US2860610A

US2860610A - Steam generating and superheating and air heating unit

Info

Publication number: US2860610A
Application number: US381813A
Authority: US
Inventors: Lewis W Heller
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1946-10-31
Filing date: 1953-09-23
Publication date: 1958-11-18
Anticipated expiration: 1975-11-18

Description

Nov. 18, 1958 1.. w. HELLER 2,860,610

STEAM GENERATING AND SUPERHEATING AND AIR HEATING UNIT Original Filed Oct. 31, 1946 2 Sheets-Sheet 1 465 2 58 W mm 94 44 7 6 F I J 43 54 M Z8 92 '88 W2 a 8 22 mo 7226 122b mm g 20 7/2 964. 7/8 84 /20 Z EEK/(1B2 4] 24 F |G.l

' IINVENTOR [en 1s Wflel/er BY M... ATTORNEY Nov. 18, 1958 L. w. HELLER 2,350,610

STEAM GENERATING AND SUPERHEATING AND AIR HEATING UNIT Original Filed Oct. 31, 1946 2 Sheets-Sheet 2 INVENTOR F 'G' 3 ZeW/s 7405 67/92 M ATTORNEY United States Patent ()fiice 2,860,610 Patented Nov. 18

STEAM GENERATING AND SUPERHEATING AND AIR HEATING UNIT Lewis W. Heller, Yardley, Pa., assignor to The Babcock .& Wilcox Company, New York, N. '17., a corporation of New Jersey Original application October 31, 1946, Serial No. 706,926, now Patent No. 2,653,447, dated September 29, 1 953. Divided and this application September 23, 1953, Serial No. 381,813

7 Claims. (Cl. 122-4) division.

The main object of the present invention is the provision of a fuel fired superheated steam generator and air heating unit in which steam superheating and high temperature air heating is accomplished by products of combustion flowing from a common furnace, while low temperature air heating is accomplished by heat transfer from a combination of the products of combustion and super-atmospheric temperature air exhausted from a multiple stage aerodynamic turbine served by the air heating unit.

A further object is the provision of a fuel fired heat absorbing unit arranged to simultaneously generate and superheat large quantities of steam and heat correspondingly large quantities of air under a substantial superatmospheric pressure, with an air delivery temperature at 1300 F. or above.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating ad vantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention:

Of the drawings:

Fig. 1 is a partly diagrammatic sectional elevation of a heat absorbing unit constructed in accordance with my invention;

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1;

Figs. 3 and 4 are sectional views taken on the lines 3- -3 and 4--4 respectively of Fig. 2; and

Fig. 5 is a fragmentary section taken on the line 55 of Fig. 1.

i The fuel fired heat absorbing unit illustrated in the drawings, as used in a binary fluid power plant of the type described, is arranged to receive a continuous supply of feed waterfrom the regenerative feed water heating portion of :the steam power plant and one or more streams of air under super-atmospheric pressure from the discharge of a compressor set, and by the burning of pulverized coal to generate high pressure superheated steam for the steam plant and also heat the air under a substantial super-atmospheric pressure to a temperature from which expansion to approximately atmospheric pressure will produce useful power in excess ofthe power requirements of the compressor.

Inasmuch as such a combined steam-air turbine plant requires heated air at or above 1200 F. and advantageously utilizes highly superheated steam in the steam section, the heat absorbing unit is arranged so that the optimum steam superheat and air temperatures may be attained, through the positioning of surfaces with respect to the heat generating furnace and by the regulation of heating gas flow over the respective surfaces.

In the construction shown by the sectional elevation of Fig. 1, a pulverized fuel burning furnace 10 is fired by a plurality of pulverized fuel burners 12 spaced transversely of the furnace and extending through a secondary air chamber 14 to direct streams of air-borne pulverized fuel received from one or more pulverizers (not shown) through burner lines 16, between spaced furnace ,wall cooling tubes 13. The secondary combustion air is supplied by one or more conduits 20 and is not only under super-atmospheric pressure but at a temperature substantially higher than atmosphere.

The furnace is formed with gas tight fluid cooled walls 22 and a fluid cooled floor 24 adapted to collect and retain a shallow pool of molten ash originating from the fuel and discharging through slag outlet 26. The fluid wall cooling tubes 10 in the present instance are water tubes arranged with water supply connections from and discharge connections to an elevated steam and water drum 23 ofthe boiler. Fluid cooling tubes conveying air or steam may be used in place of some of the water tubes or in combination therewith where radiant heating of the air or steam is desired.

The furnace 310 extends upwardly, being bounded by the wall tubes and a screen of tubes 18a positioned across the lateral gas outlet 30 and extendingbetweena junction header 32 and the lower portion of the drum. From the furnace gas outlet a rearwardly extending upright partition 33, formed in part of water tubes, divides the horizontally extending convection heating pass into a pair of parallel gas passes 34 and 36. Dampers 37 at the rear end of pass 34 permit regulation of the proportions of the gas flow through each pass. At the rear of these passes in which the convection heated tubular elements are located, a gas turning space 38 extending transversely of the unit is provided and a downwardly extending gas pass 40 with additional convection heated elements is arranged to receive heating gases from the horizontal gas flow passes. The walls defining the outer sides of the horizontal gas passes 34 and 36 and the walls of the turning space 38 are made of a gas tight construction adapted to maintain a slightly super-atmospheric pressure within the passes and the space, and they may be advantageously constructed to includeiwater or other fluid heating tubes. The walls of the down flow pass are also constructed to retain a pressure above atmosphere but as the gas temperatures will be lower, fluid heating tubes may be used primarily as structural support elements.

Below the downflow gas pass a gas-tight refractory walled .hopper bottom chamber 41 is arranged as a gas turning space, a gas and air mixing chamber and an ash separating and collecting space. A final upflowgas pass is partly formed by a plurality of transversely spaced circular gas outlet passages 42 opening to the upper rear end of the chamber 41 and each containing a tubular air heater 43. A common breeching 44 joins the passages 42 to the casing of a primary air heater 46. From the top gas outlet of the primary air heater 46, the heating gases originating in the furnace are delivered through a connector 48 to a stack discharging to atmosphere.

When a feed water economizer is used to heat the boiler feed water fro-m the temperature at. which it is discharged from the regenerative heating system of the steam turbine to or approaching the saturated steam temperature in the drum, such a feed water economizer 50 may be arranged inthe downflow gas pass 40,,with

the lower inlet header 52 receiving the feed water. The

'economizer consists of a plurality of laterally positioned multiple loop tubular elements extending across the gas pass and connected at their upper ends to an outlet header 54 which is in turn connected to the water space of the steam and water drum 28 with the customary flow regulating devices.

Water supply connections from the water space of drum 28 are provided to the lower headers for the wall tubes 18. Through transverse junction header 32 and headers 56 and 58, the convection heated steam generating tube bank located in gas pass 34 receives a supply of water to the lower ends of its L-shaped tubes 60, as shown in Fig. 3. The upper ends of the furnace wall and gas pass wall tubes are connected directly or through suitable junction headers to deliver steam and water to the drum 28.

The steam which is separated from the water in drum 28 passes through connectors 62 to an inlet header 64 of a primary superheater 76 consisting of a plurality of multiple loop elements pendantly positioned in gas pass 34 and the steam passing through the elements is collected to transverse outlet header 68. A connecting pipe 70 joins the outlet header of the primary superheater with the inlet header 72 of a secondary superheater 74 in the gas pass 36. superheater 76 is the regulating superheater while superheater 74 having a much greater amount of heat absorbing surface does the major por tion of the superheating of the steam delivered by the the drum. From outlet header 78 a pipe 81) conveys superheated steam to the steam consumers, of which the steam turbine of the combined power plant will utilize the major portion. As a means of controlling steam temperature in order to prevent overheating of tubes of the superheater 74 and also for regulating superheated steam delivery temperature, an atternperator (not shown) may be introduced intermediate the length of the flow paths of the multiple loop tubular elements which form the heat absorbing surface of the secondary superheater.

In the heating of air for utilization in the air turbine at a substantial superatmospheric pressure and a temperature above 1200 F., heat transfer surface consisting of tubular elements is so arranged that a minimum pressure drop will occur in the passage of the air from the inlet to the low temperature heaters to the air outlet of the high temperature heater, while at the same time the air heating surfaces are so arranged that they may be economically constructed.

As an alternate construction, the convection superheater 74 may be replaced as a Whole, or in part, by radiant absorption superheating elements, in which case the high temperature air heater portion 8612, which will be described hereinafter, will be brought closer to the furnace and subjected to much higher gas temperatures.

As arranged in the apparatus shown by Fig. 1, the

high pressure air heating surface is divided into low, intermediate and high temperature sections which are serially connected for air flow in counterflow relation to the heating gases. The low temperature inlet section is formed by the three upright straight tube heaters 43, receiving air at their upper ends from the discharge of the last stage compressor with the air flowing about the outside of the gas flow tubes and discharging at the lower end thereof to the inlet manifold of the intermediate section 84, which is formed by a plurality of laterally spaced multiple loop tubular elements through which the air flows. The high temperature section 86 is in the present instance formed in two portions, the inlet portion 860 being located in the down gas pass 40 directly above the economizer 50 and the serially connected outlet portion 86b in the horizontal gas pass 36 at a position rearward of superheater 74. The high pressure air heated to the operating temperature by the high temperature section is delivered from outlet mani- 4 fold 88 to the inlet of the air turbine for expansion and power generation.

The low temperature air heater section is divided into three separate laterally spaced units 43 for structural reasons inasmuch as they handle air under a substantial superatmospheric pressure. Each unit 43 consists of a closely spaced bank of upright tubes 90 arranged within a pressure restraining external metal casing 92 of circular cross-section, the tubes being secured at their upper and lower ends into perforated

tube sheets

94 and 96 respectively. The unit is supported from the structural members 98 by a plurality of brackets 100 rigidly connected to the casing so that any expansion of the casing with increase in temperature is upward from the level of the supports.

The upper tube sheet 94 is supported from the upper end of the casing 92 by a number of circumferentially spaced struts 182 so that the load of the tubes pendant from the upper sheet is carried on the casing. The pressure air inlet to the intertube spaces is formed by a circular bustle 104 of semi-circular section, and the pressure air delivered from the compressor through conduit 106 is introduced through a transverse manifold 1118 which has lateral connections 110 to the individual bustles 104. The air enters radially inward and flows downward in the tube bank to an outlet comprising an annular bustle 112 and then through lateral connections 114 to a common transverse manifold 116 connected to the air inlet ends of the multiple loop tube elements 118 of the intermediate pressure air heater 84. An expansion joint 120 is annularly arranged about each outlet opening 42 and connects each outlet with the lower tube sheet 96 of each unit. The gas leaving the outlets 42 enters the tubes at the lower ends and leaves at, the

upper end of each unit to enter the common transverse breeching connection 44 which joins the gas outlet streams of the three units together for passage through the primary air heater 46.

As the hot gases flowing in the tubes heat them to a temperature higher than that experienced by the casing, the differential elongation will be taken care of by the flexing of the lower sector of the annular bustle which extends from the outer edge of the circular tube sheet 96. By this construction an air heater can be economically constructed for heating relatively large quantities of air under pressures above atmosphere and the heating surface is so proportioned with respect to the gas flow passages that plugging of ash, etc. is avoided. The construction also lends itself to the attainment of good air temperature rise without undue air pressure drop from the inlet to the outlet.

The transverse manifold 116 constitutes an inlet chamber to which the plurality of transversely spaced tubular multiple loop air heating elements 118 of the intermediate heater 84 are connected. Elements 118 are of relatively small size and are spaced with intertube spaces to give an effective convection transfer of heat from the downwardly flowing gases about the tubes. The bank of elements 118 extends from side to side of the down gas pass 40 as defined by side walls 122a, front wall 122b, and rear wall 1220.

The upper outlet ends of the air heater tubes 118 are individually connected by vertical tube portions 118a located in the gas pass 40 to the lower inlet ends of the tubes of the high temperature section 86a. A junction manifold may be used as an alternate construction but a direct tube to tube construction is preferable. The horizontally extending elements of the section 86a are of reverse bend type and are transversely spaced between walls 122a of the downflow gas pass 40, the uppermost tube lengths being adjacent the gas turning space 38 and receiving radiant heat from the gases in that space. The forward air outlet ends of these tubes connect to a transverse junction manifold 124 extending the full Width between walls 122a,

The outlet portion 86b of the high temperature section is made up of a plurality of serially connected vertically extending inverted U-shaped tube lengths 126 receiving air from manifold 124 and delivering heated air to outlet manifold 88. Tubes 126 are transversely spaced between the sides of the gas pass 36 which is narrower than the downflow gas pass 40. The air discharged from manifold 88 is at operating pressure and temperature and is directed to the air turbine for expansion therein.

Partition 32 separating the horizontal gas flow passes 34 and 36 is made up of a row of spaced vertical extending water tubes 128 connected into the circulation of the boiler with intertube space closures of refractory held in place in the customary manner. The detail arrangement of the partition is shown by sectional elevation of Fig. 4.

The gas turning space 41 is proportioned to give a reduction in gas velocity permitting the gravity separation of ash particles for collection in the lower portion of the hopper bottom and periodic removal through sealed ash removal conduits 130. Space 41 also provides space at its rear side adjacent the gas outlets 42 to the low temperature air heaters 43, which is adaptable as the zone Z into which the bypassed air exhaust from the final stage of the air turbine may be directed and mixed with the heating gases flowing into space 41 from the downflow gas pass 40.

The exhaust air bypass from the air turbine is connected to a manifold 132 extending transversely within the space 41 at a position laterally of the gas stream discharged from the downflow gas pass 40. This manifold has a plurality of longitudinally spaced discharge nozzles 134 constructed to distribute the air from the manifold in a plurality of separate streams in mixing relationship with the gas flowing from the downflow pass subsequent to the reduction in gas velocity which promotes ash separation. The nozzles are constructed in a manner to discharge divided air streams with a minimum of pressure loss.

The primary air heater 46 positioned to receive heating gases from the breeching connection 44 is a straight tube heater in which the gases flow through the tubes and the air to be heated fiows on the outside of the tubes, the air being received from the primary air blower (not shown) of the system at inlet connection 46a and being discharged after heating by flowing downward about the tubes to outlet connection 46b.

With a heat absorbing unit consisting of the combination of steam and air heating surface constructed and arranged in a manner similar to the unit shown, it will be possible to produce superheated steam at the required rate and with the desired degree of superheat temperature control while at the same time heating air under pressure to a temperature at which it can be used to generate a subiantial amount of power. The arrangement provides for the generation of high temperature heating gases by the burning of pulverized coal under high temperature ash slagging conditions although it is obvious that other types of fuel may be satisfactorily burned in the furnace to generate the heating gases,

While in accordance with the provision of the statutes I have illustrated and described herein the best form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus and. method of operation disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a correspond me f t r f at re What is claimed is;

l, A combined steam generating, steam superheating and air heating apparatus comprising walls including steam generating tubes forming a casing enclosing a furnace chamber, means for burning fuel in said furnace chamber, a plurality of parallel flow heating gas passes opening directly to one side of said furnace chamber, steam superheating tubes arranged in one of said gas passes adjacent said furnace chamber, steam superheating tubes in a second of said gas passes adjacent said furnace chamber and serially connected to the superheater tubes in said first gas pass, air heating tubes in said second gas pass rearwardly of said superheating tubes, steam generating tubes in said first gas pass rearwardly of said superheating tubes and substantially opposite to said air heating tubes, and damper means arranged to proportion the heating gas flow between said gas passes.

2. A combined steam generating, steam superheating and air heating apparatus comprising walls forming a casing enclosing a furnace chamber, means for burning fuel in said furnace chamber, a plurality of parallel flow heating gas passes opening directly to one side of said furnace chamber, steam superheating tubes arranged in one of said gas passes adjacent said furnace chamber, steam generating tubes in said gas pass rearwardly of said superheating tubes, steam superheating tubes in a second of said gas passes adjacent said furnace chamber and serially connected to the superheater tubes in said first gas pass, air heating tubes in said second gas pass rearwardly of said superheating tubes, damper means arranged to proportion the heating gas flow between said gas passes, a common gas turning space arranged rearwardly of said gas passes, a downflow vertical gas pass opening to said gas turning space, and horizontally extending air heating tubes in said downflow gas pass connected in series with said second pass air heating tubes.

3. A combined steam generating, steam. superheating and air heating apparatus comprising walls forming a pressure-tight casing enclosing a furnace chamber, means for burning fuel in said furnace chamber, means for supplying combustion air under a superatmospheric pressure to said furnace chamber, a plurality of parallel flow heating gas passes opening directly to one side of said furnace chamber, vertically extending steam superheating tubes arranged in one of said gas passes adjacent said furnace chamber, vertically extending steam generating tubes in said gas pass rearwardly of said superheating tubes, vertically extending steam superheating tubes in a second of said gas passes adjacent said furnace chamber and serially connected to the superheater tubes in said first gas pass, vertically extending air heating tubes in said second gas pass rearwardly of said superheating tubes, and damper means arranged to proportion the heating gas flow between said gas passes.

4. A combined steam generating, steam superheating and air heating apparatus comprising walls forming a pressure-tight casing enclosing a furnace chamber, means for burning fuel in said furnace chamber, means for supplying combustion air under a superatmospheric pressure to said furnace chamber, a plurality of parallel flow heating gas passes opening directly to one side of said furnace chamber, vertically extending steam superheating tubes arranged in one of said gas passes adjacent said furnace chamber, vertically extending steam generating tubes in said gas pass rearwardly of said superheating tubes, vertically extending steam superheating tubes in a second of said gas passes adjacent said furnace chamher and serially connected to the superheater tubes in said first gas pass, vertically extending air heating tubes in said second gas pass rearwardly of said superheating tubes, damper means arranged to proportion the heating gas flow between said gas passes, a common gas turning space arranged rearwardly of said gas passes, a downflow vertical gas pass opening to said gas turning space, and horizontally extending air heating tubes in said downflow gas pass connected in series with said secondpass air heating tubes.

5. A combined steam generating, steam superheating and air heating apparatus comprising walls forming a.

pressure-tight casing enclosing .a furnace chamber, means for burning fuel in said furnace chamber, means for supplying combustion air under a superatmospheric pressure to said furnace chamber, a plurality of parallel flow heating gas passes opening directly to one side of said furnace chamber, vertically extending steam superheating tubes arranged in one of said gas passes adjacent said furnace chamber, vertically extending steam generating tubes in said gas pass rearwardly of said superheating tubes, vertically extending steam superheating tubes in a second of said gas passes adjacent said furnace chamber and serially connected to the superheater tubes in said first gas pass, vertically extending air heating tubes in said second gas pass rearwardly of said superheating tubes, damper means arranged to proportion the heating gas flow between said gas passes, a common gas turning space arranged rearwardly of said gas passes, a downflow vertical gas pass opening to said gas turning space, horizontally extending air heating tubes in said downflow gas pass connected in series with said second pass air heating tubes, a second gas turning space below said downflow gas pass, means for introducing a heated gas under a superatmospheric pressure into said second gas turning space concurrent with the heating gas flow therein, a plurality of parallel flow fluid-tight passages opening to said second gas turning space and enclosing a multiplicity of vertical heating gas conduits, and means for passing air under a superatmospheric pressure through said passages around said heating gas conduits and serially through said horizon tally and vertically extending air heating tubes.

6. A combined steam generating and air heating apparatus comprising walls forming a casing enclosing a furnace chamber, means for burning fuel in said furnace chamber, a heating gas pass opening directly to one side of said furnace chamber, steam superheating tubes arranged in said gas pass adjacent said furnace chamber, steam generating tubes in said gas pass rearwardly of said superheating tubes, air heating tubes in said gas pass rearwardly of said superheating tubes, a fluid-tight passage connected to said gas pass, a multiplicity of heating gas conduits enclosed by said fluid-tight passage, and means for passing air under a superatmospheric pressure through said passage around said heating gas conduits and then through said air heating tubes.

7. A combined steam generating and air heating apparatus comprising Walls forming a casing enclosing a furnace chamber, means for burning fuel in said furnace chamber, a heating gas pass opening directly to one side of said furnace chamber, vertically extending steam superheating tubes arranged in said gas pass adjacent said furnace chamber, vertically extending steam generating tubes in said gas pass rearwardly of said superheating tubes, vertically extending air heating tubes in said gas pass rearwardly of said superheating tubes, a common gas turning space arranged rearwardly of said gas pass, a downflow vertical gas pass opening to said gas turning space, horizontally extending air heating tubes in said downflow gas pass connected in series with said vertically extending air heating tubes, a plurality of parallel flow fluid-tight passages connected to said downflow gas pass, a multiplicity of vertical heating gas conduits en- .closed by each of said fluid-tight passages, and means for passing air under a superatmospheric pressure through said passages around said'heating gas conduits and then ser1al1y through said horizontally and vertically extend- .ing air heating tubes.

References Cited in the file of this patent UNITED STATES PATENTS 1,814,010 Snow July 14, 1931 1,872,138 Grady Aug. 16, 1932 1,878,908 Steinmuller Sept, 20, 1932 2,196,889 Bailey Apr. 9, 1940 2,357,300 Bailey Sept. 5, 1944 2,385,177 Wiederkehr Sept. 18, 1945 2,486,291 Kauer Oct. 25, 1949 2,539,255 Kauer et a1. Jan. 23, 1951 FOREIGN PATENTS 257,770 Germany 'Mar. 20, 1913