AU593104B2

AU593104B2 - Boiler with cyclonic combustion

Info

Publication number: AU593104B2
Application number: AU72691/87A
Authority: AU
Inventors: Mark Khinkis; Jacob Korenberg
Original assignee: DONLEE TECHN IN
Current assignee: DONLEE TECHNOLOGIES Inc
Priority date: 1986-11-07
Filing date: 1987-05-11
Publication date: 1990-02-01
Anticipated expiration: 2007-05-11
Also published as: NZ220266A; DK235287D0; NO871975L; JPS63131903A; EP0266857A3; FI872037A; AU7269187A; EP0266857A2; KR880006498A; DK235287A; MY100885A; NO871975D0; FI872037A0

Description

COMMONWEALTH OF AUSTRALIA 593104 Patent Act 1952 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number Lodged 72(b9/~7 Complete Specification Lodged Accepted Published nmorlmnt =dJ~e andwa Scctocn 49.

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Priority: Related Art 7 November 1986 ,Name of Applicant Address of Applicant Actual Inventor Address for Service DONLEE TECHNOLOGIES INC 693 North Hills Road, York, Pennsylvania 17402, United States of America Jacob KORENBERG; Mark KHINKIS; F.B. RICE CO., Patent Attorneys, 28A Montague Street, BALMAIN. 2041.

Complete Specification for the invention entitled: BOILER WITH CYCLONIC COMBUSTION The following statement is a full description of this invention including the best method of performing it known to us:- I I BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to boilers having cyclonic combustion.

2. Description of the Related Art In the past, cyclone combustor, have been used to produce a cyclone of turbulent gases within a combustion chamber for combusting various solid materials, including poor quality coal and vegetable refuse. Such combustors are disclosed in "Combustion in Swirling Flows: A Review", N. Syred and J.M.neer, Combustion and Flame, Volume 23, pages 143-201 (1974). A fluidized bed boiler having a cyclonic combustor is disclosed in U.S. Patent No. 4,457,289 to Korenberg. These documents are incorporated by reference in this application. A fire tube boiler having a cyclonic combustor has been commercially marketed by Cyclotherm Division, Oswego Package Boiler Co., Inc.

Although providing high specific heat release, known adiabatic cyclone combustors have the disadvantages that combustion temperature is high and NOx emissions are high. Combustion 1' is unstable at low capacity burning and high hydrodynamic turndown ratios are not possible in non-adiabatic combustors.

«The hydrodynamic turndown ratio of the boiler is defined as Sthe ratio of pressurized air flow at maximum load to pressurized air flow at minimum load and measures the ability of the boiler o operate over the extremes of its load ranges. A high turndown atio would allow a wide range in the level of steam generation -1 ah at a particular time. A wide range of steam generation is important to most efficiently allow the boiler to respond to varying steam demands.

It is an object of the present invention to provide a boiler utilizing cyclonic combustion and having a very high specific heat release, low excess air and a relatively low combustion temperature at low CO and NO x emissions.

It is also an object of the present invention to provide a boiler utilizing cyclonic combustion and which is stable at low capacity burning.

It is another object of the present invention to provide a boiler utilizing cyclonic combustion and having a high turndown ratio.

15 Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or maybe learned by practice of the invention. The objects and advantages of the invention may be realized end obtained 20 by means of the instrumentalities and combinations particularly pointed out in the appended claims.

SUMMARY OF THE INVENTION To achieve the foregoing objects, and in accordance .1V with the purposes of the invention as embodied and broadly described herein, there is provided a boiler having a t t cyclonic combustor, comprising a first chamber having a front end, a rear end and substantially cylindrical longitudinally extending outer wall which is substantially t uncooled and refractory lined; a second chamber t r.

I r -3 S having a front end, a rear end, and a substantially cylindrical longitudinally extending outer wall, the rear end of the first chamber in fluid combination with and substantially longitudinally aligned with the front end of the second chamber; means for supplying air and fuel directly into the first chamber and for forming a cyclonic flow pattern of hot gases for combustion within the first chamber and the second chamber; a substantially cylindrical exit throat at the rear end of the second chamber aligned substantially concentrically therewith for exhausting hot gases from the second chamber, the exit throat having a diameter less than the inner diameter of the second chamber; and heat exchange means surrounding t I the second chamber for substantially cooling the wall of S 15 the second chamber without substantially cooling the wall of the first chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate S 20 preferred embodiments of the invention and, together with the general description given above and the detailed description of the preferred embodiments given below, Dl serve to explain the principles of the invention.

Fig. 1 is a side elevation in cross section of a S 25 first embodiment of a boiler incorporating the teachings =of the present invention; Fig. 2 is an end view of the boiler illustrated in Fig. 1; V ci i o: Fig. 3 is a cross section view taken along line,$- /of Fig. 1; and Fig. 4 is a cross section view taken along line- of Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made in detail to the present preferred embodiment of the invention as illustrated in the accompanying drawings.

In accordance with the present invention, there is provided a boiler having a cyclonic combustor comprising a first chamber having a front end, a rear end and a substantially cyclindrical longitudinally extending outer wall which is substantially Suncooled and refractory lined; a second chamber having a front end, a rear end and a substantially cyclindrical longitudinally extending outer wall, the rear end of the first chamber in fluid Scommunication with and substantially longitudinally aligned with the front end of the second chamber; means for supplying air and 'i fuel 'directly into the first chamber and performing a cyclonic S" flow pattern of hot gases for combustion within the first chamber 4 and the second chamber; a substantially round exit throat at the rear end of the second chamber and aligned substantially concentrically therewith for exhausting hot gases from the second chamber, the exit throat having a diameter less than the inner diameter of the second chamber; and heat exchange means surrounding only the second chamber for substantially cooling the wall of the cond chamber without substantially cooling the wall of the i rst chamber.

Fig. 1 shows a horizontally disposed fire tube boiler having a cyclonic combustor in accordance with one preferred embodiment of the invention. The combustor includes a central fire tube, also known as a Morison tube, with a combustion chamber 21 including areas defined by first chamber 22 and second chamber 24. First chamber 22 includes a front end 26, a rear end 28 and a substantially cylindrical longitudinally extending outer wall which is substantially uncooled and refractory lined.

SSecond chamber 24 has a front end 32, a rear end 34 and a substantially cylindrical longitudinally extending outer wall 36, s i which is preferably constructed of metal. The rear end 2-0/of the first chamber 22 and the front end 32 of second chamber 24 are in Sr fluid communication and longitudinally aligned with each other.

Means for supplying air and fuel directly into first chamber 22 such as plenum or manifold 38 and tangential nozzles 40 form a cyclonic flow pattern of hot gases within the reaction chamber defined by first chamber 22 and second chamber 24. The fuel, which is preferably liquid or gaseous, is introduced tangentially i by nozzles 43 and may additionally or alternatively be introduced into first chamber 22 radially by nozzle 41. A substantially cylindrical exit throat 42 is positioned at rear end 34 of second Schamber 24 and aligned concentrically with second chamber 24 so that the exit throat has a diameter less than the inner diameter of second chamber 24. As embodied herein, a source of pressurized air such as a blower (not shown) feeds air from plenum or manifold 38 through nozzles 40 into the first chamber 22.

~tt -6- In accordance with the invention, it is critical that the cross sectional area of the tangential air nozzles and the geometric characteristics of first chamber 22 and second chamber 24 be adapted to provide a Swirl number (S) of at least about 0.6 and Reynolds number (Re) of at least about 18,000 which are required to create a cyclone of turbulence in first chamber 22 and second chamber 24 when operating at maximum capacity. On the other hand, the Swirl number and Reynolds number at maximum capacity must not exceed those values which would result in an unacceptable pressure drop through the tangential air nozzles 40 and the combustion chamber constituted by first chamber 22 and second chamber 24.

r It is the cyclone of turbulence which enables the achievement of specific heat release values up to and higher than 3.5 x 106 Kcal per cubic meter per hour and

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x concentration in flue gases of about 60-120 ppm and about 120-180 ppm when firing natural gas and light fuel oil, respectively. Exit throat 42 and the interior of second chamber 24 must exhibit certain geometric Scharacteristics together with the cross sectional area of the tangential air nozzles of first chamber 22 in order to provide the requisite Swirl and Reynolds number.

All of the above-noted features are explained in greater detail below and are discussed generally in article by Syred and Beer mentioned above, and the references noted in that article which are hereby incorporated by reference.

Si f .1 :iii.ii:;~l*i;iii_ 11I~I p 0*il aft o p *4 0 Pfti #44 0 7 If the combustion chamber 21 comprising first chamber 22 and second chamber 24 is designed and operated so as to achieve a Swirl number of at least about 0.6 and a Reynolds number of at least about l8000in such chamber and the ratio of the diameter of the exit throat 42 (De) to the diameter of the inner wall of the second chamber 24 De/Do defined herein as X, lies within the range of about 0.4 to about 0.7, the first chamber 22 and second chamber 24 will, during operation, exhibit larger internal reverse flow zones with as many as three concentric toroidal recirculation zones being formed.

Such recirculation zones are known generally in the field of convenional cyclone combustors. This coupled with the high level of turbulence results in significantly improved 15 heat exchange and, therefore, a relatively uniform temperature throughout combustion chambers 22 and 24.

The value of ratio X preferably lies within the range of about 0.4 to about 0.7 because as X increases, the pressure drop decreases through the combustion chamber and the Swirl number increases. Higher values of X are preferred. However, for values of X in excess of 0.7, the internal reverse flow zones are not formed sufficiently.

Heat exchange means surround second chamber 24 for substantially cooling the wall 36 of second chamber 24 25 without substantially cooling the wall 30 of first chamber 22. The heat exchange means preferably includes an outer boiler shell 48, gas tubes 50 between outer shell 48 and Morison tube 54 for p.

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44 fC 4, C 4 cC -lr-ri i -'i 8 conducting hot gases from second chamber 24, and space 52 within shell 48 outside gas tubes 50 and second chamber 24 for conducting water which is heated by the heated gases in the second chamber 24 and the gas tubes 50, all in a conventionally known manner.

f Stable combustion, even at low boiler capacity, is achieved by not cooling the walls of first chamber 22 where the air and fuel are injected, but cooling only the walls of the second chamber 24. This stable combustion enables high turndown ratios to be accomplished. For example, as a result of this construction, the turndown ratio can be increased from 4:1 up to and higher than 10:1. Excess air can be decreased from 25-30% to 5% and kept constant at 5% over the high turndown ratio of 10:1.

I 15 The flame temperature can be decreased to 2000 0 F and lower, as opposed to about 3000 F for conventional fire tube boilers. Therefore NOx emission is lower than in the standard burner/boiler unit due to the lower flame 2 temperature and lower excess air.

The central fire tube preferably includes a cylindrical tube 54 extending from, aligned and continuous with wall 36 of second chamber 24. Hot gases from the second chamber 24 pass through exit throat 42 into cylindrical tube 54.

The heat exchange means also preferably includes means such as rear compartment 56 for directing the flow of hot gases exiting cyliiidrical tube 54 from second chamber 24 through a first predetermined set of the gas tubes 50 such as those in the lower part of Fig. 1 and front compartment 58 for directing the iA ;:4

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00 0 a 0 o *0* 00 a «a o of19 a or 0 00 o a 41+ «I f@ e a 0 e 4 hot gases from the first set of gas pipes 50 to a second set of gas pipes 50 in the upper portion of Fig. 1 in the opposite direction. This is shown by the arrows indicating gas flow and is conventionally known for fire tube boilers.

As shown in Fig. 3, the means for supplying air and fuel preferably includes separate conduits for supplying air and fuel separately and directly into first chamber 22 and for mixing and combusting them in the first and second chambers 22 and 24.

The ratio between the length of the first and second chamber 22 and 24 affects the combustion temperature within the combustion chamber 21. In general, as the length of first chamber 22 decreases relative to the length of second chamber 24 the combustion temperature decreases. This ratio is important because lowering the combustion temperature lowers the NOx formation. This ratio for natural gas and fuel oil is normally less than 1.5 for a low capacity combustor and can become less than 0.5 for a very high capacity combustor. It is preferable that the first to second chamber length ratio is substantially in the range of about 0.2:1 to 1.5:1. Because of this, the combustion temperature can be less than 2000-2200°F even for high capacity combustion.

In order to prevent damage to metal wall 35 of second chamber 24 due to overheating, the front end portion 32 of wall 36 is lined with a refracto.ry material Although it is preferable that the cyclonic combustor scribed above be positioned within a boiler system, is contemplated that it can be used for purposes of a 0 1~ I~IQ

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.44 combustion or reaction without substantial boiler apparatus.

combustor Such a cyclonic combustion comprises a first chamber having a front end, a rear end and a substantially cylindrical longitudinally extending outer wall which is substantially uncooled and refractory lined; a second chamber having a front end, a rear end and a substantially cylindrical longitudinally extending outer wall, the rear end of the first chamber in fluid communication with and longitudinally aligned with the front end of the second chamber; means for supplying air and fuel directly into the first chamber and for forming a cyclonic flow pattern within the-first chamber and the second chamber; a substantially cylindrical exit throat at the rear end of the second chamber and aligned substantially concentrically therewith, the exit throat having a diameter less than the inner diameter of the second chamber; and means for substantially cooling the wall of the second chamber without S substantially cooling the wall of the first chamber.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details, representative apparatus, and illustrative examples shown and de- ,I0 scribed. Accordingly, deparatures may be made from such details without departing from the spirit or the scope of applicant's general inventive concept.

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Claims

2. The boiler of claim I including a substantially cylindrical tube extending from the rear end of the second chamber and substantially longitudinally aligned with the second chamber. I ri 4 CI C t Ct Ii I 4, t I. c .L c 4 c 4 CC t: I i ;l i ii a :lr;.;ii U 14] 1: a:ll~ 12
3. The boiler of claim 1 wherein the means for supplying air and fuel includes means for separately supplying air and fuel directly into the first chamber and for mixing and combusting them in the first and second chambers.
4. The boiler of claim 3 wherein the air supplying means and the fuel supplying means are concentric nozzles for tangentially injecting air and fuel into the first chamber. The boiler of claim 1 wherein the first to second chamber length ratio is substantially in the range of 0.2:1 to 1.5:1.
6. The boiler of claim 1 wherein the front end of the outer wall of the second chamber is lined with refractory material. :!r C C. CCC C C I I tlt 4. 9i S 9@ 0* C S. LIC I-CC C C C r- i :I i I-rr~ Paan~~l-
7. A fire tube boiler comprising: a first chamber having a front end, a rear end and a sub- stantially cylindrical longitudinally extending outer wall1 which is substantially uncooled and refractory lined; a second chamber having a front end, a rear end and a sub- stantially cylindrical longitudinally extending outer wall, the rear end of the first chautber in fluid communication with and substantially longitudinally aligned with the front end of the second chamber, the second chamber comprising at least a portion ,.Joe, of the boiler fire tube; means for supplying air and fuel directly into the first chamber and for forming a cyclonic flow pattern of hot gases within the first chamber and the second chamber; a substantially cyclindrical exit throat at the rear end of the second chamber/a. aligned substantially concentrically there- with, the exit throat having a diameter less than the inner diam- eter ok the second chamber; and heat exchange means surrounding, the second chamber for sub- stantially cooling the wall of the second chamber without sub- stantially cooling the wall of the first chamber, the heat ex- change means including an outer shell, gas tubes between the Iouter shell and the second chamber for conducting hot gases from the second chamber, and space within the shell outside the gas tubes and the second chamber for conducting water which is heated brF the heated gases in the second chamber and the gas tubes. Y4 ,swwB. 1 1 t k 14
8. The boiler of claim 7 wherein the heat exchange means includes means for directing the flow of the hot gases from the second chamvber through a first predetermined set of the gas tubes and back through a second predetermined set of the gas tubes.
9. The boiler of claim 7 including a substantially cylindrical tube extending from the rear of the second chamber and substantially longitudinally aligned with the second chamber. The boiler of claim 9 wherein the fire tube comprises the second chamber and the substantially cylindrical tube and wherein the heat exchange means includes means for directing the flow of hot gases from the cylindrical tube through the gas tubes.
11. The boiler of claim 7 wherein the gas tubes longitudinally extend parallel to the second chamber. 4 4* 44 S 4 41 49 44 S ftL I I t C 4 IC Ic C C r 1 i I i i i: r i i
12. A boiler having a cyclonic combustor, comprising: a first chamber having a front end, a rear end and a sub- stantially cylindrical longitudinally extending outer wall which is substantially uncooled and refractory lined; a second chamber having a front end, a rear end and a sub- stantially cylindrical longitudinally extending outer wall, the rear end of the first chamber in fluid communication with and substantially longitudinally aligned with the front end of the *second chamber; °1 Vmeans for supplying air and fuel directly into the-first A: 2chamber and for forming a cyclonic flow pattern of hot gjses for S°combustion within the first chamber and the second chamber, with wo a Swirl number of at4 east about 0.6 and a Reynolds number of-a-t- Least-about 18,000 at the boiler maximum capacity; I. a substantially cylindrical exit throat at the rear end of 2 the second chamber and aligned substantially concentrically therewith, the exit throat having a diameter less than the inner diameter of the second chamber; and Sheat exchange means surrounding the second chamber for sub- stantially cooling the wall of the second chamber without sub- S stantially cooling the wall of the first chamber.
13. The boiler of claim 7 wherein the ratio of the diameter of the exit throat divided by the diameter of the inside surface Sof the second chamber lies within the range of -about-0.4 to abut 0.7. I'Y 1 1 1 1., r
14. A cyclonic combustor comprising: a first chamber having a front end, a rear end and a sub- stantially cylindrical longitudinally extending outer wall which is substantially uncooled and refractory lined; a second chamber having a front end, a rear end and a sub- stantially cylindrical longitudinally extending outer wall, the rear end of the first chamber in fluid communication with and substantially longitudinally aligned with the front end of the second chamber; rt'c lb means for supplying air and fuel directly into the first chamber and for forming a cyclonic flow pattern for combustion within the first chamber and the second chamber; a substantially cylindrical exit throat at the rear end of the second chamber-as-aligned substantially concentrically there- S ,15 with, the exit throat having a diameter less than the inner diam- II eter of the second chamber; and S" means for substantially cooling the wall of the second cham- ber without substantially cooling the wall of the first chamber. Datedthis 8th day of May 1987 DONLEE TECHNOLOGIES INC. Patent Attorneys for the Applicant F.B. RICE CO.
16-i -16- i.