HK1011300B - Tube separator using free fall for separating plastic mixtures - Google Patents

Description

The present invention involves an improved device for a tube-free separator for the separation of plastic mixtures in the electrostatic field.

In recent years, electrostatic separation has been increasingly used in engineering applications, not only in minerals but also recently in the separation of plastic mixtures, especially those with similar densities and where the usual zinc flotation process fails.

For example, DE 41 27 575 describes the separation of polyethylene terephthalate (PET) and polyvinyl chloride (PVC) and DE 41 27574 describes the separation of polyethylene (PE) from polypropylene (PP).

The first step in the separation of these plastics was to use apparatus similar to that used for mineral separation, which usually has a significantly higher density and moves in relatively defined parabolic paths in the electrostatic field.

The tubes are exactly opposite each other (Fig. 1), so that the pivot points of the axis are in the upper view on a rectangle.

The tube-free separator according to SU-A-1085633 also has rows of tubes facing each other. The axis of rotation of the opposite tubes between which the separation space is formed are equally on a rectangle in the ground plane. However, unlike other tube-free separators, each electrode consists of two rows of tubes, each having the same electrical potential, and the tube axes of these two rows are arranged in a chessboard-like manner.

The behaviour of plastic particles in a free-fall separator described below would also lead to unsatisfactory separation results in the tube separator according to SU-A-1085633.

Plastics, which often have a sheet-like structure after being crushed, tend to float in the electrostatic field, bump into the electrodes, bounce off them and sometimes move relatively uncontrollably in undesirable directions.

The effect of this method is that a small number of particles appear in the inverted fractions and prevent the desired or required purity.

The technical task to be solved is to increase the cutting sharpness of a tube-free separator for the separation of plastic mixtures.

A configuration of the tubes according to claim 1 has now been found which will achieve better separation results.

If the axis of rotation of the tubes on one side is slightly shifted so that these points no longer form the angles of a rectangle but the shape of a parallelogram without right angles, the particles, when accelerated in the direction of the opposite tubes, have a chance of passing them, the probability of impact and deflection in the opposite direction being greatly reduced.

The best results are obtained when the pivot points are exactly on the centrelines, i.e. when two adjacent pivot points of the tubes in a row with a pivot point of the opposite row form an isosceles triangle.

The following examples show the results of two experiments demonstrating the effectiveness of the invention.

The arrangement of the tubes in relation to the state of the art (Fig. 1) is shown in Fig. 2 and Fig. 3 as a view. In the present example, vertical tubes of an otherwise known tube-free separator are arranged so that the distance between the tubes is 1.5 times the diameter of the individual tube.

The electrode is then placed in a position where the electrode is able to be moved in a different direction, and the electrode is then moved in a different direction, which is the same as the previously used electrode.

The results of separation tests compared the design separator with the well-known tube-free separator for the separation task Polycarbonate (PC) - Polymethamethylamethylate (PMMA) are given below.

Both types of slicer were driven with the same load under the same conditioning conditions with identical settings. Conditioning with 70 g/t of fatty acidContact at 45°C in the flow bed heater Field strength 3.5 kV/cm Relative humidity 28.4 % at room temperature 21°C

1. State of the art

	+ P %	Mittelprodukt %	- N %
Mengenausbringen	15,9	60,0	24,1

PMMA
Ausbringen	4,5	49,2	46,3
Wertstoffgehalt	13,8	40,5	95,1

PC
Ausbringen	27,7	70,5	2,3
Wertstoffgehalt	86,2	59,5	4,9

2. Tube dividers according to the invention

	+ P %	Mittelprodukt %	- N %
Mengenausbringen	27,5	39,1	33,4

PMMA
Ausbringen	4,1	26,4	69,4
Wertstoffgehalt	7,0	31,4	96,7

PC
Ausbringen	47,8	50,1	2,1
Wertstoffgehalt	93,0	68,6	3,3

The success rates show the advantage of the separator according to the invention. The average component is much lower than that of the conventional separator, the separation effect is much better. A much lower separation capacity is required.

The purities of the P and N fractions differ equally markedly. Whereas the filter of the invention separates both fractions with a purity of well over 90%, the comparison filter does so with only one fraction.

Claims (2)

1. A tube-type free-fall separator for separating plastics mixtures, comprising only two rows, which are disposed in opposite parallel relationship, of vertical tubes, between which is formed the separating space, wherein the tubes are arranged fixedly or rotatably about their own axis and to produce an electrostatic field between the rows the tubes of a row are electrically connected together and are connected to the appropriate potential of a dc voltage source, wherein each two adjacent tube axis rotational points of a row of the respective polarity, with the two oppositely disposed adjacent tube axis rotational points of the parallel row of the respective other polarity, form in plan the corners of a parallelogram which does not have any right angles.
2. A tube-type free-fall separator for separating plastics mixtures according to claim 1 characterised in that two adjacent tube axis rotational points of a row of the respective polarity, with an oppositely disposed tube axis rotational point of the parallel row of the respective other polarity, lie in plan on an isosceles triangle.