Flue Gas Conditioning Controller for Injection Rate Accuracy
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Solution Overview
Problem
Existing flue gas conditioning systems in coal-fired power plants face challenges with over- or under-injection of conditioning agents, leading to performance degradation and increased operating costs, due to the need for site-dependent adjustments based on various factors such as boiler load and coal flow.
Innovation Solution
An automated injection-rate control system that uses a combination of feed forward and feedback signals from coal flow, voltage control, sulfur dioxide emissions, opacity monitors, and other parameters to determine the optimal injection rate of conditioning agents, such as sulfur trioxide and ammonia, to prevent over- or under-injection, ensuring precise control and minimizing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual monitoring and adjustment of conditioning agent injection rate is used, then system simplicity is maintained, but over- or under-injection occurs leading to performance degradation and increased operating costs
Solution Approach 1:
The system continuously monitors multiple parameters including boiler load, coal flow rate, flue gas temperature, precipitator voltage, and opacity levels. This feedback information is processed by a controller that automatically adjusts the injection rate to maintain optimal precipitator performance and minimize emissions, eliminating manual adjustment requirements
Solution Approach 2:
The control system performs self-adjustment by automatically calculating the optimal injection rate based on real-time process conditions and controlling the injection valve accordingly. The system monitors its own performance through opacity sensors and voltage measurements, then autonomously corrects any deviations without external intervention
2Speed
If feed forward control proportional to coal flow is used, then response to boiler load changes is improved, but over- or under-injection still occurs due to site-dependent variations
Solution Approach 1:
The system combines feed-forward control based on coal flow rate with feedback from opacity monitors, voltage measurements, and temperature sensors. This dual approach allows rapid response to load changes while maintaining precision through continuous adjustment based on actual precipitator performance and environmental conditions
Solution Approach 2:
The control system dynamically adapts the injection rate based on changing operating conditions including boiler load, coal quality variations, flue gas temperature, and precipitator voltage. The controller continuously recalculates the optimal injection rate to maintain effectiveness across varying conditions rather than using a fixed proportional relationship
3Loss of energy
If overdosing of conditioning agent is avoided to reduce operating costs, then operating costs decrease, but precipitator performance may be compromised
Solution Approach 1:
The system uses opacity monitors and voltage measurements as feedback signals to determine the actual effectiveness of the conditioning agent. This allows the controller to maintain precise injection rates that optimize precipitator performance while avoiding excess injection, thereby minimizing both performance degradation and unnecessary operating costs
Solution Approach 2:
The system replaces cost-based decision making with sensor-based feedback control. Instead of using fixed injection rates or operator judgment, the system uses real-time measurements of opacity, voltage, and temperature to automatically adjust injection rates, ensuring optimal performance at minimal cost
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
The system eliminates manual adjustments, provides instant response to changes in boiler loads or coal supplies, maximizes precipitator performance, and minimizes sulfur trioxide and ammonia emissions, thereby reducing operating costs and environmental impact.
Implementation Method 1
The ammonia addition mass flow rate is adjusted responsive to the sulfur trioxide mass flow rate... The proposed CONTROLLER approach offers precise control over additives: i.e. the content of the combustion or exhaust gas stream, so that there is virtually no sulfur trioxide, sulfuric acid, or ammonia emitted to the atmosphere.
Data Source
AI summary
An FGC conditioning agent injection-control system, where conditioning agent over- or under-injection can be prevented while maximizing a precipitator's performance. The injection rate is typically regulated using feed forward signal proportional to the coal flow, which could be represented by the boiler load augmented by a feedback from the voltage control and electrical conditions in the ESP, sulfur dioxide emissions signaling any changes in the coal quality, opacity monitor data, and other parameters. Both the feed forward and the feedback information and signals from the existing injection skids are analyzed, and the optimal injection rate for the current conditions is determined. With fast, continuous and automatic sampling and analysis, the system responds quickly as each parameter changes, recalculating the optimal injection rate and automatically sends the new injection set-point to the injection skid.