CFB Boiler Bed Fuel Inventory Control via Inferential Sensing
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Solution Overview
Problem
CFB boilers face challenges in dynamically adjusting their thermal power in response to varying load demands, limiting their flexibility in meeting electrical grid requirements due to difficulties in abruptly changing thermal power.
Innovation Solution
A method and system that estimate and stabilize the bed fuel inventory (BFI) using an inferential sensor and feedback controller, allowing for immediate adjustments in primary air and fuel supply rates to optimize thermal power and maintain operation near an optimal point, prioritizing thermal power over BFI stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CFB boiler operates with stable bed fuel inventory, then combustion stability and emission control are improved, but the ability to rapidly adjust thermal power in response to varying load demands deteriorates
Solution Approach 1:
The control system performs preliminary action by predicting future bed fuel inventory levels based on current combustion rate and fuel supply rate, and adjusts the fuel supply rate in advance to prevent deviations from the target BFI. This predictive control allows the system to maintain stability while being more responsive to load changes, as the system is already prepared with adjusted fuel rates before actual deviations occur.
Solution Approach 2:
The system implements feedback control by continuously monitoring actual bed fuel inventory levels and comparing them with target values, then adjusting the fuel supply rate based on the deviation. This closed-loop feedback mechanism enables the boiler to maintain stable combustion while dynamically adapting to varying thermal power demands, resolving the contradiction between stability and adaptability.
2Productivity
If the fuel supply rate is increased to meet higher thermal power demands, then productivity is improved, but the bed fuel inventory stability deteriorates, causing oscillatory operation
Solution Approach 1:
The control system calculates the required fuel supply rate in advance based on the difference between actual and target bed fuel inventory levels, allowing the system to smoothly transition to new operating conditions without abrupt changes that would cause oscillations. This preliminary calculation of fuel rates enables productivity increases while maintaining stability.
Solution Approach 2:
The system uses feedback control to continuously monitor bed fuel inventory and adjust fuel supply rate accordingly. When thermal power demands increase, the feedback mechanism gradually increases fuel supply based on actual BFI measurements, preventing overshoot and oscillatory behavior while still achieving the required productivity increase.
3Adaptability or versatility
If the primary air supply rate is adjusted to change thermal power, then adaptability is improved, but combustion efficiency and emission control deteriorate without proper BFI stabilization
Solution Approach 1:
The control system performs preliminary adjustment of the fuel supply rate based on predicted BFI changes before actual combustion efficiency is affected. This ensures that when primary air supply is adjusted for thermal power changes, the fuel-air ratio remains optimal, maintaining combustion efficiency and emission control while achieving the desired adaptability.
Solution Approach 2:
The feedback control mechanism monitors bed fuel inventory levels and adjusts fuel supply rate to compensate for changes in primary air supply. This ensures that even when thermal power responsiveness is increased through air supply adjustments, combustion efficiency is maintained by coordinating fuel supply changes based on actual BFI measurements.
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 enhances the dynamic response of CFB boilers, stabilizes bed temperature, improves emission control, and ensures optimal desulphurization efficiency, enabling faster power adjustments and better thermal efficiency while preventing oscillatory or sluggish operations.
Implementation Method 1
A bed fuel inventory (BFI) value associated with a boiler can be estimated from measurable data (via sensing) from the boiler utilizing an inferential sensor
Implementation Method 2
The bed fuel inventory value can then be stabilized at a particular value utilizing a feedback controller electrically connected to the inferential sensor
Implementation Method 3
A circulating fluidized bed (CFB) boiler is a device for generating steam by burning fossil fuels in a combustion chamber operated under a special hydrodynamic condition
Implementation Method 4
If the air velocity is chosen properly, the solid particles dragged by the gas stream exhibit behavior very similar to a boiling liquid. This phenomenon achieved by the primary air stream is called fluidization
Implementation Method 5
the low temperatures and slow combustion allow the limestone to be added to the bed to capture sulfur oxides effectively
Data Source
AI summary
A boiler control method and system. A BFI (bed fuel inventory) value associated with a boiler can be estimated by detecting data from the boiler utilizing an inferential sensor. The bed fuel inventory value can then be stabilized at a particular value utilizing a feedback controller electrically connected to the inferential sensor, in order to optimize the bed fuel inventory value for varying operating conditions of the boiler, thereby permitting a thermal power associated with the boiler to be increased or decreased faster by respectively increasing or decreasing a primary air supply rate associated with the boiler.