WO2019180053A1 - Process for repurposing organic household waste - Google Patents

Abstract

The repurposing process comprises: - a main step of separating household waste into organic household waste on the one hand and non-organic waste on the other hand, - a main step of methanization of the organic household waste, at the end of which the organic household waste has been converted into digestate and biogas, - a main step of conversion of the digestate into fertilizer, and - a main step (400) of granulation of the fertilizer (40) in order to form organomineral fertilizer granules.

Description

 Process of recovery of organic household waste

The present invention relates to a process for recovering organic matter from household waste.

 Organic waste is the majority of municipal waste. Their elimination can be achieved in different ways. For example, organic waste can be incinerated, but it has a low calorific value, so that disposal by incineration is of little value. They can also be landfilled, in which case they release methane that can be harmful if it is not captured or recovered. These landfill materials also generate leachates that need to be treated.

 These two organic waste disposal solutions are therefore not satisfactory.

 It could therefore be worthwhile to valorize organic waste by composting or anaerobic digestion, these solutions being more ecological and more rewarding.

 However, household organic waste is not used by the fertilizer industry because of its contamination with plastic-type inert materials. As a result, household organic waste is difficult to value.

 The object of the invention is in particular to remedy this drawback by providing a method for recovering household organic waste, which is both economical and effective.

 To this end, the subject of the invention is in particular a method for recovering organic matter from household waste, characterized in that it comprises:

 - a main step of separating household waste into organic household waste without undesirable pollutants on the one hand, and non-organic waste on the other hand,

- a main stage of methanisation of organic household waste, after which the organic household waste has been transformed into digestate and biogas,

 - a main stage of transformation of digestate into organic composted fertilizer, and

 - a main step of granulation of the fertilizer, to form granules of organo-mineral fertilizer.

The invention provides for the granulation of these dried and stabilized organics (by composting and anaerobic digestion) in admixture with fertilizing materials supplying the complementary N, P, K, S and MgO elements, to constitute a concentrated enriched organic fertilizer, transportable over long distances. and enriched, necessary to the good agronomic soil management, ensuring balance and agricultural performance for sustainable agriculture with production yields meeting the growing food needs of the world population.

 This invention implements many technical solutions that allow maximum recovery of recyclable materials contained in household waste. These solutions, implemented in several references for several years, make it possible to reduce the rate of landfilling to very low values (below 20%), especially if the solid recovery fuel preparation module (CSR) is installed.

 The present invention makes it possible in particular to recover a maximum of organic materials of very high quality, thus making them perfectly compatible with a return to the ground.

 By way of example, the papers, cardboards, cardettes, magazines and newspapers are defibrated in a cylinder that is the subject of patent FR 2 964 576 filed by Alfyma, before being pre-dried and pre-fermented with the other organic materials in tubes where the material will stay at least 2 days.

 The thus prepared organic will undergo further primary refining to rid them of the last traces of unwanted (plastics and metals)

 In addition, organic cockles (fruit stones, bones and cork stoppers) are finely ground before being mixed with other organic products.

 Usually, these materials are landfilled because they are not compostable as is.

 The present invention allows the old units "called TMB Tri-Mechano-Biological" are no longer put into operation.

 This invention, which is compatible with more and more selective sorting operations at the source, including for household and professional food waste, allows units that will be turned towards an almost total recovery of household waste, and where the organic material becomes a high value merchantable product through the enrichment and granulation process presented in the present invention.

 The integration of enrichment and granulation of organic household waste allows an unparalleled return on investment ensured by the sale of the finished granulated product.

The four indissociable stages of improved separation, methanization, transformation and granulation combine synergistically to obtain a viable recovery process. The separation step makes it possible to clean the organic waste so that it is not contaminated with inert materials of the plastic type and inert in particular. In the absence of this step, it would not be possible to obtain a fertilizer acceptable by industrialists of agriculture.

 The methanation stage makes it possible, by converting the biogas generated into energy, to cover the energy requirements necessary for the implementation of the four main stages of the process. In the absence of this step, the process would require an external source of energy, which would greatly affect its financial profitability. In addition, the methanization makes it possible to obtain a digestate of better agronomic, clean quality, in particular free of bacteria, which are destroyed by this methanation. In addition, the anaerobic digestion process, by removal of carbonaceous materials transformed into biogas (CH4 and CO2), substantially concentrates (approximately 40 to 50%) the N, P and K fertilizer units contained in the residual dry matter digestate. for example the total NPK concentration of 6% on MS before 9% methanization on MS in the residual digestate.

 Finally, the transformation stage makes it possible to obtain a dry and granular fertilizer that can be packaged and transported over long distances. In the absence of this step, the raw form fertilizer would be difficult to transport, and would be transportable only over short distances, which would also affect the profitability of the process.

 A method according to the invention may further comprise one or more of the following characteristics, taken alone or in any technically feasible combination.

 - The main stage of separation includes a pre-fermentation stage, during which the household waste resides in a pre-fermentation tube for a predefined period, for example three days, to become fermented waste.

 The main separation step comprises, thanks to the pre-fermentation step, a refining step, during which a trommel separates the fermented waste particles by particle size, with for example a 50 mm mesh, part in fine waste passing through the meshes of the trommel, and secondly in non-passing waste.

- The main step of separation comprises, following the refining step, a waste treatment step, during which the fine waste passed in a succession of separation devices, including an element separation device ferrous and non-ferrous, a device for removing large inerts, a screening device, and a device for removing small inert, to, at the end of this purification step, keep only organic waste. The main methanation step comprises a fermentation step, during which the organic waste resides for a predefined duration in a digester, for example 21 days, during which it is digested, changing on the one hand into digestate and d on the other hand in biogas.

 - The main methanisation stage involves a biogas treatment step, in order to produce electricity and heat used entirely for drying the fertilizer.

 - The main stage of transformation into fertilizer includes a step of composting the digestate, at the end of which the digestate is transformed into organic composted fertilizer.

 - The main step of granulation comprises a step of mixing the fertilizer with mineral raw materials, then a step of granulation and drying of the mixture.

 The main granulation stage comprises a large screen stage and a screen stage of the ends, at the end of which substantially calibrated granules are obtained.

 - The main step of granulation comprises a coating step, during which the calibrated granules are coated, including an anti-clogging additive, to protect these granules.

 The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended figures, representing the main steps of a recovery process according to the invention, and more particularly :

 - Figure 1 schematically shows a main step 100 of separation of household waste into organic household waste on the one hand, and non-organic waste on the other hand,

 FIG. 2 schematically represents a main step 200 of methanization of organic household waste, at the end of which the organic household waste has been transformed into digestate and biogas,

 FIG. 3 schematically represents a main stage 300 for transforming the digestate into fertilizer, and

 - Figure 4 schematically shows a main stage of granulation 400 during which the fertilizer is converted into organo-mineral fertilizer granules.

The main steps 100, 200, 300 and 400 will be described in more detail below. The main waste separation step 100 is shown in FIG. 1. This separation of waste is for example carried out by means of a waste treatment facility as described in FR 0 304 005. The waste treatment facility may include provisions as described in FR 3 025 731 and / or FR 3 040 007.

 The main step of separation begins with a step 10 10 of household waste supply 10. These are for example provided by dump trucks carrying household waste to the waste treatment facility.

 The method then comprises a crane sorting step 120, making it possible to separate the large size waste 12 (called "bulky" or "monsters") from the other waste 14.

 The crane also takes care of the storage of said other waste and their introduction into the treatment facility via a conventional type of feeding device. Such a feed device regulates the flow of the waste 14 to a carrier that feeds at least one pre-fermentation tube, for example, which alternately feeds two pre-fermentation tubes.

 The method thus comprises a pre-fermentation step 130, during which the waste 14 resides in the pre-fermentation tube for a predefined duration, for example three days. This pre-fermentation allows a degradation of the organic matter.

 This degradation is notably achieved by the rise in temperature, which can reach up to 70 ° C, as well as slow self-grinding due to the rotation of the waste in each pre-fermentation tube, for the predefined period.

 Preferably, the pre-fermentation tube comprises means for reducing the humidity level.

 Following this pre-fermentation step 130, the waste is called "fermented waste 16".

 Following this step, the fermented waste 16 is taken up by at least one conveyor supplying a screening device, in particular a "trommel" type rotating screen.

 The process then comprises a primary refining step 140, during which the trommel separates the fermented waste 16 by particle size with, for example, a 50 mm mesh.

The fermented waste 16 is thus separated, on the one hand into fine waste 18 passing through the meshes of the trommel, and on the other hand into non-passing waste 20. Fine waste 18 comprises organic waste, which has been milled and degraded in the pre-fermentation tube during the pre-fermentation step 130.

 Non-conductive waste 20 does not include organic waste, and is then processed to recover valuable materials (ferrous, non-ferrous, glasses, inert washed, heavy plastics and plastic films, papers, magazines and cardboard, cardboard, etc.). during a treatment step 145. During this treatment step 145, the organic material resulting from the cleaning (in particular washing) is recovered and returned to the fraction 18.

 The method then comprises a waste treatment step 150, passing them through a succession of separation devices, in particular a ferrous element separation device 22 (for example a magnetic separator), which is non-ferrous (for example a separator eddy current device), an inert fat removal device 24, a 12 mm mesh screening device, and a small inert waste removal device 26.

 Small 26 and large 24 inert are recovered for a process 155 for treating inerts, independently of the present recovery process to recover recoverable materials (ferrous, non-ferrous, glasses, inert washed, heavy plastics and plastic films, papers, magazines and cardboard, cardboard etc.). During this step, the organic material resulting from the cleaning (in particular washing) is recovered and returned to the fraction 18.

 At the end of this purification step 150, organic waste 28 is obtained which has no undesirable pollutants, and thus in particular complies with the French standard for composts.

 The method then comprises the main step 200 of methanation, represented in FIG.

 The anaerobic digestion is carried out in an anaerobic digestion unit, in which said organic waste 28 containing no pollutants (in particular plastics) are introduced.

 These organic wastes 28 free of pollutants are first brought by a conveyor into a hopper equipped with a moving floor which leads the organic material to a two-way screw. This screw makes it possible, in a first sense, to directly feed an anaerobic digestion unit, and in a second direction opposite to the first, to supply it with a storage space for the organic material. This organic matter is subsequently reintroduced into the anaerobic digestion unit.

The anaerobic digestion unit comprises a main pump in which the organic waste 28 is received, and preferably mixed with a recirculated portion of digestate of anaerobic digestion which will be described later. The methanation unit also comprises at least one digester in which this mixture is introduced.

 Thus, the main methanation step 200 comprises a mesophilic or preferably thermophilic anaerobic digestion step 210, during which said mixture resides for a predefined duration in the digester, for example 21 days, during which it is digested, changing on the one hand in digestate 30 and on the other hand in biogas 32.

 This digest 30 is taken up by a screw which feeds a secondary pump. This secondary pump, depending on the fermentation cycle, returns the digestate to the main pump to be reinjected into the digester, or evacuates the digestate in a storage compartment waiting to be mixed with structurant (green waste) to be composted .

The biogas 32 formed by the fermentation is captured at the top of the digester and led into a storage gasometer 215, having for example a capacity of 2000 m ³ . The biogas is taken up by a compressor that feeds a container of gas processing equipment. The process then comprises a step 220 for treating the biogas 32, in particular in a cogeneration group, for example 650 kW. Thus, the main step of anaerobic digestion 200 makes it possible, by using biogas, to produce electricity. The exhaust gases of the biogas engines of the cogeneration units are advantageously sent to the granulation unit for supplying hot gas to the generator of the rotary tube dryer. These gases are then mixed with the combustion gases of a biogas burner or fuel oil.

 Biogas 32 is produced 24 hours a day all year long. Electrical production is primarily used to power the waste treatment plant, which can be powered without external energy input. Night production can be marketed on the national network.

 It should be noted that the waste treatment facility is connected to an external energy supplier, in particular to the national grid, on the one hand to, as indicated above, to supply surplus energy, and on the other hand to be fed during the initialization of the installation, before the biogas 32 is produced.

 Advantageously, a flare is located next to the gasometer 215. This flare makes it possible to secure the unit by burning the biogas 32 in excess if necessary.

 The main step 300 of transformation into fertilizer is represented in FIG.

During an optional mixing step 310, the recovered digestate 30 is associated with a structurant 34, for example ground green waste. For this purpose, the crushed green waste 34 and the organic matter resulting from the sorting or the digesters are introduced into a mixer to obtain a homogeneous product, structured and having an optimum C / N ratio.

 During a composting step 320, this product is swathed, each swath representing one week of production. These windrows are returned once a week by a swather. Under each swath, a gutter can recover fermentation juice 36, so-called leachates that are used to spray windrows to control moisture.

 These juices are centralized by gravity and then evacuated for example to a lagoon for evaporation, or advantageously used in granulation.

 The composting step 320 is carried out for a predefined period, for example 6 weeks, at the end of which the digestate 30 is transformed into compost 38.

 The method then comprises a step 330 of screening, during which the compost 38 is again screened in order to recover the structuring agents (green waste) greater than the 30 mm mesh, these structuring agents being reused in the mixer. The passer of this screening step 330 is called refined compost 40.

 The refined compost 40, containing about 65% solids, thus recovered is used in the main granulation step 400, which will now be described.

 This main transformation step is carried out by means of a granulation unit.

 The granulation unit comprises a device for weighing, dosing and mixing raw materials to be added to the compost 40 described above. These raw materials, for example five raw materials, are chosen in particular from the following list and stored in 8 dosing hoppers:

 urea (46% N) granulated or in prills;

 sulphate of ammonia (21% of N) in crystals;

 di-ammonic phosphate DAP (18% N and 46% P205) or triple superphosphate TSP (45% P205) or simple SSP (18% P205);

 potassium sulphate (for example 50% K 2 O and 61% SO 3);

 magnesium sulfate (for example 25% of MgO and 50% of SO 3) granulated or powdered;

 o a powdery filler (gypsum base, limestone, sand, etc.);

 o fines from sieving a product stored in the store to remove dust and clumps from prolonged bulk storage;

o the composted material 40 a liquid or solid granulation additive whose quantity (flow rate) is proportional to the incoming raw material flow rate and controlled by a flow control loop or a weighting test;

 Optionally, it is also possible to incorporate and dose microelements powder, which can bring according to demand the following elements: iron, zinc, manganese, boron, copper and molybdenum.

 The granulation unit further comprises a granulation line, comprising:

• a cylinder or tray granulator,

 • a dryer,

 At least one double-screen screen for the recycling of the granulation fines and the coarser ones which are crushed (these products being returned to the granulator),

A cooler, in particular a rotary cooler or preferably a two-table fluidized bed cooler fed with countercurrent in conditioned air,

 A coating machine, preferably with a rotating drum, which sprays a specific oil on the cooled granule, which prevents caking of the granules with one another and the formation of dust,

 • a bulk product storage warehouse with several boxes to store each formulation during the period of non-use of these fertilizers.

 The main granulation step 400 will now be described.

 During a step 410 of supply of raw materials, these raw materials are taken from a stock and stored in 8 hoppers.

 The raw materials are then dosed individually during a dosing step 430, and then mixed during a mixing step 440. The refined compost 40 is also introduced during this dosing step 430.

 Then, during a step 445, these mixed raw materials are sieved on a single-screen sieve and crushed rejections of the screen. Crushed materials are recycled at the top of the screen.

 The mixture thus obtained, flowing batchwise in a buffer hopper whose level is controlled, continuously supplies the granulator with an adjustable flow rate, for example by means of a belt conveyor equipped with a speed variator.

On the other hand, the dosing 430 and mixing 440 steps are provided batchwise so as to allow a precision of the dosage in adequacy with the quality standards of the finished product. The method then comprises a granulation step 450, preferably in a rotary drum granulator, during which the compost mixed with the raw materials is agglomerated into granules. Advantageously, an additive, water and steam are introduced at the same time as the mixture into the granulator to promote granulation. The raw materials are granulated with recycled hot fines and coarse grains. The recycling rate is between 2.5 and 5, preferably between 3 and 4.

 The granulator can be fed with reaction slurries, for example manufactured in a phosphoric acid neutralization unit or a sulfophosphoric mixture with anhydrous ammonia stored in a liquid tank under pressure, such as butane tanks or liquid propane. The slurry can be prepared in a tank equipped with a stirrer or, preferably, in a tubular reactor feeding the on-line granulator. The still acid slurry ends up being neutralized in the granulator by injection of liquid ammonia by injectors into the bed of product being granulated to form in situ MAP, DAP or ammonium sulfate or combinations thereof. This technique has the advantage of introducing into the process very large quantities of reaction heat, which makes it possible to significantly reduce the amount of fuel required for the dryer.

 The process then comprises a drying step 460 of the granules, by means of the dryer. Advantageously, the dryer is supplied with hot air by a burner operating with diesel or preferably with biogas whose gases are diluted by hot air recovered in the installation (gas engine exhaust gas - generator or groups of cogeneration). The gases leaving the dryer are taken up and treated before discharge to the atmosphere by cycloning and washing in a cyclonic column fed with sulfuric acid, which will fix the small amounts of ammonia released into the granulator and the dryer. This treatment complies with the most stringent international standards. A chimney channels the exit of gases on the roof. The solid elements captured by the cyclones of the air treatment are reinjected into the circuit to the granulator.

 The method then comprises a step 470 of screening large. The granules that are too big are then crushed and recycled in the granulator.

The method also includes a step 480 screen. The fine granules are returned to the granulator. Following these screening steps of the large 470 and 480 end, granules are substantially calibrated for example between 2 and 5 mm. The method then comprises a step 485 for cooling the calibrated granules in a rotary drum cooler or preferably in a fluidized bed cooler.

 The process then preferably comprises a coating step 490, during which the calibrated granules are coated, in particular with an anti-caking additive, in order to protect these granules. In this way, usable and usable fertilizer granules are obtained for spreading with any type of agricultural distributor.

 The fertilizer granules are then recovered and stored in a storage space provided for this purpose.

 The granules before shipment are sieved again. Indeed, the product stored in stores, sometimes beyond 2 months, can be mottled and dusty. The product is fed by a feeder into a hopper equipped with a sweeper to a chain hoist and metal buckets, and to a buffer hopper for feeding a batch weighing scale of capacity, for example 60 t / h, for packaging. of the finished product before shipment.

 Three types of expeditions are for example envisaged.

 In a first example, the fertilizer granules are shipped in bulk directly loaded into a dump truck positioned under a loading conveyor or under a filled hopper before loading the truck. The loading capacity is for example 60 t / h.

 In a second example, the fertilizer granules are sent in 50 kg or 25 kg bags made by a bagging line in a welded PE bag (semi-automatic presentation of the PE open mouth bag and welder) or in canvas. sewn polyethylene. The capacity is, for example, 1200 bags / hour (60 t / h in 50 kg bags and 30 t / h in 25 kg bags). The bags are then grouped in batches on pallets for example using an automatic palletizer and placed in stock awaiting shipment.

 In a third example, the fertilizer granules are shipped in large capacity bags (for example 600 kg) called "big-bags", made by a semi-automatic line setting big-bag. The capacity is for example 100 bags / h.

 Note that the invention is not limited to the embodiment described above, but could have various variants without departing from the scope of the claims.

Claims

1. Process for recovering organic matter from household waste, characterized in that it comprises:  - a main step (100) of separation of household waste (14) into organic household waste without undesirable pollutants (28) on the one hand, and non-organic waste on the other hand,  - a main stage (200) of anaerobic digestion of organic household waste (28), after which the organic household waste (28) has been transformed into digestate (30) and biogas (32),  a main stage (300) for transforming the digestate (30) into a composted organic fertilizer (38, 40), and  a main step (400) for granulating the fertilizer (40) to form granules of organo-mineral fertilizer. The upgrading process according to claim 1, wherein the main separation step (100) comprises a pre-fermentation step (130), during which the household waste (14) resides in a pre-fermentation tube for a predefined period, for example three days, to become fermented waste (16). 3. The recovery method according to claim 2, wherein the main separation step (100) comprises, thanks to the step (130) of pre-fermentation, a refining step (140), during which a trommel separates the fermented waste (16) by granulometry, with for example a mesh of 50 mm, firstly fine waste (18) passing through the meshes of the trommel, and secondly non-passing waste (20) . 4. Recovery process according to claim 3, wherein the main step of separation (100) comprises, following the refining step, a step (150) of waste treatment, during which the fine waste (18) passed through a succession of separation devices, including a ferrous (22) and non-ferrous element separating device, a large inert elimination device (24), a screening device, and a device for separating elimination of small inerts (26), at the end of this purification step (150), retain only organic waste (28). 5. Recovery method according to any one of the preceding claims, wherein the main step of anaerobic digestion (200) comprises a step (210) fermentation, during which the organic waste (28) resides for a predefined period in a digester, for example 21 days, during which it is digested, changing firstly into digestate (30) and on the other hand in biogas (32). The beneficiation process according to claim 5, wherein the main methanation step (200) comprises a step (220) of biogas treatment, in order to produce electricity and heat used entirely for the drying of the biogas. 'fertilizer. 7. recovery process according to any one of the preceding claims, wherein the main step (300) of transformation into fertilizer comprises a step (320) for composting the digestate (30), after which the digestate (30) is transformed into organic composted fertilizer (38, 40). 8. Process for recovery according to any one of the preceding claims, wherein the main step of granulation (400) comprises a step (440) of mixing the fertilizer (38, 40) with mineral raw materials, then a granulation step and drying (450) of the mixture. 9. The upgrading method according to claim 8, wherein the main granulation step (400) comprises a step (470) of large screen and a step (480) of screening purposes, at the end of which granules are obtained substantially. calibrated. The recovery method according to claim 9, wherein the main granulation step (400) comprises a coating step (490), during which the calibrated granules are coated, in particular with an anti-clumping additive, in order to protect these pellets.