EP0575499B1 - Mixing device and method for gaseous, liquid or pulverised solid substances - Google Patents

Mixing device and method for gaseous, liquid or pulverised solid substances Download PDF

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Publication number
EP0575499B1
EP0575499B1 EP92908271A EP92908271A EP0575499B1 EP 0575499 B1 EP0575499 B1 EP 0575499B1 EP 92908271 A EP92908271 A EP 92908271A EP 92908271 A EP92908271 A EP 92908271A EP 0575499 B1 EP0575499 B1 EP 0575499B1
Authority
EP
European Patent Office
Prior art keywords
flow
vortex
burner
burner according
flame
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92908271A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0575499A1 (en
Inventor
Gustaaf Jan Witteveen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0575499A1 publication Critical patent/EP0575499A1/en
Application granted granted Critical
Publication of EP0575499B1 publication Critical patent/EP0575499B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/10—Mixing by creating a vortex flow, e.g. by tangential introduction of flow components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/04—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge
    • B05B7/0416—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid
    • B05B7/0441—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid with one inner conduit of liquid surrounded by an external conduit of gas upstream the mixing chamber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/10—Spray pistols; Apparatus for discharge producing a swirling discharge
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1481—Spray pistols or apparatus for discharging particulate material
    • B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state
    • 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 
    • F23C7/00—Combustion apparatus characterised by arrangements for air supply

Definitions

  • Burner provided with means for mixing a combustion air flow with a fuel and method for realizing said mixing.
  • the invention relates to a burner provided with means for mixing a combustion air flow with a fuel, comprising
  • a burner as described in the above is known from the EP-A-0028025, fig. 7.
  • the tapering down reduces the diameter of the air flow to less than 30%, which means a reduction of cross-section to less than 9%. This means a high velocity increase and a very substantial friction, so that a relative high pressure drop for the combustion air is necessary.
  • Part of the combustion air is fed immediately into the flame room and the flow pattern obtained in said room is helicoidal.
  • the invention aims to obtain a flow pattern giving a very intensive mixing of air and fuel, so that NOx values are very low.
  • the invention provides that the tapering down reduces the diameter of the vortex chamber to 0,9 - 0,7 of its largest diameter.
  • the invention is based on the understanding that a gas flow with a strong rotation around the flow axis compared to the axial component, can, with a sudden widening of the flow diameter, create a flow pattern giving a sudden and very strong turbulence in the flow, in the following referred to as 'vortex break down'.
  • This vortex break down manifests itself in a shattering or explosion of the jet while forming very strong local turbulence which leads to an extremely thorough mixing of the substances in the flow.
  • tapering down portion can consist of a material tapering down of the chamber as defined in the above as well as of air injecting or directing means giving the combustion air flow an inwardly directed radial component.
  • the invention provides a method for mixing a combustion air flow with a gaseous, liquid or pulverized fuel in order to burn it, in which an air flow is fed to an axially symmetrical vortex chamber at the periphery of said chamber with a rotational component, said vortex chamber having an exit debouching in a flame room having a diameter of at least 2,5 times that of the contracted air flow, which is characterized in that a gaseous flow containing air with in inwardly directed radial component causes the combustion air flow to contract its cross-section in the axial direction to less than the axial cross-sectional area of the vortex room at its beginning, where it receives the combustion air flow and to 0.9 - 0.7 of its largest diameter before said contraction.
  • the tapering down portion includes at its end an angle with the axis of over 50 degrees.
  • the tapering down portion includes at its end an angle with the axis of over 50 degrees.
  • the rotation enforcing body is connected only to the outside shell of the vortex chamber.
  • the inside area of the jet which is the area within the outside shell, is also made available to the axial flow of the jet.
  • the total section becomes larger because the cross-sectional area of the outside shell is smaller than the total sectional area in the tapering down. This means a decrease of the axial velocity of the flow and, therefore, an increase of the ratio between the rotational component and the axial component of the flow.
  • the liquid or pulverized fuel is subject to the strongest atomization and mixing when it is thrown off the edge of the tapering down portion and enters the vortex break down area.
  • a very good atomization of oil which is introduced under a very low pressure, for instance 5 cm of water.
  • the vortex break down will occur when the flow section is widened. It is to be recommended that the flow section for small burners (up to circa 50 kW) will preferably be enlarged at least five times in relation to that of the tapering down, and for large ones circa 2.5 to 3.5 times.
  • the formation of nitrogen oxides can be countered by providing that the back wall of the flame room is cooled.
  • the created vortex at the widening beyond the central opening can be employed by providing that an air slot in the flame room is present near the rear wall for introducing air, burnt gas and/or waste gas that is to be destroyed by combustion. This slot pulls the gases towards the centre, where cool gas ensures a reduction in temperature of the flame base.
  • an embodiment of the invention provides that a controllable air tap is present, for air that has entirely or partially passed through the rotation enforcing body.
  • an air supply for a burner is indicated by 1 where the air has undergone pressure-increase up to 5 cm of water column or 500 N/m.
  • This air is introduced through axially and tangentially directed slots 2 to a vortex chamber 3.
  • This vortex chamber has on its exit side a tapering down portion 4, which causes the air vortex to be even stronger before flowing out.
  • the strong vortex leads to underpressure in the axial area and, therefore, to a counterflow, as is schematically indicated with the flow lines 5.
  • the slot 17 between the wall 11 and the back surface 10 may provide a secondary-air supply, if so desired.
  • the back surface 10 may be cooled, for instance by water in case the burner is used for the heating of water in, for example, a central heating boiler.
  • exhaust gas or a gaseous product that is to be burnt may be introduced, in which case the very thorough mixing by the vortex break down ensures a most efficient combustion.
  • a control may be obtained by bringing the combustion air at full speed and subsequently feeding-back part of this air, as is schematically indicated by the slots 18 that give access to a space 19 that has an air exhaust through a control cock 20.
  • the shown burner has not only a high stability in order to prevent blowing off and an exceptionally thorough mixing of combustion air and fuel and, therefore, a short flame, it also ensures that a mixture containing oxygen and nitrogen is at a high temperature for a short while only. This is an additional reason why this burner emits few nitrogen oxides.
  • the drawn vortex chamber 3 receives its rotating gas through the slots 2 forming a rotation enforcing device.
  • the axial velocity of the air flowing out is now inversely proportional to the quotient of the annular slot zone 2 and the circular opening in the tapering down portion. It is very well possible that the latter may be larger than the section of the annular slot, in which case the axial velocity is lower when flowing out of the vortex chamber than when entering it, which increases even further the ratio between the rotation velocity and the axial velocity.
  • FIG. 2 schematically shows the situation in which a rotation enforcing body 21 causes a vortex with everywhere the same angular velocity around the axis (solid body rotation).
  • This vortex is carried via the tapering down 22, which is not on scale, to a more spacious flow tube 23, in the process of which vortex break down occurs again and also the annular vortex 24,
  • This device too, causes an exceptionally intensive intermixing of the gas flow, for instance, when it contains a mixing gas, a mixing fluid or pulverized particles.
  • Fig. 4 shows a schematic cross-section that represents an advantageous form of the tapering down. It has been found that when the tapering down is too steep it causes a certain thrust and that when it is too flat it takes up too great an axial length and consequently causes too much friction. In the example of fig. 4 the angle made by the tapering down with the axis at the end of the tapering down is a little smaller than 60 degrees.
  • FIG. 5 a further example of embodiment is schematically represented.
  • the air-supply slot 2 is shown again, by which axially whirling air enters the space 31, as is indicated by the arrow 32.
  • This arrow bends inwards, because from a ring or annular slot 33 radially inflowing and tangentially whirling gas is introduced, which preferably has an axial velocity as well.
  • This is not shown in fig. 5.
  • This air forces the whirling air coming out of the annular slot 2 inwards, as a result of which the latter is narrowed and this causes an expansion of the vortex.
  • the invention not only provides a compact and most steady burner, it may also serve to manufacture a burner-spray-nozzle with a wide adjusting range. Compared to conventional pressure spray nozzles, such a burner-spray-nozzle has two advantages:
  • the invention is suitable as a spray nozzle for any type of burner that is to mix fuel with combustion air, for any application with a wide adjusting range.
  • An important application of the invention is a spray nozzle or atomizer, where the obtained very fine mist, the very thoroughly mixed gas mixture or the very homogeneous suspension of solid particles will not directly be burnt in the flame room.
  • the mixing substance is brought into rotation prior to coming into contact with the air jet. This is particularly important in the case of mixing with low-calorific gas.
  • the rotation enforcing body can have any shape, provided that it superimposes a rotation onto the gas flow.
  • it may also contain moving or rotating parts such as a blade wheel.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Nozzles For Spraying Of Liquid Fuel (AREA)
  • Lubricants (AREA)
EP92908271A 1991-03-20 1992-03-19 Mixing device and method for gaseous, liquid or pulverised solid substances Expired - Lifetime EP0575499B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL9100490 1991-03-20
NL9100490A NL9100490A (nl) 1991-03-20 1991-03-20 Inrichting voor het mengen van een gasstroom met een mengstof, brander waar een dergelijke inrichting in is toegepast en werkwijze voor het bedrijven van de brander.
PCT/NL1992/000055 WO1992016794A1 (en) 1991-03-20 1992-03-19 Mixing device and method for gaseous, liquid or pulverised solid substances

Publications (2)

Publication Number Publication Date
EP0575499A1 EP0575499A1 (en) 1993-12-29
EP0575499B1 true EP0575499B1 (en) 1996-01-31

Family

ID=19859036

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92908271A Expired - Lifetime EP0575499B1 (en) 1991-03-20 1992-03-19 Mixing device and method for gaseous, liquid or pulverised solid substances

Country Status (9)

Country Link
EP (1) EP0575499B1 (es)
AT (1) ATE133771T1 (es)
AU (1) AU1552392A (es)
CA (1) CA2106467A1 (es)
DE (1) DE69208079T2 (es)
DK (1) DK0575499T3 (es)
ES (1) ES2084355T3 (es)
NL (1) NL9100490A (es)
WO (1) WO1992016794A1 (es)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0599395A1 (en) * 1992-11-20 1994-06-01 WITTEVEEN, Gustaaf Jan Low NOx combustor
GB9320455D0 (en) * 1993-10-05 1993-11-24 Atomic Energy Authority Uk Vortex mixer
US5505615A (en) * 1994-06-15 1996-04-09 Winnox Combustion Systems, B.V. Device for mixing a gaseous fuel with air and combustor provided with such a device

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2806517A (en) * 1950-11-16 1957-09-17 Shell Dev Oil atomizing double vortex burner
US3304012A (en) * 1964-11-27 1967-02-14 Sem Bjarne Spray nozzle
CA1159356A (en) * 1979-10-25 1983-12-27 Kurt Skoog Method and device for producing microdroplets of fluid
DE3206074A1 (de) * 1982-02-17 1983-08-18 Körting Hannover AG, 3000 Hannover Brenner fuer staubfoermige, gasfoermige und/oder fluessige brennstoffe
EP0114062A3 (de) * 1983-01-18 1986-02-19 Stubinen Utveckling AB Verfahren und Vorrichtung zum Verbrennen fester Brennstoffe, insbesondere Kohle, Torf oder dergleichen, in pulverisierter Form

Also Published As

Publication number Publication date
ES2084355T3 (es) 1996-05-01
DE69208079D1 (de) 1996-03-14
DK0575499T3 (da) 1996-06-03
CA2106467A1 (en) 1992-09-21
DE69208079T2 (de) 1996-08-22
ATE133771T1 (de) 1996-02-15
NL9100490A (nl) 1992-10-16
WO1992016794A1 (en) 1992-10-01
AU1552392A (en) 1992-10-21
EP0575499A1 (en) 1993-12-29

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