FR2740365A1 - Separation and neutralisation of mixed solid wastes - Google Patents

Abstract

Separation and neutralisation of mixed solid waste into different inert fractions is obtained by a fine density separation carried out in a flux of warm air, at a temperature low enough not to carbonise the material.

Description

The invention applies to the technical field of industrial waste treatment. All common waste, household waste, ordinary industrial waste, food waste, even mixed and without prior sorting, can be neutralized, separated, and inerted by this process.

The techniques used until then in the treatment and elimination of the considered waste did not allow the taking in charge during the same treatment of all the mixed waste, of different origins and natures, without pollution during the treatment, and by generating an economically useful final residue on a large scale. The main process, incineration, released pollutants (dioxins, furans, acids, etc.) and produced toxic clinkers unfit for profitable industrial use. while being too selective about the nature of the incoming waste. Other treatments, by composting or methanisation, could only operate on the fermentable part of the material. Other methods, finally, sorted or separated certain materials, but without sterilizing or inerting all the organic materials.

The advantage of the invention is to sterilize and inert all the material constituted by the mixture of waste, by extracting and recovering certain elements contained in this waste, elements which are useless, dangerous, or toxic, on the contrary useful and recyclable, but without causing pollution during treatment, and producing an economically and technologically useful residue. This treatment takes place in two consecutive phases.

One phase consists in subjecting the fermentable organic part of the material, at the same time as the rest of the material, to a treatment combining destructuring by fine grinding and sudden dehydration, with concomitant sterilization by heating.

A second phase consists in reducing all the particles of matter to the same constant particle size, therefore to the same unit volume, in order to then be able to effect a gravimetric separation of its various constituents, put together in suspension in an air flow whose flow and the pressure are adjusted to let gravity drop the selected elements.

In the case of processing of mixed and mixed waste, the residual material leaving the treatment is a stable, homogeneous and inert powder, directly usable for making special insulating concretes, which can be stored as inert material.

In all cases, the organic fraction is sterilized, rid of all bacterial or fungal life. The treatment does not generate any pollution, direct or indirect; the water that has been used or recovered by condensation during the treatment is filtered; at the filtration outlet, the purified water can be re-used for the general needs of the operation or be discharged into the sewer; finally,
The treatment air is filtered on activated carbon and sanitized by ozonization
The accompanying drawing illustrates the invention. With reference to this drawing, the method integrates the various successive processing stations in the order of the phases of said processing.

Before the first phase, the mass of waste (1) first undergoes a preparation, namely - a first coarse grinding-shredding, with mixing of the material (2) - a magnetic removal of ferrous metallic elements (3) - a second fine grinding (5) - a magnetic sample by eddy current of the non-ferrous metallic elements (4).

After this preparation, the waste is admitted into the feed hopper of the 1 "phase circuit (6). It is first mixed there, at constant flow rate, with mineralizing additives (calcium carbonate, lime) specially dosed in depending on the nature of the waste. These additives (7) are intended to maintain the proportion of mineral filler, in the whole mass of the waste, between 15% and 20%. Then the impregnated waste is introduced by pressure into the first separator (9) to be treated at less than 200 C (180% C on average) in a flow of hot air in rapid circulation, which constitutes the treatment phase. The treatment 9 moderate temperature does not carbonize the material and does not release any solvents, which does not release toxic effluents.It also does not produce ash or slag.The extracted moisture is simply condensed and discharged to the network after a safety purification, and the dry matter e is directed into a second cold air separation circuit, where the 2 "treatment phase takes place, allowing fine separation.

In general, the treatment therefore consists of a series of operations on the material, which undergoes successively and without interruption destructuring, compression, expansion, heating, dehydration, and densimetric separation.

Mechanically and physically, the sequence of these operations is as follows: - very fine, but not pulverulent, grinding of the raw material brought to a particle size of 2 mm, with an average humidity of 40% (5) - impregnation of the comminuted product with a mineralizing additive (6) - compression by worm screw for injection into the phase device (8) - sudden expansion and dehydration of the ground material in a first stream of hot air (<200 "C) in rapid flow (9), humidity being reduced up to approximately 5%; poorly calibrated or non-homogeneous particles are decanted by gravity in the first expansion chamber (10) and set off again for grinding; very fine particles, dust and powder, are sucked up by a device high position (11) - at the end of the 10 phase, recovery of the dry matter with constant average particle size, suspended in a second stream of air at room temperature, circulating in several successive columns (12) o u the constituents separate from each other by gravity depending on the pressure of the carrier air stream in chambers or in successive expansion bells.

This is the 2nd phase of the treatment, which makes it possible to isolate and extract, in particular, heavy metals, by varying the ejection speed and the air flow rate. An air compressor (13) supplies the different positions.

The prçcjQ thus allows the elements contained in the treated material (1) to be extracted or concentrated at will, while sterilizing it. You can choose to leave the proteins, or the fibers, and remove the metal particles, or vice versa. The final treatment residue (14) is an inert, sterile dry powder.

The industrial application of the proczdE relates to waste sorting and disposal facilities.

Claims (1)

 t) Inerting and waste separation process, characterized in that it sterilizes all  mixed material of different kinds of waste, by means of an air flow treatment  medium temperature, not carbonizing the material, associated with a fine densimetric separation, the  all not causing pollution during the treatment, and producing an economically and technically useful residue, storable as an inert material.  Method according to claim 1 characterized by the course of the treatment in two phases  immediately consecutive, the first combining destructuring by fine grinding and  sudden dehydration with concomitant sterilization by heating, and the second phase reducing all the dried matter to the same constant particle size to achieve gravimetric separation of the elements suspended in an air flow whose flow and  pressure are adjusted to select items based on their density.  3) Method according to the preceding claims characterized by the coordinated succession of  destructuring, compression, expansion, heating, dehydration, and  densimetric separation, to carry out the treatment of the material considered.  4) method according to the preceding claims, characterized by the circulation of the dry matter in  several columns where its constituents separate from each other by gravity depending on the  pressure of the carrier air stream in successive chambers or expansion bells,  allowing to isolate and extract up to heavy metals.