US3457902A

US3457902A - Supplementary firing system

Info

Publication number: US3457902A
Application number: US749243A
Authority: US
Inventors: Erwin G Gjerde
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-07-15
Filing date: 1968-07-15
Publication date: 1969-07-29
Anticipated expiration: 1986-07-29

Description

ly 29, 1969 E. G. GJERDE 3,457,902

SUPPLEMENTARY FIRING SYSTEM Original Filed March 5, 1967 2 Sheets-Sheet l a H H {+2 .7 F Go I 1 I Q 50/452 f T? pom/2 q as ourPar TUZEl/VE N Z F G 5 27 FUEL 44s 64 VD 1 A 97 66 a? l INVENTOR. [QW/N I 475225 Ar 702m: KS

United States Patent Int. Cl. F22d 1/00 U.S. Cl. 122-7 16 Claims ABSTRACT OF THE DISCLOSURE A firing system for heating the exhaust from a gas turbine to an elevated temperature and injecting the heated exhaust into heat exchange relationship with a boiler for heating the boiler. The system includes a duct interconnecting the exhaust port of the turbine and the heat receiving compartment of the boiler and a frame, which has a central passage that complements the crosssectional flow area of the duct, is supported in the wall of the duct. A plurality of elongated gas conduits are arranged in spaced relationship within the passage and are supported from the frame. Each of the conduits includes a series of orifices that open toward the boiler. A plurality of burner heads, corresponding in number to the number of conduits, are supported from the respective conduits and each includes a pair of opposed side walls which cooperate to form aligned inlet and outlet openings, the respective inlets confronting the orifices of the respective conduits and being co-extensive therewith. The walls extend away from the inlet and angle inwardly toward each other to form a throat and then turn outwardly in opposite directions to form a shelf and then turn toward the boiler and extend parallel of one another to form opposite sides of a combustion chamber and finally terminate in edges which cooperate to define the outlet opening. The burners being adapted to receive at least 40% but not more than 75% of the exhaust flowing through the passage.

This is a continuation of application Serial No. 620,459, filed Mar. 3, 1967, now abandoned.

BACKGROUND OF INVENTION Field of invention.The present invention relates generally to systems for utilizing heat from the exhaust of a gas turbine and more particularly to a system that includes a heater for adding heat to the exhaust and which utilizes the heated exhaust to heat a boiler.

Description of prior art.Existing systems for heating the exhaust emitted from gas turbines include a plurality, generally six or seven, of relatively large burners or heater heads that are disposed in the duct leading from the turbine to the boiler. Heaters of this type do not provide optimum results since the turbine exhaust flowing by the heaters is not sufiiciently exposed to and mixed with the flame being emitted from the heaters. Since the heads are relatively large the flames emitted therefrom are relatively long and the projecting tips are at a relatively low temperature thus effecting ineflicient burning of the fuel.

SUMMARY OF INVENTION A particular object of the present invention is to provide a supplementary heating system that includes a gas turbine, a boiler and a duct interconnecting the exhaust port of the turbine with the heat receiving compartment of the boiler. A frame is supported in the wall of the duct and includes a central passage having a configuration that complements the internal cross-sectional flow area of the duct. A plurality of gas conduits having a series of orifices spaced along their lengths are arranged in spaced relationship throughout the passage and are supported from 3,457,902 Patented July 29, 1969 the frame with the orifices directed toward the boiler. A plurality of elongated burner heads, corresponding in number to the number of conduits, are each supported from the respective conduits and include a pair of opposed walls which cooperate to form aligned inlet and outlet openings, the respective inlets being spaced from the respective conduits and confronting the respective orifices formed by such conduits. The burner heads are sized to cumulatively receive at least 40% but not more than of the exhaust flow through said passage. The walls extend away from the inlets and angle inwardly toward each other to form a throat and then turn outwardly in opposite directions to form a shelf and then turn and extend parallel of each other and toward the boiler to form opposite walls of a combustion chamber and finally terminate in edges which cooperate to form the outlet.

Other objects and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment thereof, when taken in conjunction with the appended drawings.

DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view of a system embodying the present invention;

FIG. 2 is an elevational sectional view taken along the lines 22 of FIG. 1;

FIG. 3 is a partial view, in enlarged scale, taken from the broken-circle designated 3 in FIG. 2;

FIG. 4 is an elevational sectional view taken along the lines 4-4 of FIG. 3;

FIG. 5 is a broken horizontal sectional view, in enlarged scale, taken along the lines 5-5 of FIG. 2;

FIG. 6 is a broken horizontal sectional view, in enlarged scale, taken along the lines 6-6 of FIG. 2;

FIG. 7 is an elevational sectional view, in enlarged scale, taken along the lines 77 of FIG. 6; and

FIG. 8 is a partial exploded view, in enlarged scale, taken along the lines 88 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 it is common practice in industry to provide a gas turbine T for driving a generator G which in turn drives a work load L. The exhaust from the turbine T contains a substantial amount of heat but it is not at a high enough temperature to be utilized to heat a conventional boiler B. According to the present invention, the turbine T exhaust port is connected with the heat receiving compartment of the boiler B by a duct D which has an enlarged section in which is installed a heater H.

Referring to FIG. 2, the heater H broadly includes a frame 13 that forms a central passage 15 for passage of the turbine exhaust. A plurality of horizontally extending gas conduits 17 are spaced equidistantly from one another and are supported in the passage 15 by housings 19. Each of the conduits 17 include a series of orifices 23 spaced along their lengths and opening toward the boiler B. A plurality of elongated burner heads, generally designated 27, corresponding in number to the number of conduits 17, are supported coextensive with and behind the respective conduits and include aligned inlet and

outlet openings

29 and 31, respectively, the respective inlets facing upstream of the exhaust and confronting the orifices 23 for receiving flow as indicated by the directional arrows in FIG. 4. A flow restricting throat 33 is formed intermediate the

openings

29 and 31 and a combustion chamber 37 is formed immediately downstream thereof and is open on its downstream end to form the outlet opening 31.

More particularly the frame 13 includes four outer flanged steel beams 41 and conventional thermal lining 43 which is sandwiched between the beams 41 and refractory 45. The housings 19 are tubular in shape and are sup.- ported at their ends in aligned horizontal bores 51 and 52 formed in the refractory 47 and thermal liner 43, the bores 52 on the left-hand ends, FIG. 2, being fitted with pipes 54 which freely receive the housings 19 and allow axial movement to provide for axial thermal expansion. The tubular housings 19 form passages 53 for receiving the conduits 17 and have a series of flared apertures 57 that confront the respective orifices 23 for passage of the gas jet emitted therefrom.

Referring to FIGS. 4 and 5, the burner heads 27 are conveniently made in sections 58 and each section includes a pair of opposed end walls 56, for securing such sections to the respective housings 19, as by nut and bolt assemblies 61 which span the housings and receive curved clips 62. A pair of

opposed walls

59 and 60 cooperate to form the inlet and

outlet openings

29 and 31, respectively, angle inwardly toward each other from the inlet to form the throat 33, and then flare outwardly to form shelves 63. The

walls

59 and 60 turn downstream from the shelves 63 and extend parallel of one another to form the chamber 37 and are turned inwardly at their extremities to form confronting lips 64, the edges of the lips cooperating to define the opening 31. Vortex bars 65 are supported from the

walls

59 and 60 and confront the respective orifices 23 to interrupt the gas jet emitted therefrom and induce mixing of the unaerated gas with the aerated entering exhaust. Since the gas supplied to the conduits 17 is generally unaerated the inlet 29 is sized to assure that suflicient oxygen containing exhaust is received thereby to provide an optimum ratio of oxygen to gas in the chamber 37 during steady state operation of the system.

A particular advantage of the heater H is that the gas conduits 17 can be removed from the housings 19 for cleaning without interrupting operation of the heater. To this end each conduit 17 extends through a housing valve 66 and is communicative with a heater manifold 67 extending along one side of the frame 13. A plurality of bores 69, corresponding to the number of conduits 17, are spaced along the wall of the manifold 67 and a nipple 79 is welded into each. Conventional ball valves 81 are attached on one end to the respective nipples 79 and receive a nipple 83 on their opposite ends. A union 85 is screwed onto each of the nipples 83 and receives another nipple 87 onto which is screwed a T 89. The vertical flange of the right-hand beam 41, as viewed in FIG. 2, includes a series of horizontal bores 93 for projection of the conduits 17. Referring to FIG. 6, flanges 97 are welded to the web of such I-beam 41 and include central bores into which are welded nipples 99. The housing valves 66 are screwed onto the nipples 99 and hollow index fittings 107 are screwed into their extending ends. The fittings 107 include outwardly facing annular index surfaces 111 within their passage, such surfaces being abutted by indexing surfaces 115 formed by the inner end of index rings 117 welded to the conduits 17. Referring to FIG. 7, the rings 117 include longitudinal grooves 121 for receiving a cooperating key 123 formed by the fittings 107. With this arrangement, the conduits 17 are indexed longitudinally and radially within the housings 19 such that the orifices 23 are aligned with the apertures 57. Annular plugs 129 slide over the extending conduits 17 and thread into the fittings 107 and press packing washers 131 against the rings 117. The projecting ends of the conduits 17 are threaded for receiving unions 135 which receive nipples 137 that are threaded into the Ts 89. The unconnected end of the Ts 89 are plugged by plugs 141 and the remote end of the conduits 17 are closed off by similar plugs 142.

A vertically extending starter, generally designated 149, is centrally located in the passage and is disposed behind the above described housings 19 and supported therefrom. The starter 149 is constructed similarly to the above described conduits 17 and burner heads 27, except that it extends vertically rather than horizontally. Referring to FIG. 8, the housings 19 of the starter 149 is clamped to each of the horizontal housings 19 by means of clamps generally designated 153. These clamps 153 include a pair of oppositely facing rockers 157 that are welded together on their crossing back sides and which are interposed between the crossing housings 19. A saddle 159 includes four studs 161 projecting from its corners for over-fitting the crossing defined by the intersection of the housings 19. A pair of pipe brackets 163 each include a pair of bores 165 for receiving the studs 161 and are secured in place by nuts 167 which thread onto the studs 161.

A conventional pilot light 171, having an ignition electrode (not shown) in electrical circuitry with an electrical actuating circuit, is mounted at the bottom end of the starter 149 and receives gas from an auxiliary gas line (not shown).

A conventional flame rod is bent over the housing of the pilot light 171 and cooperates with electric circuitry (not shown) to open a solenoid valve (not shown) that controls flow to the starter 149. A flame rod 177, similar to rod 175, is bent over the upper end of the starter 149 and cooperates with electrical circuitry (not shown) to open a solenoid valve (not shown) which controls gas flow to the manifold 67. The purpose of the

rods

175 and 177 will be described hereinafter.

From the foregoing it will be apparent that when the turbine T is operated the exhaust emitted therefrom and into the duct D will be at an elevated temperature, as for instance 800 degrees F., and that when this exhaust is passed through the heater H it will be heated to an even higher temperature, as for instance 1300 degrees F., and that this relatively high temperature mass of exhaust will be extremely effective in heating the boiler B. Since the turbine exhaust is generally travelling at a relatively high velocity, as for instance 3550 feet per minute, it is desirable to slow a portion thereof down and create a relatively low pressure combustion area where combustion will be assured at all times irrespective of erratic velocity increases which may tend to blow-out the flame. Referring to FIGS. 2 and 4, it will be clear that a substantial portion depending on the size of the inlets 29 and number of heads 27, of the turbine exhaust which passes through the passage 15 will be received by the inlets 29 and will be passed through the heads 27. In order to obtain optimum heating of the exhaust and provide an even temperature profile across the crosssectional area of the duct D within a short distance downstream of the heads 27, it has been determined that the combined area of the inlets 29 should comprise between 40 and 75% of the entire area of the passage 15. Restriction of the rapidly flowing exhaust in the throat 33 and expansion in the combustion chamber 27 creates a venturi action to effect a pressure drop in the combustion chamber and such pressure drop is enhanced by the lips 64. The gas jet emitted from the orifices 23 is impinged on the vortex bars 65 to create turbulence in the chamber 37, thereby effecting mixing and aeration of the gas. When the pilot light 171 is actuated the flame rod 175 will be engulfed in flame and will generate a small amount of electric current which will effect opening of the valve (not shown) associated with the starter 149 and the flame will be propagated vertically across the center of the horizontal burner heads 27. When the flame reaches the top end of the starter 149 the flame rod 177 will be engulfed in flame and will be heated to generate electric current to open the valve (not shown) associated with the manifold 67 and the horizontal heads 27 will be ignited. The above described low pressure of the thoroughly mixed gas and exhaust in the chambers 37 will create optimum conditions for rapid combustion thus resulting in a relatively high temperature in the chambers. Such high temperature coupled with sufficient aeration of the gas will induce complete combustion of the gas within a short distance downstream of the high temperature chamber 37 and will enhance burning efficiency. As the heated mixture flows from the openings 31 it will be immediately exposed to the surrounding exhaust and the turbulence resulting from flow by and through the heads 27 will cause complete mixing with such exhaust thereby providing a uniform temperature profile across the cross-section of flow.

In industrial applications, it is common practice to recover used gas from various processes and utilize it as fuel for heaters such as heater H. Such gas generally has a relatively high level of contaminants suspended therein and when it is exposed to oxygen at comparatively high temperatures the contaminants oxidize immediately and will adhere to surrounding surfaces. Thus, when the gas is emitted from the orifice 23 oxidation takes place and slag will build-up around the walls of the orifices tending to plug them. Accordingly it is necessary to remove the conduits periodically and clean the orifice 23. A particular advantage of the present invention is that the individual conduits 17 can be removed without necessity of discontinuing operation of the heater H..This is accomplished by turning off the gas valve 81 associated with the particular conduit 17 to be removed and disconnecting the unions 85 and 135. The annular plug 129 is then removed to free the conduit 17 and such conduit is pulled from the housing 19. The valve 66 is then closed to prevent flame and hot exhaust which entered the orifices of the housings 19 from being blown out the open end of the fitting 107. Thus the removed conduit 17 can be cleaned and readied for reinstallation Without discontinuing operation of the heater H.

From the above it will be apparent that the supplementary firing system of this invention is inexpensive to manufacture and operate and that the heater H provides for proper fuel to air mixture and complete combustion of the fuel at relatively high temperature. The heater also induces thorough mixing of the heated exhaust with the unheated exhaust to assure uniform heat impingement on the boiler B.

Various modifications and changes may be made with regard to the foregoing detailed description without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. A supplementary firing system comprising:

a gas turbine;

a boiler;

a duct interconnecting the exhaust port of said turbine and the heat receiving compartment of said boiler;

a frame disposed in the wall of said duct and having a through central passage that complements the crosssectional flow area of said duct;

a plurality of elongated gas conduits supported from said frame and arranged in spaced relationship throughout said passage and each including a series of orifices spaced along its length and directed toward said boiler;

a plurality of elongated burner heads, corresponding in number to the number of said conduits are supported from said conduits and each includes .a pair of opposed side walls coextensive with said respective conduits and cooperating With one another to form aligned inlet and outlet openings, said respective inlet openings confronting said orifices included in said respective conduits, said pair of walls further extending away from said inlet opening and angling inwardly toward one another to form a throat, then turning outwardly from one another to form a shelf, then turning toward said boiler and extending parallel of one another to form opposite walls of a combustion chamber and finally terminating the edges which cooperate to define said outlet opena;

said burner heads being adapted to receive at least 40% but not more than 75% of said exhaust flowing through said passage.

2. A firing system as set forth in claim 1 wherein said burner heads include a plurality of vortex bars, corresponding in number to the number of orifices in said respective conduits, said bars confronting said respective orifices and being supported from said pair of side walls.

3. A firing system as set forth in claim 1 wherein said gas conduits extend parallel of one another.

4. A firing system as set forth in claim 3 that includes a starter, said starter including an elongated gas conduit extending transversely of and adjacent to said plurality of conduits and including a plurality of orifices spaced along its length;

a burner head supported from said conduit and including a pair of opposed side walls coextensive with said conduit and cooperating with one another to form aligned inlet and outlet openings, said inlet opening confronting said orifices, said pair of side walls further extending away from said inlet opening and angling inwardly toward one another to form a throat, then turning outwardly from one another to form a shelf, then turning toward said boiler and extending parallel of one another to form opposite walls of a combustion chamber and finally terminating in edges which cooperate to define said outlet opening.

5. A heater as set forth in claim 4 wherein said starter is disposed intermediate the ends of said plurality of conduits.

6. A heater as set forth in claim 4 that includes a flame rod having its extending portion adjacent one of said starter Walls forming said outlet whereby the latter acts as an electric ground relative thereto.

7. A heater as set forth in claim 4 that includes a pilot at one end of said starter.

8. A heater as set forth in claim 7 that includes a flame rod having its extending portion adjacent said pilot whereby the latter acts as an electric ground relative thereto.

9. A supplementary firing system, comprising:

a gas turbine;

heat-transfer means;

a duct interconnecting the exhaust port of said turbine and the heat-receiving compartment of said heattransfer means;

conduit support means disposed in the wall of said duct;

a plurality of elongated gas conduits supported from said conduit support means and arranged in spaced relationship throughout said passage, each of said gas conduits including a series of orifices spaced along its length and directed towards said heat-transfer means;

a plurality of elongated burner heads, corresponding in number to the number of said conduits supported from said conduits and each including a pair of opposed side walls coextensive with said respective conduits and cooperating with one another to form aligned inlet and outlet openings, said respective inlet openings confronting said orifices included in said respective conduits, said pair of walls further extending away from said inlet opening and angling inwardly towards one another to form a throat, then turning outwardly from one another to form opposite walls of a combustion chamber having said outlet opening; and

a vortex bar supported from each of said pair of side walls and confronting said orifices to interrupt the gas jet emitted therefrom and induce mixing and aeration of the gas with the entering exhaust, with said entering exhaust being restricted in said throat and expanded in said combustion chamber to effect a pressure drop within said combustion chamber.

10. A firing system as set forth in claim 9 wherein said burner heads are adapted to receive at least 40% but not more than 75 of said exhaust flowing through said passage.

11. A firing system as set forth in claim 9 wherein said gas conduits extend parallel of one another.

12. A firing system as set forth in claim 9 that includes a starter, said starter including an elongated gas conduit extending transversely of and adjacent to said plurality of conduits .and including a plurality of orifices spaced along its length;

a burner head supported from said conduit and including a pair of opposed side walls coextensive with said conduit and cooperating with one another to form aligned inlet and outlet openings, said inlet opening confronting said orifices, said pair of side walls further extending away from said inlet opening and angling inwardly, toward one another to form a throat, then turning outwardly from one another to form a shelf, then turning toward said boiler and extending parallel of one another to form opposite Wall of a combustion chamber and finally terminating in edges which cooperate to define said outlet opening.

13. A heater as set forth in claim 9 wherein said starter is disposed intermediate the ends of said plurality of conduits.

14. A heater as set forth in claim 9 that includes a flame rod having its extending portion adjacent one of said starter walls forming said outlet whereby the latte acts as an electric ground relative thereto.

15. A heater as set forth in claim 9 that includes a pilot at one end of said starter.

16. A heater as set forth in claim 9 that includes a flame rod having its extending portion adjacent said pilot whereby the latter acts as an electric ground relative thereto.

References Cited UNITED STATES PATENTS 2,926,493 3/ 1960 Poole et al.

CHARLES I. MYHRE, Primary Examiner