DE2900666C2 - Method and device for the separation of plastic waste of different density and shape - Google Patents

Description

a) a ratio of the diameter of the overflow (do) - to the underflow nozzle (du) between 1 and 4, preferably ■ Ό way 1 and 2.5,

b) a ratio of the length of the cylindrical upper part (W2) to its diameter (D) between 1 and 10, and

c) a cone angle / ar) between 120 and 180 ° for plastic densities greater than the carrier liquid density or between 5 and * Sf for plastic densities less than the carrier liquid density.

The invention relates to a method and a device for separating different types of plastic waste Density and shape with particles with a maximum edge length or diameter of 20 mm In granulate and / or film shape.

It is used for the separation and disposal of floating parts, including certain plastic waste belong, known from garbage (DE-OS 19 60828), the garbage gff. after crushing in one with water to transfer the filled tank and to float into the floatable and non-flood-able ones by means of slippery discharge Separate parts, whereby turbulent in the area of the water surface to accelerate the slip separation Movements are generated.

Furthermore, mixtures of different plastic waste are also used according to their density static Schwlmm-Sink-Scheider known (DE-OS 21 07 268), in which with the help of carrier liquids or Heavy beets a separation of the plastics is carried out according to their density. The carrier flow is linked The density is adjusted so that it is noticeable from the density of the plastics to be separated deviates.

Attempts have also been made to separate by flotation (Shlmollzaka, Junzo; Akira Konosu and Yuzo Hayashi: Research on the Separation of Plastic Waste. Nippon kogyo kai shl 90, (1974), H. 1042, p. 775 (17H779), (21); (Journal of the Mining and Metallurgical Institute of Japan).

With the known floating slnk-Scheldern, for example in the form of cone or box parting, plastics with density differences of up to 0.02 g / cm ³ can be separated if the natural hydrophilicity of the plastics is canceled by the addition of wetting agents, so that A sufficient wetting of the plastics with the carrier fluid occurs. The residence of the plastics in Scheidern is a function of too

wi separating plastic = Fraktlonen. Accordingly, there are generally relatively small differences in density Long corrugated tents in the swimming slnk scheldt are required between the different types of plastic. The separation process in these separators is also adversely affected by currents in the separation liquid, in particular through the discharge devices for the sinking and floating material as well as for the solids feed are inevitably generated. For this reason, the known method results in the Necessity to achieve the most turbulence-free flow management possible, both structural as well as poses procedural problems. The application of the known method leads with respect to Purity of the separation products to satisfactory results, including a selective separation of a multicomponent mixture is possible via a corresponding multi-level static density separation, whereby the

Carrier liquid in the individual stages the plastic components still present in the carrier liquid must be adjusted.

The known separation systems are structurally relatively complex and lead in relation to the structural one Effort only leads to a relatively low throughput rate, which results in a reduction in the differences in density of the plastic components to be separated reduced.

The object of the present invention is to develop a method of the type mentioned in the introduction so that a continuous separation of the plastic components from a suspension in a flow Influencing this flow is achieved at high throughput.

In order to solve the above problem, the method mentioned in the introduction is characterized by the application the Zentilrugal density separation In hydrocyclones with constant density of the separation liquid and graded Separation density of the plastics.

In this case, the plastics which are decisive for the separation are differentiated under a graduated separation density _; lent density understood.

The separation of solids from a suspension according to the density with the help of hydrocyclones is for special trap in the processing of ores, coal and salts known (DE-OS 26 12 874). There are also Process for the fractionation of suspended solids by means of hydrocyclones known, in which the Fractionation influenced by a height-controllable sludge filling in the area of the underflow nozzle is (DE-OS 26 22 880).

It is also known (US-PS 35 37 657) to use hydrocyclones arranged one behind the other for the separation of mineral substances, with carrier liquids in the individual cyclones? 2R different density are used, where fractions of different grain size are fed to be separated !: good and its underflow with the? The inlet of the next hydrocyclone is connected.

A similar arrangement is known for the separation of fibers in the pulp and wood industries (US-PS 30 39 603), in which also the lighter particles from the underflow nozzle the inlet of the next Turn the hydrocyclone supplied.

An application of aer centrifugal density separation in hydrocyclones for plastic mixtures has so far been considered impractical by experts and has therefore not been investigated further, although there is a considerable need for the separation of plastics according to their density in order to be able to reuse the plastics. Because of the low density differences between the Kunststoffarteu and because of the large difference in the shape of the particles to be separated, a separation of such plastic - ^w mixture used not considered to be practical in the individual components in highly turbulent centrifugal hydrocyclone. For the separation of plastic particles with such small density differences as they occur in practice, the experts only considered the swim-sink separation as a possible solution, because it was believed that the occurrence of turbulent flows at the low || Differences in density of the plastics to be separated would only have an unfavorable effect on the separation process, -'5

During the swim-slnk-scheldt a laminar flow of the carrier liquid is ensured

ff could.

H Notwithstanding the above considerations, it was found that with a corresponding

i% flow, which is reflected in the design of the hydrocyclone, depending on the

ff DlchtedlTerenz between the plastics to be separated and / or the carrier liquid surprisingly good -w

| 8 results could be achieved with throughput rates, -velche, based on the interface, in comparison

i * to a static floating slnk separator increased by a factor of 100.

p The hydrocyclone or hydrocyclones can thereby with a high throughput, ie a relatively high inlet

■ S speed operated throw, with a high inlet speed favorably on the separation of the

Ü Foil content of the plastic mixture has an effect. - 4S

ft The volume ratio of plastic to carrier liquid is expediently smaller in the suspensions

|| set as 1:20. Experience has shown that a higher concentration of plastic in the carrier

ψ liquid leads to a worsening of the results.

-, · .: As with the well-known Schwlmm-Slnk cut-off, it is also advisable to use

'''· ■ Hydrocyclones add a wetting agent to the carrier liquid to reduce the interfacial tension, 5 »

, τ; ■ if plastics are thrown separately that are difficult to wet by the carrier liquid.

'■ In the case of έΐΓ separation of several plastic components pu3 of a carrier liquid, one has the choice,

, ■ Either in the first stage of separation the plastic with the lowest density or the plastic with the

/ to be separated from the other plastic components with the greatest possible density. It must depend on the intended

^; . ''? · Separation process a carrier fluid appropriate density n Compared to the plastic to be separated

chosen throw.

- It is useful if, when separating several plastic components, they are connected one behind the other

-> Hydrocyclones first separate the plastic of greater density, if it forms the larger proportion

'and Throw the plastics deposited with decreasing density in the subsequent cyclones or

First the plastic with the lower density, if this forms the largest proportion, is separated and «> '■■ Throw the plastics deposited in the following cyclones with increasing density.

[■ It is useful for separating plastic with a density above 1 g / cm ¹ as the soaking liquid

y To use water with an additive to increase the density, such as CaCl or NaCl, and to separate

;> Plastics with a density of less than 1 g / cm ¹ organic liquids or mixtures of water and organic

V see liquids to be used whose density lies between the density of the plastic to be separated. The to

; ' The carrier liquids used must correspond to the respective densities of the plastics to be separated

Throw adapted, - where the difference in difference between the plastics and / or the carrier fluid is a measure of I.

^: ; represents the separation effect and also determines which plastic is through the overflow or through the under |

29 OO 666

run of the hydro cycle is discharged.

In order to keep the need for carrier liquid as low as possible, multi-stage separation is useful the plastic particles discharged with the liquid, which are fed to the next stage are previously separated from the liquid, showered and with the carrier liquid of the next stage «Commutes. The carrier fluid thus separated from the plastic particles can be returned again, as well as the support flow from the separated component of the plastic, of course, is returned and used for the preparation of new suspensions.

Experience has shown that the application of the procedure provided according to the invention leads to a separation of the various plastic components brought up to degrees of purity in the order of magnitude between 95 ίο and 99 «.

When separating PVC, flotation can be used to separate the individual PVC types can be achieved, as well as post-cleaning for other plastic components by means of flotation Is possible to further increase the degree of purity of the separated plastics and in this way the To increase the range of possible re-uses.

Systems for carrying out the method described are based on a series connection that is known per se of conical-cylindrical hydrocyclones with graduated separation density and are characterized by

a) a ratio of the diameter of the overflow (do) - to the underflow nozzle (du) between 1 and 4, preferably 2 <> I and 2.5,

b) a ratio of the length of the cylindrical upper part (HT) to its diameter (D) between 1 and 10, and

c) a cone angle (a) between 120 and 180 ° for plastic gaskets larger than the carrier gasket or between 5 and 40 ° for plastic gaskets less than the girder gasket.

In order to achieve favorable separation results, the ratio of four lengths of the cylindrical upper part (Hl) to its diameter should be measured increasingly with decreasing density difference between the plastics to be separated and the carrier liquid.

The different forms of formation of the hydrocyclones for the different plastics differ -. "> This density is of great importance.

If, for example, polyvinyl chloride (hereinafter referred to as PVC) is to be separated as the largest proportion of a mixture of polyethylene (PE), polystyrene (PS) and PVC in the first stage, water can be used as the carrier liquid according to the above, since PVC has a density of about 1.3: 7 g / cm ¹ and thus has a greater density than water. The separation of the PVC from the remaining plastic components "from the suspension takes place in accordance with the above-mentioned feature c with the aid of a slim hydrocyclone, ie a hydrocyclone whose cylindrical upper part is large in length compared to its diameter and has a cone angle between 120 and 180 ° The PVC, which has a greater density than the carrier liquid, is discharged from the underflow nozzle, while the other plastic components are discharged with the carrier liquid through the overflow nozzle.

4i The drawing gives an execution list of the process scheme for the present invention as well as the Schematic representation of the embodiments of the hydrocyclones used in this context, in a separate representation again.

It shows

Flg.! the procedural scheme,

4-leaf 2 and 3 Forms of the hydrocyclone, which are denoted by 4 and 9 in the process diagram are.

The process scheme and the reproduced hydrocyclones relate to a system for separation a plastic mixture consisting of granules of the following composition:

so fraction 1: PVC 54.0 «density = 1.38 g / cm ³

Fraction 2: PS 22.7 "density = 1.03 g / cm ³ Fraction 3: PE 23.3" density = 0.95 g / cm \

The plastic mixture from the aforementioned three fractions is first fed to a cutting mill 1, where it is crushed into plastic particles smaller than 4 mm in maximum diameter and, if necessary, fed to a mixing container 2 after washing and hygiene treatment not shown in the scheme. In which ■ a separating liquid with a density of 1.05 g / cm ^J is introduced at the same time, namely in such an amount that about 60 parts of the carrier liquid account for 1 volume part of the plastic. When separating liquid water is used with an additive in the above fractions, since the density of Trägerflfls- b "sigkelt significantly greater than the density of fraction 2 Should to in the first separation stage, the PVC contained in the largest amount of the mixture with the required degree of purity to be able to separate. The water has therefore been brought to the aforementioned density value of 1.05 g / cm ³ by adding salt, the density of the separating liquid having to be monitored and readjusted. If the PVC to be separated is not required to be of a particularly high degree of purity, it is also possible to use water without an additive 6. * to change the density of the carrier liquid.

The suspension corresponding to the stirred tank 2 is fed via the free-flow centrifugal pump 3 to the hydrocyclone 4, the dimensions and proportions of which are shown in FIG.
It can be seen that the hydrocyclone used in the first stage to separate the PVC is slim and conical

29 OO 666

1st, the cone angle only 8 ° and the ratio of the length of the cylindrical upper part to the Diameter is 4.

In the hydrocyclone 4 there is a separation in the catfish that part of the carrier liquid through the overflow with fractions 2 and 3 through the underflow the other part of the carrier liquid with fraction 1 be discharged. s

The overflow fraction A reaching the dewatering screen S, which is subsequently transferred to the agitator tank 7 is supplied, has the following composition:

Group 2: PS 49.5 » Fraction 3: PE 50.5%. ι »

The liquid draining from the dewatering screen is via the line 15 together with the drain returned to the stirred tank 2 from the dewatering screen 6 for the underflow fraction. In the drainage sieve S fractions 2 and 3 are sprayed to remove the salt residues from these fractions.

The end product B with the following composition is obtained from the dewatering screen 6 for the underflow fraction won:

Fraction 1: PVC> 99.9 * Yield> 99.9%. Fraction 1 is also sprayed off in the dewatering screen 6 in order to remove the salt residues.

The fractions 2 and 3 from the dewatering screen 5 reach the stirred tank 7, in which they ^{are suspended with a carrier liquid with a density of 0.97 g / cm 5} , for example a mixture of water and alcohol, for the separation step. Here, too, there must be ongoing leakage control and regulation. Via a free-flow centrifugal pump 8, the suspension is fed to the hydrocyclone 9, which the In F1 g. 3 reproduced - ^{5 level} training and dimensions. It is a hydrocyclone with a flat bottom, in which the cone angle <x is about 170 °. The ratio of the length of the cylindrical upper part of the hydrocyclone to its diameter is 8 in this example.

From the hydrocyclone 9 the overflow fraction reaches the Entwasserungssleb 10. In this falls Dewatering screen fraction 3 as end product C with the following composition: · '"

Group 3: PE 90.8% Yield 94.4%. The underflow fraction with the end product D of the following composition is obtained in the dewatering screen 11: - ¹⁵ Fraction 2; HP 94.4 * Yield 90.3%.

To remove the Trennflüsslgkeit of fractions 2 and 3, this can to Entwässerungssleben - ^"; from 10 and 11 are also abgebraust the Entwässerungssleben 10 and 11 reaches the separated there TrägerflOsslgkelt upper conduit 16 back into the tubular container 7..

The test data and flow rates are shown in the table below. Products C and D can, if necessary, be further processed in post-cleaning stages.

mm d " g / cm ³ bar m ^y / h V. Frac. 1 kg / h frac. 2 kg / h Frac. 3 kg / h Cyclone type Λ. 10 Pf Δ? V « 0.6 OQ ₀ ^m u ^m o ^m » m " m. step 1
Ak 1 17.5 18th 1.05 1.9 4.1 2.8 30.48 12.84 - 13.12 - Level 2
BK 4 26th 0.97 0.5 2.9 Product B:
Products: U5 11.59 12.39 0.74 d. - Diameter of the ZyUon overflow
d. - Diameter of the cyclone sub-baptism PVC content 99 ^% Yield: 99.9%
PE content 90.8% Yield: 94.4%

V. rii. - Volume or mass flows in the upper reaches of product D: PS content 94.0% Yield: 904% V "m, - volume or mass flows in the underflow

(H)

A few more examples of practical experiments are given below, as follows are listed again in a compilation.

1. Separation of the PVC surface from a PE + PS and PVC mixture

Task: 5 g / l each of PE, PS and PVC granules (grain size small 4 mm) Mixing ratio of the plastics: 1: 1 Separation medium thickness: 1.05 g / cm '

⁵ > ·

29 OO

Cyclone: SO mm 0; Length of the cylindrical part: 200 mm; Cone angle: 8 °; Overflow nozzle diameter: 17.3 mm; Underflow nozzle diameter: 10 mm.

With a throughput of 5 mVh, a PVC product is obtained with a purity of greater than 99.9% Im 5 underflow.

2. Separation of the PVC surface from a PS-PVC blend

Task: 6 g / l each PS and PVS granulate (grain size small 4 mm) "> Separation medium thickness: 1.0 g / cm '

Cyclone: SO mm 0; Length of the cylindrical part: 200 mm; Cone angle: 170 °; Overflow nozzle diameter: 17.3 mm; Underflow nozzle diameter: 10 mm.

With a throughput of 2.3 mVh, the result is a PVC output of 98.8% with a content of 15 97.3% and a PS yield of 96.8% with a content of 98.6%.

3. Separation of a PE-PS mixture

Task: each 5 g / l PE and PS granulate (grain size small 4 mm) '»Separation medium thickness: 0.97 g / cm'

Cyclone: 100 mm 0; Length of the cylindrical part: 800 mm; Cone angle: 170 °; Overflow nozzle diameter: 26 mm; Underflow nozzle diameter: 18 mm;

At a throughput of 5.7 m ^J / h, the PS product has a content of 93.4% with an output of -590.2% and the PE product has a content of 94.4% with an output of 92 , 6 ».

4. Separation of a PVC Fraktlon from a mixture of PE (granules / foils), PS (granules) and PVC

(PVCwelch granulate / Follen)

'' Task: 4 g / l each of PE, PS, PVCwelch granules (grain size small 4 mm) 2 g / l PE-PVC filament each (particle size small 4 mm)

Separating medium thickness: 1.06 g / cm * Cyclone: 100 mm 0; Length of the cylindrical part: 600 mm;

Cone angle: 14 °; Overflow nozzle diameter: 26 mm; ^v; Underflow nozzle diameter: 18.2 mm;

With a throughput of 9 m '/ h, a PVC product with a content of 99.9% was obtained

a yield of 98.256. The PVC-Gchäii in the overflow is only 0.6%.

Compilation of Examples 1 to plastic material ground up <4 mm

With- Underflow- Overflow- Amounts- Density Dmr. Cylinder. Slimness- Cone- Dif-.n- Dmr. Nozzle underflow product overflow product

play faction faction m. thin. of the long degree angle overl. Lower mated _{Common s ,: hwer A} usb. difficult AnL easy educ. easy

Medium

U: U DL Lg / d do you do / you

mm mm mm mm

1 PVC PE + PS 1: 1 1: 66 1.05 50 21 granulated granulated

2 PVC PS 1: 1 1: 82 1 50 200 granulated granulated

3 PS PE 1: 1 1: 99 0.97 100 800 granulated granulated

4 PVC PS + PE 1: 1.67 1: 74 1.06 100 600 granulated granulated

+ Foils + foils

8 ° 17.5 10 1.75 99.9

170 ° 17.5 10 1.75 97.3

170 ° 26 18 1.44 93.4

14 ° 26 18 1.44 99.9

98.8 98.0 96.8 O O 90.2 94.4 92.0 ON ON 98.2 99.4 99.9

For this purpose 2 sheets of drawings

Claims (7)

29 OO 666_ Claims: 1. Process for the separation of plastic waste of different density and shape with particles of maximum 20mm edge length or diameter in granulate and / or film form, marked s through the use of centrifugal roof separation in hydrocyclones with a constant density of the separation liquid and graduated separation density of the plastics. 2. The method according to claim 1, characterized in that the volume ratio in the suspensions of plastic to the carrier liquid is set less than 1:20. 3. The method of claim 1 or 2, characterized in that the Tragerflüssigkeit to Verminde- ^<n tion of the interfacial tension, a wetting agent is added. 4. The method according to any one of the preceding claims, characterized in that in several Interconnected separation stages first the plastic of greater density, if it has the larger Quantitative proportion forms, separates and In the subsequent separation stages the plastics with decreasing Density can be deposited, or first the plastic with the lower density, if this is the largest Quantitative share forms, separates and in the subsequent separation stages the plastics with increasing Density are deposited. 5. The method according to claim 4, characterized in that for the separation of plastics with a density above 1 g / cm ³ as the carrier liquid water, optionally with an additive to increase the density such as NaCl, and for the separation of plastics with a density less than 1 g / cm ³ organic liquid ²⁰ th or mixtures of water with organic liquids can be used. 6. The method according to any one of the preceding claims, characterized in that with multi-stage Separation of the plastic particles carried out with the liquids, which are the next step are supplied, previously separated from the liquid, sprayed and with the carrier liquid the next one Stage to be suspended. 7. Plant for performing the method according to claims 1 to 6, consisting of one per se well-known HlnterelnanderschaSaing of conical-cylindrical hydrocyclone ^ with graduated separation density, marked by