Boiler Flue Gas Velocity Control for Fouling Prevention
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Solution Overview
Problem
Existing control methods for combustion boilers, particularly fluidized bed boilers, face challenges in safely increasing thermal load under low excess oxygen conditions due to the risk of exceeding maximum flue gas velocity, leading to issues like fouling and corrosion.
Innovation Solution
A control method that sets a predetermined upper limit for flue gas velocity, monitors it, and adjusts the thermal load by decreasing fuel flow if the velocity exceeds this limit, allowing safe operation at higher thermal loads while maintaining safe flue gas velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thermal load of the boiler is increased to enhance productivity, then the boiler efficiency is improved, but the flue gas velocity exceeds the maximum design value causing fouling and corrosion
Solution Approach 1:
The control method continuously monitors flue gas velocity and compares it against a predetermined maximum design value. When the flue gas velocity approaches or exceeds the maximum design value, the system automatically reduces the thermal load to maintain safe operating conditions, preventing fouling and corrosion while maximizing productivity when conditions permit
Solution Approach 2:
The thermal load is made dynamically adjustable based on real-time flue gas velocity measurements. The system transitions from static thermal load operation to dynamic control where the thermal load automatically adapts to current operating conditions, allowing maximum productivity when flue gas velocity is safe and preventing harmful effects when velocity exceeds limits
2Reliability
If the flue gas velocity is limited to prevent fouling and corrosion, then the reliability is improved, but the thermal load must be reduced decreasing productivity
Solution Approach 1:
The system uses continuous feedback from flue gas velocity measurements to dynamically adjust the thermal load. When flue gas velocity is below the maximum design value, the thermal load can be increased to maximize productivity. When velocity approaches or exceeds the limit, the thermal load is automatically reduced to prevent fouling and corrosion, ensuring reliability while optimizing productivity at all times
3Reliability
If excess oxygen is supplied to achieve complete combustion, then the reliability is improved, but the thermal loss increases due to increased exhaust gas flow decreasing efficiency
Solution Approach 1:
The system optimizes the oxygen supply parameter by controlling the air to fuel ratio to achieve complete combustion with minimal excess oxygen. By using flue gas velocity as a control parameter and maintaining it at safe levels, the system enables operation at lower excess air ratios that would otherwise risk exceeding maximum flue gas velocity, thereby reducing thermal losses while maintaining reliable complete combustion
Data Source
AI summary
The invention is in the field of boiler control and relates to a control method for the operation of a combustion boiler, comprising providing a predetermined upper limit (VF,max) for the flue gas velocity in at least one location of the boiler; monitoring the flue gas velocity (VF) during the combustion of fuel in said at least one location of the boiler; comparing the flue gas velocity (VF) with the predetermined upper limit (VF,max); decreasing the thermal load of the boiler if the flue gas velocity exceeds the predetermined upper limit (VF,max). The invention also relates to a control system configured to execute the control method.