FR2856319A1 - Plant for biotreatment and storage of diverse solid wastes, has multifunctional drainage-, biogas removal- and leachate injection pipe network - Google Patents

Abstract

Pipework of the drainage network (19) is multifunctional. It is used in an alternating sequence to first draw out biogas (A) and then to inject leachate (I). There are three networks (9, 11) of drain pipes (19) separated by the waste (2) storage volumes (3, 4). Each network has two ends connected to pumps removing the biogas and/or injecting leachate. These are separated, and situated on either side of the waste storage volume. A vertical duct is situated at one or more of: each node of the drainage network, each free end of the network, between nodes and between nodes and free ends. Drain inclination is 5% between nodes or between a node and a free end. The subsequent drain inclination is inverted. Upper surfaces of the drains have openings (21) for biogas removal from the waste by suction, and for leachate injection. The drains are in drain trenches (8). A supplementary drainage network and its connections are detailed. The drains are used to reinject a gas into the storage volume, e.g. CO2, air or other gas. Three volumes (4) are stacked with at least three drain networks and a network for pumping excess leachate, with outlets connected to a single, vertical collection well. The plant may be complementary to an incinerator. It is a fermenting or composting treatment plant.

Description

WASTE PROCESSING AND STORAGE FACILITY

  The invention relates to a plant for bioprocessing, permanent storage and transformation / stabilization of waste with production of biogas.

  Putting it in a waste storage center is one of the means of disposal existing today. This waste mainly consists of household waste, ordinary industrial and commercial waste and refuse from 10 sorting centers. This storage technique is complementary to incineration.

  The construction of a storage center involves digging and fitting out a large cavity, also called an alveolus, constituting a storage volume, inside which the waste will be arranged in successive layers as and when of their arrival on the site. This previously crushed waste will stabilize over time, for example after about twenty to twenty-five years. Due to this burial and in the absence of oxygen, the organic substances present in the waste undergo a slow process of anaerobic degradation with production of a biogas, containing mainly methane.

  In most known installations, the biogas is collected by suction pipes for on-site combustion by a flare, for use for district heating or for producing electricity. One method for improving the yield of methanogenic thermophyllous bacteria consists in providing and regulating a degree of relative humidity substantially between 60% and 80%, the pH and the temperature (55 - 60 C) inside the storage volume. garbage. 25 State of the art The deep layers of waste are humidified by percolation of water within the storage volume, with recirculation in a closed circuit of rainwater, called leachate, having percolated by gravity through the waste. The leachate additionally ensures the transport and the good distribution of the nutrients and bacterial strains, and therefore a homogeneous stabilization of the ground waste.

  Document EP-1,193,002 discloses an installation for storing waste comprising a set of drains which are connected to each other and a device for sucking up the generated biogas. The set of drains consists of a layer of liquid-permeable aggregates inside which pass the first elements forming a biogas circulation conduit positioned in the middle of the aggregates, second elements forming the leachate circulation conduit positioned at the base aggregates and third sealed separation elements disposed between the first biogas circulation means and the second leachate circulation means.

  However, such an installation has the disadvantage that the set of drains requires the use of three separate elements which prove to be complicated to install relative to each other, resulting in an increase in the mounting cost.

  Description of the invention The main problem which the invention proposes to solve consists in providing a waste storage installation which allows an increase in the quantity of biogas produced within the volume of waste stored. A second problem is to reduce the duration of biogas production, to accelerate the obtaining of the waste stabilization phase, in order to reduce the duration and the costs associated with monitoring the installation. A third problem is to obtain an installation which is simple, multifunctional and which is inexpensive to assemble.

  The invention therefore relates to a waste storage installation, comprising at least one storage volume inside which the waste is stored and at least one network of conduits of the drain type per waste storage volume. The network of drain-type conduits is located at the upper level of the waste storage volume (s). The network of drain type conduits is used to suck up a biogas, present in the waste storage volume or volumes and generated by the anaerobic decomposition of the waste, and also to inject a leachate into the waste storage volume or volumes, to maintain and accelerate the anaerobic decomposition of waste.

  In accordance with one aspect of the present invention, the installation is characterized in that the same network of drain type conduits is intended, in a multifunctional, sequential and alternative manner, firstly for sucking the biogas and in a second time time to inject the leachate.

  In other words, a single network will simultaneously present the two functions which are those of suction of biogas and injection of leachate. These two functions will be used sequentially, with first a biogas suction phase, followed by a leachate injection phase. In the same network alternately circulates the biogas then the leachate.

  Preferably, the installation can comprise three networks of conduits of the drains type separated by waste storage volume, in order to improve the penetration density of the networks relative to the surface area of the waste storage volume.

  Also to allow optimal biogas suction and leachate injection 10 distributed over the entire surface covered by the networks, the network or networks of drain type conduits may each include two ends of connection to the pumps for sucking the biogas and / or to inject the leachate. These two ends can be separated from each other and located on either side of the waste storage volume.

  To aspirate the biogas and to inject the leachate deep into the volume, the network or networks of conduits of the drain type can advantageously further comprise a substantially vertical well. This well may be located at each node of the network of drain type conduits and / or at each free end of the network of drain type conduits and / or between a node and a free end of the network of drain type conduits 20 and / or between two nodes of the network of drain type conduits.

  The drains type duct can have a slope substantially equal to 5%, in order to avoid any stagnation of leachate in the duct. This slope may be provided between two nodes of the network of drain type conduits and / or between a node and a free end of the network of drain type conduits, with inversion of the inclination for the subsequent drain type conduit.

  Favorably, the drains type conduits can have an upper face comprising orifices for sucking up the biogas and for injecting the leachate.

  To facilitate the circulation of biogas and leachate around drain-type conduits, drain-type conduits can be inserted into draining trenches.

  To pump the excess leachate to which rainwater is added, the installation may also include a network of conduits of additional drains type per waste storage volume, located at the lower level of the waste storage volume or volumes. This additional network can be connected to a substantially vertical collection well. A third function coming in addition to the suction and injection functions is that the network of drain type conduits can be used to re-inject into the waste storage volume or volumes a gas, such as CO 2, air or others.

  For example, the installation can comprise three superimposed volumes and at least three networks of ducts of the drains type for sucking up the biogas and for injecting the leachate, as well as a network for pumping the excess leachate connected to a single outlet collection well.

Brief description of the figures

  The invention will be well understood and its various advantages and different characteristics will become more apparent from the following description, from the nonlimiting example of embodiment, with reference to the appended schematic drawings, in which: - Figure 1 shows a plan for the above the waste biotreatment storage facility; Figure 2 shows a partial perspective view of the networks inside the storage volume; - Figure 3 shows a partial cross-sectional view of a draining trench in the biogas suction function; - Figure 4 shows a partial cross-sectional view of the draining trench according to Figure 3 in the leachate injection function.

  Detailed description of the invention

  A waste storage and biogas production facility (1) is mounted from an excavation having an area, for example substantially equal to 0.5 hectares. The excavation is dug in particularly impermeable soils, such as for example marl or clay. A sealing level (not shown) protecting from perforation is provided at the bottom of the storage area, so as to constitute the bottom of the storage volume. The storage volume is then divided into cells (3).

  The waste (2) is ground to increase its exchange surface and provide better hydrodynamic conditions for recirculation. They are thus stored as soon as they arrive on site. The cells (3) themselves comprise several storage levels (4), for example three in number. In accordance with the present invention, a device for draining biogas and for recirculating liquids or leachate forming networks is used at each intermediate level (4) for filling the cells (3). These networks are arranged under an intermediate cover (6) composed of clay sand or compacted marl (permeability of the order of 1.10-9 m / s) with a thickness roughly equal to 0.50 m.

  The design of the drainage device makes it possible to envisage a sequential and alternative operation, with recirculation of leachate, reinjection of concentrates (Arrows I in Figure 4) and capture of biogas (Arrows A in Figure 3), so that the results obtained could favorably exceed the objectives set in terms of waste stabilization efficiency (2).

  The biogas collection or liquid recirculation device comprises several networks (7) of draining trenches (8), at a depth of 0.50 m to 1.50 m, arranged in spikes. The networks (7) include drains operating in the leachate reinjection phase (9), represented in medium dotted lines in FIG. 1, and drains operating in the biogas suction phase (11), represented in fine dotted lines in 15. Figure 1. The drains operating in the leachate re-injection phase (9) have vertical injection wells (12). The drains operating in the biogas suction phase (11) have vertical biogas collection wells (13).

  Each network (7) has independent segments, a central segment (11) for suction (A) and two peripheral segments (9) for injection (I). In the following phase, the operation of the segments (9 and 11) is reversed, with the central segment serving for injection and the two peripheral segments serving for suction.

  Cyclic phases are planned with aspiration-injection sequences having a duration for example equal to one week.

  Each segment is composed of a main axis and a succession of lateral spikes 25 connected to 90. The lateral spikes are connected on either side of the central segment. The central segment is split in two, with solid pipes in its center.

  The peripheral segments are connected to ears oriented towards the inside of the cell (3). The spikes of the peripheral and central segments are intertwined, with a staggered arrangement of the nodes. The distance between each node of the network (7) being approximately 20 m, the distance between trenches and node of the central and lateral segments is 10 m.

  Due to the water saturation of the biogas, the draining trenches (8) have a slope of 5% between each node of the networks (7), with inversion of the inclination relative to the draining trenches (8) beyond the node ( visible in Figure 2). The drop between the nodes spaced 20 m is therefore 1 m. Thus the relative dimension of the water line of the conduits forming drains (19) is included in the range -0.5 m and -1.5 m relative to the top of the cell (3) or the storage level (4 ) considered.

  As shown in FIGS. 3 and 4, the draining trenches (8) are produced like the entire device after complete filling of a cell bearing by taking up the crushed waste (2) compacted. This operation is carried out under operating conditions, the crushed waste (2) excess is discharged onto the cell during filling. The trenches (8) are approximately 1 m wide by 0.5 m to 1.5 m deep.

  A HDPE drain (19) of equal diameter 110 mm is placed at the bottom of the trench (8) on a bed of gravel. The drain (19) is lanterned on a single half-circumference with slots (21) of 5 mm, spaced so as not to alter the mechanical strength of the material. The slots (21) are therefore arranged towards the top of the drain (19) so as to avoid excessive pressure losses. The drain (19) thus alternately performs the double function of suction and injection.

  The trench (8) is then filled with draining gravel from the screening of site quarry materials. The trench (8) is covered with a filtering geotextile before its final closure with Miocene clay sand.

  Each network node (7) of trenches (8), each intersection and / or each free end of the network (7) is equipped with a vertical well (22) connected to the drain (19).

  The wells (22) consist of a 110 mm diameter HDPE strainer tube, surrounded by a mass of gravel. The wells (22) are drilled a minimum of 600 mm in diameter.

  The storage levels (4) having a thickness of 5 m to 6 m and in order to maintain a sufficient thickness relative to the bottom of the cell (3), the wells (22) whose apex is located at -1.5 m from the reference dimension have a maximum depth of 2 m. The other wells (22) whose top is located -0.5 m from the reference dimension have a depth of 3 m. This arrangement also makes it possible to avoid too rapid recirculation towards the bottom of the cell (3).

  At the end of the networks, the drains (19) operating in the leachate re-injection phase (9) are connected to solid HDPE pipes with a diameter of 110 mm (14). At the end of the networks, the drains (19) operating in the biogas suction phase (11) are connected to similar pipes (16). The pipes (14 and 16) are connected on the surface to a distribution manifold. From this ramp, the pipes (14 and 16) will all be overhead, in the areas that have been completely redeveloped, the pipes (14 and 16) are connected to the cover geomembrane.

  Each end of each segment, on either side of the storage cell (3), is thus connected both to a secondary pipe intended for the recirculation of liquids and a secondary pipe intended for the transport of biogas. These two access points increase the efficiency of the networks, both in suction and in injection. Control valves (17) inserted just before the corresponding pumps allow switching from injection operation to suction operation and vice versa.

  The secondary pipes of the three levels of drains (19) corresponding to the three storage levels (4) are connected at each end and for each type of network to a main pipe. The main lines are connected to a manifold serving a cell line. On the recirculation network, each manifold is supplied from a buffer tank (5 m3 to 10 m3) allowing better regulation. The buffer and feeder tanks of each cell line will be connected to the main pipeline 15 which is itself connected to the leachate and biogas management installations.

  An additional network (18), shown in rough dotted lines in FIG. 1, is mounted at the bottom of the cell (3) or of the storage level (4) and is used for the drainage of leachate at the bottom of the cell (3) by a pumping well (23).

  In the installation (1), the role of the device with these networks (7) is twofold. On the one hand, it allows optimal diffusion (I) of the humidity within the crushed waste (2) during stabilization, by recirculation of leachates treated by ultrafiltration. The main effects of this recirculation will be to maintain the humidity and temperature conditions most favorable to the development of methanogenic bacteria and to continuously supply them with nutrients. On the other hand, it makes it possible to ensure the optimal capture 25 (A) of the biogas produced, with a view to its valorization, and thus to exploit all the energy potential of the crushed waste (2) during stabilization.

  The drainage device also allows the reinjection of reverse osmosis concentrates, that is to say residues from the treatment of leachate, within the alveoli (3) at the end of stabilization. The reinjection of the concentrates favors the precipitation of the leachable elements and therefore the storage of these residues within the mass of crushed waste (2). In fact, the salts contained in the concentrate precipitate in the form of a stable matrix within the crushed waste (2). The higher the concentration of concentrates, the greater their precipitation and the crystallization of the salts on the surface.

  The objective of the reinjection is therefore a return by precipitation of the fraction initially leached into the mass of ground waste (2), and better biodegradation by anaerobic route of the organic matter contained in the ground material (2).

  Finally and as a precaution, it is envisaged to use the draining device 5 for reinjecting CO2 into the cells (3) in the extinction phase, that is to say when stopping Anaerobic fermentation, in order to inert the gas mixture. It is also possible to add fertilizer to speed up the end of the fermentation process. An injection of O2 or air is also possible in order to stop the anaerobic fermentation and allow a return to aerobic conditions.

  With the installation according to the invention, the biogas generated is captured as soon as it appears (on average after 200 days of storage). In addition, waste stabilization will take place over a period of approximately 5 years.

  The present invention is not limited to the embodiments described and illustrated. Many modifications can be made without departing from the framework defined by the scope of the set of claims.

Claims (10)

  1. Installation for bioprocessing and storage of waste, comprising: at least one storage volume (3, 4) inside which the waste (2) is stored, and - at least one network (7) of conduits of the type drains (19) per storage volume (3, 4) of the waste (2), located at the upper level of the storage volume (s) (3, 4) of the waste (2), - for sucking up a biogas, present in the or the storage volumes (3, 4) of the waste (2) and generated by the anaerobic decomposition of the waste (2), and for injecting into the storage volume (s) (3, 4) of the waste (2) a leachate, allowing to maintain and accelerate the anaerobic decomposition of waste (2), characterized in that the same network (7) of drain-type conduits (19) is intended, in a multifunctional, sequential and alternative manner, at first to aspirate the biogas (A) and then inject the leachate (I).   2. Installation according to claim 1, characterized in that it comprises three networks (9, 11) of drains type conduits (19) separated by storage volume (3, 4) of the waste (2).   3. Installation according to claim 1 or 2, characterized in that the network or networks of conduits (9, 11) of the drains type (19) each comprise two ends of connection to the pumps for sucking the biogas (A) and / or to inject the leachate (I), which are separated and located on either side of the storage volume (3, 4) of the waste (2).   4. Installation according to any one of the preceding claims, characterized in that the network or networks of conduits (9, 11) of the drains type (19) also comprise a substantially vertical well (22) located at each node of the network of drain type conduits and / or at each free end of the network of drain type conduits and / or between a node and a free end of the network of drain type conduits and / or between two nodes of the network of drain type conduits.   5. Installation according to any one of the preceding claims, characterized in that the drain type duct (19) has a slope substantially equal to 5% between two nodes of the network of drain type ducts and / or between a node and a 5 free end of the network of drain type conduits, with inversion of the inclination for the subsequent drain type conduit.   6. Installation according to any one of the preceding claims, characterized in that the drain type conduits (19) have an upper face comprising 10 orifices (21) for sucking up the biogas and for injecting the leachate.   7. Installation according to any one of the preceding claims, characterized in that the drains type pipes (19) are positioned in draining trenches (8).   8. Installation according to any one of the preceding claims, characterized in that it further comprises a network of conduits of the additional drain type (18) per storage volume (3, 4) of the waste (2), located at the level bottom of the storage volume (s) (3, 4) of the waste (2), for pumping excess leachate, and which is connected to a substantially vertical outlet collection well (23).   9. Installation according to any one of the preceding claims, characterized in that the network (7) of type drains (19) is used to reinject into the storage volume (s) (3, 4) waste (2) a gas, such as CO2, air or others.   10. Installation according to any one of the preceding claims, characterized in that it comprises three superimposed volumes (4) and at least three networks of conduits of the drains type for sucking up the biogas and for injecting the leachate, as well as a network (18) for pumping excess leachate connected to a single collection well at substantially vertical outlet (23).   Applicant GRANGEON ET FILS Agent LAURENT & CHARRAS