EP0566527B1 - Method of operation for the pit of a refuse incineration plant - Google Patents

Description

The present invention relates to a waste management method for a pit for the supply of at least one oven capable of supplying at least one boiler of an incineration plant, this pit comprising a plurality of accesses, respectively of doors , by which means of collection, for example trucks, responsible for the collection of the refuse unload their contents, and at least one means of elimination, for example a grab of overhead crane, making it possible to collect a quantity of refuse at a point on the upper surface of the pile contained in the pit in order to bring them to feeding means, for example loading hoppers, one or more incineration ovens.

Every garbage incineration plant has a garbage pit into which trucks are discharged ensuring the urban collection of household or industrial garbage. This pit plays the role of regulator, of buffer stock, between intermittent arrivals of garbage, massive at certain times of the day and the furnaces providing thermal energy to the boiler or boilers, and whose rate of elimination in tape is defined by their power.

Currently, the available volume of the pit is managed solely according to the topography of the upper surface of the garbage heap, i.e. each truck arriving to unload its contents is addressed to the door behind which the heap garbage is the lowest. Conversely, the crane operator maneuvering the overhead crane which dominates the pit feeds the hoppers of the ovens by removing material from the highest points of the pile. The topography of the refuse heap therefore plays a preponderant role in managing the entry and exit of refuse from a pit according to the prior art.

Patent US-A-4,882,903 describes an incineration plant with energy recovery where the trucks, after being weighed and their contents have been picked up, will unload their garbage on a dumping site. Subsequently, the garbage is collected and pushed to treadmills for then be sorted by conventional means before being burned. No indication is given in this document on the use of the contents of each truck; in fact it could not be used for optimizing the operation of the installation given the passage through an intermediate phase of storage on a discharge site.

In patent JP-A-58.22.203, the mass of garbage from each truck is raised in order to direct the incoming truck towards the smallest pile. No reference is made to a statement of the calorific value of incoming garbage.

The incineration plant described in US-A-5,033,011 includes a pit crane control device making it possible to raise the height of each pile by measuring the position of the crane carriage and then the length of the grab suspension cable in contact with the top surface of the pile.

The one described in Proceeding IECON'84 of October 22, 1984, by M.Kawakami et al. under the title "The full automatic control system of the refuse grabbing crane" includes a device for automatically conducting a stacking process for the homogenization of the garbage heap, without the calorific value of the incoming garbage being relieved of any kind way.

It is important that the ovens do not undergo too rapid variations of regime by successively burning garbage having a lower calorific value (PC _i ) very low then very high. This remark is also valid for the subsequent operations of purification and washing of the fumes, in particular for the operation of deNOX by treatment of the fumes with urea or ammonia, for which the temperature of the gases must be at a determined level, as constant as possible, in the combustion chamber. To obtain this in the pits managed according to the prior art, the crane operator must endeavor to homogenize the quality of the garbage contained in the pit, by constantly mixing the heterogeneous garbage dumped opposite each door. This stacking operation mobilizes staff and the overhead crane excessively.

A first object of the invention is to propose a method for managing the refuse in a refuse pit when they arrive, so as to equalize the PC _i between the different portions of the pile of refuse contained in the pit. The main advantage of a management according to this process resides in the elimination of the stacking operation and consequently a strong reduction of work for the crane operator and the overhead crane, while ensuring the supply of a fuel to PC _i relatively constant at ovens. The management of the discharge of refuse from the pit to transport it to the ovens can be carried out in the conventional manner.

This first object of the invention can be achieved by managing a pit according to the method indicated in the first claim.

A second object of the invention is to propose a method in which the management of the exit of the refuse from the refuse pit is also controlled, so as to automate the operations of stacking and removal of refuse from the pit to convey them to the ovens. The main advantage of management according to this process lies in the fact that the automation of the process makes it possible to greatly reduce the workload of the crane operator, or even to eliminate this work station.

This second object of the invention can be achieved by managing a pit according to the method indicated in the second claim.

A third object of the invention is to complete the previous process in order to further reduce the load of the crane operator while having refuse, respectively a fuel with a PC _i as homogeneous as possible.

This third object of the invention can be achieved by the management of a pit according to the method indicated in the third claim.

Another object of the invention is to propose a device, according to several embodiments, which can carry out one or the other of the preceding methods for managing a refuse pit.

This object is achieved by a device as described, according to several embodiments, in claims 4 to 15.

Finally, a final object of the invention is to propose a refuse pit which can be managed according to one of the methods mentioned above, as described in claim 16.

• la figure 1 représente une vue schématique en plan d'une partie d'une installation d'incinération d'ordures,
• la figure 2 représente une coupe longitudinale d'une fosse d'ordures prise selon la ligne II-II de la figure 1, et
• la figure 3 représente une coupe transversale d'une fosse d'ordures prise selon la ligne III-III de la figure 1.

The following description explains the invention with reference to the drawing with the figures where:

• FIG. 1 represents a schematic plan view of a part of a waste incineration installation,
• FIG. 2 represents a longitudinal section of a refuse pit taken along line II-II of FIG. 1, and
• FIG. 3 represents a cross section of a refuse pit taken along line III-III of FIG. 1.

A garbage incineration plant, only part of which is shown diagrammatically in plan in Figure 1, includes in particular a garbage pit 1, the roof of which has been removed in the figure in order to make it possible to distinguish the interior thereof , an access 2, by which the means for collecting the refuse, here trucks 3, enter the enclosure of the installation, as well as supply means 4 for incineration furnaces represented at 40 in FIG. 2.

The refuse pit 1 is of a design absolutely similar to those already known, it generally has the shape of a rectangular parallelepiped, one of the faces of which having the length of said parallelipiped is provided with a plurality of doors 10 through which the refuse are dumped by a truck 30 on a portion 50 of the rubbish heap 5 of the pit. Preferably the height of the pit is greater than its width. As seen in Figures 2 and 3, the doors 10 are generally arranged side by side on one face of the pit 1, the latter being semi-buried as in Figure 3, or an access ramp being provided so that the trucks 30 can access the doors from the outside 10. The pile of garbage 5 contained in the pit 1 has the general shape of a succession of portions of trunks of cones arranged behind each door 10. As can be seen in Figure 3, the cross section of the portion 50 of the pile 5 shows a slope rising from the bottom wall of the pit to a part of the front wall located directly under a door 10, while in Figure 2 we see that the distribution is quite irregular, some of the trunks of cones rising higher than others, depending on the number of trucks that have spilled through the door in question and the samples taken so far. In a pit managed according to the prior art, the truck 3 is first of all weighed by a balance, represented in FIG. 1 only by its platform 20, in order to know the tonnage of materials entering the pit 1, then is directed towards the door 10 where the portion 50 of the pile of garbage 5 is the lowest, while the overhead crane 11, provided with its grab 12, being able to circulate over the entire length and the entire width of the pit 1, works constantly in order to try to homogenize the heap 5 by stacking as well as possible, in order to provide the hopper shown diagrammatically in 4 with materials to be burned having a calorific power as constant as possible.

• une première touche A correspondant à des déchets très riches à très haut pouvoir calorifique inférieur (PC_i de environ 3600 kcal/kg) contenant principalement du bois ou du plastique, provenant en particulier de démolitions d'immeubles,
• une deuxième touche B, correspondant à des déchets relativement riches à haut pouvoir calorifique inférieur (PC_i de environ 3000 kcal/kg) contenant principalement du carton ou du papier, provenant en particulier de l'industrie, de l'artisanat ou du commerce,
• une troisième touche C, correspondant à des déchets moins riches à pouvoir calorifique inférieur moyen (PC_i de environ 2400 kcal/kg) contenant principalement des déchets ménagers, provenant de la récolte des sacs poubelles, et
• une quatrième touche D, correspondant à des déchets assez pauvres à faible pouvoir calorifique inférieur (PC_i de environ 500 kcal/kg) contenant principalement des déchets organiques comme de l'herbe, des feuilles ou des légumes.

A pit managed according to the garbage management method according to the invention comprises, in addition to that described above, preferably near the scale 20 which determines the mass of incoming garbage, a means of introduction 21 of the estimated calorific value garbage being weighed. For this, the driver of the truck 3 preferably has a box 21 on which he displays a code corresponding to his estimate of the calorific value of the garbage he brings; the housing can comprise, for example, several keys, each of them corresponding to a type of garbage, respectively a given lower calorific value. We can have, for example:

• a first touch A corresponding to very rich waste with very high lower calorific value (PC _i of about 3600 kcal / kg) containing mainly wood or plastic, in particular from building demolitions,
• a second key B, corresponding to relatively rich waste with a high calorific value lower (PC _i of about 3000 kcal / kg) containing mainly cardboard or paper, coming in particular from industry, crafts or commerce,
• a third key C, corresponding to less rich waste with an average lower calorific value (PC _i of around 2400 kcal / kg) containing mainly household waste, originating from the collection of garbage bags, and
• a fourth key D, corresponding to fairly poor waste with low calorific value (PC _i of about 500 kcal / kg) containing mainly organic waste such as grass, leaves or vegetables.

A fifth key M, called "moderation" can allow to qualify, for example downward, each of the previous estimates in order to take account of a particularly inhomogeneous loading from the point of view of PC _i .

Thus, using five keys, it is possible to estimate the PC _i of the load in a fairly fine way, since the driver has eight possible values. It is obvious that the introduction means can be designed differently from what has just been described, one can have a higher or lower number of keys, which gives a finer, respectively coarser choice of the PC _i , the values selected may be different from those indicated above in the form of examples, just as the means used to indicate the estimate of PC _i may be different from those described; for example, the housing 21 may include a certain number of keys relating to particular materials or types of garbage such as wood, plastic, household waste, etc., as well as other keys making it possible to display a percentage, which allows the driver to indicate the contents of his load such as: household waste - 30%, construction waste - 40%, garden waste - 30%. The box 21 can also include means 22 by which the driver indicates, in a manner known in the art, for example using a magnetic card or keys, his identity and / or the reference of his vehicle, for control.

Calculation means 6, for example a microcomputer, receive the indication of the mass of incoming garbage, weighed by the balance 20, as well as the estimated PC _i of said garbage, or their composition, introduced in the manner described above. . Since, on the other hand, the computer 6 knows the value of the average PC _i of each of the portions 50 of the pile of garbage 5 contained in the pit 1, since it has kept in memory the values corresponding to the previous arrivals and the withdrawals by the bucket 12, it can indicate to the driver, by any display means 23, to which door he must go to empty his truck, so that the average PC _i between the different portions 50 is the most homogeneous possible.

For example, as can be seen in FIG. 3, if a truck has dumped, by PC _i a given door on a portion 50 of pile 5, a load with very high value of PC _i , and that said garbage has been distributed during of their discharge in a relatively thin layer 51 on the upper surface of the portion 50, the calculation means will wait for a loading with a low PC _i value to indicate the same door to it, so that its garbage also covers in the form of a layer thin 52 those previously filed. Each portion 50 of the heap 5 therefore comprises a succession of thin layers, each of said layers possibly having a different value of PC _i , the succession of values of PC _i between the different portions 50 possibly being different for each portion 50. The succession of each layer is determined by the calculation means 6 so that the average PC _i inside a portion 50 and of the complete pile of garbage 5 is as homogeneous as possible.

During the removal of garbage by the bucket 12 of the traveling crane 11, for the supply of a hopper 4, since the bucket only collects garbage at a fairly limited point in a portion 50, it penetrates across several thin layers, so that its loading has a relatively homogeneous PC _i .

In the case where, for example, the incineration plant comprises a shredder, generally delivering an excellent quality fuel with a very high PC _i value, the means for collecting the shredded waste can be, for example, one or more belts rollers 7, including a mat 70 at least, enters through an access 13 inside the pit 1 and is capable of distributing the shredded waste on one or other of the portions 50, for example by means of dumping 71 known in the art, in order to increase the average PC _i of the portion considered. It is also possible for the conveyor belt 70 to pour the shredded waste into a determined location in the pit, an adequate program being installed in the calculation means 6, in order to automatically control the overhead crane 11 so that it distributes this waste on a heap 50 with low PC _i value.

The method of managing the refuse of a pit according to the method described above already represents a significant improvement compared to a conventional management, insofar as the ovens are supplied with a relatively constant PC _i fuel without it being necessary to stack the pile of garbage.

Simultaneously with the process described above, the pit management process can also include a management phase applied to the outlet of the waste to the incineration furnace (s).

For this, the pit 1 is equipped with detection means 8 making it possible to detect the general shape of the pile of refuse 5 as well as the height of said pile in the pit. These detection means can be of any type known in the art, consisting for example of a plurality of devices 80 arranged against the underside of the upper wall of the pit, for example a pair of devices 80 for each portion 50, the first being placed above the upper part of the portion while the second is arranged above the lower part of the same portion, as shown in FIGS. 1, 2 and 3, or else in another place as for example a single device 81 per portion 50, arranged for example against an upper part of the wall facing the doors 10, as shown in FIG. 3. Each device 80 or 81 is preferably a transmitter / receiver, transmitting and receiving electro- suitable magnetic to estimate, using the computer 6 for example, the configuration and the height of each of the portions 50. The electromagnetic radiation used must be chosen so as not to be disturbed by the dust cloud prevailing in the pit; the best results have been obtained by electromagnetic radiation corresponding to radar waves. Since, as indicated above, the shape of the refuse pile 5 inside the pit has a relatively known shape, a succession of portions of trunks of cones, it is possible to obtain a good approximation of a representation of the upper surface of the pile 5 by measuring the position only of a limited number of points on this surface. the devices 80 and 81 have been described as having simultaneously a transmission function and a reception function; it is obvious that these two functions can be dissociated, just as it is possible to use fewer devices 80 or 81 than mentioned, each of them controlling for example a larger portion of the upper surface of the pile and of even it is possible that the devices 80 or 81 are placed in other places than described, provided that they are not hindered or reached by the overhead crane 11 or the bucket 12. It is also possible to install one or more device 82 directly under the overhead crane 11, the scanning of the upper surface of the pile being made according to the movement of the overhead crane.

By a mathematical relation connecting the positions of the various measured points of the upper surface of the heap 5, it is possible to establish the general shape of this surface with sufficient precision, by the calculation means 6 (see FIG. 1) which can be the same as those managing the entrances to the pit or which may be different, for example a separate microcomputer. Thus, by detection means 8 and calculation means 6 as indicated, it is possible to know the topography of the upper surface of the pile 5 without direct vision of a crane operator. It is therefore possible, by adequate programming of the calculation means 6, to automatically control the overhead crane 11 and the bucket 12 so that the latter goes to look for material at a determined location, preferably on the most 50 high.

The topography of the upper surface of the pile 5, approximated by the calculation means 6, can be represented graphically in three dimensions on a control screen arranged for example in the control room, thus allowing the operator to make a good idea of the appearance of this surface. The calculation / graphical representation program can also represent a determined section through the pile at the operator's choice, for example a transverse section at the right of one or the other of the doors 10 or else a longitudinal section over all or only part of the length of the pit. In addition to this calculated representation of heap 5, a direct view of the pit or via a television camera and a screen can help improve the calculated representation by possibly correcting one or the other of the calculated parameters in order to improve the representation graphic of the top surface of the heap.

The calculation means 6 may include an automatic stacking program allowing this operation to be carried out without the presence of a crane operator.

Thus, from a pile 5 homogenized by control of the inputs possibly supplemented by stacking, the calculation means 6, from an adequate program, can automatically control the overhead crane 11 and the bucket 12 in order to feed the hoppers 4 of the incineration ovens 40.

The start of the loading process of a hopper 4 is preferably controlled by a detection of a minimum level of the hopper; the overhead crane 11 and the bucket 12 are then directed in order to go to be placed at a point in the pit superimposing the portion of the upper surface of the pile 5 located at the highest altitude. The bucket 12 is then open, then it is lowered to contact with the pile 5, this position being detectable by a strain gauge 13 placed on the overhead crane and which is suddenly discharged from the tare of the bucket 12. The closure bucket 12 is then controlled as well as its ascent. On the first meters of this ascent, the strain gauge 13 measures the net load collected by the bucket; if this load is less than a predetermined limit value, the raising of the bucket is interrupted and its opening is commanded again in order to discharge its content, it then descends for a new take as before. As soon as the strain gauge 13 measures a sufficient load, respectively greater than the predetermined limit value, the bucket 12 is completely raised, then moved by the overhead crane 11 in order to bring and discharge its contents into the hopper 4 from which the order to start the process had been given. The process described above by which the load of the bucket is controlled makes it possible to guarantee a sufficient supply of the hoppers, by limiting the displacements of the overhead traveling crane 11 and moreover makes it possible to guarantee that the grab has collected refuse in several of the layers 51, 52, ..., which homogenizes the calorific value of the load.

One can summarize here the various advantages brought for the exploitation of a refuse pit according to whether only its entries or its entries and its exits are managed by a method according to the invention.

In the case where only the entry of refuse into the pit is managed by the process described, tending to homogenize the pile of refuse by a controlled dumping of each truck, it is possible to dispense with the stacking operation, which greatly saves the use of the overhead crane thereby reducing the work of the crane operator.

In the case where the removal of refuse from the pit is also managed by the process described, tending to automatically control the shape and dimensions of the pile of refuse, it is possible to dispense with the presence of the crane operator, a commanding program automatically the loading operations of the oven hoppers and possibly stacking.

The use of each of the methods makes it possible to reduce the operating costs of the incineration plant, the maximum saving being achieved when both the entry and the exit of the refuse are managed by the process according to the invention.

We have seen that for the management of garbage entries, it is necessary to estimate the value of the lower calorific value of the load; from these estimates and the tonnage poured into the pit, measured by the balance 20, the calculation means 6 can continuously calculate the energy reserve available in the pit, respectively the possible operating time, thereby optimizing the operation of the ovens, which also tends to reduce operating costs. The calculated energy value of a given quantity of garbage can be compared to the energy produced by their combustion, taking into account the efficiency of the furnace. It is thus possible to determine a correlation coefficient making it possible to know whether the estimated value of the PC _i made during the weighing of the trucks is correct.

avec: E_v

= énergie de la vapeur produite par la chaudière (Mwh)

η

= rendement combiné du four et de la chaudière

P_o

= masse des ordures ayant produit Ev (kg)

PC_i

= pouvoir calorifique inférieur moyen estimé de la masse P_o (kgcal/kg)

The correlation index I _c is given by: $${\text{I}}_{\text{vs}}\text{=}\frac{{\text{E}}_{\text{v}}{\text{0.8610}}^{\text{6}}}{{\text{ηP}}_{\text{o}}{\text{· PC}}_{\text{i}}}$$

with: E _v

= energy of the steam produced by the boiler (Mwh)

η

= combined efficiency of oven and boiler

P _o

= mass of garbage having produced Ev (kg)

PC _i

= estimated lower average calorific value of the mass P _o (kgcal / kg)

If I _c is generally greater than 1, the estimated PC _i is overvalued, while if I _c is generally less than 1, the estimated PC _i is undervalued. A correction can be made either by instructing the truck drivers to correct their estimate in the desired direction, or by correcting the estimated value by an appropriate weighting in the calculation means 6. These calculations and corrections will preferably be done over a period long enough to gradually move towards an increasingly precise calculation of the thermal load available in the pit.

Using the above relation, the parameters introduced or measured elsewhere make it possible to provide operating values of the incineration plant, for example that of the energy in stock, of the number of operating hours. ovens as well as the average lower calorific value of the fuel burned during a given period. These values can also be displayed in the factory control station by appropriate means 60, in order to aid in its management.

Claims (16)

1. Method of management of refuse in a pit (1) for feeding at least one furnace able to feed at least one boiler of an incineration plant, the said pit having a plurality of accesses (10, 13) through which collecting means (30, 70) responsible for the collecting of refuse unload their contents, and at least one elimination means (11, 12) permitting the removal of a quantity of refuse at a point on the upper surface of the heap (5) contained in the said pit in order to take the refuse toward means of feeding (4) one or a plurality of incinerators,

   characterized in that

   the bulk of the contents of each of the said collecting means is measured (20),

   an estimate of the average calorific value of the contents of each of the collecting means is introduced (21) into the computation means (6),

   the said computation means (6) indicate to each of the said collecting means (30) an access (10) to the pit (1) for dumping its contents there, the said access being determined in such a way that the average calorific value of the refuse contained in the pit must be as homogeneous as possible.
2. Method according to claim 1, characterized in that

   the topography of the upper surface of the refuse heap (5) in the pit (1) is detected by detection means (8) having a plurality of electromagnetic wave transmitter-receiver devices (80, 81, 82) and is registered by the said calculation means (6),

   the said elimination means (11, 12) are actuated by the said calculation means to dump the refuse situated at a given point of the refuse heap.
3. Method of management according to claim 2, characterized in that it includes an automatically controlled piling operation.
4. Device for the management of a refuse pit according to the method of claim 1, characterized in that it comprises in particular:

   means of weighing (20) the bulk of the content of each of the collecting means (3),

   means of introducing (21) the estimated average calorific value of the contents of each of the collecting means,

   calculation means (6) permitting, starting from the mass as well as the estimated average calorific value of the contents of each of the collecting means, to determine an access (10) to the refuse pit through which the said contents are dumped onto a portion (50) of a refuse heap (5), in such a way that the average calorific value of the said heap is as homogeneous as possible.
5. Device according to claim 4, characterized in that it additionally comprises:

   means of detecting (8) the topography of the upper surface of the refuse heap having a plurality of electromagnetic wave transmitter-receiver devices (80, 81, 82),

   and in that the calculation means (6) permit recording and estimating the said topography on the basis of information provided by the said detection means and actuating the elimination means (11, 12) to dump the refuse situated at a determined point of the refuse heap.
6. Device according to claim 5, characterized in that the calculation means (6) include a programme for graphically representing the topography of the refuse heap.
7. Device according to claim 6, characterized in that the calculation means (6) permit the automatic control of the said elimination means for an automatic piling operation.
8. Device according to claim 4, characterized in that the means of introducing (21) the estimated average calorific value of the contents of each of the collecting means includes a device permitting introduction into the calculation means of at least one pre-determined calorific value or the composition of the contents of the said collecting means.
9. Device according to claim 8, characterized in that the calculation means (6) permit calculating the available thermal energy in the refuse contained in the pit.
10. Device according to claim 9, characterized in that the calculation means (6) permit calculation of a correlation coefficient by comparing the calorific energy provided by the boilers with the thermal energy calculated on the basis of the estimated average calorific value and the measurement of the bulk of each of the loads of refuse.
11. Device according to claim 10, characterized in that it additionally comprises means of displaying (60) operational parameters of the incineration installation, in particular of the stored energy and/or of the possible duration of operation of the furnaces and/or of the lower average calorific value of the burned fuel.
12. Device according to one of the claims 5 to 7 characterized in that the said transmitter-receiver devices are radar devices.
13. Device according to claim 5, characterized in that the elimination means comprise at least one traversing bridge (11) supporting a claw bucket (12), the said claw bucket being able to be actuated to remove refuse at any point of the upper surface of the refuse heap (5).
14. Device according to claim 13, characterized in that the said traversing bridge (11) is equipped with a weighing device (13) making it possible to determine the moment when the claw bucket comes into contact with a portion of the upper surface of the refuse heap as well as a minimum admissible load for the claw bucket.
15. Device according to one of the claims 9, 13, or 14, characterized in that the claw bucket can be actuated automatically to remove refuse coming from a shredder, the refuse disposed in a determined portion of the pit, for parcelling it out on another determined portion of the heap in order to regularize its calorific value.
16. Refuse pit for feed of a t least one incinerator, characterized in that it is equipped with a device according to one of the claims 4 to 15.

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