An
input–output (I/O) linearizing control scheme for a gas-fired
thermal cracking furnace is developed for a tubular reactor coil,
which is a type of tubular reactor surrounded by gas-fired burners
in the furnace. Due to the simultaneous interaction between the spatially
distributed dynamics of the reactor coil and the lumped radiating
wall, the typical proportional-integral-derivative control widely
used in industry may have insufficient performance to handle the complexity.
In this work, a feedback I/O linearizing controller is applied to
control a cracking furnace system that is described by a coupled PDE-ODE
model: ethylene dichloride cracking. The cracked gas temperature is
manipulated through the fuel gas flow to achieve the desired trajectories.
Control performances of the developed controller are illustrated through
simulation results for servo and regulatory problems. The proposed
method provides more robustness to handle control problems without
offset.
A nonlinear
optimization-based control system with analytical model
predictive control (AMPC) structure is formulated in cascade with
an off-line pseudo-steady-state calculator for an ethylene dichloride
(EDC) cracking furnace process described by a coupled partial differential
equation/ordinary differential equation model. The objective of the
proposed control system is to control the EDC cracking rate at the
desired set points by manipulating the fuel gas flow rate with constraints
to avoid extensive coke formation. To handle the complex behaviors
that are affected by radiating walls interacting with spatial dynamics
of the reactor coil, the set point calculator is employed to provide
an optimal target for the constrained optimization-based controller
in calculating the control actions. Simulation results show that the
proposed control system is successful to regulate the controlled output
at the desired set points. Control performance tests with servo and
regulatory problems demonstrate that the developed control system
is capable of providing excellent responses to achieve the desired
set point and reject process disturbance.
This work develops a control strategy to handle coupling effects between the level and pH for a pH process with multiple titrant streams. The feedback controller is formulated based on a nonlinear optimization problem of an input/output (I/O) linearization for output tracking. In order to calculate the control actions and estimate the state disturbances simultaneously, an integrated disturbance estimator is combined into the developed control structure. The proposed controller is applied to control the outlet pH and liquid level of a reactor system to achieve desired setpoints by adjusting outflow and titrating streams. Control performance of the developed control system is investigated by experimentation with a continuous bench-scale pH process that is operated under servo and regulatory problems of disturbances in the feed and titrant streams. Experimental results show that the developed controller can force the process to the desired setpoints effectively and handle the pH process with disturbances when fluctuations in pH and inlet flow of the reactor are present.
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