Flue Gas Recirculation for Absorber Vessel Corrosion Control
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Solution Overview
Problem
Ambient air ingress in dry flue gas treatment systems leads to particulate matter accumulation, corrosion, and instability in pollutant emission rates and reagent consumption due to temperature and humidity differences, causing operational inefficiencies and structural issues.
Innovation Solution
Recirculating treated flue gas to areas of ingress in the system, using an insulated duct to maintain temperature and humidity, and employing a transition piece containment vessel with isolation valves to manage particulate matter discharge without admitting ambient air, thereby stabilizing the system and reducing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ambient air is permitted to enter the absorber vessel to suspend and convey particulate matter, then particulate matter can be prevented from settling and accumulating, but the cooler ambient air causes moisture condensation that accelerates corrosion and creates adhesive mixtures that accumulate on surfaces
Solution Approach 1:
The patent introduces recirculated flue gas as an intermediary substance to replace ambient air in the absorber vessel. This recirculated gas serves as a mediator that provides the necessary turbulence and conveyance for particulate matter without introducing the harmful effects of ambient air (cooling and condensation). The recirculated gas is drawn from downstream of the induced draft fan and reintroduced into the absorber vessel, creating a closed-loop system that eliminates the need for ambient air ingress.
2Temperature
If ambient air ingress is allowed to stabilize approach temperature, then temperature control is improved, but reagent consumption and pollutant emission rates become unstable
Solution Approach 1:
The patent implements a feedback control system where the recirculation rate of flue gas is adjusted based on measured approach temperature. The system continuously monitors the approach temperature and modifies the recirculation flow to maintain the desired temperature stability. This closed-loop feedback mechanism ensures that approach temperature remains stable while avoiding the instability in emission rates and reagent consumption that occurs with ambient air ingress.
3Productivity
If ambient air is used to prevent particulate accumulation in remote regions, then flow disturbance is reduced, but additional fan power is required to compensate for the accumulated semi-solid mixture
Solution Approach 1:
The patent employs the recirculated flue gas to perform the dual function of both conveying particulate matter and maintaining appropriate temperature and humidity conditions. The recirculated gas, which would otherwise be wasted energy, is put to productive use by introducing it back into the absorber vessel. This self-service approach eliminates the need for additional fan power that would be required if ambient air were used, as the recirculated gas already has the necessary thermal and moisture properties.
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 stabilizes approach temperature, reduces particulate accumulation, minimizes corrosion, and optimizes reagent consumption by maintaining consistent gas properties, enhancing the operational efficiency and longevity of the flue gas treatment system.
Implementation Method 1
This recirculation provides the desired turbulence within remote regions of the DFGT system to reduce the amount of particulate material that may otherwise settle and accumulate in these regions
Implementation Method 2
directing it to the absorber vessel or other areas of the DFGT system at a controlled rate through an insulated duct
Implementation Method 3
This additional water preferably evaporates fully within the absorber vessel, thereby cooling and humidifying the flue gas. The difference between the dry bulb temperature and adiabatic saturation temperature of the flue gas is thereby reduced during this evaporation phase
Implementation Method 4
as the cooler ambient air mixes with the humid flue gas in these regions, the localized gas temperature falls below the adiabatic saturation point causing moisture to condense into fine liquid droplets
Data Source
AI summary
Recirculation of treated flue gas either independently or as a substitute for ambient air at specific points of ingress in a flue gas treatment system is provided to stabilize approach temperature and related parameters such as reagent consumption and pollution admission rate preventing both the accumulation of particulate matter and excessive corrosion associated with ambient air ingress. This recirculation provides a desired turbulence within remote regions of the flue gas treatment system to reduce the amount of particulate matter that may otherwise settle and accumulate in the absorber vessel or other areas of the system thereby causing particulate matter to be conveyed to the particulate removal device.