US3467069A - Recirculating type steam generator and pump arrangement - Google Patents

Recirculating type steam generator and pump arrangement Download PDF

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Publication number
US3467069A
US3467069A US693423A US3467069DA US3467069A US 3467069 A US3467069 A US 3467069A US 693423 A US693423 A US 693423A US 3467069D A US3467069D A US 3467069DA US 3467069 A US3467069 A US 3467069A
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United States
Prior art keywords
pump
flow
steam generator
pumps
valve
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Expired - Lifetime
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US693423A
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English (en)
Inventor
Carlos J Garrett Jr
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Combustion Engineering Inc
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Combustion Engineering Inc
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B29/00—Steam boilers of forced-flow type
    • F22B29/02—Steam boilers of forced-flow type of forced-circulation type
    • F22B29/023—Steam boilers of forced-flow type of forced-circulation type without drums, i.e. without hot water storage in the boiler
    • F22B29/026—Steam boilers of forced-flow type of forced-circulation type without drums, i.e. without hot water storage in the boiler operating at critical or supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B29/00—Steam boilers of forced-flow type

Definitions

  • This invention relates to through-flow steam generators of the recirculating type and in particular to a circulating pump arrangement therefor.
  • Supercritical pressure steam generators operate on the through-flow principle where a feedwater pump forces water serially through tubular heating surface within the steam generator and then to a steam turbine or other steam consuming device.
  • the water generally first flows through an economizer, then through the furnace Wall tubes and finally through the superheater.
  • a portion of the water is withdrawn downstream of the furnace wall tubes and recirculated to a location upstream of the furnace wall tubes. This provides higher flow rates through the furnace wall tubes during low load operation than would normally be experienced.
  • This high flow decreases metal temperature of the tubes due to the lower resistance of the tube-to-water film-to-heat transfer. It also decreases the temperature difference of the fluid passing through the waterwall tubes.
  • the circulating pump effecting such recirculation may be located either in the recirculating line or in the through-flow portion through which recirculation is to be effected.
  • U.S. Patents 3,135,252 and 3,135,- 249 describe the operation of such a system where the circulating pump floats on the recirculating system.
  • the temperature of the fluid leaving the furnace walls remains constant regardless of the amount of recirculation.
  • the inlet temperature to the walls varies along with the flow quantity through the walls.
  • the problems of low mass flow and poor distribution are most difficult at loads in the order of 20 percent or less of full load rating where relatively high temperature low density fluid enters the WaterWalls. Higher recirculation rates at this time would be advantageous.
  • the circulating pump is normally supplied with a spare which is arranged in parallel, and these two pumps are operated in parallel in an attempt to increase the flow rate.
  • the mass flow increase achieved by operating the two pumps in parallel is in the order of 1 to 2 percent.
  • the conventionally supplied recirculating pump and spare are arranged so that they may be operated in series flow realtion.
  • the increase in mass flow rate achieved through the furnace wall tubes by so arranging these pumps is about 10 percent rather than the 1 to 2 percent of the prior art parallel flow arrangement. Either of the two pumps may be opearted alone with the other isolated or the two pumps may be operated in series.
  • FIGURE 1 is a schematic diagram of a steam generator with the recirculating pumps in the mixed flow portion of the flow path;
  • FIGURE 2 shows the interrelation of the system resistance curve and the pump curves for parallel and series arrangement of recirculating pumps
  • FIGURE 3 is a schematic diagram of an arrangement of circulating pumps generally the same as the arrangement shown in FIGURE 1;
  • FIGURE 4 is an arrangement similar to FIGURE 3 with a slightly different valve arrangement
  • FIGURE 5 is a schematic diagram of a pumping arrangement which uses less valves but precludes parallel operation of the circulating pumps.
  • FIGURE 6 is a schematic diagram of a steam generator with the circulating pumps being located in the recirulating line.
  • feedwater pump '21 forces feedwater through the steam generator.
  • the steam generator includes economizer surface 22, furnace waterwall surface 23 and superheater 24.
  • the heated through flow is then passed through steam turbine 25 and condensed in condnser 27.
  • the waterwall surface 23 is comprised of parallel tubes lines the walls of furnace 28 with this furnace including burner 29 firing fuel into the furnace.
  • a flow division means 30 which may be a simple pipe T is provided, with recirculating line 32 containing check valve 33 being arranged to convey recirculated fluid back to a mixing vessel 34. Recirculation through this system is effected by circulating pump 35 which is located in the mixed flow portion of the through-flow path.
  • the system resistance curve on FIGURE 2 is a plot of the over-all resistance of the recirculating path when the steam generator is operated at a 20 percent through-flow. This system resistance is much steeper than a square curve for several reasons. The net hydraulic differential between the downcomer portion of the loop and the riser portion of the loop is effective to produce a pumping action through the loop. Therefore, the system resistance curve tends to approach a value less than zero as it approaches zero flow. The curve is also steep because it must be plotted against the head in feet of the fluid being pumped by pump 35 in order to produce a meaningful curve in relation to the pump curve. As the recirculation is increased at a given load, the temperature of the mixed water passing through pump 35 increases.
  • Curve 41 is a pump curve representing the characteristic of pump 35. With only this pump operating, the actual flow through the system is approximately 6000 g.p.m. as represented by point 42 at the intersection of the pump curve and the system resistance curve. With this operation, valves 2 and 3 must be opened.
  • pumps 35 and 43 may be operated in series by opening valve 4.
  • the check valve feature of valve 1 prevents reverse flow to the suction of pump 35 while the check valve feature of valve 2 prevents reverse flow from the discharge of pump 43.
  • These two pumps operating in series operate in accordance with pump curve 46. This curve intersects the system resistance curve at point 47 representing a flow of about 7300 gallons per minute. Since the density of the fluid is decreased, the resultant increase in mass flow is only in the order of 10 percent, but this is substantially greater than the increase achieved by parallel operation of the two pumps.
  • valve 4 may then be gradually opened so that the change from parallel operation to series operation may. be gradually accomplished without a sudden disturbance in the steam generating system.
  • FIGURE 3 illustrates the same valve arrangement as used in FIGURE 1 but with a slightly different schematic arrangement. It can be seen from either of these illustrations that pump 35 may be isolated to perform maintenance work or as a temporary expedient in the event of a leak by closing valves 3, 4 and 2. All flow then passes through valve 1 and circulating pump 43. Alternately, pump 43 may be isolated by closing valves 1, 4 and 5 with pump 35 operating. Many units are designed so that during high load operation circulating pump operation is not required. With the valve arrangement of FIGURES l and 3 such operation can be accomplished by closing valves 3 and 5 with the flow bypassing the pumps through valves 1, 4 and 2. During this operation neither pump 35 nor pump 43 can be isolated.
  • FIGURE 4 illustrates an alternate valve arrangement wherein valve 11 is a simple check valve in lieu of the stop check valve 1 and valve 12 is a simple check valve in lieu of the stop check valve 2.
  • Stop valve 6 is added at the discharge side of pump 35 with stop valve 7 being added at the suction side of pump 43. With this arrangement both pumps may be bypassed with valves 6 and 7 closed permitting isolation of either or both of the circulating pumps.
  • pump 35 may be isolated by closing only valves 3 and 6 while pump 43 may be isolated by closing only valves 5 and 7.
  • FIGURE 5 illustrates an alternate valving arrangement which is simpler and less expensive than the arrangements of FIGURES 3 and 4.
  • pump 35 may be isolated by closing valves 3 and 6 and pump 43 may be isolated by closing valves 5 and 7.
  • the unit may be operated by passing flow around both pumps of valves 11 and 12, if desired. Either pump may be operated alone or the two may be operated in series. This particular valving arrangement, however, precludes parallel operation of the two circulating pumps.
  • FIGURE 6 illustrates a steam generator similar to FIGURE 1.
  • the sole difference is the location of the circulating pumps which are located in the recirculating line 32 rather than in the through-flow path.
  • the pump and valve arrangement is the same as that illustrated in FIGURE 4. Since the waterwall outlet temperature does not change with recirculation, the temperature of the fluid passing to these pumps and, therefore, its density is constant at any given load. Since the steam generator is generally operated over a substantial load range of approximately a constant waterwall outlet temperature, there is little variation in density during startup since these pumps initially operate on cold and finally approach operation on 800 F. steam.
  • a supercritical pressure steam generator comprising:
  • An apparatus as in claim 1 having also: a first bypass conduit around said first pump of "sufiicient size to carry at least one pump flow and a' first valve in said first bypass conduit; a second bypass ;conduit around said second pump of sufficient size to carry at least one pump flow and a second valve in said second bypass conduit.
  • An apparatus as in claim 2 having also: a third valve upstream of said first pump, a fourth valve downstream of said first pump and upstream of said second pump, said first bypass conduit also bypassing said third and fourth valves; a fifth valve downstream of said second pump, said second bypass conduit also bypassing said fourth and fifth valves.
  • An apparatus as in claim 4 having also: a sixth valve immediately downstream of said first pump and upstream of said second bypass; and a seventh valve immediately upstream of said second pump and downstream of said first bypass.
  • An apparatus as in claim 3 having also: a third valve upstream of said first pump; a fourth valve immediately downstream of said first pump, said first bypass conduit also bypassing said third and fourth valves; a fifth valve downstream of said second pump; a sixth valve immediately upstream of said second pump; and said second bypass conduit also bypassing said fifth and sixth valves.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Control Of Non-Positive-Displacement Pumps (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
US693423A 1967-12-26 1967-12-26 Recirculating type steam generator and pump arrangement Expired - Lifetime US3467069A (en)

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US69342367A 1967-12-26 1967-12-26

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US3467069A true US3467069A (en) 1969-09-16

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US693423A Expired - Lifetime US3467069A (en) 1967-12-26 1967-12-26 Recirculating type steam generator and pump arrangement

Country Status (8)

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US (1) US3467069A (de)
BE (1) BE721177A (de)
DE (1) DE1815969B2 (de)
ES (1) ES361833A1 (de)
FR (1) FR1582462A (de)
GB (1) GB1230428A (de)
NL (1) NL6818636A (de)
SE (1) SE348043B (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006083730A2 (en) * 2005-02-02 2006-08-10 Cameron International Corporation Single-cell mechanical flotation system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012209480B4 (de) * 2012-06-05 2013-12-19 Envi Con & Plant Engineering Gmbh Hochdruck-Pumpsystem zur Förderung heißer Medien
DE102012016631A1 (de) * 2012-08-22 2014-02-27 Hydac Electronic Gmbh Einrichtung zur Bereitstellung von unter einem vorgebbaren Druck stehenden Fluiden

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2170345A (en) * 1935-12-18 1939-08-22 Babcock & Wilcox Co Vapor generator
US3135249A (en) * 1961-07-27 1964-06-02 Combustion Eng Recirculation system and method for vapor generator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2170345A (en) * 1935-12-18 1939-08-22 Babcock & Wilcox Co Vapor generator
US3135249A (en) * 1961-07-27 1964-06-02 Combustion Eng Recirculation system and method for vapor generator

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006083730A2 (en) * 2005-02-02 2006-08-10 Cameron International Corporation Single-cell mechanical flotation system
WO2006083730A3 (en) * 2005-02-02 2009-04-09 Cameron Int Corp Single-cell mechanical flotation system

Also Published As

Publication number Publication date
SE348043B (de) 1972-08-21
DE1815969B2 (de) 1972-02-17
DE1815969A1 (de) 1969-07-10
BE721177A (de) 1969-03-03
GB1230428A (de) 1971-05-05
NL6818636A (de) 1969-06-30
ES361833A1 (es) 1970-11-01
FR1582462A (de) 1969-09-26

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