FR2599124A1 - Improved installation for the destruction by incineration of household waste or other materials - Google Patents

Abstract

This installation, of the type comprising a vertical tower or column into which the materials are introduced at its upper end and incinerated at its lower end, a combustion chamber and a steam production boiler heated by burning the residual gases of combustion and or pyrolysis collected at the upper end of the column, and means for purifying the gases, comprises, directly on the boiler 28 and fed by the gaseous products of pyrolysis originating from the tower 21, means 25 between the tower and the burner on the boiler to separate the dusts of the said gaseous products, a heat exchanger 37 connected to an outlet of the boiler 28, and means 29, 33, 57 for reinjecting the said dusts into the tower 21 with primary combustion air heated beforehand in the said exchanger 37.

Description

 The present invention relates generally to the incineration of materials, homogeneous or not, having a sufficient calorific value, relative to the unit of mass, to justify their destruction by combustion.

 An excellent example of such a material is household waste, and the invention will be described below in its application to the destruction of this household waste.

 An installation for the destruction of these materials is already known, in which the materials are incinerated in a tower, or vertical column open at its two ends and in which the materials to be incinerated, in this case household waste, are loaded to the part upper part of the column, dried and pyrolyzed in the middle part and for what remains, burned and melted at its lower part, the combustible gas products resulting from these various reactions being collected in a collector at the upper part of the column and burned in a secondary combustion chamber thanks to a secondary air supply.

 The hot gaseous products leaving this secondary combustion chamber are led into a recovery boiler in which their heat is used to heat water and produce steam, the cooled gases leaving this boiler being then filtered, dedusted and finally discharged into the atmosphere.

 To promote and maintain combustion, previously heated primary air is injected at the base of the incineration column.

 The installations of this type hitherto used for the destruction by incineration of household waste do not function in a completely satisfactory manner.

 The invention therefore aims to achieve an installation of the aforementioned type allowing better incineration of materials to be destroyed with a much more economical operation in energy supply.

 It has for this purpose an installation of the aforementioned type for the destruction by incineration of various materials having a recoverable calorific value, in particular household waste, comprising an incineration and pyrolysis tower, a secondary combustion chamber for combustible gaseous products pyrolysis and a steam production boiler heated by hot gases from said secondary combustion chamber, characterized in that it comprises a burner mounted directly on the boiler and supplied with the gaseous products of pyrolysis coming from the tower , means between the tower and said burner for separating the dust from said gaseous products, a heat exchanger connected to an outlet of the boiler and means for re-injecting said dust in the tower with primary combustion air previously heated in said exchanger.

 The description which follows, with reference to the accompanying drawings by way of nonlimiting example, will make it possible to understand clearly how the invention can be put into practice.

 FIG. 1 is a diagram of an installation for incinerating household waste of the prior art.

 Figure 2 is a diagram of an installation according to the invention.

 Referring to FIG. 1, a known installation for incinerating household waste comprises an incineration tower 1 having a hearth 2 at its lower part, a lantern or gas collector 3 at its upper part.

 The manifold 3 is connected by a duct 4 in which a secondary air supply is made by a duct 19 and a fan 20 to a secondary combustion chamber 5 in which the gaseous products and the dusts from the tower are burned, the non-combustible dust settling in a receptacle 6 at the bottom of the chamber 5.

 The chamber 5 is connected by a conduit 7 to a boiler 8 which thus receives the burnt gases coming from the secondary chamber 5.

 Water entering through an inlet 9 of the boiler 8 is heated by these gases and leaves in the form of steam through an outlet 10.

 The partially cooled gases leave the boiler 8 via a duct 11 connected to a dust collector 12 having an outlet 13 for dust and connected to the atmosphere by a duct 14 comprising a fan 15 and open to the atmosphere at 18.

 A circular distribution ramp 16 supplies the hearth 2 with primary combustion air previously heated in a heating device 17 supplied by an external source of energy (not shown).

 Experience has shown that such an installation of the prior art does not function in a completely satisfactory manner.

 In fact, not only does combustion take place badly in tower 1 and the materials to be burned do not descend into it satisfactorily, but in addition the yield is low and finally ash, slag and dust must be periodically removed at three points in the installation, namely: at the lower end of the tower 1, at the lower end of the combustion chamber 5 and at the final dust collector 12. In addition, the combustion gases from chamber 5 leave in the boiler 8 a significant amount of dust, requiring frequent cleaning thereof, and therefore as many costly operating stops.

 In addition, the temperature of the primary combustion air, necessary to maintain it and melt the slag is close to 10000C, thus requiring a very high energy consumption compared to the tonnage of incinerated materials which can even double the cost. of this tonnage. Finally, the gases discharged into the atmosphere have a high content of acids, in particular hydrochloric acids.

 The installation according to the invention shown in FIG. 2 is of the same general type as that of FIG. 1, but it differs from it in several important points.

 As known per se, it comprises a combustion tower 21 comprising at its upper part means or lantern 23 for collecting the hot combustion gases, a boiler 28 and a final dust collector 32.

 The lantern 23 of the incineration tower 21 is connected by means of a two-way valve 22, on the one hand by a conduit 24 to a device 25 for filtering and dedusting gaseous products of combustion and, on the other hand, directly to the atmosphere by a conduit 26 leading to the latter at 27.

 The device 25 is of the type comprising at its lower part means 29 for removing the collected dust, and is connected by a conduit 30 to a lean gas burner 31 mounted on the boiler 28, and comprising an air inlet, as known in itself.

 The means 29 of the device 25 are connected so as to open in a pipe 33 connected to a source of steam (not shown) and opening at the outlets of the circular ramp 35 for supplying hot primary air for combustion of the hearth of the tower 21, this air being supplied by a duct 36 connected to a source 34 of pressurized air by means of a heater 37 heated by sampling the combustion gases in the boiler 28 by means of a duct 38, the outlet of the heater 37 is connected by a fan 39 and a duct 40 to an outlet 41 of the boiler 28, connected to the dust collector 32.

 The gas outlet of the dust collector 32 is connected by a conduit 42 to a device 43 for washing the gases.

 The gas washing device 43 comprises a tank 44, the bottom of which is connected to the upper part by a conduit 45 in which a pump 46 is inserted.

 The device 43 also comprises a conduit 47 for overflow of the tank and a conduit 48 connecting its upper part to the atmosphere at 27 by means of a fan 50.

 Finally, the duct 45 connected to the bottom of the tank 44 is connected by a duct 51 to a tank 52 arranged below an opening 53 for leaving the ash and slag at the bottom of the tower 21. A pump 59 is interposed in conduit 51.

 In operation, the materials to be incinerated, in this example household waste, are introduced into the upper part of the tower 21 to descend to the floor 54 to which they are brought by an agitating device 55 shown only schematically and which can be of the pallet, worm or other type.

 When combustion is started, the hot gases rise in the tower 21, heating the mass of unburned material in passing and escape through the conduit 24 to pass into the device 25.

 The dedusted gases reach the burner 31 which heats the boiler 28.

 The dust collected in the device 25 falls into the duct 33 by means of the means 29 and is entrained by steam to mix with the primary combustion air arriving via the ramp 35.

 This dust largely contains combustible particles (carbon, hydrocarbons, etc.) which activate and maintain combustion.

 The combustion gases from the burner 31 heat the water entering 56 into the boiler 28, the water vapor escaping from the boiler.

 Part of the combustion gases from the burner 31 leaves the boiler 28 through the conduit 38 to heat the primary combustion air in the device 37, by forced circulation by the fan 39, while another part of these gases leaves the the boiler 28 via the duct 41.

 Thanks to this arrangement, all of the gases leaving the boiler via the conduits 38 and 41 pass through the dust collector 32 in which the last dust (non-combustible) is collected, which is extracted therefrom by a drain 58.

 The non-combustible residues of combustion are melted and collected in the form of slag falling into the tank 52 which advantageously contains water.

 The slag falling from the floor 54 of the tower 21 partially dissolves in the water of the tank 52, thus producing an alkaline solution which is returned by the pump 59 to the tank 44 of the device 43 for washing the gases from the boiler 28 and the heater 37.

 It is understood of course that conventional means are provided (not shown, not forming part of the invention) to ensure the constancy of the water level in the tank 52, while the overflow of the washing device 43 is evacuated by exit 47.

 The gases thus passing through the alkaline solution are rid of their acidity in the device 43 and the emissions to the atmosphere are thus purified.

 It will be noted that the source of steam to which the duct 33 is connected, in order to drive the dust coming from the filter 25, can be constituted by a bypass of the outlet 57 of the boiler.

 Finally, means 60 are provided connected to a water supply, in order to allow water to be injected into the circuit to control the temperature, for safety purposes, and the gases collected in the lantern 23 can also be derived directly into the atmosphere through conduit 26.

Claims (8)

 1. Installation for the destruction of various materials by incineration, of the type comprising a vertical tower or column in which the materials are introduced at its upper end and incinerated at its bottom, a combustion chamber and a steam-producing boiler heated by the combustion of the residual combustion and pyrolysis gases collected at. the upper part of the column, and means for purifying the gases, characterized in that it comprises a burner (31) mounted directly on the boiler (28) and fed by the gaseous products of the pyrolysis coming from the tower ( 21), means (25) between the tower and said burner for separating the dust from said gaseous products, a heat exchanger (37) connected to the outlet of the boiler (28), and means (29, 33, 57) for re-injecting said dust into the tower (21) with primary combustion air previously heated in said exchanger (37).  2. Installation according to claim 1, characterized in that said means between the tower (21) and the burner (31) are constituted by a device (25) for filtration and dedusting having means (29) for removing the collected dust connected to said means (33, 57) for re-injecting said dust into the primary combustion air.  3. Installation according to claim 2, characterized in that said heat exchanger (37) is supplied on the one hand with hot combustion gas by a conduit (38) for the outlet of the gases from the boiler and on the other hand with air under pressure from an external source (34).  4. Installation according to claim 3, characterized in that the air coming from said source (34), heated in the exchanger (37) is brought by a conduit (36) to a ramp (35) of air supply combustion at the bottom of the tower (21).  5. Installation according to claim 4, characterized in that the hot combustion gases supplying said heat exchanger (37) are led, at the outlet thereof, to a dust collector (32).  6. Installation according to claim 5, characterized in that it comprises a tank (52) for recovering the residual combustion slag falling from the lower part of the tower (21), containing water in which said partially dissolves slag to form an alkaline solution, a gas washing device (43), and a pump (59) supplying the washing device (43) to which it is connected by a conduit (51).  7. Installation according to any one of claims 1 to 6, characterized in that it comprises, at the upper part of the tower (21) means (55) for agitating the materials to be incinerated.  8. Installation according to any one of claims 1 to 6, characterized in that it comprises, at the upper part of the tower, means (55) for bringing down the materials to be incinerated in the tower, as and measurement of their combustion at the bottom of it.