Catalytic denitrification control process and system for combustion flue gases
First Claim
1. A process for controlling the catalytic denitrification of flue gases by ammonia addition to the flue gas, said process comprising:
- (a) withdrawing from a combustion process a flue gas stream containing at least about 20 volume parts NOx per million of flue gas, and controllably adding ammonia gas to said flue gas stream;
(b) passing the flue gas and ammonia mixture through a catalytic denitrification unit containing a denitrification catalyst material and reducing the NOx concentration in the flue gas;
(c) obtaining a control signal based on process parameter signals including the volume flow rate of said flue gas, and determining the quantity of ammonia initially added to the flue gas so that it is less than the amount theoretically required to reduce all of the NOx in the flue gas;
(d) obtaining a trim signal based on comparing the NOx concentration measured in the flue gas downstream of the catalytic dentrification unit and a desired NOx concentration; and
(e) providing additional ammonia injection based on the trim signal by adjusting the ammonia addition flow rate as needed to provide the desired reduced NOx concentration in the flue gas being emitted to the atmosphere and to avoid excess ammonia injection and system oscillation.
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Accused Products
Abstract
A control process and system for catalytic denitrification of NOx containing flue gases derived from a fuel combustion unit such as a gas turbine by ammonia addition to the flue gas upstream of a catalytic denitrification unit. The ammonia addition rate is controlled based on a basic signal which is generated based on functional parameters including the fuel being burned, its combustion temperature, flue gas flow rate, ammonia flow rate and the catalytic activity, so as to inject initially into the flue gas stream less ammonia than is theoretically required. Then the NOx concentration in the exhaust gas downstream of the catalytic unit is compared with the appropriate standard, the ammonia quantity initially being added is further adjusted until the NOx concentration is gas emitted to the atmopshere is reduced sufficiently to meet local clean air standards while avoiding unsatisfactory excess ammonia injection and system oscillation.
66 Citations
11 Claims
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1. A process for controlling the catalytic denitrification of flue gases by ammonia addition to the flue gas, said process comprising:
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(a) withdrawing from a combustion process a flue gas stream containing at least about 20 volume parts NOx per million of flue gas, and controllably adding ammonia gas to said flue gas stream; (b) passing the flue gas and ammonia mixture through a catalytic denitrification unit containing a denitrification catalyst material and reducing the NOx concentration in the flue gas; (c) obtaining a control signal based on process parameter signals including the volume flow rate of said flue gas, and determining the quantity of ammonia initially added to the flue gas so that it is less than the amount theoretically required to reduce all of the NOx in the flue gas; (d) obtaining a trim signal based on comparing the NOx concentration measured in the flue gas downstream of the catalytic dentrification unit and a desired NOx concentration; and (e) providing additional ammonia injection based on the trim signal by adjusting the ammonia addition flow rate as needed to provide the desired reduced NOx concentration in the flue gas being emitted to the atmosphere and to avoid excess ammonia injection and system oscillation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10, 11)
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9. A process for controlling the catalytic denitrification of exhaust gas from a gas turbine by ammonia addition to the exhaust gas, said process comprising:
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(a) withdrawing from a gas turbine an exhaust gas stream containing at least about 20 volume parts NOx per million parts of exhaust gas, and controllably injecting an ammonia-containing gas stream into said exhaust gas stream so that the amount of ammonia is less than the amount theoretically required to reduce all of the NOx in the exhaust gas; (b) passing said exhaust gas and ammonia mixture through a honeycomb type catalytic denitrification unit containing a denitrification catalyst, and initially reducing NOx concentration of the exhaust gas; (c) generating a basic control signal based on process parameter signals of exhaust gas flow rate and NOx content, and the ammonia temperature, pressure and flow rate; (d) providing a trim signal based on comparing said basic signal with NOx concentration of the exhaust gas at a location downstream of said catalytic denitrification unit and desired NOx concentration; and (e) providing additional ammonia injection based on the trim signal by adjusting the ammonia injection rate as needed to provide the desired reduced NOx concentration in the turbine exhaust gas being emitted to the atmosphere and to avoid excess ammonia injection and system oscillation.
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Specification