EP0120793A1 - Automatic feeding of a multi-fuel furnace - Google Patents

Abstract

Device for automatic feeding with solid waste of a multi-fuel heat generator. The device comprises a storage hopper 1 which has at its base an Archimedean screw 2 driven when ordered with a rotary movement in one direction, then with a rotary movement of a number of turns in the other direction. It also comprises an extraction pipe 10 which opens into a vertical feed pipe 16 of the furnace, inside which pipe there is displaced a valve which is driven by an endless screw which sometimes adopts a high position above the junction of the two pipes and at other times a low position, closing the feed pipe and isolating the furnace from the whole of the installation. <IMAGE>

Description

The present invention relates to a set of devices for automatically supplying a multi-fuel boiler with corn cobs or any other fuel having the same consistency.

Corn cobs are the threshing waste from the ears of corn. They consist of the inner central part of these ears varying in length from 10 to 20 cm and a few leaves attached to it by the base. They are used dry and have a high calorific value.

It is easily understood that such a product, comprising bulky elements and a very low density, 120 kgs per m ³ , is difficult to convey to the boiler, depending on the temperature of the latter and without human intervention.

The object of the invention is to allow automatic feed regulation. It can also be applied to other materials than corn cobs, having the same consistency, for example: wood chips, crushed vine shoots, chopped straw, dry sawdust, shredded wood.

European patent application EP-A-0 056 851 discloses a device for supplying boiler with pulverulent fuel using a worm screw. Patent GB-A-1,124,399 also describes a worm screw arranged in a box which opens directly by a hatch into the discharge opening of the heat generator.

Such devices are not adapted to the problem of supplying the boiler with the aid of roundups, but because there are then two main difficulties.

-First, at the level of the extraction of the product from the storage tank by a worm: frequent jams at the end of the screw and vault of stems forming in the tank above the screw which, in this case, is no longer powered.

-Secondly, at the level of the pipes leading to the boiler: backfires risking setting fire to the storage tank. The present invention therefore aims to eliminate these drawbacks and achieve a set of storage and supply of a boiler in roundups but very reliable and can be automated so as to maintain constant the temperature of the water, heated by the boiler.

The present invention also aims to eliminate any risk of fire of the stored material, by hermetically isolating the latter from the boiler during the heating time.

The invention therefore provides an automatic feeding device, with solid waste such as corn cobs, of a multi-fuel generator comprising a loading hopper disposed above the generator, this device consisting of two complementary feeding conduits ; a first conduit at the bottom of the hopper for the transport of waste, in a substantially horizontal position and provided with an endless screw, a second conduit, substantially vertical, communicating with the first by a junction, this second conduit forming a cylinder d '' supply in which is disposed a shutter valve forming a piston and movable in this cylinder between two extreme positions one located above the junction point of the two conduits, the other located below said point, and abutting on a shutter seat.

Preferably, the two supply ducts have a slope at the bottom of their junction which extends from the end of the worm screw to the vicinity of the valve seat, and advantageously the valve of the second duct is made up of two sheets of sheet metal enclosing a plate of refractory material, this valve being driven in its movements by an endless screw cooperating with a nut driven by an electric motor, this valve being loaded by spring so as to apply pressure on the seat.

• -la vis sans fin du premier conduit possède à son extrémité voisine de la jonction des deux conduits un ressort agissant sur les déchets pour libérer l'extrémité de cette vis,
• -le dispositif comporte un appareillage électrique de commande établissant la mise en fonction de la vis et du piston pour le chargement en combustible puis par inversion leur retour à la position initiale,cette action étant fonction de la température d'eau produite par la chaudière,
• -le conduit de descente est ouvert à sa partie supérieure,au-dessus de la jonction des conduits.

According to other preferred methods:

• the endless screw of the first conduit has at its end close to the junction of the two conduits a spring acting on the waste to release the end of this screw,
• the device comprises an electrical control device establishing the activation of the screw and the piston for loading fuel then by reversing their return to the initial position, this action being a function of the temperature of water produced by the boiler,
• -the downcomer is open at its upper part, above the junction of the conduits.

To ensure the extraction of the stalks from the storage hopper and their routing inside the duct connecting the hopper to the boiler, in a regular manner and without risk of blocking or turning in a vacuum, the screw archimedes is of relatively large diameter for example 250 mm.

The screw is rotated by an electric motor which is started using a thermostatic switch as soon as the minimum desired boiler temperature is reached. The motor drives the screw in a direction of rotation for about 8 turns, which makes the value of a boiler refill enter the duct, then the motor automatically reverses the direction of rotation of the screw for about 2 turns. aims to avoid jams at the end of the screw and decompress the stalks stored in the hopper. Indeed, these driven back loosen and fall between the turns of the screw.

A clearance is provided on the side opposite to the exit of the stalks to avoid blocking of the screw in the opposite direction.

The screw is located at the base of the hopper which has two inclined planes starting from the bottom and rising towards the upper part. These inclined planes are sufficiently spaced apart at the base so that in the rotational movement the stalks are not compressed around the screw.

Leaving the storage hopper, the screw enters a preferably circular duct which envelops it, leaving between the walls and the outside of the turns of the screw a clearance at least equal to the diameter of a beaten spike, ie approximately 25 mm.

The present invention includes a system allowing the duct connecting the storage hopper to the boiler to be closed completely and at will to prevent possible backfire.

When the valve is in the lower position, it presses on a crown welded inside the conduit. This crown allows, in conjunction with the valve whose diameter is slightly smaller than the duct, to hermetically seal the latter. This crown must however have a minimum width so as not to stop the roundups when the valve is in the high position.

This crown, the surface of which is flat and perpendicular to the conduit in the example presented, may advantageously have the shape of a truncated cone whose apex would be downward. In this case, the valve will also have a truncated cone shape in its outer part, to match the shape of the stopper. This arrangement will prevent any trapping of stems or leaves at the valve seat.

According to the invention it is preferably provided that the displacement of the valve is ensured by an endless screw which is fixed in its center, extends towards the top of the conduit and passes through an electric motor by screwing in a nut driven in rotation by said motor.

When the minimum desired boiler temperature is reached, a thermostatic switch starts the motor which drives the screw upwards, thereby raising the valve above the mouth of the horizontal screw.

When this position is reached, the valve presses a limit switch which stops the rotation of the motor.

When the boiler is loaded by the extraction screw, the engine is restarted in the opposite direction and the valve descends to the lower crown serving as seat. In this position, a circular disc fixed to the upper end of the worm comes into contact with a switch and stops the rotation of the motor.

According to the invention, preferably the upper part of the cylinder in which the valve moves is not closed. This particularity allows the decompression of gases which could rise while passing under the valve in the quite exceptional case where a waste would have prevented the really hermetic closing.

The invention is also characterized by the shape of the junction of the haulage delivery conduit and the descent conduit. This junction is formed in its lower part by a pan inclined at 45 ° and 10 cm in length which reduces the connection angle. The upper part of this pan coincides with the end of the feed screw and its lower part opens just above the valve.

To properly clear this junction angle, the horizontal extraction screw is provided at its end with a spring which, by turning, relaxes and lengthens while whipping the walls, which aims to release the last impurities which could prevent the valve from closing.

To ensure that the valve is properly closed, the threaded control rod is connected to the latter by a spring qji which is slightly compressed during closing, thus avoiding any risk of deterioration.

• La figure 1 est une vue schématique en coupe longitudinale de l'ensemble de l'installation représentant le bac de stockage,la chaudière et les différents conduits les reliant.
• Les figures 2 et 3 sont des vues extérieures de cette même installation,la figure 2 étant une vue du bout du bac de stockage, face à l'axe de la vis d'extraction et de la chaudière; la figure 3 étant une vue de dessus.
• La figure 4 est une vue schématique en coupe plus détaillée de la zone de liaison du conduit d'extraction et du conduit de descente vers la chaudière,zone dans laquelle se déplace la soupape d'obturation.

A particular embodiment of a storage and supply installation for a multi-fuel boiler will be described in more detail below and by way of non-limiting indication. with corn cobs.

• Figure 1 is a schematic view in longitudinal section of the entire installation representing the storage tank, the boiler and the various conduits connecting them.
• Figures 2 and 3 are exterior views of this same installation, Figure 2 being a view of the end of the storage tank, facing the axis of the extraction screw and the boiler; Figure 3 being a top view.
• Figure 4 is a schematic view in more detail in section of the connection zone of the extraction pipe and the down pipe to the boiler, area in which the shutter valve moves.

The storage bin 1 has at its lower part a screw 2, which extends over the entire length of its base.

Two inclined planes 3 and 4 start from this base and move upwards. They are connected at their lower part by a horizontal plane 5 located under the screw and by two small planes 6 and 7 of an intermediate inclination which make it possible to separate the inclined planes 3 and 4 from the screw and thus give more clearance corn cobs when the screw turns.

The base of the sidewall 8, on the outlet side, has a circular hole which is extended towards the outside by a cylindrical conduit 10, the radius of which is equal to the radius of the screw, increased by the maximum diameter of the stalks, that is to say approximately 25 mm, in order to avoid blockage of a stalk between the screw and the duct.

At the base of the rear flank 9, facing the screw, a clearance ll, of cylindrical or parallelepiped shape, frees a space in the extension of the screw and outside the flank, this to avoid jams between the ends of the turns and the wall, during the reverse movement of the screw.

At the lower part of the storage tank, the extraction screw 2 is centered on the side of the drive by a bearing 12 and on the side of the extraction by the conduit 10 which envelops the turns.

The screw 2 does not have any turns in its part penetrating into the rear clearance space on the drive side and it ends on the extraction side, just in front of the cutaway 15 of the junction area of the extraction duct 10 and the raid descent duct 16.

The screw is rotated by an electric gear motor 13 and by a chain 14.

At the end of the screw on the extraction side, is hinged a spring 32 which sweeps the junction area forcing the last waste to fall.

The duct 16 is a cylindrical tube, it is parallel to the vertical axis of the boiler 17 and opens onto the top of the latter.

Laterally, it communicates with the extraction pipe of the hopper 10. This connection of the two pipes has in its lower part an inclined plane 15.

Inside the downcomer 16, and a few centimeters below the junction of the two conduits, is welded a crown 18 of small width which serves as a support for the valve 19.

This valve 19 consists of two sheets 20 which sandwich a washer of refractory material, such as asbestos 21, the whole being assembled by a few rivets.

At the center of the valve and perpendicular to it, an endless screw 22 is screwed into a rotating nut 23, integral with the hollow shaft of the electric motor 24.

This worm has a cylindrical axis 30 at its lower end and enters a central hole in the valve, with the possibility of sliding. A pin 23 ensures the raising of the valve while a spring 24 compresses slightly when the worm is at the end of its travel and keeps the valve 19 on its seat 18 while retaining a certain flexibility.

So that the screw is not driven in rotation by the nut 23, a finger 25, pinned on the screw through its hub, enters a vertical lumen formed in a lug 27, integral with the valve.

To prevent the valve from rotating, driven in turn, 2 round irons 28 are welded vertically on two opposite generators inside the descent cylinder 16. Two notches made _- in the upper sheet of the valve allow their passage.

The duct 16 is not closed at its upper end and opens directly into the open air to facilitate the release of gases, in the event that the valve is loosely closed.

A limit switch 29 stops the rotation of the motor when the valve 20 reaches its highest point, that is to say above. the junction of the two conduits 10 and 16.

Another limit switch 30 is actuated by a disc 31 secured to the screw 22, when the valve 20 reaches the bottom point of its travel and rests on the crown 18.

An electrical assembly of known type makes it possible to establish a supply cycle for the boiler, regulated as a function of the temperature of the water produced.

• 1)mise en rotation du moteur 24,remontée de la soupape 19 au-dessus de l'entrée du conduit d'extraction.
• 2)coupure de la remontée par l'interrupteur 29
• 3)mise en route du moteur 13 pendant environ 8 tours. La vis entraîne une recharge de rafles qui chute dans le conduit d'arrivée à la chaudière.
• 4)inversion du sens de rotation du moteur 13 pendant environ deux tours. Le ressort à l'extrémité de la vis dégage complètement les rafles pouvant deux rester à la jonction des deux conduits;les rafles se décompriment dans le conduit 10 et dans la trémie 1, elles chutent dans la vis 2.

When the water temperature is lower than desired, the cycle is established as follows:

• 1) rotation of the motor 24, raising of the valve 19 above the inlet of the extraction duct.
• 2) interruption of the ascent by switch 29
• 3) starting the engine 13 for approximately 8 turns. The screw causes a recharge of stalks which falls in the inlet pipe to the boiler.
• 4) reversing the direction of rotation of the motor 13 for approximately two turns. The spring at the end of the screw completely releases the stalks which can two remain at the junction of the two conduits; the stalks decompress in the duct 10 and in the hopper 1, they drop in the screw 2.

5) starting the motor 24 in the opposite direction. The valve descends into the conduit 16 and is applied to its seat 18 with a slight pressure due to the spring 24.

The lower limit switch 30 is actuated by the disc 31 and cuts the current.

Combustion resumes in the boiler, the water temperature rises and the cycle is stopped, it will not resume again until the temperature of this water drops below that expected.

Claims (6)

1.Automatic feed device, with solid waste such as corn cobs, of a multi-fuel generator (17) comprising a loading hopper (1) disposed above the generator, device characterized in that it is consisting of two complementary supply conduits; a first conduit (10) at the bottom of the hopper for the transport of waste, in a substantially horizontal position and provided with an endless screw (2), a second conduit (16), substantially vertical, communicating with the first by a junction, this second conduit forming a supply cylinder in which is disposed a shut-off valve (19) forming a piston and movable in this cylinder between two extreme positions, one situated above the junction point of the two conduits, the another located below said point, and abutting on a shutter seat (18). 2. Device according to claim l, characterized in that the two supply conduits have at the bottom of their junction a slope (15) which extends from the end of the worm (2) to in the vicinity of the valve seat (18). 3. Device according to claims 1 and. 2 characterized in that the valve of the second conduit consists of two sheets of sheet metal (20) enclosing a plate of refractory material (19), this valve being driven in its movements by an endless screw (22) cooperating with a nut or (23) driven by an electric motor (24), this valve being spring loaded so as to apply pressure to the seat (18). 4. Device according to any one of claims 1 to 3, characterized in that the worm (2) of the first conduit has at its end close to the junction of the two conduits a spring (32) acting on the waste to release the end of this screw. 5. Device according to any one of claims 1 to 4, characterized in that it comprises an electrical control device establishing the operation of the screw (2) and the piston (29) for loading fuel and then reversing their return to the initial position, this action being a function of the water temperature produced by the boiler. 6. Device according to any one of claims 1 to 5, characterized in that the downcomer 16 is open at its upper part, above the junction of the conduits (10) and (16).

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