FR2532040A1 - Refractory lining for furnace with oil of gas burner - Google Patents

Abstract

The refractory lining comprises e.g. ceramic heat storage material in brick or slab form arranged inside the furnace to at least partially surround the burner. This material has a flame-side inner layer with high thermally-conductivity and good thermal shock resistance. An outer layer, on the side of the heat storage material remote from the frame, has low thermal conductivity and high heat storage capacity. The heat storage material is pref. formed or assembled into a box-type or tubular insert, which may be made up of either separate slabs or several rectangular or circular rings.

Description

Device for reducing energy losses in a combustion chamber comprising an oil or az burner
The invention relates to a device for reducing energy losses in a combustion chamber comprising an oil or gas burner, in particular for operating a heating boiler, device in which a refractory accumulator material, for example ceramic, in the form of plates, bricks or the like, is stacked or arranged in the combustion chamber to at least partially surround the flame of the burners
However, these known devices for reducing energy losses in heating boilers have so far only given unsatisfactory results in practice. Their disadvantage lies in particular in the fact that the burner rises to a temperature which is too high.
The object of the present invention is therefore to improve the device of the aforementioned type so as to further increase the energy saving while keeping the burner at a temperature as low as possible.
This result is achieved according to the invention by the fact that the accumulator material of the head facing the burner flame has an internal layer of relatively high thermal conductivity and good resistance to thermal shock and, on the side opposite the flame of the burner, an outer layer of relatively low thermal conductivity and relatively high thermal capacity.

 Measurements and calculations have shown that the solution according to the invention is particularly effective at low flow temperature and low operating factor of the boiler, in particular in connection with a misty gas valve closing tightly and a draft regulator or in conjunction with an electro-mechanical control draft regulator (thus eliminating the heat check valve).

 The inner layer absorbs the thermal energy radiated by the burner flame and transmits it relatively quickly to the outer layer where it is actively stored. The heat accumulator material increases the available heat exchange surface. When the flame of the burner is stopped, the internal face of the accumulator material cools relatively quickly while most of the heat is stored in its external hood. of the burner. The energy savings were obtained in particular by the fact that the heat storage capacity of the storage material makes it possible to reduce the size of the burner burner while retaining the same heat emission. After a burner start-up, the temperature of the burnt gases increases slowly, which, in the case of intermittent operation, is equivalent to a decrease in the temperature of the burnt gases and, consequently, to an increase in efficiency. During periods of shutdown, the heat stored in the combustion chamber is returned and contributes to a large extent to the heating of the fluid to be heated. The advantages provided by the invention are especially valid in the event of a relatively low flow temperature and low factor of heating system operation. The solution according to the invention makes it possible to extend the downtime and consequently to reduce the consumption of fuel oil or gas. Despite the decrease in the temperature of the burnt gases, a more complete combustion is obtained. The heat yield is therefore increased.

 The accumulator material can preferably be produced in the form of an intermediate body in the form of a box or tubular in which the burner flame penetrates and which, on its sides, is completely surrounded by the accu: alator material, preferably at the rutin distance.

 The intermediate body is advantageously made in box form by means of individual plates or in the form of a tube by means of rings so as to allow easy installation in a combustion chamber.

The different rings of an intermediate body can be formed by individual plates or segments constituting quarter circles, semicircles or any other fraction of a circle forming sufficiently small building elements and therefore easy to maznipulerO
The individual plates, the individual segments or the rings can be connected by gluing, by clap fixing and / or by a removable assembly.

 The walls of the accumulator material can be provided with perforations. These perforations are used, if necessary, to voluntarily modify the direction of the burnt gases in order to bring them to the most favorable temperature possible2 as well as to increase the surface emitting heat of the accumulating material.

 According to another characteristic of the invention, the internal layer of the accumulator material can preferably consist of SiC or contain SiC and the external layer consist of a material with a high alumina content. This combination of the two layers constituted by a thermally relatively good conductive material and by a thermally relatively bad conductive material has proved to be particularly advantageous.

 To further enhance the effectiveness of the accumulator material according to the invention, the latter may comprise on the outer surface of its outer layer and / or of its inner layer structures increasing its surface, for example ribs.

The invention will be better understood using the description of embodiments price as examples, but not limitative, and illustrated by the appended drawing, in which
Figures 1 and 2 show schematically and in respective views (partially exploded) two embodiments of a heating installation according to the invention;
Figure 3 shows schematically and in perspective an arrangement of a material "two layers forming an intermediate body box-shaped according to the invention;
Figure 4 shows schematically and in section a heating installation comprising an accumulator material device according to the invention with tubular intermediate body;
FIG. 5 shows schematically and in perspective an accumulator device produced in the form of a tubular intermediate body according to the invention
FIG. 6 represents a diagram illustrating the temperature curve in the event of intermittent operation of the heating installation with and without the device according to the invention
FIG. 7 is a schematic view illustrating the increase in heat exchange surfaces and the resulting gain in thermal energy for the heated fluid
Figures 8a, 8b and 9a, 9b show elements in the form of plates and rings with structured surface for use in the context of the invention.

 The heating installation according to FIG. 1 comprises a combustion chamber 1 and a burner 2 placed in front. In the combustion chamber 1 is an arrangement of two-layer plates made of a refractory accumulator material 3. The accumulator material 3 constitutes an intermediate body i1 in the form of a box open on the side of the burner and into which the flame 40 Le- accumulator material 3 comprises an inner layer 9 facing the flame side 4 of the burner and an outer layer 10 facing the opposite side. The inner layer 9 is made of a refractory ceramic material of relatively high thermal conductivity and good resistance to thermal shock. The outer layer 10 is made of a refractory ceramic material of relatively low thermal conductivity and therefore of high thermal capacity. On its cssté opposite the burner 2, the intermediate body 11 in the form of a box formed by the accumulator material 3 can be closed by another vertical plate as illustrated in FIG. 3. The heating installation shown in FIG. 2 corresponds in its Prineipe to that of Figure 1. Here, however, the intermediate body 11 is tubular oralized and not in the form of a box like in Figure 1. This tubular intermediate body 11 is formed of individual segments 16. In Figures 1 and 2 , in the tube 5 connecting the combustion chamber 1 to the chimney 6 is installed a valve 7 which closes -automatically when the burner 2 stops and, during the downtime, prevents the dissipation of the heat stored in the accumulator material 3. The chimney 6 also includes a draft regulator 12 which limits the draft in the smoke tube, stabilizes the pressure in the combustion chamber and allows the chimney to be ventilated during the downtime free of hot air. In the case of an electro-mechanical draft regulator, forced ventilation is obtained.

 Figure 4 shows in section the heating installation according to Figure 2 with tubular intermediate body 11 and in which the support 13 is mounted adjustable in height in the combustion chamber 1 so that it can be installed at the correct height relative to flame 4 of the burner.

 In the embodiment according to FIG. 5, the two-layer refractory accumulator material 3 formed of individual segments 16 joined in rings constitutes a tubular intermediate body 11- which is also mounted adjustable in height on supports 13. To be able to be adapted to the depth of each combustion chamber, the support 13 is mounted telescopically adjustable in length in annular support bars 15. The tubular intermediate body 11, at its rear opening opposite the flame 4 of the burner, can between closed by a cover 14. The individual segments 16 can for example be joined by gluing to form the different rings or be assembled by any other fixing means. The segments may constitute quarter circles, semicircles or any other fraction of circles. The tubular intermediate body 11 may be in one piece in the axial direction or formed of several rings.

All the rings or some of them can have perforations in their wall 17 allowing the exhaust of the burnt gases to be oriented at will.

 P., r the curve as a function of time according to FIG. 6 of the temperature T of the combustion chamber in the event of intermittent operation of the burner 2, on the one hand, with the device according to the invention (line in solid line ) and, on the other hand, without this device (dashed line), we can observe a significant prolongation of downtime and pb.r consequently a reduction in the consumption of gas and fuel oil with the device according to invention. The corresponding fractions At of the burner on and off times are different and depend on the size of the heating installation and the heat required.

The temperature peaks of the curves are at the same height. In the case of operation with the device according to the invention, the duration of the running time is however approximately 20% less than that of operation without this device.

 As can be seen in FIG. 7, the intermediate body according to the invention extends the heat exchange from zone L1 to zone Li and L2 with a gain of thermal energy for the heated fluid.

 FIGS. 8a, 8b represent elements in the form of plates which are used in the constitution of an intermediate body il in the form of a box and which comprise, to enlarge their surface, structures in the form of ribs 8 which, in FIG. 8a , are only provided on the outer surface of the inner layer 9 of the accumulator material 3 and in FIG. 8b also on the outer surface of the outer layer 10. FIGS. 9a, 9b show corresponding elements produced in the form of rings. It is also possible to envisage an embodiment in which the structures increasing the surface are only provided on the external surface of the external layer 10.

Claims (10)

 1. Device for reducing energy losses in a combustion chamber comprising an oil or gas burner and in which a refractory accumulator material, for example ceramic, in the form of bricks, plates or the like is stacked or placed in the combustion chamber to at least partially surround the burner flame, characterized in that the accumulator material (3) on the side facing the flame (4) of the burner has an internal layer (9) with high thermal conductivity and good resistance thermal shock and, on the side opposite the flame (4), an outer layer (10) with low thermal conductivity and high thermal capacity  2. Device according to claim 1, characterized in that the accumulator material (3) is produced in the form of an intermediate body (11) in the form of a box or tubular or consists of parts assembled to form such an intermediate body .  3. Device according to claim 1 or 2, characterized in that the intermediate body (ii) is produced in the form of a box by means of individual plates or in the form of a tube by means of the rings.  4. Device according to claim 3, characterized in that the rings of the intermediate body (il) are formed by plates or individual segments (16).  5. Device according to any one of claims 1 to 4, characterized in that the individual plates, the individual segments or the rings are mutually connected by gluing, by fixing with spikes and / or by removable assembly.  6. Device according to claim 2, characterized in that the intermediate body (11) is made in one piece.  7. Device according to any one of claims 1 to 6, characterized in that bs walls of the accumulator material (9, 10) are provided with perforations (17).  8. Device according to claim 7, characterized in that the individual plates the individual segments or the rings provided with perforations (17) cause a deliberately determined deviation of the burnt gases as a function of their angular position  9. Device according to any one of claims 1 to 8, characterized in that the inner layer (9) is made of sic or contains SiC and that the outer layer (10) is made of a material with a high alumina content.  10. Device according to any one of claims 1 to 9, characterized in that the accumulator material (3) comprises structures increasing its surface, for example ribs (8), arranged on the outer surface of the outer layer ( 10) and / or the inner layer (9).