EP2584262A1 - Method for pyrolytic treatment of organic and inorganic waste in a multiple-hearth incinerator for recovering recoverable sub-products - Google Patents

Abstract

The method involves introducing and discharging organic and inorganic material into/from two ends of a multiple-hearth incinerator. The incinerator is provided with a drying zone and a pyrolytic gasification zone leading to form a gaseous phase and a solid phase. Combustion heat of a load is obtained by direct injection of air and auxiliary fuel into the kiln. The water vapor is injected at low pressure in a controlled manner in a region of the kiln staged so as to obtain a precise and uniform temperature profile in the gaseous phase and the solid phase. An independent claim is also included for a multiple-hearth and base kiln for performing a pyrolytic treatment of complex organic residue or waste containing oil for recovering recoverable sub-product.

Description

Object of the invention

The present invention relates to a pyrolytic treatment method, in a multi-storey or multi-storey oven, incorporating an adequate control of the temperature profile both at the level of the treated product and 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.

A typical stepped furnace comprises a series of circular soles, placed one above the other in a metal shell covered with refractory. 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).

• une zone de séchage des matières à traiter ;
• une zone de chauffe et gazéification pyrolytique des matières volatiles, dans une atmosphère pauvre en oxygène. Après l'étape de pyrolyse, les produits ne contiennent plus que des matières minérales et du carbone fixe ;
• une zone de combustion du carbone fixe en présence d'excès d'air.

The Applicant has developed for many years a direct pyrolysis process in multi-stage furnace, 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 a low oxygen 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.

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.

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 matter generated by the process comes 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 widely published in Europe as well as in the United States.

Requirement WO 2010/142397 discloses a process for recovering metals from a stream rich in hydrocarbons and carbonaceous residues by means of a treatment section, comprising the steps of: directing the stream into a primary treatment, carried out in one or more steps, wherein the flux 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 liquid / solid separation 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.

Requirement WO 2010/55489 discloses a method and an installation for treating materials containing a mixture of plastics and metallic materials, such as used electronic boards. 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.

Requirement 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 speed oxygen streams into the furnace heating or drying zone 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 over 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.

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

The patent US 4,261,268 discloses a method and an installation for treating 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 includes 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 volatiles. According to one embodiment of the invention, the secondary exhaust gases undergo a heat exchange with the air which is added to the oven.

The patent US 4,046,086 discloses a similar method and plant for the treatment of 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.

The patent US 4,118,220 discloses a process for treating materials containing heavy metals and carbonaceous materials, comprising the steps of continuously introducing waste to be treated by entering a first furnace while simultaneously adding air to the furnace, heating the waste in the oven 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 simultaneously discharging the exhaust gas from the oven, 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 material in the waste and separately discharging the ashes and exhaust gases from the second furnace.

Goals 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 furnace process stages.

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 wastes in a direct pyrolysis stage furnace, referred to as a "flameless" pyrolysis process, in which the materials are respectively introduced and discharged at a temperature of 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 materials, and optionally 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 into the furnace, characterized in that that low pressure water vapor is controlledly injected into at least one area of the oven so as to obtain a precise and uniform temperature profile as in the gas phase than in the solid phase.

• la pression de vapeur d'eau injectée est comprise entre 1 et 5 bars ;
• la vapeur d'eau injectée est de la vapeur sèche ;
• la vapeur d'eau injectée est de la vapeur saturante ;
• dans le cas d'une pyrolyse suivie d'une combustion de carbone fixe, la vapeur d'eau est injectée à la transition entre la zone de gazéification pyrolytique et la zone de combustion du carbone fixe ;
• la gazéification pyrolytique est effectuée en atmosphère réductrice ;
• le domaine de température couvert s'étend entre 150 et 1050°C ;
• la température maximale dans le four est réduite d'au moins 100°C par rapport à la situation où on utilise le même procédé, mais sans injection de vapeur d'eau ;
• les déchets à recycler sont des circuits électroniques usagés ;
• les déchets à recycler sont des boues contenant des hydrocarbures et/ou des métaux ;
• les déchets à recycler sont des minéraux contaminés par des hydrocarbures et autres matières volatiles ;
• les gaz de combustion et les fumées s'écoulent à contre-courant par rapport au sens de traitement des matières ;
• les gaz de combustion et les fumées sont extraits au niveau de la partie supérieure du four et les matières retraitées sont extraites au niveau de la partie inférieure du four ;
• les gaz de combustion et les fumées s'écoulent à co-courant par rapport au sens de traitement des matières ;
• les gaz de combustion et les fumées, ainsi que les matières retraitées, sont extraits au niveau de la partie inférieure du four, la pyrolyse étant réalisée entre 150 et 500°C.

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 injected water vapor pressure is between 1 and 5 bar;
• the water vapor injected is dry steam;
• the water vapor injected is saturating steam;
• in the case of a pyrolysis followed by a fixed carbon combustion, the 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 with hydrocarbons and other volatile materials;
• the flue gases and fumes flow countercurrently with respect 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 flue gases and fumes flow cocurrently with respect to the material treatment direction;
• the flue gases and 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.

Another aspect of the present invention relates to a multi-storey or multistage furnace for carrying out the method described above, comprising a series of soles or circular baking trays, arranged one above the other in a refractory-lined steel casing and a vertical rotating shaft arranged along the axis of the oven and carrying arms provided with saddles, which brew the load and move it through each hearth in a spiral path, the product to be treated being deposited at an upper sole and rasped to pass through it by orifices opening on the bottom immediately below, and so to following down the installation where the treated product is discharged, hot combustion gases circulating in the furnace to heat the charge to its reaction temperature and produce the desired reaction, in particular advanced drying, direct pyrolytic gasification and optionally a fixed carbon combustion, the combustion heat being produced by the combustion either of the constituents of the charge itself, or of carbons an auxiliary burner burned in burners located at one or more specific soles, said stepped furnace being characterized in that it further comprises low pressure steam injection nozzles located at a or more specific soles.

Description of preferred embodiments of the invention

The invention relates to a method of heat treatment by direct pyrolysis, " flameless pyrolysis " , multi- stage furnace, more specifically, residues, waste or materials containing 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 makes it possible, by a controlled and staged injection of low pressure steam into the stage reactor, to control accurate and uniform way 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, dry or saturated water vapor pressure will advantageously be between 1 and 5 bar. The water vapor will also be injected into one or more soles of the reactor depending on the desired result. 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 "flameless" direct pyrolysis method can be applied generally in countercurrent operation, i.e. the flue gases are extracted at the top of the reactor and the product solid 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 efficiently processes products rich in hydrocarbons or generating a great deal of combustible volatiles during direct pyrolysis.

This process can be applied to both hydrocarbon-rich sludges and residues and contaminated soils, electronic waste ("electronic scrap ") or minerals contaminated with hydrocarbons or other volatile matter.

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 mode of arrangement of the burners, their adjustment and the arrangement of steam introduction nozzles allow an optimization of the pyrolysis "without flame" in the heart of the reactor with multiple soles.

The temperature profiles obtained by applying "flameless" pyrolysis over direct conventional pyrolysis clearly demonstrate the merits of the present invention and its application to a multitude of residues and byproducts for recovery.

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.

Excess air (or lambda) expresses the amount of air in excess of the minimum amount of air required for complete (or stoichiometric) combustion. We work here in reducing atmosphere, so with air defect (lambda <1).

Apart from "flameless" pyrolysis, it is not possible to control the temperature of the phase gaseous 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 liberate the metals (eg tungsten oxides) and again to 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.

"Flameless" pyrolysis makes it possible to accurately 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 with 6 soles, for example, a steam at a pressure of 2.5 bar is injected into the hearth 3. This vapor expands 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. <u> Table 1 </ u> Time (min) Temperature (° C) lambda 0 552 0, 87 17 741 0, 97 35 732 0.73 50 713 0.73 Conventional pyrolysis Time (min) Temperature (° C) lambda 0 643 0.72 10 547 0.75 20 576 0.77 30 542 0.74 40 514 0.71 Pyrolysis "without flame" (invention) Time (min) Temperature (° C) lambda 0 559 0, 67 15 542 0, 69 30 637 0.75 60 713 0.74 90 737 0, 61 Conventional pyrolysis Time (min) Temperature (° C) lambda 0 670 0.54 30 559 0.77 45 587 0.77 60 594 0.74 90 581 0.74 Pyrolysis "without flame" (invention) Time (h) Tfg sole 1 Tfg sole 2 Tfg sole 3 Tfg sole 4 Tfg sole 5 Tfg sole 6 (° C ° (° C) (° C) (° C) (° C) (° C) Conventional pyrolysis 0 589 845 978 692 609 486 0.5 588 859 961 690 611 463 1 639 887 1014 706 623 513 Pyrolysis "without flame" (invention) 1.5 655 862 959 704 620 524 2 675 864 910 694 618 524 2.5 701 828 901 689 611 518 3 709 811 878 688 609 514 3.5 719 798 907 693 611 518 4 728 790 899 697 614 524 4.5 735 799 871 692 611 528 5 738 805 901 698 617 530 5.5 745 807 887 696 613 532 6 743 813 880 681 614 529 6.5 760 805 867 684 612 530

Claims (16)

A process for the reprocessing, recycling or separation of materials or waste in a direct pyrolysis stage furnace, 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. oven, said oven comprising sequentially, starting from the first end, a drying zone, a pyrolytic gasification zone leading to the formation of a gas phase comprising volatile matter and a solid phase comprising fixed carbon and materials mineral, and optionally 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 into the furnace, characterized in that water vapor at low pressure is injected in a controlled manner into at least one zone of the stepped furnace so as to obtain a tem profile precise and uniform temperature in both the gas phase and the solid phase. Process according to Claim 1, characterized in that the injected water vapor pressure is between 1 and 5 bar. Process according to claim 1, characterized in that the injected water vapor is dry steam. Process according to claim 1, characterized in that the injected water vapor is saturating vapor. Process according to Claim 1, characterized in that , in the case of pyrolysis followed by fixed carbon combustion, the water vapor is injected at the transition between the pyrolytic gasification zone and the carbon combustion zone. fixed. Process according to Claim 1, characterized in that the pyrolytic gasification is carried out in a reducing atmosphere. Process according to Claim 1, characterized in that the temperature range covered is between 150 and 1050 ° C. Process according to Claim 1, characterized in that the maximum temperature in the furnace is reduced by at least 100 ° C compared to the situation where the same process is used, but without the injection of water vapor. Process according to Claim 1, characterized in that the waste to be recycled is used electronic circuits. Process according to Claim 1, characterized in that the waste to be recycled is sludge containing hydrocarbons and / or metals. Process according to Claim 1, characterized in that the waste to be recycled is minerals contaminated with hydrocarbons and other volatile materials. Process according to Claim 1, characterized in that the combustion gases and the fumes flow countercurrently with respect to the material treatment direction. Process according to claim 12, characterized in that the combustion gases and fumes are extracted at the upper part of the furnace and that the reprocessed materials are extracted at the lower part of the furnace. Process according to Claim 1, characterized in that the combustion gases and the flue gases flow cocurrently with respect to the material treatment direction. Process according to Claim 14, characterized in that the combustion gases and fumes, as well as the reprocessed materials, are extracted at the lower part of the furnace, the pyrolysis being carried out at between 150 and 500 ° C. A multi-storey or multi-deck furnace for carrying out the method according to any one of the preceding claims, comprising a series of circular soles or baking trays, arranged one above the other in a lined steel casing refractory and a vertical rotary shaft disposed along the axis of the furnace and carrying arms provided with râbles, which stir the load and move through each hearth in a spiral path, the product to be treated being deposited at the level of an upper sole and rasped to pass through it by openings opening on the bottom immediately below, and so on down the installation where the treated product is discharged, hot combustion gases flowing in the oven for heating the charge to its reaction temperature and producing the desired reaction, in particular advanced drying, direct pyrolytic gasification and optionally fixed carbon combustion, the combustion heat being produced by the combustion either of the constituents of the charge itself or of auxiliary fuel burned in burners located at one or more specific soles, said stage furnace being characterized by that it further comprises steam injection nozzles of low pressure water located at one or more specific sole.