Circulating Fluidized Bed Coal-Saving Optimization Control Method - Intelligent Computing for Sustainable Energy and Environment - page 304

circulating fluidized bed boiler mechanism and the linear model, and proposed
multivariable decoupling PID control method. Since then, fuzzy-PID control
(such as [3] and [4]), BP neural network control ([5]), and other control method
have been proposed. In order to handle the physical constraints, the predictive
control strategy in [6] has been applied in the control of CFB boilers.
In recent years, with the increasing energy demand, policies of energy saving
and environmental protection are promulgated. How to reduce coal consumption,
or improve the eciency of coal has become the industrial focus of attention. By
the experiments of raw materials, Yanxiao Zhong and his team studied influences
of pulverized coal fineness on the combustion eciency and then proposed to
improve the economizer effect by pretreatment of coal in [7]. In terms of process,
[8] suggested to use the cycle steam pipe to dryer pretreatment coal to improve
coal-fired eciency and then to save coal. On the other hand, Lv Wenxiang
and his colleague proposed adaptive optimization method based on intelligent
optimal control strategy to ensure that the boiler runs with a high combustion
eciency to achieve both normal operation and environmental protection[9].
Pretreatment of coal can contribute greatly to the combustion eciency. But
it also results in the cost for equipment investment to the end user. For the
control of a CFB boiler, to achieve the dual purpose of circulating fluidized bed
boiler coal-saving and the normal operation is a multi-objective optimization
control problem. For the similar purpose, a real time optimization (RTO) layer
can be designed for system operating point optimization. As mentioned in [10],
the combination of the technique of RTO and DMC can be expected to reduce
more than 30% of fuel in the industrial fuel gas system.
In order to reduce the coal consumption of a CFB boiler, this paper refers
the idea of RTO to design the DMC controller where the coal consumption is
added into the objective function of DMC. Meanwhile, in order to achieve the
goal of saving coal further, the DMC adopts the zone control strategy. That
means, the operation point of circulating fluidized bed boiler can be adaptively
chosen near the ideal operating point. This provides the freedom to reduce the
coal consumption. The permitted zone of operation point can be chosen accord-
ing to the actual requirements of the circulating fluidized bed boiler. The final
simulation verifies that the proposed method can achieve a remarkable reduction
of coal consumption.
This paper is organized as follows. Section 2 introduces the related technology,
including the CFB boiler, DMC, and RTO. Section 3 proposes the coal-saving
control algorithm. And Section 4 gives a case study about a 150 t/h boiler of a
power plant in Sichuan, which verifies the effectiveness of the proposed method.
2 The Problem Formulation and Background Technology
2.1 The CFB Boiler
The circulating fluidized bed boiler is a typical MIMO thermal system, whose
main input and output relationships are shown in Fig. 1.