Abstract
The objective of this paper is to show the design and application of pass temperature balance control system using an improved predictive functional control method in eight 800 tone/year USC ethylene cracking furnaces. The advanced pass temperature balance controller is developed using the proposed method and implemented in proprietary APC-ISYS software, which is connected to Yokogawa distributed control system via an OPC server. The advantage of it lies in the fact that the dynamics of pass temperature with nonlinearity and time delay are described by Takagi–Sugeno model and transformed into time-varying extended state space model, and thus, the proposed controller can regulate pass temperature based on the extended state space formulation. In addition, the control law with a linear iterative form, easily applied to industrial process, is derived. The robust analysis for the set point, input disturbance and output disturbance to the output verifies the ability of tracking and disturbance rejection of the proposed method. Application results from an industrial furnace are shown to be markedly better in terms of lower variability in the outlet temperature of both the passes compared to the current proportional–integral–derivative control scheme.
Highlights
Ethylene cracking furnace is a vital equipment to petrochemical industry in which a lot of important chemical products, such as propylene, ethylene, butadiene, benzene, dimethylbenzene, and so on, can be obtained by the high-temperature cracking reaction.[1]
Using the improved predictive functional control (IPFC) approach, the advanced pass temperature balance controller is developed and implemented in proprietary APC-ISYS software, which is connected to Yokogawa distributed control system (DCS) system via an OPC server
The design and application of pass temperature balance control using proposed IPFC algorithm on the ethylene cracking furnace are presented in this paper
Summary
Ethylene cracking furnace is a vital equipment to petrochemical industry in which a lot of important chemical products, such as propylene, ethylene, butadiene, benzene, dimethylbenzene, and so on, can be obtained by the high-temperature cracking reaction.[1]. The pass temperature of the ethylene cracking furnace is a complex process dynamic with multi-input and multi-output, nonlinearity and large delay as well as many of unknown disturbances. The fuzzy model (Equation (39)) is employed in the advanced pass temperature controller (IPFC) The parameters of it are H = 15, Tr = 0:5s, Ts = 1s, Q = diag(0:9, 0:9, 0:9, 0:9, 1, 1), and R = diag(1, 1) that are acquired by repeated offline test. The results of the pass temperature (TIC112126A and TIC112326A in the south) in chamber A are presented in Figures 7, 9, 11 and 13 From these figures, a better control performance can be seen with the IPFC compared to the PID, Su and Li38 and standard PFC. Compared to Su and Li,[38] PID controller and standard PFC, the developed pass temperature controller can achieve the improved control performance with regard to the set point tracking and disturbance rejection
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