GB1593220A

GB1593220A - Separation of a mixture of paper and plastics foil

Info

Publication number: GB1593220A
Application number: GB21694/78A
Authority: GB
Original assignee: Esmil BV
Current assignee: Esmil BV
Priority date: 1977-05-31
Filing date: 1978-05-23
Publication date: 1981-07-15
Also published as: IT7868233A0; NL7705925A; DE2823885A1; AT364242B; ATA392778A; NL179665B; NL179665C; FR2392721B1; BR7803498A; IT1108505B; SE7806263L; FR2392721A1; BE867621A; CH633199A5

Abstract

For example in domestic rubbish, the majority is composed of paper and plastic. In order to be able to separate these two portions from each other as well as possible, the rubbish mixture (4) which has been prepared in terms of size is moistened before the separation into the two portions. It has been established in this case that the later separation will be more efficient if the moistening liquid is fed to the mixture in a finely divided manner, that is for example by a spray (6), and if simultaneously with this moistening the mixture is intensively mixed, for example by means of a conveyor and mixing screw (8). The latter is situated in this case in a trough (1). Also, in this process less water than hitherto is required. <IMAGE>

Description

(54) SEPARATION OF A MIXTURE OF PAPER AND PLASTICS FOIL (71) We, ESMIL B.V. of Stationsstraat 48, Amersfoort, The Netherlands, a Dutch limited liability Company do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a method of separating a mixture consisting mainly of a paper fraction and a plastics foil fraction, and is particularly useful as a step in the treatment of domestic waste.

To separate a mixture consisting mainly of fractions of paper and plastics foil, it is known prior to separating them, to moisten the mixture (see laid open Dutch patent application 74.03554). Because of the difference in absorption of water of paper and plastics foil, the moistening causes these two fractions to behave differently in an air sifter so that they can be separated more satisfactorily. It has, however, appeared that in practice this separation leaves something to be desired.

An object of the invention is to make it possible to increase the degree of separation achieved in this process considerably.

According to the invention there is provided a method of separating a mixture consisting mainly of a paper fraction and a plastics foil fraction, wherein the mixture is moistened and then separated, characterized by application to the mixture of moistening liquid in divided form and thorough mixing with said liquid prior to the separation. Preferably, the mixing with the moistening liquid takes place in a trough containing a rotating mixing and conveying element which conveys the mixture along the trough while mixing it.

It has appeared that the separation process can be markedly improved by the measures proposed by the invention, i.e. applying the liquid in divided form (for example by spraying) and then thoroughly mixing it with the mixture to be separated. It has in particular been found that the degree of separation of paper and plastics foil can be raised from previous values of 35 to 40% to values of 70 to 80%. As a result, the separated end products of the method may be very much more useful for further processing and also simpler equipment may suffice for air sifting the paper and plastics fractions to separate them.

Another advantage obtainable is that the liquid, being applied in divided form, can be utilized more fully, so that with a small quantity of liquid better separation results may be achieved. This is for example shown by the fact that it is not necessary for the element supplying the liquid, e.g. a spray, to cover the whole length of the trough, but that it can be sufficient to place this element above only the first portion of the trough travelled by the mixture.

Good results may be achieved using a trough with a width of 40 to 80 cm in which there is a mixer screw measuring 7 to 12 m in length and having a blade diameter of 40 to 80 cm and a pitch of 15 to 30 cm. Using this device it has been found advisable to rotate the mixer screw at 40 to 90 rpm (revolutions per minute). It is then preferably to feed 100 to 200 g moistening liquid per kg of treated mixture. If the amount of liquid is outside these limits, the degree of separation may be undesirably reduced.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawing, in which the single figure is a diagrammatic side view of apparatus for preparing the mixture for separation.

The figure shows a trough 1 at whose supply end a supply belt 2 introduces a mixture 4 out of a chute. This mixture mainly (e.g. at least 50% preferably more) consists of sheets of paper and pieces of plastics foil, such as is obtained in the treatment of domestic waste.

Near the beginning of the trough 1 (nearer than is indicated in the diagrammatic drawing) there is provided a spraying system 6, from which divided sprays of water from a storage tank 5 can be sprayed onto the mixture. At the discharge end of the trough, the moistened mixture is ejected onto a conveyor belt system 7, by which it is conveyed to an air sifter (not shown) for separation of the two fractions.

The trough is provided with a mixer screw 8, the dimensions of which are such that on the one hand the mixture is conveyed from the supply end towards the conveyor belt system 7, while at the same time the mixture is thoroughly mixed with the water sprayed on from the sprays 6 and thus is intensively exposed to the effects of the water.

In a particular preferred embodiment, the width of the trough is 50 cm, and the length of the mixer screw 8 is 800 cm. The blade diameter of the mixer screw is 48.5 cm. the pitch of the mixer screw is 20 cm and in operation the screw is driven at 80 rpm. This equipment is suitable for treating 13000 kg of mixture per hour. With a feed rate of 115 g water from the sprays 6 per kg of mixture, a degree of separation of 80% was achieved in a wind sifter fitted after conveyor belt 7.

The method specifically described above only constitute one embodiment typical of the invention. A large number of variations are possible and can be envisaged, and all such come within the scope of the invention.

WHAT WE CLAIM IS:- 1. A method of separating a mixture consisting mainly of a paper fraction and a plastics foil fraction wherein the mixture is moistened and then separated, characterized by application to the mixture of moistening liquid in divided form and thorough mixing with said liquid prior to the separation.

2. A method according to claim 1 wherein the mixing with the moistening liquid takes place in a trough containing a rotating mixing and conveying element which conveys the mixture along the trough while mixing it.

3. A method according to claim 2 wherein the liquid is sprayed onto the mixture in the trough.

4. A method according to claim 3, wherein the liquid is sprayed onto the mixture by liquid supply means mounted above the first portion of the trough travelled by material in the trough.

5. A method according to any one of claims 2 to 4 wherein the trough has a width in the range 40 to 80 cm and the rotating element is rotated at a sspeed in the range 40 to 90 rpm.

6. A method according to any one of claims 1 to 5 wherein the amount of moistening liquid applied is in the range 100 to 200 g per kg of mixture treated.

7. A method of treating amixture of paper and plastics foil substantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. than is indicated in the diagrammatic drawing) there is provided a spraying system 6, from which divided sprays of water from a storage tank 5 can be sprayed onto the mixture. At the discharge end of the trough, the moistened mixture is ejected onto a conveyor belt system 7, by which it is conveyed to an air sifter (not shown) for separation of the two fractions. The trough is provided with a mixer screw 8, the dimensions of which are such that on the one hand the mixture is conveyed from the supply end towards the conveyor belt system 7, while at the same time the mixture is thoroughly mixed with the water sprayed on from the sprays 6 and thus is intensively exposed to the effects of the water. In a particular preferred embodiment, the width of the trough is 50 cm, and the length of the mixer screw 8 is 800 cm. The blade diameter of the mixer screw is 48.5 cm. the pitch of the mixer screw is 20 cm and in operation the screw is driven at 80 rpm. This equipment is suitable for treating 13000 kg of mixture per hour. With a feed rate of 115 g water from the sprays 6 per kg of mixture, a degree of separation of 80% was achieved in a wind sifter fitted after conveyor belt 7. The method specifically described above only constitute one embodiment typical of the invention. A large number of variations are possible and can be envisaged, and all such come within the scope of the invention. WHAT WE CLAIM IS:-

1. A method of separating a mixture consisting mainly of a paper fraction and a plastics foil fraction wherein the mixture is moistened and then separated, characterized by application to the mixture of moistening liquid in divided form and thorough mixing with said liquid prior to the separation.