FR2863920A1 - Treating and valorizing flow of waste involves gasification phase using superheated steam - Google Patents

Abstract

The gasification phase has a first step of pyrolysis supplying at its outlet pyrolysis gases (103) and carbonated solid materials (101, 102), followed by a gasification of the solid amterials and pyrolysis gases to supply at the outlet a purified gas (GE) which can be stored with the intention of energetic valorisation : The gasification stage includes the channelling and injection of the solid materials and the pyrolysis gases in a dense fluidised bed furnace (301), with the pyrolysis gases forming the means (305) of fluidisation in the furnace. The process includes a stage of crushing the carbonated solid materials after pyrolysis so only fine materials (102) pass to the gasification stage. The refuse from the crusher (103) is calcinated or burned, sorted and the carbonated fraction reinjected into the pyrolysis furnace. The pyrolysis gases are used as the means of pneumatic transport for the fine solid materials from the pyrolysis stage to the dense fluidised bed furnace. The pyrolysis gases are blown by a steam jet (104) to form a flow of steam and pyrolysis gases (105) and a rotating gate (106) is used to allow the fine solid materials to be transported. The steam flow (V) is generated internally using a cooler (501) for the process gases (GP) supplied from the outlet from the dense fluidised bed furnace. A separation stage separates the solid material from the flow of steam and pyrolysis gas which carried them to a cyclonic device (302) to be injected into the dense fluidised bed furnace. The pyrolysis gas (GV) is heated using a heat exchanger (303) before injection as the means of fluidisation. The purified gas and other gases and/or exhaust generated by the process are recycled in a post-combustion chamber (304) to supply at its outlet high temperature exhaust (FF) for use as a heating flow in the pyrolysis stage to dry and pyrolyse the flow of waste (FxE) entering the pyrolysis stage. The high temperature exhausts are also used as a heating flow in the exchanger. The solid residues (SI) form the fluidised bed furnace undergo combustion using a circulating fluidized bed furnace (306). The combustion temperature of the circulating fluidized bed furnace is controlled to allow sand to be recovered in suspension in the exhaust and reinjected into the dense fluidized bed furnace. The exhaust from the post-combustion chamber is treated and cooled in a heat exchanger (401) using ambient air as the cooling fluid. The heated air is recycled at least in part as combustion air in the circulating fluidised bed furnace. The process includes an integrated mechano-biological treatment and composting of the industrial and/or household waste and/or biomass to supply the combustible material from the waste CDD), by separating the fermentable materials, crushing and sorting the valorisable materials, inert materials and unburnable materials to provide a stock of combustible materials of constant quality to form the inlet flow of waste (FxE) to the pyrolysis stage. These combustible materials are formed into briquettes by compression. An independent claim is made for an installation to carry out the above process.

Description

PROCESS FOR PROCESSING AND VALORIZING WASTE

  The present invention relates to the treatment and recovery of household and / or industrial waste and / or biomass alone or mixed. The present invention relates to a process for the treatment and economic, ecological and efficient recovery of this waste. In the present invention, the main valorization consists in producing a fuel gas with a high hydrogen content which can be used in particular for the generation of electricity.

  Various methods of treatment and recovery of waste are known, namely: - The mechanical-biological treatment that combines a mechanical sorting by screening, visual control on tape, densimetric table, a biological treatment performed in one or more steps. This treatment is not generally considered as an optimal waste recovery. Indeed only a compost of mediocre quality is valued. The other treatment residues are discharged to landfill. This represents a large volume, which in fact undergoes disposal (landfilling) prohibiting any valuation.

  - Treatment by pyrolysis or thermolysis which consists of a decomposition of organic matter by heat in the absence of oxygen. The terms thermolysis and pyrolysis refer to the same decomposition phenomenon, but obtained at different temperatures: at low temperature for thermolysis (generally 450 to 650 ° C.), at higher temperatures for pyrolysis (generally 800 to 900 ° C.). In the following, the term pyrolysis is used as generally referring to the process of decomposition at high temperature, in the absence of oxygen, both at low and high temperature. A pyrolysis furnace generally comprises an airtight cavity surrounded by an envelope in which fumes circulate at high temperature. The waste to be treated is brought into the cavity which is maintained in slight depression. The flow of combustion fumes circulating in the envelope causes a rise in temperature in the cavity, which allows the decomposition of the organic materials contained in the waste residing in the cavity in carbonaceous solids (or pyrolysis cokes) and in a mixture of combustible gases called pyrolysis gas.

  The carbonaceous solids from such a furnace are a heterogeneous mixture of solids consisting of metals, minerals, semicoke and various adsorbed pollutants. For these reasons, these materials are difficult to valorize.

  The gas is recoverable, either internally by incineration in the process to produce heat, or externally after a thorough purification to rid it of tars, dusts and acid gases, for the production of thermal energy (burners, boilers ...).

  - Superheated steam gasification, which is a process for recovering fuels from waste, biomass and more particularly forest biomass, combustible waste from forestry or the primary wood processing industry, bark or sawdust wood, forest residues, thinning wood or biomass from dedicated forest plantations of short or very short rotation coppice type (poplar, eucalyptus, willow), ...

  This gasification process uses gasification and fluidized bed combustion reactors. Since the gasification reaction is endothermic and the combustion reaction is exothermic, the heat required for the gasification is supplied by the combustion of recycled gas and residual gasification coke via a circulating hot sand flow. Superheated steam gasification produces mainly process gas, ash, landfill, and fumes, which are discharged into the atmosphere after treatment.

  The quality of the process gas thus produced varies according to the type of waste treated, the composition of the waste and the moisture content of this waste. The gasification plants are relatively large with regard to the power energy gas produced.

  An object of the invention is a waste treatment and recovery method, which incorporates waste recovery techniques while allowing to significantly reduce the residual amount to be disposed of in a landfill.

  An object of the invention is to substitute for waste treated in the gasification process, pyrolysis coke and pyrolysis gas (preferably previously cracked), so as to allow, for installations of the same size, a consequent increase the power energy gas produced.

  An object of the invention is to ensure a constant quality of input supply of the superheated steam gasification process, to provide a substantially constant quality process gas.

  The invention therefore relates to a method for treating and recovering a waste stream, comprising a gasification phase with superheated steam, characterized in that said phase comprises a prior pyrolysis step providing pyrolysis gas at the outlet. and carbonaceous solids followed by a gasification step of said carbonaceous solids and said pyrolysis gases, to output a clean gas suitable for storage for recovery.

  According to one aspect of the invention, the treatment and upgrading method comprises a prior step of mechano-biological treatment and composting of household and / or industrial waste and / or biomass capable of supplying combustible materials derived from waste, comprising steps of separating the fermentable materials, refining compost obtained from said fermentable materials, screening and sorting of recoverable metals, inert and uncrushable, so as to constitute a stock of combustible materials derived from waste, of substantially constant quality, said stock forming the waste stream entering from the pyrolysis step.

  The invention also relates to a waste treatment and recovery plant implementing a method according to the invention.

  Other advantages and characteristics of the invention will appear more clearly on reading the description which follows, given by way of indication and not limitation of the invention and with reference to the accompanying drawings, in which: - Figure 1 is a diagram principle of a method of treatment and recovery of waste according to the invention; FIG. 2 is a flowchart of the first phase of a treatment and recovery process according to the invention, corresponding to the mechanical-biological treatment and composting phase, with the output of a waste-derived fuel intended for feeding the second phase; FIG. 3 is a block diagram of a device for treating and recovering waste-derived fuel supplied at the outlet of the first phase, implementing the second phase of a treatment and recovery process according to the invention, and FIG. 4 is a flowchart of the second phase of a treatment and recovery process according to the invention, corresponding to the superheated steam gasification phase.

  An installation according to the invention makes it possible to treat the different categories of waste and to optimize them optimally. The schematic diagram of such an installation is shown in FIG.

  The categories of waste treated include: - Residual household waste (that is to say excluding those collected through recycling channels), rated OMR, Ordinary industrial waste combustible, rated DIB, which include for example woods demolition, paperboard, pallets, ... etc, excluding organic or fermentable materials, - Green waste and waste from the food industry, noted DVA, biomass of forest origin and waste from the industry of first processing of wood, sludge from sewage treatment plants, unpolluted, noted STEPnp.

  The installation implements the following treatment phases: O Mechanical-biological treatment and composting, with integrated recovery, which treats all the aforementioned waste classes, and provides at the output: compost, recoverable ferrous metals, inert materials (glasses, gravel, minerals ...) landfilled or recovered, unburnable landfill, and a fuel derived from waste, noted CDD which feeds the next phase of treatment O. This CDD fuel is in the form of solid blocks (cubes), and may be stored in silos on the site, if necessary, depending on the flow.

  Gasification treatment with superheated steam, incorporating a prior pyrolysis step. This treatment phase is fed by the stock of CDD fuel, and possibly also by ordinary industrial waste directly combustible. It is also possible to treat polluted sewage sludge.

  Fumes, ashes, and a purified fuel gas with a high heat content with a high hydrogen content are obtained at the outlet.

  OO Production of electricity from purified gas. This electricity production can be obtained in different ways, using one or more gas engines, or one or more gas turbines. One can also have a combined cycle gas engine - steam turbine, or gas turbine-steam turbine. In these combined cycles, one can still have an organic Rankine cycle, instead of the steam turbine. These various methods of producing electricity from purified process gas and high temperature combustion fumes are well known to those skilled in the art. It is also possible after adjusting the hydrogen content of the purified gas, in particular by gas permeation, to feed a fuel cell.

  An example of implementation of the mechano-biological treatment and composting phase according to the invention is shown in FIG.

  The mechano-biological treatment and composting phase mainly comprises the following steps: a). Coarse screening of OMR residual household waste, to remove coarse waste. This operation typically uses a trommel bag opener 1, with a mesh of 200 millimeters for example, from which emerge in the lower part the fine waste OMRf intended to be treated in bio-reactor with green waste (start of fermentation) and in the upper part OMRg coarse waste, mostly non-fermentable.

  The OMRg coarse waste is conveyed on tape to a visual checkpoint 2 on a belt (carpet) to extract the imbroyables from the flow. The imbroyables typically include metals and inert massive, for example bricks, large metal parts, etc. They feed a stock of unmovable I, destined for landfilling in a Class II landfill.

  b). Coarse screening of ordinary industrial waste and / or biomass, designated in the figures by reference DIB. This screening is typically performed by means of a trommel 3, with a mesh of 50 millimeters, for example, which emerge on one side of fine waste DIBf and on the other of waste coarse DIBg. The DIBg coarse waste is conveyed on tape to the visual inspection station 2 to extract the imbroyables from the flow. From the visual control station 2 stand out the refusal Rf of the screening stations 1 and 3, intended to be ground.

  vs). Stabilization in bio-reactor 4 of fine wastes OMRf and green waste and / or agri-food fermentable DVA. This DVA waste is preferably pre-milled, by means of a dedicated shredder 5. At the outlet of the bioreactor, which consists mainly of a rotary drum with air and water injection pipes and in which the material is maintained during a determined stabilization period, typically 72 hours, to start the fermentation. At the outlet, stabilized DS waste is obtained, the degradation of the organic material of which is typically of the order of about 30%.

  The vapors and vapors that emerge from this process are typically treated with a bio-filter 6 (condensation and washing) prior to discharge to the atmosphere.

  The DS stabilized waste coming out of this bioreactor is conveyed to a screening station 7, typically using a trommel, with a mesh of 70 millimeters, for example, which makes it possible to separate the coarse DSg (Refusal of the screen, to extract the waste from the waste stream). coarse mainly made of plastic, glass, wood and non-fermentable waste.On exit, we obtain the DSF stabilized waste (sieve passersby).

  d). Grinding non-fermentable waste freed from imbroyables, ie refusals Rf and DSg from different screening stations 1, 3 and 7, after extraction of uncrushable (visual control station 2) where appropriate. The grinding device 8 used will typically be a rotary shear. The result is waste (mostly non-fermentable) shredded DB.

  It should be noted that the grinding step takes place only after the waste from the residual household waste has been screened before (sieve 1) and after (sieve 7) stabilization in the bio-reactor 4, which makes it possible to significantly limit the presence of plastic or glass in the compost.

  e). Defrosting of DSF stabilized wastes prior to their transportation to a biological treatment platform 9.

  The de-ironing step is typically carried out by means of a magnetic pulley 10. The ferrous metals thus extracted feed a stock 11 of ferrous metals for external recovery.

  f). Composting in the biological treatment platform 9.

  In the example, this platform is presented as a closed building and implements a wind-controlled composting process in windrows, typically for 90 days, with forced aeration, humidification and mechanized periodic turning. A biofilter 12 is provided for the treatment of building air and fog generated by the handling of compost.

  Air and water supplies are needed to feed the composting process. This platform can also treat unpolluted STEPnp sludge from sewage treatment plants. Polluted sludge can not be treated in this process because it would prevent the production of compost of agronomic quality, and thus hinder the external valuation of compost produced.

  Composting of the compost, typically by means of a screen and a densimetric table.

  The composting screen 13 of the compost, typically a 30 mm mesh trommel, for example, makes it possible to remove the coarse parts of the compost, of which non-ferrous metals will typically be found (the ferrous metals have already been removed, before passing through composting phase), but also non-compostable coarse materials: wood, plastics, coarse minerals.

  The passers of the compost ripening screen 13 are then sorted by means of a densimetric table 17, which allows the heavy fraction to be discarded, typically the small-particle glasses and pebbles. There emerges a refined compost 18 of high quality, ready for external valorization.

  The heavy fraction removed by the densimetric table 17 supplies a stock 15 of inert materials.

  h). Extraction of the ferrous remains in the waste sent to the sorting table 13, that is to say: the refusals (the coarse) of the screen of the step g) of compost ripening, the crushed DB of step d) grinding, and passers DIBf of step b) of screening DIB waste (ordinary industrial waste and / or non-fermentable biomass). At this stage 13 of the process, the ferrous metals are extracted, which will feed the stock 11 of valuable ferrous materials. The rest of the flow is "the degraded fuel".

  i). Extraction of heavy constituents from the de-waxed fuel stream, typically by means of a ballistic separator 14. A ballistic separator is a high-speed conveyor that makes it possible to eject the various constituents of the flow according to their density. This ballistic separator is more particularly used to remove massive constituents, such as non-ferrous metals and massive minerals, from the stream. These ejected constituents constitute a stock of inert materials, destined for landfill, typically in Class III landfill. The outflow of the ballistic separator 14 is in the form of a CDD fuel mill.

  j). Densification of the fuel mill, typically by means of a device 16 of briquetting press: these CDD fuel briquettes from waste can be easily stored, without particular problems of storage, because they are solids, relatively dry, and their The shape of cubes or briquettes makes handling and storage easy to automate. Thus, this densification makes it possible to optimize handling and storage with a view to gasification. For example, briquettes are cubes 30 to 35 millimeters apart. The density of the CDD fuel thus obtained with a process according to the invention is of the order of 700 Kg / m3. A 2800 m3 CDD fuel storage allows, for example, one month of shutdown of a treatment unit of 80 000 t / yr of household waste (stage O of the treatment and recovery process according to the invention), without requiring recourse. to a landfill. This is one of the advantageous aspects of the treatment and upgrading process according to the invention, because it saves landfill costs during the annual cessation of gasification. It allows a flexibility of operation of the treatment plant, because the easy storage of the fuel allows an independent valuation of the supplies of waste or biomass.

  At the end of this mechano-biological treatment with integrated recovery, according to the invention, the following stocks are obtained: - stock I uncrushable, landfilled; - stock 11 ferrous, for external valuation; - stock 15 of inert, for landfill; refined compost 18, of agronomic quality, for external valorization; and CDD stock of waste derived fuel, in briquettes (cubes).

  This CDD stock of briquette fuel accounts for 30 to 35% of the incoming flow in phase O. Regardless of the quality of the wastes entering the O phase of mechanical-biological treatment according to the invention, the screening chain at various points The process ensures consistent quality of this output CDD fuel especially for moisture content and ash content.

  This CDD fuel stock feeds the superheated steam gasification process according to the invention.

  FIG. 3 represents a flowchart illustrating phase O of gasification with superheated steam, implemented in a waste treatment and recovery process according to the invention.

  The incoming flow of FxE waste to be treated and upgraded to purified gas in this phase O mainly comprises the CDD stock resulting from phase O of mechanical-biological treatment of waste. It may also include ordinary industrial waste: packaging paper, mixed plastics, crushed tires ... (excluding organic matter, fermentable) collected by industrial companies and previously milled DIBb. It is still possible to treat polluted sludge from STEPp wastewater treatment plants at this stage.

  The device for implementing this phase O for treating and upgrading the incoming waste stream FxE into purified gas comprises schematically, and as shown in FIG. 3, a pyrolysis device 100, a calciner 200 for reducing the ash content coarse solids from pyrolysis, a gasification device 300, and a device 400 for energy recovery and treatment of fumes from the pyrolysis and gasification devices.

  The FxE inflow feeds the pyrolysis device 100, to obtain by decomposition at high temperature (thermal cracking of the organic material), in the absence of oxygen, carbonaceous solids and pyrolysis gases. Preferably, the carbonaceous solids are screened, the rejections of screening being routed to the calciner 200, which reduces them to ash, for discharge (Class II landfill).

  According to the invention, the fine carbonaceous pyrolysis solids which have passed the screen and the pyrolysis gases are transported in a vapor flow Fv at the inlet of the gasification device, keeping them at a predetermined temperature Ti to prevent the condensation of the tars. contained in the pyrolysis gases.

  At the outlet of the gasification device, ashes are obtained for landfilling (Class II landfill) and process gas, which can be upgraded internally, for the pyrolysis and gasification processes, and externally for the production of electricity after filtration and purification by a suitable treatment device 500.

  The fumes emitted by the pyrolysis and gasification devices 100 are suitably fed, by sealed conduits, to the energy recovery and flue gas treatment device 400, from which clean fumes, discharged from the atmosphere, emerge. atmosphere and dust destined for landfill (Class I landfill).

  In more detail, and in relation with the flowchart of FIG. 4, the pyrolysis device comprises a pyrolysis furnace 110 into which the incoming FxE waste stream is introduced.

  Preferably, the pyrolysis furnace 110 is provided at the outlet of an internal screen (not shown), so as to separate the coarse fraction 101 from the fine carbonaceous solids. This coarse fraction 101 is fed to a calciner 200. The resulting ashes 201 are destined for landfill (Class III landfill).

  In a variant not shown, the rejects of the screen 103 are crushed, sorted and the carbon fraction reinjected at the inlet of the pyrolysis furnace 110.

  The fine fraction 102 of the carbonaceous solids from the pyrolysis and the pyrolysis gases 103 constitute the input elements of the superheated steam gasification process.

  The pyrolysis furnace 110 is maintained in slight depression to prevent pyrolysis gas leakage 103 to the outside. The screening of the coalests 103 at the pyrolysis outlet, with extraction and / or reprocessing, advantageously allows the use of the pyrolysis gases as means of pneumatic transport of the fine fraction 102 of the carbonaceous solids resulting from the pyrolysis, up to an oven dense fluidized bed 301 of the device 300 for gasification with superheated steam. These pyrolysis gases are also injected into the dense fluidized bed furnace, and used as fluidization media 305 in the dense fluidized bed furnace 301, preferably after high temperature cracking by means of a heat exchanger.

  Preferably, the pyrolysis gases 103 are sucked by a steam ejector 104, so as to form a flow 105 of vapor and gas in a sealed pipe. A rotary lock 106 which receives the fine fraction 102 of the carbonaceous solids makes it possible to inject this fine fraction into the stream of vapor and gas. Thus, steam V is used as inert transport fluid (ie not reacting in terms of combustion) with respect to pyrolysis gases and fine carbonaceous solids. This steam V is in practice supplied internally by the gasification process itself. This flow of steam is supplied at a temperature Tv which makes it possible to maintain the temperature of the flow 105 above a sufficient temperature T1, typically greater than or equal to 350 ° C., so as to prevent the condensation of the tars and condensable hydrocarbons contained in the gases. For example Tv will be of the order of 400 C. The pipes are maintained at a sufficient temperature, greater than or equal to the temperature Tv of the flow, by electrical tracing and appropriate insulation. Valves v1, v2 are provided upstream of the ejector 104, to regulate the flow of gas 103 and the vapor flow V. The resulting flow Fv can transport the carbonaceous solids to the gasification device 300.

  The gasification device comprises a separator 302 (cyclone enclosure) suitable for separating the solid products S from the gaseous products GV of the stream Fv that it receives from the pyrolysis device 100. The separator 302 thus receives at its inlet the stream Fv of steam and of pyrolysis gas with the carbonaceous solid material in suspension, and delivers, on the one hand, the solids S and, on the other hand, a stream of gas GV, comprising the pyrolysis gases 105, the vapor V and particles of ultra coke. end.

  The solids S thus separated are introduced into the chamber of a dense fluidized bed furnace 301.

  The GV stream of steam and pyrolysis gas contains in particular incondensable gases, tars, water vapor and ultra-fine coke. It is thus preferably provided a high temperature cracking of this GV stream allowing the vapor oxidation of tars and ultra-fine coke, before using this stream as fluidization media 305 in the dense fluidized bed furnace of the process. gasification.

  For this purpose, the gaseous waste gas GV at the outlet of the separator 302, maintained at the temperature Tv, is fed into a gas / gas exchanger 303 (also called "cracker" according to the current English terminology), by a pipe maintained at a temperature of 30.degree. temperature greater than or equal to the temperature Tv of the flow (electrical tracing, insulation).

  A gas / gas exchanger typically comprises, at the primary, a heated flow and at the secondary a heating flow. In the application, the heated flow is the GV gas flow and the heating flow is a high temperature flue gas FF, typically 1000 C, provided by a post combustion chamber 304 whose role will be detailed later. This heating flux FF makes it possible to bring the flow of gas GV at high temperature by heat exchange, allowing the vapor oxidation of tars and ultra-fine coke, and their transformation into incondensable hydrocarbons, such as methane, of the ethylene, carbon dioxide (CO2), hydrogen (H2), ... etc. Thus, the steam which was used for the pneumatic transport of the carbonaceous pyrolysis solids to the first fluidized bed furnace 301 has another function which is to allow the cracking of the tars and ultra-fine coke contained in the pyrolysis gases 103 from pyrolysis and transported in the GV flow. The cracking of the tars will be completed in the oven 301 which we will detail below.

  At the outlet of the gas / gas exchanger 303, a high temperature gas stream (around 850 ° C. for example) is obtained which is used as fluidization medium 305 in the dense fluidized bed furnace 301. The dense fluidized bed furnace 301 is a vertical type oven in

  The example. It includes a sand bed. The fluidization medium 305 thus makes it possible to form a flow of hot sand circulating inside the furnace. The carbonaceous solids S injected into the furnace are mixed with this flow. Such an oven makes it possible, in a known manner, to gasify the organic materials with steam in an atmosphere maintained at high temperature by the flow of hot flowing sand. The sand bed is a stabilizing element of the process. It serves as a catalyst for the conversion of heavy tar elements present in the solid stream S. In practice, for example, sand of the class of silicates, such as olivine, is used. This sand can be doped, with nickel for example, to increase the performance of cracking tars. It is indeed very important that all tars are burnt, because the presence of tars in the process gas output is very detrimental to the recovery of process gas. Indeed, tars pose big problems in thermal machines (engines and gas turbines).

  The sand is provided, at the start of the installation, with a specific inlet Es and extra, if necessary, to maintain a sufficient granular bed. In general, a sand purge SP outlet is provided to remove sand when the level of the granular bed is too great. This sand can be directly dumped (Class II landfill).

  Furnace 301 springs up, a "process" gas GP, ie a gas from the process and below, a mixture SI of sand and unburnt solids.

  Advantageously, this SI mixture of sand and unburnt is conveyed to a second fluidized bed furnace 306. This second furnace 306 will be rather of circulating fluidized bed type (also called mobile cocurrent bed). It is a vertical oven in the example. In the invention, this oven is temperature controlled in a suitable manner, so as to obtain the complete combustion of the process residues, without risk of melting of the sand (melting temperature greater than 950 C). The sand is then driven with the fumes, at high temperature. Controlling the flow of combustion air injected under the bed makes it possible to control the flow of sand caused by the fumes. This high temperature sand flow contains the makeup energy delivered to the dense fluidized bed gasification furnace. In this way, the sand of the mixture SI can be dosed for re-injection into the first furnace 301. The dense fluidized bed furnace 301 thus operates in an almost closed cycle for the supply of sand, at least between the various operations of maintenance and maintenance purge.

  In practice, the operation of the circulating fluidized bed furnace 306 is used to obtain fumes at a temperature close to 900.degree. C. These fumes with the entrained sand are maintained at this temperature by means of a suitable duct (insulation). and fed to a separator 307 (cyclonic enclosure) to separate the gas from the sand. The gas is injected at the inlet of the afterburner chamber 304, while the high temperature sand from the cyclone chamber 307 is reintroduced into the first dense fluidized bed furnace 301.

  The circulating fluidized bed furnace 306 has a diameter much smaller than the first furnace 301. In practice, it serves to burn all residues Res-f of phase O: the residues SI (unburned sand + coke) of furnace 301, but also the residues resulting from the filtration and purification phase of the process gas, detailed below.

  AIR-c combustion air is supplied to the circulating fluidized bed furnace by the smoke energy recovery device 400. It is at a temperature of about 400 C in practice. If necessary, to improve the combustion, by controlling the temperature in the furnace, another hot air inlet AIR-h is preferably provided in the upper part of the oven 306, also supplied by the energy recovery device 400. fumes, and a cold gas inlet AIR-f in the lower part, above the fluidized bed, preferably supplied by the purified gas Ge (which is at a temperature of the order of 50 C or less) provided in removed from the device 500 for filtering and purifying the process gas. The regulation of the combustion is obtained by means of valves v3, v4, v5 making it possible to regulate the combustion air inlet AIR-c, the hot air inlet AIR-h in the upper part and the gas inlet cold AIR-f in the lower part.

  Finally, the fluidized bed furnace 306 comprises a purge outlet, which allows, in operation or maintenance, to evacuate the excess ash. These ashes are destined for landfill (Class II landfill).

  The gasification device 300 according to the invention further comprises an afterburner chamber. This chamber has several functions: to complete the combustion of the pyrolysis gases resulting from the process, in particular the various pollutants POL resulting from the filtration and purification phase of the GP process gas, the FcAL fumes from the calciner 200, and the fumes Fu from the circulating fluidized bed furnace 306, after passage through the separator 307. An emergency inlet is provided, controlled by a valve v6, thereby allowing the process gas GP generated by the furnace 301 to be discharged, in the case a failure of the device 500 for treating and filtering this process gas.

  An AIR-PC hot air supply, typically provided by the smoke energy recovery device 400, ensures the oxygen content required by the regulations. The temperature of the fumes is regulated by the GE gas purge injection in the chamber 304. These are usual methods for regulating the post-combustion chambers of gaseous effluents.

  This chamber 304 provides high temperature FF fumes, of the order of 1000 C.

  These fumes are used in particular, as has been seen above as secondary heating flux of the gas / gas exchanger 303.

  They are also used in the pyrolysis furnace as a source of heat necessary for pyrolysis.

  As a reminder, a pyrolysis furnace comprises in practice two zones, a first waste drying zone and a second pyrolysis zone itself. The high temperature FF fumes (1000 C) circulate around these two zones and emerge through a smoke outlet provided in each of the two zones (outputs S1 and S2).

  Thus, pyrolysis can be described as autothermal: the heat required for the reaction is generated internally by the combustion process of non-gasified cokes. It is however necessary to provide a steam boiler (not shown) for the start phase of the pneumatic transport, cracking and gasification process (ovens 301 and 306).

  The energy recovery and flue gas treatment device 400 receives the fumes from the afterburner chamber 304, after passing through the pyrolysis device (outputs S1, S2), and in the gas / gas exchanger 303.

  These are fumes at high temperature FHT, of the order of 800 C for the heating fumes of the pyrolysis device, and of the order of 700 C for those of the exchanger 303.

  The temperature of these fumes is lowered by means of an air / smoke exchanger 401, which receives at the secondary, the ambient air (at 20 C typically) and the fumes high temperature FHT primary. At the outlet, a heated air flow is obtained, and cooled fumes. This exchanger advantageously allows the supply to the circulating fluidized bed furnace 306, AIR-c combustion air and hot air AIR-h, from the heated air flow.

  The cooled fumes have a temperature below 200 C. They are then conveyed to conventional filtration and purification circuits: typically a contact reactor 402, using activated carbon and lime as reagents, a bag filter 403, which allows to capture dust and reaction products, to be dumped (Class I landfill). A suction fan 404 brings the fumes thus filtered into a chimney 405 for venting into the atmosphere.

  According to one aspect of the invention, the step of treating the flue gases from the post-combustion chamber 304 comprises a regulation of the flue gas flow capable of controlling the pyrolysis as a function of the moisture content of the FxE incoming waste stream. .

  In an exemplary practical embodiment, the FHT fumes are not mixed in the exchanger 401. There is therefore a corresponding output for each FHT source of smoke, with control valves v7, v8, v9 fumes at the outlet of the exchanger 401, one for each smoke inlet. In the example, there is thus the valve v7 for the fumes of the output SI of the pyrolysis furnace 110, the valve v8, for the fumes of the output S2 of the pyrolysis furnace 110 and the valve v9 for the fumes at the outlet of the exchanger 303 of the gasification device 300. These control valves will allow the modulation of the energy flow delivered to the pyrolysis device, depending on the moisture content of the incoming flow FxE to be treated. They will also make it possible to interrupt the pyrolysis reaction, by closing the corresponding valves v7 and v8, and opening the valve v9 corresponding to the exchanger: thus, all the smoke FF supplied by the post-combustion chamber is " sucked "by the gas / gas exchanger 303. These valves advantageously placed in the cooled smoke stream may be of current manufacture.

  Such an arrangement makes it possible to optimally and optimally use the heat produced in the gasification device 300 for pyrolysis. The energy-gas yield produced by an installation produced according to the invention is thus very efficient.

  In addition, the prior pyrolysis of the waste before gasification makes it possible to reduce the size of equipment intended for gasification significantly. This saves the structural and maintenance costs of the structure.

  The integration of a mechanical-biological treatment and composting makes it possible, in addition to the valorization of the compost, to supply to the gasification process, a CDD fuel of quasi-constant quality, independently of the quality of the waste delivered at the entrance of the installation. In particular, it is possible to guarantee reduced moisture and ash content at the pyrolysis inlet.

  The integration of a prior pyrolysis step upstream of the gasification provides the first furnace 301, a fuel that can be described as completely dry and of fine particle size. The quality of the gas produced and the kinetics of reaction are significantly improved. In addition, this pyrolysis step contributes to reducing the costs of structure and maintenance, because this reduced moisture content and ash allows treatment and filtration of process gas much less expensive in terms of processing time, amount of necessary reagents and flow to be treated, as the treatment and filtration facilities required in the gasification structures, which deal directly with biomass or wet CDD.

  In practice, the process gas treatment and filtration device thus comprises, in a conventional manner: a smoke tube boiler 501, the function of which is to cool the process gas GP that leaves the oven 301 at a temperature of the order of 800 to 900 C, to bring it to a temperature of the order of 200 C. An air condenser 502 is provided in parallel, which makes it possible to evacuate the excess heat, especially in the degraded operating modes of the structure, for example, at the end of the operating cycle. The steam generated is mainly used to supply steam V used as a carrier fluid for carbonaceous solids and pyrolysis gases. It is also used in addition in the oven 301, as needed.

  The cooled process gases GPr that emerge from the boiler 501 enter a dedusting device, or bag filter 502, which makes it possible to remove the carbonaceous dust carried by the process gas. The CAR carbon residues thus recovered are part of the residues Res-F brought into the oven 306, to be gasified in air.

  The filtered cooled process gases GPrf at the outlet of the dedusting device 502 are fed to an oil scrubber 503, whose function is to pick up the tars by spraying oil (vegetable oil, animal fat, liquid fuel, etc.) and to complete the cooling of the process gases GPrf, to bring them to a temperature close to ambient temperature (<50 C).

  More specifically, the circulation of cooled oil ensures the condensation of residual tars. The excess oil H feeds the stream of residues Res-F brought into the oven 306, to be gasified in air.

  Finally, the carbon dioxide and various gaseous pollutants POL are extracted from these process gases filtered, washed and cooled, by a suitable device 504. They are brought into the post combustion chamber 304.

  GE purified gas is obtained. This gas is partially recycled internally, in the afterburner chamber 304 (to ensure temperature control), and in the fluidized bed furnace 306 (during startup phases). It can be advantageously valued externally. For this purpose is conventionally provided a pressurized water washing (ejector washer) to put the purified gas GE pressurized, typically 10 bar. This gas can be stored at room temperature, typically in a metallic spherical gasometer. The gas thus stored can then be used in particular to produce electricity, by thermal machines, for example machines using one or more gas engines, or one or more gas turbines, or any other known technique.

  Thus, does the invention make it possible, on the one hand, by combining pyrolysis and gasification with superheated steam, to provide a gas of very good quality at lower cost: autothermal operation (except at start-up), recycling of fumes, steam to transport the flow Fv between the pyrolysis unit and that of gasification, efficient removal of tars.

  The process is particularly advantageous combined with a mechanobiological treatment and prior composting, allowing on the one hand a thorough integrated recovery, and on the other hand to provide a particularly dense dry CDD fuel flow, which allows flexible management of the stock CDD between the two phases, the mechanobiological and composting treatment phase and the gasification phase, and contributes to the very good quality, continuously, of the purified gas. Variants of the waste treatment and recovery process can be envisaged without departing from the scope of the invention: characteristics of screening devices or ballistic separators, composting methods, use of pyrolysis or thermolysis furnaces, vertical or horizontal, processing variants and filtration of fumes, process gas ...

Claims (19)

  1. Process for the treatment and recovery of a waste stream comprising a superheated steam gasification phase, characterized in that said phase comprises a prior pyrolysis step providing pyrolysis gases (103) and carbonaceous solids at the outlet (101, 102), followed by a gasification step of said carbonaceous solids and said pyrolysis gases, to provide at the output a purified gas (GE) capable of being stored for energy recovery.   2. Process of treatment and recovery according to claim 1, characterized in that the gasification step comprises the routing and injection of the carbonaceous solids and pyrolysis gases in a dense fluidized bed furnace (301), said pyrolysis gas being used as a fluidizing medium (305) in said furnace.   3. Processing and recovery process according to claim 2, characterized in that it comprises a step of screening the carbonaceous solids leaving the pyrolysis to pass only the fine carbonaceous solids (102) to the gasification step .   4. Method of treatment and recovery according to claim 3, characterized in that the sieve refusals (103) are calcined (200).   5. Method of treatment and recovery according to claim 3, characterized in that the screen rejections (103) are crushed, sorted and the carbon fraction reinjected at the input of the pyrolysis furnace (110).   6. Processing and recovery process according to any one of claims 3 to 5, characterized in that said pyrolysis gases (103) are used as pneumatic conveying means of the fine carbonaceous solids (102) at the end of the step pyrolysis, to said dense fluidized bed furnace (301).   7. Process of treatment and recovery according to claim 6, characterized in that said pyrolysis gases are sucked by a steam ejector (104), so as to form a stream of steam and pyrolysis gas (105) and in that a rotary sluice (106) is used to allow the transport in said flow of said fine carbonaceous solids (102).   8. Process of treatment and recovery according to claim 6 or 7, characterized in that said vapor stream (V) is generated internally by means of a cooling device (501) of the process gas (GP) output dense fluidized bed furnace (301).   9. Processing and recovery process according to any one of claims 6 to 8, characterized in that it comprises a separation step in which the fine carbonaceous solids are separated from the flow of steam and pyrolysis gas (105). which transports them by means of a cyclone device (302) to be injected into said dense gasification fluidized bed furnace (301).   10. Process of treatment and recovery according to claim 2 or 9, characterized in that the pyrolysis gas (Gv) is heated by means of a heat exchanger (303), before injection as a fluidization medium (305) in said dense fluidized bed furnace (301).   11. Processing and recovery process according to any one of the preceding claims, characterized in that it provides for the recycling of the purified gas (GE) and other gases and / or fumes generated by the process in a post-consumer chamber. combustion (304) to provide at the output of the high temperature fumes (FF) suitable for use as heating flow in the pyrolysis step, to obtain the drying and pyrolysis of the incoming waste stream (FxE) of the step of pyrolysis.   12. Process of treatment and recovery according to claim 11 in combination with claim 10, characterized in that said high temperature fumes (FF) provided by the afterburner chamber are used as heating flux in said exchanger (303).   13. Process of treatment and recovery according to any one of claims 2 to 12, characterized in that it comprises a step of burning solid residues (SI) from the dense fluidized bed furnace (301), by means of a circulating fluidized bed furnace (306).   14. Process of treatment and recovery according to claim 13, characterized in that it comprises a regulation of the combustion temperature in said circulating fluidized bed furnace (306), for recovering the sand suspended in the fumes, and re-injecting it into the dense fluidized bed furnace (301).   15. Process of treatment and recovery according to any one of claims 11 to 14, characterized in that it comprises a step of treating the fumes from the post-combustion chamber (304) comprising a regulation of the flue gas suitable to control the pyrolysis as a function of the moisture content of the incoming waste stream (FxE).   16. Process of treatment and recovery according to the preceding claim, in combination with claim 13, characterized in that it comprises a step of cooling the fumes by means of an exchanger (401) using the ambient air as cooling flow the heated air supplied at output being recycled at least in part as combustion air (AIR-c) in the circulating fluidized bed furnace (306).   17. Processing and recovery process according to any one of claims 1 to 16, characterized in that it comprises an integrated step of mechano-biological treatment and composting industrial waste and / or household and / or biomass capable of providing waste-derived combustible materials (DSC), including steps of separating the fermentable materials, refining compost obtained from said fermentable materials, screening and sorting the recoverable metals, inerts and imbroyables, so as to constitute a stock of waste materials derived from waste (CDD), of substantially constant quality, said stock forming the incoming waste stream (FxE) of the pyrolysis step.   18. The method of claim 17, characterized in that it comprises a step of shaping press briquettes of said waste-derived combustible materials (CDD).   19. Waste treatment and recovery plant according to one of the preceding claims.