CA1234918A - Method and apparatus for obtaining maximum spray flow limit of attemperators - Google Patents
Method and apparatus for obtaining maximum spray flow limit of attemperatorsInfo
- Publication number
- CA1234918A CA1234918A CA000494739A CA494739A CA1234918A CA 1234918 A CA1234918 A CA 1234918A CA 000494739 A CA000494739 A CA 000494739A CA 494739 A CA494739 A CA 494739A CA 1234918 A CA1234918 A CA 1234918A
- Authority
- CA
- Canada
- Prior art keywords
- enthalpy
- attemperator
- steam
- spray flow
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007921 spray Substances 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 13
- 229920006395 saturated elastomer Polymers 0.000 claims description 9
- 238000012937 correction Methods 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 16
- 230000000875 corresponding effect Effects 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 239000002826 coolant Substances 0.000 description 3
- 238000009529 body temperature measurement Methods 0.000 description 2
- 239000000654 additive Substances 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012797 qualification Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22G—SUPERHEATING OF STEAM
- F22G5/00—Controlling superheat temperature
- F22G5/12—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Steam Boilers And Waste-Gas Boilers (AREA)
- Electrostatic Spraying Apparatus (AREA)
- Measuring Volume Flow (AREA)
Abstract
METHOD AND APPARATUS FOR OBTAINING MAXIMUM
SPRAY FLOW LIMIT OF ATTEMPERATORS
ABSTRACT OF THE DISCLOSURE
An apparatus and method determines maximum spray flow limit for an attemperator by using attemperator inlet pressure and temperature to calculate enthalpy. The enthalpy contributed by water spray flow to the attemperator is also used in the calculation to determine enthalpy per unit load. The enthalpy per unit load is multiplied by the actual load of the boiler being serviced by the attemperator to produce a maximum spray flow limit for the attemperator.
SPRAY FLOW LIMIT OF ATTEMPERATORS
ABSTRACT OF THE DISCLOSURE
An apparatus and method determines maximum spray flow limit for an attemperator by using attemperator inlet pressure and temperature to calculate enthalpy. The enthalpy contributed by water spray flow to the attemperator is also used in the calculation to determine enthalpy per unit load. The enthalpy per unit load is multiplied by the actual load of the boiler being serviced by the attemperator to produce a maximum spray flow limit for the attemperator.
Description
~2~
The present invention relates in general to boilers and in particular to a new and useful method and apparatus of determining the maximum spray limit for the attemperator of a boiler.
It known to utilize attemperators to reduce or control the temperature of superheated steam generated in a boiler. See STEA~I, ITS GENERATION AND USEJ 39th ed., 1978 by Babcock and Wilcox, a ~lc~ermott Company.
The use of a microprocessor to calculate and display 10 margin to saturation in the reactor coolant system of a nuclear reactor is disclosed in "DESIGN AND QUALIFICATION OF A
MICROPROCESSOR SUBCOOLED MARGIN MONITOR" IEEE TRANSACTIONS ON
NUCLE~R SCIENCE, Vol. NS-28, No. 1, Feb. 1981 by R.M. Caruso and R.P. Daigle. This article discloses how pre9sure and temperature readings from the reactor coolant system can be used in conjunction with steam tables programmed into the microprocessor to provide an indication of margin to saturation ; ~ (that is the safety factor remaining before the coolant ;5 saturated with steam), which determination can be utilized to 20 activate an alarm or other suitable equipment.
U.S. patent 3,~28,557 to Rivers discloses an apparatus for controlling the amount of chemical additives added to water being supplied to the boiler, and the blowdown rate for the boiler (rate of removing liquid from the boiler) according to the measured conductivity of a sample of boiler water tapped from the blowdown line of the boiler. This reference is relevant for its showing of an electronic mechanism for controlling at least one parameter of a boiler.
The limit for spray flow of spray water to kno~n 30 attemperators have in the past been determined by measuring the steam temperature leaving the attemperator. This requires ~;~3~9~8 establishing a spray flow limit above saturation temperature since once saturation temperature is reached, the temperature does not change as spray flow is increased. Problems have also been experienced in reading the temperature due to cooling effects of the thermowell by spray water.
The present invention is drawn to a me-thod and apparatus for eliminating the prior art problems in controlling the maximum spray flow limit. According to the invention spray limit is calculated from inlet temperature and pressure readings 10 as well as flow measurements. These measurements are utilized to indicate the steam and water enthalpies (heat content) entering the attemperator. The limit is based on design information and does not require field information.
Determination of maximum spray flow, according to the invention, is based on a heat balance calculation around the attemperator. Since the outlet of the attemperator is known from design information, to make the calculation, only measurements to determine inlet conditions are required. The ratio of spray flow to outlet steam flow is the same ratio as 20 inlet steam enthalpy minus limit enthalpy divided by inlet steam enthalpy minus spray medium enthalpy.
For attemperators using water as the spray medium, only a temperature measurement is required to determine enthalpy.
This is because the effect of pressure is small. Spray water enthalpy may also be established as a function of load from the plant heat balance information which information is available from the manufac-turer of a turbine to be powered by the boiler.
This is acceptable because spray water enthalpy does not have a major effect on the heat balance calculation around the 30 attemperator.
The limit enthalpy can be determined from only a ~2349~
pressure reading since -the desired temperature can be established in -the design stage oE the unit. The limit can be taken from a curve rela-ting ac-tual temperature to saturation temperature or if required, the limit could be lowerecl~to helow the saturation curve for the fluid passing through the attemperator. The limit can be reduced because it does not require making the attemperator outlet temperature measurement.
A lower limit in the design stage would result in a cost reduction since some units may not require two stages of 10 attemperation if additional spray can be placed through the first attemperator.
The determination of steam enthalpy entering the attemperator requires both a temperature and a pressure measurement. By assuming either a constant temperature or enthalpy, a base enthalpy can be established as a function of the other measurement (e.g. pressure). Actual enthalpy is then determined by modifying the base enthalpy for actual temperature and pressure. The accuracy of the enthalpy is a function of the factors used to modify the base enthalpy.
Accordingly, the present invention provides a method of determining the maximum spray flow of an attemperator comprising measuring the inlet temperature and pressure of the attemperator, using the inlet pressure to determine a base steam inlet enthalpy for steam at a known temperature, using the base enthalpy and a correction factor based on the inlet temperature to establish a corrected base enthalpy, subtracting the corrected base enthalpy from actual steam inlet enthalpy calculated as a function of the inlet pressure to obtain an enthalpy difference, dividing the enthalpy difference by a 30 spray inlet enthalpy difference which is obtained by subtrac-ting the corrected base inlet enthalpy from the spray inlet enthalpy representing enthalpy of spray flow on the attemper-ator and multiplying the product of the division by a value corresponding to the main steam flow to obtain the maximum ~3~9~ 3 spray flow limit.
To effect the measurement the invention provides a device comprising:
a first temperature sensor for sensing the tempera-ture of inlet steam to the attemperator;
a pressure sensor for measuring the pressure of inlet steam to the attemperator;
a first constant value function block for containing a value corresponding to a selected operating temperature;
a first subtraction unit function block connected to said first constant value function block and to said tempera-ture sensor, for taking the difference between the actual inlet temperature of steam to the attemperator and the selected operating temperature;
a second constant value function block connected to said first subtraction unit function block for multiplying the output of said first subtraction unit function block by a selected constant which is a characteristic of the attemper-ator;
a first function block connected to said pressure sensor for genexating a multiplication factor which is a characteristic of the attemperator and is a function of the inlet steam pressure to the attemperator;
a first multiplication block connected to said second constant value function block and to said first function block, for generating a temperature correction for enthalpy;
a second function block connected to said pressure sensor for generating a steam enthalpy for steam at a selected operating temperature as a function of the inlet steam pressure to the attemperator;
a summing block connected to said first multiplica-tion block and to said second function block for generating a quantity corresponding to the actual steam enthalpy entering the attemperator;
a third function block connected to said pressure sensor for generating a quantity corresponding to the enthalpy 9~
- 4a -of saturated steam as a function of the inlet steam pressure to the attemperator;
a second subtraction unit function block connected to said summing block and to said third function block for taking the difference between said actual steam enthalpy and the enthalpy for saturated steam;
means for measuring the enthalpy of the spray flow to the attemperator;
a third subtraction unit function block connected to said summing block and said enthalpy measuring means for taking the difference between the actual steam enthalpy and the enthalpy of the spray flow;
a division block connected to said second and said third subtraction unit function blocks for dividing an output of said second subtraction unit function block by an output of said third subtraction unit function block; and a second multiplication block connected to said division block, having means for receiving a value corres-ponding to a load on the attemperator, for multiplying a quotient from the division block by the load to generate the maximum spray flow limit.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
In the drawings:
Fig. 1 is a block diagram showing an apparatus which can be - ~ ~ 3 ~9 ~ ~
utilized to practice the inventive method;
Fig. 2 is a graph showing a firs~ function which is related to attemperator inlet pressure and can be used as a correction value for obtaining a base steam inlet en~halpy value;
Fig. 3 is a graph shol~ing a second function which is related to attemperator inlet pressure and establishes a base enthalpy value for steam at a kno~n temperature;
Fig. 4 is a graph relating attemperating inlet pressure to a third function corresponding to a limit enthalpy; and Fig. 5 is a graph relatin~ unit load or main steam flow in percent to a fourth function which can be used to obtain the spray water enthalpy.
.
I DESC~IP~ION O~ THE PREFERRED EMBODI~IENTS
Referring to Fig. 1, the invention embodied therein comprises a method of determining a maximum spray flow limit which is output on a line 44, on the basis of inlet parameters for the attemperator including attemperator inlet pressure and temperature. The inle~ pressure of the attemperator is taken by a pressure sensor 10 and the inlet temperature is taken by a temperature sensor 12. Element 14 provides a constant corresponding to a preselected $emperature, in this case 750F, -~which is utilized to obtain a base enthalpy quantity as will be explained later. The value of 750 F is subtracted from the actual temperature supplied by temperature sensor 12, 25 in a comparator or subtraction unit 16. The ~esult of the ~;
subtraction is multiplied by a constant, in this case of l.5, in a function block 18. This constant is a function of the `
attemperator structure. The output of function block 18 .....
`:
1~3~91B
represents a correction for temperature and is multiplied by the output of a function block 22. As shown in Fig. 2, function block 22, will output a quantity up to 1, depending on ~he pressure supplied to function block 22 by pressure sensor 10. The multiplication takes place in bloc~ 20 and the output of block 20 corresponds to a corrected temperature influence on the actual enthalpy.
The temperature influence is supplied to a summing block 28 as is the output of a function bloc~ 24. The output of function block 24 is illustrated in Fig. 3 and is related to the attemperator inlet pressure. This second function corresponds to a base enthalpy for the preselected temperature of 750 F.
A limit enthalpy function is generated by the third function block 26 from the inlet pressure and is chosen to be that for saturated steam. The difference between the saturated steam enthalpy and the base enthalpy is taken in a second subtract-ing unit 30.
Spray water enthalpy is determined by multiplying spray water temperature from second temperature sensor 40, in a constant factor function block ~ . The spray water temperature was multiplied by 0.91, a characteristic of the attemperator.
The value from function block 38 was subtracted from the base enthalpy from box 28 and the results of subtracting units 30 and 34 were divided in division unit 32.
An alternate way of incorporating the influence of the spray water is by using a fourth function block 42 which can be connected directly to the division unit 32. The curve of Fig. 5 shows how the unit load or main steam flow (in percent) ...
~ .
1~349~
is related to the fourth function and can result in the spraywater enthalpy.
The result of the divlsion in function block 32 is multiplied in multiplication block 36 by the unit load or main steam flow which is provided on line 46. This results in a maximum spray flow which is output on line 44.
An example of the invention follows.
EXAMPLE
For a main steam flow of 1,600 Mlb/Hr, a pressure of inlet steam of 2,000 PSIG was assumed. A temperature of inlet steam was assumed at 800 F and a spray water temperature was assumed at 310 F. The pressure and temperature readings are assumed from field measurements.
For 2,000 PSIG attemperator inlet pressure, the three functions yielded values as follows:
f(x)l 0.6 f(X)2 = 1,292 BTU/LB
f(x)3 = 1,127 BTU/LB
Attemperator inlet temperature - 750 F - 50 F. This calculation is achieved in function blocks 16.
Correction to base steam inlet enthalpy is (50 F) (1.5) (0.6) = 45 BTU/LB
This results from the use of function blocks 18,20 and 22 with ~23~9~
the 45 BTU/LB being OUtpllt from function block 20.
The steam inlet enthalpy is obtained in summation box 28 as:
1,292 + 45 = 1337 BTU/LB.
Steam inlet enthalpy as calculated by function blocks 40 and 38 is:
(310) (0.91) = 282 BTU~LB.
Maximum spray flow can thus be calculated by function blo~ks 26, 30, 32, 34 and 36 as well as the value on line 46 (representing the load of 1,600 ML~/HR) as follows:
(1600 MLB/HR ~l337 _ 282 ].
Ma~imum spray flow limit thus = 303 MLB/HR. This value is output on line 44.
The acceptability of the inventive procedure can be determined by calculating the actual outlet steam condition and comparing it to the saturation curve which was assumed to be the limit enthalpy. Inlet steam at 800 F and 2000 PSIG pressure produces an actual enthalpy of 1335 BTU/LB. Spray water at 310 F produces an actual enthalpy of 284 BTU/LB. Attempera-tor heat balance is thus (1297 MLB/HR) (1335 BTU/LB) + (303 MLB/HR) (284 BTU/LB) 1600 MLB/HR = outlet steam enthalpy.
Outlet steam enthalpy is calculated to 1136 BTU/LB which agrees quite well with the saturation enthalpy at 2000 PSIG
of 1137 BTU/LBo While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
The present invention relates in general to boilers and in particular to a new and useful method and apparatus of determining the maximum spray limit for the attemperator of a boiler.
It known to utilize attemperators to reduce or control the temperature of superheated steam generated in a boiler. See STEA~I, ITS GENERATION AND USEJ 39th ed., 1978 by Babcock and Wilcox, a ~lc~ermott Company.
The use of a microprocessor to calculate and display 10 margin to saturation in the reactor coolant system of a nuclear reactor is disclosed in "DESIGN AND QUALIFICATION OF A
MICROPROCESSOR SUBCOOLED MARGIN MONITOR" IEEE TRANSACTIONS ON
NUCLE~R SCIENCE, Vol. NS-28, No. 1, Feb. 1981 by R.M. Caruso and R.P. Daigle. This article discloses how pre9sure and temperature readings from the reactor coolant system can be used in conjunction with steam tables programmed into the microprocessor to provide an indication of margin to saturation ; ~ (that is the safety factor remaining before the coolant ;5 saturated with steam), which determination can be utilized to 20 activate an alarm or other suitable equipment.
U.S. patent 3,~28,557 to Rivers discloses an apparatus for controlling the amount of chemical additives added to water being supplied to the boiler, and the blowdown rate for the boiler (rate of removing liquid from the boiler) according to the measured conductivity of a sample of boiler water tapped from the blowdown line of the boiler. This reference is relevant for its showing of an electronic mechanism for controlling at least one parameter of a boiler.
The limit for spray flow of spray water to kno~n 30 attemperators have in the past been determined by measuring the steam temperature leaving the attemperator. This requires ~;~3~9~8 establishing a spray flow limit above saturation temperature since once saturation temperature is reached, the temperature does not change as spray flow is increased. Problems have also been experienced in reading the temperature due to cooling effects of the thermowell by spray water.
The present invention is drawn to a me-thod and apparatus for eliminating the prior art problems in controlling the maximum spray flow limit. According to the invention spray limit is calculated from inlet temperature and pressure readings 10 as well as flow measurements. These measurements are utilized to indicate the steam and water enthalpies (heat content) entering the attemperator. The limit is based on design information and does not require field information.
Determination of maximum spray flow, according to the invention, is based on a heat balance calculation around the attemperator. Since the outlet of the attemperator is known from design information, to make the calculation, only measurements to determine inlet conditions are required. The ratio of spray flow to outlet steam flow is the same ratio as 20 inlet steam enthalpy minus limit enthalpy divided by inlet steam enthalpy minus spray medium enthalpy.
For attemperators using water as the spray medium, only a temperature measurement is required to determine enthalpy.
This is because the effect of pressure is small. Spray water enthalpy may also be established as a function of load from the plant heat balance information which information is available from the manufac-turer of a turbine to be powered by the boiler.
This is acceptable because spray water enthalpy does not have a major effect on the heat balance calculation around the 30 attemperator.
The limit enthalpy can be determined from only a ~2349~
pressure reading since -the desired temperature can be established in -the design stage oE the unit. The limit can be taken from a curve rela-ting ac-tual temperature to saturation temperature or if required, the limit could be lowerecl~to helow the saturation curve for the fluid passing through the attemperator. The limit can be reduced because it does not require making the attemperator outlet temperature measurement.
A lower limit in the design stage would result in a cost reduction since some units may not require two stages of 10 attemperation if additional spray can be placed through the first attemperator.
The determination of steam enthalpy entering the attemperator requires both a temperature and a pressure measurement. By assuming either a constant temperature or enthalpy, a base enthalpy can be established as a function of the other measurement (e.g. pressure). Actual enthalpy is then determined by modifying the base enthalpy for actual temperature and pressure. The accuracy of the enthalpy is a function of the factors used to modify the base enthalpy.
Accordingly, the present invention provides a method of determining the maximum spray flow of an attemperator comprising measuring the inlet temperature and pressure of the attemperator, using the inlet pressure to determine a base steam inlet enthalpy for steam at a known temperature, using the base enthalpy and a correction factor based on the inlet temperature to establish a corrected base enthalpy, subtracting the corrected base enthalpy from actual steam inlet enthalpy calculated as a function of the inlet pressure to obtain an enthalpy difference, dividing the enthalpy difference by a 30 spray inlet enthalpy difference which is obtained by subtrac-ting the corrected base inlet enthalpy from the spray inlet enthalpy representing enthalpy of spray flow on the attemper-ator and multiplying the product of the division by a value corresponding to the main steam flow to obtain the maximum ~3~9~ 3 spray flow limit.
To effect the measurement the invention provides a device comprising:
a first temperature sensor for sensing the tempera-ture of inlet steam to the attemperator;
a pressure sensor for measuring the pressure of inlet steam to the attemperator;
a first constant value function block for containing a value corresponding to a selected operating temperature;
a first subtraction unit function block connected to said first constant value function block and to said tempera-ture sensor, for taking the difference between the actual inlet temperature of steam to the attemperator and the selected operating temperature;
a second constant value function block connected to said first subtraction unit function block for multiplying the output of said first subtraction unit function block by a selected constant which is a characteristic of the attemper-ator;
a first function block connected to said pressure sensor for genexating a multiplication factor which is a characteristic of the attemperator and is a function of the inlet steam pressure to the attemperator;
a first multiplication block connected to said second constant value function block and to said first function block, for generating a temperature correction for enthalpy;
a second function block connected to said pressure sensor for generating a steam enthalpy for steam at a selected operating temperature as a function of the inlet steam pressure to the attemperator;
a summing block connected to said first multiplica-tion block and to said second function block for generating a quantity corresponding to the actual steam enthalpy entering the attemperator;
a third function block connected to said pressure sensor for generating a quantity corresponding to the enthalpy 9~
- 4a -of saturated steam as a function of the inlet steam pressure to the attemperator;
a second subtraction unit function block connected to said summing block and to said third function block for taking the difference between said actual steam enthalpy and the enthalpy for saturated steam;
means for measuring the enthalpy of the spray flow to the attemperator;
a third subtraction unit function block connected to said summing block and said enthalpy measuring means for taking the difference between the actual steam enthalpy and the enthalpy of the spray flow;
a division block connected to said second and said third subtraction unit function blocks for dividing an output of said second subtraction unit function block by an output of said third subtraction unit function block; and a second multiplication block connected to said division block, having means for receiving a value corres-ponding to a load on the attemperator, for multiplying a quotient from the division block by the load to generate the maximum spray flow limit.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
In the drawings:
Fig. 1 is a block diagram showing an apparatus which can be - ~ ~ 3 ~9 ~ ~
utilized to practice the inventive method;
Fig. 2 is a graph showing a firs~ function which is related to attemperator inlet pressure and can be used as a correction value for obtaining a base steam inlet en~halpy value;
Fig. 3 is a graph shol~ing a second function which is related to attemperator inlet pressure and establishes a base enthalpy value for steam at a kno~n temperature;
Fig. 4 is a graph relating attemperating inlet pressure to a third function corresponding to a limit enthalpy; and Fig. 5 is a graph relatin~ unit load or main steam flow in percent to a fourth function which can be used to obtain the spray water enthalpy.
.
I DESC~IP~ION O~ THE PREFERRED EMBODI~IENTS
Referring to Fig. 1, the invention embodied therein comprises a method of determining a maximum spray flow limit which is output on a line 44, on the basis of inlet parameters for the attemperator including attemperator inlet pressure and temperature. The inle~ pressure of the attemperator is taken by a pressure sensor 10 and the inlet temperature is taken by a temperature sensor 12. Element 14 provides a constant corresponding to a preselected $emperature, in this case 750F, -~which is utilized to obtain a base enthalpy quantity as will be explained later. The value of 750 F is subtracted from the actual temperature supplied by temperature sensor 12, 25 in a comparator or subtraction unit 16. The ~esult of the ~;
subtraction is multiplied by a constant, in this case of l.5, in a function block 18. This constant is a function of the `
attemperator structure. The output of function block 18 .....
`:
1~3~91B
represents a correction for temperature and is multiplied by the output of a function block 22. As shown in Fig. 2, function block 22, will output a quantity up to 1, depending on ~he pressure supplied to function block 22 by pressure sensor 10. The multiplication takes place in bloc~ 20 and the output of block 20 corresponds to a corrected temperature influence on the actual enthalpy.
The temperature influence is supplied to a summing block 28 as is the output of a function bloc~ 24. The output of function block 24 is illustrated in Fig. 3 and is related to the attemperator inlet pressure. This second function corresponds to a base enthalpy for the preselected temperature of 750 F.
A limit enthalpy function is generated by the third function block 26 from the inlet pressure and is chosen to be that for saturated steam. The difference between the saturated steam enthalpy and the base enthalpy is taken in a second subtract-ing unit 30.
Spray water enthalpy is determined by multiplying spray water temperature from second temperature sensor 40, in a constant factor function block ~ . The spray water temperature was multiplied by 0.91, a characteristic of the attemperator.
The value from function block 38 was subtracted from the base enthalpy from box 28 and the results of subtracting units 30 and 34 were divided in division unit 32.
An alternate way of incorporating the influence of the spray water is by using a fourth function block 42 which can be connected directly to the division unit 32. The curve of Fig. 5 shows how the unit load or main steam flow (in percent) ...
~ .
1~349~
is related to the fourth function and can result in the spraywater enthalpy.
The result of the divlsion in function block 32 is multiplied in multiplication block 36 by the unit load or main steam flow which is provided on line 46. This results in a maximum spray flow which is output on line 44.
An example of the invention follows.
EXAMPLE
For a main steam flow of 1,600 Mlb/Hr, a pressure of inlet steam of 2,000 PSIG was assumed. A temperature of inlet steam was assumed at 800 F and a spray water temperature was assumed at 310 F. The pressure and temperature readings are assumed from field measurements.
For 2,000 PSIG attemperator inlet pressure, the three functions yielded values as follows:
f(x)l 0.6 f(X)2 = 1,292 BTU/LB
f(x)3 = 1,127 BTU/LB
Attemperator inlet temperature - 750 F - 50 F. This calculation is achieved in function blocks 16.
Correction to base steam inlet enthalpy is (50 F) (1.5) (0.6) = 45 BTU/LB
This results from the use of function blocks 18,20 and 22 with ~23~9~
the 45 BTU/LB being OUtpllt from function block 20.
The steam inlet enthalpy is obtained in summation box 28 as:
1,292 + 45 = 1337 BTU/LB.
Steam inlet enthalpy as calculated by function blocks 40 and 38 is:
(310) (0.91) = 282 BTU~LB.
Maximum spray flow can thus be calculated by function blo~ks 26, 30, 32, 34 and 36 as well as the value on line 46 (representing the load of 1,600 ML~/HR) as follows:
(1600 MLB/HR ~l337 _ 282 ].
Ma~imum spray flow limit thus = 303 MLB/HR. This value is output on line 44.
The acceptability of the inventive procedure can be determined by calculating the actual outlet steam condition and comparing it to the saturation curve which was assumed to be the limit enthalpy. Inlet steam at 800 F and 2000 PSIG pressure produces an actual enthalpy of 1335 BTU/LB. Spray water at 310 F produces an actual enthalpy of 284 BTU/LB. Attempera-tor heat balance is thus (1297 MLB/HR) (1335 BTU/LB) + (303 MLB/HR) (284 BTU/LB) 1600 MLB/HR = outlet steam enthalpy.
Outlet steam enthalpy is calculated to 1136 BTU/LB which agrees quite well with the saturation enthalpy at 2000 PSIG
of 1137 BTU/LBo While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
Claims (7)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of determining the maximum spray flow limit of an attemperator having a spray flow thereto, comprising:
measuring the inlet temperature of steam to the attemperator;
measuring the inlet pressure of steam to the attemperator;
calculating the enthalpy added to the attemperator by the spray flow;
calculating a temperature correction to enthalpy based on the measured inlet temperature;
obtaining a base enthalpy quantity for steam at a known temperature as a function of the inlet pressure;
adding the base enthalpy quantity to the temperature correction to generate a steam inlet enthalpy quantity;
obtaining a saturated steam enthalpy quantity as a function of the inlet pressure;
subtracting the saturated steam enthalpy quantity from the steam inlet enthalpy quantity to obtain a first difference value;
subtracting the spray flow enthalpy from the steam inlet enthalpy quantity to obtain a second difference value;
dividing the first difference value by the second difference value to obtain a quotient and multiplying said quotient by a load through the attemperator to generate the maximum spray flow limit.
measuring the inlet temperature of steam to the attemperator;
measuring the inlet pressure of steam to the attemperator;
calculating the enthalpy added to the attemperator by the spray flow;
calculating a temperature correction to enthalpy based on the measured inlet temperature;
obtaining a base enthalpy quantity for steam at a known temperature as a function of the inlet pressure;
adding the base enthalpy quantity to the temperature correction to generate a steam inlet enthalpy quantity;
obtaining a saturated steam enthalpy quantity as a function of the inlet pressure;
subtracting the saturated steam enthalpy quantity from the steam inlet enthalpy quantity to obtain a first difference value;
subtracting the spray flow enthalpy from the steam inlet enthalpy quantity to obtain a second difference value;
dividing the first difference value by the second difference value to obtain a quotient and multiplying said quotient by a load through the attemperator to generate the maximum spray flow limit.
2. A method according to claim 1, wherein a main steam flow passes through the attemperator, the method including using the main steam flow as the load which is multiplied by the quotient to obtain the maximum spray flow limit.
3. A method according to claim 1, wherein the spray flow enthalpy is obtained by sensing the temperature of the spray flow and multiplying the temperature of the spray flow by a constant.
4. A method according to claim 1, wherein the spray flow enthalpy is obtained as a function of the attemperator load.
5. A device for determining the maximum spray flow limit of an attemperator having a spray flow thereto, comprising:
a first temperature sensor for sensing the temperature of inlet steam to the attemperator;
a pressure sensor for measuring the pressure of inlet steam to the attemperator;
a first constant value function block for containing a value corresponding to a selected operating temperature;
a first subtraction unit function block connected to said first constant value block and to said temperature sensor, for taking the difference between the actual inlet temperature of steam to the attemperator and the selected operating temperature;
a second constant value function block connected to said first subtraction unit function block for multiplying the output of said first subtraction unit function block by a selected constant which is a characteristic of the attemperator;
a first function block connected to said pressure sensor for generating a multiplication factor which is a characteris-tic of the attemperator and is a function of the inlet steam pressure to the attemperator;
a first multiplication block connected to said second constant value function block and to said first function block, for generating a temperature correction for enthalpy;
a second function block connected to said pressure sensor for generating a steam enthalpy for steam at a selected operating temperature as a function of the inlet steam pressure to the attemperator;
a summing block connected to said first multiplication block and to said second function block for generating a quantity corresponding to the actual steam enthalpy entering the attemperator;
a third function block connected to said pressure sensor for generating a quantity corresponding to the enthalpy of saturated steam as a function of the inlet steam pressure to the attemperator;
a second subtraction unit function block connected to said summing block and to said third function block for taking the difference between said actual steam enthalpy and the enthalpy for saturated steam;
means for measuring the enthalpy of the spray flow to the attemperator;
a third subtraction unit function block connected to said summing block and to said enthalpy measuring means for taking the difference between the actual steam enthalpy and the enthalpy of the spray flow;
a division block connected to said second and said third subtraction unit function blocks for dividing an output of said second subtraction unit function block by an output of said third subtraction unit function block; and a second multiplication block connected to said division block having means for receiving a value corresponding to a load on the attemperator, for multiplying a quotient from the division block by the load to generate the maximum spray flow limit.
a first temperature sensor for sensing the temperature of inlet steam to the attemperator;
a pressure sensor for measuring the pressure of inlet steam to the attemperator;
a first constant value function block for containing a value corresponding to a selected operating temperature;
a first subtraction unit function block connected to said first constant value block and to said temperature sensor, for taking the difference between the actual inlet temperature of steam to the attemperator and the selected operating temperature;
a second constant value function block connected to said first subtraction unit function block for multiplying the output of said first subtraction unit function block by a selected constant which is a characteristic of the attemperator;
a first function block connected to said pressure sensor for generating a multiplication factor which is a characteris-tic of the attemperator and is a function of the inlet steam pressure to the attemperator;
a first multiplication block connected to said second constant value function block and to said first function block, for generating a temperature correction for enthalpy;
a second function block connected to said pressure sensor for generating a steam enthalpy for steam at a selected operating temperature as a function of the inlet steam pressure to the attemperator;
a summing block connected to said first multiplication block and to said second function block for generating a quantity corresponding to the actual steam enthalpy entering the attemperator;
a third function block connected to said pressure sensor for generating a quantity corresponding to the enthalpy of saturated steam as a function of the inlet steam pressure to the attemperator;
a second subtraction unit function block connected to said summing block and to said third function block for taking the difference between said actual steam enthalpy and the enthalpy for saturated steam;
means for measuring the enthalpy of the spray flow to the attemperator;
a third subtraction unit function block connected to said summing block and to said enthalpy measuring means for taking the difference between the actual steam enthalpy and the enthalpy of the spray flow;
a division block connected to said second and said third subtraction unit function blocks for dividing an output of said second subtraction unit function block by an output of said third subtraction unit function block; and a second multiplication block connected to said division block having means for receiving a value corresponding to a load on the attemperator, for multiplying a quotient from the division block by the load to generate the maximum spray flow limit.
6. A device according to claim 5, wherein said enthalpy measuring means comprises a second temperature sensor for taking the temperature of the spray flow to the attemperator, and a third constant value function block for multiplying the temperature of the spray flow by a constant which is a characteristic of the attemperator.
7. A device according to claim 5, wherein said enthalpy measuring means comprises a fourth function block for generating a value corresponding to the enthalpy of the spray flow as a function of the load on the attemperator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66927184A | 1984-11-07 | 1984-11-07 | |
| US669,271 | 1984-11-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1234918A true CA1234918A (en) | 1988-04-05 |
Family
ID=24685765
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000494739A Expired CA1234918A (en) | 1984-11-07 | 1985-11-06 | Method and apparatus for obtaining maximum spray flow limit of attemperators |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0184334A1 (en) |
| JP (1) | JPS61153303A (en) |
| AU (1) | AU4822085A (en) |
| CA (1) | CA1234918A (en) |
| ES (1) | ES8801024A1 (en) |
| IN (1) | IN165703B (en) |
| ZA (1) | ZA857665B (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3121442A1 (en) * | 1981-05-29 | 1983-01-05 | Steag Ag, 4300 Essen | Method for controlling the temperature of steam flowing in a line by injection, and arrangement for implementing the method |
| JPS5888505A (en) * | 1981-11-20 | 1983-05-26 | 株式会社日立製作所 | Turbine bypass system temperature reduction control device |
-
1985
- 1985-10-01 IN IN689/CAL/85A patent/IN165703B/en unknown
- 1985-10-02 AU AU48220/85A patent/AU4822085A/en not_active Withdrawn
- 1985-10-04 ZA ZA857665A patent/ZA857665B/en unknown
- 1985-10-31 ES ES548465A patent/ES8801024A1/en not_active Expired
- 1985-11-06 JP JP60247301A patent/JPS61153303A/en active Pending
- 1985-11-06 CA CA000494739A patent/CA1234918A/en not_active Expired
- 1985-11-06 EP EP85308068A patent/EP0184334A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| AU4822085A (en) | 1986-05-15 |
| IN165703B (en) | 1989-12-23 |
| ES548465A0 (en) | 1987-12-01 |
| ES8801024A1 (en) | 1987-12-01 |
| EP0184334A1 (en) | 1986-06-11 |
| JPS61153303A (en) | 1986-07-12 |
| ZA857665B (en) | 1986-05-28 |
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