US5357741A — NOx and CO control for gas turbine

Claim 1

Independent Claim 168 words

A system for automatically maintaining substantially constant NO x emissions and minimum CO emissions from a gas turbine burning a gaseous or liquid fossil fuel injected into a combustor through at least one fuel input valve comprising: means for determining the actual fuel flow, W f , injected into the combustor; a steam source; a steam valve coupled between said steam source and said combustor for coupling a predetermined amount of steam, W s , into the combustor; and means for automatically controlling the steam valve position to provide a steam flow, W s , that gives a steam-to-fuel ratio, SFR, that will maintain substantially constant nitrogen oxide emissions and minimal carbon monoxide emissions from the gas turbine according to the formula (W s =SFR ×W f ) where W s equals steam flow in pounds per hour, W f equals fuel flow in pounds per hour and SFR equals the steam-to-fuel ratio corrected for variations in relative humidity, ambient temperature, fuel heating value, and turbine firing temperature.

Claim 2

Independent Claim 168 words

A system for automatically maintaining substantially constant NO x emissions and minimum CO emissions from a gas turbine burning a gaseous or liquid fossil fuel injected into a combustor through at least one fuel input valve comprising: means for determining the actual fuel flow, W f , injected into the combustor; a steam source; a steam valve coupled between said steam source and said combustor for coupling a predetermined amount of steam, W s , into the combustor; and means for automatically controlling the steam valve position to provide a steam flow, W s , that gives a steam-to-fuel ratio, SFR, that will maintain substantially constant nitrogen oxide emissions and minimal carbon monoxide emissions from the gas turbine according to the formula (W s =SFR ×W f ) where W s equals steam flow in pounds per hour, W f equals fuel flow in pounds per hour and SFR equals the steam-to-fuel ratio corrected for variations in relative humidity, ambient temperature, fuel heating value, and turbine firing temperature.

Claim 3

Dependent Claim 29 words

A system as in claim 1 wherein the steam-to-fuel ratio is a straightline function with respect to turbine firing temperature, T 5 , according to the equation: SFR=0.0011T.sub.5 -0.5325.

Claim 4

Dependent Claim 125 words

A system as in claim 2 further including: means for generating a first electrical signal representing W f in pounds per hour as a function of the angular position of the fuel input valve; means for generating a second electrical signal representing relative humidity in percent; means for generating a third electrical signal representing a fuel heating value, HV, in BTU/SCF; means for generating a fourth electrical signal representing ambient air temperature, T 2 , in degrees Fahrenheit; means for generating a fifth electrical signal representing turbine load as a function of turbine firing temperature T 5 in degrees Fahrenheit; and means for generating a sixth electrical signal representing steam flow, W s in pounds per hour as a function of said steam valve position.

Claim 5

Dependent Claim 70 words

A system as in claim 3 including means to generate a corrected steam/fuel ratio, SFR, according to the equation: SFR=(A+B)-E where A=a correction factor to the SFR for ambient air temperature T 2 ; B=a correction factor to the SFR with changes in fuel heating value, HFV, corrected for ambient temperature T 2 and turbine firing temperature T 5 ; and E=a correction factor to the SFR for humidity variations.

Claim 6

Dependent Claim 84 words

A system as in claim 4 wherein said means for generating the correction factor "A" further includes: means for multiplying the fifth electrical signal, T 5 , by the constant 0.0011 and subtracting 0.5325 from the result to obtain Y 1 ; means for multiplying the fourth electrical signal, T 2 , by the constant 0.0003 to obtain Y 2 ; and means for subtracting Y 2 from Y 1 according to the equation (A=Y 1 -Y 2 )=[0.0011T 5 -0.5325 ]-0.0003T 2 .

Claim 7

Dependent Claim 171 words

A system as in claim 5 wherein said means for generating the correction factor B further includes: means for generating a first correction value by modifying the second electrical signal, HV, with constants for a range of HV values according to the equations: Y.sub.3 =-0.008333HV+7.084973 for 800<HV ≦825 BTU/SCF Y.sub.3 =-0.042000HV+34.860000 for 825<HV ≦830 BTU/SCF Y.sub.3 =+0.006561HV-5.445398 for 830<HV ≦896 BTU/SCF Y.sub.3 =+0.003451HV-2.659000 for 896<HV ≦998 BTU/SCF means for generating a second correction factor by multiplying the fourth electrical signal, T 2 , by a first constant and adding a second constant to the result according to the equations: Y.sub.4 =0.001795T.sub.2 +0.894100 for T.sub.2 <59° and Y.sub.4 =1 for T.sub.2 ≧59° ; means for generating a third correction value by multiplying the fifth electrical signal, T 5 , by a first constant and subtracting a second constant from the result according the equation: Y.sub.5 =0.00741T.sub.5 -0.092530; and means for multiplying the first, second and third correction values together to obtain the correction factor "B" according to the equation: B=Y.sub.3 ×Y.sub.4 ×Y.sub.5.

Claim 8

Dependent Claim 96 words

A system as in claim 6 wherein the correction factor, E, also includes correction factors C and D according to the equation: E=(C+D)·RH/100 where C=Y 6 ×Y 7 , Y 6 equals a correction for SFR versus humidity variations (RH) as a function of ambient temperature T 2 , and Y 7 is a function of the turbine firing temperature, T 5 , and D=Y.sub.8 ×Y.sub.9, where Y 8 equals a correction for SFR versus fuel heating value as a function of humidity (RH) and Y 9 is a function of ambient temperature, T 2 .

Claim 9

Dependent Claim 90 words

A system as in claim 7 further comprising: means for generating a correction factor Y 6 by varying the fourth electrical signal, T 2 , with constants for a range of T 2 values according to the equations: ##EQU6## means for generating the correction factor, Y 7 , by multiplying the fifth electrical signal T 5 by a constant 0.00047 and adding the constant 0.307 to the result according to the equation: Y.sub.7 -0.00047T.sub.5 +0.307; and means for multiplying the signals Y 6 and Y 7 to obtain C=Y.sub.6 ×Y.sub.7.

Claim 10

Dependent Claim 79 words

A system as in claim 8 further including: means for generating the correction factor, Y 8 . by varying the third electrical signal with constants for a range of HV values according to the equations: ##EQU7## means for generating the correction factor, Y 9 , by varying the fourth electrical signal T 2 with constants for a range of T 2 values according to the equations: ##EQU8## means for multiplying Y 8 and Y 9 to obtain D=Y.sub.8 ×Y.sub.9.

Claim 11

Dependent Claim 63 words

A system as in claim 9 wherein the means for generating the correction factor E comprises: means for adding C+D, means for dividing the second electrical signal, RH, by 100 to obtain a value representing relative humidity in percent; and means for multiplying the sum of C+D by the divided second electrical signal, RH/100, to obtain the correction factor E for relative humidity.

Claim 12

Dependent Claim 23 words

A system as in claim 10 further including: means for adding (A+B); and means for subtracting E from said (A+B) to obtain SFR=(A+B)-E.

Claim 13

Dependent Claim 29 words

A system as in claim 11 further comprising means for multiplying (A+B)-E=SFR by the first electrical signal, W f , to obtain the sixth electrical signal, W s .

Claim 14

Dependent Claim 54 words

A system as in claim 12 further comprising: means for coupling said sixth electrical signal, W s , to said steam valve for positioning said steam valve to allow sufficient steam to said combustor to satisfy the equation: W.sub.s =SFR×W.sub.f thereby maintaining substantially constant NO x emissions and minimizing CO emissions from said turbine.

Claim 15

Independent Claim 160 words

A method for automatically maintaining substantially constant nitrogen oxide and minimizing CO emissions from a gas turbine burning a gaseous or liquid fossil fuel injected into a combustor through at least one fuel input valve comprising the steps of: determining the actual fuel flow, W f , injected into the combustor; providing a steam source; coupling a steam valve between the steam source and the combustor for providing a predetermined amount of steam, W s , into the combustor; and automatically controlling the steam valve to provide a steam flow, W s , that provides a steam-to-fuel ratio, SFR, that will maintain substantially constant nitrogen oxide and carbon monoxide emissions from the gas turbine according to the formula: W.sub.s =SFR×W.sub.f where W s equals steam flow in pounds per hour, W f equals fuel flow in pounds per hour and SFR equals the steam-to-fuel ratio corrected for variations in relative humidity, ambient temperature, fuel heating value, and turbine firing temperature.

Claim 16

Independent Claim 160 words

A method for automatically maintaining substantially constant nitrogen oxide and minimizing CO emissions from a gas turbine burning a gaseous or liquid fossil fuel injected into a combustor through at least one fuel input valve comprising the steps of: determining the actual fuel flow, W f , injected into the combustor; providing a steam source; coupling a steam valve between the steam source and the combustor for providing a predetermined amount of steam, W s , into the combustor; and automatically controlling the steam valve to provide a steam flow, W s , that provides a steam-to-fuel ratio, SFR, that will maintain substantially constant nitrogen oxide and carbon monoxide emissions from the gas turbine according to the formula: W.sub.s =SFR×W.sub.f where W s equals steam flow in pounds per hour, W f equals fuel flow in pounds per hour and SFR equals the steam-to-fuel ratio corrected for variations in relative humidity, ambient temperature, fuel heating value, and turbine firing temperature.

Claim 17

Dependent Claim 33 words

A method as in claim 14 further comprising the step of relating the turbine firing temperature, T 5 , to the turbine load as a straightline function according to the equation: SFR=0.0011T.sub.5 -0.5325.

Claim 18

Dependent Claim 117 words

A method as in claim 15 further including the steps of: generating a first electrical signal representing W f in pounds per hour as a function of the angular position of the fuel input valve; generating a second electrical signal representing relative humidity, RH, in percent; generating a third electrical signal representing fuel heating value, HV, in BTU/SCF; generating a fourth electrical signal representing ambient air temperature, T 2 , in degrees Fahrenheit; generating a fifth electrical signal representing turbine load as a function of turbine firing temperature, T 5 , in degrees Fahrenheit; and generating a sixth-electrical signal representing steam flow, W s , in pounds per hour as a function of said steam valve position.

Claim 19

Dependent Claim 67 words

A method as in claim 16 including the step of generating a corrected SFR according to the equation: SFR=(A+B)-E where A=a correction factor to the SFR for ambient temperature, T 2 ; B=a correction factor to the SFR for changes in fuel heating value, FHV, corrected for ambient temperature T 2 and turbine firing temperature T 5 ; and E=a correction factor for relative humidity variations, RH.

Claim 20

Dependent Claim 72 words

A method as in claim 17 wherein the step of generating the correction factor A further includes the steps of: multiplying the fifth electrical signal, T 5 , by the constant 0.0011 and subtracting 0.5325 from the result to obtain Y 1 ; multiplying the fourth electrical signal, T 2 , by the constant 0.0003 to obtain Y 2 ; and subtracting Y 2 from Y 1 according to the equation: ##EQU9##

Claim 21

Dependent Claim 146 words

A method as in claim 18 wherein the step of generating the correction factor B further includes the steps of: generating a first correction value by modifying the second electric signal, HV, with constants for a range of HV values according to the equations: ##EQU10## means for generating a second correction value by multiplying the fourth electrical signal, T 2 , by a first constant and adding a second constant to the result according to the equations: Y.sub.4 =0.001795T.sub.2 +0.894100 for T.sub.2 <59° and Y.sub.4 =1 for T.sub.2 ≧59° ; generating a third correction value by multiplying the fifth electrical signal, T 5 , by a first constant and subtracting a second constant from the result according to the equation: Y.sub.5 =0.000741T.sub.5 -0.092530; and multiplying the first, second and third correction values together to obtain the correction factor, B, according to the equation: B=Y.sub.3 ×Y.sub.4 ×Y.sub.5.

Claim 22

Dependent Claim 99 words

A method as in claim 19 further including the step of adding correction factors C and D to obtain the correction factor E according to the equation: E=(C+D)·RH/100 where C equals Y 6 ×Y 7 ,Y 6 is a correction for SFR versus humidity variations (RH) as a function of ambient temperature T 2 and Y 7 is a function of turbine firing temperature T 5 and D=Y.sub.8 ×Y.sub.9 where Y 8 equals a correction for SFR versus fuel heating values as a function of humidity (RH) and Y 9 is a function of ambient temperature T 2 .

Claim 23

Dependent Claim 90 words

A method as in claim 20 further comprising the steps of: generating a correction factor, Y 6 , by varying the fourth electrical signal, T 2 , with constants for a range of T 2 values according to the equations: ##EQU11## generating the correction factor, Y 7 , by multiplying the fifth electrical signal, T 5 , by a constant 0.00047 and adding the constant to 0.307 to the result according to the equation: Y.sub.7 =0.00047T.sub.2 +0.307; and multiplying the signals Y 6 and Y 7 to obtain C=Y.sub.6 ×Y.sub.7.

Claim 24

Dependent Claim 91 words

A method as in claim 21 further including the steps of: generating the correction factor, Y 8 , by varying the third electrical signal with constants for a range of HV values according to the equations: ##EQU12## generating the correction factor Y 9 by varying the fourth electrical signal T 2 with constants for a range of T 2 values according to the equations: Y.sub.9 =0.003220T.sub.2 +0.050000 for T.sub.2 ≦67.4° F. Y.sub.9 =0.022500T.sub.2 -1.250000 for 67.4° F. <T.sub.2 ≦100° F.; and multiplying Y 8 and Y 9 to obtain D=Y.sub.8 ×Y.sub.9.

Claim 25

Dependent Claim 61 words

A method as in claim 22 wherein the step of generating the correction factor E further comprises the steps of: adding C+D; dividing the second electrical signal, RH, by 100 to obtain a value representing relative humidity in percent; and multiplying the sum of C+D by the divided second electrical signal, RH/100 to obtain the correction factor E for relative humidity.

Claim 26

Dependent Claim 23 words

A method as in claim 23 further including the steps of: adding A+B; and subtracting E from the quantity (A+B) to obtain SFR=(A+B)-E.

Claim 27

Dependent Claim 36 words

A method as in claim 24 further comprising the step of multiplying (A+B)-E=SFR by the first electrical signal, W f , to obtain the sixth electrical signal, W s , according to the equation: W.sub.s =SFR×W.sub.f.

Claim 28

Dependent Claim 51 words

A method as in claim 25 further comprising the step of coupling the sixth electrical signal, W s , to the steam valve for positioning the steam valve to allow sufficient steam to said combustor to satisfy the equation: W.sub.s =SFR×W.sub.f. thereby minimizing NO x and CO emissions from said turbine.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-10-24	1998-04-25	1998-10-25	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-10-24	2002-04-25	2002-10-25	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-10-24	2006-04-25	2006-10-25	$7700.00	Window Closed / Lapsed

NOx and CO control for gas turbine

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