US2684664A - Boiler feed system - Google Patents

Boiler feed system Download PDF

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Publication number
US2684664A
US2684664A US379197A US37919753A US2684664A US 2684664 A US2684664 A US 2684664A US 379197 A US379197 A US 379197A US 37919753 A US37919753 A US 37919753A US 2684664 A US2684664 A US 2684664A
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Prior art keywords
deaerator
feed
pump
water
condenser
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Expired - Lifetime
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US379197A
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English (en)
Inventor
Hillier Harold
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Weir Group PLC
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G&J Weir Ltd
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Publication date
Priority to BE488178D priority Critical patent/BE488178A/xx
Priority claimed from GB240049A external-priority patent/GB657191A/en
Priority to US78960A priority patent/US2656823A/en
Priority claimed from US78960A external-priority patent/US2656823A/en
Priority to FR984114D priority patent/FR984114A/fr
Application filed by G&J Weir Ltd filed Critical G&J Weir Ltd
Priority to US379197A priority patent/US2684664A/en
Application granted granted Critical
Publication of US2684664A publication Critical patent/US2684664A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D19/00—Degasification of liquids
    • B01D19/0068—General arrangements, e.g. flowsheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D19/00—Degasification of liquids
    • B01D19/0063—Regulation, control including valves and floats

Definitions

  • This invention relates to boiler feed systems with provision for removing gaseous impurities from the feed water.
  • the present invention provides an improved boiler feed system in which the feed water discharged by the condensate extraction pump to the boiler feed pump passes preferentially through a deaerator wherein a deaerating action is superimposed upon the deaerating action to which the feed water has already been subjected in the condenser.
  • This deaerator may also be used for port service on board ship when the main condensing plant is closed down, either operating in series with an auxiliary condensing plant or in parallel, as may be preferred.
  • the discharge of the main condenser extraction pump is connected direct to the boiler feed pump suction and in parallel also to the float-controlled inlet of a deaerator, with the object of passing the discharge of such pump preferentially into the deaerator in which it is subjected to deaerating action and from which it is subsequently removed by a deaerator extraction pump which discharges into the closed feed line nearer to the boiler feed pump suction than the point in the closed feed line connected to the inlet to said deaerator.
  • the boiler feed pump pref erably takes water from the discharge of the deaerator extraction pump, but can also take water, when necessary, direct from the discharge of the condenser extraction pump.
  • the boiler feed system claimed herein includes a non-return valve in the closed feed line between the condenser extraction pump discharge to the deaerator and the deaerator extraction pump discharge to the boiler feed pump, whereby to prevent the deaerator extraction pump from discharging back into the deaerator.
  • the relation of the discharge pressure capacity characteristic of the deaerator extraction pump and the discharge pressure capacity characteristic of the condenser extraction pump is such that up to the pro-determined maximum capacity of the deaerator extraction pump the boiler feed pump takes its supply of water preferentially from the deaerator extraction pump discharge.
  • the quantity of water passing through the deaerator at any given boiler load is determined by the discharge pressure capacity characteristics of the condenser extraction pump and the deaerator extraction pump under the control of a floatoperated water inlet valve on the deaerator, the float being operated by the rise and fall of the water level in the bottom of the deaerator whereby a fall in the float increases the flow of water into the deaerator and vice versa.
  • Heat exchange apparatus may be provided in the discharge line from the condenser extraction pump for heating the feed water before it can pass into the deaerator, and deaeration may be effected in the deaerator by the flash of such heated feed water, the boiling pressure in the deaerator being maintained by a connection to the main condenser whereby vapor and noncondensable gases can flow to the main condenser, or by means of a steam ejector which discharges into a condenser from which the air can escape to the atmosphere.
  • An air ejector may be arranged to discharge to the main condenser whereby boiling pressure can be ensured in the deaerator without any heating of the condensate before it passes into the deaerator.
  • Additional heating steam may be supplied to the deaerator so that deaeration is assisted by heating of the water in its passage through the deaerator, air and non-condensable gases being withdrawn as mentioned above.
  • the capacity of the deaerating vessel may be equal to the capacity of the boiler feed pump or the capacity of the deaerator may be less or greater than the boiler feed pump capacity by a predetermined amount.
  • a feed supply pump may be arranged to draw water from a feed tank and discharge through the float operated valve to the deaerator, the arrangement being such that all feed water to be deaerated must pass by way of the feed tank to the deaerator or from drainage lines direct into the deaerator wherein it is subjected to deaerating action before it is delivered by the deaerator extraction pump to the suction of the boiler feed pump.
  • Feed pumps of different capacity may be available for port use and for sea service, respectively, or there may be provided restriction means whereby under port operating conditions the sea service feed pump is restricted to a capacity not exceeding the capacity of the deaerator.
  • a direct connection may be made from the boiler feed pump suction to the 1 main feed tank through a non-return valve which will normally be kept closed by the pressure of the deaerator and condenser extraction pumps, but will permit the feed pump to draw water direct from the feed tank in case of emergency.
  • Fig. l is a diagrammatic arrangement of a closed boiler feed system provided with additional means for deaerating the feed water in accordance with the invention
  • Fig. 2 illustrates the preferred arrangement of discharge pressure capacity characteristics for the condenser extraction pump and the deaerator extraction pump
  • Fig. 3 shows diagrammatically two or more boiler feed systems in accordance with the invention connected so that they may be operated satisfactorily in parallel;
  • Fig. 4a. and Fig. 4b illustrate the preferred arrangements of discharge pressure capacity characteristics for the condenser extraction pump and deaerator extraction pump when operating two or more closed feed systems in parallel in accordance with the invention.
  • Air and other non-condensable gases are drawn off through air off-takes 5 arranged substantially remote from the water level in the base of the condenser so that a negligible air pressure exists on the surface of the water in the well 3. All condensate passing through the condenser is thus subjected to the deaerating action of the steam in the base of the condenser before it is withdrawn by the condensate extraction pump 6.
  • the condensate extraction pump discharges through heat exchange apparatus such as the air ejector l and the feed heater 8 to the point 9 where it is provided with alternative paths direct to the boiler feed pump H3 or to the deaerating apparatus Ii.
  • the well 3 in the condenser 2 is provided with a float I2 coupled as illustrated diagrammatically to make-up and overflow valves l3 and H3, respectively.
  • a rise in water level in the condenser 2 takes place operating the float l2 which opens the overflow valve l4 and allows surplus water to pass from the condensate discharge line leading from pump 6, after the outlet from the heater 8, by way of pipe E5, the overflow valve H3 and the pipe IE to an external feed tank If.
  • the main feed pump l0 discharges the water supplied to it by way of the heat exchanger [9, and the boiler feed regulator 25] into the boiler 2 I.
  • Heating steam which may be bled steam from the main turbine l, or exhaust steam, or heating steam from any source, may be supplied to the heat exchangers 8 and [9.
  • the deaerator H is provided with a deaerator extraction pump 22 which discharges by way of a pipe 23 to the closed feed system where it enters the closed feed system at the point 24.
  • the point Rd is on the down-stream side of the closed feed system relatively to the point 9, so that Water discharged by the deaerator extraction pump 22 preferentially flows into the suction of the feed pump it and any water which is not taken by the boiler feed pump I0 passes by way of the pipe 25 and pipe 26 to the deaerator inlet valve 27.
  • the valve 2? is controlled by the float 28 which follows the water level in the base of the deaerator H. Water passing through the float-controlled valve 2"! passes by way of a heat exchanger 25?
  • heating steam from any suitable source may be passed into the deaerator through a pipe 35 provided with a control valve 36 to maintain a desired predetermined pressure in the deaerator l I.
  • the exhaust steam from such turbine may be led into the deaerator or a suitable heat exchanger asshown, surplus exhaust steam from the turbine passing by way of a surplus steam valve 38 to the main condenser.
  • the auxiliary feed pump 39 may be driven by a steam turbine 4! which exhausts into the heating steam supply line 35 to the deaerator l I, any surplus steam passing by way of a surplus steam
  • the auxiliary condenser 43 may be provided with a condensate extraction pump 44 which discharges any condensate from the auxiliary condenser through a heat exchanger 45 and a pipe 46 to the feed tank ll, preferably into the suction of the deaerator supply pump 40.
  • the condensate extraction pump 6 can discharge water direct to the suctionof the boiler feed pump Ill through the pipe 25.
  • the boiler feed pump Hi can draw water direct from the feed tank I! by way of the pipe 23, the non-return valve 49 and the pipe 50 connecting to the feed tank 11.
  • the non-return valve 49 is maintained in its closed position in normal operation by the discharge pressure set up by the deaerator extraction pump 22 and the condensate extraction pump 6.
  • Other non-return or check valves are provided in the system and indicated in the same manner as the valve 49, sometimes adjacent to a cut-off valve.
  • Fig. 2 shows the preferred relative discharge pressure capacity characteristics of the condenser extraction pump and the deaerator extraction pump. Assuming that the condenser extraction pump 6 is designed for a discharge pressure capacity characteristic shown by the line AB, the point E represents the maximum feed flow required by the boiler feed pump.
  • the deaerator extraction pump 22 is designed for a discharge pressure capacity characteristic such as CD, where CD intersects the characteristic AB at the point E corresponding to maximum feed flow. This ensures that the pressure at the discharge of the deaerator extraction. pump will be equal to or greater than the discharge pressure of the condenser extraction pump atall flows between zero and maximum feed flow. Provision may be made for variable speed of the driver of the deaerator extraction pump so that the discharge pressure capacity characteristic CD can be raised or lowered as desired.
  • the discharge characteristics AB and CD are measured at the common point 9 in the discharge lines after allowance for friction between the respective pumps and the common point 9 in the discharge lines.
  • the pressures at the boiler feed pump suction will be determined by the balancing of the quantity of water discharged by the condenser extraction pump and the quantity of water discharged by the deaerator extraction pump as determined by their characteristics fora common discharge pressure and the fiow required through the boiler feed D p- Assuming, for example, that the boiler feed regulator 20' closes and reduces the feed flow to the boilers, so that the main extraction pump discharge pressure at the point 9 moves to GHJ, then the quantity of water passing to the boilers will be equal to OK which is the quantity of water discharged by the condenser extraction pump, which passes through the deaerator, and the quantity of water discharged by the deaerator extraction pump is equal to CL where the quantity OK passes into the boiler feed pump while the quantity KL passes back through the floatcontrolled inlet valve 2'!
  • the quantity of water dis charged by the condenser extraction pump 6 is the quantity of water which passes through the boiler feed pump l0, so that, if the feed regulator closes further until noflow is passing into the boiler, the pressure will rise to the line AM at the suction of the boiler feed pump, no water will be discharged by the condenser extraction pump into the deaerator, and the deaerator extraction pump will discharge a quantity equal to ON which quantity will flow back through the float-controlled valve into the deaerator and will be in continuous circulation through the deaerating apparatus.
  • the flow through the deaerator varies between the maximum feed flow OF and a minimum flow ON while the flow from the condenser extraction pump varies from the maximum OF to zero. Since the capacity and discharge pressure of the deaerator extraction pump 22 are always equal to or greater than the condenser extraction pump 6, the water taken by the boiler feed pump will preferentially be the water discharged by the deaerator extraction pump and will therefore have been twice subjected to the deaerating action of, first, the main deaerating condenser and, second, the deaerating apparatus II. The arrangement is such therefore as to ensure the maximum possible deaeration of all feed water discharged by the boiler feed pump to the boilers.
  • the characteristic CD may be arranged to be more closely similar to the characteristic AE, or the point of intersection between the two char acteristics may be arranged to be less or greater than the maximum feed flow OF to the boilers.
  • a prime sufiix is attached to those of the upper system and a double prime suflix is attached to those of the lower system in Fig. 3.
  • cross connecting pipes and valves are arranged as shown diagrammatically in Fig. 3.
  • a cross connection is provided between the external feed tanks ll and Il" so that any differences in the weight of water discharged through the external feed tanks H and I1 and through the overflow valves i4 and M" or other sources of supply can balance out through the cross connection 5
  • a cross connection 52 is provided between the discharges of the condenser extraction pumps 6' and 6" so that the pumps have a common discharge line to the deaerator H or ii" which is in operation. Isolating valves are provided so that, if one deaerator is shut down, all connections to that deaerator are closed, and the condensate is discharged by the condenser pump associated with that deaerator through the cross connection pipe 52 to the other deaerator which is in operation with the other condenser extraction pump.
  • a cross connection line 53 may be provided between the discharge lines of the deaerator extraction pumps 22 and 22" so that the deaerator extraction pump on the deaerator i i or I I" which is in operation can discharge through such connection 53 to any of the several boiler feed pumps l9 and it! which may be in service.
  • the said cross connection 53 will enable the several deaerator extraction pumps 22 and 22 to deliver in common to a single boiler feed pump or more feed pumps which may be in service. Inequalities in the fiow through the several condenser extraction pumps 6 and 6 will cause the water levels in the condenser wells to rise or fall, thereby causing the make-up valves l3 and.
  • cross connections are provided between all the several pumps and the several feed pumps.
  • One common feed tank may be arranged to serve several closed feed systems, and, where several feed tanks are used, the effect of using the cross connection 5
  • the cross connections 52 and 53 enable any single deaerator H or H" to be in operation or two or more deaerators to be in operation in parallel with a common discharge to any feed pump or feed pumps which are in operation.
  • the action of the float-controlled valves is such that the whole system is completely automatic from no load to full load and vice versa, and the operation of the float controls ensures that the pumps in the system have a satisfactory suction head at all times and are constrained to operate at all times along their natural discharge pressure characteristics, while the changes in flow through the deaerator are reduced to a minimum so that the pressure and temperature conditions in the deaerator are the optimum for deaeration and the satisfactory operation of the pumping units.
  • the deaerator may be operated without any additional heating and to ensure adequate deaeration there may be provided an ejector 58 to Withdraw the air and non-condensable gases from the deaerator and discharge to a suitable place under vacuum such as the main condenser 2.
  • th capacity of the deaerating apparatus should be equal to the maximum feed flow through the pump but for economy reasons it may be acceptable to provide a deaerating apparatus of smaller capacity.
  • Figs. 4a. and 4b show preferred relative discharge pressure ca pacity characteristics of the condenser extraction pumps and the deaerator extraction pumps suitable for the parallel operation of two or more closed feed systems in accordance with Fig.3.
  • the condenser extraction pump discharge pressure capacity characteristic is shown by the line AB, where point E represents the maximum feed flow required by the boiler feed pump of one system. If two condenser extraction pumps are in service in parallel operation, the combined discharge pressure capacity characteristic of th two pumps is as shown by the line AB2, where point E2 represents the combined maximum feed flow required by the boiler feed pumps of the two systems. If one boiler feed pump only is in service, the pressure developed by the combined condenser extraction pumps at the maximum feed flow for that boiler feed pump is as shown by the point P.
  • l'he deaerator extraction pump is preferably designed for a pressure capacity characteristic such as CD, where CD intersects the maximum feed flow line at the point Q, where this point is equal to or greater than the point P. This ensures that the pressure at the discharge of 9 the deaerator extraction pump will be equal to or greater than the discharge pressure of the condenser extraction pump at all flows between zero and maximum feed flow with one boiler feed pump in operation.
  • non-return valves 59 and 60 are preferably provided in the system according to Fig. 3 to prevent such an occurrence, the non-return valves 59 and 69 being maintained in their closed position in normal, operation by the discharge pressure set up by the respective deaerator extraction pumps 22' and 22 which is in excess of the discharge pressure of the respective condenser extraction pumps 6' and 6".
  • the non-return valve or valves will open and permit the condenser extraction pump or pumps to discharge direct to the suction of the boiler feed pump or pumps.
  • the conditions illustrated in Fig. 4a may in some systems result in excessively high discharge pressures from the deaerator extraction pump.
  • the condenser extraction pump driver may therefore be provided with means whereby the speed of that pump can be varied.
  • the line AB shows the discharge pressure capacity characteristic for the condenser extraction pump when operating under the solo system, the line A132 representing the combined characteristic of two condenser pumps operating in parallel.
  • Means is preferably provided for varying the speed of the condenser pump, so that the combined characteristic'is lowered to (1172 where ab is the characteristic for each pump operating alone. This will enable the deaerator extraction pump to be operated at a discharge pressure capacity characteristic corresponding to CD with a combined characteristic for two pumps corresponding to CD2, the said characteristic being substantially lower than the corresponding characteristics in Fig. la.
  • the condenser extraction pump may be operated along the line AB with the deaerator extraction pump cperating along the line CD.
  • the condenser pump characteristic is lowered to cab with a combined characteristic of M72 in connection with which either a single deaerator extraction pump with a characteristic of AB or two deaerator extraction pumps with a characteristic of A132 can be operated satisfactorily.
  • the water taken by the boiler feed pump will preferentially be the water discharged by the deaerator extraction pump and will therefore have been twice subjected to the ate satisfactorily, and the pumps are constrained to operate at all times along their natural discharge pressure capacity characteristics.
  • the whole of the water discharged to the boilers is first subjected to the deaerating action of the condenser 2 and subsequently to the deaerating action of the deaerator H, and any surplus of water discharged by the respective pumps is subjected to a repeated deaerating action before passing to the boiler feed pump for discharge to the boilers.
  • a closed feed system for a steam boiler including a condenser for the condensation of steam initially generated in the boiler, a condensate extraction pump connected into the lower portion of the condenser, a boiler feed pump connected into the boiler, a feed line connecting the discharge of the condensate extraction pump with the suction side of the boiler feed pump, a deaerator for deaerating the water normally supplied to the boiler by the boiler feed pump, a deaerator extraction pump connected into the lower portion of the deaerator and having its discharge connected into said feed line, a water supply conduit one end of which is connected to said feed line upstream of the discharge connection from said deaerator extraction pump and the other end of which is connected to said deaerator, a float-controlled water inlet valve in said Water supply conduit connected into the deaerator responsive to changes in the water level in the deaerator, said valve opening on a fall of the water level in the deaerator and closing on a rise of the water level in the deaerator, and a non
  • a closed feed system for a steam boiler including a condenser for the condensation of steam initially generated in the boiler, a condensate extraction pump having its suction side connected into the lower portion of the condenser for withdrawing condensate therefrom, a boiler feed pump having its discharge side connected into the boiler for delivering feed water thereto, a feed line connecting the discharge side of the condensate extraction pump with the suction side of the boiler feed pump, a deaerator for deaerating the water normally supplied to the boiler by the boiler feed pump, a conduit for supplying water to the deaerator from said feed line one end of which is connected into said feed line downstream of the condensate extraction pump, the other end of said conduit being connected into said deaerator, means associated with the deaerator for collecting the deaerated water produced in the deaerator, a deaerator extraction pump having its suction side connected into the lower portion of said means associated with the deaerator for withdrawing deaerated water therefrom and having its discharge side connected into
  • a closed feed system as claimed in claim 2 including an external feed water tank, means for conducting the water discharged by the condensate extraction pump in excess of that admitted to the deaerator by the control valve into the external feed tank, and means for passing water directly from the external feed water tank into said water supply conduit upstream of the control valve in said conduit for delivery through the control valve to the deaerator.
  • a closed feed water system including a steam boiler, a boiler feed pump, a condenser for the condensation of steam initially generated by the boiler, a condensate extraction pump having its suction side connected into the lower portion of the condenser, a feed line connecting the discharge side of the condensate extraction pump with the suction side of the boiler feed pump, and a deaerator for deaerating the water to be supplied to the boiler, which method comprises passing a stream of condensate from the condenser into the feed line and from said line under pressure into the upper portion of the deaerator ior deaeration therein, deaerating the stream of condensate introduced into the upper portion of the deaerator, collecting and maintaining a body of the deaerated water produced in the deaerator, passing a stream of deaerated water from said body of water under pressure into the feed line and through the boiler feed pump for delivery to the boiler as feed water therefor, maintaining a higher pressure on the stream of de
  • a closed feed system for a steam boiler including a condenser for the condensation of steam initially generated in the boiler, an external feed tank, a condensate extraction pump having its suction side connected into the lower portion of the condenser for withdrawing condensate therefrom, a float-controlled inlet valve for said condenser, said valve being closed at an intermediate water level in the condenser base and full open at a lower level to permit make-up water to pass from the external feed tank into the condenser, a floatcontrolled overflow valve for said condenser, said overflow valve being closed at an intermediate water level in the condenser well and full open at a higher level to permit the condenser extraction pump to discharge surplus water to the external feed tank, a boiler feed pump having its discharge side connected into the boiler for delivering feed water thereto, a feed line connecting the discharge side of the condensate extraction pump with the suction side of the boiler feed pump, a deaerator for deaerating the water normally supplied to the boiler by the

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  • Chemical Kinetics & Catalysis (AREA)
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US379197A 1949-01-28 1953-09-09 Boiler feed system Expired - Lifetime US2684664A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE488178D BE488178A (th) 1949-01-28
US78960A US2656823A (en) 1949-01-28 1949-03-01 Boiler feed system
FR984114D FR984114A (fr) 1949-01-28 1949-03-24 Perfectionnements apportés aux systèmes d'alimentation des chaudières
US379197A US2684664A (en) 1949-01-28 1953-09-09 Boiler feed system

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB240049A GB657191A (en) 1949-01-28 1949-01-28 Improvements in or relating to boiler feed systems
US78960A US2656823A (en) 1949-01-28 1949-03-01 Boiler feed system
US379197A US2684664A (en) 1949-01-28 1953-09-09 Boiler feed system

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US2684664A true US2684664A (en) 1954-07-27

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US379197A Expired - Lifetime US2684664A (en) 1949-01-28 1953-09-09 Boiler feed system

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FR (1) FR984114A (th)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4353204A (en) * 1979-02-21 1982-10-12 Hitachi, Ltd. Method of water level control for a combined cycle power plant and control system therefor

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2371443A (en) * 1942-03-02 1945-03-13 G & J Weir Ltd Closed feed system for steam power plants
US2626005A (en) * 1949-01-08 1953-01-20 Worthington Corp Method and apparatus for removal of ammonia in boiler feedwater systems

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2371443A (en) * 1942-03-02 1945-03-13 G & J Weir Ltd Closed feed system for steam power plants
US2626005A (en) * 1949-01-08 1953-01-20 Worthington Corp Method and apparatus for removal of ammonia in boiler feedwater systems

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4353204A (en) * 1979-02-21 1982-10-12 Hitachi, Ltd. Method of water level control for a combined cycle power plant and control system therefor

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BE488178A (th)
FR984114A (fr) 1951-07-02

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