FR2795003A1 - Process and installation for the treatment of waste products by three phase separation with production of a combustible product - Google Patents

Abstract

New treatment of waste products comprising isolation of 4 product categories including compost material, light non-biodegradable and combustible products and ultimate heavy inert waste materials by 3 main stages: (1) a primary mechanical separation; (2) a second bioseparation; and (3) a final mechanical separation. Independent claims are also included for the combustible solid obtained and the installation for effecting the process.

Description

The present invention relates to a process for preparing a fuel from household and industrial waste.

The technical field of the invention is that of the waste treatment industries.

The methods traditionally used to dispose of waste are landfilling and incineration, which cause soil and / or air pollution, respectively.

Incineration consists of removing part of the waste in the form of heat and energy (70% on average); the other part (30%) comprising many polluting substances (dust and volatile compounds, clinker and flue gas treatment products) is sent to the atmosphere and to landfills. This process amounts to burning, without knowing the nature and the exact composition of the product entering, a mixture of water (the waste comprises at least 30% water) and combustible material (plastics, paper and cardboard). This archaic process, with deplorable energy efficiency (250 kW per ton of waste burned) due to the nature of the product and the type of installation, requires to compensate for the nuisances and the risks that it puts to the environment a technology. sophisticated to recover some calories and avoid pollution of the air and water by its discharges. Such a process is expensive, is a source of pollution and therefore does not constitute a solution for optimal recovery of waste.

The landfill has a lifespan limited to the volume available but in addition it does not eliminate waste. They are buried mixed without leaving the possibility of recovering later recoverable products. It is a costly process to protect against pollution, which is limited in time and space and provides no compensating resources. Household and similar industrial waste is composed of materials which, once separated, offer an economic and industrial interest because they can replace after recycling and regeneration to raw materials or products of high added value.

An object of the invention is to provide a waste treatment process and installation which makes it possible to obtain, among other products obtained, a combustible product, which are improved.

Many attempts have been made to prepare a combustible product from waste, but none has to date been used for industrial purposes.

For example, the patent application FR2759707 describes a process for preparing a combustible product from industrial waste which comprises successively the following steps - waste is separated containing so-called light products, such as plastic films, paper , cardboard, textiles, carpets, on the one hand, waste containing so-called heavy products such as rigid or dense plastics, - one or more grindings followed by a separation of metals, - waste containing products so-called heavy so treated to a screening for separating the waste into three fractions called large, medium and fine, - the average fraction of particle size ranging from 10 to 30 mm is subjected to a densimetric separation by application of an air flow resulting in two so-called heavy and light fractions, - the light fraction is compacted by extrusion to increase its density i nitrate of between 0.1 and 0.2 at a final density of between 0.2 and 0.40.

A disadvantage of this process is that it does not allow to treat unsorted waste which contains materials of animal or vegetable origin, and which therefore contain a high proportion of water. In addition, since this document gives no numerical indication, it is impossible to know the proportion of waste finally used as fuel.

An object of the invention is to provide an efficient and cost effective method and installation for separating waste into several categories of products at least one of which can be used as fuel having qualities comparable to that of fossil fuels.

The invention is based on an improved waste sorting method which comprises three main successive stages of treatment: a first sort (or separation) mechanical and / or manual, followed by a second separation using worms, which is itself even followed by a third mechanical separation; the second separation is obtained by separation of waste ingested by worms on the one hand, non-worm waste on the other hand.

The first sorting, called preparatory sorting, is intended to extract waste bulky products, recyclable clean products as well as toxic products requiring special treatment; this first sorting preferably comprises a step of separation into two fractions by screening (by a rotary trommel): the two fractions obtained preferably each undergo a subsequent manual sorting operation allowing the extraction (separate) of clean bulky products and products. toxic; the remaining waste of the coarse fraction is crushed and then mixed with the remaining waste of the less coarse fraction.

This first phase of preparatory sorting makes it possible to improve the yield of the next step of sorting by worms, in particular by earthworms, by decreasing, generally by at least 5%, the volume and mass of the waste undergoing this treatment. by worms, and avoiding to decimate the worm population with toxic products.

The resulting product is preferably subjected to a step of bacterial degradation prior to sorting with worms, in order to further improve the efficiency of the following step: this step generally makes it possible to reduce the mass of waste by 20% to 40% about 25% to 35%, especially by separation of water and organic matter.

The worm sorting phase makes it possible to clean the non-ingested waste, which can represent between 20% and 40% of the waste subjected to this sorting phase, and to separate it easily from the remaining mass (60% to 80%) at the bottom of the tank (litter).

The subsequent mechanical sorting stage preferably comprises a trommel screening and / or ventilated densimetric screening stage (e) for separating the waste into at least three separate products, as well as a magnetic separation.

According to another aspect, the invention consists in proposing a sorting facility for household or industrial waste which essentially comprises: a preparative sorting station partly mechanical (including a trommel) and partly manual, preferably at least one tank or closed tunnel (for anaerobic fermentation) or open (for aerobic oxidation), suitable for receiving sorted waste, - at least one open tank or tunnel for treatment with worm-like worms, sorted waste and the case optionally fermented or oxidized, - a station for secondary mechanical sorting and refining of products (litter) ingested by worms comprising a trommel and / or a ventilated densimetric separator.

The advantages provided by the invention will be better understood through the following description which refers to the appended drawing, which illustrates without any limiting nature of the preferred embodiments of the invention.

In the drawings, the same or similar elements bear, unless otherwise indicated, the same references from one figure to another.

The single figure schematically illustrates a waste treatment plant according to the invention. The waste to be treated 1 is separated by a rotating trommel 2 into a fine fraction 3, preferably less than 200 millimeters in size, and into a large fraction 4, preferably greater than 200 millimeters in size.

Each of the fractions 3, 4 then undergoes manual sorting on a sorting table installed in a pressurized and air-conditioned room, respectively marked 5, 6; this makes it possible to remove clean recyclable materials (as well as bulky and toxic ones) from the flow to be treated, whose mass is of the order of 1 to 10% of the waste 1; the fat fraction then undergoes grinding 7 before being mixed (in 8) with the sorted fine fraction; this mixture representing 90% to 99% of the waste 1, is transported and deposited in a unit 9 of fermentation (or oxidation).

In this stage of bacterial hygiene, the waste, by fermentation of biodegradable materials by the action of specialized bacteria and the control of physico-chemical parameters (humidity, temperature, oxygen content), reach and are maintained at a temperature of preferably of the order of 60 to 70 C for several days, which destroys the vast majority of pathogens. This stage can be carried out in closed enclosure (tunnels or biodigestors tubes) or in Andean under shelter or in open air. Allochthonous bacteria that are compatible with the subsequent treatment by earthworms and selected to reduce nuisances (odors), accelerate the fermentation process and subsequently promote ingestion by earthworms.

Next comes the so-called biological separation of litter-sanitized waste into bins by earthworms. This treatment makes it possible, after digestion and restitution of the waste ingested by earthworms, to have two products easy to separate by mechanical means (manual or mechanical raking of the upper layer not ingested by earthworms and sieving) - on the one hand 11 non-biodegradable and inert to coarse granulometry (plastic, glasses, ferrous and non-ferrous metals, porcelain etc ...), which are recovered in the upper part of the biological sorting tanks 10; - On the other hand a product 12 fine particle size, forming an organic fertilizer rich in wet, odorless, stable and easy to use, which is recovered at the bottom of the tanks; this product generally represents of the order of 10% to 30% by mass of the initial waste 1.

For the sorting and mechanical refining of these two products, several operations are preferably carried out - raking the surface of the litter to remove the light and bulky undigested elements before depositing a new layer of hygienized product on the litter; - Unpacking 13 followed by sieving 14 (by a trommel with two sieves) products returned to the litter bottom, allows to separate the elements in three classes 15 to 17 of decreasing particle size.

The refining of the fertilizer 17 (with fine granulometry, in particular less than 3 millimeters) on a ventilated densimetric table 21, makes it possible to separate the densest elements 18 (glass, porcelain) from the lombri-compost 19, and combustible dusts 20 ; a densimetric sorting and dusting (by a table 22) of medium grain products, allows the same way to separate the refusal 18 fertilizer <B> 19, </ B> and combustible dusts 20; a third density sorting table 23 allows separation of the refusal 18 of the combustible materials.

At the end of this treatment, four categories of products are available - vermicompost 19, marketable as fine and mineralized organic nitrogen fertilizer, - compost <B> 19, </ B> well provided with marketable wood constituents as an amendment to improve soil structure and erosion control; - non-biodegradable and combustible light mixed products which may be used for energy recovery; - dense, inert, coarse and fine products which are considered ultimate waste.

In an alternative embodiment, the process according to the invention can be applied as follows to clean or slightly soiled waste sorted either by a selective and separative collection, or to the materials 11 separated by raking the upper part of the tanks 10 as previously described.

The waste is separated into three fractions by passing through a ventilated trommel - a fine and light fraction consisting of dust and inert products separated by ventilation, - an upper fraction (more than 60 to 120 mm) which is fed to a carpet successively to sorters of recyclable waste, regenerable waste and combustible waste, - a lower fraction (less than 60 to 120 mm) which is fed to a carpet successively to sorters of recyclable waste, regenerable waste and combustible waste.

The distribution of the waste to be sorted into two streams makes it possible to increase the productivity of the sorting unit.

The manual sorting operations are performed in a pressurized and ventilated room. The products are separated and dumped by operators in troughs feeding containers, under the sorting tables, from where they are transported after conditioning to storage areas.

The waste comes from sorting tables, separated into different categories - clean materials such as metals, glasses, plastics and other directly recyclable products are processed and shipped to the consumer industries, - regenerable materials (plastics) that we do not does not want to find in the process of combustion in view of their toxicity, but the valuation of which can offer an economically interesting added value, - combustible materials, - fermentable materials intended for the manufacture of compost and refuse sorting whose fraction the coarser is crushed. All materials go under an electromagnetic carpet (or separator) that recovers ferrous metals that have escaped manual sorting.

All sorted waste is distributed over storage areas pending recovery for recovery or disposal.

The refusal of sorting is sent to a composting unit for mixed waste.

The preparation of waste by sorting and shredding is different depending on whether composting is done by mechanical turning (Andean and biodigester tubes) or without turning (tunnels, pits and heaps). the material intended for composting without turning must contain structuring elements which maintain a good air circulation within it during the fermentation phases and be matured after maturation; For waste treatment centers, the production of tunnel compost is one of the well-mastered solutions (Andean, brick or bio-digester tubes) that can be economically and technically attractive.

The fermentable materials and the small shredding sorting refusals contain structuring materials that provide a percentage of empty voids sufficient to promote the flow of air during fermentation.

This fraction of waste is placed in a closed fermentation tunnel where the fermentation parameters (temperature, humidity, lacunae oxygen level) are regularly measured by probes and regulated by a permanently adjusted ventilation and water spraying. evolution of fermentation.

After about two weeks, the fermentation phase (characterized by a rise in temperature up to 70 C, by a loss of water, by the destruction of pathogens and parasitic worms) is completed.

The material hygienized by the rise in temperature is then removed from the tunnel and then is aerated and separated into two fractions by a trommel.

The upper fraction (above 30 to 60 mm) passes a sorting table where the elements that can be used as fuel are separated.

The lower fraction (below 30 to 60 mm) is sent to a maturation tunnel where the stability of the compost is tested and the humus production reactions (humidification) are ensured by the control of the temperature, the aeration and the moisture of the compost. The lack of temperature rise during this operation is a good stabilization criterion. At the end of the maturation, usually after two weeks, the temperature of the compost is below 40 C.

At the end of maturation, the compost according to its quality is either sent to biological sorting by vermicomposting, or directly processed in refining plants (14, 21, 22, 23) of the sorting unit described above.

Compost cleared of unwanted material is stored before packing and shipping.

Thanks to the combination of the sorting steps of the process according to the invention, a compost of higher quality is obtained than that of the existing waste treatment installations which produce a crushed mixture containing a multitude of non-fermentable products, unfit for the quality of a product. truly usable compost.

The fermentation can be carried out in closed enclosure to considerably reduce the duration of the decomposition cycle; the rise in temperature (thermophilic phase) is accelerated and results, initially, in the self-sterilization of the product (destruction of pathogenic germs); no odor spreads outside the fermenter because the operation occurs in a vacuum and the injected air is filtered by a biofilter before being discharged to the outside; control of the fermentation is ensured by the control of temperature, water (humidity), air (oxygen) and mechanical mixing.

The composting unit concerns fermentable waste (green waste, agriculture and agro-food industry, local communities) from a selective collection.

The composting operation includes the two phases of fermentation and maturation of the waste. These operations carried out in aerobic form, can be undertaken in Andean outdoor or under shelter, in closed enclosures biodigesters tubes or tunnels according to the available right-of-way and the volume of waste to be treated.

The resulting raw compost can be either mixed with hygienized waste from a previous sort to adjust the production of organic products to market demand and the required quality standards, or refined with the refining equipment of the sorting unit. previously described to produce varieties of composts suitable for different soil amendment uses.

For fuel preparation, the fuel fraction is washed and dried before being stored in silo.

Manually sorted materials (plastics, paper, cardboard, wood and derivatives) are ground separately and stored in silos.

Under each silo, a weigh-metering device allows to know continuously the quantity of product entering and leaving as well as its density and its humidity; it makes it possible to adjust the quantities of materials to the manufacture of the fuel. These products, at 3% maximum humidity, are introduced into a fluidizer mixer to form a homogeneous mixture of combustible materials, respecting pre-established proportions to about 10%, so as to have a constant PCI. The fuel manufactured can be compared to coal because its heating value (ICP) is half that of fuel.

The mixture is conditioned after a finer grinding - either in the form of a log of 4 to 9 cm in diameter through the passage in a hydraulic press at 600 bar pressure, where under the effect of the rise in temperature the particles amalgamate by the creep of plastics, which then forms an envelope that protects the finished product for possible storage; - or under vacuum in waterproof bags.

This conditioning allows the fuel to be stored for later use on site, or transported and used elsewhere. At this stage, the fuel can be stored for a long time, stored if possible in a ventilated compartment, without risk of pollution.

In another preferred embodiment, the fermented waste is sieved (before ingestion by the earthworms) in order to extract the larger portions that are not unmanageable by the worms.

The fuel obtained by the process according to the invention is in the form of particles advantageously having the following characteristics: average particle size in a range from 0.5 to 10 mm, in particular of the order of 1 to 5 mm, and still 1 to 3 mm; - plastic content in a range of 20 to 80% (by weight); - content of essentially cellulosic materials (paper, cardboard, wood) in the range of 20% to 80% (by mass); - mineral content of less than 10%.

These particles are in the form of a mixture of sheets, fibers, granules and / or powder; the solid fuel used preferably has an ICP in the range of 4000 to 8000 kcal / kg.

Claims (8)

1. A method of waste treatment, characterized in that it comprises three main successive phases: a first mechanical separation, followed by a second separation involving worms, which is itself followed by a third mechanical separation. 2. The method of claim 1, wherein the first separation comprises a screening step followed by sorting, and wherein the sorted large fraction (4) is milled and then mixed with the fraction (3) smaller. 3. Method according to any one of claims 1 or 2, which comprises an aerobic or anaerobic bacterial degradation step followed by a digestion step by earthworms. 4. Method according to any one of claims 1 to 3, wherein the third phase of mechanical sorting comprises a screening step followed by a densimetric separation step, and comprises a separation of dust (20). 5. Solid fuel obtainable by a process according to any one of claims 1 to 4. 6. Fuel according to claim 5, which is in the form of particles having the following characteristics - average particle size in a range from 0.5 to 10 mm, in particular of the order of 1 to 5 mm and still 1 at 3 mm; - plastic content in a range from 20% to 80% by weight; - essentially cellulosic material content (paper, cardboard, wood) in the range of 20% to 80% by mass; - mineral content of less than 10%. 7. Household or industrial waste sorting installation essentially comprising: - a part (5, 6, 7) of preparatory sorting in mechanical part, comprising a trommel, and partly manual, - at least one tank (10) or open tunnel for treatment with earthworm-type worms, sorted and, where appropriate, fermented or oxidised waste, - a secondary mechanical sorting station for products ingested by worms containing a trommel (14) and / or a ventilated density separator (21, 22). 8. Installation according to claim 7, which further comprises at least one tank (9) or tunnel, closed for anaerobic fermentation or open for aerobic oxidation, suitable for receiving the sorted waste.