NOx Removal from CO2-Rich Flue Gas via Chemical Absorption
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Solution Overview
Problem
Existing methods for reducing NOx in oxy-firing combustion systems are inefficient and can affect combustion process efficiency, and they struggle with the low solubility of NO compared to NO2, limiting the effectiveness of NOx removal from CO2 rich flue gas streams.
Innovation Solution
A system and method that utilizes a gas/liquid scrubber with pressurized CO2 rich flue gas and an absorbing additive like sodium sulfite, sodium thiosulfate, and triethylenediamine, along with a pH adjustment agent, to convert NO2 into nitric acid and subsequently remove NOx by increasing pressure to favor NO2 absorption, using the gas processing unit's compression sections to enhance NOx removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If combustion temperature, fuel flow rate, or combustion gas flow rate are adjusted to reduce NOx formation, then NOx emissions are reduced, but combustion process efficiency deteriorates
Solution Approach 1:
The patent extracts the NOx removal function from the combustion process itself by introducing a separate absorption system. The absorbing additive (sodium sulfite solution) is injected into the combustion chamber where it chemically reacts with and removes NOx from the flue gas, allowing the combustion process to operate at optimal efficiency while NOx is separately captured and removed.
Solution Approach 2:
The patent introduces an intermediary substance (absorbing additive/sodium sulfite) that mediates between the combustion process and NOx emissions. This additive acts as a chemical mediator that selectively reacts with NOx in the flue gas, enabling NOx removal without directly interfering with the combustion efficiency.
2Object-generated harmful factors
If flue gases are recirculated into the combustion chamber to limit NOx emissions, then NOx emissions are reduced, but device complexity and energy consumption increase
Solution Approach 1:
The patent extracts the NOx control function from the complex flue gas recirculation system and implements it through a simpler chemical absorption approach. Instead of mechanically recirculating large volumes of flue gas, the system injects absorbing additive directly into the combustion chamber where it chemically captures NOx in place.
Solution Approach 2:
The patent replaces the mechanical flue gas recirculation system with a chemical absorption system. Instead of using mechanical means to recirculate and cool flue gases to reduce NOx, the system uses chemical reaction between the absorbing additive and NOx to achieve emission control with simpler equipment.
3Object-generated harmful factors
If absorption techniques are used to remove NOx from flue gas, then NOx removal effectiveness is improved, but the low solubility of NO compared to NO2 limits removal efficiency
Solution Approach 1:
The patent changes the chemical parameters of the absorption system by using sodium sulfite (Na2SO3) and its derivatives as absorbing additives. These compounds have high reactivity toward NOx species and can effectively absorb both NO and NO2 through chemical reaction, overcoming the solubility limitation of conventional physical absorption methods.
Solution Approach 2:
The patent employs composite chemical systems including sodium sulfite, sodium thiosulfate, and other absorbing additives that work synergistically to enhance NOx removal. The combination of different chemical compounds creates a more effective absorption system that addresses the limitations of individual substances.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively shifts the NOx concentration to favor NO2 absorption, allowing for efficient removal of NOx from the CO2 rich flue gas stream without additional energy expenditure, maximizing NO2 recovery and minimizing NOx emissions.
Implementation Method 1
an absorbing additive like sodium sulfite, sodium thiosulfate, and triethylenediamine, along with a pH adjustment agent, to convert NO2 into nitric acid and subsequently remove NOx
Implementation Method 2
using the gas processing unit's compression sections to enhance NOx removal efficiency
Data Source
AI summary
A system for reducing NOx in a flue gas stream, including an absorption element, a first inlet in fluid communication with the chamber configured to deliver a pressurized flue gas to the chamber, and a second inlet in fluid communication with the chamber configured to deliver an absorbing additive to the chamber. An outlet is in fluid communication with the chamber to exhaust from the chamber flue gas that has contacted the absorbing additive. A method for reducing NOx in a flue gas including the steps of: providing a flue gas in a chamber of an absorption element, providing an absorbing additive so that it contacts at least a portion of the flue gas, and exhausting at least a portion of the flue gas from the chamber.