Regenerative burner

Abstract

A regenerative burner comprising at least one first burner and one second burner, that can be configured alternately in an ignited configuration and an extinguished configuration, is described. The regenerative burner also comprises a first ceramic element of the first burner and a second ceramic element of the second burner both arranged to accumulate heat from flue gases and transfer it to the air delivered to the first burner or the second burner. Advantageously, the regenerative burner comprises at least one refractory filter positioned between the first burner and the first ceramic element or positioned between the second burner and the second ceramic element. The refractory filter is configured to intercept the flue gases generated by the second burner or the first burner and traveling to the first ceramic element or the second ceramic element, respectively.

Description

[0001] Regenerative burner

[0002] ***

[0003] DESCRIPTION

[0004] Field of the Invention

[0005] The present invention relates to the field of high temperature heating furnaces. Specifically, the present invention relates to a regenerative burner that can be used, for example, for a steel furnace - forging, rolling, annealing or reheating furnaces - or a furnace of a waste incinerator.

[0006] State of the art

[0007] As is well known, various types of high-temperature heating furnaces (henceforth simply "furnaces") are used in the iron and steel industry; for example forging furnaces, rolling furnaces, annealing furnaces and reheating furnaces are used. In order to bring the products (slabs, metal pipes, billets etc.) to the desired temperature, furnaces can be equipped with regenerative burners.

[0008] According to the most common embodiment, regenerative burners are arranged in series along the product movement surface in the furnace, that is, along the movable surface of the furnace. Possibly the surface can also be stationary.

[0009] Regenerative burners have a structure that is symmetrical with respect to a plane of symmetry orthogonal to the furnace movement surface; in practice, each regenerative burner can be divided into two parts: a first part that is located, for example, to the left of the plane of symmetry, and a second part that is located, for example, to the right of the plane of symmetry.

[0010] As the second part is substantially a mirror image of the first part (and vice versa), the regenerative burner has a symmetrical structure.

[0011] A regenerative burner 100 according to the known art is shown schematically in Figure 1 , and the plane of symmetry a of the regenerative burner 100 is also shown. The movable surface of the furnace 101 and the respective furnace 102 are also schematically shown. The regenerative burner 100 has a first part 103 shown to the left of the plane of symmetry a, and a second part 104 shown to the right of the plane of symmetry a: the first part 103 and the second part 104 are each other's mirror image with respect to the plane of symmetry a.

[0012] With reference to the first part 103, it can be seen that the regenerative burner 100 has a line 105 for delivering combustion air, which, for the sake of simplicity, will be referred to simply as "air", a corresponding valve 106 to open or close the air passage in the line 105, a burner 107, a line 108 for discharging flue gases, and a corresponding valve 109 to open or close the flue gas passage through the line 108. As is well known, an element made of ceramic material is housed at the burner 107, and therefore it is referred to in the industry as ceramic element or ceramic mass. In Figure 1 , the ceramic element is denoted by reference 110. The ceramic element 110 can be placed in a manifold duct upstream of the burner 107.

[0013] For example, the ceramic element 110 can be made of one of the following materials: mullite, alumina, cordierite, refractory materials with high resistance to thermal shocks and alloyed with high thermal conductivity elements.

[0014] The second part 104 has the same components as the first part 103; in particular, it comprises: an air delivery line 111 , a corresponding valve 112, a burner 113, a flue gas exhaust line 114, a corresponding valve 115, and a ceramic element 116 housed at the burner 113.

[0015] As is well known, the symmetrical structure of the regenerative burner 100 allows the burners 107 e 113 to be operated alternately: when one is ignited the other is extinguished, and vice versa. In practice, an operating cycle of the regenerative burner comprises a first step in which the burner 107 is ignited and the burner 113 is extinguished and a second step in which the burner 107 is extinguished and the burner 113 is ignited. These cycles are repeated throughout the service life of the steel furnace.

[0016] Therefore, the air delivery lines 105 and 111 and the flue gas exhaust lines 108 and 114 are alternately opened and closed by the corresponding valves.

[0017] For example, Figure 1 shows the step in which the burner 107 is ignited and the burner 113 is extinguished: the arrows in Figure 1 denote the air and flue gas paths.

[0018] Air flows into the burner 107 through the line 105 (the valve 106 is open) and the flue gas exhaust line 108 is closed by the corresponding valve 109.

[0019] Air is used in the combustion operated by the burner 107 and the flue gases generated by the burner 107 passes through the burner 113 (extinguished) and are discharged through the flue gas exhaust line 114 (the valve 115 is open), the air delivery line 111 being closed by the corresponding valve 112.

[0020] After this first step, the burner 107 is extinguished and the burner 113 is ignited. As a result, the air delivery line 105 is closed by the corresponding valve 106 and the air delivery line 111 for delivering air to the burner 113 is opened instead. Correspondingly, the flue gas exhaust line 108 is opened and the flue gas exhaust line 114 is closed by the corresponding valve 115.

[0021] Once the operation of the burner 113 is over, the cycle is repeated.

[0022] The regenerative burner 100 allows energy to be saved precisely because of the alternating operation of the burner 107 and the burner 113; indeed, when the burner 107 is ignited, the flue gases produced by this burner pass through the burner 113 and the respective ceramic element 116. Since these flue gases are hot, they heat the ceramic element 116.

[0023] When the burner 107 is extinguished and the burner 113 is ignited, air flowing from the line 111 to feed the burner 113 passes through the ceramic element 116; the air is heated as it passes through the ceramic element 116 and is therefore preheated when it is used by the burner 113.

[0024] This way, less energy is required for the burner 113 to heat the product in the furnace 102. When the burner 113 is ignited, the flue gases cause the ceramic element 110 to be heated, which will transfer heat to the air delivered from line 105 when the burner 107 will be ignited.

[0025] Generally, each burner 107, 113 remains ignited for a time interval between 20 seconds and 100 seconds, which corresponds to the time required to heat the ceramic element of the extinguished burner.

[0026] As is well known, whilst the ceramic elements 110, 116 allow the energy used by the burners 107, 113 to be reduced, the very presence of the ceramic elements 110, 116 is a critical issue for the operation and maintenance of regenerative burners.

[0027] This is also officially recognized in the document “Best Available Techniques (BAT) Reference Document for the Ferrous Metals Processing Industry” ( Industrial Emissions Directive 2010 / 75 / EU (Integrated Pollution Prevention and Control) - Aries, E., Gomez Benavides, J., Mavromatis, S., Klein, G., Chronopoulos, G., Roudier, S - 2022 https7 / ejppcbJrc?eQ.eyropa,eij / reference / ferrous-mQtals--processsng--jndijStry) .

[0028] Indeed, flue gases passing through the ceramic elements 110, 116 are laden with residues produced by the combustion operated by the burners 107, 113: these residues are deposited in the ceramic elements 110, 116 and, over time, clog them.

[0029] In addition, the flue gases contain acidic substances that cause corrosion of the ceramic elements 110, 116 and damage the valves that regulate the air delivery or flue gas or other component escape.

[0030] Due to these aspects, the ability of the ceramic elements 110, 116 to ensure adequate heat transfer rapidly deteriorates. There is therefore a need for frequent replacement of these ceramic elements.

[0031] This obviously causes an increase in costs and makes the system less efficient, as it must be operated periodically to replace the ceramic elements or other components of the regenerative burner.

[0032] The above problems are also recognized for other types of regenerative burners, such as rotary burners comprising a plurality of burners, radiant-tube burners, and in general also regenerative burners used in furnaces for waste incinerator.

[0033] CN 1171536 describes a regenerative burner according to the preamble of claim 1. In an embodiment described in this document, the regenerative burner may have a filter arranged in series with honeycomb elements which allow heat to be stored; the filter has high heat resistance and is made as a spherical body (or an assembly of multiple spherical bodies as shown in Figure 9B). It is described that this embodiment may be useful to prevent clogging in case molten dust is generated during the use of the regenerative burner.

[0034] Such a solution, however, can give frequent problems of blockage to the passage of delivered air and / or flue gases and require frequent filter replacement. In addition, the solution according to CN 1171536 may not be efficient in terms of heat exchange between the filter and the flue gases or delivered air.

[0035] Other solutions according to the known art are described in CN 206094076 and US 4983118.

[0036] Summary of the invention

[0037] Object of the present invention is to provide a regenerative burner which is easy and inexpensive to make and which ensures both adequate passage of delivered air or flue gases through the filter and adequate heat exchange between filter and flue gases or between filter and delivered air.

[0038] Another object of the present invention is to provide a regenerative burner that allows the frequency of replacement of the ceramic elements to be reduced, the maintenance costs of the regenerative burner to be lowered, and its efficiency to be increased.

[0039] Therefore, a first aspect of the present invention relates to a regenerative burner according to claim 1 .

[0040] The regenerative burner according to claim 1 is designed to be used in a high temperature heating furnace, such as in a furnace of an iron and steel plant (forging furnace, rolling furnace, annealing furnace, reheating furnace, etc.) or in an incinerator furnace. Therefore, it is clear that "high-temperature heating furnace" means any furnace used to heat a product to high temperature regardless of the particular heat treatment that takes place therein. In practice, the present invention is directed to a regenerative burner for a high-temperature heating furnace. A high-temperature heating furnace (henceforth simply "furnace") has a furnace, and the regenerative burner according to the present invention can be used to heat the respective furnace and one or more possible products therein. As is well known, the furnace can have a surface, which can be movable or stationary, on which the products to be heated (slabs, metal pipes, billets, waste, etc.) are placed and can be heated by means of one or more regenerative burners according to the present invention.

[0041] The regenerative burner can be made, in its general aspects, according to the known art. Specifically, the regenerative burner comprises at least one first burner and one second burner that are suitable for generating a flame to heat the products in the furnace. In other words, the regenerative burner may comprise two or more burners.

[0042] The first burner and second burner can be configured alternately in an ignited configuration corresponding to the first burner or second burner generating a flame, or heat, and in an extinguished configuration corresponding to the first burner or second burner not generating a flame, or heat.

[0043] Basically, when the first burner is ignited the second burner is extinguished, and when the first burner is extinguished the second burner is ignited.

[0044] The regenerative burner preferably comprises an air delivery line for delivering air to the first burner that can also be arranged to discharge the flue gases generated by the second burner, and another air delivery line for delivering air to the second burner that can also be arranged to discharge the flue gases generated by the first burner.

[0045] In the context of the present invention, flue gas means a combustion product of the first burner or second burner. The flue gases produced by the first and second burners contain combustion residues, or simply "residues" of different sizes.

[0046] As is well known, the regenerative burner comprises a first ceramic element, or a first ceramic mass, and a second ceramic element, or a second ceramic mass.

[0047] Preferably, the first ceramic element is located at the first burner while the second ceramic element is located at the second burner. The first ceramic element and the second ceramic element can be housed in a manifold duct positioned upstream of the corresponding burner.

[0048] As is well known, their function is, in a first step, to accumulate the heat or energy of the flue gases and, in a second step, to transfer this heat or energy to the air delivered.

[0049] Basically, when the first burner is ignited, the flue gases pass through the second ceramic element, which heats up by absorbing their heat, or energy. When the first burner is extinguished and the second burner is ignited, air passes through the second ceramic element and heats up. Therefore, the second ceramic element transfers heat to the air, and the second burner uses less energy to operate, that is, it consumes less fuel (such as methane gas).

[0050] The first ceramic element operates in a manner that mirrors the second one: it heats up when the second burner is ignited and then transfers heat to the air delivered to the first burner.

[0051] The regenerative burner comprises at least one refractory filter, i.e. a filter made of refractory material.

[0052] For the purpose of the present invention, refractory filter may mean a filter made of a refractory material, that is, one that is capable of withstanding high temperatures (e.g., up to 1650°C) without undergoing significant alteration.

[0053] This at least one refractory filter is positioned between the first burner and the first ceramic element or between the second burner and the second ceramic element. In practice, the at least one refractory filter can be located at the first burner or at the second burner. The at least one refractory filter is positioned at the first burner or the second burner, meaning that it can be positioned upstream (or downstream depending on the direction considered) of one of them. For example, the at least one refractory filter can be positioned in a manifold duct together with the first ceramic element or the second ceramic element.

[0054] Regardless of how the regenerative burner is made, the function of the at least one refractory filter is to filter flue gases coming from the second burner and traveling to the first ceramic element or to filter the flue gases coming from the first burner and traveling to the second ceramic element. Therefore, in light of the operation of the regenerative burner, the at least one refractory filter is functionally arranged between the first ceramic element and the second burner or between the second ceramic element and the first burner.

[0055] In practice, the at least one refractory filter is configured to intercept the flue gases generated by the second burner or the first burner in ignited configuration and traveling to the first ceramic element or the second ceramic element, respectively.

[0056] The presence of the at least one refractory filter allows flue gases to be filtered before they are intercepted by the first ceramic element or the second ceramic element; in practice, the at least one refractory filter ensures that the amount of residues from the flue gases deposited on the first ceramic element or the second ceramic element is not such as to jeopardize the functionality of the regenerative burner and require frequent and costly maintenance.

[0057] The at least one refractory filter allows these benefits to be achieved mainly in two ways.

[0058] First of all, the at least one refractory filter acts as a very filter that can physically stop flue gas residues, or a part of them, thus preventing them from reaching the first ceramic element or the second ceramic element.

[0059] In addition, the at least one refractory filter causes a decrease in the size of the residues which successfully pass through it. This may be due to turbulent motions and collisions that occur while passing through the refractory filter. Therefore, even if some of the residues reach the first ceramic element or the second ceramic element, their size is limited and does not cause the problems described above with reference to regenerative burners according to known art, that is, those without the at least one refractory filter.

[0060] The at least one refractory filter allows flue gas residues to be trapped in a regenerative burner compartment where it is easier to expel the residues themselves into the furnace, where they can be more easily removed.

[0061] This helps to limit the number of interventions required for cleaning and replacement of the various components of the regenerative burner.

[0062] In addition, the at least one refractory filter at least partially stops the acidic components in the flue gases, so that the regenerative burner components are less damaged.

[0063] These advantages allow maintenance costs of the regenerative burner to be decreased and the efficiency thereof to be increased, since the first ceramic element or second ceramic element remain less clogged by the residues in the flue gases than in the case of regenerative burners without a refractory filter.

[0064] Advantageously, the at least one refractory filter comprises a plurality of through holes.

[0065] Basically, flue gases or delivered air pass through the at least one refractory filter by traveling along the through holes.

[0066] This is an advantage compared to the way of implementing the solution described in CN 1171536, since the through holes allow flue gases or delivered air to pass properly without creating frequent blockages while ensuring appropriate heat exchange between the at least one refractory filter and delivered air or flue gases.

[0067] Preferably, these through holes extend along a first direction corresponding, in use, to the direction the flue gases have when passing through the at least one refractory filter toward the first ceramic element or the second ceramic element.

[0068] Preferably, the diameter of the through holes is between 15.0 mm and 60.0 mm. Preferably, said through holes have a circular section. Preferably, the at least one refractory filter has an average of 30-70 holes / m2, preferably 54-60 holes / m2, still more preferably 57 holes / m2(obviously considered with respect to the two opposite faces in which the through holes are cut).

[0069] Preferably, the through holes extend at least 250 mm; more preferably, the length of the through holes extends between 250 mm and 1900 mm. For example, the through holes can be 300 mm, 800 mm, 1000 mm or 1500 mm long.

[0070] Obviously, the through holes extend for a length that corresponds to that of the corresponding at least one refractory filter.

[0071] The at least one refractory filter is made of low / medium-cement content concrete or any other material, or combination of high-density materials, resistant to thermal shocks and alloyed with high-thermal conductivity elements.

[0072] The first ceramic element and the second ceramic element can be made of one or more of the following materials: mullite, alumina, cordierite or any other material, or combination of refractory materials, with high resistance to thermal shocks and alloyed with high-thermal conductivity elements.

[0073] Preferably, the first ceramic element and the second ceramic element comprise a plurality of through holes extending along a second direction corresponding, in use, to the direction in which flue gases or air passing through the first ceramic element or the second ceramic element flow.

[0074] Preferably, the holes of the first ceramic element and / or the second ceramic element have a circular, or honeycomb, or square or rectangular section. Preferably, the first ceramic element and / or the second ceramic element have an average of 1-10 holes / cm2.

[0075] An additional advantage of the at least one refractory filter is that, in addition to the ceramic elements, it acts as a component capable of absorbing heat from the flue gases of the first burner or second burner and transferring it to the air delivered to the second burner or the first burner.

[0076] In the preferred embodiment, the regenerative burner comprises two refractory filters: a first refractory filter and a second refractory filter. The first refractory filter is positioned between the first ceramic element and the first burner, so as to intercept the flue gases generated by the second burner when it is ignited and which travel to the first ceramic element; the second refractory filter is positioned between the second ceramic element and the second burner, so as to intercept the flue gases generated by the first burner when it is ignited and which travel to the second ceramic element.

[0077] This makes it possible to preserve the functionality of both ceramic elements and to maximize the benefits achievable with this solution, including in terms of heat transfer.

[0078] According to a preferred embodiment, the regenerative burner comprises a pair of burners. In particular, the first burner and the second burner are arranged on opposite sides of a plane of symmetry of the regenerative burner and are therefore spaced apart from each other.

[0079] In practice, the regenerative burner may have a plane of symmetry which divides the regenerative burner into two parts, and, indeed, the first burner and the second burner are positioned mirroring each other with respect to this plane of symmetry.

[0080] When the regenerative burner is part of a high-temperature heating furnace equipped with a furnace and a movable or stationary surface on which the products to be heated are placed, the first burner and the second burner are positioned on opposite sides of the furnace or movable surface. In particular, the plane of symmetry of the regenerative burner is preferably orthogonal to the surface of the furnace.

[0081] The first burner and second burner face each other. In other words, the first burner and the second burner are arranged to generate a flame, or heat, in the direction of each other, that is, in the direction of the plane of symmetry.

[0082] The regenerative burner comprises a first air delivery line designed for delivering air to the first burner in an ignited configuration, and a second air delivery line designed for delivering air to the second burner in an ignited configuration.

[0083] In practice, the first air delivery line and the second air delivery line, when open, allow air to be brought to the first burner and the second burner, respectively. Obviously, for the purposes of the present invention, air means combustion air required for the operation of the first burner and the second burner. Preferably, the first air delivery line is connected, or linked, to the first burner and the second air delivery line is connected, or linked, to the second burner.

[0084] The first air delivery line and the second air delivery line preferably have one or more respective valves designed to open or close the passage of air into the respective first air delivery line or second air delivery line toward the corresponding burner.

[0085] The regenerative burner also comprises a first flue gas exhaust line and a second flue gas exhaust line.

[0086] The first flue gas exhaust line is positioned at the first burner, that is, it is connected, or linked, to the first burner, whereas the second flue gas exhaust line is positioned at the second burner, that is, it is connected, or linked, to the second burner.

[0087] The first flue gas exhaust line is designed to discharge the flue gases generated by the second burner when the latter is in the ignited configuration, whereas the second flue gas exhaust line is designed to discharge the flue gases generated by the first burner when the latter is in the ignited configuration.

[0088] In practice, when the first burner is ignited, air is brought to the first burner via the first air delivery line, and the flue gases are brought out of the plant via the second flue gas exhaust line by passing through the second burner, which is extinguished; when the second burner is ignited, air is brought to the second burner via the second air delivery line, and the flue gases are discharged via the first flue gas exhaust line by passing through the first burner, which is extinguished. Alternatively, the regenerative burner can be a rotary regenerative burner that comprises a plurality of burners and is of the type shown in Figure 2.21 on p. 55 of the document mentioned above "Best Available Techniques (BAT) Reference Document for the Ferrous Metals Processing Industry" (year 2022). Or it can be a regenerative radiant-tube burner of the type shown on page 581 "Best Available Techniques (BAT) Reference Document for the Ferrous Metals Processing Industry" (year 2022) comprising a first burner and a second burner and a single line combined with each of the first burner and the second burner. This line alternately functions as an air delivery line or a flue gas exhaust line.

[0089] In its second aspect, the present invention relates to a high-temperature heating furnace comprising one or more regenerative burners. The high- temperature heating furnace can be a steel furnace (such as a forging furnace, rolling furnace, annealing furnace, reheating furnace) or an incinerator furnace. Brief list of the figures

[0090] Further characteristics and advantages of the invention will be more evident by the review of the following specification of a preferred, but not exclusive, embodiment which is depicted for illustration purposes only and without limitation, with the aid of the attached drawings, in which:

[0091] - figure 1 is a schematic elevation view of a regenerative burner according to the known art;

[0092] - figure 2 is a schematic elevation view of a preferred embodiment of a regenerative burner according to the present invention;

[0093] - figure 3 is a sectional view considered with respect to a plane orthogonal to the plane of symmetry [3 shown in Figure 2 and relating to the refractory filter 19 and the ceramic element 17;

[0094] - figure 4 is a sectional view considered with respect to a plane parallel to the plane of symmetry [3 shown in Figure 2 and relating to the refractory filter 19 and the ceramic element 17;

[0095] - figure 5 is a schematic top view of a steel furnace comprising a regenerative burner 1 of the type shown in figure 2 and a regenerative burner T of the type shown in figure 1 ; this figure refers to an experimental test;

[0096] - figure 6 corresponds to pictures of the ceramic elements 11 and 17 of the regenerative burner 1 shown in Figure 5, at the end of the experimental test;

[0097] - figure 7 corresponds to pictures of the ceramic elements 110 and 116 of the regenerative burner T shown in Figure 5, at the end of the experimental test.

[0098] Detailed description of the invention

[0099] Figure 2 schematically shows a preferred embodiment of a regenerative burner according to the present invention; the regenerative burner is denoted by the reference number 1 .

[0100] The regenerative burner 1 may have the general features of a regenerative burner according to the known art, such as described above with reference to Figure 1 .

[0101] The regenerative burner 1 is combined with a furnace in an iron and steel plant, for example, it may be part of a forging furnace, rolling furnace, annealing furnace or reheating furnace.

[0102] For this reason, Figure 2 shows the movable surface of the furnace 2, on which the products heated in the furnace are moved, and the furnace 3 where precisely the heating of products by the regenerative burner 1 takes place. The surface where the products are placed can be stationary.

[0103] The regenerative burner 1 has a plane of symmetry (3, that is, it comprises a first part 4 (shown on the left) and a second part 5 (shown on the right) mirroring each other with respect to the plane of symmetry [3.

[0104] In a known way, each of the first part 4 and the second part 5 comprises: an air delivery line 6, 12 for delivering air, a corresponding valve 7, 13 to open or close the air passage in the line 6 or 12, a burner 8, 14, a flue gas exhaust line 9, 15 for discharging the flue gases produced by the respective burner 8, 14, and a respective valve 10, 16 to close or open the flue gas passage in the line 9, 15.

[0105] The regenerative burner 1 also comprises a ceramic element housed at each of the burners 8, 14. Specifically, a ceramic element 11 is housed at the burner 8 and a ceramic element 17 is housed at the burner 14.

[0106] The regenerative burner 1 can operate according to the known art: the burners 8 and 14 are ignited and extinguished alternately so as to heat the ceramic element 17 or 11 of the opposite part 5, 4 and preheat the air that will later be delivered by the line 12 or 6 of the part 5, 4.

[0107] The ceramic elements 11 , 17 can be made according to the known art. For example, each ceramic element 11 , 17 can be made in one piece or can be composed of one or more units arranged side by side to form precisely one ceramic element.

[0108] The ceramic elements can be made of a material selected from: mullite, alumina, cordierite or any other material, or combination of refractory materials, with high resistance to thermal shocks and alloyed with high-thermal conductivity elements.

[0109] Each of the ceramic elements 11 , 17 has a plurality of through holes formed along the traveling direction of air or flue gases through the regenerative burner 1 .

[0110] These holes may have a section with a circular, or honeycomb, or square, or rectangular shape, etc.

[0111] Each hole can have an average size between 2.0 mm and 5.0 mm.

[0112] Preferably, the ceramic elements 11 , 17 have an average of 1 -10 holes / cm2(obviously considered with respect to the two faces in which the holes open).

[0113] The regenerative burner comprises at least one filter made of refractory material, hereinafter referred to as "refractory filter", at one of the two burners 8, 14 and arranged between the ceramic element 11 , 17 and the respective burner 8, 14.

[0114] For example, the regenerative burner 1 may comprise a refractory filter 18 placed at the burner 8 and arranged between the ceramic element 11 and the burner 8, or a refractory filter 19 placed at the burner 14 and arranged between the ceramic element 17 and the burner 14.

[0115] Preferably, the regenerative burner 1 comprises two refractory filters: a first refractory filter 18 positioned at the burner 8 and a second refractory filter 19 positioned at the burner 14.

[0116] The refractory filters 18 and 19 are precisely made of refractory material, that is, a material capable of withstanding high temperatures for long periods while remaining chemically inert.

[0117] For example, the refractory filters 18, 19 can be made of low / medium- cement content concrete or any other material, or combination of high-density materials, resistant to thermal shocks and alloyed with high-thermal conductivity elements.

[0118] The refractory filters 18, 19 have a plurality of through holes designed to intercept the flow of air or flue gases passing alternately into the corresponding burner s, 14.

[0119] Preferably, these holes have a circular section.

[0120] Preferably, the diameter of these holes is between 15.0 mm and 60.0 mm.

[0121] For example, these through holes can extend along 300 mm, 800 mm or 1000 mm.

[0122] Preferably, these holes are formed by arranging a series of tubes wrapped with an insulating material in the regenerative burner 1 , or in a separable portion of the regenerative burner 1 , and then providing a refractory material casting. Once the refractory material has solidified, the tubes are pulled out (this operation is facilitated by the presence of the insulating material) so as to obtain this refractory filter 18, 19. If the refractory filter 18, 19 had been formed in a separable portion of the regenerative burner 1 , that portion, with the respective refractory filter 18, 19, is obviously combined with the rest of the regenerative burner 1 .

[0123] Preferably, the refractory filters 18, 19 have an average of 30-70 holes / m2, preferably 54-60 holes / m2, still more preferably 57 holes / m2 (obviously considered with respect to the two opposite faces in which the holes are cut).

[0124] Regardless of how the regenerative burner 1 is made (i.e., how the components and manifolds are arranged with respect to each other), the refractory filters 18, 19 intercept flue gases which are traveling to the respective ceramic element 11 , 17 and are produced by the opposite burner 14, 8.

[0125] With reference to the arrows denoting the direction of air and flue gases in Figure 2 and taking into consideration the normal operation of a regenerative burner, it is clear that: when the burner 8 is ignited and the burner 14 is extinguished, air is delivered to the burner 8 via the line 6, passes through the ceramic element 11 and the refractory filter 18, and is used as comburent by the burner 8 which generates the flame that heats the furnace 3.

[0126] The flue gases produced by the burner 8 are discharged through the second part 5, i.e., through the flue gas exhaust line 16 (as denoted in Figure 2 by the respective arrows).

[0127] Therefore, the flue gases pass through the ceramic element 17: in regenerative burners according to the known art, the residues and acid substances in the flue gases accumulate in the ceramic element 17 and reach the line 15, thus causing the damage exposed above in reference to the known art.

[0128] These drawbacks can be minimized thanks to the refractory filter 19, as the residues and acidic substances are intercepted by the refractory filter 19 and reach the ceramic element 17 and the following components of the regenerative burner 1 in smaller quantities.

[0129] When the burner 8 is extinguished and the burner 14 is ignited, the operation is reversed: the refractory filter 18 at least partially intercepts and traps the residues and acid substances produced by the burner 14, thus preventing them from reaching the ceramic element 11 and the line 9 in significant quantities.

[0130] In practice, the refractory filters 18, 19 cause the residues passing through the filter holes to be filtered and disintegrated due to the turbulence and shocks generated as they pass through the holes of the refractory filters 18, 19.

[0131] At the same time, the refractory filters 18, 19 act as a physical filter for acidic substances in the flue gases, which remain at least partially trapped in the refractory filters 18, 19 without passing through.

[0132] For example, Figures 3 and 4 show schematic views of sections of the regenerative burner 1 at the refractory filter 19 and the corresponding ceramic element 17.

[0133] Figure 3 is a section considered with respect to a plane orthogonal to the plane of symmetry (3, whereas Figure 4 is a section considered with respect to a plane parallel to the plane of symmetry [3.

[0134] The direction of flue gas flow is denoted by the arrows in Figure 4.

[0135] Figures 3 and 4 also schematically show the holes 22 of the refractory filter 19.

[0136] The Applicant carried out a qualitative experimental test to evaluate the filtering capabilities of the refractory filters 18, 19.

[0137] This experimental test will be described with reference to Figures 5-7.

[0138] Figure 5 is a schematic top view of the furnace 120 used: it is a rolling furnace comprising a movable surface 2' for moving billets in the direction denoted by the arrow in Figure 5.

[0139] Of course, it is possible to use the regenerative burner 1 in any other high-temperature heating furnace, such steel furnaces or incinerator furnaces.

[0140] The furnace 120 comprises several regenerative burners arranged in series on the sides of the movable surface 2'.

[0141] The regenerative burner 1 , highlighted with a circle, and a regenerative burner T, highlighted with a square, can be recognized among various regenerative burners. The regenerative burner 1 is of the type described in Figures 2-4: it comprises two burners 8, 14, two corresponding ceramic elements 11 , 17 and the refractory filters 18, 19 (not visible in Figure 5). The regenerative burner T is of the type described in Figure 1 , i.e., it comprises two burners 107, 113, two corresponding ceramic elements 110, 116 (not shown in Figure 5) and is without refractory filters.

[0142] The furnace 120 was operated by alternately igniting the burners of each regenerative burner, as described above.

[0143] In addition, the furnace 120 was kept operational for 12 months and, at the end, the condition of the ceramic elements was visually compared.

[0144] Figures 6 and 7 are precisely pictures of the ceramic elements 11 , 17 of the regenerative burner 1 and the ceramic elements 110, 116 of the regenerative burner T, respectively.

[0145] It is evident that a higher level of residues is deposited on the surface of the ceramic elements of the burner T; indeed, the ceramic elements of the regenerative burner 1 are almost free of residues.

[0146] In practice, by comparing Figures 6 and 7, it can be seen that the refractory filters 18, 19 protect the ceramic elements 11 , 17 from accumulation of residues present in the flue gases generated by the burners, thus ensuring greater efficiency over time, a longer service life, and allowing maintenance / replacement costs which burden the regenerative burners to be limited.

[0147] Refractory filters 18, 19 are less expensive than ceramic elements; therefore, replacing the refractory filters 18, 19 is less expensive than replacing the ceramic elements. In addition, the presence of the refractory filters 18, 19 allows residues to accumulate in compartments of the regenerative burner where it is easier for them to be ejected into the furnace when the respective air delivery line is opened.

[0148] This means that costs and the need for maintenance and replacement operations on the plant can be further decreased.

[0149] The test showed that the residues on the ceramic elements 11 , 17 are smaller in size than those which normally accumulate on the ceramic elements of regenerative burners without refractory filters; clearly, the refractory filters not only act as a filter for larger residues, but also reduce the residues that successfully pass through the filter, thus reducing their harmfulness to the ceramic elements.

[0150] The use of the refractory filters 18, 19 did not cause any pressure drop in either the flue gas calibration step or the air delivery calibration step.

[0151] Finally, it has been observed that the refractory filters 18, 19 make it possible to increase the capacity of the regenerative burner 1 to save energy by extracting heat from the flue gases and transferring it to the delivered air.

[0152] In a test carried out in situations similar to the previous one, two thermocouples TC1 , TC2 were placed upstream and downstream of the refractory filter 19, at the location shown in Figure 4.

[0153] Two similar thermocouples were placed in the same positions in a regenerative burner without refractory filters.

[0154] The tables below show, for each regenerative burner, the data relating to the operation of the regenerative burner for 5 consecutive hours; in particular, the minimum and maximum differences between the temperature T2 detected by the thermocouple TC2 and the temperature T1 detected by the thermocouple TC1 , and the average of the differences for each hour of operation, are shown.

[0155] Table 1 corresponds to data detected for the regenerative burner T without refractory filters:

[0156] Table 2 corresponds to data detected for the regenerative burner 1 equipped with refractory filters

[0157] It is clear that the presence of the refractory filters results in a more pronounced difference between the temperature T2 and the temperature T1. This proves that heat transfer is more pronounced if a regenerative burner 1 equipped with refractory filters is used.

[0158] These data show that it is possible to achieve greater efficiency in heat exchange by using a regenerative burner 1 and, therefore, also further reduce the costs required to operate the plant.

[0159] It is likely that this advantage is achieved, firstly, by the very fact that refractory filters are provided that allow the useful surface area for heat exchange to be increased, and secondly, by the fact that refractory filters allow the amount of residues deposited on the ceramic elements and the size of the residues themselves to be limited; therefore, not only the refractory filters increase the useful life of the ceramic elements, but also allow the efficiency of the ceramic elements in heat exchange to be maintained high over time.

[0160] In order to meet contingent and specific requirements, several variations and modifications could be made by a field technician to the illustrated and described embodiments of present invention, provided that all are included in the protection scope of the invention as defined by the following claims.

Claims

CLAIMS1. A regenerative burner (1 ) comprising: at least one first burner (8) and one second burner (14) that can be configured alternately in an ignited configuration and an extinguished configuration, and at least one first ceramic element (11 ) and one second ceramic element (17), said first ceramic element (11 ) and said second ceramic element (17) being suitable for accumulating the heat of the flue gases generated by the second burner (14) and the first burner (8), respectively, in ignited configuration, and to transfer said accumulated heat to the air delivered to the first burner (8) and the second burner (14), respectively, in ignited configuration, and comprising at least one refractory filter (18, 19) positioned: between said first burner (8) and said first ceramic element (11 ), or between said second burner (14) and said second ceramic element (17), wherein said at least one refractory filter (18, 19) is configured to intercept the flue gases generated by the second burner (14) in the ignited configuration and traveling to the first ceramic element (11 ) or to intercept the flue gases generated by the first burner (8) in ignited configuration and traveling to the second ceramic element (17), characterized in that said at least one refractory filter (18, 19) comprises a plurality of through holes (22).

2. Regenerative burner (1 ) according to claim 1 , wherein said through holes (22) are formed in opposite surfaces of said at least one refractory filter (18, 19).

3. Regenerative burner (1 ) according to claim 1 or 2, wherein said through holes (22) extend along a first direction corresponding, in use, to the direction of the flow of the flue gases traveling to said first ceramic element (11 ) or said second ceramic element (17).

4. Regenerative burner (1 ) according to claims 1-3, wherein saidthrough holes (22) have a diameter between 15.0 mm and 60.0 mm.

5. Regenerative burner (1 ) according to claims 1-4, wherein the through holes (22) have density of 30-70 holes / m2, preferably 54-60 holes / m2, still more preferably 57 holes / m2.

6. Regenerative burner (1 ) according to claims 1-5, wherein the through holes (22) extend along at least 250 mm.

7. Regenerative burner (1 ) according to any one of the preceding claims, wherein said at least one refractory filter (18, 19) is made of low / medium-cement content concrete or any other material, or combination of high-density materials, resistant to thermal shocks and alloyed with high- thermal conductivity elements.

8. Regenerative burner (1 ) according to any one of the preceding claims, wherein said first ceramic element (11 ) and said second ceramic element (17) are made of one or more of the following materials: mullite, alumina, cordierite, or any other material, or combination of refractory materials, with high resistance to thermal shocks and alloyed with high-thermal conductivity elements.

9. Regenerative burner (1 ) according to any one of the preceding claims, wherein each of said first ceramic element (11 ) and second ceramic element (17) comprises a plurality of through holes having a circular or honeycomb, or square or rectangular shaped section.

10. Regenerative burner (1 ) according to any one of the preceding claims, wherein said at least one refractory filter (18, 19) is suitable for accumulating the heat of the flue gases generated by said second burner (14) or said first burner (8) in ignited configuration and to transfer the accumulated heat to the air delivered to said first burner (8) or said second burner (14), respectively, in ignited configuration.

11. Regenerative burner (1 ) according to any one of the preceding claims, comprising a first refractory filter (18) and a second refractory filter (19), and wherein:- said first refractory filter (18) is positioned between said first burner (8) and said first ceramic element (11 ), said first refractory filter (18) being configured to intercept the flue gases generated by said second burner (14) in ignited configuration, and- said second refractory filter (19) is positioned between said second burner (14) and said second ceramic element (17), said second refractory filter (19) being configured to intercept the flue gases generated by said first burner (8) in ignited configuration.

12. Regenerative burner (1 ) according to any one of the preceding claims, comprising: a first air delivery line (6) for delivering air to said first burner (8) and a second air delivery line (12) for delivering air to said second burner (14); a first flue gas exhaust line (9) for discharging flue gases generated by said second burner (14), said first flue gas exhaust line being linked, or connected, to said first burner (8), and a second flue gas exhaust line (15) for discharging flue gases generated by said first burner (8), said second flue gas exhaust line (15) being linked, or connected, to said second burner (14), wherein each of said lines (6, 9, 12, 15) is provided with one or more valves (7, 10, 13, 16) configured to open or close the respective line (6, 9, 12, 15), and wherein: said first burner (8) in ignited configuration corresponds to said first air delivery line (6) open and said second flue gas exhaust line (15) open, said second burner (14) being in extinguished configuration, said first flue gas exhaust line (9) being closed and said second air delivery line (12) being closed, and said second burner (14) in ignited configuration corresponds to said second air delivery line (12) open and said first flue gas exhaust line (9) open, said first burner (8) being in extinguished configuration, said second flue gas exhaust line (15) being closed and said first air delivery line (6) beingclosed.

13. Regenerative burner according to any one of preceding claims 1- 11 , comprising: a first single line connected, or linked, to said first burner and configured to alternately deliver air to said first burner in ignited configuration and to discharge the flue gases generated by said second burner in ignited configuration, a second single line connected, or linked, to said second burner and configured to alternately deliver air to said second burner in ignited configuration and to discharge the flue gases generated by said first burner in ignited configuration, said regenerative burner being a rotary regenerative burner comprising a plurality of burners or a regenerative radiant-tube burner.

14. A high-temperature heating furnace comprising a furnace (3) and one or more regenerative burners (1) according to one or more of preceding claims 1-13, which are arranged to heat products in the furnace (3).

15. Furnace according to claim 14, said furnace being either a steel furnace or a furnace of a waste incinerator.

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