tank ( 2 ) and only the amount of separating medium in the circulating tank ( 25 ) is replaced, which is carried away from the system by the dewatered light and heavy fraction and this amount supplied is controlled via the fill level measuring device ( 4 ) is fed to the circulation container ( 25 ) in the circulation container ( 25 ).