EP1080164A1

EP1080164A1 - Installation for thermolysis processing of waste with fumes that have a low free oxygen content

Info

Publication number: EP1080164A1
Application number: EP99973715A
Authority: EP
Inventors: Philippe Milles; Lionel Pasquinucci; Tamim Dabbagh
Original assignee: Nexus Technologies SAS
Current assignee: Nexus Technologies SAS
Priority date: 1999-02-25
Filing date: 1999-02-25
Publication date: 2001-03-07
Also published as: CA2326108A1; WO2000050537A1; AU2252400A; BR9909883A; KR20010042978A; CN1298438A; JP2002537475A

Abstract

The installation comprises: a thermolysis chamber (12), a combustion chamber (19) that is connected to the thermolysis chamber for the combustion of thermolysis gas and to provide a supply of combustion gas, a turbulent burner (18) mounted on the combustion chamber (19) for the combustion of gas resulting from the thermolysis chamber (12), an afterburn chamber (23) that is connected to the combustion chamber (19) so that part of the combustion gas produced in said chamber can undergo post-combustion, whereby the other part of the gas is introduced into the thermolysis chamber (12), a preheated combustive oxygen supply line (22) for the burner (18) and means for adjusting the amount of oxygen that is supplied to the burner (18) of the combustion chamber (19) in order to produce combustion gas that is practically devoid of free oxygen at the exit thereof.

Description

Installation of thermolvtic treatment of wastes with low oxygen free fumes

The present invention relates to the thermolytic treatment of waste, such as for example industrial and / or urban waste.

Already known from document EP-A-0 524 847, an industrial and / or urban waste treatment installation, comprising in particular a thermolysis reactor which operates in a vertical moving bed.

More specifically, the waste is introduced into the upper part of the thermolysis reactor and passes by gravity into the substantially vertical reactor. The hot gases are introduced at the base of the reactor, percolate in an ascending current through the waste bed and gradually transfer their energy to the solids. These hot gases are, according to one embodiment of the installation (installation in FIG. 2 of the aforementioned document), essentially constituted by effluents resulting from combustion of thermolysis effluents in a fluidized bed, the oxygen content of which is controlled. This oxygen content control is carried out using a servo loop.

The hot solids, essentially made up of coke and mineral matter, are evacuated from the reactor by a line located at the bottom of the latter. According to this document, certain wastes have a very heterogeneous character, which causes significant fluctuations in the calorific value of the thermolysis gases. The combustion of such products with burners would therefore lead to problems of flame stability.

This is why a fluidized bed was chosen, because it allows, thanks to its high thermal inertia, to ensure stable combustion of the thermolysis gases, even when the calorific value of the gases to be burned decreases. noticeably.

As already mentioned above, part of the fumes produced by the reactor operating in a fluidized bed is directed to the waste thermolysis reactor, the other part serving to preheat the combustion air. The quantity of combustion air introduced into the reactor operating in a fluidized bed is therefore adjusted so as to permanently maintain a low oxygen content for the thermolysis gases, as has already been said.

According to this document, the oxygen content of the hot gases used for thermolysis is less than 10%, preferably less than 4%, by volume.

The present invention aims to improve this type of installation. To this end, it offers an installation for thermolytic treatment of waste comprising: - a chamber for thermolysis of waste by direct contact with a hot gaseous fluid, a line for introducing hot gaseous fluid into the chamber, an extraction line gases present in the chamber, a combustion chamber fluidly connected to the extraction line so as to be able to burn gases from the thermolysis chamber and to the introduction line to supply it with combustion gases from the combustion of gases from the thermolysis chamber, characterized by a turbulence burner mounted on the combustion chamber and connected to the extraction line to burn the gases from the thermolysis chamber, an afterburner chamber, fluidly connected to the combustion chamber and suitable for subjecting part of the combustion gases produced in the combustion chamber to afterburning, the other part of these gases z of combustion being introduced into the introduction line, - a line for supplying oxidizing oxidizer preheated to a predetermined temperature, for the burner, and means for adjusting the quantity of oxygen supplied to the burner of the combustion chamber, to produce at the outlet of this combustion chamber combustion gases practically devoid of free oxygen. Thanks to such arrangements, it is possible to optimally manage the oxygen content of the combustion gases sent to the thermolysis chamber. In particular, the turbulence burner _. allows optimal mixing and, therefore, optimal combustion of oxidizing oxygen with combustible thermolysis gases diluted in a very large volume of inert combustion fumes from the previous treatment cycle. It is therefore possible to best adjust, with the adjusting means, the quantity of oxidizing oxygen supplied to this burner so that the combustion gases intended to be reinjected into the thermolysis chamber are practically free of free oxygen.

Furthermore, post-combustion makes it possible to complete the combustion poor in oxygen having taken place in the combustion chamber for the part of combustion gases or fumes not reinjected into the thermolysis chamber.

There is therefore at the outlet of the post-combustion chamber combustion gases or fumes whose thermal energy is directly recoverable, without additional treatment.

According to preferred arrangements, possibly combined: a heat exchanger is placed on the introduction line to preheat the combustion air to a temperature between 600 and 800 ° C; the burner is also supplied with propane or natural gas; - The combustion gases entering the thermolysis chamber are maintained at a temperature between 450 ° C and 750 ° C, preferably around 650 ° C; the thermolysis chamber is maintained at a constant pressure of between 100 mbar and 1.2 bar; - the afterburner chamber supplies a steam generator; solid residues from the thermolysis chamber are sorted and the fraction of solid carbonaceous residues resulting therefrom is conveyed to another combustion chamber to be burned there, this other combustion chamber also supplying another steam generator; the vapor fractions from each of the steam generators are aggregated to be used as energy for the production of electricity.

These latter provisions make it possible to burn all the combustible products from the waste on site, with a view to producing steam and, consequently, electricity. The thermolysis chamber can be of the horizontal type, in which the products are carried by carriages moved through the thermolysis chamber by a mechanical assembly. In this case, fluid connection means, adapted to establish a temporary fluid connection between the introduction line and a connection zone provided on the carriage and communicating with the zone for receiving the solid products from the carriage, are provided.

According to another aspect, original in itself, the thermolysis chamber is constituted by a charging oven comprising: an opening for loading waste which can be sealed, an opening for emptying solid residues from thermolysis from the oven, which can be sealed, means for receiving a stationary load of waste in the oven, means for introducing recycled thermolysis gas, constituting the hot gases, into the oven and directly into the stationary load to perform thermolysis by direct contact of the waste with these hot gases, and means for exiting the thermolysis gases formed in the furnace by thermolytic treatment of the waste.

Such an oven is particularly advantageous in that it makes it possible to treat bulky waste, such as tires. More particularly, such an oven solves the problem of blocking the introduction and extraction systems. of products existing in the case of vertical fluidized bed ovens, such as that which is the subject of the abovementioned document EP-A1-0 524 847, when the products are heterogeneous, that is to say of non-constant particle size. Preferably: the receiving means are mounted movable between a position for receiving the waste during the thermolytic treatment and a position for emptying the solid residues of thermolysis through the emptying opening; the receiving means are provided with means for passing hot gases to the stationary load of waste; the introduction means introducing the hot gases under the receiving means; cooling means are provided under the oven to cool the solid residues of thermolysis.

Other objects, characteristics and advantages of the invention appear from the description which follows, given by way of nonlimiting example, with reference to the appended drawings, in which: FIG. 1 is a schematic view of an installation in accordance with a preferred embodiment of the invention; and Figure 2 is a schematic elevational view in longitudinal section of a thermolysis charge furnace according to the invention. Figure 1 illustrates a preferred embodiment of the installation according to the present invention.

In this installation, the waste to be treated is conveyed in a crusher 9 and then loaded into a carriage 11 by a conveyor system 10. The carriages 11 used in the installation of FIG. 1 can for example be of the type of those described in international patent application WO-98/16594 and which allow an injection of hot gases directly into the load of waste to be treated.

The carriages 11 loaded with waste are then brought, one by one, to a thermolysis chamber or oven 12 equipped, for this purpose, with a sealed entry door 13. waterproof inlet 13.

In order to avoid the penetration of oxygen into the thermolysis oven 12 during the transfer of a carriage inside thereof, the carriage 11 can be brought to the oven 12 by a charger (not shown), in which the carriage 11 has been placed under an inert atmosphere. During the transfer of the carriage 11 in the oven 12, means for establishing a sealed connection between the oven 12 and the charger, such as a bellows, are deployed, to effect a transfer from the carriage 11 to the oven 12 under an inert atmosphere.

The installation comprises a line 14 for introducing the hot gaseous fluid into the thermolysis furnace 12. As will be described in more detail below, this hot gaseous fluid consists of combustion gases resulting from the combustion of thermolysis previously extracted from the thermolysis oven 12.

This introduction line has several branches 14a-14i each ending in fluid connection means (for example a telescopic bellows, not shown in FIG. 1) to establish a temporary fluid connection between the introduction line 14 and a zone connection provided on each of the carriages 11 and communicating with a waste reception area of these carriages 11. As has already been said, this allows the hot gaseous fluid to be injected directly into the waste charge to perform thermolysis.

Hot gaseous fluid (combustion gases, also called

"smoke" below) is injected at a temperature between 450 ° C and 750 ° C, preferably at a temperature of about 650 ° C in the thermolysis oven 12 which is maintained at a constant pressure between 100 mbar and 1.2 bar.

Thus, the waste is first of all dehydrated and then brought to their thermolysis temperature as each carriage 11 advances in the thermolysis oven 12 and is connected to the successive branches 14a-14i of the introduction line 14.

After treatment, each carriage 11 loaded with solid residues is recovered, under an inert atmosphere, for example by means of the aforementioned charger, at the location of a sealed exit door 15 from the oven 12.

The treatment of these solid residues will also be described in more detail below. The thermolysis gases formed in the furnace 12 are extracted therefrom by an extraction line 16 with several branches 16a-16i. This extraction is carried out using pumping means placed on the extraction line 16. These means have not been shown in FIG. 1 and can, for example, be constituted by a booster. The introduction lines 14 and extraction lines 16 are preferably insulated to, on the one hand, bring the thermolysis gases to high temperature in a combustion chamber described below and, on the other hand, keep at high temperature the hot gaseous fluid to be introduced into the thermolysis furnace 12. The thermolysis gases coming from the thermolysis furnace 12 are brought by the extraction line 16 to a dust separator 17. After being freed of their dust, the thermolysis gases are supplied to a burner 18 from a combustion chamber 19, via a line 20.

This burner 18 is a swirl burner, of the type sold by the company BLOOM.

The burner 18 has, moreover, an inlet 21 of propane or natural gas making it possible in particular to make a make-up, to provide a support or pilot flame, and to start the thermolysis process.

An oxidizing oxygen supply line 22 is also connected to this burner 18. The oxidizing oxygen can be pure oxygen or come from air or from air enriched with oxygen.

Before being injected into the burner 18, this oxidizing oxygen is preheated to a temperature between 600 and 800 ° C. To this end, the supply line 22 passes through two heat exchangers 23, 24 before serving an afterburner chamber 25 then the burner 18.

More specifically, this oxygen supply line 22 oxidizer is connected, on the one hand, to an auxiliary burner 26 of the afterburner chamber 25 and to a hearth 27 of this chamber 25, which is connected to an outlet 28 of the combustion chamber 19.

In this regard, it should be noted that, in other embodiments, a smoke transfer line could separate the hearth 27 and, consequently, the afterburner chamber 25, from the outlet 28 of the combustion chamber 19.

The burner 26 is also equipped with a propane or natural gas inlet 29, which can be connected to the same source as the inlet 21 of the burner

18. Means for adjusting the quantity of oxygen supplied to the burner

18 of the combustion chamber 19 are also provided for producing at the outlet of this combustion chamber 19 combustion gases practically free of free oxygen (oxygen content preferably less than 0.5%). These adjustment means also serve, in the case of the present preferred embodiment, to manage the quantity of oxygen supplied to the afterburner chamber 25.

It may for example be an oxygen meter 30 placed on the introduction line 14, at the outlet of the combustion chamber 19, and connected to a system of servo-controlled valves, shown diagrammatically at 31 and placed on the line supply 22 of oxidizing oxygen. The connection between the oxygen meter 30 and the servo valve system 31 has not been shown in FIG. 1, for the sake of clarity.

Part of the combustion gases or smoke from the combustion chamber 19 therefore leave it via the line 14 fitted, for this purpose, with a pumping unit 32. The other part of the smoke, not used for recycling in the thermolysis oven 12, is sent to the post-combustion chamber 25, to improve the combustion before being upgraded as described below.

The fumes from the combustion chamber 19 and the afterburner chamber 25 pass through the exchangers 23 and 24 respectively to preheat the combustion air to a temperature between 600 and one of its ends to an oxygen source 33, followed by a pumping group 34, passes through the exchangers 23 and 24 before serving the burners 18 and 26.

As a variant, it is of course possible to replace these two exchangers 23, 24 with a single dual-circuit exchanger, or even to use only one single-circuit exchanger.

The installation of FIG. 1 aimed at treating on site all of the products of thermolysis, the fumes leaving the afterburner chamber

25 are brought by a line 35, which passes through the exchanger 24, to a steam generator 36, for example of the double circulation boiler type supplied with water (37).

In the present case, the steam produced supplies the turbo-alternator unit 38 for the production of electricity. The condensed water produced by this unit is evacuated via line 39. As a variant, it is of course possible to produce hot water with the fumes coming from the afterburner chamber 25, instead of producing electricity.

The cooled fumes are extracted from the generator 36 by a line 40 equipped with a pumping group 41, and sent in a bag filter 42 to separate the solid particles therefrom, before these fumes are discharged into the atmosphere by a chimney 43.

The pumping unit 41, constituted for example by an extraction fan, also regulates the separation between the fumes intended for the furnace 12 and those intended for the afterburner chamber 25, the flow rate being controlled by the pressure in the furnace 12. A Safety procedure, notably involving pumping groups or fans 32 and 41, also makes it possible to avoid the passage of oxygen from the afterburner 25 to the combustion chamber 19.

Each carriage 11 loaded with solid thermolysis residues is brought by the aforementioned charger to a cooling unit 44, also equipped to prevent penetration of free oxygen into this charger. equipped to avoid penetration of free oxygen into this charger.

Once in the unit 44, the carriage 11 is poured onto a conveyor which passes the solid residues into a swimming pool 45 to cool them.

Then, these residues are subjected to settling at 46, then are screened at 47. The screen has, here, a hole diameter equal to 8 mm. The particles having passed through the screen are then subjected to an attrition step at 48, then are again screened by means of a screen 49 having this time, a hole diameter equal to 0.8 mm. By means of this screening, the carbon fraction is separated from the inorganic fraction. The carbon fraction is further subjected to a draining step at 50 before being brought, for storage, into a silo 51. The inorganic fraction is subjected to a sorting step at 52. Following this sorting, minerals are recovered (53), magnetic materials (54) and non-magnetic materials (55). During sorting, the metals are also subjected to a compaction step. The particles which at 47 have been retained by the screen, are brought to a flotation tank 56.

The densest materials (metals ...) are collected at the bottom of the basin and sent to 52 for separation. The less dense materials (carbon fractions) are recovered at the top of the tank 56 and brought into a grinder 57 where they are reduced to a size less than 0.8 mm.

Then these carbonaceous particles are also subjected to drainage at 50, then sent to the silo 51.

The silo 51 feeds a dense fluidized bed oven 58 intended to burn the carbonaceous or coal fraction stored in the silo 51. The fumes produced in this oven 58 pass through a steam generator 59 supplied with water (60). The fraction of steam leaving this generator 59 is supplied, with that leaving the generator 36, to the turbo-alternator unit 38.

The fumes produced in the oven 58 also pass through an economizer 61 which preheats the oxidizing oxygen intended for the oven 58. This oxidizing oxygen is brought to the oven 58 by a line 62 connected to a source 63 of pure oxygen, of pure air or of air enriched with oxygen and equipped with a pumping group 64.

The fumes leaving the economizer 61 are brought by a line 65, equipped with a pumping group 66, to the bag filter 42. The ashes collected at the bottom of the oven 58 are collected and evacuated at 67, while the ashes collected at the top of the oven 58 are recycled therein via a line 68.

One end of this line 68 is, moreover, also connected to the bottom of the bag filter 42. The rest of the evacuation residues leaving through the bottom of the bag filter 42 is evacuated at 69.

According to the variant of FIG. 2, the thermolysis chamber consists of a charge thermolysis oven 112.

This oven 112 is vertical and sealed in its upper and lower ends, during the thermolytic treatment, by panels 170, 171 movable in translation in a horizontal plane.

The panel 170 makes it possible to close the loading opening of the oven 112, which is substantially transverse to the longitudinal axis of this same oven 112, while the panel 171 is intended to close the emptying opening of this oven 112, which, for its part, also extends substantially transversely to the aforementioned axis.

The drain opening opens onto a buried pool 172 for recovering solid thermolysis residues.

To receive a stationary load of waste to be treated discontinuously, a fixed tank 173 is mounted in the oven 112, between the panels 170 and 171.

This tray 173 is provided with a bottom consisting of a grid in two parts 174. Each of the two parts of the grid 174 is pivotally movable between a horizontal position in which they are in line with one another to receive a load of waste and a position away from one another and emptying through the emptying opening, after removal of the panel 171. A side inlet 175 of recycled thermolysis gas opens into the oven 112 under the grid 174. This inlet is connected to the introduction line 14 of the installation of FIG. 1, when the oven 112 replaces the horizontal oven 12 of the Figure 1. Thus, the recycled thermolysis gases enter the waste charge after passing through the grid 174 to perform thermolysis by direct contact of hot gases with a stationary charge of waste to be treated.

The thermolysis gases formed in the oven 112 are extracted therefrom by a lateral outlet 176 connected, in the case where the oven 112 is used within the framework of the installation of FIG. 1, to the extraction line 16 .

The furnace 112 is supplied with waste by gravity by means of a feeder 177 movable horizontally above this furnace 112.

For this purpose, a tray 178, similar to tray 173, is installed in the charger 177. It will be observed in this regard that the lower end of the charger 177 is not closed.

According to a variant of this embodiment, the charger can be replaced by a charger supplying the oven by a lateral opening, by means of a conveyor belt.

Such a charger can also be mounted movable in translation to serve a battery of thermolysis ovens.

Lateral injection of hot gases into the load is also possible.

It is also possible to provide for lateral emptying of the residues by means of a waste receiving plate mounted movable in tilting. It goes without saying that the above description has been offered only by way of nonlimiting example and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention.

Claims

1. Installation for thermolytic treatment of waste comprising: a thermolysis chamber (12) for waste by direct contact with a hot gaseous fluid, a line for introducing (14) hot gaseous fluid into the chamber, an extraction line ( 16) of the gases present in the chamber, a combustion chamber (19) fluidly connected to the extraction line (16) so as to be able to burn gases from the thermolysis chamber (12) and to the introduction line (14) for supplying it with combustion gases from the combustion of gases from the thermolysis chamber (12), characterized by a turbulence burner (18) mounted on the combustion chamber (19) and connected to the line extraction (16) to burn the gases from the thermolysis chamber (12), an afterburner (25) fluidly connected to the combustion chamber (19) and adapted to subject part of the combustion gases produced in the combustion chamber (19) at u no post-combustion, the other part of these combustion gases being introduced into the introduction line (14), a supply line (22) of oxidizing oxygen preheated to a predetermined temperature, for the burner (18), and means for adjusting the quantity of oxygen supplied to the burner (18) of the combustion chamber (19), in order to produce at the outlet of this combustion chamber (19) combustion gases practically devoid of free oxygen.

2. Installation according to claim 1, characterized in that the thermolysis chamber is constituted by a charging oven comprising: - a waste loading opening which can be closed in leaktight manner, an opening for emptying solid thermolysis residues which can be sealed, means for receiving (174) a stationary load of waste into the oven, - means for introducing (175) recycled thermolysis gases, constituting the hot gases, in the furnace, directly in the stationary load to carry out a thermolysis by direct contact of the waste with these hot gases, and means of outlet (176) of the thermolysis gases formed in the furnace by thermolytic treatment of the waste.

3. Installation according to any one of the preceding claims, characterized in that a heat exchanger (23, 24) is placed on the introduction line (14) to preheat the combustion air to a temperature between 600 and 800 ° C.

4. Installation according to any one of the preceding claims, characterized in that the burner (18) is also supplied with propane or natural gas.

5. Installation according to any one of the preceding claims, characterized in that the combustion gases entering the thermolysis chamber are maintained at a temperature between 450 ° C and 750 ° C, preferably around 650 ° C.

6. Installation according to any one of the preceding claims, characterized in that the thermolysis chamber is maintained at a constant pressure of between 100 mbar and 1.2 bar.

7. Installation according to any one of the preceding claims, characterized in that the afterburner chamber (25) feeds a steam generator (36).

8. Installation according to any one of the preceding claims, characterized in that the solid residues coming from the thermolysis chamber are sorted and the fraction of carbon-containing solid residues resulting therefrom is conveyed to another combustion chamber (58) to be burnt, this another combustion chamber (58) also supplying another steam generator (59).

9. Installation according to claims 7 and 8, characterized in that the vapor fractions from each of the steam generators (36, 59) are combined to be valued in energy form for the production of electricity.

10. Installation according to claim 1, characterized in that the thermolysis chamber (12) is of the horizontal type, in which the waste is carried by carriages (11) moved through the chamber by a mechanical assembly.

11. Installation according to claim 2, characterized in that the receiving means (174) are mounted movable between a position for receiving the waste during the thermolytic treatment and a position for emptying the solid residues of thermolysis by the emptying opening.

12. Installation according to claim 2 or 11, characterized in that the receiving means are provided with means for passing hot gases to the stationary load of waste, the introduction means introducing the hot gases under the receiving means.

13. Installation according to any one of claims 2, 11 and 12, characterized in that cooling means are provided under the oven to cool the solid residues of thermolysis.