EP0107527B1 - Device of the boiler-type using a solid-liquid suspension of the coal-water-type as fuel - Google Patents

Abstract

1. A boiler type device for the industrial production of thermal fluid such as water vapor, including : - a first combustion zone (5) of stretched cylindrical shape, of length L and diameter D, inclined with respect to the horizontal plane, activated with a rotating motion and equipped with a combustion organ (4). - a second combustion zone (12), distinct from the preceding one, called a solidification zone, of depth P, with I and height H, in which : a) a fraction of the calories contained in the combustion products is transferred by radiation to a receiving panel equipped with cold tubes (13) in which the fluid to be reheated is circulating, and in which b) non combustible particles, melted or dough-like and in suspension in the gaseous current are solidified, with the so-called solidification zone having in its lower part hopper for recovering slag, a third zone (17) for thermal exchange by convection via a tubuar network (18) equipped in its lower part with dust hoppers (21) and connected to the flushing systems (24) for gas and unwatering (25), characterized by the fact that the combustion organ (4) is a multi-fluid burner adapted to burn solid fuel suspended in a liquid, and that in the first combustion zone (5) the fuel is pulverized axially by an auxiliary fluid adapted to the fuel being used, and that the combustion zones shown (5, 12) and the solidification zone are associated via the following geometrical relationships expressed as a function of the parameter D : 3.25 D =< L 3.25 D =< 2.25 D =< I 4. D =< H

Description

• - sur grille, le charbon étant alors chargé dans la chambre de combustion en masse c'est-à-dire que les particules de charbon présentent des dimensions importantes (de l'ordre de quelques centimètres).
• - sous forme pulvérisée, le charbon étant finement broyé à des dimensions fines (quelques dizaines de microns) et entraîné par un jet d'air de pulvérisation.
• - en litfluidisé, le charbon étant alors broyé à des dimensions de l'ordre de quelques millimètres. Cette dernière technique, assez récente, peut présenter diverses variantes de réalisation au niveau du type de lit mis en oeuvre.

The present invention relates to boiler-type devices making it possible to carry out the combustion of liquid solid mixtures, for example coal-water and to recover the calories produced - in the form of hot fluids under pressure. Coal combustion is usually carried out using the following main techniques:

• - On a grid, the coal then being loaded into the mass combustion chamber, that is to say that the coal particles have large dimensions (of the order of a few centimeters).
• - in pulverized form, the carbon being finely ground to fine dimensions (a few tens of microns) and entrained by a jet of atomizing air.
• - in litfluidized, the carbon then being ground to dimensions of the order of a few millimeters. This latter technique, which is fairly recent, can present various variant embodiments in terms of the type of bed used.

All these techniques present serious operating problems, scouring, evacuation of slag and ash, dusting, safety devices etc ... and often impose significant implementation constraints on the choice of coal, particle size and the conduct of the units.

Finally, in the last few years, research and experiments have been started to study the combustion processes of coal-fuel mixtures and to a lesser degree the coal-water suspensions. The objective of these studies is the more or less partial substitution of coal for fuel oil, with the aim of using as much as possible the existing installations planned for liquid hydrocarbons.

The invention relates to devices of the boiler type which overcome most of the drawbacks mentioned above.

The technological background of the invention is to be considered in the following patents, none of them nevertheless, constituting prior art in any way whatsoever:

FR-A-2 088 628, US-A-1 705 383, DE-A-2 418 504 and GB-A-714 749.

• . d'utiliser dans le même appareil une large gamme de nature de charbon, ou même d'utiliser du charbon tout venant et même avantageusement les sous produits tels que fines, poussières, schlamms etc...
• . d'éliminer de façon quasi-absolue les problèmes de sécurité
• . de résoudre au mieux le problème de l'évacuation automatique des scories
• . d'offrir des comportements en combustion voisins de ceux des brûleurs à gaz et à fuel et donc des possibilités de souplesse de fonctionnement analogues à celles obtenues avec ces combustibles.

The invention allows in particular:

• . to use a wide range of charcoal in the same device, or even to use charcoal from all sources and even advantageously by-products such as fines, dust, schlamms, etc.
• . virtually eliminate security concerns
• . to best solve the problem of automatic slag removal
• . offer combustion behaviors similar to those of gas and oil burners and therefore possibilities of operating flexibility similar to those obtained with these fuels.

• - une première zone dite de combustion équipée d'un organe de combustion multifluides à pulvérisation axiale par fluide auxiliaire adapté au combustible utilisé, de forme cylindrique allongée, légèrement inclinée sur l'horizontale et animée d'un mouvement de rotation
• - une deuxième zone, totalement distincte de la précédente, dite zone de solidification dans laquelle, d'une part, une fraction des calories contenues dans les produits de la combustion est transférée par rayonnement à une paroi réceptrice équipée de tubes froids dans lesquels circule le fluide à réchauffer et d'autre part, les particules non combustibles, fondues ou pâteuses en suspension dans le flux gazeux sont solidifiées, ladite zone de solidification comportant dans sa partie basse une trémie de récupération des scories
• - une troisième zone d'échange thermique par convection sur un faisceau tubulaire, équipée dans sa partie basse de trémies à poussières et raccordée au système d'épuration des gaz et d'exhaure.

The subject of the present invention is a device for the industrial production of steam or thermal fluid, using as fuel a solid-liquid suspension, characterized in that it comprises:

• - a first so-called combustion zone equipped with a multifluid combustion member with axial spraying by auxiliary fluid adapted to the fuel used, of elongated cylindrical shape, slightly inclined to the horizontal and driven by a rotational movement
• - a second zone, completely distinct from the previous one, known as the solidification zone in which, on the one hand, a fraction of the calories contained in the products of combustion is transferred by radiation to a receiving wall equipped with cold tubes in which the fluid to be heated and on the other hand, the non-combustible, molten or pasty particles suspended in the gas flow are solidified, said solidification zone comprising in its lower part a hopper for recovering slag
• - a third heat exchange zone by convection on a tube bundle, equipped in its lower part with dust hoppers and connected to the gas purification and dewatering system.

The cylindrical combustion zone is equipped with a single multi-fluid type burner attached to the fixed end of the cylinder opposite the solidification zone and whose axis coincides with that of the combustion zone. A pumping system adapted to the fuel used (solid-liquid suspension) is used to introduce said fuel into the burner which also receives the auxiliary spraying gaseous fluid as well as the combustion air. The injection of all the active fluids into the hearth that constitutes the combustion zone is necessarily axial.

The combustion zone is highly insulated by means of refractory products forming a radiant hot wall held in place by a metal casing.

The spraying mentioned above is carried out at an effective pressure generally between 0.5 and 2 bars.

The combustion zone is of elongated cylindrical shape, that is to say its length (L) will be at least equal to 3.25 times the inside diameter (D) of the cylinder.

In order to allow satisfactory evacuation of the slag which generally forms in the liquid state in this combustion zone, it will be inclined to the horizontal by an angle between 2 and 8 °. In addition, this zone will be rotated at a slow speed of the order of 1 to 5 revolutions per minute by means of a conventional roller or chain drive system.

At the outlet of this combustion zone is disposed a so-called solidification zone, of vertical axis, distinct from the combustion zone with which it communicates. This solidification zone will have a volume generally between 10 and 15 times the volume of the combustion zone. It will advantageously take the form of a rectangular parallelepiped whose depth (P) will be at least equal to (L) length of the area of combustion, a width (1) at least equal to 2.25 D and a height (H) at least equal to 4 D.

This solidification zone comprises on its side walls, constituted by a refractory insulating material held in place by a metallic envelope, cold tubes containing the pressurized fluid to be heated by radiation. In addition, it has in its lower part a hopper for recovering the slag from the combustion zone and the ash from the solidification zone.

At the end of the solidification zone is arranged perpendicularly a horizontal convection zone equipped with a bundle of exchanger tubes operating by convection, and hoppers for recovering the dust present.

According to an alternative embodiment of the device of the invention, this convectian zone can be arranged vertically so that the fumes flow from top to bottom, the main thing being that the gas stream is subjected to a significant change in direction.

The solid-liquid suspension used as fuel in the device of the invention could for example be a mixture of finely ground coal, that is to say of which the particles will generally have a diameter of less than 100 microns and water or any other suitable liquid such as animal or vegetable oils, alcohols or fuels. The content of the mixture in liquid is preferably between 30 and 50% (weight).

• La figure 1 représente une coupe schématique longitudinale d'un exemple du dispositif selon l'invention.
• La figure 2 représente une vue schématique de la zone de solidification (12).

The device of the invention will be better understood in the light of the embodiment below described with reference to FIGS. 1 and 2.

• Figure 1 shows a schematic longitudinal section of an example of the device according to the invention.
• FIG. 2 represents a schematic view of the solidification zone (12).

The combustion zone (5) is supplied with solid-liquid suspension via the line (1). Lines (2) and (3) lead the spray air and the combustion air respectively to the multi-fluid burner (4).

This burner (4) is arranged on the fixed front wall (6) of the zone (5). The walls of this area are made of refractories (7) with a thickness of about 350 mm, held in place by the metallic outer casing (8). The area (5) inclined at an angle a of 3.5 ° to the horizontal is rotated by means of a system comprising a drive roller (9) and a support roller (10) on which the raceways (11). ).

The zone (5) opens onto a solidification zone (12), taking the form of a rectangular parallelepiped. The inside of the walls of the zone (12) is lined with tubes (13) intended for heat exchange by radiation, said walls being made of an insulating refractory lining inside (14) of approximately 100 mm thickness maintained in placed by a metal casing (15). In the lower part of the zone (12) is arranged a hopper (16) intended to collect the slag and the ash. The walls of the hopper are made in a similar way to that of the heat exchange part of the zone (12).

The zone (12) opens onto a convection zone (17) arranged perpendicular to the zone (12). This zone (17) is equipped with a battery of tubes (18) intended for heat exchange by convection. Lines (19) collect the steam-water emulsion produced by both the tubes (13) and the tubes (18) to direct it to the separator flask (20). The zone (17) is equipped at its lower part with hoppers (21) for the recovery of dust conveyed by the gas flow and possible deposits on the tubes (18), detached by means of a conventional blowing system not shown. The walls of the zone (17) consist of an insulating refractory (22) with a thickness of approximately 50 mm held in place by the envelope (23).

At the exit of the zone (17) the cooled gas flow is sucked by the exhaust (25) through a dust collector (24) before discharge to the chimney (26).

The device of the invention described above is implemented according to the process described below with a coal-water suspension as fuel. This suspension consists of a weight mixture of 40% water, 60% carbon. This carbon was finely ground in an aqueous medium so as to obtain a particle size centered on 35 microns with a maximum of 100 microns. The viscosity of the mixture is reduced by adding an appropriate surfactant.

The fuel is introduced by volumetric pumping into the burner, the latter being supplied separately with compressed air sprayed at 0.7 bar effective and with combustion air. The spray is injected into the axis of the combustion zone, the design of which allows the total combustion of the coal contained in the suspension within this zone itself with a combustion rate reaching 600 therms per m3 of combustion zone. The ignition of the fuel is ensured automatically by the temperature level prevailing in the zone preheated to 1100 ° C with conventional fuel. Therefore the temperature in steady state is of the order of 1400 ° C. The thermal load is modulated as required by direct action on the supply volumetric pump. The flexibility thus obtained allows an instantaneous variation of the calorific flow in the proportions of 1/5 to 5/5. At the temperatures reached, the ash contained in the coal is in the liquid state in fine suspension in the combustion gases. A fraction of these particles is deposited in contact with the refractory walls on which they flow by gravity. Their evacuation is ensured by the conjunction of the inclination of the zone on the horizontal and its slow rotation.

The possible concretions which can form on the walls are also eliminated as they are detached. The latter results in particular from the non-stick nature of the wall vis-à-vis the slag.

The hot gases (around 1400 ° C) produced in the combustion zone penetrate into the solidification zone. The gases in this zone cool down by radiation towards the cold walls lined with tubes, which automatically causes the concomitant cooling of the fine ashy molten particles transported within the gas stream. In this zone the temperature of the gas goes from 1400 to 850 ° C approximately. The hopper located at the lower part of this zone receives on the one hand the molten ash and the concretions coming from the combustion zone and on the other hand those which could form on the part of the wall facing combustion, then detach. The gases from the solidification zone penetrate into the convection zone where they are cooled, to a temperature of approximately 250 ° C. in contact with the bundles of exchanger tubes. In this area a fraction of lice _"Sieres deposits on the tubes where they are driven by a conventional method for blow molding.

Hoppers arranged at the base receive the dust falling by gravity. The water-steam emulsion generated in the exchange beams of the solidification and convection zones is collected at the top and directed towards the separating flask.

The gases from the convection zone are dusted in a conventional manner before being discharged to the chimney.

The devices of the invention are particularly advantageous because they allow the use of coals of all kinds as liquid fuel under particularly favorable operating conditions, particularly in terms of handling, ash extraction, flexibility of operation. and security.

In addition, it should be noted that by using the means of the invention it is easy to convert coal to existing boilers, and designed for conventional hydrocarbon fuels. For this, it will suffice essentially to add a combustion zone according to the invention to adapt to the characteristics of the existing boiler.

Claims (3)

1. A boiler type device for the industrial production of thermal fluid such as water vapor, including:

- a first combustion zone (5) of stretched cylindrical shape, of length L and diameter D, inclined with respect to the horizontal plane, activated with a rotating motion and equipped with a combustion organ (4).

- a second combustion zone (12), distinct from the preceding one, called a solidification zone, of depth P, width I and height H, in which: a) a fraction of the calories contained in the combustion products is transferred by radiation to a receiving panel equipped with cold tubes (13) in which the fluid to be reheated is circulating, and in which b) non combustible particles, melted or dough-like and in suspension in the gaseous current are solidified, with the so-called solidification zone having in its lower part hopper for recovering slag,

a third zone (17) for thermal exchange by convection via a tubuar network (18) equipped in its lower part with dust hoppers (21) and connected to the flushing systems (24) for gas and unwatering (25), characterized by the fact that the combustion organ (4) is a multi-fluid burner adapted to. burn solid fuel suspended in a liquid, and that in the first combustion zone (5) the fuel is pulverized axially by an auxiliary fluid adapted to the fuel being used, and that the combustion zones shown (5,12) and the solidification zone are associated via the following geometrical relationships expressed as a function of the parameter D:

2. A device which according to claim 1 is characterized by the fact that the first combustion zone (5) is inclined with respect to the horizontal plane by an angle between 2 and 8°.

3. A device which according to claim 1 is characterized by the fact that the first combustion zone (5) is put into rotating mction at a speed between 1 and 5 rpm.

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