EP0118363A2 - Installation of and method for heating by means of immersed firing - Google Patents

Abstract

1. A heating plant comprising a tank containing a bath (3) to be heated by means of a submerged combustion burner (4) and a means (26) which is partially immersed in the bath in order to confine beneath it, in a space (32) provided for the purpose, the smoke of combustion produced by the said burner, characterised in that in order to obtain heating temperatures which are clearly in excess of 60 degrees C, and for example as high as 90 degrees C, with a satisfactory degree of efficiency, the plant (1) is equipped at the smoke outlet, above the said confining means (26), with a washing tower (8) comprising, in counter-current with the smoke, a series of cascades forming a plurality of curtains of water (R1-R4) which are substantially continuous and which are disposed in series in the path of the smoke, the said curtains being supplied by a flow of cold water (10) which is to be heated by the plant, the said cascades comprising walls (15) for forming the curtains of water (R1-R4) provided partly at the top and partly at the bottom with means such as teeth (16), projecting ridges (17) and orifices (18) which ensure continuous formation of the curtains, with no tear-away, over all their width, and further characterised in that the said smoke confining means takes the form of a plate (26) covering the major part of the surface of the bath (3), the said plate comprising a substantially horizontal surface (29) edged by a wall (30) extending upwardly and downwardly beyond it, disposing above it a space (31) for collecting water which falls from the washing tower.

Description

The present invention relates to an installation and a method making it possible to improve the operating characteristics of a heating installation of the submerged combustion type.

For various applications, in particular industrial heating, swimming pool heating and the like, installations using submerged combustion burners are sometimes used.

The advantage of such installations is that, due to the bubbling of the combustion gases in the water to be heated, most of the latent heat of condensation of the fumes is recovered, at least if the temperature of the bath does not is not too high. Under such conditions, yields are commonly obtained calculated on the lower calorific value (PCI) greater than 100%, and frequently of the order of 105%.

This technique also has the advantage that the heat exchanger is very simplified in construction, being mostly made up of a kind of duct extending the combustion chamber into which the burner opens.

If it is desired to obtain relatively high bath temperatures, and in particular above 60 ° C., the efficiency of submerged combustion decreases. If special precautions are not taken, the yield even drops to zero for a bath temperature close to 90 ° C, temperature from which the heat provided by combustion is practically only used to evaporate water. from the bath, water vapor which escapes with the fumes to the chimney.

In certain installations, however, attempts have been made by various means to use the principle of submerged combustion to obtain bath temperatures above 60 ° C., and this, with suitable yields. To achieve this goal, it was recommended that the cold water from the returns or the bath supply be passed through the fumes, so as to condense and recover the heat of vaporization of the water and the products of combustion. Known solutions are complicated, requiring the use of expensive and power-consuming circulation pumps, and the results obtained are generally unsatisfactory in terms of yield, especially as soon as the bath temperature must exceed 70 or 80 ° C. .

The object of the invention is, in a submerged combustion installation, to solve the abovementioned problems, by proposing a simple installation making it possible to obtain very.

good operating yields with bath temperatures of around 90 ° C.

To this end, the heating installation of the submerged combustion type is characterized according to the invention in that the installation on the outlet of the fumes above the bath to be heated is equipped with a washing tower comprising against -current with the fumes a series of cascades forming several substantially continuous water curtains arranged in series on the path of the fumes, said curtains being supplied by a flow of cold water to be heated from the installation, said cascades comprising formation walls water curtains provided in the upper part and in the lower part with means such as teeth, projecting edges and orifices ensuring continuous formation without tearing. curtains across their entire width.

According to another characteristic of the invention, a tray is provided, covering most of the surface of the bath, placed below the washing tower, said tray having a substantially horizontal surface bordered by a wall projecting above and below it by providing above a volume of water collection falling from the washing tower and below a volume of containment of fumes rising from the bath. By using the above-mentioned means, it becomes possible to reach bath temperatures in the region of 90 ° C., with entirely satisfactory combustion yields. Provided only that the cold water returns to the washing tower are at a suitable temperature, sufficiently low, for example close to 40 ° C. or lower.

The installation can be run continuously or discontinuously depending on usage.

In continuous use, in accordance with an improvement of the invention, the bath water outlet flow rate is controlled and the heating of the bath is controlled to the maximum desired temperature, for example 88 ° C. when said flow rate is greater than a determined minimum flow rate, while when this flow rate is less than this determined minimum flow rate the bath is only heated to a selected minimum determined temperature, for example 70 ° C., so as to instantly satisfy the demand needs.

• La figure 1 montre en coupe,schématiquement une installation à combustion submergée pour le chauffage de l'eau à des températures supérieures à 60°C conçue selon l'art antérieur,
• La figure 2 montre en vue en coupe schématique à plus grande échelle une partie de l'installation illustrée à la figure 1 modifiée selon des perfectionnements conformes à l'invention,
• La figure 3 montre en vueperspective à plus grande échelle comment sont formées les parois d'une cuvette de rétention d'eau pour la formation des cascades dans la tour comme illustré à la figure 2,
• La figure 4 montre en vueperspective de façon schématique et avec arrachements un plateau destiné à coopérer dans le bain avec la tour de lavage,
• La figure 5 montre schématiquement une vue en coupe faite sensiblement selon le plan V-V de la figure 4,
• La figure 6 montre de façon schématique comme la figure 1 une installation modifiée selon l'invention avec différents organes de commande et de contrôle de cette installation.

The invention and its implementation will appear more clearly with the aid of the description which follows, given with reference to the accompanying drawings in which:

• FIG. 1 shows in section, schematically a submerged combustion installation for heating water to temperatures above 60 ° C. designed according to the prior art,
• FIG. 2 shows in schematic sectional view on a larger scale part of the installation illustrated in FIG. 1 modified according to improvements in accordance with the invention,
• Figure 3 shows in perspective view on a larger scale how the walls of a water retention basin are formed for the formation of waterfalls in the tower as illustrated in Figure 2,
• FIG. 4 shows in perspective view schematically and with cutaway a plate intended to cooperate in the bath with the washing tower,
• FIG. 5 schematically shows a sectional view made substantially along the plane VV of FIG. 4,
• Figure 6 shows schematically like Figure 1 a modified installation according to the invention with different command and control of this installation.

Referring first to Figure 1 there is illustrated an installation identified as a whole 1 comprising a tank 2 containing a water bath 3 to be heated by means of a submerged combustion burner 4 opening into the tank in a combustion chamber 5 continuing with an exchanger 6. The products of combustion of the combustible gas usually used are essentially carbon dioxide and water vapor. Most of the water vapor condenses in the bath water (if the bath is not too hot) to which the latent heat of vaporization of fumes is given up, while the incondensables are evacuated to the chimney 7 .

As mentioned above, such an installation works with very good efficiency if the bath temperature is below approximately 60 ° C. On the other hand, above this temperature the yield decreases very quickly because the heat provided by the combustion of the burner is used to vaporize an increasingly large quantity of water, which is sent to the chimney 7 as a waste. The yield drops to zero around 90 ° C.

In accordance with the prior art when it is desired with a submerged combustion installation to obtain a temperature of the bath 3 above 60 ° C and with an acceptable operating efficiency, a washing tower 8 is provided before the chimney 7 in which is sprayed as indicated in 9 the cold water supplied by a pipe 10 from the installation returns or of supplements. The cold return 10 brings in the hot water discharge at 11. The washing tower 8 allows, by spraying cold water at 9 going against the flow of hot fumes rising from the partially condensing the water vapor tending to escape from the installation, and finding correct operating efficiencies. The installation is only relatively effective insofar as the spraying 9 is done under high pressure of multiple very fine jets, which requires the use of a relatively powerful pump 12 and the use of spraying grids at the level the injection 9. These grids have tendance.à clogging _', owing in particular lime deposits.

The overall yield of the installation is not very good and decreases again if the flow rate for using hot water is low and that consequently the cold returns are at low flow rate or at a temperature not low enough.

Reference will now be made to FIG. 2 representing a washing tower modified in accordance with the invention.

The washing tower 8 disposed above the upper volume 13 of the tank 2 not occupied by the bath to be heated 3 essentially comprises according to the invention a series of cascades forming a plurality of substantially continuous water channels R1, R2, R3, R4 arranged in series on the smoke path materialized by the arrows. Each curtain is formed from a water retention basin C1, C2, C3, C4 formed essentially by an inclined wall 14 at the bottom ending, on the raised side of the wall against the wall of the washing tower 8 , and on the other side, leaving a reduced passage section S for the fumes, by a substantially vertical wall 15.

As can be seen more clearly in FIG. 3, the wall 15 on which the curtain of the waterfall is formed, comprises at its upper part a toothed rim 16, which ensures a good distribution of the flow of water along the entire wall 15, even if the edge 16 is not perfectly horizontal. Without such a measure, the curtain could only form on one side.

On the other hand, the wall 15 descends very notably below the bottom plate 14, so as to present a lower rim 17 which projects below the wall 14; this measurement is necessary so as to prevent the curtain of water which must form on the edge 17 from rising by capillary action below the bottom surface 14 of the bowl, creating tears in the curtain. In addition, orifices 18 are advantageously provided in the vicinity of the lower edge 17 of the wall 15, so as to ensure a good distribution of the cascade along the edge 17, the orifices 18 working a little similarly to the teeth of the rim 16.

By the use of these various means, it is ensured- to obtain curtains R1, R2 ... perfectly continuous, without tearing and through which the fumes will therefore have to clear a passage, the installaton ensuring a 'good water contact -smoke, therefore effective condensation of the water vapor contained in the fumes.

The upper bowl C1 is supplied by a perforated cold water return pipe 19 which acts as a diffuser 9 in FIG. 1 but does not have the drawbacks thereof. However, this supply is used to form a sort of last curtain R5 before the smoke leaves the chimney 7, and the smoke is guided to the chimney entrance by deflectors 20 also forming fins of condensation.

The bowls are arranged one above the other in a staggered manner so as to protrude about half their length - above the lower bowl. Advantageously. each curtain R is received before falling into the lower bowl on a cup 21 forming a gutter located slightly above the upper level of the lower bowl. The gutters 21 thus form splashes and break the curtain in its lower part further increasing the exchange by contact between the water and the fumes.

On the other hand, under each bowl C are formed condensation fins 22 which protrude below the surface 14 of the bottom of the bowls promoting the exchange and cooling of the fumes which are at a temperature higher than that of the bowl forming deflector under which they are guided. The fins 22 stop before the surface of the front wall 15, so as to avoid the possibilities of raising the curtain of water under the bowl, as mentioned above.

_E as given at the output of the bath hot fumes are advantageously thermally insulating the scrubber, at least in its lower part, as illustrated at 23. Furthermore, where washing of the tower does not enter a great height in the tank 2, in particular when the height of the installation must be limited, provision is made for a widening of the connection section by tilting the connection wall as indicated at 24.

Reference will now be made to FIGS. 4 and 5 in which are illustrated other means working in conjunction with the washing tower to improve the efficiency of the installation. In Figure 4 we find in external view the washing tower 8 with the chimney 7 and the inlet of the cold water returns feeding the conduit 19.We tore off and exploded% the top 25 of the tank, so as to leave see below a plate 26 whose construction and use will be described below. We also see in the tank 2 the burner 4 with the combustion chamber 5 and the exchanger 6 from which the fumes escape inside the bath.

The plate 26 covers most of the surface of the bath, presenting only a notch 27 for the passage of the burner 4 and leaving all around it an annular passage 28 (FIG. 5) between the wall of the tank and it.

The plate 26 comprises a substantially horizontal surface 29 bordered by a wall 30 projecting above and below the surface 29, providing above there a volume 31 for collecting water falling from the washing tower 8 and below a volume 32 for confining the fumes rising from the bath as illustrated by the bubbles 33 in FIG. 5.

In normal operation of the installation, that is to say when the burner is supplied, the plate 26 is partly immersed in the bath 3, so that there is a certain back pressure which must be overcome by the fumes s accumulating in the confinement volume 32 to pass under the lower edge 33 of the volume 32 to escape towards the washing tower. The surface 29 of the plate has at its lower part exchange fins 34 forming a projection favoring the condensation of fumes under the effect of colder water falling from the washing tower 8 contained in the volume 31 of the plate. Preferably, regulation of the system is ensured, as will be described below so as to obtain a difference in level h between the free surface of the bath 3 and the level 35 of the bath in the confinement space 32, of the order of 15 to 20 centimeters, that is to say an overpressure of the order of 15 to 20 millibars. Such work in "overpressure" compared to atmospheric pressure is interesting, in that it improves the exchange and condensation yields.

With an installation of the type described above, tests have shown that it was possible to obtain a yield of 103% on PCI with a water return temperature close to 35 ° C and a water outlet temperature 88 ° C. Of course the yield increases if the cold water returns are made at a temperature lower than 35 ° C, which can be the case for many uses, in particular when there is no recycling of the water or partial recycling.

The operation of the installation described above does not pose any problem if it is a case of discontinuous punctual use, for example an industrial bath heating at a determined temperature.

On the other hand, if it is a question of more or less continuous use, during which one wishes to have at all times a minimum temperature of the bath and at certain time only higher temperatures and / or high hot water flows, can proceed as described below to obtain the best possible plant operation.

Reference will now be made to FIG. 6 in which a schematic description has been made of how the submerged combustion reaction can be advantageously carried out.

In Figure 6 we see the different main elements of the installation which have been identified by the same reference numbers as in the previous figures. The burner 4 of the installation is supplied with gas by a pipe 36 and with air by a pipe 37. It will first of all be assumed that the installation is intended to normally supply a certain flow of hot water leaving at a determined temperature, for example between 70 and 88 ° C.

Under such operating conditions, the installation is advantageously piloted as follows.

The flow rate of water leaving the bath is checked by means of a measuring device 38. When this flow rate is greater than a determined minimum flow rate, the heating of the bath is controlled to the maximum temperature, which is detected by any suitably placed probe. Of course at the water outlet flow hot, drawn off at 11 corresponds to a substantially equivalent flow of cold water supplied at 10. This flow is controlled by a solenoid valve 39 whose electrical control 40 is connected as indicated at 41 to a level probe 42 which stops the supply cold water when the level of the bath tends to become too high in the tank, that is to say to submerge the plate 26. In fact, the proper functioning of the burner requires relatively precise determined pressure conditions outside of which a good combustion could not be obtained. Another probe (not shown), similarly controls the supply of cold water through line 10 when the level of the bath drops below a predetermined level, for example such as level 43 below which the optimal overpressure h in the confinement chamber 32 would no longer be obtained (FIG. 5). When the maximum bath temperature is reached, the measurement thermostat (not shown) cuts off the supply to the burner. The level of the bath drops due to the cancellation of the overpressure in the confinement chamber 32, for example substantially at the level marked 44 in FIG. 6. No cold water supply is allowed as long as the level in the chamber does not descend below a determined critical level measured for example by a probe 45 which controls the supply of cold water and prohibits under such conditions the ignition of the burner 4, as long as the level of the bath has not traced back.

In addition, in order to maintain the temperature of the bath at a minimum desired temperature, for example 70 ° C., the heating of the bath is stopped at this temperature if the sampling flow rate measured by the measuring device 38 is less than a predetermined minimum flow.

There are of course other procedures for operating the installation. Thus, according to a variant, the cold recycling or make-up water is brought at 10 into the washing tower, each time the level of the bath tends to fall below a determined minimum level, such as for example as measured by the probe 45. Simultaneously, the heating of the bath is controlled to a selected minimum temperature, for example 70 ° C., and the supply of cold water is stopped when the bath has risen to a maximum threshold determined, for example measured by probe 42. Heating to a higher temperature of the bath is only controlled when the bath level drops below threshold 42, which means that hot water was taken in 11 in the bath. A siphon forming an overflow 46 avoids exceeding the level of the threshold 42 in the absence of withdrawal of hot water in the bath and under the effect of condensation occurring in the washing tower and in the volume 13 above the bath.

It will be noted that the various means of the invention allow easy operation of the installation with excellent yields, thanks in particular to the effective contact between the fumes loaded with saturated vapors and the cold water returns and, on the other hand, thanks to the operation. under slight combustion overpressure improving efficiency. In addition, the pressure losses both on the smoke circuit and on the water recycling circuit are reduced to completely acceptable values and corresponding to normal gas and air supply pressures, no pump or booster 'being necessary.

Claims (10)

₁ . Heating installation of the submerged combustion type characterized in that in order to obtain with good yields heating temperatures clearly above 60 ° C., and for example going up to around 90 ° C., the installation is fitted (1 ) on the outlet of the fumes above the bath (3) to be heated by a washing tower (8) comprising in counter-current with the fumes a series of cascades forming several substantially continuous water curtains R arranged in series on the smoke path, said curtains being supplied by a flow of cold water (10) to be heated from the installation, said cascades comprising walls (15) for forming water curtains R provided at the top and bottom means such as teeth (16), projecting edges (17) and orifices (18) ensuring continuous formation without tearing of the curtains over their entire width. 2. Installation according to claim 1 characterized in that each cascade is fed by a bowl C formed essentially by an inclined wall (14) bottom ending on the raised side of the wall against the wall of the washing tower (8) and on the other side, leaving a reduced passage section S for the flue gases by a wall (15) mentioned above substantially vertical provided at the top with teeth or cutouts (16) ensuring the formation of the water curtain over the entire width of overflow of the waterfall and the lower part of which projects (17) below the contiguous lower wall (14) of the bowl. 3. Installation according to claim 2 characterized in that each bowl C is staggered relative to the lower bowl so as to provide a longer winding path for the fumes, each upper bowl overhanging about half of its length at - above the lower bowl. 4. Installation according to claim 3 characterized in that each curtain of water R is received above the level of the lower bowl C in a discharge gutter (21). 5. Installation according to one of claims 2 to 4 characterized in that condensation fins (22) protrude under the bottom surface (14) of the bowls C. 6. Installation according to one of the preceding claims characterized in that the washing tower (8) comprises at its base an enlarged connection section (24) with the volume (13) of the bath. 7. Installation according to one of the preceding claims characterized in that there is provided a tray (26) covering most of the surface of the bath (3) placed above the washing tower (8), said tray comprising a substantially horizontal surface (29) bordered by a wall (30) projecting above and below it, providing above it a volume (31) for collecting water falling from the washing tower and above a volume (32) for confining the fumes rising from the bath. 8. Method for operating an installation according to any one of the preceding claims, characterized in that the water outlet flow rate (11) from the bath is controlled and the heating of the bath is controlled up to at the maximum desired temperature (for example 88 ° C.) when said flow rate is greater than a determined minimum flow rate while when this flow rate is less than this determined minimum flow rate, the bath is only heated to a selected minimum determined temperature (e.g. 70 ° C). 9. A method of operating an installation according to any one of claims 1 to 7, characterized in that cold recycling or make-up water is brought into the bath by making it penetrate (10) at the top of the washing tower (8) each time the level of the bath drops below a determined minimum threshold (45), simultaneously the heating of the bath is controlled to a selected minimum determined temperature (for example 70 ° C.) , the supply of cold water is stopped when the bath has risen to a determined maximum threshold (42) and heating at a higher temperature of the bath is only controlled when the level of the bath drops below the maximum threshold determined above. 10. Method according to claim 8 or claim 9 characterized in that in operation of the installation controls the level (43) of the bath so that the plate (26) is partially submerged over a determined height.

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