Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
  • F23D11/10—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour
  • F23D11/101—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour medium and fuel meeting before the burner outlet
  • F23D11/102—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour medium and fuel meeting before the burner outlet in an internal mixing chamber
  • F23D11/103—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour medium and fuel meeting before the burner outlet in an internal mixing chamber with means creating a swirl inside the mixing chamber
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
  • F23D11/36—Details
  • F23D11/38—Nozzles; Cleaning devices therefor
  • F23D11/383—Nozzles; Cleaning devices therefor with swirl means

Definitions

• the present invention relates to devices and methods for the internal assisted spraying of a fuel liquid.
• the efficient combustion of a liquid in a thermal home requires its spraying in fine drops that evaporate under the effect of the heat that prevails in the home.
• the evaporated liquid then burns with an oxidant inside the fireplace.
• the spraying is carried out by tearing a jet of the liquid by a gas flow at high speed so as to form a spray ("spray") of drops of liquid dispersed in the gas phase.
• the spraying step is essential because the properties of the flame obtained at the outlet of the spraying device are highly dependent on the quality and the properties of the spray formed, such as the average size of the drops, the size distribution of the drops, the length of the spray. penetration of the spray, the angle of the spray and its ejection speed.
• the emission of unburned particles strongly depends on the size of the drops.
• Unburned can be contained in soot formed by the incomplete combustion of the light fractions of the combustible liquid in a locally hot and oxygen-deficient zone. Unburned can also be present in the form of large hollow carbonaceous solid particles, called cenospheres, which result from the incomplete combustion of the larger drops.
• the unburnt once removed from the hot areas of the flame, limit the energy efficiency of the home and constitute a significant part of the pollutants emitted by the facility and whose nature and quantity are regulated more and more severely. Without special precautions, the problem of unburnt is increased in the case of oxy-combustion where the flame volume is normally lower.
• Distinction is made between the internal assisted spray and the external assisted spray.
• Coaxial type external assisted atomizing sprayers for liquid fuel such as those described in the literature (Engineering Technology - "Combustion Equipment for Liquid and Gaseous Fuels", “Atomization &Sprays” - AH Lefebvre), are robust and high quality spray. These injectors produce very fine sprayed streams through the use of a large amount of high speed spray gas.
• the mass ratios of spray gas flow rate on the liquid fuel flow (A / F) involved are of the order of 20 to 40% and up to 70% in the case described in EP-A- 0687858.
• the large amount of spray gas flowing around the fuel injection provides insulation and a thermal buffer which limits the rise in the temperature of the liquid fuel and its coking on or inside the sprayer.
• the counterpart is the degradation of the energy efficiency due to the introduction into the focus of a large amount of gas that is generally totally or mostly inert (at the level of combustion) by the sputtering gas.
• inert at the level of combustion
• FR-A-9509199 and FR-A-9907030 Powerful internal assisted spray systems are described in FR-A-9509199 and FR-A-9907030. These consist of a stack of several successive pellets: primary and secondary nozzle in the case of FR-A-9509199. atomizer, spray nozzle and sleeve in the case of FR-A-9907030. These technologies involve a spraying of the liquid assisted by a gas under pressure inside the spraying device and produce sprayed jets consisting of very fine drops .
• the main drawback of these internal assisted spray technologies lies in their high sensitivity to coking by coking the liquid fuel and the resulting deteriorations, especially in the case of oxy-combustion.
• Y-type internal assisted spray devices generally consist of a single pellet. They are thus more robust vis-à-vis the heat flow.
• Engineing Technique "Combustion Equipment for Liquid and Gaseous Fuel", “Atomization &Sprays” - AH Lefebvre
• EP-A-0676244 their main disadvantage is their limited performance.
• these injectors produce spray jets characterized by an average size of the drops and a higher proportion of large drops, which will be responsible for unburnt formation and energy efficiency limitation.
• the concept of these sprayers is based on an annular channel guiding the liquid fuel in the central channel of spray gas to create fine drops.
• thermal resistance of these concepts is relatively limited, especially in the case of oxygen combustion, since inside the atomizer before mixing with the sputtering gas, the liquid fuel is subjected to the heat fluxes of the flame. without thermal protection by the spray gas system, as is the case for external power sprayers.
• This post-mixing burner sprayer comprises: (1) a liquid fuel passage having a first relatively small cross section section, a second cone-shaped cross section section and a relatively large third cross section section; third section communicating with a furnace zone; and (2) three to seven gaseous spray fluid passages, said passages having an injection end in communication at an angle of 45 ° to 75 ° with the fuel passage.
• the spray fluid passages terminate near the inlet of the second cone-shaped section so as to direct the spray fluid into this second section near the beginning of the cone.
• This sprayer may consist of a monobloc. By a "monobloc" is understood an integrally formed part, unlike an assembled part.
• the sprayer according to EP-A-0263250 thus makes it possible to avoid the problems associated with sprayers comprising several pellets.
• the performance of the sprayer according to EP-A-263250 remains limited with, as is the case with sprayers of the Y type, spray jets characterized by average sizes of relatively large drops and a large quantity of large drops.
• the present invention aims to allow the spraying of a fuel liquid by assisted internal spraying with a reduced amount of spraying, with a good quality spray pattern, that is to say: (a) whose drops are of medium size (often expressed in "Sauter average diameter” or “DMS", in English: “ Skip Mean Diameter “or” SMD ”) sufficiently low and (b) with a small percentage of large drops.
• the present invention relates in particular to an injector for injecting a spray of a combustible liquid.
• the spray is more particularly injected into a combustion zone through an outlet opening of the injector, the combustion zone being located downstream of this outlet opening.
• the injector includes an internal assisted spray block.
• the spray block includes a downstream injection face that has the exit aperture.
• the block also includes an open downstream combustible liquid passage and two to six spray gas lines.
• the combustible liquid passage passes through the block and ends with the outlet opening.
• the passage includes a narrow portion and a pre-spray chamber.
• the passage has a longitudinal axis of symmetry and a variable cross section in circular substance, preferably circular.
• a cross section variable in circular substance is a substantially circular section of variable diameter.
• the longitudinal axis of the passage defines a flow direction Df of the combustible liquid.
• a circular or substantially circular cross section is distinguished in particular from an annular cross section in that, in the case of a circular section or in substance, the entire area of the circle defined by the cross section is available for the flow of a fluid through the passage in the direction Df.
• the narrow part of the passage has a diameter ⁇ 1
• the pre-spray chamber is in the extension and downstream of the narrow part. It is of diameter greater than the diameter ⁇ of the narrow part.
• This pre-spray chamber has an inlet opening. It ends with the outlet opening of the injector which is located opposite the inlet opening of the chamber.
• the chamber has a length Le in the direction Df between its inlet opening and the outlet opening and a mean diameter ⁇
• the narrow portion of the passage opens into the pre-spray chamber through the inlet opening.
• the passage terminates at its downstream end through the outlet opening of the injector.
• said outlet opening of the injector is also the outlet opening of the pre-spray chamber.
• the length Le of the pre-spray chamber is less than or equal to the average diameter ⁇ of this chamber.
• the spray gas pipes comprise end sections of diameter t> g, with t> g ⁇ 1.
• Each terminal section opens into the narrow part of the passage near the inlet opening of the chamber.
• Each end section defines a flow direction Dg of the sputtering gas.
• the end sections open into the narrow portion so that the flow directions Dg of the sputtering gas form angles Qgf between 30 ° and 90 ° with the flow direction Df of the fuel liquid.
• the end sections open into the narrow portion tangentially to the narrow portion. In this manner, the sputtering gas impacts the combustible liquid and imparts a helical motion to the combustible liquid.
• the average diameter of the chamber corresponds to the average value of the diameter of the chamber over the entire length of the chamber.
• the average diameter ⁇ of the chamber corresponds to the diameter of the cylinder.
• the average diameter ⁇ of the chamber will be the means of the diameter of the inlet opening and the diameter of the 'exit opening. It should be noted that, when the diameter of the pre-spraying chamber is not constant, it is preferable for the diameter to increase towards the outlet opening, so as to avoid coalescence of drops of the liquid.
• the passage of the injector according to the invention is an open downstream end passage, whose outlet opening is therefore not provided with such a cover, such a cover or such hat.
• the spray block advantageously comprises three to five spray gas lines.
• a block with three pipes of spray gas is preferred because efficient and simple to achieve.
• the spray block is preferably a monoblock, which makes it possible to better seal the spray block.
• the length Le of the chamber is 0.2 to 1 times the mean diameter ⁇ of the chamber, that is to say: 0.2 ⁇ ( t> c ⁇ Le ⁇ ⁇ , preferably: 0 , 2x ( t> c ⁇ The ⁇ ⁇ , ⁇
• the probability of coalescence increases and we observe a larger number of large drops in the spray and an increase in the DMS.
• the pre-spraying chamber advantageously comprises at least one substantially cylindrical section. According to a preferred embodiment, the chamber is entirely substantially cylindrical.
• the chamber or a section of the chamber is substantially cylindrical when the walls of the chamber / section have an angle ac with the flow direction Df of the fuel liquid from 0 ° to 7 ° ( in the direction of said flow).
• the substantially cylindrical section may in particular constitute the downstream section of the chamber.
• the substantially cylindrical section ends directly with the exit opening. It is also possible that the substantially cylindrical section opens into a frustoconical section flaring towards the outlet opening, that is to say a frustoconical section whose walls form a higher angle at 7 ° with the direction of flow Df of the combustible liquid (in the direction of said flow).
• the pre-spraying chamber may also comprise a frustoconical transient section (flaring towards the outlet opening) connecting the inlet opening of the chamber with the substantially cylindrical section, the transient section thereby forming the transition between the narrow portion of the liquid fuel passage and the substantially cylindrical section of the chamber.
• the transient section advantageously has a length Ltr ⁇ 1 ⁇ 4 x Le, preferably ⁇ 1/8 x Le and more preferably ⁇ 1/10 x Le.
• the transient section has a fairly wide cone angle Otr, for example greater than 60 ° and less than 90 ° (in the direction of flow of the combustible liquid).
• the flow directions Dg of the sputtering gas form angles Qgf between 35 ° and 85 ° with the flow direction Df of the fuel fluid, preferably between 40 ° and 80 °. .
• the ratio between the diameter ⁇ of the pre-spray chamber and the diameter ⁇ of the narrow portion of the fuel liquid passage upstream of the chamber is preferably less than 3 ° C. i.e. 1 ⁇ / ⁇ ⁇ 3, preferably 1, 1 ⁇ / ⁇ ⁇ 2.
• the ratio between the diameter ⁇ g of the end sections of the spray gas pipes and the diameter ⁇ of the narrow portion of the fuel liquid passage, in which the spray gas pipes open, is desirably between 0.1 and 1, that is to say: 0.1 ⁇ g / ⁇ f ⁇ 1, 0; and preferably between 0.2 and 0.8, i.e., 0.2 ⁇ g / ⁇ f ⁇ 0.8.
• the present invention also relates to a burner for the combustion of a combustible liquid comprising an injector according to any one of the embodiments described above.
• the burner is not limited to a particular type.
• the burner may in particular be a burner for staged combustion or for non-staged combustion. It may comprise a refractory block which surrounds the injector according to the invention.
• the invention also relates to an oven for the combustion of a combustible liquid comprising a thermal hearth equipped with at least one injector and / or at least one burner according to any one of the embodiments described above. above.
• This furnace comprises a combustion zone downstream of the outlet opening of said injector.
• the invention is of interest for a wide range of furnaces, such as the following ovens: furnaces for combustion of liquid waste, steam production boilers, melting furnaces, reheating furnaces, clinker furnaces, precalcination plants, coking ovens, etc.
• the invention is however of particular interest for furnaces for the combustion of liquid waste, which are often difficult to burn and for which environmental regulations are often very strict.
• the invention is thus particularly interesting for cold wall furnaces.
• An example of cold wall furnaces are boilers.
• the thermal energy generated by combustion is used to heat a coolant, typically water or steam, flowing through one or more pipes.
• the thermal energy is transferred to the heat transfer fluid through the wall or walls of the pipe or pipes. Since said walls are in direct contact with the heat transfer liquid to be heated, their temperature remains well below the temperature prevailing in the combustion zone.
• Cold-walled similar furnaces are used for the heat treatment of liquids or gaseous phases, such as the "cracking" or "reforming" of petrochemicals.
• the present invention also relates to an internal assisted sputtering method of a fuel liquid by means of an injector according to any one of the embodiments described above.
• the fuel liquid passage is fed with fuel liquid and b. the spray gas lines are fed with pressurized spray gas, and this so that the combustible liquid has a flow velocity Vf in the narrow part of the passage and so that the spray gas has a flow velocity Vg in the terminal sections of the pipes, with Vg> vf.
• the pulverized fuel liquid thus obtained is injected into a combustion zone through the outlet opening of the injector.
• the sputtering gas impacts the combustible liquid and imparts a helical movement to the combustible liquid. It has been found that, in particular by virtue of this helical movement of the combustible liquid, it is possible to produce, with the same ratio of spraying gas / liquid fuel, a pulverized jet consisting of drops of medium size which are lower and with a lower percentage. large drops or to achieve a spray jet consisting of drops with the same average size and with a similar percentage of large drops, but with a ratio of reduced fuel gas / liquid fuel.
• the end sections of the spray gas pipes open into the narrow portion of the fuel liquid passage upstream of the pre-spray chamber so that the sputtering gas imparts a helical motion to the fuel liquid. inside the narrow part of the passage.
• the pipes are fed with pressurized spraying gas so that the flow velocity Vg of the sputtering gas in the terminal sections of the pipes is greater than 80 m / s and preferably less than 600 m / sec. s.
• the flow velocity Vg of the sputtering gas in the end sections can be between 80 m / s and the speed of sound, or, when the end sections have appropriate nozzles for supersonic injection, between the velocity of the sound. and 600 m / s.
• the passage is supplied with combustible liquid and the pipes are fed with pressurized spray gas so as to obtain a spray of the combustible liquid in the spraying gas coming out of the fuel.
• the pre-spraying chamber with an ejection speed of between 1 and 400 m / s, preferably between 100 and 350 m / s.
• the ejection rate corresponds to the ratio between the volumetric flow rate of the spray gas and the average section of the pre-spray chamber.
• the ejection speed corresponds to the ratio between the volumetric flow rate of the spray gas and ( ⁇ x d> c 2 ) / 4.
• the pipes are preferably fed with the pressurized spray gas so that the spray gas has a pressure between 1 and 10 bar in the end sections of said pipes.
• the sputtering gas may especially be selected from steam, air, oxygen-enriched air, oxygen, recycled fumes and CO2.
• the combustible liquid may be a liquid waste.
• the fuel liquid can also be a liquid fuel or a solid fuel in liquid suspension (often referred to as "slurry").
• the fuel liquid is a liquid fuel
• it can be chosen in particular from light fuel oils, heavy fuel oils and petroleum residues.
• the quality of the spray jets that can be obtained by virtue of the invention makes the invention particularly useful for the internal assisted spraying of heavy fuel oils.
• the spraying gas is advantageously steam. It should be noted that liquid fuels are highly appreciated by manufacturers for their relatively low cost compared to gaseous fuels easier to burn.
• the solid fuel is advantageously pulverulent coal.
• the suspension may in particular be an aqueous suspension.
• the invention also relates to a method of burning a combustible liquid in a thermal furnace, wherein the combustible liquid is: (a) pulverized and injected into a combustion zone by an internal assisted sputtering method according to any one of embodiments described above, and (b) burned with an oxidant in this combustion zone.
• Said combustion zone is typically located inside a thermal focus.
• the oxidant may in particular be air, air enriched with oxygen or oxygen.
• the invention is particularly advantageous when the oxidant is oxygen or enriched air having an oxygen content of at least 80. % vol and up to 100% vol.
• the oxidant may also advantageously be a gas containing between 21% vol and 100% vol of oxygen and between 20% vol and 0% vol nitrogen, for example: a mixture of oxygen and CO2 or a mixture of oxygen with recycled fumes.
• this sputtering gas may constitute at least a portion of the oxidant used for combustion of the combustible liquid.
• FIGS. 1 to 4 in which:
• FIG. 1 is a partial schematic perspective and transparent representation of a spray block of an injector according to the invention with a cylindrical pre-spray chamber and three spray gas lines, and
• FIGS. 2a, 2b and 2c are partial schematic representations in section of a spray block of an injector according to the invention with a cylindrical pre-spray chamber and three spray gas lines, FIG. transverse section at the level of the prepulverisation chamber, FIG. 2a being a longitudinal section along the plane AA through the axis of one of said conduits and FIG. 2b being a longitudinal section along the plane BB through the axis of the passage. , and
• FIGS. 3a, 3b and 3c are diagrammatic representations similar to FIGS. 2a, 2b and 2c, but showing a spray block with a pre-spray chamber whose main part is a first frustoconical section and which also comprises a second section. frustoconical downstream of the first, and
• the injector spray block 1 comprises (i) a liquid fuel passage 30 having a narrow portion 31 of diameter ⁇ , (ii) three pressurized spray gas lines 20 having end sections 21 of diameters t> g tangential to said narrow portion 31 of the liquid fuel passage 30 and a mixing chamber of the two phases, said pre-spray chamber 10, of average diameter ⁇ and length Le.
• the diameter of the chamber 10 is greater than that of the narrow portion 31 of the fuel liquid passage 30, the latter diameter being itself greater than the diameter of the end sections 21 of the spray gas lines 20.
• the length Le of the pre-spraying chamber is short: less than or equal to its mean diameter ⁇ This characteristic avoids degrading the sputtering by the confinement and coalescence of the ligament structures and limits the rise in temperature of the sputtering / liquid gas mixture fuel thus avoiding coking of the combustible liquid and clogging of the injector.
• the liquid fuel is pulverized into fine ligamentous structures and in fine drops under the effect of pressurized spray gas injected at high speed via the terminal sections 21 of the pipes 20.
• Said end sections 21 being tangential in the flow of fuel in the narrow portion 31 of the passage 30, the injection of the sputtering gas gives the mixture of sputtering gas / liquid fuel a helical movement (schematically represented by the arrows 40 in Figure 4). This promotes the spraying of the liquid.
• the spraying of the liquid is thus carried out by several phenomena: ⁇ the high speed of the sputtering gas creates high shear rates,
• the spray gas being injected under high pressure typically greater than 2 or 3 bar
• its expansion is accompanied by a shock wave in the pre-spraying chamber 10 further promoting the bursting of the liquid in fine structures.
• the fuel oil injected at low speed is sprayed into fine drops and fine ligament structures at the inlet of the pre-spray chamber 10 by the three tangential injections of pressurized spray gas.
• This is possible in particular thanks to the high three-dimensional shear rates created with the high gas injection speeds (> 80 m / s for a pressure greater than 2 bar), the helical flow of the gas / liquid mixture.
• the chamber 10 is characterized by a length less than or equal to its diameter ⁇ (Le ⁇ ) thus avoiding the coalescence of the drops and ligaments in larger structures and the rise in temperature of the liquid fuel.
• the length Le of the chamber 10 corresponds to the distance, measured in the direction D f , between the inlet opening of the chamber 10 and the outlet opening 50 of the injector.
• the mean diameter ⁇ of the chamber is defined such that the ejection speed of the dispersed liquid / gas mixture in the combustion zone 100 downstream of the outlet opening 50 is between 1 and 400 m / s, preferably between 100 and and 350 m / s.
• the angle of attack Qgf of the tangential spray air injections on the liquid fuel flow can vary from 30 ° to 90 ° depending on the desired penetration length. Indeed, the higher the angle of attack Qgf, the more the spray will be short and vice versa. This sizing parameter allows the device to be adjusted to different burners or processes depending on the desired flame length.
• the injector according to the invention is a highly efficient spraying tool. It achieves spray performance at least equivalent to the best sprayers of the prior art especially in terms of low spraying gas flow rates (ratio between the flow rates of sputtering gas and combustible liquid).
• the injector is very reliable thanks to a simple design allowing a monobloc construction highly resistant to the high temperatures of the spray block. It allows a very fine spraying of the combustible liquid and to limit the rise in temperature of the pre-atomized fuel gas / spray mixture prior to ejection into the furnace through the outlet opening.
• the injector according to the invention with a monobloc sprayer makes it possible to avoid fuel liquid leaks and thus the degradation of the spray and the clogging of the sprayer by formation of coke.
• this injector and the burner according to the invention have a particularly low risk of clogging, this injector and this burner are particularly suitable for being used for spraying a combustible liquid in a combustion zone whose atmosphere is highly charged with condensable material (s) and / or pulverulent solid material (s).
• the injector according to the invention makes it possible to obtain a spray jet consisting of very fine drops for low relative flow rates of sputtering gas (low sputtering gas (air) / liquid fuel (fuel oil) mass ratio) right out of the 'injector.
• sputtering gas low sputtering gas (air) / liquid fuel (fuel oil) mass ratio
• this improved internal spraying process produces a dispersed mixture of liquid in the spray gas as soon as it is released without forming a real liquid core.
• the drop size distributions obtained with this device belong to a particularly fine spray, since for mass ratios of spray gas flow rate on the liquid fuel flow rate of 5 to 15%, the DMS values change from 80 ⁇ to less than 60 ⁇ when the spraying gas is air and the fuel liquid is heavy fuel No. 2 at 1 10 ° C.
• the pulverized jet formed is also very homogeneous, since the measured drop sizes are similar to the center and the periphery of the spray.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Nozzles For Spraying Of Liquid Fuel (AREA)
• Nozzles (AREA)

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• 2011
  • 2011-12-21 FR FR1162173A patent/FR2984995A1/fr active Pending
• 2012
  • 2012-12-11 US US14/367,412 patent/US20140329187A1/en not_active Abandoned
  • 2012-12-11 EP EP12812296.7A patent/EP2795191A2/de not_active Withdrawn
  • 2012-12-11 CA CA2857562A patent/CA2857562A1/fr not_active Abandoned
  • 2012-12-11 WO PCT/FR2012/052875 patent/WO2013093289A2/fr not_active Ceased

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