A Discrete Time Model of Boiler Drum and Heat Exchanger QAD Model BDT 921 Tatang Mulyana * , Mohd Nor Mohd Than ** , Dirman Hanafi *** * Faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia (UTHM) Locked Bag 101, Parit Raja, 86400 Batu Pahat, Johor Darul Ta’zim E-mail: tatang@uthm.edu.my , ** Faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia (UTHM) Locked Bag 101, Parit Raja, 86400 Batu Pahat, Johor Darul Ta’zim E-mail: mnmt@uthm.edu.my , *** Faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia (UTHM) Locked Bag 101, Parit Raja, 86400 Batu Pahat, Johor Darul Ta’zim E-mail: dirman@uthm.edu.my Abstract A boiler drum and heat exchanger QAD Model BDT921 that is installed in the Control Laboratory is being used as a model plant to achieve the digital control system design since it is analog in nature. The digital control design need a mathematical model of the system is designed. This paper covers a discrete time model of boiler drum and heat exchanger QAD Model BDT 921. The model is obtained from parameter gain values of the real system and then this model will simulate using MATLAB program. The proportional integral differential (PID) controllers are being chosen as the control element in discrete form as the real system is using the same control element. The output responses behave as the second order system with a closed correlation in rise times and peak times compared with data obtained from experiment and simulation results. With regarding to the analysis done, the digital control can be implemented to the boiler drum and heat exchanger control system and for further viewing, to be controlled digitally with computer in the control room. 1 Introduction Boiler drum and heat exchanger are commonly used in industries in almost all process and power plants to generate steam for the main purpose of electricity generation via steam turbines [1,2]. The real system of boiler drum and heat exchanger QAD Model BDT921 that installed in the Control Laboratory in University Tun Hussein Onn Malaysia (UTHM) is showed in Figure 1 and Figure 2, and the piping and instrumentation drawing (P&ID) of the system is showed in Figure 3. This paper covered the study of overall process operation of boiler drum and heat exchanger as a control system plants. It encompassed the explanations of the roles of each instrument and control elements such as control valves and PID controllers. This paper will cover a discrete time model of the control systems. It then can be analyzed with using MATLAB software to find control response characteristics. After getting the right simulation value for the control system, we go further with the digitization of the simulation. While simulating, the analog to digital converter is not used because of the continuous transfer function was replaced with the discrete transfer function. Therefore, the input signal is processed in discrete function. The discrete transfer function obtained from the continuous transfer function by using certain syntax from MATLAB command window. Sampling time can be changed due to the system requirement. Figure 1 – The boiler drum and heat exchanger QAD Model BDT 921 (Real system) International Conference on Instrumentation, Control & Automation ICA2009 October 20-22, 2009, Bandung, Indonesia ©2009 ICA, ISBN 978-979-8861-05-5 154