Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
  • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
  • F23C6/042—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with fuel supply in stages
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C5/00—Disposition of burners with respect to the combustion chamber or to one another; Mounting of burners in combustion apparatus
  • F23C5/08—Disposition of burners
  • F23C5/32—Disposition of burners to obtain rotating flames, i.e. flames moving helically or spirally
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/125—Radiant burners heating a wall surface to incandescence
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/126—Radiant burners cooperating with refractory wall surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
  • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
  • F23L7/007—Supplying oxygen or oxygen-enriched air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
  • F23N5/006—Systems for controlling combustion using detectors sensitive to combustion gas properties the detector being sensitive to oxygen
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
  • F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
  • F24H1/40—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes
  • F24H1/403—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes the water tubes being arranged in one or more circles around the burner
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
  • F24H1/46—Water heaters having plural combustion chambers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C2201/00—Staged combustion
  • F23C2201/40—Intermediate treatments between stages
  • F23C2201/401—Cooling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C2203/00—Flame cooling methods otherwise than by staging or recirculation
  • F23C2203/10—Flame cooling methods otherwise than by staging or recirculation using heat exchanger
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
  • F23C2900/03003—Annular combustion chambers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2207/00—Ignition devices associated with burner
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/08—Measuring temperature
  • F23N2225/16—Measuring temperature burner temperature
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/26—Measuring humidity
  • F23N2225/30—Measuring humidity measuring lambda
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N3/00—Regulating air supply or draught
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/30—Technologies for a more efficient combustion or heat usage
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

• the present invention relates to a boiler and a method for operating said boiler according to the introduction of the main claim.
• the boiler herein is intended to be advantageously used for conventional purposes, where a carrier fluid is required, such as water for example, for heating rooms or for producing hot water for sanitary use.
• a carrier fluid such as water for example, for heating rooms or for producing hot water for sanitary use.
• boilers presently available on the market provide for heat exchange between a heat source made up of hot fumes produced in a burner upon combustion of a fuel such as a gas or an oil derivative, and a carrier fluid, usually water, which is adapted to carry the heat taken up from the fumes up to the users for various purposes generally for heating rooms or for producing hot water for sanitary use.
• a carrier fluid usually water
• Heat-exchange between the fumes and the carrier fluid usually occurs through a cast iron or steel exchanger at temperatures typically below 900° C. At such temperatures, the heat exchange within the exchanger occurs due to thermal convection and radiation phenomena in a substantially equivalent manner.
• the amount of air employed usually exceeds the gas amount in order to carry out a particularly oxidizing reaction meant to fully exploit the combustion of the fuel.
• condensation boilers In order to increase the efficiency of boilers of the known type condensation boilers have been recently introduced, which not only exploit the heat deriving from combustion (low heat value l.h.v.) but also the latent heat of water vapor contained in the exhaust gases (high heat value). Therefore, this technique allows exploiting energy which would otherwise be discharged from the flue together with exhaust gases. During condensation latent heat is transferred from the gases to the water. By exploiting this technique, the temperature of the exhaust gases, which are discharged from the boiler, is only slightly higher than the temperature of the water returning to the boiler thus allowing achieving high efficiencies. The condensation of moisture present in the fumes depends on the temperature of the water returning to the boiler but also on the residual oxygen content of the combustion fumes.
• Boilers of the known type do not ensure stoichiometric chemical reactions and at these temperatures they give rise to a number of combustion products, resulting in the diffusion of a number of pollutants into the atmosphere.
• pollutants emitted from boilers are of gaseous type, such as ozone, nitrogen oxides, sulfur dioxide etc. and of solid type, such as unburnt particles, condensation aggregates, carbon particles etc.
• a main object of the present finding is therefore to overcome the drawbacks encountered in boilers of the known type, by providing a boiler as well as a method for operating said boiler which allow increasing the efficiency of the boiler.
• Another object of the present finding is to provide a boiler as well as a method for operating said boiler which can reduce the production of pollutants. Another object of the present finding is to provide a boiler as well as a method for operating said boiler operatively totally safe.
• a further object of the present finding is to provide a boiler which is easy to install and operatively totally reliable.
• a further object of the present finding is to provide a boiler of particularly reduced dimensions with respect to the power produced.
• FIG. 1 shows an overall schematic view of the boiler subject of the present invention with a part in cross-section to highlight other parts better;
• - figure 2 shows a cross-section view of the boiler subject of the present invention with some parts cut away to highlight other parts better;
• - figure 3 shows a perspective view of an enlarged detail of the boiler subject of the present invention relating to the fuel-comburent air supply unit;
• FIG. 4 shows a perspective view of an enlarged detail of the boiler subject of the present invention relating to a plate exchanger.
• the boiler comprises a support structure 2, which can be of a per se entirely traditional type and it is preferably intended to provide a support on the ground, and a burner 3 mounted on the support structure 2, in whose combustion chamber 4 a comburent air and fuel mixture is injected, by means of a suitable supply unit 10, for generating a flow of hot fumes indicated by arrows 5 through oxidation reactions.
• the enthalpy generated by the combustion present in the fumes is transferred to a carrier fluid 6 of a hydraulic circuit (not illustrated in detail), preferably made up of water, by means of suitable heat exchange means that, according to the present invention, are obtained in at least two subsequent stages through a first and a second heat exchanger indicated with 7 and 8, respectively.
• the first exchanger 7 comprises in particular a jacket 50 inside which fume pipes run, indicated with 60 in the boiler example of figure 2 not perfectly corresponding to that of the boiler illustrated in figure 1.
• a ceramic material pipe 9 is provided inside the combustion chamber 4 to convey the fumes between the first exchanger 7 and the second exchanger 8 while the supply unit 10, in turn, is formed by a plurality of nozzles 11 arranged spaced from each other inside the burner 3, around the pipe 9 and susceptible to generate a flame adapted to lick or to contact the outer surface of the pipe 9.
• the ceramic material pipe 9 reaches very high temperatures typically comprised in the range between 1200 and 2200°C and preferably between 1500 and 1800°C.
• the combustion chamber 4 of burner 3 has an annular shape with the pipe 9 coaxially arranged therein along the vertical axis Z.
• the nozzles 11 of the supply unit 10 are arranged around the pipe 9 in one or more substantially circular trajectories, and they are directed in such a manner to touch the pipe 9 with the flame generated by the mixture emitted in a downward direction substantially along the whole length of the pipe 9 to make temperatures even along its entire extension.
• the ceramic material chosen is silicon carbide.
• the supply unit 10 is made up of several nozzle groups 11 (three groups according to the example of the drawings attached) arranged on concentric rings 12 and each directed with the nozzles 11 so as to reach the pipe 9 with the flame at different heights.
• the high temperature attained by the pipe 9 determines a high radiation pressure susceptible to transmit a high enthalpy to the shell of the first exchanger 7, which increases the efficiency of the boiler 1.
• a transport wall 70 in order to direct the flame and hot combustion fumes along the pipe 9 provided for is a transport wall 70, partly delimiting the combustion chamber 4, advantageously substantially concentric with the pipe 9 and open at the lower end to allow recirculation of fumes towards and into the first exchanger 7, as indicted by the arrows in figure 1.
• the energy transmitted by radiation follows a law according to which it varies as fourth power of temperature.
• the use of ceramics in the boiler allows achieving very high temperatures capable of radiating high thermal powers thus increasing the efficiency of heat exchanges with the carrier fluid.
• a further advantage of ceramics lies in the low oxidation thereof and hence in the long durability of the parts made from this material.
• the high temperature attained by the pipe 9 together with the high thermal inertia cause a rapid combustion of any unburnt particles which may come into contact with the same.
• the juxtaposition of the groups of nozzles 11 at the edges of the flames determines higher chances of burning all the unburnt particles, which would otherwise typically gather in the coldest spots of the flame.
• the mixture introduced by the nozzles 11 is such to create a non stoichiometric combustion, which is poor in oxygen as compared to the stoichiometric reaction, and such to leave a small percentage of unburnt gases, for example around 0.1 %o up to some percentage.
• the fumes produced (sin gas) contain water vapor CO 2 and H 2 and thus still hold some usable energy.
• Hot fumes produced by the combustion cool down upon contact with the first exchanger 7 which surrounds the combustion chamber 3 as an outer shell.
• the first exchanger 7 lowers the temperature of the fumes to a range between 700 and 900 0 C, thus creating conditions for the production of pollutants such as reducing agglomerates, unburnt gases and carbon particles in particular.
• the first exchanger 7 is advantageously provided by several spaces delimited by septa or by jackets or liquid transport pipes within which fume pipes are arranged.
• a lambda probe 120 is inserted, capable of detecting the amount of oxygen present in the fumes downstream of the burner 3 through the analysis of the radiations emitted.
• the aim of such probe 120 will be made clear hereinafter.
• the flow of fumes enters into the pipe 9 through its first end 13 arranged in the lower part of the boiler 1.
• the fumes are reheated instantaneously inside the pipe 9 to enable a post- combustion so as to burn said pollutants and unburnt gases.
• the pipe 9 has a temperature on its outer surface ranging from 1500 to 1900°C and a temperature on the inner surface ranging from 800 to 1200°C.
• the above-mentioned post-combustion is facilitated by the introduction into the pipe 9 from its lower end 13, of an amount of oxygen by means of at least one injector 14 and at a rate preferably comprised between 0.3 and 0.6 m /h.
• Such introduction is regulated in an accurate manner by the lambda probe 120, which detects the amount of oxygen required by the fumes to carry out a completely stoichiometric final combustion leading to the complete combustion of all unburnt gases.
• the same lambda probe 120 or a different probe or sensor determines instead the control of the mixture introduced by the nozzles to create the first non stoichiometric combustion, which will be slightly poor in oxygen as already mentioned.
• the mixture shall be kept with a low amount of oxygen according of the detection abilities of the lambda probe.
• the system for introducing the amount of oxygen shall only absorb a power of up to 1 kw and preferably comprises a compressor, a dehumidifier, a dehumidified compressed air tank, a molecular sieve separator and an oxygen tank.
• the initiation of post-combustion in pipe 9 is further facilitated by providing a plasma torch or a 1-3 kw power post-combustor nozzle for introducing fuel also arranged at the first end 13 of pipe 9.
• the irradiation of the inner wall of the pipe 9 facilitates the combustion of the fumes passing through the same pipe within a period of time preferably comprised between 0.6 and 1 second and preferably about 0.8 sec. Therefore, during the stoichiometric post-combustion, the fumes exiting the ceramic pipe were cleared of the unburnt particles still present and also all the carbon particles accumulated in the low temperature step (about 800 0 C) following cooling down in the first exchanger 7 were burnt.
• experimental data revealed very low emissions of both gaseous and solid pollutants exiting the boiler subject of the present invention.
• the hot fumes exiting the second end 15 of the pipe 9 made of ceramic material pass through the second exchanger 8 to transfer heat to the carrier fluid which has already been advantageously partially heated in the first exchanger 7.
• the boiler 1 is kept under depression through a fan 21 arranged downstream of the second exchanger 8 along the discharge flue of the fumes 22.
• the second exchanger 8 is an exchanger having superimposed plates 16 contained within a cylindrical jacket 17, longitudinally passed though by carrier fluid channels 18 and transver sally by the fumes.
• the flow of fumes enters into the central opening 19 and it is directed by suitable closures 40 to pass through the plates 16 horizontally up to the outer jacket 17, as indicated by the arrows in figure 4, hence finding its way onto the upper layer of plates 16 as the carrier fluid passes through the vertical pipes 18 connected at their ends to U-shaped connectors 20.
• the second exchanger mainly serves to adjust the temperature of the fumes to an ideal operating value (for example 95°) below the dew temperature to recover all the condensation energy and at the same time sufficient to allow the normal discharge of fumes.
• Such ideal temperature is maintained through feedback of the operation of the second exchanger based on the temperature value in such a manner that when the temperature drops below the set ideal value a lower water flow circulation occurs in the second exchanger, and on the contrary when the temperature rises above such value a greater liquid circulation occurs in the second exchanger.
• the temperature value of the fumes is detected by means of a special sensor arranged in their path.
• a single heat exchange water circuit may be provided, in which the flow of carrier fluid is directed in a regulated manner to the second exchanger through a valve. Therefore, two exchanger bodies are preferably provided being totally distinct and separated and supplied by a single heat exchange circuit.
• the nozzles 11 are arranged on the rings oriented to determine a flow of fumes in the combustion chamber 4 having a helical trajectory around the pipe 9.
• the walls of the pipe 9 made of ceramic material have a porosity adapted to allow a clean and filtered hot gas flow to pass through the pipe, which increases the temperature thus facilitating post-combustion.
• a further object of the present invention is a method for operating the boiler described above which comprises a first combustion step for generating hot fumes intended for exchanging thermal power with a carrier fluid in a first exchanger and for heating a pipe made of ceramic material, a second combustion step inside said pipe of unburnt residues and pollutants present in the fumes and an amount of oxygen introduced into said pipe at a rate controlled by a lambda probe.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Control Of Steam Boilers And Waste-Gas Boilers (AREA)

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• 2007
  • 2007-02-28 IT IT000066A patent/ITPD20070066A1/it unknown
• 2008
  • 2008-02-27 WO PCT/IB2008/000422 patent/WO2008104859A2/en not_active Ceased
  • 2008-02-27 EP EP08719172A patent/EP2122245A2/de not_active Withdrawn

Non-Patent Citations (1)

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