EP1555483A2 - Milling process using pendular grinding apparata and closed-circuit pendular grinding apparata suitable for such a process - Google Patents

Abstract

A pendulum roller mill for the grinding of combustible products, comprising an upper ring (31) serving as a support for the race (32) and a base structure provided with a sole (34), and means for preventing the deposition of combustible particles in the air inlet circuit of the mill, characterized in that said means for preventing the deposition of combustible particles in the air inlet circuit of the mill comprises an outer wall (33) conical or cylindrical aperture piercing (35), providing the connection between said upper ring and said sole. <IMAGE> <IMAGE>

Description

The present invention relates to improving characteristics use of comminuting mills, more particularly mills pendulums in a closed circuit, and especially such grinders used for direct heating.

In a ventilated mill, the air used to transport the product is sucked by the main fan and passes successively through the grinder, the selector, the cyclone and / or the filter, the fan and returns to the mill (closed circuit) or part in the atmosphere (open circuit).

The mill is therefore part of an air circuit that can be closed or open.

Closed circuit

In a closed circuit the cyclone and / or filtered air leaving the fan returns to new in the crusher, except for what needs to be evacuated, ie excess air and water vapor extracted during the event of drying.

In a first case, after cyclone and fan, only the excess air and the water vapor is sucked through a filter by a second fan and rejected to the atmosphere. See Fig. 1 (Conventional closed circuit, the filter does not than the dewatering. Indirect heating with CP silo).

In a 2d case they are sent to the burner as combustion air, so without any filter. See Fig. 2 (Direct heating without intermediate storage of Pulverized Fuel).

In a third case, all the air flow, cyclone or not, is sent to the filter, before being sucked by the fan. See Fig. 3 (Closed circuit with filter in the circuit, handling all the flow).

This avoids the recirculation of unwanted fine particles.

At the outlet of the fan, part of the gas flow returns to the mill and the other part is released to the atmosphere.

But this arrangement is more expensive because the filter has to treat a big air flow.

In all 3 cases, the air that is not in excess is recirculated, which offers two benefits: calorie saving and the ability to keep the bass oxygen content in the case of grinding-drying materials flammable, as hot air comes from flue gas.

Open circuit

In an open circuit all the air is filtered as in the 3rd case already evoked, but there is no recirculation and all air is rejected to the atmosphere. See Fig. 4 (Open circuit with filter in the circuit, processing all the flow. Indirect heating with CP silo). This provision cumulates 3 disadvantages: expensive big filter, waste of calories and inerting expensive.

All types of grinders can operate according to these systems.

But the pendular vertical mills (fixed track), are the best adapted drying, because they benefit from a better heat exchange thanks to the bed fluidized wet material during grinding.

The present invention relates to grinders working in a closed circuit, following the 2d case, without filter. See Fig. 2.

The invention aims to adapt the mill base and the circuit hot gases, which prevents dead zones where deposits accumulate subject to possible spontaneous combustion.

To achieve this objective the invention provides a pendulum roller mill in a closed circuit, for grinding combustible products, comprising a upper ring, serving as support for the raceway and a basic structure provided with a sole, and means to avoid filing of combustible particles in the air inlet circuit of the mill, said means to prevent the deposition of combustible particles in the circuit mill inlet air inlet comprising a conical outer wall or cylindrical, opening aperture, providing the connection between said ring upper and said sole.

In a preferred embodiment of the invention the hot air is brought in the grinding chamber by ducts passing through said openings avoiding contact of hot air with said basic structure.

According to a feature of the invention, the supply of hot air comes from preferably an overhead collector remote from the mill.

According to another preferred feature of the invention, said means for avoid the deposition of combustible particles in the air intake circuit of the mill, may also include hot air injectors directed down the entire inner perimeter, into the mass of the fluidized bed.

The mill according to the invention preferably further comprises coulters lifters ensuring mechanical fluidization of the mass of the bed.

In a particularly preferred embodiment of the invention, said means to prevent the deposition of combustible particles in the circuit the air inlet of the mill, realize a hot air supply circuit leading to the movement of air and particles down and to the evacuation of the fine particles in the grinding chamber.

The invention also relates to a method of grinding products fuels using an upper ring mill and structure base for a grinding sole, which method avoids the deposit of combustible particles in the grinder and direct contact with hot air introduced into the mill with the basic structure of the mill.

In a preferred embodiment of the invention the hot air introduced into the crusher, comes from an air collector.

According to a feature of the invention, the hot air is preferably injected down the whole inner perimeter of the crusher, into the mass of a bed mechanically fluidized by lifting coulters.

According to another particularity of the invention, the hot air is preferably injected at high speed down the fluidized mass of a product to to dry and grind.

In a particularly preferred embodiment of the invention, the air hot brought into the mill performs a circuit in such a way that the air and suspended fine particles move downwards, thus ensuring the evacuation of the fine particles in the grinding chamber.

les figure 1 - 4 représentent, schématiquement, des installations de broyage connues selon l'art antérieur ;

la figure 5 représente, schématiquement, un mode de réalisation d'une installation de broyage selon l'invention ;

les figures 6 et 7 représentent, schématiquement, la base d'un broyeur pendulaire traditionnel (montrée en coupe en vue latérale et en coupe vue du haut) ;

les figures 8 et 9 représentent, schématiquement, un mode de réalisation de la base d'un broyeur pendulaire selon l'invention (montré en coupe en vue latérale et en coupe vue du haut);

la figure 10 représente, schématiquement, un mode de réalisation d'amenée d'air dans le broyeur selon l'invention.

Hereinafter, the invention is explained in more detail with reference to the accompanying drawings, in which

Figures 1 - 4 show, schematically, known grinding facilities according to the prior art;

FIG. 5 represents, schematically, an embodiment of a grinding installation according to the invention;

Figures 6 and 7 show, schematically, the base of a traditional pendulum mill (shown in section in side view and sectional view from above);

Figures 8 and 9 show schematically an embodiment of the base of a pendulum mill according to the invention (shown in section in side view and sectional view from above);

Figure 10 shows schematically an embodiment of air supply in the mill according to the invention.

In these figures corresponding elements are designated by the same reference, namely
a pendulum mill (1),
food (2)
a selector (3)
a return of refusal (4)
a cyclone (5)
filter (s) (6)
fan (s) (7)
a hot air inlet (8)
product output (s) (9)
an outlet to a pulverized fuel silo (10)
a burner (11)
a partial recirculation of recycled air (12)
a partial exit of recycled air (13)
a partial exit of filtered air (exhaure) (14)
an airlock (15)
flowmeter for pulverized fuel (16)

1°) la volute entourant la base du broyeur a été supprimée et

2°) le ventilateur est placé près du cyclone au lieu du broyeur.

The installation of FIG. 5, according to the invention (involving a direct heating without intermediate storage of the fuel) has a flow sheet identical to that of the installation of FIG. 2. but

1 °) the volute surrounding the mill base has been removed and

2 °) the fan is placed near the cyclone instead of the mill .

The method having the additional advantage of reducing the constraints thermal, and also and mainly to reduce the cost of manufacturing the crusher, it is interesting to also apply the new design in the treatment of inert materials.

à table-piste en rotation dans lesquels les gaz chaud n'atteignent le produit humide qu'à la sortie de la table, où il a été partiellement broyé.

à piste fixe et pendules en rotation, dans lesquels les gaz chaud atteignent le produit humide dès son entrée dans le broyeur. Ces broyeurs pendulaires à piste fixe, sont les mieux adaptés au séchage, car il profitent d'un meilleur échange thermique grâce au lit fluidisé de

la matière humide en cours de broyage.

According to the current technique, there are 2 families of Vertical Grinders:

rotary table-track in which the hot gases reach the wet product at the exit of the table , where it was partially crushed.

fixed track and rotating pendulums, in which the hot gases reach the wet product as soon as it enters the mill . These fixed-track pendulum mills are best suited for drying because they benefit from better heat exchange thanks to the fluidized bed of

the wet material being crushed.

It is to the grinders of the second family that the invention can be applied. Those of the first family have, with regard to drying, an incorrigible vice, because the hot air is not instantly in contact with the cold product and wet.

Description of the traditional base of a pendulum mill (Fig. 6 and 7)

The fixed track consists of a ring (21) of large section capable of resist rolling of pebbles.

This ring is shielded by a wear part (22) called bearing (ring) pendulum rollers (rollers).

This massive ring is supported by a multitude of columns (23) which rest on a disc-shaped sole (24) held by anchor bolts, at the foundation.

The columns serve as blades allowing the passage of the air used for the transport of the crushed material. This is high temperature air if the product is to dry.

The entire ring, columns and footing is called the base.

The base is surrounded by a volute-shaped box, which distributes the air, possibly at high temperature, all around through the blades.

A large surface of the base serves as the inner wall of the supply volute hot air at high speed and high heat transfer.

Description of the new base according to the invention (Figures 8, 9 and 10)

The vanes, providing the connection between the upper ring (31), supporting the track (32) and the sole (34) are replaced by a cone or an outer cylinder (33).

The cone, or cylinder, (33) is pierced with openings (35) through which air supply ducts (36), possibly at high temperature in the case of simultaneous drying during grinding.

There is therefore no more volute (see description of Figure 5, page 5, point 1 °) This avoids the direct contact of the base with the gas at high temperature, which reduces thermal stress and external radiation , while improving the thermal efficiency.

The air circuit after the cyclone has no rising part where material could be deposited. This is recirculating material, in the case of a closed grinding circuit with filter only on the dewatering.

The hot air is then channeled to the entire inner perimeter of the mill base, where it is injected down into the mass of the fluidized bed mechanically by the lifting coulters.

By ensuring a better injection (penetration) of the high-temperature gases at high speed downwards from the fluidized mass of the product to be dried and milled, the efficiency of the heat exchange is improved.
This improved heat exchange efficiency decreases
the temperature of the gases in the grinding chamber,
the external radiation of the walls of the latter,
the heating of nearby devices such as gearbox, motor, ...

But the most important :

The invention makes it possible to use pendulum mills for direct heating, without storage! (expensive and dangerous) crushed fuel.

(It should be noted that rotating track mills and fixed pendulums already allowed direct heating, thanks to their variable capacity, but see defects above).

After selection, the crushed fuel is separated from the transport air via a cyclone equipped at the exit of a device for measuring the actual flow of combustible. See fig. 5.

This measurement of the actual fuel flow informs the personnel and allows to constantly monitor and adapt the power of the flame, in modifying the fuel flow successively feeding the mill and the burner.

The crusher must be of variable capacity by speed variation and / or by pressure variation of the rollers on the track, according to the described technique in the patent application PCT patent application BE02 / 00012.

After the exit of the fan, placed after the cyclone, air still slightly dusty is divided into 2 flows.

First we provide the air flow necessary for combustion. Via a fan ensuring the necessary pressure and thanks to a venturi on remix the pulverized fuel, the flow of which has been measured, with the air of combustion. This mixture is then sent, by the burner, into the combustion chamber.

Before the invention, the excess air had to be evacuated to the chamber of to avoid any deposit likely to enter spontaneous combustion.

Now the air coming out of the cyclone and not used for combustion is recirculated to the mill with all the advantages mentioned. He is added gases at high temperature, to ensure the heat input necessary.

Le procédé permet d'éviter tout dépôt de combustible dans la volute du broyeur pendulaire travaillant dans un circuit fermé. Ce procédé apporte en plus des avantages techniques cités ci-après et de prix de revient. Il s'appuie sur les adaptations suivantes.

Le remplacement des aubes, assurant la liaison entre l'anneau supérieur (supportant le chemin de roulement), et la semelle, par une paroi extérieure conique ou cylindrique, percée d'ouvertures. Voir Fig. 8 .

Les ouvertures permettant le passage des conduits d'amenée d'air chaud indépendants de la base, évitant ainsi le contact direct de l'air chaud avec la structure de la base et son échauffement inutile et le risque de brûlure Voir Fig. 8 - 10.

L'amenée d'air chaud provenant d'un collecteur aérien, en remplacement de la volute au niveau du sol. Ceci évite tout dépôt dans ce collecteur. Voir Fig. 10.

Les injecteurs d'air chaud vers le bas de tout le périmètre intérieur, dans la masse du lit fluidisé mécaniquement par les socs releveurs. Voir Fig. 10.

En assurant une meilleure injection (pénétration) des gaz à haute température à grande vitesse vers le bas de la masse fluidisée du produit à sécher et à broyer, on améliore l'efficacité de l'échange thermique

Le circuit d'amenée d'air chaud réalisé de telle sorte que l'air et les fines particules en suspension se déplacent vers le bas, assurant ainsi l'évacuation des fines particules dans la chambre de broyage et empêchant tout dépôt dangereux. Voir Fig. 10.

The essential aspects of the invention are the following:

The method avoids any fuel deposition in the volute of the commuter mill working in a closed circuit. This process provides in addition to the technical advantages mentioned below and cost. It is based on the following adaptations.

The replacement of the vanes , ensuring the connection between the upper ring (supporting the raceway), and the sole, by a conical or cylindrical outer wall, pierced with openings. See Fig. 8.

The openings allowing the passage of the hot air supply ducts independent of the base , thus avoiding the direct contact of the hot air with the structure of the base and its unnecessary heating and the risk of burning See Fig. 8 - 10.

The supply of hot air from an overhead collector, replacing the volute at ground level . This avoids any deposit in this collector. See Fig. 10.

The hot air injectors down the entire inner perimeter, in the mass of the fluidized bed mechanically by the lifting coulters. See Fig. 10.

By ensuring a better injection (penetration) of the high-temperature gases at high speed downwards from the fluidized mass of the product to be dried and milled, the efficiency of the heat exchange is improved.

The hot air supply circuit is designed in such a way that air and fine particles in suspension move downwards, thus ensuring the removal of fine particles in the grinding chamber and preventing any dangerous deposition. See Fig. 10.

Claims (10)

A closed-circuit pendulum roller mill for grinding fuel products, comprising an upper ring, serving as a support for the raceway and a base structure provided with a sole, and means for preventing the deposition of combustible particles in the grinder air inlet circuit, characterized in that said means for preventing the deposition of combustible particles in the air inlet circuit of the mill comprises a conical or cylindrical outer wall, pierced by opening, providing the connection between said upper ring and said sole. Crusher according to claim 1, characterized in that hot air is fed into the grinding chamber through ducts passing through said openings, avoiding contact of the hot air with said basic structure. Crusher according to claim 2, characterized in that the supply of hot air comes from an air collector remote from the mill. The mill according to any one of the preceding claims 1, characterized in that said means for preventing the deposition of combustible particles in the air inlet circuit of the mill comprises hot air injectors directed downwards. the entire inner perimeter, in the mass of the fluidized bed. Crusher according to claim 4, characterized in that it comprises lifting coulters ensuring mechanical fluidization of the mass of the bed. Crusher according to either of the preceding claims, characterized in that said means for preventing the deposition of combustible particles in the air inlet circuit of the mill, realize a hot air supply circuit leading to the moving the air and particles down and evacuating the fine particles in the grinding chamber. A method of grinding combustible products using a grinder comprising an upper ring, serving as a support for the raceway and a base structure provided with a sole, which method avoids the deposition of combustible particles in the mill, characterized in that the process avoids the direct contact of hot air introduced into the mill, with the basic structure of the mill. Process according to Claim 7, characterized in that the hot air introduced into the mill is from an overhead collector. Process according to either of Claims 7 and 8, characterized in that hot air is injected downwards from the entire internal perimeter of the mill, into the mass of a fluidized bed mechanically by lifting coulters. . Method according to one or other of the preceding claims, characterized in that the hot air supplied to the mill carries out a circuit in such a way that the air and fine particles in suspension move downwards, thus ensuring evacuation of the fine particles in the grinding chamber.

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