EP0419365A1 - Device for injecting sludge into an incinerator - Google Patents

Abstract

Device making it possible to carry out the injection of sludge, originating in particular from waste-water purification stations, into the combustion chamber of an incinerator, in particular a domestic-waste incinerator, characterised in that it comprises at least one injector (10) of small diameter which passes through the means for thermal protection of the combustion chamber and is fed, according to a constant flow rate for all the injectors, by means of a distribution chamber (12), each injector being constituted by a tube (18) which has a cylindrical shape and comprises an endpiece of conical shape (20), on the combustion chamber side, with the large angle situated on the side of the outlet of the sludge from the injector, and in that the thermal control of each injector is carried out so as to obtain a linear temperature gradient all along the injector, carrying out the formation in the injector, gradually during injection, of a calibrated roll of sludge comprising a surface crust in the zone close to the combustion chamber. <IMAGE>

Description

The present invention relates to a device for carrying out an introduction by injection of sludge into the combustion chamber of an incinerator.

It is known that the combustion of sludge from wastewater treatment plants can be carried out in a household waste incineration oven. However, this combustion raises problems which are difficult to solve, in particular because of the high moisture content of the sludge and the need to ensure a regular and homogeneous introduction of the sludge into the incineration furnace.

At the present time, there are various methods and devices used for the introduction of sludge into household waste incineration ovens, among which there may be mentioned in particular:
- The introduction of sludge into the feed chute receiving the garbage using a feed system, for example of the Archimedes screw type. Such a solution leads to heterogeneity in the concentration of sludge at the level of the feed screw, which results in poor combustion;
- Pre-conditioning the sludge into granules with a low moisture content which are introduced into the combustion chamber of the incineration furnace at the same time as household waste, in the feed hopper of the latter. This known technique requires thermal drying which is costly in energy and investment without counting the handling, treatment and transport of the sludge, which of course increases the cost prices and can cause nuisance for the operating personnel;
- the projection of the sludge on the combustion grate of the incinerator using a feed system ensuring the crumbling of this sludge which must be distributed on the combustion grate. The difficult problem to solve here is that of the calibration of the sludge and its distribution over the surface of the combustion grate.

The present invention proposes to provide a solution which deviates from the solutions previously used to ensure the introduction of sludge into the combustion chamber of an incinerator by allowing a homogeneous supply of sludge by injection into the combustion chamber, according to a constant flow and in a form ensuring a fast combustion and without nuisance.

Consequently, the subject of the present invention is a device making it possible to inject sludge originating in particular from wastewater treatment plants, into the combustion chamber of an incinerator, in particular of a household waste incinerator. , characterized in that it comprises at least one injector of small diameter, passing through the thermal protection means of the combustion chamber and supplied, at a constant flow rate for all the injectors, via a distribution chamber, each injector being made up of a tube having a cylindrical shape and comprising a conical shaped end piece, combustion chamber side, with the wide angle situated on the side of the sludge outlet side of the injector and in that the thermal regulation of each inj ector is carried out so as to obtain a linear temperature gradient all along the injector by carrying out the training in the injector, as and when measured e of the injection of a calibrated rod of sludge comprising a superficial crust in the zone close to the combustion chamber.

According to a characteristic of the present invention, the diameter of each of the injectors is between 10 and 40 mm.

According to the invention, each of the injectors is provided with a cooling system designed so as to circulate a cooling fluid, in particular water, in an enclosure delimited between the injection tube and a sleeve surrounding said tube on the side of the foot of the injector, the injection of the coolant such as water into said enclosure being effected by a supply line opening into this enclosure under the injection tube, on the side of the injector foot, this cooling fluid vaporizing in said enclosure.

According to another characteristic of the device which is the subject of the present invention, the distribution chamber is of generally tubular shape, with constant section, and the surface of its straight section perpendicular to its longitudinal axis is greater than the sum of the surfaces of the sections of inlet of the injection tubes which open into the lower part of this distribution chamber. The sludge supply to this distribution chamber can be carried out either by one of its ends or from its upper surface, an evacuation for emptying being provided at one of the ends of the supply chamber.

According to the present invention, means are provided for ensuring the unclogging and / or cleaning and / or sealing of the different injectors, each of these means being constituted by a rod passing through the distribution chamber and penetrating into the tube. the corresponding injector up to the conical part of the latter, the diameter of each of the rods being less than that of the bore of the cylindrical part of the injection tube. These rods can be operated either manually or by any suitable motor device such as in particular jacks. They may be provided with recall means.

According to the invention, the sealing of each of said rods through the body of the distribution chamber is ensured by a system of seals and a grease box and the cooling of each of the rods when it is withdrawn from the injection tube. corresponding, after cleaning and / or sealing is obtained by passing the rod through the mass of sludge present in the distribution chamber and through the grease contained in said grease box.

• - la figure 1 est une vue schématique en plan de dessus illustrant un mode de réalisation du dispositif objet de la présente invention ;
• - la figure 2 est une vue de détail représentant en coupe axiale verticale un injecteur de boues conforme à la présente invention ;
• - la figure 3 est également une vue de détail en coupe par un plan vertical selon l'axe d'un injecteur et de sa tige de nettoyage et/ou d'obturation correspondante et ;
• - la figure 4 est également une vue de détail en coupe partielle Par un plan vertical illustrant un exemple de montage d'un injecteur de boues sur la paroi de la chambre de combustion d'un incinérateur.

Other characteristics and advantages of the present invention will emerge from the description given below with reference to the appended drawings which illustrate an example of it - an embodiment devoid of any limiting character. In the drawings:

• - Figure 1 is a schematic plan view from above illustrating an embodiment of the device object of the present invention;
• - Figure 2 is a detail view showing in vertical axial section a sludge injector according to the present invention;
• - Figure 3 is also a detail view in section on a vertical plane along the axis of an injector and its corresponding cleaning and / or sealing rod and;
• - Figure 4 is also a detail view in partial section on a vertical plane illustrating an example of mounting a sludge injector on the wall of the combustion chamber of an incinerator.

As specified above, the device which is the subject of the invention comprises at least one injector making it possible to introduce the sludge into the combustion chamber of an incinerator by passing through the thermal protections of this chamber or of the screens boiler furnaces. The problem solved by the invention is to provide a homogeneous and constant flow of sludge into this combustion chamber and for this purpose, in accordance with the invention, the sludge is spun through each injector which is thermally regulated so to calibrate the mud flange thus introduced into the combustion chamber.

Referring to the drawings, it can be seen that the device which is the subject of the present invention essentially comprises the following elements:
- at least one injection tube designated as a whole by the reference 10;
a chamber 12 of particular configuration making it possible to produce a homogeneous distribution and at a constant flow rate of each injector 10 leading to this distribution chamber;
- Means designated as a whole by the reference 16 making it possible to cool the injectors 10;
- Means designated as a whole by the reference 14 which are designed so as to provide cleaning and / or cleaning and / or sealing of each injector 10 and;
- Means for performing a drain and cleaning during prolonged shutdown of the device.

It is also possible, according to the invention, to provide a system for managing, by automaton, the various commands and the safety features of this sludge injection device.

Referring more particularly to FIG. 2, it can be seen that each injector consists of a tube 18 of cylindrical shape, the mouth side 20 of which has a conical shape with a large diameter located on the side of the sludge outlet, this in particular in order to 'avoid jams, as will be described below. The other end of the injection tube 18 is fixed to the distribution chamber 12 by any suitable means, for example by a system of flanges and nuts as can be clearly seen in FIG. 2.

Each of the injectors has a small inlet diameter which, according to the present invention, is between 10 and 40 mm. Its length is for example of the order of 350 mm between the entry of the sludge at the foot of the injector and their exit at the end of the nozzle 20 of the latter.

FIG. 4 illustrates by way of non-limiting example a method of mounting an injector 10 on the fin of the screen tubes 60 of the wall 62 of a household waste incineration oven. We can consider other fastening systems for example directly on the structure of the combustion chamber or in the masonry of an incinerator without recovery system.

The sludge supply to each injector such as 10 is carried out using the distribution chamber 12 to which the sludge is delivered using a supply pump (not shown in the drawing). As can be seen in FIG. 3, this chamber is in the form of a body 40 of generally tubular shape, the upper part 42 of which is removable so as to be able to act as an inspection hatch. The introduction of sludge into this distribution chamber can be carried out either through one of the end walls of the chamber or by means of an introduction orifice provided on the upper part 42 of the body of this room. In the nonlimiting exemplary embodiment shown in the drawing, the introduction of the sludge is carried out by means of a supply pipe 44, at one of the ends of the body 40, on which a inlet valve 46. The end of the body of the distribution chamber opposite the arrival of the sludge (tubing 44) is provided with a sewerage tubing 36 provided with a valve 38.

As can be seen in Figure 3, the lower part of the body 40 of the distribution box has orifices 48 on each of which opens an injector. According to the invention, to ensure a homogeneous supply and at constant flow rate of each injector such as 10, the surface of the cross section perpendicular to its longitudinal axis, of the distribution chamber 12, is greater than the sum of the surfaces of the orifices 48 through which the sludge supply to each injector tube takes place.

The part located on the foot side of each injector (that is to say on the side of the distribution chamber 12) is provided with a sleeve 22 surrounding the cylindrical tube 18 thereby providing a chamber 24 in which a cooling fluid circulates , in particular water, which vaporizes in said chamber. This coolant is introduced into the chamber 24 using a supply pipe which opens out through an orifice 26 provided under the lower part of the sleeve 22 as can be see in Figure 2, this orifice 26 being located near the foot of the injector. The coolant outlet takes place through an orifice 28 disposed on the sleeve 22 opposite the orifice 26. In FIG. 1 we can see the pipe 30 which makes it possible to supply the fluid with cooling. The fact of introducing this cooling fluid from below the tube of each injector makes it possible to obtain a difference in level with the outlet orifice 28, which ensures the constitution of a guard, the overflow being able to possibly be poured into the tube 36 for draining the body of the distribution chamber 12 downstream of the drain valve 38 of this body. The flow rate of this fluid can be adjusted either manually or automatically using a valve 32 mounted on the tube 30, this valve being able to be controlled in flow rate thanks to a sensor and to a temperature regulator 34 which are placed on the wall of the distribution chamber 12 (FIG. 3).

Cooling of the injectors such as 10 by circulation of water is necessary in particular in the case of a rise in temperature beyond the acceptable limit for all the components of the device. The cooling during the injection of the sludge being obtained by the circulation of the sludge through the injector.

The invention provides means for ensuring cleaning and / or cleaning and / or sealing of each injector tube. In the embodiment shown in the drawings and more particularly in Figure 3, these means comprise for each injector a rod 50 which passes through the wall of the body 40 of the distribution chamber through an orifice 49 which is located in view of the orifice 48 through which the sludge supply to the injector concerned takes place. This rod has a diameter smaller than that of the tube 18 of the injector and its stroke is determined so that it penetrates this tube up to the conical part 20 of the latter. By way of nonlimiting example, it will be indicated that for a value of injector inlet diameter of 22 mm each cleaning rod will have a diameter of 20 mm. The end piece of the rod 50 acts as a cookie cutter with the orifice 48. The rods such as 50 can be actuated by any suitable means, in particular using cylinders 52, pneumatic, hydraulic, supplied with the aid of a distributor 78 or mechanical cylinders. A system of seals, for example a lip seal 54 is interposed between each rod 50 and a spacer 56 ensuring the connection between the body 40 of the distribution chamber and the cylinder of each jack 52 and a box is further provided. grease 58 which is placed in front of the fixing means of each jack 52.

During the injection of the mud each rod such as 50 is in the retracted position, as shown in FIG. 3, and the movements of advancement and retreat of the rods such as 50 only intervene in the event of stuffing of an injector. In this case, at each prolonged stop of the device, the rod 50 is introduced into the tube of the corresponding injector and it is maintained in this position in order to fulfill the following functions:
- stop the injection of sludge;
- obstruct the entry into the device of gases or high temperatures prevailing in the incinerator;
- prevent drying of the mud;
- isolate the sludge supply body from the distribution chamber 12 in order to ensure its cleaning.

It will be noted that according to the present invention, each rod 50 when it is withdrawn from an injector 10 after cleaning is cooled by passing through the mass of sludge which is contained in the distribution chamber 12 and then by passing through the grease enclosed in the grease box 58. Furthermore, the presence of this grease which is deposited in the form of a thin film on the outer periphery of the rod 50 makes it possible to ensure self-cleaning of this rod by avoiding collage of sludge.

Means are also provided for draining and cleaning the device described above during prolonged shutdown of the device according to the invention. In fact, in the event of the device stopping, it is necessary to drain and clean the distribution chamber 12 in order to avoid the accumulation of sludge and their drying in this chamber.

The device therefore comprises cleaning nozzles such as 64 which are preferably arranged on the upper part of the body 34 (see FIG. 3), these nozzles 64 being able to be alternately supplied with compressed air and pressurized water respectively using supply circuits 66, 68 and valves 70 and 72.

The emptying is carried out by closing the valve 46 for supplying sludge, by opening the valve 70 of the compressed air circuit 66 so as to supply the cleaning nozzles 64 leading to the distribution chamber 12. The sludge contained in this chamber is driven through the injector (s) such as 10 and the level of sludge in the chamber 12 drops to the upper part of the holes 48 on which the injectors open. The compressed air inlet valve 70 is then closed, the injectors are closed by means of the rods 50, the drain valve 38 is opened and the cleaning water inlet valve 72 is opened . This water introduced into the distribution chamber 12, using the nozzles 64, cleans this chamber and the debris is expelled towards the sewer through the evacuation pipe 36. When the cleaning is finished, the valve 72 is closed. . When the injection device is put back into operation, the valve 38 is closed, the sludge supply valve 46 is opened and the device can be returned to operation on the understanding that the rods 50 are in the retracted position. The injector sludge supply can then resume.

It will be noted that this system of cleaning nozzles 64 can also be used for the introduction under pressure of a disinfectant product into the distribution chamber.

The device which is the subject of the invention makes it possible to produce a homogeneous supply and at constant flow rate of the sludge into the combustion chamber of an incinerator. This supply takes place in the form of a rod which is spun through each of the injectors. Taking into account the temperature regulation according to a linear gradient along each of the injectors, a calibrated and homogeneous supply is obtained. In addition, the characteristic according to which the nozzle of each injector is of conical shape allows penetration of the hot gases coming from the combustion chamber between the external periphery of the rod formed and the wall of the nozzle of the injector, which ensures the formation of a superficial crust on the rod improving the combustion of the latter and also effecting a self-cleaning of the end of each injector.

According to the present invention, it is preferable to use a plurality of injectors regularly distributed along the base of the distribution chamber. Excellent results have been obtained on an incineration furnace having a flow rate of 6 tonnes / hour of household waste with a device according to the invention, as described above comprising 22 injectors each having an internal diameter of 22 mm , the hourly sludge injection rate then being 1 ton / hour, the injected sludge having a dry matter content of 25%. The injection pressure in the distribution chamber 12 was 0.8 bar.

The device which is the subject of the present invention can operate without automation with a simple overpressure alarm in the body of the distribution chamber and a system for controlling the stopping of the sludge pump in this chamber in the event that the critical threshold, this alarm can be controlled from a pressure sensor 74. However, it may be preferable to provide automation in particular in order to reduce very significantly the monitoring and intervention times. According to a characteristic of the present invention, this automation allows:
- maintain an appropriate pressure inside the distribution chamber 12;
- ensure that an injector is cleaned as soon as the pressure rises;
- Check the stroke of the rods 50 for cleaning and sealing the injectors;
- trigger the alarms;
- controlling the sludge feed pump in the distribution chamber 12;
- to clean the injector tubes at determined frequencies.

The automation equipment used comprises pressure sensors 74 placed at the entrance to the distribution chamber, a programmable controller 76 and a cooling control system comprising in particular the thermostatic valve 32 provided on the supply line 30 for injector coolant.

• 1° - Un premier seuil de surpression, le plus bas, indiquant soit un bourrage d'un ou de plusieurs injecteurs ou d'orifices tels que 48 de la chambre de distribution 12, soit un changement de la qualité de la boue injectée. On déclenche alors une alarme.
• 2° - Un deuxième seuil de surpression, continuation de la montée en pression, l'automate 76 envoie alors un signal électrique au distributeur 78 du vérin 52 concerné. La tige 50 de ce vérin fait alors un aller et retour dans la tubulure de l'injecteur correspondant pour en assurer le débourrage.
• 3° - Troisième seuil de surpression, la surpression maximale est atteinte, l'automate 76 arrête alors l'alimentation électrique de la pompe d'amenée des boues.

According to the invention, three overpressure thresholds can be provided:

• 1 ° - A first overpressure threshold, the lowest, indicating either a blockage of one or more injectors or orifices such as 48 of the distribution chamber 12, or a change in the quality of the slurry injected. An alarm is then triggered.
• 2 ° - A second overpressure threshold, continuation of the pressure build-up, the automaton 76 then sends an electrical signal to the distributor 78 of the cylinder 52 concerned. The rod 50 of this jack then goes back and forth in the tubing of the corresponding injector to ensure cleaning.
• 3 ° - Third overpressure threshold, the maximum overpressure is reached, the automaton 76 then stops the electrical supply to the sludge supply pump.

According to the invention, a programmed cleaning cycle can be provided, the execution of which makes it possible to avoid reaching the pressure and maintain a constant calibration of the sludge (s) introduced by the injector (s) into the incinerator.

Finally, according to the invention, magnetic end-of-travel sensors are shown diagrammatically at 80 in FIG. 3, making it possible to detect operating anomalies of the cleaning means and to facilitate interventions.

Claims (10)

1. Device making it possible to inject sludge originating in particular from wastewater treatment plants, into the combustion chamber of an incinerator, in particular of a household waste incinerator, characterized in that it comprises at least one injector (10) of small diameter, passing through the thermal protection means of the combustion chamber and supplied, at a constant flow rate for all the injectors, via a distribution chamber (12), each injector consisting of a tube (18) having a cylindrical shape and comprising a conical shaped nozzle (20), on the combustion chamber side, with the wide angle situated on the side of the sludge outlet of the injector and in that the thermal regulation of each injector is carried out so as to obtain a linear temperature gradient all along the injector by carrying out the formation in the injector, as the injection takes place, of a flange ca freed from sludge with a surface crust in the area near the combustion chamber. 2. Device according to claim 1, characterized in that the diameter of each of the injectors (10) is between 10 and 40 mm. 3. Device according to one of claims 1 or 2, characterized in that each of the injectors (10) is provided with a cooling system (16) designed so as to produce a circulation of a cooling fluid, in particular of water, in an enclosure (24) delimited between the injection tube (18) and a sleeve (22) surrounding said tube on the side of the foot of the injector, injecting the coolant such as water in said enclosure being effected by a supply pipe (30) opening into this enclosure by an orifice (26) positioned under the injection tube, on the side of the injector foot, this cooling fluid vaporizing in said enclosure. 4. Device according to any one of the preceding claims, characterized in that the distribution chamber (12) comprises a body (40) of generally tubular shape and of constant section, and the surface of its cross section perpendicular to its longitudinal axis is greater than the sum of the surfaces of the sections of the orifices (48) for entry of the injection tubes which open into the lower part of this distribution chamber. 5. Device according to claim 4, characterized in that the supply of sludge to this distribution chamber can be carried out by an intake pipe (44) provided either at one of its ends or on its upper surface, an outlet (36) being provided for emptying at the end opposite to the supply. 6. Device according to any one of the preceding claims, characterized in that means are provided for ensuring the unclogging and / or cleaning and / or sealing of the different injectors, each of these means being constituted by a rod (50) passing through the wall of the distribution chamber (12) and penetrating into the tube of the corresponding injector up to the conical part of the latter, the diameter of each of the rods being less than that of the bore of the cylindrical part of the injection tube. 7. Device according to claim 6, characterized in that said rods (50) can be operated either manually or by any suitable motor device such as in particular pneumatic, hydraulic or mechanical jacks and they can be provided with return means. 8. Device according to one of claims 6 or 7, characterized in that the sealing of each of said rods (50) through the wall of the body (40) of the distribution chamber is ensured by a system of seals ( 54) and a grease box (58) and the cooling of each of the rods when it is withdrawn from the corresponding injection tube, after cleaning and / or sealing is obtained by passage of the rod through the mass of sludge present in the distribution chamber and through the grease contained in said grease box. 9. Device according to any one of the preceding claims, characterized in that a drainage and cleaning system is provided during prolonged stops of the device which comprises cleaning nozzles (64) opening into the supply chamber ( 12) and through which compressed air is successively blown to expel the sludge in the different injectors, then pressurized water and / or a disinfectant liquid for cleaning the distribution chamber. 10. Device according to any one of the preceding claims, characterized in that it operates under the control of an automation system comprising a programmable controller (76), pressure sensors (74) placed at the input of the distribution chamber and a system for regulating the cooling of the injectors, the automation being designed so as to ensure the following functions: maintaining the correct value of the pressure inside the distribution chamber 12; cleaning of any of the injectors as soon as the pressure rises therein; check the stroke of the rods (50) of the cleaning and sealing means of the injectors; trigger alarms; control the sludge feed pump of the distribution chamber; clean the injectors according to programmed frequencies.

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