FI81393C - Method and apparatus for separating plastic particles by electrical means from solutions, especially cellulose and paper fiber solutions - Google Patents

Description

81393 1 Method and apparatus for electrically separating plastic particles from solutions, in particular cellulose and paper fiber grades 5 10

The invention relates to a method for electrically separating plastic particles from solutions, in particular cellulose and paper fiber solutions.

The invention further relates to an apparatus for applying the above method.

In the past, electronic methods for removing harmful plastics have been used mainly only in connection with some wastewater clarification methods, flotation and some plastic testing methods. The removal of plastic from cellulose-20 fibers has instead been based mainly on the density of the plastic, either in the liquid phase or in centrifugal processes.

Plastic is present as a harmful substance among some liquid substances, e.g. among cellulose. It is an object of the invention to provide a method for separating plastic from such liquid substances. In general, the electrical conductivity of plastics is poor because plastics are insulating materials. The surface resistance of plastics varies in the range of 10 ^ - ΙΟ ^^ Π-, due to which the adhesion properties of plastics are poor and their wetting is difficult. Due to poor electrical conductivity, plastics usually leave local charge areas due to machining, abrasion, and other treatments. In plastics, the mobility of electrons is poor, which means that potential differences in different parts of the product cannot be triggered.

The plastics form their own electrical voltage series, which is shown up to coarse-35 in Table 1.

2 81393 1 Table 1. Triboelectric series + Kanlnhair Bakelite 5 Cellulose acetate

Glass

Quartz

Hair

Villa 10 Nylon 6

Nallon 66 Cat Hair Viscose Cotton 15 Leather

Wood

Paper

Amber

metals

20 PVC

ebonite

Polystyrene

polyethylene

Teflon 25 - Cellulose nitrate

The purpose of the method and device according to the invention is to remove harmful plastic particles from electrically liquid substances. The method and apparatus according to the invention 30 are mainly characterized in that the plastic particles in solution are electrically separated by placing an anode and a cathode and a reference electrode in the solution and adjusting the anode and cathode potential so that the anode potential is at most 2800 mV S.C.E or cathode potential Other advantageous features of the method and device according to the invention are set out in claims 2-10 and 12.

Il 3 81393 1 The method and apparatus according to the invention will now be described in detail with reference to the figures of the accompanying drawing, in which Fig. 1 shows the result curve of a series of experiments using 5 methods according to the invention, Fig. 2 schematically shows an apparatus according to the invention.

In the method of the invention, a liquid substance containing harmful plastic particles is passed between or near two electrodes. In this case, the harmful plastic particles adhere to the second electrode. Different grades of plastic need different electrode potentials to adhere to the electrode. The anode potential is up to 2800 mV S.C.E or the cathode potential is at least -3500 mV S.C.E.

15

The method according to the invention can be enhanced by selectively providing gas evolution at the electrodes, which is done by adjusting the potentials of the electrodes appropriately.

Figure 1 shows the results of a series of experiments using the method according to the invention. In the test series, stainless steel was used as the cathode material and the harmful plastic particles were in aqueous solution. The test series had a 45 ° angle, with buoyancy. In the figure, the x-axis represents the potential and the y-axis the number of plastic particles adhering to the electrode and the percentage of particles adhering to the electrode out of the total number of particles in solution. It can be seen from the figure that at certain potential values almost all the plastic particles adhered to the electrode. The following notations have been used in the figure to represent the different experiments:

30 Experiments 52-69 O

70 - 77 c = i 78 - 91 Δ 92 - 114 o 35 The material of the electrodes used in the method is, for example, stainless CrNi steel, aluminum alloy or copper metal. Electrodes made of or coated with inert metals are also suitable for use in connection with the method. The material of the electrodes can also be graphite or carbon fiber.

Especially in situations where the liquid substance flows, the electrodes are installed in the optimum position and the optimum shape, e.g. lamellar, reticulated or plate-like, is selected for them.

Figure 2 shows an apparatus for applying the method according to the invention. According to the figure, the liquid substance 1 containing the plastic-10 particles is in the container 5 or the like. A voltage is applied to the electrodes 2 and 3, respectively, via the power supply 10 via the terminals 20 and 30. When there is a potential difference between electrodes 2 and 3, the particles adhere to an electrode with a suitable potential. The potential of the second electrode is monitored by means of the reference electrode 4 and the data is transmitted to the data unit 12, which further transmits the measurement results to the decision unit 11. The decision unit 11 controls the operation of the power supply 10 so that the required potentials remain suitable. A voltmeter 13 is connected to the second electrode, by means of which the electrode voltage.

20

In the device according to the invention, the cleaning of the electrodes 2 and 3 can be performed by adjusting the potential between the electrodes so that strong gas formation takes place at the electrodes. Such potential differs significantly from the potential used in separation.

25

The invention has been described above with reference to only one preferred embodiment thereof. However, this is in no way intended to limit the invention to this example only, but many modifications are possible within the scope of the inventive idea 30 defined by the following claims.

II

35

Claims (12)

A method for separating plastic particles from solutions, in particular cellulose and paper fiber solutions, characterized in that the plastic particles in the solution (1) are electrically separated by placing an anode and a cathode (2 and 3) and a reference electrode (4) and adjusting the anode and cathode (2 and 3). ) so that the anode potential does not exceed 2800 mV SCE or the cathode potential does not exceed -3500 mV SCE 10 A method according to claim 1, characterized in that the method is enhanced by adjusting the potentials of the electrodes (2,3) to areas in which gas evolution is selectively induced by the electrodes (2,3). 15 Method according to Claim 1 or 2, characterized in that the potential of the anode is preferably +1200 to -300 mV S.C.E or the potential of the cathode is preferably +120 to -2100 mV S.C.E. Method according to one of Claims 1 to 3, characterized in that at least the second electrode (2,3) is lamellar. Method according to one of Claims 1 to 4, characterized in that the at least one electrode (2,3) is reticulated. 25 5,81393 ^ Claims Method according to one of Claims 1 to 3, characterized in that the at least one electrode (2,3) is plate-shaped. Method according to one of Claims 1 to 6, characterized in that the material of the electrode (2,3) is at least partially made of stainless steel CrNi. Method according to one of Claims 1 to 6, characterized in that the material of the electrode (2,3) is at least partly an aluminum alloy. 6 81393 Method according to one of Claims 1 to 6, characterized in that the material of the electrode (2,3) is at least in part copper copper. Method according to one of Claims 1 to 6, characterized in that the material of the electrodes (2,3) is graphite or carbon fiber. Apparatus for applying a method according to one of claims 1 to 10 for electrically separating plastic particles from solutions, in particular cellulose and paper fiber solutions, characterized in that the plastic particles in solution (1) are electrically separated by placing an anode and cathode (2,3) and a reference electrode (4) and adjusting the potential of the anode and cathode (2,3) so that the anode potential is not more than 2800 mV SCE or the cathode potential is at least 15 -3500 mV SCE Device according to Claim 11, characterized in that, in order to clean the electrodes (2,3), the potential of the electrodes (2,3) is chosen such that it differs considerably from the potential used in the separation. 25 30 35 II 7 81393