Abstract:
Boiler is the heart of the chemical process industries like fertilizer manufacturing plant.
Automatic boiler control system is desirable for safe, economic and reliable operation of the
industry. Conventional three elements Proportional plus Integral plus Derivative (PID)
controller are generally used in the different control loops of the boiler. Main drawback of the
use of this type of the controller is the adjustment of controller's parameters such as gain,
reset time and dead time due to change of operating point of the process. However, the
application of Self Tuning Controller (STC) and Model Reference Adaptive Controllers
(MRAC) can overcome tllis drawback in the case of linear process plant. The boiler plant is
highly nonlinear plant. Thus a neural network based integrated control system is proposed
to control an industrial boiler. A 120 ton per hour capacity boiler of the Zia Fertilizer
Company Limited (ZFCL), Ashuganj, Bangladesh is taken as reference boiler for the case
study. The process lIlverse dynamic modelling technique is applied to design the proposed
controller. A multilayer feedforward and diagonal recurrent neural network is trained to
identify the unknown inverse dynamic model of the boiler plant by general backpropagation
and dynamic back propagation training algorithm respectively. The training data was
collected from the computer data bank of the reference boiler. After investigating the
peIformance of both network, the feedforward network arcllitecture is selected for the
proposed controller. Using the weights of the network a new, software controller is then
developed for integrated control system of the ZFCL boiler. The developed controller is
tested by using the boiler input - output data that are not used during the training. The
output response of the developed controller is compared with that of the existing PID
controller. Both responses are very close to each other. The developed controller output is
then converted into signal using pulse width control teclmique. 'nlese signals can then be
used for on-line regulation of the control valves through parallel port of the computer. The
average value of tile pulse indicates the percentage of the valve opening.
