Fluidized Bed Boiler Combustion Optimizer is a supervisory level control application for optimum combustion control of fluidized bed boilers. The application is suitable for both Bubbling Fluidized Bed (BFB) and Circulating Fluidized Bed (CFB) Boilers
The purpose of the application is to achieve easier and more stable operation, minimize flue gas emissions (SO2, NOx etc.) and to improve the combustion efficiency, while keeping selected process variables such as bed, combustion chamber (furnace) and cyclone temperatures within acceptable limits. When obtaining a more stable operation also the O2-content in the flue gases can be minimized which leads to a higher overall boiler efficiency and thus more economical operation. Improved combustion control is especially needed in boilers utilizing several different fuels with (large) variations in both the amount of the various fuels and in the fuel quality (heating value, moisture content etc.). Fuzzy Logic is therefore especially suitable for fluidized bed boilers firing fuels such as sludge, wood waste, bark and low-grade brown coal.
The Fluidized Bed Boiler Combustion Optimizer is part of the metsoDNA Energy application network, and the controls and user interface are fully integrated within the metsoDNA Energy.
Features
Fluidized Bed Boiler Combustion optimizer is a software product consisting of fuzzy controllers, calculated process variables and the user interface for tuning and user operations.
The application consist of the following subtasks:
Fuel heat value calculation
Calculation of the total combustion air
Control of total combustion air
Bed Temperature control
Furnace temperature control
O2/CO-optimization
Fuel feed controls
NOx-control
SO2-control
The structure of each fuzzy controller is the same. Each controller can have several measurements and one control output. The fuzzy controller can be divided into three sub functions: fuzzification, rule base and defuzzification. These sub functions are realized with fuzzy control function blocks included in the metsoDNA Energy application network, featuring built-in management for faulty signals, forced control and manual/auto changes.
The fuzzy controllers are connected to the base level controls through parameters and controller set points.
Benefits
Using Fuzzy Logic in combustion optimization and control offers the following advantages:
The multivariable control application is optimizing between several control targets continuously
Easy implementation of process knowledge into a control algorithm
The application is running completely in the metsoDNA Energy environment
With tuning displays it is easy to test different kinds of control rules or select measurements during the commissioning phase
Linguistic and readable control laws
The supervisory fuzzy logic control can be added to the basic level controls with minor changes even after the initial installation of the automation system.
The following results and benefits have been achieved by using fuzzy logic in the control of a fluidized bed boiler:
Better overall process control
More stable operation (combustion)
Control available in whole range
Smaller variations in fluidized boiler bed temperatures
Increased efficiency (O2 minimized)
Minimized emission (NOx, SO2, CO)
System Environment
The Fluidized Bed Boiler Combustion Optimizer is executed in the process control and operation activities of metsoDNA.
