Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
  • F27B9/20—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path
  • F27B9/24—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path being carried by a conveyor
  • F27B9/2407—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path being carried by a conveyor the conveyor being constituted by rollers (roller hearth furnace)
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories or equipment specially adapted for furnaces of these types
  • F27B9/36—Arrangements of heating devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
  • F27D17/10—Arrangements for using waste heat
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
  • F27D17/10—Arrangements for using waste heat
  • F27D17/17—Arrangements for using waste heat for preheating fluids, e.g. air or gases
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D99/00—Subject matter not provided for in other groups of this subclass
  • F27D99/0001—Heating elements or systems
  • F27D99/0033—Heating elements or systems using burners
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories or equipment specially adapted for furnaces of these types
  • F27B9/36—Arrangements of heating devices
  • F27B2009/3638—Heaters located above and under the track
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories or equipment specially adapted for furnaces of these types
  • F27B9/36—Arrangements of heating devices
  • F27B2009/3653—Preheated fuel
  • F27B2009/3661—Preheated fuel preheated with the exhaust gases

Definitions

• the present invention belongs to the sector of manufacturing ceramic tiles and claddings, and within this sector, more specifically to the single-channel and double-channel roller kilns currently using air or preheated air to react with a gaseous fuel such as natural gas, and more recently hydrogen.
• the present invention relates to a new combustion system in which a kiln is completely transformed from air/fuel combustion to oxygen/fuel combustion entirely or partially, in which nitrogen is almost completely eliminated since it is not involved in the combustion reaction. In this way, the consumption of natural gas or the fuel used is drastically reduced. Furthermore, a gas and oxygen preheating system is used, harnessing the hot fumes coming from the combustion or from the cooling area to increase energy efficiency thereof.
• the invention is based on the harnessing latent heat in the exhaust fumes from the kiln to heat the fuel and the oxidizing agent.
• the adiabatic flame temperature is increased from about 2200°C to 3080°C, improving the energy transfer to the roller plane by the radiation phenomenon; therefore, since the piece can be overheated, the gas flow is reduced, thereby entailing a saving of about 50%.
• the invention therefore provides for the complete transformation of a ceramic kiln to oxy-combustion technology with preheating of the fuel and oxidizing agent.
• This can be installed in the combustion fume outlet, in the rapid cooling area or a combination thereof.
• the object of the invention is to reduce fuel consumption by also reducing the carbon emissions produced during the combustion reactions of the hydrocarbons used up until now.
• Ceramic roller kilns with air/gas technology with the preheating of oxidizing agent for firing ceramic tiles or even with self-recovery burners are already known today.
• the kiln is transformed from air-gas technology to oxy-combustion, eliminating almost entirely the nitrogen from the air that is not involved in combustion, therefore reducing fuel consumption.
• the combustion air lines are completely eliminated and replaced with a new oxygen line with all the regulating and control equipment thereof; this oxygen can be supplied by means of a liquid oxygen tank or by means of an oxygen production plant operating with molecular sieves.
• the new kiln or modification of the existing kiln that is proposed fully solves the problems set forth above in a fully satisfactory manner as it is embodied in a countercurrent-type radiation heat recovery unit, which in a first step is responsible for preheating an air stream up to about 400°C, using the residual heat or energy from the exhaust fumes of the ceramic kiln, or from a radiation recovery unit located in the rapid cooling area, or a combination of both.
• This heat recovery unit is installed at the fume outlet of the kiln in question and has a passage for the primary fluid with the minimum possible obstruction.
• An air dilution controlled by means of a servomotor or the like can be installed to protect the heat recovery unit from temperatures exceeding 500°C.
• the first heat exchanger which will mainly be the oxygen heat exchanger, since, for safety reasons, it can work at higher temperatures than in the case of natural gas or hydrogen.
• This convection-type heat exchanger is conceived as a shell and tube countercurrent type using, as the primary fluid, air in the "tube” area and, as the secondary fluid, oxygen in the "shell” area, although other arrangements may be valid to obtain the desired oxygen temperature.
• This second step it goes from having a preheated air stream of up to about 400°C to having an air stream of about 400°C and an oxygen stream of about 300°C.
• the latter i.e., oxygen, is ready to be introduced into the burners to subsequently oxidize the fuel, thereby producing the combustion reaction.
• the excess hot air at about 350°C will be used to preheat mainly the fuel, using a heat exchanger similar to the one used for preheating the oxygen.
• This second exchanger is mainly by convection and is conceived as a shell and tube countercurrent type using, as the primary fluid, air in the "tube” area and, as the secondary fluid, fuel in the "shell” area, although other arrangements may be valid to obtain the desired fuel temperature.
• This third step goes from having a preheated air stream to having an air stream at about 300°C and a gaseous fuel stream at about 250°C.
• the latter i.e., fuel, is ready to be introduced into the burners to be subsequently oxidized with the oxidizing agent and produce the combustion reaction.
• the burners are, basically, in two preferably concentric conduits having a variable section, in which the fuel gas circulates through the central tube and the oxygen through the outer tube.
• These conduits are made of a material resistant to high temperatures, with a low coefficient of expansion and resistant, above all, to oxidation.
• the burner has an external heat insulation to reduce insulation losses, a feature that is only found in this technology, since in conventional oxy-combustion burners it is not necessary to insulate the conduits because the gas and oxygen are at room temperature.
• These concentric conduits transport both reagents to the refractory material duct where they meet and the combustion reaction takes place.
• the diameters, angles and arrangement of the nozzles are optimized to achieve uniformity in the flame temperature profile for the even distribution of energy across the width of the kiln.
• This equipment is responsible for drawing in outside air through a grating near the kiln and then blowing and passing it through the fume heat recovery unit or the rapid cooling radiation recovery unit, then through the oxygen exchanger and finally through the gas heat exchanger with sufficient energy to maintain a minimum working flow rate and both a dynamic and static pressure, high enough to withstand the relatively high pressure drops of recovery units and exchangers, so as to be able to transfer heat with the smallest surface.
• Group 1 corresponding to the elements already existing in a conventional kiln (some of which can be refitted):
• Group 2 Corresponding to the elements making up the essence of the invention, which are not included in the current state of the art and therefore are novel.
• the kiln of the invention is based on the conventional structuring of a kiln for firing ceramic tiles, in which the pieces enter by means of the ceramic rollers (1.1) through the area where there is located the combustion fume outlet (1.2) for the exit of fumes by draft induced as a result of a fume fan (1.3) expelling the gases produced by combustion into the atmosphere or into the purification system.
• the pieces start out in the heating and firing area (1.5) and end up in the cooling area (1.7), said areas being separated by the firewall (1.6), and everything is in turn surrounded by the refractory insulation (1.4) to prevent energy losses to the outside.
• the ceramic pieces go through a plurality of air-gas burners (1.12) to the refrigerating area where rapid cooling area is located, where cooling takes place with air blown by the rapid cooling fan (1.8). After that is the indirect cooling area, where a less abrupt temperature drop occurs as a result of the cooling air suction fan (1:10). Lastly, the pieces go to the end of the final cooling area (1.11), where they achieve the temperature necessary so that they can be handled.
• a fume recovery unit (2.2) In the event that a fume recovery unit (2.2) is used, it is intercalated in the current stack or combustion fume outlet (1.2), and in the event that the cooling recovery unit (2.3) is used, it is located in the rapid cooling area after the firewall (1.6) in the final cooling area (1.7)
• this hot airflow is connected to one or mas oxygen heat exchangers (2.4) along the kiln and on same to heat oxygen.
• the outlet for the hot air going through said oxygen heat exchangers (2.4) is connected to a gas exchanger (2.5) to preheat both the oxidizing agent (oxygen) and the fuel (natural gas).
• the air with residual heat is conveyed to the recirculation valves (2.6), where it is decided whether the residual heat is recirculated to the system or, conversely, the heat is expelled to the outside, in its entirety or partially.
• the hot gas and oxygen enter the oxy-combustion burners (2.7), located transversely to the direction of the ceramic tiles arranged in a generally staggered manner both in the upper chamber of the ceramic rollers and in the lower part thereof, thereby comprising the heating and firing area (1.5).

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Tunnel Furnaces (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=93150783

Family Applications (1)

Country Status (2)

Citations (3)

• 2024
  • 2024-05-31 ES ES202431032U patent/ES1311232Y/es active Active
• 2025
  • 2025-01-28 EP EP25154321.1A patent/EP4656995A1/fr active Pending

Patent Citations (3)

Also Published As

Similar Documents

Legal Events