WO2013057073A1 - Pyrolytic method for processing organic and inorganic residues in multiple-hearth furnace for recovering useful by-products - Google Patents

Abstract

The present invention relates to a method for reprocessing, recycling, or separating materials or waste in a multiple-hearth furnace via direct pyrolysis, called "flameless" pyrolysis, characterised in that the steam has a pressure of between 1 and 5 bar and is injected in a controlled manner in the pyrolytic gasification area of the multiple-hearth furnace so as to obtain a precise, uniform temperature profile in both the gaseous phase and the solid phase.

Description

 PROCESS FOR THE PYROLYTIC TREATMENT OF ORGANIC AND INORGANIC STOVE OVEN RESIDUES FOR RECOVERING VALUABLE BY-PRODUCTS

Object of the invention

 The present invention relates to a pyrolytic treatment process, in a multi-storey oven or furnace, incorporating adequate control of the temperature profile both at the level of the treated product than at the level of the gas phase. This method applies to direct pyrolysis where the reactor burners are in direct contact with the gases resulting from the process. State of the art

 It is known that pyrolysis is a thermal process for converting solids and liquids into gaseous compounds and solid residues consisting of fixed carbon and mineral materials.

Direct pyrolysis means a process using an oven where burners are mounted directly on the furnace and produce a flame.

[0004] A typical stepped furnace comprises a series of circular soles placed one above the other in a metal casing covered with refractory material. A vertical rotating shaft located along the axis of the furnace carries a series of arms provided with saddles which move the load in a spiral path through each sole. The materials to be treated are loaded at the upper sole and grated through it through orifices to the sole immediately below and so on. After having gone through all the soles, the treated materials are discharged at the bottom of the oven. The hot gases circulate in the furnace often counter-currently to heat the charge to its reaction temperature and produce the desired reaction. The heat is provided by the combustion of the materials themselves in the feed or by auxiliary fuel. When the auxiliary fuel is required, the combustion is either directly induced by burners located at specific soles (direct cooking) or indirectly via a separate chamber (indirect cooking).

The Applicant has developed for many years a direct pyrolysis process in multi-stage oven, followed by a possible combustion of fixed carbon. In this context, the stepped heat treatment requires adapting the conventional storey furnace which must have:

 a drying zone for the materials to be treated;

 a zone for heating and pyrolytic gasification of the volatile materials, in an oxygen-poor atmosphere. After the pyrolysis step, the products contain only mineral matter and fixed carbon;

 a fixed carbon combustion zone in the presence of excess air.

[0006] The direct pyrolysis process has a number of advantages over the indirect pyrolysis process. First, while the direct process is done in a multi-stage furnace, the indirect process generally requires another type of furnace, the rotary kiln. In this, the presence of gaseous materials requires inert the entry and exit of the reactor, given the risk of explosion inherent. In addition, the loss of energy is greater since it is necessary to heat the envelope with a gas indirectly. Finally, the rewiring is less good and it is difficult to treat residues such as oils for example.

 [0007] The direct pyrolysis process in a multi-stage furnace makes it possible to treat many residues such as sewage sludge or WWTP, industrial sludge, industrial residues composed of mixtures of organic and inorganic matter, etc. and has been applied industrially in many European countries (Germany, France, Switzerland, etc.).

In conventional pyrolysis, the combustible volatile materials generated by the process come into contact with the flame of the burners. The presence of residual oxygen then causes flame propagation (fugitive flames) and a chain reaction. Uncontrolled temperatures may be encountered at the gas phase and at the level of the treated product, with consequent problems of partial melting or sintering of the grated product, for example in the form of slag, necessitating stopping of the product. installation or outright the abandonment of pyrolysis for the treatment of certain products.

 The conventional pyrolysis process has been the subject of numerous publications in Europe as well as in the United States.

The application WO 2010/142397 discloses a method for recovering metals from a stream rich in hydrocarbons and carbonaceous residues by means of a treatment section, comprising the following steps: sending the stream in a primary treatment, carried out in one or more steps, wherein the stream is treated in the presence of a fluxing agent in a suitable apparatus at a temperature between 80 and 180 ° C, preferably between 100 and 160 ° C and subjected to a liquid separation. solid to obtain a clarified product consisting essentially of liquids and a cake (oil cake), optionally subjecting the separated cake to drying, in order to remove from the cake the hydrocarbon component whose boiling point is below a temperature of between 300 and 350 ° C, to send the cake, optionally dried, to a secondary heat treatment comprising: "Flameless" pyrolysis of the cake carried out between 400 and 800 ° C., preferably between 500 and 670 ° C., an oxidation of the pyrolysis residue carried out in an oxidizing environment and at temperatures between 400 and 800 ° C, preferably between 500 and 700 ° C.

 The application WO 2010/55489 discloses a method and an installation for the treatment of materials containing a mixture of plastics and metallic materials, such as used electronic cards. The method comprises the following steps: grinding the materials to be treated; pyrolysis of crushed materials; a first magnetic separation carried out on the materials having undergone pyrolysis, providing on the one hand a ferrous metal fraction and on the other hand non-ferrous residues; a second magnetic separation carried out on the non-ferrous residues, providing on the one hand a non-ferrous metal fraction and on the other hand non-magnetic residues.

EP 843 142 discloses an improved apparatus and method for effectively treating materials, for example incinerating waste, particularly dewatered sludge, in a multi-stage furnace by injecting high velocity oxygen streams into the furnace. heating or drying zone of the furnace to increase the mixing of the turbulent gas phase, to facilitate the total combustion of carbon monoxide and hydrocarbons in the gas phase, in order to obtain lower emissions, to increase the convection at above the sludge in the course of drying in order to increase the drying speed and to ignite sludge during drying, in order to further increase their drying rate. The facility and process provide an increase in sludge flow and a reduction in carbon monoxide, nitrogen oxides and hydrocarbon emissions.

 The application EP 2,083,954 discloses a waste treatment process containing precious metals, comprising the following successive steps: placing the waste in contact with a composition based on molten lead; skimming of the mixture obtained and refining of the skimmed mixture by electrolysis so as to recover the precious metals.

US Patent 4,261,268 discloses a method and an installation for the treatment of waste in a countercurrent furnace in which the materials are introduced at one end of the furnace and discharged at the other end. Air is introduced simultaneously into the furnace and the combustion gases flow countercurrently with respect to the treatment of the materials and escape to a first end of the furnace. The furnace has a natural tendency to form treatment zones comprising sequentially, starting from the first end of the furnace, a drying zone, a carbonization and combustion zone of the volatile materials, a fixed carbon combustion zone and a zone Ash cooling. The method comprises the steps of purging the secondary exhaust gases from the furnace medium, substantially between the fixed carbon combustion zone and the carbonization and combustion zone of the volatile materials. According to one embodiment of the invention, the secondary exhaust gases undergo a heat exchange with the air which is added to the oven. US Patent 4,046,086 discloses a similar method and installation for treating waste containing alkali metals. The maximum temperature in the furnace is maintained at about 1400 ° F (760 ° C), directly near the surface of the bed of material to be treated.

 US Patent 4,118,220 discloses a process for treating materials containing heavy metals and carbonaceous materials, comprising the steps of continuous introduction of waste to be treated by entering a first furnace while simultaneously adding air to the furnace, heating the waste in the furnace until they are in a state of carbonization and from there unloading of the furnace materials and passage of them in a secondary treatment apparatus, while discharging simultaneously the exhaust gas from the furnace, recovering and removing, by chemical leaching, heavy metals from the waste in the secondary treatment apparatus, then passing the remainder of the waste to a second furnace to burn the remaining carbonaceous materials in the waste and separate discharge of ash and exhaust from the second furnace.

US 4,046,085 discloses a method and an installation for the treatment of waste in a countercurrent furnace, where the materials to be treated are introduced at a first end of the furnace and the treated materials are discharged at the other end. . The combustion gases flow countercurrently with respect to the flow of material and escape at the first end of the furnace. The oven has a natural tendency to form treatment zones, in particular sequentially from the first end of the furnace, a drying zone, a combustion zone generating fixed carbon and volatile matter, a fixed carbon combustion zone and an ash cooling zone. The process is characterized by the presence of a step of adding an oxidizing agent including water vapor to the fixed carbon combustion zone. The resulting "gas-to-water reaction" (H ₂ O + CO → CO ₂ + H ₂ ) has the effect of significantly increasing the rate of gasification.

Aims of the invention

 The present invention aims to overcome the problems of the state of the art.

 In particular, the invention aims to reprocess or recycle complex residues or waste, containing organic materials such as oils to recover solids, including minerals such as precious metals or rare earths.

 The invention also aims to control the temperature of the step oven process.

 The invention also aims to limit the crystallographic transformations of the material to be reprocessed and the formation of sintered materials, bottom ash.

Main characteristic elements of the invention

The present invention relates to a process for the reprocessing, recycling or separation of materials or waste in a staged oven by direct pyrolysis in air defect (lambda <1) and in the presence of steam. water, referred to as a "flameless" pyrolysis process, in which the materials are respectively introduced and discharged at a first end and a second end of the furnace, said furnace comprising sequentially, starting from the first end, a drying zone, a zone pyrolytic gasification leading to the formation of a gaseous phase comprising volatile and of a solid phase comprising fixed carbon and mineral matter, optionally followed by a fixed carbon combustion zone in excess of air, the heat of combustion of the charge being obtained by direct injection of air and auxiliary fuel in the furnace, characterized in that the steam is controlledly injected into the pyrolytic gasification zone of the furnace at a pressure of between 1 and 5 bar, so as to obtain a precise and uniform temperature profile both in the gas phase only in the solid phase.

 According to particular or preferred embodiments of the invention, the method further comprises one or a suitable combination of at least two of the following characteristics:

 the water vapor injected is dry steam;

 the injected water vapor is saturating vapor;

- in the case of pyrolysis followed by a fixed carbon combustion, steam is injected at the transition between the pyrolytic gasification zone and the fixed carbon combustion ^zone. ;

 the pyrolytic gasification is carried out in a reducing atmosphere;

 the temperature range covered is between 150 and 1050 ° C .;

 - the maximum temperature in the oven is reduced by at least 100 ° C compared to the situation where the same process is used, but without the injection of water vapor;

- the waste to be recycled is used electronic circuits;

 the waste to be recycled is sludge containing hydrocarbons and / or metals;

- the waste to be recycled is minerals contaminated by hydrocarbons and other volatile materials; - The flue gases and fumes flow counter-current to the material treatment direction;

 - the flue gases and fumes are extracted at the top of the furnace and the reprocessed materials are extracted at the bottom of the furnace;

 the combustion gases and the fumes flow in co-current with respect to the material treatment direction;

 the combustion gases and the fumes, as well as the reprocessed materials, are extracted at the lower part of the furnace, the pyrolysis being carried out between 150 and 500 ° C.

Description of preferred embodiments of the invention

The invention relates to a thermal treatment process by direct pyrolysis in air defect and in the presence of water vapor, "flameless without pyrolysis" (flameless pyrolysis), multi-storey, more specifically, residues , or waste materials containing ^'.Des inorganic materials and organic materials. This process requires precise control of the temperature at both the gaseous phase and the solid phase.

According to the invention, the "flameless" pyrolysis allows, by a controlled and staged injection of low pressure steam into the stage reactor, at the level of the pyrolytic gasification zone (on one or more soles), precisely and uniformly control the temperature profile in the solid product and in the gas phase. Steam injection prevents volatiles from igniting, flame spread and uncontrolled increase in temperature. The injected water vapor pressure, dry or saturating, will advantageously be between 1 and 5 bar. In the case of pyrolytic gasification followed by the combustion of the fixed carbon, the steam is preferably injected into the hearth where the transition zone exists between the end of the pyrolysis and the beginning of the combustion of the fixed carbon.

 According to the present invention, the "flame-free" direct pyrolysis method can be applied generally in counter-current operating mode, that is to say that the fumes are extracted at the upper part of the reactor. and the solid product is extracted at the bottom of the reactor. However, for temperature-based direct pyrolysis applications (typically between 150 and 400 ° C), the process can also be applied in co-current mode of operation in the reactor. In this specific case, the fumes and solids are both extracted at the bottom of the reactor.

The process of the invention can effectively treat products rich in hydrocarbons or generating a lot of volatile fuel during direct pyrolysis.

 This process can be advantageously applied to both hydrocarbon-rich sludge and residues and contaminated soil, electronic scrap or minerals contaminated with hydrocarbons or other volatile materials. .

 This process makes it possible to work over very wide temperature ranges, ranging from 150 ° C. to over 1000 ° C. and with very reducing gas phase atmospheres.

The arrangement of the burners, their adjustment and the provision of steam introduction nozzles allow optimization of "flameless" pyrolysis in the core of the multi-solenoid reactor.

 The temperature profiles obtained by applying "flameless" pyrolysis with respect to direct conventional pyrolysis clearly demonstrate the merits of the present invention and its application to a multitude of residues and by-products in order to their valuation. Example 1 Mixture of Metals, Glass Fibers and Epoxy Resins (Table 1)

 The purpose of the treatment is to release metals and glass fibers from their epoxy matrix. The process consists of "flameless" pyrolysis at low temperatures. Table 1 gives a comparison between "flameless" pyrolysis and conventional pyrolysis. It can be seen that the method according to the invention makes it possible to prevent the temperature from running over time.

The excess air (or lambda) expresses the amount of air in excess of the minimum amount of air necessary for complete combustion (or stoichiometric). We work here in reducing atmosphere, so with air defect (lambda <1). Depletion of the oxygen atmosphere avoids oxidation and combustion which produces flames.

 Outside the pyrolysis "without flame", it is not possible to control the temperature of the gas phase and corollary that of the solid phase, which generates sintering and melting in the solid phase.

Example 2: Treatment of metals mixed with oils and water (Table 2)

The purpose of the treatment is to release the metals (for example tungsten oxides) and again from control the temperature of the gas phase to avoid raising the temperature of the solid phase uncontrollably. In the conventional oxidation method, the temperature rises with the release of volatile matter. The fixed carbon is encapsulated by coating with the volatile materials. This method poses cooling problems.

 Pyrolysis "without flame" allows to precisely control the temperature of the gas phase and the solid phase.

Example 3: Sludge treatment by pyrolysis and fixed carbon combustion (Table 3)

In a furnace 6 soles, for example, a steam at a pressure of 2.5 bar is injected into the hearth 3. This steam relaxes completely as soon as it enters the reactor. "Flameless" pyrolysis makes it possible to control the temperature of the gaseous phase (Tfg) in the transition zone, that is to say at the level of the hearth 3 in the present case (see Table 3 in grayed), between pyrolysis and burning of fixed carbon. The temperature of the raked solid product is not measured here. The injection of steam makes it possible to reduce the temperature of 100-150 ° C in the feedstock and thus to minimize the risks of sintering (formation of bottom ash) in the gaseous phase, as illustrated by the example below.

Claims

 1. Process for the reprocessing, recycling or separation of materials or waste in a staged kiln by direct pyrolysis in air defect (lambda <1) and in the presence of water vapor, referred to as the "flame-free" pyrolysis process Wherein the materials are respectively introduced and discharged at a first end and a second end of the furnace, said furnace comprising sequentially, starting from the first end, a drying zone, a pyrolytic gasification zone leading to the formation of a gaseous phase comprising volatile matter and a solid phase comprising fixed carbon and mineral matter, optionally followed by a fixed carbon combustion zone in excess of air, the heat of combustion of the charge being obtained by direct injection of air and auxiliary fuel in the furnace, characterized in that the water vapor is injected in a controlled manner into the gasification zone pyrolytic step oven, at a pressure between 1 and 5 bar, so as to obtain a precise and uniform temperature profile in both the gas phase and the solid phase.  2. Method according to claim 1, characterized in that the water vapor injected is dry steam.  3. Method according to claim 1, characterized in that the injected water vapor is saturating steam. 4. Method according to claim 1, characterized in that, in the case of a pyrolysis followed by a fixed carbon combustion, the water vapor is injected at the transition between the pyrolytic gasification zone and the combustion zone. fixed carbon. 5. Process according to claim 1, characterized in that the pyrolytic gasification is carried out in a reducing atmosphere.  6. Process according to claim 1, characterized in that the temperature range covered is between 150 and 1050 ° C.  7. Method according to claim 1, characterized in that the maximum temperature in the oven is reduced by at least 100 ° C compared to the situation where the same method is used, but without the injection of water vapor.  8. Method according to claim 1, characterized in that the waste to be recycled are used electronic circuits.  9. Method according to claim 1, characterized in that the waste to be recycled are sludges containing hydrocarbons and / or metals.  10. Method according to claim 1, characterized in that the waste to be recycled are minerals contaminated with hydrocarbons and other volatile materials.  11. The method of claim 1, characterized in that the combustion gases and fumes flow countercurrently with respect to the material treatment direction.  12. The method of claim 11, characterized in that the flue gases and fumes are extracted at the top of the furnace and in that the reprocessed materials are extracted at the bottom of the furnace. 13. The method of claim 1, characterized in that the combustion gases and fumes flow cocurrently with respect to the treatment direction of the materials. 14. The method of claim 13, characterized in that the combustion gases and fumes, as well as the reprocessed materials, are extracted at the bottom of the furnace, the pyrolysis being carried out between 150 and 500 ° C.