Adaptive control system for reagent distribution control in SCR reactors

1. A method for controlling dosage of a reagent in a selective catalytic reduction (SCR) system comprising the steps of:

a) providing the system with a plurality of reducing agent injection nozzles, each nozzle being configured and adapted to be independently calibrated during an SCR reaction when the system is in operation;

b) determining an influence coefficient for each injection nozzle for a catalyst independently of the other injection nozzles, wherein the influence coefficient for each injection nozzle is based on a constant flow from the respective nozzle and a fraction of the constant flow that appears at each of a plurality of downstream grid points; and

c) optimizing flow of reducing agent from each injection nozzle based on the influence coefficients to minimize a sum of deviation from the mean value of reducing agent to NO x ratio across a surface of the catalyst, wherein the flow of reducing agent is optimized based on the following equations:

B

i

=

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j

=

1

N

⁢

⁢

K

ij

⁢

X

j

AMM

avg

=

∑

i

=

1

M

⁢

⁢

B

i

M

∑

i

=

1

M

⁢

⁢

D

i

=

∑

i

=

1

M

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ABS

[

B

i

A

i

-

AMM

avg

∑

j

=

1

M

⁢

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A

j

M

]

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∑

j

=

1

N

⁢

⁢

X

j

=

∑

i

=

1

M

⁢

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A

i

×

η

wherein:

N=Number of Injection nozzles,

M=Number of grid measurement points,

X j =Flow rate of reducing agent at the j th injection nozzle,

A i= NO x concentration at the inlet catalyst face in ppm at the i th grid measurement point,

B i= Reducing agent concentration in ppm at the i th grid measurement point,

K ij= Influence coefficient at the i th grid point for the j th injection valve, and is defined as the fraction of the flow at the j th injection valve that appears at the i th grid point,

AMM avg= Average reducing agent concentration in ppm across the whole reactor cross section,

D i= Absolute value of deviation from the mean value of reducing agent to NO x ratio at the i th grid point, and

η=NOx Reduction Efficiency.

2. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 1 , wherein the optimizing step occurs manually.

3. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 1 , wherein the optimizing step occurs via an automated control system in communication with the plurality of injection nozzles.

4. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 1 , wherein the optimizing step occurs before the SCR reaction has begun.

5. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 4 , further comprising at least one second optimization step which occurs during the SCR reaction.

6. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 1 , wherein the step of determining the influence coefficient includes measuring the contaminant levels proximate at least one measurement point downstream of the injection nozzles.

7. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 6 , wherein the step of determining the influence coefficient includes measuring the contaminant levels at least one measurement point upstream of the injection nozzles and at least one point downstream of the injection nozzles.

8. A method for controlling the dosage of a reagent in a selective catalytic reduction system as recited in claim 1 , wherein the system has fewer than 25 injection nozzles.

9. A method for controlling the dosage of a reagent in a selective catalytic reduction system as recited in claim 8 , wherein the system has 2 injection nozzles.

10. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 1 , wherein each injection nozzle has a diameter from about 0.5 inches to about 10 inches.

11. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 10 , wherein each injection nozzle has a diameter from about 1 inch to about 8 inches.

12. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 11 , wherein each injection nozzle has a diameter from about 2 inches to about 6 inches.

13. A method for controlling the dosage of a reagent in a selective catalytic reduction (SCR) system as recited in claim 1 , wherein the plurality of injection nozzles forms a grid system having a plurality of branches wherein at least two of the grid branches are capable of being independently calibrated.

14. A machine readable medium containing program instructions for controlling dosage of a reagent in a selective catalytic reduction (SCR) system, the program comprising:

a) a code segment for instructing a processor to determine an influence coefficient for each of a plurality of reducing agent injection nozzles for a catalyst independent of the other injection nozzles, wherein each nozzle is configured and adapted to be independently calibrated during an SCR reaction when the system is in operation, wherein the influence coefficient for each injection nozzle is based on a constant flow from the respective nozzle and a fraction of the constant flow that appears at each of a plurality of downstream grid points; and

b) a code segment for instructing the processor to optimize flow of reducing agent from each injection nozzle based on the influence coefficients to minimize a sum of deviation from the mean value of reducing agent to NO x ratio across a surface of the catalyst, wherein the code segment for instructing the processor to optimize flow of reducing agent includes instructions to optimize based on the following equations:

B

i

=

∑

j

=

1

N

⁢

⁢

K

ij

⁢

X

j

AMM

avg

=

∑

i

=

1

M

⁢

⁢

B

i

M

∑

i

=

1

M

⁢

⁢

D

i

=

∑

i

=

1

M

⁢

⁢

ABS

[

B

i

A

i

-

AMM

avg

∑

j

=

1

M

⁢

⁢

A

j

M

]

⁢

⁢

∑

j

=

1

N

⁢

⁢

X

j

=

∑

i

=

1

M

⁢

⁢

A

i

×

η

wherein:

N=Number of Injection nozzles,

M=Number of grid measurement points,

X j =Flow rate of reducing agent at the j th injection nozzle,

A i =NOx concentration at the inlet catalyst face in ppm at i th the grid measurement point,

B i= Reducing agent concentration in ppm at the i th grid measurement point,

K ij= Influence coefficient at the i th grid point for the j th injection valve, and is defined as the fraction of the flow at the j th injection valve that appears at the i th grid point,

AMM avg= Average reducing agent concentration in ppm across the whole reactor cross section,

D i =Absolute value of deviation from the mean value of reducing agent to NO x ratio at the i th grid point, and

η=NOx Reduction Efficiency.