AU2013336281B2

AU2013336281B2 - Line for treating waste consisting of household waste and/or biowaste

Info

Publication number: AU2013336281B2
Application number: AU2013336281A
Authority: AU
Inventors: Sylvie Fleury
Original assignee: Suez International SAS
Current assignee: Suez International SAS
Priority date: 2012-10-26
Filing date: 2013-10-24
Publication date: 2018-03-01
Anticipated expiration: 2033-10-24
Also published as: WO2014064639A3; EP2911811A2; ES2624301T3; FR2997322A1; WO2014064639A2; AU2013336281A1; FR2997322B1; EP2911811B1; CA2888941C; CA2888941A1; PL2911811T3

Abstract

The invention relates to a line for treating waste consisting of residual household waste and/or biowaste, which includes: means for storing waste, means for sorting products of different particle sizes, means for directing the products having a larger particle size toward at least one treatment unit, and at least one digester (B) for the methanisation of products having a smaller particle size. According to the invention, the sorting means supply a fraction of products having a particle size of less than 20 mm, at least one digester (B) is used for the methanisation of the fraction having a particle size of less than 20 mm, and the treatment line includes at least one low-temperature thermal dryer (ST) which is supplied with the digestate from the fraction having a particle size of less than 20 mm.

Description

The invention relates to a line for treating waste consisting of residual household waste and/or biowaste, which includes: means for storing waste, means for sorting products of different particle sizes, means for directing the products having a lar ger particle size toward at least one treatment unit, and at least one digester (B) for the methanisation of products having a smaller particle size. According to the invention, the sorting means supply a fraction of products having a particle size of less than 20 mm, at least one digester (B) is used for the methanisation of the fraction having a particle size of less than 20 mm, and the treatment line in eludes at least one low-temperature thermal dryer (ST) which is supplied with the digestate from the fraction having a particle size of less than 20 mm.

(57) Abrege : Ligne de traitement de dechets constitues d'ordures menageres residuelles et/ou de biodechets, comprenant:des moyens de stockage des dechets,des moyens de [Suite sur la page suivante] wo 2014/064639 A3 lllllllllllllllllllllllllllllllllllll^ tri entre des produits de granulometries differentes,des moyens pour diriger les produits de plus forte granulometrie vers au moins une unite de traitement, et au moins un digesteur(B)pour la methanisation de produits de granulometrie plus faible; les moyens de tri sont prevus pour foumir une fraction de produits de granulometrie inferieure a 20mm,au moins un digesteur (B) est affecte a la methanisation de cette fraction de granulometrie inferieure a 20mm,et la ligne de traitement comprend au moins un secheur ther mique basse temperature(ST)qui est alimente par le digestat issu de la fraction de granulometrie inferieure a 20mm.

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LINE FOR TREATING WASTE CONSISTING OF HOUSEHOLD WASTE AND/OR BIOWASTE

The invention relates to a line for treating waste consisting of residual household waste and/or biowaste, said treatment line being for the purpose of separating the organic matter and the matters with a high LHV (lower heating value), of the type of those which comprise :

- means for storing waste,

- means for separating recoverable matters,

- means for sorting products of different particle sizes,

- means for directing the products having a larger particle size to at least one treatment unit, in particular for energy recovery,

- and at least one digester for the methanization of products with a higher organic content, having a smaller particle size.

The waste to which the treatment line relates comprises in particular household waste, the fermentable fraction of waste, biowaste originating from selective collections, pulp from industrial waste bioconditioners, and mixtures of urban, agricultural and industrial organic waste.

A conventional treatment line includes a waste preparation step (sorting, grinding, etc.), a dry or wet methanization step, and a step of treating the digestates originating from the methanization of the waste, via the conventional route of composting and/or stabilizing and/or spreading and/or biodrying in tunnels, in windrows or under sacks.

Methanization is an anaerobic process for degradation of putrescible organic matter contained in household waste, whether it is raw waste or biowaste derived from

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- 2 selective collectives. Presorting is carried out upstream of the digester for the methanization, and is adapted according to the methanization process envisioned. Various particle size fractions are then intended for organic or thermal treatment processes, of the stabilizing, composting or biodrying type.

Household waste and biowaste have very heterogeneous particle sizes and qualities. The heterogeneity of the matter, even after sorting, is complex and unstable. The matters constituting the digestate leaving the digester contain inert materials such as glass, stones, and also plastics and possibly traces of ferrous and nonferrous metals. The major part is, however, organic and energy-giving and this digestate is generally treated by composting, stabilizing and/or biodrying.

Biodrying treatment, for example of tunnel or windrow type, requires large ground areas. The hydric and odorous flows are difficult to manage. This treatment is accompanied by strong releases of odors and requires complex management of the unchanneled liquors .

Dry digestion manages heterogeneous waste of which the dryness is between 30% and 50%, advantageously 37%. The dryness on leaving digestion is about 22% to 40%, advantageously 28%. The digestates produced are sometimes dehydrated, by pressing or another technique, in particular centrifugation, and are then intended for composting, or else spread, stabilized or biodried.

Wet digestion, which sometimes involves prior hydrolysis, displays the same characteristics of dryness of exiting digestates of between 12% and 5%, advantageously equal to 6% or 7%. A production of excess liquors on site is often the source of odors and

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2013336281 22 Dec 2017 of additional specific treatments. The same constraints apply on the downstream procedures.

Such solutions have several drawbacks.

A large area of land is required, in particular for tunnel biodrying. In the heart of a town, it is often difficult to acquire the areas required for such biodrying treatment.

The problem of odors on the site and at the periphery of the site is difficult to solve with extensive conventional treatments of digestates. These processes do not make it possible to satisfy the requirements, regarding odors, without restrictive implementations of civil engineering with buildings.

The operating conditions, in terms of gaseous pollutants of aerosols and of aerial 10 microorganisms, are difficult with regard to operator health. Operators of waste methanization/composting units are subjected to strong operating constraints, such as the obligatory wearing of a mask. Streams loaded with pollutants, even though they are treated and renewed, are sometimes difficult to tolerate. The impregnation of odors in digestate treatment halls and tunnels is strong. Exposure to ammonia is controlled but still difficult to accept.

The airflow rates required by a tunnel biodrying technique are considerable and energy consuming.

Embodiments of the invention desirably at least partly remedy the abovementioned drawbacks, and in particular minimize the area required for the treatment of waste and optimize the environmental conditions, in particular regarding odors, and the health conditions regarding operators.

According to the present invention, there is provided a treatment line for treating waste consisting of residual household waste and/or biowaste, for the purpose of separating the organic matter and the matters with a high LHV, comprising: means for storing waste, means for separating recoverable matters, means for sorting products having different particle sizes, means for directing the products of larger particle size to at least one treatment unit, and at least one digester for the methanization of products with a higher organic content, having a

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2013336281 22 Dec 2017 smaller particle size, wherein: the sorting means are provided in order to supply a fraction of products having a particle size of less than 20 mm, at least one digester is used for the methanization of this fraction having a particle size of less than 20 mm, and the treatment line comprises at least one low-temperature thermal dryer, which is fed with the digestate derived from the fraction having a particle size of less than 20 mm.

Preferably, the means for directing the products of larger particle size to at least one treatment unit is for energy recovery. Preferably, the temperature of the thermal dryer is below 9 5 °C and above 60°C,

Advantageously, the sorting means are provided in order to supply a fraction of products 10 having a particle size of 0-10 mm, at least one digester is used for the methanization of this fraction having a particle size of 0-10 mm, and the low-temperature thermal dryer is fed with the digestate from this digester.

Preferably, the treatment line comprises:

a first branch for the matters having a larger particle size, comprising:

at least one first digester (A) used for the methanization of said matters having a larger particle size, at least one centrifuge or one press to which the digestate from the first digester is subjected, at least one biodrying tunnel for the matters from the centrifuge or from the press, a second branch for the matters having a smaller particle size, comprising:

at least one second digester (B) used for the methanization of the matters having a smaller particle size,

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- 5 - at least one mixer between the digestate from the second digester (B) and the sludge from the centrifuge, or the pressate, of the first branch,

- at least one intensive thermal dryer to which the mixture from the mixer is subjected.

The treatment line advantageously comprises:

- sorting means providing a production of 0-60 mm, 10-20 mm and 0-10 mm fractions,

- at least one first digester (A) for the 0-60 mm and 10-20 mm fractions which are methanized with structuring agent, in particular vegetable fibers, then subjected to a press and/or a centrifuge for the production of presscakes and/or of centrifugation sludge,

- at least one second digester (B) for the 0-10 mm fraction which is methanized without structuring agent and is not dehydrated on exiting,

- a mixer for mixing the digestate from the second digester with the sludge from centrifugation of the digestate originating from the first digester (A) ,

- at least one low-temperature intensive thermal dryer in which the mixture exiting the mixer or the digester is dried,

- and at least one maturing/biodrying tunnel for the presscake of the 0-60 mm and 10-20 mm fraction.

The treatment line may comprise:

- a first separating drum, the meshes of which correspond to a particle size of between 100 and 500 mm, in particular equal to 300 mm,

- an energy recovery station for energy recovery from the oversize of the first separating drum,

- a second separating drum with meshes that are smaller than those of the first drum, in particular with meshes of 60 mm, to which the undersize of the first drum is sent,

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- 6 - a fermentor to which the oversize of the second drum is sent, after having gone through a sorting step which extracts the metallic products, in particular the ferrous products,

- a third separating drum, the meshes of which correspond to a particle size of 20 mm, which receives the products exiting the fermentor, the oversize of the third drum being directed to the energy recovery station,

- means for separating the undersize, having passed through the meshes of the third drum, into a fraction having a particle size of between 10 and 20 mm, directed to a mixer, and a fraction having a particle size of 0-10 mm, directed to the second digester .

The mixer, which receives the fraction having a particle size of between 10 and 20 mm, also receives the undersize which has passed through the second separating drum, the mixed products exiting the mixer being introduced into the first digester.

In the case of a treatment line for biowaste, this line advantageously comprises:

- a biowaste grinder,

- screening means for supplying a fraction of products having a particle size of less than 20 mm and a fraction of products having a larger particle size,

- at least one digester used for the methanization of the products having a particle size of less than 20 mm,

- an intensive thermal dryer to which the digestate from the digester is subjected, after optionally having passed through a centrifuge or a press.

A low-temperature thermal dryer comprises means for blowing hot air, at a temperature generally below 95°C

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- 7 and above 60°C, onto the matters to be dried placed on at least one conveyor belt, which is preferably permeable to air, and a closed circuit for distributing the drying air, the assembly being confined in a closed chamber, comprising an inlet for the products to be dried and an outlet for the dried products.

The thermal dryer can be controlled such that the final dryness on exiting the thermal dryer is between 50% and 90%, depending on the expectations of the operation.

The setting up of a low-temperature thermal dryer makes it possible to channel the streams, in particular the ammoniacal stream, in a confined piece of industrial equipment and to modulate the dryness on exiting according to use purposes.

The floor area of such an intensive thermal dryer is much smaller than that of a tunnel biodryer.

Despite the heterogeneous nature of the waste treated by the invention, and the presence of unwanted material and inert material, the preparation of a digestate from a fraction having a predetermined small particle size has made it possible to treat this digestate using an intensive thermal dryer essentially used for products which are homogeneous, especially with regard to particle size, and devoid of inert materials.

The treatment line makes it possible to treat various types of waste, namely urban waste, municipal waste and/or biowaste, derived from an organic selective collection, and/or mixtures of urban, industrial, or even agricultural substrates.

According to the invention, the upstream sorting of the matters makes it possible to produce a finer digestate

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- 8 with a rheology suitable for intensive thermal treatment.

When the waste consists of residual household waste, the treatment line is provided for distinguishing the organic uses to which the entering raw matters will be put, namely distinguishing a standardized composting from a simple stabilized material.

The invention combines oversize from digestion liquor centrifugation with finer digestates of fractions between 5 and 20 mm, according to the treatment processes. It is therefore possible, on the same site, to replace a portion of tunnel biodrying with a portion of low-temperature intensive drying, and to thus considerably reduce the land occupied.

In conventional biodrying, the exiting dryness of the digestates is from 40% to 55%. It is extremely difficult and expensive, in terms of energy consumption, to want to exceed this dryness.

According to the invention, with an intensive thermal dryer, the final dryness can be controlled according to the expectations of the operation:

- if the site is in the town center and the digestates must be agronomically exploited, composting will be required offsite, and the digestates will be dried to between 50% and 90%, advantageously 65%. These digestates will be composted after transportation;

- if the site is in the town center and it is desirable to use the digestates via energy or chemical routes, an optimum dryness of between 70% and 90% will be desired on exiting the lowtemperature intensive dryer.

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2013336281 22 Dec 2017

This treatment modularity, and the wide range of dryness possible, are novel and unexpected compared with the conventional waste treatment techniques in question.

In addition, the use of digestates that have been thermally dried in a waste composting site posed a problem. Indeed, it is necessary to be able to judge the correct dryness which maintains a minimal biological flora, capable of reactivating in composting, or else an organic matter sufficiently accessible for the biological activity of the composting. According to embodiments of the invention, the compostability conditions (addition of structuring agents, type of structuring agents, amounts, biochemical parameters, etc.), the compressibility of the mixture (determination of the gap space or porosity), the composting time (aeration requirements, kinetics, etc.) and the evolution of maturity during the process are evaluated during the intensive thermal drying in order to correctly define the optimum dryness of the matters at the thermal dryer outlet.

The present invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings briefly described as follows.

Fig. 1 is a simple block diagram of a line for treating waste.

Fig. 2 is a more detailed diagram of a part of the treatment line of fig. 1.

Fig. 3 is a block diagram of another part of the line for treating waste.

Fig. 4 is a diagram of the part of the treatment line comprising the intensive thermal dryer, and

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	- 10 -
Fig .	5 is a block diagram of a line for treating biowaste according to the invention.
For	a better understanding of the description, a
section relating to terms used is given hereinafter.

Fermentor = reactor for mixing the matter for a given time in order to ensure matter separation and to prepare a fermentable part for digestion.

Digester = closed chamber in which predominantly bacterial microorganisms assimilate the matter, under anaerobic conditions, and produce biogas, and a residue called digestate.

Digestate = matter exiting the digester, in liquid or pasty form, which can comprise solid matters in suspension, among which organic matter, inert materials and unwanted materials.

Biogas = gaseous product emanating from biochemical reactions for decomposition of the organic matter in the digester.

SRF = solid recovered fuel.

By way of nonlimiting information, the compositions of the matters constituting the waste are the following:

RHW: Residual household waste

This is the household waste consisting of waste collected from houses, and also the waste that can be likened to household waste of commercial or small-scale origin insofar as it is collected together with the waste from homes.

Solids: 30% to 40% by weight Nonsynthetic organic matters/solids: 40%

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- 11 Organic matters/solids: 55% to 70%

Up to	40%	by	weight	of	fermentable materials
Up to	17%	by	weight	of	textiles
Up to	12%	by	weight	of	plastics
Glasses :	3%	to	11% by	weight

Metals: 2% to 5% by weight Inert materials: 5% by weight.

Biowaste derived from the selective collection from homes

Solids (dryness) 20% to 45% by weight Organic matters/solids: 60% to 90%

Content of undesirable materials: from 2% to 10% by weight

Undesirable materials: glasses, metals, plastics, textile fibers. Among the unwanted materials, glasses represent approximately 5% by weight.

With reference to fig. 1 of the drawings, a simplified block diagram of a treatment line according to the invention for residual household waste and optionally biowaste can be seen. The matters have undergone upstream sorting, and a buffer pit T1 contains matters which have a particle size of between 0-60 mm and matters which, after having been passed through a fermentor and having undergone a second sorting, have a particle size of between 10-20 mm. A pit T2 is dedicated to biowaste or to green waste, after optional grinding and optional screening.

The matters taken from the pits ΤΙ, T2 are introduced into a digester A of a first branch of the treatment line. The digester A produces biogas discharged via an outlet which is not represented, and a digestate directed to a press P, in particular a screw press, the pressing cake of which is sent to a biodrying tunnel BS, while the liquor or pressate is sent to a

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- 12 centriguge C. The liquor from the centrifuge is recirculated along a pass N to the inlet of the digester A. The centrifugation sludge CB is directed to a mixer M.

A buffer pit T3 is used for intermediate storage of a fraction of matters having a particle size of between 0-10 mm. These matters are introduced into a digester B of a second branch of the treatment line. The digester B gives, on exiting, a fine digestate DF which is sent to the mixer M so as to form, with the centrifugation relatively homogeneous mixture. This and is directed to an after having optionally sludge CB, a mixture exits the mixer M intensive thermal dryer ST, undergone an extrusion in an extruder EX suitable for conditioning the matter in the form of cords a few centimeters long, promoting drying.

As a variant, as illustrated in dashes on fig. 1, the mixer M may be located upstream of the digester B; in this case, the digester B treats, as a mixture, the matters from the buffer pit T3, with the centrifugation sludge CB, and the fine digestate DF is directed to the intensive thermal dryer ST, optionally passing through the extruder EX.

The thermal dryer ST is a closed-circuit hot-air circulation dryer for drying the matters which circulate on at least one conveyor belt, which is preferably permeable to air. The dryer comprises a chamber with an inlet for the products to be dried and an outlet for the dried products. Means for heating the drying air are provided, as are means for heat recovery, in particular by steam condensation. The temperature of the hot drying air is below 95°C, generally about from 80 to 85°C, and above 60°C.

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- 13 The sorting system of the line for treating waste can be seen on fig. 2. A pit 1 or a slab is provided for the storage of the waste which is removed by a grabbing device G so as to be introduced into a separating drum 2 (or Trommel), the meshes of which correspond to a large particle size, in particular equal to 300 mm or more. The meshes of the drum may be circular, polygonal or oblong. The indicated value of 300 mm is not limiting, and this value may be between 100 and 500 mm as appropriate.

The oversize from the drum 2, the particle size of which is greater than the mesh dimensions, is directed to a station 3 for energy recovery from the SRF (solid recovered fuel) oversize.

The undersize, i.e. the matters which have passed through the meshes of the drum 2, are sent to a second separating drum 4 with meshes that are smaller than those of the drum 2, in particular with meshes of 60 mm. The oversize from the drum 4, consisting of products having a particle size larger than 60 mm according to the nonlimiting example given, is directed to a fermentor 5, after having passed through a sorting station 6 which extracts the metallic products, in particular the ferrous products.

The products exiting the fermentor 5 are introduced into a third separating drum 7, the meshes of which are smaller than those of the drum 4 and correspond to a particle size of 20 mm. The oversize from the drum 7, corresponding to products having a particle size larger than 20 mm, is directed to the energy recovery unit 3. The undersize, having passed through the meshes of the drum 7, consist mainly of organic matters having a particle size of less than 20 mm and is directed to a ballistic separator 8 followed by a trampoline screen 9, with meshes of 10 mm. The oversize from the screen

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- 14 9, corresponding to a particle size of between 10 and 20 mm, is directed to a mixer 10. The undersize from the screen 9, corresponding to a particle size of 010 mm, is directed to a ballistic separator 8a, then to a mixer 11.

The undersize from the separating drum 4, having a particle size of less than 60 mm, is directed to the mixer 10, while passing through a station 12 for sorting metallic products, in particular ferrous products, and then a ballistic separator 13 which discards the densest products, in particular the mineral products. The undersize 14 is essentially organic and introduced into the mixer 10.

The mixed products exiting the mixer 10 are introduced into one or more digesters A (fig. 3) so as to undergo therein a methanization treatment. The digestate exiting the digester A is sent to the press P from which is extracted, via an outlet 15, a presscake 16 consisting of wet heterogeneous solids. These solids 16 are directed from an outlet 17 either to a biodrying tunnel BS, or to composting 18, or stabilizing 19, or spreading 2 0.

The liquor 21, or pressate, exiting the press P is directed to a centrifuge C. The centrifuge C delivers, with an outlet 22, flocculated or nonflocculated centrifugation sludge CB and also a liquor 23, of which a part 24a is recirculated to the digester A, while another part 24b is recirculated, at the inlet of the digester A, to the mixer 10, as illustrated in dashes on fig. 3, or downstream, after having optionally passed through a liquor treatment unit 25, in order to extract mainly the aqueous ammonia and to eliminate the excess liquid phase. A fraction 26 of the digestates exiting the digester A can also be recirculated.

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- 15 All of the paths taken by the products introduced into the digester A and treated on exiting this digester constitute a first branch of the line for treating matters of which the particle size is between 0 and 60 mm, without having undergone fermentation, and matters of which the particle size is between 10 and 20 mm after having passed through the fermentor 5 of fig. 2. Another branch of the treatment line corresponds to the mixer 11 which can be replaced with a buffer unit which serves as an intermediate storage, or as a wet hydrolysis unit.

The products exiting the mixer 11 (fig. 3) or the unit mentioned above are directed to a digester or a set of digesters B so as to undergo methanization therein. The digestate exiting the digester B is generally directed to a press P2, a fraction R of this digestate being recirculated to the top of the digester B. The pressing liguor J2 is sent to a centrifuge C2. The liguor JC2 exiting this centrifuge C2 can be recirculated to the inlet of the digester B after passing through a liguor treatment unit H2. Liguor fractions Wl, W2 taken upstream and downstream of the unit H2 can be sent to discharge. The centrifugation sludge produced by the centrifuge C2 is sent to a tank K2.

The solids exiting the press P2 form a fine digestate DF. As illustrated on fig. 4, the digestate DF originating from the second branch of the treatment line comprising the digester B is mixed, in a mixer M, with the centrifugation sludge CB, or the pressate, from the other branch of the treatment line.

The mixture from the mixer M is introduced into an intensive low-temperature thermal dryer ST. The low temperature denotes a temperature below 95°C, preferably below 85°C, and above 60°C. The drying is

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- 16 carried out with hot air partially circulating in a closed circuit.

The centrifugation sludge collected in the tank K2 (fig. 3) can also be mixed, in the mixer M, with the digestate DF and the centrifugation sludge CB from the first treatment line branch. The mixture thus produced makes it possible to obtain a product which can be accepted by an intensive low-temperature thermal dryer ST .

As a variant, the centrifugation sludge collected in the tank K2 can be sent upstream of the digester B.

It appears to be particularly advantageous to mix and dry the digestate DF and the centrifugation sludge CB together in order to fix, at the desired level, the final dryness of the dried sludge and to thus minimize energy consumption. The presence of fibrous elements in the digestate makes it possible to structure the dried sludge and to avoid going through a tacky phase during drying which would require the final dryness to be increased up to a minimum of 85%, which would be the case for centrifugation sludge alone. This is a surprising and unexpected result provided by the invention .

The drying, by means of a low-temperature intensive thermal dryer ST, of the mixture produced with a crude digestate derived from products of which the particle size is 0-10 mm and centrifugation sludge has proved to be possible, whereas, according to the usual recommendations, a low-temperature thermal dryer should not be used with a substantially heterogeneous digestate. The particle size of the mixture obtained between the digestate DF and the centrifugation sludge CB and optionally CB2 is suitable for a process of extrusion of the products after drying.

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- 17 The thermal dryer(s) generally comprise(s) condensation batteries for recovering energy, in the form of hot water, in particular at 60°C, used to heat the air of the maturation or biodrying tunnels.

According to the invention, the fine digestate exiting the digester B or BI can be introduced directly into the mixer M, or the thermal dryer, without being dehydrated beforehand, in particular by pressing and/or centrifugation. The non-dehydrated 0-10 mm crude digestate, exiting the digester B or BI, and not having undergone any pressing and therefore any addition of structuring agents in the form of green waste, generally has a dryness of 25% to 30% before entering the dryer, and a particle size of less than 10 mm. It is a product which is relatively homogeneous and fine.

The nonflocculated centrifugation sludge has a dryness of 35% to 40%, for a particle size of less than 5 mm. It is also a product which is homogeneous and fine. The flocculated centrifugation sludge has a dryness of approximately 30% for a particle size of less than 5 mm. It is also a product which is homogeneous and fine .

The preparation of the product upstream of the intensive thermal dryer, formed by the fine digestate, and generally mixed with the centrifugation sludge, results in an appearance and a particle size which are compatible with an extrusion process carried out before introducing the matters to be dried into the thermal dryer. For heterogeneous digestate, the particle size is not compatible with such an extrusion.

The dehydrated or non-dehydrated digestate contains many fibrous elements: there is no change in state from the liquid phase to the solid phase. It is possible to

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- 18 stop the drying, carried out by the intensive thermal dryer, at the desired dryness, of 60% to 95%. The resulting product will not stick and will be easily handleable.

Fig. 5 is a block diagram of a treatment line according to the invention dedicated solely to biowaste collected in particular in organic trashcans. This treatment line comprises a reception zone 27 consisting of a slab or a pit. A transfer means, which is not represented, takes matters from the reception zone and introduces them into a grinder 28 which gives, at the outlet, matters of which the particle size is between 20 and 70 mm, advantageously about 50 mm. The matters exiting the grinder 28 are directed to a separating drum 29 with meshes of 20 mm. The oversize 30, having a particle size larger than 20 mm, is directed to an energy recovery unit 3a. The undersize 31, having a particle size of less than 20 mm, is directed to a mixer Ml which makes it possible to regulate the feed of the digester. The outlet 32 of the mixer is connected to a digester BI for the methanization of the matters originating from the biowaste.

The digester BI, like the digesters A and B, comprises a biogas outlet not represented on the diagram. The digestate which exits via a pipe 33 is sent to an intensive thermal dryer ST1, after optionally passing through a press P3. Before entering the thermal dryer ST1, the matter is advantageously subjected to an extrusion, in an extruder that is not represented, so as to be conditioned in the form of cords a few centimeters in length, which are introduced into the thermal dryer ST1. This conditioning of the matter promotes drying.

The matter sorting carried out according to the invention upstream of the digesters makes it possible

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- 19 to produce, with the digester B or Bi, treating the matters having a small particle size, a fine digestate which has a rheology suitable for an intensive thermal dryer .

Thus, starting from heterogeneous matters containing inert materials and metals, which cannot a priori be suitable for a low-temperature intensive thermal dryer, the invention makes it possible to treat close to half the waste using a low-temperature intensive thermal dryer replacing one or more biodrying tunnels, the land occupied by which is much greater.

The 0-8 mm up centrifugation products which and the mixed sorted, fine low-temperature to 0-10 mm digestates oversizes constitute can be subjected to intensive thermal drying, while the heterogeneous products corresponding to the particle sizes of 0-60 mm and 10-20 mm are directed to biodrying tunnels.

number of temperature digestates

As it happens, a single low-temperature intensive thermal dryer can have the drying capacity of four or five biodrying tunnels. The solution of the invention makes it possible to reduce by more than half the biodrying tunnels by setting up lowintensive thermal dryers for the finest combined with all the centrifugation refluxes. The drying airflow is channeled and directed to deodorization. The working environment is considerably improved compared with composting and with a biodrying tunnel.

The amount of effluents that is recovered in a treatment line with a thermal dryer is the same, at identical final dryness, as in a conventional treatment line with a biodrying tunnel. However, not pressing generates a smaller production of centrifuged liquors and it is possible to envision reducing or even

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2013336281 22 Dec 2017 eliminating the biological treatment of the pressing liquors, whence an additional gain in space.

The drying condensates of the thermal dryer have a low SM (suspended matter) load and a relatively low nitrogen load, and are easier to treat than the pressing liquors. A physical treatment, in particular by evapoconcentration, can be envisioned for resolving the excess effluents at lower cost and in a smaller space.

The areas where there is a saving with a treatment line comprising an intensive thermal dryer consist:

of the areas that would have been occupied by the biodrying tunnels for the 0-10 mm fine digestate and the centrifugation sludge;

of the area of the 0-10 mm digestate dehydration hall; of the area of the refining hall;

of the reduction in size of the water treatment unit; of the reduction in size of the deodorizing unit.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word comprise, and variations such as comprises and comprising, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

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2013336281 22 Dec 2017

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A treatment line for treating waste consisting of residual household waste and/or biowaste, for the purpose of separating the organic matter and the matters with a high LHV, comprising:

5 means for storing waste, means for separating recoverable matters, means for sorting products having different particle sizes, means for directing the products of larger particle size to at least one treatment unit, and at least one digester for the methanization of products with a higher organic

10 content, having a smaller particle size, wherein:

the sorting means are provided in order to supply a fraction of products having a particle size of less than 20 mm, at least one digester is used for the methanization of this fraction having a particle size

15 of less than 20 mm, and the treatment line comprises at least one low-temperature thermal dryer, which is fed with the digestate derived from the fraction having a particle size of less than 20 mm.
2. A treatment line according to claim 1, wherein the means for directing the products of larger particle size to at least one treatment unit is for energy recovery.

20 3. A treatment line according to claim 1 or claim 2, wherein the temperature of the thermal dryer is below 95°C and above 60°C.

4. The treatment line as claimed in any one of the preceding claims, wherein the sorting means are provided in order to supply a fraction of products having a particle size of 0-10 mm, at least one digester is used for the methanization of this fraction having a particle size of 025 10 mm, and the low-temperature thermal dryer is fed with the digestate from this digester.

5. The treatment line as claimed in any one of the preceding claims, wherein it comprises: a first branch for the matters having a larger particle size, comprising:

at least one first digester used for the methanization of said matters having a larger particle size,

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2013336281 22 Dec 2017 at least one centrifuge and/or one press to which the digestate from the first digester is subjected;

at least one biodrying tunnel for the matters from the centrifuge or from the press,

5 a second branch for the matters having a smaller particle size, comprising:

at least one second digester used for the methanization of the matters having a smaller particle size, at least one mixer between the digestate of the second digester and the sludge from the centrifuge, or the pressate, of the first branch,

10 and at least one intensive thermal dryer to which the mixture from the mixer is subjected.

6. The treatment line as claimed in any one of the preceding claims, wherein it comprises: sorting means providing a production of 0-60 mm, 10-20 mm and 0-10 mm fractions, at least one first digester for the 0-60 mm and 10-20 mm fractions which are

15 methanized with structuring agent, then subjected to a press and/or a centrifuge for the production of presscakes and/or of centrifugation sludge, at least one second digester for the 0-10 mm fraction which is methanized without structuring agent and is not dehydrated at the outlet, a mixer for mixing the digestate from the second digester with the sludge from 20 centrifugation of the digestate originating from the first digester, at least one low-temperature intensive thermal dryer in which the mixture exiting the mixer or the digester is dried, and at least one maturing/biodrying tunnel for the presscake of the 0-60 mm and

10-20 mm fraction.

25 7. A treatment line according to claim 6, wherein the structuring agent is vegetable fibers.

8. The treatment line as claimed in claim 6 or claim 7, wherein it comprises:

a first separating drum, the meshes of which correspond to a particle size of between

100 and 500 mm, an energy recovery station for recovering energy from the oversize of the first 30 separating drum,

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2013336281 22 Dec 2017 a second separating drum with meshes that are smaller than those of the first drum, to which the undersize of the first drum is sent, a fermentor to which the oversize of the second drum is sent, after having gone through a sorting step which extracts the metallic products,

5 a third separating drum, the meshes of which correspond to a particle size of 20 mm, which receives the products exiting the fermentor, the oversize of the third drum being directed to the energy recovery station, means for separating the undersize, having passed through the meshes of the third drum, into a fraction having a particle size of between 10 and 20 mm, directed to a mixer, and

10 a fraction having a particle size of 0 -10 mm, directed to the second digester.

9. A treatment line according to claim 8, wherein the mesh of the first separating drum corresponds to a particle size of 300 mm.

10. A treatment line according to claim 8 or claim 9, wherein the mesh of the second separating drum corresponds to a particle size of 60 mm.

15 11. A treatment line according to any one of claims 8 to 10, wherein the metallic products are ferrous products.

12. The treatment line as claimed in any one of claims 8 to 11, wherein the mixer which receives the fraction having a particle size of between 10 and 20 mm, also receives the undersize which has passed through the second separating drum, the mixed products exiting

20 the mixer being introduced into the first digester.

13. The treatment line as claimed in claim 1, for biowaste, wherein it comprises: a bio waste grinder, screening means for supplying a fraction of products having a particle size of less than 20 mm and a fraction of products having a larger particle size,

25 at least one digester used for the methanization of the products having a particle size of less than 20 mm, and at least one intensive thermal dryer to which the digestate from the digester (B1) is subjected after optionally being passed through a centrifuge or a press.

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2013336281 22 Dec 2017

14. The treatment line as claimed in any one of the preceding claims, wherein the thermal dryer is controlled such that the final dryness at the outlet of the thermal dryer is between 50% and 90%, according to the expectations of the operation.

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