WO2019153030A1 - Boiler nozzle and air distributor - Google Patents

Boiler nozzle and air distributor Download PDF

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Publication number
WO2019153030A1
WO2019153030A1 PCT/AU2018/050107 AU2018050107W WO2019153030A1 WO 2019153030 A1 WO2019153030 A1 WO 2019153030A1 AU 2018050107 W AU2018050107 W AU 2018050107W WO 2019153030 A1 WO2019153030 A1 WO 2019153030A1
Authority
WO
WIPO (PCT)
Prior art keywords
nozzle
air distributor
accordance
aperture
passage
Prior art date
Application number
PCT/AU2018/050107
Other languages
French (fr)
Inventor
Xianqun ZHANG
Original Assignee
Evernal Technology Pte Ltd
FARRANDS, Sam
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Evernal Technology Pte Ltd, FARRANDS, Sam filed Critical Evernal Technology Pte Ltd
Priority to PCT/AU2018/050107 priority Critical patent/WO2019153030A1/en
Publication of WO2019153030A1 publication Critical patent/WO2019153030A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
    • C10J3/46—Gasification of granular or pulverulent flues in suspension
    • 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 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2200/00—Details of gasification apparatus
    • C10J2200/15—Details of feeding means
    • C10J2200/152—Nozzles or lances for introducing gas, liquids or suspensions
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
    • C10J2300/0953—Gasifying agents
    • C10J2300/0956—Air or oxygen enriched air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K11/00—Plants characterised by the engines being structurally combined with boilers or condensers
    • F01K11/02—Plants characterised by the engines being structurally combined with boilers or condensers the engines being turbines
    • 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
    • F23C2900/10007—Spouted fluidized bed combustors

Definitions

  • a nozzle and air distributor comprising a plurality of air nozzles for a boiler (e.g. a fluidised bed boiler).
  • the nozzle and air distributor may be used to supply a fluidising medium (e.g. air) into the boiler to fluidise a bed of granular material (e.g. coal).
  • the nozzle may include a body (e.g. a tube) that extends along a longitudinal axis of the body and a plurality of apertures radially spaced about a side wall of the body for supplying air into the boiler.
  • Fluidised bed boiler technology is a clean coal combustion technology. It has the advantages of extensive fuel adaptability, good load adjustment, low nitrogen oxide (NOx) combustion and extensive adaptability to various coal compositions.
  • Fluidised bed boilers may include a furnace within which a bed of material (e.g. a mixture of crushed coal and limestone) is contained. The bottom of the bed is supported by a water cooled air distributor with air nozzles that discharge air into the bed of material to fluidise the material for combustion. Secondary air is typically supplied above the air distributor to stage the combustion process and reduce the formation of NOx. Fluidised bed boilers may recirculate the fuel material (e.g. a circulating fluidised bed boiler). In a circulating fluidised bed boiler (CFB), steam may be released from an upper portion of the boiler furnace and into a cyclonic separator, where suspended material is removed from the gas and returned to the furnace. The steam may then be directed towards a steam generator for the production of power.
  • a circulating fluidised bed boiler CFB
  • steam may be released from an upper portion of the boiler furnace and into a cyclonic separator, where suspended material is removed from the gas and returned to the furnace. The steam may then be directed towards a steam generator for the production of power.
  • the structure and size of an air distributor play an important part in ensuring the safe and economical operations of a fluidised bed boiler.
  • the air distributor may have a basic structure of a membrane water wall with air nozzles installed on its fins. Air flows from the air chamber into the furnace at high speed via the orifices of the air nozzles.
  • Traditional fluidised bed boiler nozzles include bell type, T type, pig-tail type and directional type nozzles.
  • Bell type nozzles are the most used nozzle for fluidised bed boilers.
  • Traditional bell type air nozzles may consist of an inner pipe of a smaller diameter and an air nozzle of a larger diameter.
  • the air nozzle and the inner pipe may be connected by screw thread or by welding.
  • the bell type air nozzle may have the benefits of uniform fluidisation and easy installation and maintenance, reduced blocking and reduced abrasion relative to other traditional fluidised bed boiler nozzles.
  • the disadvantage of bell type air nozzles is that such air nozzles require high standards for design and processing techniques. Inappropriate design or processing techniques may result in increased abrasion of the air nozzles in use, which may result in a significant increase in power consumption of the fans that supply air to the air distributor.
  • a nozzle for supplying a fluidising medium into an air distributor of a boiler, the boiler having a furnace for a bed of granulated material.
  • the nozzle may comprise; a body extending along a longitudinal axis between a proximal end and a distal end of the body, the proximal end being adapted to connect to the air distributor, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end for receipt of the fluidising medium from the air distributor and closed at the distal end; the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal axis between the proximal and distal ends of the body; and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
  • each aperture is fluidically connected to the passage such that the fluidising medium is able to be discharged from the passage and into the granulated material of the boiler to fluidise the material.
  • the plurality of apertures are evenly spaced about the side wall of the body.
  • the plurality of apertures are disposed towards the proximal end of the body.
  • each aperture is oval in shape, a major axis of the oval being substantially parallel to the longitudinal axis of the body and a minor axis of the oval being substantially perpendicular to the longitudinal axis of the body.
  • the length of each aperture, measured along the major axis of the oval, is greater than the width of each aperture, as measured along the minor axis of the oval.
  • the plurality of apertures comprise eight apertures evenly spaced about the side wall of the body.
  • each aperture is configured to discharge air directly from the passage and in a direction that is substantially perpendicular to the longitudinal axis.
  • the body further comprises a cover portion configured to close the passage at the distal end of the body, the cover portion being disposed substantially
  • the cover portion is integrally formed with the side wall of the body.
  • the cover portion is configured to prevent the discharge of the fluidising medium from the distal end of the body.
  • the body is in the form of a cylinder.
  • the side wall comprises a first annular wall portion disposed towards the distal end of the tube, the first wall portion having a first wall thickness, and a second annular wall portion connected to the first wall portion and disposed towards the proximal end of the tube, the second wall portion having a second wall thickness, wherein the second wall thickness is greater than the first wall thickness such that a first internal diameter of the first wall portion is greater than a second internal diameter of the second wall portion.
  • the second wall portion is configured to receive a tube of the air distributor and thereby connect the nozzle to the air distributor.
  • the side wall further comprises an annular tapered lip that extends between the first and second wall portions, the tapered lip being disposed within the tube.
  • the air distributor may comprise; a plurality of cooling fluid distribution conduits, each conduit extending along a longitudinal axis of the conduit and being disposed along a plane that is substantially traverse to the longitudinal conduit axes; the plurality of conduits being connected to a cooling fluid source and arranged to cool the air distributor; a plurality of air distribution conduits, the air distribution conduits arranged to direct the fluidising medium from a fluidising medium source towards the furnace; and a plurality of nozzles, each nozzle comprising; a body extending along a longitudinal nozzle axis between a proximal end of the body and a distal end of the body, the longitudinal nozzle axis being substantially perpendicular to the longitudinal conduit axis, the proximal end of the body being adapted to connect to one of the plurality of air distribution conduits, the body defining a passage therein
  • each aperture has a cross-sectional area that is defined by a length and a width of each aperture.
  • an aperture ratio of the air distributor is between 2.5 and 5%, the aperture ratio being calculated by multiplying the number of nozzles by the number of apertures in each nozzle by the cross-sectional area of each aperture to form a first value, dividing the first value by the first surface area of the air distributor to form a second value, and converting the second value into a percentage value that represents the aperture ratio.
  • the aperture ratio of the air distributor is between 3 and 4%.
  • each aperture is fluidically connected to the passage such that the fluidising medium is able to be discharged from the passage and into the granulated material of the boiler to fluidise the material in use.
  • the plurality of apertures are evenly spaced about the side wall of the body and disposed towards the proximal end of the body.
  • each aperture is oval in shape, a major axis of the oval being parallel to the longitudinal nozzle axis of the body and a minor axis of the oval being perpendicular to the longitudinal nozzle axis of the body.
  • the length of each aperture, measured along the major axis of the oval, is greater than the width of each aperture, as measured along the minor axis of the oval.
  • the plurality of apertures comprise eight apertures evenly spaced about the side wall of the body.
  • each aperture is configured to discharge air directly from the channel and in a direction that is substantially perpendicular to the longitudinal nozzle axis.
  • the body further comprises a cover configured to close the passage at the distal end of the body, the cover being disposed substantially perpendicular to the longitudinal nozzle axis and integrally formed with the side wall of the body.
  • the cover portion is configured to prevent the discharge of the fluidising medium from the distal end of the body.
  • the side wall comprises a first annular wall portion disposed towards the distal end of the body, the first wall portion having a first wall thickness, and a second annular wall portion connected to the first wall portion and disposed towards the proximal end of the body, the second wall thickness being greater than the first wall thickness such that an first internal diameter of the first wall portion is greater than the second internal diameter of the second wall portion.
  • the second wall portion is configured to receive one of the plurality of air distribution conduits and thereby connect the nozzle to the air distributor.
  • the boiler may comprise; a storage apparatus for storing granulated material; a furnace connected to the silo such that the furnace is able to receive the granulated material, the furnace being configured to bum the granulated material to form a heated gas having suspended granulated material; a separator connected to an upper portion of the furnace such that the separator is able to receive the heated gas from the furnace, the separator being configured to separate the granulated material from the gas, the separator being connected to a lower portion of the furnace and to a steam turbine such that the separated granulated material is able to be returned to the lower portion of the furnace and the gas is able to be discharged towards the steam turbine; and an air distributor disposed at the lower portion of the furnace, the air distributor comprising; a plurality of cooling fluid distribution conduits, each conduit extending along a longitudinal axis of the conduit and being disposed along a plane that is substantially traverse to the longitudinal conduit axes
  • Also disclosed herein is a method of modifying a nozzle configured for supplying a fluidising medium into a boiler having a furnace for a bed of granulated material and an air distributor, the nozzle comprising a body extending along a longitudinal axis between a proximal end and a distal end, the proximal end being adapted to connect to the air distributor, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end for receipt of the fluidising medium from the air distributor, the body having a side wall that surrounds the passage and extends along the longitudinal axis between the proximal and distal ends of the body, and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body, the method comprising reducing a cross sectional area
  • reducing the cross sectional area of each aperture comprises adding a material to each aperture.
  • the method may further comprise closing the distal end of the body such that in use the fluidising medium is prevented from being discharged from the distal end of the body.
  • closing the distal end of the body comprises filling an aperture disposed at the distal end of the body.
  • FIG. 1 shows a schematic view of a CFB boiler in accordance with an embodiment of the present disclosure
  • FIG. 2 shows a perspective view of an air distributor in accordance with an
  • FIGs. 3a-b show cross sectional views through the side (a) and top (b) of a boiler nozzle in accordance with an embodiment of the present disclosure
  • Figs. 4a-b show a perspective view (a) and another cross sectional view (b) of the nozzle shown in Figs. 3a-b;
  • FIG. 5 show a perspective view (a) and another cross sectional view (b) of a nozzle prior to modification.
  • a nozzle for supplying a fluidising medium, in the form of air, into a boiler.
  • the air is heated to approximately 2lO°C.
  • the boiler is shown in the form of a CFB boiler.
  • Fig. 1 shows a schematic view of a CFB boiler.
  • the CFB boiler 1 includes a storage apparatus, in the form of a silo 2, for storing granulated material (e.g. crushed coal).
  • the CFB boiler includes a silo 3 for storing an additional granulated material (e.g. limestone).
  • the silos 2 and 3 provide the granulated materials stored therein to a furnace 4 within the boiler (e.g. a chamber).
  • the furnace 4 is configured to burn fuel having a low calorific value (e.g. a mixture of coal and limestone having a calorific value at 12,258 kJ/kg) to form a heated gas.
  • the wall 5 of the furnace 4 may be in the form of a water cooled jacket that surrounds the furnace 4.
  • An air distributor 6 is disposed at a lower portion 7 (e.g. at the bottom) of the furnace 4.
  • the air distributor is shown in more detail in Fig. 2.
  • the air distributor 6 includes a plurality of cooling fluid distribution conduits 8, each conduit extending along a longitudinal axis (A) of the conduit 8.
  • the conduits 8 are disposed along a plane (not shown) that is substantially traverse to the longitudinal conduit axes A (e.g. parallel to the floor of the furnace).
  • the conduits 8 are connected to a cooling fluid source (e.g. a water source) and are arranged to cool the air distributor 6. Additional conduits 9 may be directed into the water cooled jacket that may surround the boiler furnace 4 (see Fig. 1).
  • a plurality of air distribution conduits 10 direct air from a fluidising medium source, in the form of a fan 16 (see Fig. 1) towards the furnace 4.
  • the CFB boiler 1 includes a separator, in the form of a cyclonic separator 11, that is connected to an upper portion 12 of the boiler furnace 4 such that the separator 11 is able to receive the heated gas (e.g. steam) from the furnace 4.
  • the separator is configured to separate granulated material entrained within the steam and return the granulated material to the lower portion 7 of the furnace 4.
  • the steam is discharged into a flue duct 13 whereby a heat exchanger 14 is positioned.
  • the heat exchanger 14 is connected to a steam collector 15. Steam produced by the heat exchanger 14 and stored within the steam collector 15 is then directed towards a steam turbine (not shown) for the production of power.
  • steam produced in the water cooled wall 5 can also be directed towards the steam collector.
  • the air distributor is connected to a plurality of boiler nozzles that supply air into the boiler furnace to fluidise the bed of fuel material located within the boiler furnace.
  • the nozzle will now be described in detail with respect to Figs. 3a-b and Figs. 4a-b.
  • Figs. 3a-b show cross sectional views through the side (Fig. 3a) and the top (Fig. 3b) of the nozzle.
  • Figs. 4a-b show a side view of the nozzle (Fig. 4a) and another cross sectional view through the side of the nozzle (Fig. 4b).
  • the nozzle 100 includes a body, in the form of a cylinder 101, extending along a longitudinal nozzle axis (B) of the cylinder 101 between a proximal end 102 and a distal end
  • the proximal end 102 of the nozzle 100 is adapted to connect (e.g. welded, screw-fitted, friction fitted, etc.) to the air distributor (see Fig. 1).
  • the cylinder defines a passage 104 therein that extends between the proximal 102 and distal ends 103 of the cylinder 101.
  • the passage 104 is open at the proximal end 102 of the cylinder 101 such that the passage
  • the passage 104 is able to receive air from the air distributor (see Fig. 1).
  • the passage 104 is closed at the distal end 103 such that air is prevented from being discharged from the distal end 103 of the nozzle 100.
  • the cylinder 101 includes a side wall 105 that surrounds the passage 104 and extends parallel to the longitudinal axis B between the proximal 102 and distal ends 103 of the cylinder.
  • the side wall 105 is annular (e.g. tubular).
  • the shape of the side wall 105 generally corresponds to the shape of the body of the nozzle 100.
  • the side wall may be substantially rectangular in shape.
  • a plurality of apertures (e.g. orifices) 106 extend through the side wall 105 of the cylinder 101 for supplying the air from the passage 104 into the bed of material within the boiler.
  • the apertures 106 are radially spaced about the side wall 105 of the cylinder 101.
  • Each aperture 106 is fluidically connected to the passage 104 such that air is able to be discharged from the passage 104 and into the bed of material within the boiler furnace (see Fig. 1) to fluidise the bed of fuel material for combustion.
  • the plurality of apertures 106 are evenly spaced about the side wall 105 of the cylinder 101.
  • the plurality of apertures 106 are disposed towards the proximal end 102 of the cylinder 101.
  • the positioning of the apertures 106 at the proximal end 102 of the cylinder 101 causes the air to turn at the distal end 103 of the nozzle 100 and then be discharged through the apertures 106. This arrangement may
  • each aperture 106 is oval in shape.
  • a major axis C (see Fig. 3a) of each oval is parallel to the longitudinal axis B of the cylinder 101.
  • a minor axis D (see Fig. 4a) of each oval is offset from and perpendicular to the longitudinal axis A of the cylinder 101.
  • the length of each aperture 106, measured along the major axis C of the oval, is greater than the width of each aperture 106, as measured along the minor axis D of the oval. In the detailed embodiment, the length of each aperture 106 is 14.2mm and the width of each aperture 106 is l2mm.
  • each aperture 106 is 17.5mm and the width of each aperture 106 is l2mm. In the detailed embodiment, eight apertures 106 are evenly spaced about the side wall 105 of the cylinder 101. Each aperture 106 is configured to discharge air directly from the passage 104 and in a direction that is substantially perpendicular to the longitudinal nozzle axis B.
  • the cylinder 101 includes a cover 107 that is configured to close the passage 104 at the distal end 103 of the cylinder 101.
  • the cover 107 is disposed substantially perpendicular to the longitudinal nozzle axis B.
  • the cover 107 is integrally formed with the side wall 105 of the cylinder 101.
  • the cover 107, or a portion of the cover 107 may be a separate structure that is connected (e.g. welded, screw-fitted, etc.) to the side wall 105 of the cylinder 101.
  • the cover 107 is configured to prevent the discharge of the air from the distal end 103 of the cylinder 101.
  • no apertures are disposed through the side wall 105 at the distal end 103 of the cylinder 101 to prevent the discharge of the air from the distal end 103 of the cylinder 101.
  • the side wall 105 of the cylinder 101 includes a first annular wall portion 108 disposed towards the distal end 103 of the cylinder 101.
  • the first wall portion 108 has a first wall thickness (shown as E in Fig. 4b).
  • the side wall 105 of the cylinder 101 includes a second annular wall portion 109 that is connected to the first wall portion 108 and disposed towards the proximal end 102 of the cylinder 101.
  • the second wall portion 109 has a second wall thickness (shown as F in Fig. 4b).
  • the second wall thickness is greater than the first wall thickness such that an internal diameter of the first wall portion 108 is greater than the internal diameter of the second wall portion 109.
  • the second wall portion 109 is configured to receive a conduit of the air distributor 6 (see Fig. 1) and thereby connect the nozzle 100 to the air distributor 6.
  • the side wall 105 further comprises an annular tapered lip 110 (see Fig. 4b) that extends between the first 108 and second 109 wall portions and that is disposed within the cylinder 101.
  • the air distributor 6 has a first surface area G that is measured substantially parallel to the plane of the air distributor 6.
  • the surface area of the air distributor is similar the cross sectional area of the boiler furnace chamber.
  • each aperture 106 has a cross-sectional area that is defined by the width and length of each aperture 106.
  • An aperture ratio of the air distributor is the ratio between the total area of apertures 106 on all air nozzles 100 and the area G of the air distributor 6. It is expressed as a percentage and can be calculated using the following formula:
  • n the number of air nozzles
  • m the number of apertures on each air nozzle
  • a x the cross sectional area of a single aperture on a single air nozzle, m 2 ;
  • a b the cross sectional area of the air distributor, m 2 .
  • the aperture ratio of the air distributor is between 3 and 4%.
  • the aperture ratio is 3.07% and when the apertures are 17.5mm x l2mm, the aperture ratio is 3.94%.
  • FIG. 5a shows a side view of the nozzle 200.
  • Fig. 5b shows a cross sectional view through the nozzle 200 shown in Fig. 5a.
  • the nozzle includes eight apertures 201 spaced radially about the side wall 202 of the nozzle 200.
  • the nozzle 200 also includes an aperture 203 disposed in the upper portion 204 of the nozzle 200. The aperture 203 allows for air to be discharged through the upper portion 204 of the nozzle 200 and in a direction (see arrow H in Fig.
  • each aperture is approximately 12.5mm in width and 20mm in length and, prior to modification of the nozzle 200, the air distributor to which a plurality of nozzles 200 are connected has a cross-sectional area of 34.9m2 and an aperture ratio at 4.6%.
  • Example 1
  • Example 1 investigates a first modification of the nozzle 200 involves sealing (e.g. closing) the aperture 203 disposed in the upper portion 204 of the nozzle 200 and reducing the length of each of the remaining apertures 201 to 17.5mm.
  • metallic material e.g. a material that is similar to the body
  • the nozzle is similar in structure to the nozzle shown in Figs 3 & 4. This modification reduces the aperture ratio of the associated air distributor from 4.6% to 3.94%.
  • Table 1 The results of tests conducted on the modified nozzle are show in Table 1 below.
  • the resistance of the air chamber e.g. the furnace 4, see Fig. 1
  • the resistance of the air distributor increases by 350Pa relative to the air distributor resistance prior to modification.
  • a second modification of the nozzle 200 involves sealing (e.g. closing) the aperture 203 disposed in the upper portion 204 of the nozzle 200 and reducing the length of each of the remaining apertures 201 to 14.2mm.
  • the nozzle has the structure of the nozzle shown in Figs 3 & 4. This modification reduces the aperture ratio of the air distributor from 4.6% to 3.07%.
  • Table 2 The results of tests conducted on the modified nozzle are show in Table 2 below.
  • a large aperture ratio can cause fluctuation of air pressure in the air chamber.
  • the tests on the air distributor having the above described nozzles and an aperture ratio of 3.07% included measuring the distributor resistance of the cold empty bed (without bed materials) under different air volumes to obtain the resistance characteristic curve of the cold temperature air distributor.
  • the calculation formulas for determining an air distributor's resistance characteristic were derived from the data obtained.
  • the calculation formula for determining resistance of an air distributor is as follows:
  • P bf the resistance of air distributor, Pa
  • the overall functionality of the CFB boiler air nozzles may be improved by reducing the aperture cross-sectional area and the aperture ratio of the air distributor.
  • the disclosed nozzle and nozzle modifications may enhance uniformity of air distribution of the air distributor and thus its resistance characteristics.
  • the operating parameters of the CFB boiler using the disclosed nozzle and following modification of the nozzles indicate increased uniformity of temperature distribution on the boiler bed surface and a significant reduction in coking, poor slag discharge and air nozzle abrasion. Consequently, the disclosed nozzle and nozzle modifications may prolong the boiler's safe operation cycle and provide economic benefits.
  • the disclosed nozzle and nozzle modification may be particularly useful for high density fuel (e.g. high density coal gangue) that is traditionally difficult fluidise.
  • high density fuel e.g. high density coal gangue
  • the air velocity through the air nozzle may be increased from 35.98m/s to 42.83m/s
  • the volume of the fluidised air may be decreased from 120000Nm3/h to 95000 Nm3/h
  • the pressure of the air chamber may be increased from 2120Pa to 2260Pa. This may enable the coarse particles of the high density fuel (e.g. coal gangue) to suspend and combust using relatively low volumes of fluidised air, thereby solving the slagging problem and technical difficulties during low dispatch.
  • the problems associated with slag leakage may be solved at the same time, as the disclosed nozzle may provide for stabilised boiler operation under various dispatch levels.
  • An example of the high density coal gangue fuel that is suitable for use with the disclosed nozzle is shown in the table below.

Abstract

Disclosed herein is a nozzle and air distributor comprising a plurality of air nozzles for a fluidised bed boiler. The nozzle and air distributor may be used to supply air into the boiler to fluidise a bed of coal. The nozzle may include a tube that extends along a longitudinal axis of the body and a plurality of apertures radially spaced about a side wall of the body for supplying air into the boiler.

Description

Boiler Nozzle and Air Distributor
Technical Field
[0001] Disclosed herein is a nozzle and air distributor comprising a plurality of air nozzles for a boiler (e.g. a fluidised bed boiler). The nozzle and air distributor may be used to supply a fluidising medium (e.g. air) into the boiler to fluidise a bed of granular material (e.g. coal). The nozzle may include a body (e.g. a tube) that extends along a longitudinal axis of the body and a plurality of apertures radially spaced about a side wall of the body for supplying air into the boiler.
Background Art
[0002] Fluidised bed boiler technology is a clean coal combustion technology. It has the advantages of extensive fuel adaptability, good load adjustment, low nitrogen oxide (NOx) combustion and extensive adaptability to various coal compositions.
[0003] Fluidised bed boilers may include a furnace within which a bed of material (e.g. a mixture of crushed coal and limestone) is contained. The bottom of the bed is supported by a water cooled air distributor with air nozzles that discharge air into the bed of material to fluidise the material for combustion. Secondary air is typically supplied above the air distributor to stage the combustion process and reduce the formation of NOx. Fluidised bed boilers may recirculate the fuel material (e.g. a circulating fluidised bed boiler). In a circulating fluidised bed boiler (CFB), steam may be released from an upper portion of the boiler furnace and into a cyclonic separator, where suspended material is removed from the gas and returned to the furnace. The steam may then be directed towards a steam generator for the production of power.
[0004] The structure and size of an air distributor play an important part in ensuring the safe and economical operations of a fluidised bed boiler. The air distributor may have a basic structure of a membrane water wall with air nozzles installed on its fins. Air flows from the air chamber into the furnace at high speed via the orifices of the air nozzles. Traditional fluidised bed boiler nozzles include bell type, T type, pig-tail type and directional type nozzles.
[0005] Bell type nozzles are the most used nozzle for fluidised bed boilers. Traditional bell type air nozzles may consist of an inner pipe of a smaller diameter and an air nozzle of a larger diameter. The air nozzle and the inner pipe may be connected by screw thread or by welding. The bell type air nozzle may have the benefits of uniform fluidisation and easy installation and maintenance, reduced blocking and reduced abrasion relative to other traditional fluidised bed boiler nozzles. The disadvantage of bell type air nozzles is that such air nozzles require high standards for design and processing techniques. Inappropriate design or processing techniques may result in increased abrasion of the air nozzles in use, which may result in a significant increase in power consumption of the fans that supply air to the air distributor.
[0006] In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.
Summary
[0007] Disclosed herein is a nozzle for supplying a fluidising medium into an air distributor of a boiler, the boiler having a furnace for a bed of granulated material. The nozzle may comprise; a body extending along a longitudinal axis between a proximal end and a distal end of the body, the proximal end being adapted to connect to the air distributor, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end for receipt of the fluidising medium from the air distributor and closed at the distal end; the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal axis between the proximal and distal ends of the body; and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
[0008] In some forms, each aperture is fluidically connected to the passage such that the fluidising medium is able to be discharged from the passage and into the granulated material of the boiler to fluidise the material. [0009] In some forms, the plurality of apertures are evenly spaced about the side wall of the body.
[0010] In some forms, the plurality of apertures are disposed towards the proximal end of the body.
[0011] In some forms, each aperture is oval in shape, a major axis of the oval being substantially parallel to the longitudinal axis of the body and a minor axis of the oval being substantially perpendicular to the longitudinal axis of the body.
[0012] In some forms, the length of each aperture, measured along the major axis of the oval, is greater than the width of each aperture, as measured along the minor axis of the oval.
[0013] In some forms, the plurality of apertures comprise eight apertures evenly spaced about the side wall of the body.
[0014] In some forms, each aperture is configured to discharge air directly from the passage and in a direction that is substantially perpendicular to the longitudinal axis.
[0015] In some forms, the body further comprises a cover portion configured to close the passage at the distal end of the body, the cover portion being disposed substantially
perpendicular to the longitudinal axis.
[0016] In some forms, the cover portion is integrally formed with the side wall of the body.
[0017] In some forms, the cover portion is configured to prevent the discharge of the fluidising medium from the distal end of the body.
[0018] In some forms, the body is in the form of a cylinder.
[0019] In some forms, the side wall comprises a first annular wall portion disposed towards the distal end of the tube, the first wall portion having a first wall thickness, and a second annular wall portion connected to the first wall portion and disposed towards the proximal end of the tube, the second wall portion having a second wall thickness, wherein the second wall thickness is greater than the first wall thickness such that a first internal diameter of the first wall portion is greater than a second internal diameter of the second wall portion. [0020] In some forms, the second wall portion is configured to receive a tube of the air distributor and thereby connect the nozzle to the air distributor.
[0021] In some forms, the side wall further comprises an annular tapered lip that extends between the first and second wall portions, the tapered lip being disposed within the tube.
[0022] Also disclosed herein is an air distributor for supplying a fluidising medium into a boiler having an internal furnace for a bed of granulated material. The air distributor may comprise; a plurality of cooling fluid distribution conduits, each conduit extending along a longitudinal axis of the conduit and being disposed along a plane that is substantially traverse to the longitudinal conduit axes; the plurality of conduits being connected to a cooling fluid source and arranged to cool the air distributor; a plurality of air distribution conduits, the air distribution conduits arranged to direct the fluidising medium from a fluidising medium source towards the furnace; and a plurality of nozzles, each nozzle comprising; a body extending along a longitudinal nozzle axis between a proximal end of the body and a distal end of the body, the longitudinal nozzle axis being substantially perpendicular to the longitudinal conduit axis, the proximal end of the body being adapted to connect to one of the plurality of air distribution conduits, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end to receive the fluidising medium from the connected air distribution conduit and closed at the distal end; the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal nozzle axis between the proximal and distal ends of the body; and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
[0023] In some forms, wherein the air distributor has a first surface area that is substantially parallel to the plane of the air distributor and each aperture has a cross-sectional area that is defined by a length and a width of each aperture.
[0024] In some forms, an aperture ratio of the air distributor is between 2.5 and 5%, the aperture ratio being calculated by multiplying the number of nozzles by the number of apertures in each nozzle by the cross-sectional area of each aperture to form a first value, dividing the first value by the first surface area of the air distributor to form a second value, and converting the second value into a percentage value that represents the aperture ratio.
[0025] In some forms, the aperture ratio of the air distributor is between 3 and 4%.
[0026] In some forms, each aperture is fluidically connected to the passage such that the fluidising medium is able to be discharged from the passage and into the granulated material of the boiler to fluidise the material in use.
[0027] In some forms, the plurality of apertures are evenly spaced about the side wall of the body and disposed towards the proximal end of the body.
[0028] In some forms, each aperture is oval in shape, a major axis of the oval being parallel to the longitudinal nozzle axis of the body and a minor axis of the oval being perpendicular to the longitudinal nozzle axis of the body.
[0029] In some forms, the length of each aperture, measured along the major axis of the oval, is greater than the width of each aperture, as measured along the minor axis of the oval.
[0030] In some forms, the plurality of apertures comprise eight apertures evenly spaced about the side wall of the body.
[0031] In some forms, each aperture is configured to discharge air directly from the channel and in a direction that is substantially perpendicular to the longitudinal nozzle axis. [0032] In some forms, the body further comprises a cover configured to close the passage at the distal end of the body, the cover being disposed substantially perpendicular to the longitudinal nozzle axis and integrally formed with the side wall of the body.
[0033] In some forms, the cover portion is configured to prevent the discharge of the fluidising medium from the distal end of the body.
[0034] In some forms, the side wall comprises a first annular wall portion disposed towards the distal end of the body, the first wall portion having a first wall thickness, and a second annular wall portion connected to the first wall portion and disposed towards the proximal end of the body, the second wall thickness being greater than the first wall thickness such that an first internal diameter of the first wall portion is greater than the second internal diameter of the second wall portion.
[0035] In some forms, the second wall portion is configured to receive one of the plurality of air distribution conduits and thereby connect the nozzle to the air distributor.
[0036] Also disclosed herein is a circulating fluidised bed boiler. The boiler may comprise; a storage apparatus for storing granulated material; a furnace connected to the silo such that the furnace is able to receive the granulated material, the furnace being configured to bum the granulated material to form a heated gas having suspended granulated material; a separator connected to an upper portion of the furnace such that the separator is able to receive the heated gas from the furnace, the separator being configured to separate the granulated material from the gas, the separator being connected to a lower portion of the furnace and to a steam turbine such that the separated granulated material is able to be returned to the lower portion of the furnace and the gas is able to be discharged towards the steam turbine; and an air distributor disposed at the lower portion of the furnace, the air distributor comprising; a plurality of cooling fluid distribution conduits, each conduit extending along a longitudinal axis of the conduit and being disposed along a plane that is substantially traverse to the longitudinal conduit axes; the plurality of conduits being connected to a cooling fluid source and arranged to cool the air distributor; a plurality of air distribution conduits, the air distribution conduits arranged to direct the fluidising medium from a fluidising medium source towards the furnace; and a plurality of nozzles, each nozzle comprising; a body extending along a longitudinal nozzle axis between a proximal end of the body and a distal end of the body, the longitudinal nozzle axis being substantially perpendicular to the longitudinal conduit axis, the proximal end of the body being adapted to connect to one of the plurality of air distribution conduits, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end to receive the fluidising medium from the connected air distribution conduit and closed at the distal end; the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal nozzle axis between the proximal and distal ends of the body; and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
[0037] Also disclosed herein is a method of modifying a nozzle configured for supplying a fluidising medium into a boiler having a furnace for a bed of granulated material and an air distributor, the nozzle comprising a body extending along a longitudinal axis between a proximal end and a distal end, the proximal end being adapted to connect to the air distributor, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end for receipt of the fluidising medium from the air distributor, the body having a side wall that surrounds the passage and extends along the longitudinal axis between the proximal and distal ends of the body, and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body, the method comprising reducing a cross sectional area of each aperture.
[0038] In some forms, reducing the cross sectional area of each aperture comprises adding a material to each aperture.
[0039] In some forms, the method may further comprise closing the distal end of the body such that in use the fluidising medium is prevented from being discharged from the distal end of the body.
[0040] In some forms, closing the distal end of the body comprises filling an aperture disposed at the distal end of the body.
Brief Description of Drawings
[0041] Various embodiments/aspects of the invention will now be described with reference to the following drawings in which,
[0042] Fig. 1 shows a schematic view of a CFB boiler in accordance with an embodiment of the present disclosure;
[0043] Fig. 2 shows a perspective view of an air distributor in accordance with an
embodiment of the present disclosure;
[0044] Figs. 3a-b show cross sectional views through the side (a) and top (b) of a boiler nozzle in accordance with an embodiment of the present disclosure;
[0045] Figs. 4a-b show a perspective view (a) and another cross sectional view (b) of the nozzle shown in Figs. 3a-b; and
[0046] Fig. 5 show a perspective view (a) and another cross sectional view (b) of a nozzle prior to modification.
Detailed Description
[0047] Disclosed herein is a nozzle for supplying a fluidising medium, in the form of air, into a boiler. In some forms, the air is heated to approximately 2lO°C. In the detailed form, the boiler is shown in the form of a CFB boiler. Fig. 1 shows a schematic view of a CFB boiler. The CFB boiler 1 includes a storage apparatus, in the form of a silo 2, for storing granulated material (e.g. crushed coal). The CFB boiler includes a silo 3 for storing an additional granulated material (e.g. limestone). The silos 2 and 3 provide the granulated materials stored therein to a furnace 4 within the boiler (e.g. a chamber). The furnace 4 is configured to burn fuel having a low calorific value (e.g. a mixture of coal and limestone having a calorific value at 12,258 kJ/kg) to form a heated gas. The wall 5 of the furnace 4 may be in the form of a water cooled jacket that surrounds the furnace 4.
[0048] An air distributor 6 is disposed at a lower portion 7 (e.g. at the bottom) of the furnace 4. The air distributor is shown in more detail in Fig. 2. The air distributor 6 includes a plurality of cooling fluid distribution conduits 8, each conduit extending along a longitudinal axis (A) of the conduit 8. The conduits 8 are disposed along a plane (not shown) that is substantially traverse to the longitudinal conduit axes A (e.g. parallel to the floor of the furnace). The conduits 8 are connected to a cooling fluid source (e.g. a water source) and are arranged to cool the air distributor 6. Additional conduits 9 may be directed into the water cooled jacket that may surround the boiler furnace 4 (see Fig. 1). A plurality of air distribution conduits 10 direct air from a fluidising medium source, in the form of a fan 16 (see Fig. 1) towards the furnace 4.
[0049] Referring again to Fig. 1, the CFB boiler 1 includes a separator, in the form of a cyclonic separator 11, that is connected to an upper portion 12 of the boiler furnace 4 such that the separator 11 is able to receive the heated gas (e.g. steam) from the furnace 4. The separator is configured to separate granulated material entrained within the steam and return the granulated material to the lower portion 7 of the furnace 4. The steam is discharged into a flue duct 13 whereby a heat exchanger 14 is positioned. The heat exchanger 14 is connected to a steam collector 15. Steam produced by the heat exchanger 14 and stored within the steam collector 15 is then directed towards a steam turbine (not shown) for the production of power. In some embodiments, steam produced in the water cooled wall 5 can also be directed towards the steam collector.
[0050] The air distributor is connected to a plurality of boiler nozzles that supply air into the boiler furnace to fluidise the bed of fuel material located within the boiler furnace. The nozzle will now be described in detail with respect to Figs. 3a-b and Figs. 4a-b. Figs. 3a-b show cross sectional views through the side (Fig. 3a) and the top (Fig. 3b) of the nozzle. Figs. 4a-b show a side view of the nozzle (Fig. 4a) and another cross sectional view through the side of the nozzle (Fig. 4b).
[0051] The nozzle 100 includes a body, in the form of a cylinder 101, extending along a longitudinal nozzle axis (B) of the cylinder 101 between a proximal end 102 and a distal end
103 of the cylinder 101. The proximal end 102 of the nozzle 100 is adapted to connect (e.g. welded, screw-fitted, friction fitted, etc.) to the air distributor (see Fig. 1). The cylinder defines a passage 104 therein that extends between the proximal 102 and distal ends 103 of the cylinder 101. The passage 104 is open at the proximal end 102 of the cylinder 101 such that the passage
104 is able to receive air from the air distributor (see Fig. 1). The passage 104 is closed at the distal end 103 such that air is prevented from being discharged from the distal end 103 of the nozzle 100.
[0052] The cylinder 101 includes a side wall 105 that surrounds the passage 104 and extends parallel to the longitudinal axis B between the proximal 102 and distal ends 103 of the cylinder. In the detailed form, the side wall 105 is annular (e.g. tubular). The shape of the side wall 105 generally corresponds to the shape of the body of the nozzle 100. For example, when the nozzle body is rectangular, the side wall may be substantially rectangular in shape. A plurality of apertures (e.g. orifices) 106 extend through the side wall 105 of the cylinder 101 for supplying the air from the passage 104 into the bed of material within the boiler. The apertures 106 are radially spaced about the side wall 105 of the cylinder 101.
[0053] Each aperture 106 is fluidically connected to the passage 104 such that air is able to be discharged from the passage 104 and into the bed of material within the boiler furnace (see Fig. 1) to fluidise the bed of fuel material for combustion. The plurality of apertures 106 are evenly spaced about the side wall 105 of the cylinder 101. The plurality of apertures 106 are disposed towards the proximal end 102 of the cylinder 101. The positioning of the apertures 106 at the proximal end 102 of the cylinder 101 causes the air to turn at the distal end 103 of the nozzle 100 and then be discharged through the apertures 106. This arrangement may
substantially prevent slag leakage.
[0054] In the detailed embodiment, each aperture 106 is oval in shape. A major axis C (see Fig. 3a) of each oval is parallel to the longitudinal axis B of the cylinder 101. A minor axis D (see Fig. 4a) of each oval is offset from and perpendicular to the longitudinal axis A of the cylinder 101. [0055] The length of each aperture 106, measured along the major axis C of the oval, is greater than the width of each aperture 106, as measured along the minor axis D of the oval. In the detailed embodiment, the length of each aperture 106 is 14.2mm and the width of each aperture 106 is l2mm. In another form, the length of each aperture 106 is 17.5mm and the width of each aperture 106 is l2mm. In the detailed embodiment, eight apertures 106 are evenly spaced about the side wall 105 of the cylinder 101. Each aperture 106 is configured to discharge air directly from the passage 104 and in a direction that is substantially perpendicular to the longitudinal nozzle axis B.
[0056] The cylinder 101 includes a cover 107 that is configured to close the passage 104 at the distal end 103 of the cylinder 101. The cover 107 is disposed substantially perpendicular to the longitudinal nozzle axis B. In the detailed form, the cover 107 is integrally formed with the side wall 105 of the cylinder 101. In an alternative form, the cover 107, or a portion of the cover 107, may be a separate structure that is connected (e.g. welded, screw-fitted, etc.) to the side wall 105 of the cylinder 101. The cover 107 is configured to prevent the discharge of the air from the distal end 103 of the cylinder 101. Further, in the detailed form, no apertures are disposed through the side wall 105 at the distal end 103 of the cylinder 101 to prevent the discharge of the air from the distal end 103 of the cylinder 101.
[0057] As shown in Fig. 4b, the side wall 105 of the cylinder 101 includes a first annular wall portion 108 disposed towards the distal end 103 of the cylinder 101. The first wall portion 108 has a first wall thickness (shown as E in Fig. 4b). The side wall 105 of the cylinder 101 includes a second annular wall portion 109 that is connected to the first wall portion 108 and disposed towards the proximal end 102 of the cylinder 101. The second wall portion 109 has a second wall thickness (shown as F in Fig. 4b). The second wall thickness is greater than the first wall thickness such that an internal diameter of the first wall portion 108 is greater than the internal diameter of the second wall portion 109.
[0058] The second wall portion 109 is configured to receive a conduit of the air distributor 6 (see Fig. 1) and thereby connect the nozzle 100 to the air distributor 6. In the detailed
embodiment, the side wall 105 further comprises an annular tapered lip 110 (see Fig. 4b) that extends between the first 108 and second 109 wall portions and that is disposed within the cylinder 101. [0059] As shown in Fig. 2, the air distributor 6 has a first surface area G that is measured substantially parallel to the plane of the air distributor 6. The surface area of the air distributor is similar the cross sectional area of the boiler furnace chamber. As previously detailed, each aperture 106 has a cross-sectional area that is defined by the width and length of each aperture 106.
[0060] An aperture ratio of the air distributor is the ratio between the total area of apertures 106 on all air nozzles 100 and the area G of the air distributor 6. It is expressed as a percentage and can be calculated using the following formula:
Figure imgf000014_0001
Wherein: h— aperture ratio, %;
n— the number of air nozzles;
m— the number of apertures on each air nozzle;
Ax — the cross sectional area of a single aperture on a single air nozzle, m2; Ab— the cross sectional area of the air distributor, m2.
[0061] In the detailed embodiment, the aperture ratio of the air distributor is between 3 and 4%. When the apertures are 14.2mm x 12 mm (cross sectional area of l39mm), the aperture ratio is 3.07% and when the apertures are 17.5mm x l2mm, the aperture ratio is 3.94%.
[0062] Also disclosed herein is a method of modifying an existing boiler nozzle to reduce the aperture ratio of an air distributor. The nozzle prior to modification is shown in Figs. 5a-b. Fig. 5a shows a side view of the nozzle 200. Fig. 5b shows a cross sectional view through the nozzle 200 shown in Fig. 5a. The nozzle includes eight apertures 201 spaced radially about the side wall 202 of the nozzle 200. The nozzle 200 also includes an aperture 203 disposed in the upper portion 204 of the nozzle 200. The aperture 203 allows for air to be discharged through the upper portion 204 of the nozzle 200 and in a direction (see arrow H in Fig. 5b) that is substantially perpendicular to the discharge direction (see arrow I in Fig. 5b) of the radially spaced apertures 201. Each aperture is approximately 12.5mm in width and 20mm in length and, prior to modification of the nozzle 200, the air distributor to which a plurality of nozzles 200 are connected has a cross-sectional area of 34.9m2 and an aperture ratio at 4.6%. Example 1
[0063] Example 1 investigates a first modification of the nozzle 200 involves sealing (e.g. closing) the aperture 203 disposed in the upper portion 204 of the nozzle 200 and reducing the length of each of the remaining apertures 201 to 17.5mm. In the detailed form, metallic material (e.g. a material that is similar to the body) is added to the apertures to close or reduce the cross sectional area of the apertures. Following modification, the nozzle is similar in structure to the nozzle shown in Figs 3 & 4. This modification reduces the aperture ratio of the associated air distributor from 4.6% to 3.94%. The results of tests conducted on the modified nozzle are show in Table 1 below.
Figure imgf000015_0001
Table 1: Experimental Data of Cold Test on Empty Bed of Air Distributor after the First Modification
[0064] After the modification, the resistance of the air chamber (e.g. the furnace 4, see Fig. 1) increases significantly, and the resistance of the air distributor increases by 350Pa relative to the air distributor resistance prior to modification.
[0065] A second modification of the nozzle 200 involves sealing (e.g. closing) the aperture 203 disposed in the upper portion 204 of the nozzle 200 and reducing the length of each of the remaining apertures 201 to 14.2mm. Following modification, the nozzle has the structure of the nozzle shown in Figs 3 & 4. This modification reduces the aperture ratio of the air distributor from 4.6% to 3.07%. The results of tests conducted on the modified nozzle are show in Table 2 below.
Figure imgf000016_0001
Table 2: Experimental Data of Cold Test on Empty Bed of Air Distributor after the Second Modification
[0066] Testing conducted on the nozzles following the second modification showed that the underrun and coking problems present in system prior to modification (e.g. a result of the air distributor’s low resistance and uneven fluidisation) were substantially resolved by the second modification to the nozzles. Consequently, the CFB boiler maintained improved functioning and stable combustion. The second modification results in the aperture air velocity increasing to 42.83m/s from 35.98m/s prior to modification. Further, under standard operating conditions, the air flow to maintain normal fluidisation decreases from l20000Nm3/h prior to modification to 95000Nm3/h following modification.
[0067] Cold testing of the nozzles was conducted to evaluate the nozzle performance. In particular, the air distributor having an aperture ratio of 3.07% was compared with an air distributor having an aperture ratio of 4.6%. An aperture ratio of 4.6% is a common aperture ratio of existing CFB boilers. This aperture ratio is commonly selected to reduce resistance of the air distributor. The inventor has discovered that problems with a relatively high aperture ratio include:
• Severe abrasion of air nozzles.
o During operation of the CFB boiler, the primary air and materials inside the furnace commonly abrade the apertures of the air nozzles. The irregular increase of aperture size causes uneven air distribution around the air nozzles which then affects the even fluidisation of bed materials in the furnace. o Coal feeding systems are usually unsophisticated devices, and the particle size of coal fed into the furnace are often large and uneven, which results in severe abrasion of air nozzles. Further, the fuel may contain a high percentage of gangue. Unsophisticated coal crusher systems may not be able to supply crushed fuel that meets the required particle size of the CFB boiler, which affects the fluidised air volume in the furnace and makes it difficult to control the air pressure. The large size of fuel materials deposited at the bottom of the air distributor also requires high air velocities for fluidisation. However, high air velocities can impact the neighbouring air nozzles by causing increased abrasion.
o During operation, severe abrasion of air nozzles can cause high replacement rates for air nozzles and extended maintenance and repair work.
• Slag leakage of air chamber.
o A large aperture ratio can cause fluctuation of air pressure in the air chamber.
This may result in materials being sucked into the air chamber through the apertures of air nozzles, resulting in slag leakage of the air chamber.
• Coking in the boilers (particularly in case of low load of boilers where it may be difficult to control air volume).
[0068] The tests on the air distributor having the above described nozzles and an aperture ratio of 3.07% included measuring the distributor resistance of the cold empty bed (without bed materials) under different air volumes to obtain the resistance characteristic curve of the cold temperature air distributor. The calculation formulas for determining an air distributor's resistance characteristic were derived from the data obtained. The calculation formula for determining resistance of an air distributor is as follows:
Pbf = 6.83 lxlO 10 x (273 + t) x g0 2
Wherein: Pbf— the resistance of air distributor, Pa;
t— the temperature of air chamber, °C;
Qo— fluidization air volume, Nm3/h. [0069] Using the above formula, when the airflow in the fluidised bed was 95,000Nm3/h, the resistance of the air distributor was 29l4Pa, which is within a reasonable resistance range for CFB boiler operation.
[0070] About 700mm (depth) of bed material was fed into the boiler furnace prior to conducting the test. The air flow was gradually increased and the pressure in the air chamber was recorded, along with the pressure at the furnace outlet and other parameters to calculate the total resistance characteristic curve. According to the test curve, the materials in the chamber were normally fluidised when the airflow reached 56000Nm3/h.
[0071] An air distribution uniformity test was conducted after the resistance test of bed materials. The fluidisation airflow when shutting down the primary fan was 120000Nm3/h.
Upon observation of the interior of the furnace, no obvious roughness on the furnace bed was observed and the flatness was generally sufficient. The test results showed that the air distributor in accordance with the detailed embodiments possessed reasonable resistance characteristics and good air distribution uniformity after modification to the air nozzles.
[0072] The overall functionality of the CFB boiler air nozzles may be improved by reducing the aperture cross-sectional area and the aperture ratio of the air distributor. The disclosed nozzle and nozzle modifications may enhance uniformity of air distribution of the air distributor and thus its resistance characteristics. The operating parameters of the CFB boiler using the disclosed nozzle and following modification of the nozzles indicate increased uniformity of temperature distribution on the boiler bed surface and a significant reduction in coking, poor slag discharge and air nozzle abrasion. Consequently, the disclosed nozzle and nozzle modifications may prolong the boiler's safe operation cycle and provide economic benefits.
[0073] The disclosed nozzle and nozzle modification may be particularly useful for high density fuel (e.g. high density coal gangue) that is traditionally difficult fluidise. By reducing the aperture ratio from approximately 4.6% to approximately 3.07%, the air velocity through the air nozzle may be increased from 35.98m/s to 42.83m/s, the volume of the fluidised air may be decreased from 120000Nm3/h to 95000 Nm3/h and the pressure of the air chamber may be increased from 2120Pa to 2260Pa. This may enable the coarse particles of the high density fuel (e.g. coal gangue) to suspend and combust using relatively low volumes of fluidised air, thereby solving the slagging problem and technical difficulties during low dispatch. Further, the problems associated with slag leakage may be solved at the same time, as the disclosed nozzle may provide for stabilised boiler operation under various dispatch levels. An example of the high density coal gangue fuel that is suitable for use with the disclosed nozzle is shown in the table below.
Figure imgf000019_0001
[0074] The word‘comprising’ and forms of the word‘comprising’ as used in this description and in the claims does not limit the invention claimed to exclude any variants or additions.
[0075] Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.

Claims

Claims
1 A nozzle for supplying a fluidising medium into an air distributor of a boiler, the boiler having a furnace for a bed of granulated material, the nozzle comprising;
a body extending along a longitudinal axis between a proximal end and a distal end of the body, the proximal end being adapted to connect to the air distributor, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end for receipt of the fluidising medium from the air distributor and closed at the distal end;
the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal axis between the proximal and distal ends of the body; and
a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
2 A nozzle in accordance with claim 1, wherein each aperture is fluidically connected to the passage such that the fluidising medium is able to be discharged from the passage and into the granulated material of the boiler to fluidise the material.
3 A nozzle in accordance with any one of the preceding claims, wherein the plurality of apertures are evenly spaced about the side wall of the body.
4 A nozzle in accordance with any one of the preceding claims, wherein the plurality of apertures are disposed towards the proximal end of the body.
5 A nozzle in accordance with any one of the preceding claims, wherein each aperture is oval in shape, a major axis of the oval being substantially parallel to the longitudinal axis of the body and a minor axis of the oval being substantially perpendicular to the longitudinal axis of the body.
6 A nozzle in accordance with claim 5, wherein the length of each aperture, measured along the major axis of the oval, is greater than the width of each aperture, as measured along the minor axis of the oval.
7 A nozzle in accordance with any one of the preceding claims wherein the plurality of apertures comprise eight apertures evenly spaced about the side wall of the body. 8 A nozzle in accordance with any one of claims 1 to 7, wherein each aperture is configured to discharge air directly from the passage and in a direction that is substantially perpendicular to the longitudinal axis.
9 A nozzle in accordance with any one of claims 1 to 8, wherein the body further comprises a cover portion configured to close the passage at the distal end of the body, the cover portion being disposed substantially perpendicular to the longitudinal axis.
10 A nozzle in accordance with claim 9, wherein the cover portion is integrally formed with the side wall of the body.
11 A nozzle in accordance with claim 9 or 10, wherein the cover portion is configured to prevent the discharge of the fluidising medium from the distal end of the body.
12 A nozzle in accordance with any one of the preceding claims, wherein the body is in the form of a cylinder.
13 A nozzle in accordance with claim 12, wherein the side wall comprises a first annular wall portion disposed towards the distal end of the tube, the first wall portion having a first wall thickness, and a second annular wall portion connected to the first wall portion and disposed towards the proximal end of the tube, the second wall portion having a second wall thickness, wherein the second wall thickness is greater than the first wall thickness such that a first internal diameter of the first wall portion is greater than a second internal diameter of the second wall portion.
14 A nozzle in accordance with claim 13, the second wall portion is configured to receive a tube of the air distributor and thereby connect the nozzle to the air distributor.
15 A nozzle in accordance with claim 14, wherein the side wall further comprises an annular tapered lip that extends between the first and second wall portions, the tapered lip being disposed within the tube.
16 An air distributor for supplying a fluidising medium into a boiler having an internal furnace for a bed of granulated material, the air distributor comprising; a plurality of cooling fluid distribution conduits, each conduit extending along a longitudinal axis of the conduit and being disposed along a plane that is substantially traverse to the longitudinal conduit axes;
the plurality of conduits being connected to a cooling fluid source and arranged to cool the air distributor;
a plurality of air distribution conduits, the air distribution conduits arranged to direct the fluidising medium from a fluidising medium source towards the furnace; and
a plurality of nozzles, each nozzle comprising;
a body extending along a longitudinal nozzle axis between a proximal end of the body and a distal end of the body, the longitudinal nozzle axis being substantially perpendicular to the longitudinal conduit axis, the proximal end of the body being adapted to connect to one of the plurality of air distribution conduits, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end to receive the fluidising medium from the connected air distribution conduit and closed at the distal end;
the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal nozzle axis between the proximal and distal ends of the body; and
a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
17 An air distributor in accordance with claim 16, wherein the air distributor has a first surface area that is substantially parallel to the plane of the air distributor and each aperture has a cross-sectional area that is defined by a length and a width of each aperture.
18 An air distributor in accordance with claim 17, wherein an aperture ratio of the air distributor is between 2.5 and 5%, the aperture ratio being calculated by multiplying the number of nozzles by the number of apertures in each nozzle by the cross-sectional area of each aperture to form a first value, dividing the first value by the first surface area of the air distributor to form a second value, and converting the second value into a percentage value that represents the aperture ratio. 19 An air distributor in accordance with claim 18, wherein the aperture ratio of the air distributor is between 3 and 4%.
20 An air distributor in accordance with any one of claims 16 to 19, wherein each aperture is fluidically connected to the passage such that the fluidising medium is able to be discharged from the passage and into the granulated material of the boiler to fluidise the material in use.
21 An air distributor in accordance with any one of claims 16 to 20, wherein the plurality of apertures are evenly spaced about the side wall of the body and disposed towards the proximal end of the body.
22 An air distributor in accordance with any one of claims 16 to 21, wherein each aperture is oval in shape, a major axis of the oval being parallel to the longitudinal nozzle axis of the body and a minor axis of the oval being perpendicular to the longitudinal nozzle axis of the body.
23 An air distributor in accordance with claim 22, wherein the length of each aperture, measured along the major axis of the oval, is greater than the width of each aperture, as measured along the minor axis of the oval.
24 An air distributor in accordance with any one of claims 16 to 23, wherein the plurality of apertures comprise eight apertures evenly spaced about the side wall of the body.
25 An air distributor in accordance with any one of claims 16 to 24, wherein each aperture is configured to discharge air directly from the channel and in a direction that is substantially perpendicular to the longitudinal nozzle axis.
26 An air distributor in accordance with any one of claims 16 to 25, wherein the body further comprises a cover configured to close the passage at the distal end of the body, the cover being disposed substantially perpendicular to the longitudinal nozzle axis and integrally formed with the side wall of the body.
27 An air distributor in accordance with any one of claims 16 to 26, wherein the cover portion is configured to prevent the discharge of the fluidising medium from the distal end of the body. 28 An air distributor in accordance with any one of claims 16 to 27, wherein the side wall comprises a first annular wall portion disposed towards the distal end of the body, the first wall portion having a first wall thickness, and a second annular wall portion connected to the first wall portion and disposed towards the proximal end of the body, the second wall thickness being greater than the first wall thickness such that an first internal diameter of the first wall portion is greater than the second internal diameter of the second wall portion.
29 An air distributor in accordance with claim 28, the second wall portion is configured to receive one of the plurality of air distribution conduits and thereby connect the nozzle to the air distributor.
30 A circulating fluidised bed boiler comprising; a storage apparatus for storing granulated material;
a furnace connected to the silo such that the furnace is able to receive the granulated material , the furnace being configured to burn the granulated material to form a heated gas having suspended granulated material;
a separator connected to an upper portion of the furnace such that the separator is able to receive the heated gas from the furnace, the separator being configured to separate the granulated material from the gas, the separator being connected to a lower portion of the furnace and to a steam turbine such that the separated granulated material is able to be returned to the lower portion of the furnace and the gas is able to be discharged towards the steam turbine; and an air distributor disposed at the lower portion of the furnace, the air distributor comprising;
a plurality of cooling fluid distribution conduits, each conduit extending along a longitudinal axis of the conduit and being disposed along a plane that is substantially traverse to the longitudinal conduit axes;
the plurality of conduits being connected to a cooling fluid source and arranged to cool the air distributor;
a plurality of air distribution conduits, the air distribution conduits arranged to direct the fluidising medium from a fluidising medium source towards the furnace; and a plurality of nozzles, each nozzle comprising; a body extending along a longitudinal nozzle axis between a proximal end of the body and a distal end of the body, the longitudinal nozzle axis being substantially perpendicular to the longitudinal conduit axis, the proximal end of the body being adapted to connect to one of the plurality of air distribution conduits, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end to receive the fluidising medium from the connected air distribution conduit and closed at the distal end;
the body having a side wall that surrounds the passage and extends substantially parallel to the longitudinal nozzle axis between the proximal and distal ends of the body; and
a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body.
31 A boiler in accordance with claim 30, the air distributor being as defined in any one of claims 16 to 29.
32 A method of modifying a nozzle configured for supplying a fluidising medium into a boiler having a furnace for a bed of granulated material and an air distributor, the nozzle comprising a body extending along a longitudinal axis between a proximal end and a distal end, the proximal end being adapted to connect to the air distributor, the body defining a passage therein that extends between the proximal and distal ends of the body, the passage being open at the proximal end for receipt of the fluidising medium from the air distributor, the body having a side wall that surrounds the passage and extends along the longitudinal axis between the proximal and distal ends of the body, and a plurality of apertures, each aperture extending through the side wall of the body for supplying the fluidising medium from the passage into the granulated material of the boiler, wherein the apertures are radially spaced about the side wall of the body, the method comprising reducing a cross sectional area of each aperture.
33 A method in accordance with claim 32, wherein reducing the cross sectional area of each aperture comprises adding a material to each aperture. 34 A method in accordance with claim 32 or 33, further comprising closing the distal end of the body such that in use the fluidising medium is prevented from being discharged from the distal end of the body.
35 A method in accordance with claim 34, wherein closing the distal end of the body comprises filling an aperture disposed at the distal end of the body.
PCT/AU2018/050107 2018-02-12 2018-02-12 Boiler nozzle and air distributor WO2019153030A1 (en)

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