FR2811232A1 - Industrial and domestic waste recycling system consists of shredding and predigesting by physical and chemical action before mixing with soil - Google Patents

Abstract

The procedure consists of dispersing the waste material in the soil after pre-digesting and removing pollutants. The waste (1) is passed through shredders (3) and mixed with alkaline and acid chemical reagents (6, 7) which must be able to interact without counteracting one another or the assimilating nature of the soil. The treated shredded material, with pH level adjusted, is then mixed with slurry or earth and spread over soil with micro-organisms that are allogenic or endemic to the receiving soil.

Description

-1 - The process applies to the industrial recycling of so-called waste

banal, that is to say little or not

  toxic, and little or not inert, which represent the largest share of contemporary waste.

  Ordinary, industrial and household waste is usually eliminated by concentrating and confining it underground. However, excessive concentration and confinement of untreated waste can create local pollution accumulations which remain dangerously progressive in the long term, and which nature has great difficulty in absorbing. With the process, it becomes possible to quickly recycle this waste, by decontaminating it, by pre-digesting it, then by dispersing it in the soil, within a homogeneous mixture having a composition close to that of the earth. This enriches the receiving soil while allowing it to finish naturally transforming the treated waste into healthy and useful elements. The aim of the process is to allow natural agents to exercise their physico-chemical, mechanical and biological action, so as to be able to integrate into a cultivable soil an external material composed of treated waste, without upsetting the intrinsic assimilative power of the soil. , characterized here as an existing balanced mixture

  of mineral and organic elements, this assimilating power then being favored by the pre-

  physico-chemical digestion and by the preliminary decontamination of waste.

  In the process, the pre-digestion does not result from a progressive composting by biological agents, but from a fast physico-chemical treatment. For this, the external material provided is prepared to remove any polluting character or counteracting the desired effect, and to facilitate the consecutive action of natural agents, the main ones being: - variation in humidity and pH, especially after percolation atmospheric water - action of solar radiation (especially ultraviolet and infrared) - local variations in temperature, which can be large in short cycles,

  - action of animal and plant microorganisms on and in the mass.

  The purpose of the preparation by the process is to promote reactions in the mixture between the elements of the waste between them, on the one hand, and between the waste and the receiving medium, on the other hand, the treatment applied to the waste for this purpose. using coordinated and complementary means - physical means: increase in the contact surface, and homogeneous humidified mixture - chemical means: depollution, and pre-digestion by hydrolysis and variations in pH Thus, the main treatment phases are successively: - a pre -humidification (H20 = up to 35% of the total mass) - very fine grinding, to physically destructure the material and increase the contact surface of the solid particles, so as to intensify the reactions and exchanges in the treated mass, - impregnation with a basic reactive mixture, causing chemical destructuring with alkaline hydrolysis, under controlled humidity (H20 = from 50% to 60% of the m complete enough) - rapid, intense stirring, to obtain a homogeneous mixture, in a fluidized bed, where the successive contacts between all the interactive surfaces are multiplied,

  - an adjustment of the pH using propionic acid (or any other acid with equivalent effect).

  - 2- The depollution action includes a biological sanitation action and an action to block

  possible heavy trace metals, in insoluble chemical structures.

  Biological sanitation is carried out jointly by hydrolysis, by the caustic action of

  reagents, and by the variation of pH over a short period. In these phases of treatment, micro-

  organisms of the material brought in are rapidly destructured, this material remaining assimilable

  then by endemic micro-organisms of the receiving soil, without thwarted interactions.

  The mixed alkaline reagents (pH 12 to 13) are chosen both for their low impact on the natural environment, for their caustic properties, for their potential for soil target amendment, as well as for their capacity to insolubilize heavy metals in stable complexes despite re-acidification of the treated mass (wide choice of hydroxides, carbonates, silicates, calcium aluminates, sodium, magnesium, etc.). The mixture, as a choice of reagents, and in respective proportions of the reactants, is to be adapted to each particular case as a function, for example, of the limit values for chemical or biological oxygen demand imposed by technical and / or regulatory requirements. The acid then used is chosen for its combined potential for biological sanitation and odor control in the fermentable part of the mixture, in addition to its ability to restore the pH in the previously alkalized mixture, with a minimum of annoying interactions with the contact with the alkaline mixture used (recommended acid: propionic acid). The final pH of the treated mixture is adjusted by metered addition of this acid to

  correspond to that of the receiving environment (existing soil), i.e. an average acidity of 5 to 7.

  The figure which illustrates an example of application of the process (fig. 1) describes a modular installation

  compact, where several pieces of equipment are assembled in a movable set, cable of frames-

  juxtaposed and coordinated containers.

  Ordinary industrial waste is dumped in bulk (inlet A) in a first mill (1), preferably with slow rotation, which reduces their average particle size between 0 and 35 mm approximately. They are taken up by a lifting belt conveyor, to be discharged into a second refiner mill (3), preferably with rapid rotation. During their transit on tape, the waste can be freed from the massive metallic elements that it may possibly contain, by the action of a magnetic device (2). One or more successive refiner mills can be used, depending on the flow and wear constraints imposed by the operation, so as to obtain a final average particle size of approximately 4 to 8 mm. In the last refiner mill, the crushed waste is sprinkled with water in fine droplets (9), so as to give it an average humidity of the order of 35%, while containing the dust caused by rapid grinding. The fine wet ground material is taken up and raised by an endless screw conveyor, to be poured into the first tank of a double mixing hopper (4). This hopper is composed of two twin tanks, each bottom of which is fitted with a worm extractor, whose rotation regime allows the respective flow of material to be dosed, towards a common exhaust o the

  material from each tank mixes with the other during its transit, in controlled proportions.

  -3- The second tank of the mixing hopper receives the contribution of a soft, moist substrate (entry B) which can be earth from construction site excavation, or mud for cleaning waterways or water treatment stations. water treatment. The respective average proportions, in equivalent dry matter mass, are approximately one part of crushed waste for two parts of sludge or soil. We seek the balance between organic and mineral loads according to the quality objectives of the final mixture

  treated, in particular for the amendment of the receiving soil.

  The final mud / waste mixture is extracted from the double hopper by a common exhaust, and it pours into a mixer (5), provided with blades and coulters producing both the translation and the mixing of the mixture set in very rapid rotation (fluidized bed). During brewing, the mixture

  receives a metered load of reactive products, alkaline then acid, under controlled humidity.

  The humidity is adjusted so as to bring the whole mixture to approximately 60% of H 2 O. A first alkaline preparative reagent (for example magnesium lime) can be introduced into the fine wet ground material leaving the last mill, during its pouring into the double hopper. In the mixer (5), the mixture becomes physically homogeneous, and chemically modified by the action of the alkaline reactive mixture injected at point C, under joint spraying of water injected at point E. The alkaline reactive mixture produces a hydrolysis of the fraction organic fermentable and insolubilization of heavy metals possibly present in the mixture. The usual proportion of alkaline reagents at pH 12-13 can vary from 4% to 12%, in mass ratio of the mixture to be treated, in particular depending on its organic part and its heavy metal content. The alkaline reaction is stopped when the translational mixture reaches point D, where it receives a supply of acid product, which quickly restores the pH to a determined level. The proportion of acid is determined by tests, on the occasion of each particular mixture. Probes measure humidity and pH in

  various points in the circuit of matter.

  The treated material is finally extracted from the mixer (outlet AB) to be put in a heap in the open air, from where it can be taken up and conditioned, the conditioning being able to consist of inoculating it with bacterial strains (in lyophilized form by example) supplementing, by

  as necessary, the action of endemic strains of the final receptor soil.

  Other configurations, using non-twin hoppers to receive respectively the sludge / earth and crushed waste, treated in one or more mixers, operating in

  continuous or in batches, can also apply the process under satisfactory conditions.

  The process can be applied industrially in installations, temporary or permanent, for processing waste. Its implementation being possible by means of particularly simple and compact devices and equipment, this makes it possible to constitute displacement, able, even mobile processing units, quickly assembled in container frames or on interconnected road trailers, which further favors the logistics of industrial application. -4-

Claims (4)

  1) Process carrying out the rapid recycling of waste, by cleaning it up, reducing it to fine particles (1) (3), and pre-digesting it by physico-chemical process, then by dispersing it in the soil, within '' a homogeneous mixture having a composition close to that of the earth, the chemical reagents added (6) (7) being chosen and dosed to work in reciprocal synergy without contradicting the intrinsic assimilative power of the earth and the interactions with the natural environment, allowing natural agents to best exercise their assimilative and purifying power over   all of the material dispersed in the soil.   2) Method according to claim 1, characterized in that the preparation of mixed waste aims to promote only the most useful reactions between the elements of the waste between them, on the one hand, and between the waste and the receiving medium, d on the other hand, the whole making it possible to obtain a recomposable cultivable soil, the chemical reactive mixtures being chosen and dosed accordingly, so as to apply special reactive mixtures which have both caustic properties, which are biodegradable, which produce a slight impact on the natural receiving environment, and which have a biological sanitation power, the combination of these properties   constituting an important element of the process.   3) Method according to claims 1 and 2, characterized by rapid pre-digestion without   prior biological decomposition (composting), by simple physicochemical reaction associating the consecutive action of two kinds of reagents, one (6) being strongly alkaline and producing hydrolysis with insolubilization of heavy metals, the other (7) being strongly acidic and suddenly restoring the pH of the treated mass to a neutral to slightly acidic level, the hydrolysis and the abrupt change in pH immediately producing a destructuration of living organisms and a pre-digestion of the fermentable organic mass, so as to make the treated mixture   then more easily assimilated by ambient microorganisms.   4) Method according to claims 1 to 3, characterized in that the material pre-digested with   physico-chemical treatment can immediately after being sown with allogenic microorganisms (bacteria in particular) so as to supplement or replace the action of the agents of the receiving soil.