AU577366B2 - Controlled flow, split stream burner assembly with sorbent injection - Google Patents

Description

FORM 7& 8 AUSTRALIA r'-AENTS ACT 1952 PATENT DECLARATION FORM (CONVENTION OR NON-CONVENTION) LH19SJ 1 DECLARATION IN SUPPORT 0 F APPLICATION FOR A PATENT FOSTER WHEELER ENERGY CORPORATIONI Insert name of In support of the application made by. applicant. for a patent for an invention entitled: CONTROLLED FLOW, SPLIT STREAM BURNER Insert title of invention, ASSEMBLY WITH SORBENT INJECTION Insert full name(s) 3=J FOSTERP WIT4P.LT.R F.T'JRGY CORPORAT-ON and addressles) of 11 0 Roiitii nrama-Aieniie person(s) making Ti 4 r 4-,m Mr-. -ccxi 0'7r)'40 rT7 declaretion. If applicant a company I, James T. Samuel of -the above address person must be authorised to make declaration. do solemnly and sincerely declare as follows: 1. koM.oWc are the applicant(a) fer the patent. *Delete alternatives OR I am authorized by the abovementioned applicant to make this declaration on its which do not apply behalf, 2. IaM/W8~ are thg acti-al notrc of the Inventien, Insert name(s) and OR (b) addressles) of actual Joel Vatsky Inventor(s), 15 Edcjewood Terrace. Millburn, New Jersey USA

0 is/a~pethe actual inventor(.Q of the invention and the facts upon which the applicantHs) Is/af,-entitled lQiart.1detalls of to make the application are as follows:- entitlement to apply, a.signe%of inventor(s) Applicant is Assignee of Inventor Assicxned to Foster WheelerEneravyloxnatoi by virtue of an assignment executedlimtJQ-, 1e o New Jersey on June 15, 1984 3. The basic applicationW~ as defined by Section 141 of the Act waS/NU(Kamade in the follow- ing country or countries on the following date A by the following applicant.e in the United states r n A ril 27 1. of America Delete 3 and 4 if application non- by Je Vatsky -on 19 convention. Otherwise insert details of basic in on 19 0 appoIcationls). by on 19

uy

4. The basic application(-.,) referred to in paragraph 3 of this Declaration was&vcqAahe first applicatiort(O made in a Convention country in respect of the invention the subject of the application. Jersey Place and date of Declared at Livingston. New/ ,thisj 1 ,day of April1 19 lelgfa~ure.

NO ATTESTATION FRTRPP WRflFTRP ENERGY CORPORAM~ION OR SEAL Signature of declarant(s). To: The Commissioner of Patents, lis T. Samuel, Secretary Australia

SANDE RCOCK, SMITH BEADLE, P.O. Box 410, Hawthorn, 3122, Australia cables: Sandpat Melbourne telex, 34491, Sandpat

I (12) PATENT ABRIDGMENT (11) Document No. AU-B-41495/85 (19) AUSTRALIAN PATENT OFFICE (10) Acceptance No. 577366 t i i_

(54) Title CONTROLLED FLOW, SPLIT STREAM BURNER ASSEMBLY WITH SORBENT JINJECTION (51)4 International Patent Classification F23N 005/24 F23D 001/00 (21) Application No. 41495/85 (22) Application Date t 22.04.85 Priority Data (31) Number (32) Date (33) Country 604706 27.04.84 US UNITED STATES OF AMERICA (43) Publication Date 31.10.85 (44) Publication Date of Acce'pted Application 22.09.88 (71) Applicant FOSTER WHEELER ENERGY CORPORATION (72) Inventor JOEL 7ATSKY (74) Attorney or Agent SANDERCOCK, SMITH BEADLE MELBOURNE (56) Prior Art Documents US 4400151 (57) Claim

1. A burner assembly for particulate fuel comprising an

annular f jel passage defined by an inner tubular member and

an outer tubular member extending around said inner tubular

member in a coaxial relation thereto, an inlet located at

one end of said passbge fn' -eceiving fuel and adapted to

direct such fuel tang-,otlpiml thAnui Lo, a nozzle located at the other end of said passage for discharging said fuel, an enclosure extending over said fuel passage and carry an

i inlet for receiving air, means for directing said air from

said nclosure towards said nozzle in two radially spaced, parall el p'ths s,0ading around said passage, sleeve disposed within stDd passage for dividing the stri.am into

two radially spaced parallel annular streams such that a substantial portion of said particulate fuel flows into the said outer annular stream as a consequence of centrifugal

forces, the assembly including means for regulating the flow

L p

(11) AU-B-41495/85 -2- 577366

rate in at least one of said parallel annular streams, at

least one air inlet opening formed in a portion of said

outer tubular member for admitting air to said outer annular

stream as it discharges from said nozzle, and means for

injecting sorbent into the radially outer path at said

nozzle for capturing the sulfur produced as a result of

combustion of said fuel.

N

_AU TRAA Ld-

Form PATENTS ACT 1952

COMPLETE SP-ECIFICATION (OR IG INAL) FOR OFFICE ''SE Short Title:

Int. CI:

Application Number., Lodged:

Complete Specification-Lodged; Accepted: Lapsed: Published:

Priority:

0Aelited Art:

TO BE COMPLETED BY APPLICANT 0 FOSTER WHEELER ENERGY CORPORATION 0 bo

110 South Orange Avenue, Livingston, 0g New a)ersey 07039. United States of America

9 Actual Inventor: JOEL VATSKY

:A Idress for Service: SZ NDERCOCK, SMITH BEADLE 203 Riversdale Road, Box~ 410), HAW~THORN. VIC. 3122.

Complete Specification for the invention entitled CON~TROLLED FLOW, SPLIT STREAM, BUMIER ASSEMT3LY WITH SORBENT INJECTION The following statement is a full description of this invention, including the best methodilof performing it known to me:- Note: The description Is 6 be typad In double spacing, pica type fc!!o,In an arei not exceeding 250 mm iftdepth and 160 mm In width, on tough white paper of good quality and Wtig to be inserted Inside this forin, 14166177-L Poinled by C. 3. THOMPSON, Acting Commuonwezt o Government Printer, canbtraa

-1-

This invention relates generally to a burner assembly

and nore particularly to an improved burner assembly which operates in a manner to reduce the formation of nitrogen oxides and sulfur dioxides as a result of fuel combustion.

In a typical arrangement for burning coal in a vapor

generator, several burners are disposed in communication

with the interior of the furnace and operate to burn a mix- ture of air and pulverized coal. The burners used in these

arrangements are generally of the type in which a fuel-air mixture is continuously injected through a nozzle so as to form a single, relatively large, flame. In the burning of coal in this manner, unacceptable

Slevels of sulfur dioxide are produced which must be reduced 440*

in order to meet government standards of air quality. Also, when the flame temperature at the burner exceeds 2800 0 F, the

amount of fixed nitrogen removed from the combustion sup-

20 porting air rises exponentially with increases in the tem- perature. This condition leads to the production of high

levels of nitrogen oxides in the final combustion products, which also causes severe air pollution problems.

B 2

a* peatre Thi codto led to th rdcio fhg

-2-

Control of sulfur dioxide emissions is usually achieved by external means such as wet or dry flue gas

desulfurization. In-situ control within the furnace)

has been under investigation for many years and utilizes

either a pre-mixing of limestone (or other sorbent) with coal, or an injection of pulverized sorbent external to the

burner throat through separate ports or small injection nozzles. However, both of these techniques have distinct

drawbacks. The injection of the sorbent with the coal

usually yields low sulfur dioxide capture ratios due to deadburning of the sorbent and can lead to increased

slagging. The external injection of the sorbent requirus S •0 numerous wall penetrations, tube bends and expensive piping o0 Sa 00~ and burner staging controls for the ports.

o175 Also, sorbent injection between or above the burners can SO

b0I* S limit sulfur capture due to several effects:

Inadequate mixing between the products of combustion and the sorbent particles;

Insufficient residence time in the bviler's radiant 9 004l o20 zone; and @4 S .5 Increased slagging and sorbent deposition to the

4.r o. boiler's sidewalls when sorbent is injected to the

lower burner levels of a multiple level boiler. This

injection location also reduces sulfur capture since 4 4 S

~1C~

sorbent particles can be re-entrained in the high temperature portion of the flame.

These deficiencies can be corrected by injecting sorbent in

conjunction with an internally staged low NOx burner. This

type of burner reduces N0 x by at least as compared to

turbulent burners, without simultaneous use of external com-

bustion air staging systems such as overfire or tertiary air ports. However, when overfire air ports are used, NO x

reductions as great as 75% can be obtained. An internally-

staged low NO burner can be defined as one which yields fuel-rich and fuel-lean zones within a flame envelope simi-

lar to that of a turbulent burner. This is in contrast to

delayed mining burners which produce very long narrow flames a S which gradually combust the fuel over a substantially

wo S15 greater distance than is characteristic of either turbulent

99 Sor internally staged burners.

Other attempts, including two-stage combustion, flue gas 0

recirculation and the introduction of an oxygen-deficient

fuel-air mixture suppress the flame temperature and reduce

20 the quantity of available oxygen during the combustion pro- 9

4 cess and thus reduce the formation of nitrogen oxides. .9

,jl 'i 9' However, although these attempts singularly may produce some 904

beneficial results they have not resulted in a reduction of'

nitrogen oxides 6t minimum levels. Also, these attempts I

4 9 4 .9

1 have often resulted in added expense in terms of increased

2 construction costs and have led to other related problems

3 such as the production of soot and the like, nor do they

4 lend themselves to sulfur control via sorbent injection.

It is therefore an object of the present invention to

6 provide a burner assembly which operates in a manner to

7 considerably reduce the production of sulfur dioxides and

8 nitrogen oxides in the combustion of fuel without any

9 significant increase in cost or other related problems.

o °o 10 The invention therefore provides a burner assembly for

11 particulate fuel comprising an annular fuel passage defined

12 by an inner tubular member and an outer tubular member

13 extending around said inner tubular member in a coaxial 14 relation thereto, an inlet located at one end of said

passage for receiving fuel and adapted to direct such fuel

16 tangentially thereinto, a nozzle located at the other end of a 00 17 said passage for discharging said fuel, 0 00 an enclosure

18 extending over said fuel passage and carry an inlet for

0. 19 receiving air, means for directing said air from said

en( losure towards said nozzle in two radially spaced,

a0 21 parallel paths extending around said passage, a sleeve 22 disposed within said passage for dividing the stream into

23 two radially spaced parallel annular streams such that a

24 substantial portion of said particulate fuel flows into the

said outer annular stream as a consequence of centrifugal

26 forces, the assembly including means for regulating the flow

27 rate in at least one of said parallel annular streams, at

I28 least one air inlet opening formed in a portion of said

29 outer tubular member for admitting air to said outer annular

I_~___~car-~--irtPLFaiurriYP=r~

5

1 stream as it discharges from said nozzle, and means for

2 injecting sorbent into the radially outer path at said

3 nozzle for capturing the sulfur produced as a result of

4 combustion of said fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

6 The above brief description as well as further objects,

7 features and advantages of the preser.t invention will be

8 more fully appreciated by reference to the following

9 detailed description of presently preferred but nonetheless

,I 10 illustrative embodiments in accordance with the present

11 invention when taken in conjunction with the accompanying

12 drawings wherein:

13 FIG.1 is a sectional view depicting the burner assembly

*14 of the present invention;

FIG.2 is a partial perspective view of a cqmponent of

16 the burner assembly of FIG. 1;

A 17 FIG.3 is an enlarged elevational view, partially cut-

18 away, of the burner portion of the assembly of the present

S19 invention;

FIG.4 is an end view of the burner portion of FIG.3;

S° 21 and o, o

22 FIG.5 is a cross-sectional view taken along the line

23 5 of FIG.3.

24 DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring specifically to Figw r 1 of the drawings the

26

1* 7 0> b reference numeral 10 refers in general to a burner assembly which is disposed in axial alignment with a through opening

12 formed in a front wall 14 of a conventional furnace. It

is understood that the furnace includes a back wall and side

walls of an appropriate configuration to define a combustion

chamber 16 immediately adjacent the opening 12. Also simi-

lar openings are provided in the furnace front wall 14 for

accommodating additional burner assemblies identical to the

burner assembly 10. The inner surface of the wall 14 as

well as the other walls of the furnace are lined within an

appropriate thermal insulation material 18 and, while not

specifically shown, it is understood that the combustion

S chamber 16 can also be lined with boiler tubes through which 000 0

a heat exchange fluid, such as water, is circulated in a 0a

conventional manner for the purposes of producing steam.

e It is also understood that a vertical wall is disposed O

in a spaced parallel relationship with the furnace wall 14

in a direction opposite that of the furnace opening 12 along

with correspondingly spaced top, bottom and side walls to

i*20 form a plenum chamber, or wind box, for receiving combustion o supporting air, commonly referred to as "secondary air", in

a conventional manner. The burner assembly 10 includes a nozzle 20 having an

inner,tubular member 22 and an outer tubular member 24. a S2

I u

The outer tubular member 24 extends over the inner tubular

member 22 in a coaxial, spaced relationship thereto to

define an annular passage 26 which extends towards the fur-

nace opening 12.

A tangentially disposed inlet 28 communicates with the

outer tubular member 24 for introducing a stream of fuel

into the annular passage 26 as will be explained in further

detail later.

A pair of spaced annular plates 30 and 32 extend around

the burner 20, with the inner edge of the plate 30 ter-

minating on the outer tubular member 24. A liner member 34

extends from the inner edge of the plate 32 and in a general

longitudinal direction relative to the burner 20 and ter- One a minates adjacent the insulation material 18 just inside the p 000q

15 wall 14. An additional annular plate 38 extends around the pp 60009 0 410 0*000 Dap ps S burner 20 in a spaced, parallel relation with the plate pra An air divider sleeve 40 extends from the irnne surface of

the plate 38 and between the liner 34 and the nozzle 20 in a substantially parallel relation to the burner 20 and the oPD (I °20 liner 34 to define two air flow passages 42 and 44. P.O p P *pI A plurality of outer register vanes 46 are pivotally ,,Q o pY mounted between the plates 30 and 32 to control the swirl of

secondary air from the wind box to the air flow passages 42

SO 4 and 44. In a similar manner a plurality of inner register 5* P *0

0*a P.

-I

1 vanes 48 are pivotally mounted between the plates 30 and 38

2 to further regulate the swirl of the secondary air passing

3 through the annular passage 44. It is understocd that

4 although only two register vanes 46 and 48 are shown in

FIG.1, several more vanes extend in a circumferentially

6 spaced relation to the vanes shown. Also, the pivotal

7 mounting of the register vanes 46 and 48 may be done in any

8 conventional manner, such as by mounting the vanes on shafts

9 (shown schematically in FIG. 1) and journaling the shafts in p e*

10 proper bearings formed in the plaLes 30, 32 and 38. Also,

11 the position of the vanes 46 and 48 may be adjustable by

12 means of cranks or the like. Since these types of

13 components are conventional they are not shown in the 446

14 drawings nor will be described in any further detail.

A plurality of sorbent injectors 49 are provided, each

16 of which extends through the plates 30 and 38, between two o e

Soo 17 vanes 48 and into the air flow passage 42. The inlet end

18 portion (not shown) of each injector 49 is connected to a o 19 source of sorbent such as limestone, Ca(0H)2, or the like,

and the discharge end is located at the opening 12 of the

21 front wall 14. The sorbent may be transported through the 00 0

old 22 injectors by means of air, steam or as a slurry. Although

23 not clear from the drawing, it is understood that more than

24 two injectors 49 can be provided in a equilangularly spaced

relation around the nozz.le 20, and that the velocity of

26 injection and injection angle can

A ?(27

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be coatrolled at each injector in a conventional manner.

The quantity of air flow .!rom the wind box into the register vanes 46 is controlled by movement of a sleeve which is slidabl. disposed on the outer periphery of the

plate 32 and is movable parallel to the -ongitudinal axis of

the burner nozzle 20. An elongated worm gear 52 is provided for moving the sleeve 50 and is better ahown in Figure 2.

The worm gear 52 has one end portion suitab'Ly connected to

an appropriate drive means (not shown) for rotating the wcrm

gear and the other end provided with threads 52a. The worm gear 52 extends through a bushing 54 (FIG. 1) which is

attached to the plate 30 to provide rotatable support. The threads 52a of the worm gear 52 mesh with appropriate aper-

00e tures 55 formed in the sleeve 50 so that, upon rotation of 4

0o 15 the worm gear, the sleeve moves lonqitudinally with respect 6OQ.,6 to the longitudial axis of the burner 20 and across the atr 00oo inlet defined by the plates 30 and 32. In this manner, the quantity of combustion supporting air from the wind box passing through the air flow passages 42 and.44 can be ~Q p 0 20 co'itrolled by axial displacement of the sleeve 50. A per- C Op p t.0 forated air hood 56 extends between the plates 30 an9 32 C COt? *0~9 C immediately downstream of the sleeve 50 to permit indepen-

dent measinrement of the air flow to the burner

0O 4 Ab shown in FIGS. 3-5, which depict the details of the

tk 0 i nozzle 20, the end portion of the outer tubular member 24 and the corresponding end portion of the inner tubular member 22 are tapered slightly radially inwardly toward the furnace opening 12. A divider cone 58 extends between the inner tubular member 22 and the out-. tubular member 24. The divider cone 58 had a straight portion 58a (FIG.

which extends between the straight portions of inner tubular

member 22 and the outer,tubular member 24, and a tapered

*portion 58b which extends between the tapered portions of

the tubular members for the entire lengths thereof. The

function of the divider cone 58 will be described in greater

detail later.

A plurality of V-shaped splitters CO are circumferen- *oo tially spaced in the annular space between the outer tubular

S 15 member 24 and the divider cone 58 in the outlet end portion of the nozzle 20. As shown in FIGS. 3 and 4, four such 6ne splitters 60 are spaced at 90° intervals and extend i'.om the

outlet to a point approximately midway between the tapered portions of the tubular members 22 and 24. Each splitter

A 20 is formed by two plate members welded together at their ends to form a V-shape. The plate members are-also welded along I their respective longitudinal edges to the outer tubular

member 24 and the divider cone 58 to support the splitters

and the divider Oone in the nozzle 20. The apex of each

O splitter 60 is disposed upstream of the nozzle outlet so that the fuel-air stream flowing in the annular space bet- ween the divider cone 58 and the outer tubular member 24 will be directed into the adjacent spaces defined between the splitters to facilitate the splitting of the fuel stream into four separate streams.

Four pie-shaped openings 62 are formed through the outer

tubular member 24 and respectively ext.--nd immediately over

the splitters 60. These openings are for the purpose of

admitting secondary air from the inner air flow passage 44

(FIG. 1) into the annular space defined between the divider

cone 58 and thi outer tubular member 24 for reasons that

44 S will be explained in detail later. 4..

44, a As shown in FIG. 5, a tip 64 is formed on the end of the 4 Of5 tapered portion of the inner tubular member 22 and is 94 4 i'vovable relative to the latter member by means of a plura- 0* 4 a 4g4 lity of rods 66 extending within the tubular member and

affixed to the inner wall1 of the tip. The other ervds of the rods 66 can be connected to any type of actuator device (not 9

044 ~'20 shown) such as a hydraulic cylinder of the like to effect 4 44 o u a longitudinal movement of the rods arg2 therefore the tip 64

4 in a conventional mannez.

It can be appreciated from a view of FIG. 5 that the

ow 41 longitudinal movement of the tip 64 varies the effective V outlet opening defined between t.he tip and the divider cone

58 so that the amount of fuel-air flowing through this

opening can be regulated. Since the divider cone 58 divides

the fuel-air mixture flowing through the annular passage 26

into two radially spaced parallel streams extending to either side of the divider cone 58, it can be appreciated that movement of the tip 64 regulates the relative flow of

the two streams while varying their velocity.

it is understood that appropriate ignitors can be pro-

vided adjacc.nt the outlet of the nozzle 20 for igniting the coal as it discharges from the nozzle. Since these ignitors

are Qf a conventional design they have not been shown in the

14 drawings in the interest.of clarity. qIn opEorrtiQn of the burner assembly fti z.

the movable sleeve 50 associated with each burner is adjusted during initial start up to accurately balance 0 0a the air to each burner. After the initial balancing, no

further movement of the sleeves 50 are needed since normal control of the secondary air floi. to the burners is 00 So SOS a 1120 accomplished by operation of the outer burner vanes 46. 0 00

0 ao 4 However, if desired, flow control can be accomplished by the

0 to sleeve.

Fuel, preferably in the form of pulverized coal

I suspended or entrained within a source of primary air, is a o 04

44 0~d

_o r- -r llr*u~ i .3 :i s Cls~li i introduced into the tangential inlet 28 where it swirls through the annular chamber 26. Since the pulverized coal introduced into the inlet 28 is heavier than the air, the pulverized coal will tend to move radially outwardly towards the inner wall of the outer tubular member 24 under the centrifugal forces thus produced. As a result, a great majority of the coal along with a relatively small portion of air enters the outer annular passage defined between the outer tubular member 24 and.the divider cone 58 (FIG.

where it encounters the apexes of the splitters 60. The stream is thus split into four equally spaced streams which discharge from the nozzle outlet and, upon ignition, form four separate flame patterns. Secondary air from the inner

air passage 44 (FIG. 1) passes through the inlets 62 formed

15 in the outer tubular member 24 and enters the annular passage between the latter member and the divider cone 58 to supply secondary air to the streams of coal and air

discharging from the outlet. The remaining portion of the air-coal mixture passing

through the annular passage 26 enters the annular passage defined between the divider cone 58 and the inner tubular ao a member 22. The mixture entering this annular passage is 0* mostly air due to the movement of the coal radially out- wardly, as described above. The position of the movable tip

C P LI

ii. i

IJ

64 can be adjusted to precisely control the relative amount,

and therefore velocity, of the air and coal discharging from

the nozzle 20 from the annular passages between the outer

tubular member 24 and the divider cone 58 and between the

divider cone and the inner tubular member 22. Secondary air from the wind box is admitted th.ough the

perforated hood 56 and into the inlet between the plates 2")

and 32. The axial and radial velocities of the air are

controlled by the register vanes 46 and 48 as it passes

through the air flow passages 42 and 44 and into the furnace opening 12 for mixing with the coal from the nozzle 20. The

igniters are then shut off after steady s;tate combustion has

been achieved.

Sorbent is injected, by the injectors 49, into the

*15 secondary air stream flowing through the flow passage 42 at

S° the opening 12 to capture the sulfur dioxide produced as a

result of combustion of the coal. 0 a

Sc As a result of the foregoing, several advantages result ouao

from the burner assembly of the present invention. For

example, since the pressure drop across the perforated air

hoods 56 associated with the burner assemblies can be equalized by balancing the secondary air flow to each burner

by initially adjusting the sleeves 50, a substantially uni- form flue gas distribution can be obtained across the fur- form flue gas distribution can be obtained across the fur-

0° O

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p

nace. This also permits a common wind box to be used and

enables the unit to operate at lower excess air with signi- ficant reductions in both nitrogen oxides and carbon monoxi-

des. Also, the provision of separate registec vanes 46 and

48 for the outer and inner air flow passages 42 and 44 enables secondary air distribution and flame shape to be

independently controlled resulting in a significant reduc-

tion of nitrogen oxides, and a more gradual mixing of the

primary air coal stream with the secondary air since both

stre-is enter the furnace on parallel paths with controlling

mixing. Further, the provision of multiple flame patterns

results in a greater flame radiation, a lower average flame

temperature and a shorter residence time of the gas com- 4

0o 440

9,, '15 ponents within the flame at a maximum temperature, all of 00

which, as stated above, contribute to reduce the formation

of nitric oxides. *a e 0 *i0 Still further, the provision of the tangential inlet 26 provides excellent distribution of the fuel around the annu-

lar space 26 in the nozzle 20, resulting in move complete combustion and reduction of carbon loss and making it 4.r 9* S possible to use individual burners with capacities signifi- 9 an. cantly higher than otherwise could be used. 'Provision of

the inlet openings 62 in the outer tubular member permits

4. 9 49

U I I -'FT-

the introduction of a portion of the secondary air to be

entrained with the fuel-air stream passing through the annu- lar passage between the outer tubular member 24 and the

divider cone, since the majority of this stream will be pri-

marily pulverized coal. As e result, a substantially uni- form air-coal ratio across the entire cross-section of the

air-coal stream is achieved. Also, the provision of the movable tip 64 to regulate the flow of the coal-air mixture

passing through the inner annular passage defined between

the divider cone 58 and the inner tubular member 22 enable the air flow on both sides of the divider cone to be regu-

lated thereby optimizing the primary air velocity with respect to the secondary air velocity.

Also, by injecting the sorbent into the outer secondary *15 air annulus the particles will by-pass the hottest part of the flame so that a minimum of deadburning of the sorbent

will occur. Also, since the sorbent particles will be

rapidly entrained in the swirling secondary air from this outer secondary annulus they will be intimately mixed with

the products of combustion as soon after passing the peak

0 flame temperature zone as is feasible. This increases the a U efficiency of the sulfur capture and results in capture

that is equal to or better than capture methods external to the burner throat.

0

00

0 0 ft m Pr

It is understood that several variations and additions may be made to the foregoing within the scope of the inven- tion. For example, since the arrangement of the present

invention permits the admission of air at less than

stoichiometric for further reductions in NOx emmissions,

overfire air ports, or the like can be provided as needed to

supply air to complete the combustion. Also, the distribu-

tion of the sorbent injectors 49 around the periphery of the burner can be varied to obtain optimum sulfur capture.

Additionally, the burner levels which receive sorbent injec- tors are dependent on the number of burner levels, slagging

characteristics of the coal ash and the gas temperature at

the exit to the furnaces radiant zone. Boilers .with three

or more burner levels need only have the top two levels con- tain sorbent injectors. This is sufficient to provide an effective calcination zone for calcium-based sorbents along with a long residence time for sulfation reactions to occur P

4 001PO 0 prior to the furnace exit. P

As will be apparent to those skilled in the art,

various changes and modifications may be made to the embodi- ments of the present invention without departure from the

P' spirit vnd scope of the present invention as defined in the

appended claims and the legal equivalent.

The ci-.ims form part of the disclosure of this

specification.

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hi i 18 it- s i 1 The claims defining the invention:

2 1. A burner assembly for particulate fuel comprising an

3 annular fuel passage defined by an inner tubular member and

4 an outer tubular member extending around said inner tubular

member in a coaxial relation thereto, an inlet located at

6 one end of said passage for receiving fuel and adapted to

7 direct such fuel tangentially thereinto, a nozzle located at

8 the other end of said passage for discharginp said fuel, an

9 enclosure extending over said fuel passage and carry an

inlet for receiving air, means for directing said air from

11 said enclosure towards said nozzle in two radially spaced,

12 parallel paths extending around said passage, a sleeve

1 tl 13 disposed within said passage for dividing the stream into 14 ttt 01 14 two radially spaced parallel annular streams such that a

substantial portion of said particulate fuel flows into the

said outer annular stream as a consequence of centrifugal

forces, tire assembly including means for regulating the flow

rate in at least one of said parallel annular streams, at

least one air inlet opening formed in a portion of said

outer tubular member for admitting air to said outer annular to 4 9 8

stream as it discharges from said nozzle, and means for 9 04

injecting sorbent into the radially outer path at said

nozzle for capturing the sulfur produced as a result of

combustion of said fuel.

2. A burner assembly according to Claim 1, wherein said

sorbent is pre-pdalerised and is transported with air,

steam, or as a slurry.

3. A burner assembly according to Claim 1 or Claim 2,

wherein the inlet to the annular passage is a pipe disposed

I

1 tangentially relative thereto.

2 4. A burner assembly according to any preceding Claim,

3 further comprising means for regulating the quantity of air

4 entering said enclosure,

5. A burner assembly according to Claim 4, wherein said

6 regulating means comprises a sleeve movable across the inlet

7 to said enclosure to vary the size of said inlet.

8 6. A burner assembly according to Claim 5, further

9 comprising a perforated hood extending across the inlet of

0 0 10 said enclosure and co-operating with said movable sleeve to O049 Q a0

11 control the quantity of air entering said enclosure.

12 7. A burner assembly according to Claim 4, Claim or

00 13 Claim 6, further comprising means disposed in sid air paths 00 14 for regulating the quantity of air flowing therethrough. IQC) 15 8. A burner assembly according to any preceding claim, cc 0 404 4040 16 further comprising means for splitting-up oae of said air 0

17 streams as it discharges from said nozzle so that upon

18 ignition of said particulate fuel, a plurality oF flame

f* 0 19 patterns are formed. 0 08 20 9. A burner assembly according to Claim 8, wherein said 4 4* 21 spli. ing means extends between said outer tubular member

22 and said sleeve and splits up said outer stream.

23 10. A burner assembly according to Claim 9, wherein said Alp

24 splitting means comprises a plurality of V-shaped members 00s~" 0*~ .6 25 extending in a circumferentially spaced relctionship in the 00i I 9

26 annular space between said outer tubular member and said

27 sleeve and disposed in said passage to that the apex of each

28 member faces upstream and said outer stream flows against

S29 said members which direct said stream into the spaces

n, r, :II between said members.

11. A burner according to any preceding Claim, wherein said

flow rate regulating means comprises a movable tip disposed

at the nozzle on the end of said inner tubular member and

movable thereto.

12. A burner assembly substa. tiilly as hereinbefore

described with reference to the accompanying drawings.

DATED THIS 29th July, 1988

SANDERCOCK, SMITH BEADLE 4

@4 0 Fellows Institute of Patent

Attorneys of Australia. 4

4 Patent Attorneys for the Applicant 444$ 4 4944d FOSTER WHEELER ENERGY CORPORATION

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